Monday, 27 June 2022

Lupine Publishers| The Gompertz Length Biased Exponential Distribution and its application to Uncensored Data

 Lupine Publishers| Journal of Biostatistics & Biometrics



Abstract

This paper proposes a generalization of the length biased exponential distribution, called the Gompertz length biased exponential (GLBE) distribution. Some of the basic properties of the proposed model were derived in minute details and model parameters estimated by the maximum likelihood estimate method. The adequacy of the model is empirically validated with the use of real - life data.

Keywords: Exponential Distribution; Length Biased; Gompertz Generalized Family Of Distribution; Quantile Function; Hazard Functions; Survival Function

Introduction

Length biased distributions are special case of the more general form known as weighted distribution [1], first introduced by [2] to model ascertainment bias and formalized in a unifying theory by [3]. Lifetime data may be modeled with several existing distributions, although the existing models are not adequate or are less representative of actual data in many situations. Therefore, the development of compound distributions that could better describe certain phenomena and make them more flexible than the baseline distribution is of great importance [4]. Thus, the choice of the model is also an important issue for reliable model parameter estimation. Some exponential distribution generalizations for modeling lifetime data due to some interesting advantages have been recently proposed [5]. In recent years many exponential distribution generalizations have been developed, such as the Marshall Olkin length biased exponential distribution [5], exponentiated exponential [6,7], generalized exponentiated moment exponential [8], extended exponentiated exponential [19], Marshall-Olkin exponential Weibull [10], Marshall-Olkin generalized exponential [5], and exponentiated moment exponential [11] distributions.

A random variable X is said to have a length biased exponential distribution with parameter \beta if its probability density function (pdf) and cumulative distribution function (cdf) is given by equation (1) and (2) respectively [12]:

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Where is the scale parameter.

The survival function is given by the equation

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The hazard function is

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And the reversed hazard rate function is

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Alzaatreh et al. [13] defined the cumulative distribution function of the Transformed-Transformer (T-X) family of distributions by;

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And the corresponding probability density function by;

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Morad Alizadeh et al [14] defined the cumulative distribution function and probability density function of the Gompertz Generalized family of distribution by setting

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respectively. Where \theta and \gamma are additional shape parameters whose role is to vary the tail length.

Thus, we proposed a new generalization of the length biased exponential distribution called the Gompertz length biased exponential (Go-LBE) distribution. In the rest of the paper, we define the Go-LBE model and plots for different parameter values in Section 2; some of the statistical properties of the proposed Go-LBE distribution are discussed in minute details in section 3, Application of the Go-LBE distribution to a lifetime data in section 4. The concluding remark is presented in section 5.

Gompertz Length Biased Exponential (Go-LBE) Distribution

The cumulative distribution function of the

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Figure 1: Graph for Go-LBE cumulative distribution function at different parameter values.

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Figure 2: Graph for Go-LBE probability density function at different parameter values.

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Figure 3: Graph for Go-LBE survival function at different parameter values.

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Figure 4: Graph for Go-LBE hazard function at different parameter values.

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Figure 5: Histogram of the fitted distributions.

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Figure 6: Empirical cdf of the fitted distributions.

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Some Statistical Properties of the Go-LBE Distribution

Basic properties such as the asymptotic behavior, parameter estimation and order statistics of the Go-LBE distribution are discussed in minute details.

Asymptotic Behavior

Here we critically examine the behavior of the Go-LBE model in equation (11) as x→0 and as x→∞

This indicates that the Gompertz length biased exponential distribution is unimodal. A clear observation of Figure 2 shows the Go-LBE model has only one peak. This supports our claim that the Go-LBE distribution has only one mode.

Parameter Estimation

Using maximum likelihood estimation techniques, we estimate the unknown parameter of the Go-LBE model based on a complete sample. Let X...Xn indicate a random sample of the complete Go-LBE distribution data, and then the sample’s likelihood function is given as;

We can now express the log likelihood function as;

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By taking the derivative with respect toθ ,γ andβ , and fixing the outcome to zero, we have;

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Solving equation (18)-(20) iteratively, will give the estimate of the parameters of the Go-LBE model.

Order Statistics

We considered a random sample denoted by from the densities of the Go-LBE distribution. Then,

The probability density function of the order statistics for the Go-LBE distribution is given as;

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The Go-LBE distribution has minimum order statistics given as;

Data Analysis

Here, we provide an application of the Gompertz length biased exponential distribution by comparing the results of the model fit with that of other Gompertz- G family of distributions. The data set we employ is the uncensored strength of 1.5cm glass fibre data previously used by Bourguignon M et al. [15], Merovci F et al. [16]. This data set will be used to compare between fits of the Gompertz length biased exponential distribution (Go-LBE) with that of Gompertz-Exponential (Go-E), Gompertz-Lomax (Go-L), and, Gompertz-Weibull (Go-W). The data is presented below (Tables 1 & 2):

Table 1: Descriptive Statistics on Cancer Stem Cell Data.

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Table 2: MLEs, SW, AD and K–S of parameters for Cancer Stem Cell data.

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0.55, 0.74, 0.77, 0.81, 0.84, 1.24, 0.93, 1.04, 1.11, 1.13, 1.30, 1.25, 1.27, 1.28, 1.29, 1.48, 1.36, 1.39, 1.42, 1.48, 1.51, 1.49, 1.49, 1.50, 1.50, 1.55, 1.52, 1.53, 1.54, 1.55, 1.61, 1.58, 1.59, 1.60, 1.61, 1.63, 1.61, 1.61, 1.62, 1.62, 1.67, 1.64, 1.66, 1.66, 1.66, 1.70, 1.68, 1.68, 1.69, 1.70, 1.78, 1.73, 1.76, 1.76, 1.77, 1.89, 1.81, 1.82, 1.84, 1.84, 2.00, 2.01, 2.24

For all competing distributions using the strength of glass fibre data set, Table 2 shows parameter estimate and the value for the Shapiro Wilk (S-W), Anderson Darling (AD), and the Kolmogorov Smirnov (K-S) statistic (Table 3).

From Table 3, the Go-LBE has the highest log-likelihood values and the lowest AIC, CAIC, BIC and HQIC values; hence, it is chosen as the most appropriate model amongst the considered distributions.

Table 3: Log-likelihood, AIC, AICC, BIC and HQIC values of models fitted for Cancer Stem Cell data.

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Conclusion

This research has successfully extended the length biased exponential distribution. Densities and basic statistical expressions were briefly derived. The performance of the proposed Gompertz length biased exponential distribution was compared to existing models in literature based on the negative log likelihood, AIC, CAIC, BIC and HQIC values. Based on the lowest criterion values, we therefore conclude that the Gompertz length biased exponential distribution is the most suitable model amongst the considered models and indeed a very competent model for describing life-time situations.

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Saturday, 25 June 2022

Lupine Publishers | Heterobimetallic Aryloxides of Titanatranes with Aluminum Alkyls for Ring opening polymerization (ROP) of rac-Lactide

 Lupine Publishers | Journal of Organic and Inorganic Chemical Sciences


Abstract

The titanatrane titanium complexes were treated with Aluminum Alkyls to prepare their bimetallic derivatives (1a-4a). The compounds were confirmed by means of NMR and elemental analysis. The complexes were used as catalysts for ring opening polymerization of racemic lactide. The complexes exhibit high activity and selectivity in the polymerization process.

