We have quantitated the phase preferences of all of the quantitatively significant lipids of fatt... more We have quantitated the phase preferences of all of the quantitatively significant lipids of fatty acid-homogeneous Acholeplasma laidlawii membranes by determining the effect of small amounts of each lipid on the lamellarheversed hexagonal phase transition temperature of a phosphatidylethanolamine matrix of identical fatty acid composition using differential scanning calorimetry. We find that the incorporation of small amounts of these lipids produce effects ranging from a moderate depression to a marked elevation of the lamellarheversed hexagonal phase transition temperature of the corresponding phosphatidylethanolamine. Thus, although the total membrane lipids from this organism form only lamellar phases under physiological conditions, the individual membrane lipids appear to exhibit a wide range of phase preferences. Phosphatidylglycerol and diglucosyldiacylglycerol seem to have relatively strong and weak preferences for the lamellar liquid-crystalline phase, respectively, while monoglucosyldiacylglycerol, and especially acyl polyprenyl glucoside, strongly prefers the reversed hexagonal phase. Most notable in this regard is the phase preference of glycerylphosphoryldiglucosyldiacylglycerol, which strongly destabilizes the reversed hexagonal phase and which we show in the accompanying paper Biochemistry 34, 13818-138241 actually prefers the normal micellar phase in isolation. The presence of normal, lamellar, and reversed phase-preferring lipids in a single membrane has important implications for understanding the physical basis of lipid organization and biosynthetic regulation in this and possibly in other organisms. We also show that the characteristic effect of the individual A . laidlawii membrane lipids on the lamellarheversed hexagonal phase transition temperature of the phosphatidylethanolamine matrix is not well correlated with their polar headgroup intrinsic volumes. This result indicates that the effective cross-sectional area of the polar headgroups of these lipid species must be strongly influenced by factors such as charge, hydration, orientation, and motional freedom, as well as by intrinsic headgroup volume.
We have realized and measured a GaAs nanocavity in a slab photonic crystal based on the design by... more We have realized and measured a GaAs nanocavity in a slab photonic crystal based on the design by Kuramochi et al. [Appl. Phys.Lett., 88 , 041112, (2006)]. We measure a quality factor Q=700,000, which proves that ultra-high Q nanocavities are also feasible in GaAs. We show that, due to larger two-photon absorption (TPA) in GaAs, nonlinearities appear at the microwatt-level and will be more functional in gallium arsenide than in silicon nanocavities.
We investigate the nonlinear response of photonic crystal waveguides with suppressed two-photon a... more We investigate the nonlinear response of photonic crystal waveguides with suppressed two-photon absorption. A moderate decrease of the group velocity (∼ c/6 to c/15, a factor of 2.5) results in a dramatic (× 30) enhancement of three-photon absorption well beyond the expected scaling, ∝ 1/v 3 g . This non-trivial scaling of the effective nonlinear coefficients results from pulse compression, which further enhances the optical field beyond that of purely slow-group velocity interactions. These observations are enabled in mm-long slow-light photonic crystal waveguides owing to the strong anomalous group-velocity dispersion and positive chirp. Our numerical physical model matches measurements remarkably.
To estimate whether treatment with intravenous nitroglycerin for uterine relaxation increases the... more To estimate whether treatment with intravenous nitroglycerin for uterine relaxation increases the chance of successful external cephalic version.
Journal of Bioinformatics and Computational Biology, 2009
Post hoc assignment of patterns determined by all pairwise comparisons in microarray experiments ... more Post hoc assignment of patterns determined by all pairwise comparisons in microarray experiments with multiple treatments has been proven to be useful in assessing treatment effects. We propose the usage of transitive directed acyclic graphs (tDAG) as the representation of these patterns and show that such representation can be useful in clustering treatment effects, annotating existing clustering methods, and analyzing sample sizes. Advantages of this approach include: (1) unique and descriptive meaning of each cluster in terms of how genes respond to all pairs of treatments; (2) insensitivity of the observed patterns to the number of genes analyzed; and (3) a combinatorial perspective to address the sample size problem by observing the rate of contractible tDAG as the number of replicates increases. The advantages and overall utility of the method in elaborating drug structure activity relationships are exemplified in a controlled study with real and simulated data.
