547 research outputs found
Endoscopic submucosal dissection vs laparoscopic colorectal resection for early colorectal epithelial neoplasia
published_or_final_versio
Short- and medium-term outcomes of accelerated infant growth in a Hong Kong Chinese birth cohort.
1. In a large, population representative,Chinese birth cohort, higher birth weight and rapid growth, particularly at 0-3 months, were associated with higher body mass index (BMI) at 7 years. 2. Boys born heavy who had grown fast had the highest BMI, but rapid growth had the largest impact in lighter-born boys. 3. Rapid growth at 0-3 months or 3-12 months was not associated with a compensatory lower risk of serious infectious morbidity. 4. The ability to grow fast may be an embodiment of good health status, rather than fast growth being causally protective.published_or_final_versio
An exploratory study on the social and genotypic clustering of HIV infection in men having sex with men
OBJECTIVE: To explore the clustering of HIV infected men having sex with men (MSM) using social network approach in conjunction with the phylogenetic relationship of the virus strains. DESIGN: An exploratory study incorporating social network and phylogenetic analysis. METHODS: Recently diagnosed HIV-infected MSM attending one major HIV specialist clinic in Hong Kong were recruited in the study involving the administration of a self-administered questionnaire on behaviours and partnership patterns using a Likert Scale, the results of which were assessed using social network analysis and in context of the phylogenetic analysis from sequencing the HIV-1 pol gene, as part of the clinical investigation for genotypic resistance. Clusters were defined using social and molecular methods. RESULTS: An 'Internet-centred' cluster and 'Sauna-centred' cluster could be delineated using correspondence analysis and network diagrams. The main distinguishing features of MSM in the 'Internet-centred' social cluster were: younger age, higher education level, and multiple partner types. Three genetic clusters could be identified in the phylogenetic tree, two of which associated with Internet use and one with sauna for sex partnership. There were partial overlaps between social and genetic clusters. Characteristically, the virus strains in sauna users were more disperse compared with the closely knit configuration of those using Internet. CONCLUSION: The principle of the duality of place and person can be strategically applied in epidemiologic investigation. The characterization of MSM cluster using anonymized network data provides a potentially powerful tool for informing public health intervention. © 2009 Lippincott Williams & Wilkins, Inc.postprin
Hoxb3 negatively regulates Hoxb1 expression in mouse hindbrain patterning
The spatial regulation of combinatorial expression of Hox genes is critical for determining hindbrain rhombomere (r) identities. To address the cross-regulatory relationship between Hox genes in hindbrain neuronal specification, we have generated a gain-of-function transgenic mouse mutant Hoxb3 Tg using the Hoxb2 r4-specific enhancer element. Interestingly, in r4 of the Hoxb3 Tg mutant where Hoxb3 was ectopically expressed, the expression of Hoxb1 was specifically abolished. The hindbrain neuronal defects of the Hoxb3 Tg mutant mice were similar to those of Hoxb1 -/- mutants. Therefore, we hypothesized that Hoxb3 could directly suppress Hoxb1 expression. We first identified a novel Hoxb3 binding site S3 on the Hoxb1 locus and confirmed protein binding to this site by EMSA, and by in vivo ChIP analysis using P19 cells and hindbrain tissues from the Hoxb3 Tg mutant. We further showed that Hoxb3 could suppress Hoxb1 transcriptional activity by chick in ovo luciferase reporter assay. Moreover, in E10.5 wildtype caudal hindbrain, where Hoxb1 is not expressed, we showed by in vivo ChIP that Hoxb3 was consistently bound to the S3 site on the Hoxb1 gene. This study reveals a novel negative regulatory mechanism by which Hoxb3 as a posterior gene serves to restrict Hoxb1 expression in r4 by direct transcriptional repression to maintain the rhombomere identity. © 2011 Elsevier Inc.postprin
Electric Field Effects on Graphene Materials
Understanding the effect of electric fields on the physical and chemical
properties of two-dimensional (2D) nanostructures is instrumental in the design
of novel electronic and optoelectronic devices. Several of those properties are
characterized in terms of the dielectric constant which play an important role
on capacitance, conductivity, screening, dielectric losses and refractive
index. Here we review our recent theoretical studies using density functional
calculations including van der Waals interactions on two types of layered
materials of similar two-dimensional molecular geometry but remarkably
different electronic structures, that is, graphene and molybdenum disulphide
(MoS). We focus on such two-dimensional crystals because of they
complementary physical and chemical properties, and the appealing interest to
incorporate them in the next generation of electronic and optoelectronic
devices. We predict that the effective dielectric constant () of
few-layer graphene and MoS is tunable by external electric fields (). We show that at low fields ( V/\AA)
assumes a nearly constant value 4 for both materials, but increases at
higher fields to values that depend on the layer thickness. The thicker the
structure the stronger is the modulation of with the electric
field. Increasing of the external field perpendicular to the layer surface
above a critical value can drive the systems to an unstable state where the
layers are weakly coupled and can be easily separated. The observed dependence
of on the external field is due to charge polarization driven by
the bias, which show several similar characteristics despite of the layer
considered.Comment: Invited book chapter on Exotic Properties of Carbon Nanomatter:
Advances in Physics and Chemistry, Springer Series on Carbon Materials.
