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PubMed2007

A survey of recent developments in ab initio valence bond theory.

Starting from the 1980s and onwards, Valence Bond theory has been enjoying renaissance that is characterized by the development of a growing number of ab initio methods, and by many applications to chemical reactivity and to the central paradigms of chemistry. Owing the increase of computational power of modern computers and to significant advances in the methodology, valence bond theory begins to offer a sound and attractive alternative to Molecular Orbital theory. This review aims at summarizing the most important developments of ab initio valence bond methods during the last two or three decades, and is primarily devoted to a description of what the various methods can actually achieve within their specific scopes and limitations. Key available softwares are surveyed.

Journal Article↗
PubMedDate not supplied

Technique of color Doppler quantification of vascularity in transplanted kidneys.

A new technique for the quantification of vascularity based on the analysis of color Doppler images is described. We utilized velocity information obtained directly from cineloops transferred to a computer for off-line analysis. This methodology was used in transplanted kidneys to assess parenchymal vascularity on the basis of percentage color pixel density and mean flow velocity in mid-kidney cross-sectional regions of interest and the distance from the most peripheral color pixels to the capsule of the kidney. Other color Doppler quantitative methods have lacked reproducibility, and therefore before evaluation of the clinical usefulness of this technique, intraobserver reproducibility and interobserver reliability were assessed in 42 patients; no statistically significant variation was demonstrated. In 13 patients with normally functioning transplants, the mean maximum color pixel density was 34.7+/-13.4%, the mean flow velocity was 5.2+/-0.9 cm/second, and the mean distance to the capsule was 3.3+/-1.1 mm.

Adult↗
PubMed1991

Quantitative image analysis with densitometry for immunohistochemistry and autoradiography of receptor binding sites--methodological considerations.

Major technical progress in the development of computer-based image analysis has made possible the entry of autoradiography and immunohistochemistry into a new era where quantification by densitometry has become easily accessible. Autoradiography could become quantitative and displayed adequate reproducibility with the help of emulsion-coated films and the use of scales of standards of known radioactivity exposed and analyzed in parallel to the tissue sections. Immunohistochemistry after revelation by a color-based enzymatic technique can also become quantitative, providing that standardization of the crucial steps of the procedure and calibration through a parallel treatment of a scale of antigen standards can be ensured. Such an approach is described here in the rat with reference to tyrosine hydroxylase (TH), the main synthesizing enzyme for catecholamines, and with dopamine (DA) itself, a catecholaminergic neurotransmitter. The different parts of the procedure, which can influence the results, such as the fixation of the animals by perfusion and the evaluation of the fluctuations via the calibration curve, are discussed in detail. Biological validation of the proposed procedure is described by reference to experiments already well documented biochemically, such as the induction effect of reserpine on TH in the rat locus coeruleus and the depleting effect of alpha-methyltyrosine (AMPT), a well-known blocker of TH activity, on rat striatal DA content. Finally the importance of restricting the measurements to the (pseudo)linear portion of the calibration curve is illustrated by the autoradiographic identification of the differential intrastriatal repartition of the dopaminergic D1 and D2 receptor sites, particularly the dual patch-matrix compartments.

Animals↗
PubMed1994

Formulation optimization of indomethacin gels containing a combination of three kinds of cyclic monoterpenes as percutaneous penetration enhancers.

A computer optimization technique based on response surface methodology was applied for the optimization of a hydrogel formulation containing indomethacin as a model drug. As the penetration enhancer, a combination of three cyclic monoterpenes, limonene, menthol, and cineole, was employed. Pharmacokinetic parameters, from an in vivo percutaneous absorption study on rats of model formulations prepared according to the composite experimental design for five factors, were determined as prime response variables. The skin damage evoked by each formulation was microscopically judged and graded as the response variable concerning skin safety. The response variables were predicted by multiple regression equations comprising combinations of the five formulation factors. The regression equations for the response variables assembled as a simultaneous optimization problem based on the generalized distance function. The simultaneous optimum was predicted as a function of individual optima within a 95% confidence region. The predicted response values for the optimum formulation have been successfully validated in a repeated in vivo percutaneous absorption study.

