Multiple-scattering effects in quasielastic alpha-4He scattering

A multiple-scattering series for describing the quasielastic peak in nucleus-nucleus collisions is derived using the high-energy optical model. The effects of multiple knockout of target nucleons and internal excitation of the projectile are studied and found to be important for large energy loss and momentum transfers in inclusive alpha-4He scattering at 7 GeV/c. An approximate evaluation of higher-order inelastic collision terms is considered for forward-peaked wave functions and is demonstrated to be accurate.     

Characterisation of high Mr wheat glutenin polymers by agarose gel electrophoresis and dynamic light scattering

Agarose gel electrophoresis has been used to separate the complex mixture of wheat gluten polymers into fractions ranging in Mr, determined by dynamic light scattering, from about 500,000 to over 5x10(6). The separation is reliable and reproducible and well suited to the routine analysis of multiple samples.     

Problems in timing of respiration with the nasal thermistor technique

Twelve normal control phakic eyes together with a number of other pseudophakic groups each consisting of 6 eyes were enrolled in this study of spatial and quantitative measurement of glare disabilities in the static visual field (Perimetric Glare Test) using an OCTOPUS 500E automated perimeter with an attached glare source. These groups were a 6 mm no hole lens group, a 6 mm 4 hole lens group, a 5.5 x 6.5 mm 2 hole lens group, a 5.0 x 6.0 mm no hole lens group and a diffractive multifocal group. Glare disabilities in the visual field were minimum in the control group. The 6 mm no hole lens group and the diffractive multifocal group showed no statistical significance compared the control group. Groups with the two types of ovoid lens and the 6 mm 4 hole lens group showed a statistically higher degree and a greater extent of glare disabilities in the static visual field than the control group. Careful selection of appropriate patients to receive implants of small efficient optic IOLs, such as IOLs with positioning holes and ovoid lenses, according to the preoperative pupil size under scotopic or mesopic condition and efficient lens optic size are important in order to reduce hole and edge glare. The diffractive multifocal IOLs group showed a slightly higher degree and a greater extent of glare than the control group and the 6 mm no hole monofocal lens group but the difference was very small and statistically insignificant. Therefore the effects of diffractive microstructure on glare disabilities were considered to be slight and clinically acceptable.     

In vitro and in vivo antibacterial activities of TOC-50, a new parenteral cephalosporin, against Enterococcus faecalis

The object of the study was to compare resting pupil diameter in darkness and light, and the pupillary darkness and light reflexes between a group of young and elderly healthy subjects. Twelve young (eight men, four women; median age 19.5 years) and 14 elderly subjects (six men, eight women; median age 69 years) participated. Pupil diameter was monitored with an infra-red television pupillometer. Resting pupil size was measured in light (16 and 32 Cd m-2) and in darkness. The darkness reflex was elicited by switching off the ambient illumination (16 Cd m-2) for 1 s. The light reflex was elicited in darkness by short (200 ms) pulses of green (peak wavelength 565 nm) light at four ascending stimulus intensities (8.5 x 10(-3), 7.0 x 10(-2), 0.43 and 1.84 mW cm-2). The amplitude (mm) and maximum velocity (mm s-1) of the darkness reflex and the latency (ms), amplitude (mm), maximum constriction velocity (mm s-1) and 75% recovery time (s) of the light reflex were measured. The resting pupil diameter was found to be smaller in the elderly group at all three illumination levels (p = 0.001). The amplitude and maximum dilatation velocity of the darkness reflex were smaller for the elderly group (p = 0.001). The amplitude of the light reflex at the three highest light intensities and maximum constriction velocity at all light intensities were smaller in the elderly group (p = 0.002). Seventy-five per cent recovery time was longer in the elderly group (p = 0.02). There was no difference in the latency of the light reflex response between the two groups. The reduced pupil size, diminished darkness reflex amplitude and velocity, and prolonged recovery time of light reflex are consistent with sympathetic deficit in old age. Although the reductions in light reflex amplitude and constriction velocity in the elderly group at first sight would indicate a parasympathetic deficit in old age, they are more likely to be secondary to the grossly diminished pupil size.     

