Publications by authors named "Keith Powell"

We measure the photothermal nonlinear response in suspended cubic silicon carbide (3C-SiC) and 3C-SiC-on-insulator (SiCOI) microring resonators. Bi-stability and thermo-optic hysteresis is observed in both types of resonators, with the suspended resonators showing a stronger response. A photothermal nonlinear index of 4.

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Owing to its attractive optical and electronic properties, silicon carbide is an emerging platform for integrated photonics. However an integral component of the platform is missing-an electro-optic modulator, a device which encodes electrical signals onto light. As a non-centrosymmetric crystal, silicon carbide exhibits the Pockels effect, yet a modulator has not been realized since the discovery of this effect more than three decades ago.

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Article Synopsis
  • * After annealing, our optical resonators achieve quality factors exceeding 41,000 and significantly lower propagation losses of 7 dB/cm, improving from 24 dB/cm in non-annealed chips.
  • * The improved performance is due to better SiC crystallinity and reduced surface roughness, while the thermo-optic coefficient remains stable and comparable to bulk SiC, indicating our method is effective for high-performance SiC circuits.
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The UK needs to step up its tree-planting efforts to make a dent on climate change. Here, suggests that vets could bring clients together to provide the money and land for such projects.

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Background And Purpose: Our initial aim was to generate cannabinoid agents that control spasticity, occurring as a consequence of multiple sclerosis (MS), whilst avoiding the sedative side effects associated with cannabis. VSN16R was synthesized as an anandamide (endocannabinoid) analogue in an anti-metabolite approach to identify drugs that target spasticity.

Experimental Approach: Following the initial chemistry, a variety of biochemical, pharmacological and electrophysiological approaches, using isolated cells, tissue-based assays and in vivo animal models, were used to demonstrate the activity, efficacy, pharmacokinetics and mechanism of action of VSN16R.

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Background: An advantage of using silver fluoride treatments for carious primary teeth in outreach programs especially where dental resources are limited is that the treatments can be carried out by dental auxiliaries. One limitation to date is that assessments of lesion status have been based on a tactile test where a sharp probe or explorer is drawn across the surface of a lesion to assess its hardness. This is a technique-sensitive step and has the potential for iatrogenic damage, especially when a lesion is deep.

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Objective: Febrile infants younger than 60 days are at risk for serious bacterial infections (SBIs) and often undergo extensive laboratory investigation and hospitalization. We aim to determine the diagnostic value of serum procalcitonin (PCT) concentration for identification of febrile infants at low risk for SBI in comparison to the Rochester Criteria (RC).

Methods: Infants 2 to 60 days of age with rectal temperature 38°C were enrolled between May 2004 and March 2007.

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Structural biology studies typically require large quantities of pure, soluble protein. Currently the most widely-used method for obtaining such protein involves the use of bioinformatics and experimental methods to design constructs of the target, which are cloned and expressed. Recently an alternative approach has emerged, which involves random fragmentation of the gene of interest and screening for well-expressing fragments.

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The efficacy of protein-based medicines can be compromised by their rapid clearance from the blood circulatory system. Achieving optimal pharmacokinetics is a key requirement for the successful development of safe protein-based medicines. Protein PEGylation is a clinically proven strategy to increase the circulation half-life of protein-based medicines.

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This paper presents analytical tools developed for estimating the effects of structural vibration on closed-loop adaptive optics system image quality. The general equation for the normalized intensity distribution of an image subject to structural vibration is derived. The resulting two-dimensional theoretical point spread function is computed numerically and compared with empirical data obtained on sky at the Multiple Mirror Telescope Observatory.

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Neural activity in the lateral intraparietal area (LIP) has been associated with attention to a location in visual space, and with the intention to make saccadic eye movement. In this study we show that neurons in LIP respond to recently flashed task-irrelevant stimuli and saccade targets brought into the receptive field by a saccade, although they respond much to the same stimuli when they are stable in the environment. LIP neurons respond to the appearance of a flashed distractor even when a monkey is planning a memory-guided delayed saccade elsewhere.

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Exploitation of potential new targets for drug and vaccine development has an absolute requirement for multimilligram quantities of soluble protein. While recombinant expression of full-length proteins is frequently problematic, high-yield soluble expression of functional subconstructs is an effective alternative, so long as appropriate termini can be identified. Bioinformatics localizes domains, but doesn't predict boundaries with sufficient accuracy, so that subconstructs are typically found by trial and error.

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The purpose of the study was to determine the effect of ethyl vinyl chloride vapocoolant spray on pain reported by children undergoing intravenous cannulation. A randomized, double-blinded, placebo-controlled trial was conducted on eligible children between the ages of 9 and 18 years seen in a pediatric emergency department and requiring intravenous cannulation. Informed consent was obtained, and children were randomized to receive ethyl vinyl chloride spray, isopropyl alcohol spray, or no spray (control group).

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A 7-month-old boy became difficult to arouse, was limp and had blue extremities 8 hours after immunization with intravenous poliovirus, diphtheria-tetanus toxoids-acellular pertussis, Haemophilus influenzae type b-hepatitis B virus and pneumococcal vaccines. The hypotonic-hyporesponsive episode had resolved by the time the infant was seen in an emergency department 1 hour later. The report describes hypotonic-hyporesponsive episode, encourages reporting of vaccine-associated adverse events and discusses prognosis and implications for subsequent immunization.

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Missed appointment rates (MAR) of pediatric patients insured by Medicaid and seen in a traditional hospital-based continuity (teaching) clinic were compared to the rates for the same patients after their care had been transitioned to a community practice. The hypothesis is that when rewarded with shorter waiting times, a less chaotic environment, and more pediatrician continuity, the MAR for patients insured by Medicaid would be lower in the practice setting than it had been in continuity clinic. The MAR decreased from 33% in the continuity clinic in 1999 to 18% in the community practice in 2001 (p<0.

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Urinary tract infection (UTI) is a major concern in young febrile children. Current recommendations favor use of urine obtained by bladder catheterization or aspiration, but opinion varies as to the best ancillary tests to predict a positive culture and guide initial management. The utility of dipstick leukocyte esterase, blood, and nitrite; unspun urine leukocyte count; gram stain of cytocentrifuged urine; and standard spun sediment examination was evaluated in 142 febrile, < 5-year-old children seen in the Emergency Department, 25 of whom had culture-proven UTI.

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A noninvasive temporal artery thermometer that uses arterial heat balance technology has been compared to rectal and ear thermometry and is available in the marketplace. This study was undertaken to establish mean temperatures and temperatures 2 standard deviations above the mean for healthy infants, children, and adolescents. Temperatures were measured in healthy patients 0 to 18 years of age using a noninvasive temporal artery thermometer.

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This review describes the current state of biocatalysis in the chemical industry. Although we recognize the advantages of chemical approaches, we suggest that the use of biological catalysis is about to expand dramatically because of the recent developments in the artificial evolution of genes that code for enzymes. For the first time it is possible to consider the rapid development of an enzyme that is designed for a specific chemical reaction.

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It was the impression of 1 of the authors that band counts in febrile infants < or =60 days of age were much higher as reported from the clinical laboratory at Children's Hospital Medical Center of Akron, Ohio, than they had been at Strong Memorial Hospital in Rochester, New York. Absolute band counts (ABC) from 119 febrile infants < or =60 days of age seen in the emergency department of Children's Hospital Medical Center of Akron for whom blood culture results were known were obtained retrospectively and compared with results from a prospective study conducted in Rochester. In Akron, 45% of the infants had elevated band counts and 16% had no other risk factor for serious bacterial infection compared with 5.

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