Engineering of impact ionization characteristics in In0.53Ga0.47As/Al0.48In0.52As superlattice avalanche photodiodes on InP substrate

We report on engineering impact ionization characteristics of In_0.53Ga_0.47As/Al_0.48In_0.52As superlattice avalanche photodiodes (InGaAs/AlInAs SL APDs) on InP substrate to design and demonstrate an APD with low k-value. We design InGaAs/AlInAs SL APDs with three different SL periods (4 ML, 6 ML, and 8 ML) to achieve the same composition as Al_0.4Ga_0.07In_0.53As quaternary random alloy (RA). The simulated results of an RA and the three SLs predict that the SLs have lower k-values than the RA because the electrons can readily reach their threshold energy for impact ionization while the holes experience the multiple valence minibands scattering. The shorter period of SL shows the lower k-value. To support the theoretical prediction, the designed 6 ML and 8 ML SLs are experimentally demonstrated. The 8 ML SL shows k-value of 0.22, which is lower than the k-value of the RA. The 6 ML SL exhibits even lower k-value than the 8 ML SL, indicating that the shorter period of the SL, the lower k-value as predicted. This work is a theoretical modeling and experimental demonstration of engineering avalanche characteristics in InGaAs/AlInAs SLs and would assist one to design the SLs with improved performance for various SWIR APD application.

Gas Chromatographic/Electron Capture Detection Method for Determination of Chlorinated Acids in Water: Collaborative Study

A U.S. Environmental Protection Agency (USEPA) inter laboratory method validation study was conducted on USEPA Method 515.1, "Determination of Chlorinated Acids in Water by Gas Chromatography with an Electron Capture Detector. "This method is one of the 6 pesticide methods developed for the USEPA National Pesticide Survey (NPS). Method recovery and precision for analyses of sub-ppb to low-ppb concentrations of chlorinated acids were determined in reagent water and finished drinking waters. The analytes evaluated in the study included the 12 pesticides that were quantitatively measured in the National Pesticide Survey (bentazon, 2,4-D, 2,4-DB, 3,5-dichlorobenzoic acid, DCPA-diacid, dicamba, dichlorprop, 5-hydroxydicamba, pentachlorophenol, picloram, 2,4,5- T, and 2,4,5-TP) and 5 pesticides (acif luorfen, chloramben, dalapon, dinoseb, and 4-n it ro phenol) that were only qualitatively assessed in the National Pesticide Survey because of recognized method imprecision. The study design was based on Youden's nonreplicate plan for collaborative tests of analytical methods. The waters were spiked with 17 chlorinated acids, each at 6 concentration levels, prepared as 3 Youden pairs. Eight laboratories extracted the spiked test waters at pH <2 with ethyl ether, performed a solvent exchange with methyl tert-butyl ether, prepared methyl esters of the extracted acids using diazomethane, and analyzed an aliquot of each derivatized extract by gas chromatography with electron capture detection. The submitted data were analyzed using a USEPA computer program, which measured recovery and precision for each of the 17 compounds and compared the performance of the method between water types. Method 515.1 was judged acceptable for the 12 NPS analytes recovered quantitatively; mean percent recoveries at 10-15 times the method detection limits ranged from 79 to 105% in reagent water and from 75 to 123% in finished drinking water. In reagent water, overall precision (reproducibility relative standard deviation, RSDR) ranged from 9.6 to 34.2% and in finished drinking water, the RSDR ranged from 11.9 to 37.0%. Single-analyst precision (RSD for repeatability, RSDr) ranged from 5.8 to 17.7% in reagent water and from 4.6 to 27.9% in drinking water. Results for the 5 other NPS analytes were too inaccurate or imprecise and, for these compounds, supported use of the method for qualitative measurements only; the 5 compounds are not included in the adopted method. The method has been adopted first action by AOAC INTERNATIONAL for determination of residues of 12 chlorinated acids in finished drinking water.

