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In this article the authors formulates basic types of English abstract and discuss frequent problems in the writing of the English abstracts carried in Chinese medical journals.
Biolarvicides, based on mosquitocidal toxins of certain strains of Bacillus sphaericus and Bacillus thuringiensis var israelensis H-14 (Bti) are highly effective against mosquito larvae at very low doses and safe to other non-target organisms. During past two decades various biolarvicide formulations produced in India and abroad have been tested at Malaria Research Centre and some formulations have undergone large-scale operational trials. Biolarvicide formulations of B. sphaericus are useful in the control of Culex and certain Anopheles spp, such as An. stephensi and An. subpictus, but not much effective against An. culicifacies and almost ineffective against Aedes aegypti. Repeated application of B. sphaericus in the same habitat, however, results in the development of resistance in larvae of target mosquitoes. In view of its low specificity for An. culicifacies and the potential for resistance in An. stephensi, B. sphaericus has limited prospects for control of malaria vectors. However, with some resistance management, B. sphaericus can still be used against Culex mosquitoes. On the other hand Bti formulations, which have broader spectrum of activity against Aedes, Culex and Anopheles spp, have not shown significant development of resistance in mosquitoes but their activity in field, particularly against surface feeding anopheline larvae is affected by various bioenvironmental factors, thus requiring weekly application in most habitats. To overcome this problem development of slow release formulations and genetically engineered biolarvicides by transplanting mosquitocidal toxin genes of Bti and B. sphaericus in some other environmentally compatible organisms have been investigated by different scientists.
Adolescent dating violence is an important juncture in the developmental pathway to adult partnership violence. As a window of opportunity for positive change, the present review considers the theoretical and empirical work on adolescent dating and dating violence. A consideration of the scope of the problem, developmental processes, and theoretical formulations precede a review of six relationship violence prevention programs designed for and delivered to youth. Five programs are school-based and one operates in the community. Prevention is targeted toward both universal (e.g., all high school students) and selected adolescent populations (e.g., youths with histories of maltreatment, or problems with peer aggression). Programs addressed specific skills and knowledge that oppose the use of violent and abusive behavior toward intimate partners; one program addressed interpersonal violence more generally, and was also included in this review because of its implications for dating violence initiatives. Positive changes were found across studies in violence-related attitudes and knowledge, also, positive gains were noted in self-reported perpetration of dating violence, with less consistent evidence in self-reported victimization. However, these findings should be considered preliminary due to limited follow-up and generalizability. Conceptual and methodological issues are discussed with a view toward improving assessment methods and research design.
The diversity of functional forms and strategies in plant communities is essential to the maintenance of the services that ecosystems provide humanity, and ultimately to the homeostasis of the biosphere. This diversity emerges from evolutionary forces operating at lower levels; these exploit the opportunities for specialization presented by exogenous and endogenous spatial and temporal heterogeneity. Two major theoretical approaches have been taken to understand how strategies arise and are maintained: optimization models, which consider the fitnesses of types in isolation, and game-theoretic methods, which take frequency dependence into account. The game-theoretic approach is more powerful, but also more challenging to apply. For some relatively simple problems in the study of biodiversity, we show how the game-theoretic formulation can be translated into an equivalent problem in optimization. More generally, however, new techniques will be needed to explore the dynamics of multiple coexisting types and strategies.
Oil-in-water emulsion formulations are useful for the parenteral administration of drugs which have significant delivery problems. Drugs may be incorporated into emulsion formulations either by emulsification of the drug dissolved in the oil phase, or by extemporaneous addition of a concentrated solution in a cosolvent to a commercial i.v. emulsion. Examples are given of the use of parental emulsion dosage forms for the delivery of drugs which have low water solubility, lack stability to hydrolysis, are irritant or have substantial affinity for plastic infusion sets. These examples are largely drawn from studies of novel cytotoxic agents. Emulsion dosage forms may also have some potential for site-directed drug delivery or for sustained release applications. The potential hazards of parenteral emulsions and some of the means of size determination of the dispersed oil droplets are also examined.
