Optimizing single-photon-source heralding efficiency at 1550 nm using periodically poled lithium niobate

We explore the feasibility of using high conversion-efficiency periodically-poled crystals to produce photon pairs for photon-counting detector calibrations at 1550 nm. The goal is the development of an appropriate parametric down-conversion (PDC) source at telecom wavelengths meeting the requirements of high-efficiency pair production and collection in single spectral and spatial modes (single-mode fibers). We propose a protocol to optimize the photon collection, noise levels and the uncertainty evaluation. This study ties together the results of our efforts to model the single-mode heralding efficiency of a two-photon PDC source and to estimate the heralding uncertainty of such a source.Comment: 14 pages, 2 tables and 3 figures, final version accepted by Metrologi

Unintended weight loss in the elderly living at home: the aged in homecare project (Adhoc)

Objective: To describe associations between unintended weight loss (UWL) and characteristics of nutritional status. Design: A comparative cross-sectional assessment study at 11 sites in Europe. The target population was a stratified random sample of 4,455 recipients of home care (405 in each random sample from 11 urban areas) aged 65 years and older. Measurements: the Resident Assessment Instrument for Home Care, version 2.0. Epidemiological and medical characteristics of clients and service utilisation were recorded in a standardized, comparative manner. UWL was defined as information of 5% or more weight loss in the last 30 days (or 10% or more in the last 180 days). Results: The final sample consisted of 4,010 persons; 74% were female. The mean ages were 80.9 ± 7.5 years (males) and 82.8 ± 7.3 years (females). No associations were found between single diagnoses and UWL, except for cancer. Cancer patients were excluded from further analyses. Persons with a Cognitive Performance Scale value (CPS) > 3 (impaired) had increased risk of UWL (OR = 2.0) compared with those scoring < 3 (less impaired). Only in the oldest group did we find a significant association between UWL and reduction in ADL and IADL functions, comparing those who scored 3 or less with those who scored more than 3 (disabled). A binary logistic regression model explained 26% of UWL: less than one meal/day, reduced appetite, malnutrition, reduced social activity, experiencing a flare-up of a recurrent or chronic problem, and hospitalisation were important indicators. Conclusion: We recommend a regular comprehensive assessment in home care to identify clients with potential risk factors for weight loss and malnutrition, in particular those discharged from hospital, and those with physical dependency or cognitive problems. This study may provide incentives to create tailored preventive strategies

Home care needs of extremely obese elderly european women

Objective: To examine the health and needs of extremely obese women aged over 65 years receiving home care in Europe. Study design: A cross-sectional assessment study based on the Aged in Home Care (AdHOC) project recruited 2974 women aged 65 or over who were receiving home care at 11 sites in European countries. Extreme obesity was defined as ‘Obesity of such a degree as to interfere with normal activities, including respiration’. Main outcome measures: Resident Assessment Instrument for Home Care (RAI-HC version 2.0); Activity of Daily Living Scale; Instrumental Activity of Daily Living Scale; the Minimum Data Set Cognitive Performance Scale; and a health profile. Results: One hundred and twenty women (4.0%) were extremely obese. They were younger than their thinner counterparts, with a median age of 78.3 versus 83.3 years, and they more often had multiple health complaints and needed more help with mobility outside the home. The extremely obese had received home care longer than the non-extremely obese (median 28.7 versus 36.6 months). Extremely obese women also needed more help with personal care than the other group and, due to lower age, they were less cognitively impaired. Conclusions: Extreme obesity is a problem that increasingly affects home care of elderly women

Class I major histocompatibility complexes loaded by a periodate trigger

Class I major histocompatibility complexes (MHCs) present peptide ligands on the cell surface for recognition by appropriate cytotoxic T cells. The unstable nature of unliganded MHC necessitates the production of recombinant class I complexes through in vitro refolding reactions in the presence of an added excess of peptides. This strategy is not amenable to high-throughput production of vast collections of class I complexes. To address this issue, we recently designed photocaged MHC ligands that can be cleaved by a UV light trigger in the MHC bound state under conditions that do not affect the integrity of the MHC structure. The results obtained with photocaged MHC ligands demonstrate that conditional MHC ligands can form a generally applicable concept for the creation of defined peptide−MHCs. However, the use of UV exposure to mediate ligand exchange is unsuited for a number of applications, due to the lack of UV penetration through cell culture systems and due to the transfer of heat upon UV irradiation, which can induce evaporation. To overcome these limitations, here, we provide proof-of-concept for the generation of defined peptide−MHCs by chemical trigger-induced ligand exchange. The crystal structure of the MHC with the novel chemosensitive ligand showcases that the ligand occupies the expected binding site, in a conformation where the hydroxyl groups should be reactive to periodate. We proceed to validate this technology by producing peptide−MHCs that can be used for T cell detection. The methodology that we describe here should allow loading of MHCs with defined peptides in cell culture devices, thereby permitting antigen-specific T cell expansion and purification for cell therapy. In addition, this technology will be useful to develop miniaturized assay systems for performing high-throughput screens for natural and unnatural MHC ligands

