bluuebunny/crossref_metadata_2025 huggingface dataset:
Imputation methods for missing data for polygenic models
Authors: Fridley Brooke , Rabe Kari , Andrade Mariza de
Published: December 2003

Methods to handle missing data have been an area of statistical research for many years. Little has been done within the context of pedigree analysis. In this paper we present two methods for imputing missing data for polygenic models using family data. The imputation schemes take into account familial relationships and use the observed familial information for the imputation. A traditional multiple imputation approach and multiple imputation or data augmentation approach within a Gibbs sampler for the handling of missing data for a polygenic model are presented.

We used both the Genetic Analysis Workshop 13 simulated missing phenotype and the complete phenotype data sets as the means to illustrate the two methods. We looked at the phenotypic trait systolic blood pressure and the covariate gender at time point 11 (1970) for Cohort 1 and time point 1 (1971) for Cohort 2. Comparing the results for three replicates of complete and missing data incorporating multiple imputation, we find that multiple imputation via a Gibbs sampler produces more accurate results. Thus, we recommend the Gibbs sampler for imputation purposes because of the ease with which it can be extended to more complicated models, the consistency of the results, and the accountability of the variation due to imputation.
Multiple imputation methods for longitudinal blood pressure measurements from the Framingham Heart Study
Authors: Kang Terri , Kraft Peter , Gauderman W James , Thomas Duncan
Published: December 2003

Missing data are a great concern in longitudinal studies, because few subjects will have complete data and missingness could be an indicator of an adverse outcome. Analyses that exclude potentially informative observations due to missing data can be inefficient or biased. To assess the extent of these problems in the context of genetic analyses, we compared case-wise deletion to two multiple imputation methods available in the popular SAS package, the propensity score and regression methods. For both the real and simulated data sets, the propensity score and regression methods produced results similar to case-wise deletion. However, for the simulated data, the estimates of heritability for case-wise deletion and the two multiple imputation methods were much lower than for the complete data. This suggests that if missingness patterns are correlated within families, then imputation methods that do not allow this correlation can yield biased results.
Comparison of significance level at the true location using two linkage approaches: LODPAL and GENEFINDER
Authors: Hsu Fang-Chi , Hetmanski Jacqueline B , Li Lan , Markakis Diane , Jacobs Kevin , Shugart Yin Yao
Published: December 2003

Background

We compare two new software packages for linkage analysis, LODPAL and GENEFINDER. Both allow for covariate adjustment. Replicates 1 to 3 of Genetic Analysis Workshop 13 simulated data sets were used for the analyses. We described the results of searching for evidence of loci contributing to a simulated quantitative trait related to systolic blood pressure (SBP). Individuals with SBP greater than 130 mm Hg were defined as affected individuals, and all others as unaffected. Total cholesterol was treated as a covariate.

Results

Using LODPAL, the power of detecting one of the three major genes related to SBP is 44.4% when a LOD score of 1 is used as the cut-off point. The power of GENEFINDER is lower than that of LODPAL. It is 22.2%.

Conclusions

Based on the limited comparison, LODPAL provided the more reasonable power to detect linkage compared to GENEFINDER. After adjusting for the total cholesterol covariate, the current version of both programs appeared to give a high number of false positives.
Evidence for bivariate linkage of obesity and HDL-C levels in the Framingham Heart Study
Authors: Arya Rector , Lehman Donna , Hunt Kelly J , Schneider Jennifer , Almasy Laura , Blangero John , Stern Michael P , Duggirala Ravindranath
Published: December 2003

Background

Epidemiological studies have indicated that obesity and low high-density lipoprotein (HDL) levels are strong cardiovascular risk factors, and that these traits are inversely correlated. Despite the belief that these traits are correlated in part due to pleiotropy, knowledge on specific genes commonly affecting obesity and dyslipidemia is very limited. To address this issue, we first conducted univariate multipoint linkage analysis for body mass index (BMI) and HDL-C to identify loci influencing variation in these phenotypes using Framingham Heart Study data relating to 1702 subjects distributed across 330 pedigrees. Subsequently, we performed bivariate multipoint linkage analysis to detect common loci influencing covariation between these two traits.

Results

We scanned the genome and identified a major locus near marker D6S1009 influencing variation in BMI (LOD = 3.9) using the program SOLAR. We also identified a major locus for HDL-C near marker D2S1334 on chromosome 2 (LOD = 3.5) and another region near marker D6S1009 on chromosome 6 with suggestive evidence for linkage (LOD = 2.7). Since these two phenotypes have been independently mapped to the same region on chromosome 6q, we used the bivariate multipoint linkage approach using SOLAR. The bivariate linkage analysis of BMI and HDL-C implicated the genetic region near marker D6S1009 as harboring a major gene commonly influencing these phenotypes (bivariate LOD = 6.2; LODeq = 5.5) and appears to improve power to map the correlated traits to a region, precisely.

