Tracking and Data Relay Satellite System (TDRSS)

The DSN (Deep Space Network) mission support requirements for the Tracking and Data Relay Satellite System (TDRSS) are summarized. The TDRSS consists of four identical satellites in geosynchronous orbits (35,800 km) and a dedicated ground station. The payload of each satellite is a telecommunications service system that relays communication signals between low earth-orbiting user spacecraft and the TDRSS ground terminal. Mission objectives are outlined and the DSN support requirements are defined through the presentation of tables and narratives describing the spacecraft flight profile; DSN support coverage; frequency assignments; support parameters for telemetry, command and support systems; and tracking support responsibility

P-I-N diode switch

Solid state switches use the same voltage and power supply as the RF amplifier. This simplifies circuit design and reduces input power requirements

Climate Change in the High Andes:implications and adaptation strategies for small-scale farmers

Abstract: Global climate change represents a major threat to sustainable farming in the Andes. Farmers have used local ecological knowledge and intricate production systems to cope, adapt and reorganize to meet climate uncertainty and risk, which have always been a fact of life. Those traditional systems are generally highly resilient, but the predicted effects, rates and variability of climate change may push them beyond their range of adaptability. This article examines the extent of actual and potential impacts of climate variability and change on small-scale farmers in the highland Andes of Bolivia, Ecuador and Peru. It describes how climate change impacts agriculture through deglaciation, changes in hydrology, soil and pest and disease populations. The article highlights some promising adaptive strategies currently in use by or possible for producers, rural communities and local institutions to mitigate climate change effects while preserving the livelihoods and environmental and social sustainability of the regio

Inhibitors of \u3cem\u3eN\u3csup\u3eα\u3c/sup\u3e\u3c/em\u3e-acetyl-l-ornithine Deacetylase: Synthesis, Characterization and Analysis of their Inhibitory Potency

A series of N α-acyl (alkyl)- and N α-alkoxycarbonyl-derivatives of l- and d-ornithine were prepared, characterized, and analyzed for their potency toward the bacterial enzyme N α-acetyl-l-ornithine deacetylase (ArgE). ArgE catalyzes the conversion of N α-acetyl-l-ornithine to l-ornithine in the fifth step of the biosynthetic pathway for arginine, a necessary step for bacterial growth. Most of the compounds tested provided IC50 values in the μM range toward ArgE, indicating that they are moderately strong inhibitors. N α-chloroacetyl-l-ornithine (1g) was the best inhibitor tested toward ArgE providing an IC50 value of 85 μM while N α-trifluoroacetyl-l-ornithine (1f), N α-ethoxycarbonyl-l-ornithine (2b), and N α-acetyl-d-ornithine (1a) weakly inhibited ArgE activity providing IC50 values between 200 and 410 μM. Weak inhibitory potency toward Bacillus subtilis-168 for N α-acetyl-d-ornithine (1a) and N α-fluoro- (1f), N α-chloro- (1g), N α-dichloro- (1h), and N α-trichloroacetyl-ornithine (1i) was also observed. These data correlate well with the IC50 values determined for ArgE, suggesting that these compounds might be capable of getting across the cell membrane and that ArgE is likely the bacterial enzymatic target

Air Toxics under the Big Sky: A Real-World Investigation To Engage High School Science Students

This paper describes a problem-based chemistry education model in which students perform scientific research on a local environmentally relevant problem. The project is a collaboration among The University of Montana and local high schools centered around Missoula, Montana. Air Toxics under the Big Sky involves high school students in collecting air samples inside and outside their homes within and near Missoula. As part of this program, teachers, students, and university researchers investigate the relationship between air pollutants and their harmful respiratory effects. Students experience scientific research, use scientific equipment, gain an insight into the relationship between the environment and public health, and develop scientific hypotheses. UM benefits by having a pipeline of high school students, several of whom participated in the program while in high school and now attend UM. The local community benefits from the work students and university researchers have done producing high-quality data that are being used in a tracking database for respiratory disease in western Montana. Student research efforts have culminated in three annual symposia that allowed students to present their results at a public forum

Histocompatibility and liver transplant outcome. Does HLA exert a dualistic effect?

