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PubMed1973

Some problems of field research.

For the results of ergonomic research to be of value it must be validated on the shop floor and this involves field experiments. The aim of this article is to formulate some generally applicable ideas on the problems and strategies involved in field research. The points to be made derive from experience of research in the field extending over some 20 years. It is hoped that a realistic assessment of the problems will help contribute to their solution.

Journal Article↗
PubMed2003

New ways of looking at experimental phasing.

In the original work by Blow and Crick, experimental phasing was formulated as a least-squares problem. For good data on good derivatives this approach works reasonably well, but we now attempt to extract more information from poorer data than in the past. As in many other crystallographic problems, the assumptions underlying the use of least squares for phasing are not satisfied, particularly for poor derivatives. The introduction of maximum likelihood (and more powerful computers) has led to substantial improvements. For computational convenience, these new methods still make many assumptions about the independence of different measurements and sources of error. A more general formulation for the probability distributions underlying likelihood-based methods for both experimental phasing and molecular-replacement phasing is reviewed. In the new formulation, all the structure factors associated with a particular hkl are considered to be related by a complex multivariate normal distribution. When it is assumed that certain errors are independent, the general formulation reduces to current likelihood targets. However, the new formulation makes the necessary assumptions more explicit and points the way to improving phasing using both isomorphous and anomalous differences.

Crystallography, X-Ray↗
PubMed1991

Bioavailability study of a freeze-dried sodium phenytoin-milk formulation.

The problematic bioavailability of phenytoin's (5,5-diphenylhydantoin) oral formulations serves as a stimulus for examining new formulations and/or administration conditions that may provide more predictable absorption. Attempts to achieve more consistent peroral phenytoin bioavailability from conventional solid dosage forms include changes of binder and crystal size, use of salt form, and inclusion of the drug in cyclodextrins. In addition, various factors which may affect the environment and/or the physiology of the upper gastrointestinal tract can profoundly affect the absorption of phenytoin. Among other approaches, the use of drug-milk freeze-dried formulations has been proposed to overcome problems associated with dissolution-limited bioavailability. The effect has been attributed to the formation of an amorphous precipitate during the drying process which facilitates the re-dissolution of the drug during the regeneration of the milk solution. In this work, we report comparative bioavailability studies utilizing a freeze-dried sodium phenytoin-milk formulation and a capsule formulation administered with either water or milk. In addition, the interaction of the drug with milk components was evaluated in vitro through binding and solubility studies.

Administration, Oral↗
PubMed1998

Finite element implementation of anisotropic quasi-linear viscoelasticity using a discrete spectrum approximation.

The objective of this work was to develop a theoretical and computational framework to apply the finite element method to anisotropic, viscoelastic soft tissues. The quasilinear viscoelastic (QLV) theory provided the basis for the development. To allow efficient and easy computational implementation, a discrete spectrum approximation was developed for the QLV relaxation function. This approximation provided a graphic means to fit experimental data with an exponential series. A transversely isotropic hyperelastic material model developed for ligaments and tendons was used for the elastic response. The viscoelastic material model was implemented in a general-purpose, nonlinear finite element program. Test problems were analyzed to assess the performance of the discrete spectrum approximation and the accuracy of the finite element implementation. Results indicated that the formulation can reproduce the anisotropy and time-dependent material behavior observed in soft tissues. Application of the formulation to the analysis of the human femur-medial collateral ligament-tibia complex demonstrated the ability of the formulation to analyze large three-dimensional problems in the mechanics of biological joints.

Biomechanical Phenomena↗
PubMed1997

Characterization and stability of various liposome-encapsulated enoxacin formulations.