UV-induced ligand exchange in MHC class I protein crystals

High-throughput structure determination of protein−ligand complexes is central in drug development and structural proteomics. To facilitate such high-throughput structure determination we designed an induced replacement strategy. Crystals of a protein complex bound to a photosensitive ligand are exposed to UV light, inducing the departure of the bound ligand, allowing a new ligand to soak in. We exemplify the approach for a class of protein complexes that is especially recalcitrant to high-throughput strategies: the MHC class I proteins. We developed a UV-sensitive, “conditional”, peptide ligand whose UV-induced cleavage in the crystals leads to the exchange of the low-affinity lytic fragments for full-length peptides introduced in the crystallant solution. This “in crystallo” exchange is monitored by the loss of seleno-methionine anomalous diffraction signal of the conditional peptide compared to the signal of labeled MHC β2m subunit. This method has the potential to facilitate high-throughput crystallography in various protein families

Molecular characterization of hepatitis B virus X gene in chronic hepatitis B patients

BACKGROUND: HBV-X protein is associated with the pathogenesis of HBV related diseases, specially in hepatocellular carcinomas of chronic patients. Genetic variability of the X gene includes genotypic specific variations and mutations emerging during chronic infection. Its coding sequence overlaps important regions for virus replication, including the basal core promoter. Differences in the X gene may have implications in biological functions of the protein and thus, affect the evolution of the disease. There are controversial results about the consequences of mutations in this region and their relationship with pathogenesis. The purpose of this work was to describe the diversity of HBV-X gene in chronic hepatitis patients infected with different genotypes, according to liver disease. METHODS: HBV-X gene was sequenced from chronic hepatitis B patient samples, analyzed by phylogeny and genotyped. Nucleotide and aminoacid diversity was determined calculating intragenetic distances. Mutations at 127, 130 and 131 aminoacids were considered in relation to liver disease. RESULTS: The most prevalent genotype detected in this cohort was F (F1 and F4), followed by D and A. Most of the samples corresponding to genotypes A and F1 were HBeAg(+) and for genotypes D and F4, HBeAg(−) samples were represented in a higher percentage. Intragenetic distance values were higher in HBeAg(−) than in positive samples for all genotypes, and lower in overlapped regions, compared to single codification ones. Nucleotide and aminoacid diversities were higher in HBeAg(−), than in HBeAg(+) samples. CONCLUSIONS: Independently of the infecting genotypes, mutations at any of 127, 130 and/or 131 aminoacid positions and HBeAg(−) status were associated with mild liver disease in this cohort

The Palomar Testbed Interferometer Calibrator Catalog

The Palomar Testbed Interferometer (PTI) archive of observations between 1998 and 2005 is examined for objects appropriate for calibration of optical long-baseline interferometer observations - stars that are predictably point-like and single. Approximately 1,400 nights of data on 1,800 objects were examined for this investigation. We compare those observations to an intensively studied object that is a suitable calibrator, HD217014, and statistically compare each candidate calibrator to that object by computing both a Mahalanobis distance and a Principal Component Analysis. Our hypothesis is that the frequency distribution of visibility data associated with calibrator stars differs from non-calibrator stars such as binary stars. Spectroscopic binaries resolved by PTI, objects known to be unsuitable for calibrator use, are similarly tested to establish detection limits of this approach. From this investigation, we find more than 350 observed stars suitable for use as calibrators (with an additional $\approx 140$ being rejected), corresponding to $\gtrsim 95$ sky coverage for PTI. This approach is noteworthy in that it rigorously establishes calibration sources through a traceable, empirical methodology, leveraging the predictions of spectral energy distribution modeling but also verifying it with the rich body of PTI's on-sky observations.Comment: 100 pages, 7 figures, 7 tables; to appear in the May 2008ApJS, v176n

Hepatitis B Virus Genotyping Among Chronic Hepatitis B Individuals With Resistance to Lamivudine in Shahrekord, Iran

Background: Hepatitis B infection, caused by hepatitis B Virus (HBV), is one of the major global public health problems. Hepatitis B Virus genotypes appear to show varying geographic distribution with possible pathogenic and therapeutic differences. Knowledge of HBV genotypes is very important for clinical treatment. Lamivudine is a nucleoside analogue that is clinically used to treat chronic hepatitis B infection. However, the main problem with the application of lamivudine is the development of viral resistance to the treatment with this anti viral drug. Besides, it has been suggested that lamivudine-resistant HBV may be genotype dependent. However, HBV genotype distribution and the biological relevance in this region are poorly understood. Objectives: The current study aimed to determine hepatitis B genotypes and their correlation with lamivudine-resistant HBV frequency among patients with chronic hepatitis B from Shahrekord, Iran. Methods and Materials: Hepatitis B virus DNA was detected by conventional PCR in some of the serum samples obtained from HBsAg-positive Chronic Hepatitis B (CHB) patients who were referred to Health Centers of Shahrekord for routine monitoring of the disease. Subsequently, using real-time PCR, the DNA samples were used for genotyping and analysis of resistance to lamivudine. Results: The DNA was detected in 23 out of 116 (19.82%) of the studied samples. Genotypes D and C were found in 17 out of 23 (73.9%), and in 6 out of 23 (26.1%) of the samples, respectively. To the authors' best knowledge, the current study is the first report on isolation of Genotype C from Iran. Two out of 17 (11.76%), and 6 out of 6 (100%) of genotypes D and C were resistant to lamivudine, respectively. Resistance to this drug was significantly different between genotypes C and D (P < 0.001). Conclusions: In addition to genotype D, other lamivudine resistant hepatitis B genotypes might be distributed in Iran