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At least 271 records · Page 15Linked to original sources
PubMed2004

[Reconstruction of the mandibular model using a three-dimensional laser scanner].

OBJECTIVE: To construct a three-dimensional (3D) mandibular model using a 3D laser scanner, and explore a new method for reconstructing the finite element geometry model. METHODS: A mandible specimen was scanned with the 3D laser scanner to form the point clouds of the mandibular surface, which were subsequently aligned for reconstruction of the mandibular model. RESULT: A 3D model of the mandible surface was reconstructed, which could be used for finite element simulation. CONCLUSION: The 3D laser scanning system can be used to reconstruct the 3D model with irregular geometry for finite element simulation.

Adult↗
PubMed1999

Motion transparency: making models of motion perception transparent.

In daily life our visual system is bombarded with motion information. We see cars driving by, flocks of birds flying in the sky, clouds passing behind trees that are dancing in the wind. Vision science has a good understanding of the first stage of visual motion processing, that is, the mechanism underlying the detection of local motions. Currently, research is focused on the processes that occur beyond the first stage. At this level, local motions have to be integrated to form objects, define the boundaries between them, construct surfaces and so on. An interesting, if complicated case is known as motion transparency: the situation in which two overlapping surfaces move transparently over each other. In that case two motions have to be assigned to the same retinal location. Several researchers have tried to solve this problem from a computational point of view, using physiological and psychophysical results as a guideline. We will discuss two models: one uses the traditional idea known as 'filter selection' and the other a relatively new approach based on Bayesian inference. Predictions from these models are compared with our own visual behaviour and that of the neural substrates that are presumed to underlie these perceptions.

Journal Article↗
PubMed1988

Sheltering--a protective measure following an accidental atmospheric release from a nuclear power plant.

The effectiveness of sheltering the population for reducing radiological effects following an accidental release of radioactivity at a nuclear power plant was investigated. Different levels of respiratory protection and the administration of a thyroid blocking agent were also studied as possible complements to sheltering. Specific conditions were assumed, concerning the high protection factors of regular buildings and the high availability of civil defense shelters. Computations were performed by means of a probabilistic consequence model, which allows a comprehensive description of exposure modes and processes dealing with the implementation of sheltering and which takes into account a broad range of radiological effects. Sheltering, even in regular buildings, was found to be efficient in reducing early fatalities and other non-stochastic effects. However, it was shown that respiratory protection is also needed in order to alleviate stochastic effects and that, for this purpose, expedient individual filtration methods may be satisfactory. Under the conditions studied, sheltering was found to be preferable in most cases over evacuation, as the main immediate protective measure, unless evacuation can be carried out before the radioactive cloud reaches the populated area.

Accidents↗
PubMed1989

Morphometric evaluation of human lens opacification.

A method of classifying cataractous changes in excised human lenses, based on separate and independent photographic documentation, with consequent quantitative evaluation of lens opacification is proposed. The degree of lens clouding was evaluated quantitatively by measuring the optical density index and the area of the zones of clouding with certain optical density parameters (equidensities) by use of an image analyser. This technique produced an image in which contrast represented different zones of lens clouding in the frontal projection, and allowed their contribution to the total lens area to be determined. The precise topography of the opacities was established. The classification data obtained for different clinical types of cataracts can be simplified according to the needs of the scientist in his effort to measure clinically or scientifically significant quantitative associations between laboratory measures and cataractous changes.

Aged↗
PubMed2026

SAIGE-GPU: accelerating genome- and phenome-wide association studies using GPUs.