Administration, Topical↗
PubMed1998

A multiscale model of plant topological structures

In applications dealing with plant growth modeling, increasing attention is being devoted to the topological structure of plants. Different models, based on tree-graphs, have been introduced to represent plants. These models assume that the scale of description is fixed. However, this hypothesis is too restrictive for new modeling applications that aim to tackle analysis or simulation of plant growth at different time and space scales. In order to make such multiscale descriptions available to computer applications, we have defined a general methodology for measuring and representing multiscale plant topological structures. This paper discusses the design of a model of plant topological structures and sketches out its general formal properties. The model supports multiscale, attributed and time-varying descriptions of plants. It is intended to be used for plant analysis methodologies and plant growth simulations.Copyright 1998 Academic Press Limited

Journal Article↗
PubMed1990

Monte Carlo methods of neutron beam design for neutron capture therapy at the MIT Research Reactor (MITR-II).

Monte Carlo methods of coupled neutron/photon transport are being used in the design of filtered beams for Neutron Capture Therapy (NCT). This method of beam analysis provides segregation of each individual dose component, and thereby facilitates beam optimization. The Monte Carlo method is discussed in some detail in relation to NCT epithermal beam design. Ideal neutron beams (i.e., plane-wave monoenergetic neutron beams with no primary gamma-ray contamination) have been modeled both for comparison and to establish target conditions for a practical NCT epithermal beam design. Detailed models of the 5 MWt Massachusetts Institute of Technology Research Reactor (MITR-II) together with a polyethylene head phantom have been used to characterize approximately 100 beam filter and moderator configurations. Using the Monte Carlo methodology of beam design and benchmarking/calibrating our computations with measurements, has resulted in an epithermal beam design which is useful for therapy of deep-seated brain tumors. This beam is predicted to be capable of delivering a dose of 2000 RBE-cGy (cJ/kg) to a therapeutic advantage depth of 5.7 cm in polyethylene assuming 30 micrograms/g 10B in tumor with a ten-to-one tumor-to-blood ratio, and a beam diameter of 18.4 cm. The advantage ratio (AR) is predicted to be 2.2 with a total irradiation time of approximately 80 minutes. Further optimization work on the MITR-II epithermal beams is expected to improve the available beams.

Brain Neoplasms↗
PubMed1983

Emotional states and pain: intraindividual and interindividual measures of association.

The present study investigated the correlation between cancer pain severity and mood states, and addressed methodological issues involved in measuring the association between these groups of variables. Five monthly interviews were administered to 95 cancer pain patients; each interview contained four measures of pain severity and the Profile of Mood States (POMS). The relationships between the two sets of variables were assessed using both interindividual (cross-sectional) and intraindividual (within-subject) methods of correlational analysis. Both types of analyses suggested small but significant positive correlations between the pain measures and negative mood states, and inverse correlations between pain and positive mood. The data also indicated that patients reported high levels of pain but reported little mood disturbance. In addressing methodological issues, the study clarified conceptual and computational differences between the two types of correlational analyses and indicated the appropriate applications of each method.

Affective Symptoms↗
PubMed1997

[Calibration of clinical databanks with "virtual patients"].