Conclusions

We found substantial evidence for a quantitative trait locus with pleiotropic effects, which appears to influence both BMI and HDL-C phenotypes in the Framingham data.
Genetic analysis of common factors underlying cardiovascular disease-related traits
Authors: Liu Xiao-Qing , Hanley Anthony JG , Paterson Andrew D
Published: December 2003

Background

Cardiovascular disease-related traits, such as body mass index (BMI), systolic blood pressure (SBP), triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL), and glucose levels (GLUC), have moderate to high correlations with each other. We hypothesized that there might be some common factors underlying the correlations of these traits, and attempted to identify these factors and their genetic structures. Cross-sectional measurements from the 330 extended Framingham Heart Study families were used in this study. Principal component factor analysis was applied to obtain the factors that were then analyzed using variance components linkage analysis.

Results

With the above six traits three factors were generated: BMI-SBP-GLUC, HDL-TG, and TC-TG. The heritabilities for these factors were 32%, 45%, and 49%, respectively. Comparing the linkage results of the factors with the results of their component traits, evidence for linkage was observed for the TC-TG factor to a locus on chromosome 2p23 with a two-point LOD score 2.73 (marker GATA8F07) and a multipoint LOD score 1.81 (at 54 cM), while the LOD scores for TC and TG did not exceed 1 at this region.

Conclusion

Our analysis showed a locus on chromosome 2 might have a pleiotropic effect on the cardiovascular disease-related traits TC and TG.
Localization of genes involved in the metabolic syndrome using multivariate linkage analysis
Authors: Olswold Curtis , Andrade Mariza de
Published: December 2003

There are no well accepted criteria for the diagnosis of the metabolic syndrome. However, the metabolic syndrome is identified clinically by the presence of three or more of these five variables: larger waist circumference, higher triglyceride levels, lower HDL-cholesterol concentrations, hypertension, and impaired fasting glucose. We use sets of two or three variables, which are available in the Framingham Heart Study data set, to localize genes responsible for this syndrome using multivariate quantitative linkage analysis. This analysis demonstrates the applicability of using multivariate linkage analysis and how its use increases the power to detect linkage when genes are involved in the same disease mechanism.
Identification of genes for complex disease using longitudinal phenotypes
Authors: Pankratz Nathan , Mukhopadhyay Nitai , Huang Shuguang , Foroud Tatiana , Kirkwood Sandra Close
Published: December 2003

Using the simulated data set from Genetic Analysis Workshop 13, we explored the advantages of using longitudinal data in genetic analyses. The weighted average of the longitudinal data for each of seven quantitative phenotypes were computed and analyzed. Genome screen results were then compared for these longitudinal phenotypes and the results obtained using two cross-sectional designs: data collected near a single age (45 years) and data collected at a single time point. Significant linkage was obtained for nine regions (LOD scores ranging from 5.5 to 34.6) for six of the phenotypes. Using cross-sectional data, LOD scores were slightly lower for the same chromosomal regions, with two regions becoming nonsignificant and one additional region being identified. The magnitude of the LOD score was highly correlated with the heritability of each phenotype as well as the proportion of phenotypic variance due to that locus. There were no false-positive linkage results using the longitudinal data and three false-positive findings using the cross-sectional data. The three false positive results appear to be due to the kurtosis in the trait distribution, even after removing extreme outliers. Our analyses demonstrated that the use of simple longitudinal phenotypes was a powerful means to detect genes of major to moderate effect on trait variability. In only one instance was the power and heritability of the trait increased by using data from one examination. Power to detect linkage can be improved by identifying the most heritable phenotype, ensuring normality of the trait distribution and maximizing the information utilized through novel longitudinal designs for genetic analysis.
Correlation between quantitative traits and correlation between corresponding LOD scores: detection of pleiotropic effects
Authors: Ulgen Ayse , Han Zhihua , Li Wentian
Published: December 2003

Background

We address the question of whether statistical correlations among quantitative traits lead to correlation of linkage results of these traits. Five measured quantitative traits (total cholesterol, fasting glucose, HDL cholesterol, blood pressure, and triglycerides), and one derived quantitative trait (total cholesterol divided by the HDL cholesterol) are used for phenotype correlation studies. Four of them are used for linkage analysis.

Results

We show that although correlation among phenotypes partially reflects the correlation among linkage analysis results, the LOD-score correlations are on average low. The most significant peaks found by using different traits do not often overlap.

Conclusion

Studying covariances at specific locations in LOD scores may provide clues for further bivariate linkage analyses.
Risk factors for coronary artery disease and the use of neural networks to predict the presence or absence of high blood pressure
Authors: Falk Catherine T
Published: December 2003

Background

The Framingham Heart Study was initiated in 1948 as a long-term longitudinal study to identify risk factors associated with cardiovascular disease (CVD). Over the years the scope of the study has expanded to include offspring and other family members of the original cohort, marker data useful for gene mapping and information on other diseases. As a result, it is a rich resource for many areas of research going beyond the original goals. As part of the Genetic Analysis Workshop 13, we used data from the study to evaluate the ability of neural networks to use CVD risk factors as training data for predictions of normal and high blood pressure.

Results

Applying two different strategies to the coding of CVD risk data as risk factors (one longitudinal and one independent of time), we found that neural networks could not be trained to clearly separate individuals into normal and high blood pressure groups. When training was successful, validation was not, suggesting over-fitting of the model. When the number of parameters was reduced, training was not as good. An analysis of the input data showed that the neural networks were, in fact, finding consistent patterns, but that these patterns were not correlated with the presence or absence of high blood pressure.

