Structured light, transmission, and scattering

Numerous theoretical and experimental studies have established the principle that beams conveying orbital angular momentum offer a rich scope for information transfer. However, it is not clear how far it is practicable to operate such a concept at the single-photon level - especially when such a beam propagates through a system in which scattering can occur. In cases where scattering leads to photon deflection, it produces losses; however in terms of the retention of information content, there should be more concern over forward scattering. Based on a quantum electrodynamical formulation of theory, this paper aims to frame and resolve the key issues. A quantum amplitude is constructed for the representation of single and multiple scattering events in the propagation an individual photon, from a suitably structured beam. The analysis identifies potential limitations of principle, undermining complete fidelity of quantum information transmission

Music in sport and exercise: An update on research and application

The full text of this article can be viewed at the link below.In spring 1999, almost a decade ago, the first author published in The Sport Journal an article titled “Music in Sport and Exercise: Theory and Practice.” The present article’s origins are in that earlier work and the first author’s research while a master’s student at the United States Sports Academy in 1991–92. To a greater degree than in the original 1999 article, this article focuses on the applied aspects of music in sport and exercise. Moreover, it highlights some new research trends emanating not only from our own publications, but also from the work of other prominent researchers in the field. The content is oriented primarily towards the needs of athletes and coaches

Metamodulation of a spinal locomotor network by nitric oxide

Flexibility in the output of spinal networks can be accomplished by the actions of neuromodulators; however, little is known about how the process of neuromodulation itself may be modulated. Here we investigate the potential "meta"-modulatory hierarchy between nitric oxide (NO) and noradrenaline (NA) in Xenopus laevis tadpoles. NO and NA have similar effects on fictive swimming; both potentiate glycinergic inhibition to slow swimming frequency and GABAergic inhibition to reduce episode durations. In addition, both modulators have direct effects on the membrane properties of motor neurons. Here we report that antagonism of noradrenergic pathways with phentolamine dramatically influences the effect of the NO donor S-nitroso-N-acetylpenicillamine (SNAP) on swimming frequency, but not its effect on episode durations. In contrast, scavenging extracellular NO with 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide(PTIO) does not influence any of the effects of NA on fictive swimming. These data place NO above NA in the metamodulatory hierarchy, strongly suggesting that NO works via a noradrenergic pathway to control glycine release but directly promotes GABA release. We confirmed this possibility using intracellular recordings from motor neurons. In support of a natural role for NO in the Xenopus locomotor network, PTIO not only antagonized all of the effects of SNAP on swimming but also, when applied on its own, modulated both swimming frequency and episode durations in addition to the underlying glycinergic and GABAergic pathways. Collectively, our results illustrate that NO and NA have parallel effects on motor neuron membrane properties and GABAergic inhibition, but that NO serially metamodulates glycinergic inhibition via NA.Publisher PDFPeer reviewe

Functional expression of the polymeric immunoglobulin receptor from cloned cDNA in fibroblasts.

The polymeric immunoglobulin receptor, a transmembrane protein, is made by a variety of polarized epithelial cells. After synthesis, the receptor is sent to the basolateral surface where it binds polymeric IgA and IgM. The receptor-ligand complex is endocytosed, transported across the cell in vesicles, and re-exocytosed at the apical surface. At some point the receptor is proteolytically cleaved so that its extracellular ligand binding portion (known as secretory component) is severed from the membrane and released together with the polymeric immunoglobulin at the apical surface. We have used a cDNA clone coding for the rabbit receptor and a retroviral expression system to express the receptor in a nonpolarized mouse fibroblast cell line, psi 2, that normally does not synthesize the receptor. The receptor is glycosylated and sent to the cell surface. The cell cleaves the receptor to a group of polypeptides that are released into the medium and co-migrate with authentic rabbit secretory component. Cleavage and release of secretory component do not depend on the presence of ligand. The cells express on their surface 9,600 binding sites for the ligand, dimeric IgA. The ligand can be rapidly endocytosed and then re-exocytosed, all within approximately 10 min. Very little ligand is degraded. At least some of the ligand that is released from the cells is bound to secretory component. The results presented indicate that we have established a powerful new system for analyzing the complex steps in the transport of poly-Ig and the general problem of membrane protein sorting

Seasonal and inter-annual temperature variability in the bottom waters over the western Black Sea shelf

Long-term changes in the state of the Bottom Shelf Water (BSW) on the Western shelf of the Black Sea are assessed using analysis of intra-seasonal and inter-annual temperature variations. For the purpose of this study the BSW is defined as such shelf water mass between the seabed and the upper mixed layer (bounded by the σθ = 14.2 isopycnal) which has limited ability to mix vertically with oxygen-rich surface waters during the warm season due to formation of a seasonal pycnocline. A long-term time series of temperature anomalies in the BSW is constructed from in-situ observations taken over the 2nd half of the 20th century. The BSW is shown to occupy nearly half of the shelf area during the summer stratification period (May–November).The results reveal a warm phase in the 1960s/70s, followed by a cold phase between 1985 and 1995 and a further warming after 1995. The transition between the warm and cold periods coincides with a regime shift in the Black Sea ecosystem. While it was confirmed that the memory of winter convection is well preserved over the following months in the deep sea, the signal of winter cooling in the BSW significantly reduces during the warm season. The potential of the BSW to ventilate horizontally during the warm season with the deep-sea waters is assessed using isopycnic analysis of temperature variations. It is shown that temperature in the BSW is stronger correlated with the temperature of Cold Intermediate Waters (CIW) in the deep sea than with the severity of the previous winters, thus indicating that the isopycnal exchanges with the deep sea are more important for inter-annual/inter-decadal variability of the BSW on the western Black Sea shelf than effects of winter convection on the shelf itself

Small Telescope Exoplanet Transit Surveys: XO

The XO project aims at detecting transiting exoplanets around bright stars from the ground using small telescopes. The original configuration of XO (McCullough et al. 2005) has been changed and extended as described here. The instrumental setup consists of three identical units located at different sites, each composed of two lenses equipped with CCD cameras mounted on the same mount. We observed two strips of the sky covering an area of 520 deg$^2$ for twice nine months. We build lightcurves for ~20,000 stars up to magnitude R~12.5 using a custom-made photometric data reduction pipeline. The photometric precision is around 1-2% for most stars, and the large quantity of data allows us to reach a millimagnitude precision when folding the lightcurves on timescales that are relevant to exoplanetary transits. We search for periodic signals and identify several hundreds of variable stars and a few tens of transiting planet candidates. Follow-up observations are underway to confirm or reject these candidates. We found two close-in gas giant planets so far, in line with the expected yield.Comment: Invited review, 25 pages, 16 figure

The role of structural characteristics in problem video game playing: a review

The structural characteristics of video games may play an important role in explaining why some people play video games to excess. This paper provides a review of the literature on structural features of video games and the psychological experience of playing video games. The dominant view of the appeal of video games is based on operant conditioning theory and the notion that video games satisfy various needs for social interaction and belonging. However, there is a lack of experimental and longitudinal data that assesses the importance of specific features in video games in excessive video game playing. Various challenges in studying the structural features of video games are discussed. Potential directions for future research are outlined, notably the need to identify what problem (as opposed to casual) players seek from the video games they play