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At least 883 records · Page 49Linked to original sources

PubMed1990

Boron neutron capture therapy of a rat glioma.

The purpose of the present study was to utilize a well-established rat glioma to evaluate boron neutron capture therapy for the treatment of malignant brain tumors. Boron-10 (10B) is a stable isotope which, when irradiated with thermal neutrons, produces a capture reaction yielding high linear energy transfer particles (10B + 1nth----[11B]----4He(alpha) + 7Li + 2.79 MeV). The F98 tumor is an anaplastic glioma of CD Fischer rat origin with an aggressive biological behavior similar to that of human glioblastoma multiforme. F98 cells were implanted intracerebrally into the caudate nuclei of Fischer rats. Seven to 12 days later the boron-10-enriched polyhedral borane, Na2B12H11SH, was administered intravenously at a dose of 50 mg/kg body weight at varying time intervals ranging from 3 to 23.5 hours before neutron irradiation. Pharmacokinetic studies revealed blood 10B values ranging from 0.33 to 10.5 micrograms/ml depending upon the time after administration, a T1/2 of 6.2 hours, normal brain 10B concentrations of 0.5 microgram/g, and tumor values ranging from 1.1 to 12.8 micrograms/g. No therapeutic gain was seen if the capture agent was given at 3 or 6 hours before irradiation with 4 x 10(12) n/cm2 (10 MW-min; 429 cGy). A 13.5-hour preirradiation interval resulted in a mean survival of 37.8 days (P less than 0.01), compared to 30.5 days (P less than 0.03) for irradiated controls and 22.1 days for untreated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2004

Optimal cutoff of the hybrid capture II human papillomavirus test for self-collected vaginal, vulvar, and urine specimens in a colposcopy referral population.

OBJECTIVE: To estimate the optimal relative light unit ratio, as a measure of viral load, of the Hybrid Capture II human papillomavirus (HPV) test in self-collected specimens for detecting cervical intraepithelial neoplasia (CIN). METHODS: Two hundred women referred for colposcopy with abnormal cytologic, self-collected vaginal and vulvar swabs and urine for HPV testing. The receiver operating characteristic (ROC) curve method was used to estimate optimal cutoffs for the Hybrid Capture II test. The reference standard was colposcopy, with directed biopsy as required. RESULTS: The estimated optimal cutoffs of the relative light unit ratio for detecting CIN 2 or higher for urine, vulvar, and vaginal samples gave sensitivities of 72.4%, 82.8%, and 89.0% and specificities of 57.0%, 52.1%, and 55.9%, respectively. At the manufacturer's recommended 1.0 cutoff, sensitivities were 44.8%, 62.1%, and 86.2% for urine, vulvar, and vaginal samples, with specificities of 69.7%, 62.7%, and 53.5%, respectively. The likelihood ratios (likelihood of being truly positive after a positive test result) were similar for the optimal and the 1.0 cutoff. CONCLUSIONS: The ROC curve methods did not improve the overall diagnostic accuracy of the Hybrid Capture II test compared with the 1.0 relative light unit ratio cutoff.

Journal Article↗

PubMed2003

High proteinase 3-anti-neutrophil cytoplasmic antibody (ANCA) level measured by the capture enzyme-linked immunosorbent assay method is associated with decreased patient survival in ANCA-associated vasculitis with renal involvement.

Wegener granulomatosis (WG) and microscopic polyangiitis (MP), diseases associated with antineutrophil cytoplasmic antibodies (ANCA), had an extremely poor prognosis before the introduction of cyclophosphamide and corticosteroids for their treatment. However, there is still reduced patient survival, and some studies have documented severe side effects of the immunosuppressants used. This 10-yr follow-up study assessed 117 consecutive patients with WG or MP with biopsy-confirmed renal involvement. The cumulative relative patient survival was lower: 0.664 for women and 0.648 for men. The causes of death (n = 64) were in most cases registered as associated with the vasculitic disease. Analysis of possible predictive factors for patient survival by multiple Cox regression analysis revealed that a very high level of proteinase 3 (PR3)-ANCA measured by the capture ELISA method, a diagnosis of MP, and older age were factors predicting poorer patient survival. High levels of B-thrombocytes at time of diagnosis were associated with a better prognosis. For patients surviving the first year, remission-sustaining therapy with azathioprine for longer than 12 mo was associated with improved patient survival. Thirty-nine patients developed end-stage renal failure. Elevated serum creatinine at time of diagnosis and a very high level of PR3-ANCA by capture ELISA were factors predicting a higher risk for renal failure during follow-up. The epitope on PR3 assessed by capture ELISA needs to be further analyzed and explored: it seemed to implicate poorer patient and renal survival in WG or MP with renal involvement.

