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At least 127 records · Page 7Linked to original sources

PubMed1999

An EGS4-ready tomographic computational model of a 14-year-old female torso for calculating organ doses from CT examinations.

Fifty-four consecutive CT scans have been used to construct a tomographic computational model of a 14-year-old female torso suitable for the determination of organ doses from CT. The model, known as ADELAIDE, is in the form of an input file compatible with user codes based on XYZDOS.MOR from the readily available EGS4 Monte Carlo radiation transport code. ADELAIDE's dimensions are close to the Australian averages for her age so the model is representative of a 14-year-old girl. The realistic anatomy in the model differs considerably from that in Cristy's 15-year-old mathematical computational model by having realistically shaped organs that are appropriately located within a real external contour. Average absorbed dose to organs from simulated CT examinations of the chest and abdomen have been calculated for ADELAIDE using EGS4 within a geometry specific to the General Electric Hi-Speed Advantage CT scanner and using an x-ray spectrum calculated using data from the scanner's x-ray tube. The simulations include the scanner's beam shaping filter and patient table. It is suggested that the resulting values have fewer possible sources of uncertainty than organ doses derived from dose coefficients calculated for a MIRD style model with mathematical anatomy and a spectrum that may not match that of the scanner. The organ doses were normalized using the scanner's CTDI measured free-in-air and an EGS4 simulation of the CTDI measurement. Effective dose to the torso from 26-slice chest and 24-slice abdomen examinations (at 120 kV, 200 mAs, 7 mm slices) is 4.6 +/- 0.1 mSv and 4.3 +/- 0.1 mSv respectively.

Adolescent↗

PubMed1983

[Comparison of 4 methods of evaluating protein quality in vegetable sources].

This study compares the practical value of the following methods: protein efficiency ratio (PER), blood urea concentration in rats (BUC), relative nutritive value (RNV), and predicted protein value (PPV) to evaluate the protein quality of 41 diets of plant origin. Results demonstrated low correlations between PER and RNV (r = 0.66), PER and PPV (r = 0.53), RNV and PPV (r = 0.54), whereas there was a high negative correlation between PER and BUC (r = -0.89). These different procedures can be useful and valid for distinct and well-defined objectives, but the evaluation of results must be made in accordance with the purpose of the experiment. In assessing the protein quality of foodstuffs, it is therefore recommended that mathematical computer models be developed which take into account the cybernetic system of the amino acid metabolism. This would definitely reduce the actual need of expensive long-term biological assays.

Amino Acids↗

PubMed1981

Spectral analysis in clinical electro-encephalography.

In the past two years the above computerisations have been applied as a routine in over 2500 EEG recordings in our department. From the experience gained with this type of registration, processing and presentation of the EEG signals it appears that the scope of electro-encephalographic examination has been considerably extended. This is evident from the following examples 1. Communication between EEG specialists and non-EEG specialists over electro-encephalographic examination is improved considerably by means of this way of data reduction and topographical presentation. 2. As far as the discriminating power is concerned, it appears that, for example, small differences in frequency of cerebral activities in for example slight unilateral or local disorders of the circulation in the brain can be indicated by the computer analysis, even if it is invisible to the naked eye [10]. 3. Further statistical analysis of various parameters has become possible by distinguishing between normal and abnormal importance in distinguishing between normal and abnormal EEG's of one and the same patient, the difference can be indicated both objectively and quantitatively. 4. By means of electrical filing of EEG signals simultaneous with the usual paper filing, there is the possibility of applying newly developed statistical and mathematical computer programs to the stored EEG data of patients whose brain disorders have been definitively diagnosed.

Electroencephalography↗

PubMed1996

IBIS version 3: an OSF/Motif-based interface for IBIS--integrated biological imaging system.

IBIS is a set of computer programs dedicated to the processing of electron micrographs, mainly for structural analysis of biological macromolecules. We present IBIS version 3, a UNIX/OSF/Motif 1.2-based package which carries out and provides visual display of the many operations essential to image analysis. To ensure portability, the software is written in FORTRAN 77 for computing mathematical functions and in C for display routines. A description of the IBIS OSF/Motif interface is given with the new functions added to the original version. IBIS v.3 is available free of charge to other laboratories on the internet via anonymous ftp (URL: ftp://ftp.univ-rennes1.fr/pub/ incoming/IBIS.tar.Z).

