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At least 253 records · Page 14Linked to original sources
PubMed2003

A polymer/semiconductor write-once read-many-times memory.

Organic devices promise to revolutionize the extent of, and access to, electronics by providing extremely inexpensive, lightweight and capable ubiquitous components that are printed onto plastic, glass or metal foils. One key component of an electronic circuit that has thus far received surprisingly little attention is an organic electronic memory. Here we report an architecture for a write-once read-many-times (WORM) memory, based on the hybrid integration of an electrochromic polymer with a thin-film silicon diode deposited onto a flexible metal foil substrate. WORM memories are desirable for ultralow-cost permanent storage of digital images, eliminating the need for slow, bulky and expensive mechanical drives used in conventional magnetic and optical memories. Our results indicate that the hybrid organic/inorganic memory device is a reliable means for achieving rapid, large-scale archival data storage. The WORM memory pixel exploits a mechanism of current-controlled, thermally activated un-doping of a two-component electrochromic conducting polymer.

Journal Article↗
PubMed2006

Structure of phase change materials for data storage.

Phase change materials based on chalcogenide alloys play an important role in optical and electrical memory devices. Both applications rely on the reversible phase transition of these alloys between amorphous and metastable cubic states. However, their atomic arrangements are not yet clear, which results in the unknown phase change mechanism of the utilization. Here using ab initio calculations we have determined the atomic arrangements. The results show that the metastable structure consists of special repeated units possessing rocksalt symmetry, whereas the so-called vacancy positions are highly ordered and layered and just result from the cubic symmetry. Finally, the fast and reversible phase change comes from the intrinsic similarity in the structures of the amorphous and metastable states.

Journal Article↗
PubMed2006

Ion trajectory simulation for electrode configurations with arbitrary geometries.

A multi-particle ion trajectory simulation program ITSIM 6.0 is described, which is capable of ion trajectory simulations for electrode configurations with arbitrary geometries. The electrode structures are input from a 3D drawing program AutoCAD and the electric field is calculated using a 3D field solver COMSOL. The program CreatePot acts as interface between the field solver and ITSIM 6.0. It converts the calculated electric field into a field array file readable by ITSIM 6.0 and ion trajectories are calculated by solving Newton's equation using Runge-Kutta integration methods. The accuracy of the field calculation is discussed for the ideal quadrupole ion trap in terms of applied mesh density. Electric fields of several different types of devices with 3D geometry are simulated, including ion transport through an ion optical system as a function of pressure. Ion spatial distributions, including the storage of positively charged ions only and simultaneous storage of positively/negatively charged ions in commercial linear ion traps with various geometries, are investigated using different trapping modes. Inelastic collisions and collision induced dissociation modeled using RRKM theory are studied, with emphasis on the fragmentation of n-butylbenzene inside an ideal quadrupole ion trap. The mass spectrum of 1,3-dichlorobenzene is simulated for the rectilinear ion trap device and good agreement is observed between the simulated and the experimental mass spectra. Collisional cooling using helium at different pressures is found to affect mass resolution in the rectilinear ion trap.

Journal Article↗
PubMed1989

[Field localization and verification system for proton beam radiotherapy in deep-seated tumors].

It has been recognized that, for precise localization and verification of radiation fields, a marking drawn on the skin surface is not entirely reliable because its position relative to bony structures or internal organs is not stationary. This is especially true when treating deep-seated tumors located below the clavicle. In proton beam radiotherapy at the University of Tsukuba, we ristrict the margins around the target volume. Therefore, special care in field localization and verification is needed, and we make it a rule to take X-ray pictures on each treatment day. To accomplish this, we have developed a localize-and-verify system by using fluoroscopic techniques and combining it with a real-time digital image processing device. This allows for the formation of a digital image of the proton field and storage it in the optic disc. By using this system as well as verification films, filed placement errors were measured in 10 patients with deep-seated tumors. Out of a total of 190 localizations, 22% exhibited a field placement error of more than 5 mm, where patient positioning and field localization were done by using skin drawings aligned with laser beams. This result strongly suggests the necessity for daily localization and verification of radiation fields, as is being done by us, for precision in the execution of proton beam radiation therapy.

Adult↗
PubMed2004

Viscoelasticity of human alveolar epithelial cells subjected to stretch.

