Insights into the Silver Reflection Layer of a Vertical LED for Light Emission Optimization

In this work, Ag as a highly reflective mirror layer of gallium nitride (GaN)-based blue vertical light-emitting diodes (VLEDs) has been systematically investigated by correlating scanning electron microscopy/energy dispersive X-ray spectroscopy/transmission Kikuchi diffraction/electron backscatter diffraction, aberration-corrected scanning transmission electron microscopy, and atomic force microscopy techniques. In the context of high-efficiency lighting, three critical aspects have been scrutinized on the nanoscale: (1) chemical diffusion, (2) grain morphology, and (3) surface topography of the Ag layer. We found that nanoscale inhomogeneous distribution of In in InGaN/GaN quantum wells (QWs), interfacial diffusion (In/Ga out-diffusion into the Ag layer and diffusion of Ag into p-GaN and QWs), and Ag agglomeration deteriorate the light reflectivity, which account for the decreased luminous efficiency in VLEDs. Meanwhile, the surface morphology and topographical analyses revealed the nanomorphology of the Ag layer, where a nanograin size of ∼300 nm with special nanotwinned boundaries and an extremely smooth surface of ∼3-4 nm are strongly desired for better reflectivity. Further, on the basis of these microscopy results, suggestions on light extraction optimization are given to improve the performance of GaN-based blue VLEDs. Our findings enable fresh and deep understanding of performance-microstructure correlation of LEDs on the nanoscale, providing guidance to the design and manufacture of high-performance LED devices.

Learning preferences and learning styles: a study of Wessex general practice registrars

BACKGROUND

Experienced trainers know that individual registrars react very differently to identical learning experiences generated during the year in practice. This divergence reflects differences in registrars' learning styles. Only one study of United Kingdom (UK) general practitioners' learning styles has been undertaken. Learning style theory predicts that matching learning preference with learning style will enhance learning. This paper researches for the first time the evidence in the setting of UK general practice.

AIM

To determine, for the general practice registrars within the Wessex Region, the nature of their learning preferences and learning styles and correlations between them.

DESIGN OF STUDY

A descriptive confidential postal questionnaire survey.

SETTING

Fifty-seven registrars identified in the Wessex Region with a minimum experience of six months in general practice.

METHOD

The questionnaire gathered demographic data (sex, age, experience in general practice, years post-registration, and postgraduate qualifications). Learning preferences were elicited using a six-point Likert scale for learning experiences. The Honey and Mumford Learning Style Questionnaire (LSQ) elicited the registrars' learning styles. A second questionnaire was sent to non-responders.

RESULTS

The response rate was 74%. Registrars report that interactive learning with feedback is preferred, but more passive learning formats remain valued. A wide range of learning style scores was found. The Honey and Mumford LSQ mean scores fell within the reflector-theorist quadrant. Evidence for correlations between learning preferences and learning styles was also found, in particular for the multiple choice question and audit components of summative assessment.

CONCLUSION

A wide range of registrar learning styles exists in Wessex, and initial correlations are described between learning preferences and learning styles as predicted by style theory. This work sets the stage for a shared understanding and use of learning style theory to enhance professional learning throughout a GP's career. More research is needed in this domain.

Cloning and characterization of a secreted frizzled-related protein that is expressed by the retinal pigment epithelium

The Wnt/frizzled cell signaling pathway has been implicated in the determination of polarity in a number of systems, including the Drosophila retina. The vertebrate retina develops from an undifferentiated neuroepithelium into an organized and laminated structure that demonstrates a high degree of polarity at both the tissue and cellular levels. In the process of searching for molecules that are preferentially expressed by the vertebrate retinal pigment epithelium (RPE), we identified secreted frizzled-related protein 5 (SFRP5), a member of the SFRP family that appears to act by modulating Wnt signal transduction. SFRP5 is highly expressed by RPE cells, and is also expressed in the pancreas. Within the retina, the related molecule SFRP2 is expressed specifically by cells of the inner nuclear layer. Thus, photoreceptors are likely to be bathed by two opposing gradients of SFRP molecules. Consistent with SFRP5 's postulated role in modulating Wnt signaling in the retina, it inhibits the ability of Xwnt-8 mRNA to induce axis duplication in Xenopus embryos. The human SFRP5 gene consists of three coding exons and it maps to chromosome 10q24.1; human SFRP2 maps to 4q31.3. Based on the biology and complementary expression patterns of SFRP2 and SFRP5, we suggest that they may be involved in determining the polarity of photoreceptor, and perhaps other, cells in the retina.

Identification of significant variation in the composition of lipophosphoglycan-like molecules of E. histolytica and E. dispar

The lipophosphoglycan-like (LPG-like) molecules of E. histolytica virulent strains are clearly distinct from those of the avirulent E. histolytica and E. dispar strains. Abundant 'LPG' levels are apparently limited to virulent strains, while lipophosphopeptidoglycans ('LPPG's) are common to both virulent and avirulent strains of E. histolytica and E. dispar. It is therefore conceivable that 'LPPG' performs a function that is essential to survival within the host, while the 'LPG' performs a more specific function related to virulence.