Conclusion

Neural network analysis, applied to risk factors for CVD in the Framingham data, did not lead to a clear classification of individuals into groups with normal and high blood pressure. Thus, although high blood pressure may itself be a risk factor for CVD, it does not appear to be clearly predictable using observations from a set of other CVD risk factors.
Quantitative trait linkage analysis of longitudinal change in body weight
Authors: Golla Astrid , Strauch Konstantin , Dietter Johannes , Baur Max P
Published: December 2003

One of the great strengths of the Framingham Heart Study data, provided for the Genetic Analysis Workshop 13, is the long-term survey of phenotypic data. We used this unique data to create new phenotypes representing the pattern of longitudinal change of the provided phenotypes, especially systolic blood pressure and body weight. We performed a linear regression of body weight and systolic blood pressure on age and took the slopes as new phenotypes for quantitative trait linkage analysis using the SOLAR package. There was no evidence for heritability of systolic blood pressure change. Heritability was estimated as 0.15 for adult life "body weight change", measured as the regression slope, and "body weight gain" (including only individuals with a positive regression slope), and as 0.22 for body weight "change up to 50" (regression slope of weight on age up to an age of 50). With multipoint analysis, two regions on the long arm of chromosome 8 showed the highest LOD scores of 1.6 at 152 cM for "body weight change" and of >1.9 around location 102 cM for "body weight gain" and "change up to 50". The latter two LOD scores almost reach the threshold for suggestive linkage. We conclude that the chromosome 8 region may harbor a gene acting on long-term body weight regulation, thereby contributing to the development of the metabolic syndrome.
A model-integrated multipoint Bayesian analysis of hypertension in the Framingham Heart Study data finds little evidence of linkage
Authors: Logue Mark W , Goedken Rhinda J , Vieland Veronica J
Published: December 2003

This Genetic Analysis Workshop 13 contribution presents a linkage analysis of hypertension in the Framingham data based on the posterior probability of linkage, or PPL. We dichotomized the phenotype, coding individuals who had been treated for hypertension at any time, as well as those with repeated high blood pressure measurements, as affected. Here we use a new variation on the multipoint PPL that incorporates integration over the genetic model. PPLs were computed for chromosomes 1 through 5, 11, 14, and 17 and remained below the 2% assumed prior probability of linkage for 73% of the locations examined. The maximum PPL of 4.5% was obtained on chromosome 1 at 178 cM. Although this is more than twice the assumed prior probability of linkage, it is well below a level at which we would recommend committing substantial additional resources to molecular follow-up. While the PPL analysis of this data remains inconclusive, Bayesian methodology gives us a clear mechanism for using the information gained here in further studies.
Linkage analysis of systolic blood pressure: a score statistic and computer implementation
Authors: Wang Kai , Peng Yingwei
Published: December 2003

A genome-wide linkage analysis was conducted on systolic blood pressure using a score statistic. The randomly selected Replicate 34 of the simulated data was used. The score statistic was applied to the sibships derived from the general pedigrees. An add-on R program to GENEHUNTER was developed for this analysis and is freely available.
Nonparametric longitudinal allele-sharing model
Authors: Kulle Bettina , Köhler Karola , Rosenberger Albert , Loesgen Sabine , Bickeböller Heike
Published: December 2003

Basically no methods are available for the analysis of quantitative traits in longitudinal genetic epidemiological studies. We introduce a nonparametric factorial design for longitudinal data on independent sib pairs, modelling the phenotypic quadratic differences as the dependent variable. Factors are the number of alleles shared identically by descent (IBD) and the age categories at which the dependent variable is measured, allowing for dependence due to age. To identify a linked marker a rank statistic tests the influence of IBD group on phenotypic quadratic differences. No assumptions are made on normality or variances of the dependent variable. We apply our method to 71 sib pairs from the Framingham Heart Study data provided at the Genetic Analysis Workshop 13. For all 15 available markers on chromosome 17 we analyzed the influence on systolic blood pressure. In addition, different selection strategies to sample from the whole data are discussed.
Detecting susceptibility genes in case-control studies using set association
Authors: Kim Sung , Zhang Kui , Sun Fengzhu
Published: December 2003

Complex diseases are generally caused by intricate interactions of multiple genes and environmental factors. Most available linkage and association methods are developed to identify individual susceptibility genes assuming a simple disease model blind to any possible gene - gene and gene - environmental interactions. We used a set association method that uses single-nucleotide polymorphism markers to locate genetic variation responsible for complex diseases in which multiple genes are involved. Here we extended the set association method from bi-allelic to multiallelic markers. In addition, we studied the type I error rates and power for both approaches using simulations based on the coalescent process. Both bi-allelic set association (BSA) and multiallelic set association (MSA) tests have the correct type I error rates. In addition, BSA and MSA can have more power than individual marker analysis when multiple genes are involved in a complex disease. We applied the MSA approach to the simulated data sets from Genetic Analysis Workshop 13. High cholesterol level was used as the definitive phenotype for a disease. MSA failed to detect markers with significant linkage disequilibrium with genes responsible for cholesterol level. This is due to the wide spacing between the markers and the lack of association between the marker loci and the simulated phenotype.
Comparison between two analytic strategies to detect linkage to obesity with genetically determined age of onset: the Framingham Heart Study
Authors: Engelman Corinne D , Brady Heather L , Baron Anna E , Norris Jill M
Published: December 2003

Background

Genes have been found to influence the age of onset of several diseases and traits. The occurrence of many chronic diseases, obesity included, appears to be strongly age-dependent. However, an analysis of potential age of onset genes for obesity has yet to be reported. There are at least two analytic methods for determining an age of onset gene. The first is to consider a person affected if they possess the trait before a certain age (an early age of onset phenotype). The second is to define the phenotype based on the residual from a survival analysis.

