Efficient photon number detection with silicon avalanche photodiodes

We demonstrate an efficient photon number detector for visible wavelengths using a silicon avalanche photodiode. Under subnanosecond gating, the device is able to resolve up to four photons in an incident optical pulse. The detection efficiency at 600 nm is measured to be 73.8%, corresponding to an avalanche probability of 91.1% of the absorbed photons, with a dark count probability below 1.1x10^{-6} per gate. With this performance and operation close to room temperature, fast-gated silicon avalanche photodiodes are ideal for optical quantum information processing that requires single-shot photon number detection

Probing higher order correlations of the photon field with photon number resolving avalanche photodiodes

We demonstrate the use of two high speed avalanche photodiodes in exploring higher order photon correlations. By employing the photon number resolving capability of the photodiodes the response to higher order photon coincidences can be measured. As an example we show experimentally the sensitivity to higher order correlations for three types of photon sources with distinct photon statistics. This higher order correlation technique could be used as a low cost and compact tool for quantifying the degree of correlation of photon sources employed in quantum information science

A systematic review of ICD complications in randomised controlled trials versus registries: is our 'real-world' data an underestimation?

Implantable cardioverter defibrillator (ICD) implantation carries a significant risk of complications, however published estimates appear inconsistent. We aimed to present a contemporary systematic review using meta-analysis methods of ICD complications in randomised controlled trials (RCTs) and compare it to recent data from the largest international ICD registry, the US National Cardiovascular Data Registry (NCDR). PubMed was searched for any RCTs involving ICD implantation published 1999-2013; 18 were identified for analysis including 6433 patients, mean follow-up 3 months-5.6 years. Exclusion criteria were studies of children, hypertrophic cardiomyopathy, congenital heart disease, resynchronisation therapy and generator changes. Total pooled complication rate from the RCTs (excluding inappropriate shocks) was 9.1%, including displacement 3.1%, pneumothorax 1.1% and haematoma 1.2%. Infection rate was 1.5%.There were no predictors of complications but longer follow-up showed a trend to higher complication rates (p=0.07). In contrast, data from the NCDR ICD, reporting on 356 515 implants (2006-2010) showed a statistically significant threefold lower total major complication rate of 3.08% with lead displacement 1.02%, haematoma 0.86% and pneumothorax 0.44%. The overall ICD complication rate in our meta-analysis is 9.1% over 16 months. The ICD complication reported in the NCDR ICD registry is significantly lower despite a similar population. This may reflect under-reporting of complications in registries. Reporting of ICD complications in RCTs and registries is very variable and there is a need to standardise classification of complications internationally

Beyond Node Degree: Evaluating AS Topology Models

This is the accepted version of 'Beyond Node Degree: Evaluating AS Topology Models', archived originally at arXiv:0807.2023v1 [cs.NI] 13 July 2008.Many models have been proposed to generate Internet Autonomous System (AS) topologies, most of which make structural assumptions about the AS graph. In this paper we compare AS topology generation models with several observed AS topologies. In contrast to most previous works, we avoid making assumptions about which topological properties are important to characterize the AS topology. Our analysis shows that, although matching degree-based properties, the existing AS topology generation models fail to capture the complexity of the local interconnection structure between ASs. Furthermore, we use BGP data from multiple vantage points to show that additional measurement locations significantly affect local structure properties, such as clustering and node centrality. Degree-based properties, however, are not notably affected by additional measurements locations. These observations are particularly valid in the core. The shortcomings of AS topology generation models stems from an underestimation of the complexity of the connectivity in the core caused by inappropriate use of BGP data

Parametric modeling of probability of bank loan default in Kenya

Commercial banks in Kenya are the key players not only in the financial market but also in spurring the economic growth that has been witnessed in the country in the recent past. Besides Safaricom and East Africa Breweries, the other top ten most profitable companies in Kenya are the Commercial banks. The biggest part of these huge profits emanates from the interests charged on loans they advance to their customers. If these loans non-perform, these blue chip companies will come tumbling down and the entire economy will be threatened. This makes the study on probability of a customer defaulting very useful while analyzing the credit risk policies. In this paper, we use a raw data set that contains demographic information about the borrowers. The data sets have been used to identify which risk factors associated with the borrowers contribute towards default. These risk factors are gender, age, marital status, occupation and term of loan. Results show that male customers have high odds (1.91) of defaulting compared to their female counter parts, single customers have a higher likelihood (odds of 1.48) of defaulting compared to their married customers, younger customers have high odds of defaulting unlike elderly customers, financial sector customers have equallikelihood of default as support staff customers and long term loans have less likelihood of defaulting compared to short term loans.Key words: The logistic model, the logit transformation, parameter estimatio

High performance liquid chromatographic determination of proguanil after derivatisation with sodium benzoxazole-2-sulphonate