The necessity for antibacterial agents with greater intracellular efficacy has led to the development of endocytosable drug carriers such as liposomes. Enoxacin was selected as a model drug incorporated in various liposome formulations as a therapeutic dosage form using the ethanol injection method and freeze-drying. Liposomal behavior after preparation and stability test was characterized by determining the physicochemical properties of enoxacin encapsulation percent, vesicle size and turbidity. The non-phospholipid formulation of stratum corneum liposomes showed the highest encapsulation efficiency after preparation among nine liposomal formulations. The addition of dissacharides in liposomes also enhanced the encapsulation of enoxacin due to the protection of phospholipid bilayers during the freeze-drying process. The liposomes with negatively charged component and dissacharides showed lower enoxacin leakage after five weeks of storage at 45 degrees C, suggesting these formulations have high stability in long-term storage. The negative liposomes showed a different behavior than others in their decrease of size and turbidity during storage, possibly due to high surface charges of the negative formulation. Cholesterol stabilized bilayers interacted with plasma and high density lipoprotein (HDL) retained enoxacin in the vesicles. Nevertheless, liposomes with cholesterol caused a hydrolysis problem after incubation with normal saline. The formulation with trehalose not only showed high stability in storage but also in plasma and HDL. This suggested trehalose was useful to incorporate with phospholipids to produce a highly encapsulated and stabilized liposomes of enoxacin. This study also demonstrated that thought is required in utilizing turbidity as a direct index of liposomal vesicle size.

Anti-Infective Agents↗
PubMed1989

Tenoxicam milk formulation in the treatment of rheumatic conditions.

Tenoxicam milk formulation is a new galenical form of a non-steroidal anti-inflammatory drug (NSAID). It is especially suitable for patients having compliance problems or difficulty in swallowing tablets. This formulation has proved to be a useful alternative oral treatment in various rheumatic conditions. Combining rapid onset of action and maintenance of active plasma levels, tenoxicam achieved good clinical efficacy and tolerability in the vast majority of the patients studied.

Administration, Oral↗
PubMed1997

Psychosomatic problems and stress in adolescence.

Psychosomatic problems are common in adolescents, and stress frequently plays a role in their development and maintenance. Armed with an understanding of the stressors experienced by adolescents, the individual's vulnerabilities and competencies and their level of social support, the physician can systematically assess each of these factors. Once the assessment is complete, a management plan can be formulated to address the particular psychosomatic problem. Symptom relief, stress reduction, and promotion of competence are important interventions that can be initiated by the primary care physician. When referrals are made for counseling and other stress management techniques, the primary care physician should maintain contact with the patient and family and remain an integral part of the management team. Incorporating brief discussions about the potential role of stress in health and illness into anticipatory guidance sessions may also help prevent the development of psychosomatic problems in adolescents.

Abdominal Pain↗
PubMed2006

History and current perspectives on the use of drug formulations to decrease the abuse of prescription drugs.

This article is part of a supplemental issue of the journal devoted entirely to papers on how abuse liability of medications is affected by their formulation for medical use. This article reviews the history of abuse and addiction to medications in the United States and the legislation designed to control these problems. The provisions in legislation related specifically to formulations of medications designed to decrease their abuse potential will be noted. In addition, the role of the College on Problems of Drug Dependence (CPDD) as an organization initially founded to develop analgesic medications with less abuse potential than morphine is briefly reviewed. Examples of current approaches to the development of formulations of medications to decrease their abuse potential discussed in detail in the articles to follow are outlined. Finally, the use of behavioral economic analyses to better delineate the relative abuse potential of new medication formulations is discussed.

Chemistry, Pharmaceutical↗
PubMed2005

Modeling Rayleigh and Stoneley waves and other interface and boundary effects with the parabolic equation.

An improved approach for handling boundaries, interfaces, and continuous depth dependence with the elastic parabolic equation is derived and benchmarked. The approach is applied to model the propagation of Rayleigh and Stoneley waves. Depending on the choice of dependent variables, the operator in the elastic wave equation may not factor or the treatment of interfaces may be difficult. These problems are resolved by using a formulation in terms of the vertical displacement and the range derivative of the horizontal displacement. These quantities are continuous across horizontal interfaces, which permits the use of Galerkin's method to discretize in depth. This implementation extends the capability of the elastic parabolic equation to handle arbitrary depth dependence and should lead to improvements for range-dependent problems.

