SEARCH · PubMed Health

Results for “Computer Graphics”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 829 records · Page 46Linked to original sources

PubMed1983

Molecular modelling studies on the non-covalent intercalative interactions between DNA and the enantiomers of anti-benzo[a]pyrene 7,8-diol-9,10-epoxide.

The non-covalent intercalative interactions between a deoxydinucleoside model for DNA and the enantiomers of anti-benzo[a]pyrene diol-epoxide, have been studied by molecular mechanics and computer graphics methods. Stereoselective differences between major and minor groove sites, and between the enantiomers have been found in terms of attractive close contacts.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed1995

Random dot motion perimetry in patients with glaucoma and in normal subjects.

PURPOSE: To determine whether patients with primary open-angle glaucoma have an increase in size thresholds, prolongation of reaction times, and greater localization errors to random dot motion stimuli than normal subjects. METHODS: Motion perimetry, a computer graphics method of visual field testing, quantitates a subject's ability to detect a correlated shift in position of dots within a defined circular area against a background of fixed dots. We measured motion thresholds, the smallest detectable circular dot motion target, at the Humphrey 24-2 test loci. By using the subject's light-pen responses to the location of the targets, we computed motion size threshold, reaction times, and localization errors (number of pixels from where the subject touched the monitor to the target center). With motion perimetry and conventional automated perimetry, we tested one eye in each of 25 patients with primary open-angle glaucoma and 25 age-matched control subjects. We then generated total deviation pointwise probability plots for the patients with primary open-angle glaucoma. RESULTS: Patients with primary open-angle glaucoma had increased mean motion size threshold (P < .001) and increased localization errors (P < .002), compared with the control subjects. With the probability plot analysis, there was good correlation of the visual field defects between the two perimetry tests. Additionally, motion perimetry identified nerve fiber bundle-like defects in 12 patients that were not detected with conventional automated perimetry. CONCLUSIONS: Patients with primary open-angle glaucoma had abnormal motion perception with an increase in spatial localization error.

Adult↗

PubMed1998

Variability of the planarity of the human aortic bifurcation.

The susceptibility of vascular branches to atherosclerosis is believed to be due in part to the unusual fluid dynamic environments that the vessel wall experiences in these regions. As vascular geometry is a primary determinant of the local haemodynamic environment, it is of interest to quantitate the geometric features of vascular branches and their variability. The present research focusses on branch planarity, using axial magnetic resonance images of the aortic bifurcations of 20 healthy subjects. The in vivo images were processed to obtain vector representations of the vessel axes at the bifurcation, from which the planarity of the bifurcation was derived using a novel robust definition. Three-dimensional reconstructions of the bifurcations were rendered using computer graphics techniques to demonstrate the variability of the planarity of this region of the vasculature; this variability might be related to variable predispositions to atherosclerosis at the aortic bifurcation.

Aorta, Abdominal↗

PubMed2006

InSilicoSpectro: an open-source proteomics library.

We present a new proteomics open-source project, InSilicoSpectro, aimed at implementing recurrent computations that are necessary for proteomics data analysis. Illustrative examples are mass list file format conversions, protein sequence digestion, theoretical peptide and fragment mass computations, graphical display, matching with experimental data, isoelectric point estimation, and peptide retention time prediction. The project library is written in Perl, a widely used scripting language in bioinformatics, and it offers a unique framework of integrated objects to implement complex proteomics data analyses. For instance, only a few lines of code are required to digest a protein with fixed and variable modifications, label peptides with 18O, compute the fragmentation spectra and display their match with experimental spectra. We believe that InSilicoSpectro will be of great help to bioinformaticians, without detailed knowledge of proteomics specifics, and to mass spectrometrists with computer programming interest as well.

Amino Acid Sequence↗

PubMed1998

Reconstruction of three-dimensional digital teeth.

OBJECTIVE: Dental anatomy is one of the most important basic courses in the education of dentistry. The deep understanding of both the external and internal morphologic characteristics is very important to the teaching, research and clinical practice of dentistry. METHODS: In the present study, 32 permanent teeth from the skull specimen of a young man were individually embedded in black fluid resin, each in special containers. They were ground by a numerically-controlled grinding machine at intervals of 0.2 mm per layer. A distinct outline of the tooth could be seen on every section. Black and white photographs were taken and scanned into a computer by a film-scanner to obtain sequences of two-dimensional images of the tooth sections. After pattern recognition, all of the images of each tooth were piled up at intervals of 0.2 mm by the technique of computerized reconstruction. RESULTS: The three-dimensional stereo tooth models were built up from two-dimensional data. On the basis of those models, computer graphic techniques were used to highlight, smooth, and shade the teeth. These digital teeth and dentitions could function as a series of computerized teaching models. Their high resolution and accuracy could meet the basic demands of dentistry. CONCLUSIONS: The present study developed new techniques of model preparation, image input, and 3-D reconstruction. These digital teeth and dentitions provide an important foundation for the application of computer imaging, CAD/CAM, computer-assisted instruction, and virtual reality in dentistry.