The scientific value of multicenter studies is still questionable, as there are no methods available that allow to determine whether in fact identical items are recorded in the same way in different centers. Subjective classifications (for example according to the New York Heart Association (NYHA)), definitions of items, documentation habits and procedures may not be comparable in different hospitals. For that reason the concept of a "virtual patient" for calibration of database systems was developed as a new methodological approach. The "virtual patients" describes a computer program that includes and uses multimedia-tools to represent an exactly defined patient. A sound card enables a patient to talk and to represent intracardial and intrapulmonary sounds. Additional information including echocardiographic sequences, perioperative video sequences, x-ray analysis, angiograms, etc. is represented in the program. Thus during the perioperative course of a patient the complete relevant pre-, intra- and postoperative information regarding the patient is provided. Any physician participating in a multicenter study is asked to record the data of this virtual patient and to store it in a database system using the sheets applied in a multicenter study. As the patient is exactly defined (virtual patient) incorrect classifications and incomplete recordings, etc. can easily be detected and discussed. The virtual patient is a tool that allows calibration of database systems by direct comparison of the documentation technique between different physicians and different hospitals participating in multicenter studies. It is thus a multimedia-instrument to support standardization and quality assurance of database systems.

Calibration↗
PubMed2004

Maternal-fetal status of copper, iron, molybdenum, selenium and zinc in insulin-dependent diabetic pregnancies.

OBJECTIVE: The objective was to assess the status of essential trace elements such as copper, iron, molybdenum, selenium and zinc in insulin-dependent diabetic pregnancies at term and to compare the data with a control group. Fetal-maternal ratios of the elements and copper:zinc ratio were also computed in the control and study populations. METHODOLOGY: Samples from maternal vein, umbilical artery and umbilical vein of diabetic and control women were collected at the time of spontaneous delivery or cesarean section and activities of trace elements evaluated by atomic absorption spectrophotometry. RESULTS: Cu, Fe, Mo, Se and Zn concentrations in maternal venous blood averaged 2,156, 2,020, 13, 102 and 656 microg/l in control women (n=17) while in the diabetic group (n=14), the corresponding values for the trace elements averaged 3,135, 3,675, 15, 85 and 628 microg/l respectively. Values for copper and molybdenum were significantly higher (p<0.05) in the study group compared to control while those of zinc, iron and selenium were not significantly different (p>0.05). Iron and molybdenum values were significantly higher (p<0.05) and that of zinc significantly lower (p<0.05) in umbilical arterial samples of diabetic group compared to controls. In the case of molybdenum, copper the values were significantly higher (p<0.05) in umbilical venous samples of diabetic group compared to that of control. Significant differences in Cu:Zn ratio of maternal venous and umbilical samples and fetal-maternal ratios of some elements were noted between control and study group as well. CONCLUSION: We speculate that altered status of some essential trace elements and altered antioxidant mineral ratio observed in insulin dependent diabetic patients could have deleterious influences on the health of the mother as well as the fetus and newborn.

Adolescent↗
PubMed1994

Microbiological collaborative studies for quality control in food laboratories: reference material and evaluation of analyst's errors.

Working groups of the Federal Health Office in Germany and of the International Dairy Federation (IDF) have developed a quality assurance system to assess the analyst performance for colony count methods. The experiment design consists of several dilution series produced from a homogeneous sample suspension. Each series contains a number of twofold dilution steps with parallel plates on each level. The structure of this design permits a detailed analysis of the total variance and identification of analysts' methodological errors as single effects. A computer-based interpretation aid may classify the laboratory as working in correspondence with good laboratory practice ('acceptable') or, otherwise, furnishing 'to good' or 'unacceptable' results. Some examples are given for deviation depending on individual faults. Both, internal quality assurance and collaborative studies demand suitable reference samples. The reference material used has to meet certain requirements concerning homogeneity, contamination level and microbiological stability during a period of storage and transport. A naturally contaminated sample material was prepared, which has been used successfully in microbiological collaborative studies.

Animals↗
PubMed1986

Some methodological aspects of estimating cosmic ray exposures in orbital flights.

Computations of the transmission functions of cosmic rays penetrating the geomagnetic field are discussed. Results of LET spectra calculations both inside and outside the spacecraft COSMOS-1129 are presented. Comparison of calculations and measured results shows (in interval 10-5 x 10(3) MeV/cm) a difference of less than 30%. The need for further systematic low altitude particle measurements for the purpose of developing dynamic models of particle populations is stressed.

