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At least 307 records · Page 17Linked to original sources
PubMed2004

Effect of University of Wisconsin organ-preservation solution on haemorheology.

In conventional cold-storage organ preservation, the donor organ is flushed with University of Wisconsin (UW) solution at 0-4 degrees C. The initial flush is used to wash out blood from the microcirculation to allow optimal preservation with the UW solution. The component hydroxyethyl starch (HES) of UW is known to cause relatively high viscosity and a possible interaction with blood, i.e. increased red blood cell (RBC) aggregation. The aim of this study was to investigate the influence of the HES component on the viscosity of UW and the aggregation behaviour of blood during washout. Viscosity aspects were measured with a cone-plate rheometer. HES-induced RBC aggregation was studied by means of an optical aggregation measuring device. The experiments were carried out with rat whole blood and mixtures of rat whole blood with UW-solution and UW without HES (UWmod), at 4 degrees C. The viscosity of blood at 4 degrees C is two-times higher than at 37 degrees C; the UW/blood mixture at 4 degrees C is 1.3-times more viscous than blood at 37 degrees C; the 4 degrees C UWmod/blood mixture equals the viscosity of blood at 37 degrees C. The UW/blood mixture shows a ninefold increased aggregation compared with whole blood. These aggregates are larger than the diameter of the sinusoids in the rat liver. A mixture of whole blood and UWmod shows a lower aggregation than blood. Apart from an increased viscosity, HES in UW causes increased RBC aggregation. The aggregates are larger than the diameter of the sinusoids. Initial washout could be optimised by pre-flushing to improve the viability of the liver and to decrease delayed graft function.

Adenosine↗
PubMed1996

Short communication: use of the output video signal for dynamic range, brightness control and image memory assessment in X-ray fluoroscopy.

The output video signal from three X-ray fluoroscopy machines was recorded with a storage oscilloscope to calculate the dynamic range of their image intensifier television camera chains. The two MERATE MTH90 and MGR50hf machines employed the same imaging chain but the response of the former to exposure was significantly lower because of a three channel light distribution optical system which was installed but not used. The CGR Stenoscope machine was found to have a very narrow dynamic range to the extent that it was not usable. Additional measurements on the CGR machine showed that the image intensifier brightness control mechanism would produce stabilized brightness in less than 0.4 s and it proved to be faster than the manual selection of exposure parameters. The quality of the image stored in the memory device on the same system was compared with the original by subtracting the two video signals on the oscilloscope and thus acquiring a quantitative measure of their difference.

Fluoroscopy↗
PubMed2002

Optimization of bacteriorhodopsin for bioelectronic devices.

Bacteriorhodopsin (BR) is the photoactive proton pump found in the purple membrane of the salt marsh archaeon Halobacterium salinarum. Evolution has optimized this protein for high photochemical efficiency, thermal stability and cyclicity, as the organism must be able to function in a hot, stagnant and resource-limited environment. Photonic materials generated via organic chemistry have yet to surpass the native protein in terms of quantum efficiency or cyclicity. However, the native protein still lacks the overall efficiency necessary for commercial viability and virtually all successful photonic devices using bacteriorhodopsin are based on chemical or genetic variants of the native protein. We show that genetic engineering can provide significant improvement in the device capabilities of proteins and, in the case of bacteriorhodopsin, a 700-fold improvement has been realized in volumetric data storage. We conclude that semi-random mutagenesis and directed evolution will play a prominent role in future efforts in bioelectronic optimization.