Alveolar epithelial cells undergo stretching during breathing and mechanical ventilation. Stretch can modify cell viscoelastic properties, which may compromise the balance of forces in the alveolar epithelium. We studied the viscoelasticity of alveolar epithelial cells (A549) subjected to equibiaxial distention with a novel experimental approach. Cells were cultured on flexible substrates and subjected to stepwise deformations of up to 17% with a device built on an inverted microscope. Simultaneously, cell storage (G') and loss (G'') moduli were measured (0.1-100 Hz) with optical magnetic twisting cytometry. G' and G'' increased with strain up to 64 and 30%, respectively, resulting in a decrease in G''/G' (15%). This stretch-induced response was inhibited by disruption of the actin cytoskeleton with latrunculin A. G' increased with frequency following a power law with exponent alpha = 0.197. G'' increased proportionally to G' but exhibited a more marked frequency dependence at high frequencies. Stretching (14%) caused a fall in alpha (13%). At high stretching amplitudes, actual cell strain (14.4%) was lower than the applied substrate strain (17.3%), which could indicate a partial cell detachment. These data suggest that cytoskeletal prestress modulates the elastic and frictional properties of alveolar epithelial cells in a coupled manner, according to soft glassy rheology. Stretch-induced cell stiffening could compromise the balance of forces at the cell-cell and cell-matrix adhesions.

Actins↗
PubMed2006

High-optical-throughput individual nanoscale aperture in a multilayered metallic film.

The optical transmission of an individual subwavelength aperture in a multilayered metal film is shown to be enhanced compared with that of a homogeneous metal film. The enhancement effect is due to the light coupling to surface plasmon excitation facilitated by a film periodicity. The sensitivity of the transmission to the dielectric filling of the aperture is also shown. The latter effect can be used to switch and control the transmittance. Devices based on enhanced transmission through nanosized apertures can find applications in high-density optical and magneto-optical data storage, high-resolution microscopy, and photolithography, where nanoscale light sources with high-optical-power throughput are required, as well as in sensor applications.

Journal Article↗
PubMedDate not supplied

Digitizing stereoscopic optic nerve head photographs for storage and viewing using a personal computer.

Careful examination and monitoring of optic nerve head changes is essential in the treatment of patients with glaucoma. This often results in accumulation of numerous photographs and required appropriate storage space. A simple, inexpensive, and efficient means of storing and viewing stereoscopic optic nerve head photographs is described. Images were acquired with a fundus camera, on a color slide film. Slides were then scanned and digitized. A handheld stereoscope was used for stereoscopic viewing on a computer monitor. A scanning resolution of 300 dpi appeared optimal. At this resolution, the storage utilization was 16 kilobytes and the scanning time was 160 seconds per patient.

Computer Storage Devices↗
PubMed2004

Grid-type metal ion architectures: functional metallosupramolecular arrays.

Recent advances in supramolecular coordination chemistry allow access to transition-metal complexes of grid-type architecture comprising two-dimensional arrays of metal ions connecting a set of organic ligands in a perpendicular arrangement to generate a multiple wiring network. General design principles for these structures involve the thermodynamically driven synthesis of complex discrete objects from numerous molecular components in a single overall operation. Such supramolecular metal ion arrays combine the properties of their constituent metal ions and ligands, showing unique optical, electrochemical, and magnetic behavior. These features present potential relevance for nanotechnology, particularly in the area of supramolecular devices for information storage and processing. Thus, a dense organization of addressable units is represented by an extended "grid-of-grids" arrangement, formed by interaction of grid-type arrays with solid surfaces.

Journal Article↗
PubMed1984

Quantitative assessment of platelet morphology by light scattering: a potential method for the evaluation of platelets for transfusion.

Normal fresh platelets are discoid, and platelets that have been stored become spherical. Discoid morphology correlates with normal viability and imparts to a platelet suspension a "streaming" appearance when agitated. We developed a device that quantitates the percent of discoid cells in a suspension by means of laser light scattering at low angles. It performs this assay within 3 minutes on platelets contained in a plastic blood bag. The ability of the device to quantitate discoid platelets was demonstrated in the following ways: (1) comparison of percentage discs calculated from light-scattering data with visually observed optical streaming; (2) correlation of percentage discs from light scattering with the percentage determined by phase microscopy; and (3) observation of changes during room temperature storage. Platelet suspensions containing extreme (dendritic and balloon) forms were examined, and we conclude that these forms do not significantly affect the light-scattering assay. The optical measurements were also used to accurately approximate the total platelet counts of the suspensions. This device may have a role in the evaluation of platelets for transfusion.

Blood Platelets↗
PubMed1986

CD-ROM. A new advance in medical information retrieval.

The massive production of medical information is being met by new technologies for storing and retrieving knowledge. Recent years have witnessed the maturation of time-sharing information utilities into a full-blown industry. In medicine these services have provided bibliographic information but have recently expanded to full-text availability of journals and books. Now optical storage technology, most conspicuously the compact disk read only memory (CD-ROM), provides similar massive information storage and retrieval affordable to microcomputer users. Such devices might replace many of the functions of time-sharing.

