Coherence Volume Research Articles

Optical Coherence Tomography Retinal Thickness and Volume Measurements in X-Linked Retinoschisis

To analyze retinal thickness and volume measurements of X-linked retinoschisis patients by spectral-domain optical coherence tomography (SD OCT) and correlate these findings with visual acuity and patient age. Retrospective comparative case series. Sixty-three eyes of 33 male patients with X-linked retinoschisis were gleaned from a SD OCT database at the University of Illinois at Chicago. Forty-one eyes of 21 patients with low refractive error, no visualimpairment, and no known retinal disease served as age-similar controls. The mean age of the retinoschisis patients was 26.4 years. The mean age of patient controls was 30.0 years. Full-thickness, inner and outer retina thickness, and volume measurements were determined by SD OCT. Foveal schisis was observed in 81% of retinoschisis patients. Patients with foveal schisis tended to be younger than patients lacking foveal schisis. Inner and outer foveal thickness and volume measurements were increased in retinoschisis patients compared to controls. Outer retinal perifoveal and parafoveal thicknesses and volumes were consistently increased in retinoschisis patients relative to controls. In contrast, inner retinal perifoveal and parafoveal thickness and volume measurements were decreased in retinoschisis patients compared to controls. Worse visual acuity correlated with thinning of the temporal perifoveal inner retina and thickening of the inner fovea. Full-thickness measurements and inner retina and outer retina thickness and volume measurements tended to decrease with patient age. Increased inner retinal foveal thickness and decreased perifoveal inner retinal thickness correlates with worse visual acuity and overall retinal thickness decreases with age in X-linked retinoschisis.

Book Review: Universities and Colleges as Economic Drivers

With so much written on the topic of the impact of universities on economic development, one could question the contributions that could result from yet another edited volume on this topic. Despite the crowded literature, this book is a valuable contribution of well-written chapters on specific topics that connect together to form a coherent volume. Although Universities and Colleges as Economic Drivers is the product of a 2011 SUNY conference, the book speaks to issues of national concern of interest to higher education professionals, economic development practitioners, state policy makers, and those interested in the relationship between universities and economic development. Following a foreword byNancy Zimpher, chancellor of the State University of New York, the book has 10 chapters that address particular aspects of the relationship between higher education and economic development. A dominant theme of the book is the challenge in measuring the myriad ways universities contribute to economic growth and development, as almost eve1y chapter concludes with a call for better measures andmore data to clarity this relationship. The first chapter by Lane shows that there is growing international recognition that universities are important to economic growth in developed innovation-based economies but that much more work is needed to measure the economic development contributions of universities. The chapter shows that many universities now place economic development as a central element of their institutional mission. This chapter is followed by a contribution by Gais and Wright that provides a good summary of the various ways that universities contribute to economic development. Such ways include the role of universities as spender and consumer, the contribution universities make to human capital development, research and development (R&D) and entrepreneurship, business assistance such as through providing business services and student workers, and supporting community vitality. The chapter does miss the important role that universities make in providing leadership to regional economic development activities and perhaps being the catalyst for changing regional economic development trajectories.

Microstructure of the Nialv Alloys Subjected to the Hpt Deformation

Some attention in physical metallurgy is devoted to the mechanisms of decomposition of the disordered phases via eutectoid transformation accompanied by the atomic ordering. In case of the non-pearlitic modes of transformation this concerns intermetallic phases of the general description A3B-A3C. The application of intensive deformation like HPT may introduce opposite mechanisms introducing some degree of the metastable disordered phase structure at room temperature. The paper presents results of the phase composition and microstructure studies of the alloys of composition Ni75AlxVy (where x =15, 10, 5 and y =10, 15, 20), which undergo the solid-state eutectoid decomposition at temperature 1281 K, in the equilibrium conditions. The alloys achieved by the cold crucible levitation method were later intensively deformed with the method of high pressure torsion (HPT). The alloys after HPT revealed homogenous, metastable L12 (Ni3Al) structure in place of the eutectoid product L12-D022. The average size of the Sherrer’s coherent diffraction volumes did not exceed 9 nm, suggesting nano-structure of the material. Transmission electron microscopy (TEM) and high resolution electron microscopy (HRTEM) revealed that the micro- and nano- deformation twins were the main feature of the microstructure, dividing volume into cells of the sizes similar to the coherent volumes. The HPT deformation did not influence atomic order. The results are compared with those achieved for the injection cast samples.

