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The control of Johne's disease requires the identification of Mycobacterium avium ssp. paratuberculosis (MAP)-positive herds. Boot swabs and liquid manure samples have been suggested as an easy-to-use alternative to sampling individual animals in order to diagnose subclinical Johne's disease at the herd level, but there is a need to evaluate performance of this approach in the field. Using a logistic regression model, this study aimed to calculate the threshold level of the apparent within-herd prevalence as determined by individual faecal culture, thus allowing the detection of whether a herd is MAP positive. A total of 77 boot swabs and 75 liquid manure samples were taken from 19 certified negative and 58 positive dairy herds. Faecal culture, three different polymerase chain reaction (PCR) methods and the combination of faecal culture with PCR were applied in order to detect MAP. For 50% probability of detection, a within-herd prevalence threshold of 1·5% was calculated for testing both matrices simultaneously by faecal culture and PCR, with the threshold increased to 4·0% for 90% probability of detection. The results encourage the use of boot swabs or liquid manure samples, or a combination both, for identifying MAP-positive herds and, to a certain extent, for monitoring certified Johne's disease-negative cattle herds.
Polycrystalline diamond films previously grown on silicon were polished to an RMS roughness of 15 nm and bonded to the silicon in a dedicated ultrahigh vacuum bonding chamber. Successful bonding under a uniaxial mechanical stress of 32 MPa was observed at temperatures as low as 950°C. Scanning acoustic microscopy indicated complete bonding at fusion temperatures above 1150°C. Cross-sectional transmission electron microscopy later revealed a 30 nm thick intermediate amorphous layer consisting of silicon, carbon and oxygen.
The damage introduced by CH4/H2 reactive ion etching (RIE) and its recovery after thermal annealing has been investigated by Hall measurements and low temperature photoluminescence (PL) on pseudomorphic AlGaAs/InGaAs modulation doped structures. After plasma exposure, the PL intensity has significantly decreased and shifted in energy. In order to study the recovery of the damage introduced by the plasma, thermal annealing was done at temperatures between 350 and 500°C. We observed that the luminescence emission is totally recovered after annealing at 450°C. Hall measurements at room temperature (RT) and at 77K showed that the electrical characteristics of these structures can be restored only after thermal annealing at 500°C.
The optimised etching conditions have been applied in a fabrication process for submicron dry gate recessed pseudomorphic delta-doped AlGaAs/InGaAs modulation doped field effect transistors (MODFETs). For a 0.25 mm gatelength device the maximum DC transconductance value was as high as 680 mS/mm. The same value was extracted from measurements at 15 GHz.
A new class of (meth)acrylate substituted alkoxysilanes has been developed. These are synthesized by addition of the H-S- or H-Si-unit of thiosilanes (e.g. HS- (CH2)3-SiCH3(OCH32)or hydrosila-nes to one (meth) acrylate C=C bond of commercially available di-, tri-, tetra- or penta-(meth)acrylate compounds. The alkoxysilyl groups allow the formation of an inorganic Si-O-Si-network by a hydrolysis and polycondensation reaction (sol-gel process), and the (meth)acrylate groups are available for thermally or photochemical ly induced organic polymerisation. The elegant procedure for the synthesis of a wide variety of multifunctional alkoxysilanes and the preparation of optical lenses will be discussed.
Multifunctional acrylate alkoxysilanes synthesized from commercial acrylate compounds and mercapto-substituted alkoxysilanes were used as precursors in the development of materials for various purposes. The alkoxysilyl groups are available for the construction of an inorganic backbone by the sol-gel process, and the acrylate groups for building an organic polymeric matrix by thermal or photochemical curing.
Tailoring the material properties is achieved by use of specific molecular structures and functionalities within the monomeric compounds. Linear and branched structural units influence the mechanical properties (modulus of elasticity, abrasion resistance, flexural strength). Rapidly UV-cured materials have been prepared for use as primary or secondary coatings for silica optical fibres with improved adhesion under humid conditions. Further organic modification results in polymers which can be used for manufacturing lenses of high optical quality. Preliminary attempts to draw fibres have also been successful.
Diamond nucleation has been investigated on a variety of potential heteroepitaxial substrate materials. Previous work in this laboratory has demonstrated heteroepitaxial nucleation on both Si and SiC substrates via bias-enhanced nucleation (BEN). In this study the effects of BEN of diamond on refractory metal substrates is investigated in detail. Initial data suggest a strong correlation between the carbide forming nature of the substrate material and the rate of nucleation during biasing. Our second avenue of research involves low pressure diamond growth on nickel. This material is a promising material due to its close lattice match and recent evidence of epitaxy reported by other researchers. To form heteroepitaxial diamond on nickel a high temperature pretreatment routine has been established and is the basis for this area of research. The relative importance of hydrogen absorption during this routine is explored and correlated to the formation and degree of diamond epitaxy.
