Resonances of periodic metal-dielectric structures at the infrared wavelength region

Metal meshes have been used as reflectors in radar receivers for wavelength much longer than the periodic constant of the conducting wires and as optical reflectors in a FabryPerot in the far infrared. Cross shaped metal meshes can be used as band pass filters but the design theory and near field properties have not been known. Transmittance of thin, single-layer and multiplayer metal meshes has been investigated using Micro-Strips, yielding numerical solutions of Maxwell\u27s equations. The near field effect was studied for two alignment configurations of cross shaped metal meshes, both free standing and with dielectrics, and transmission line theory was applied for the interpretation as an oscillator mode model. The model for the interpretation of the mode of a single mesh uses a pair of coupled surface wave (that is one standing wave on each side). The transmiftance of multi-layer metal meshes are interpreted as modes composed of resonance modes of the single mesh, the Fabry-Perot modes depending on the separation of the meshes, and their interaction. Experimental data for thick inductive cross shaped metal meshes agree very well with Micro-Stripes calculations in the long wavelength region and with Fourier Modal method calculations in the short wavelength. The transmittances of all these meshes show similar resonance peaks and the same dependence on thickness of the short wavelength peaks, suggesting that the interpretation using the oscillator mode model is valid in the short and long wavelength region. Stacks of thin metal meshes have been studied with Micro-Strips and transmission line theory. Narrow transmission regions for inductive meshes and narrow bandgap regions for capacitive meshes may be obtained from layered structures for the aligned configuration and spacing of 1/4 resonance wavelength of a single layer

FMRFamide-like peptides expand the behavioral repertoire of a densely connected nervous system

Animals, including humans, can adapt to environmental stress through phenotypic plasticity. The free-living nematode Caenorhabditis elegans can adapt to harsh environments by undergoing a whole-animal change, involving exiting reproductive development and entering the stress-resistant dauer larval stage. The dauer is a dispersal stage with dauer-specific behaviors for finding and stowing onto carrier animals, but how dauers acquire these behaviors, despite having a physically limited nervous system of 302 neurons, is poorly understood. We compared dauer and reproductive development using whole-animal RNA sequencing at fine time points and at sufficient depth to measure transcriptional changes within single cells. We detected 8,042 genes differentially expressed during dauer and reproductive development and observed striking up-regulation of neuropeptide genes during dauer entry. We knocked down neuropeptide processing using sbt-1 mutants and demonstrate that neuropeptide signaling promotes the decision to enter dauer rather than reproductive development. We also demonstrate that during dauer neuropeptides modulate the dauer-specific nictation behavior (carrier animal-hitchhiking) and are necessary for switching from repulsion to CO_2 (a carrier animal cue) in nondauers to CO_2 attraction in dauers. We tested individual neuropeptides using CRISPR knockouts and existing strains and demonstrate that the combined effects of flp-10 and flp-17 mimic the effects of sbt-1on nictation and CO_2 attraction. Through meta-analysis, we discovered similar up-regulation of neuropeptides in the dauer-like infective juveniles of diverse parasitic nematodes, suggesting the antiparasitic target potential of SBT-1. Our findings reveal that, under stress, increased neuropeptide signaling in C. elegans enhances their decision-making accuracy and expands their behavioral repertoire

Hormonal Signal Amplification Mediates Environmental Conditions during Development and Controls an Irreversible Commitment to Adulthood

