OH 1720 MHz Masers in Supernova Remnants --- C-Shock Indicators

Recent observations show that the OH 1720 MHz maser is a powerful probe of the shocked region where a supernova remnant strikes a molecular cloud. We perform a thorough study of the pumping of this maser and find tight constraints on the physical conditions needed for its production. The presence of the maser implies moderate temperatures (50 -- 125 K) and densities ($\sim 10^5 cm^{-3}$), and OH column densities of order $10^{16} cm^{-2}$. We show that these conditions can exist only if the shocks are of C-type. J-shocks fail by such a wide margin that the presence of this maser could become the most powerful indicator of C-shocks. These conditions also mean that the 1720 MHz maser will be inherently weak compared to the other ground state OH masers. All the model predictions are in good agreement with the observations.Comment: 16 pages, 5 Postscript figures (included), uses aaspp4.sty. To appear in the Astrophysical Journa

Selective Precipitation and Purification of Monovalent Proteins Using Oligovalent Ligands and Ammonium Sulfate

This paper describes a method for the selective precipitation and purification of a monovalent protein (carbonic anhydrase is used as a demonstration) from cellular lysate using ammonium sulfate and oligovalent ligands. The oligovalent ligands induce the formation of protein–ligand aggregates, and at an appropriate concentration of dissolved ammonium sulfate, these complexes precipitate. The purification involves three steps: (i) the removal of high-molecular-weight impurities through the addition of ammonium sulfate to the crude cell lysate; (ii) the introduction of an oligovalent ligand and the selective precipitation of the target protein–ligand aggregates from solution; and (iii) the removal of the oligovalent ligand from the precipitate by dialysis to release the target protein. The increase of mass and volume of the proteins upon aggregate formation reduces their solubility, and results in the selective precipitation of these aggregates. We recovered human carbonic anhydrase, from crude cellular lysate, in 82% yield and 95% purity with a trivalent benzene sulfonamide ligand. This method provides a chromatography-free strategy of purifying monovalent proteins—for which appropriate oligovalent ligands can be synthesized—and combines the selectivity of affinity-based purification with the convenience of salt-induced precipitation.Chemistry and Chemical Biolog

An evaluation of Bradfordizing effects

The purpose of this paper is to apply and evaluate the bibliometric method Bradfordizing for information retrieval (IR) experiments. Bradfordizing is used for generating core document sets for subject-specific questions and to reorder result sets from distributed searches. The method will be applied and tested in a controlled scenario of scientific literature databases from social and political sciences, economics, psychology and medical science (SOLIS, SoLit, USB Köln Opac, CSA Sociological Abstracts, World Affairs Online, Psyndex and Medline) and 164 standardized topics. An evaluation of the method and its effects is carried out in two laboratory-based information retrieval experiments (CLEF and KoMoHe) using a controlled document corpus and human relevance assessments. The results show that Bradfordizing is a very robust method for re-ranking the main document types (journal articles and monographs) in today’s digital libraries (DL). The IR tests show that relevance distributions after re-ranking improve at a significant level if articles in the core are compared with articles in the succeeding zones. The items in the core are significantly more often assessed as relevant, than items in zone 2 (z2) or zone 3 (z3). The improvements between the zones are statistically significant based on the Wilcoxon signed-rank test and the paired T-Test

Thermoelastic Damping in Micro- and Nano-Mechanical Systems

The importance of thermoelastic damping as a fundamental dissipation mechanism for small-scale mechanical resonators is evaluated in light of recent efforts to design high-Q micrometer- and nanometer-scale electro-mechanical systems (MEMS and NEMS). The equations of linear thermoelasticity are used to give a simple derivation for thermoelastic damping of small flexural vibrations in thin beams. It is shown that Zener's well-known approximation by a Lorentzian with a single thermal relaxation time slightly deviates from the exact expression.Comment: 10 pages. Submitted to Phys. Rev.

