1,111 research outputs found
Wave-vector and polarization dependence of conical refraction
We experimentally address the wave-vector and polarization dependence of the
internal conical refraction phenomenon by demonstrating that an input light
beam of elliptical transverse profile refracts into two beams after passing
along one of the optic axes of a biaxial crystal, i.e. it exhibits double
refraction instead of refracting conically. Such double refraction is
investigated by the independent rotation of a linear polarizer and a
cylindrical lens. Expressions to describe the position and the intensity
pattern of the refracted beams are presented and applied to predict the
intensity pattern for an axicon beam propagating along the optic axis of a
biaxial crystal
Polarization tailored novel vector beams based on conical refraction
Coherent vector beams with involved states of polarization (SOP) are
widespread in the literature, having applications in laser processing,
super-resolution imaging and particle trapping. We report novel vector beams
obtained by transforming a Gaussian beam passing through a biaxial crystal, by
means of the conical refraction phenomenon. We analyze both experimentally and
theoretically the SOP of the different vector beams generated and demonstrate
that the SOP of the input beam can be used to control both the shape and the
SOP of the transformed beam. We also identify polarization singularities of
such beams for the first time and demonstrate their control by the SOP of an
input beam
Intermittent suckling in combination with an older weaning age improves growth, feed intake and aspects of gastrointestinal tract carbohydrate absorption in pigs after weaning
This study tested the hypothesis that intermittent suckling (IS) with or without an older weaning age would improve post-weaning gastrointestinal tract (GIT) carbohydrate absorptive capacity in pigs while reducing post-weaning stress and aspects of the inflammatory response. Three weaning regimes using primiparous sows were compared: (1) conventional weaning (CW28) (n = 22), where piglets were weaned conventionally at day 28; (2) IS28 (n = 21), where IS started at day 21 until weaning at day 28; and (3) IS35 (n = 21), where IS started at day 28 until weaning at day 35. Sugar absorption tests (10% mannitol or 10% galactose) were used to measure GIT absorptive capacity. All measured parameters were compared in relation to weaning across treatments (i.e., different physiological ages were compared). The IS35 pigs grew fastest in the 12 days after weaning (p < 0.01) and had the highest solid feed intake before and after weaning (p < 0.05). Irrespective of treatment, pre-weaning mannitol levels were higher than post-weaning levels (p < 0.01), whereas post-weaning galactose levels were highest in IS35 pigs (p < 0.01). Cytokine data did not show any treatment effects. In conclusion, these data suggest that IS in combination with an older weaning age (day 35) improved post-weaning adaptation as evidenced by improvements in performance measures and galactose absorption. However, IS28 did not improve post-weaning performance
On the dual-cone nature of the conical refraction phenomenon
In conical refraction (CR), a focused Gaussian input beam passing through a biaxial crystal and parallel to one of the optic axes is transformed into a pair of concentric bright rings split by a dark (Poggendorff) ring at the focal plane. Here, we show the generation of a CR transverse pattern that does not present the Poggendorff fine splitting at the focal plane, i.e., it forms a single light ring. This light ring is generated from a nonhomogeneously polarized input light beam obtained by using a spatially inhomogeneous polarizer that mimics the characteristic CR polarization distribution. This polarizer allows modulating the relative intensity between the two CR light cones in accordance with the recently proposed dual-cone model of the CR phenomenon. We show that the absence of interfering rings at the focal plane is caused by the selection of one of the two CR cones. (C) 2015 Optical Society of Americ
Prevalence and treatment of hypertension, diabetes and asthma in Kenya: A representative household survey in eight counties in 2016
Objectives: In 2014, 27% of total deaths in Kenya were due to non-communicable diseases (NCDs). The objectives of this study were: 1) To report on the prevalence of households with members diagnosed and treated for hypertension, diabetes, and asthma in eight counties in Kenya, and 2) To explore possible reasons for the variation in prevalence of these three NCDs in the different counties. Design, Setting andSubjects: A total of 7,870 households in a representative sample in eight Kenyan counties were screened for the presence of any non-communicable disease. Diagnosis and treatment data on these NCDs was collected and compared using county specific independent data from the 2014 Kenyan Demographic Health Survey (DHS).Main Outcome Measures: Over all the eight surveyed counties, 10.7% of households reported having one or more individuals with an NCD. The county specific prevalence varied from 3% to 30.2%. Of the 7,870 households surveyed, 6.9% reported having a diagnosis of hypertension, 3.2% of asthma, and 2.3% of diabetes.Results: The strongest explanatory variables for the variation in overall prevalence of NCDs related to access to health services and lifestyle risk factors. Conclusion: The prevalence of reported NCDs varies considerably between counties in Kenya. Reasons may relate to a lack of access to diagnostic facilities or ifferences in lifestyle risk factors. We recommend a comprehensive field survey of biometric, health access, and lifestyle risk factors to determine the true prevalence and related risk factors for NCDs in Kenya
Blue-detuned optical ring trap for Bose-Einstein condensates based on conical refraction
We present a novel approach for the optical manipulation of neutral atoms in annular light structures produced by the phenomenon of conical refraction occurring in biaxial optical crystals. For a beam focused to a plane behind the crystal, the focal plane exhibits two concentric bright rings enclosing a ring of null intensity called the Poggendorff ring. We demonstrate both theoretically and experimentally that the Poggendorff dark ring of conical refraction is confined in three dimensions by regions of higher intensity. We derive the positions of the confining intensity maxima and minima and discuss the application of the Poggendorff ring for trapping ultra-cold atoms using the repulsive dipole force of blue-detuned light. We give analytical expressions for the trapping frequencies and potential depths along both the radial and the axial directions. Finally, we present realistic numerical simulations of the dynamics of a 87Rb Bose-Einstein condensate trapped inside the Poggendorff ring which are in good agreement with corresponding experimental results
Glial D-Serine Gates NMDA Receptors at Excitatory Synapses in Prefrontal Cortex.
