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Selected AbstractsVARYING EFFECT OF FERTILITY DETERMINANTS AMONG MIGRANT AND INDIGENOUS FEMALES IN THE TRANSITIONAL AGRO-ECOLOGICAL ZONE OF GHANAGEOGRAFISKA ANNALER SERIES B: HUMAN GEOGRAPHY, Issue 1 2007Samuel Nii Ardey Codjoe ABSTRACT. The transitional agro-ecological zone of Ghana, located between the richly endowed south and the impoverished north, has attracted seasonal and permanent farm migrants, mainly from northern Ghana, who now live side by side with the indigenous people. While migrants have higher numbers of Muslims, indigenous people are mainly Christians. Although the majority of the migrants live in migrant quarters with less favourable socio-economic conditions, they are more successful farmers and therefore wealthier. The objectives are to examine the varying effect of fertility determinants among migrants and indigenous females. This paper uses data collected in 2002 among 194 females aged 15 to 49 years. Multiple regression models are used to assess fertility determinants. Results show that although migrant households were wealthier, migrant females were more traditional. They had more children living in foster care, and a lower proportion of them approved of men participating in household activities. In addition, they were less well educated, recorded higher infant mortality, gave birth earlier and used less contraception. Furthermore, while a female's migration status is statistically significant so far as non-proximate determinants of fertility are concerned, the same variable is not significant with respect to proximate determinants. In addition, a married female migrant would on average have almost one more child compared to her indigenous counterpart, and migrant females who had experienced the loss of a child would on average have 2.5 more children compared to their indigenous counterparts. Finally, more affluent migrant females have 0.08 fewer children compared to their indigenous counterpart. [source] Multilevel analysis of effects of individual characteristics and household factors on self-rated health among older adults in rural VietnamGERIATRICS & GERONTOLOGY INTERNATIONAL, Issue 2 2010Hoang Van Minh Aim: This paper aims to describe self-rated health (SRH) status among older adults in a rural community of Vietnam, and examine individual and household-level factors associated with good health rating among the study populations. Methods: The study was carried out in the Bavi district, a rural community located 60 km west of Hanoi, the capital, within the Epidemiological Field Laboratory of Bavi (FilaBavi) in Vietnam in 2006. All people aged 50 years and over who lived within the district were surveyed. Face-to-face household interviews were conducted by trained surveyors using standard World Health Organization/INDEPTH network questionnaire,summary version. A logistic multilevel modeling approach was applied to analyze the association between SRH and both individual and household-level factors. Results: The proportion of people aged 50 years and older in FilaBavi reported having good/very good health and poor/very poor health was 15.1% and 24.8%, respectively. SRH status was reported to be better among: (i) men; (ii) younger people; (iii) people with higher education; (iv) people who were currently in marital a partnership; (v) those from wealthier households; and (vi) those who were living in riverside/island or highland areas compared to those of other categories of the same variable. Conclusion: The findings reveal that there exist problems of inequality in health among older adults in the study setting by sex, age, education, wealth status and place of residence. We also found a considerable contribution of the household-level factors to SRH of the study populations.. [source] Predicting the signs of forecast errorsJOURNAL OF FORECASTING, Issue 5 2010Nazaria Solferino Abstract The signs of forecast errors can be predicted using the difference between individuals' forecasts and the average of earlier forecasts of the same variable. It is possible to improve forecasts without worsening any. It is difficult to reconcile this result with the rational expectations hypothesis because the average of earlier forecasts is in the information set of the forecasters. Copyright © 2009 John Wiley & Sons, Ltd. [source] The multi-chain Markov switching modelJOURNAL OF FORECASTING, Issue 7 2005Edoardo Otranto Abstract In many real phenomena the behaviour of a certain variable, subject to different regimes, depends on the state of other variables or the same variable observed in other subjects, so the knowledge of the state of the latter could be important to forecast the state of the former. In this paper a particular multivariate Markov switching