Anatomy, Cross-Sectional↗

PubMed1992

Genetic and biochemical characterization of the trpB8 mutation of Escherichia coli tryptophan synthase. An amino acid switch at the sharp turn of the trypsin-sensitive "hinge" region diminishes substrate binding and alters solubility.

The trpB8 mutation of Escherichia coli tryptophan synthase is unique in that the cells bearing this lesion are not only capable of utilizing indole for growth, but they also accumulate indole, under conditions of tryptophan limitation. The lesion was shown by DNA sequencing to be a G to C transversion at nucleotide 5528 of the trp operon, resulting in a Gly to Arg switch at codon 281. Gly-281, within the trypsin-sensitive "hinge" region, is invariant among all known beta polypeptides. The catalytic activity of the mutant beta 2(B8) protein is dramatically stimulated by alpha subunit, both in vivo and in vitro. In the absence of alpha subunit, ammonium ion effectively stimulated the activity in an apparently cooperative manner. The pH optimum for the mutant subunit was 9.8, which is 2 units higher than that of wild type. In contrast to the wild-type subunit, beta(B8) partially aggregated within cells upon overexpression. At the optimal concentration of ammonium ions (2.25 M), the beta 2(B8) mutant enzyme displayed lower affinity than wild-type enzyme toward indole and L-serine, but the Vmax was almost unchanged. The physicochemical behavior of beta 2(B8) is supported by computer graphic modeling studies. An open versus closed model of conformational change within the beta 2 protein is proposed. A plausible role for the hinge region is discussed.

Amino Acid Sequence↗

PubMedDate not supplied

Stereotactic irradiation therapy. Physical and dosimetric problems.

In stereotactic irradiation by external beams there are many problems involved with dosimetry of small fields, three-dimensional representation of dose distribution, radiobiological involvement of tissue response to total dose and fractionation. Dosimetric problems arise by critical dimension of dosimetric chambers and by difficulties of films calibration. The amount of data required for a correct three-dimensional simulation of isodose curves, tumor and anatomical structures require a very speed computer system, sophisticated computer graphic techniques and calculation algorithm. By use the linear quadratic model of cell survival, maps of combined dose and biological effect (isoeffect curves) are also obtained.

Brain Neoplasms↗

PubMed1988

Dimensional measurements on images from a video camera or cassette recorder using a BBC microcomputer.

We have developed a system that enables a BBC microcomputer to make dimensional measurements on images from a video camera or cassette recorder without a framestore. The RGB output of the computer is synchronized to the output of the camera or recorder and the two displayed simultaneously on the same monitor. Measurements can be made directly from the displayed image using points indicated by the computer graphics cursor via its keyboard. Distances can be measured with a precision of about 0.4%. The system is very versatile but is especially useful for measuring the freeze-frame output from a Philips standard videotape.

Computers↗

PubMed1986

Results of computer-assisted stereotactic laser resection of deep-seated intracranial lesions.

A computer-assisted stereotactic system has been developed for the precise resection of deep-seated intracranial neoplasms. After the tumor volume is reconstructed from computed tomographic and magnetic resonance imaging data, a computer-monitored, stereotactically directed carbon dioxide laser is used to vaporize the intracranial tumor. A computer graphics terminal is used to monitor the position of the laser in relationship to the planar slices through the tumor, which are reformatted orthogonally to the surgical plane of view. This procedure produced satisfactory postoperative neurologic results in 36 of the 41 patients who underwent treatment. The system provides precise surgical control in three-dimensional space for the safe resection of substantial amounts (as assessed by postoperative computed tomography) of intra-axial neoplasms.

Adolescent↗

PubMedDate not supplied

Evaluation of a low-cost 3D sound system for immersive virtual reality training systems.

Since Head Mounted Displays (HMD), datagloves, tracking systems, and powerful computer graphics resources are nowadays in an affordable price range, the usage of PC-based "Virtual Training Systems" becomes very attractive. However, due to the limited field of view of HMD devices, additional modalities have to be provided to benefit from 3D environments. A 3D sound simulation can improve the capabilities of VR systems dramatically. Unfortunately, realistic 3D sound simulations are expensive and demand a tremendous amount of computational power to calculate reverberation, occlusion, and obstruction effects. To use 3D sound in a PC-based training system as a way to direct and guide trainees to observe specific events in 3D space, a cheaper alternative has to be provided, so that a broader range of applications can take advantage of this modality. To address this issue, we focus in this paper on the evaluation of a low-cost 3D sound simulation that is capable of providing traceable 3D sound events. We describe our experimental system setup using conventional stereo headsets in combination with a tracked HMD device and present our results with regard to precision, speed, and used signal types for localizing simulated sound events in a virtual training environment.

Acoustics↗

PubMed1988

The tertiary structure of Aspergillus saitoi minor ribonuclease (Ms) predicted from the structure of RNase T1.

