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H Lu

Publications and source records attributed to H Lu.

At least 37 records · Page 2Linked to original sources
PubMed2004

Observation by an air-shower array in Tibet of the multi-TeV cosmic-ray anisotropy due to terrestrial orbital motion around the Sun.

We report on the solar diurnal variation of the galactic cosmic-ray intensity observed by the Tibet III air shower array during the period from 1999 to 2003. In the higher-energy event samples (12 and 6.2 TeV), the variations are fairly consistent with the Compton-Getting anisotropy due to the terrestrial orbital motion around the Sun, while the variation in the lower-energy event sample (4.0 TeV) is inconsistent with this anisotropy. This suggests an additional anisotropy superposed at the multi-TeV energies, e.g., the solar modulation effect. This is the highest-precision measurement of the Compton-Getting anisotropy ever made.

Journal Article↗
PubMed2004

Intrinsic electron accumulation at clean InN surfaces.

The electronic structure of clean InN(0001) surfaces has been investigated by high-resolution electron-energy-loss spectroscopy of the conduction band electron plasmon excitations. An intrinsic surface electron accumulation layer is found to exist and is explained in terms of a particularly low Gamma-point conduction band minimum in wurtzite InN. As a result, surface Fermi level pinning high in the conduction band in the vicinity of the Gamma point, but near the average midgap energy, produces charged donor-type surface states with associated downward band bending. Semiclassical dielectric theory simulations of the energy-loss spectra and charge-profile calculations indicate a surface state density of 2.5 (+/-0.2)x10(13) cm(-2) and a surface Fermi level of 1.64+/-0.10 eV above the valence band maximum.

Journal Article↗
PubMed2004

Removing the effect of SVD algorithmic artifacts present in quantitative MR perfusion studies.

Quantitative cerebral blood flow (CBF) values can be obtained from dynamic susceptibility contrast (DSC) MR perfusion studies using the standard singular value decomposition (sSVD) deconvolution algorithm. Reports in the literature from simulation and in vivo studies suggest that CBF estimates obtained using sSVD deconvolution depend on the arterial-tissue delay (ATD). By contrast, Fourier transform (FT) deconvolution produces CBF estimates that are independent of ATD. The diagnostic reliability of quantitative CBF measurements to define areas of normal tissue flow and tissue at risk is brought into doubt by such gross sensitivity to the specifics of the deconvolution approach. This variation of CBF values with ATD is shown to be an artifact associated with the current implementation of the sSVD deconvolution algorithm. A reformulated version of the SVD deconvolution algorithm (rSVD) is presented and compared to the standard SVD algorithm through simulation and patient case studies.

Algorithms↗
PubMed2004

Probing the origins and control of shrinkage stress in dental resin-composites: I. Shrinkage stress characterization technique.

The accurate and reliable characterization of the polymerization shrinkage stress is becoming increasingly important, as the shrinkage stress still is a major drawback of current dimethacrylate-based dental materials and restricts its range of applications. The purpose of this research is to develop a novel shrinkage stress measurement device to elucidate the shrinkage stress evolution of dental restorative composites while allowing for controlled sample deformation during the polymerization. Furthermore, the device is designed to mimic the clinically relevant cusp-to-cusp displacement by systematically adjusting the instrument compliance, the bonded surface area/unbonded area by sample geometry, and the total bonded area by sample diameter. The stress measurement device based on the cantilever beam deflection theory has been successfully developed and characterized using a commercial dental composite. It was shown that this device is a highly effective, practical and reliable shrinkage stress measurement tool, which enables its facile applications to the investigation of shrinkage stress kinetics of both commercial and experimental composites, as well as for probing various aspects that dictate shrinkage stress development.

Biocompatible Materials↗
PubMed2004

Improved Poisson intensity estimation: denoising application using Poisson data.

Recently, Timmermann and Nowak developed algorithms for estimating the means of independent Poisson random variables. The algorithms are based on a multiscale model where certain random variables are assumed to obey a beta-mixture density function. Timmermann and Nowak simplify the density estimation problem by assuming the beta parameters are known and only one mixture parameter is unknown. They use the observed data and the method of moments to estimate the unknown mixture parameter. Taking a different approach, we generate training data from the observed data and compute maximum likelihood estimates of all of the beta-mixture parameters. To assess the improved performance obtained by the proposed modification, we consider a denoising application using Poisson data.

