The observation and simulation of diurnal surface thermal contrast in an Alaskan alpine pass

A simple surface climate simulator was employed in the analysis of thermal regimes in rough alpine terrain at Chitistone Pass, Alaska. The simulator favorably abstracts observations of thermal regimes on flat and sloping surfaces with variable thermal and radiative properties. It is shown that slope and exposure control variations in surface thermal regimes. The simulator predicts these controls and it is suggested that simulation of surface thermal regimes can be performed before and after field investigations, thus increasing the effective information content of thermal maps acquired using aircraft and orbital platforms. It is concluded that the removal by spatial filtering of the low frequency effects of slope and exposure on thermal maps is necessary before site material effects can be discriminated and analyzed. Ein einfaches Rechenmodell des Bodenklimas wurde auf die Analyse des Temperaturregimes im unebenen Terrain des Chitistone-Passes in Alaska angewandt. Das Modell bildet die beobachteten Temperaturregime ebener und geneigter Bodenflächen mit veränderlichen Wärmeleit- und Strahlungscharakteristiken zufriedenstellend ab. Es wird gezeigt, daß Hangneigung und Hanglage im wesentlichen das Bodentemperaturregime bedingen. Das Modell sagt diese Bedingungsfaktoren richtig voraus. Es wird daher vorgeschlagen, daß Modellrechnungen vor und nach Feldmessungen angestellt werden sollten, um den effektiven Informationsgehalt der Temperaturverteilungskarten zu erhöhen, die von Flugzeugen oder Satelliten vermessen wurden. Es wird darauf hingewiesen, daß die Unterdrückung niederfrequenter Effekte von Hangneigung und Hanglage auf die kartographisch festgehaltene Temperaturverteilung notwendig ist, bevor Bodenbeschaffenheitseffekte diskriminiert und analysiert werden können. Diese Unterdrückung kann durch räumliche Filterung geschehen.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41669/1/704_2005_Article_BF02243725.pd

Ballistic-electron-emission spectroscopy of Al<SUB>x</SUB>Ga<SUB>1-x</SUB>As/GaAs heterostructures: conduction-band offsets, transport mechanisms, and band-structure effects

We report an extensive investigation of semiconductor band-structure effects in single-barrier AlxGa1-xAs/GaAs heterostructures using ballistic-electron-emission spectroscopy (BEES). The transport mechanisms in these single-barrier structures were studied systematically as a function of temperature and Al composition over the full compositional range (0&#8804;x&#8804;1). The initial (&#915;) BEES thresholds for AlxGa1-xAs single barriers with 0&#8804;x&#8804;0.42 were extracted using a model which includes the complete transmission probability of the metal-semiconductor interface and the semiconductor heterostructure. Band offsets measured by BEES are in good agreement with previous measurements by other techniques which demonstrates the accuracy of this technique. BEES measurements at 77 K give the same band-offset values as at room temperature. When a reverse bias is applied to the heterostructures, the BEES thresholds shift to lower voltages in good agreement with the expected bias-induced band-bending. In the indirect band-gap regime (x&gt;0.45), spectra show a weak ballistic-electron-emission microscopy current contribution due to intervalley scattering through AlxGa1-xAs X valley states. Low-temperature spectra show a marked reduction in this intervalley current component, indicating that intervalley phonon scattering at the GaAs/AlxGa1-xAs interface produces a significant fraction of this X valley current. A comparison of the BEES thresholds with the expected composition dependence of the AlxGa1-xAs &#915;, L, and X points yields good agreement over the entire composition range

Effects of Human Choices on Characteristics of Urban Ecosystems

Most urban ecology in cities remains an ecology in cities rather than an ecology of cities. Accomplishing the latter requires the inclusion of humans within the concept of ecosystem, both how humans alter the properties of urban ecosystems and how these alterations in turn influence human well-being. These influences are both direct (e.g., physiological and psychological influences on the human organism) and indirect, by influencing ecosystem sustainability. For the 2007 ESA meeting, Larry Baker, Loren Byrne, Jason Walker, and Alex Felson organized a symposium to address the relationships among human choices and urban ecosystems. In the introductory talk of this symposium, these authors discussed how the cumulative effect of individual household choices can have major effects on the properties of urban ecosystems

The Role of luxS in the Middle Ear Streptococcus pneumoniae Isolate 947

The LuxS protein, encoded by luxS, is required for the production of autoinducer 2 (AI-2) in Streptococcus pneumoniae. The AI-2 molecule serves as a quorum sensing signal, and thus regulates cellular processes such as carbohydrate utilisation and biofilm formation, as well as impacting virulence. The role of luxS in S. pneumoniae biology and lifestyle has been predominantly assessed in the laboratory strain D39. However, as biofilm formation, which is regulated by luxS, is critical for the ability of S. pneumoniae to cause otitis media, we investigated the role of luxS in a middle ear isolate, strain 947. Our results identified luxS to have a role in prevention of S. pneumoniae transition from colonisation of the nasopharynx to the ear, and in facilitating adherence to host epithelial cells.Alexandra Tikhomirova, Erin B. Brazel, Kimberley T. McLean, Hannah N. Agnew, James C. Paton and Claudia Trappett

