Les symptômes négatifs dans la schizophrénie, le plus souvent chroniques et prédictifs du fonctionnement actuel et futur des patients, restent actuellement difficiles à traiter tant sur le plan médicamenteux que psychothérapique. Or, il s’agit d’un groupe de symptômes vaste et hétérogène qu’il est difficile d’étudier dans son ensemble. C’est pourquoi, nous avons choisi de nous intéresser à l’un d’entre eux : l’apathie à la fois symptôme cardinal dans les descriptions précoces de la schizophrénie et symptôme transnosographique. Dans la schizophrénie, il est également admis qu’il existe des troubles de la motivation qui entrent dans la description des symptômes négatifs. Les données de la littérature suggèrent qu’il existerait uniquement sur un plan conceptuel un lien entre motivation et apathie. L’objectif principal de cette étude transversale est de rechercher s’il existe une association entre motivation et apathie chez des patients souffrant de schizophrénie. Soixante-quinze patients hospitalisés ayant un diagnostic de schizophrénie selon les critères du DSM IV, âgés de 18 à 60 ans ont été inclus. Les critères de jugement principaux sont :

– l’Apathie évaluée par deux échelles dont la « Lille Apathy Rating Scale » (LARS) ;

– la Motivation explorée par la BIRT Motivation Questionnaire (BMQ), par une échelle de sensibilité à la punition et à la récompense et par une tâche d’apprentissage par renforcement.

Les résultats montrent que les patients apathiques sont significativement moins motivés et plus sensibles à la punition que les patients non apathiques, et présentent une corrélation positive significative entre les scores obtenus à la LARS et à la BIRT (p < 0,001). Il existe donc une association entre motivation et apathie chez des patients souffrant de schizophrénie montrant que plus les patients sont apathiques, moins ils sont motivés. Une meilleure compréhension de cette symptomatologie négative doit permettre le développement de stratégies thérapeutiques spécifiques.

Objectives: Prior research has identified numerous genetic (including sex), education, health, and lifestyle factors that predict cognitive decline. Traditional model selection approaches (e.g., backward or stepwise selection) attempt to find one model that best fits the observed data, risking interpretations that only the selected predictors are important. In reality, several predictor combinations may fit similarly well but result in different conclusions (e.g., about size and significance of parameter estimates). In this study, we describe an alternative method, Information-Theoretic (IT) model averaging, and apply it to characterize a set of complex interactions in a longitudinal study on cognitive decline. Methods: Here, we used longitudinal cognitive data from 1256 late–middle aged adults from the Wisconsin Registry for Alzheimer’s Prevention study to examine the effects of sex, apolipoprotein E (APOE) ɛ4 allele (non-modifiable factors), and literacy achievement (modifiable) on cognitive decline. For each outcome, we applied IT model averaging to a set of models with different combinations of interactions among sex, APOE, literacy, and age. Results: For a list-learning test, model-averaged results showed better performance for women versus men, with faster decline among men; increased literacy was associated with better performance, particularly among men. APOE had less of an association with cognitive performance in this age range (∼40–70 years). Conclusions: These results illustrate the utility of the IT approach and point to literacy as a potential modifier of cognitive decline. Whether the protective effect of literacy is due to educational attainment or intrinsic verbal intellectual ability is the topic of ongoing work. (JINS, 2019, 25, 119–133)

In recent decades, there has been growing interest among farming and scientific communities toward integrated crop–range–livestock farming because of evidence of increased crop production, soil health, environmental services and resilience to increased climatic variability. This paper reviews studies on existing cropping systems and integrated crop–range–livestock systems across the USA which are relevant in the context of summarizing opportunities and challenges associated with implementing long-term crop–range–livestock systems research in the highly variable environment of the central High Plains. With precipitation ranging from 305 to 484mm and uncertain irrigation water supply, this region is especially vulnerable to changing moisture and temperature patterns. The results of our review indicate that diverse crop rotations, reduced soil disturbance and integrated crop–livestock systems could increase economic returns and agroecosystem resilience. Integrating agricultural system components to acquire unique benefits from small- to medium-sized operations, however, is a challenging task. This is because assessment and identification of suitable farming systems, selection of the most efficient integration scheme, and pinpointing the best management practices are crucial for successful integration of components. Effective integration requires development of evaluation criteria that incorporate the efficiency of approaches under consideration and their interactions. Therefore, establishing the basis for more sustainable farming systems in the central High Plains relies on both long-term agricultural systems research and evaluation of short-term dynamics of individual components.