Measurement of the full distribution of persistent current in normal-metal rings.

We have measured the persistent current in individual normal metal rings over a wide range of magnetic fields. From this data, we extract the first six cumulants of the single-ring persistent current distribution. Our results are consistent with the prediction that this distribution should be nearly Gaussian for diffusive metallic rings. This measurement highlights the sensitivity of persistent current to the mesoscopic fluctuations within a single isolated coherent volume.

School-age effects of the newborn individualized developmental care and assessment program for preterm infants with intrauterine growth restriction: preliminary findings

BackgroundThe experience in the newborn intensive care nursery results in premature infants’ neurobehavioral and neurophysiological dysfunction and poorer brain structure. Preterms with severe intrauterine growth restriction are doubly jeopardized given their compromised brains. The Newborn Individualized Developmental Care and Assessment Program improved outcome at early school-age for preterms with appropriate intrauterine growth. It also showed effectiveness to nine months for preterms with intrauterine growth restriction. The current study tested effectiveness into school-age for preterms with intrauterine growth restriction regarding executive function (EF), electrophysiology (EEG) and neurostructure (MRI).MethodsTwenty-three 9-year-old former growth-restricted preterms, randomized at birth to standard care (14 controls) or to the Newborn Individualized Developmental Care and Assessment Program (9 experimentals) were assessed with standardized measures of cognition, achievement, executive function, electroencephalography, and magnetic resonance imaging. The participating children were comparable to those lost to follow-up, and the controls to the experimentals, in terms of newborn background health and demographics. All outcome measures were corrected for mother’s intelligence. Analysis techniques included two-group analysis of variance and stepwise discriminate analysis for the outcome measures, Wilks’ lambda and jackknifed classification to ascertain two-group classification success per and across domains; canonical correlation analysis to explore relationships among neuropsychological, electrophysiological and neurostructural domains at school-age, and from the newborn period to school-age.ResultsControls and experimentals were comparable in age at testing, anthropometric and health parameters, and in cognitive and achievement scores. Experimentals scored better in executive function, spectral coherence, and cerebellar volumes. Furthermore, executive function, spectral coherence and brain structural measures discriminated controls from experimentals. Executive function correlated with coherence and brain structure measures, and with newborn-period neurobehavioral assessment.ConclusionThe intervention in the intensive care nursery improved executive function as well as spectral coherence between occipital and frontal as well as parietal regions. The experimentals’ cerebella were significantly larger than the controls’. These results, while preliminary, point to the possibility of long-term brain improvement even of intrauterine growth compromised preterms if individualized intervention begins with admission to the NICU and extends throughout transition home. Larger sample replications are required in order to confirm these results.Clinical trial registrationThe study is registered as a clinical trial. The trial registration number is NCT00914108.

Plasmonic enhancement of High Harmonic Generation revisited: Predominance of Atomic Line Emission

We demonstrate nanostructure-enhanced extreme ultraviolet fluorescence from noble gases driven by low-energy, few-cycle light pulses. Despite suffi cient local inten- sities, plasmon-enhanced high harmonic generation is not observed, which follows from the small, nanometer-size coherent source volume.

Imaging subtle faults using azimuthal coherence attribute: A case study from Central Saudi Arabia

ABSTRACT The coherence attribute is an edge detection method that is widely used for interpreting faults on 3-D seismic time slices. The traditional coherence attribute is calculated on migrated volumes using traces from all available azimuths. It has recently been shown that calculating coherence along specific azimuths can enhance the detection of faults running perpendicular to those azimuths. In this study, we applied azimuthal coherence attribute analysis on a 3-D seismic data set from a gas field in Central Saudi Arabia. We generated four migrated 3-D data volumes sorted by azimuth in addition to a conventional full-azimuth volume. We then calculated the coherence attribute for all volumes and compared each azimuthal coherence volume to the conventional full-azimuth coherence volume. The azimuthal coherence results exhibited an improved definition for faults whose strikes are perpendicular to the sorting azimuth. More specifically, systems of NW-trending discontinuities were imaged more clearly in the NE-SW oriented coherence volume than it was in the full-azimuth coherence volume. The reason for this enhancement is the fact that seismic waves tend to avoid passing through the fault when they propagate parallel to the fault strike therefore missing the effects of the fault while they must pass through the fault when propagating perpendicular to the fault strike which results in better illumination of the fault.

