A case of true hermaphroditism reveals an unusual mechanism of twinning

Traditionally twins are classified as dizygous or fraternal and monozygous or identical (Hall Twinning, 362, 2003 and 735-743). We report a rare case of 46,XX/46,XY twins: Twin A presented with ambiguous genitalia and Twin B was a phenotypically normal male. These twins demonstrate a third, previously unreported mechanism for twinning. The twins underwent initial investigation with 17-hydroxyprogesterone and testosterone levels, pelvic ultrasound and diagnostic laparoscopy. Cytogenetic analysis was performed on peripheral blood cells and skin fibroblasts. Histological examination and Fluorescence in situ hybridization studies on touch imprints were performed on gonadal biopsies. DNA analysis using more than 6,000 DNA markers was performed on skin fibroblast samples from the twins and on peripheral blood samples from both parents. Twin A was determined to be a true hermaphrodite and Twin B an apparently normal male. Both twins had a 46,XX/46,XY chromosome complement in peripheral lymphocytes, skin fibroblasts, and gonadal biopsies. The proportion of XX to XY cells varied between the twins and the tissues evaluated. Most significantly the twins shared 100% of maternal alleles and approximately 50% of paternal alleles in DNA analysis of skin fibroblasts. The twins are chimeric and share a single genetic contribution from their mother but have two genetic contributions from their father thus supporting the existence of a third, previously unreported type of twinning.

A four-variable model for the pattern-forming mechanism in Hydra

A generalized Gierer-Meinhardt model has been used to account for the transplantation experiments in Hydra. In this model, a cross inhibition between the two organizing centres (namely, head and foot) are assumed to be the only mode of interaction in setting up a stable morphogen distribution for the pattern formation in Hydra.

A capability-based view of organisational renewal : Combining opportunity- and advantage-seeking growth in large, established European and North American wood-industry companies

The purpose of this study was to extend understanding of how large firms pursuing sustained and profitable growth manage organisational renewal. A multiple-case study was conducted in 27 North American and European wood-industry companies, of which 11 were chosen for closer study. The study combined the organisational-capabilities approach to strategic management with corporate-entrepreneurship thinking. It charted the further development of an identification and classification system for capabilities comprising three dimensions: (i) the dynamism between firm-specific and industry-significant capabilities, (ii) hierarchies of capabilities and capability portfolios, and (iii) their internal structure. Capability building was analysed in the context of the organisational design, the technological systems and the type of resource-bundling process (creating new vs. entrenching existing capabilities). The thesis describes the current capability portfolios and the organisational changes in the case companies. It also clarifies the mechanisms through which companies can influence the balance between knowledge search and the efficiency of knowledge transfer and integration in their daily business activities, and consequently the diversity of their capability portfolio and the breadth and novelty of their product/service range. The largest wood-industry companies of today must develop a seemingly dual strategic focus: they have to combine leading-edge, innovative solutions with cost-efficient, large-scale production. The use of modern technology in production was no longer a primary source of competitiveness in the case companies, but rather belonged to the portfolio of basic capabilities. Knowledge and information management had become an industry imperative, on a par with cost effectiveness. Yet, during the period of this research, the case companies were better in supporting growth in volume of the existing activity than growth through new economic activities. Customer-driven, incremental innovation was preferred over firm-driven innovation through experimentation. The three main constraints on organisational renewal were the lack of slack resources, the aim for lean, centralised designs, and the inward-bound communication climate.

Male traits and herd reproductive capability in tropical beef cattle. 1. Experimental design and animal measures

Research into the genetics of whole herd profitability has been a focus of the Beef Cooperative Research Centre for Beef Genetic Technologies over the past decade and it has been identified that measures of male reproduction may offer a potential indirect means of selecting for improved female reproduction. This paper describes the experimental design and provides a descriptive analysis of an array of male traits in Brahman and Tropical Composite genotypes managed under the medium to high stress, semi-extensive to extensive production systems of northern Australia. A total of 1639 Brahman and 2424 Tropical Composite bulls with known pedigrees, bred and raised in northern Australia, were evaluated for a comprehensive range of productive and reproductive traits. These included blood hormonal traits (luteinising hormone, inhibin and insulin-like growth factor-I); growth and carcass traits (liveweight, body condition score, ultrasound scanned 12-13th rib fat, rump P8 fat, eye muscle area and hip height); adaptation traits (flight time and rectal temperature); and a bull breeding soundness evaluation (leg and hoof conformation, sheath score, length of everted prepuce, penile anatomy, scrotal circumference, semen mass activity, sperm motility and sperm morphology). Large phenotypic variation was evident for most traits, with complete overlap between genotypes, indicating that there is likely to be a significant opportunity to improve bull fertility traits through management and bull selection.