Recent studies by a number of research groups have shown that the structure of epitaxial BiFeO3 (BFO) films changes drastically as a function of substrate-induced biaxial compression, with the crystal structure changing from one being nearly rhombohedral (R-like) to one being nearly tetragonal (T-like), where the “T-like” structure is characterized by a highly enhanced c/a ratio of out-of-plane c to in-plane a lattice parameters. In this work, we show that the critical compressive strain σc necessary to induce this transition can be reduced significantly by substituting 10% Ba for Bi [Bi0.9Ba0.1FeO3−δ (BBFO)] and that the “T-like” phase in both BBFO and BFO is stable up to the decomposition temperatures of the films in air. Furthermore, our results show that the BBFO solid solution shows clear ferromagnetic properties in contrast to its undoped BFO counterpart.

Eimeria maxima (Weybridge) and E. maxima (indentata) were distinguished by the electrophoretic mobility of phosphoglucomutase. This enzyme was used as a marker to detect the transfer of methyl benzoquate resistance between resistant and sensitive lines of these parasites.

Three grasses and two legumes, each at two stages of maturity, were fed to three fistulated sheep and samples of the feed, and faeces and contents of the reticulo-rumen, abomasum and ileum were collected for the determination of particle size by wet sieving. Modulus of fineness (MF) was calculated for all particulate matter that failed to pass a 0·15 mm screen. Resistance to flow from the rumen of feed particles of different sizes was also calculated.

The mean MF of the reticulo-rumen contents was 2·56 compared with 5·72 for the feed. Material leaving the rumen and found in the abomasum had a MF of 1·67 and subsequent changes were small and not significant; ileum 1·63, faeces 1·80. Particles greater than 1·18 mm passed out of the reticulo-rumen although the quantity was small (1–3%). The resistance to flow of particles of different sizes from the reticulo-rumen was closely related to particle size with no difference between grasses and legumes or between young and mature forages.

It was concluded that in modelling the flow of particles from the reticulo-rumen a non-compartmentalized approach should be adopted, but if a simple two-compartment model is required then a critical sieve size of about 1·18 mm may be useful, since less than 5% of the particulate material is retained on this sieve size.

Competition between parasite species has been predicted to be an important force shaping parasite and host ecology and evolution, although empirical data are often lacking. Using the Mus musculus-Schistosoma mansoni and Schistosoma rodhaini host-parasite systems we characterized mate choice and inter-specific competition between these two schistosome species. Simultaneous infections revealed species-specific mate preferences for both species as well as suggesting mating competition, with male S. rodhaini appearing dominant over male S. mansoni. S. rodhaini homologous pairs were also shown to have increased reproduction per paired female in the presence of a competitor in simultaneous infections. Overall total reproductive success was, however, similar between the two species under conditions of direct competition due to the greater initial infectivity of S. mansoni in comparison to S. rodhaini. Inter-specific competition was also implicated as increased parasite virulence to the host. The potential effects of such interactions on parasite and host ecology and evolution in nature are discussed.

ZnO is a very promising material for spintronics applications, with many groups reporting room temperature ferromagnetism in films doped with transition metals during growth or by ion implantation. In films doped with Mn during PLD, we find an inverse correlation between magnetization and electron density as controlled by Sn doping. The saturation magnetization and coercivity of the implanted single-phase films were both strong functions of the initial anneal temperature, suggesting that carrier concentration alone cannot account for the magnetic properties of ZnO:Mn and factors such as crystalline quality and residual defects play a role. Plausible mechanisms for the ferromagnetism include the bound magnetic polaron model or exchange is mediated by carriers in a spin-spilt impurity band derived from extended donor orbitals. Spin-dependent phenomena in ZnO may lead to devices with new or enhanced functionality, such as polarized solid-state light sources and sensitive biological and chemical sensors.

