Optical Polarization Analogs in Inelastic Free Electron Scattering

Advances in the ability to manipulate free electron phase profiles within the electron microscope have spurred development of quantum-mechanical descriptions of electron energy loss (EEL) processes involving transitions between phase-shaped transverse states. Here, we elucidate an underlying connection between two ostensibly distinct optical polarization analogs identified in EEL experiments as manifestations of the same conserved scattering flux. Our work introduces a procedure for probing general tensorial target characteristics including global mode symmetries and local polarization

Inelastic scattering of transversely structured free electrons from nanophotonic targets: Theory and computation

Recent advancements in abilities to create and manipulate the electron's transverse wave function within the transmission electron microscope (TEM) and scanning TEM (STEM) have enabled vectorially-resolved electron energy loss (EEL) and gain (EEG) measurements of nanoscale and quantum material responses using pre- and post-selected free electron states. This newfound capability is prompting renewed theoretical interest in quantum mechanical treatments of inelastic electron scattering observables and the information they contain. Here, we present a quantum mechanical treatment of the inelastic scattering of free electrons between pre- and post-selected transverse states with fully-retarded electron-sample interactions for both spontaneous EEL and continuous-wave laser-stimulated EEG measurements. General expressions for the state-resolved energy loss and gain rates are recast in forms amenable to numerical calculation using the method of coupled dipoles. We numerically implement our theory within the $e$-DDA code, and use it to investigate specific examples that highlight its versatility regarding the number, size, geometry, and material composition of the target specimen, as well as its ability to describe matter-wave diffraction from finite nanoscopic targets

Drought alters the spatial distribution, grazing patterns, and radula morphology of a fungal-farming salt marsh snail

Contains fulltext : 208086.pdf (publisher's version ) (Open Access

Caribbean Sea Soundscapes: Monitoring Humpback Whales, Biological Sounds, Geological Events, and Anthropogenic Impacts of Vessel Noise

Assessing marine soundscapes provides an understanding of the biological, geological and anthropogenic composition of a habitat, including species diversity, community composition, and human impacts. For this study, nine acoustic recorders were deployed between December 2016 and June 2017 off six Caribbean islands in several Marine Parks: the Dominican Republic (DR), St. Martin (SM), Guadeloupe east and west (GE, GW), Martinique (MA), Aruba (AR), and Bonaire (BO). Humpback whale song was recorded at five sites on four islands (DR, SM, GE, GW, and MA) and occurred on 49–93% of recording days. Song appeared first at the DR site and began 4–6 weeks later at GE, GW, and MA. No song was heard in AR and BO, the southernmost islands. A 2-week period was examined for the hourly presence of vessel noise and the number and duration of ship passages. Hourly vessel presence ranged from low (20% – DR, 30% – SM), medium (52% – MA, 54% – BO, 77% – GE) to near continuous (99% – GW; 100% – AR). Diurnal patterns were observed at BO, GE, and MA with few to no vessels present during night time hours, possibly reflecting the activity of recreational craft and fishing vessels. At the DR and GW sites, vessel traffic was ubiquitous for most of the day, likely reflecting heavy cruise ship and container ship presence. Soundscapes were diverse across islands with persistent fish choruses, sporadic sperm whale (Physeter macrocephalus) and dolphin (Delphinidae) presence at BO, minke whales (Balaenoptera acutorostrata) from late December to late February at MA and an earthquake recorded across all sites. These analyses provide an important first step in characterizing the health and species richness in Caribbean marine parks and demonstrate a surprising high anthropogenic foot print. Vessel traffic in particular contributes adversely to marine soundscapes, masking marine mammal sounds, potentially changing typical animal behavior and raising the risk of ship strike