Virulent and avirulent Entamoeba histolytica and E. dispar differ in their cell surface phosphorylated glycolipids

Virulent strains of Entamoeba histolytica have been reported to produce a mixture of phosphoglycoconjugates that share some structural features with the lipophosphoglycans (LPGs) of Leishmania. Purification of these glycoconjugates is essential to their precise structural characterization. In this study we have extracted 'LPG-like' molecules from various virulent E. histolytica strains and purified on the basis of charge differences, 2 apparently related glycoconjugates a 'LPG' and a 'lipophosphopeptidoglycan (LPPG)'. In marked contrast to the abundance of these 'LPG' and 'LPPG' molecules in the virulent strains, avirulent E. histolytica and E. dispar strains produce either very low, or no detectable levels of LPG, and either low levels or modified forms of 'LPPG'. Monospecific polyclonal antibodies prepared against that 'LPG' of the virulent strain HM-1:1MSS c16 identified epitopes shared between both the 'LPG' and the 'LPPG' of this and other virulent strains, using Western blot analysis. Flow cytometric analysis of a range of strains using these antibodies identified a surface distribution of these molecules and confirmed a correlation between surface exposure of epitopes bound by these antibodies and parasite virulence.

Studies of copper transport in cultured bovine chondrocytes

Copper serves as the cofactor for a number of important enzymes in cartilage, as well as in other tissues, including lysyl oxidase, superoxide dismutase, and cytochrome oxidase. Ceruloplasmin is responsible for the transport of approx. 95% of the copper in serum, but the mechanisms for intracellular copper transport are unknown. We have demonstrated recently that a high-molecular-weight cartilage glycoprotein, referred to as CMGP, has regions of sequence homology with ceruloplasmin. CMGP also binds copper and has at least some oxidase activity similar to that of ceruloplasmin. Other tissues synthesize intracellular ceruloplasmin-like proteins. The present report represents part of an effort to examine the hypothesis that CMGP is a copper transport protein in chondrocytes and to characterize the enzymatic activities of CMGP. These studies demonstrate that CMGP is the principal chondrocyte protein labeled by 67Cu in vitro and that the label is localized to the mitochondria, cytosol, and membrane fractions of sucrose gradients, suggesting copper transport through the cell. In parallel experiments, [3H]leucine was incorporated into proteins corresponding to the subunits and fragments of CMGP, as described previously, and in a similar distribution among the subcellular fractions as labeled copper. Additionally, CMGP has oxidase and ferroxidase activities similar to those of ceruloplasmin.

Recognizing and treating delirium in patients admitted to general hospitals

We report a retrospective study of 59 patients for whom our university hospital nursing service had required the use of lay sitters because of the need for constant observation. Of 54 charts examined, 28 noted a need for psychiatric consultation, mostly because of delirious states. Quality of care deficits discerned included (1) inadequate pharmacotherapy of alcoholic and nonalcoholic delirium, (2) inadequate search for treatable causes of delirium (thyroid, B12, and folate deficiencies), (3) insufficient awareness of persistent cognitive deficits, which influence the patient's ability to care for himself or give informed consent. The knowledge and skills deficits we found are not unique to this hospital and reflect the failure of most graduate programs to reinforce basic psychiatric teaching. The quality of care issues indicate that more serious consideration should be given to providing necessary psychiatric training.

Gross and microscopic anatomy of the vagal innervation of the rat heart

Intrinsic cardiac ganglia and their vagal innervation are described from gross and microscopic dissections and functional studies in the anesthetized, open-chest, adult rat. Dissecting microscope sketches of the ventral and dorsal aspects of the rat heart provide gross descriptions of the anatomical course of the vagal cardiac nerves. Histological sectioning of adipose tissue packets surrounding the terminal endings of vagal branches distributed to the roots of the great cardiac vessels (aorta, pulmonary artery, precaval veins) revealed clusters of autonomic ganglia. These packets or "fat pads" were located: (1) along the dorsal surface of the right precava and extending medially toward the aortic root, (2) deep to the aortic arch, (3) in the angle between the root of the left precava and the pulmonary artery on the superior-dorsal surface of the left atrium, and (4) in the rostro-dorsal interatrial septum. Vagal distributions of small terminal branches were traced to each of these pads, which contained numerous autonomic ganglia. Electrical excitation of right or left cervical vagus elicited varying degrees of sinus slowing, slowing of A-V conduction, and suppression in atrial contractile force. Very small quantities (0.5 mg in 10 microliters saline) of the ganglionic blocking agent, hexamethonium (C6) were injected selectively into a single fat pad, followed by repetition of right or left vagal stimulation, with careful analysis of changes in heart rate (paced and unpaced), A-V conduction, and contractile force.