Computer Communication Networks↗

PubMedDate not supplied

Anatomical macroelements in the study of craniofacial rat growth.

In order to avoid the arbitrary division of biological structures, rational polynomial interpolants are utilized to study growth. The major advantage of this method is the elimination of artificial internal element boundaries through anatomical structures. Since the boundary element methodology is employed in the finite element setting, other benefits, without additional computer coding, include the ability to use elements with any number of sides and reference frame invariance. Longitudinal landmark coordinates from midsagittal X-ray tracings of 22 albino female rat skulls of various ages were averaged. The skull was partitioned into three macroelements: a neural skull and two functionally distinct portions of the facial skull--olfactory and respiratory. The digital computer programming was carried out in the computer mathematics environment of Mathematica. Maximum elongation ratios were calculated for approximately 400 interior points. The elongation ratios in the neural skull compared well with previously documented growth behavior of internal brain structures. The calculated ratios from the facial skull were used to analyze the behavior of macroelement interpolation close to common anatomical boundaries.

Animals↗

PubMed1995

A study of planning and mathematics instruction for students with learning disabilities.

The purpose of this study was to extend research in training the use of cognitive strategies or planning to mathematical computation for 4 students with specific learning disabilities. A cognitive education method utilized in previous research was duplicated. It was expected that students would find the instruction differentially effective based upon their initial scores on a measure of planning. Using the Planning, Attention, Simultaneous, Successive model as a base, a cognitive instruction which facilitated planning was provided to two students with low scores on planning, obtained using an experimental version of the Das-Naglieri Cognitive Assessment System, and two students with average planning scores. All students completed three sessions of baseline and seven sessions of cognitive instruction in addition and multiplication. During the cognitive instruction phase, 5-min. sessions of self-reflection and verbalization of strategies about the mathematics problems were conducted after each initial 10-min. session of mathematics. Scores on addition problems showed that all students improved. On multiplication, however, 2 students with low planning scores improved considerably but not 2 with higher planning scores. Implications are provided.

Child↗

PubMed1990

Long-term arterial pressure control: an analysis from animal experiments and computer and graphic models.

Long-term arterial pressure control is very different from acute control, because many of the acute control systems are overridden by a single long-term mechanism that has little to do with short-term control. This is the renal fluid volume mechanism for pressure control. It is based on a simple functional property of the kidney: as the arterial pressure rises, the kidney output of water and electrolytes increases dramatically. When the output rises above the net intake of water and electrolytes, negative body fluid balance occurs, causing both the body fluid volume and the pressure to decrease. This decrease continues until the kidney fluid output exactly balances the net fluid intake. Conversely, if the pressure falls below the exact level for balance, intake becomes greater than output; then fluid builds up in the body and the pressure rises until intake and output again exactly balance each other. This fluid mechanism for pressure control has been known from the beginning of blood pressure research. However, its overpowering importance was not appreciated until a mathematical computer analysis in 1966 demonstrated the renal-fluid feedback mechanism to have infinite feedback gain for long-term pressure control. This is the principal topic of the present review.

Animals↗

PubMed2004

Uniform sampling of steady-state flux spaces: means to design experiments and to interpret enzymopathies.

Reconstruction of genome-scale metabolic networks is now possible using multiple different data types. Constraint-based modeling is an approach to interrogate capabilities of reconstructed networks by constraining possible cellular behavior through the imposition of physicochemical laws. As a result, a steady-state flux space is defined that contains all possible functional states of the network. Uniform random sampling of the steady-state flux space allows for the unbiased appraisal of its contents. Monte Carlo sampling of the steady-state flux space of the reconstructed human red blood cell metabolic network under simulated physiologic conditions yielded the following key results: 1), probability distributions for the values of individual metabolic fluxes showed a wide variety of shapes that could not have been inferred without computation; 2), pairwise correlation coefficients were calculated between all fluxes, determining the level of independence between the measurement of any two fluxes, and identifying highly correlated reaction sets; and 3), the network-wide effects of the change in one (or a few) variables (i.e., a simulated enzymopathy or fixing a flux range based on measurements) were computed. Mathematical models provide the most compact and informative representation of a hypothesis of how a cell works. Thus, understanding model predictions clearly is vital to driving forward the iterative model-building procedure that is at the heart of systems biology. Taken together, the Monte Carlo sampling procedure provides a broadening of the constraint-based approach by allowing for the unbiased and detailed assessment of the impact of the applied physicochemical constraints on a reconstructed network.

