Unipolar transport and shot noise in metal-semiconductor-metal structures

We carry out a self-consistent analytical theory of unipolar current and noise properties of metal-semiconductor-metal structures made of highly resistive semiconductors in the presence of an applied bias of arbitrary strength. By including the effects of the diffusion current we succeed in studying the whole range of carrier injection conditions going from low level injection, where the structure behaves as a linear resistor, to high level injection, where the structure behaves as a space charge limited diode. We show that these structures display shot noise at the highest voltages. Remarkably the crossover from Nyquist noise to shot noise exhibits a complicated behavior with increasing current where an initial square root dependence (double thermal noise) is followed by a cubic power law.

Transport properties across the La2/3Ca1/3MnO3/SrTiO3 heterointerface

The transport properties across La2/3Ca1/3MnO3/SrTiO3 (LCMO/STO) heterostructures with different thicknesses of the STO insulating barrier have been studied by using atomic force microscopy measurements in the current sensing (CS) mode. To avoid intrinsic problems of the CS method we have developed a nanostructured contact geometry of Au dots. The conduction process across the LCMO/STO interface exhibits the typical features of a tunneling process.

Electrical transport quantum effects in the In0.53Ga0.47As/In0.52Al0.48As heterostructure on silicon

Electrical transport in a modulation doped heterostructure of In0.53Ga0.47As/In0.52Al0.48As grown on Si by molecular beam epitaxy has been measured. Quantum Hall effect and Subnikov¿De Haas oscillations were observed indicating the two¿dimensional character of electron transport. A mobility of 20¿000 cm2/V¿s was measured at 6 K for an electron sheet concentration of 1.7×1012 cm¿2. Transmission electron microscopy observations indicated a significant surface roughness and high defect density of the InGaAs/InAlAs layers to be present due to the growth on silicon. In addition, fine¿scale composition modulation present in the In0.53Ga0.47As/In0.52Al0.48As may further limit transport properties.

Transport of a biocontrol Pseudomonas fluorescens through 2.5-m deep outdoor lysimeters and survival in the effluent water

Application of wild-type or genetically-modified bacteria to the soil environment entails the risk of dissemination of these organisms to the groundwater. To measure vertical transport of bacteria under natural climatic conditions, Pseudomonas fluorescens strain CHA0 was released together with bromide as a mobile tracer at the surface of large outdoor lysimeters. Two experiments, one starting in autumn 1993 and the other in spring 1994 were performed. Shortly after a heavy rainfall in late spring 1994, the released bacteria were detected for the first time in effluent water from the 2.5-m-deep lysimeters in both experiments, i.e. 210 d and 21 d, respectively, after inoculation. Only a 10−9 to 10−8 fraction of the inoculum was recovered as culturable cells in the effluent water, but a larger fraction of the CHA0 cells was in a non-culturable state as detected with immunofluorescence microscopy. As much as 50% of the mobile tracer percolated through the lysimeters, indicating that, compared with bromide, bacterial cells were retained in soil. In the second part of this study, persistence of CHA0 in groundwater microcosms consisting of lysimeter effluent water was studied for 380 d. Survival of the inoculant as culturable cells was better under anaerobic than under aerobic conditions. However, a large fraction of the cells became non-culturable in both cases. When the experiment was performed with filter-sterilized effluent water, the total count of introduced bacteria did not decline with time. In conclusion, the biocontrol strain was transported in low numbers to a potential groundwater level under natural climatic conditions, but could persist for an extended period in groundwater microcosms.

Old world arenaviruses enter the host cell via the multivesicular body and depend on the endosomal sorting complex required for transport.

The highly pathogenic Old World arenavirus Lassa virus (LASV) and the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) use α-dystroglycan as a cellular receptor and enter the host cell by an unusual endocytotic pathway independent of clathrin, caveolin, dynamin, and actin. Upon internalization, the viruses are delivered to acidified endosomes in a Rab5-independent manner bypassing classical routes of incoming vesicular trafficking. Here we sought to identify cellular factors involved in the unusual and largely unknown entry pathway of LASV and LCMV. Cell entry of LASV and LCMV required microtubular transport to late endosomes, consistent with the low fusion pH of the viral envelope glycoproteins. Productive infection with recombinant LCMV expressing LASV envelope glycoprotein (rLCMV-LASVGP) and LCMV depended on phosphatidyl inositol 3-kinase (PI3K) as well as lysobisphosphatidic acid (LBPA), an unusual phospholipid that is involved in the formation of intraluminal vesicles (ILV) of the multivesicular body (MVB) of the late endosome. We provide evidence for a role of the endosomal sorting complex required for transport (ESCRT) in LASV and LCMV cell entry, in particular the ESCRT components Hrs, Tsg101, Vps22, and Vps24, as well as the ESCRT-associated ATPase Vps4 involved in fission of ILV. Productive infection with rLCMV-LASVGP and LCMV also critically depended on the ESCRT-associated protein Alix, which is implicated in membrane dynamics of the MVB/late endosomes. Our study identifies crucial cellular factors implicated in Old World arenavirus cell entry and indicates that LASV and LCMV invade the host cell passing via the MVB/late endosome. Our data further suggest that the virus-receptor complexes undergo sorting into ILV of the MVB mediated by the ESCRT, possibly using a pathway that may be linked to the cellular trafficking and degradation of the cellular receptor.