MOTIVATION: Genome-wide association studies (GWAS) at biobank scale are computationally intensive, especially for admixed populations requiring robust statistical models. SAIGE is a widely used method for generalized linear mixed-model GWAS but is limited by its CPU-based implementation, making phenome-wide association studies impractical for many research groups. RESULTS: We developed SAIGE-GPU, a GPU-accelerated version of SAIGE that replaces CPU-intensive matrix operations with GPU-optimized kernels. The core innovation is distributing genetic relationship matrix calculations across GPUs and communication layers. Applied to 2068 phenotypes from 635 969 participants in the Million Veteran Program, including diverse and admixed populations, SAIGE-GPU achieved a 5-fold speedup in mixed model fitting on supercomputing infrastructure and cloud platforms. We further optimized the variant association testing step through multi-core and multi-trait parallelization. Deployed on Google Cloud Platform and Azure, the method provided substantial cost and time savings. AVAILABILITY AND IMPLEMENTATION: Source code and binaries are available for download at https://github.com/saigegit/SAIGE/tree/SAIGE-GPU-1.3.3. A code snapshot is archived at Zenodo for reproducibility (DOI: [10.5281/zenodo.17642591]). SAIGE-GPU is available in a containerized format for use across HPC and cloud environments and is implemented in R/C++ and runs on Linux systems.

Genome-Wide Association Study↗
PubMed1977

The clouded crystal ball and the library profession.

Growing awareness of the transition from an industrial age to a communication- and knowledge-based economy appears reflected in some changing directions in libraries. Major trends include (1) a change in management practices, (2) a realignment of operational goals away from technical processing activities to client-oriented outreach services, and (3) the identification of educational functions as a primary professional role. The twin concepts of knowledge utilization and information brokering are beginning to have an impact on the definition of the librarian's role.

Computer-Assisted Instruction↗
PubMed2003

Preliminary estimation of the rainfall chemical composition evaluated through the scavenging modeling for north-eastern Amazonian region (Amapá state, Brazil).

Numerical modeling of scavenging processes has been compared with data obtained for rainwater and aerosol chemistry at Serra do Navio, in the state of Amapá in the Brazilian Amazon region. Sulfate, nitrate and ammonium concentrations were determined in rainwater samples collected from May 1995 until June 1997. The levels of these same chemicals were also determined in aerosols for the same period and region. Scavenging processes have been evaluated on a rainfall event basis, via numerical modeling, in order to simulate the rainwater concentrations and compare them with the observed data. RAMS (Regional Atmospheric Modeling System) was used to simulate cloud structures. A model of below-cloud scavenging was evaluated, as well. The determinations made from the results of the scavenging model are the following: a) aerosol vertical profiles are quite important to rainwater concentrations; b) modeled sulfate in rainwater is a better fit to the observed data values than ammonium and nitrate; c) the obtained sulfate aerosol concentrations samples are similar to ones found in the literature, although the sulfate concentrations in rainwater are much lower than other studies in the literature; d) the in-cloud scavenging process dominates, e) our modeled results, using an input gas vertical profile extracted from the ABLE2B experimental data set, present a smaller ratio between gas and aerosol scavenging than found in other studies in the literature, other studies may have had larger rainfall times, which increase the importance of gas phase scavenging.

Aerosols↗
PubMed2001

N-Acetylcarnosine, a natural histidine-containing dipeptide, as a potent ophthalmic drug in treatment of human cataracts.