Bacteriorhodopsins↗
PubMed2000

Soft-mode hardening in SrTiO3 thin films

Understanding the behaviour of the dielectric constant in ferroelectric thin films remains a challenging problem. These ferroelectric materials have high static dielectric constants, and so are important for their applications in high-storage-density capacitor structures such as dynamic random access memory (DRAM). But the dielectric constant tends to be significantly reduced in thin films, thereby limiting the potential benefit of ferroelectrics for memory devices. Extensive studies have shown that this phenomenon could be caused by a 'dead layer' of very low dielectric constant between the ferroeletric film and the electrode. And, although very few direct measurements are in fact available, it has been recognized that the lattice dynamical properties in the thin films should also play a key role in the reduction of the dielectric constant. Here we report far-infrared ellipsometry and low-frequency dielectric measurements in SrTiO3 thin films, which demonstrate that the Lyddane-Sachs-Teller relation between the optical-phonon eigenfrequencies and the dielectric constant is fully maintained, as is the case in the bulk material. This indicates that the dramatic reduction of the dielectric constant is a consequence of a profound change of the lattice dynamical properties, in particular of the reduced softening of its lowest optical-phonon mode. Our results therefore provide a better understanding of the fundamental limitations of the dielectric constant values in ferroelectric thin films.

Journal Article↗
PubMed1991

Network system: the integrated picture archiving and communication system with the hospital information system.

We describe the outline of Hokkaido University picture archiving and communication system (HU-PACS) and its network functions. HU-PACS processes 0.5 Gbytes of images daily through 10 acquisition devices. Functional integration of hospital information system (HIS) and PACS has been implemented. The HU-PACS can access common data base with HIS. Multi-image data-base systems provide fast throughput of image retrieval. The system is composed of 4 modules: (1) 2 image data-base systems (IDS), (2) 1 image management system (IMS), (3) image display terminals (IDT), and (4) 8 image acquisition nodes interfaced to 10 modalities and 1 film scanner. These 4 modules are connected by branch and loop type local area networks (LAN). HU-PACS has functions other than basic PACS functions. Images in optical disk library (ODL) are loaded onto magnetic disks (MD) in advance according to patient booking information, the images expected to be viewed are transferred to the local storage automatically, and the desired images can be pre-downloaded into local storage by instruction through HIS terminals.

Computer Communication Networks↗
PubMed1978

[Experience in application of electronic data processing in routine medical microbiology (author's transl)].

Experiences in a two years application of electronic data processing in medical routine microbiology are reported. Optical mark reader forms serve as request forms as well as workprotocol. On the left two thirds of these forms (Fig. 1 and 2) the patients data including clinical statements, and the kind of specimen to be investigated (sputum, smear etc.) as well as results not essential for the printout of laboratory reports are filled in. On the right third of the optical mark reader form, in which area the Bell & Howell document reader can read pencil marks, the patients identification number, the tests requested and all results are marked right at the work bench. As shown in the flow diagram (Fig. 3) after completion of the investigation the date on the mark reader forms are read mechanically and the test results are printed (Fig. 5) by means of the computer. In addition, the data processing system, which proved to be very flexible, performs all necessary types of administrative work as filing of laboratory data in a coded form on cards for permanent storage (Fig. 7) statistics and the printout of bills (Fig. 6). The processing of routine microbiology date is achieved by a Siemens DVA 404/3 (64 kbt) connected for magnetic disc device (2993 Mio bytes), and a line printer (60,000 lines per hour) and dialog display monitors, which are used simultaneously for the on line and off line handling of all the data in clinical chemistry-, serology- and hematology-departments of the same institute.

Computers↗
PubMed2006

Direct electronic measurement of the spin Hall effect.

The generation, manipulation and detection of spin-polarized electrons in nanostructures define the main challenges of spin-based electronics. Among the different approaches for spin generation and manipulation, spin-orbit coupling--which couples the spin of an electron to its momentum--is attracting considerable interest. In a spin-orbit-coupled system, a non-zero spin current is predicted in a direction perpendicular to the applied electric field, giving rise to a spin Hall effect. Consistent with this effect, electrically induced spin polarization was recently detected by optical techniques at the edges of a semiconductor channel and in two-dimensional electron gases in semiconductor heterostructures. Here we report electrical measurements of the spin Hall effect in a diffusive metallic conductor, using a ferromagnetic electrode in combination with a tunnel barrier to inject a spin-polarized current. In our devices, we observe an induced voltage that results exclusively from the conversion of the injected spin current into charge imbalance through the spin Hall effect. Such a voltage is proportional to the component of the injected spins that is perpendicular to the plane defined by the spin current direction and the voltage probes. These experiments reveal opportunities for efficient spin detection without the need for magnetic materials, which could lead to useful spintronics devices that integrate information processing and data storage.