Adolescent↗

PubMed2004

Evasive mimicry: when (if ever) could mimicry based on difficulty of capture evolve?

We elucidate the conditions under which an easy-to-catch edible prey species may evolve to resemble another edible species that is much more difficult to capture ('evasive Batesian mimicry'), and the conditions under which two or more edible but hard-to-catch species evolve a common resemblance ('evasive Mullerian mimicry'). Using two complementary mathematical models, we argue that both phenomena are logically possible but that several factors will limit the prevalence of these forms of mimicry in nature. Evasive Batesian mimicry is most likely to arise when it is costly in time or energy for the predator species to pursue evasive prey, when mimics are encountered less frequently than evasive models and where there are abundant alternative prey. Evasive Mullerian mimicry, by contrast, is most likely to arise when evasive prey species differ in abundance, predators are slow to learn to avoid evasive prey and evading capture is costly to the prey. Unequivocal evidence for evasive Batesian or Mullerian mimicry has not yet been demonstrated in the field, and we argue that more empirical work is needed to test whether putative examples are indeed a result of selection to signal difficulty of capture.

Adaptation, Physiological↗

PubMed1989

Use of an antigen-capture assay for characterisation of monoclonal antibodies to mycobacterial lipoarabinomannan.

Monoclonal antibodies directed to six separate antigen molecules of Mycobacterium leprae have been tested in an antigen-capture assay based on combined use of polyclonal ("capture") and monoclonal ("detector") antibody reagents. This approach provides a potentially versatile, sensitive and specific assay for detection and relative quantitation of M. leprae antigens. Characterisation of monoclonal antibodies to mycobacterial lipoarabinomannan (LAM-B) by the antigen-capture assay indicates that some of the antigenic determinants present on LAM-B from M. leprae may be either absent altogether or present at much lower concentrations on the corresponding LAM-B structure form M. tuberculosis.

Antibodies, Monoclonal↗

PubMed2002

Microtubule capture by the cleavage apparatus is required for proper spindle positioning in yeast.

Cell division is the result of two major cytoskeletal events: partition of the chromatids by the mitotic spindle and cleavage of the cell by the cytokinetic apparatus. Spatial coordination of these events ensures that each daughter cell inherits a nucleus. Here we show that, in budding yeast, capture and shrinkage of astral microtubules at the bud neck is required to position the spindle relative to the cleavage apparatus. Capture required the septins and the microtubule-associated protein Kar9. Like Kar9-defective cells, cells lacking the septin ring failed to position their spindle correctly and showed an increased frequency of nuclear missegregation. Microtubule attachment at the bud neck was followed by shrinkage and a pulling action on the spindle. Enhancement of microtubule shrinkage at the bud neck required the Par-1-related, septin-dependent kinases (SDK) Hsl1 and Gin4. Neither the formin Bnr1 nor the actomyosin contractile ring was required for either microtubule capture or microtubule shrinkage. Together, our results indicate that septins and septin-dependent kinases may coordinate microtubule and actin functions in cell division.

Actomyosin↗

PubMed2005

Excitation of multiphase waves of the nonlinear Schrödinger equation by capture into resonances.

A method for adiabatic excitation and control of multiphase ( N -band) waves of the periodic nonlinear Schrödinger (NLS) equation is developed. The approach is based on capturing the system into successive resonances with external, small amplitude plane waves having slowly varying frequencies. The excitation proceeds from zero and develops in stages, as an (N+1) -band (N=0,1,2,...) , growing amplitude wave is formed in the (N+1) th stage from an N -band solution excited in the preceding stage. The method is illustrated in simulations, where the excited multiphase waves are analyzed via the spectral approach of the inverse scattering transform method. The theory of excitation of 0- and 1-band NLS solutions by capture into resonances is developed on the basis of a weakly nonlinear version of Whitham's averaged variational principle. The phenomenon of thresholds on the driving amplitudes for capture into successive resonances and the stability of driven, phase-locked solutions in these cases are discussed.

