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Low Threshold (low + threshold)
Selected AbstractsLow Thresholds in Polymer Lasers on Conductive Substrates by Distributed Feedback Nanoimprinting: Progress Toward Electrically Pumped Plastic LasersADVANCED MATERIALS, Issue 7 2009Ebinazar B. Namdas A light-emitting transistor (LEFET) architecture with a distributed feedback (DFB) resonator structure nanoimprinted into the gain medium offers a route to achieving an electrically pumped plastic laser. A 2D DFB laser provides lower lasing thresholds than a 1D DFB laser under identical conditions. The 2D DFB lasers exhibit excellent characteristics with lasing threshold and slope efficiency of 32,nJ/pulse and 1.2%, respectively. [source] Diamond plates on dome-like particles: preparation, characterization and field emission propertiesJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2010Rajanish N. Tiwari Thin diamond microplates have been grown on dome-like/hemispherical carbon particles on titanium carbide by a microwave plasma chemical vapour deposition (MPCVD) method using a gas mixture of methane and hydrogen. The diamond microplates have a thickness of about 200,nm. A thin (300,nm) film of titanium carbide was formed during carburization of sputtered titanium on an Si(100) substrate in MPCVD. The hemispherical carbon particles were covered with diamond microplates. The diamond microplates are isolated electron-emitting spherules and exhibit a low threshold (50,V,µm,1) and high current density (0.92,mA,cm,2) in their field emission properties. A possible mechanism for the formation of the diamond microplates and hemispherical carbon particles is presented. [source] Portosystemic pressure gradient during transjugular intrahepatic portosystemic shunt with Viatorr stent graft: What is the critical low threshold to avoid medically uncontrolled low pressure gradient related complications?JOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 1 2008Hwan-Hoon Chung Abstract Background:, Inappropriately decreased portosystemic pressure gradient (PSG) during transjugular intrahepatic portosystemic shunt (TIPS) can cause fatal complications but the critical low threshold of PSG is still not clear. The aim of the present study was to evaluate the critical low threshold of PSG during TIPS. Methods:, Sixty-six patients with cirrhosis who successfully underwent de novo TIPS with Viatorr stent grafts were studied. Medically uncontrolled low pressure gradient (LPR) complication was defined as when a patient died, or when acute transplantation or a TIPS reduction procedure was performed due to refractory encephalopathy or the deterioration of hepatic function within 3 months after the procedure. For the determination of the risk group for medically uncontrolled LPR complications, the Child-Pugh score and the model of end-stage liver disease (MELD) score showing a 100% negative predictive value was decided on as a threshold for each score. The risk group was defined when either of both scores was higher than its threshold. For the determination of a critical low post-TIPS PSG, a value of post-TIPS PSG showing the highest discrimination power on the receiver operating characteristic (ROC) curve in the risk group was decided on as a critical low threshold of PSG. The medically uncontrolled LPR complication rates of the patients with the determined threshold or lower were evaluated for the risk group. Results:, Medically uncontrolled LPR complications developed in nine patients (13.6%). Five patients died and four patients had TIPS reduction procedures. Patients with more than 10 on the Child-Pugh score or more than 14 on the MELD score were determined to be the risk group and 34 patients were included. The critical lower threshold of the post-TIPS PSG showing the highest discrimination power on the ROC curve was 5 mmHg (sensitivity 100%, specificity 72%), and the medically uncontrolled LPR complication rates of the patients with 5 mmHg or lower on the post-TIPS PSG were 56.3% (9/16) in the risk group. Conclusions:, The critical threshold of the post-TIPS PSG to avoid the medically uncontrolled LPR complications of TIPS was >5 mmHg. The PSG should not be reduced below this level in the risk group. [source] Continuously tunable S and C+L bands ultra wideband erbium-doped fiber ring laserLASER PHYSICS LETTERS, Issue 8 2009Q. Wang Abstract This paper presents an ultra wideband