Time domain analysis of embolic signals can be used in place of high-resolution Wigner analysis when classifying gaseous and particulate emboli

The sample-volume length (SVL) of an embolic signal has previously been used to differentiate between gaseous and particulate emboli and has been calculated using high-resolution Wigner analysis. Although successful, this method of analysis is not widely available to other groups using transcranial Doppler ultrasound (TCD) to classify emboli. The SVL of embolic signals can also be calculated using time domain analysis, which is a far simpler method and potentially available to all TCD users. The aim of this study was to compare the SVL of embolic signals calculated using Wigner analysis and time domain analysis to assess whether or not time domain analysis can replace Wigner analysis to classify emboli. In total, 215 particulate and 100 gaseous emboli were recorded onto digital audiotape and analysed off-line. Two SVLs for each embolic signal were calculated by measuring embolic duration and velocity in the time domain and with Wigner analysis. Receiver operator characteristic (ROC) curves were plotted to assess the optimum SVL threshold for each method, and levels of sensitivity and specificity were defined. The optimum SVL threshold using Wigner analysis was 1.28 cm, yielding 93% sensitivity and 97% specificity. Using time domain analysis, the optimum threshold was 1.12 cm, yielding 90% sensitivity and 96% specificity. The methods were compared statistically (chi2) using their optimum thresholds, and were found not to be statistically different for classifying particles p=0.283) or gaseous emboli (p=0.700). This study has shown that the SVL of embolic signals, used to differentiate particulate from gaseous emboli, can be calculated more simply in the time domain, which yields as accurate results as calculating the SVL using Wigner analysis.     

Flow cytometric light scattering analysis, acrosome reaction, reactive oxygen species production and leukocyte contamination of semen preparation in prediction of fertilization rate in vitro

The effects on fertilization of the morphology of spermatozoa, acrosome reaction, reactive oxygen species (ROS) production, leukocyte contamination and the light scattering in flow cytometry of semen preparation were investigated in 73 couples undergoing their first in-vitro fertilization treatment. All men had normal concentrations of spermatozoa with sufficient motility (> or = 50%) and yield (> or = 6 x 10(6)) in the semen preparation on the day of oocyte retrieval. The light scattering properties of all cells present in the semen preparation, as assessed with flow cytometry, were correlated with fertilization. The proportion of metaphase I oocytes was also correlated with the fertilization rate of all collected oocytes and of metaphase II oocytes. ROS production, leukocyte contamination, spontaneous or calcium ionophore-stimulated acrosome reaction, percentage of normal morphology, and multiple anomalies index had no independent contribution.     

Heat transfer and fluid flow in the welding arc

Through the numerical solution of the Navier/Stokes equation, the energy transport equation, and the magnetic diffusion equation, a mathematical model has been developed to predict the velocity, temperature, and current density distributions in inert gas welding arcs. Although the model has one adjustable parameter, the cathode current density, it was found that a single value of this variable was sufficient to provide internally consistent results for a range of arc lengths and arc currents representative of welding. The computed temperature distributions in the arc were found to be in good agreement with spectroscopically measured temperatures taken from the literature, and similar agreement was obtained between the predicted and measured current density distributions at the surface of water cooled copper anodes. The mechanisms of heat and momentum transfer to the anode were investigated in the light of recent findings concerning the anode boundary layer and the presence of negative anode fall voltages. The predicted convective heat fluxes to the anode were found to be generally consistent with experimental data.     

Hemostasis in endodontic microsurgery

Although quantification of the lesion burden from serial MR examinations of patients with multiple sclerosis (MS) is a common technique to assess disease activity in clinical trials, pathologic change may occur within a lesion without a corresponding change in volume. Therefore, measures of lesion volume and composition may improve the sensitivity of detecting disease activity. A new technique has been developed that provides information about the intensity composition of MS lesions in standard spin-echo MR examinations. The new technique is based on the multispectral "feature space" intensity distributions of the lesions and normal tissues. Analysis of MR examinations of materials with known T1 and T2 times showed that feature space position from spin-echo examinations is largely determined from proton density (rho), T2, and the interecho delay. Information about intensity composition was obtained by reducing the multidimensional intensity distribution to one dimension while minimizing the loss of information. This technique was used to analyze eight lesions in standard spin-echo MR examinations of three patients with MS. Lesion distributions were compared between examinations by first calibrating the examinations based on the intensity distributions of cerebrospinal fluid (CSF), an internal reference tissue. Many of the lesion distributions had a distinctive peak at low intensity, corresponding to normal-appearing white matter (WM). Within the lesion distributions, increases in high intensity peaks generally were accompanied by reductions in the WM peak. Serial analysis of the lesion distributions revealed some dramatic fluctuations, even when lesion volume remained constant.     