Algorithms↗
PubMed2003

Genetic basis of heterosis explored by simple sequence repeat markers in a random-mated maize population.

The genetic basis of heterosis in crop plants has not been completely resolved. Our objective in this study was to determine the level of dominance for quantitative trait loci (QTLs) that underlie heterosis in maize (Zea mays L.). An F2 population of an elite maize single cross, LH200 x LH216, was random mated for three generations in an attempt to break up repulsion linkages that might lead to pseudo-overdominance. The population was analyzed with 160 simple-sequence repeat markers. Phenotypic data analyses indicated overdominance for grain yield and partial dominance for plant height, grain moisture and stalk lodging. A total of 28 QTLs were identified for grain yield, 16 for grain moisture, 8 for stalk lodging, and 11 for plant height. For grain yield, 24 QTLs (86%) showed overdominance. In contrast, most of the QTLs for plant height, grain moisture and stalk lodging showed partial to complete dominance. Little epistasis was detected among the QTLs for any of the traits. Our results can be interpreted in one of two ways, or a combination of both: (1) QTLs for grain yield in maize exhibit true overdominance, or (2) QTLs for grain yield show partial to complete dominance, but they are so tightly linked such that three generations of random mating failed to separate their individual effects.

Chromosome Mapping↗
PubMed2003

A human homolog of the yeast gene encoding tRNA 2'-phosphotransferase: cloning, characterization and complementation analysis.

The Saccharomyces cerevisiae TPT1 gene plays a role in removing the 2'-phosphate from ligated tRNA during the maturation of pre-tRNA. Here we reported the cloning and characterization of the human TRPT1 gene as a homolog of yeast TPT1. The TRPT1 gene is located at human chromosome 11q13 and encodes a polypeptide of 253 amino acids. BLAST searches with its amino acid sequence revealed the ubiquitous occurrence of TRPT1 homologs and their functional relationships with the presence of the DUF60/KptA domain. Northern analysis demonstrated that the gene is primarily expressed in heart and skeletal muscle, with lower or undetectable levels in other tissues studied. A plasmid-shuffling experiment showed that the human TRPT1 gene could complement the tpt1 mutation in S. cerevisiae

Amino Acid Sequence↗
PubMed2003

Survival of avian influenza virus H7N2 in SPF chickens and their environments.

The survival or clearance of the avian influenza virus (AIV) of subtype H7N2 in its chicken host was evaluated using experimentally infected specific pathogen free (SPF) chickens of different age groups. Birds of different ages were successfully infected with infectious doses ranging between 10(4.7) and 10(5.7) ELD50 per bird. In infected birds, the infective virus was undetectable usually by the third week following exposure. The infectivity or inactivation time of the H7N2 AIV in various environmental conditions was studied using chicken manure, heat, ethanol, pH, and disinfectants. The H7N2 AIV was effectively inactivated by field chicken manure in less than a week at an ambient temperature of 15-20 degrees C. At a pH 2, heating at 56 degrees C, and exposure to 70% ethanol or a specific disinfectant, the AIV infectivity was destroyed in less than 30 min.

Animals↗
PubMed2003

Epidemiology, production losses, and control measures associated with an outbreak of avian influenza subtype H7N2 in Pennsylvania (1996-98).