A study was designed to document and quantify the changes in lens clarity over 6 and 24 months in 2 groups of 49 volunteers (76 eyes) with an average age of 65.3 +/- 7.0 enrolled at the time of diagnosis of senile cataracts of minimal to advanced opacification. The patients received N-acetylcarnosine, 1% sol (NAC) (26 patients, 41 eyes = Group II), placebo composition (13 patients, 21 eyes) topically (two drops, twice daily) to the conjunctival sac, or were untreated (10 patients, 14 eyes); the placebo and untreated groups were combined into the control (reference) Group I. Patients were evaluated upon entry, at 2-month (Trial 1) and 6-month (Trial 2)-intervals for best corrected visual acuity (b/c VA), by ophthalmoscopy and the original techniques of glare test (for Trial 1), stereocinematographic slit-image and retro-illumination photography with subsequent scanning of the lens. The computerized interactive digital analysis of obtained images displayed the light scattering/absorbing centers of the lens into 2-D and 3-D scales. The intra-reader reproducibility of measuring techniques for cataractous changes was good, with the overall average of correlation coefficients for the image analytical data 0.830 and the glare test readings 0.998. Compared with the baseline examination, over 6 months 41.5% of the eyes treated with NAC presented a significant improvement of the gross transmissivity degree of lenses computed from the images, 90.0% of the eyes showed a gradual improvement in b/c VA to 7-100% and 88.9% of the eyes ranged a 27-100% improvement in glare sensitivity. Topographic studies demonstrated less density and corresponding areas of opacification in posterior subcapsular and cortical morphological regions of the lens consistent with VA up to 0.3. The total study period over 24 months revealed that the beneficial effect of NAC is sustainable. No cases resulted in a worsening of VA and image analytical readings of lenses in the NAC-treated group of patients. In most of the patients drug tolerance was good. Group I of patients demonstrated the variability in the densitometric readings of the lens cloudings, negative advance in glare sensitivity over 6 months and gradual deterioration of VA and gross transmissivity of lenses over 24 months compared with the baseline and 6-month follow-up examinations. Statistical analysis revealed the significant differences over 6 and 24 months in cumulative positive changes of overall characteristics of cataracts in the NAC-treated Group II from the control Group I. The N-acetylated form of natural dipeptide L-carnosine appears to be suitable and physiologically acceptable for nonsurgical treatment for senile cataracts.

Age Factors↗
PubMed1990

A therapy against vasospasm after subarachnoidal haemorrhage: clinical experience of balloon angioplasty.

Vasospasm is a phenomenon often present in human cases after subarachnoidal haemorrhage. Its aetiology and pathophysiology are unknown. As a result, cases of vasospasm do not respond to any known pharmacological therapy. We present in this paper, a practical application of intravascular surgery for vasospasm. In this procedure the requirement for a portable digital subtraction unit, transcranial Doppler sonography, and being able to determine quickly the neurological state of the patient are very important points. The use of monitoring equipment is especially indispensable during the carrying out of percutaneous transluminal angioplasty (PTA), which should be performed as soon as possible after the occurrence of vasospasm. The case of a 54-year-old male patient suffering from a ruptured anterior cerebral artery aneurysm was studied. Neck clipping was performed on the second day. On the fifth day the neurological state was stupor, and transcranial Doppler sonography (TCD) revealed a flow velocity of over 100 cm s-1. PTA was performed on the sixth day. The bilateral middle cerebral artery was dilated and the flow velocity slowed to within the normal range. The neurological state improved to clouding of consciousness after PTA. On the eighteenth day, the patient's consciousness and bilateral carotid angiograms revealed the vessels to be dilated still. It was concluded that PTA therapy, and the use of a portable digital subtraction unit and TCD sonography, for vasospasm caused by subarachnoidal haemorrhage is useful and effective.

Angioplasty, Balloon↗
PubMed1999

Cooperative symmetry-breaking by actin polymerization in a model for cell motility.

Polymerizing networks of actin filaments are capable of exerting significant mechanical forces, used by eukaryotic cells and their prokaryotic pathogens to change shape or to move. Here we show that small beads coated uniformly with a protein that catalyses actin polymerization are initially surrounded by symmetrical clouds of actin filaments. This symmetry is broken spontaneously, after which the beads undergo directional motion. We have developed a stochastic theory, in which each actin filament is modelled as an elastic brownian ratchet, that quantitatively accounts for the observed emergent symmetry-breaking behaviour. Symmetry-breaking can only occur for polymers that have a significant subunit off-rate, such as the biopolymers actin and tubulin.

Actins↗
PubMed2004

Assessment of brain tumor angiogenesis inhibitors using perfusion magnetic resonance imaging: quality and analysis results of a phase I trial.