A simple, fast and reproducible method for the determination of proguanil using high performance liquid chromatographic with UV/Fluorescence detection is described. Proguanil was derivatised to its corresponding derivative [(N1-(4-chlorophenyl)-N5-(1 -methyl ethyl) imidocarbonimideamide-Nbenzoxazole]. The derivatisation reaction was conducted in methanol at 60°C using sodium benzoxazole-2-sulphonate under alkaline conditions. The resulting derivative was extracted with chloroform after which the extract was observed under UV lamp at 254 nm before TLC and HPLC analysis. Similarly, the derivatisation process was adapted for derivatisation of proguanil in urine sample. The reaction proceeded smoothly and rapidly. The extraction process was not cumbersome and eliminated the need for costly extraction and evaporation equipments. The resulting derivative fluorensced intensely under UV lamp. Direct HPLC analysis of the reaction mixture was found possible without interferences from excess reagent and endogeneous compounds like ammonium salts. The derivative eluted in less than seven minutes thus making the method suitable for routine use. The calibration plot was linear over the concentration range. A correlation regression of the order of 0.94 was obtained from the calibration curve which indicated a strong relationship between the instrument response and the concentration of proguanil. The discussion also summarizes the derivatisation chemistry that have not being fully explored to date but may find utility in future development of highly sensitive analytical methods for biquanide drugs

Adherence to national guidelines in prevention of mother to child transmission of HIV

Background: Mother-to-child transmission (MTCT) of Human Immunodeficiency Virus (HIV) contributes to over 90% of the paediatric HIV infections. The national PMTCT guidelines make recommendations for specific interventions to reduce perinatal transmission. Data on adherence to the guidelines by caregivers and quality of PMTCT care is however limited.objective: To evaluate the extent to which PMTCT care offered to HIV positive women admitted for delivery at Kenyatta National Hospital (KNH) and Pumwani Maternity Hospital (PMH) adheres to National Guidelines in order to reduce vertical transmission of HIV during labour and delivery.Design: A cross-sectional study.Setting: Kenyatta National Hospital and Pumwani Maternity Hospitalfrom January to April 2009.Subjects: All consenting HIV positive women admitted to the labour wards at the two facilities and planned for delivery.Results: A total of 370 women were enrolled, 266 at Pumwani Maternity Hospital and 104 at Kenyatta National Hospital. Among the enrolled women 357 (96.4%) had been counselled on vertical transmission and 205(55.4%) had HIV disease staging by CD4 cell count. There were no significant differences between the two study sites in the proportion of women counselled on MTCT (p=0.398) and receiving HIV disease staging by CD4 testing (p=0.28). Three hundred and forty nine (94.3%) women were offered varied ARV regimens for PMTCT. 101(27.3%) received HAART, 94(26.9%) were given single dose nevirapine and 130(37%) received AZT+NVP combination prophylaxis. Twenty one women received no ARV prophylaxis. Overall, 268 women (72.5%) had spontaneous vertex delivery. An episiotomy rate of 7% was observed and no vacuum delivery was recorded. A Caesarean section rate of 27.5% was recorded with PMTCT as aan indication in almost half of the cases. Women delivered at KNH were more likely to receive HAART (p<0.001) and to be delivered by elective caesarean (p<0.001).Conclusion: A great majority of HIV positive women admitted for delivery received counseling on vertical transmission and were offered ARVs for PMTCT. Many women did not get CD4 measurement and clinical staging as recommended in the National guidelines

Yaws

Introduction Yaws, caused by Treponema pallidum ssp. pertenue, is endemic in parts of West Africa, Southeast Asia and the Pacific. The WHO has launched a campaign based on mass treatment with azithromycin, to eradicate yaws by 2020. Sources of data We reviewed published data, surveillance data and data presented at yaws eradication meetings. Areas of agreement Azithromycin is now the preferred agent for treating yaws. Point-of-care tests have demonstrated their value in yaws. Areas of controversy There is limited data from 76 countries, which previously reported yaws. Different doses of azithromycin are used in community mass treatment for yaws and trachoma. Growing points Yaws eradication appears an achievable goal. The programme will require considerable support from partners across health and development sectors. Areas timely for developing research Studies to complete baseline mapping, integrate diagnostic tests into surveillance and assess the impact of community mass treatment with azithromycin are ongoing

Information-Theoretic Active Learning for Content-Based Image Retrieval

We propose Information-Theoretic Active Learning (ITAL), a novel batch-mode active learning method for binary classification, and apply it for acquiring meaningful user feedback in the context of content-based image retrieval. Instead of combining different heuristics such as uncertainty, diversity, or density, our method is based on maximizing the mutual information between the predicted relevance of the images and the expected user feedback regarding the selected batch. We propose suitable approximations to this computationally demanding problem and also integrate an explicit model of user behavior that accounts for possible incorrect labels and unnameable instances. Furthermore, our approach does not only take the structure of the data but also the expected model output change caused by the user feedback into account. In contrast to other methods, ITAL turns out to be highly flexible and provides state-of-the-art performance across various datasets, such as MIRFLICKR and ImageNet.Comment: GCPR 2018 paper (14 pages text + 2 pages references + 6 pages appendix

Casting Light on Dark Matter

The prospects for detecting a candidate supersymmetric dark matter particle at the LHC are reviewed, and compared with the prospects for direct and indirect searches for astrophysical dark matter. The discussion is based on a frequentist analysis of the preferred regions of the Minimal supersymmetric extension of the Standard Model with universal soft supersymmetry breaking (the CMSSM). LHC searches may have good chances to observe supersymmetry in the near future - and so may direct searches for astrophysical dark matter particles, whereas indirect searches may require greater sensitivity, at least within the CMSSM.Comment: 16 pages, 13 figures, contribution to the proceedings of the LEAP 2011 Conferenc