Postruminal Flow of Glutamate Linearly Increases Small Intestinal Starch Digestion in Cattle

Improving performance and efficiency among cattle fed corn-based diets could have large benefit to cattle production in the United States. Starch escaping ruminal fermentation is not efficiently digested in the small intestine; however, postruminal flows of casein (i.e., milk protein) or glutamate (an amino acid or building block of protein) increase small intestinal starch digestion in cattle. The objective of this study was to determine responses of small intestinal starch digestion in cattle to increasing amounts of postruminal glutamate. Increasing amounts of duodenal glutamate linearly increased small intestinal and postruminal starch digestion. These data indicate that postruminal glutamate can provide benefit to cattle fed corn-based diets

Genetics of human neural tube defects

Neural tube defects (NTDs) are common, severe congenital malformations whose causation involves multiple genes and environmental factors. Although more than 200 genes are known to cause NTDs in mice, there has been rather limited progress in delineating the molecular basis underlying most human NTDs. Numerous genetic studies have been carried out to investigate candidate genes in cohorts of patients, with particular reference to those that participate in folate one-carbon metabolism. Although the homocysteine remethylation gene MTHFR has emerged as a risk factor in some human populations, few other consistent findings have resulted from this approach. Similarly, attention focused on the human homologues of mouse NTD genes has contributed only limited positive findings to date, although an emerging association between genes of the non-canonical Wnt (planar cell polarity) pathway and NTDs provides candidates for future studies. Priorities for the next phase of this research include: (i) larger studies that are sufficiently powered to detect significant associations with relatively minor risk factors; (ii) analysis of multiple candidate genes in groups of well-genotyped individuals to detect possible gene–gene interactions; (iii) use of high throughput genomic technology to evaluate the role of copy number variants and to detect ‘private’ and regulatory mutations, neither of which have been studied to date; (iv) detailed analysis of patient samples stratified by phenotype to enable, for example, hypothesis-driven testing of candidates genes in groups of NTDs with specific defects of folate metabolism, or in groups of fetuses with well-defined phenotypes such as craniorachischisis

Why dig looted tombs? Two examples and some answers from Keushu (Ancash highlands, Peru)

Looted tombs at Andean archaeological sites are largely the result of a long tradition of trade in archaeological artefacts coupled with the 17th century policy of eradicating ancestor veneration and destroying mortuary evidence in a bid to “extirpate idolatry”. On the surface, looted funerary contexts often present abundant disarticulated and displaced human remains as well as an apparent absence of mortuary accoutrements. What kind of information can archaeologists and biological anthropologists hope to gather from such contexts? In order to gauge the methodological possibilities and interpretative limitations of targeting looted tombs, we fully excavated two collective funerary contexts at the archaeological site of Keushu (district and province of Yungay, Ancash, Peru; c. 2000 B.C.-A.D. 1600), which includes several dozen tombs, many built under large boulders or rock shelters, all of which appear disturbed by looting. The first is located in the ceremonial sector and excavation yielded information on four individuals; the second, in the funerary and residential sector, held the remains of seventy individuals - adults and juveniles. Here, we present and discuss the recovered data and suggest that careful, joint excavations by archaeologists and biological anthropologists can retrieve evidence of past mortuary practices, aid the biological characterisation of mortuary populations and help distinguish between a broad range of looting practices and post-depositional processes

Constraining Strong Baryon-Dark Matter Interactions with Primordial Nucleosynthesis and Cosmic Rays