Computers↗
PubMed2000

The historical development of cryogenically cooled monochromators for third-generation synchrotron radiation sources.

In the period of the late-1980s, before the construction of multi-GeV third-generation storage rings with their intense insertion-device sources, the perceived number one problem for X-ray instrumentation was proper cooling of the first optical element in the beamline. This article, first given as an acceptance speech for the Compton Award ceremony at the Advanced Photon Source, presents a somewhat historical and anecdotal overview of how cryogenically cooled monochromator optics have been developed to provide a monochromator cooling solution adequate for today's power levels. A series of workshops and international collaborations were the key components for the progress and final success of this development.

Journal Article↗
PubMed2000

Electrophoretic assembly of colloidal crystals with optically tunable micropatterns

The production of materials with micrometre- and submicrometre-scale patterns is of importance in a range of applications, such as photonic materials, high-density magnetic data storage devices, microchip reactors and biosensors. One method of preparing such structures is through the assembly of colloidal particles. Micropatterned colloidal assemblies have been produced with lithographically patterned electrodes or micromoulds. Here we describe a different method that combines the well-known photochemical sensitivity of semiconductors with electric-field-induced assembly to create ordered arrays of micrometre-sized colloidal particles with tunable patterns. We show that light affects the assembly processes, and demonstrate how to produce patterns using electrophoretic deposition in the presence of an ultraviolet (UV) illumination motif. The distribution of current across an indium tin oxide (ITO) electrode can be altered by varying the illumination intensity: during the deposition process, this causes colloidal particles to be swept from darkened areas into lighted regions. Illumination also assists in immobilizing the particles on the electrode surface. Although the details of these processes are not well understood, the patterning effects of the UV light are discussed in terms of alterations in the current density that affects particle assembly on an ITO electrode.

Journal Article↗
PubMed2004

Ultra-large-scale syntheses of monodisperse nanocrystals.

The development of nanocrystals has been intensively pursued, not only for their fundamental scientific interest, but also for many technological applications. The synthesis of monodisperse nanocrystals (size variation <5%) is of key importance, because the properties of these nanocrystals depend strongly on their dimensions. For example, the colour sharpness of semiconductor nanocrystal-based optical devices is strongly dependent on the uniformity of the nanocrystals, and monodisperse magnetic nanocrystals are critical for the next-generation multi-terabit magnetic storage media. For these monodisperse nanocrystals to be used, an economical mass-production method needs to be developed. Unfortunately, however, in most syntheses reported so far, only sub-gram quantities of monodisperse nanocrystals were produced. Uniform-sized nanocrystals of CdSe (refs 10,11) and Au (refs 12,13) have been produced using colloidal chemical synthetic procedures. In addition, monodisperse magnetic nanocrystals such as Fe (refs 14,15), Co (refs 16-18), gamma-Fe(2)O(3) (refs 19,20), and Fe(3)O(4) (refs 21,22) have been synthesized by using various synthetic methods. Here, we report on the ultra-large-scale synthesis of monodisperse nanocrystals using inexpensive and non-toxic metal salts as reactants. We were able to synthesize as much as 40 g of monodisperse nanocrystals in a single reaction, without a size-sorting process. Moreover, the particle size could be controlled simply by varying the experimental conditions. The current synthetic procedure is very general and nanocrystals of many transition metal oxides were successfully synthesized using a very similar procedure.

Crystallization↗
PubMed2004

Replica-molded high-Q polymer microresonators.

Ultrahigh-Q microtoroids on a chip are applied as replication masters to demonstrate replica-molded high-Q microresonator arrays. Replica Q factors are nearly material loss limited, affirming the integrity of the replication process, and are as high as 5 x 10(6), or nearly a factor of 40 greater than previous polymer-based devices. Because the molding process is nondestructive, both the master and the molds can be reused. Additionally, by using a novel optical polymer (Vicast), we demonstrate storage of high-Q microresonators in the mold for weeks, providing a method to preserve the whispering-gallery Q factor.

Journal Article↗
PubMed2006

Tuning the magnetic coupling across ultrathin antiferromagnetic films by controlling atomic-scale roughness.

Characterization and control of the interface structure and morphology at the atomic level is an important issue in understanding the magnetic interaction between an antiferromagnetic material and an adjacent ferromagnet in detail, because the atomic spins in an antiferromagnet change direction on the length scale of nearest atomic distances. Despite its technological importance for the development of advanced magnetic data-storage devices and extensive studies, the details of the magnetic interface coupling between antiferromagnets and ferromagnets have remained concealed. Here we present the results of magneto-optical Kerr-effect measurements and layer-resolved spectro-microscopic magnetic domain imaging of single-crystalline ferromagnet-antiferromagnet- ferromagnet trilayers. Atomic-level control of the interface morphology is achieved by systematically varying the thicknesses of the bottom ferromagnetic and the antiferromagnetic layer. We find that the magnetic coupling across the interface is mediated by step edges of single-atom height, whereas atomically flat areas do not contribute.