An outbreak of H7N2 low-pathogenicity (LP) avian influenza (AI) occurred in a two-county area in Pennsylvania from December of 1996 through April of 1998. The outbreak resulted in infection of 2,623,116 commercial birds on 25 premises encompassing 47 flocks. Twenty-one (one premise with infection twice) of the twenty-five infected premises housed egg-laying chickens and one premise each had turkeys, layer pullets, quail, and a mixed backyard dealer flock. Despite dose proximity of infected flocks to commercial broiler flocks, no infected broilers were identified. Experimentally, when market age broilers were placed on an influenza-infected premise they seroconverted and developed oviduct lesions. The outbreak was believed to have originated from two separate introductions into commercial layer flocks from premises and by individuals dealing in sales of live fowl in the metropolitan New York and New Jersey live-bird markets. Source flocks for these markets are primarily in the northeast and mid-Atlantic areas, including Pennsylvania. Mixed fowl sold include ducks, geese, guinea hens, quail, chukar partridges, and a variety of chickens grown on perhaps hundreds of small farms. Infections with the H7N2 AI virus were associated with variable morbidity and temporary decreases in egg production ranging from 1.6% to 29.1% in commercial egg-laying chickens. Egg production losses averaged 4.0 weeks duration. Mortality ranged from 1.5 to 18.3 times normal (mean of 4.3 times normal). Duration of mortality ranged from 2 to 13 weeks (average of 3.9 weeks) in flocks not depopulated. Lesions observed were primarily oviducts filled with a mucous and white gelatinous exudates and atypical egg yolk peritonitis. Quarantine of premises and complete depopulation were the early measures employed in control of this outbreak. Epidemiological studies suggested that depopulation furthered the spread of influenza to nearby flocks. Thereafter, later control measures included quarantine, strict biosecurity, and controlled marketing of products.

Animals↗
PubMed2003

Summary of the 2001-02 Pennsylvania H7N2 low pathogenicity avian influenza outbreak in meat type chickens.

H7N2 low-pathogenicity (LP) avian influenza (AI) virus was isolated from chickens submitted to the Pennsylvania Animal Diagnostic Laboratory System on December 4 and 5, 2001. The cases were from two broiler breeder flocks in central Pennsylvania that had clinical signs of an acute, rapidly spreading respiratory disease. Seroconversion to AI virus was detected on follow-up sampling. Subsequently, H7N2 LPAI virus was isolated in five different broiler flock cases submitted between December 14, 2001, and January 3, 2002. Clinical signs and lesions in broilers, when present, were compatible with multicausal respiratory disease. With the exception of one broiler flock that was processed, birds from all of the virus positive flocks were euthanatized in-house within 11 days of the original case submission date. Increased surveillance of poultry flocks within 10-mile radius zones centered at the foci of the positive farms continued until March 1, 2002. No additional cases were detected.

Animals↗
PubMed2002

Allozyme polymorphisms of maize populations from southwestern China.

Maize ( Zea mays L.) is one of the most-important food crops in southwestern China. The diversity of maize populations from southwestern China has been evaluated on the basis of agronomic and morphological data, but not on marker data. Our objectives were to evaluate the allozyme polymorphism of these populations, and group the populations on the basis of allozyme data. We analyzed 27 maize populations from southwestern China and two populations [BS13(S)C2 and Lancaster] from the USA for genetic variation at 18 allozyme loci. We found a total of 69 alleles at 18 allozyme loci with an average of 3.8 alleles per locus. Compared with inbreds, hybrids, and populations from the U.S. Corn Belt, the 27 Chinese populations had a significantly higher ( p<0.01) number of allozyme alleles per locus. Maize populations from southwestern China have accumulated abundant genetic diversity, and might be valuable germplasm for broadening the genetic base of U.S. Corn Belt breeding germplasm. The analyses of allele-frequency distributions and the expected heterozygosity also reflected the differences between the Chinese and the U.S. germplasm. The Chinese populations might be valuable germplasm for complementing U.S. Corn Belt breeding germplasm. The analysis of gene diversity showed that 77% of the allozyme variation resided within populations and 23% between populations. This result suggested that breeders should identify one or a few Chinese populations with the best agronomic performance, and exploit the genetic variation within these selected populations. Cluster analysis classified the 29 populations into four main groups. Groupings based on allozyme data could be useful for classifying the populations into different heterotic groups and, consequently, exploiting them in hybrid breeding.

Journal Article↗
PubMed2002

One-week omeprazole, furazolidone and amoxicillin rescue therapy after failure of Helicobacter pylori eradication with standard triple therapies.