The Moyer reading technique re-evaluated

The purpose of the study was to design treatment programmes for various types of reading disorder in such a way as to allow a valid evaluation of their efficacy, i.e. in a way which allows specific treatment effects to be distinguished from non-specific treatment effects (e.g., the effects of attention from a helpful person), and from changes unrelated to treatment (e.g. spontaneous recovery). In particular, the intention was to investigate whether specific forms of therapeutic intervention help specific forms of disorder. Studies on five patients with different patterns of reading difficulty showed that specific treatment programmes were responsible for significant improvement in the patients' reading performance.

Chronic monitoring of intracranial pressure using an in vivo calibrating sensor: experience in patients with pseudotumor cerebri

A number of reliable methods are available for the short term monitoring of intracranial pressure (ICP). However, the danger of infection and the need for external connections make the use of these methods for extended periods inappropriate. Most previously described devices for chronic monitoring of ICP are of limited value because of uncertain drift from zero-point readings. The Hittman-Meyer ICP sensor approaches the ideal for a long term monitoring device. It is fully implantable and is accurate over a wide range of pressures and for extended periods. It is designed so that in vivo calibration may be performed in a noninvasive fashion. We report the use of this device in eight patients with pseudomotor cerebri. It has functioned accurately for periods ranging up to 14 months after implantation and has proven to be a valuable aid in the management of these patients. (Neurosurgery, 5: 666-670, 1979).

Serial computerized tomographic scanning and the prognosis of severe head injury

Serial (two or three) computerized tomographic (CT) scans were performed on a series of 58 patients with severe head injury. The protocol called for scans to be done upon admission and on Days 3 and 7 after injury. New lesions (i.e., lesions not visualized on the initial CT scans but appearing on subsequent scans) were a frequent finding, occurring in over half of all patients. For the purposes of this study a new lesion was classified as edema involving two or more lobes, extra-axial hematoma, parenchymal hemorrhage, or infarction. Significant correlation was found between good outcome and the absence of new lesions and between bad outcome and the development of new lesions (p less than 0.001). Several patients did well in spite of the development of new lesions, but these patients were unique in that most had small, unilateral parenchymal hematomas located at or near the frontal or temporal poles. In most cases, patients who did poorly in spite of not developing new lesions had severe injuried visualized on their initial scans (massive intracerebral hematoma, hemorrhage of the corpus callosum) or succumbed to medical complications. The pertinent literature is reviewed, and other CT findings associated with a poor prognosis are noted. The authors suggest that serial CT scanning may be used to make prognostic assessments in severely head-injured patients and may be of value in increasing the confidence in and accuracy of assessments made on clinical grounds alone. (Neurosurgery, 5: 566--569, 1979).

Dexamethasone and severe head injury. A prospective double-blind study

A prospective double-blind study of the effects of dexamethasone administration on the outcome of patients with severe head injuries was performed. Patients were stratified for severity of neurological injury and were treated with placebo, low-dose dexamethasone (16 mg/day), or high-dose dexamethasone (96 mg/day) for a period of 6 days. Outcome was evaluated at 6 months following injury. Of the 76 patients available for analysis, a good outcome was achieved in 37% of placebo-treated patients, 44% of low-dose-treated patients, and 29% of high-dose-treated patients. These differences are not statistically significant. Similarly dexamethasone administration had no statistically significant effect on intracranial pressure patterns or serial neurological examinations during hospitalization. Gastrointestinal bleeding occurred in only one patient. Good outcome was associated with age under 10 years, lighter depth of coma on admission, and the preservation of brain-stem reflexes upon admission. A recalculation of data in previous clinical series purporting to show an improvement in outcome as a result of corticosteroid therapy shows no significant difference in outcome when steroid- and placebo-treated patients are compared. In our series, 90% of all deaths were caused by recurrent intracranial hematomas, medical complications, or diffuse brain injuries with parenchymal hemorrhage and tissue disruption -- causes of death which cannot be affected by corticosteroid therapy. The study suggests that dexamethasone in either high or low dosages has no significant effect on morbidity and mortality following severe head injury.

Neurodiagnostic studies and the management of head injury

The rational management of patients with head injury calls for the closest cooperation between the radiologist and neurosurgeon. Until the last three to four years, cerebral angiography had been considered the diagnostic procedure of choice for the management of patients with suspected traumatically induced intracranial mass lesions. Experience with CT scanning now indicates that for a number of reasons this procedure is to be preferred in the diagnosis of head injuries. It is more rapid than angiography, routinely visualizes the entire brain, is noninvasive, resolves lesions that are much smaller than any visualized by angiography and defines the density and thus the nature of traumatic lesions in a manner not possible with previously employed techniques. Using CT scanning in a sequential fashion we have routinely been able to visualize the appearance of new lesions in the post-traumatic period and have as well, been able to develop insights into the temporal appearance and disappearance of white matter edema as measured by Hounsfield numbers. In the late post-traumatic period, it has been valuable in defining hydrocephalus, porencephaly and other post-traumatic lesions that have a significant bearing on both therapy and prognosis.