Male traits and herd reproductive capability in tropical beef cattle. 2. Genetic parameters of bull traits

A total of 4063 young bulls of two tropical genotypes (1639 Brahman and 2424 Tropical Composite) raised in northern Australia were evaluated for a comprehensive range of production and reproduction traits up to 24 months of age. Prior to weaning, peripheral blood concentrations of luteinising hormone (LH) and inhibin were measured at 4 months of age. At weaning (6 months) blood insulin-like growth factor-1 (IGF-I) and flight time were recorded. Body composition traits of fat depth and eye-muscle area were determined by ultrasonography at 15 months of age when additional measurements of liveweight, hip height and body condition score were recorded. Bull breeding soundness was evaluated at similar to 12, 18 and 24 months of age when measurements of scrotal circumference, sheath score, semen mass activity, progressive motility of individual sperm and percent morphologically normal sperm were recorded. Magnitude of heritability and genetic correlations changed across time for some traits. Heritability of LH, inhibin, IGF-I and of 18-month scrotal circumference, mass activity, progressive motility and percent normal sperm was 0.31, 0.74, 0.44, 0.75, 0.24, 0.15 and 0.25, respectively, for Brahmans and 0.48, 0.72, 0.36, 0.43, 0.13, 0.15 and 0.20, respectively, for Tropical Composites. Inhibin and IGF-I had moderate genetic association with percent normal sperm at 24 months in Brahmans but low to negligible associations in Tropical Composites. Body condition score in Brahmans and sperm motility (mass and individual) traits in both genotypes had moderate to strong genetic correlation with percent normal sperm and may prove useful candidates for indirect selection. There is scope to increase scrotal circumference by selection and this will be associated with favourable correlated responses of improved semen quality in both genotypes. The lack of genetic antagonism among bull traits indicates that selection for improved semen quality will not adversely affect other production traits.

Mechanism of the thermal decomposition of polystyrene peroxide

The thermal degradation of polystyrene peroxide was carried out using differential scanning calorimetry. The activation energy (E) was found to be 136 kJ mole–1 at all extents of decomposition. TheE value was found to correspond to-O-O-dissociation. The order of reaction was found to decrease from 2 to 1 as the decomposition progresse.

Mechanism of improvement in oil spreadability of aluminium alloy-graphite particle composites

The spreadability of SAE-30 oil on Al-12 Si base (LM-13) alloy containing dispersed graphite particles about 50 μm average size in its matrix is found to be greater than on either LM-13 with no graphite or brass. It is also found that the spreadability on LM-13 base alloys increase with increasing volume of graphite dispersion in the matrix of these alloys. Further increases in the spreadability of oil on machined LM-13-graphite particle composite test surfaces occur if these are rubbed initially against control discs of either LM-13 or grey cast iron. The formation of a triboinduced graphite-rich layer, confirmed by esca, appears to be responsible for the improved oil spreadability on the rubbed test surfaces of LM-13 base alloys as compared to the as-machined test surfaces prior to rubbing. The triboinduced layer of graphite is apparently responsible for the observed reduction in the friction, wear and seizing tendency of triboelements made from aluminium alloy-graphite particle composites.

HPLC analysis of plant sterol oxidation products

Increased interest in the cholesterol-lowering effect of plant sterols has led to development of plant sterol-enriched foods. When products are enriched, the safety of the added components must be evaluated. In the case of plant sterols, oxidation is the reaction of main concern. In vitro studies have indicated that cholesterol oxides may have harmful effects. Due their structural similarity, plant sterol oxidation products may have similar health implications. This study concentrated on developing high-performance liquid chromatography (HPLC) methods that enable the investigation of formation of both primary and secondary oxidation products and thus can be used for oxidation mechanism studies of plant sterols. The applicability of the methods for following the oxidation reactions of plant sterols was evaluated by using oxidized stigmasterol and sterol mixture as model samples. An HPLC method with ultraviolet and fluorescence detection (HPLC-UV-FL) was developed. It allowed the specific detection of hydroperoxides with FL detection after post-column reagent addition. The formation of primary and secondary oxidation products and amount of unoxidized sterol could be followed by using UV detection. With the HPLC-UV-FL method, separation between oxides was essential and oxides of only one plant sterol could be quantified in one run. Quantification with UV can lead to inaccuracy of the results since the number of double bonds had effect on the UV absorbance. In the case of liquid chromatography-mass spectrometry (LC-MS), separation of oxides with different functionalities was important because some oxides of the same sterol have similar molecular weight and moreover epimers have similar fragmentation behaviour. On the other hand, coelution of different plant sterol oxides with the same functional group was acceptable since they differ in molecular weights. Results revealed that all studied plant sterols and cholesterol seem to have similar fragmentation behaviour, with only relative ion abundances being slightly different. The major advantage of MS detection coupled with LC separation is the capability to analyse totally or partly coeluting analytes if these have different molecular weights. The HPLC-UV-FL and LC-MS methods were demonstrated to be suitable for studying the photo-oxidation and thermo-oxidation reactions of plant sterols. The HPLC-UV-FL method was able to show different formation rates of hydroperoxides during photo-oxidation. The method also confirmed that plant sterols have similar photo-oxidation behaviour to cholesterol. When thermo-oxidation of plant sterols was investigated by HPLC-UV-FL and LC-MS, the results revealed that the formation and decomposition of individual hydroperoxides and secondary oxidation products could be studied. The methods used revealed that all of the plant sterols had similar thermo-oxidation behaviour when compared with each other, and the predominant reactions and oxidation rates were temperature dependent. Overall, these findings showed that with these LC methods the oxidation mechanisms of plant sterols can be examined in detail, including the formation and degradation of individual hydroperoxides and secondary oxidation products, with less sample pretreatment and without derivatization.