AIM: To test the efficacy of omeprazole, furazolidone and amoxicillin triple therapy for the treatment of Helicobacter pylori infection after failure of standard first-line therapy recommended by the Asia-Pacific Consensus on the management of H. pylori infection. METHODS: Patients with failed H. pylori eradication received omeprazole, 20 mg, furazolidone, 100 mg, and amoxicillin, 1 g, all twice daily for 1 week. Endoscopy (CLO test, histology and culture) was performed before treatment. Post-treatment H. pylori status was determined by 13C-urea breath test 6 weeks later. RESULTS: Fifty patients were recruited. Resistance to metronidazole, clarithromycin and both drugs was in the range of 50-64%, 60-75% and 40-50%, respectively, after failure of first-line therapy. Amoxicillin resistance was not found. The intention-to-treat and per protocol H. pylori eradication rates were 52% and 53%, respectively. Patients with double resistance to metronidazole and clarithromycin showed the lowest eradication rate (38%), which was significantly lower than that of patients with sensitive strains (88%). Side-effects were minimal and compliance was excellent (98%). CONCLUSIONS: One-week omeprazole, furazolidone and amoxicillin rescue therapy achieved a high eradication rate in strains sensitive to metronidazole and clarithromycin. This is a cheap and safe rescue regimen when guided by pre-treatment sensitivity testing.

Adult↗
PubMed2002

Apigenin--strong cytostatic and anti-angiogenic action in vitro contrasted by lack of efficacy in vivo.

The cancer chemopreventive agent apigenin also has strong cytostatic and anti-angiogenic effects in vitro. We now investigated its efficacy against experimental Lewis lung carcinomas (LLC), C-6 gliomas and DHDK 12 colonic cancers in vivo. Tumour bearing mice received 50 mg/kg/day apigenin in three different galenical formulations during 12 days in 8-hourly intervals. Only weak effects of apigenin on the size and the number of new tumour blood vessels of both established and newly transplanted tumours were recorded although the intratumoural necrosis was elevated (45 +/- 15% vs. 20 +/- 7% (control), p < 0.05%). These results contrast sharply with the high in vitro sensitivity of LLC, C-6, DHDK 12 and endothelial cells to apigenin where complete growth suppression occurs at concentrations beyond 30 g/ml. Possible causes are discussed.

Animals↗
PubMed2001

Enhancement of Fas ligand-induced inhibition of neointimal formation in rabbit femoral and iliac arteries by coexpression of p35.

Adenovirus-mediated gene transfer of Fas ligand (FasL) inhibits neointimal formation in balloon-injured rat carotid arteries. Vascular smooth muscle (VSM) cells coexpressing murine FasL and p35, a baculovirus gene that inhibits caspase activity, are not susceptible to FasL-mediated apoptosis in vitro but are capable of inducing apoptosis of VSM cells that do not express p35. We reasoned that coexpression of p35 in FasL-transduced VSM cells in vivo would promote their survival, enhance FasL-induced apoptosis of adjacent VSM cells, and thereby facilitate a greater inhibition of neointimal formation. In balloon-injured rabbit femoral arteries, either Ad2/FasL/p35 or Ad2/FasL was infused into the injured site and withdrawn 20 min later. Both vectors induced a dose-dependent reduction (p < 0.05) of the neointima-to-media ratio when assessed 14 days later. However, Ad2/FasL/p35 exhibited a significantly greater inhibition of neointimal formation than Ad2/FasL. In a more clinically relevant model of restenosis, rabbit iliac arteries were injured with an angioplasty catheter under fluoroscopic guidance. Adenoviral vectors were delivered locally to the injured site over a period of 2 min, using a porous infusion balloon catheter. Twenty-eight days after gene transfer angiographic and histologic assessments indicated a significant (p < 0.05) inhibition of iliac artery lumen stenosis and neointimal formation by Ad2/FasL/p35 (5 x 10(11) particles per artery). The extent of inhibition was comparable to that achieved with Ad2/TK, an adenoviral vector encoding thymidine kinase (5 x 10(11) particles per artery) and coadministration of ganciclovir for 7 days. These data suggest that coexpression of p35 in FasL-transduced VSM cells is more potent at inhibiting neointimal formation and as such represents an improved gene therapy approach for restenosis.

Adenoviruses, Human↗
PubMed2001

Stability criteria for delayed neural networks.

In this paper, delay-independent global asymptotic and exponential stability for a class of delayed neural networks (DNN's) is investigated, and some criteria are established to ensure stability of DNN's by applying the Lyapunov direct method. These criteria are expressed by imposing constraints on weight matrices of the networks, and they are easy to verify and so are applicable in the design of DNN's. Comparisons between our criteria and some earlier results are also made; it is shown that our results generalize some existing criteria in the literature.

Biophysical Phenomena↗