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PubMed2003

Emissions and environmental implications of mercury from artisanal gold mining in North Sulawesi, Indonesia.

In artisanal gold mining practiced in North Sulawesi Island, Indonesia, gold is separated from ore by the use of mercury, which forms an amalgam with gold. All related processes are undertaken with a low level of technical knowledge and skills, no regulation, and with disregard for the safety of human and environment health. The situation is generating serious potential health and environmental risks in the area. As part of an ongoing monitoring program, total mercury concentrations were examined in water, bottom sediment and fish samples from three main rivers in Talawaan Watershed, which receives drainage from gold mining practices. Monitoring began in May-June 2000, almost 2 years after artisanal gold mining had begun. At that time, the mercury concentration in the sediment was generally low, except in places close to the gold processing plants. In the present study, a more systematic sampling and analysis was conducted in May-June 2001. Bottom surface sediments, water, and fish samples were collected at 12 sites along the three main rivers in the watershed. In addition, one site outside the watershed was sampled to serve as a control. Sample collections were conducted in three phases in duplicate, with two-week intervals between each phase. The mercury concentration observed in this study indicated that an increase took place along the three main rivers in the watershed. Solutions to this problem must be formulated as soon as possible in order to avoid a major health, economic, and ecological disaster arising from the continuing discharge of Hg. The present study proposes that mercury dispersion occur downstream of the mining.

Animals↗
PubMed2003

Sensorimotor transformations in cortical motor areas.

A central problem in motor research has been to understand how sensory signals are transformed to generate a goal-directed movement. This problem has been formulated as a set of coordinate transformations that begins with an extrinsic coordinate frame representing the spatial location of a target and ends with an intrinsic coordinate frame describing muscle activation patterns. Insight into this process of sensorimotor transformation can be gained by examining the coordinate frames of neuronal activity in interconnected regions of the brain. We recorded the activity of neurons in primary motor cortex (M1) and ventral premotor cortex (PMv) in a monkey trained to perform a task which dissociates three major coordinate frames of wrist movement: muscle, wrist joint, and an extrinsic coordinate frame. We found three major types of neurons in M1 and PMv. The first type was termed 'extrinsic-like'. The activity of these neurons appeared to encode the direction of movement in space independent of the patterns of wrist muscle activity or joint movement that produced the movements. The second type was termed 'extrinsic-like with gain modulation'. The activity of these neurons appeared to encode the direction of movement in space, but the magnitude (gain) of neuronal activity depended on the posture of the forearm. The third type was termed 'muscle-like' since their activity co-varied with muscle activity. The great majority of the directionally-tuned neurons in the PMv were classified as 'extrinsic-like' (48/59, 81%). A smaller group was classified as 'extrinsic-like with gain modulation' (7/59, 12%). In M1, the three types of neurons were more equally represented. Our results raise the possibility that cortical processing between M1 and PMv may contribute to a sensorimotor transformation between extrinsic and intrinsic coordinate frames. Recent modeling studies have demonstrated the computational plausibility of such a process.

Animals↗
PubMed2003

P systems with deadlock.

Rewriting P systems with parallel application of evolution rules, as defined in Besozzi et al. [Parallel rewriting P systems with deadlock. In: Hagiya, M., Ohuchi, A. (Eds.), Pre-Proceedings of DNA8 Conference, Hokkaido University, Japan, June 2002a, pp. 171-183], are considered here. Different kinds of parallelism methods are defined for string rewriting. The notion of deadlock is then introduced to describe situations where rules with mixed target indications are simultaneously applied to a common string. The generative power of parallel P systems with deadlock is analyzed, with respect to Lindenmayer systems, and some relations among different types of parallel P systems with or without deadlock, allowing to rewrite all occurrences of a single symbol, or all the symbols applying either any of the rules or only those belonging to a specific set (table) of rules are studied. Some open problems are also formulated.

Algorithms↗
PubMed1997

Parallel simulation of accretive growth and form in three dimensions.

A geometric model for diffusion-limited radiate accretive growth is used to simulate the emergence of growth and form of a certain class of organisms and crystals. In the model, layered structures are generated by the construction of new layers on top of the previous ones, the local growth velocities are determined by the local nutrient concentration gradients. The simulation of nutrient-limited growth in three dimensions (3D) is computationally very expensive. This paper presents a methodology to formulate the geometrical problem in terms of a 3D Laplace solver and maps this solver on a parallel platform. The aim of this paper is to demonstrate that this hybrid method is capable of simulating two typical properties of radiate accretive growth: (1) the indeterminateness of the growth process; and (2) the strong impact of the physical environment on the growth process.

Animals↗
PubMed2002

Crystal growth and structure of a new hormonal derived compound.

