Experiments in Nonisothermal Diffusion of Moisture in Wood. Part II.

This paper is the second in a series of papers reporting on experiments in nonisothermal diffusion of moisture in wood. Additional experimental steps to those series previously reported and one more series are included here. A reversal of flux direction was observed in all three series of experiments as the relative humidity of the warm side was increased.The results were analyzed using the general sorption data presented in the USDA Wood Handbook using two equations. The first of each is based on a gradient of activated moisture content, and the second is based on a gradient of chemical potential which contains an additional term to account for the effect of the temperature gradient. Both equations predicted reversal of flux direction, but the second equation (chemical potential) generally provided the best fit to the experimental results

Pathfinder Technology Demonstrator: Demonstrating Novel CubeSat Technologies in Low Earth Orbit

NASA\u27s Pathfinder Technology Demonstrator (PTD) project will test the operation of a variety of novel CubeSat technologies in low-Earth orbit, providing significant enhancements to the performance of these small and effective spacecraft. Each Pathfinder Technology Demonstrator mission will consist of a 6-unit (6U) CubeSat weighing approximately 12 kilograms and measuring 30 centimeters x 25 centimeters x 10 centimeters. The PTD project led by NASA\u27s Ames Research Center at Moffett Field, California, in collaboration with NASA\u27s Glenn Research Center in Cleveland, Ohio and a commercial partner will benefit future missions by demonstrating the operation of new subsystem technologies on orbit. These technologies include propulsion systems that provide the capability to maneuver small science platforms and send small spacecraft to deep space; novel technologies to stabilize spacecraft, and laser communications systems that will greatly increase the amount of data that can be transmitted from the spacecraft to the ground. As small spacecraft increase mobility and capability, NASA benefits by flight-qualifying these subsystems, providing access to low cost, highly capable, science and technology platforms that can operate from the near-Earth to the deep space environment. The PTD mission is funded through NASA\u27s Small Spacecraft Technology Program (SSTP), which is chartered to develop and mature technologies to enhance and expand the capabilities of small spacecraft with a particular focus on communications, propulsion, pointing, power, and autonomous operations. The SSTP is one of nine programs within NASA\u27s Space Technology Mission Directorate. This paper will include an overview of the PTD project, the PTD spacecraft bus interfaces and capabilities as an adaptable, commercially developed small satellite bus for LEO technology demonstration, potential types of payloads, expected timeframe and flights, and how the PTD project will be a pathfinder for novel small spacecraft technologies to be flight demonstrated for science, commercial, and governmental use

Conformational effects of nucleotide exchange in ras p21 proteins as studied by fluorescence spectroscopy

AbstractThe intrinsic fluorescence properties of the oncogene protein p21N-ras, p21H-ras and one of its transforming mutants, p21N-ras (Va1112), have been investigated. A mutant containing a single tryptophan at position 28 in p21H-ras (Trp28) has been specifically engineered to provide a probe of protein conformation on nucleotide binding. The proteins produced essentially similar circular dichroism spectra typical of alpha/beta proteins. A decrease in the intensity of the fluorescence emission spectrum due to tyrosine occurred on GDP/GTP nucleotide exchange in the native and mutant proteins. Selective excitation of the single tryptophan in p21 produced a decrease in fluorescence intensity which was accompanied by a blue shift in the wavelength of maximum emission on nucleotide exchange. A reduction in the residual Mg2+ ion concentration enhanced this effect

A Cationic Amphiphilic Random Copolymer with pH-Responsive Activity against Methicillin-Resistant Staphylococcus aureus.