N-methyl-D-aspartate receptors (NMDARs) subserve numerous neurophysiological and neuropathological processes in the cerebral cortex. Their activation requires the binding of glutamate and also of a coagonist. Whereas glycine and D-serine (D-ser) are candidates for such a role at central synapses, the nature of the coagonist in cerebral cortex remains unknown. We first show that the glycine-binding site of NMDARs is not saturated in acute slices preparations of medial prefrontal cortex (mPFC). Using enzymes that selectively degrade either D-ser or glycine, we demonstrate that under the present conditions, D-ser is the principle endogenous coagonist of synaptic NMDARs at mature excitatory synapses in layers V/VI of mPFC where it is essential for long-term potentiation (LTP) induction. Furthermore, blocking the activity of glia with the metabolic inhibitor, fluoroacetate, impairs NMDAR-mediated synaptic transmission and prevents LTP induction by reducing the extracellular levels of D-serine. Such deficits can be restored by exogenous D-ser, indicating that the D-amino acid mainly originates from glia in the mPFC, as further confirmed by double-immunostaining studies for D-ser and anti-glial fibrillary acidic protein. Our findings suggest that D-ser modulates neuronal networks in the cerebral cortex by gating the activity of NMDARs and that altering its levels is relevant to the induction and potentially treatment of psychiatric and neurological disorders
The native cistrome and sequence motif families of the maize ear
Elucidating the transcriptional regulatory networks that underlie growth and development requires robust ways to define the complete set of transcription factor (TF) binding sites. Although TF-binding sites are known to be generally located within accessible chromatin regions (ACRs), pinpointing these DNA regulatory elements globally remains challenging. Current approaches primarily identify binding sites for a single TF (e.g. ChIP-seq), or globally detect ACRs but lack the resolution to consistently define TF-binding sites (e.g. DNAse-seq, ATAC-seq). To address this challenge, we developed MNase-defined cistrome-Occupancy Analysis (MOA-seq), a high-resolution (< 30 bp), high-throughput, and genome-wide strategy to globally identify putative TF-binding sites within ACRs. We used MOA-seq on developing maize ears as a proof of concept, able to define a cistrome of 145,000 MOA footprints (MFs). While a substantial majority (76%) of the known ATAC-seq ACRs intersected with the MFs, only a minority of MFs overlapped with the ATAC peaks, indicating that the majority of MFs were novel and not detected by ATAC-seq. MFs were associated with promoters and significantly enriched for TF-binding and long-range chromatin interaction sites, including for the well-characterized FASCIATED EAR4, KNOTTED1, and TEOSINTE BRANCHED1. Importantly, the MOA-seq strategy improved the spatial resolution of TF-binding prediction and allowed us to identify 215 motif families collectively distributed over more than 100,000 non-overlapping, putatively-occupied binding sites across the genome. Our study presents a simple, efficient, and high-resolution approach to identify putative TF footprints and binding motifs genome-wide, to ultimately define a native cistrome atlas
Coordination of Chloroplastic Metabolism in N-Limited Chlamydomonas reinhardtii by Redox Modulation (I. The Activation of Phosphoribulosekinase and Glucose-6-Phosphate Dehydrogenase Is Relative to the Photosynthetic Supply of Electrons)
Coordination of Chloroplastic Metabolism in N-Limited Chlamydomonas reinhardtii by Redox Modulation (II. Redox Modulation Activates the Oxidative Pentose Phosphate Pathway during Photosynthetic Nitrate Assimilation)
- …