Passive myocardial material properties have been measured previously by subjecting test samples of myocardium to in vitro load-deformation analysis or, in the intact heart, by pressure-volume relationships. A new method for determining passive material properties, described in this paper, couples a p-version finite element model of the heart, a nonlinear optimization algorithm and a dense set of transmural measured strains that could be obtained in the intact heart by magnetic resonance imaging (MRI) radiofrequency tissue tagging. Unknown material parameters for a nonlinear, nonhomogeneous material law are determined by solving an inverse boundary value problem. An objective function relating the least-squares difference of model-predicted and measured strains is minimized with respect to the unknown material parameters using a novel optimization algorithm that utilizes forward finite element solutions to calculate derivatives of model-predicted strains with respect to the material parameters. Test cases incorporating several salient features of the inverse material identification problem for the heart are formulated to test the performance of the inverse algorithm in typical experimental conditions. Known true material parameters can be determined to within a small tolerance and random noise is shown not to affect the stability of the inverse solution appreciably. On the basis of these validation experiments, we conclude that the inverse material identification problem for the heart can be extended to solve for unknown material parameters that describe in vivo myocardial material behavior.
Topical problems of modern disinfectology are formulated in connection with differences in the resistance of different microbial groups, species, strains to disinfectants, as well as with the "critical ability" of instruments and, accordingly, with different requirements to the necessary levels of decontamination. Factors determining the effectivity of disinfection are described. Requirements to "ideal" disinfectants and disinfectological technologies are considered. The problems of harmonization of approaches to the evaluation of Russian and foreign disinfectological methods and bringing them closer together are discussed.
We develop a general theoretical framework for the recently proposed importance sampling method for enhancing the efficiency of rare-event simulations [W. Cai, M. H. Kalos, M. de Koning, and V. V. Bulatov, Phys. Rev. E 66, 046703 (2002)], and discuss practical aspects of its application. We define the success/fail ensemble of all possible successful and failed transition paths of any duration and demonstrate that in this formulation the rare-event problem can be interpreted as a "hit-or-miss" Monte Carlo quadrature calculation of a path integral. The fact that the integrand contributes significantly only for a very tiny fraction of all possible paths then naturally leads to a "standard" importance sampling approach to Monte Carlo (MC) quadrature and the existence of an optimal importance function. In addition to showing that the approach is general and expected to be applicable beyond the realm of Markovian path simulations, for which the method was originally proposed, the formulation reveals a conceptual analogy with the variational MC (VMC) method. The search for the optimal importance function in the former is analogous to finding the ground-state wave function in the latter. In two model problems we discuss practical aspects of finding a suitable approximation for the optimal importance function. For this purpose we follow the strategy that is typically adopted in VMC calculations: the selection of a trial functional form for the optimal importance function, followed by the optimization of its adjustable parameters. The latter is accomplished by means of an adaptive optimization procedure based on a combination of steepest-descent and genetic algorithms.
A reaction probability is required to calculate the rate constant of a diffusion-dominated reaction. Due to the complicated geometry and potentially high dimension of the reaction probability problem, it is usually solved by a Brownian dynamics simulation, also known as a random walk or path integral method, instead of solving the equivalent partial differential equation by a discretization method. Building on earlier work, this article completes the development of a robust importance sampling algorithm for Brownian dynamics-i.e., biased Brownian dynamics with weight control-to overcome the high energy and entropy barriers in biomolecular association reactions. The biased Brownian dynamics steers sampling by a bias force, and the weight control algorithm controls sampling by a target weight. This algorithm is optimal if the bias force and the target weight are constructed from the solution of the reaction probability problem. In reality, an approximate reaction probability has to be used to construct the bias force and the target weight. Thus, the performance of the algorithm depends on the quality of the approximation. Given here is a method to calculate a good approximation, which is based on the selection of a reaction coordinate and the variational formulation of the reaction probability problem. The numerically approximated reaction probability is shown by computer experiments to give a factor-of-two speedup over the use of a purely heuristic approximation. Also, the fully developed method is compared to unbiased Brownian dynamics. The tests for human superoxide dismutase, Escherichia coli superoxide dismutase, and antisweetener antibody NC6.8, show speedups of 17, 35, and 39, respectively. The test for reactions between two model proteins with orientations shows speedups of 2578 for one set of configurations and 3341 for another set of configurations.
