The hardness-duration correlation in the two classes of gamma-ray bursts

The well-known hardness-duration correlation of gamma-ray bursts (GRBs) is investigated with the data of the 4B catalog. We find that, while the hardness ratio and the duration are obviously correlated for the entire set of the 4B catalog, they are not at all correlated for the two subsets divided at the duration of 2 seconds. However, for other subsets with comparable sizes, the two quantities are significantly correlated. The following conclusions are then reached: (1) the existence of two classes of GRBs is confirmed; (2) the hardness ratio and the duration are not at all correlated for any of the two classes; (3) different classes of GRBs have different distributions of the hardness ratio and the duration and it is this difference that causes the correlation between the two quantities for the entire set of the bursts.Comment: 5 pages, 1 figure, accepted for publication in PAS

Exact ground states for the four-electron problem in a two-dimensional finite Hubbard square system

We present exact explicit analytical results describing the exact ground state of four electrons in a two dimensional square Hubbard cluster containing 16 sites taken with periodic boundary conditions. The presented procedure, which works for arbitrary even particle number and lattice sites, is based on explicitly given symmetry adapted base vectors constructed in r-space. The Hamiltonian acting on these states generates a closed system of 85 linear equations providing by its minimum eigenvalue the exact ground state of the system. The presented results, described with the aim to generate further creative developments, not only show how the ground state can be exactly obtained and what kind of contributions enter in its construction, but emphasize further characteristics of the spectrum. On this line i) possible explications are found regarding why weak coupling expansions often provide a good approximation for the Hubbard model at intermediate couplings, or ii) explicitly given low lying energy states of the kinetic energy, avoiding double occupancy, suggest new roots for pairing mechanism attracting decrease in the kinetic energy, as emphasized by kinetic energy driven superconductivity theories.Comment: 37 pages, 18 figure

PERT: A Method for Expression Deconvolution of Human Blood Samples from Varied Microenvironmental and Developmental Conditions

The cellular composition of heterogeneous samples can be predicted using an expression deconvolution algorithm to decompose their gene expression profiles based on pre-defined, reference gene expression profiles of the constituent populations in these samples. However, the expression profiles of the actual constituent populations are often perturbed from those of the reference profiles due to gene expression changes in cells associated with microenvironmental or developmental effects. Existing deconvolution algorithms do not account for these changes and give incorrect results when benchmarked against those measured by well-established flow cytometry, even after batch correction was applied. We introduce PERT, a new probabilistic expression deconvolution method that detects and accounts for a shared, multiplicative perturbation in the reference profiles when performing expression deconvolution. We applied PERT and three other state-of-the-art expression deconvolution methods to predict cell frequencies within heterogeneous human blood samples that were collected under several conditions (uncultured mono-nucleated and lineage-depleted cells, and culture-derived lineage-depleted cells). Only PERT's predicted proportions of the constituent populations matched those assigned by flow cytometry. Genes associated with cell cycle processes were highly enriched among those with the largest predicted expression changes between the cultured and uncultured conditions. We anticipate that PERT will be widely applicable to expression deconvolution strategies that use profiles from reference populations that vary from the corresponding constituent populations in cellular state but not cellular phenotypic identity

The Role of Individual Variables, Organizational Variables and Moral Intensity Dimensions in Libyan Management Accountants’ Ethical Decision Making

This study investigates the association of a broad set of variables with the ethical decision making of management accountants in Libya. Adopting a cross-sectional methodology, a questionnaire including four different ethical scenarios was used to gather data from 229 participants. For each scenario, ethical decision making was examined in terms of the recognition, judgment and intention stages of Rest’s model. A significant relationship was found between ethical recognition and ethical judgment and also between ethical judgment and ethical intention, but ethical recognition did not significantly predict ethical intention—thus providing support for Rest’s model. Organizational variables, age and educational level yielded few significant results. The lack of significance for codes of ethics might reflect their relative lack of development in Libya, in which case Libyan companies should pay attention to their content and how they are supported, especially in the light of the under-development of the accounting profession in Libya. Few significant results were also found for gender, but where they were found, males showed more ethical characteristics than females. This unusual result reinforces the dangers of gender stereotyping in business. Personal moral philosophy and moral intensity dimensions were generally found to be significant predictors of the three stages of ethical decision making studied. One implication of this is to give more attention to ethics in accounting education, making the connections between accounting practice and (in Libya) Islam. Overall, this study not only adds to the available empirical evidence on factors affecting ethical decision making, notably examining three stages of Rest’s model, but also offers rare insights into the ethical views of practising management accountants and provides a benchmark for future studies of ethical decision making in Muslim majority countries and other parts of the developing world