PURPOSE: To determine thresholds of quality for a T2*-weighted perfusion magnetic resonance imaging (MRI) study and evaluate the effects of an angiogenesis inhibitor on relative blood flow and volume changes in brain tumor patients in a multi-institution setting. MATERIALS AND METHODS: A total of 36 volunteers from four participating institutions with clinically diagnosed malignant gliomas were studied using perfusion MRI protocols. These included a baseline study and follow-up studies every eight weeks to evaluate the effect of an anti-angiogenic agent on tumor perfusion. Quality tests were performed on the perfusion imaging data by defining statistical thresholds of acceptance. Region of interest (ROI) analysis was performed on tumors and kinetic parameters were normalized with respect to normal tissue. RESULTS: Statistical thresholds for goodness of the gamma variate fit, T2* recovery, and mean signal full-width half-minimum (FWHMin) were computed for our data sets with a 99% one-sided confidence interval; these were 6.91%, 79.48%, and 23.35 seconds, respectively. Decreases in-blood volume and flow measurements were observed in patients with documented clinical response. CONCLUSION: Malignant brain tumors have altered perfusion parameters that may be used to understand and monitor neovascularization. This permits non-invasive assessment of the efficacy of angiogenesis inhibiting drugs.

Angiogenesis Inhibitors↗
PubMed2005

Mesoporous benzene-silica hybrid materials with a different degree of order in the wall structure: an IR comparative study.

Recent joint IR and computational work (Onida et al. J. Phys. Chem B 2005) has allowed a detailed characterization of the isolated silanols at the surface of highly ordered benzene-silica hybrid material. In the present paper, a similar characterization is provided for a less ordered sample. The comparison permits the assignment of IR features to the interaction of silanols either with one another or with benzene rings of the structure. The extent of structural imperfections appears to be limited, for example, no more than pairs of interacting silanols are found, readily healed by thermal treatment. Evidence is also provided that probe molecules with simultaneous H-acceptor and H-donor properties (benzene, methylacetylene) may interact with both the acidic proton in silanols and the electronic cloud in the framework aromatic rings.

Benzene↗
PubMed2005

A phenomenological theory of spatially structured local synaptic connectivity.

The structure of local synaptic circuits is the key to understanding cortical function and how neuronal functional modules such as cortical columns are formed. The central problem in deciphering cortical microcircuits is the quantification of synaptic connectivity between neuron pairs. I present a theoretical model that accounts for the axon and dendrite morphologies of pre- and postsynaptic cells and provides the average number of synaptic contacts formed between them as a function of their relative locations in three-dimensional space. An important aspect of the current approach is the representation of a complex structure of an axonal/dendritic arbor as a superposition of basic structures-synaptic clouds. Each cloud has three structural parameters that can be directly estimated from two-dimensional drawings of the underlying arbor. Using empirical data available in literature, I applied this theory to three morphologically different types of cell pairs. I found that, within a wide range of cell separations, the theory is in very good agreement with empirical data on (i) axonal-dendritic contacts of pyramidal cells and (ii) somatic synapses formed by the axons of inhibitory interneurons. Since for many types of neurons plane arborization drawings are available from literature, this theory can provide a practical means for quantitatively deriving local synaptic circuits based on the actual observed densities of specific types of neurons and their morphologies. It can also have significant implications for computational models of cortical networks by making it possible to wire up simulated neural networks in a realistic fashion.

Journal Article↗
PubMed1989

Interstitial deletion 2q14q21.

A girl with multiple congenital anomalies and a tendency to severe pyogenic infections was found to have an interstitial deletion of chromosome band 2q14----q21. Unusual facial manifestations included enophthalmos, long philtrum, micrognathia, narrow forehead, prominent glabella, and depressed nasal bridge. Unilateral corneal clouding, with Peters-like anomaly; agenesis of the corpus callosum; brain atrophy; and heart, kidney, hand, and dermatoglyphic anomalies were additional findings. Eye anomalies were observed in five of 22 patients with deletions of chromosome 2q. In comparing these cases, it seems that deletions of bands 2q21 and 2q31 are variably associated with microphthalmia, corneal clouding, cataracts, and Peters anomaly. Measurement of protein C and interleukin-1 (IL-1) did not show a gene dose effect, but the pyogenic infections and low IgA found in this patient may reflect an abnormality of IL-1 not detectable by our methods.