Animals↗

PubMed2002

Prediction of response to hormonal treatment in metastatic breast cancer.

Prediction of outcome and individualization of therapeutic strategies are challenging problems in oncology. Predictive parameters for response to hormonal treatment include the expression of hormone receptor, the extent and location of metastatic spread, disease-free interval, patient age, response to prior hormonal therapy, grading, and more recently, some molecular markers like the expression of HER-2/neu. The use of conventional statistics for prediction of response to hormonal treatment is limited by non-linearities and complex interactions between predictive factors. Modern computational mathematical models like artificial neural networks, entropy-based inductive algorithms or chi(2) interaction detection algorithms can describe these interactions and generate classification models and decision structures. They can be used to predict the clinical outcome for individual patients. In contrast to conventional methods, the level of confidence for the predictions can reach 90% and more. This might be an important step towards further individualization of therapeutic strategies.

Antineoplastic Agents, Hormonal↗

PubMed2003

Stepping up the pace of discovery: the genomes to life program.

Genome to life (GTL), the U.S Department of Energy Office of Science's systems biology program, focuses on environmental microbiology. Over the next 10 to 20 years, GTL's key goal is to understand the life processes of thousands of microbes and microbial systems in their native environments. This focus demands that we address huge gaps in knowledge, technology, computing, data capture and analysis, and systems-level integration. Distinguishing features include (1) strategies for unprecedented, comprehensive, and high-throughput data collection; (2) advanced computing, mathematics, algorithms, and data-management technologies; (3) a focus on potential microbial capabilities to help solve energy and environmental challenges; and (4) new research and management models that link production-scale systems biology facilities in an accessible environment. This unprecedented opportunity to provide the scientific foundation for solving urgent problems in energy, global climate change, and environmental cleanup demands that we take bold steps to achieve a much faster, more efficient pace of biological discovery.

Biological Science Disciplines↗

PubMed2006

Use of dimensional analysis to reduce medication errors.

The purpose of this pilot study was to determine whether using dimensional analysis as the method of mathematical computation could reduce nursing medication calculation errors. The sample for this study consisted of second-year baccalaureate nursing students in a required clinical skills course. Students in the control group were taught medication calculations using the traditional math method during one semester, whereas students in the experimental group were taught the same material using dimensional analysis during the next semester. Analysis of the collected data from a medication dosage calculation examination revealed the dimensional analysis group scored with greater accuracy than the traditional math group.

Attitude of Health Personnel↗

PubMed2004

Computational protein biomarker prediction: a case study for prostate cancer.

BACKGROUND: Recent technological advances in mass spectrometry pose challenges in computational mathematics and statistics to process the mass spectral data into predictive models with clinical and biological significance. We discuss several classification-based approaches to finding protein biomarker candidates using protein profiles obtained via mass spectrometry, and we assess their statistical significance. Our overall goal is to implicate peaks that have a high likelihood of being biologically linked to a given disease state, and thus to narrow the search for biomarker candidates. RESULTS: Thorough cross-validation studies and randomization tests are performed on a prostate cancer dataset with over 300 patients, obtained at the Eastern Virginia Medical School using SELDI-TOF mass spectrometry. We obtain average classification accuracies of 87% on a four-group classification problem using a two-stage linear SVM-based procedure and just 13 peaks, with other methods performing comparably. CONCLUSIONS: Modern feature selection and classification methods are powerful techniques for both the identification of biomarker candidates and the related problem of building predictive models from protein mass spectrometric profiles. Cross-validation and randomization are essential tools that must be performed carefully in order not to bias the results unfairly. However, only a biological validation and identification of the underlying proteins will ultimately confirm the actual value and power of any computational predictions.

Biomarkers, Tumor↗

PubMed1994

Thermography for the clinical assessment of inferior alveolar nerve deficit: a pilot study.

