Boosting Solar Cell Photovoltage via Nanophotonic Engineering.

Approaching the theoretically limiting open circuit voltage (Voc) of solar cells is crucial to optimize their photovoltaic performance. Here, we demonstrate experimentally that nanostructured layers can achieve a fundamentally larger Fermi level splitting, and thus a larger Voc, than planar layers. By etching tapered nanowires from planar indium phosphide (InP), we directly compare planar and nanophotonic geometries with the exact same material quality. We show that the external radiative efficiency of the nanostructured layer at 1 sun is increased by a factor 14 compared to the planar layer, leading to a 70 mV enhancement in Voc. The higher voltage arises from both the enhanced outcoupling of photons, which promotes radiative recombination, and the lower active material volume, which reduces bulk recombination. These effects are generic and promise to enhance the efficiency of current record planar solar cells made from other materials as well.

Integration of a scanning ion conductance microscope into phase contrast optics and its application to the quantification of morphological parameters of selected cells.

We have previously described a pulse-mode scanning ion conductance microscope to investigate membrane surfaces and volume changes of individual cells in culture. We have now developed a miniaturized scanning headstage that enables us to select individual cells for recording under phase contrast optics, considerably improving the selection of individual cells for scanning as well as the positioning of the scanning frames with respect to the position of the cell somata. We show an application in which surfaces and volumes of somata and processes of cultured cells from the central nervous system were quantified separately.

Monitoring cell movements and volume changes with pulse-mode scanning ion conductance microscopy.

Here we describe the use of pulse-mode scanning ion conductance microscopy (SICM) to observe volume changes and cell membrane movements during the locomotion of cultured cells in the range of minutes to several hours. The microscope is based on the pulse-mode SICM previously developed for stable imaging of single cells in culture. Our instrument uses current pulses to control the distance between cell surface and electrode tip as well as a back-step mode to prevent contact of tip and membrane during lateral movements of the probe. We performed repeated scans of cell surfaces using feedback-controlled piezoactors to position the electrode. Using patch-clamp-type electrode tips the height of cells could reproducibly be measured with a standard deviation of 50 nm. To quantify and separate changes in cell position and volume occurring between consecutive scans, a program was written to subtract images and calculate volume changes. Examples of repeated scans show that membrane movements in the range of 30 min to a few hours can be quantitatively monitored with a lateral resolution of 500 nm using difference images and that faster movements in the range of minutes can be recorded at defined cell sections using the line scan mode. Difference images indicate that volume changes can affect cell surfaces inhomogeneously, emphasizing the role of the cytoskeleton in the stabilization of cell shape.

Pulse-mode scanning ion conductance microscopy--a method to investigate cultured hippocampal cells.

Scanning ion conductance microscopy (SICM) takes advantage of the increase in the resistance which occurs if a glass microelectrode is closely approached to a poorly conducting membrane (Science 243 (1989) 641) and has been shown to be a promising technique to study membranes of living cells (Biophys J 73 (1997a) 653; J Microsc 188 (1997b) 17). Based on a newly designed set-up on top of an inverted light microscope in combination with a speed optimized low noise intracellular amplifier, a novel mode for control of the distance between the probe and surface has been developed. By application of current pulses, the change in the resistance is monitored independently from electrode drift and parasitic DC currents. We demonstrate the applicability by showing first high-resolution images of neural cells produced with the pulse-mode operated SICM.

Costing of consumables: use in an intensive care unit.

In 1991, the Intensive Care Unit (ICU) at Middlemore Hospital manually costed the treatment and care of asthmatic patients. This was long-winded and labour-intensive, but provided hard data to support anecdotal beliefs that intensive care patients are more expensive than was currently believed or accepted. It is a known problem that funder and provider organizations see a huge disparity on the funding issue. With additional accurate information on the actual cost of individual patients, which can be grouped into disease categories, funding applications can be backed with accurate, up-to-date quantitative data. After a long preparation time, we are now costing individual patient stays in the ICU. Each individual resource was established, costed and entered into an MS ACCESS computerized database. Schedules have been prepared for updating prices, as these change. The final report available gives a detailed list of resource use within certain categories. Some items proved to be impractical to cost on an individual patient basis, and these have been grouped together, costed, and divided by the number of patient days for the last year, and assigned to each individual patient as an hourly unit cost. Believed to be a world-first, this information now forms the basis for variance reporting and pricing.

