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At least 613 records · Page 34Linked to original sources
PubMed1997

Does surgical removal of primary melanoma trigger growth of occult metastases? An analytical epidemiological approach.

BACKGROUND: In several human tumor systems a potential role of surgical removal of the primary tumor upon metastatic tumor growth has been evaluated, as it has been in experimental models. The present study addresses the question of whether the removal of primary melanomas disinhibits growth of metastatic disease and results in more rapid progression. METHODS: In a data set of 1224 primary cutaneous melanomas the risk of "thin" melanomas to develop metastases within 1 year was compared with the risk of matched pairs of "thick" melanomas to present metastases at the time of diagnosis. For this purpose, a pairwise matching procedure based on certain assumptions as to tumor volume and tumor doubling time has been applied. RESULTS: When a long tumor doubling time is assumed (200, 400, or 800 days), the tumors removed seem to have a significantly higher risk of metastases to become clinically apparent within 1 year than the matched pairs of tumors to present metastatic disease at the time of diagnosis (chi-square < 0.01). When short tumor doubling time is assumed (50 or 100 days), the difference is not significant, but there also seems to be no benefit for the operated patients. CONCLUSION: In the present data set there is evidence that surgery of primary melanoma may enhance tumor growth at metastatic sites.

Austria↗
PubMed1988

Localization of cations by pyroantimonate. I. Influence of fixation on distribution of calcium and sodium. An approach by analytical ion microscopy.

A modification of the potassium pyroantimonate (PA) method for localization of calcium and sodium was tested using skeletal muscle of mouse. Massive diffusion of these cations, depending on the method of fixation, was demonstrated by analytical ion microscopy (AIM) images on the optical microscopy level. Rapid penetration of the fixative appeared to be the principal condition that reduced diffusion of Ca2+ and Na+. Paraformaldehyde (2%) appeared more efficient than glutaraldehyde (1%) for preserving metal composition. Addition of 1% phenol strikingly improved the quality of the AIM images. Supersaturated PA (4%) appeared to retain about 10 times more sodium in the tissue than insaturated PA (2%). The role of different buffers is also discussed, particularly collidine, which permitted better preservation of sodium. Fixation with this buffer should be very useful for study by AIM of large-scale distribution of sodium. These results are analyzed at the ultrastructural level in the accompanying report.

Animals↗
PubMed2003

Analysis of overlapping bands by an analytic geometric approach: the potential of band-stripping and the complementary matching method in extraction of band components from overlapping bands.

As a novel method for extracting individual band components from heavily overlapping bands, we propose a band stripping/complementary matching method that is based on first-derivative-second-derivative (D1-D2) plots of an experimental spectrum, coupled with a new concept called a complementary band. By using the concept of complement of a set, the ith band can be indirectly expressed by using a complementary band created by subtracting all the bands, exclusive of the ith estimated band, from an experimental spectrum. The degree of coincidence of both shapes between an estimated band and its complementary band provides a very suitable measure for the quality of fit for each individual band. The analysis method consists of two stages. The first stage is concerned with the geometric approach, which estimates a set of values for the parameters of a component band in the overlapping bands, and repeats band decomposition of the remaining bands in the same manner after removing the estimated band from the overlapping bands. The second stage is to minimize the difference between the profiles of the estimated band and its complementary band by a least-squares optimization and then determine the optimum values of the band parameters with the best-fit band shape. The algorithm and procedures of this method are illustrated by use of a synthetic spectrum consisting of a number of component bands, a background component, and random noise. The quality of fit is so satisfactory in terms of the coincidence between the individual estimated band and the corresponding complementary one that visual observation permits us to determine the optimum estimates of the band parameters and avoid potential problems of curve fitting.

Journal Article↗
PubMed2003

Band analysis of temperature-dependent near-infrared spectra of oleic acid in the pure liquid state by the analytic geometric approach.

The applicability of the band-stripping and complementary matching method has been demonstrated by the analysis of temperature-dependent near-infrared (NIR) absorption spectra in the 7500-6500 cm(-1) region of oleic acid (cis-9-octadecenoic acid) in the pure liquid state. This method is based on first derivative-second derivative pair (D1-D2) plots and a new concept called the complementary band, cBDi, created by subtracting all the rest of the bands, exclusive of the ith estimated band, eBDi, from an experimental spectrum. The degree of coincidence of both band shapes provides a suitable measure for the quality of fit for each individual component band. It has been confirmed from the present analysis of the NIR spectra of oleic acid measured over a temperature range of 16-79 degrees C that the change of the peak intensity of the component band at around 6915 cm(-1) due to the first overtone of an O-H stretching vibration of the monomer has two transition points around 35 and 55 degrees C. Moreover, the present study has provided new insight into the analysis of temperature-dependent spectral variations of oleic acid. Among the three temperature ranges, 16-35 degrees C, 35-55 degrees C, and 55-79 degrees C, in the first range the band near 6915 cm(-1) shows a slight increase and in the second range it has a linear intensity change with a slope of 0.002 a.u./degree C. In the third range, a rapid increase of the peak intensity is observed. This band exists even at 15 degrees C (just below the melting point) and shows a shift from 6910 to 6915 cm(-1) and a band narrowing from 85 to 80 cm(-1) (full width at half-height) over a temperature range of 16 to 79 degrees C. Furthermore, it has been found that there are two broad bands at around 6835 and 6778.