model is developed to represent this case. The transition probabilities of this model are characterized by the dependence on the regime of the other variables. The estimation of the transition probabilities provides useful information for the researcher to forecast the regime of the variables analysed. Theoretical background and an application are shown. Copyright © 2005 John Wiley & Sons, Ltd. [source] Measuring the Accuracy of Facial Approximations: A Comparative Study of Resemblance Rating and Face Array MethodsJOURNAL OF FORENSIC SCIENCES, Issue 1 2008Carl N. Stephan Ph.D. Abstract:, The success of facial approximation is thought to depend, at least in part, upon the "accuracy" of the constructed face. However, methods of accuracy assessment are varied and this range in methods may be responsible for the disparate results reported in the literature. The aim of this study was to determine if the accuracy results of one facial approximation were comparable across two different assessment methods (resemblance ratings and simultaneous face array tests using unfamiliar assessors) and if resemblance ratings co-varied with recognition responses. True-positive recognition performance from the facial approximation was poor (21%) while resemblance scores using the same facial approximation were moderately high (3 out of 5 on a five-point scale). These results are not, therefore, consistent and indicate that either different variables are being evaluated by the methods, or the same variable is being examined but with different weight/calibration. Further resemblance ratings tests of the facial approximation to three foil faces from the face array revealed that resemblance scores were similar irrespective of which face was compared, and did not closely correspond with the degree of recognition performance. This was especially the case for isolated comparisons of single faces to the facial approximation. Collectively, these results indicate that resemblance ratings are: (i) insensitive measures of a facial approximation's accuracy; and (ii) inconsistent with results of unfamiliar simultaneous face-array recognition results. These data suggest that familiar and unfamiliar recognition tests should be given increased weight in contrast to current resemblance rating tests. [source] Trend estimation of financial time seriesAPPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 3 2010Víctor M. Guerrero Abstract We propose to decompose a financial time series into trend plus noise by means of the exponential smoothing filter. This filter produces statistically efficient estimates of the trend that can be calculated by a straightforward application of the Kalman filter. It can also be interpreted in the context of penalized least squares as a function of a smoothing constant has to be minimized by trading off fitness against smoothness of the trend. The smoothing constant is crucial to decide the degree of smoothness and the problem is how to choose it objectively. We suggest a procedure that allows the user to decide at the outset the desired percentage of smoothness and derive from it the corresponding value of that constant. A definition of smoothness is first proposed as well as an index of relative precision attributable to the smoothing element of the time series. The procedure is extended to series with different frequencies of observation, so that comparable trends can be obtained for say, daily, weekly or intraday observations of the same variable. The theoretical results are derived from an integrated moving average model of order (1, 1) underlying the statistical interpretation of the filter. Expressions of equivalent smoothing constants are derived for series generated by temporal aggregation or systematic sampling of another series. Hence, comparable trend estimates can be obtained for the same time series with different lengths, for different time series of the same length and for series with different frequencies of observation of the same variable. Copyright © 2009 John Wiley & Sons, Ltd. [source] A Power Efficient Electronic Implant for a Visual Cortical NeuroprosthesisARTIFICIAL ORGANS, Issue 3 2005Jonathan Coulombe Abstract:, An integrated microstimulator designed for a cortical visual prosthesis is presented, along with a pixel reordering algorithm, together minimizing the peak total current and voltage required for stimulation of large numbers of electrodes at a high rate. In order to maximize the available voltage for stimulation at a given supply voltage for generating biphasic pulses, the device uses monopolar stimulation, where the return electrode voltage is dynamically varied. Thus, the voltage available for stimulation is maximized, as opposed to the conventional fixed return voltage monopolar