Results

No regions provided evidence for linkage at the more stringent level of p < 0.001. However, five regions showed consistent suggestive evidence for linkage (one marker with p < 0.01 and a second contiguous marker at p < 0.05). These regions were chromosome 1 (280–294 cM) and chromosome 16 (56–64 cM) for overweight using the survival analysis residual method and chromosome 13 (102–122 cM), chromosome 17 (127–138 cM), and chromosome 19 (23–47 cM) for obese before age 35.

Conclusion

Only one region (chromosome 19 at 23–47 cM) showed somewhat consistent results between the two analytic methods. Potential reasons for inconsistent results between the two methods, as well as their strengths and weaknesses, are discussed. The use of both methods together to explore the genetics of the age of onset of a trait may prove to be beneficial in determining a gene that is linked only to an early age of onset phenotype versus one that determines age of onset through all age groups.
Linkage mapping of total cholesterol level in a young cohort via nonparametric regression
Authors: Ghosh Saurabh , Bertelsen Sarah , Reich Theodore
Published: December 2003

Background

Compared to model-based approaches, nonparametric methods for quantitative trait loci mapping are more robust to deviations in distributional assumptions. In this study, we modify a nonparametric regression method and the "contrast function"- based regression method to analyze total cholesterol level in the younger cohort (the offspring generation) of the Genetic Analysis Workshop 13 simulated data set.

Results

We obtained significant evidence of linkage near four of the six non-sex-specific genes in at least 30% of the replicates.

Conclusions

The proposed nonparametric method seems to be a powerful robust alternative to distribution-based methods.
Familial aggregation of components of the multiple metabolic syndrome in the Framingham Heart and Offspring Cohorts: Genetic Analysis Workshop Problem 1
Authors: Lee Kristine E , Klein Barbara EK , Klein Ronald
Published: December 2003

Background

The multiple metabolic syndrome is defined by a clustering of risk factors for cardiovascular disease. We sought to evaluate the familial correlations of the components of the syndrome using data from the Framingham Heart Study original and offspring cohorts as provided for the Genetic Analysis Workshop 13. Measures of plasma cholesterol (total and HDL), body mass index (BMI), and systolic blood pressure were used from selected calendar years of exams. Familial correlations were calculated using FCOR in S.A.G.E.

Results

The sibling correlations were relatively high for all measures and exams, from 0.17 for systolic blood pressure to 0.27 for HDL cholesterol. The parent-child correlations were very similar, except for systolic blood pressure. The avuncular correlations were much smaller and the cousin correlations were even smaller. For HDL cholesterol the avuncular correlation was half the sibling correlation and the cousin correlation was half that again. Spousal correlations ranged from 0.07 for systolic blood pressure to 0.34 for BMI. Correlations were somewhat lower from 1984 to 1987 examinations than from 1971 to 1975 examinations, except for spousal correlations for systolic blood pressure and BMI.

Conclusion

The results of the family pair correlations are suggestive of genetic determinants of lipid levels and BMI. These components have been shown to be predictive of cardiovascular disease as well as diabetes. Genes in common with each of the components might also influence development of cardiovascular disease and diabetes, both complex diseases.
The early warning symptom intervention for patients with bipolar affective disorder
Authors: Morriss Richard
Published: December 2003

Randomised controlled trials and surveys of patients' experiences indicate that the recognition and prompt treatment of early warning signs of relapse in selected patients with bipolar affective disorder are effective in lengthening the time to the next manic relapse and improving function. Improvements in patient coping mechanisms allied to these techniques can prevent some depressive episodes. The intervention is described in some detail and conditions under which it is most likely to be effective or to fail are reviewed. If the intervention is to be successful, patients must be carefully selected, early warning signs and symptoms must be analysed in detail, it must be a central feature of the care plan and the service must be ready to respond quickly to a patient's early warning symptoms.
How to make journal clubs interesting
Authors: Swift Geraldine
Published: December 2003

Almost all psychiatric training programmes include a journal club. These clubs are experiencing a revival as a result of the introduction of a critical review paper into Part II of the MRCPsych examinations. Successful clubs are generally those with a single designated leader and mandatory attendance; provision of food is also helpful. A number of possible formats are discussed, designed to make the club an entertaining and stimulating experience.
Non-attendance rates among patients attending different grades of psychiatrist and a clinical psychologist within a community mental health clinic
Authors: McIvor Ronan , Ek Emma , Carson Jerome
Published: December 2003

Aims and Method

To examine non-attendance rates in patients seen by psychiatrists of different grades and a consultant clinical psychologist. Rates were obtained from the patient administration system over a 21-month period.