Vesicle size distributions measured by flow field-flow fractionation coupled with multiangle light scattering

The separation method, flow field-flow fractionation (flow FFF), is coupled on-line with multiangle laser light scattering (MALLS) for simultaneous measurement of the size and concentration of vesicles eluting continuously from the fractionator. These size and concentration data, gathered as a function of elution time, may be used to construct both number- and mass-weighted vesicle size distributions. Unlike most competing, noninvasive methods, this flow FFF/MALLS technique enables measurement of vesicle size distributions without a separate refractive index detector, calibration using particle size standards, or prior assumptions about the shape of the size distribution. Experimentally measured size distributions of vesicles formed by extrusion and detergent removal are non-Gaussian and are fit well by the Weibull distribution. Flow FFF/MALLS reveals that both the extrusion and detergent dialysis vesicle formation methods can yield nearly size monodisperse populations with standard deviations of approximately 8% about the mean diameter. In contrast to the rather low resolution of dynamic light scattering in analyzing bimodal systems, flow FFF/MALLS is shown to resolve vesicle subpopulations that differ by much less than a factor of two in mean size.     

Field margin reduction using intensity-modulated x-ray beams formed with a multileaf collimator

PURPOSE: In axial, coplanar treatments with multiple fields, the superior and inferior ends of a planning target volume (PTV) are at risk to get underdosed due to the overlapping penumbras of all treatment fields. We have investigated a technique using intensity modulated x-ray beams that allows the use of small margins for definition of the superior and inferior field borders while still reaching a minimum PTV-dose of 95% of the isocenter dose. METHODS AND MATERIALS: The applied intensity modulated beams, generated with a multileaf collimator, include narrow (1.1-1.6 cm) boost fields to increase the dose in the superior and inferior ends of the PTV. The benefits of this technique have been assessed using 3D treatment plans for 10 prostate cancer patients. Treatment planning was performed with the Cadplan 3D planning system (Varian-Dosetek). Dose calculations for the narrow boost fields have been compared with measurements. The application of the boost fields has been tested on the MM50 Racetrack Microtron (Scanditronix Medical AB), which allows fully computer-controlled setup of all involved treatment fields. RESULTS: Compared to our standard technique, the superior-inferior field length can be reduced by 1.6 cm, generally yielding smaller volumes of rectum and bladder in the high dose region. For the narrow boost fields, calculated relative dose distributions agree within 2% or 0.2 cm with measured dose distributions. For accurate monitor unit calculations, the phantom scatter table used in the Cadplan system had to be modified using measured data for square fields smaller than 4 x 4 cm2. The extra time needed at the MM50 for the setup and delivery of the boost fields is usually about 1 min. CONCLUSION: The proposed use of intensity modulated beams yields improved conformal dose distributions for treatment of prostate cancer patients with a superior-inferior field size reduction of 1.6 cm. Treatments of other tumor sites can also benefit from the application of the boost fields.     

Ballistic Testing of Polymer Composites to Manufacture Emergency Safe House Shelters

Ballistic impact testing was carried out on panels of both S-2 glass/epoxy system and graphite/epoxy laminates with and without polycarbonate facing. Both the striking velocity and exit velocity were measured using magnetic sensors. The energy absorbed and the ballistic limit for each specimen were calculated using the principal of conservation of momentum. The Florence model was adopted in making theoretical prediction for the absorbed energy and the ballistic limit. The bicomponent composites have demonstrated potential concepts that can provide protection for the shelter against ballistic penetrations.     

Salt-dependent DNA superhelix diameter studied by small angle neutron scattering measurements and Monte Carlo simulations

Using small angle neutron scattering we have measured the static form factor of two different superhelical DNAs, p1868 (1868 bp) and pUC18 (2686 bp), in dilute aqueous solution at salt concentrations between 0 and 1.5 M Na+ in 10 mM Tris at 0% and 100% D2O. For both DNA molecules, the theoretical static form factor was also calculated from an ensemble of Monte Carlo configurations generated by a previously described model. Simulated and measured form factors of both DNAs showed the same behavior between 10 and 100 mM salt concentration: An undulation in the scattering curve at a momentum transfer q = 0.5 nm-1 present at lower concentration disappears above 100 mM. The position of the undulation corresponds to a distance of approximately 10-20 nm. This indicated a change in the DNA superhelix diameter, as the undulation is not present in the scattering curve of the relaxed DNA. From the measured scattering curves of superhelical DNA we estimated the superhelix diameter as a function of Na+ concentration by a quantitative comparison with the scattering curve of relaxed DNA. The ratio of the scattering curves of superhelical and relaxed DNA is very similar to the form factor of a pair of point scatterers. We concluded that the distance of this pair corresponds to the interstrand separation in the superhelix. The computed superhelix diameter of 16.0 +/- 0.9 nm at 10 mM decreased to 9.0 +/- 0.7 nm at 100 mM salt concentration. Measured and simulated scattering curves agreed almost quantitatively, therefore we also calculated the superhelix diameter from the simulated conformations. It decreased from 18.0 +/- 1.5 nm at 10 mM to 9.4 +/- 1.5 nm at 100 mM salt concentration. This value did not significantly change to lower values at higher Na+ concentration, in agreement with results obtained by electron microscopy, scanning force microscopy imaging in aqueous solution, and recent MC simulations, but in contrast to the observation of a lateral collapse of the DNA superhelix as indicated by cryo-electron microscopy studies.     