Measuring conduct and cost parameters in the Spanish air transport market

This paper estimates a model of airline competition for the Spanish air transport market. I test the explanatory power of alternative oligopoly models with capacity constraints. In addition, I analyse the degree of density economies. Results show that Spanish airlines conduct follows a price-leadership scheme so that it is less competitive than the Cournot solution. I also find evidence that thin routes can be considered as natural monopolies

Agricultural phosphorus and water quality : sources, transport and management

Selostus: Maatalous, fosfori ja veden laatu: alkuperä, kulkeutuminen ja vesistökuormituksen hallinta

Case management for frequent users of the emergency department: study protocol of a randomised controlled trial.

BACKGROUND: We devised a randomised controlled trial to evaluate the effectiveness and efficiency of an intervention based on case management care for frequent emergency department users. The aim of the intervention is to reduce such patients' emergency department use, to improve their quality of life, and to reduce costs consequent on frequent use. The intervention consists of a combination of comprehensive case management care and standard emergency care. It uses a clinical case management model that is patient-identified, patient-directed, and developed to provide high intensity services. It provides a continuum of hospital- and community-based patient services, which include clinical assessment, outreach referral, and coordination and communication with other service providers. METHODS/DESIGN: We aim to recruit, during the first year of the study, 250 patients who visit the emergency department of the University Hospital of Lausanne, Switzerland. Eligible patients will have visited the emergency department 5 or more times during the previous 12 months. Randomisation of the participants to the intervention or control groups will be computer generated and concealed. The statistician and each patient will be blinded to the patient's allocation. Participants in the intervention group (N = 125), additionally to standard emergency care, will receive case management from a team, 1 (ambulatory care) to 3 (hospitalization) times during their stay and after 1, 3, and 5 months, at their residence, in the hospital or in the ambulatory care setting. In between the consultations provided, the patients will have the opportunity to contact, at any moment, the case management team. Participants in the control group (N = 125) will receive standard emergency care only. Data will be collected at baseline and 2, 5.5, 9, and 12 months later, including: number of emergency department visits, quality of life (EuroQOL and WHOQOL), health services use, and relevant costs. Data on feelings of discrimination and patient's satisfaction will also be collected at the baseline and 12 months later. DISCUSSION: Our study will help to clarify knowledge gaps regarding the positive outcomes (emergency department visits, quality of life, efficiency, and cost-utility) of an intervention based on case management care. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01934322.

Selection methods regulate evolution of cooperation in digital evolution.

A key, yet often neglected, component of digital evolution and evolutionary models is the 'selection method' which assigns fitness (number of offspring) to individuals based on their performance scores (efficiency in performing tasks). Here, we study with formal analysis and numerical experiments the evolution of cooperation under the five most common selection methods (proportionate, rank, truncation-proportionate, truncation-uniform and tournament). We consider related individuals engaging in a Prisoner's Dilemma game where individuals can either cooperate or defect. A cooperator pays a cost, whereas its partner receives a benefit, which affect their performance scores. These performance scores are translated into fitness by one of the five selection methods. We show that cooperation is positively associated with the relatedness between individuals under all selection methods. By contrast, the change in the performance benefit of cooperation affects the populations' average level of cooperation only under the proportionate methods. We also demonstrate that the truncation and tournament methods may introduce negative frequency-dependence and lead to the evolution of polymorphic populations. Using the example of the evolution of cooperation, we show that the choice of selection method, though it is often marginalized, can considerably affect the evolutionary dynamics.

Retrospective analysis of stored dried blood spots from children with cystic fibrosis and matched controls to assess the performance of a proposed newborn screening protocol in Switzerland.

BACKGROUND: Newborn screening (NBS) for Cystic Fibrosis (CF) has been introduced in many countries, but there is no ideal protocol suitable for all countries. This retrospective study was conducted to evaluate whether the planned two step CF NBS with immunoreactive trypsinogen (IRT) and 7 CFTR mutations would have detected all clinically diagnosed children with CF in Switzerland. METHODS: IRT was measured using AutoDELFIA Neonatal IRT-Kit in stored NBS cards. RESULTS: Between 2006 and 2009, 66 children with CF were reported, 4 of which were excluded for various reasons (born in another country, NBS at 6 months, no informed consent). 98% (61/62) had significantly higher IRT compared to matched control group. There was one false negative IRT result in an asymptomatic child with atypical CF (normal pancreatic function and sweat test). CONCLUSIONS: All children but one with atypical CF would have been detected with the planned two step protocol.