Journal Article↗
PubMed2001

Management of the picture archiving and communications system archive at Texas Children's Hospital.

As hospitals convert from conventional film-based imaging to picture archival and communications systems (PACS), methods for managing an enormous library of images must change considerably. While most hospitals are required to retain general, nonmammographic, radiologic images for 7 years beyond the examination date, our pediatric hospital must maintain images until the child's eighteenth birthday, plus the 5-year statute of limitations. Although the physical extent of an electronic archive is tiny compared with a film archive, a long-range strategy is required to ensure that electronic images acquired today can be retrieved and viewed 23 years in the future. Challenges to the long-term stability of the electronic archive include the limited and uncertain shelf life of high-density electronic storage media, the finite maintainability of the electromechanical systems for reading the media, the short product lifetime of software for accessing the images, rapid development of higher density storage products, and the exponential advancement of computer and networking technology that fuels product obsolescence. Since we cannot assure the function of our current archive in two decades, we are committed to a continual process of migration of old electronic image data to newer media and systems. As an early-adopter of PACS technology, Texas Children's Hospital's (TCH) archive management experience is relevant to others. Although not filled to capacity, our first digital archive, based on phase-change write-once-read-many (WORM) technology, was forced into an inactive status by software and hardware changes. Our second set of archives was partially filled with low-density magneto-optical disk (MOD) media, when the drives were upgraded to high density and then filled to capacity. This undesirable situation forced us into shelf management of media. Our third-generation archive is based on a helical tape library with the capacity to contain 7 years of examinations. We will describe the motivation for data migration, limitations in the methods available to perform the migration, and unanticipated benefits of the migration process.

Computer Communication Networks↗
PubMed2006

An aluminium nitride light-emitting diode with a wavelength of 210 nanometres.

Compact high-efficiency ultraviolet solid-state light sources--such as light-emitting diodes (LEDs) and laser diodes--are of considerable technological interest as alternatives to large, toxic, low-efficiency gas lasers and mercury lamps. Microelectronic fabrication technologies and the environmental sciences both require light sources with shorter emission wavelengths: the former for improved resolution in photolithography and the latter for sensors that can detect minute hazardous particles. In addition, ultraviolet solid-state light sources are also attracting attention for potential applications in high-density optical data storage, biomedical research, water and air purification, and sterilization. Wide-bandgap materials, such as diamond and III-V nitride semiconductors (GaN, AlGaN and AlN; refs 3-10), are potential materials for ultraviolet LEDs and laser diodes, but suffer from difficulties in controlling electrical conduction. Here we report the successful control of both n-type and p-type doping in aluminium nitride (AlN), which has a very wide direct bandgap of 6 eV. This doping strategy allows us to develop an AlN PIN (p-type/intrinsic/n-type) homojunction LED with an emission wavelength of 210 nm, which is the shortest reported to date for any kind of LED. The emission is attributed to an exciton transition, and represents an important step towards achieving exciton-related light-emitting devices as well as replacing gas light sources with solid-state light sources.

Journal Article↗
PubMed1988

Electronic imaging in endoscopy.