Results

A planned linear contrast showed that the clinical psychologist's patients had the lowest rate of non-attendance (7.8%), followed in turn by those of consultant psychiatrists (18.6%), specialist registrars (34%) and senior house officers (37.5%).

Clinical Implications

Factors such as continuity of care, perceived clinical competence and the provision of non-medical interventions might have an impact on attendance rates. These results indicate the difficulty in reconciling the training needs of junior doctors with the provision of continuity and quality of care for patients. Reminder systems for people seeing training doctors might be an effective way of reducing non-attendance rates.
Using evidence-based dissemination and implementation strategies to improve routine communication between general practitioners and community mental health teams
Authors: White Tracy , Marriott Sarah
Published: December 2003

Aims and Method

To improve the quality of written communication between general practitioners (GPs) and community mental health team (CMHT) members concerning patients newly referred to two inner-city CMHTs. Following a benchmark audit of a random sample of referral and assessment letters, locally agreed good practice protocols were shared widely, accompanied by a dissemination and implementation strategy.

Results

Significant improvements occurred in both GP and CMHT letters; these were most dramatic after 1 year, but tailed off considerably in the second year despite continued efforts to implement the protocols' standards.

Clinical Implications

Planned dissemination and implementation strategies can help to improve routine clinical communication between CMHTs and GPs through the use of good practice protocols, thus improving shared working between primary and secondary care providers.
The amygdala and sexual drive: Insights from temporal lobe epilepsy surgery
Authors: Baird Amee D. , Wilson Sarah J. , Bladin Peter F. , Saling Michael M. , Reutens David C.
Published: December 2003

The aim of this study was to explore the relationship between the amygdala and human sex drive. We compared amygdalar volume in groups of patients with or without sexual changes after temporal lobe resection and in age‐matched neurologically normal subjects. Forty‐five patients with intractable temporal lobe epilepsy who underwent surgical resection in the Comprehensive Epilepsy Program at the Austin and Repatriation Medical Centre completed a semistructured interview and questionnaire relating to sexual outcome after surgery. Volumetric analyses of both amygdalae were conducted on the patients' preoperative T1‐weighted magnetic resonance imaging scans and those of 46 neurologically normal controls. Patients who reported a postoperative sexual increase had a significantly larger amygdalar volume contralateral to the site of their resective surgery than patients with a sexual decrease or no change than control subjects. There was a significant positive relationship between contralateral amygdalar volume and the maximum degree of sexual change. We have demonstrated a relationship between contralateral amygdalar volume and sexual outcome in patients undergoing temporal lobe resection. This finding provides evidence for an important role of the amygdala in regulating human sexual behavior. A larger contralateral amygdala may contribute to the expression of increased or improved sexuality after temporal lobe resection.
The α‐Addition of Immonium Ions and Anions to Isonitriles Accompanied by Secondary Reactions
Authors: Ugi Ivar
Published: December 2003

The α‐addition of immonium ions and anions (OH−, SeH−, S2O3 2−, N3− NCO− NCS−, RCO2 −, ROCO2−) to isonitriles, accompanied by secondary reactions provides a means for the one‐stage synthesis of organic nitrogen compounds starting with two to five different components. Thus, by the condensations of amines (ammonia, primary, and secondary aliphatic and aromatic amines, hydrazines) and aldehydes or ketones with isonitriles and acids, a number of α‐aminocarboxylic acid amides, thioamides, selenoamides, 1,5‐disubstituted retrazoles, hydantoin imides, thiohydantoin imides, α‐acylamino carboxylic acid amides, oligopeptide derivatives, β‐lactams, derivatives of penicillanic acid, urethanes, diacylimides, and various hydrazine derivatives, can be prepared. The reactions are easily carried out and take place under mild conditions. Yields of more than 90% are frequently encountered.
The Oxidation of Olefins with Palladium Chloride Catalysts
Authors: Smidt Juergen , Hafner W. , Jira R. , Sieber R. , Sedlmeier J. , Sabel A.
Published: December 2003

The oxidation of olefins to carbonyl compounds with palladium compounds, especially the oxidation of ethylene to acetaldehyde, is at present carried out on a technical scale. The reaction takes place via a palladium‐olefin complex, the formation of which is inhibited by halide ions. Hydrolysis to the carbonyl compound is inhibited by hydrogen ions. The knowledge gained by studying the reaction of olefins with pure solutions of palladium salts allows important conclusions to be drawn concerning the action of technical catalyst solutions containing copper and palladium chloride.
Organic N‐Sulfinyl Compounds
Authors: Kresze G. , Maschke A. , Albrecht R. , Bederke K. , Patzschke H. P. , Smalla H. , Trede A.
Published: December 2003

The nitrogen‐sulpher linkage in compounds of the type RNSO is capable of undergoing addition. For N‐sulfinylsulfonamides in particular, the reactivity is increased so greatly that new type of compounds may be obtained by cyclic addition or migration of the sulfinyl group.
Recent Studies on Fluroalkyls and Related Compounds
Authors: Emeléus H. J.
Published: December 2003

The discovery of trifluorodomethane some 14 years ago opened up a wide range of possibilitis for the preparation of new organometallic and organometalloidal compounds containing fluroalkyl radicals. Simultaneously it offered for the first time the possibility of enamining and explaining the differences between such compounds and their alkyl or aryl analogues. A brief recaptiulation of some earlier results is given, followed by a review of recent progress, espically in the chemistry of fluoroalkyls of sulphur and nitrogen as well as certain of the metallic elememts.
The Stereochemistry of Organosilicon Compounds
Authors: Sommer L. H.
Published: December 2003

Optically active organosilicon compounds having reactive functional groups bonded to asymmetric silicon have recently been synthesized and their study has revealed that many organosilicon reactions are stereospecific.