The assumption is made that the formulation of relations as independent components (IC) is a main feature of computations accomplished by the brain. Further, it is assumed that memory traces made of non-orthonormal ICs make use of feedback architectures to form internal representations. Feedback then leads to delays, and delays in cortical processing form an obstacle to this relational processing. The problem of delay compensation is formulated as a speed-field tracking task and is solved by a novel control architecture. It is shown that in addition to delay compensation the control architecture can also shape long-term memories to hold independent components if a two-phase operation mode is assumed. Features such as a trisynaptic loop and a recurrent collateral structure at the second stage of that loop emerge in a natural fashion. Based on these properties a functional model of the hippocampal loop is constructed.
The Fourier modal method for crossed gratings with square symmetry is reformulated by use of a group-theoretic approach that we developed recently. In the new formulation, a crossed-grating problem is decomposed into six symmetrical basis problems whose field distributions are the symmetry modes of the grating. Then the symmetrical basis problems are solved with symmetry simplifications, whose solutions are superposed to get the solution of the original problem. Theoretical and numerical results show that when the grating is at some Littrow mountings, the computation efficiency can be improved effectively: The memory occupation is reduced by 3/4 and the computation time is reduced by a factor from 25.6 to 64 in different incident cases. Numerical examples are given to show the effectiveness of the new formulation.
Highly-interconnected networks of nonlinear analog neurons are shown to be extremely effective in computing. The networks can rapidly provide a collectively-computed solution (a digital output) to a problem on the basis of analog input information. The problems to be solved must be formulated in terms of desired optima, often subject to constraints. The general principles involved in constructing networks to solve specific problems are discussed. Results of computer simulations of a network designed to solve a difficult but well-defined optimization problem--the Traveling-Salesman Problem--are presented and used to illustrate the computational power of the networks. Good solutions to this problem are collectively computed within an elapsed time of only a few neural time constants. The effectiveness of the computation involves both the nonlinear analog response of the neurons and the large connectivity among them. Dedicated networks of biological or microelectronic neurons could provide the computational capabilities described for a wide class of problems having combinatorial complexity. The power and speed naturally displayed by such collective networks may contribute to the effectiveness of biological information processing.
Dynamic decision analysis concerns decision problems in which both time and uncertainty are explicitly considered. Two major challenges in dynamic decision analysis are on proper formulation of a model for the problem and effective elicitation of the numerous time-dependent conditional probabilities for the model. Based on a new, general dynamic decision modeling framework called DynaMoL (Dynamic decision Modeling Language), we propose a data-driven approach to addressing these issues. Our approach uses available problem data from large medical databases, guides the decision modeling at a proper level of abstraction and establishes a Bayesian learning method for automatic extraction of the probabilistic parameters. We demonstrate the theoretical implications and practical promises of this new approach to dynamic decision analysis in medicine through a comprehensive case study in the optimal follow-up of patients after curative colorectal cancer surgery.
The theory of complex systems, such as neural assemblies or lattices of chaotic oscillators has generated many new problems including the synchronization or regularization of the cooperative behavior of systems consisting of chaotic elements, regular spatial patterns in "chaotic" lattices, and so on. A number of these problems were discussed at the International School in Nonlinear Science-95 (Nizhniy Novgorod, Russia). In this overview we try to formulate some of the most interesting problems that were discussed at that meeting. (c) 1996 American Institute of Physics.
Analytical reconstruction of 3D curves from their stereo images is an important issue in computer vision. We present an optimization framework for such a problem based on a nonuniform rational B-spline (NURBS) curve model that converts reconstruction of a 3D curve into reconstruction of control points and weights of a NURBS representation of the curve, accordingly bypassing the error-prone point-to-point correspondence matching. Perspective invariance of NURBS curves and constraints deduced on stereo NURBS curves are employed to formulate the 3D curve reconstruction problem into a constrained nonlinear optimization. A parallel rectification technique is then adopted to simplify the constraints, and the Levenberg-Marquardt algorithm is applied to search for the optimal solution of the simplified problem. The results from our experiments show that the proposed framework works stably in the presence of different data samplings, randomly posed noise, and partial loss of data and is potentially suitable for real scenes.