Alloys based on intermetallic compounds such as Ti3Al (alpha-two), offer excellent elevated temperature strength and creep resistance. These same properties, however, combined with the susceptibility of the materials to interstitial element contamination, limit the use of “conventional” thermomechanical processing (TMP) in the production of sheet product forms. Plasma spraying of intermetallic alloys offers an alternative, near net shape processing path to produce homogeneous sheet products, having fine grained, equiaxed microstructures. This paper details the microstructural evolution and associted mechanical properties of Ti-24A1-11Nb (at.%) processed to sheet form using RF plasma spraying. The response of the microstructure/tensile properties of the plasma sprayed alpha-two to various controlled heat treatments is discussed.
This paper presents new results concerning diffusion at the interface between Al and its oxide, due to electromigration in Al interconnects. The results show that the phenomenon is an important and general one. Significant large-scale modification of the surface of Alalloy conductors was observed after electromigration stress under a wide range of different conditions: 1) in a number of different alloys (Al-Si, Al-Cu, Al-Si-V & Al-Si-V-Pd), 2) with and without passivation, 3) over an extended temperature range, 4) over an extended range of current density, and 5) with a number of different underlayers (SiO2, W-Ti (no vacuum-break before Al deposition) and W-Ti (oxidized surface before Al deposition)). After electromigration stressing, the surface showed height variations: at certain locations the original thickness remained, while at adjacent locations the thickness was reduced; as much as 150nm in 2500 hrs, for Al-Si on oxidized W-Ti metallization. Damage by thinning has received little attention in the past. Based on the results presented, a model for the underlying mechanism is proposed. In this model Al atoms diffuse concurrently along the interface between the Al-metal and its oxide, and through the grain boundaries, even at low stress conditions and in non-bamboo lines.
A new bias-enhanced nucleation method based on an AC-bias step to form highly oriented diamond (HOD) nuclei on silicon substrates is presented. The uniformity of the nucleated film and the bias time strongly depended on the substrate temperature and the substrate holder. In our case the shortest bias time and highest nucleation densities were achieved at ∼ 850°C while using a graphite susceptor. Following this nucleation enhancement step the diamond films were grown out using conditions employing an α-parameter slightly greater than 2. This ultimately leads to extremely smooth and well-faceted (100) textured HOD films which could be used as substrates for the fabrication of electronic devices.
Schottky diodes with high rectification ratios and high breakdown voltages have been fabricated for the first time via selective growth of the active boron doped diamond layers on these HOD films. Results of the growth procedure and diode performance will be given.
A novel family of inorganic-organic copolymers (ORMOCER*s) derived from urethaneand thioether(meth)acrylate alkoxysilanes has been successfully exploited for a variety of diverse applications. In order to widen the range of applications an additional functionality (carboxy group) has been incorporated in this silane type. Conventional sol-gel processing facilitates the formation of an inorganic “Si-O-Si”-network via hydrolysis and polycondensation reactions of alkoxysilyl moieties and in addition, the (meth)acrylate groups are available for radically induced polymerization to obtain a complementary organic polymeric structure. The presence of a carboxy group would appear to have great potential for a range of diverse areas of application, such as an internal catalyst for the sol-gel process, complexation of elements such as Zr and Ti, increasing the adhesion to various substrates and modification of solubility. A number of novel silanes and their syntheses will be described in this paper.
Nose, throat and finger carriage of Staphylococcus aureus was investigated in a series of random samples from a normal European population.
No evidence for a seasonal trend in carriage was found but the intersample variation between successive random samples was obtained. The mean nasal carrier rate was 29 % with a standard deviation of 7 %.
No association was found between nasal or throat carriage of staphylococci and stay in hospital or antibiotic therapy but respondents with penicillin-resistant staphylococci in the nose had skin infections more frequently than those with penicillin-sensitive strains.
Evidence was obtained for a family, perhaps genetic, ‘predisposition’ to carry staphylococci in the nose.
Techniques have been developed to produce microbial phytase for addition to diets for simple-stomached animals, with the aim to improve phosphorus availability from phytate-P in plant sources. The activityof the crude microbial phytase showed pH optima at pH 5-5 and 2·5. The enzyme was able to degradephytate in vitro in soya-bean meal, maize and a liquid compound feed for pigs. When microbial phytasewas added to low-P diets for broilers the availability of P increased to over 60 % and the amount of Pin the droppings decreased by 50%. The growth rate and feed conversion ratio on the low-P dietscontaining microbial phytase were comparable to or even better than those obtained on control diets.Addition of microbial phytase to diets for growing pigs increased the apparent absorbability of P by24%. The amount of P in the faeces was 35% lower.
The impact of the 1930s depression on the Philippines shows a mixed picture, differing according to region and social class. Most probably the Philippines as a whole suffered less than neighbouring countries. Comparative figures show that for the years 1934 to 1938, consumption levels in the Philippines were the highest in Asia outside Japan. However, national averages do not tell the whole story. Declining prices hit agrarian commodities unevenly, and as each commodity was concentrated in a particular ecological region, the regional impact of the crisis was uneven.