Mathematics↗
PubMed2005

Experimental approaches and analytical technique for determining heavy metals in fallen dust at ferrosilicon production factory in Edfu, Aswan, Egypt.

In this study aimed to evaluate the pollution extent of metals and nonmetals inside and outside the ferrosilicon production factory in Edfu, Aswan, Egypt, raw materials (quartz, cokes, iron oxides), ferrosilicon alloy, silica fume, dust and suspended dust (at different sites) samples were collected from the factory, and fallen dust samples were collected from outside the factory, horizontally (at different sites and different distance and directions) and vertically (at different floors in the selected buildings). Gravimetric methods, X-ray fluorescence (XRF), flame photometer, wide range carbon determinator and atomic absorption spectroscopy tools were used for elements determination. The results indicating that the fallen dust and its element contents on southern factory walls being higher than those on eastern factory walls may be due to the nature of the dusts and effects of wind force and wind direction. Fallen dust levels in different regions outside the factory were found to be affected by the distance, direction and floors. The nature of dust samples was affected by gravity and the suspended dust in different factory units depended on the work capacity and method of handling materials by personnel in different production units. Silica fume was a complicated problem, had dangerous effect against the workers' health, and was characterized by high concentrations of SiO(2) (90.6%approximately 93.6%) and heavy metals (Mn, 420.6 x 10(-6) approximately 520.3 x 10(-6); Fe, 2354 x 10(-6)approximately 2685 x 10(-6); Co, 80.7 x 10(-6) approximately 101.6 x 10(-6) and Ni, 5.3 x 10(-6) approximately 6.05 x 10(-6)). The TSP (Total Suspended Particulate) levels in all factory units were higher than the recommended air quality value (70 microg/m(3)) under Egyptian law. The effect of ferrosilicon factory fallen dust on the surrounding regions decreased with increasing distance between the factory and these regions. The suspended dust samples in the factory units and their components greatly exceeded national and international standards, so health and environmental criteria must be enforced on these units.

Dust↗
PubMed2000

[Diagnosis related groups and cost by service: an approach to analytic accounting in ophthalmology].

PURPOSE: To establish the annual cost of the Ophthalmology Service in < > Hospital, according to its admission activity. Our last objective is to publish the management terms in our ophthalmology specialty. METHODS: We have done a one year analytic study of 766 patients classified into Diagnosis Related Groups (DRGs) in relation to the annual cost of this activity in our service. RESULTS: We have determined the annual cost of our service as well as the DRGs of the studied sample. The most frequent DRG was number 39 (crystalline procedures), 65% of the sample. We have obtained an average stay lower than the national average stay in each group. CONCLUSIONS: At present, this systematic study and evaluation of annual cost in our specialty is a necessity because it permits a correct future planning by ordering the main objectives, a better use of resources and to know the impact of the service in the economy of the hospital. The modern hospital is a service company and not relating the assistential quality with the cost may cause a crisis of the Health National System.

Accounting↗
PubMedDate not supplied

FT-IR spectroscopy and chemometrics as a useful approach for determining chemical-physical properties of gasoline, by minimizing analytical times and sample handling.

Since recently Mid-Infrared Spectroscopy is being used in the petrol industry for determining important chemical-physical properties of gasoline. This technique enables to achieve results similar to those obtainable with standard methods at shorter times, lower costs and safer sample handling. This can be obtained by employing multivariate regression models in the framework of a chemometric analytical approach. In the present work some gasoline properties including density, Reid vapor pressure, Research Octane Number, aromatic hydrocarbons content and fraction recovered at 70 degrees C were determined with standard methods (ISO, CEN, ASTM) on 93 samples of unleaded gasoline produced in an oil refinery. The same samples were also analyzed by FT-IR spectrophotometry, recording absorptions of seven characteristic bands. The obtained values of chemical-physical and spectroscopic properties were used to develop and validate a multivariate regression model. This established an experimental correlation between these two sets of variables derived from the same gasoline samples. The model was able to correctly predict the chemical physical properties of a set of unknown gasoline samples produced in the same refinery starting from the spectroscopic ones.

