Energy spectrum and density of states for a graphene quantum dot in a magnetic field

In this paper, we determine the spectrum and density of states of a graphene quantum dot in a normal quantizing magnetic field. To accomplish this, we employ the retarded Green function for a magnetized, infinite-sheet graphene layer to describe the dynamics of a tightly confined graphene quantum dot subject to Landau quantization. Considering a δ((2))(r) potential well that supports just one subband state in the well in the absence of a magnetic field, the effect of Landau quantization is to 'splinter' this single energy level into a proliferation of many Landau-quantized states within the well. Treating the graphene sheet and dot as a closed system subject to a fully Hermitian Hamiltonian (including boundary conditions), there is no indication of decay of the Landau-quantized graphene dot states into the quantized states of the host graphene sheet for 'tight' confinement by the δ((2))(r) potential well, notwithstanding extension of the dot Green function (and eigenfunctions) outside the δ((2))(r) potential well.

Rat Dlx5 is expressed in the subventricular zone and promotes neuronal differentiation

The molecular mechanisms and potential clinical applications of neural precursor cells have recently been the subject of intensive study. Dlx5, a homeobox transcription factor related to the distal-less gene in Drosophila, was shown to play an important role during forebrain development. The subventricular zone (SVZ) in the adult brain harbors the largest abundance of neural precursors. The anterior SVZ (SVZa) contains the most representative neural precursors in the SVZ. Further research is necessary to elucidate how Dlx5-related genes regulate the differentiation of SVZa neural precursors. Here, we employed immunohistochemistry and molecular biology techniques to study the expression of Dlx5 and related homeobox genes Er81 and Islet1 in neonatal rat brain and in in vitro cultured SVZa neural precursors. Our results show that Dlx5 and Er81 are also highly expressed in the SVZa, rostral migratory stream, and olfactory bulb. Islet1 is only expressed in the striatum. In cultured SVZa neural precursors, Dlx5 mRNA expression gradually decreased with subsequent cell passages and was completely lost by passage four. We also transfected a Dlx5 recombinant plasmid and found that Dlx5 overexpression promoted neuronal differentiation of in vitro cultured SVZa neural precursors. Taken together, our data suggest that Dlx5 plays an important role during neuronal differentiation.

[Epidemiological study of high risk human papillomavirus infection in 25 to 54 years old married women in Beijing.]

OBJECTIVE

To investigate high risk human papillomavirus (HR-HPV) prevalence among married women in Beijing and to study the high risk factors.

METHODS

During March 2007 to September 2008, a total of 6185 married women sampled from 137 communities in 12 districts were screened by HR-HPV DNA test and cytological test. The interview was carried out with unified questionnaires. The database was set up and twice entered in EpiData 3.0. After checked up, the data were analyzed in SPSS 15.0.

RESULTS

(1) The HR-HPV infection rate was 9.89%. The HR-HPV infection rate of the city zone, the suburb and the exurb were 9.34%, 10.51% and 9.51% (P > 0.05). The HR-HPV infection rate of the native and the outlander were 9.53%, 11.30% (P < 0.05). (2) The age distribution of HR-HPV infection was that the rate was around 10% among 25 to 44 age groups, which was the highest (11.21%) in 30 to 34 age group; then the rate was descended as the age raising, the rate of 50 to 54 age group was the lowest (7.78%). (3) Multiple logistic regression showed that the related risk factors of HR-HPV infection mainly included 1000 RMB and above of family income per person per month, possessing more than 1 sexual partner of her husband, outlander and high levels of education. (4) The prevalence of cervical intraepithelial neoplasia (CIN) in HR-HPV positive group was significantly higher than that in HR-HPV negative group (29.76% vs 3.32%, P < 0.01).

CONCLUSIONS

(1) The HR-HPV infection rate among aged 25 to 54 years was 9.9% and there was no significant difference in area distribution. (2) The high risk population which should strengthen screening was the married bearing-age women with high level of family income, outlander, high levels of education and her husband possessing more than 1 sexual partner. (3) HR-HPV infection is the main risk factor for CIN and cervical cancer, while does not provide a causal relationship with them. The high risk population should be checked regularly to understand the development of HR-HPV infection and CIN incidence.

