Negative-weight percolation

We describe a percolation problem on lattices (graphs, networks), with edge weights drawn from disorder distributions that allow for weights (or distances) of either sign, i.e. including negative weights. We are interested whether there are spanning paths or loops of total negative weight. This kind of percolation problem is fundamentally different from conventional percolation problems, e.g. it does not exhibit transitivity, hence no simple definition of clusters, and several spanning paths/loops might coexist in the percolation regime at the same time. Furthermore, to study this percolation problem numerically, one has to perform a non-trivial transformation of the original graph and apply sophisticated matching algorithms. Using this approach, we study the corresponding percolation transitions on large square, hexagonal and cubic lattices for two types of disorder distributions and determine the critical exponents. The results show that negative-weight percolation is in a different universality class compared to conventional bond/site percolation. On the other hand, negative-weight percolation seems to be related to the ferromagnet/spin-glass transition of random-bond Ising systems, at least in two dimensions.Comment: v1: 4 pages, 4 figures; v2: 10 pages, 7 figures, added results, text and reference

Single And Double-electron Removal From H− In Energetic Collisions With Multiply-charged Argon Ions

Absolute cross-sections have been measured and compared to CTMC-calculations for single and double-electron removal from H− in collisions with Arq+ ions (q ≤ 8) at Ec.m. = 50 keV. The single-electron removal cross-sections are found to scale with q1.3, and for the H− + Ar4+ system, this cross-section is found to have a weak energy dependence from 3 keV to 100 keV. A major implication of our measurements is that plasma neutralizers based on multiply charged ions for high-efficiency conversion of intense H− beams into H0 gain little in expected reduced length due to the inapplicability of q2-scaling in the H− single-electron removal cross-section. © 1989, IOP Publishing Ltd

HIV/AIDS Mobile Applications: An Assessment for At-Risk Populations in Thailand

There is not adequate case management and reporting of HIV/AIDS among the most at-risk populations in Thailand due in part to a lack of appropriate technology. The goal of this project was to determine the most effective mobile application or application features for HIV/AIDS management from the perspectives of the target populations, case managers, and Population Services International. We produced a framework for evaluating existing and future applications, developed a prototype application, and provided recommendations for related projects

Gemcitabine and carboplatin in intensively pretreated patients with metastatic breast cancer

Background: Patients with metastatic breast cancer (MBC) are increasingly exposed to anthracyclines and taxanes either during treatment of primary breast cancer or during initial therapy of metastatic disease. The combination of gemcitabine and carboplatin was therefore investigated as an anthracycline- and taxane-free treatment option. Patients and Methods: MBC patients previously treated with chemotherapy were enrolled in a multicenter phase II study. Treatment consisted of gemcitabine (1,000 mg/m(2) i.v. on days 1 and 8) and carboplatin (AUC 4 i.v. on day 1) applied every 3 weeks. Results: Thirty-nine patients were recruited, and a total of 207 treatment cycles were applied with a median of 5 cycles per patient. One complete response and 11 partial responses were observed for an overall response rate of 31% (95% CI: 17-48%). Twelve patients (31%) had stable disease. Median time to progression was 5.3 months (95% CI: 2.6-6.7 months) and median overall survival from start of treatment was 13.2 months (95% CI: 8.7-16.7 months). Grade 3/4 hematological toxicity included leukopenia (59%/5%), thrombo-cytopenia (26%/23%) and anemia (10%/0%). Nonhematological toxicity was rarely severe. Conclusion: Combination chemotherapy with gemcitabine and carboplatin is an effective and generally well-tolerated treatment option for intensively pretreated patients with MBC. Due to a considerable incidence of severe thrombocytopenia it would be reasonable to consider starting gemcitabine at the lower dose level of 800 mg/m(2). Copyright (c) 2008 S. Karger AG, Basel

Soliton compression and supercontinuum spectra in nonlinear diamond photonics

We numerically explore synthetic crystal diamond for realizing novel light sources in ranges which are up to now difficult to achieve with other materials, such as sub-10-fs pulse durations and challenging spectral ranges. We assess the performance of on-chip diamond waveguides for controlling light generation by means of nonlinear soliton dynamics. Tailoring the cross-section of such diamond waveguides allows to design dispersion profiles with custom zero-dispersion points and anomalous dispersion ranges exceeding an octave. Various propagation dynamics, including supercontinuum generation by soliton fission, can be realized in diamond photonics. In stark contrast to usual silica-based optical fibers, where such processes occur on the scale of meters, in diamond millimeter-scale propagation distances are sufficient. Unperturbed soliton-dynamics prior to soliton fission allow to identify a pulse self-compression scenario that promises record-breaking compression factors on chip-size propagation lengths