State-of-the-art in product service-systems

A Product Service-System (PSS) is an integrated combination of products and services. This western concept embraces a service-led competitive strategy, environmental sustainability, and the basis to differentiate from competitors who simply offer lower priced products. This paper aims to report the state-of-the-art of PSS research by presenting a clinical review of literature currently available on this topic. The literature is classified and the major outcomes of each study are addressed and analysed. On this basis, this paper defines the PSS concept, reports on its origin and features, gives examples of applications along with potential benefits and barriers to adoption, summarises available tools and methodologies, and identifies future research challenges

The interplay of DNA methylation over time with Th2 pathway genetic variants on asthma risk and temporal asthma transition

BackgroundGenetic effects on asthma of genes in the T-helper 2 (Th2) pathway may interact with epigenetic factors including DNA methylation. We hypothesized that interactions between genetic variants and methylation in genes in this pathway (IL4, IL4R, IL13, GATA3, and STAT6) influence asthma risk, that such influences are age-dependent, and that methylation of some CpG sites changes over time in accordance with asthma transition. We tested these hypotheses in subsamples of girls from a population-based birth cohort established on the Isle of Wight, UK, in 1989.ResultsLogistic regression models were applied to test the interaction effect of DNA methylation and SNP on asthma within each of the five genes. Bootstrapping was used to assess the models identified. From 1,361 models fitted at each age of 10 and 18 years, 8 models, including 4 CpGs and 8 SNPs, showed potential associations with asthma risk. Of the 4 CpGs, methylation of cg26937798 (IL4R) and cg23943829 (IL4) changes between ages 10 and 18 (both higher at 10; P?=?9.14?×?10?6 and 1.07?×?10?5, respectively).At age 10, the odds of asthma tended to decrease as cg12405139 (GATA3) methylation increased (log-OR?=??12.15; P?=?0.049); this effect disappeared by age 18. At age 18, methylation of cg09791102 (IL4R) was associated with higher risk of asthma among subjects with genotype GG compared to AG (P?=?0.003), increased cg26937798 methylation among subjects with rs3024685 (IL4R) genotype AA (P?=?0.003) or rs8832 (IL4R) genotype GG (P?=?0.01) was associated with a lower asthma risk; these CpGs had no effect at age 10. Increasing cg26937798 methylation over time possibly reduced the risk of positive asthma transition (asthma-free at age 10???asthma at age 18; log-OR?=??3.11; P?=?0.069) and increased the likelihood of negative transition (asthma at age 10???asthma-free at age 18; log-OR?=?3.97; P?=?0.074).ConclusionsThe interaction of DNA methylation and SNPs in Th2 pathway genes is likely to contribute to asthma risk. This effect may vary with age. Methylation of some CpGs changed over time, which may influence asthma transition

Poliartritis asociada a leishmaniasis en un canino del nordeste argentino

<p In one of the stages of leishmaniasis an immune-mediated reaction occurs, with formation of immune complexes that are deposited at the joint level, among other places. The objective of the present work was to report the radiological findings observed in a canine, female, mixed, with a positive diagnosis of leishmaniasis and signs of joint disease. Radiologically, erosive alterations were observed in the joints of both sides of the carpus and tarsus. The northeastern region of Argentina is considered as a moderate to intense transmission area of leishmaniasis, the infrequent presentation signs of osteoarticular disease must be taken into account. The importance of these radiological manifestations relies in the fact that they reflect the macroscopic pathological anatomy of the disease and allows to identify the stage in which the lesion is located at the articular level, making it possible to carry out a differential diagnosis with other arthropathies. p> En una de las etapas de la leishmaniasis se produce una reacción inmunomediada, con formación de complejos inmunes que se depositan -entre otros lugares- a nivel articular. El objetivo del presente trabajo fue reportar los hallazgos radiológicos observados en un canino hembra, mestizo, con diagnóstico positivo de leishmaniasis y signos de enfermedad articular, entre otros propios de la infección. Radiológicamente se observaron alteraciones erosivas en las articulaciones de ambos lados del carpo y del tarso. El nordeste argentino es considerado como un área de transmisión moderada a intensa de leishmaniasis, razón por la cual los infrecuentes signos de presentación de patologías osteoarticulares deben ser tenidos en cuenta en esta enfermedad. La importancia de las manifestaciones radiológicas reside en el hecho de que reflejan la anatomía patológica macroscópica de la enfermedad y permiten identificar la etapa en la que se encuentra la lesión a nivel articular, posibilitando la realización un diagnóstico diferencial con otras artropatías.