Heart‐beat‐phase‐coherent Doppler optical coherence tomography for measuring pulsatile ocular blood flow

We introduce a Doppler OCT (DOCT) platform that is fully synchronized with the heart-beat via a pulse oximeter. The system allows reconstructing heart-beat-phase-coherent quantitative DOCT volumes. The method is to acquire a series of DOCT volumes and to record the pulse in parallel. The heartbeat data is used for triggering the start of each DOCT volume acquisition. The recorded volume series is registered to the level of capillaries using a cross-volume registration. The information of the pulse phase is used to rearrange the tomograms in time, to obtain a series of phase coherent DOCT volumes over a pulse. We present Doppler angle independent quantitative evaluation of the absolute pulsatile blood flow within individual retinal vessels as well as of the total retinal blood flow over a full heartbeat cycle.

Application of Different Algorithms to Predict the Faults and Fractures in Carbonate Formation

The application of coherent cube and volume curvature algorithm to analyze and process the three-dimensional seismic data of Ordovician carbonate rocks in the Tazhong area of Tarim Basin, and to predict the faults and fractures development. After the comparison, coherent cube algorithm is fit for prediction of main faults development with the clear result in oilfield exploration stage , volume curvature algorithm is fit for prediction of faults and fractures development with the abundant information in oilfield development stage. Therefore, according to different purposes of exploration and development, different algorithms could be applied to prediction of faults and fractures. This would be useful to guide the oilfield exploration and development.

Partially coherent light-emitting diode illumination for video-rate in-line holographic microscopy

The light of a light-emitting diode or a common thermal source, such as a tungsten filament lamp, is known to be quasi-incoherent. We generated partially coherent light of these sources with a volume of coherence in the micrometer range of 5-100 μm3 by spatial and spectral filtering. The corresponding degree of partial coherence was adapted for microscopic interference setups, such as a digital in-line holographic microscope. The practicability of the sources was determined by the spectral emittance and the resulting signal-to-noise ratio (SNR) of the detector. The microscale coherence in correlation with the SNR and its resolution for microscopy were analyzed. We demonstrate how low-light-level, non-laser sources enable holographic imaging with a video frame rate (25 frames/s), an intermediate SNR of 8 dB, and a volume of coherence of 3.4×10(4) μm3. Holograms of objects with a lateral resolution of 1 μm were achieved using a microscope lens (50×/NA=0.7) and a CCD camera featuring a 4-12 bit dynamic range.

Dimensional transition and carrier dynamics in CdxZn1−xTe/ZnTe nanostructures on Si substrates

We investigate the dimensional transition and carrier dynamics in CdxZn1−xTe/ZnTe nanostructures with various Cd mole fractions, grown on Si substrates. Atomic force microscopy images show that the dimensional transition from quantum dots (QDs) to quantum wires occurs with increasing Cd mole fraction. The activation energy of the electrons confined in CdxZn1−xTe QDs with a Cd mole fraction of 0.6 is higher than that of electrons confined in CdxZn1−xTe nanostructures. In addition, the radiative recombination rate shows a linear dependence on the length of the CdxZn1−xTe nanostructures, which is well explained in terms of the “coherence volume” of the bound excitons.

Critical dimensions of highly lattice mismatched semiconductor nanowires grown in strain-releasing configurations

Growing large defect-free semiconductor nanowires (NW) on lattice-mismatched substrates is important for solar cell applications. Here, we evaluate the critical dimensions of NWs in several strain-releasing growth configurations of interest to experimentalists. We quantify the expected increase in NW volume that may be grown coherently for NWs stacked on lattice mismatched pillars and embedded quantum dot (QD) layers, compared to NWs grown on simple substrates. We also calculate the variations in strain energy for NWs positioned off-axis from embedded QDs, as may occur during fabrication. We predict significant increases in coherent NW volume allowing greater absorption efficiency in solar cells.

Photorefractive properties for holographic application of Ce:Fe:LiNbO3 crystals with various [Li]/[Nb] ratios

Ce:Fe:LiNbO3 crystals with various [Li]/[Nb] ratios were grown by the Czochralski method from melts having compositions varying between 48.6 and 58 mol% Li2O. The Ce, Li and Nb concentrations in the grown Ce:Fe:LiNbO3 crystals were analyzed by the inductively coupled plasma atomic emission spectrometer (ICP-AES). It was found that as the [Li]/[Nb] ratio increases in the melt, the [Li]/[Nb] ratio in the crystal and the distribution coefficients of Ce ions increase also. The photorefractive properties of the Ce:Fe:LiNbO3 crystals were experimentally studied by the two-wave coupling method. The results show that as the [Li]/[Nb] ratio increases, the dynamic range decreases, but the photorefractive sensitivity and the signal-to-noise ratio improve. In a coherent volume 0.192 cm3 of a Ce:Fe:LiNbO3 crystal with [Li]/[Nb] ratio of 1.2, 3800 holograms with 800×600 pixels have been successfully multiplexed in a compact volume holographic data storage system.

