A Simulation Method to Resolve Hydrodynamic Interactions in Colloidal Dispersions

A new computational method is presented to resolve hydrodynamic interactions acting on solid particles immersed in incompressible host fluids. In this method, boundaries between solid particles and host fluids are replaced with a continuous interface by assuming a smoothed profile. This enabled us to calculate hydrodynamic interactions both efficiently and accurately, without neglecting many-body interactions. The validity of the method was tested by calculating the drag force acting on a single cylindrical rod moving in an incompressible Newtonian fluid. This method was then applied in order to simulate sedimentation process of colloidal dispersions.Comment: 7pages, 7 figure

An alternative implementation of the Lanczos algorithm for wave function propagation

We reformulate the Lanczos algorithm for quantum wave function propagation in terms of variational principle. By including some basis states of previous time steps into the variational subspace, the resultant accuracy increases by several orders. Numerical errors of the alternative method accumulate much slower than that of the original Lanczos method. There is almost no extra numeric cost for the gaining of the accuracy, i.e., the accuracy increase needs no extra operations of the Hamiltonian acting on state vectors, which are the major numeric cost for wave function propagation. A wave packet moving in a 2-dimensional H\'enon-Heiles model serves as an illustration. This method is suitable for small time step propagation of quantum wave functions in large scale time dependent calculations where the operations of the Hamiltonian acting on state vectors are expensive.Comment: To appear in J. Phys.

Condom use and incident sexually transmitted infection after initiation of long-acting reversible contraception

Background Use of more effective contraception may lead to less condom use and increased incidence of sexually transmitted infection. Objective The objective of this study was to compare changes in condom use and incidence of sexually transmitted infection acquisition among new initiators of long-acting reversible contraceptives to those initiating non-long-acting reversible contraceptive methods. Study Design This is a secondary analysis of the Contraceptive CHOICE Project. We included 2 sample populations of 12-month continuous contraceptive users. The first included users with complete condom data (baseline, and 3, 6, and 12 months) (long-acting reversible contraceptive users: N = 2371; other methods: N = 575). The second included users with 12-month sexually transmitted infection data (long-acting reversible contraceptive users: N = 2102; other methods: N = 592). Self-reported condom use was assessed at baseline and at 3, 6, and 12 months following enrollment. Changes in condom use and incident sexually transmitted infection rates were compared using χ2 tests. Risk factors for sexually transmitted infection acquisition were identified using multivariable logistic regression. Results Few participants in either group reported consistent condom use across all survey time points and with all partners (long-acting reversible contraceptive users: 5.2%; other methods: 11.3%; P < .001). There was no difference in change of condom use at 3, 6, and 12 months compared to baseline condom use regardless of method type (P = .65). A total of 94 incident sexually transmitted infections were documented, with long-acting reversible contraceptive users accounting for a higher proportion (3.9% vs 2.0%; P = .03). Initiation of a long-acting reversible contraceptive method was associated with increased sexually transmitted infection incidence (odds ratio, 2.0; 95% confidence ratio, 1.07–3.72). Conclusion Long-acting reversible contraceptive initiators reported lower rates of consistent condom use, but did not demonstrate a change in condom use when compared to preinitiation behaviors. Long-acting reversible contraceptive users were more likely to acquire a sexually transmitted infection in the 12 months following initiation

The evaluation of liver fibrosis regression in chronic hepatitis C patients after the treatment with direct-acting antiviral agents – A review of the literature

The second-generation of direct-acting antiviral agents are the current treatment for chronic viral hepatitis C infection. To evaluate the regression of liver fibrosis in patients receiving this therapy, liver biopsy remains the most accurate method, but the invasiveness of this procedure is its major drawback. Different non-invasive tests have been used to study changes in the stage of liver fibrosis in patients with chronic viral hepatitis treated with the second-generation of direct-acting antiviral agents: liver stiffness measurements (with transient elastography or acoustic radiation force impulse elastography) or different scores that use serum markers to calculate a fibrosis score. We prepared a literature review of the available data regarding the long-term evolution of liver fibrosis after the treatment with direct-acting antiviral agents for chronic viral hepatitis C

Women’s Empowerment and Contraceptive Method Use in Egypt

Egypt’s fertility rate reached a 25-year high of 3.5 births per woman in 2014.It is assumed that women’s empowerment plays an important role in women’s choice of a specific contraceptive method. This research brief, by former PRC postdoctoral fellow Goleen Samari, found that use of long-acting methods fell in Egypt between 2005 and 2014, while use of short-acting methods increased. She also found that women’s empowerment increases the likelihood of contraceptive use in Egypt.Population Research Cente

On photon statistics parametrized by a non-central Wishart random matrix

In order to tackle parameter estimation of photocounting distributions, polykays of acting intensities are proposed as a new tool for computing photon statistics. As unbiased estimators of cumulants, polykays are computationally feasible thanks to a symbolic method recently developed in dealing with sequences of moments. This method includes the so-called method of moments for random matrices and results to be particularly suited to deal with convolutions or random summations of random vectors. The overall photocounting effect on a deterministic number of pixels is introduced. A random number of pixels is also considered. The role played by spectral statistics of random matrices is highlighted in approximating the overall photocounting distribution when acting intensities are modeled by a non-central Wishart random matrix. Generalized complete Bell polynomials are used in order to compute joint moments and joint cumulants of multivariate photocounters. Multivariate polykays can be successfully employed in order to approximate the multivariate Mendel-Poisson transform. Open problems are addressed at the end of the paper.Comment: 18 pages, in press in Journal of Statistical Planning and Inference, 201

Sliding mode control based piezoelectric actuator control

In this paper a method for piezoelectric stack actuator control is proposed. In addition a brief discussion about the usage of the same methods for estimation of external force acting to the actuator in contact with environment is made. The method uses sliding mode framework to design both the observer and the controller based on an electromechanical lumped model of the piezoelectric actuator. Furthermore, using a nonlinear differential equation the internal hysteresis disturbance is removed from the total disturbance in an attempt to estimate the external force acting on the actuator. It is then possible to use this external force estimate as a means of force control of the actuator. Simulation and experiments are compared for validating the disturbance and external force estimation technique. Some experiments that incorporate disturbance compensation in a closed-loop SMC control algorithm are also presented to prove the effectiveness of this method in producing high precision motion

Explicit recognition of emotional facial expressions is shaped by expertise: evidence from professional actors

Can reading others' emotional states be shaped by expertise? We assessed processing of emotional facial expressions in professional actors trained either to voluntary activate mimicry to reproduce character's emotions (as foreseen by the “Mimic Method”), or to infer others' inner states from reading the emotional context (as foreseen by “Stanislavski Method”). In explicit recognition of facial expressions (Experiment 1), the two experimental groups differed from each other and from a control group with no acting experience: the Mimic group was more accurate, whereas the Stanislavski group was slower. Neither acting experience, instead, influenced implicit processing of emotional faces (Experiment 2). We argue that expertise can selectively influence explicit recognition of others' facial expressions, depending on the kind of “emotional expertise”