The development of reliable and thermally stable Ohmic and Schottky contacts to ZnO is one of the critical issues related to the fabrication of ZnO-based UV light emitters/detectors and field effect transistors. To date, a number of different metallization schemes and surface cleaning procedures prior to metal deposition have been examined for rectifying contacts on n-ZnO. While these reports have shown that low reactive metals such as Au, Ag and Pd form rectifying contacts with Schottky barrier heights in the 0.6-0.8 eV range, the thermal stability of these contacts is usually extremely poor, with degradation occurring even at 60°C for Au/n-ZnO. One approach to achieving increased barrier heights that has proven successful for GaAs, InP, InGaAs and other compound semiconductors is the use of cryogenic deposition temperatures. In this context, we report in this work on the effect of cryogenic temperature metal deposition on the contact properties of Pd, Pt, Ti, and Ni on single-crystal n-type ZnO. Deposition at both room and low temperature produced contacts with Ohmic characteristics for Ti and Ni metallizations. In comparison, both Pd and Pt contacts showed rectifying characteristics after deposition. All rectifying contacts exhibited barrier heights around 1-2 eV and idealities between 1 and 2. Low temperature deposition gave higher resistances in comparison to room temperature deposition for all cases. Larger contacts also corresponded to an increase in resistance. Changes in contact behavior were measured on Pd to anneal temperatures of ∼300°C, showing an increase in barrier height along with a decrease in ideality with increasing temperature. This difference with annealing temperature is in sharp contrast to previous results for Au contacts to ZnO. There were no differences in near-surface stoichiometry for the different deposition temperatures; however low temperature contacts demonstrated some cracking in Pt and Pd, probably due to surface stress.

The development of new etching and contact metallurgies for the ZnO/ZnMgO/ZnCdO materials system and various approaches for realizing ZnO LEDs are reviewed. ZnO nanorod MOSFETs and pH sensors have been demonstrated. In addition, selective detection of hydrogen with Pt-coated single ZnO nanorods is discussed discussed. The Pt-coated single nanorods show a current response approximately a factor of three larger at room temperature upon exposure to 500ppm H2 in N2 than thin films of ZnO. The power consumption of these sensors can be very small (in the nW range) when using discontinuous coatings of Pt. Once the Pt coating becomes continuous, the current required to operate the sensors increases to the μW range. The ZnO nanorods are insensitive to oxygen in the measurement ambient.

This paper reviews of some of the progress made in the development of ZnO-based light emitting diodes (LEDs). n-ZnO/p-AlGaN-based heterostructures have been successfully for the fabrication of UV emitting LEDs that have operated at temperatures up to 650K, suggesting an excitonic origin for the optical transitions. RF-plasma-assisted molecular beam epitaxy has been used to grow epitaxial CdxZn1-xO films on GaN/sapphire structure. These films have a single-crystal wurtzite structure as demonstrated by structural and compositional analysis. High quality CdxZn1-xO films were grown with up to x=0.78 mole fraction as determined by RBS and SIMS techniques. Optical emission ranging from purple (Cd0.05Zn0.95O) to yellow (Cd0.29Zn0.71O) was observed. Compositional fluctuations in a Cd0.16Zn0.84O films were not detected by spatially resolved CL measurements, although intensity fluctuation with features of ∼0.5 μm diameter were seen on the intensity maps. Time resolved photoluminescence shows multi-exponential decay with 21 psec. and 49±3 psec. lifetimes, suggesting that composition micro-fluctuations may be present in Cd0.16Zn0.84O film.

ZnO thin films have been epitaxially grown on r-plane sapphire by RF-plasma-assisted molecular beam epitaxy. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies indicate that the epitaxial relationship between ZnO and r-plane sapphire is (1120)ZnO // (1102)sapphire and [0001]ZnO // [1101]sapphire. Atomic force microscopy measurements reveal islands extended along the sapphire [1101] direction. XRD omega rocking curves for the ZnO (1120) reflection measured either parallel or perpendicular to the island direction suggest the defect density anisotropy along these directions. Due to the small lattice mismatch along the ZnO [0001] direction, few misfit dislocations were observed at the ZnO/Al2O3 interface in the high-resolution cross-sectional TEM image with the zone axis along the ZnO [1100] direction.

Single ZnO nanowire metal-oxide semiconductor field effect transistors (MOSFETs) were fabricated using nanowires grown by site selective Molecular Beam Epitaxy. When measured in the dark at 25°C, the depletion-mode transistors exhibit good saturation behavior, a threshold voltage of ∼-3V and a maximum transconductance of order 0.3 mS/mm. Under ultra-violet (366nm) illumination, the drain-source current increase by approximately a factor of 5 and the maximum transconductance is ∼ 5 mS/mm. The channel mobility is estimated to be ∼3 cm2 /V.s, which is comparable to that reported for thin film ZnO enhancement mode MOSFETs and the on/off ratio was ∼25 in the dark and ∼125 under UV illumination.