Photostability of Isovaline and its Precursor 5-Ethyl-5- methylhydantoin Exposed to Simulated Space Radiations

Aqueous solutions of isovaline and its precursor molecule, 5-ethyl-5-methylhydantoin, were irradiated with ultraviolet and γ-ray photons, to evaluate their structural stability against space radiation. The degree of photolysis was measured and irradiation products were identified using chiral, reversed-phase and ion-exchange high-performance liquid chromatography. The experimental results show that the degree of photolysis of 5-ethyl-5-methylhydantoin is more significant than that of isovaline under ultraviolet light irradiation, while the results under γ-ray irradiation are the opposite. As the products of isovaline photolysis, aspartic acid, serine, glutamic acid and alanine were dominantly detected

Effects of Noise Bandwidth and Amplitude Modulation on Masking in Frog Auditory Midbrain Neurons

Natural auditory scenes such as frog choruses consist of multiple sound sources (i.e., individual vocalizing males) producing sounds that overlap extensively in time and spectrum, often in the presence of other biotic and abiotic background noise. Detection of a signal in such environments is challenging, but it is facilitated when the noise shares common amplitude modulations across a wide frequency range, due to a phenomenon called comodulation masking release (CMR). Here, we examined how properties of the background noise, such as its bandwidth and amplitude modulation, influence the detection threshold of a target sound (pulsed amplitude modulated tones) by single neurons in the frog auditory midbrain. We found that for both modulated and unmodulated masking noise, masking was generally stronger with increasing bandwidth, but it was weakened for the widest bandwidths. Masking was less for modulated noise than for unmodulated noise for all bandwidths. However, responses were heterogeneous, and only for a subpopulation of neurons the detection of the probe was facilitated when the bandwidth of the modulated masker was increased beyond a certain bandwidth – such neurons might contribute to CMR. We observed evidence that suggests that the dips in the noise amplitude are exploited by TS neurons, and observed strong responses to target signals occurring during such dips. However, the interactions between the probe and masker responses were nonlinear, and other mechanisms, e.g., selective suppression of the response to the noise, may also be involved in the masking release

An Extended Search for Circularly Polarized Infrared Radiation from the OMC-1 Region of Orion

Original article can be found at :--http://www.journals.uchicago.edu/--Copyright The American Astronomical SocietyWe present new observations of circular polarization (CP) at 2.2 m in the Orion (OMC-1) molecular cloud. Our results extend a previously published study of the region.We show that the degree of CP correlates spatially with the molecular cloud and appears to be generally very low in regions dominated by H ii.We detect a feature with 3%–5% CP that extends approximately 60" to the southwest of the BN/IRc2 region. Although the morphology of the observed CP is broadly consistent with a model in which radiation from a central source (probably IRc2) is scattered by aligned spheroidal grains, we conclude that dichroic extinction in the foreground molecular cloud also plays a major role in its production. Implications of our results for the hypothesis that CP radiation imposes chiral asymmetry upon prebiotic organicmolecules in protoplanetary disks are discussed.Mechanisms invoked to explain the observed CP in the near infrared can also produce CP in the range of ultraviolet wavelengths capable of chiral selection by photolysis; however, the polarized flux is likely to be of limited spatial extent and to have lower percentage CP compared with the infrared.Peer reviewe

The spread ofrate and correlation in stationary cortical

network

Effect of Multispecies Cover Crop Mixture on Soil Properties and Crop Yield

Multispecies cover cropping has become popular in recent years because of the multiple ecosystem benefits compared with single- or double- species cover cropping. However, scientific studies on the effects of multispecies cover cropping—especially in the southern United States—are limited. A field study was initiated in 2013 at the University of Tennessee’s Research and Education Center in Milan, TN, to assess the agronomic and soil responses from single-, double-, and multispecies cover cropping in corn ( L.)–soybean [ (L.) Merr.] systems. After 3 yr, we found that a multispecies mixture of legumes, grasses, and spp. significantly increased soybean yield, gravimetric soil water content, and soil inorganic nitrogen as compared to the less-diverse treatments and a no-cover control. However, after 3 yr, cover cropping did not increase soil organic carbon. Although multispecies cover cropping exhibited a positive effect on yield and some soil properties after 3 yr, we plan to continue collecting multiple years of data from this field trial