Self-interacting dark matter (SIDM) was introduced by Spergel & Steinhardt to address possible discrepancies between collisionless dark matter simulations and observations on scales of less than 1 Mpc. We examine the case in which dark matter particles not only have strong self-interactions but also have strong interactions with baryons. The presence of such interactions will have direct implications for nuclear and particle astrophysics. Among these are a change in the predicted abundances from big bang nucleosynthesis (BBN) and the flux of gamma-rays produced by the decay of neutral pions which originate in collisions between dark matter and Galactic cosmic rays (CR). From these effects we constrain the strength of the baryon--dark matter interactions through the ratio of baryon - dark matter interaction cross section to dark matter mass, $s$. We find that BBN places a weak upper limit to this ratio $< 10^8 cm^2/g$. CR-SIDM interactions, however, limit the possible DM-baryon cross section to $< 5 \times 10^{-3} cm^2/g$; this rules out an energy-independent interaction, but not one which falls with center-of-mass velocity as $s \propto 1/v$ or steeper.Comment: 17 pages, 2 figures; plain LaTeX. To appear in PR

FIRST SEARCHES FOR OPTICAL COUNTERPARTS TO GRAVITATIONAL-WAVE CANDIDATE EVENTS

During the LIGO and Virgo joint science runs in 2009-2010, gravitational wave (GW) data from three interferometer detectors were analyzed within minutes to select GW candidate events and infer their apparent sky positions. Target coordinates were transmitted to several telescopes for follow-up observations aimed at the detection of an associated optical transient. Images were obtained for eight such GW candidates. We present the methods used to analyze the image data as well as the transient search results. No optical transient was identified with a convincing association with any of these candidates, and none of the GW triggers showed strong evidence for being astrophysical in nature. We compare the sensitivities of these observations to several model light curves from possible sources of interest, and discuss prospects for future joint GW-optical observations of this type

Anisotropy of exciton migration in poly(p-phenylene vinylene)

The dynamics of the exciton transport in poly(p-phenylene vinylene) (PPV) blended with a low concentration of fullerene molecules is monitored by time-resolved photoluminescence measurements. The diffusion driven motion of excitons toward these scavengers is modeled using a theory based on a random walk of a particle on lattice sites with traps. From this analysis an exciton diffusion constant of (4±0.5)×10−4 cm2/s and a diffusion length of 7 nm are obtained. These exciton transport parameters are equivalent to results obtained in bilayer polymer/fullerene heterostructures, demonstrating that the exciton dynamics in PPV are dominated by a one-dimensional migration perpendicular to the film.

Exciton quenching in poly(phenylene vinylene) polymer light-emitting diodes

The quenching of excitons at the metallic cathode of a polymer light-emitting diode (PLED) has been investigated by time-resolved photoluminescence. The decay of the luminescence is analyzed including both nonradiative energy transfer to the metallic cathode and exciton diffusion. Incorporation of the resulting exciton density profiles into a PLED device model consistently describes the reduction of the quantum efficiency at low bias voltage.

Migration-assisted energy transfer at conjugated polymer/metal interfaces

The dynamics of exciton quenching in a conjugated polymer due to the presence of metal films is analyzed using time-resolved photoluminescence. The quenching is governed by direct radiationless energy transfer to the metal and is further enhanced by diffusion of excitons into the depletion area of the exciton population at the polymer/metal interface. The time-resolved luminescence is described by a numerical exciton diffusion model with the energy transfer incorporated via long-range dipole-dipole interaction at the metallic mirror. This allows us to disentangle the contributions from direct energy transfer to the metal and exciton migration, to the exciton quenching process. For an aluminum electrode strong exciton quenching occurs in a region of typically 15 nm, which can be decomposed in a characteristic energy-transfer range of 7.5 nm and an exciton diffusion length of 6 nm.

Dynamics of exciton diffusion in poly(p-phenylene vinylene)/fullerene heterostructures

The exciton diffusion process in a poly(p-phenylene vinylene)- (PPV-)based derivative is investigated using time-resolved photoluminescence in conjugated polymer/fullerene heterostructures. The decay of the luminescence in the polymer/fullerene heterostructures is governed by exciton diffusion and subsequent dissociation at the polymer/fullerene interface. The decay curves of polymer layers with varying thickness are consistently modeled using an exciton diffusion constant of 3 × 10−4 cm2/s. The resulting exciton migration radius amounts to 6 nm, which is a measure for the active part of the PPV/fullerene heterojunction for photovoltaic applications.