Can comprehensive specialised end-of-life care be provided at home? Lessons from a study of an innovative consultant-led community service in the UK

The Midhurst Macmillan Specialist Palliative Care Service (MMSPCS) is a UK, medical consultant-led, multidisciplinary team aiming to provide round-the-clock advice and care, including specialist interventions, in the home, community hospitals and care homes. Of 389 referrals in 2010/11, about 85% were for cancer, from a population of about 155 000. Using a mixed method approach, the evaluation comprised: a retrospective analysis of secondary-care use in the last year of life; financial evaluation of the MMSPCS using an Activity Based Costing approach; qualitative interviews with patients, carers, health and social care staff and MMSPCS staff and volunteers; a postal survey of General Practices; and a postal survey of bereaved caregivers using the MMSPCS. The mean cost is about 3000 GBP (3461 EUR) per patient with mean cost of interventions for cancer patients in the last year of life 1900 GBP (2192 EUR). Post-referral, overall costs to the system are similar for MMSPCS and hospice-led models; however, earlier referral avoided around 20% of total costs in the last year of life. Patients and carers reported positive experiences of support, linked to the flexible way the service worked. Seventy-one per cent of patients died at home. This model may have application elsewhere.

The views of older women towards mammographic screening: a qualitative and quantitative study

Background:

Mammographic screening has improved breast cancer survival in the screened age group. This improved survival has not been seen in older women (>70 years) where screening uptake is low. This study explores the views, knowledge and attitudes of older women towards screening.

Methods:

Women (>70 years) were interviewed about breast screening. Interview findings informed the development of a questionnaire that was sent to 1000 women (>70 years) to quantify their views regarding screening.

Results:

Twenty-six women were interviewed and a questionnaire was designed. The questionnaire response rate was 48.3% (479 out of 992). Over half (52.9%, 241 out of 456) of the respondents were unaware that they could request a mammography by voluntary self-referral and were unaware how to arrange this. Most (81.5%, 383 out of 470) had not attended breast screening since turning 70 years. Most (75.6%, 343 out of 454) felt screening was beneficial and would attend if invited. Most (90.1%, 412 out of 457) felt screening should be offered to all women regardless of age or health.

Conclusions:

There is a lack of knowledge about screening in older women. The majority felt that invitation to screening should be extended to the older age group regardless of age or health. The current under-utilised system of voluntary self-referral is not supported by older women.

Seroprevalence of hepatitis C in intravenous opioid users presenting in the early phase of injecting drug use in Singapore

INTRODUCTION

All over the world, Hepatitis C virus (HCV) accounts for an estimated 130 million chronic infections. Injection drug use has become one of the most important risk factors for HCV, and within the injection drug user population, the prevalence of HCV antibody ranges from 70 to 95 percent depending on an individual's length of use and the prevalence of infection in the community. This study was undertaken to determine the prevalence of and the risk factors for Hepatitis C antibodies in injecting drug users presenting to the Community Addictions Management Programme (CAMP) in Singapore.

METHODS

Eligibility criteria for inclusion in this study were all intravenous buprenorphine users presenting to CAMP. 106 subjects, who consented to the study, completed an interviewer-administered questionnaire, and underwent a urine and blood analysis.

RESULTS

The prevalence rate for HCV was 42.5 percent among the subjects included in our study. The odds of seroprevalence in those sharing needles were 5.6 times that of those who were not, and the odds of seroprevalence among those using with others (peers or partners) were 6.3 times, as compared to among those who were individual users. Racial differences were also seen, but these could be accounted for by the sharing of needles.

CONCLUSION

This study provides important local data at the onset of an early buprenorphine-injecting epidemic in Singapore. This data is useful for disease prevention and healthcare planning.