A kinematically unbiased, all-sky search for nearby, young, low-mass stars

The past two decades have seen dramatic progress in our knowledge of the population of young stars of age $< 200\,$Myr that lie within $150\,$pc of the Sun. These nearby, young stars, most of which are found in loose, comoving groups, provide the opportunity to explore (among many other things) the dissolution of stellar clusters and their diffusion into the field star population. Here, we exploit the combination of astrometric and photometric data from {\it Gaia} and photometric data from GALEX (UV) and 2MASS (near-IR) in an attempt to identify additional nearby, young, late-type stars. Specifically, we present a sample of 146 GALEX UV-selected late-type (predominantly K-type) field stars with {\it Gaia}-based distances $< 125\,$pc (based on {\it Gaia} Data Release 1) that have isochronal ages $< 80\,$Myr even if equal-components binaries. We investigate the spectroscopic and kinematic properties of this sample. Despite their young isochronal ages, only $\sim 10$ per cent) of stars among this sample can be confidently associated with established nearby, young moving groups (MGs). These candidate MG members include 5 stars newly identified in this study. The vast majority of our sample of 146 nearby young star candidates have anomalous kinematics relative to the known MGs. These stars may hence represent a previously unrecognised population of young stars that has recently mixed into the older field star population. We discuss the implications and caveats of such a hypothesis---including the intriguing fact that, in addition to their non-young-star-like kinematics, the majority of the UV-selected, isochronally young field stars within $50\,$pc appear surprisingly X-ray faint

Hadron Energy Reconstruction for the ATLAS Calorimetry in the Framework of the Non-parametrical Method

This paper discusses hadron energy reconstruction for the ATLAS barrel prototype combined calorimeter (consisting of a lead-liquid argon electromagnetic part and an iron-scintillator hadronic part) in the framework of the non-parametrical method. The non-parametrical method utilizes only the known $e/h$ ratios and the electron calibration constants and does not require the determination of any parameters by a minimization technique. Thus, this technique lends itself to an easy use in a first level trigger. The reconstructed mean values of the hadron energies are within $\pm 1$ of the true values and the fractional energy resolution is $[(58\pm3)/\sqrt{E}+(2.5\pm0.3)$. The value of the $e/h$ ratio obtained for the electromagnetic compartment of the combined calorimeter is $1.74\pm0.04$ and agrees with the prediction that $e/h > 1.7$ for this electromagnetic calorimeter. Results of a study of the longitudinal hadronic shower development are also presented. The data have been taken in the H8 beam line of the CERN SPS using pions of energies from 10 to 300 GeV.Comment: 33 pages, 13 figures, Will be published in NIM

The COMPASS Experiment at CERN

The COMPASS experiment makes use of the CERN SPS high-intensitymuon and hadron beams for the investigation of the nucleon spin structure and the spectroscopy of hadrons. One or more outgoing particles are detected in coincidence with the incoming muon or hadron. A large polarized target inside a superconducting solenoid is used for the measurements with the muon beam. Outgoing particles are detected by a two-stage, large angle and large momentum range spectrometer. The setup is built using several types of tracking detectors, according to the expected incident rate, required space resolution and the solid angle to be covered. Particle identification is achieved using a RICH counter and both hadron and electromagnetic calorimeters. The setup has been successfully operated from 2002 onwards using a muon beam. Data with a hadron beam were also collected in 2004. This article describes the main features and performances of the spectrometer in 2004; a short summary of the 2006 upgrade is also given.Comment: 84 papes, 74 figure

Comparison of vaginal microbiota sampling techniques: Cytobrush versus swab

© 2017 The Author(s). Evidence suggests the vaginal microbiota (VM) may influence risk of persistent Human Papillomavirus (HPV) infection and cervical carcinogenesis. Established cytology biobanks, typically collected with a cytobrush, constitute a unique resource to study such associations longitudinally. It is plausible that compared to rayon swabs; the most commonly used sampling devices, cytobrushes may disrupt biofilms leading to variation in VM composition. Cervico-vaginal samples were collected with cytobrush and rayon swabs from 30 women with high-grade cervical precancer. Quantitative PCR was used to compare bacterial load and Illumina MiSeq sequencing of the V1-V3 regions of the 16S rRNA gene used to compare VM composition. Cytobrushes collected a higher total bacterial load. Relative abundance of bacterial species was highly comparable between sampling devices (R 2 = 0.993). However, in women with a Lactobacillus-depleted, high-diversity VM, significantly less correlation in relative species abundance was observed between devices when compared to those with a Lactobacillus species-dominant VM (p = 0.0049). Cytobrush and swab sampling provide a comparable VM composition. In a small proportion of cases the cytobrush was able to detect underlying high-diversity community structure, not realized with swab sampling. This study highlights the need to consider sampling devices as potential confounders when comparing multiple studies and datasets