Abbrevations: ROP: Ring Opening Polymerization; LA: Rac-lactide

Introduction

Olefin polymerization catalysis [1a-1b] continues to be an area of considerable importance to both the academic and industrial communities, and a wide range of reports are appearing on the efficient catalyst designs and application in various catalytic systems. Recently, the work on bimetallic complexes and in particularly bimetallic oxides is gaining considerable attention due to the "cooperativity" or "communication" between neighboring repeating units [2a-2d]. Since heterometallic alkoxides are potential molecular precursors of multicomponent oxides, they are thus of interest for applications in catalysis as well as in material science. Heterometallic alkoxide derivatives have been postulated to act as catalysts in Ziegler-Natta polymerization [3a,3b] or olefin metathesis reactions, [3c] and exhibit high activity and produce polymers with different microstructure. These heterometallic complexes were also found active in nitrogen activation," but detailed characterization is lacking [4].

The main disadvantage of mononuclear catalysts is the need of large amount of MAO or expensive fluorinated borate activators to obtain adequate polymerization activity, which causes concern over the high cost of metallocene catalysts and the high ash content (Al2O3) of the product polymers. Consequently, there is a great need to develop new catalyst systems that can provide high catalytic activity with no need for a large amount of expensive cocatalysts. We were thus interested in designing the catalysts which can exhibit high activity in the polymerization without or with very less amount of cocatalysts. For this, we used atrane ligands which have a nitrogen atom that facilitates coordination in a chelate fashion when necessary by providing the metal with additional electronic density [5a-e]. Although there have been many reports on the complexes based on atrane ligands, application of these complexes in polymerization reactions are very limited [6a-c].

We recently reported that heterobimetallic complexes of titanium iso-propoxide and aluminum alkyl containing bis (aryloxo) ethanolamine ligand were effective as catalysts precursor for ethylene polymerization even in the absence of cocatalysts [7]. We then extended the chemistry to tris (aryloxo) amine based ligands [8]. Furthermore, we reported that titanatranes bearing terminal substituted aryloxo ligands exhibit the highest activity in ethylene polymerization [9]. To the best of our knowledge these complexes are the best catalysts for ethylene polymerization among all the titanatranes reported so far. We became interested in isolating the bimetallic complexes of titatnium bearing aryloxo terminal ligands with aluminum alkyls to understand the plausible mechanism of polymerization process and the effect of substituents on the nature of heterobimetallic complexes. In this contribution we report the isolation, structural characterization of the titanatranes bearing aryloxo terminal ligand with the aluminum alkyls and their catalytic activity in ethylene and Ring Opening Polymerization (ROP) of rac- lactide.

Results and Discussion

The titanatranes and their bimetallic derivatives are prepared as reported earlier [8]. The following complexes were confirmed by NMR and elemental analysis. The pure crystalline products were used for the polymerization process (Figure 1). There has been considerable attention on the study of ring-opening polymerization (ROP) of cyclic esters such as rac-lactide (LA) with metal complexes for the past few decades [10a-b]. Various types of metal alkoxides such as tin [11a-e], aluminum, zinc , magnesium, iron [12a-b], lanthanide [13a-c], and lithium [14] organometallic complexes have been found to be active LA polymerization catalysts, and many afford materials with controlled molecular weights and narrow molecular weight distributions. Despite the fact that some excellent initiators have been reported for the polymerization of LA, the search for new catalysts that generate well-defined polylactides remains of keen interest. The roles of the structure of metal alkoxide complexes in determining molecular weights and molecular weight distributions, as well as the polymerization pathway, are significant current research issues.

Figure 1: Bulk Polymerization of rac-Lactide (rac-LA).

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Recently, Verkade et al. [15a-b] reported that several titanium alkoxides showed reasonably good catalytic activity in the bulk homopolymerization of rac-LA at 130 °C. Harada et al. [16] also reported the living polymerization of LA by a Ti chloride complex, whose chloride apparently plays the same role as an alkoxide. We thus believed it would be interesting to test heterobimetallic titanium catalysts and compare the activity and control of the molecular and physical properties of the PLA produced by mononuclear and binuclear complexes with well-defined ligand environments. Here, we describe discrete heterobimetallic titanium alkoxide/aryloxide complexes and their bimetallic derivatives for the study of the ROP of LA under bulk polymerization conditions. We also demonstrate the difference in monometallic and bimetallic catalysts towards the ROP of rac-Lactide.

Preliminary results on the use of heterobimetallic catalysts for the bulk polymerization of rac-LA are summarized for 1a-4a, are presented in Table 1. Polymerizations were performed at 130 °C with the [LA]/[Ti] ratio fixed at 300. This table reveals that all the titanium compounds catalyze LA polymerization. Moreover, it appears that chelation aluminium methyl to the tripodal tetradentate ligand significantly decreases the polydispersity index and polymer yield. However, some transesterification probably occurred during the polymerization reaction since the polydispersity indices of both PLA products were somewhat higher than expected for a controlled polymerization. The bimetallic complexes exhibit high activity and produce polylactide with high molecular weight and lower polydispersity compare to their mononuclear precursors [15].

Table 1: Ring opening polymerization (ROP) of rac -Lactide Data for Heterobimetallic complexes.

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LA (2.027g) LA/Ti = 300, polymerization temperature = 130 °C, time = 20min.

The weight average molecular weight (M ), the number average molecular weight (M ), and the polydispersity index (PDI) M /M ) were determined by GPC.

Figure 2:

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The preference for heterotacticity in our poly (rac-LA) are comparatively stronger for bimetallic complexes than their mononuclear precursor compounds and are similar to the previous reports by Kasperczyk et al. [17]. This may be due to the initiating alkoxide/aryloxide group which dissociate relatively easily from the titanium in bimetallic complexes than their monometallic precursors in the early stage of polymerization so that it can be utilized to initiate LA polymerization and provide a means of controlling the molecular weight by functioning as an end group. It appears that the initiating group is the highly bulky i-Pr alkoxide (in 1 and 3) or i-Pr-phenolate (2 and 4) group in monometallic, similar to the observation made by Verkade et al. [15] But the scenario in bimetallic complexes is complicated. We assume that the initiating group may be similar to the mononuclear complexes, although the insertion of lactide into Ti-O of the aryloxo arm or alkoxo arm cannot be ruled out (Figure 2) and (Table 1).

Concluding remarks

The titanatrane titanium complexes and their bimetallic derivatives exhibit high activity and selectivity in bulk polymerization of rac-Lactide. Bimetallic complexes (Ti-Al) exhibit higher activity and produces high molecular weight compared to their monometallic counterpart [5b]. This may be due to the better electronic and steric environment in bimetallic complexes. The polylactide obtained in this process is heterotactic in nature. Further investigations of mechanism in this process are on in our laboratory.