Respect: improving student writing.

Respect is central to the process of teaching writing, especially the respect that flows from asking students to write about their own personal experiences. The author offers suggestions on how to help students overcome their dislike of writing, address some of their writing deficits, and ultimately begin to enjoy writing.

The reliability and validity of PSE assessments by lay interviewers: a national population survey.

Studies employing psychiatric rating instruments administered by lay interviewers need to demonstrate the reliability and validity of subject classification. In a national population study utilizing the short form of the Present State Examination, audiotapes of interviews were used to demonstrate the reliability of ratings. The classification of 'cases' was found to be related to self-reports of nervous trouble and help-seeking for such problems. Associations between the rate of psychiatric disorder and demographic factors were similar to those found in previous community surveys. In general, the method of psychiatric assessment was considered to be satisfactory. Recommendations are made for the monitoring of interviews in similar large-scale investigations.

The concept of a 'case' in psychiatric population surveys.

A series of in-patients, a series of out-patients and a series of women from a general population sample, all aged under 65, and all living in the same area of south-east London, were examined using the ninth edition of the Present State Examination (PSE). An 'index of definition' (ID), based on number, type and severity of PSE symptoms, was constructed in order to define a threshold point above which sufficient information was available to allow classification into one of the functional psychoses or neuroses. The index specified 8 levels of definition of disorder; the threshold point for a 'case' lying between levels 4 and 5. The identification of 'cases' by this means in the general population series was highly concordant with global clinical judgement. When the 3 series were compared, the in-patient series contained the most definite cases, the outpatient series was intermediate, and the general population series was characterized mainly by below-threshold conditions. Disorders above the threshold point were classified using the CATEGO program. The clinical severity of the depressive disorders and anxiety states identified in this way in the 3 series was compared on the basis of symptom and syndrome profiles and PSE scores. As expected, the inpatients had the most severe, and the general population 'cases' the least severe disorders. It is suggested that the PSE-ID-CATEGO techniques can be used to help standardize certain aspects of case-finding and case-description in both referred and non-referred populations and thereby make the results of surveys more comparable.

Reliability of the PSE (ninth edition) used in a population study.

A random sample of 237 women in a south-east London area were seen by non-medical interviewers, trained to use a standard technique (the Present State Examination) to elicit and record psychiatric symptoms. Ninety-five were interviewed a second time by psychiatrists, who also rated audiotape recordings. The reproducibility of the techniques is adequate though not as high, in some respects, as that obtained from out-patient or in-patient samples. This is true at the level of symptom, syndrome, total score, and index of definition of psychiatric disorder. It is concluded that non-medical interviewers can obtain as high reproducibility as psychiatrists on most of the non-psychotic sections of the PSE if they have appropriate training. Repeatability is lower than reproducibility, partly due to fluctuations in clinical condition, partly to environmental changes between interviews, and partly to differential responses to medical and non-medical interviews. Over a short period of time, such as a week, repeatability is satisfactory.

"New" long-stay psychiatric patients: a national sample survey of fifteen mental hospitals in England and Wales 1972/3.

Four hundred "new" long-stay patients were studied and assessments of their needs for treatment and accommodation were made. About one third appeared to need further care in hospital. A further third could possibly be discharged if suitable accommodation in the community were available: most of this group were more handicapped than present residents in hostels. The remaining third had diverse needs; many were multiply handicapped--for example, by physical disability or mental retardation in addition to psychiatric disorder. At the moment the psychiatric hospital is virtually the only agency to accept the care of such people.