Ultra-Small-Angle X-ray Scattering—X-ray Photon Correlation Spectroscopy: A New Measurement Technique for <Emphasis Type="Italic">In-Situ</Emphasis> Studies of Equilibrium and Nonequilibrium Dynamics

Ultra-small-angle X-ray scattering—X-ray photon correlation spectroscopy (USAXS-XPCS) is a new measurement technique for the study of equilibrium and slow nonequilibrium dynamics in disordered materials. This technique fills a gap between the accessible scattering vector ranges of dynamic light scattering (DLS) and XPCS. It also overcomes the limits of visible light scattering techniques imposed by multiple scattering and is suitable for the study of optically opaque materials containing near-micrometer-sized structures. In this article, we present an overview of the important technical aspects of USAXS-XPCS and offer a few examples as well as future outlooks to illustrate the capability of USAXS-XPCS for monitoring equilibrium and nonequilibrium dynamics.     

Macromolecular diffusion of biological polymers measured by confocal fluorescence recovery after photobleaching

Fluorescence recovery after photobleaching with an unmodified confocal laser scanning microscope (confocal FRAP) was used to determine the diffusion properties of network forming biological macromolecules such as aggrecan. The technique was validated using fluorescein isothiocyanate (FITC)-labeled dextrans and proteins (molecular mass 4-2000 kDa) at 25 degrees C and with fluorescent microspheres (207 nm diameter) over a temperature range of 5-50 degrees C. Lateral diffusion coefficients (D) were independent of the focus position, and the degree and extent of bleach. The free diffusion coefficient (Do) of FITC-aggrecan determined by confocal FRAP was 4.25 +/- 0.6 x 10(-8) cm2 s-1, which is compatible with dynamic laser light scattering measurements. It appeared to be independent of concentration below 2.0 mg/ml, but at higher concentrations (2-20 mg/ml) the self-diffusion coefficient followed the function D = Do(e)(-Bc). The concentration at which the self-diffusion coefficient began to fall corresponded to the concentration predicted for domain overlap. Multimolecular aggregates of aggrecan ( approximately 30 monomers) had a much lower free diffusion coefficient (Do = 6.6 +/- 1.0 x 10(-9) cm2 s-1) but showed a decrease in mobility with concentration of a form similar to that of the monomer. The method provides a technique for investigating the macromolecular organization in glycan-rich networks at concentrations close to those found physiologically.     

Measured molecular coherent scattering form factors of animal tissues, plastics and human breast tissue

Photon scattering angular distributions from various animal tissues were measured at two energies of a monochromatic synchrotron x-ray beam. Two plastics and human breast tissue were also measured. From these two measurements, the molecular coherent scattering form factor of each material was extracted. A new data analysis technique that uses Monte Carlo based corrections for air scattering, incoherent scattering and multiple scattering was used. The form factors of the 16 materials are presented in tabular form, suitable for use in computer calculations.     

Size Distributions and Light Scattering Features of Minerogenic Particles in a Stream during Runoff Events

Inorganic (minerogenic) particles received from streams during runoff events cause undesirable increases in turbidity (Tn; i.e., the light scattering coefficient, b) in many lakes and reservoirs. Quantification of particle inputs in the context of turbidity impacts and representative light scattering calculations (submodel), the necessary components in the development of a mechanistic multiple particle class model to simulate these impacts, are described for Schoharie Creek, N.Y. Light scattering attributes of minerogenic particles, including number concentration (N), size distribution (PSD), composition, and projected area per unit volume (PAVm), are quantified for three runoff events through analyses by scanning electron microscopy interfaced with automated X-ray microanalysis and image analysis (SAX). The combined credibility of the light scattering submodel and SAX to represent the light scattering features of minerogenic particles is depicted by the consistency of calculated scattering efficiencies with theory and the strength of the reported Tn-PAVm relationship. Particles in the size range of 2–10?μm were responsible for b and Tn in the stream, with greater contributions by the larger particles of this range at elevated stream flows. Empirical relationships are developed to predict N and PSD from Tn or stream flow.     