An analysis of more than 500 liver transplants has demonstrated that HLA compatibility is associated with diminished allograft survival. Liver transplants with zero mismatches for class I and/or class II HLA antigens have shown significantly lower acturial survival rates than transplants with one or more mismatches for these loci. In a group of 199 failed liver allografts from patients undergoing retransplantation, a higher incidence of failure due to rejection correlated with a lower degree of HLA compatibility especially for HLA-DR. In contrast, the incidence of liver transplant failures due to primary nonfunction was relatively higher with HLA-DR compatible transplants. Considering the role of HLA as a restriction element in cellular interactions during the immune response, these findings suggest that HLA compatibility may have a dualistic effect on liver transplant outcome. On one hand, HLA compatibility reduced transplant rejection - and on the other hand, it may enhance other immunological mechanisms leading to allograft dysfunction, particularly in patients at risk of developing recurrent autoimmune diseases or infection

Facilitative effects of learner-directed codeswitching : Evidence from Chinese learners of English

This study examines the interaction between learner-oriented codeswitching (CS) practices and the degree to which intermediate Chinese L2 learners of English engage in classroom interaction. The guiding questions are whether the teacher's CS use facilitates classroom interaction at moderate L2 proficiency, and if so, at which specific stages of the lesson, and to what extent. A systematic comparison of two classroom types was carried out in the same Chinese secondary school, with English-only instruction versus with English–Chinese CS. A combination of quantitative and qualitative analyses was based on class observations (two classes per type) and subsequent teacher interviews. CS behaviour was analysed in relation to the particular teaching focus of the task at hand. Interviews included a stimulated recall technique using selected CS extracts to enrich insights from the teachers' perspective. The results showed a higher student response frequency as well as a longer mean utterance length in CS classes. Overall, codeswitches were systematically distributed across lesson stages and were closely related to changes in the teaching focus. These findings call for an optimal use of CS in instructed environments so as to maximise its benefits via a sensitive adjustment to specific pedagogic aims

Inter-community and on-farm asymmetric organic matter allocation patterns drive soil fertility gradients in a rural Andean landscape

Soil fertility in agricultural landscapes is driven by complex interactions between natural and anthropogenic processes, with organic matter (OM) inputs playing a critical role. Asymmetric allocation patterns of these resources among communities and within individual farms can lead to soil fertility gradients. However, the drivers and consequences of such patterns in different socioecological contexts remains poorly documented and understood. The objective of this study was to address this gap by assessing asymmetric OM allocation patterns and the associated consequences for soil fertility management in three indigenous communities located in the Central Ecuadorian Andes. We found that both distance from homestead and perception of fertility were associated with asymmetric OM allocation patterns to fields as well as with soil fertility gradients within farms. For example, soil organic carbon (SOC), total nitrogen (N), available phosphorus (P), and exchangeable potassium (K) all decreased with distance from the homestead, while SOC, total N, and available P were positively correlated with a farmer's perception of soil fertility. We note that these fertility gradients remained even in the case of increased farm-level OM inputs. Overall OM allocation patterns differed significantly among communities and were associated with significant differences in soil fertility, with the highest levels of available P and exchangeable K found in the community with the highest OM inputs. The results of this study indicate the importance of asymmetric OM allocation patterns encountered at different scales, both within farms and among neighboring communities, in rural Andean landscapes and their significant interactions with soil fertility gradients.</p

The T2K ND280 Off-Axis Pi-Zero Detector

The Pi-Zero detector (P{\O}D) is one of the subdetectors that makes up the off-axis near detector for the Tokai-to-Kamioka (T2K) long baseline neutrino experiment. The primary goal for the P{\O}D is to measure the relevant cross sections for neutrino interactions that generate pi-zero's, especially the cross section for neutral current pi-zero interactions, which are one of the dominant sources of background to the electron neutrino appearance signal in T2K. The P{\O}D is composed of layers of plastic scintillator alternating with water bags and brass sheets or lead sheets and is one of the first detectors to use Multi-Pixel Photon Counters (MPPCs) on a large scale.Comment: 17 pages, submitted to NIM