The 17alpha-acetoxy-6-hydroxymethyl-3,20-dioxo-19-nor-pregna-4,6-diene (C(23)H(30)O(5)), a new hormonal derived compound presenting a potential therapeutic interest for a pharmaceutical formulation, raises a problem as it precipitates spontaneously when in contact with an aqueous solution. The solubilization of this potential pharmaceutical drug was investigated to control and/or prevent crystal formation in the presence of water. The solubility limit of this potential drug, either in Cremophor(R) EL or RH40, was determined to be 2.6% (w/w). In addition, crystal growth of this compound solubilized in Cremophor(R) and in contact with aqueous environment was undertaken to improve crystal quality and size and subsequently to determine its three dimensional structure. We used a system that allows slow single crystal growth at room temperature. The crystallization system that we set-up comprised an interface between two solutions: one containing the compound solubilized either in Cremophor(R) RH40 or EL and the other containing water and glycine. The crystal structure was established by single crystal X-ray diffraction analysis. The structure refinement study revealed the presence of one water molecule with strong intermolecular hydrogen bonding leading to an atomic arrangement corresponding to an infinite chain in the [001] direction.

Crystallization↗
PubMed2000

Concepts and items in measuring social harm from drinking.

Social epidemiological traditions of asking about problems related to drinking are considered. The issue of the attribution of the problem to drinking, and variations in formulations concerning this, are discussed. Social problems from drinking are inherently properties of social interactions, so that they are composed both of behaviour deemed problematic and of a reaction by another. Most items measuring social harm asked of the drinker him/herself are concerned with major social roles, and problems in the particular life area of the role (work, family, friendships, etc.). Some ask the respondent to attribute the problems to alcohol, some ask about others' attributions to alcohol, and some ask about "objective" problem indicators, although these usually have the respondent's attribution to drinking built in. The possibility of a more systematic way of covering different aspects of interactional problems, as reported by the drinker, is considered. Traditions of questioning the person on the other side of the interaction--i.e., items about others' troubles with drinking, and the effect of these on the respondent--are also discussed, and possibilities for bringing questions asked of the drinker and questions asked of interacting others into the same frame are considered.

Adolescent↗
PubMed1999

Overdose with sustained-release lithium preparations.

Acute lithium intoxication is potentially lethal. Compared to conventional lithium preparations, sustained-release lithium formulations present specific problems for medical practice in the case of overdose. We report a case of intoxication with 8000 mg of sustained-release lithium carbonate preparation (Teralithe 400 LP(R)). Twenty-five hours after the ingestion, the patient was still asymptomatic, despite a serum level in the toxic range. After comparison of this case with reports found in the Medline database, we consider the clinical management of such cases.

Adult↗
PubMed2004

Experimental results on the recognition of embryos in human assisted reproduction.

The recognition of embryos suitable for transfer in human assisted reproduction is important, and there is evidence that the morphology of the cells may influence the results achievable. A procedure for this recognition problem has been formulated based on morphological attributes of the images of the embryos, and it is therefore useful to compare the recognition of experts with that of a machine programme. The aim of this paper is to compare the precision in the recognition of viable embryos by a group of experts to that of a machine recognition procedure, both for a basic set of embryos and a blind set. Experts were asked to classify the images of 249 embryos transferred to 73 patients, indicated as the training set and another set of 103 embryos transferred to 35 patients called the blind set. A machine programme was used for the same classification. For all the experts the results were statistically not significantly different from independence, which means that viable embryos are not recognized as such for both data sets. Instead, the machine algorithm recognizes in a statistically significant way, the membership class for the embryos submitted. Cell morphology is important for IVF, but differences do not appear to be discernable by the senses, clinical insight, experience and/or training, while classification by machine methods provides more accurate results, which could be improved by enlarging the training set.

Adult↗
PubMed2006

Transdermal selegiline: the new generation of monoamine oxidase inhibitors.

The clinical use of monoamine oxidase inhibitors (MAOIs) has declined due to concerns about food and drug interactions and waning physician experience. Evidence indicates that MAOIs are effective in depressive disorders, in particular depression with atypical features. Efforts to address safety issues have led to the development of more selective and reversible MAOIs, such as moclobemide. Selegiline, a selective monoamine oxidase B inhibitor, has been approved for the adjunctive treatment of Parkinson's disease at low doses. At higher doses, oral selegiline is also effective in major depressive disorder (MDD) but loses its selectivity and has the potential for tyramine interactions. To overcome these problems, a transdermal formulation of selegiline, the selegiline transdermal system (STS), was developed with novel pharmacokinetic and pharmacodynamic properties. Compared with oral administration, transdermal selegiline leads to sustained plasma concentrations of the parent compound, increasing the amount of drug delivered to the brain and decreasing metabolite production. In addition, STS allows targeted inhibition of central nervous system monoamine A (MAO-A) and monoamine B isoenzymes with minimal effects on MAO-A in the gastrointestinal and hepatic systems, thereby reducing the risk of interactions with tyramine-rich foods (the "cheese-reaction"). Clinical trials have found 6 mg/24 hours of STS to be effective in MDD without the need for dietary restrictions. The efficacy and safety profile of STS supports its use in MDD. It is possible that STS may demonstrate benefit in MDD with atypical features or MDD resistant to other antidepressants. However, more research is needed. Clinicians should familiarize themselves with the properties and indications for the new generation of MAOIs.