X-ray imaging optimization using virtual phantoms and computerized observer modelling

This study develops and demonstrates a realistic x-ray imaging simulator with computerized observers to maximize lesion detectability and minimize patient exposure. A software package, ViPRIS, incorporating two computational patient phantoms, has been developed for simulating x-ray radiographic images. A tomographic phantom, VIP-Man, constructed from Visible Human anatomical colour images is used to simulate the scattered portion using the ESGnrc Monte Carlo code. The primary portion of an x-ray image is simulated using the projection ray-tracing method through the Visible Human CT data set. To produce a realistic image, the software simulates quantum noise, blurring effects, lesions, detector absorption efficiency and other imaging artefacts. The primary and scattered portions of an x-ray chest image are combined to form a final image for computerized observer studies and image quality analysis. Absorbed doses in organs and tissues of the segmented VIP-Man phantom were also obtained from the Monte Carlo simulations. Approximately 25,000 simulated images and 2,500,000 data files were analysed using computerized observers. Hotelling and Laguerre-Gauss Hotelling observers are used to perform various lesion detection tasks. Several model observer tasks were used including SKE/BKE, MAFC and SKEV. The energy levels and fluence at the minimum dose required to detect a small lesion were determined with respect to lesion size, location and system parameters.

A quantitative analysis of passive electrolocation behavior in electric fish

Weakly electric fish of the families Gymnotidae and Hypopomidae (Gymnotiformes) are able to locate the electric discharges from conspecifics or from dipole electrodes, and they demonstrate this by making rapid, well-directed approaches toward these electrical sources. A video tracking system was used to follow the movements of electric fish in a large tank and an analytic method was used for computing the direction and magnitude of the electric field anywhere within the cylindrical test tank. Using a static analysis method, we describe the posture of test fish relative to the electric fields during their approaches to stationary or moving electrical stimuli. Using a dynamic analysis, we examine the movements of the fish including the sign and magnitude of velocity and bending in response to electric fields. Electric fish seek to maintain a zero error angle between their body orientation and the local electric field. They do so by bending their body in the direction of the local electric field. The response has a delay of approximately 0.5 s. Swimming in reverse inverts the direction of the bend. These fish also use 'V-turns' to redirect their swim directions when encountering rapidly-changing electric fields.

Initial experience with clozapine in Woodbridge Hospital

OBJECTIVES

This study was performed to evaluate the efficacy and side-effect profile of the atypical neuroleptic clozapine in local Asian patients with treatment-resistant schizophrenia.

METHOD

Patients were treated with 12 weeks of clozapine after undergoing a washout of all previous neuroleptics. They were assessed weekly on the Brief Psychiatric Rating Scale (BPRS), Clinical Global Impression (CGI) and the Simpson-Angus Scale for Extrapyramidal Side-Effects.

RESULTS

Clinical improvement (according to criteria established a priori) at study end point was shown in 78.9% of the patients. There was no statistical difference in the incidence of the extrapyramidal side-effects at starting and end points. The mean daily dosage was 356.6 mg. The most common adverse effect was hypersalivation.

CONCLUSION

Clozapine is effective and well tolerated in local patients with treatment-resistant schizophrenia.

Clinical evaluation and plasma clozapine concentrations in Chinese patients with schizophrenia

The relationships between clozapine dosages, plasma concentrations, and clinical responses in Chinese schizophrenics were studied. Fourteen treatment-refractory schizophrenic patients were treated with clozapine for 12 weeks. Patients were assessed before and after 6 and 12 weeks of treatment using the Brief Psychiatric Rating Scale (BPRS), the Clinical Global Impression (CGI), and the Simpson-Angus Scale for Extrapyramidal Side Effect. Plasma clozapine concentrations were determined by high-performance liquid chromatography. Ten patients (71.4%) responded after 12 weeks of treatment. Although the mean daily dosage at week 12 (373 +/- 90 mg/day) was lower than that reported in American trials (444 mg/day), the mean plasma clozapine concentration attained (1,078 +/- 385 ng/ml) was higher. This higher concentration may be due to the lower body wight and the preponderance of women among our patients, absence of smoking and alcohol use, and/or ethnic difference between Chinese and non-Chinese. There was wide interindividual variation in the plasma clozapine concentrations. Compared with other studies, the plasma clozapine concentrations and the response rate were higher. Although the sample size was small, the findings are suggestive of pharmacokinetic and pharmacodynamic ethnic differences in Chinese with clozapine therapy.

