Geometrical Phase Transition on WO3_3 Surface

A topographical study on an ensemble of height profiles obtained from atomic force microscopy techniques on various independently grown samples of tungsten oxide WO$_3$ is presented by using ideas from percolation theory. We find that a continuous 'geometrical' phase transition occurs at a certain critical level-height $\delta_c$ below which an infinite island appears. By using the finite-size scaling analysis of three independent percolation observables i.e., percolation probability, percolation strength and the mean island-size, we compute some critical exponents which characterize the transition. Our results are compatible with those of long-range correlated percolation. This method can be generalized to a topographical classification of rough surface models.Comment: 3 pages, 4 figures, to appear in Applied Physics Letters (2010

Ancilla-assisted sequential approximation of nonlocal unitary operations

We consider the recently proposed "no-go" theorem of Lamata et al [Phys. Rev. Lett. 101, 180506 (2008)] on the impossibility of sequential implementation of global unitary operations with the aid of an itinerant ancillary system and view the claim within the language of Kraus representation. By virtue of an extremely useful tool for analyzing entanglement properties of quantum operations, namely, operator-Schmidt decomposition, we provide alternative proof to the "no-go" theorem and also study the role of initial correlations between the qubits and ancilla in sequential preparation of unitary entanglers. Despite the negative response from the "no-go" theorem, we demonstrate explicitly how the matrix-product operator(MPO) formalism provides a flexible structure to develop protocols for sequential implementation of such entanglers with an optimal fidelity. The proposed numerical technique, that we call variational matrix-product operator (VMPO), offers a computationally efficient tool for characterizing the "globalness" and entangling capabilities of nonlocal unitary operations.Comment: Slightly improved version as published in Phys. Rev.

Gold nanoparticle and mean inactivation dose of human intestinal colon cancer HT-29 cells

Background: Mean inactivation dose is a useful radiobiological parameter for the comparison of human cell survival curves. Objectives: Given the importance and accuracy of these parameters, in the present study, the radio sensitivity enhancement of colon cancer (HT-29) cells in the presence of gold nanoparticles (GNPs) were studied using the mean inactivation dose (MID). Materials and Methods: Naked-GNPs with 50 nm diameters were incubated with HT-29 cells. The cytotoxicity and uptake of these particles on HT-29 cells were assessed. After determining the optimum GNPs concentration, the cells were incubated with gold nanoparticle for 24 hours. The change in the MID value as well as the radio sensitization enhancement under irradiation with 9 MV X-ray beams in the presence of GNPs were evaluated by multiple (3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium)MTS assay. Results: Cell survival in the presence of GNPs was more than 90% and the maximum uptake of GNPs was observed at 60 μM of gold nanoparticles. In contrast, in the presence of GNPs combined with radiation, cell survival and MID value significantly decreased, so that the radio sensitization enhancement was 1.4. Conclusions: Due to the significant reduction in the mean inactivation dose of colon cancer cells in the presence of gold nanoparticles, it seems that GNPs are suitable options to achieve a new approach in order to improve radiotherapy efficiency without increasing the prescribed radiation dose

Linear Relationship Statistics in Diffusion Limited Aggregation

We show that various surface parameters in two-dimensional diffusion limited aggregation (DLA) grow linearly with the number of particles. We find the ratio of the average length of the perimeter and the accessible perimeter of a DLA cluster together with its external perimeters to the cluster size, and define a microscopic schematic procedure for attachment of an incident new particle to the cluster. We measure the fractal dimension of the red sites (i.e., the sites upon cutting each of them splits the cluster) equal to that of the DLA cluster. It is also shown that the average number of the dead sites and the average number of the red sites have linear relationships with the cluster size.Comment: 4 pages, 5 figure

On designing observers for time-delay systems with nonlinear disturbances

This is the post print version of the article. The official published version can be obtained from the link below - Copyright 2002 Taylor & Francis LtdIn this paper, the observer design problem is studied for a class of time-delay nonlinear systems. The system under consideration is subject to delayed state and non-linear disturbances. The time-delay is allowed to be time-varying, and the non-linearities are assumed to satisfy global Lipschitz conditions. The problem addressed is the design of state observers such that, for the admissible time-delay as well as non-linear disturbances, the dynamics of the observation error is globally exponentially stable. An effective algebraic matrix inequality approach is developed to solve the non-linear observer design problem. Specifically, some conditions for the existence of the desired observers are derived, and an explicit expression of desired observers is given in terms of some free parameters. A simulation example is included to illustrate the practical applicability of the proposed theory.The work of Z. Wang was supported in part by the University of Kaiserslautern of Germany and the Alexander von Humboldt Foundation of Germany