The present paper deals with the problem of correlation of configuration for six key compounds containing the α‐naphthylphenylmethylsityl group. The solution of this problem by the use of chemical and physical methods is described. In addition the stereochemistry of more than twenty stereospecific reactions of silicon is considered. The probable fundamental relationships between organosilicon stereochemistry and the reaction mechanisms of monofunctional R3SiY compounds are discussed in a preliminary way.
A New Type of Converter for Ammonia Synthesis
Authors: Hinrichs H. , Niedetzky J.
Published: December 2003

A comparison of known types of converters used for the synthesis of ammonia, and an evaluation of their respective advantages and disadvantages are given. A new type of converter is described, in which catalyst contact beds alternate with heat exchange regions. This arrangement permits both close control of the operating temperature at or near optimum conditions and utilization of the excess heat of reaction for preheating the reaction gases.
Chemical Reactions and Mircotacticity of High Ploymers
Authors: Smets G.
Published: December 2003

The reaction course and kinetics of interfunctional reactions with polymers are determined by the microtacticity of the polymer chain. Among other things, this is shown by the hydrolysis of ester and amide polymers of different tacticities, and by ring‐closure reactions (anhydride formation). The physical and physico‐chemical properties are also governed by the tacticity.
The Chemical Basis of Ancient Greek Vase Painting
Authors: Hofmann U.
Published: December 2003

In classical times, black‐ and red‐figured vases were an important Greek export article, balancing payments resulting from grain import. This was especially true in Athens. The red pigment was always Fe2O3, and the black Fe3O4. A carefully chosen clay containing iron, which could be formed by hand with a simple potter's wheel, was used for thr vessel. The fired ceramic usually provided the red of the vessels. For the black painting, and for the occasionally used red painting (Intentional Red), a layer of finely elutriated clay was painted on. The vessel was fired between 800 and 900 °C, first under oxidizing conditions, then under reducing, and finally again under oxidizing conditions. From the reproductions of Adam Winter it may be concluded that an illitic clay was used for the black figure painting. During the reductive firing, the painted layer became impervious by sintering owing to the K2O content of the clay. A kaolinitic clay, poorer in K2O, served for the red painting. This clay remained porous on reduction and was reoxidized, like the ceramic of the vessel, in the second oxidation. For the terra sigillata of the Romans, the entire surface of the vessel was covered with a clay slip, which on firing under oxidizing conditions at higher temperatures, gave a hard surface, so that the vessel; could be used as table utensils.
Small Rings with Carbon‐Carbon Triple Bonds
Authors: Wittig G.
Published: December 2003

Over the last few years, numerous hydrocarbon ring structures with triple bonds have been studied, e.g. cycloalkynes, heterocyclic compounds with triple bonds, and particularly dehydrobenzene (better known in the Anglo‐American literature as benzyne). Dehydrobenzene has not yet isolated. The prospects of doing so are discussed.
Copolymers and Fibers from Vinylidenedicarbonitrile
Authors: Sprague B. S. , Greene H. E. , Reuter L. F. , Smith R. D.
Published: December 2003

Vinyldendicarbonitrile (Vinylidene cyanide) on free redical catalyzed copolymerization shows a much stronger tendency to form 1:1 alternating copolymers than acrylonitrile. While bulk poly(vinylidene cyanide) fails to crystallize, despite its molecular symmetry, several alternating copolymers are readily crystallizable, notably those containing butadiene, isoprene, isobutylene, or vinylidene chloride. Fibers have been prepared from a number of the higher melting copolymers and examined for physical properties. Fibers from the vinyl acetate and vinyl chloride copolymers show expectional elastic behavior both when dry and wet. The fiber from the vinylidene cyanide |vinyl acetate alternating copolymer (Darvan® nytril fiber) is only moderately oriented and is characterized by exceptional softness and excellent elastic recovery and resilience, both when dry and wet.
Pyrrolidone, Capryllactam and Laurolactam as new Monomers for Polyamide Fibers
Authors: Dachs K. , Schwartz E.
Published: December 2003

The industrial production of capryllactam (1‐azacyclononan‐2‐one) and of laurolactam (1‐azacyclotridecan‐2‐one) starts with cyclization of acetylene or butadeine to give cyclooctatetraene or cyclooctadiene, or cyclization of butadiene to give cyclododecatriene. Further steps are: oxidation of the cyclic hydrocarbon to the ketone, formation of the oxime, and rearrangement of the latter with sulfuric acid. Pyrrolidone can be prepared from acetylene and formaldehyde by way of butyrolactone. The behavior of the lactams during polycondensation is described and the properties of the resulting fibers are compared with those of the known polyamide fibers.
Attempts to Synthetize Tetramethylyclobutadiene
Authors: Criegee R.
Published: December 2003