The economic decline in the advanced capitalist countries was transmitted to the tropical colonies through four mechanisms — the decline in trade, the change in relative prices in favour of the advanced countries, the decline in capital flows to the colonies, and finally a steep decline in the world price level. The Philippines was affected by all these mechanisms, but less severely than some of its neighbours, because its status as a colony and trading partner of the United States provided it with a number of privileges. Although the country could not escape from price declines, some of its export commodities found a protected market in the United States, enabling it to maintain export volumes and (in the case of sugar) its price level.
Trade between the Philippines and the United States had increased very considerably over the years. The Payne-Aldrich Tariff Act of 1909 and the Underwood Tariff Act of 1913 had instituted reciprocal free trade between the two countries. When the depression hit the United States, the American Government adopted various trade restrictions. The Smoot-Hawley Tariff Act of 1930 substantially increased the import duty on Cuban sugar, but not on Philippine sugar. The Jones-Costigan Act of 1934 applied quotas on sugar imports into the United States, but the Philippines received a much more favourable quota than did Cuba.
My essay in celebration of the Journal's anniversary sketches what may be the concluding chapter in a study of Vietnam in the thirteenth and fourteenth centuries when the Tran dynasty reigned (1226–1400). In 1225 the Tran family overthrew the last emperor of the previous dynasty, the Ly (1009–1225) and hitherto the only long lived one. The Ly imperial line, in fact, lasted nearly fifty years longer than its successor. Nevertheless, the Tran is unquestionably the most renowned of all Vietnamese dynasties on account of its victories when Kubilai Khan's armies attacked three times in the thirteenth century. Yet one has to ask what kind of dynasty it was and how the country it ruled should be defined. Should one look to China, the source of the dynastic institution, for guidance or should one look elsewhere? An event in 1237 suggests ambiguity. That year officials were required to offer betel and tea to the emperor when he was departing from the Eastern Pier near the capital. “Betel and tea” bring Southeast Asia as well as China into the picture.
Modifications of a recent model by Izumi et al.1 on diffusion controlled growth of YBa2Cu3O7−x (123) superconductors are proposed, taking into account especially the engulfment process of the Y2BaCuO5 (211) particles into the solidifying 123 interface. The proposed modifications are evidenced by experimental results and applied to explain microstructural features of the 123 superconducting material. In particular, the 1:1 correlation between 123 platelet thickness (planar defect spacing) and 211 particle size as described by Jin et al.2 is explained by an observed bridge growth resulting in a zipper-like mechanism. By this mechanism the platelets grow together in an oriented way leading to a quasi single crystalline material.
A continuous in vitro method for the estimation of the bioavailability of minerals and trace elements is presented. This in vitro method is believed to be more representative of in vivo physiological conditions than in vitro methods based on equilibrium dialysis, because dialysable components are continuously removed from the pancreatic digestion mixture. The continuous in vitro method is compared with the equilibrium in vitro method with respect to the dialysability of Ca, Mg, Fe, Cu and Zn from eight different types of bread (varying in phytic acid content). The results show a pronounced effect of continuous removal of dialysable components from the pancreatic digestion mixture on the dialysability of minerals and trace elements. Furthermore, removal of dialysable components influences the effect of phytic acid on the bioavailability of minerals and trace elements. For these two reasons the importance of removal of dialysable components in vitro for the estimation of bioavailahility in vivo needs further investigation. The bioavailability of minerals and trace elements from bread samples is not related to the phytic acid content only. Therefore, the effect of phytic acid on the bioavailability of minerals and trace elements cannot be studied separately from the effects of other components on bioavailability.
A group of 48 adolescents who recently attempted suicide and 66 depressed adolescents were compared on sociodemographic, behavioural, psychological and relational variables. The variables which proved significant were used in different combinations in stepwise logistic regression analyses, resulting in seven variables which served as the content of an index of risk. The sensitivity of the index was 90% and the specificity 83%. At one-year follow-up the occurrence of a suicide attempt correlated with score on the instrument.
Techniques have been developed to produce microbial phytase for addition to diets for simple-stomached animals, with the aim to improve phosphorus availability from phytate-P in plant sources. The activity of the crude microbial phytase showed pH optima at pH 5.5 and 2.5. The enzyme was able to degrade phytate in vitro in soya-bean meal, maize and a liquid compound feed for pigs. When microbial phytase was added to low-P diets for broilers the availability of P increased to over 60% and the amount of P in the droppings decreased by 50%. The growth rate and feed conversion ratio on the low-P diets containing microbial phytase were comparable to or even better than those obtained on control diets. Addition of microbial phytase to diets for growing pigs increased the apparent absorbability of P by 24%. The amount of P in the faeces was 35% lower.