Perceptions of HIV Virologic Control Strategies among Younger and Older Age Groups of People Living with HIV in the United States: A Cross-Sectional Survey

Two HIV virologic control advances are in various stages of development, including long-acting antiretroviral therapy (ART) formulations and strategies aimed at sustained ART-free HIV control. Perceptions of risks and benefits toward HIV virologic control strategies may be different based on an individual's age due to differing experiences of the impacts of the domestic HIV epidemic, altruistic attitudes toward research participation, and general levels of engagement in health care. We examined preferences of HIV virologic control strategies by age groups. In 2018, we conducted a nationwide, online cross-sectional survey to examine differences in HIV virologic control strategies among a sample of people living with HIV who were = 50 years of age. From a total of 281 participants, 3 findings were noteworthy: (1) Participants = 50 years; (2) participants >= 50 years of age were more motivated by altruistic notions compared with those = 50 years. Our analysis provides a deeper understanding of differences in perceptions among various age groups regarding desirable future ART characteristics, and motivations and barriers to participating in HIV cure-related strategies. Our findings can help inform community engagement and education, and assist researchers in tailoring study design and recruitment efforts to major age groups

Approximation Algorithms for Computing Maximin Share Allocations

We study the problem of computing maximin share allocations, a recently introduced fairness notion. Given a set of n agents and a set of goods, the maximin share of an agent is the best she can guarantee to herself, if she is allowed to partition the goods in any way she prefers, into n bundles, and then receive her least desirable bundle. The objective then is to find a partition, where each agent is guaranteed her maximin share. Such allocations do not always exist, hence we resort to approximation algorithms. Our main result is a 2/3-approximation that runs in polynomial time for any number of agents and goods. This improves upon the algorithm of Procaccia and Wang (2014), which is also a 2/3-approximation but runs in polynomial time only for a constant number of agents. To achieve this, we redesign certain parts of the algorithm in Procaccia and Wang (2014), exploiting the construction of carefully selected matchings in a bipartite graph representation of the problem. Furthermore, motivated by the apparent difficulty in establishing lower bounds, we undertake a probabilistic analysis. We prove that in randomly generated instances, maximin share allocations exist with high probability. This can be seen as a justification of previously reported experimental evidence. Finally, we provide further positive results for two special cases arising from previous works. The first is the intriguing case of three agents, where we provide an improved 7/8-approximation. The second case is when all item values belong to {0, 1, 2}, where we obtain an exact algorith

Reasons People Living with HIV Might Prefer Oral Daily Antiretroviral Therapy, Long-Acting Formulations or Future HIV Remission Options

A growing body of research is beginning to elucidate reasons people living with HIV (PLWHIV) might prefer oral daily antiretroviral treatment (ART) compared with emerging long-acting ART (LA-ART) or HIV remission strategies under investigation. Our objective is to provide qualitative insights into the reasons why PLWHIV might prefer one of these HIV control therapies over others. From May to August 2018, we implemented a semistructured cross-sectional survey of PLWHIV in the United States to better understand patient preferences around various HIV treatment and remission options. Using free text, respondents were asked to explain why they preferred one HIV control option over the other two. We analyzed responses to the open-ended survey questions on reasons for preferring oral daily ART versus LA-ART versus HIV remission strategies using conventional content analysis. The results showed that PLWHIV preferred oral daily ART because of its familiarity and known safety and efficacy profile, whereas those who preferred LA-ART would value the convenience it offers. Finally, HIV remission strategies would be preferred to avoid taking ART altogether. The qualitative results provide insights into reasons why PLWHIV in the United States might prefer oral daily ART versus novel therapies. More importantly, they provide information to better align HIV virological control strategies with end-user perspectives. To make informed choices around evolving HIV therapeutics, PLWHIV and HIV care providers would benefit from decision tools to better assess options and trade-offs. More research is needed on how best to effectively support PLWHIV and HIV care providers in shared decision-making