tunable silicabased erbium doped fiber ring laser (EDFRL) that can be continuously tuned in S and C+L bands from 1475 to 1619 nm. It is the first time that a fiber ring laser's tuning range reaches 144 nm using a standard silica-based C-band erbium-doped fiber as gain media. In the laser configuration two isolators are used in the fiber loop for suppressing the ASE in C-band and elevating the lasing gain in S-band. As a result the available lasing wavelength is extended toward the shorter wavelength of the gain bandwidth. The optimized erbium-doped fiber length, output coupling ratio and pumping laser power have been obtained through experimental study. This ring fiber laser has simple configuration, low threshold, flat laser spectral distribution and high signal-to-ASE-noise ratio. The laser will have many potential applications in fiber sensor wavelength interrogation, high-resolution spectroscopy and fiber optic communications. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Acquired Ichthyosis as a Manifestation of Acute Cutaneous Graft-Versus-Host DiseasePEDIATRIC DERMATOLOGY, Issue 1 2007Jennifer Huang M.D. While some authors have suggested the association of acquired ichythosis with cutaneous graft-versus-host disease, the evidence to support this association is rare. We describe a patient who developed enteritis secondary to acute graft-versus-host disease and had concomitant ichthyosiform lesions. Several months later, he was diagnosed with cutaneous graft-versus-host disease. This patient is presented to suggest that acquired ichthyosis is an underrecognized manifestation of acute cutaneous graft-versus-host disease. Given the important prognostic implications of this diagnosis, we recommend a low threshold for performing a skin biopsy to rule out GVHD in the appropriate clinical setting. [source] Absence of corneal endothelium injury in non-human primates treated with and without ophthalmologic drugs and exposed to 2.8,GHz pulsed microwaves,,BIOELECTROMAGNETICS, Issue 4 2010Shin-Tsu Lu Abstract Microwave-induced corneal endothelial damage was reported to have a low threshold (2.6,W/kg), and vasoactive ophthalmologic medications lowered the threshold by a factor of 10,0.26,W/kg. In an attempt to confirm these observations, four adult male Rhesus monkeys (Macaca mulatta) under propofol anesthesia were exposed to pulsed microwaves in the far field of a 2.8,GHz signal (1.43,±,0.06,µs pulse width, 34,Hz pulse repetition frequency, 13.0,mW/cm2 spatial and temporal average, and 464,W/cm2 spatial and temporal peak (291,W/cm2 square wave equivalent) power densities). Corneal-specific absorption rate was 5.07,W/kg (0.39,W/kg/mW/cm2). The exposure resulted in a 1.0,1.2,°C increase in eyelid temperature. In Experiment I, exposures were 4,h/day, 3 days/week for 3 weeks (nine exposures and 36,h total). In Experiment II, these subjects were pretreated with 0.5% Timolol maleate and 0.005% Xalatan® followed by 3 or 7 4-h pulsed microwave exposures. Under ketamine,xylazine anesthesia, a non-contact specular microscope was used to obtain corneal endothelium images, corneal endothelial cell density, and pachymetry at the center and four peripheral areas of the cornea. Ophthalmologic measurements were done before and 7, 30, 90, and 180 days after exposures. Pulsed microwave exposure did not cause alterations in corneal endothelial cell density and corneal thickness with or without ophthalmologic drugs. Therefore, previously reported changes in the cornea exposed to pulsed microwaves were not confirmed at exposure levels that are more than an order of magnitude higher. Bioelectromagnetics 31:324,333, 2010. Published 2010 Wiley-Liss, Inc. [source] Appropriate antenatal corticosteroid use in women at risk for preterm birth before 34 weeks of gestationBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 8 2010R Mahony Please cite this paper as: Mahony R, McKeating A, Murphy T, McAuliffe F, O'Herlihy C, Foley M. Appropriate antenatal corticosteroid use in women at risk for preterm birth before 34 weeks of gestation. BJOG 2010;117:963,967. Objective, To determine the utilisation of antenatal corticosteroid administration in women presenting at risk of preterm birth (PTB) in a centre where tocolytics are not prescribed. Design, A prospective cohort study. Setting, Tertiary referral centre, Dublin, Ireland. Population, Four hundred and fourteen consecutive women presenting at risk