Ribonuclease Ms from Aspergillus saitoi is a small acidic protein (11,714 Da) containing 106 amino acids of known sequence. Unlike other enzymes belonging to the RNase T1 family this ribonuclease is base-unspecific. Using interactive computer graphics and energy minimisation we predicted the structure of RNase Ms on the basis of sequence homology to RNase T1 of known structure. In this report the predicted structure of this protein is presented and characterised.

Amino Acid Sequence↗

PubMed2003

An algorithm to delineate and integrate topological basins in a three-dimensional quantum mechanical density function.

The growing activity in the area of Quantum Chemical Topology warrants a new algorithm to delineate topological basins in 3D scalar fields other than the electron density. A method based on the "octal tree search algorithm" of computer graphics is proposed to reach this goal. We illustrate the algorithm on the L(r) function, which is the negative of the Laplacian of the electron density. Because of its complicated topology, even in a simple test molecule such as water, it benefits from the octal tree algorithm as a robust, compact, and general technique to find the boundaries of topological basins. For the first time, we are able to compute the population and volume of the core and valence (bonding and nonbonding, i.e., lone pair) basins given by L(r)'s topology.

Journal Article↗

PubMed1989

Malar augmentation. Patient classification and placement.

Aesthetic malar augmentation is described to improve the appearance of patients with flattening of the malar eminence, to create a more youthful appearance of the face, to make the face more oval in appearance, and to de-emphasize prominent nasal or mental profiles. Detailed preoperative analysis of surgical candidates has not been reported. Twenty models studied by photogrammetry of frontal, lateral, and oblique views were analyzed to synthesize ideal measurements of an aesthetic face with particular attention to points describing the malar mound. Photographs of patients operated on were analyzed using computer graphics to compare the synthesized ideal and surgical results. Ideal candidates are defined as those patients with ptotic malar mounds with adequate soft tissue to create a balanced and harmonious result. Examples of candidates and potential pitfalls are presented.

Adult↗

PubMed1984

Actinidin hydrolysis of substituted-phenyl hippurates: a quantitative structure-activity relationship and graphics comparison with hydrolysis by papain.

The hydrolysis of 29 phenyl hippurates (XPhOCOCH2NHC(=O)C6H5) by the cysteine protease actinidin has been studied and a quantitative structure-activity relationship (QSAR) has been formulated: log 1/Km = 0.74 sigma + 0.50 pi'3 + 0.24MR4 + 2.90. In this expression Km is the Michaelis constant, sigma is the Hammett constant, pi'3 is the hydrophobic parameter for the more hydrophobic of the two meta substituents, and MR4 is the molar refractivity of para substituents. The QSAR for actinidin is compared with a similar one obtained for another cysteine plant protease papain. A color stereo computer graphics model constructed from the X-ray crystallographic coordinates of actinidin is compared with those of our previously reported models for papain.

Cysteine Endopeptidases↗

PubMed1996

Study of structure-activity correlation in destruxins, a class of cyclodepsipeptides possessing suppressive effect on the generation of hepatitis B virus surface antigen in human hepatoma cells.

A new destruxin [destruxin E2 chlorohydrin] was isolated from the culture medium of Metarrhizium anisopliae and its structure was determined by NMR spectroscopy and mass spectrometry. As compared with other destruxins, the new destruxin showed a lower suppressive activity on the production of hepatitis B virus surface antigen in human hepatoma Hep3B cells. NMR study coupled with molecular modeling by computer graphics has revealed that the hydrophobicity nature of the convex surface characteristic of all destruxin molecules plays an important role in their biological activity.

Antiviral Agents↗

PubMed1995

Diagnostic decision support for prostate lesions.

The diagnostic evaluation of premalignant and malignant lesions of the prostate may benefit from the application of an inference network. Used as a diagnostic decision support system, an inference network provides standardized assessment of diagnostic clues which is supported by computer graphics and comparison imagery, uncertainty management by possibility and probabilistic schemes and the systematic combination of different pieces of diagnostic evidence. This assessment results in a numeric measure of belief in the final diagnosis.

Diagnosis, Computer-Assisted↗

PubMed1985

The cellular dynamics of pattern formation in the eye of Drosophila.

The establishment and early development of the ommatidial bundles in the presumptive eye of Drosophila have been investigated using electron microscopic serial sectioning. A progression of developmental stages has been characterized. Initially simple, symmetrically constructed bundles develop into asymmetrical, more complex constructions. Computer graphic reconstruction has been used to show the three-dimensional structure of the various ommatidial bundles. Autoradiography has been used to locate the position of a region of cell division which is intimately associated with the formation of the ommatidial bundles.

Animals↗

PubMedDate not supplied

Diagnostic marker displays for intermediate cells from the uterine cervix.

Studies have shown the existence of computer-recognizable subvisual markers in intermediate cells from different cervical conditions that show good potential for discriminating between such "normal" cells from patients with normal, severe dysplasia/carcinoma in situ or invasive cancer cytologies. This paper presents examples of computer graphic displays, based on these markers, that could provide recognizable diagnostic clues to the cytologist, with a discussion of some of the factors involved in the interpretation of such displays.

Cervix Uteri↗