Journal Article↗
PubMed1982

Perspectives of cooperation of CMEA countries in combatting influenza.

Results of cooperation of CMEA countries in combatting influenza on the basis of coordination of studies for 1977-1979 are presented. The most important result is the creation of prerequisites for setting up fundamentally new tasks in the development of long-term cooperation of CMEA countries in combatting influenza. The principles of common strategy and tactics of combatting influenza have been formulated for all these countries. The problems of standardization of the preparations, integration of their production, general methodological approaches to their use and evaluation, the complex character of applying contemporary means of combatting influenza on limited territories, and others, are discussed. The most important scientific tasks in the sphere of development and evaluation of the effectiveness of new anti-influenza preparations have been formulated.

Cuba↗
PubMed2005

An approach toward the problem of outliers in QSAR.

Compounds that have unexpected biological activity and are unable to fit in a QSAR model are known as outliers. These are valuable in defining the limitations under which compounds act by a common molecular mechanism modeled by one or more descriptors, and also in defining the experimental limitations of the biological test data. Thus, the outliers should be submitted to particular attention to see if the reason for their peculiarity can be determined. Separating these outliers from the main data set and formulating another QSAR can resolve the problem. Our result shows that these outliers may be acting by a different mechanism or interacting with the receptor in different modes.

Animals↗
PubMed2005

Mathematical analysis of an age-structured population model with space-limited recruitment.

In this paper, we investigate structured population model of marine invertebrate whose life stage is composed of sessile adults and pelagic larvae, such as barnacles contained in a local habitat. First we formulate the basic model as an Cauchy problem on a Banach space to discuss the existence and uniqueness of non-negative solution. Next we define the basic reproduction number R0 to formulate the invasion condition under which the larvae can successfully settle down in the completely vacant habitat. Subsequently we examine existence and stability of steady states. We show that the trivial steady state is globally asymptotically stable if R0 < or = 1, whereas it is unstable if R0 > 1. Furthermore, we show that a positive (non-trivial) steady state uniquely exists if R0 > 1 and it is locally asymptotically stable as far as absolute value of R0 - 1 is small enough.

Animals↗
PubMed1992

Expert nurses' clinical reasoning under uncertainty: representation, structure, and process.

How do expert nurses reason when planning care and making clinical decisions for a patient who is at risk, and whose outcome is uncertain? In this study, a case study involving a critically ill elderly woman whose condition deteriorated over time, was presented in segments to ten expert critical care nurses. Think aloud method was used to elicit knowledge from these experts to provide conceptual information about their knowledge and to reveal their reasoning processes and problem-solving strategies. The verbatim transcripts were then analyzed using a systematic three-step method that makes analysis easier and adds creditability to study findings by providing a means of retracing and explaining analysis results. Findings revealed information about how patient problems were represented during reasoning, the manner in which experts subjects structured their plan of care, and the reasoning processes and heuristics they used to formulate solutions for resolving the patient's problems and preventing deterioration in the patient's condition.

Aged↗
PubMed2003

Assessment of RAPTOR's linear programming approach in CAFASP3.

We have developed a new algorithm based on the mathematical theory of linear programming (LP) and implemented it in our program RAPTOR. Our new approach provides an elegant formulation of the protein-threading problem, overcomes the intractability problem of protein threading, in practice, and allows us to use existing powerful linear programming software to obtain optimal protein threading solutions. CASP5 and CAFASP3 gave us the first chance to test RAPTOR in an unbiased way. RAPTOR was ranked as the top individual (automatic) server for fold recognition by the CAFASP3 organizers. In this short article, we describe RAPTOR's LP formulation, assess RAPTOR's performance in CAFASP3/CASP5, explain why it has superceded other existing automatic individual methods, and point out its strengths, limitations, extensions, and prospects for improvement.

Algorithms↗
PubMed2003

Risk modeling, assessment, and management of lahar flow threat.