approach, and impedance is significantly lower than can be achieved using bipolar stimulation with microelectrodes. This enables the use of a low voltage power supply, minimizing power consumption of the device. An important constraint resulting from this stimulation strategy, however, is that current generation needs to be simultaneous and in-phase for all active parallel channels, imposing heavy stress on the wireless power recovery and regulation circuitry in large electrode count systems such as a visual prosthesis. An ordering algorithm to be implemented in the external controller of the prosthesis is then proposed. Based on the data for each frame of the video signal to be transmitted to the implant, the algorithm minimizes the total generated current standard deviation between time multiplexed stimulations by determining the most appropriate combination of parallel stimulation channels to be activated simultaneously. A stimulator prototype has been implemented in CMOS technology and successfully tested. Execution of the external controller reordering algorithm on an application specific hardware architecture has been verified using a System-On-Chip development platform. A near 75% decrease in the total stimulation current standard deviation was observed with a one-pass algorithm, whereas a recursive variation of the algorithm resulted in a greater than 95% decrease of the same variable. [source] Which clinical factors predict response to prophylactic lithium?BIPOLAR DISORDERS, Issue 5 2005A systematic review for bipolar disorders Objectives:, The aim of this study was to systematically integrate the available evidence on response prediction to prophylactic lithium based on clinical factors. Methods:, Each clinical variable that was related to lithium response in at least one prior study was examined with respect to response prediction. If several studies were located for the same variable, results were integrated using the meta-analytic approach as suggested by DerSimonian and Laird which was developed for substantial heterogeneity in primary studies. Results:, Of 42 potential clinical predictors investigated, five variables were identified as possible response predictors of prophylactic lithium: [1] An episodic pattern of mania-depression-interval, and [2] a high age of illness onset were identified as potentially protective against a recurrence under lithium. [3] A high number of previous hospitalizations, [4] an episodic pattern of depression-mania-interval, and [5] continuous cycling were identified as potential risk factors. Six further variables were found to be significantly related to lithium response, though calculation of fail-safe numbers indicates that current evidence is not sufficient to hold these variables as reliable predictors of lithium response. All effect-sizes relating clinical predictors to response were small to moderate. Conclusions:, Although a few variables are quite robustly supported as response-predictors in this review, a more in-depth analysis of each potential predictor is needed. As none of the potential predictors had a very strong impact on response, prediction of lithium response should be based on a multitude of variables. [source] Neural Network Earnings per Share Forecasting Models: A Comparative Analysis of Alternative MethodsDECISION SCIENCES, Issue 2 2004Wei Zhang ABSTRACT In this paper, we present a comparative analysis of the forecasting accuracy of univariate and multivariate linear models that incorporate fundamental accounting variables (i.e., inventory, accounts receivable, and so on) with the forecast accuracy of neural network models. Unique to this study is the focus of our comparison on the multivariate models to examine whether the neural network models incorporating the fundamental accounting variables can generate more accurate forecasts of future earnings than the models assuming a linear combination of these same variables. We investigate four types of models: univariate-linear, multivariate-linear, univariate-neural network, and multivariate-neural network using a sample of 283 firms spanning 41 industries. This study shows that the application of the neural network approach incorporating fundamental accounting variables results in forecasts that are more accurate than linear forecasting models. The results also reveal limitations of the forecasting capacity of investors in the security market when compared to neural network models. [source] What shields some can shackle others: the approach-related consequences of threat categorisations vary by agreeablenessEUROPEAN JOURNAL OF PERSONALITY, Issue 7 2005Michael D. Robinson It is common to think that threat categorisation tendencies (TCTs) should undermine a person's subjective well-being. However, recent