Interpretation of the hydrogen anomaly in neutron and electron compton scattering

AbstractIn Compton scattering with neutrons in the energy range 20–120 eV, it has been observed that the relative H/M cross sections in a variety of H‐containing materials are 20–40% lower than expected from the composition ratio H/M (M being a heavier element in the same compound). The same phenomenon has also been observed in Compton scattering with electrons of 2 and 20 keV energy. There is, at present, no consensus about the reason for these anomalies. In this theory, they are explained as a result of interference when the scattering particle interacts with more than one hydrogen nucleus. The coherence volume of the actual setup, which limits the number of interfering particles, is therefore an important parameter. It is shown here that the large zero‐point motion of the hydrogen nuclei leads to reductions in the scattering intensity from interfering pairs. Coherence is preserved over the sub‐fs scattering times relevant for this process, even in the condensed systems studied. It is gradually lost when the scattering time is increased, which happens when the neutron energy is reduced (as reflected in lower anomalies for smaller scattering angles). Explicit expressions for the decoherence effect are presented and compared with experimental observation for a selection of observed H‐ and D‐containing systems. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012

Spectral domain optical coherence tomography for higher precision in the evaluation of vitreoretinal adhesions in exudative age-related macular degeneration

AimThe role of changes at the vitreoretinal interface and vitreomacular traction forces in pathogenesis, and the course of exudative age-related macular degeneration (AMD) need further exploration. This study examines the...

Transition from coherent mesoscopic single-particle transport to Josephson proximity current

The transport through a metal-superconductor interface is governed by a special charge conversion process, the Andreev reflection, where each incident electron drags another electron with itself to form a Cooper pair. At the normal side a hole is left behind dressed by superconducting correlations. For a low transparency interface the simultaneous transfer of two charges is strongly suppressed leading to a reduced conductance. Here we demonstrate that this reduced conductance can be turned to an infinite one by tuning the nanoscale geometry. Creating variable size nanojunctions between a thin metallic film and a superconducting tip we study how multiple phase-coherent scatterings enhance the superconducting correlations at the normal side. By increasing the coherent volume of carriers initially the transmission through the interface is continuously enhanced. However, as the phase-coherent volume reaches the opposite surface of the thin film a resonator is formed, and a robust transition is induced due to Cooper pair condensation.

Single-electron pulses for ultrafast diffraction

Visualization of atomic-scale structural motion by ultrafast electron diffraction and microscopy requires electron packets of shortest duration and highest coherence. We report on the generation and application of single-electron pulses for this purpose. Photoelectric emission from metal surfaces is studied with tunable ultraviolet pulses in the femtosecond regime. The bandwidth, efficiency, coherence, and electron pulse duration are investigated in dependence on excitation wavelength, intensity, and laser bandwidth. At photon energies close to the cathode's work function, the electron pulse duration shortens significantly and approaches a threshold that is determined by interplay of the optical pulse width and the acceleration field. An optimized choice of laser wavelength and bandwidth results in sub-100-fs electron pulses. We demonstrate single-electron diffraction from polycrystalline diamond films and reveal the favorable influences of matched photon energies on the coherence volume of single-electron wave packets. We discuss the consequences of our findings for the physics of the photoelectric effect and for applications of single-electron pulses in ultrafast 4D imaging of structural dynamics.

Theory of magnon-driven spin Seebeck effect

The spin Seebeck effect is a spin-motive force generated by a temperature gradient in a ferromagnet that can be detected via normal metal contacts through the inverse spin Hall effect [K. Uchida {\it et al.}, Nature {\bf 455}, 778-781 (2008)]. We explain this effect by spin pumping at the contact that is proportional to the spin-mixing conductance of the interface, the inverse of a temperature-dependent magnetic coherence volume, and the difference between the magnon temperature in the ferromagnet and the electron temperature in the normal metal [D. J. Sanders and D. Walton, Phys. Rev. B {\bf 15}, 1489 (1977)].