Endoscopy evolved from a hollow tube view of visually restricted areas into an expansive, distal representation of the anatomy. Rod lens telescopes, improved coherent imaging bundles, superior light sources, and other optical advances enhanced endoscopic observations. Yet complicated endoscopic procedures remained visible to the endoscopist alone, relegating assistance and consultation to verbal description of sophisticated visual observation. Instrumentational advances alone did not promote three crucial elements: participation, cooperation and documentation. The importance of these elements has increased with the need for coordinated assistance in complex operative endoscopic manipulations, as well as in a visual record for improved documentation and consultation. New imaging technologies are supplanting the unwieldy, often daunting equipment once required for photodocumentation. The charged couple device (CCD) 2/3 and 1/2 in. "chip" video camera miniaturization provides nearly weightless TV coobservation. Distal chip placement has created the "video endoscope". Combined with the 8 mm tape format, the chip has created a lightweight, single unit camera, monitor, and recorder. A recent advantage, magnetic disc recording, permits still video storage of up to 25 images. An electronic printer produces a hard color copy (4 x 5), which is inserted in the chart before the patient leaves the endoscopy room. The cost of the equipment can be shared in multidisciplinary institutions.

Costs and Cost Analysis↗
PubMed2004

Subwavelength-scale tailoring of surface phonon polaritons by focused ion-beam implantation.

Recent advances in optical nanotechnologies by controlling surface plasmon polaritons in metallic nanostructures demonstrate high potential for subwavelength-scale waveguiding of light, data storage, microscopy or biophotonics. Surprisingly, surface phonon polaritons-infrared counterparts to surface plasmon polaritons-have not been widely explored for nanophotonic applications. As they rely on the infrared or terahertz excitation of lattice vibrations in polar crystals they offer totally different material classes for nanophotonic applications, such as semiconductors and insulators. In an initial step towards nanoscale surface phonon photonics we show evidence that the local properties of surface phonon polaritons can be tailored at a subwavelength-scale by focused ion-beam modification of the crystal structure, even without significant alteration of the surface topography. Such single-step-fabricated, monolithic structures could be used for controlling electromagnetic energy transport by surface phonon polaritons in miniaturized integrated devices operating at infrared or terahertz frequencies. We verify the polaritonic properties of an ion-beam-patterned SiC surface by infrared near-field microscopy. The near-field images also demonstrate nanometre-scale resolved infrared mapping of crystal quality useful in semiconductor processing or crystal growth.

Carbon Compounds, Inorganic↗
PubMed2004

Magnetic phase control by an electric field.

The quest for higher data density in information storage is motivating investigations into approaches for manipulating magnetization by means other than magnetic fields. This is evidenced by the recent boom in magnetoelectronics and 'spintronics', where phenomena such as carrier effects in magnetic semiconductors and high-correlation effects in colossal magnetoresistive compounds are studied for their device potential. The linear magnetoelectric effect-the induction of polarization by a magnetic field and of magnetization by an electric field-provides another route for linking magnetic and electric properties. It was recently discovered that composite materials and magnetic ferroelectrics exhibit magnetoelectric effects that exceed previously known effects by orders of magnitude, with the potential to trigger magnetic or electric phase transitions. Here we report a system whose magnetic phase can be controlled by an external electric field: ferromagnetic ordering in hexagonal HoMnO3 is reversibly switched on and off by the applied field via magnetoelectric interactions. We monitor this process using magneto-optical techniques and reveal its microscopic origin by neutron and X-ray diffraction. From our results, we identify basic requirements for other candidate materials to exhibit magnetoelectric phase control.

Journal Article↗
PubMed2004

Prolonged intracranial pressure (ICP) monitoring in non-traumatic pediatric neurosurgical diseases.