research has suggested that the hedonic impact of such tendencies varies considerably according to a person's traits. The present research seeks to extend such a perspective by considering potential interactions between TCTs and the trait of agreeableness. TCTs were measured through the use of choice reaction time tasks contrasting the threat and non-threat categories. As expected, TCTs were not correlated with the trait of agreeableness, but interacted with this trait in predicting the dependent measures. Within three studies involving 184 undergraduates, TCTs were associated with the higher levels of approach-related behaviour and positive emotion among disagreeable individuals, but lower levels of these same variables among agreeable individuals. The authors suggest that threat categorisation tendencies psychologically protect or burden the individual, depending on the levels of agreeableness. Copyright © 2005 John Wiley & Sons, Ltd. [source] Risk Factors for Vertebral Deformities in Men: Relationship to Number of Vertebral DeformitiesJOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2000A. A. Ismail Abstract Recent epidemiological studies suggest a similar overall prevalence of vertebral deformity in men to that in women, though the influence of increasing age on the prevalence of vertebral deformity is less marked in men. However, most affected men have only a single or two vertebral deformities, which may be unrelated to osteoporosis. The aim of this study was to examine the role of risk factors, previously demonstrated to be associated with vertebral osteoporosis in females, in men with single/dual deformities compared to those with multiple deformities. Age stratified random samples of men aged 50 years and over were recruited from population registers in 30 European centers as part of the European Vertebral Osteoporosis Study (EVOS). Subjects had a lateral spinal radiograph and the presence of vertebral deformity was determined using the McCloskey algorithm. Lifestyle and other risk factor data were obtained from an interviewer-administered questionnaire. In all 6937 men with a mean age of 64.4 (SD = 8.5) years were studied of whom 738 (10.6%) subjects had one or two deformities, and 109 (1.6%) subjects had three or more deformities. There was a marked increase in the prevalence of multiple vertebral deformities with increasing age, but only a modest effect of age on the prevalence of single deformities. Associations between various risk factors for osteoporosis and vertebral deformity were analyzed separately in men with single/dual vertebral deformity from those with three or more deformities using logistic regression. After adjustment for age, there were statistically significant associations between the following risk factors and multiple deformities: previous hip fracture (odds ratio [OR] 10.5), lack of regular physical activity (OR 2.9), low body mass (OR 2.5), and previous steroid use (OR 2.3). By contrast, there were only weak associations with these same variables in males with single/dual deformities and, apart from poor self-reported general health, all of the 95% confidence intervals spanned unity. There was no difference in the reporting of very heavy levels of physical activity under the age of 50 years between men with single/dual deformities and those with multiple deformities. In conclusion, men with multiple deformities showed a similar pattern of risk factor association to those seen in women with vertebral deformity, in contrast to men with single/dual deformities. (J Bone Miner Res 2000;15:278,283) [source] Hermit crabs, humans and Mozambique mangrovesAFRICAN JOURNAL OF ECOLOGY, Issue 3 2001David K. A. Barnes Abstract There is a complex interrelationship between upper shore hermit crabs (such as Coenobita sp. and Clibanarius sp.), coastal human populations and mangrove forests in Mozambique. The abundance, activity, shell selection and behaviour of three species of hermit crab are related to the level of mangrove cover. With increased density of mangrove trees, the study species of hermit crab changed in abundance, tended to become diurnal, spent more time feeding and were clustered in larger groups when doing so, and selected longer spired shells. All five of the same variables are also linked to the proximity and activity of humans through both direct and indirect actions. Direct effects included a tendency to nocturnal activity with proximity to human activity; indirect effects included increased and more clumped food supplies, and shell middens from intertidal harvesting and deforestation. Mangroves are important to local human populations as well as to hermit crabs, for a wide variety of (similar) reasons. Mangroves provide storm shelter, fisheries and fishery nursery grounds