Neurosensory deficit is a major complication encountered in maxillofacial surgery. This study assessed the ability of electronic thermography to identify inferior alveolar nerve deficits in a pilot clinical study. The study population comprised six patients with inferior alveolar nerve deficit and 12 normal subjects. Frontally projected facial thermograms were taken on 18 subjects and measured using an Agema 870 unit and thermal image computer. Mathematical analysis of thermal measurements included temperature and delta T calculations of the anatomic zone over the mental region of the face. Results included (1) high levels of thermal symmetry of the chin in normal subjects (delta T = 0.1 degree C, standard deviation = 0.1 degree C); (2) low levels of thermal symmetry in patients with inferior alveolar nerve deficits (delta T = +0.5 degree C, standard deviation = 0.2 degree C); (3) statistically significant differences in delta T values (t = 4.82, P > .001) in patients with inferior alveolar nerve deficit; and (4) absolute temperature variations of the mental region in both groups. This pilot study demonstrated thermal asymmetry in patients with inferior alveolar nerve deficit and suggests that electronic thermography has promise as a simple, objective, noninvasive method for evaluating nerve deficits. However, more extensive studies are needed before thermographic procedures are accepted clinically.

Adult↗

PubMed1990

The modified minimal model: application to measurement of insulin sensitivity in children.

The modified minimal model (MMM), a recently introduced method that assesses insulin sensitivity (SI) by a computed mathematical analysis of the relation between the change in insulin and glucose clearance after a bolus of iv glucose, followed 20 min later by a bolus of tolbutamide, has been standardized in adults, but this method has not been validated in children. We performed an abbreviated 90-min MMM test in 50 children who were siblings of patients with insulin-dependent diabetes mellitus and 7 healthy adult volunteers and compared the results to the standard 180-min MMM test in 11 of these subjects. The cohort consisted of 29 prepubertal children [16 males and 13 females; 8.7 +/- 2.0 (mean +/- SEM) yr old]; 16 pubertal children defined as less than 17 yr of age and Tanner stage 2-5 (8 males and 8 females; 13.4 +/- 1.8 yr old), and 12 postpubertal subjects (7 males and 5 females; 18.2 +/- 0.9 yr old), with no significant difference in the weight for length index (WLI) among the 3 groups and with sera of all subjects negative for islet cell antibodies and insulin autoantibodies. The test procedure consisted of 3 baseline blood samples over 30 min, followed at zero time by 0.3 g/kg 25% dextrose infused iv over 1 min and an iv injection of tolbutamide (5 mg/kg) 20 min later; sequential blood samples for glucose and insulin measurements were withdrawn from zero time until completion 90 or 180 min later. In the 11 subjects who underwent both the standard and the abbreviated tests, there was no significant difference between the SI estimated by the 2 methods provided that glucose and insulin values were interpolated at 180 min during the computer calculations of the abbreviated test. Using the 90-min abbreviated test, the SI of the pubertal subjects (2.92 +/- 0.45) was markedly less than that of the prepubertal subjects (6.57 +/- 0.45; P = 0.0001). While the postpubertal group value of 4.63 +/- 0.86 was significantly higher than that of the pubertal group (P = 0.0001), the pre- and postpubertal groups remained significantly different (P = 0.0001). The 10 obese subjects with WLI greater than 120% had a lower SI (3.5 +/- 0.53) than the 47 nonobese subjects with WLI less than 120% (SI = 5.48 +/- 0.42; P less than 0.04), and there was a negative correlation between SI and WLI. None of the study subjects experienced symptomatic hypoglycemia during the test.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed1997

Fine-needle aspiration cytology in tumors and tumor-like conditions of the oral and maxillofacial region: diagnostic reliability and limitations.

