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PubMed1980

The philosophy and nature of surgical research.

The author's aim is to stimulate potential surgical scientists to appreciate various aspects of surgical research, including its definition, current image, importance, motivation and philosophy, as well as the personal qualities of a surgical scientist. As guidelines for the potential surgical scientist the nature of the scientific method is described in terms of the following 16 phases of what one might call "the cycle of surgical research": recognize an unsolved clinical problem; think; review the scientific literature; ask an intelligent question; formulate an hypothesis; plan the research protocol; seek collaboration; apply for funding; conduct the investigation; collect and analyse the data; interpret the data; draw valid conclusions; answer the original question; present results at a meeting; publish a scientific paper; apply new knowledge to the original problem.

General Surgery↗
PubMed2002

Positron emission tomography partial volume correction: estimation and algorithms.

Partial volume effects in positron emission tomography (PET) lead to quantitative under- and over-estimations of the regional concentrations of radioactivity in reconstructed images and corresponding errors in derived functional or parametric images. The limited resolution of PET leads to "tissue-fraction" effects, reflecting underlying tissue heterogeneity, and "spillover" effects between regions. Addressing the former problem in general requires supplementary data, for example, coregistered high-resolution magnetic resonance images, whereas the latter effect can be corrected for with PET data alone if the point-spread function of the tomograph has been characterized. Analysis of otherwise homogeneous region-of-interest data ideally requires a combination of tissue classification and correction for the point-spread function. The formulation of appropriate algorithms for partial volume correction (PVC) is dependent on both the distribution of the signal and the distribution of the underlying noise. A mathematical framework has therefore been developed to accommodate both of these factors and to facilitate the development of new PVC algorithms based on the description of the problem. Several methodologies and algorithms have been proposed and implemented in the literature in order to address these problems. These methods do not, however, explicitly consider the noise model while differing in their underlying assumptions. The general theory for estimation of regional concentrations, associated error estimation, and inhomogeneity tests are presented in a weighted least squares framework. The analysis has been validated using both simulated and real PET data sets. The relations between the current algorithms and those published previously are formulated and compared. The incorporation of tensors into the formulation of the problem has led to the construction of computationally rapid algorithms taking into account both tissue-fraction and spillover effects. The suitability of their application to dynamic and static images is discussed.

Algorithms↗
PubMed2002

Nurses' decision-making in collecting information for the assessment of patients' nursing problems.

1. The paper addresses two questions: Firstly, what kind of information do nurses acquire from cancer patients for purposes of judging their patients' problems and preparing a care plan? Secondly, how systematically do nurses proceed in the decision-making process from the formulation of initial assumptions about the patient's situation to the final definition of problems? 2. The instrument used for data collection was a computer-simulated case description compiled by a team of four nursing researchers and one medical researcher. The case description was based on a real patient history. 3. The sample consisted of 107 Registered Nurses on four oncology, two internal medicine and five surgical wards of two central university hospitals in Finland. Data were collected in autumn 1998 and spring 1999 using a laptop computer and a tape recorder. 4. The four most important problems identified by nurses at baseline were pain (85%), pain medication (59%), family situation (66%) and spread of cancer (49%). Presented with a list of 23 options, they obtained additional information on average on 13 areas. Almost one-third collected information from 16 to 22 areas. On average nurses identified 12 of the 28 nursing problems specified. A statistically significant association was observed between information acquisition and problem definition in seven different variables. These had to do with pain, general condition and prognosis. 5. Nurses adequately prioritized their patients' problems and systematically collected data on those problems. On the other hand they also identified a number of problems that were not relevant to the situation.

Clinical Competence↗
PubMed1999

[Philosophy, a mirror for science?].

The author regrets the lack of philosophical knowledge (in circles of dentistry) to judge the scientific base of research. The western epistemology is explained by referring to the models of reasoning used in both medicine and dentistry. Referring to the 17th century philosophers, the methodical doubt, the genesis of more general points of view, the problem of measurement, the set up of experiments and the formulation of laws are discussed. Referring to the 18th and 19th century philosophers, the question of perception, correlation, interaction with the experiment and hypothesis relating to their probability are discussed. The 20th century philosophers are the occasion to discuss the influence of experimental models on data, the problem of the operation of this information, of the scientific terminology and of variability of theories, data and methods. The author claims a formation in scientifical philosophy for postgraduate students and is also emphasizing that students in the basic education level should be able to deal with scientific literature in a critical way.

Education, Dental↗
PubMed2000

Imaging the electrical activity of the brain: ELECTRA.