Experimental Section

General Procedures. All experimental manipulations were carried out under an atmosphere of dry nitrogen using standard Schlenk techniques or using a Vacuum Atmospheres drybox unless otherwise specified. All chemicals used were of reagent grades and were purified by standard purification procedures. Toluene (anhydrous grade, Kanto Kagaku Co., Ltd.) and n-octane (anhydrous grade, Aldrich) for polymerization were stored in a bottle in the drybox in the presence of molecular sieves (a mixture of 3A 1/16, 4A 1/8, and 13X 1/16). Polymerization grade ethylene (purity > 99.9%, Sumitomo Seika Co. Ltd.) was used as received. Toluene and AlMe3 from the commercially available methylaluminoxane [PMAO-S, 9.5wt% (Al) toluene solution, Tosoh Finechem Co.] were removed under reduced pressure (at ca. 50 °C for removing toluene and AlMe3 and then heated at >100 °C for 1 h for completion) in the drybox to give white solids. Bis (2-hydroxy-3,5-dimethylbenzyl) ethanolamine and tris(2-hydroxy-3,5-di-tert-butylbenzyl)amine were prepared according to a published procedure [18]. The titanatranes containing phenoxy terminal ligands Ti(O-2,6- iPr2C6H3){(O-2,4-Me2C6H2-6-CH2)2(OCH2CH2)N} and Ti(O-2,6- iPr2C6H3) [(O-2,4-Me2C6H2-6-CH2)3N] were prepared according to the previous report [9].

Molecular weights and molecular weight distributions for polyethylene were measured by gel permeation chromatography (Tosoh HLC- 8121GPC/HT) with a polystyrene gel column (TSK gel GMHHR-H HT x 2, 30cm *7.8mmΦ, ranging from <102 to <2.8x108 MW) at 140 °C using o-dichlorobenzene containing 0.05 w/v % 2,6-di-tert-butyl-p-cresol as eluent. The molecular weight was calculated by a standard procedure based on the calibration with standard polystyrene samples. All 1H and 13C NMR spectra were recorded on a JEOL JNMLA 400 spectrometer (399.65MHz for 1H, 100.626MHz for 13C). All deuterated NMR solvents were stored over molecular sieves under a nitrogen atmosphere in the drybox, and all chemical shifts are given in ppm and referenced to SiMe4 (TMS). All spectra were obtained in the solvent indicated at 25 °C unless otherwise specified. Elemental analyses were performed by using PE2400II Series (Perkin-Elmer Co.) [19].

Procedure for rac-Lactide Polymerization, LA bulk polymerizations were carried out by charging a stirring bar, 2.00g of LA, and then the appropriate amount of catalyst precursor to a 10ml Schlenk flask. The flask was then immersed in an oil bath at 130 °C, and after the appropriate time, the reaction was terminated by the addition of 5ml of methanol. The precipitated polymers were dissolved in a minimum amount of methylene chloride, and then, excess methanol was added. The resulting reprecipitated polymers were collected, washed with 50ml of methanol, and dried in vacuo at 50 °C for 12h [20a-b].

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Friday, 24 June 2022

Lupine Publishers | To Examine the Relationship and Strength of Alcohol-Related Intimate Partner Violence in sub-Saharan Africa

 Lupine Publishers | Journal of Research & Reviews


Abstract

Alcohol-related intimate partner violence (IPV) is a serious public health issue which has attracted a lot of research and debates. While some studies have reported the relationship between alcohol and IPV to be linear, others have reported threshold effects. While some studies have found the link to be strong, others have reported weak or no association. Using Logistic regression and meta-analysis, the relationship, strength of relationship and possible moderators of the alcohol-IPV link are investigated in ten sub-Saharan African countries. The results indicates that while alcohol consumption is associated with IPV in three of the countries, alcohol abuse was associated with IPV in the other seven countries lending support for both the linear and threshold effects in sub-Saharan Africa. The meta-analysis showed a strong association between alcohol and physical IPV while a weaker association was observed for the alcohol- sexual IPV link. Moderator analysis showed that the strength of the alcohol-IPV link in sub-Saharan Africa varies with wealth index, marital length, and marital status, and jealousy, place of residence and justification of the use of violence. The nature of moderation was different between countries. The results of this study can be applied to plan country specific and multi-faceted intervention programs.

Keywords: Alcohol; Intimate Partners; Violence; Sub-Saharan Africa

Introduction

Intimate partner violence (IPV) is defined as any physical, psy-chological or sexual harm that is caused by the actions of a present or previous intimate partner [1]. It a major public health issue and violates women's human rights [1]. Cross sectional studies have shown that 10-69 per cent of women of reproductive age experience physical violence at least once in their lifetime while 6-59% report an attempt or actual sexual violence by their intimate partners [2]. Intimate partner violence takes place in all backgrounds and among all socioeconomic, religious and cultural groups with women bearing the global burden [1]. Prevalent rates are different across countries with rates between 11-52% in developing coun-tries [3]. IPV has been reported to lead to physical injuries, loss of pregnancy and complications during pregnancy [2]. It can also result in emotional problems such as depression and suicide [2] and victims have been reported to resort to use of drugs and alcohol as a means of coping with the abuse [4].

Several risk factors such as young age, low education, occu-pation, experiencing parental violence, drug and alcohol use, con-trolling behaviour by the husband [5], justification of wife beating [6] and so on has been reported to increase the odds of IPV; of these, alcohol consumption has been consistently implicated [2,7] with the prevalence of alcohol-related IPV differing in diverse countries [2]. Although an association between alcohol and IPV has been established in previous studies, there are arguments on the role of alcohol in IPV, the effect of alcohol and the strength of the association between alcohol and IPV. Although alcohol-related IPV is a widely researched topic, only some research has been done in sub-Saharan Africa [8,9] and none has investigated the magnitude of the association across countries in Sub-Saharan Africa. The aim of this study was to determine the type of association between alcohol and IPV in sub-Saharan Africa and also examine the strength of the relationship between alcohol and IPV in Sub-Saharan Africa.

Methodology

For the quantitative study, secondary analysis and meta-analy-sis were used to analyze cross-sectional data from the demographic and health surveys of ten countries in sub-Saharan Africa (Burkina Faso, Ghana, Kenya, Liberia, Malawi, Nigeria, Sao Tome and Prin-cipe, Tanzania, Zambia and Zimbabwe). Since the aim of this re-search was to determine the relationship between alcohol and IPV in sub-Saharan Africa, a quantitative research design was adopted because it is an appropriate method for showing associations and quantifying relationships between variables [10]. In order to examine the relationship and moderators of the alcohol-IPV link in sub-Saharan Africa, a secondary analysis of previously conducted primary studies of ten countries in sub-Saharan Africa was carried out. This is the method of choice for this research as it takes a cross national perspective which requires that data from several countries in sub-Saharan Africa be analysed. Data sets for this study were also easier to access and raise little or no ethical issues as re-spondents are already made anonymous.

Data Collection Methods

This study did not collect primary data but accessed data of the demographic and health survey of ten sub-Saharan Africa countries (Burkina Faso, Ghana, Kenya, Liberia, Malawi, Nigeria, Sao Tome and Principe, Tanzania, Zambia and Zimbabwe). Large sample sizes were used with high response rate thereby ensuring that statistically significant relationships are detected. Access to the data sets was gained by requesting permission from Demographic and Health Survey (DHS). Approval from DHS was granted by email. Data was identified using the domestic violence questionnaire. The identified data sets were downloaded to the researcher's personal computer using SPSS (version 19) software. Variables in the study were identified using the DHS recode manual.