In this report, we demonstrate the pH-dependent, in vitro antimicrobial activity of a cationic, amphiphilic random copolymer against clinical isolates of drug-resistant Staphylococcus aureus. The polymer was developed toward a long-term goal of potential utility in the treatment of skin infections. The proposed mechanism of action of the polymer is through selectively binding to bacterial membranes and subsequent disruption of the membrane structure/integrity, ultimately resulting in bacterial cell death. The polymer showed bactericidal activity against clinical isolates of methicillin-resistant or vancomycin-intermediate S. aureus. The polymer was effective in killing S. aureus at neutral pH, but inactive under acidic conditions (pH 5.5). The polymer did not exhibit any significant hemolytic activity against human red blood cells or display cytotoxicity to human dermal fibroblasts over a range of pH values (5.5-7.4). These results indicate that the polymer activity was selective against bacteria over human cells. Using this polymer, we propose a new potential strategy for treatment of skin infections using the pH-sensitive antimicrobial polymer agent that would selectively target infections at pH-neutral wound sites, but not the acidic, healthy skin

Pathogenic Epitopes of Autoantibodies in Pemphigus Reside in the Amino-Terminal Adhesive Region of Desmogleins Which Are Unmasked by Proteolytic Processing of Prosequence

Pemphigus targets desmogleins (Dsgs), which are thought to be synthesized as inactive precursor proteins with prosequences that are cleaved by substilisin-like proprotein convertases, such as furin, to yield mature adhesive molecules. We hypothesized that some pemphigus pathogenic antibodies (Abs), which presumably interfere with adhesion, only bind the mature form. A pathogenic and three non-pathogenic anti-Dsg1 monoclonal Abs (mAbs) isolated from a pemphigus foliaceus (PF) patient, were used for immunoprecipitation and ELISA of recombinant precursor and mature Dsg1. The pathogenic Ab binds mature Dsg1, whereas non-pathogenic Abs bind either only the precursor or both the precursor and mature Dsg1. Competition ELISA showed that the majority of PF sera target the same or nearby epitopes defined by the pathogenic anti-Dsg1 mAb that blocked >20% binding of 29 out of 40 PF sera. Furthermore, the immunoreactivity of 45 PF sera against the mature Dsg1 was 3.2 fold stronger than that against the precursor Dsg1 by ELISA. Similar results were observed in anti-Dsg3 Abs in 47 pemphigus vulgaris sera, suggesting that most pemphigus sera target epitopes that are unmasked by proteolytic processing. These findings support the idea that at least some pathogenic pemphigus autoantibodies induce the loss of cell adhesion by directly binding the trans-interaction site of Dsgs

Comprehensive analysis of the chromatin landscape in Drosophila melanogaster.

Chromatin is composed of DNA and a variety of modified histones and non-histone proteins, which have an impact on cell differentiation, gene regulation and other key cellular processes. Here we present a genome-wide chromatin landscape for Drosophila melanogaster based on eighteen histone modifications, summarized by nine prevalent combinatorial patterns. Integrative analysis with other data (non-histone chromatin proteins, DNase I hypersensitivity, GRO-Seq reads produced by engaged polymerase, short/long RNA products) reveals discrete characteristics of chromosomes, genes, regulatory elements and other functional domains. We find that active genes display distinct chromatin signatures that are correlated with disparate gene lengths, exon patterns, regulatory functions and genomic contexts. We also demonstrate a diversity of signatures among Polycomb targets that include a subset with paused polymerase. This systematic profiling and integrative analysis of chromatin signatures provides insights into how genomic elements are regulated, and will serve as a resource for future experimental investigations of genome structure and function

Impact of target site distribution for Type I restriction enzymes on the evolution of methicillin-resistant Staphylococcus aureus (MRSA) populations.

A limited number of Methicillin-resistant Staphylococcus aureus (MRSA) clones are responsible for MRSA infections worldwide, and those of different lineages carry unique Type I restriction-modification (RM) variants. We have identified the specific DNA sequence targets for the dominant MRSA lineages CC1, CC5, CC8 and ST239. We experimentally demonstrate that this RM system is sufficient to block horizontal gene transfer between clinically important MRSA, confirming the bioinformatic evidence that each lineage is evolving independently. Target sites are distributed randomly in S. aureus genomes, except in a set of large conjugative plasmids encoding resistance genes that show evidence of spreading between two successful MRSA lineages. This analysis of the identification and distribution of target sites explains evolutionary patterns in a pathogenic bacterium. We show that a lack of specific target sites enables plasmids to evade the Type I RM system thereby contributing to the evolution of increasingly resistant community and hospital MRSA