The construction of a tomography of neuronal sources is limited by a lack of information. A possible way around this problem is to change the biophysical model that underlies the statement of the inverse problem, i.e., searching for magnitudes that can be better determined from the available data. In this report, we describe a mathematical characterization of the type of currents that are actually able to produce the scalp-recorded EEG. Considering this characterization, we reformulate the bioelectric inverse problem. This approach, called ELECTRA, yields some advantages over the classical formulation in terms of the current density vector: (1) the number of unknowns can be reduced, which is equivalent to increasing the number of independent measurements, (2) the constraints used to reformulate the problem are undeniable since they do not imply any hypothesis about brain function but are instead based on the character of the measurements, and (3) existing experimental evidence suggests that the proposed source model characterizes the type of currents that arise in excitable tissues. We conclude that if the latter fact proves to be true for brain tissues, then no additional information is added to the inverse problem by using a more general source model than the one proposed here. Images obtained using this method for synthetic data, as well as early and middle components of human visual evoked responses to checkerboard stimuli, are presented to illustrate the characteristics of the reconstructed maps and their interpretation.

Brain↗
PubMed2004

Polymeric controlled release formulations of niclosamide for control of Biomphalaria alexandrina, the vector snail of schistosomiasis.

Schistosomiasis is one of the most important public health problems in many developing countries. The present study was conducted to investigate the effect of the polymeric niclosamide formulations against Biomphalaria alexandrina snails, the intermediate host of Schistosoma mansoni in Egypt. Three new polymeric formulations were prepared for the molluscicide niclosamide. The formulations were prepared either by the chemical modifications of poly(glycidyl methacrylate) or by physical entrapment of the niclosamide in calcium alginate beads. The release of the niclosamide from the polymeric formulations was investigated. The activity of the prepared formulations against Biomphalaria alexandrina was investigated. The results obtained revealed higher potency for polymerized niclosamide B3 than B1; the lowest potency was revealed for B2. After an exposure period of 24 hours, LC(50) values were 0.073, 0.098 and 1.09 ppm for B3, B1 and B2, respectively. In addition, the molluscicidal potency of the test polymeric niclosamide was age-dependent, where old snails were more tolerant to the test solutions than young and newly hatched snails. The results also indicated that the molluscicidal activity of B3 was extended for 21 days and 17 days for B1, compared with 5 days for free niclosamide. However, the molluscicidal potency of the polymerized niclosamide was increased after boiling for one hour, and was increased with increasing the pH of the medium to pH 9. In addition, their potency was increased with decreasing the water hardness concentrations (CaCO(3)).Molluscicidal activity of free niclosamide and its polymeric formulations vs. exposure time.

Animals↗
PubMed2004

New formulations of existing antidepressants: advantages in the management of depression.

For nearly 50 years, antidepressant drugs have been the first-line treatment for various forms of depression. Despite their widespread use, these medications have significant shortcomings, in particular problems of patient compliance due to adverse effects. The introduction of new formulations of existing antidepressant medications may provide patients with benefits in terms of convenience of use. As a consequence, improvements in compliance may lead to better antidepressant efficiency.An orally disintegrating formulation of mirtazapine (mirtazapine SolTab), a once-weekly formulation of fluoxetine, an enantiomer-specific formulation of citalopram (escitalopram), an extended-release formulation of venlafaxine (venlafaxine XR), a controlled-release formulation of paroxetine (paroxetine CR) and intravenous formulations of some of the newer antidepressants have all been evaluated in limited clinical trials. In this article, a review of the pharmacokinetics and clinical evaluations of these formulations is presented. While there do not appear to be major clinical advantages for the new formulations in terms of antidepressant efficacy, none of them is less efficacious than their older counterpart. Indeed, some of the new formulations are more acceptable to patients (fluoxetine once-weekly, paroxetine CR), others have pharmacokinetic advantages (venlafaxine XR, paroxetine CR), while others may have a faster onset of effect (mirtazapine SolTab, intravenous formulations). Further evaluation of some formulations is still required (mirtazapine SolTab, fluoxetine once-weekly), while others (venlafaxine XR, escitalopram) are finding widespread acceptance in clinical practice.

Animals↗
PubMed1997

Bioavailability of different artemisinin tablet formulations in rabbit plasma--correlation with results obtained by an in vitro dissolution method.

The demonstration of a good overall correlation with in vivo data is the ultimate proof of qualification for any dissolution-rate test. For artemisinin, a very hydrophobic compound at a high content in oral solid dosage forms, all official dissolution apparatus were estimated unsuitable. A modified two phase partition-dissolution method was applied to solve this problem. This study reports on the bioavalability of three different formulations of artemisinin tablets in rabbit plasma. Artemisinin concentrations in plasma were determined by liquid chromatography. A linear correlation between results obtained by the partition-dissolution method described and the obtained in vivo data confirmed the validity of the dissolution method.