Sample/Sampling Strategy

This study used quota sampling to identify DHS surveys con-ducted between 2006 and 2011 made available by 2012 in sub-Sa-haran Africa. For this research, only countries from sub-Saharan Af-rica were included because the main independent variable (alcohol consumption) was not measured in North African countries as con-sumption is prohibited. The data for each country was the most re-cent. This was to ensure that results reflected the current strength of the alcohol-IPV link and that recommendations are made based on current evidence. All datasets included asked questions on domestic violence and covered the topic of alcohol consumption and frequency at which husband/partner gets drunk because of the fact that the focus of this study is on alcohol-related IPV.

Data Analysis

Data analysis was carried out using SPSS (version 19.0) and Revman Meta-analysis software.

Univariate Analysis: Frequencies were used to determine the prevalence of the different forms of IPV, alcohol consumption and alcohol related IPV in the ten countries included in this study.

Logistic Regression: In order to determine the type of relationship between alcohol and intimate partner violence in sub-Saharan Africa, a logistic regression of the four category alcohol measure was carried out by comparing non-drinkers to drinkers (drinkers who never got drunk, who got drunk sometimes and those who got drunk often). Results are reported as B (Standard Error), odd ratios (OR) and 95%CI for OR. A significant Wald test p-value indicates a significant difference between the categories and non-drinkers.

Meta-Analysis: In order to investigate the strength of the alcohol-IPV link in sub-Saharan Africa, a meta-analysis was car-ried out using the Revman software. This was done by comparing non-abusers (non-drinkers and drinkers who never got drunk) and abusers of alcohol (husbands who got drunk sometimes and often). Based on the assumption that effects may vary across samples and studies [11], random effects model was used. The random effects model was used in this study because of the heterogeneous nature of the studies and because this model generates results that are generalisable to the sub-Saharan Africa population. The heteroge-neity of the result was investigated using the Cochran's Q test [12]. A significant I2 shows heterogeneity among included studies with higher values indicating increased differences within study [12]. Due to the high heterogeneity between countries included in the meta-analysis, further moderation analysis was carried out.

Hierarchical Logistic Regression: Using the method described by Field [13], hierarchical logistic regression was used to study the moderator effects of the independent variables on the al- cohol-IPV link. In order to account for the complex sampling used in the DHS survey, the probability of being administered the domestic violence questionnaire and to adjust for the probability of non-re-sponse [14]; all analyses were conducted using the domestic violence sample weight.

Ethical Issues

One of the ethical issues with conducting a secondary data anal-ysis is the permission to access datasets. Approval was sought by the researcher and access was granted. The DHS also operate a no data sharing policy. To ensure data protection, memory sticks and computers were password protected to guard against unauthorised access. It is also important to confirm that the data obtained from the primary study was ethically obtained. The primary DHS study was done with the informed consent of the subjects and confidenti-ality obtained with the National ethics committees of the different countries approving the surveys. Furthermore, the datasets have been made anonymous by removing all identifier information.

Results

The study population consisted of women aged 15-49 years old and men aged 15-59 years old in ten countries in sub-Saharan Af-rica. Six hundred and eighty-two couples were interviewed in Sao Tome and Principe, 873 in Tanzania and 883 in Ghana. The largest numbers of 5566 couples were included in Nigeria while 3488 and 3051 couples participated in Burkina Faso and Malawi respectively (Figure 1). Of these numbers, the highest percentage of women were in the 25-29 years' age group with this group accounting for 22.1% of the women in Burkina Faso, 27% in Kenya, 25.8% in Malawi and 27.7% in Tanzania. For the men, 22.6%, 20.8%, 21.3% and 21.4% were in the 30-34 years' age group in Kenya, Malawi, Zimbabwe and Zambia respectively. In Ghana (19.8%), Liberia (21.5%) and Nigeria (19.8%), the highest proportion of the male participants were in the 35-39 years’ age group (Figures 2a & 2b).

Figure 1: Number of Participants in the Study.

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Figure 2a: Age group of the Women

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In Burkina Faso, 82.3% of the women had no education compared to 77.0% of the men. Zimbabwe and Sao Tome and Principe were found to have the highest number of couple who have had any form of education with 94.2% of the women and 99.4% of the men having a primary, secondary or higher education in Sao Tome and Principe. In Zimbabwe, only 2.7% of the women and 1.2% of the men have had no education at all. 5.2% of the women in Burkina Faso and 6.6% of the women in Tanzania reported having a second-ary education compared to 41.5% and 62.1% in Ghana and Zimbabwe respectively (Figures 3a & 3b).

Employment Status

Highest proportions of women who are unemployed were in Zimbabwe, Kenya, Zambia and Malawi with 62.3%, 61.6%, 48.3% and 42.3% of the women reporting that they have no paid employment respectively. The highest number of women who were em- ployed was reported in Ghana (88.5%), Tanzania (86%), Burkina Faso (78.6%) and Nigeria (64.4%). For the men, the highest rate of unemployment was in Zimbabwe (24.2%), Malawi (6.9%) and Liberia (6.3%) (Figure 4). When wealth index was considered, Figures 5 show that 24.5% and 22.3% of Nigerians in the study population were in the poorest and poorer wealth indexes respectively. Kenya, Sao Tome and Ghana have the highest percentages of 30.2%, 25.4% and 23.4% of the couples in the richest wealth index while 21% of the couples in Burkina Faso, 21.4% in Liberia, 21.9% in Malawi and 19.2% in Zambia were in the middle wealth index.

Figure 2b: Age Group of the Men.

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Figure 3A: Education Level of the Women.

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Prevalence of Intimate Partner Violence

The prevalence of emotional IPV was lowest in Burkina Faso (10.8%) and highest in Liberia (36.3%). In Ghana, 31.4% of the women reported experiencing emotional IPV while 32.3% reported same in Burkina Faso. The percentage of emotional IPV is closest in Sao Tome and Principe and Zimbabwe with 25% of the women reporting emotional IPV in Sao Tome and Principe and 25.2% in Zimbabwe. The percentage of women who reported sexual IPV ranged from as low as 1.2% in Burkina Faso to as high as 15.8% in Zimbabwe. Figures in Zambia and Malawi are closest to Zimbabwe with 15.6% of the women in Zambia and 15.4% of the women in the study population experiencing sexual violence from their husbands or partners. Zambian women reported the highest prevalence of physical IPV (44.9%) while the lowest percentage of reported physical IPV was 11.5% in Burkina Faso.

Figure 3b: Education Level of the Men.

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Figure 4: Employment Rate.

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Figure 5: Wealth Index of Participants in the Study.

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In Kenya and Liberia, 32% and 35% of the women reported physical IPV. When all three forms of IPV were considered, prevalence rate was highest in Zambia (51.9%) followed by Liberia (50.3%) and lowest in Burkina Faso (16.7%). In general, the prevalence of physical and emotional IPV were higher than that of sexual IPV indicating that women are less likely to experience or report sexual IPV in sub-Saharan Africa (Figure 6).

Figure 6: Prevalence of Intimate Partner Violence in sub -Saharan Africa.

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Prevalence of Alcohol-Related Intimate Partner Violence

Figure 7: Prevalence of Intimate Partner Violence in sub -Saharan Africa.