Chemistry, Physical↗
PubMed1999

Determination and application of desirable analytical performance goals: the ISO/TC 212 approach.

Desirable analytical performance goals are needed to place clinical laboratories' quality management plan on a rational basis. While the most important basis of desirable analytical performance goals is medical needs, a well-established quality management plan must take into account economic and regulatory needs. There are many approaches that have been proposed for determining desirable analytical performance goals. The ISO/TC 212 approach for rationalizing the various approaches for determining desirable analytical performance goals, which is based on the ability to meet medical needs, is presented.

Clinical Laboratory Techniques↗
PubMed2001

Dynamic analyses of mother-child interactions in functional and dysfunctional dyads: a synergetic approach.

Describes the application of a new analytical approach (derived from synergetics, a complex dynamic systems theory) to home observational data of mother-child interactions in average dyads and dyads with children referred for disruptive behavior problems at home and school (n = 11 in each group). Results show that (1) the two groups differed in their daily interactions in predictable ways, and (2) the most frequent patterns of interactions observed in the two groups brought them back repeatedly to behave in similar ways toward each other. The findings are in keeping with a body of literature on mother-child interactions. However, they add to it by providing multivariate. graphical representations of these interactions and by offering a conceptual framework within which to move from an observational to an inferential level of analysis. At that level, the transactional processes that are characteristic of functional and dysfunctional relationships may become apparent.

Affect↗
PubMedDate not supplied

Antivascular cancer treatments: functional assessments by dynamic contrast-enhanced magnetic resonance imaging.

New anticancer therapeutics that target tumor blood vessels promise improved efficacy and tolerability in humans. Early phase 1 drug trials have shown that the maximum tolerated dose may be inappropriate for more advanced clinical studies with efficacy endpoints. More advanced clinical trials have demonstrated that morphologic assessments of tumor response are of limited value for gauging the efficacy of treatment. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can serve as pharmacodynamic indicator of biological activity for antivascular cancer drugs by helping to define the biologically active dose. DCE-MRI studies may also predict the efficacy of treatment on the basis of changes observed. If DCE-MRI is to be used for the selection of antivascular drugs that advance into efficacy trials, then it will be necessary to develop standardized approaches to measurement and robust analytic approaches with clear accepted endpoints specified prospectively that have biological validity. Such developments will be essential for multicenter trials in which it will be necessary to establish effective cross-site standardization of measurements and evaluation.

Angiogenesis Inhibitors↗
PubMedDate not supplied

Comparative analysis of illicit heroin samples.

The comparative analysis of street heroin samples is still an object of scientific discussion. A combination of a wide range of analytical techniques is necessary to obtain a valid amount of information about the sample composition, and it is impossible to define an unique analytical approach. We suggest a complete analytical sequence based on analysis of volatile compounds, opiates, diluents, adulterants and metals, by head space gas chromatography (HS/GC), gas chromatography mass spectrometry (GC/MS), thin layer chromatography (TLC), high pressure liquid chromatography (HPLC) and atomic absorption (AA) using a sample amount as low as 50-100 mg. The outlined procedure can be successfully applied to routine work, thus obtaining suitable information about a sample's chemical composition. This helps to attribute or exclude common sources of separate specimens. Results obtained on 33 street heroin samples confiscated in the metropolitan area of Rome are listed.

Chromatography, Gas↗
PubMedDate not supplied

Construction of confidence intervals for neural networks based on least squares estimation.

We present the theoretical results about the construction of confidence intervals for a nonlinear regression based on least squares estimation and using the linear Taylor expansion of the nonlinear model output. We stress the assumptions on which these results are based, in order to derive an appropriate methodology for neural black-box modeling; the latter is then analyzed and illustrated on simulated and real processes. We show that the linear Taylor expansion of a nonlinear model output also gives a tool to detect the possible ill-conditioning of neural network candidates, and to estimate their performance. Finally, we show that the least squares and linear Taylor expansion based approach compares favorably with other analytic approaches, and that it is an efficient and economic alternative to the nonanalytic and computationally intensive bootstrap methods.

Confidence Intervals↗
PubMed2004

Incorporating children's toxicokinetics into a risk framework.

