Preliminary candidate advanced avionics system for general aviation

An integrated avionics system design was carried out to the level which indicates subsystem function, and the methods of overall system integration. Sufficient detail was included to allow identification of possible system component technologies, and to perform reliability, modularity, maintainability, cost, and risk analysis upon the system design. Retrofit to older aircraft, availability of this system to the single engine two place aircraft, was considered

THE IMPLICATIONS OF A NORTH AMERICAN FREE TRADE AREA FOR AGRICULTURE

This is one of two papers commissioned by the International Agricultural Trade Research Consortium on various aspects related to the agricultural sector of a prospective North American Free Trade Agreement. The companion paper to this one has been prepared by a working group chaired by Thomas Grennes, North Carolina State University. To minimize duplication with the Grennes paper, this paper has given greater attention to the general trade policy issues raised by a NAFTA, institutional factors, additional commodity detail in cereals, fruit and vegetables, and the relevance of other regional trade agreements such as the Canada-U.S. Trade Agreement. This work has also benefitted from an earlier report and its annexes, prepared for the Fraser Institute, under the direction of Tim Josling.International Relations/Trade,

Flow-through Capture and in Situ Amplification Can Enable Rapid Detection of a Few Single Molecules of Nucleic Acids from Several Milliliters of Solution

Detecting nucleic acids (NAs) at zeptomolar concentrations (few molecules per milliliter) currently requires expensive equipment and lengthy processing times to isolate and concentrate the NAs into a volume that is amenable to amplification processes, such as PCR or LAMP. Shortening the time required to concentrate NAs and integrating this procedure with amplification on-device would be invaluable to a number of analytical fields, including environmental monitoring and clinical diagnostics. Microfluidic point-of-care (POC) devices have been designed to address these needs, but they are not able to detect NAs present in zeptomolar concentrations in short time frames because they require slow flow rates and/or they are unable to handle milliliter-scale volumes. In this paper, we theoretically and experimentally investigate a flow-through capture membrane that solves this problem by capturing NAs with high sensitivity in a short time period, followed by direct detection via amplification. Theoretical predictions guided the choice of physical parameters for a chitosan-coated nylon membrane; these predictions can also be applied generally to other capture situations with different requirements. The membrane is also compatible with in situ amplification, which, by eliminating an elution step enables high sensitivity and will facilitate integration of this method into sample-to-answer detection devices. We tested a wide range of combinations of sample volumes and concentrations of DNA molecules using a capture membrane with a 2 mm radius. We show that for nucleic acid detection, this approach can concentrate and detect as few as ∼10 molecules of DNA with flow rates as high as 1 mL/min, handling samples as large as 50 mL. In a specific example, this method reliably concentrated and detected ∼25 molecules of DNA from 50 mL of sample

Supporting Peer Help and Collaboration in Distributed Workplace Environments

Special Issue on Computer Supported Collaborative LearningIncreasingly, organizations are geographically distributed with activities coordinated and integrated through the use of information technology. Such organizations face constant change and the corresponding need for continual learning and renewal of their workers. In this paper we describe a prototype system called PHelpS (Peer Help System) that facilitates workers in carrying out such "life long learning". PHelpS supports workers as they perform their tasks, offers assistance in finding peer helpers when required, and mediates communication on task-related topics. When a worker runs into difficulty in carrying out a task, PHelpS provides a list of other workers who are ready, willing and able to help him or her. The worker then selects a particular helper with PHelpS supporting the subsequent help interaction. The PHelpS system acts as a facilitator to stimulate learning and collaboration, rather than as a directive agent imposing its perspectives on the workers. In this way PHelpS facilitates the creation of extensive informal peer help networks, where workers help one another with tasks and opens up new research avenues for further exploration of AI-based computer-supported collaborative learning. (http://aied.inf.ed.ac.uk/members98/archive/vol_9/greer/full.html

Escherichia coli YafP protein modulates DNA damaging property of the nitroaromatic compounds

Escherichia coli SOS functions constitute a multifaceted response to DNA damage. We undertook to study the role of yafP, a SOS gene with unknown function. yafP is part of an operon also containing the dinB gene coding for DNA Polymerase IV (PolIV). Our phylogenetic analysis showed that the gene content of this operon is variable but that the dinB and the yafP genes are conserved in the majority of E. coli natural isolates. Therefore, we studied if these proteins are functionally linked. Using a murine septicaemia model, we showed that YafP activity reduced the bacterial fitness in the absence of PolIV. Similarly, YafP increased cytotoxicity of two DNA damaging nitroaromatic compounds, 4-nitroquinoline-1-oxide (NQO) and nitrofurazone, in the absence of PolIV. The fact that PolIV counterbalances YafP-induced cytotoxicity could explain why these two genes are transcriptionally linked. We also studied the involvement of YafP in genotoxic-stress induced mutagenesis and found that PolIV and YafP reduced NQO-induced mutagenicity. The YafP antimutator activity was independent of the PolIV activity. Given that YafP was annotated as a putative acetyltransferase, it could be that YafP participates in the metabolic transformation of genotoxic compounds, hence modulating the balance between their mutagenicity and cytotoxicity

Towards understanding crime dynamics in a heterogeneous environment:A mathematical approach