The 1991 eruption of Mount Pinatubo in the Philippines is considered one of the most violent and destructive volcanic activities in the 20th century. Lahar is the Indonesian term for volcanic ash, and lahar flows resulting from the massive amount of volcanic materials deposited on the mountain's slope posed continued post-eruption threats to the surrounding areas, destroying lives, homes, agricultural products, and infrastructures. Risks of lahar flows were identified immediately after the eruption, with scientific data provided by the Philippine Institute of Volcanology, the U.S. Geological Survey, and other research institutions. However, competing political, economic, and social agendas subordinated the importance of scientific information to policy making. Using systemic risk analysis and management, this article addresses the issues of multiple objectives and the effective integration of scientific techniques into the decision-making process. It provides a modeling framework for identifying, prioritizing, and evaluating policies for managing risk. The major considerations are: (1) applying a holistic approach to risk analysis through hierarchical holographic modeling, (2) applying statistical methods to gain insight into the problem of uncertainty in risk assessment, (3) using multiobjective trade-off analysis to address the issue of multiple decisionmakers and stakeholders in the decision-making process, (4) using the conditional expected value of extreme events to complement and supplement the expected value in quantifying risk, and (5) assessing the impacts of multistage decisions. Numerical examples based on ex post data are formulated to illustrate applications to various problems. The resulting framework from this study can serve as a general baseline model for assessing and managing risks of natural disasters, which the Philippines' lead agency-the National Disaster Coordinating Council (NDCC)-and other related organizations can use for their decision-making processes.

Journal Article↗
PubMed1994

Nursing/pharmacy interface: a TQM project.

W. Edwards Deming's seven-step quality improvement process provided a sequential pathway to facilitate problem-solving allowing the pharmacy and nursing departments to formulate a systems perspective rather than an individual point of view. Both departments identified problems with the Medication Administration Record and defined three key outcomes needed to signify process improvement.

Communication↗
PubMed1995

The cognitive component of nursing assessment: an analysis.

This paper presents an analysis of the cognitive component of nursing assessment, complimenting the growth in knowledge of other important aspects of assessment. The purpose of the paper is to provide a framework for understanding how nurses structure assessment problems and the types of judgements they make. The thrust of the analysis is based on a comparison between nursing assessment and medical diagnosis, since the cognitive component and judgements formed in medical diagnosis have been more fully articulated. The results suggest that there may be similarities between the cognitive strategies used in nursing assessment and those used in medical diagnosis, particularly in relation to the gathering and organization of information. But the purpose of the information search appears to be different. In medical diagnosis the aim is to establish an explanation for the patient's presenting problem. In nursing assessment, on the other hand, the aim appears to be to provide an accurate picture of the patient's current condition or situation. The assessments formulated fit the definition of a judgement and, in common with medical diagnoses, include some form of prediction. Unlike the medical diagnoses, however, which usually remain stable throughout treatment, the assessments need to change as the patient's condition changes. The cognitive component of assessment has significant implications for nurse education and clinical practice. Further understanding of how nurses structure assessment problems and formulate judgements is therefore needed. The findings may also help to clarify the meaning of nursing diagnosis.

Cognition↗
PubMed2004

Frequency domain formulation of active parametric deformable models.

Active deformable models are simple tools, very popular in computer vision and computer graphics, for solving ill-posed problems or mimic real physical systems. The classical formulation is given in the spatial domain, the motor of the procedure is a second-order linear system, and rigidity and elasticity are the basic parameters for its characterization. This paper proposes a novel formulation based on a frequency-domain analysis: The internal energy functional and the Lagrange minimization are performed entirely in the frequency domain, which leads to a simple formulation and design. The frequency-based implementation offers important computational savings in comparison to the original one, a feature that is improved by the efficient hardware and software computation of the FFT algorithm. This new formulation focuses on the stiffness spectrum, allowing the possibility of constructing deformable models apart from the elasticity and rigidity-based original formulation. Simulation examples validate the theoretical results.

Journal Article↗