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Figure 7 shows the prevalence of alcohol-related intimate part-ner violence among married and cohabiting women in sub-Saharan Africa. The prevalence of alcohol related physical IPV was between 21.2 to 53.9% in this study. The highest prevalence rate of alcohol-related sexual violence was 19.9% in Malawi while the lowest prevalence of 8.8% was reported in Nigeria. The prevalence of alcohol-related emotional IPV ranged from 21.3% in Burkina Faso to 43.1% in Tanzania. When all three forms of IPV were considered, prevalence rates ranged from as 16.7% in Burkina Faso to as high as 51.9% in Zambia.

Relationship between Alcohol and Intimate Partner Vi-olence

The relationship between alcohol and intimate partner violence was investigated by conducting a logistic regression of intimate partner violence (physical, sexual or emotional IPV) and the four level drinking variables. The significance of the effect of each level of the drinking variable on IPV was assessed using the Wald's test. Odd ratios (Exp B) with the 95% confidence intervals, standard error and Wald's test p values are presented. In Burkina Faso, the odds of women experiencing any form of IPV (physical, sexual or emotional IPV) is 1.7 times higher in women whose husbands never got drunk than in women whose husbands never drink while the odds of experiencing IPV is 2.23 (1.66-3.00) and 2.77 (1.82-4.21) greater in women whose husbands never got drunk compared to women whose husbands never drink in Nigeria and Sao Tome and Principe respectively. The Wald’s test shows that there is a significant difference in the odds of experiencing IPV by women whose husbands drink but never got drunk and women whose husbands never drink. The results show that in Burkina Faso, Nigeria and Sao Tome and Principe, alcohol consumption rather than alcohol abuse is associated with intimate partner violence indicating that there is a linear relationship between alcohol and IPV in these countries.

In Ghana, the odd of perpetrating intimate partner violence is 2.29 (1.66-3.16) in men who got drunk sometimes and 3.36 (2.04-5.54) in men who got drunk often compared to non-drinkers. While the OR for experience of intimate partner violence is 7.12 (4.3011.81) in women whose husbands often abuse alcohol in Kenya, the OR for IPV by women whose husbands often get drunk is 2.72 (1.81-4.08) in Liberia. In Malawi, husbands/partners who get drunk sometimes are 1.45 times more likely to abuse their partners compared to men husbands or partners who do not drink alcohol while the odds of perpetrating IPV is 4 times higher in husbands who get drunk often. Wald's test p values showed that there is no significant difference in the odds of women experiencing intimate partner violence in women whose husbands drink but never got drunk and women whose husbands never drink in Ghana, Kenya, Liberia, Malawi, Tanzania, Zambia and Zimbabwe. This indicates that it is alcohol abuse rather than drinking of alcohol that is associated with intimate partner violence. These full results are presented in Table 1 below.

Table 1: The effect of alcohol on intimate partner violence in sub

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The Strength of the Alcohol-Intimate Partner Violence Link in sub-Saharan

a. Effect of Alcohol on Physical Intimate Partner Violence

Figure 8 showed the result of the meta-analysis to determine the strength of the alcohol-physical intimate partner violence in ten sub-Saharan Africa countries. A total of 22,120 participants were used in the study. Of these numbers, 6,271 were in the group of women whose husbands drink abuse alcohol while 15,849 were in the group of were in the group of women whose husbands/partners do not abuse alcohol. While 2,576 women reported experiencing physical intimate partner violence in the first group, a total of 2,698 women reported physical IPV in the other group. The results show the test for heterogeneity, I2=93% indicating a high degree of heterogeneity between the ten countries included in the analysis. The odds ratio is 2.91 (95% CI (2.24-3.79) showing that there is a strong association between alcohol and physical intimate partner violence in sub-Saharan Africa. The overall effect Z =7.96 and was statistically significant (p<0.00001). This indicates that the strength of the alcohol-physical IPV link is strong in sub-Saharan Africa.

Figure 8: Effect of Alcohol on Physical IPV in SSA.

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b. Effect of Alcohol on Sexual Intimate Partner Violence

The meta-analysis to determine the effect of alcohol on sexual IPV is presented in Figure 9. A total of 22,104 women were included in the study. 6,266 were in the alcohol abuse group while 15,838 were in the non- alcohol abuse group. Of the 6,266 women in the alcohol abuse group, 971 reported experiencing sexual IPV while 1,006 reported sexual IPV in the non-alcohol abuse group. The above results show an I2 value of 70% indicating heterogeneity between studies. An OR of 2.15 (95%CI=1.78-2.60) means that women in sub-Saharan Africa are two times more likely to report sexual violence when their husbands/partners abuse alcohol than when they do not. An odd ratio of 2.15 shows that there is a small effect size for the alcohol-sexual violence link in sub-Saharan Africa. The overall effect Z=7.87 (0.00001) is highly significant indicating that the effect of alcohol on IPV is highly significant. These results imply that the strength of the alcohol-sexual IPV link is weak in sub-Saharan Africa.

Figure 9: Effect of Alcohol on Sexual Intimate Partner Violence in sub-Saharan Africa.

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c. Effect of Alcohol on Emotional Intimate Partner Violence

A total of 22,112 respondents took part in the study to deter-mine the effect of alcohol on emotional intimate partner violence. A total of 5,151 participants reported experiencing emotional intimate partner violence. Of this number, 2,182 reported that their husbands abuse alcohol while 2,969 reported that their husbands never abuse alcohol. The result of the meta-analysis is presented in Figure 10 below. The results above show that women whose husbands abuse alcohol are 2.36 times more likely to report emotional intimate partner violence in sub-Saharan Africa OR=2.36 (95%1.96-2.83). This means that there is a moderate effect size for the association between alcohol and emotional intimate partner violence in sub-Saharan Africa. An I2 value of 85% indicates high heterogeneity between studies. The overall effect Z was highly significant (Z=9.15, p<0.00001)

Discussion

Prevalence of Intimate Partner Violence in SSA

In this study, the prevalence of physical intimate partner violence is 44.9% in Zambia, 28.9% in Zimbabwe and 19.9% in Mala wi. These values are similar to the 45%, 28% and 20% reported by Hindin et al. [15] for Zambia, Zimbabwe and Malawi respectively. On the other hand, the 32% and 32.2% prevalence rates reported for Kenya and Tanzania herein are lower than the 39% reported by Hindin et al. [15] and the 48% observed by Tumwesigye et al. [16] for Uganda which is a neighboring East African country. The percentage of physical IPV in other countries in this study ranged from between 11.5% in Burkina Faso to 28.5% in Sao Tome and Principe. While some of these rates are similar to figures reported in other sub-Saharan African countries, others are less. For instance, the 28.5% prevalence reported here is similar to the 29% reported for Rwanda [15]. However, the 11.5% reported for Burkina Faso is lower than rates reported anywhere in sub-Saharan Africa but similar to the 12% reported for Haiti [3]. These differences in prevalence rates may be as a result of the questions used to assess physical IPV.

Figure 10: Effect of Alcohol on Emotional Intimate Partner Violence in SSA.

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This study asked respondents whether husband/partner has ever threatened or attacked them with a gun/knife or other weapons while the Hindin et al. [15] separated this question into threat and actual attack. Combining these two questions would mean that women who have experienced both threat and the act can only give one response to both questions leading to the lower rates obtained in this study. In this study, 16.1% of women in Nigeria re-ported physical IPV. This is slightly higher than the 15% reported by Antai et al. [17] using the same study data. While the Antai et al. [17] study used the individual recode which is a sample of legally married women, the present study used a sample of currently married/cohabiting women. This is consistent with findings that the prevalence of IPV is higher in currently married than legally married women [15]. In spite of these observed differences in the prevalence of physical IPV in some sub-Saharan African countries in this study, the observed prevalence of 11.5 to 44.9% in this study is consistent with that reported in other studies [2,3,16-18].