Abnormalities, Multiple↗
PubMed2005

Re-treatment of a lung tumour using a simple intensity-modulated radiotherapy approach.

We present a lung tumour case where, although the proximal spinal cord had already reached its dose tolerance, re-treatment was indicated. Minimization of the cord dose was defined as the main constraint for this case, however additional dose to the heart was considered. A simple (4 field) intensity-modulated radiotherapy (IMRT) treatment which proved superior to the standard conformal plan was developed using the Computerized Medical Systems (CMS) XiO treatment planning system. The IMRT plan was found to be superior to the conventional conformal plan regarding tumour coverage. It provided 100% saturation of the planning target volume (PTV) by the 95% isodose cloud, whereas the latter only provided 77% coverage. A step and shoot delivery using 10 intensity levels was developed and subsequently delivered for this patient. We considered it to be a routine application of IMRT and an important example of how it can offer benefit in individual and appropriate cases where conventional treatment is inadequate.

Carcinoma, Non-Small-Cell Lung↗
PubMed1998

An unusual cause of low back pain? A case report.

STUDY DESIGN: Case report. OBJECTIVE: To highlight the evaluation of a patient with low back pain after an incidental radiographic finding clouded routine management. SUMMARY OF BACKGROUND DATA: Greenfield filters have been used for 20 years with good results. Complications have been seen and documented, but the natural history of filter placement in young patients is not fully appreciated. A prong from a Greenfield filter embedded within a vertebral body has been reported once as an incidental finding in a patient undergoing prophylactic monitoring for recurrence of tumor. METHODS: A 31-year-old woman had a pulmonary embolus after surgery for a benign adnexal mass. A bleeding complication occurred after systemic anticoagulation, and a vena caval filter was placed to limit the possibility of further emboli. The patient was referred to the orthopedic clinic 5 years later with low back pain and an unusual finding on computer tomographic scan: One prong of the filter was embedded within a vertebral body. RESULTS: A bone scan was obtained to evaluate the status of bone activity around the prong. Bone reaction was not evident. Conservative management of her low back pain was instituted, and after 2 years, the patient remains asymptomatic. CONCLUSION: The overall use of vena caval filters has produced favorable results, although numerous complications have been reported. All long-term sequelae have not been completely identified.

Adult↗
PubMed1983

Sinusitis: induced subdural empyema.

In 17 cases of sinusitis-induced subdural empyema, all but 5 occurred in boys or men aged 13 to 33 years. Clinical features were headaches and fever (14 patients), nuchal rigidity (10), and seizures (8). Seven patients had periorbital cellulitis, and 15 had radiographic clouding of at least one sinus. Only five patients had a history of sinusitis. CT identified the empyema accurately in seven patients but failed in two patients who developed subdural empyema while being treated for sinusitis-induced cerebritis. Ten patients had specific bacteriologic etiologies determined by culture of empyema, blood, or sinuses.

Adolescent↗
PubMed1990

CT of the paranasal sinuses: study of a control series in relation to endoscopic sinus surgery.

A control series of biplane CT scans of the paranasal sinuses, derived from patients examined for orbital tumours, is described. The scans were assessed for the presence of anatomical variants in the middle meatus, said to contribute to meatal stenosis, and for signs of asymptomatic infection revealed by the presence of clouding or mucosal thickening in the sinuses. Of the anatomical variants, only concha bullosa (pneumatisation of the middle turbinate) was associated with a high incidence of infection in the sinuses (85 per cent). Evidence of asymptomatic sinus infection was as high as 39 per cent overall, the highest incidence occurring in the ethmoid cells (28 per cent). Isolated ethmoid clouding on CT was observed in 15 per cent and is likely to be found in as many as one in seven of the adult population in the UK. It is concluded that in the majority of patients clouding confined to a few ethmoid cells shown on CT is without clinical significance. The evidence from the control series did not support the concept that most sinus infection starts in the middle meatus. The presence of a large reservoir of quiescent or chronic sinus infection in the control group suggests that in most instances sinusitis derives from a recrudescence of this pre-existing infection.

Endoscopy↗