Nonlinear dc transport in graphene

Considering electron-impurity, electron-acoustic-phonon and electron-optical-phonon scatterings, the nonlinear steady-state transport properties of graphene are studied theoretically by means of the balance equation approach. We find that the conductivity as a function of electric field strength, E, exhibits strongly nonlinear behavior for E larger than a critical value, E(c)≈0.1 kV cm(-1). With the increase of E from zero, the conductivity first decreases slowly and then it falls rapidly when E>E(c). The dependence of electron temperature on E is also demonstrated.

Properties of murine embryonic stem cells maintained on human foreskin fibroblasts without LIF

In embryonic stem (ES) cells, leukemia inhibitory factor (LIF)/STAT3, wnt and nodal/activin signaling are mainly active to control pluripotency during expansion. To maintain pluripotency, ES cells are typically cultured on feeder cells of varying origins. Murine ES cells are commonly cultured on murine embryonic fibroblasts (MEFs), which senesce early and must be frequently prepared. This process is laborious and leads to batch variation presenting a challenge for high-throughput ES cell expansion. Although some cell lines can be sustained by exogenous LIF, this method is costly. We present here a novel and inexpensive culture method for expanding murine ES cells on human foreskin fibroblast (HFF) feeders. After 20 passages on HFFs without LIF, ES cell lines showed normal expression levels of pluripotency markers, maintained a normal karyotype and retained the ability to contribute to the germline. As HFFs do not senesce for at least 62 passages, they present a vast supply of feeders.

Unfolding core asymmetries with x-ray emission images in symmetry diagnostic experiments

A novel inversion technique is proposed to unfold core asymmetries at the source with x-ray emission images, which were obtained from imploded surrogate capsules in symmetry diagnostic experiments. The axisymmetrical core emission can be expanded as a Fourier series, with Legendre polynomials and spherical Bessel functions as bases concerned with polar angle and radius, respectively. A least-squares estimator is employed to obtain the unknown coefficients from its two-dimensional image data. The unfolded Legendre coefficients can be further used to test modeling of drive asymmetries in hohlraums. This technique is also demonstrated with a proof-of-principle experiment performed on the Shenguang II laser facility [L. Zunqi et al., Chin. J. Lasers B10, 6 (2001)].

Study of the sensitivity of gas sensing by use of index-guiding photonic crystal fibers

We demonstrate an absorption transmission spectrum of CH(4) in a 16.9 cm long index-guiding photonic crystal fiber (PCF) fabricated in our laboratory. One of the main factors to improve the sensitivity is to increase the fraction of power in PCF cladding air holes. We study the fraction of power in PCF cladding air holes as a function of the index-guiding PCF parameters. We found that a PCF with small spacing and a large air-filling ratio has a higher fraction of power in its cladding air holes. At the same time the mode area in this PCF is small and would generate strong nonlinear effects in the fiber. If we use a PCF in which the core is formed by missing seven air holes, it is immediately obvious that the PCF used as a sensor has higher sensitivity and a larger mode area.

Characterisation of plasmids encoding CTX-M-3 extended-spectrum β-lactamase from Enterobacteriaceae isolated at a university hospital in Taiwan