The Effect of 53 micron IR Radiation on 18 cm OH Megamaser Emission

OH megamasers (OHMs) emit primarily in the main lines at 1667 and 1665 MHz, and differ from their Galactic counterparts due to their immense luminosities, large linewidths and 1667/1665 MHz flux ratios, which are always greater than one. We find that these maser properties result from strong 53 micron radiative pumping combined with line overlap effects caused by turbulent linewidths of about 20 km/s; pumping calculations that do not include line overlap are unreliable. A minimum dust temperature of about 45 K is needed for inversion, and maximum maser efficiency occurs for dust temperatures in the range 80 - 140 K. We find that warmer dust can support inversion at lower IR luminosities, in agreement with observations. Our results are in good agreement with a clumpy model of OHMs, with clouds sizes about 1 pc and OH column densities about 5e16 cm^2, that is able to explain both the diffuse and compact emission observed for OHMs. We suggest that all OH main line masers may be pumped by far-IR radiation, with the major differences between OHMs and Galactic OH masers caused by differences in linewidth produced by line overlap. Small Galactic maser linewidths tend to produce stronger 1665 MHz emission. The large OHM linewidths lead to inverted ground state transitions having approximately the same excitation temperature, producing 1667/1665 MHz flux ratios greater than one and weak satellite line emission. Finally, the small observed ratio of pumping radiation to dense molecular gas, as traced by HCN and HCO$^+$, is a possible reason for the lack of OH megamaser emission in NGC 6240.Comment: Accepted to ApJ, 26 pages including 1 table and 7 figure

H2O Maser Polarization of the Water Fountains IRAS 15445-5449 and IRAS 18043-2116

We present the morphology and linear polarization of the 22-GHz H2O masers in the high-velocity outflow of two post-AGB sources, d46 (IRAS 15445-5449) and b292 (IRAS 18043-2116). The observations were performed using The Australia Telescope Compact Array. Different levels of saturated maser emission have been detected for both sources. We also present the mid-infrared image of d46 overlaid with the distribution of the maser features that we have observed in the red-shifted lobe of the bipolar structure. The relative position of the observed masers and a previous radio continuum observation suggests that the continnum is produced along the blue-shifted lobe of the jet. It is likely due to synchrontron radiation, implying the presence of a strong magnetic field in the jet. The fractional polarization levels measured for the maser features of d46 indicate that the polarization vectors are tracing the poloidal component of the magnetic field in the emitting region. For the H2O masers of b292 we have measured low levels of fractional linear polarization. The linear polarization in the H2O maser region of this source likely indicates a dominant toroidal or poloidal magnetic field component. Since circular polarization was not detected it is not possible to determine the magnetic field strength. However, we present a 3-sigma evaluation of the upper limit intensity of the magnetic field in the maser emitting regions of both observed sources.Comment: 7 pages, 4 figures, 1 table. To be published in Monthly Notices of the Royal Astronomical Societ

Molecules in G1.6-0.025 - 'Hot' Chemistry in the Absence of Star Formation at the Periphery of the Galactic Center Region

We present molecular line mapping of the Giant Molecular Cloud G1.6-0.025, which is located at the high longitude end of the Central Molecular Zone of our Galaxy. We assess the degree of star formation activity in that region using several tracers and find very little. We made a large scale, medium (2') resolution map in the J = 2-1 transition of SiO for which we find clumpy emission over a ~0.8 x 0.3 degree-sized region stretching along the Galactic plane. Toward selected positions we also took spectra in the easy to excite J_k=2_k-1_k quartet of CH3OH and the CS 2-1 line. Throughout the cloud these \meth lines are, remarkably, several times stronger than, both, the CS and the SiO lines. The large widths of all the observed lines, similar to values generally found in the Galactic center, indicate a high degree of turbulence. Several high LSR velocity clumps that have 0-80 km/s higher velocities than the bulk of the molecular cloud appear at the same projected position as "normal" velocity material; this may indicate cloud-cloud collisions. Statistical equilibrium modeling of the CH3OH lines observed by us and others yield relatively high densities and moderate temperatures for a representative dual velocity position. We find 8 10^4 cm-3/30 K for material in the G1.6-0.025 cloud and a higher temperature (190 K), but a 50% lower density in a high velocity clump projected on the same location. Several scenarios are discussed in which shock chemistry might enhance the CH3OH and SiO abundances in G1.6-0.025 and elsewhere in the Central Molecular Zone.Comment: 51 pages incl. 9 figures and 6 Tables, ApJ (in press