for adjacent human settlements, but they also harbour mosquito populations and their removal provides valuable building materials and fuel. Hermit crabs may be useful (indirectly) to coastal human populations by being a source of food to certain commercial species, and by quickly consuming rotting/discarded food and faeces (thereby reducing disease and pests). They can also cause minor problems to coastal human populations because they use shells of (fisheries) target mollusc species and can be more abundant than the living molluscs, thereby slowing down effective hand collection through confusion over identification. The mixture of positive and negative attributes that the three groups impart to each other in the Quirimba Archipelago, northern Mozambique, is discussed. Résumé Il existe des interrelations complexes entre les Bernard-l'Ermite du haut littoral (tels que Coenobita sp. Et Clibanarius sp.), les populations humaines côtières et les forêts de mangroves au Mozambique. L'abondance, l'activité, le choix de la coquille et le comportement de trois espèces de Bernard-l'Ermite sont liés au degré de couverture de la mangrove. Lorsque la densité des arbres de la mangrove augmente, l'abondance des espèces étudiées de Bernard-l'Ermite change, ils ont tendance à devenir diurnes, passent plus de temps à se nourrir et se rassemblent à ces moments-là en plus grands groupes, et ils choisissent aussi de plus longues coquilles. Les cinq mêmes variables sont aussi liées à la proximité et à l'activité des hommes, directement et indirectement. Parmi les effets directs, on compte une tendance à une activité nocturne lorsque les activités humaines sont proches ; les effets indirects incluent des apports de nourriture et de débris de coquilles accrus et plus regroupés résultant des marées et de la déforestation. Les mangroves sont aussi importantes pour les populations locales que pour les Bernard-l'Ermite, pour toute une série de raisons (semblables). Les mangroves constituent un abri en cas de tempête, un terrain de pêche et de frai dont bénéficient les populations humaines voisines, mais elles renferment aussi beaucoup de moustiques, et leur bois fournit un bon matériau de construction et du combustible. Les Bernard-l'Ermite peuvent être (indirectement) utiles aux populations côtières car certaines espèces commerciales sont comestibles et que tous consomment rapidement les restes de nourriture en décomposition et les excréments (réduisant ainsi les risques de maladie et d'animaux nuisibles). Ils peuvent aussi causer des problèmes mineurs aux populations côtières parce qu'ils utilisent la coquille d'espèces de mollusques qui font l'objet de la pêche et qu'ils peuvent être plus abondants que les mollusques eux-mêmes, ce qui ralentit la pêche manuelle à cause du besoin d'identification. On discute le mélange de qualités négatives et positives que les trois groupes représentent les uns pour les autres dans l'Archipel de Quirimba, au nord du Mozambique. [source] A common model approach to macroeconomics: using panel data to reduce sampling errorJOURNAL OF FORECASTING, Issue 3 2005William T. Gavin Abstract Is there a common model inherent in macroeconomic data? Macroeconomic theory suggests that market economies of various nations should share many similar dynamic patterns; as a result, individual country empirical models, for a wide variety of countries, often include the same variables. Yet, empirical studies often find important roles for idiosyncratic shocks in the differing macroeconomic performance of countries. We use forecasting criteria to examine the macrodynamic behaviour of 15 OECD countries in terms of a small set of familiar, widely used core economic variables, omitting country-specific shocks. We find this small set of variables and a simple VAR ,common model' strongly support the hypothesis that many industrialized nations have similar macroeconomic dynamics. Copyright © 2005 John Wiley & Sons, Ltd. [source] Around the world with the model for end-stage liver diseaseLIVER TRANSPLANTATION, Issue 10 2003Richard B. Freeman Jr MD Background: Indices for predicting survival are essential for assessing prognosis and assigning priority for liver transplantation in patients with liver cirrhosis. The model for end stage liver disease (MELD) has been proposed as a tool to predict mortality risk in cirrhotic patients. However, this model has not been validated beyond its original setting. Aim: To evaluate the short and medium term survival prognosis of a European series of cirrhotic patients by means of MELD compared with the Child-Pugh score. We also assessed correlations between the MELD scoring system and the degree of impairment of liver function, as evaluated by the monoethylglycinexylidide (MEGX) test. Patients and