CTX-M-3 is the most common extended-spectrum beta-lactamase produced by Enterobacteriaceae in Taiwan. The present study was conducted to characterise the genetic environment surrounding bla(CTX-M-3). A total of 11 ceftriaxone-resistant isolates were studied: Escherichia coli (n=4), Klebsiella pneumoniae (n=5) and Salmonella enterica serotypes Anatum (SA831R) and Potsdam (SC72). Molecular methods used included polymerase chain reaction, sequencing, DNA-DNA hybridisation, conjugation, physical mapping and restriction fragment length polymorphism (RFLP) analysis. All isolates examined carried bla(CTX-M-3) on large plasmids (>70kb). The resistance plasmids of the two Salmonella and two K. pneumoniae strains (KP104 and KP116) were confirmed to be conjugative in vitro. RFLP analysis indicated that the plasmids were different. Physical mapping also revealed the difference between the two Salmonella plasmids, pSA831R (82kb) and pSC72 (74kb). An insertion sequence, ISEcp1, was found upstream of each bla(CTX-M-3) gene. However, sequencing of downstream regions of the bla genes showed two different patterns: the presence of orf477 in pSA831R and of orf1-mucA in pSC72, pKP104 and pKP116. IncI1-type oriT and nikA sequences were present in the plasmids of all the clinical isolates tested, except S. Anatum. Different bla(CTX-M-3)-carrying plasmids were identified among the enterobacteria studied. The presence of ISEcp1 in all isolates may be associated with the widespread resistance among Enterobacteriaceae. Although the plasmids were not identical, they appeared to belong to the same incompatibility group (IncI1-like plasmids), suggesting that they are genetically related but may have evolved divergently over time.

White organic light-emitting devices with Sm:Ag black cathode

White organic light-emitting device (WOLED) with Sm:Ag black cathode was first reported. The effect of the black cathode on the performances (such as efficiency, luminance, contrast ratio at different angle and EL spectra, etc) of the WOLEDs was discussed. We found that the efficiency of the WOLED with Sm:Ag was comparable to that of the device with conventional Mg:Ag cathode. For example, the efficiency of the device with Sm:Ag cathode is just 15% lower than that of the device with Mg:Ag cathode. However, the contrast ratio (CR) of the device with black cathode is 105:1 under 140 lx ambient lighting at a high brightness of 1000 cd/m(2), which is four times better than that of the device with Mg:Ag cathode. Besides, the CR of the WOLED with Sm:Ag cathode is insensitive to the viewing angle less than 50 degrees .

Contrast and efficiency enhancement in organic light-emitting devices utilizing high absorption and high charge mobility organic layers

Organic light-emitting devices utilizing copper phthalocyanine (CuPc) and C(60) as the hole- and electron-injection layers were reported. Compared with a conventional device without CuPc and C(60) layers, the improvement of the contrast is more than 100% under 140-lx ambient lighting at a brightness of 300 cd/m(2). A maximum current efficiency of 3.93 cd/A, which is higher than 3.62 cd/A for a conventional device, was obtained at 9 V. The device has a maximum luminance of 17170 cd/m(2) at 15 V. The high contrast and high efficiency of the device are attributed to the high absorption and high charge mobility of CuPc and C(60) films.

Analysis of MS2Bnap genomic DNA homologous to MS2 gene from Arabidopsis thaliana in two dominant digenic male sterile accessions of oilseed rape (Brassica napus L.)

PCR technique was employed to isolate gene homologous to the MS2Bnap (X99922.1) from two rapeseed (Brassica napus L.) dominant digenic male sterile lines, namely 220A (male sterile) and 220B (male fertile), 6A (male sterile) and 6C (male fertile). The isolated 2,581 bp sequences from 220A (named 220A-gDNA, GenBank accession number AY288778), 220B (220B-gDNA, AY257490), 6A (6A-gDNA, DQ060318) and 6C (6C-gDNA, DQ060319) all contained six introns. Forty-one single nucleotide polymorphism (SNP) sites were detected by alignment of these four sequences, seven of them dispersed in the exon regions. Two SNPs (1247, 1656) were detected between 220A-gDNA and 220B-gDNA, and the one at nucleotide 1247 of 220A-gDNA with A replaced by C was a missense mutation, which may be the putative male sterility site in 220A. All eight SNPs identified between 6A-gDNA and 6C-gDNA were located in the third intron, so the proteins encoded by them are the same. The one SNP between 6A-/6C-gDNA and 220A-/220B-gDNA at nucleotide 2474 of 220A-/220B-gDNA with C replaced by G was a missense mutation. Mutation site of BNMS2PROT (CAA68190.1) encoded by MS2Bnap in 220A(254) and 6A/6C(584) is different, which indicated dominant digenic male sterile line 220AB and 6CA have some difference in the molecular level. Comparison of structure of MS2Bnap in B. napus with that of MS2 in Arabidopsis thaliana revealed that the similarity of exons between these two genes is higher than that of introns.