BACKGROUND: A limited number of studies have addressed the methods, indications and particular problems that may occur when programming prolonged intracranial pressure (ICP) monitoring in pediatric patients. Parenchymal fiberoptic transducers have been shown to give reliable ICP readings; moreover, they present a relatively low rate of complications, are easily placed and, as they are solid state, they are not subject to obstruction. MATERIAL/METHODS: A recently developed fiberoptic ICP transducer (Codman intraparenchymal sensor) was used to continuously monitor intracranial pressure in seventy children with non-traumatic neurosurgical diseases. The admitting diagnoses were hydrocephalus or shunt-related problems in 33 cases, single-suture (5 cases) or complex (16 cases) craniosynostosis in 21 patients, and sylvian scissure arachnoid cyst (SAC) in 16 cases. A software (ICP monitoring release) designed in our department was used for ICP recording storage and analysis. RESULTS: Raised ICP values were found in six of the seventeen patients with a suspected active hydyrocephalus, 24% of children with non-syndromic craniosynostosis, 52.8% of syndromic craniosynostosis patients, 50% or the children with a Type 11 SAC and two of the three patients with Type II SAC. CONCLUSIONS: Overall, prolonged ICP monitoring proved to be extremely useful in guiding surgical indications. The fiberoptic device used in our unit was shown to be reliable and associated with a relatively low rate of complications. Finally, the software allowed easy review and analysis of the obtained data.

Arachnoid Cysts↗
PubMed2005

Ultrafast non-thermal control of magnetization by instantaneous photomagnetic pulses.

The demand for ever-increasing density of information storage and speed of manipulation has triggered an intense search for ways to control the magnetization of a medium by means other than magnetic fields. Recent experiments on laser-induced demagnetization and spin reorientation use ultrafast lasers as a means to manipulate magnetization, accessing timescales of a picosecond or less. However, in all these cases the observed magnetic excitation is the result of optical absorption followed by a rapid temperature increase. This thermal origin of spin excitation considerably limits potential applications because the repetition frequency is limited by the cooling time. Here we demonstrate that circularly polarized femtosecond laser pulses can be used to non-thermally excite and coherently control the spin dynamics in magnets by way of the inverse Faraday effect. Such a photomagnetic interaction is instantaneous and is limited in time by the pulse width (approximately 200 fs in our experiment). Our finding thus reveals an alternative mechanism of ultrafast coherent spin control, and offers prospects for applications of ultrafast lasers in magnetic devices.

Journal Article↗
PubMed2006

Early opacification of silicone intraocular lenses: Laboratory analyses of 6 explants.

PURPOSE: To report laboratory analyses of 6 intraocular lenses (IOLs) explanted from patients who had visual disturbances caused by early postoperative opacification of the lens optic. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. METHODS: Six patients with 3-piece silicone lenses presented with optic cloudiness as early as a few hours after implantation. The lenses were implanted in 4 locations in Brazil and in France. The lenses in Brazil were stored at the same location before implantation. Gross and microscopic analyses were performed (dry and hydrated states). One half of each specimen underwent gas chromatography/mass spectrometry (GC/MS) analysis and/or extraction by isopropyl alcohol or acetonitrile. One lens also underwent scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS). The IOLs were examined for the presence of contaminants or deposits that could cause fast optic opacification. RESULTS: The IOLs showed a white optic discoloration in the hydrated state but became transparent on complete dehydration. Suspect exogenous chemical compounds were identified in GC/MS analyses; general classes included terpenes and ketones, typically found in industrial cleaning agents and fumigants. Surface analysis (SEM and EDS) did not show any significant deposits on the external surfaces and sagittal cut in 1 of the specimens. CONCLUSIONS: Most IOLs are enclosed in semipermeable packages to allow sterilization by ethylene oxide gas. During cleaning or disinfection of storage rooms, aerosolized solutions may introduce chemicals through the package and onto the IOLs. This may cause surface changes in the IOL, promoting opacification by water ingress in the aqueous environment. Cleaning and disinfection procedures of IOL storage areas should be monitored carefully.

Aged↗
PubMed1995

Clinical use of a digital simulator for rapid setup verification in high dose rate brachytherapy.