Journal Article↗

PubMed2006

Analytical model of magnetic nanoparticle transport and capture in the microvasculature.

An analytical model is presented for predicting the transport and capture of therapeutic magnetic nanoparticles in the human microvasculature. The nanoparticles, with surface bound drug molecules, are injected into the vascular system upstream from malignant tissue, and are captured at the tumor site using a local applied magnetic field. The applied field is produced by a rare-earth cylindrical magnet positioned outside the body. An analytical expression is derived for predicting the trajectory of a particle as it flows through the microvasculature in proximity to the magnet. In addition, a scaling relation is developed that enables the prediction of the minimum particle radius required for particle capture. The theory takes into account the dominant magnetic and fluidic forces, which depend on the position and properties of the magnet, the size and magnetic properties of the nanoparticles, the dimensions of the microvessel, the hematocrit level of the blood, and the flow velocity. The model is used to study noninvasive drug targeting, and the analysis indicates that submicron particles can be directed to tumors that are several centimeters from the field source.

Antineoplastic Agents↗

PubMed2000

Electron capture by the image charge of a metal nanoparticle

We have measured absolute cross sections for the capture of low-energy electrons by large free sodium nanoclusters ( approximately 10(4) atoms, or 4 nm radius). To explain the results, it is necessary to go beyond the commonly used induced-dipole approximation and to employ the full image-charge interaction potential which accounts for the finite size of the particle. This potential yields an exact analytical expression for the capture cross section and leads to good agreement with the data. It is suggested that electron capture may provide a useful tool for size characterization of nanoparticle beams.

Journal Article↗

PubMed2001

Rate-equation approach to island capture zones and size distributions in epitaxial growth.

Understanding and predicting the effects of correlations between island size and the rate of monomer capture has been shown to be the central problem in predicting the island-size distribution in submonolayer growth. Here we summarize a method which involves a self-consistent coupling of evolution equations for the capture-zone distributions with rate equations for the island-size distribution. The method has been successfully applied to irreversible submonolayer growth in both one and two dimensions to predict the size-dependent capture numbers and island-size distributions.

Journal Article↗

PubMed2001

Total, partial, and electron-capture cross sections for ionization of water vapor by 20-150 keV protons.

We present experimental results for proton ionization of water molecules based on a novel event by event analysis of the different ions produced (and lost). We are able to obtain mass analyzed product ion signals (e.g., H2O+, OH+, O+, O++, H+) in coincidence with the projectile analyzed after the collision, i.e., either being H+, neutral H after single electron capture during the ionization event, or H- after double electron capture. After proper calibration we are thus able to determine a complete set of cross sections for the ionization of a molecular target by protons including the total and the partial cross sections and in addition also the direct ionization and the electron capture cross sections.

Journal Article↗

PubMed2003

Effect of collective response on electron capture and excitation in collisions of highly charged ions with fullerenes.

Projectile deexcitation Lyman x-ray emission following electron capture and K excitation has been studied in collisions of bare and Li-like sulphur ions (of energy 110 MeV) with fullerenes (C(60)/C(70)) and different gaseous targets. The intensity ratios of different Lyman x-ray lines in collisions with fullerenes are found to be substantially lower than those for the gas targets, both for capture and excitation. This has been explained in terms of a model based on "solidlike" effect, namely, wakefield induced stark mixing of the excited states populated via electron capture or K excitation: a collective phenomenon of plasmon excitation in the fullerenes under the influence of heavy, highly charged ions.

Journal Article↗

PubMed2003

Consequences of nuclear electron capture in core collapse supernovae.

The most important weak nuclear interaction to the dynamics of stellar core collapse is electron capture, primarily on nuclei with masses larger than 60. In prior simulations of core collapse, electron capture on these nuclei has been treated in a highly parametrized fashion, if not ignored. With realistic treatment of electron capture on heavy nuclei come significant changes in the hydrodynamics of core collapse and bounce. We discuss these as well as the ramifications for the postbounce evolution in core collapse supernovae.

Journal Article↗

PubMed2004

Capture into resonance: a method for efficient control.