Administration, Cutaneous↗
PubMed1996

Nursing documentation in patient records: experience of the use of the VIPS model.

The VIPS model for the documentation of nursing care in patient records was scientifically developed and published in 1991, with the aim of supporting the systematic documentation of nursing care and promoting individualized care. As the model seemed to be accepted and used in many parts of Sweden, a study was conducted in order to gather further information on the validity of the model, to describe the clinical and educational experience of its use and to refine it. Experience of the use of the model was gathered from a review of the scientific papers and other reports on it, from questionnaires addressed to nurses (n = 514), from comments by key informants, and from interviews with faculty members at all the nursing schools in the country. The findings showed that an intense process of change and development was occurring regarding nursing documentation. However, there were limitations in the use of the entire nursing process, especially in the specification of patient problems and the formulation of nursing diagnoses and nursing interventions. The keywords (Swedish spelling) of the VIPS model had good content validity in different areas of nursing care. The findings also indicated the need for further elaboration and revision of some of the keywords. A revised version of the VIPS model based on these findings is presented.

Health Knowledge, Attitudes, Practice↗
PubMed2001

How gap genes make their domains: An analytical study based on data driven approximations.

We consider a mathematical formulation of the problem of protein production during segment determination in the Drosophila blastoderm, together with some preliminary results of its analytical study. We reformulate the spatial difference equations as a set of nonlinear partial differential equations and obtain their dimensionless form in the continuum limit. Using previous results obtained by the gene circuit method, we find an asymptotic statement of the problem with a small parameter. Some results of the comparison method applied to the model are obtained, and exact stationary upper solutions are derived. They exhibit distinctive features of localized bell-shaped structures. (c) 2001 American Institute of Physics.

Journal Article↗
PubMed1999

Bifurcations and selection of equilibria in a simple cosymmetric model of filtrational convection.

A three-dimensional set of ordinary differential equations that constitutes a simple abstract model of Darcy convection is investigated. The model reproduces a number of effects that are typical for dynamic systems with nontrivial cosymmetry. Nontrivial cosymmetry can give rise to a continuous family of equilibria where, in this case, the equilibrium stability spectrum varies along the family. The family of equilibria and its stability are examined analytically, and special bifurcations that occur in the system are investigated. It is shown that discrete and continual symmetries, called "flash symmetries," can be present in the system for certain parameter values. Computer experiments on the selection of equilibria in the symmetric and cosymmetric cases have been carried out. They showed that, for initial points that are far enough from a cycle of equilibria, the neighborhood of a single equilibrium is established in the case of cosymmetry, but all the equilibria are equivalent in the case of symmetry. The authors hope that these results, as well as the formulation of the problems and the approach to their solution, will serve as a sample in the investigation of more complex systems in mathematical physics. (c) 1999 American Institute of Physics.

Journal Article↗
PubMed2004

Analytic density-functional self-consistent-field theory of diblock copolymers near patterned surfaces.

Analytical solutions are derived for the density profiles and the free energies of compressible diblock copolymer melts (or incompressible copolymer solutions) near patterned surfaces. The density-functional self-consistent-field theory is employed along with a Gaussian chain model for bonding constraints and a random mixing approximation for nonbonded interactions. An analytical solution is rendered possible by expanding the chain distribution function around an inhomogeneous reference state with a nontrivial analytical solution, by retaining the linear terms, and by requiring consistency with the homopolymer limit. The density profiles are determined by both real and complex roots of a sixth-degree polynomial that may easily be obtained by solving a generalized eigenvalue problem. This analytical formulation enables one to efficiently explore the large nine-dimensional parameter space and can serve as a first approximation to computationally intensive studies with more detailed models. Illustrative computations are provided for uniform and patterned surfaces above the order-disorder transition. The results are consistent with the previous self-consistent-field calculations in that lamellar ordering appears near the surface above the order-disorder transition and the lamella order perpendicular or parallel to the surface depending on the commensurability between the periods of the surface pattern and the density oscillations.

Journal Article↗
PubMed2002

Parallel processing of serial movements in prefrontal cortex.