Streptococcus pneumoniae Strains Isolated From a Single Pediatric Patient Display Distinct Phenotypes

Streptococcus pneumoniae is the leading cause of bacterial paediatric meningitis after the neonatal period worldwide, but the bacterial factors and pathophysiology that drive pneumococcal meningitis are not fully understood. In this work, we have identified differences in raffinose utilization by S. pneumoniae isolates of identical serotype and sequence type from the blood and cerebrospinal fluid (CSF) of a single pediatric patient with meningitis. The blood isolate displayed defective raffinose metabolism, reduced transcription of the raffinose utilization pathway genes, and an inability to grow in vitro when raffinose was the sole carbon source. The fitness of these strains was then assessed using a murine intranasal infection model. Compared with the CSF isolate, mice infected with the blood isolate displayed higher bacterial numbers in the nose, but this strain was unable to invade the ears of infectedmice. A premature stop codon was identified in the aga gene in the raffinose locus, suggesting that this protein likely displays impaired alpha-galactosidase activity. These closely related strains were assessed by Illumina sequencing, which did not identify any single nucleotide polymorphisms (SNPs) between the two strains. However, these wider genomic analyses identified the presence of an alternative alpha-galactosidase gene that appeared to display altered sequence coverage between the strains, which may account for the observed differences in raffinose metabolic capacity. Together, these studies support previous findings that raffinose utilization capacity contributes to disease progression, and provide insight into a possible alternative means by which perturbation of this pathway may influence the behavior of pneumococci in the host environment, particularly in meningitis.Hannah N. Agnew, Erin B. Brazel, Alexandra Tikhomirova, Mark van der Linden, Kimberley T. McLean, James C. Paton, and Claudia Trappett

Dietary zinc and the control of Streptococcus pneumoniae infection

© 2019 Eijkelkamp et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Human zinc deficiency increases susceptibility to bacterial infection. Although zinc supplementation therapies can reduce the impact of disease, the molecular basis for protection remains unclear. Streptococcus pneumoniae is a major cause of bacterial pneumonia, which is prevalent in regions of zinc deficiency. We report that dietary zinc levels dictate the outcome of S. pneumoniae infection in a murine model. Dietary zinc restriction impacts murine tissue zinc levels with distribution post-infection altered, and S. pneumoniae virulence and infection enhanced. Although the activation and infiltration of murine phagocytic cells was not affected by zinc restriction, their efficacy of bacterial control was compromised. S. pneumoniae was shown to be highly sensitive to zinc intoxication, with this process impaired in zinc restricted mice and isolated phagocytic cells. Collectively, these data show how dietary zinc deficiency increases sensitivity to S. pneumoniae infection while revealing a role for zinc as a component of host antimicrobial defences

Association studies of up to 1.2 million individuals yield new insights into the genetic etiology of tobacco and alcohol use.

Tobacco and alcohol use are leading causes of mortality that influence risk for many complex diseases and disorders1. They are heritable2,3 and etiologically related4,5 behaviors that have been resistant to gene discovery efforts6-11. In sample sizes up to 1.2 million individuals, we discovered 566 genetic variants in 406 loci associated with multiple stages of tobacco use (initiation, cessation, and heaviness) as well as alcohol use, with 150 loci evidencing pleiotropic association. Smoking phenotypes were positively genetically correlated with many health conditions, whereas alcohol use was negatively correlated with these conditions, such that increased genetic risk for alcohol use is associated with lower disease risk. We report evidence for the involvement of many systems in tobacco and alcohol use, including genes involved in nicotinic, dopaminergic, and glutamatergic neurotransmission. The results provide a solid starting point to evaluate the effects of these loci in model organisms and more precise substance use measures

Oligodendrocyte differentiation from adult multipotent stem cells is modulated by glutamate

We used multipotent stem cells (MSCs) derived from the young rat subventricular zone (SVZ) to study the effects of glutamate in oligodendrocyte maturation. Glutamate stimulated oligodendrocyte differentiation from SVZ-derived MSCs through the activation of specific N-methyl--aspartate (NMDA) receptor subunits. The effect of glutamate and NMDA on oligodendrocyte differentiation was evident in both the number of newly generated oligodendrocytes and their morphology. In addition, the levels of NMDAR1 and NMDAR2A protein increased during differentiation, whereas NMDAR2B and NMDAR3 protein levels decreased, suggesting differential expression of NMDA receptor subunits during maturation. Microfluorimetry showed that the activation of NMDA receptors during oligodendrocyte differentiation elevated cytosolic calcium levels and promoted myelination in cocultures with neurons. Moreover, we observed that stimulation of MSCs by NMDA receptors induced the generation of reactive oxygen species (ROS), which were negatively modulated by the NADPH inhibitor apocynin, and that the levels of ROS correlated with the degree of differentiation. Taken together, these findings suggest that ROS generated by NADPH oxidase by the activation of NMDA receptors promotes the maturation of oligodendrocytes and favors myelination