Integron-associated imipenem resistance in Acinetobacter baumannii isolated from a regional hospital in Taiwan

We investigated the genetic properties of imipenem-resistant Acinetobacter baumannii collected from a regional hospital in Taiwan. Pulsed-field gel electrophoresis demonstrated that the isolates were genetically diverse. Polymerase chain reaction, DNA sequencing, and DNA-DNA hybridisation showed that the bla(IMP-1) gene resided as a cassette in a plasmid-borne class 1 integron in two isolates. The majority of the resistant isolates were plasmid-less and carried no bla(IMP), bla(VIM) or bla(CFI) genes, indicating that other uncharacterised metallo-beta-lactamases or mechanisms other than enzyme production are involved in carbapenem resistance in this group of A. baumannii. We conclude that multidrug resistance of A. baumannii was a combined effect of lateral gene transfer and clonal spread of multiple resistant clones. Strict measures should be implemented to control the further spread of resistance.

DOT and timely treatment completion among Asian-born immigrant tuberculosis patients

SETTING

A large urban tuberculosis (TB) control program.

OBJECTIVES

To identify factors associated with directly observed therapy (DOT) participation and to quantify how early use of DOT affected treatment duration.

DESIGN

A retrospective study of 731 Asian-born patients with drug-susceptible Mycobacterium tuberculosis isolates who were verified in New York City between 1993 and 1997 and completed treatment.

RESULTS

Overall, 297 (41%) of 731 patients in the study participated in DOT for some or all of their TB treatment. DOT participation was significantly associated with TB disease in a pulmonary site (adjusted odds ratio [aOR] 2.85, 95% CI 1.86-4.35), more recent year of diagnosis (aOR 1.70, 95% CI 1.50-1.94) and male sex (aOR 1.86, 95% CI 1.30-2.66). Patients who received > or = 70% of their TB treatment at a health department chest clinic were also significantly more likely to participate in DOT (aOR 3.83, 95% CI 2.55-5.74). Among 297 DOT patients, those who completed treatment by 9 months received a greater amount of treatment by DOT during the first 4 months of treatment than those who took longer to complete treatment.

CONCLUSION

Earlier DOT participation can lead to overall shorter treatment duration. Health care providers should encourage TB patients to participate in DOT as early as possible in their TB treatment.

Thomson scattering measurements of heat flux from ion-acoustic waves in laser-produced aluminum plasmas

Thomson scattering (TS) measurements are performed at different locations in a laser-produced aluminum plasma. Variations of the separation, wavelength shift, and asymmetric distribution of the two ion-acoustic waves are investigated from their spectral-time-resolved TS images. Detailed information on the space-time evolution of the plasma parameters is obtained. Electron distribution and variation of the heat flux in the plasma are also obtained for a steep temperature gradient.

Volumetric productivity improvement for endoglucanase of Trichoderma pseudokoingii S-38

AIMS

The objective of this study was to design an economically feasible process for endoglucanase (EG) production.

METHODS AND RESULTS

Trichoderma pseudokoingii S-38 EG synthesis was studied. Initially, either glucose at 2.5, 5 or 10 g l-1, or cellulose powder (CF11) at 5 g l-1 was used as the sole carbon source. The results showed that enzyme synthesis and biomass formation were closely correlated, and both were affected by the carbon source. To improve EG volumetric product efficiency, a new technique was developed. Glucose and CF11 (2.5 and 5 g l-1, respectively) were used as initial carbon source, and glucose was added at 2.5 g l-1 day-1. EG activity, volumetric and specific EG productivities were 6.17 IU l-1, 53 IU l-1 h-1 and 114.3 IU (g cell protein)-1 h-1, respectively. Batch production in a 2-l laboratory fermenter confirmed the advantage of the technique. The product contained 10.86 IU ml-1 EG activity in 88 h. The volumetric and specific EG productivities were 123.4 IU l-1 h-1 and 177.8 IU (g cell protein)-1 h-1, respectively.