Recent psychoanalytic studies have contributed significantly to our understanding of how the formation of self-image groupings (the body self, the self experienced as individuated, and the grandiose self) integrate to form a cohesive sense of self. In addition to our increased knowledge of the normal development, we have a richer understanding of vulnerability to fragmentation of the sense of self. Knowledge of the development of the sense of a cohesive self and its vulnerability to fragmentation are applied to illnesses familiar to psychoanalysts. During normal adjustment reactions different aspects of the self predominate. In most such instances, images of the self can be balanced so that self-cohesion is retained. In the conflicts of the psychoneurotic, aspects of the self may be defensively segregated. Psychoanalysis must enable these aspects of the self to come into awareness and be blended into the general experiencing of the self; rarely does the threat of loss of self-cohesion present a special problem in working on this with a psychoneurotic patient. In contrast, the narcissistic personality and borderline personality disorders present specific problems centering on the potential of the patients to experience fragmentation of their sense of self. Clinical vignettes and theoretical formulations contrast these with the familiar problems that arise in the treatment of the psychoneuroses. The therapist's full empathic contact and a correct strategy of interventions arise from the appreciation of the presence or absence in the patient of threatened fragmentation of the cohesive sense of self.
Novel tretinoin cream and gel formulations have been developed that incorporate polyolprepolymer-2, which is a material designed to help retain drug molecules in and on the skin when applied in topical vehicles. The results of preclinical and clinical investigations have confirmed the beneficial impact of such a vehicle on tretinoin tolerability. In vitro studies with selected polyolprepolymer-containing formulations have reduced initial and cumulative tretinoin percutaneous penetration, and guinea pig studies showed that the gel formulation containing polyolprepolymer-2 caused less erythema and edema than did the corresponding commercially-available tretinoin gel formulation. Human studies with tretinoin containing polyolprepolymer-2 have consistently demonstrated a favorable tolerability profile when compared with commercially-available tretinoin. Use of the polyolprepolymer-2-containing tretinoin formulation in human studies has resulted in reductions in peeling--a problem commonly associated with use of standard tretinoin formulations. These reductions in irritation have not been at the expense of efficacy; acne clinical trial results indicate comparable effectiveness between tretinoin containing polyolprepolymer2 and commercially-available tretinoin.
Variation in moisture content of the capsule shells either due to the change of storage conditions or the moisture transfer between the capsule shell and its contents may lead to undesired physical properties, such as capsule brittleness and stickiness. DMP 504, a developmental bile-acid sequestrant, is a strongly basic anion-exchange polymer which contains randomly distributed primary, secondary, tertiary, and quaternary amine groups in their hydrochoride salt form. The alkylammonium groups which comprise this polymer form a random network containing a high level of branching and a low level of cross-linking. DMP 504 is very hygroscopic and has a tendency to gain or lose moisture with ease. The transfer of moisture from the capsule shell to DMP 504 powder contained in a hard gelatin capsule can be expected, and if a low water content of the capsule shell is achieved, the capsules become brittle and fracture easily. The sorption isotherm for DMP 504 was generated by storing the drug substance under various relative humidity conditions. After equilibrium, the moisture contents for the samples of individual isotherm points were measured by thermogravimetric analyses. This report applies the sorption-desorption moisture transfer (SDMT) model to predict the equilibrium relative humidity in a system containing DMP 504 in hard gelatin capsules and to establish target loss on drying values for DMP 504 and the capsule shell. Application of this SDMT model resulted in finding a solution to the brittleness problem. The moisture levels of capsule shells and contents for two formulations in a 12-month stability program are also reported here. Results of this study further demonstrate that the SDMT model can be used as a tool to guide the formulator to select optimal initial moisture contents for the empty capsule shell and the formulation to avoid the incidence of brittle capsule problems.