Attempts to prepare cyclobutadiene, which is primarily of theoretical interest, or one of its derivatives have so far led only to products structurally closely related to tetramethylcyclobutadiene. It has not been possible to prepare the compound itself nor to establish unequivocally that it occurs as a reaction intermediate.
Reactivity of Dichloro‐ and Trichloropyrimidyl Dyes and the Sensitivity of their Dyeings to Hydrolysis
Authors: Thumm O. , Benz J.
Published: December 2003

Several examples are used to show that the reactivity of dichloro‐ and trichloropyrimidyl dyes and the sensitivity of their dyeings to hydrolysis are determined by the nature of the bridge unit between the chromophore and the reactive system. The tendency of the dyeings to hydrolyze in acid and, more particularly, in alkaline media increases with increasing reactivity of the dyes. In alkaline media, dyeings made with dyes containing oxygen bridges are cleaved mainly between the reactive system and the chromophore, while in dyeings made with dyes containing imino or methylimino bridges, the linkage between the reactive system and the cellulose is hydrolyzed.
Automatic Activity Measurements during the Separation of Radioactive Compounds by Thin‐Layer Chromatography
Authors: Schulze P.‐E. , Wenzel M.
Published: December 2003

A method was developed for continuous automatic measurement of the radioactivity distribution of weak β‐emitters on open columns, for example, thin‐layer chromatograms. It may be used for analytical separations, as well as for preparative separations on a semi‐micro scale. During the measurements the substances are not contaminated by addition of other materials.
High‐temperature Chlorination of Amines and Acylamines
Authors: Holtschmidt H.
Published: December 2003

High‐temperature chlorination of acyl derivatives of primary and secondary amines and of tertiary alkyl amines usually yields compounds containing either the imidochloride (monochloromethyleneamino) group or the dichloroisocyanide (dichloromethyleneamino) group . In many cases, yields in the range of 80 to 95% are obtaied. Several ring‐opening and ring‐closing reactions ocurring under the conditions of high‐temperature chlorination ae described.
Low‐Temperature Polymerization of Ethylene
Authors: Bestian H. , Clauss K. , Jensen H. , Prinz E.
Published: December 2003

A two‐component organometallic catalyst of composition CH3TiCl3·CH3AlCl2 effects high‐speed polymerization of ethylene in the presence of chlorinated hydrocarbons at low temperatures. The catalyst does not undergo any alteration in the process. In contrast to the Ziegler catalysts, the titanium remains quadrivalent. Olefins of low‐molecular‐weight and with branched structures are produced. It proved possible to isolate the primary products of the polymerization at −50 to −100°C and to elucidate the mode of their formation from a knowledge of their structures. The findings are incompatible with either a cationic or anionic reaction mechanism. A novel type of mechanism is proposed, whereby the catalyst is supposed to have an ionic structure and molecular growth proceeds via π‐complex formation of the olefin with the titanium cation. The formation of ethylene/olefin copolymers is also discussed.
Organic Derivatives of Mica‐type Layer‐Silicates
Authors: Weiss Armin
Published: December 2003

Mica‐type layer‐silicates such as montmorillonite and vermiculite are capable of exchanging their cations for other (including organic) cations, just like the zeolites. These derivatives swell in a variety of liquids. This paper presents a survey of the structures of organic derivatives of mica‐type layer‐silicates and illustrates some possibilities for their industrial utilization.
(Halogenomethyl)pyridines and (Halogenomethyl)quinolines
Authors: Mathes W. , Schüly H.
Published: December 2003

Hitherto, 2‐ and 4‐trihalogenomethyl‐pyridines and ‐quinolines were the only compounds of this type readily assessible by direct halogenation with free halogen. The particularly important and highly reactive monohalogenomethyl compounds had to be prepared by roundabout means, except in special cases. In the present article, a method is described for direct monochlorination of 2‐methyl groups in heterocyclic bases on a technical scale. A reveiw is also given of the preparation and properties of (halogenomethyl) pyridines and (halogenomethyl)quinolines.
Gas Chromatographic Investigation of Racemization during Peptide Synthesis
Authors: Weygand F. , Prox A. , Schmidhammer L. , König W.
Published: December 2003

It is shown that the methyl esters of many diastereoisomeric N‐trifluoroacetyldipeptides can be separated by gas chromatography on Golay columns. This makes it possible for the first time to carry out accurate quantitative investigations of recemization occurring during peptide synthesis without resort to measurements of optical rotation or enzymatic cleavage, and witout having to isolate the peptides. Some well‐known methods of forming peptides were examined using the synthesis of the methyl ester of carbobenzoxy‐L‐valyl‐L‐valine as an example. The synthesis of the methyl ester of N‐trifluoroacetyl‐L‐valyl‐L‐valine was investigated as a model for the linking of peptides. The influence on racemization of numerous factors was determined. General conclusions could be drawn regarding peptide synthesis.
Preparative and Analytical Separation of Organic Compounds by Means of Chromatography on Polyamide
Authors: Endres Horst , Hörmann Helmut
Published: December 2003