Ground states of 2d +-J Ising spin glasses via stationary Fokker-Planck sampling

We investigate the performance of the recently proposed stationary Fokker-Planck sampling method considering a combinatorial optimization problem from statistical physics. The algorithmic procedure relies upon the numerical solution of a linear second order differential equation that depends on a diffusion-like parameter D. We apply it to the problem of finding ground states of 2d Ising spin glasses for the +-J-Model. We consider square lattices with side length up to L=24 with two different types of boundary conditions and compare the results to those obtained by exact methods. A particular value of D is found that yields an optimal performance of the algorithm. We compare this optimal value of D to a percolation transition, which occurs when studying the connected clusters of spins flipped by the algorithm. Nevertheless, even for moderate lattice sizes, the algorithm has more and more problems to find the exact ground states. This means that the approach, at least in its standard form, seems to be inferior to other approaches like parallel tempering.Comment: v1: 13 pages, 7 figures; v2: extended tex

Indoor NO2 air pollution and lung function of professional cooks

Studies ofcooking- generated NO2 effects are rare in occupational epidemiology. in the present study, we evaluated the lung function of professional cooks exposed to NO2 in hospital kitchens. We performed spirometry in 37 cooks working in four hospital kitchens and estimated the predicted FVC, FEV1 and FEF25-75, based on age, sex, race, weight, and height, according to Knudson standards. NO2 measurements were obtained for 4 consecutive days during 4 different periods at 20-day intervals in each kitchen. Measurements were performed inside and outside the kitchens, simultaneously using Palm diffusion tubes. A time/exposure indicator was defined as representative of the cumulative exposure of each cook. No statistically significant effect of NO2 exposure on FVC was found. Each year of work as a cook corresponded to a decrease in predicted FEV1 of 2.5% (P=0.046) for the group as a whole. When smoking status and asthma were included in the analysis the effect of time/exposure decreased about 10% and lost statistical significance. On predicted FEF25-75, a decrease of 3.5% (P=0.035) was observed for the same group and the inclusion of controllers for smoking status and asthma did not affect the effects of time/exposure on pulmonary function parameter. After a 10-year period of work as cooks the participants of the study may present decreases in both predicted FEV1 and FEF25-75 that can reach 20 and 30%, respectively. the present study showed small but statistically significant adverse effects of gas stove exposure on the lung function of professional cooks.Univ São Paulo, Fac Med, Lab Poluicao Atmosfer Expt, BR-01246903 São Paulo, SP, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Med, Disciplina Clin Med,Grp Fisiopatol Pulmonar & Pol, São Paulo, SP, BrazilABC, Fac Med, Dept Saude Coletividade, Santo Andre, SP, BrazilUniv Catolica Santos, Programa Posgrad Saude Coletiva, Santos, SP, BrazilCtr Univ Araraquara, Lab Fisioterapia Cardioresp, Araraquara, SP, BrazilUniv Estadual Paulista, Inst Quim, Araraquara, SP, BrazilHarvard Univ, Sch Publ Hlth, Dept Environm Hlth, Exposure Epidemiol & Risk Program, Boston, MA 02115 USAUniv Santo Amaro, Fac Med, Programa Pediat Ambiental, São Paulo, SP, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Med, Disciplina Clin Med,Grp Fisiopatol Pulmonar & Pol, São Paulo, SP, BrazilWeb of Scienc

Learning vector quantization and relevances in complex coefficient space

In this contribution, we consider the classification of time series and similar functional data which can be represented in complex Fourier and wavelet coefficient space. We apply versions of learning vector quantization (LVQ) which are suitable for complex-valued data, based on the so-called Wirtinger calculus. It allows for the formulation of gradient-based update rules in the framework of cost-function-based generalized matrix relevance LVQ (GMLVQ). Alternatively, we consider the concatenation of real and imaginary parts of Fourier coefficients in a real-valued feature vector and the classification of time-domain representations by means of conventional GMLVQ. In addition, we consider the application of the method in combination with wavelet-space features to heartbeat classification

Inference of hidden structures in complex physical systems by multi-scale clustering

We survey the application of a relatively new branch of statistical physics--"community detection"-- to data mining. In particular, we focus on the diagnosis of materials and automated image segmentation. Community detection describes the quest of partitioning a complex system involving many elements into optimally decoupled subsets or communities of such elements. We review a multiresolution variant which is used to ascertain structures at different spatial and temporal scales. Significant patterns are obtained by examining the correlations between different independent solvers. Similar to other combinatorial optimization problems in the NP complexity class, community detection exhibits several phases. Typically, illuminating orders are revealed by choosing parameters that lead to extremal information theory correlations.Comment: 25 pages, 16 Figures; a review of earlier work