Editors: Mihai V. Putz and Ottorino Ori (11 pages, 4 figures, 30 references
Neurogenesis Drives Stimulus Decorrelation in a Model of the Olfactory Bulb
The reshaping and decorrelation of similar activity patterns by neuronal
networks can enhance their discriminability, storage, and retrieval. How can
such networks learn to decorrelate new complex patterns, as they arise in the
olfactory system? Using a computational network model for the dominant neural
populations of the olfactory bulb we show that fundamental aspects of the adult
neurogenesis observed in the olfactory bulb -- the persistent addition of new
inhibitory granule cells to the network, their activity-dependent survival, and
the reciprocal character of their synapses with the principal mitral cells --
are sufficient to restructure the network and to alter its encoding of odor
stimuli adaptively so as to reduce the correlations between the bulbar
representations of similar stimuli. The decorrelation is quite robust with
respect to various types of perturbations of the reciprocity. The model
parsimoniously captures the experimentally observed role of neurogenesis in
perceptual learning and the enhanced response of young granule cells to novel
stimuli. Moreover, it makes specific predictions for the type of odor
enrichment that should be effective in enhancing the ability of animals to
discriminate similar odor mixtures
Circadian analysis of myocardial infarction incidence in an Argentine and Uruguayan population
BACKGROUND: The occurrence of variations in the spectrum of cardiovascular disease between different regions of the world and ethnic groups have been the subject of great interest. This study report the 24-h variation of myocardial infarction (MI) occurrence in patients recruited from CCU located in Argentina and Uruguay. METHODS: A cohort of 1063 patients admitted to the CCU within 24 h of the onset of symptoms of an acute MI was examined. MI incidence along the day was computed in 1 h-intervals. RESULTS: A minimal MI incidence between 03:00 and 07:00 h and the occurrence of a first maximum between 08:00 and 12:00 h and a second maximum between 15:00 and 22:00 h were verified. The best fit curve was a 24 h cosinor (acrophase ~ 19:00 h, accounting for 63 % of variance) together with a symmetrical gaussian bell (maximum at ~ 10:00 h, accounting for 37 % of variance). A similar picture was observed for MI frequencies among different excluding subgroups (older or younger than 70 years; with or without previous symptoms; diabetics or non diabetics; Q wave- or non-Q wave-type MI; anterior or inferior MI location). Proportion between cosinor and gaussian probabilities was maintained among most subgroups except for older patients who had more MI at the afternoon and patients with previous symptoms who were equally distributed among the morning and afternoon maxima. CONCLUSION: The results support the existence of two maxima (at morning and afternoon hours) in MI incidence in the Argentine and Uruguayan population
Observation of the nonlinear Hall effect under time reversal symmetric conditions
The electrical Hall effect is the production of a transverse voltage under an
out-of-plane magnetic field. Historically, studies of the Hall effect have led
to major breakthroughs including the discoveries of Berry curvature and the
topological Chern invariants. In magnets, the internal magnetization allows
Hall conductivity in the absence of external magnetic field. This anomalous
Hall effect (AHE) has become an important tool to study quantum magnets. In
nonmagnetic materials without external magnetic fields, the electrical Hall
effect is rarely explored because of the constraint by time-reversal symmetry.
However, strictly speaking, only the Hall effect in the linear response regime,
i.e., the Hall voltage linearly proportional to the external electric field,
identically vanishes due to time-reversal symmetry. The Hall effect in the
nonlinear response regime, on the other hand, may not be subject to such
symmetry constraints. Here, we report the observation of the nonlinear Hall
effect (NLHE) in the electrical transport of the nonmagnetic 2D quantum
material, bilayer WTe2. Specifically, flowing an electrical current in bilayer
WTe2 leads to a nonlinear Hall voltage in the absence of magnetic field. The
NLHE exhibits unusual properties sharply distinct from the AHE in metals: The
NLHE shows a quadratic I-V characteristic; It strongly dominates the nonlinear
longitudinal response, leading to a Hall angle of about 90 degree. We further
show that the NLHE directly measures the "dipole moment" of the Berry
curvature, which arises from layer-polarized Dirac fermions in bilayer WTe2.
Our results demonstrate a new Hall effect and provide a powerful methodology to
detect Berry curvature in a wide range of nonmagnetic quantum materials in an
energy-resolved way
A Review of Supercapacitors: Materials Design, Modification, and Applications
This is the final version. Available on open access from MDPI via the DOI in this recordSupercapacitors (SCs) have received much interest due to their enhanced electrochemical performance, superior cycling life, excellent specific power, and fast charging–discharging rate. The energy density of SCs is comparable to batteries; however, their power density and cyclability are higher by several orders of magnitude relative to batteries, making them a flexible and compromis-ing energy storage alternative, provided a proper design and efficient materials are used. This review emphasizes various types of SCs, such as electrochemical double-layer capacitors, hybrid su-percapacitors, and pseudo-supercapacitors. Furthermore, various synthesis strategies, including sol-gel, electro-polymerization, hydrothermal, co-precipitation, chemical vapor deposition, direct coating, vacuum filtration, de-alloying, microwave auxiliary, in situ polymerization, electro-spin-ning, silar, carbonization, dipping, and drying methods, are discussed. Furthermore, various func-tionalizations of SC electrode materials are summarized. In addition to their potential applications, brief insights into the recent advances and associated problems are provided, along with conclu-sions. This review is a noteworthy addition because of its simplicity and conciseness with regard to SCs, which can be helpful for researchers who are not directly involved in electrochemical energy storage.Saudi Aramco Chair ProgrammeEngineering and Physical Sciences Research Council (EPSRC
Simple isatin derivatives as free radical scavengers: Synthesis, biological evaluation and structure-activity relationship
To develop more potent small molecules with enhanced free radical scavenger properties, a series of N-substituted isatin derivatives was synthesized, and the cytoprotective effect on the apoptosis of PC12 cells induced by H2O2 was screened. All these compounds were found to be active, and N-ethyl isatin was found with the most potent activity of 69.7% protective effect on PC12 cells. Structure-activity relationship analyses showed the bioactivity of N-alkyl isatins decline as the increasing of the chain of the alkyl group, furthermore odd-even effect was found in the activity, which is interesting for further investigation
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