Ex vivo light dosimetry and Monte Carlo simulations for endobronchial photodynamic therapy

The light distribution during photodynamic therapy of the bronchial tree has been estimated by measuring the fluence rate in ex vivo experiments on dissected pig bronchi. The trachea was illuminated (630 nm) with a cylindrical diffuser and the fluence rate was measured with a fibre optic isotropic probe. The experiment with the diffuser on the central axis was also simulated with Monte Carlo techniques using the optical properties that were determined with a double-integrating-sphere set-up. The results from ex vivo experiments and the Monte Carlo simulations were found to agree within the error of measurement (15%), indicating that the Monte Carlo technique can be used to estimate the light distribution for varying geometries and optical properties. The results showed that the light fluence rate in the mucosa of the tracheal tract may increase by a factor of six compared to the fluence rate in air (in the absence of tissue). This is due to the scattering properties of the tissue and the multiple reflections within the cavity. Further ex vivo experiments showed that the positioning of the diffuser is critical for the fluence rate in the lesion to be treated. When the position of the diffuser was changed from the central axis to near the lesion, the fluence rate in the mucosa increased significantly by several orders of magnitude as compared to the initial (central) illumination. The inter- and intraspecimen variations in this increase were large (+/- 35%) because of variations in optical and geometrical properties and light source positioning, respectively. These variations might cause under- or overdosage resulting in either insufficient tumour necrosis or excessive normal tissue damage.     

The molecular weights, mass distribution, chain composition, and structure of soluble fibrin degradation products released from a fibrin clot perfused with plasmin

We used a perfused clot system to study the degradation of cross-linked fibrin. Multiangle laser light scattering showed that plasmin-mediated cleavage caused the release of noncovalently associated fibrin degradation products (FDPs) with a weight-averaged molar mass (Mw) of approximately 6 x 10(6) g/mol. The Mw of FDPs is dependent on ionic strength, and the Mw observed at 0.15 M NaCl resulted from the self-association of FDPs having Mw of approximately 3.8 x 10(6) g/mol. Complete solubilization required the cleavage of approximately 25% of fragment D/fragment E connections, with 48% alpha-, 62% beta-, and 42% gamma-chains cleaved. These results showed that D-E cleavage cannot be explained by a random mechanism, implying cooperativity. Gel filtration and multiangle laser light scattering showed that FDPs range from 2.5 x 10(5) to 1 x 10(7) g/mol. In addition to fragment E, FDPs are composed of fragments ranging from 2 x 10(5) Da (D-dimer, or DD) to at least 2.3 x 10(6) Da (DX8D). FDP mass distribution is consistent with a model whereby FDPs bind to fibrin with affinities proportional to fragment mass. Root mean square radius analysis showed that small FDPs approximate rigid rods, but this relationship breaks down as FDPs size increases, suggesting that large FDPs possess significant flexibility.     

Preparation and characterization of biodegradable nanospheres composed of methoxy poly(ethylene glycol) and DL-lactide block copolymer as novel drug carriers

We synthesized amphiphilic diblock copolymer based on methoxy poly(ethylene glycol) (MePEG) and dl-lactide with different molar composition in bulk without catalyst. Using the resulting amphiphilic diblock copolymers, we prepared drug-loaded polymeric nanospheres by micelle formation through solution behavior of amphiphilic copolymer in selective solvents. The structure of MePEG/dl-lactide diblock copolymers was identified by IR, WAXD, GPC, 1H-NMR. The size of nanosphere measured by dynamic light scattering showed a narrow monodisperse size distribution and average diameter less than 200 nm. From the surface chemical composition of nanosphere by ESCA, the presence of MePEG chains on the nanosphere layers was confirmed. The critical micelle concentration of ML50 sample investigated by fluorescence spectroscopy was 1.44x10-7 mol/l which is lower than common low molecular weight surfactants. In addition, we could obtain nanospheres having a relatively high drug-loading of about 33.0% when the feed weight ratio of indomethacin to polymer was 1:1. In vitro release experiments of the indomethacin-loaded MePEG/dl-lactide nanospheres exhibited sustained release behavior without any burst effects. The results of cytotoxicity tests showed that the MePEG/dl-lactide nanospheres didn't induce any relevant cell damage.