methods: We retrospectively evaluated survival of a cohort of 129 cirrhotic patients with a follow up period of at least one year. The Child-Pugh score was calculated and the MELD score was computed according to the original formula for each patient. All patients had undergone a MEGX test. Multivariate analysis was performed on all variables to identify the parameters independently associated with one year and six month survival. MELD values were correlated with both Child-Pugh scores and MEGX test results. Results: Thirty one patients died within the first year of follow up. Child-Pugh and MELD scores, and MEGX serum levels were significantly different among patients who survived and those who died. Serum creatinine, international normalized ratio, and MEGX60 were independently associated with six month mortality while the same variables and the presence of ascites were associated with one year mortality. MELD scores showed significant correlations with both MEGX values and Child-Pugh scores. Conclusions: In a European series of cirrhotic patients the MELD score is an excellent predictor of both short and medium term survival, and performs at least as well as the Child-Pugh score. An increase in MELD score is associated with a decrease in residual liver function. [source] The psychosocial impact of parental cancer on children and adolescents: a systematic reviewPSYCHO-ONCOLOGY, Issue 2 2007Tessa Osborn Abstract This review aimed to identify (i) whether early stage parental cancer is associated with an increased risk of psychosocial difficulties amongst children and adolescents; (ii) which factors are associated with variations in psychosocial functioning amongst these children and adolescents. Searches of four electronic databases and the reference lists of relevant articles revealed 10 studies which satisfied the inclusion criteria for the first review question and thirteen studies for the second. Limitations in methodological quality and modest numbers of studies examining the same variables, restricted the conclusions which could be drawn. Overall, the evidence suggests that children and adolescents do not generally experience elevated levels of serious psychosocial difficulties compared to reference groups, but they are at a slightly increased risk for internalising type problems. Adolescent daughters appear to be the most negatively affected group. The prevalent use of measures of child psychopathology may be masking more context-specific problems and lower levels of distress. Family variables, especially family communication/expressiveness, are consistently associated with child/adolescent psychosocial functioning and there is suggestive evidence for the role of maternal depression/adjustment and parenting variables. There is little evidence that medical/treatment variables are important predictors of child outcomes. These findings have implications for identifying families with children most in need of support and indicating variables to target in interventions. Copyright © 2007 John Wiley & Sons, Ltd. [source] Berry size and vine water deficits as factors in winegrape composition: Anthocyanins and tanninsAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2 2004GASPAR ROBY Abstract Soluble solids, seed tannin, skin tannin, and skin anthocyanin were measured in fruit from Cabernet Sauvignon vines that had experienced either High, Control or Low water status during ripening. Berries from each treatment were segregated into 6 size categories at harvest in order to test independently for relationships due to size compared with those due to water deficits. Berry content of all solutes increased approximately in proportion to the increase in berry size. Deviations from proportionality caused Brix and anthocyanin concentration (mg per unit berry fresh mass) to decrease, and the concentration of skin tannin to remain unchanged or decrease slightly with increasing berry size. The concentration of seed tannin did not decrease and appeared to increase with berry size in multiple-seeded berries. In comparison with skin tannin or anthocyanin content, seed tannin content varied more with berry size and less with vine water status. In addition to decreasing berry size, water deficits increased the amount of skin tannin and anthocyanin per berry and the concentrations of skin tannin and anthocyanins, but did not significantly affect the content or concentration of seed tannin. The results show that there are effects of vine water status on fruit composition that arise independently of the resultant differences in fruit size. The effect of vine water status on the concentration of skin tannin and anthocyanin was greater than the effect of fruit size on those same variables. However, the increases in skin tannin and anthocyanin