Apart from physical IPV, the prevalence of sexual and emotion-al IPV was also examined. Results indicated that the rates of sexual IPV ranged from 1.2% in Burkina Faso to 15.8% in Zimbabwe. These rates are similar to the 3 to 16% prevalence rates reported in existing literatures for sub-Saharan Africa [15,17]. The prevalence of emotional IPV in this study ranged from 10.8% in Burkina Faso to 36.3% in Liberia. This is higher than the prevalence rates of 10.4 to 22.7% reported elsewhere [19]. When all three forms of IPV were considered, the prevalence rates increased for all ten countries and were higher than that reported in previous studies. For example, Hindin et al. [15] reported a prevalence of 45% for Zambia in their studies while this study shows a prevalence of 51.9% for Zambia when all forms of IPV were considered. It can thus be argued that studies investigating only one form of IPV result in an under estimation of the magnitude of IPV. Overall, the prevalence of sexual violence in this study was consistently lower than that reported for physical and emotional violence across all countries included in this work.

Prevalence of Alcohol-Related Intimate Partner Violence

The prevalence of alcohol IPV was between 29.9% to 60.1% when of physical, sexual or emotional IPV is considered. These rates are higher than the 33.9 to 49.5% reported for countries in sub-Saharan Africa [15,16] and 10.5 to 55% reported elsewhere [2]. However, this is lower than the 65% rate reported in South Africa [2]. The higher rates reported in this study is as a result of the fact that this study investigated the experience of all three forms of IPV indicating that previous studies may have been subject to an under reporting of prevalence rates of IPV as only physical or sexual IPV are usually investigated. The lower prevalence of alcohol-related IPV in this study compared to the 65% prevalence reported in South Africa can be explained by the fact that while the present study investigated the prevalence of women ever experiencing alcohol-related IPV, the South African study reported prevalence for the past twelve months.

Following the same trend as IPV, it is possible that the occur-rence of current alcohol-related violence may be higher than past occurrence. Women who have experienced alcohol-related violence may recall these incidents more since they are more recent than if they took place a long time ago. Another possible explanation for this is that in South Africa, it is believed that alcohol causes aggres-sion and this has led men to drink in order to carry out violent acts [2] thereby increasing the rate of alcohol-related violence in South Africa compared to other sub-Saharan African countries.

The Relationship between Alcohol and Intimate Partner Violence in SSA

In all ten countries, alcohol was consistently linked to women's experience of intimate partner violence with the nature of the re-lationship varying across different countries. The findings of this study showed that in seven out of the eleven countries (Ghana, Ken-ya, Liberia, Malawi, Tanzania, Zambia and Zimbabwe), there was no significant difference in the odds of experiencing IPV in women whose husbands/partners never consumed alcohol and those whose husbands/partners never got drunk. This is consistent with the findings in several literatures [2,3,16]. This can be explained by the fact that for alcohol to significantly increase the odds of perpetrating intimate partner violence, alcohol consumption has to surpass a particular amount or rate of consumption.

This explanation is consistent with that put forward by propo-nents of the threshold effect who argue that it is not alcohol con-sumption per se that contributes to intimate partner violence but alcohol abuse. Conversely, in Burkina Faso, Nigeria and Sao Tome and Principe, women whose husbands consumed alcohol but never got drunk were significantly more likely to experience any of physical, sexual or emotional intimate partner violence than women whose husbands never consumed alcohol. This is similar to the report of Bangdiwala et al. [20] who reported a strong linear re-lationship for the alcohol-IPV link. These results are in agreement with the justification put forward by the proponents of the linear effect conceptualization who maintain that alcohol abuse increases the odds of intimate partner violence and that these odds increases with increase in the quantity of alcohol consumed.

In Kenya alone, the odds of alcohol increasing the odds of in-timate partner violence only reached statistical significance in the women whose husbands/partners often got drunk. This indicates that in Kenya, it is the frequency of alcohol abuse and not abuse alone that contributes to the alcohol-IPV link. Drawing from the multiple threshold conceptualisation [21], it is possible that the likelihood of experiencing intimate partner violence in Kenya is already very high that alcohol consumption or less frequent alcohol abuse does not significantly contribute to an increased odd of intimate partner violence while more frequent alcohol abuse may increase the frequency and severity of intimate partner violence in this sample thereby increasing the likelihood of intimate partner violence in this group.

The findings of this study support both the linear and threshold conceptualisation of the alcohol-IPV link. This suggests that the type of relationship between alcohol and intimate partner violence varies across countries in sub-Saharan Africa with most countries showing a threshold effect. This observed difference could be as a result of differences in drinking pattern. In the seven countries where threshold effects were observed, large percentages (86.3 to 99.1%) of men who drink get drunken showing drinking cultures that are supportive of alcohol abuse.

Strength of Alcohol-Intimate Partner Violence Link in SSA

A meta-analysis of the ten countries included in this study showed an odds ratio of 2.91 (95%CI, 2.24-3.39) for physical IPV which shows that women whose husbands abuse alcohol are almost thrice as likely to experience IPV than women whose husbands do not abuse alcohol. This shows a strong association between alcohol and intimate partner violence in sub-Saharan Africa. This is consistent with the strong association reported in a meta-analysis by Gil-Gonzalez et al. [22]. The strong association between alcohol and physical IPV in this study can be explained by the culture of masculinity in sub-Saharan Africa. It is considered masculine for men to drink and it is also seen as a thing of pride for a man to be feared and respected by his wife. It is also generally acceptable for men to physically reprimand their wives if they feel that the women have erred in anyway.

On the other hand, a small but significant relationship was observed for alcohol and sexual intimate partner violence in this study. This is similar to the report of Tang and Lai [23] who report-ed a significant but weak association between alcohol abuse and sexual intimate partner violence. This weak association could be as a result of the fact that in African society, sex is considered a private matter not to be discussed with strangers. There is also shame as-sociated with being raped and made to perform unwanted sexual acts and women are often blamed for it and this may result in under reporting. Women may also consider that being made to perform any form of sexual act is acceptable so long as it is within a marriage or committed relationship and may not consider this as IPV. For example, it is commonly believed in Africa that a man cannot rape his wife. Hence forced sexual intercourse in a marriage is not considered rape but seen as a normal part of the relationship. When the severity of intimate partner. Based on the results from this re-search, it can be argued that the strength of the alcohol-IPV link in sub-Saharan Africa depends on the type of IPV measured.

Conclusion

The purpose of this research work is to identify the relationship, strength of relationship between alcohol and intimate partner violence in sub-Saharan Africa. Results of this study show that alcohol is consistently associated with intimate partner violence in all ten countries included in this study with the strength of this relationship depending on the form of intimate partner violence. While a linear relationship was found between alcohol and intimate partner violence in Burkina Faso, Nigeria and Sao Tome and Principe, a threshold effect was observed in the remaining seven countries with the odds of alcohol-related intimate partner violence increasing with increase in alcohol consumption and alcohol abuse. The strength of the alcohol-intimate partner violence link was also found to be dependent on the effects of other variables in some countries with the direction of moderation different in the countries where these moderation effects are present.