The mechanism of manganese electrodeposition

The mechanism of manganese electrodeposition from a sulphate bath on to a stainless-steel substrate has been studied by using current efficiency data to resolve the totali-E curves. A simple, two-step electron transfer mechanism:is proposed to explain the following experimentally obtained parameters: cathodic and anodic transfer coefficients, reaction order and stoichiometric number. The mechanism also explains the effect of pH oni o,Mn and on the corrosion currents.

Neutrinos and Thermal Leptogenesis

One of the unanswered questions of modern cosmology is the issue of baryogenesis. Why does the universe contain a huge amount of baryons but no antibaryons? What kind of a mechanism can produce this kind of an asymmetry? One theory to explain this problem is leptogenesis. In the theory right-handed neutrinos with heavy Majorana masses are added to the standard model. This addition introduces explicit lepton number violation to the theory. Instead of producing the baryon asymmetry directly, these heavy neutrinos decay in the early universe. If these decays are CP-violating, then they produce lepton number. This lepton number is then partially converted to baryon number by the electroweak sphaleron process. In this work we start by reviewing the current observational data on the amount of baryons in the universe. We also introduce Sakharov's conditions, which are the necessary criteria for any theory of baryogenesis. We review the current data on neutrino oscillation, and explain why this requires the existence of neutrino mass. We introduce the different kinds of mass terms which can be added for neutrinos, and explain how the see-saw mechanism naturally explains the observed mass scales for neutrinos motivating the addition of the Majorana mass term. After introducing leptogenesis qualitatively, we derive the Boltzmann equations governing leptogenesis, and give analytical approximations for them. Finally we review the numerical solutions for these equations, demonstrating the capability of leptogenesis to explain the observed baryon asymmetry. In the appendix simple Feynman rules are given for theories with interactions between both Dirac- and Majorana-fermions and these are applied at the tree level to calculate the parameters relevant for the theory.

Kinetics and Mechanism of the Transformation of Vaterite to Calcite

The transformation of vaterite to calcite was investigated systematically. The transition temperature and the energetics of the transformation were determined from differential thermal curves. The variations of lattice constants and crystallite size, accompanying the transformation were studied by X-ray diffractometry. The kinetics of transformation were investigated in the temperature range 460–490°C. The kinetic data were analysed with the help of three separate solid-state models.

Mechanism of adsorption effects on electrode kinetics: Part I: Selection rules in the case of low coverage by molecular surfactants

It is shown that the effect of adsorption of inert molecules on electrode reaction rates is completely accounted for, by introducing into the rate equation, adsorption-induced changes in both the effective electrode area as well as in the electrostatic potential at the reaction site with an additional term for the noncoulombic interaction between the reactant and the adsorbate. The electrostatic potential at the reaction site due to the adsorbed layer is calculated using a model of discretely-distributed molecules in parallel orientation when adsorbed on the electrode with an allowance for thermal agitation. The resulting expression, which is valid for the limiting case of low coverages, is used to predict the types of molecular surfactants that are most likely to be useful for acceleration and inhibition of electrode reactions.

Mechanism of vapour phase oxidation of anthracene over cobalt molybdate catalyst

Vapour phase oxidation of anthracene over cobalt molybdate catalyst was investigated in an isothermal flow reactor in the temperature range of 280—340°C. Fifteen different models based on redox, Langmuir—Hinshelwood and Rideal mechanisms were tested in order to elucidate the mechanism of the above reaction. These models were compared on the basis of three criteria and were finally discriminated employing the non-intrinsic parameter method. Two-stage redox mechanism was found to explain the data satisfactorily.

Studies on the Mechanism of Action of Miconazole: Effect of Miconazole on Respiration and Cell Permeability of Candida albicans

The antifungal drug, miconazole nitrate, inhibits the growth of several species of Candida. Candida albicans, one of the pathogenic species, was totally inhibited at a concentration of approximately 10 μg/ml. Endogenous respiration was unaffected by the drug at a concentration as high as 100 μg/ml, whereas exogenous respiration was markedly sensitive and inhibited to an extent of 85%. The permeability of the cell membrane was changed as evidenced by the leakage of 260-nm absorbing materials, amino acids, proteins, and inorganic cations. The results we present clearly show that the drug alters the cellular permeability, and thus the exogenous respiration becomes sensitive to the drug.