Short-range orientation in electric fish: an experimental study of passive electrolocation

Gymnotiform electric fish are capable of locating and approaching an electrically discharging conspecific over a range of 1-2 m in a behavior called passive electrolocation. This paper investigates the movements of two species in experiments with approaches to stationary dipoles that are either silenced or jumped to a new direction during an approach. Gymnotus carapo fail to find an electrode source in trials in which the dipole electrode is switched off in mid-track. They slow their approach, become disoriented and drift away from the target within seconds of the field being switched off. This result suggests that the fish are unable to construct a cognitive map of a dipole source from brief exposure to local electrosensory stimuli. The second set of trials shows that Brachyhypopomus diazi and Gymnotus carapo bend their body to track electric vectors which are suddenly jumped to a new direction. The latency of the bend response is 0.5 s after the jump. Bending initiates a turn that reduces to zero the error between the fish's direction and the electric field vector and helps keep the fish aligned with the local electric field vector. Together, these experiments suggest that passive electrolocation is stimulus-bound and that these fish find the electrical sources simply by tracking instantaneous local electric current vectors.

Dyscalculia and dyslexia after right hemisphere injury in infancy

OBJECTIVE

To use the findings from neuropsychological evaluation and functional magnetic resonance imaging (fMRI) to assess interhemispheric reorganization of function after early unilateral brain injury.

DESIGN AND METHODS

The study focused on one case of early brain injury that resulted in both dyscalculia and dyslexia. Brain injury was studied using both structural and fMRI. Intellectual function was evaluated using the Wechsler Intelligence Scale for Children, Third Edition, while visuospatial skills were assessed using the Block Design subtest of the Wechsler Intelligence Scale for Children, Third Edition, and Judgment of Line Orientation subtest. The Selective Reminding Test and the Recurring Figures Test were used to evaluate memory and orientation; language and speech skills were evaluated using the Boston Naming Test, Controlled Oral Word Association, Gates-MacGinitie Reading Test, and color naming. Various methods were used to study arithmetic skills, including the Wide Range Achievement Test-Revised and the Peabody Individual Achievement Test. The control group for fMRI consisted of nine normal subjects.

SETTING

Neuropsychological laboratory in primary care hospital.

PATIENT

A 17-year-old boy who had sustained a closed head injury associated with a partially depressed, right parietal skull fracture, and right temporal hemorrhage in a motor vehicle crash at age 7 months (November 9, 1977). Subsequent social behavior was normal, but the patient had difficulty throughout school in mathematics and spelling and was characterized as having a "short attention span."

INTERVENTION

None.

MAIN OUTCOME MEASURES

Standardized tests of arithmetic and reading supplemented by an assessment of calculation and quantitative skills. While performing calculations, fMRI disclosed predominantly left hemisphere activation involving the frontal and posterior parietal regions, whereas this task produced bilateral activation of the supramarginal gyrus in seven of nine normal subjects.

RESULTS

Neuropsychological findings confirmed the presence of dyscalculia and dyslexia despite normal intellectual functioning. Visuospatial skills ranged from the low normal to average level. The fMRI findings were consistent with early interhemispheric transfer of visuospatial skills normally committed to the right parietal area to the left parietal region. The patient's dyscalculia and reading ability raise a question of acquired left parietal dysfunction as a consequence of the competition between verbal and visuospatial functions for left hemisphere representation.

CONCLUSION

Interhemispheric reorganization of function may be bidirectional rather than a feature unique to the left hemisphere substrate for language.