Characterization of A Novel Avalanche Photodiode for Single Photon Detection in VIS-NIR Range

In this work we investigate operation in the Geiger mode of the new single photon avalanche photo diode (SPAD) SAP500 manufactured by Laser Components. This SPAD is sensitive in the range 400-1000nm and has a conventional reach-through structure which ensures good quantum efficiency at the long end of the spectrum. By use of passive and active quenching schemes we investigate detection efficiency, timing jitter, dark counts, afterpulsing, gain and other important parameters and compare them to the "standard" low noise SPAD C30902SH from Perkin Elmer. We conclude that SAP500 offers better combination of detection efficiency, low noise and timing precision

The thermal expansion coefficients of the alpha and beta polymorphic forms of p-aminobenzoic acid in relation to their bulk crystal chemistry

The thermal expansion behaviour of the alpha and beta polymorphs of para-aminobenzoic acid are presented and discussed in terms of the bulk crystal chemistry and the associated strengths of the constituent intermolecular synthons for these two materials. Analysis of temperature dependant powder diffraction data over the temperature range 298.15–403.15 K facilitates calculation of the linear thermal expansion coefficients: αa = 8.36 × 10−06 K−1, αb = 94.5 × 10−06 K−1 and αc = 9.91 × 10−06 K−1 for the alpha polymorph and αa = 21.5 × 10−06 K−1, αb = 48.5 × 10−06 K−1 and αc = 2.22 × 10−06 K−1 for the beta polymorph. The exceptionally large increase in the thermal expansion of the b axis for the alpha form reflects the weak dispersive interactions which propagate along this axis. In contrast, the a and c axes contain relatively strong hydrogen bonds which stabilise the lattice and limit thermal expansion. The thermal expansion of the beta form reflects the more isotropic nature of the intermolecular synthons for this polymorph in comparison to the alpha form. The thermal expansion of the b axis of the beta form is larger than that of the a and c axes but to a much lesser extent than that observed for the alpha form. This is rationalised through identification of a hydrogen bonding component which contributes to the stabilisation of the b axis in comparison to the almost fully dispersive nature found in the alpha structure

Revealing the Roles of Desolvation and Molecular Self-Assembly in Crystal Nucleation from Solution: Benzoic and p -Aminobenzoic Acids

There has been much recent interest in the role of solution chemistry and in particular the importance of molecular self-assembly in the nucleation of crystalline phases. Techniques such as FTIR and NMR have highlighted the existence of solution-phase dimers which in many cases mirror the structural synthons found in the resulting macroscopic crystals. However, there are no reported examples in which this new insight into the solution phase has been linked directly to the kinetics of crystal nucleation. Here for the first time, using a combination of solution FTIR, computational chemistry, and measured crystal nucleation rate data, such a link is demonstrated for p-aminobenzoic (PABA) and benzoic acids nucleating from polar and nonpolar solvents. Solute dimerization and desolvation are found to be rate-determining processes in the overall nucleation pathway

Pain and Frailty in Hospitalized Older Adults

Introduction: Pain and frailty are prevalent conditions in the older population. Many chronic diseases are likely involved in their origin, and both have a negative impact on quality of life. However, few studies have analysed their association. Methods: In light of this knowledge gap, 3577 acutely hospitalized patients 65 years or older enrolled in the REPOSI register, an Italian network of internal medicine and geriatric hospital wards, were assessed to calculate the frailty index (FI). The impact of pain and some of its characteristics on the degree of frailty was evaluated using an ordinal logistic regression model after adjusting for age and gender. Results: The prevalence of pain was 24.7%, and among patients with pain, 42.9% was regarded as chronic pain. Chronic pain was associated with severe frailty (OR = 1.69, 95% CI 1.38–2.07). Somatic pain (OR = 1.59, 95% CI 1.23–2.07) and widespread pain (OR = 1.60, 95% CI 0.93–2.78) were associated with frailty. Osteoarthritis was the most common cause of chronic pain, diagnosed in 157 patients (33.5%). Polymyalgia, rheumatoid arthritis and other musculoskeletal diseases causing chronic pain were associated with a lower degree of frailty than osteoarthritis (OR = 0.49, 95%CI 0.28–0.85). Conclusions: Chronic and somatic pain negatively affect the degree of frailty. The duration and type of pain, as well as the underlying diseases associated with chronic pain, should be evaluated to improve the hospital management of frail older people

The multifaceted spectrum of liver cirrhosis in older hospitalised patients: Analysis of the REPOSI registry

Background: Knowledge on the main clinical and prognostic characteristics of older multimorbid subjects with liver cirrhosis (LC) admitted to acute medical wards is scarce. Objectives: To estimate the prevalence of LC among older patients admitted to acute medical wards and to assess the main clinical characteristics of LC along with its association with major clinical outcomes and to explore the possibility that well-distinguished phenotypic profiles of LC have classificatory and prognostic properties. Methods: A cohort of 6,193 older subjects hospitalised between 2010 and 2018 and included in the REPOSI registry was analysed. Results: LC was diagnosed in 315 patients (5%). LC was associated with rehospitalisation (age-sex adjusted hazard ratio, [aHR] 1.44; 95% CI, 1.10-1.88) and with mortality after discharge, independently of all confounders (multiple aHR, 2.1; 95% CI, 1.37-3.22), but not with in-hospital mortality and incident disability. Three main clinical phenotypes of LC patients were recognised: relatively fit subjects (FIT, N = 150), subjects characterised by poor social support (PSS, N = 89) and, finally, subjects with disability and multimorbidity (D&M, N = 76). PSS subjects had an increased incident disability (35% vs 13%, P < 0.05) compared to FIT. D&M patients had a higher mortality (in-hospital: 12% vs 3%/1%, P < 0.01; post-discharge: 41% vs 12%/15%, P < 0.01) and less rehospitalisation (10% vs 32%/34%, P < 0.01) compared to PSS and FIT. Conclusions: LC has a relatively low prevalence in older hospitalised subjects but, when present, accounts for worse post-discharge outcomes. Phenotypic analysis unravelled the heterogeneity of LC older population and the association of selected phenotypes with different clinical and prognostic features

Nanostructure of thin silicon films by combining HRTEM, XRD and Raman spectroscopy measurements and the implication to the optical properties

A series of thin silicon films with different degrees of crystallinity were prepared by decomposition of silane gas highly diluted with hydrogen, in radiofrequency glow discharge. The crystallite size, shape, and the portion of crystalline phase were investigated by high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy (RS), and X-ray powder diffraction (XRD). The absorption coefficient (a) was calculated from the measurement of UV–vis-transmittance. By using RS, the volume fractions of the crystalline phase were estimated from the ratio of the integrated intensities of transversal optical (TO)-related crystalline and amorphous bands. These results were in excellent agreement with the mean crystallite sizes measured in HRTEM images and crystallite sizes refined from XRD measurements. The red shift of absorption, appearing as a result of the increase of the crystal fraction, depends on the size and distribution of nanocrystals