Children's responses to environmental toxicants will be affected by the way in which their systems absorb, distribute, metabolize, and excrete chemicals. These toxicokinetic factors vary during development, from in utero where maternal and placental processes play a large role, to the neonate in which emerging metabolism and clearance pathways are key determinants. Toxicokinetic differences between neonates and adults lead to the potential for internal dosimetry differences and increased or decreased risk, depending on the mechanisms for toxicity and clearance of a given chemical. This article raises a number of questions that need to be addressed when conducting a toxicokinetic analysis of in utero or childhood exposures. These questions are organized into a proposed framework for conducting the assessment that involves problem formulation (identification of early life stage toxicokinetic factors and chemical-specific factors that may raise questions/concerns for children); data analysis (development of analytic approach, construction of child/adult or child/animal dosimetry comparisons); and risk characterization (evaluation of how children's toxicokinetic analysis can be used to decrease uncertainties in the risk assessment). The proposed approach provides a range of analytical options, from qualitative to quantitative, for assessing children's dosimetry. Further, it provides background information on a variety of toxicokinetic factors that can vary as a function of developmental stage. For example, the ontology of metabolizing systems is described via reference to pediatric studies involving therapeutic drugs and evidence from in vitro enzyme studies. This type of resource information is intended to help the assessor begin to address the issues raised in this paper.

Adult↗
PubMed1997

Analysis and quantification of mental stress and fatigue using Maxwell relations from thermodynamics.

Several experimental and theoretical techniques have been developed to analyze both physical and psychological stresses. These techniques have relied mainly on certain parameters based on physiological, behavioral, and performance related data. This study is based on a thought experiment which describes the technique to quantify mental stress based on physiological responses using the entropy concept. It relates different physiological parameters using the Maxwell relations of thermodynamics with a systems approach. Data for testing this analytical approach were obtained from an experimental study which was conducted to determine the effects of a mentally stressful situation (final examination) on the common physiological responses (blood pressure, pulse rate, and oral body temperature) of students. The results indicated that the imposed mental stress causes significant changes in physiological responses. The Maxwell relations of thermodynamics were used to quantify the level of stress under different conditions. The results obtained from these relations validated the principles of thermodynamics as applied to the human system.

Adolescent↗
PubMed1998

Solid-phase microextraction with temperature-programmed desorption for the analysis of iodination disinfection byproducts.

An analytical approach for the determination of chlorination and iodination disinfection byproducts based on solid-phase microextraction (SPME) was developed. Solid-phase microextraction presents a simple, rapid, sensitive, and solvent-free approach to sample preparation in which analytes in either air or water matrixes are extracted into the polymeric coating of an optical fiber. Analytes are subsequently thermally desorbed in the injection port of a gas chromatograph for separation, detection, and quantitation. Thermal degradation of iodoform was observed during desorption from a polyacrylate fiber in initial GC/MS and GC/ECD experiments. Experiments were designed to determine SPME conditions that would allow quantification without significant degradation of analytes. Isothermal and temperature-programmed thermal desorptions were evaluated for efficacy in transferring analytes with wide-ranging volatilities and thermal stabilities into chromatographic analysis columns. A temperature-programmed desorption (TPD) (120-200 degrees C at 5 degrees C/min with an on-column injection port or 150-200 degrees C at 25 degrees C/min with a split/splitless injection port) was able to efficiently remove analytes with wide-ranging volatilities without causing thermal degradation. The SPME-TPD method was linear over 2-3 orders of magnitude with an electron capture detector and detection limits were in the submicrogram per liter range. Precision and detection limits for selected trihalomethanes were comparable to those of EPA method 551. Extraction efficiencies were not affected by the presence of 10 mg/L soap, 15 mg/L sodium iodide, and 6000 mg/L sodium thiosulfate. The SPME-TPD technique was applied to the determination of iodination disinfection byproducts from individual precursor compounds using GC/MS and to the quantitation of iodoform at trace levels in a water recycle system using GC/ECD.

Disinfectants↗
PubMedDate not supplied

Experimental assessment of phased-array heating of neck tumours.

An investigation of phased-array microwave systems (PAMS) for non-invasively inducing hyperthermia, primarily in neck lesions, has been done with implications for applications at other sites such as lung and pelvis. Our general approach was to combine numerical and analytical approaches with parallel experimental studies. In this paper we will concentrate only on the experimental aspects. The object, such as a homogeneous cylindrical phantom or a neck phantom, was encircled with several standard applicators driven by a single source, but with relative phase and amplitude control over each applicator. The relative phases of the applicators were adjusted by using an implanted monopole antenna connected to an HP network analyser. Power was applied and the specific absorption rate (SAR) was determined by using split phantoms and thermography or by measuring temperature transients dT/dt, recorded by implanted thermometer probes. We found that at 915 MHz for our applicators (SMA Co.) the centre of an 11 cm diameter muscle-like phantom heated to about 33% of the value at the surface in front of the applicator. Similarly, we were able to show significant SAR at the centre of realistically sized neck phantoms using four phased apertures of 915 MHz. Furthermore, substantial improvement was observed if the frequency was lowered to about 400 MHz.

Animals↗