Crime data provides information on the nature and location of the crime but, in general, does not include information on the number of criminals operating in a region. By contrast, many approaches to crime reduction necessarily involve working with criminals or individuals at risk of engaging in criminal activity and so the dynamics of the criminal population is important. With this in mind, we develop a mechanistic, mathematical model which combines the number of crimes and number of criminals to create a dynamical system. Analysis of the model highlights a threshold for criminal efficiency, below which criminal numbers will settle to an equilibrium level that can be exploited to reduce crime through prevention. This efficiency measure arises from the initiation of new criminals in response to observation of criminal activity; other initiation routes - via opportunism or peer pressure - do not exhibit such thresholds although they do impact on the level of criminal activity observed. We used data from Cape Town, South Africa, to obtain parameter estimates and predicted that the number of criminals in the region is tending towards an equilibrium point but in a heterogeneous manner - a drop in the number of criminals from low crime neighbourhoods is being offset by an increase from high crime neighbourhoods

Mechanistic Evaluation of the Pros and Cons of Digital RT-LAMP for HIV-1 Viral Load Quantification on a Microfluidic Device and Improved Efficiency via a Two-Step Digital Protocol

Here we used a SlipChip microfluidic device to evaluate the performance of digital reverse transcription-loop-mediated isothermal amplification (dRT-LAMP) for quantification of HIV viral RNA. Tests are needed for monitoring HIV viral load to control the emergence of drug resistance and to diagnose acute HIV infections. In resource-limited settings, in vitro measurement of HIV viral load in a simple format is especially needed, and single-molecule counting using a digital format could provide a potential solution. We showed here that when one-step dRT-LAMP is used for quantification of HIV RNA, the digital count is lower than expected and is limited by the yield of desired cDNA. We were able to overcome the limitations by developing a microfluidic protocol to manipulate many single molecules in parallel through a two-step digital process. In the first step we compartmentalize the individual RNA molecules (based on Poisson statistics) and perform reverse transcription on each RNA molecule independently to produce DNA. In the second step, we perform the LAMP amplification on all individual DNA molecules in parallel. Using this new protocol, we increased the absolute efficiency (the ratio between the concentration calculated from the actual count and the expected concentration) of dRT-LAMP 10-fold, from 2% to 23%, by (i) using a more efficient reverse transcriptase, (ii) introducing RNase H to break up the DNA:RNA hybrid, and (iii) adding only the BIP primer during the RT step. We also used this two-step method to quantify HIV RNA purified from four patient samples and found that in some cases, the quantification results were highly sensitive to the sequence of the patient’s HIV RNA. We learned the following three lessons from this work: (i) digital amplification technologies, including dLAMP and dPCR, may give adequate dilution curves and yet have low efficiency, thereby providing quantification values that underestimate the true concentration. Careful validation is essential before a method is considered to provide absolute quantification; (ii) the sensitivity of dLAMP to the sequence of the target nucleic acid necessitates additional validation with patient samples carrying the full spectrum of mutations; (iii) for multistep digital amplification chemistries, such as a combination of reverse transcription with amplification, microfluidic devices may be used to decouple these steps from one another and to perform them under different, individually optimized conditions for improved efficiency

Statistical Model of Heavy-Ion Fusion-Fission Reactions

Cross-section and neutron-emission data from heavy-ion fusion-fission reactions are consistent with the fission of fully equilibrated systems with fission lifetime estimates obtained via a Kramers-modified statistical model which takes into account the collective motion of the system about the ground state, the temperature dependence of the location and height of fission transition points, and the orientation degree of freedom. If the standard techniques for calculating fission lifetimes are used, then the calculated excitation-energy dependence of fission lifetimes is incorrect. We see no evidence to suggest that the nuclear viscosity has a temperature dependence. The strong increase in the nuclear viscosity above a temperature of approximately 1.3 MeV deduced by others is an artifact generated by an inadequate fission model.Comment: Full paper submitted to PRC to accompany our recently published Phys. Rev. Lett. 101, 032702 (2008

Pollution Abatement from Cattle Feedlots in Northeastern Colorado and Nebraska

Climatic factors, feedlot runoff, and organic material in the runoff were evaluated in experimental and commercial feedlots. The effects of slope, stocking rates, terraces, basins, and holding ponds were evaluated to obtain the best controls for containing runoff. In eastern Nebraska, 70 cm annual precipitation produces 23 cm of runoff; whereas, in northeastern Colorado, 37 cm annual precipitation gives only 5.5 cm of runoff. Large applications of runoff liquid, up to 91 cmon grass-Ladino and 76 cm on corn, in Nebraska did not decrease yields; however, in northeastern Colorado, the concentrated high-salt runoff required dilution before direct application to crops. The organic manure-soil interface severely restricts the movement of water, nitrates, organic substances, and air into the soil beneath feedlots. The amounts of N03-N in soil cores taken from Nebraska feedlots and croplands ranked as follows: abandoned feedlots\u3e feedlot cropland\u3e upland feedlots\u3e river valley feedlots\u3e manure mounds\u3e alfalfa\u3e grassland. Feedlots contribute NH3, amines, carbonyl sulfide, H2S, and other unidentified substances to the atmosphere. Ammonia and amine can be scavenged from the air by green plants and water bodies. Anaerobic conditions in feedlots are conducive to the production of carbonyl sulfide, H2S, and amines. Management practices, such as good drainage, that enhance aeration will decrease the evolution of these compounds