Animals↗
PubMed1999

Pesticide monitoring and its health problems in Egypt, a Third World country.

Health profiles for 300 pesticide formulators and 300 pesticide applicators revealed peripheral neuritis (> 40%), psychiatric manifestations (> 40%), electroencephalographic (EEG) changes (> 25%), and hepatorenal dysfunction (> 80%); all these manifestations were confirmed by different diagnostic tools. The frequency of carrier state of hepatitis (HbsAg) was 7.4% and of transitory state was 21.5%. The cytogenetic changes were confirmed by measuring chromosomal aberrations (CAs) among formulators and applicators, and proved to be more than twice those of controls. Pesticides residues among 130 milk, cheese, butter, yoghurt and milk powder samples (DDT, HCH and Dieldrin) were confirmed. Registration schemes, and post-registration programs (monitoring requirements, training needs and control of pesticide and fertilizer imports) should be mandatory.

Adult↗
PubMed2000

Grating theory: new equations in Fourier space leading to fast converging results for TM polarization.

Using theorems of Fourier factorization, a recent paper [J. Opt. Soc. Am. A 13, 1870 (1996)] has shown that the truncated Fourier series of products of discontinuous functions that were used in the differential theory of gratings during the past 30 years are not converging everywhere in TM polarization. They turn out to be converging everywhere only at the limit of infinitely low modulated gratings. We derive new truncated equations and implement them numerically. The computed efficiencies turn out to converge about as fast as in the TE-polarization case with respect to the number of Fourier harmonics used to represent the field. The fast convergence is observed on both metallic and dielectric gratings with sinusoidal, triangular, and lamellar profiles as well as with cylindrical and rectangular rods, and examples are shown on gratings with 100% modulation. The new formulation opens a new wide range of applications of the method, concerning not only gratings used in TM polarization but also conical diffraction, crossed gratings, three-dimensional problems, nonperiodic objects, rough surfaces, photonic band gaps, nonlinear optics, etc. The formulation also concerns the TE polarization case for a grating ruled on a magnetic material as well as gratings ruled on anisotropic materials. The method developed is applicable to any theory that requires the Fourier analysis of continuous products of discontinuous periodic functions; we propose to call it the fast Fourier factorization method.

Journal Article↗
PubMed1991

[Problems of biomimetic chemistry].

The main goals of biomimetic chemistry have been formulated on the basis of the concept of biochemical organization. Biomimetic chemistry is defined as a science which employs the principles of biochemical organization (i. e., the principles of structural organization, functioning and regulation of biological systems at the levels corresponding to biomacromolecules, supramolecular complexes and subcellular structures) for the construction of artificial systems with predetermined properties or for conferring desired properties on natural biochemical systems with the help of artificial elements. The relationships between biomimetics and biochemical modelling are discussed. As examples of biomimetic systems, some enzymes entrapped into hydrated reverse micelles of a surfactant in an organic solvent and conjugates of proteins with polyalkylene oxidases are considered.

Biochemical Phenomena↗
PubMed1978

[Problems of formal organizational structure of industrial health care complexes].

The author formulates the thesis that the description of organizational structure of industrial health care complex calls for isolation of the following aspects:--structure of territorial links--systemof organizational units and divisions--organization of basic functions--structure of management--structure of supervision of middle and lowe-level personnel--composition of health care complex council--system of accessibility ranges. Each of the above aspects has been considered on the basis of operative rules of law, using organizational analysis methods.

Administrative Personnel↗
PubMed2004

Global core recommendations for a musculoskeletal undergraduate curriculum.

OBJECTIVE: To develop core recommendations for the learning outcomes of an undergraduate curriculum in musculoskeletal conditions for any parts of the globe. METHODS: Recommendations were developed by wide consultation with experts in orthopaedics, rheumatology, osteoporosis, and rehabilitation from all parts of the world who had interest and experience in these specialties, with the support of international and national societies. All possible knowledge, skills, and attitudes that might be of relevance to musculoskeletal conditions were initially considered and then reduced to those considered essential for all doctors. RESULTS: The recommendations focus on (a) basic skills to assess and diagnose musculoskeletal problems; (b) the competency to assess specific common or urgent musculoskeletal problems; (c) the theoretical background of the conditions and their management; and (d) the core knowledge necessary to support diagnosis and management, including basic sciences. At the end of the course, all students should be able to differentiate normal from abnormal locomotor symptoms in a patient, determine the relevant investigations and interpret the results, formulate a limited differential diagnosis, recognise the impact of the problem on the individual patient, and make an appropriate management plan. CONCLUSIONS: The recommendations set global standards for the minimum level of competence in managing patients with musculoskeletal problems. They define what all doctors should know when graduating from medical school, regardless of further specialisation. They are intended to form the basis of a curriculum for a musculoskeletal course and can be adapted for any medical school in any country throughout the world.