The results also show that when the three forms of IPV were measured, the prevalence of both IPV and alcohol-related IPV were higher than that of existing literatures suggesting that studies of IPV estimating only one or two forms of IPV are subject to under es-timation of the magnitude of his huge public health problem. These findings have potentially important implications for public health promotion, policy and practice. The implication of the findings of this research is that interventions for tackling alcohol-related IPV should be multifaceted and should address behavioural, cultural and social change

Study Limitations

Despite the above strengths, the result of this study should be interpreted bearing in mind several limitations. First, because the information on problem drinking was provided by women, there is the possibility of misclassification bias. Responses were not taken from men about their drinking and IPV perpetration and this would have been valuable in corroborating the women report. There is also a tendency for recall bias as IPV may have taken place at a different time from alcohol abuse. Classification of drinking as sometimes or often drunk makes the report subjective rather than objective and may have led to results showing a stronger relationship between alcohol and IPV in sub-Saharan Africa. This is because studies have shown that studies assessing alcohol abuse is more associated with IPV than those measuring quantities [24].

Even though the results of this research are to a great extent consistent with those reported for community samples in other studies, it cannot be generalised to clinical samples of alcohol abusers or IPV perpetrators because studies have shown that the magnitude of the association between alcohol and IPV is stronger in clinical than community samples [24]. Finally, because this study analysed data from cross sectional studies which are ecological in nature, it is difficult to know if problem drinking took place before IPV or vice versa. It is possible that perpetrators of IPV are more likely to misuse alcohol or that individual's use alcohol to cope with stressful life events hence causality cannot be assumed.

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Thursday, 23 June 2022

Lupine Publishers | The History of Opcab (Off Pump) Coronary Surgery

 Lupine Publishers | Journal of Surgery


Opinion

After the advent of the heart-lung machine, few surgeons continued to use the OPCAB technique, Among those were Benetti and Buffolo from South America, who published in the early 1990s the first two large series on OPCAB surgery [1-3]. Several surgical approaches were tested, such as full sternotomy, no spreading sternotomy including left, anterolateral, Posterolateral and right anterolateral thoracotomies, as well as partial sternotomy [3]. The video-assisted techniques in the nineties allowed us, for the first time, to dissect the left internal thoracic artery (LITA) without opening the pleura cavity. The LITA was anastomosed to the left anterior descending (LAD) through a small left anterior thoracotomy and the MIDCAB operation was create [4-6].

Some technological development we invented, allow us to trained surgeons in 45 countries of the world [7,8]. BY 1999 more than 11 000 (10%) coronary operations were performed on the beating heart [9]. Although the MIDCAB is a good operation full or partial lower sternotomy carries little morbidity and allows excellent access for LAD and right coronary artery anastomoses. With further experience, the circumflex marginal vessels can be approached [10]. In 1997, we performed for the first time an ambulatory coronary bypass through a xiphoid lower sternotomy incision (MINI OPCAB) using 3D technology to assist in the operation [11,12]. In 1998 Didier Loulmet perform the first endoscopic bypass using robotic [13].

We used the right mammary as inflow from many years in sternotomy off pump when the patient had a porcelain aorta. And we expand this thecnique for the MINI OPCAB operation [14]. Despite advances in cardiopulmonary bypass (CPB) is still associated with significant morbidity due to its un-physiological nature. The morbidity rate has indeed remained high, particularly in the ever-increasing high-risk surgical population presenting with co-morbidities [15]. The contact of blood components with the artificial surfaces of the bypass circuit, aortic cross-clamping and reperfusion injury are considered the main causative factors of inflammatory response following cardiac surgery [16,17], no pulsatile flow, hypothermia, duration of CPB, hypo perfusion, and micro emboli contribute to end organ injury [18,19]. OPCAB surgery, by means avoiding CPB and cardioplegic arrest, produce significant benefits. In special in high risk patients OPCAB is an operation establish today world wide .The future requires to expand a bypass operation more minimally invasive: means apart of avoid the pump small incision; easy to reproduce and with possibilities to be done in the entire world.

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Wednesday, 22 June 2022

Lupine Publishers| Study the Corrosion and Corrosion Protection of Brass Sculpture by Atmospheric Pollutants in Winter Season

 Lupine Publishers| Journal of Material Science



Abstract

Brass is an important metalloid which is used in construction of sculptures. It is noticed that sculpture of brass is corroding due to interaction of pollutants. The pollutants develop chemical and electrochemical reaction on the surface of base material. Their concentrations of corrosive pollutants are increased in winter season. The air quality becomes very poor in winter season. Inside sculpture different forms of corrosion are observed like galvanic, pitting, stress, crevice etc. The major components of pollutants are oxides of carbon, oxides of nitrogen, oxides of sulphur, ammonia, ozone and particulates. Among these pollutants oxides of sulphur and ammonia are major corroder of brass. Ammonia is observed moist air to form ammonium hydroxide. It produces chemical reaction with brass metal and form complex compounds like [Zn(NH4)4](OH)2, [Zn(NH4)4]SO4, [Zn(NH4)]CO3, [Cu(NH4)4](OH)2, [Cu(NH4)4]SO4, [Cu(NH4)]CO3 etc. Oxides of sulphur react with moist air to exhibit sulphurous and sulphuric acids. They interact with brass to develop corrosion cell zinc metal and it is oxidized into Zn2+ ions and these ions are active to humidity and carbon dioxide to yield Zn(OH)2.ZnCO3.2H2O. Copper is converted into Cu2+ and it reacts with moist air and carbon dioxide to produce Cu(OH)2.Cu(CO3)2 and these complex compound detached on the surface of brass metal by rain water. These pollutants change their physical, chemical and mechanical properties and they also tarnish their facial appearance. Brass’ sculpture is affected by uniform corrosion. This type of corrosion can be control by nanocoating and electrospray techniques. For this work (6Z)-5,8-dihydrazono- 5,8-dibenzo[a,c][8]annulene and TiO2 are used as nanocoating and electrospray materials. The corrosion rate of material was determined by gravimetric and potentiostat technique. The nanocoating and electrospray compounds are formed a composite layer on surface of base metal. The formation of composite layer is analyzed by thermal parameters like activation energy, heat of adsorption, free energy, enthalpy and entropy. These thermal parameters were calculated by Arrhenius, Langmuir isotherm and transition state equations. Thermal parameters results are depicted that both materials are adhered with sculpture through chemical bonding. The surface coverage area and coating efficiency indicates that nanocoating and electrospray are produced a protective barrier in ammonia and sulphur dioxide atmosphere.