PURPOSE: Fractionated high dose rate (HDR) brachytherapy provides a number of technical advantages over conventional implant therapy in that (a) it can be carried out on an outpatient basis, (b) personnel exposure is reduced to insignificant levels, and (c) patient motion during irradiation is minimized, resulting in a more accurate delivery of the planned radiation dose distribution to the target and critical structures. The patient discomfort associated with the repeated applicator insertions and/or treatment setups can be alleviated to the extent that the setup time is held to a minimum. This work describes the use of a prototype digital simulator to obtain fast, high-quality digital images for rapid setup verification. METHODS AND MATERIALS: The digital imaging system of the prototype simulator consists of a charge-coupled device (CCD) camera, which views the x-ray image optically transmitted from a conventional phosphor screen. Treatment is carried out with a remote afterloading HDR unit immediately after setup verification with the patient on the simulator stretcher. The high-resolution digital images are processed and displayed in about 5 s, as opposed to a minimum of approximately 2 min for film. RESULTS: The imaging system has been evaluated for a variety of implant types, both intracavitary and interstitial. The digital radiographs provided permanent high-resolution images as required in most cases for precise applicator positioning. The gray scale manipulation capabilities were found to be useful for imaging in regions of different density, such as lung and soft tissue, in the same radiograph. The advantages of short image acquisition and display times were observed in all cases, but were most evident in the intraluminal procedures, which sometimes involved several pretreatment applicator adjustments at a time of considerable patient discomfort. CONCLUSION: Pretreatment imaging is necessary to fully exploit the technical advantages of HDR brachytherapy. High-quality digital radiography offers unique advantages in HDR setup and verification by providing fast high-resolution, undistorted images with software manipulation capabilities and permanent storage of images.

Brachytherapy↗
PubMed1992

Quantitative optical determination of the viability of platelet concentrates.

An optical method to assess platelet viability in platelet transfusion concentrates has been developed which is based on the observation that healthy, discoid platelets transmit more light in shear flow than aged, spherical cells. Using a specially designed glass channel, the rise in transmission of light through platelet samples with agitation is referenced against a measurement of transmission without flow. Referencing the measurements may minimize the effects of red blood cell contamination, as well as other variations among platelet packs such as plasma characteristics and plastic container variability. At an optimal frequency of agitation, the ratio of the transmission of light with agitation to that of the sample at rest is found to correlate highly with the concentration of discoid platelets, r = 0.92 to 0.95 (P less than 0.001), for light sources including a HeNe laser and two LEDs. Using this index, the discoid platelet counts of twelve platelet packs are estimated and compared with manual counts. The mean difference between the two methods was 0.009 x 10(9) discoid platelets ml-1 with a standard deviation of 0.11 x 10(9) cells ml-1. We conclude that the method may be applied to the development of a non-invasive device to monitor the concentration of viable, discoid platelets in storage.

Blood Platelets↗
PubMed2005

Feedback system of a liquid-nitrogen-cooled double-crystal monochromator: design and performances.

A new set-up is reported of an indirect cryogenic cooling system for a double-crystal monochromator which runs on the BM30b/FAME beamline at the ESRF (Grenoble, France). This device has been conceived to limit the vibrations on the first diffracting crystal and to maintain it at a constant temperature. These points are crucial for maximizing the beamline stability. Moreover, the relative angular position of the second crystal can be dynamically adjusted by a piezoelectric transducer coupled with a feedback system in order to always be at the maximum of the rocking curve during an X-ray absorption spectroscopy scan. The temperature is stabilized to an accuracy of 0.01 degrees , with two principal consequences. The energy resolution is close to the theoretical value [DeltaE/E = 5.6 x 10(-6) for Si(220)] and the precision of the energy positioning is extremely good even if the power load changes. A feedback mechanism allows a permanent and automatic optimization of the angle between the two crystals of the monochromator. The intensity of the monochromatic beam remains optimized (i) when the intensity of the electron beam decreases in the storage ring and (ii) during an energy scan.

Cryopreservation↗