BACKGROUND: Fine-needle aspiration cytology (FNAC) is a well established diagnostic technique. The purpose of the current study was to evaluate its diagnostic accuracy, sensitivity, and specificity in tumors and tumor-like conditions in the oral and maxillofacial region. METHODS: The results of 1022 cases of FNAC performed over a 7-year period (1990-1996) were retrospectively reviewed and analyzed. The material was collected from 228 major salivary glands, 67 perioral soft tissues and facial bones, 139 tumors of the oral cavity, 18 paranasal tumors, 41 oropharyngeal lesions, and 21 nasopharyngeal lesions, whereas 508 cases represented cervical lymph nodes. RESULTS: In 804 cases FNAC established or documented the initial diagnosis whereas in 198 cases it confirmed suspected recurrences. Definitive histologic diagnosis was established in 809 of the 1022 cases after surgical treatment and the histologic diagnoses were compared with preoperative FNAC results. In 20 cases the cytologic material was considered unsatisfactory and therefore the cytologic diagnosis was impossible to establish. In 12 of these cases diagnosis was made based on histologic examination after surgery. Malignancy was found in three of the latter cases. In the total number of 1022 cases there were 18 false-negative and 2 false-positive cytologic results. In another 19 cases a difference in the histologic type of the lesion was found. The diagnostic accuracy of the method was 98.2% with a sensitivity of 96.2% and a specificity of 99.4%. CONCLUSIONS: Four major causes of error were identified: material adequacy criteria, sampling technique, cytologic interpretation, and limitations of the procedure. FNAC proved to be a safe, accurate, inexpensive, and patient-friendly in the effort to establish preoperative diagnosis in tumors and tumor-like conditions of the oral and maxillofacial region. The authors have proposed modification in the mathematic computation of diagnostic accuracy, adding the parameter of nonconcordance with histologic typing of FNAC.

Adult↗

PubMed1977

The validity of two clinical tests of visual-motor perception.

The study investigated the relative efficiency of the Bender and MPD as assessors of achievement-related errors in visual-motor perception. Clinical experience with these two tests suggests that beyond first grade the MPD is more sensitive than the Bender for purposes of measuring deficits in visual-motor perception that interfere with effective classroom learning. The sample was composed of 153 third-grade children from two upper-middle-class elementary schools in a surburban school system in central Ohio. For three of the four achievement criteria, the results were clearly congruent with the hypothesis stated above. That is, SpCD errors from the MPD not only showed significantly higher negative rs with the criteria (reading vocabulary, reading comprehension, and mathematics computation) than Koppitz errors from the Bender, but also accounted for a much higher proportion of the variance in these criteria. Thus, the findings suggest that psychologists engaged in the assessment of older children seriously should consider adding the MPD to their assessment battery.

Achievement↗

PubMed1994

A special-purpose computer for molecular dynamics: GRAPE-2A.

Molecular dynamics simulations have been extensively used in research of proteins. Since these simulations are quite computer intensive, their acceleration is of main interest of the research. In molecular dynamics simulations, almost all computing time is consumed in calculating the forces between particles, e.g., Coulomb and van der Waals forces. We have designed and built GRAPE-2A (GRAvity PipE 2A), a special-purpose computer for use in simulations of classical many-body systems. GRAPE-2A calculates forces exerted on a particle from the other particles. GRAPE-2A can calculate force of an arbitrary functional form of a central force. The host computer, which is connected to GRAPE-2A through the VME bus, performs other calculations such as time integration. The peak speed of GRAPE-2A is 180 Mflops. We can also stimulate systems with periodic boundary conditions by the Ewald method, using GRAPE-2A and another special-purpose computer, WINE (Wave space INtegrator for the Ewald method).

Computer Simulation↗

PubMed1989

Converting relative risks to absolute risks: a graphical approach.

This paper presents a graphical method for converting relative risks to absolute risks. These absolute risk estimates are a function of the patient's current age, the patient's risk of developing cancer relative to some baseline population, the age specific cancer hazard in the baseline population, and the patient's competing mortal risk from all other causes. Graphs for breast cancer morbidity in women, cardiovascular mortality in men, and lung cancer morbidity in men illustrate the method. These graphs provide the probability of developing cancer in the next twenty years given the patient's current age and relative risk. They are derived under the proportional hazards model. A graph for lung cancer in men that uses a plausible exponential hazards model is also provided. The paper illustrates the importance of competing mortal hazard from other causes on absolute cancer risk. The strengths and weaknesses of this method are discussed. The graphs presented in this paper may be used as an aid in clinical decision making and in patient counselling.

Adult↗