CONCLUSIONS

These results suggest that optimization of the ratio of glucose to CF11 for balancing the induction and growth rate in the production of EG may lead to technical and economical benefits.

SIGNIFICANCE AND IMPACT OF THE STUDY

A new technique was developed for the production of EG which improves both the volumetric product efficiency and the specific activity.

Radiation-induced magnetoresistance oscillation in a two-dimensional electron gas in Faraday geometry

Microwave-radiation induced giant magnetoresistance oscillations recently discovered in high-mobility two-dimensional electron systems are analyzed theoretically. Multiphoton-assisted impurity scatterings are shown to be the primary origin of the oscillation. Based on a theory which considers the interaction of electrons with electromagnetic fields and the effect of the cyclotron resonance in Faraday geometry, we are able not only to reproduce the correct period, phase, and the negative resistivity of the main oscillation, but also to predict the secondary peaks and additional maxima and minima observed in the experiments. These peak-valley structures are identified to relate, respectively, to single-, double-, and triple-photon processes.

Inhibition of protein phosphatase 2A- and protein phosphatase 1-induced tau hyperphosphorylation and impairment of spatial memory retention in rats

Tau hyperphosphorylation leads to formation of paired helical filament/neurofibrillary tangles, the hallmark lesion seen in Alzheimer's disease (AD) brain. An imbalanced regulation in protein kinases and protein phosphatases in the affected neurons is proposed to be a reasonable causative factor to the disease process. To verify the hypothesis, we have injected in the present study calyculin A, a potent and specific inhibitor of protein phosphatase (PP) 2A and PP1, into rat hippocampus bilaterally, thus reproduced an Alzheimer's-like deficiency in dephosphorylation system. It was found that calyculin A-injected rats developed lesions in spatial memory retention in Morris water maze test. At mean time, tau was hyperphosphorylated at Ser396/Ser404 (PHF-1) and Ser-262/Ser-356 (12E8) sites determined both by immunohistochemistry and Western blot. It is implicated that (1) PP2A and PP1 participate in the in vivo regulation of tau phosphorylation, and down-regulation of the two phosphatases will result in tau hyperphosphorylation; (2) hyperphosphorylation of tau at PHF-1 and 12E8 sites might be crucial to affect spatial memory in AD.

Arsenic trioxide in comparison with chemotherapy and bone marrow transplantation for the treatment of relapsed acute promyelocytic leukaemia

BACKGROUND

The best overall treatment strategy for patients with acute promyelocytic leukaemia (APL) in relapse with chemotherapy, bone marrow transplantation (BMT) or arsenic trioxide (As(2)O(3)) based therapy remains undefined.

PATIENTS AND METHODS

We reviewed the clinical course and treatment outcome of 143 APL cases seen in four major hospitals in Hong Kong over a 10-year period.

RESULTS

Complete remission (CR) was attained in 113 cases (79%) with all-trans retinoic acid (ATRA) and chemotherapy. Relapse occurred at a median of 16 months in 54 cases, with a 3-year disease free survival of 56%. Post-relapse treatment was successful in 41 cases (76%), giving an actuarial 3-year overall survival (OS) of 81% from CR1. Three different protocols were used: chemotherapy alone (n = 19), allogeneic BMT (n = 14) and an As(2)O(3)-based regimen (n = 21). Chemotherapy was associated with the highest treatment-related mortality (TRM) at 53%, giving a CR2 rate of 47%. TRM was 36% for BMT. The CR2 rate for the As(2)O(3)-based regimen was 100%, with no TRM. However, 38% of As(2)O(3) treated patients had subsequent relapses, which were further salvaged in 75% by combined As(2)O(3) plus ATRA. The actuarial OS for the three protocols leveled off by 2 years at 82% for As(2)O(3), 43% for BMT and 23% for chemotherapy (P = 0.0004).