Journal Article↗
PubMed2000

Fred Hollows lecture: digital screening for eye disease.

The purpose of this study was to explore progress, in the adaptation to community screening for blinding eye disease, of digital imaging devices and technology for storage and transmission. Available imaging systems were compared to gold standard clinical photography in terms of sensitivity and specificity for diagnosis of common blinding eye conditions. Since the use of expensive non-portable imaging devices is likely to be limited for widespread community screening purposes, a portable fundus camera (Nidek, Chiyoda-ku, Japan) and a prototype monocular digital indirect ophthalmoscope constructed at the Lions Eye Institute (LEI) were selected for comparative trials for the screening of optic disc cupping, glaucoma and clinical signs of diabetic retinopathy. Fifty-one eyes of 27 consecutive patients being assessed at the LEI clinic for glaucoma were dilated and photographed with a Zeiss retinal camera, and digital images were taken with the portable Nidek NM100 fundus camera (Carl Zeiss, Oberkochen, Germany) or with a prototype digital monocular indirect ophthalmoscope. Vertical cup: disc ratios (VCDR) were measured on the disc photographs by one ophthalmologist while three other clinicians were presented with compressed digital images in random order to estimate VCDR. Field trials were also carried out to demonstrate the practicality of compression, local storage and then transmission by mobile telephone ISDN lines and satellite, of optic discs and fundus images of patients with diabetes in either rural Western Australia or Surabaya, Indonesia. Kappa values of correlations of measurement of agreement between measured and estimated VCDR were 0.87, 0.45 and 0.84, respectively, for the three observers, corresponding to a specificity of 79-97% and a sensitivity of 70-95%. The portable Nidek fundus camera was also assessed for specificity and sensitivity in the diagnosis of diabetic retinopathy in comparison to standard Zeiss fundus camera photographs. Of 49 eyes in 25 consecutive patients attending the LEI clinic for assessment of diabetic retinopathy, three ophthalmologists assessed photographs and images in random order. When used for screening diabetic retinopathy, the digital images of the Nidek camera were graded as adequate quality in only 56% of eyes compared to 93% of the photographs. The kappa value of agreement in analysis of diabetic retinopathy was only 0.30. The prototype digital monocular indirect ophthalmoscope compared favourably with the Nidek camera. At 1:5 compression, images of size 36 kB transmitted from Surabaya to Perth took 29 s on the mobile telephone, while uncompressed images took 170 s. Images compressed 1:5 were transmitted in 60 s using the satellite telephone, while the uncompressed images took 240 s. Satellite transmission was more expensive but the lines were more stable than telephone connections from Indonesia. Digital imaging is becoming a powerful tool for ophthalmology in clinical records, teaching and research, and interoffice diagnostic opinions. It also has enormous potential for community screening for blinding eye diseases, such as glaucoma and diabetic retinopathy. Inexpensive portable imaging devices that are easy to use, and on which local health workers might be trained, must be developed and validated in terms of sensitivity and specificity of performance. The technology of image capture, image compression, transmission, data base storage and analysis is rapidly evolving and becoming less expensive.

Diabetic Retinopathy↗
PubMed2002

Hand-held digital video-camera for eye examination and follow-up.

We developed a hand-held digital colour video-camera for eye examination in primary care. The device weighed 550 g. It featured a charge-coupled device (CCD) and corrective optics. Both colour video and digital still images could be taken. The video-camera was connected to a PC with software for database storage, image processing and telecommunication. We studied 88 normal subjects (38 male, 50 female), aged 7-62 years. It was not necessary to use mydriatic eye drops for pupillary dilation. Satisfactory digital images of the whole face and the anterior eye were obtained. The optic disc and the central part of the ocular fundus could also be recorded. Image quality of the face and the anterior eye were excellent; image quality of the optic disc and macula were good enough for tele-ophthalmology. Further studies are needed to evaluate the usefulness of the equipment in different clinical conditions.

Adolescent↗
PubMed1986

X ray microscopy--state of the art and expected developments.

The Göttingen X ray microscope at the electron storage ring BESSY in Berlin and X ray microscopy experiments with biological specimens are described. A look ahead to future developments--optics for higher resolution and with better efficiency, detector devices with higher detective quantum efficiency, and the development of a laboratory X ray microscope with a plasma X ray source--is taken.

Electron Probe Microanalysis↗