Clinical Competence↗
PubMed1979

[Comparative study of relative biovailability of several spironolactone formulations in a steady-state test (author's transl)].

By the US Food and Drug Administration spironolactone is regarded as a drug with problems related to bioavailability. A steady-state study was performed comparing the 50- and 100-mg formulations of two manufacturers with each other. Applying a fluorimetric method to both canrenone and canrenoate--the major biologically active metabolites of spironolactone--the two brands were compared in 11 volunteers for the 50 mg, and in 10 volunteers for the 100 mg dosage form.

Adult↗
PubMed1985

Mechanisms of epithelial invagination.

This review is concerned with the mechanical forces that cause epithelial sheets to invaginate during morphogenesis. Interest in this problem is currently increasing and a variety of models, each with a different emphasis, have been formulated to explain mechanical aspects of epithelial folding. A critical evaluation of the experimental evidence bearing on this problem leads to the following conclusions. (1) The most popular model of invagination, one based on microfilament-mediated cell shape change, should be re-examined, given the limitations of the experimental evidence usually offered in its support. Recent experiments with permeabilized epithelia offer a promising approach for confirming the validity of this model. (2) Current hypotheses based on disparities in the adhesive properties of epithelial cells are consistent with available data, but appear to be impossible to test directly at this time. (3) There is evidence that suggests that cell growth and division are involved in invagination during the branching morphogenesis of some epithelio-mesenchymal organs, but it has been shown that these processes are not involved in other cases. (4) Recent studies demonstrate that some epithelial invaginations are accompanied by movements of cells, both in the form of rearrangement (exchange of nearest neighbors) and involution (flow of surrounding cells into the invaginating region). (5) A general conclusion that may be drawn from the data now available is that several different mechanisms of epithelial folding operate during morphogenesis.

Actin Cytoskeleton↗
PubMed1994

Absorption of a hypotonic oral rehydration solution in a human model of cholera.

The development of oral rehydration solutions (ORSs) has been one of the important therapeutic advances of this century. The optimal formulation, however, of ORSs for both cholera and other infective diarrhoeas is still debated. Part of the problem in developing ORSs has been the lack of adequate test systems for the assessment of new formulations before clinical trial. We have developed a jejunal perfusion, cholera toxin induced, secretory model in humans and have compared net water and solute absorption from a hypotonic ORS (HYPO-ORS: sodium 60 mmol/l, glucose 90 mmol/l, osmolality 240 mOsm/kg) and the British Pharmacopoeia recommended ORS (UK-ORS: sodium 35 mmol/l, glucose 200 mmol/l, osmolality 310 mOsm/kg) in six healthy volunteers. A plasma electrolyte solution (PES) was also perfused in all subjects to confirm a secretory state. Only HYPO-ORS reversed sodium secretion to absorption (p < 0.01). Both ORSs promoted net water absorption but this was greatest with HYPO-ORS (p < 0.01). Glucose and potassium absorption rates were similar for both ORSs whereas chloride absorption mirrored sodium absorption and was greatest from HYPO-ORS (p < 0.05). These results, in a biologically relevant model of secretory diarrhoea, suggest it may be possible to achieve improved rates of rehydration by the use of hypotonic ORS with mid range sodium concentrations.

Adult↗
PubMed2001

Periodic orbit description of nonadiabatic quantum dynamics.

Classical periodic orbits associated with the nonadiabatic dynamics of a spin-boson-type problem are introduced. To facilitate a classical description of spin states, the formulation employs an exact mapping of the discrete quantum variables onto continuous degrees of freedom. Adopting a one-dimensional spin-boson model, the shortest periodic orbits of the problem are identified and used to analyze the nonadiabatic quantum dynamics. The possibility of directly observing these vibronic periodic orbits in femtosecond time-resolved experiments is discussed.

Journal Article↗
PubMed1985

Particulate contamination in ampoules.

The particulate contamination in 19 formulations of solutions in ampoules supplied by eight South African manufacturers, thirty-three batches in all, was analysed using a HIAC PC 320 light blockage particle analyser linked to a CMB 60 sensor. Results showed that the level of contamination was generally low and that, where comparisons could be made, manufacturers both of the ampoules and the solutions maintained similarly high standards. Problems in this field appeared to be related to the formulation or the quality of the raw material.

Drug Contamination↗

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