To achieve large changes in adiabatic invariants using small control input, a conservative dynamical system must possess an internal resonance. Capture into resonance is an inherently probabilistic process. We propose a control method to make it more structured. We study the motion of charged particles in an electromagnetic field as an example of such a system. When the nominal dynamics brings particles close to a resonance surface, a short control pulse forces the capture of a particle into the resonance with the wave. A captured particle is transported by the wave across the energy levels. The second pulse releases a particle from the resonance when the desired energy level is achieved. We discuss the distribution of energy achieved by the method.

Journal Article↗

PubMedDate not supplied

Real-time 3D human capture system for mixed-reality art and entertainment.

A real-time system for capturing humans in 3D and placing them into a mixed reality environment is presented in this paper. The subject is captured by nine cameras surrounding her. Looking through a head-mounted-display with a camera in front pointing at a marker, the user can see the 3D image of this subject overlaid onto a mixed reality scene. The 3D images of the subject viewed from this viewpoint are constructed using a robust and fast shape-from-silhouette algorithm. The paper also presents several techniques to produce good quality and speed up the whole system. The frame rate of our system is around 25 fps using only standard Intel processor-based personal computers. Besides a remote live 3D conferencing and collaborating system, we also describe an application of the system in art and entertainment, named Magic Land, which is a mixed reality environment where captured avatars of human and 3D computer generated virtual animations can form an interactive story and play with each other. This system demonstrates many technologies in human computer interaction: mixed reality, tangible interaction, and 3D communication. The result of the user study not only emphasizes the benefits, but also addresses some issues of these technologies.

Art↗

PubMed2002

Causal capture: contextual effects on the perception of collision events.

In addition to perceiving the colors, shapes, and motions of objects, observers can perceive higher-level properties of visual events. One such property is causation, as when an observer sees one object cause another object to move by colliding with it. We report a striking new type of contextual effect on the perception of such collision events. Consider an object (A) that moves toward a stationary object (B) until they are adjacent, at which point A stops and B starts moving along the same path. Such "launches" are perceived in terms beyond these kinematics: As noted in Michotte's classic studies, observers perceive A as being the cause of B's motion. When A and B fully overlap before B's motion, however observers often see this test event as a completely noncausal "pass": One object remains stationary while another passes over it. When a distinct launch event occurs nearby, however, the test event is "captured": It too is now irresistibly seen as causal. For this causal capture to occur, the context event need be present for only 50 ms surrounding the "impact," but capture is destroyed by only 200 ms of temporal asynchrony between the two events. We report a study of such cases, and others, that help define the rules that the visual system uses to construct percepts of seemingly high-level properties like causation.

Adult↗

PubMed2002

Evidence for attentional capture by a surprising color singleton in visual search.

Three experiments were conducted to investigate whether surprising color singletons capture attention. Participants performed a visual search task in which a target letter had to be detected among distractor letters. Experiments 1 and 2 assessed accuracy as the dependent variable. In Experiment 1, the unannounced presentation of a color singleton 500 ms prior to the letters (and in the same position as the target letter) resulted in better performance than in the preceding conjunction search segment, in which no singleton was presented, and performance was as good in this surprise-singleton trial as in the following feature search segment, in which the singleton always coincided with the target. In contrast, no improvement was observed when the color singleton was presented simultaneously with the letters in Experiment 2, indicating that attentional capture occurred later in the surprise trial than in the feature search segment. In Experiment 3, set size was varied, and reaction time was the dependent variable. Reaction time depended on set size in the conjunction search segment, but not in the surprise trial nor in the feature search segment. The results of the three experiments support the view that surprising color singletons capture attention independently of a corresponding attentional set.

Adult↗

PubMed1999

The use of mixed logit models to reflect heterogeneity in capture-recapture studies.

We examine issues in estimating population size N with capture-recapture models when there is variable catchability among subjects. We focus on a logistic-normal mixed model, for which the logit of the probability of capture is an additive function of a random subject and a fixed sampling occasion parameter. When the probability of capture is small or the degree of heterogeneity is large, the log-likelihood surface is relatively flat and it is difficult to obtain much information about N. We also discuss a latent class model and a log-linear model that account for heterogeneity and show that the log-linear model has greater scope. Models assuming homogeneity provide much narrower intervals for N but are usually highly overly optimistic, the actual coverage probability being much lower than the nominal level.

Animals↗