Gravitational-wave Detection With Matter-wave Interferometers Based On Standing Light Waves

We study the possibility of detecting gravitational-waves with matter-wave interferometers, where atom beams are split, deflected and recombined totally by standing light waves. Our calculation shows that the phase shift is dominated by terms proportional to the time derivative of the gravitational wave amplitude. Taking into account future improvements on current technologies, it is promising to build a matter-wave interferometer detector with desired sensitivity.Comment: 7 pages, 3 figures. To be published in General Relativity and Gravitatio

Photoconductivity of biased graphene

Graphene is a promising candidate for optoelectronic applications such as photodetectors, terahertz imagers, and plasmonic devices. The origin of photoresponse in graphene junctions has been studied extensively and is attributed to either thermoelectric or photovoltaic effects. In addition, hot carrier transport and carrier multiplication are thought to play an important role. Here we report the intrinsic photoresponse in biased but otherwise homogeneous graphene. In this classic photoconductivity experiment, the thermoelectric effects are insignificant. Instead, the photovoltaic and a photo-induced bolometric effect dominate the photoresponse due to hot photocarrier generation and subsequent lattice heating through electron-phonon cooling channels respectively. The measured photocurrent displays polarity reversal as it alternates between these two mechanisms in a backgate voltage sweep. Our analysis yields elevated electron and phonon temperatures, with the former an order higher than the latter, confirming that hot electrons drive the photovoltaic response of homogeneous graphene near the Dirac point

Observation of Parametric Instability in Advanced LIGO

Parametric instabilities have long been studied as a potentially limiting effect in high-power interferometric gravitational wave detectors. Until now, however, these instabilities have never been observed in a kilometer-scale interferometer. In this work we describe the first observation of parametric instability in an Advanced LIGO detector, and the means by which it has been removed as a barrier to progress

AGAMOUS Terminates Floral Stem Cell Maintenance in Arabidopsis by Directly Repressing WUSCHEL through Recruitment of Polycomb Group Proteins

Floral stem cells produce a defined number of floral organs before ceasing to be maintained as stem cells. Therefore, floral stem cells offer an ideal model to study the temporal control of stem cell maintenance within a developmental context. AGAMOUS (AG), a MADS domain transcription factor essential for the termination of floral stem cell fate, has long been thought to repress the stem cell maintenance gene WUSCHEL (WUS) indirectly. Here, we uncover a role of Polycomb Group (PcG) genes in the temporally precise repression of WUS expression and termination of floral stem cell fate. We show that AG directly represses WUS expression by binding to the WUS locus and recruiting, directly or indirectly, PcG that methylates histone H3 Lys-27 at WUS. We also show that PcG acts downstream of AG and probably in parallel with the known AG target KNUCKLES to terminate floral stem cell fate. Our studies identify core components of the network governing the temporal program of floral stem cells

How do stream organisms respond to, and influence, the concentration of titanium dioxide nanoparticles? A mesocosm study with algae and herbivores

The biologically active properties of many nanomaterials, coupled with their rapidly expanding production and use, has generated concern that certain types of nanoparticles could have unintended impacts when released into natural ecosystems. In the present study, the authors report the results of an experiment in which they grew three common species of stream algae as monocultures and together as polycultures in the biofilms of stream mesocosms that were exposed to 0, 0.1, or 1.0 ppm nanoparticle titanium dioxide (nTiO 2 ). The nTiO 2 did not alter the growth trajectory of any algal biofilm over 10+ generations. However, Ti accrual in biofilms not only differed among the algal species but was also higher in polycultures than in the average monoculture. Variation in accrual among species compositions was readily predicted by differences in the total biomass achieved by the different biofilms. When biofilms were fed to the herbivorous snail Physa acuta at the end of the experiment, initial concentrations of nTiO 2 did not alter short‐term rates of herbivory. However, because of differences in palatability among the algae, biofilm composition influenced the amount of nTiO 2 that accumulated in the herbivore tissue. The results have important implications for understanding how efficiently nTiO 2 is removed from surface waters and the potential transfer of nanomaterials to higher trophic levels. Environ. Toxicol. Chem. 2012; 31: 2414–2422. © 2012 SETACPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/93650/1/1962_ftp.pd

Graphene plasmonics

Two rich and vibrant fields of investigation, graphene physics and plasmonics, strongly overlap. Not only does graphene possess intrinsic plasmons that are tunable and adjustable, but a combination of graphene with noble-metal nanostructures promises a variety of exciting applications for conventional plasmonics. The versatility of graphene means that graphene-based plasmonics may enable the manufacture of novel optical devices working in different frequency ranges, from terahertz to the visible, with extremely high speed, low driving voltage, low power consumption and compact sizes. Here we review the field emerging at the intersection of graphene physics and plasmonics.Comment: Review article; 12 pages, 6 figures, 99 references (final version available only at publisher's web site

A Case of Sparganosis That Presented as a Recurrent Pericardial Effusion

Sparganosis is caused by a larval tapeworm of the genus Spirometra, which commonly invades subcutaneous tissue, but less frequently invades muscle, intestines, spinal cord, and the peritoneopleural cavity. The authors managed a female patient who presented with a recurrent pericardiopleural effusion and peripheral eosinophilia. The anti-sparganum-specific IgG serum level was significantly higher than normal control levels. In this patient, sparganosis was caused by the ingestion of raw frogs in an effort to control her thyroid disease. The recurrent pericardiopleural effusion and peripheral eosinophilia were controlled by 3 consecutive doses of praziquantel (75 mg/kg/day). The patient is doing well 4 years after presentation. Sparganosis should be considered a rare, but possible cause of recurrent pericardial effusion and peripheral eosinophilia. Immunoserologic testing using enzyme linked immunosorbent assays can be helpful in diagnosing human sparganosis, especially in cases without a subcutaneous lump or mass. Praziquantel is an alternative treatment for sparganosis in surgically-unresectable cases