Many animals can choose between different developmental fates to maximize fitness. Despite the complexity of environmental cues and life history, different developmental fates are executed in a robust fashion. The nematode Caenorhabditis elegans serves as a powerful model to examine this phenomenon because it can adopt one of two developmental fates (adulthood or diapause) depending on environmental conditions. The steroid hormone dafachronic acid (DA) directs development to adulthood by regulating the transcriptional activity of the nuclear hormone receptor DAF-12. The known role of DA suggests that it may be the molecular mediator of environmental condition effects on the developmental fate decision, although the mechanism is yet unknown. We used a combination of physiological and molecular biology techniques to demonstrate that commitment to reproductive adult development occurs when DA levels, produced in the neuroendocrine XXX cells, exceed a threshold. Furthermore, imaging and cell ablation experiments demonstrate that the XXX cells act as a source of DA, which, upon commitment to adult development, is amplified and propagated in the epidermis in a DAF-12 dependent manner. This positive feedback loop increases DA levels and drives adult programs in the gonad and epidermis, thus conferring the irreversibility of the decision. We show that the positive feedback loop canalizes development by ensuring that sufficient amounts of DA are dispersed throughout the body and serves as a robust fate-locking mechanism to enforce an organism-wide binary decision, despite noisy and complex environmental cues. These mechanisms are not only relevant to C. elegans but may be extended to other hormonal-based decision-making mechanisms in insects and mammals

The "Head Snap": A Subtle Clinical Feature During the Finger–Nose–Finger Maneuver in Essential Tremor

Background:: Essential tremor is characterized by several hyperkinetic movements, including arm and head tremors.  We report another movement of the head in patients with essential tremor, which we term the "head snap." This was observed as a jerking motion of the head in some patients while they performed the finger-nose-finger maneuver. Methods:: We compared the prevalence of the head snap in essential tremor patients vs. Parkinson's disease patients. We also assessed the clinical correlates of the head snap.  Results:: Ten (20%) of 50 essential tremor patients exhibited a head snap of any severity (rating ≥0.5) vs. 0 of 50 Parkinson's disease patients (p = 0.001). Patients with head snap had more severe arm tremor on Archimedes spiral drawings (p = 0.019) and were more likely to have head tremor (p = 0.03) than those without it. Conclusions: This sign could be a useful aid in the clinical diagnosis of tremor.</p

Ambiguity Function Analysis For Passive Radar System Performance

Passive coherent location (PCL) systems can employ a variety of terrestrial broadcast signals for target detection and ranging. Through analysis of the ambiguity function, one can determine a signal\u27s suitability for this application. The main parameters of concern are amplitude, range resolution, Doppler resolution and sidelobe ratios. This paper presents an analysis of several recorded signals in terms of their suitability for PCL. We also discuss the effects of compromise when choosing between performance in range or Doppler resolution, signal processing gain, and surveillance volume

Postural and Intention Tremors in Essential Tremor and Parkinson's Disease

<p>VIDEOTAPE LEGEND</p> <p>1. Clinical Impression 1: Proximal (i.e., wrist) postural tremor rather than distal (MCP + phalanges [including thumb]) postural tremor occurs in the left arm of this ET patient.</p> <p>2. Clinical Impression 1: Proximal (i.e., wrist) postural tremor rather than distal (MCP + phalanges [including thumb]) postural tremor occurs in the right arm of this ET patient.</p> <p>3. Clinical Impression 1: Distal (esp. MCP) postural tremor rather than proximal (i.e., wrist, elbow, shoulder) postural tremor occurs in the left arm of this PD patient.</p> <p>4. Clinical Impression 2: Postural tremor, as seen in the right arm of this ET patient, typically produces wrist flexion-extension rather than wrist pronation-supination.</p> <p>5. Clinical Impression 2: Postural tremor, as seen in the right arm of this ET patient, involves wrist flexion-extension.</p> <p>6. Clinical Impression 2: Postural tremor, as seen in the right arm of this PD patient, typically produces wrist pronation-supination rather than flexion-extension.</p> <p>7. Clinical Impression 2: Postural tremor, as seen in the right arm of this PD patient, typically produces wrist pronation-supination.</p> <p>8. Clinical Impression 4: Intention tremor, which often occurs in ET (see left arm), is rare in PD.</p> <p>9. Clinical Impression 4: Intention tremor, which often occurs in ET (see left arm), is rare in PD.</p> <p>10. Clinical Impression 4: Intention tremor is not seen in this PD patient.</p> <p>11. Clinical Impression 4: Intention tremor is not seen in this PD patient.</p