Cosmic Radiation↗
PubMedDate not supplied

Three-dimensional reconstruction of the cochlea from two-dimensional images of optical sections.

This paper describes a methodology for three-dimensional (3D) computer-aided reconstruction of the guinea pig cochlea using orthogonal-plane fluorescence optical sectioning. Specimens are sectioned optically, allowing them to remain intact during observation. Equations to correct the data for specimen translation and rotation are developed and 3D reconstructions of the scala tympani, round window membrane, and cochlear aqueduct are presented. The error associated with the reconstruction is estimated to be < 19 microns.

Animals↗
PubMed2005

Biliary tree and cholecyst: post surgery imaging.

Recently, with improvements in surgical techniques there has been a substantial reduction in the incidence of biliary complications of hepatobiliary surgery. Nevertheless, bile duct injuries and other post-cholecystectomy complications are a serious problem and a major cause of morbidity and mortality. Early complications may include bile duct injury caused by mistakenly placed clips, erroneous cutting of bile ducts based on misinterpretation of biliary anatomy, periductal bile leakage that causes edema, fibrosis and secondary stricturing, and ischemia due to injury to the right hepatic artery. Bile duct strictures are the most common of the late complications and can develop a few months or many years after surgery. Early detection and accurate diagnosis have a fundamental importance for the successful treatment of these complications. Therefore, early and meaningful application of the imaging methods immediately after detection of the first symptoms is essential. Peroperative ultrasound and direct iodine contrast application into the biliary tree (operative cholangiography) are highly important for immediate visualization of the complications during surgery. Ultrasound can be used to aid in identification of ductal structures and the cholangiogram should be obtained to document the anatomy. Plain abdominal film could be made in the patients in poor clinical conditions after biliary surgery. Oral cholecystography has largely been replaced by ultrasonography (US) for evaluation of cholelithiasis and complications like post-cholecystectomy fluid collections. The same methodology replaced the conventional intravenous cholangiography. Nowadays computed tomography (CT), endoscopic retrograde cholangiopancreatography (ERCP), magnetic resonance cholangiography (MRCP) and ultrasound (US) have essential roles as primary imaging modalities after biliary tree and gallbladder surgery in the evaluation of associated complications and residual biliary stones. We review the role of the imaging in complications after biliary tree and gallbladder surgery.

Biliary Tract Diseases↗
PubMed2005

Lung volume assessment for a cross-comparison of two breathing-adapted techniques in radiotherapy.

PURPOSE: To assess the validity of gated radiotherapy of lung by using a cross-check methodology based on four-dimensional (4D)-computed tomography (CT) exams. Variations of volume of a breathing phantom was used as an indicator. METHODS AND MATERIALS: A balloon was periodically inflated and deflated by a medical ventilator. The volume variation (DeltaV) of the balloon was measured simultaneously by a spirometer, taken as reference, and by contouring 4D-CT series (10 phases) acquired by the real-time position management system (RPM). Similar cross-comparison was performed for 2 lung patients, 1 with free breathing (FB), the other with deep-inspiration breath-hold (DIBH) technique. RESULTS: During FB, DeltaV measured by the spirometer and from 4D-CT were in good agreement: the mean differences for all phases were 8.1 mL for the balloon and 10.5 mL for a patient-test. End-inspiration lung volume has been shown to be slightly underestimated by the 4D-CT. The discrepancy for DeltaV between DIBH and end-expiration, measured from CT and from spirometer, respectively, was less than 3%. CONCLUSIONS: Provided that each slice series is correctly associated with the proper breathing phase, 4D-CT allows an accurate assessment of lung volume during the whole breathing cycle (DeltaV error <3% compared with the spirometer signal). Taking the lung volume variation into account is a central issue in the evaluation and control of the toxicity for lung radiation treatments.

Humans↗
PubMed2005

A mobile element based phylogeny of Old World monkeys.

