Entropically stabilized local dipole formation in lead chalcogenides

We report the observation of local structural dipoles that emerge from an undistorted ground state on warming, in contrast to conventional structural phase transitions in which distortions emerge on cooling. Using experimental and theoretical probes of the local structure, we demonstrate this behavior in binary lead chalcogenides, which were believed to adopt the ideal, undistorted rock-salt structure at all temperatures. The behavior is consistent with a simple thermodynamic model in which the emerging dipoles are stabilized in the disordered state at high temperature due to the extra configurational entropy despite the fact that the undistorted structure has lower internal energy. Our findings shed light on the anomalous electronic and thermoelectric properties of the lead chalcogenides. Similar searches may show that the phenomenon is more widespread.     

A cost/benefit study of paratuberculosis certification in French cattle herds

Paratuberculosis has received increasing attention in France because of the important losses this disease may provoke. The use of certification schemes has proven its effectiveness for the protection of healthy herds against diseases transmitted mainly by trade. The economic justification of such schemes in the particular case of paratuberculosis is studied, for French cattle herds, using a cost/benefit approach. The basic economical hypotheses and estimates have been proposed and carefully examined by a working group composed of paratuberculosis experts and field specialists. By adopting the point of view of a breeder that buys animals, we first estimated the benefits resulting from the non-introduction of the disease. They were then compared with the costs resulting from the fact that the vendor reports its own certification costs on the price of the animals he sells. Two average herds (the mean French beef herd and the mean French dairy herd), and two certification levels were studied. The results show that, currently, the use of the certification is not very economically profitable in French cattle herds. This conclusion, however should be reappraised if the certification costs decrease, for example with the commercialization of diagnostic tests on mixtures.     

Trial design to estimate the effect of vaccination on tuberculosis incidence in badgers

The principal wildlife reservoir of Mycobacterium bovis in Ireland is the European badger. Studies in the Republic of Ireland (RoI) have shown that badgers culled in association with cattle herd tuberculosis breakdowns (focal culling) have a higher prevalence of infection than the badger population at large. This observation is one rationale for the medium term national strategy of focal badger culling. A vaccination strategy for the control of bovine tuberculosis (bTB) in badgers is a preferred long-term option. The Bacillus Calmette-Guérin (BCG) vaccine has been shown to decrease disease severity in captive badgers under controlled conditions. As the vaccine has been tested in a controlled environment with precise information on infection pressure, it cannot be assumed a priori that the effects of vaccination are similar in the wild, where other environmental and/or ecological factors prevail. For this reason we have designed a vaccine field trial to assess the impact of vaccination on the incidence of TB infection in a wild badger population. The selected study area for the vaccine trial (approximately 755 square kilometers) is divided into three zones each of which has similar characteristics in terms of size, number of main badger setts, cattle herds, cattle and land classification type. Three vaccination levels (100%, 50% and 0%) will be allocated to the three zones in a way that a gradient of vaccination coverage North to South is achieved. The middle zone (zone B) will be vaccinated at a 50% coverage but zone A and C will be randomly allocated with 100% or 0% vaccination coverage. Vaccination within zone B will be done randomly at individual badger level. The objective of this paper is to describe the design of a field tuberculosis vaccination trial for badgers, the epidemiological methods that were used to design the trial and the subsequent data analysis. The analysis will enable us to quantify the magnitude of the observed vaccination effect on M. bovis transmission in badgers under field conditions and to improve our knowledge of the biological effects of vaccination on susceptibility and infectiousness.     

Predicting the potential geographic distribution of Bactrocera bryoniae and Bactrocera neohumeralis(Diptera: Tephritidae) in China using MaxEnt ecological niche modeling

Bactrocera bryoniae and Bactrocera neohumeralis are highly destructive and major biosecurity/quarantine pests of fruit and vegetable in the tropical and subtropical regions in the South Pacific and Australia. Although these pests have not established in China, precautions must be taken due to their highly destructive nature. Thus, we predicted the potential geographic distribution of B. bryoniae and B. neohumeralis across the world and in particular China by ecological niche modeling of the Maximum Entropy(Max Ent) model with the occurrence records of these two species. Bactrocera bryoniae and B. neohumeralis exhibit similar potential geographic distribution ranges across the world and in China, and each species was predicted to be able to distribute to over 20% of the globe. Globally, the potential geographic distribution ranges for these two fruit fly species included southern Asia, the central and the southeast coast of Africa, southern North America, northern and central South America, and Australia. While within China, most of the southern Yangtze River area was found suitable for these species. Notably, southern China was considered to have the highest risk of B. bryoniae and B. neohumeralis invasions. Our study identifies the regions at high risk for potential establishment of B. bryoniae and B. neohumeralis in the world and in particular China, and informs the development of inspection and biosecurity/quarantine measures to prevent and control their invasions.     

Impact of vitronectin concentration and surface properties on the stable propagation of human embryonic stem cells

The standard method for culturing human embryonic stem cells (hESC) uses supporting feeder layers of cells or an undefined substrate, Matrigel(?), which is a basement membrane extracted from murine sarcoma. For stem cell therapeutic applications, a superior alternative would be a defined, artificial surface that is based on immobilized human plasma vitronectin (VN), which is an adhesion-mediating protein. Therefore, VN adsorbed to diverse polymer surfaces was explored for the continuous propagation of hESC. Cells propagated on VN-coated tissue culture polystyrene (TCPS) are karyotypically normal after >10 passages of continuous culture, and are able to differentiate into embryoid bodies containing all three germ layers. Expansion rates and pluripotent marker expression verified that a minimal VN surface density threshold is required on TCPS. Further exploration of adsorbed VN was conducted on polymer substrates with different properties, ranging from hydrophilic to hydrophobic and including cationic and anionic polyelectrolyte coatings. Despite differing surface properties, these substrates adsorbed VN above the required surface density threshold and were capable of supporting hESC expansion for >10 passages. Correlating wettability of the VN-coated surfaces with the response of cultured hESC, higher cell expansion rates and OCT-4 expression levels were found for VN-coated TCPS, which exhibits a water contact angle close to 65°. Importantly, this simple, defined surface matches the performance of the benchmark Matrigel, which is a hydrogel with highly complex composition.     

Laboratory studies with antifeedants against larvae of Boarmia (Ascotis) selenaria on alfalfa

The antifeedant effect of five organotin compounds (fentin acetate, fentin hydroxide, fentin chloride, cyhexatin and fenbutatin oxide) and of three other compounds known to possess antifeeding activity (guazatine triacetate, 4′-chloroacetophenone isobutyrylhydrazone and thiram) was investigated by feeding treated alfalfa to larvae of Boarmia selenaria. The three fentins and cyhexatin were highly active at 0.1 g litre^?1, the order of activity at this concentration being fentin chloride > fentin hydroxide > fentin acetate ? cyhexatin, whereas the other compounds were practically inactive at either this or a somewhat higher concentration (0.5 g litre^?1). Guazatine triacetate had a concentration-independent antifeedant effect at much higher concentrations (5–20 g litre^?1).