John Magilton, Frances Lee and Anthea Boylston (eds), ‘Lepers outside the gate’: excavations at the cemetery of the Hospital of St James and St Mary Magdalene, Chichester, 1986–87 and 1993, Chichester Excavations vol. 10, CBA Research Report 158, York, Council for British Archaeology, 2008, pp. xxiii, 294, illus., and CD-ROM, £40.00 (paperback 978-1-9-0277-1-74-8).

Though a long time in the making, a volume on the leprosy hospital of St James and St Mary Magdalene in Chichester has finally arrived. This book is an interim account and claims to be the largest published sample of an English leprosarium and almshouse. The cemetery dates from the twelfth to the seventeenth century with two distinct phases of use. The leprosarium phase (area A) dates from the twelfth to the late fifteenth century with 126 mainly male individuals. The second phase (area B) is the almshouse phase and dates from the late fifteenth to the seventeenth century with 258 individuals showing a typical demographic profile. The work is divided into four sections to allow readers of different backgrounds to access their topic of particular interest with ease. The main chapters deal with: leprosy hospitals in general, the history and archaeology of the hospital in Chichester, the human skeletal remains, and, finally, an overview of the results. Magilton places the archaeological findings in their social context thus allowing an appreciation of the implications of the disease in society and the attitudes held by the clergy, physicians and the population in general. He successfully links the history to osteology by drawing on the results of the skeletal analysis discussed in later chapters. I expected the book to be somewhat fragmentary given the large number of authors involved (ten in all), but this is not the case; there are connections between the chapters so that they form a largely coherent volume. It does not matter that some topics are repeated as this allows the reader to select specific chapters. I was somewhat confused about the extent of the osteological analysis carried out by each researcher but assume that all research was based on the demographic profiles generated on the enclosed CD, while each author carried out his or her own analysis of the individual topics discussed in the various chapters. Two chapters (Donald Ortner, and Frances Lee and Keith Manchester) in particular address the topic of leprosy and its diagnosis. Ortner provides a well considered account of previous diagnosis of leprosy and the problems of differential diagnosis. He also discusses the terminology that should be used for describing signs of the disease in skeletal material. This chapter is an excellent guideline for osteologists who wish to learn more about how to recognize leprosy and the pitfalls in doing so. Lee and Manchester provide a more general account of the condition, including the effects on the soft tissue followed by a discussion of the cases in the Chichester sample. Some chapters are perhaps less relevant to the topic of leprosy, but none the less provide an insight into the work carried out on the skeletal collection in general. Some discussions on other diseases such as trauma, joint disease and cranial asymmetry attempt to link their findings to the overarching topic of leprosy. Unfortunately the chapters fail to explain if the analyses were made with leprosy as the prime consideration from the outset or whether these are retrospective considerations. The book is aimed at a general readership, with the bonus of a CD for those particularly interested in the archaeology and osteology of the site. A comprehensive glossary of medical terms has been provided for the reader, less familiar with the terminology of skeletal analysis. The CD provides an individual breakdown of all the skeletons included in the book and is the way forward for any publication of such magnitude, though it might have been more beneficial to provide the individual skeletal data in a more quantifiable medium such as a spreadsheet. The final discussion is in fact a summary of the main findings in each chapter and provides a good overview. One could have wished for a slightly more extended discussion drawing together the chapters and the future research potential of the material. Despite the monumental task of bringing together all the different strands of research, overall this volume is very readable. It provides an excellent insight into the historical and archaeological research on leprosy undertaken to date.

Three-dimensional imaging of strain in a single ZnO nanorod

Nanoscale structures can be highly strained because of confinement effects and the strong influence of their external boundaries. This results in dramatically different electronic, magnetic and optical material properties of considerable utility. Third-generation synchrotron-based coherent X-ray diffraction has emerged as a non-destructive tool for three-dimensional (3D) imaging of strain and defects in crystals that are smaller than the coherence volume, typically a few cubic micrometres, of the available beams that have sufficient flux to reveal the material's structure. Until now, measurements have been possible only at a single Bragg point of a given crystal because of the limited ability to maintain alignment; it has therefore been possible to determine only one component of displacement and not the full strain tensor. Here we report key advances in our fabrication and experimental techniques, which have enabled diffraction patterns to be obtained from six Bragg reflections of the same ZnO nanocrystal for the first time. All three Cartesian components of the ion displacement field, and in turn the full nine-component strain tensor, have thereby been imaged in three dimensions.