Prospects for atomic magnetometers employing hollow core optical fibre

Presently, among the most demanding applications for highly sensitive magnetometers are Magnetocardiography (MCG) and Magnetoencephalography (MEG), where sensitivities of around 1pT.Hz<sup>-1/2</sup> and 1fT.Hz<sup>-1/2</sup> are required. Cryogenic Superconducting Quantum Interference Devices (SQUIDs) are currently used as the magnetometers. However, there has been some recent work on replacing these devices with magnetometers based on atomic spectroscopy and operating at room temperature. There are demonstrations of MCG and MEG signals measured using atomic spectroscopy These atomic magnetometers are based on chip-scale microfabricated components. In this paper we discuss the prospects of using photonic crystal optical fibres or hollow core fibres (HCFs) loaded with Rb vapour in atomic magnetometer systems. We also consider new components for magnetometers based on mode-locked semiconductor lasers for measuring magnetic field via coherent population trapping (CPT) in Rb loaded HCFs

Output power limitations and improvements in passively mode locked GaAs/AlGaAs quantum well lasers

We report a novel approach for increasing the output power in passively mode locked semiconductor lasers. Our approach uses epitaxial structures with an optical trap in the bottom cladding that enlarges the vertical mode size to scale the pulse saturation energy. With this approach we demonstrate a very high peak power of 9.8 W per facet, at a repetition rate of 6.8 GHz and with pulse duration of 0.71 ps. In particular, we compare two GaAs/AlGaAs epilayer designs, a double quantum well design operating at 830 nm and a single quantum well design operating at 795 nm, with vertical mode sizes of 0.5 and 0.75 μm, respectively. We show that a larger mode size not only shifts the mode locking regime of operation toward higher powers, but also produces other improvements with respect to two main failure mechanisms that limit the output power, catastrophic optical mirror damage and catastrophic optical saturable absorber damage. For the 830-nm material structure, we also investigate the effect of nonabsorbing mirrors on output power and mode locked operation of colliding pulse mode locked lasers

Passively mode-locked semiconductor laser for coherent population trapping in ⁸⁷Rb

Passively mode-locked semiconductor laser for coherent population trapping in <sup>87</sup>Rb is reported. The laser material used is a 793nm GaAs/Al<sub>x</sub>Ga<sub>1-x</sub>As single quantum well (QW) graded index separate confinement heterostructure

The hepatitis D virus in Italy. A vanishing infection, not yet a vanished disease

Introduction: Hepatitis D Virus (HDV) infection is vanishing in Italy. It is therefore believed that hepatitis D is no longer a medical problem in the domestic population of the country but remains of concern only in migrants from HDV-endemic areas. Objectives: To report the clinical features and the medical impact of the residual domestic HDV infections in Italy. Methods: From 2010 to 2019, one hundred ninety-three first-time patients with chronic HDV liver disease attended gastroenterology units in Torino and San Giovanni Rotondo (Apulia); 121 were native Italians and 72 were immigrants born abroad. For this study, we considered the 121 native Italians in order to determine their clinical features and the impact of HDV disease in liver transplant programs. Results: At the last observation the median age of the 121 native Italians was 58 years. At the end of the follow-up, the median liver stiffness was 12.0 kPa (95% CI 11.2–17.4), 86 patients (71.1%) had a diagnosis of cirrhosis; 80 patients (66.1%) remained HDV viremic. The ratio of HDV to total HBsAg transplants varied from 38.5% (139/361) in 2000–2009 to 50.2% (130/259) in 2010–2019, indicating a disproportionate role of hepatitis D in liver transplants compared to the minor prevalence of HDV infections in the current scenario of HBsAg-positive liver disorders in Italy. Conclusion: Though HDV is vanishing in Italy, a legacy of ageing native-Italian patients with advanced HDV liver disease still represents an important medical issue and maintains an impact on liver transplantation

A new approach for identifying non-pathogenic mutations. An analysis of the cystic fibrosis transmembrane regulator gene in normal individuals

Given q as the global frequency of the alleles causing a disease, any allele with a frequency higher than q minus the cumulative frequency of the previously known disease-causing mutations (threshold) cannot be the cause of that disease. This principle was applied to the analysis of cystic fibrosis transmembrane conductance regulator (CFTR) mutations in order to decide whether they are the cause of cystic fibrosis. A total of 191 DNA samples fl-om random individuals from Italy, France, and Spain were investigated by DGGE (denaturing gradient gel electrophoresis) analysis of all the coding and proximal non-coding regions of the gene. The mutations detected by DGGE were identified by sequencing. The sample size was sufficient to select essentially all mutations with a frequency of at least 0.01. A total of 46 mutations was detected, 20 of which were missense mutations. Four new mutations were identified: 1341+28 C/T, 2082 C/T, L1096R, and I1131V. Thirteen mutations (125 G/C, 875+40 A/G, TTGAn, IVS8-6 5T, IVS8-6 9T, 1525-61 A/G, M470V, 2693 T/G, 3061-65 C/A, 4002 A/G, 4521 G/A, IVS8 TG10, IVS8 TG12) were classified as non-CF-causing alleles on the basis of their frequency. The remaining mutations have a cumulative frequency far exceeding q; therefore, most of them cannot be CF-causing mutations. This is the first random survey capable of detecting all the polymorphisms of the coding sequence of a gene