A key idea in Lashley's formulation of the problem of serial order in behavior is the postulated neural representation of all serial elements before the action begins. We studied this question by recording the activity of individual neurons simultaneously in small ensembles in prefrontal cortex while monkeys copied geometrical shapes shown on a screen. Monkeys drew the shapes as sequences of movement segments, and these segments were associated with distinct patterns of neuronal ensemble activity. Here we show that these patterns were present during the time preceding the actual drawing. The rank of the strength of representation of a segment in the neuronal population during this time, as assessed by discriminant analysis, predicted the serial position of the segment in the motor sequence. An analysis of errors in copying and their neural correlates supplied additional evidence for this code and provided a neural basis for Lashley's hypothesis that errors in motor sequences would be most likely to occur when executing elements that had prior representations of nearly equal strength.

Animals↗
PubMed1984

Neuromotor synergies as a basis for coordinated intentional action.

Although neurally based units of action (neuromotor synergies) have often been proposed as a possible basis for coordinated intentional as well as automatic actions, the idea has rarely been translated into sets of testable hypotheses. This essay examines four issues which should facilitate the development of such hypotheses: (a) definitions of neuromotor synergies, (b) criteria for recognizing and comparing synergies in automatic and intentional actions, (c) problems in representing systems of synergies, and (d) models for generating intentional actions from sets of neuromotor synergies. Limitations of, and support for the neuromotor synergy hypothesis are discussed, both in general and for the specific cases of postural synergies and cervico-spinal reflexes. Although current data do not provide conclusive support for or against the neuromotor synergy hypothesis, the problem can be formulated in ways open to experimental investigation.

Journal Article↗
PubMed2006

How not to criticize the precautionary principle.

The precautionary principle has its origins in debates about environmental policy, but is increasingly invoked in bioethical contexts. John Harris and Søren Holm argue that the principle should be rejected as incoherent, irrational, and representing a fundamental threat to scientific advance and technological progress. This article argues that while there are problems with standard formulations of the principle, Harris and Holm's rejection of all its forms is mistaken. In particular, they focus on strong versions of the principle and fail to recognize that weaker forms, which may escape their criticisms, are both possible and advocated in the literature.

Bioethical Issues↗
PubMed2000

Critical illness polyneuropathy: a summary of the literature on rehabilitation outcome.

PURPOSE: To evaluate the available literature on outcome of critical illness polyneuropathy (CIP) and to identify rehabilitation problems. METHODS OF STUDY SELECTION: A literature search in electronic databases. Primary articles on outcome in CIP using the classification of ICIDH or Quality of Life were enrolled in this study. Because of the types of study design, the lack of information regarding validity and the variability, a quantitative analysis was not possible. Instead, the overall results were evaluated in a qualitative approach. RESULTS: In the literature minimal attention was given to the rehabilitation aspects and long-term outcome of patients with CIP. Outcome measures were mainly used on the level of impairments and in lesser extent on the level of disabilities. One year after the onset of CIP, muscle weakness and decreased sensory function were frequently observed. Reported functional disabilities were dependency in Activities of Daily Living (ADL) and walking disabilities. CONCLUSION: The specific course and long-term outcome of CIP remains unclear. Research on the course and long-term functional outcome in CIP is necessary in order to identify rehabilitation problems and to formulate treatment strategies specifically directed towards the outcome of CIP.

Activities of Daily Living↗
PubMed2002

Minimizing delivery time and monitor units in static IMRT by leaf-sequencing.

Intensity-modulated radiation therapy (IMRT) requires the determination of the appropriate multileaf collimator settings to deliver an intensity map. The purpose of this work was to attempt to reduce the number of segments required for IMRT delivery and the number of monitor units required to deliver an intensity map. An intensity map may be written as a matrix. Leaf sequencing was formulated as a problem of decomposing the matrix into a series of sub-matrices. Sets of random intensity matrices were created and the segmentations produced by applying different algorithms were compared. The number of segments, important if verification and record (VR) overhead is significant, and beam on times were examined. It is shown that reducing the value of the matrix entries by the maximum amount at each stage results in the smallest number of steps. Reducing the 2-norm (sum of the squares) of the matrix entries by the maximum amount at each step results in the smallest beam on time. Three new algorithms are introduced, two of which produce results that are superior to those generated by the algorithms of other researchers. The resulting methods can be expanded upon to include tongue and groove effects and leaf inter-digitization. With square random matrices of the order 15, the reduction in beam time and segmentation is up to 30-40%. Compared to previous algorithms, those presented here have demonstrated a reduction in the beam on time required to deliver an intensity map by 30-40%. Similarly, the number of segments needed to deliver an intensity map is also reduced.

Algorithms↗