We investigate the nonlinear response of GaAs-based photonic crystal cavities at time scales whic... more We investigate the nonlinear response of GaAs-based photonic crystal cavities at time scales which are much faster than the typical thermal relaxation rate in photonic devices. We demonstrate a strong interplay between thermal and carrier induced nonlinear effects. We have introduced a dynamical model entailing two thermal relaxation constants which is in very good agreement with experiments. These results will be very important for Photonic Crystal-based nonlinear devices intended to deal with practical high repetition rate optical signals. PACS numbers: 42.70.Qs,42.65.Pc
The Use of a Tablet Computer to Complete the DASH Questionnaire
The Journal of Hand Surgery, 2012
To determine whether electronic self-administration of the Disabilities of the Arm, Shoulder, and... more To determine whether electronic self-administration of the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire using a tablet computer increased completion rate compared with paper self-administration. We gave the DASH in self-administered paper form to 222 new patients in a single hand surgeon's practice. After a washout period of 5 weeks, we gave the DASH in self-administered tablet computer form to 264 new patients. A maximum of 3 questions could be omitted before the questionnaire was considered unscorable. We reviewed the submitted surveys to determine the number of scorable questionnaires and the number of omitted questions in each survey. We completed univariate analysis and regression modeling to determine the influence of survey administration type on respondent error while controlling for patient age and sex. Of the 486 total surveys, 60 (12%) were not scorable. A significantly higher proportion of the paper surveys (24%) were unscorable compared with electronic surveys (2%), with significantly more questions omitted in each paper survey (2.6 ± 4.4 questions) than in each electronic survey (0.1 ± 0.8 questions). Logistic regression analysis revealed survey administration mode to be significantly associated with DASH scorability while controlling for age and sex, with electronic survey administration being 14 times more likely than paper administration to yield a scorable DASH. In our retrospective series, electronic self-administration of the DASH decreased the number of omitted questions and yielded a higher number of scorable questionnaires. Prospective, randomized evaluation is needed to better delineate the effect of survey administration on respondent error. Administration of the DASH with a tablet computer may be beneficial for both clinical and research endeavors to increase completion rate and to gain other benefits from electronic data capture.
The perifused posterior cardinal vein of the American eel (Anguilla rostrata) releases spontaneou... more The perifused posterior cardinal vein of the American eel (Anguilla rostrata) releases spontaneously dopamine (DA), norepinephrine (NE), and epinephrine (E). NE and E are secreted by innervated chromaffin cells, while DA is most likely released from a component of the vascular wall. Stimulation with acetylcholine strongly enhances the release of DA and E, and to a lesser degree the release of NE. Nicotine stimulates the release of all three catecholamines. Muscarine reduces the basal release of NE. Muscarine does not prevent nicotinic stimulation of NE and E release, but abolishes the nicotine effect on DA release. The muscarinic antagonist atropine stimulates the release of NE, but not of DA and E. The -adrenergic receptor antagonist propranolol suppresses the acetylcholine-stimulated release of NE and E, and reduces the DA response. From these findings, it appears that (1) nicotinic receptors regulate NE and E secretion from the chromaffin cells, (2) muscarinic receptors inhibit basal NE release, and (3) acetylcholine-stimulated release of NE and E requires the interaction with adrenergic receptors. On the other hand, DA release involves both nicotinic and adrenergic receptors, while the reduction of nicotine-stimulated (but not basal) DA release involves muscarinic receptors.
Economic and Environmental Benefits of Biodiversity
BioScience, 1997
A ll ecosystems and human so-cieties depend on a healthy and productive natural envi-ronment that... more A ll ecosystems and human so-cieties depend on a healthy and productive natural envi-ronment that contains diverse plant and animal species. The earth's biota is composed of an estimated 10 mil-lion species of plants, animals, and microbes (Pimm et al. 1995). In the United ...
ORCAD là một công cụ thiết kế mạch điện tử đơn giản và phổ biến. Cũng có rất nhiều phần mềm thiết... more ORCAD là một công cụ thiết kế mạch điện tử đơn giản và phổ biến. Cũng có rất nhiều phần mềm thiết kế mạch điện tử khác, tuy nhiên, chúng tôi chọn sử dụng phần mềm này, vì bộ công cụ này được đánh giá là khá mạnh.
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