CONCLUSIONS

Our results suggest that As(2)O(3) may be superior to chemotherapy and BMT for the treatment of APL in relapse.

Bilateral parotid and submandibular gland enlargement: rare features of Wegener's granulomatosis

Wegener's granulomatosis is a potentially fatal disease of unknown origin affecting mainly the upper and lower respiratory tracts and kidneys. Prompt recognition of the more unusual presentations of the disease is necessary to ensure early treatment. We present a case of a 46-year-old female with bilateral submandibular and parotid gland enlargement. Parotid or submandibular salivary gland enlargement is a rare presenting feature of Wegener's granulomatosis. Common to 80 per cent of these cases is nasal involvement, while ear pathology or lung lesions may occur in the remaining cases. The diagnosis is both clinical and pathological, biopsy of suspicious tissue, serum c-ANCA levels and a chest X-ray are valuable investigations. Treatment with immunosuppressive therapy is essential, and usually ensures a long-term remission.

A surprisingly mild and versatile method for palladium-catalyzed Suzuki cross-couplings of aryl chlorides in the presence of a triarylphosphine

In the presence of new air-stable triarylphosphine 2, palladium-catalyzed Suzuki reactions of a wide array of aryl chlorides can be accomplished in uniformly good yield, including couplings of very sterically demanding and electronically deactivated substrates; activated aryl chlorides can be coupled at room temperature. In terms of scope and mildness, Pd-2 compares well with other catalyst systems that have been described for Suzuki reactions of aryl chlorides, thereby establishing that triarylphosphines should be regarded as fertile ground for future ligand-design efforts for palladium-catalyzed couplings of aryl chlorides.

Comparisons of hydroperoxide isomerase and monooxygenase activities of cytochrome P450 for conversions of allylic hydroperoxides and alcohols to epoxyalcohols and diols: probing substrate reorientation in the active site

Ferric cytochrome P450 (P450) catalyzes intramolecular rearrangements of hydroperoxides to diols by heterolytic scission of the O-O bond and insertion of the terminal oxygen atom into the resulting alcohol. The goals of this work were to further characterize the regio- and stereochemistry of P450 isomerase activity using allylic hydroperoxides and to compare these reactions with NADPH-supported monooxygenations of the corresponding alcohols. Microsomes from phenobarbital-treated rats or purified P450 2B1 catalyzed the conversions of several peroxyquinols, including 2-tert-butyl-4-hydroperoxy-4-methylcyclohexa-2,5-dien-1-one (BMPOOH) and its 2,6-dimethyl derivative (TMPOOH), to diols and to alpha,beta-epoxyquinols by predominant (>93%) cis addition of oxygen to the least hindered double bond. Monooxygenation of the 4-hydroxy analogues (quinols) yielded identical cis-epoxyquinols, and both isomerization and monooxygenation reactions exhibited similar enantioselectivities (32-74% enantiomer excess). Regioselectivities were similar for BMPOOH and BMPOH (epoxyquinol:diol ratios of 5.8-7.6), but quite different for TMPOOH and TMPOH (ratios of 0.6 and 6.4, respectively). Bulky peroxyquinols and quinols derived from the A-rings of 17beta-estradiol and estrone were utilized to further compare these reactions. Both estradiol derivatives underwent approximately equal amounts of 6beta-hydroxylation and 1,2-epoxidation. The estrone derivatives also underwent 6beta-hydroxylation, but only estrone quinol yielded a second product consistent with hydroxylation at position 16. The results support several conclusions. (i) Allylic hydroperoxides may be isomerized to alpha,beta-epoxyalcohols by a heterolytic O-O cleavage mechanism with high stereoselectivity. (ii) Hydroperoxide isomerization is an efficient process relative to monooxygenation. (iii) Isomerase substrates remain in proximity to the P450 oxoferryl intermediate and are rapidly captured by the oxidant. Monooxygenase substrates, on the other hand, may bind to ferric P450 in multiple orientations and undergo more extensive substrate reorientation prior to oxidative attack.