Columns of polyamide are well suited for chromatographic separation of numerous organic compounds, especially phenols, carboxylic acids, and aromatic nitro compounds. The method is also useful for isolating naturally occurring compounds on a preparative scale. The affinity of phenols for polyamides is due to the formation of hydrogen bonds to the peptide linkages of the polyamide, while aromatic nitro compounds are retained by means of free amino groups in the polymer. Quinones react irreversibly with the free amino groups of the polyamide. Quinones are not retained by acetylated polyamides although phenols are.
Mass Transport in Metallic Solids
Authors: Wever H.
Published: December 2003

Mass transport in a metallic solid requires that the lattice units exchange places. This is made possible by lattice defects. Also, a circular interchange has to be discussed. Driving forces cause the superposition of directional motion over the random motion of site exchange: When a chemical potential gradient exists, isothermal diffusion occurs; with an electrical potential gradient, electrolytic transport takes place; and with a temperature gradient, the effect is thermal diffusion. Both concentrational changes and dimensional changes may accompany these processes. From observation of these phenomena, the mechanism by which lattice particles change places can be deduced. In addition, it is possible to calculate characteristic data, such as migration energy, imaginary change, and heat of transportation.
Syntheses with s‐Triazine
Authors: Grundmann Ch.
Published: December 2003

The preparation and properties of s‐triazine are discussed. Nucleophilic reagents (even water) readily attack s‐triazine. Thus, open‐chain and heterocyclic compounds, e.g. formamidines, aminomethylene compounds, and triazole, pyridine, and pyrimidine deravatives are accessible from s‐triazine. With amidines and imido ethers substituted triazines are obtained (by trans‐triazination).The latter are formed via open‐chain intermediates.
Recent Investigations of Sulfur‐Nitrogen Compounds
Authors: Glemser O.
Published: December 2003

The preparation, properties, and structure of cyclic and acyclic sulfur‐nitrogen halides are discussed. In the cyclic compounds, SN rings with localised and delocalized π‐bonds occur. In acyclic halides, SN triple bonds are observed. Organic iminosulfur dihalides are discussed.
Kinetics and Mechanism of 1,3‐Dipolar Cycloadditions
Authors: Huisgen R.
Published: December 2003

Criteria for the mechanism of 1,3‐dipolar cycloadditions which lead to 5‐membered rings are provided by the stereoselectivity observed with cis‐trans isomeric dipolarophiles, by the effect of solvent and substituents on the rate constants, by the activation parameters, and by orientation phenomena. A concerted addition, which can also be described in terms of molecular orbitals and in which the two new σ‐bonds are formed simultaneously, although not necessarily at equal rates, offers the best explanation of the experimental facts.
New Developments in the Chemistry of Polyphosphanes
Authors: Wiberg E. , Van Ghemen M. , Müller‐Schiedmayer G.
Published: December 2003

While silicon and sulfur, which are situated to the left and to the right of phosphorus in the periodic table, from numerous chain and cyclic Si–Si and S–S‐compounds with varying numbers of members, until recently the polyphosphance chemistry has been limited to the two‐membered compounds diphosphane P2H4 and its derivatives. A number of results obtained in studies on polyphosphanes carried out in recent years will therefore be discussed, which, together with some more recent work by other authors, have led to an expansion of our knowledge of the prepration and properties of straight and branched‐chain as well as of cyclic and polycylic –P–P‐systems.
Some Aspects of the Chemistry of Organoselenium Compounds
Authors: Gosselck J.
Published: December 2003

In this article, the gradations in reactivity of organic oxygen, sulfur, and selenium compounds of equivalent structure (“isologues”) are reviewed. New or improved methods for the preparation of organoselenium compounds (especially saturated and unsaturated selenides) are described. The addtion of selenols onto acetylenic triple bonds cheifly to cisadducts.
Reactions of Olefins with the Titanium‐Carbon Bond
Authors: Bestian H. , Clauss K.
Published: December 2003

At low temperatures, ethylene and α‐olefins (Δ1‐olefins or 1‐alkenes) are rapidly converted into oligomrs by the two‐component organometallic catalyst CH3TiCl3·CH3AlCl2. To achieve smooth oligomerizations, aromatic or chlorinated hydrocarbons must be used as solvents. Although the activity of the titanium‐carbon bond is enhanced by the aluminum component of the catalyst, the aluminum and its methyl group do not participate in the reaction proper; the latter proceeds exclusively at the titanium‐carbon bond. The reaction will olefins can be used as an analytical method for the quantitative determination of the titanium‐carbon bond in admixture with the organoaluminum component. It is thus possible to follow the reaction leading to formation of the catalyst from titanium tertrachloride, as well as the processes occurring at the titanium‐carbon bond during the oligomerization of olefins. All the observations indicate that the catalyst possesses an ionic structure which is determined by the solvent. It is shown that the initial reaction step probably involves formation of a complex between the olefin and the alkyltitanium cation. The reaction scheme proposed is based on organometallic reactions which are characterized by carbanion and hydride transfers within the olefin‐cation complex. This mechanism, which is unusual for Ziegler catalysts, is due to the predominance of hydride transfers.