that accompanied water deficits appear to result more from differential growth sensitivity of inner mesocarp and exocarp than direct effects on phenolic biosynthesis. [source] A risk index for early node-negative breast cancer,BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 5 2006J. Boyages Background: This study compared the application of the St Gallen 2001 classification with a risk index developed at the New South Wales Breast Cancer Institute (BCI Index) for women with node-negative breast cancer treated without adjuvant systemic therapy. Methods: The BCI risk categories were constructed by identifying combinations of prognostic indicators that produced homogeneous low-, intermediate- and high-risk groups using the same variables as in the St Gallen classification. Results: The BCI low-risk category consisted of women aged 35 years or more with a grade 1 oestrogen receptor (ER)-positive tumour 20 mm or less in diameter, or with a grade 2 ER-positive tumour of 15 mm or less. This category constituted 40·1 per cent of patients, with a 10-year distant relapse-free survival (DRFS) rate of 97·2 per cent. The BCI intermediate-risk category included women aged 35 years or more with a grade 2 ER-positive tumour of diameter 16,20 mm, or a grade 1 or 2 ER-negative tumour measuring 15 mm or less, and comprised 12·1 per cent of the women, with a 10-year DRFS rate of 88 per cent. The high-risk category comprised 47·7 per cent of women, with a 10-year DRFS rate of 68·4 per cent. Conclusion: If confirmed in other data sets, the BCI Index may be used to identify women at low risk of distant relapse (2·8 per cent at 10 years) who are unlikely to benefit from adjuvant systemic therapy, and women at intermediate risk of distant relapse (12 per cent at 10 years) in whom the benefit of adjuvant systemic therapy is small. Copyright © 2006 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source] New Predictive Correlations for the Drop Size in a Rotating Disc Contactor Liquid-Liquid Extraction ColumnCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 2 2007M. Ismail Al-Rahawi Abstract Sauter mean drop sizes (d32) generated from a hole distributor in liquid extraction RDC columns were studied under various conditions. Experiments were designed to generate data required to determine the main variables that control the drop sizes in RDCs. Two precise correlations were proposed for predicting d32 in a RDC extraction column. The first was based on operating variables, hole-distributor diameter, disc speed, column geometry, and system physical properties. The second one considered the same variables, except the column geometry. This model can be used for design purposes. The two correlations are the first of their type to consider the distributor hole inlet diameter in a RDC column. This diameter has been neglected by previous investigators. The maximum standard deviation for all data is 0.75,%, with a maximum absolute error of 6.8,%. [source] Comparison of human and porcine aortic valvesCLINICAL ANATOMY, Issue 3 2003Eugene K.W. Sim Abstract We compared the anatomy of human and porcine aortic valves. Porcine hearts were collected from the abattoir. Human hearts from patients who had died of non-cardiac causes were examined in the mortuary; only undamaged and anatomically normal hearts were used. Silicon casts were prepared by injecting engineering silicon at 80 mm Hg into the aortic arch. Various features of the aortic valve were measured: circumference, length between the commissural end point and central point of coaptation, surface diameter, and surface area. In total, 12 porcine and 12 human aortic valves were studied. The average circumferences of the human and porcine aortic valves were 8.00 ± 0.2 (SD) cm and 7.90 ± 1.0 cm, respectively. The central point of coaptation in human valves was skewed toward the left coronary cusp, whereas in porcine valves it was skewed toward the non-coronary cusp. In human aortic valves, the non-coronary cusp had the largest surface diameter and surface area with mean measurements of 3.6 ± 0.2 cm and 1.230 ± 0.228 cm2, respectively; the left coronary cusp was smallest for the same variables with measurements of 3.1 ± 0.3 cm and 0.898 ± 0.357 cm2. In porcine valves, the right coronary cusp had the largest surface diameter and surface area with mean measurements of 3.9 ± 0.7 cm and 1.716 ± 0.81 cm2, respectively; the non-coronary cusp was the smallest for the same variables with measurements of 2.9 ± 0.5 cm and 1.023 ± 0.659 cm2. These differences suggest that when using porcine valves as transplant material (e.g., stentless valves), geometric considerations, such as commissural length, may be important. Clin. Anat. 16:193,196, 2003. © 2003 Wiley-Liss, Inc. [source] | |||||||||||||||||||