of PTB. Methods, Clinical details were collated prospectively on all booked patients who presented at risk of PTB (i.e. at <34 weeks of gestation) during 2008. Main outcome measure, Rate of administration of antenatal corticosteroids in PTB. Results, Of 8985 deliveries, 414 women (5%) presented at <34 weeks of gestation with a clinical potential for PTB, of whom 277 (67%) received antenatal corticosteroids. Amongst women delivering at <34 weeks of gestation, 93% (80/86) received any corticosteroids and 76% (65/86) received a complete course. The ratio of women given a complete course of corticosteroids to the number who actually delivered before 34 weeks of gestation was 4:1 overall. Analysis by indication for PTB revealed this ratio to be 15:1 in suspected preterm labour (PTL), 8:1 in antepartum haemorrhage (APH), and 2:1 in both preterm prelabour rupture of membranes (PPROM) and medically indicated PTB (MIPTB). Seven of ten multiparae (70%) who delivered prematurely during the study period following PTL had a history of previous PTL before 34 weeks of gestation. Conclusion, The ratio of maternal antenatal corticosteroid administration for potential versus actual PTB at <34 weeks of gestation was high in categories such as PTL and substantial APH, whereas selection in PPROM and MIPTB approached 100%. There should be a low threshold for single course therapy for women with prior PTL before 34 weeks of gestation. [source] 4345: Confusion and controversies in diagnosis and treatment of myastheniaACTA OPHTHALMOLOGICA, Issue 2010E EGGENBERGER Myasthenia gravis is an afferent ocular motor mimic. The disease may appear with any pattern of pupil-sparing, painless ocular misalignment with or without ptosis; accordingly, common mistaken diagnoses included CN3 palsy or internuclear ophthalmoplegia. Variability adds to diagnostic confusion, as patients may be asymptomatic and have a normal exam at certain stages in the disease. Clinical context remains the first diagnostic key, however, lab and electrophysiology are very helpful. Acetylcholine receptor antibodies are present in approximately 50% of ocular MG, but are highly specific. Single fiber EMG is perhaps the most sensitive test, being abnormal in approximately 90% of cases. Treatment is symptom dependent; pyridostigmine is often used as initial therapy and quite effective for ptosis and dysphagia, while additional immunosuppressives are often required for diplopia. We often initiate therapy with low dose every other day prednisone, and have a low threshold to add mycophenolate mofetil. [source] Predictive factors for successful sacral nerve stimulation in the treatment of faecal incontinence: a 10-year cohort analysisCOLORECTAL DISEASE, Issue 3 2008T. C. Dudding Abstract Objective, Sacral nerve stimulation (SNS) is an established treatment for faecal incontinence. We aimed to identify specific factors that could predict the outcome of temporary and permanent stimulation. Method, A cohort analysis was performed to identify potential predictive factors in 81 patients who underwent temporary SNS at a single institution over a 10-year period (June 1996 to June 2006). Data were obtained from prospectively collected patient symptom diaries and quality of life questionnaires, operation reports, anorectal physiological studies, endoanal ultrasound images and radiology of lead placement. Results, Clinical outcome of temporary screening was not affected by patient gender, age, body mass index, severity or length of symptoms. The need for a repeated temporary procedure was associated with subsequent failure during screening (P = 0.008). A low threshold to obtain a motor response during temporary lead insertion was associated with improved outcome (P = 0.048). Evidence of anal sphincter trauma was associated with a greater risk of failure (P = 0.040). However, there was no difference in medium-term outcome between patients with external anal sphincter (EAS) defects and patients with intact anal sphincter muscles. Conclusion, Variables have been identified that help to predict the outcome of SNS. The presence of an EAS defect should not preclude treatment. [source] Patterns Of Quantitative Sensation Testing Of Hypoesthesia And Hyperalgesia Are Predictive Of Diabetic Polyneuropathy,a Study Of Three CohortsJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 2 2000P.J. Dyck OBJECTIVE,To test quantitative sensation testing (QST) patterns of hypoesthesia and hyperalgesia as indicators of diabetic polyneuropathy (DPN) and its severity. RESEARCH DESIGN AND METHODS,We used Computer-Assisted Sensory Examination IV characterized the QST results of the foot of each patient in three diabetic cohorts (similar to 1,500 patients) as hyperesthetic (less than or equal to 2.5th percentile), low-normal (2.5th,50th percentiles), high-normal (50th,97.5th percentiles), or hypoesthetic (greater than or equal to 97.5th percentile), and tested associations with symptoms, impairments, and test abnormalities. RESULTS,Overall neuropathic impairment was most severe in the pancreas-renal transplant and nerve growth factor cohorts, but it was much less severe in the population-based Rochester Diabetic Neuropathy Study (RDNS) cohort. The frequency distribution of sensory abnormalities mirrored this difference. When the QST spectra of diabetic cohorts were compared with those of the control subject cohort for vibration and cooling sensations, the only abnormality observed was hypoesthesia, which was expressed as an increased number of subjects with values at or above the 97.5th percentile or by an increased percentage of cases with high-normal values. Symptoms and impairments of DPN were significantly more frequent in the subjects with Values at or above the 97.5th percentile than in the subjects whose values were between the 50th and 97.5th percentiles. For heat pain (HP) sensation thresholds (intermediate pain severity [HP:5], pain threshold [HP:0.5], and pain-stimulus response slope [HP:5-0.5]), an increased frequency of both hypoalgesia and hyperalgesia was observed (especially in the RDNS cohort). Steeper pain-stimulus response slopes were significantly associated with sensory symptoms, including severity of pain. CONCLUSIONS,1) Decreased vibratory sensation (hypoesthesia) appears to be characteristic of mild DPN, whereas pan-modality hypoesthesia is characteristic of severe DPN. 2) A shift of vibratory and cold detection thresholds and also of attributes of nerve conduction and a measure of autonomic dysfunction from low-normal (2.5th,50th percentiles) to high-normal (50th,37.5th percentiles) appears to precede overt expression of DPN and to thereby provide evidence of subclinical abnormality. 3) Heat stimulus-induced hyperesthesia (low thresholds) occurs especially in mild DPN, and, because it correlates with DPN symptoms and impairments, it must be attributed to hyperalgesia rather than to supersensitivity. Therefore, hypoalgesia or hyperalgesia may be an indicator of early DPN. [source] Do pollen carryover and pollinator constancy mitigate effects of competition for pollination?OIKOS, Issue 7 2009Benjamin R. Montgomery Pollinator constancy and pollen carryover are both thought to mitigate competitive effects that result when shared pollinators cause loss of pollen to heterospecific flowers. I present analytical and simulation models to investigate how pollinator constancy and pollen carryover interact with each other and with the relationship between pollen receipt and seed set to determine pollination success in competitive environments. With inconstant pollinators, increased pollen carryover reduces variance in pollen receipt without affecting average pollen receipt. Consequently, for flowers requiring at least a threshold quantity of pollen for success, rare flowers with inconstant pollinators benefit from reduced carryover, especially for high pollen receipt thresholds, whereas common flowers benefit from increased carryover, especially for low receipt thresholds. Pollinator constancy is predicted to increase pollen receipt, especially if pollen carryover rates are low. As a result, increased pollinator constancy reduces the range of pollen receipt thresholds for which carryover is beneficial. Similarly, for flowers whose pollination success is a convex function of pollen receipt, carryover is expected to increase fecundity if pollinators are inconstant, but with even a low degree of pollinator constancy, carryover reduces fecundity. These results predict that rare plants with many ovules per flower benefit from dispersing aggregations of pollen, especially if their pollinators exhibit constancy, whereas plants with inconstant pollinators and low thresholds of pollen receipt benefit from pollen grains dispersing individually to increase the number of flowers reached by the pollen. [source] | |||||||||||||