Keywords: Brass sculpture; Corrosion; Atmospheric pollutants; Nanocoating; Electrospray; Sulphur dioxide; Composite barrier

Introduction

The sculpture of brass comes in contact of contaminated air thus its deterioration starts for protection various types methods can be applied [1]. Brass [2] has major components is copper and zinc. Zn reacts the hot air to produce ZnO which is active in humidity [3] to convert into Zn(OH)2. In moist air [4], they form CuO, ZnO, Cu(OH)2 and Zn(OH)2. Both metals are active with sulphur to yield Cu2S, CuS and ZnS and these metallic sulphides [5] react with moist air to give Cu(OH)2, Zn(OH)2, CuSO4 and ZnSO4. The hydroxides of these metals interact with CO2 to produce CuCO3 and ZnCO3. Sulphur dioxide [6] is a culprit of brass. It undergoes with Cu(OH)2 and Zn(OH)2 to convert into CuSO4 and ZnSO4. Moist SO2 yields H2SO3 and H2SO4 whereas they create acidic environment [7] for brass and generate corrosion cell on their surface. It accelerates disintegration [8] in metal components of sculpture of brass. Brass is highly sensitive to ambient of ammonia gas [9]. It interacts with humid atmosphere [10] to NH4OH and it deposits on the surface brass metal [11] thus it converts into a complex layer of [Cu(NH3)4] (OH)2 and [Zn(NH3)4](OH)2 that layer erosion starts in rain water. [Cu(NH3)4](OH)2 and [Zn(NH3)4](OH)2 complex compounds [12] come in contact of H2SO4 environment to produce [Cu(NH3)4]SO4 and [Zn(NH3)4]SO4 that complex layer is eroded in rain water. In acidic medium brass outer face has developed CuSO4 and ZnSO4 when dust particulates [13] are deposited on their surface which contains Fe to remove Cu and Zn from outer surface. Dust particulates are possessed oxides of alkali metal in presence of moisture, it produces NaOH or KOH [14] that is create hostile environment for Zn and it forms complex compound [15] Na2[Zn(OH)4]or Na[Zn(OH)3.H2O] or Na[Zn(OH)3.(H2O)3]. The oxides of NO2 reacts with moist air to give HNO3 that acid produces chemical reaction with Cu and it converted into Cu(NO3)2. Some organic acids [16] available in air like acetic acid which develop corrosive environment for Cu and Zn which converts Cu into Cu2(CH3COO)4.H2O and Zn into (CH3COO)6. Zn4O complex compounds [17]. They are eroded by rain water on the surface of brass. Organic compounds [18] like amnio and sulpur increased day by day in atmosphere. They develop hostile environment for brass and corroding it. Corrosive pollutants [19] concentrations like oxides of carbon, oxides of nitrogen, oxides of sulphur, hydride of sulphur and nitrogen, ozone and particulates are enhanced due to industrials wastes, effluents, flues and other factors are like burning of coals, woods and cow dung cakes. Harmful pollutants [20] come into atmosphere through agricultural wastes, human wastes, pharmaceutical wastes, household wastes, food wastes and decomposition of living things. Various types of transports like road, water and air are evolving CO, NO2 and SO2 gases which produce acidic environments for brass. Several types of techniques are used to control the corrosion of brass like metallic coating; polymeric coating, paint coating, organic and inorganic coating of materials but these didn’t give satisfactory results in corrosive medium. Some organic and inorganic inhibitors are applied to protect the corrosion of materials in acidic but they provide good results. Hot dipping, electroplating and galvanization techniques is used as protective tools for brass corrosion in acidic medium but these methods don’t shave base metals. In this work it is to mitigate corrosion of brass corrosion by nanocoating and filler techniques. These materials form composite barrier on the surface base metal and blocked porosities and stop diffusion or osmosis process of pollutants.

Experimental

Brass coupons 15sqcm were taken for experimental analysis. Samples surface were rubbed with emery paper, rinsed with acetone, dry them and kept into desiccators. Sample kept 20meter height of roof in open sky and it observed that colour of brass can be changed. Corrosion rate was determined in winter season by weight loss method. The concentration of SO2 in November 75ppm, December 90ppm, January 105ppm and February 120ppm and temperatures recorded in this period were 298K, 294K, 291K and 295K. Synthesis organic compound (6Z)-5,8-dihydrazono- 5,8-dibenzo[a,c][8]annulene used as nanocoating and TiO2 as filler and corrosion of brass metal calculated in above mentioned concentrations and temperatures in winter season. Both compounds formed a composite barrier on surface of base metal (Figures 1-4). Surface adsorption phenomenon studied by thermal parameters like activation energy, heat of adsorption, free energy, enthalpy and entropy.Potentiostat/Galvanostat model EG&G used for corrosion potential, corrosion current and corrosion current density. Brass sample put between H2|Pt electrode as auxiliary electrode and Hg2Cl2|HgCl2 electrode reference electrode.

Figure 1: .

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Figure 2:

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Figure 3:

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Figure 4:

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Synthesis of (6Z)-5,8-dihydrazono-5,8-dibenzo[a,c][8] annulene

Phenatharene was oxidized into [1,1’-biphenyl]-2,2’- dicarboxylic acid by the use of H2O2 in presence of CH3COOH. When [1,1’-biphenyl]-2,2’-dicarboxylic acid was treated in PCl5 in benzene solution at 0 oC temperature, [1,1’-biphenyi]-2,2’-dicarbonyl chloride was obtained. It reacted with diazomethane to produce yield [1,1’-biphenyl]-2,2’-dicarboxodiazomethan which heated Cu(acac)2 in presence THF to yield (Z)-dibenzo[a,c][8]annulene- 5,8-dione. It was used with hydrazine hydrate in ethyl alcohol to give (6Z)-5,8-dihydrazone-5,8-dihydrodibenzo[a,c][8]annulene.

Results and Discussion

Brass metal was exposed in moist SO2 environment in 75ppm, 90ppm, 105ppm and 120ppm concentrations and 298 0K, 294 0K, 291 0K and 295 0K temperatures. The corrosion rate of brass metal was determined in winter season without coating and with coating (6Z)-5,8-dihydrazone-5,8-dihydrodibenzo[a,c][8]annulene and TiO2 electrospray of by weight loss formula K= 534 W/DAT (where W is weight loss, D is density and T is time) and their values were mentioned in (Table 1)

Table 1:Corrosion of Brass Sculpture in Winter Season in SO2 medium.

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The corrosion rate of brass metal was recorded in the months of November, December, January and February, the results (Table 1) was shown that corrosion rate of metal increased in January to February but theses values were reduced with coating and filler materials like (6Z)-5,8-dihydrazone-5,8-dihydrodibenzo[a,c][8] annulene and TiO2. It was clearly noticed in (Figure 5) K versus Month. Brass metal kept into 75ppm, 90ppm, 105ppm and 120ppm of SO2 medium in month of Nov, Dec, Jan and Feb without coating. It was coated with 25mM, 30mM, 40mM and 45mM concentrations of (6Z)-5,8-dihydrazone-5,8-dibenzo[a,c][8]annulene, and again kept into same concentrations of SO2. After coating of (6Z)-5, 8-dihydrazone-5,8-dibenzo[a,c][8]annulene electrospray coating of TiO2 used at 5mM, 10mM, 15mm and 20mM concentrations and same concentrations SO2 Nov to Feb. The corrosion rates of in these three cases were written in (Table 1). These results were shown that corrosion rates without coating increased, it values decreased coating with (6Z)-5, 8-dihydrazone-5,8-dibenzo[a,c][8]annulene but their values more reduced with TiO2 electrospray. These trends were shown in (Figure 6) which plotted K versus C. The corrosion rates of brass metal at different temperatures 298 0K, 294 0K, 291 0K and 295 0K without and with coating were recorded in (Table 1). The addition of nanocoating and electrospray were reduced the corrosion rates as temperatures variation, it noticed in K versus T in (Figure 7).

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