SINEs (Short INterspersed Elements) are a class of non-autonomous mobile elements that are <500 bp in length and have no open reading frames. Individual SINE elements are essentially homoplasy free with known ancestral states, making them useful genetic systems for phylogenetic studies. Alu elements are the most successful SINE in primate genomes and have been utilized for resolving primate phylogenetic relationships and human population genetics. However, no Alu based phylogenetic analysis has yet been performed to resolve relationships among Old World monkeys. Using both a computational approach and polymerase chain reaction display methodology, we identified 285 new Alu insertions from sixteen Old World monkey taxa that were informative at various levels of catarrhine phylogeny. We have utilized these elements along with 12 previously reported loci to construct a phylogenetic tree of the selected taxa. Relationships among all major clades are in general agreement with other molecular and morphological data sets but have stronger statistical support.

Alu Elements↗
PubMedDate not supplied

Midwifery education models. A contemporary review.

Midwifery education has a rich tradition of blending innovation with educational methods that have demonstrated their value to the profession. Examples of innovations that have influenced midwifery education include the use of the asynchronous modular system, the development of distance methodologies, and most recently the use of computer and telecommunications technologies to mediate education. This study was designed to explore trends in approaches to the education of midwives in both traditional and distance education programs. Program directors were surveyed and interviewed to assess their degree of instructional synchrony, their use of distance modalities, and their predominate methods of curriculum presentation. Results of the survey suggest that programs are using a variety of these approaches to educate their students. Decisions to integrate new educational technologies appear to be based on institutional values, community resources, and student needs.

Education, Nursing, Graduate↗
PubMed2003

New method for simultaneous anatomical and functional studies of articular joints and its application to the human knee.

In this paper a new methodology is described for the acquisition and computer elaboration of joint anatomy and motion data and the study of their correlation. The method uses a particular commercial electrogoniometer never used before for biomechanic investigations and software developed by the author for numerical interpolations and interactive display of the anatomical structures during joint motion. The original data acquisition protocol and computer elaboration software are described in detail, the theoretical and experimental accuracy of the method is reported and the original features and potential benefits of this approach in the field of joint biomechanics are discussed. Finally an experimental application for geometrical and functional analysis of the knee is presented as a practical example.

Biomechanical Phenomena↗
PubMed2004

Study of the extraction procedure by experimental design and validation of a LC method for determination of flavonoids in Citrus bergamia juice.

A reversed-phase high-performance liquid chromatographic (HPLC) separation with photo-diode array detection was developed for the simultaneous determination of flavonoids extracted from Citrus bergamia juice. It employs a C18 reversed-phase column and a linear gradient elution system with methanol/water with 5% acetic acid (v/v), as mobile phase. The method was validated in terms of detection limits (LOD), quantitation limits (LOQ), linearity, precision and accuracy. Limits of detection ranged from a low of 0.007 mg ml(-1) (narirutin) to a high of 0.018 mg ml(-1) (didymin). The limits of quantitation were between a low of 0.011 mg ml(-1) (7-OH flavanone) and a high of 0.024 mg ml(-1) (didymin). An excellent linear response was observed over the range specified for all analytes, as confirmed by the correlation coefficient with ranged from 0.9982 and 0.9999. The intra-day R.S.D.% ranged from 0.11 to 3.64%. The intermediate precision R.S.D.% were not higher than 7.62%. The accuracy of the method was confirmed with an average recovery ranging, except for neoeriocitrin, between 88.07% and 102.45%. Since the extraction conditions can affect analyte recovery, a suitable optimization strategy of the procedure was needed. The experimental parameters optimized were extraction time, temperature, and solvents. A multivariate approach was used to provide direct evaluation of the selected variables and related interactions. The D-optimal design was constructed by applying the exchange algorithm. All experimental results were computed by NEMROD-W software. This methodology led us to obtain the best recovery for all the flavonoids in the least number of experiments.

Chromatography, Liquid↗