A new approach of nonparametric estimation of incidence and lifetime risk based on birth rates and incident events

<p>Abstract</p> <p>Background</p> <p>Incidence and lifetime risk of diabetes are important public health measures. Traditionally, nonparametric estimates are obtained from survey data by means of a Nelson-Aalen estimator which requires data information on both incident events and risk sets from the entire cohort. Such data information is rarely available in real studies.</p> <p>Methods</p> <p>We compare two different approaches for obtaining nonparametric estimates of age-specific incidence and lifetime risk with emphasis on required assumptions. The first and novel approach only considers incident cases occurring within a fixed time window–we have termed this <it>cohort-of-cases </it>data–which is linked explicitly to the birth process in the past. The second approach is the usual Nelson-Aalen estimate which requires knowledge on observed time at risk for the entire cohort and their incident events. Both approaches are used on data on anti-diabetic medications obtained from Odense Pharmacoepidemiological Database, which covers a population of approximately 470,000 over the period 1993–2003. For both methods we investigate if and how incidence rates can be projected.</p> <p>Results</p> <p>Both the new and standard method yield similar sigmoidal shaped estimates of the cumulative distribution function of age-specific incidence. The Nelson-Aalen estimator gives somewhat higher estimates of lifetime risk (15.65% (15.14%; 16.16%) for females, and 17.91% (17.38%; 18.44%) for males) than the estimate based on cohort-of-cases data (13.77% (13.74%; 13.81%) for females, 15.61% (15.58%; 15.65%) for males). Accordingly the projected incidence rates are higher based on the Nelson-Aalen estimate–also too high when compared to observed rates. In contrast, the cohort-of-cases approach gives projections that fit observed rates better.</p> <p>Conclusion</p> <p>The developed methodology for analysis of cohort-of-cases data has potential to become a cost-effective alternative to a traditional survey based study of incidence. To allow more general use of the methodology, more research is needed on how to relax stationarity assumptions.</p

Enhanced antibacterial activity of silver nanoparticles/halloysite nanotubes/graphene nanocomposites with sandwich-like structure

A sandwich-like antibacterial reagent (Ag/HNTs/rGO) was constructed through the direct growth of silver nanoparticles on the surface graphene-based HNTs nanosheets. Herein, various nanomaterials were combined by adhesion effect of DOPA after self-polymerization. Ag/HNTs/rGO posses enhanced antibacterial ability against E. coli and S. aureus compared with individual silver nanoparticles, rGO nanosheets or their nanocomposites

Building generic anatomical models using virtual model cutting and iterative registration

Article deposited according to publisher policy posted on SHERPA/RoMEO, 30/07/2010.YesFunding provided by the Open Access Authors Fund

Retinoic acid induces HL-60 cell differentiation via the upregulation of miR-663

<p>Abstract</p> <p>Background</p> <p>Differentiation of the acute myeloid leukemia (AML) cell line HL-60 can be induced by all trans-retinoic acid (ATRA); however, the mechanism regulating this process has not been fully characterized.</p> <p>Methods</p> <p>Using bioinformatics and <it>in vitro </it>experiments, we identified the microRNA gene expression profile of HL-60 cells during ATRA induced granulocytic differentiation.</p> <p>Results</p> <p>Six microRNAs were upregulated by ATRA treatment, miR-663, miR-494, miR-145, miR-22, miR-363* and miR-223; and three microRNAs were downregulated, miR-10a, miR-181 and miR-612. Additionally, miR-663 expression was regulated by ATRA. We used a lentivirus (LV) backbone incorporating the spleen focus forming virus (SFFV-F) promoter to drive miR-663 expression, as the CMV (Cytomegalovirus) promoter is ineffective in some lymphocyte cells. Transfection of LV-miR-663 induced significant HL-60 cell differentiation <it>in vitro</it>.</p> <p>Conclusions</p> <p>Our results show miR-663 may play an important role in ATRA induced HL-60 cell differentiation. Lentivirus delivery of miR-663 could potentially be used directly as an anticancer treatment in hematological malignancies</p

The effects of environmental disturbances on tumor growth

In this study, the analytic expressions of the steady probability distribution of tumor cells were established based on the steady state solution to the corresponding Fokker-Planck equation. Then, the effects of two uncorrelated white noises on tumor cell growth were investigated. It was found that the predation rate plays the main role in determining whether or not the noise is favorable for tumor growth.Comment: 14 pages, 11 figures. Note: The paper will be published on volume 42 of the Brazilian Journal of Physic