On the axial chirality of leucoindigo.

The diagonal components and the trace of two tensors which account for chiroptical response of the leucoindigo molecule C 16 H 12 N 2 O 2 that is, static anapole magnetizability, and dynamic electric dipole-magnetic dipole polarisability depending on the frequency of impinging light, are a function of the ϕ dihedral angle of torsion about the central CC bond, assumed to lie in the y direction of the coordinate system. They vanish for symmetry reasons at ϕ = 0 ∘ and ϕ = 180 ∘ , corresponding respectively to C 2 v and C 2 h point group symmetries, that is, cis and trans conformers characterized by the presence of molecular symmetry planes. Nonetheless, diagonal components and average value of static anapole polarizability and optical rotation tensors vanish at ϕ = 90 ∘ , where leucondigo is unquestionably chiral from the geometrical viewpoint. Vanishing values of the average chiroptical properties have been observed also in the proximity of other ϕ angles. Attempts have been made to explain the occurrence of accidental zeros of chiroptical properties in terms of transition frequencies and scalar products appearing in the numerator of their quantum mechanical definitions. Within the electric dipole approximation, the presence of anomalous vanishing values of tensor components of anapole magnetizability and electric-magnetic dipole polarizability is ascribed to physical achirality, arising from the lack of either toroidal or spiral electron flow along the x , y and z directions.

Optical scintillation in a maritime environment.

Free space optical propagation affects many application areas, including communication, LIDAR, and directed energy. Optical turbulence causes dynamic changes in the propagated beam that can impact these applications. A primary measure of these effects is the optical scintillation index. In this work, we report on a comparison of experimental measurements of optical scintillation, conducted on a 16 km range across the Chesapeake Bay over a period of three months, to model predictions. Models for turbulence parameters were based on NAVSLaM, a Monin Obhukov similarity theory, and used environmental measurements taken on the range simultaneously with the scintillation measurements. These parameters were then used in two different classes of optical scintillation models: Extended Rytov theory, and wave optic simulation. We show that wave optics simulation matched the data much better than Extended Rytov theory, and that prediction of scintillation using environmental parameters is possible. In addition, we show that optical scintillation over water has different characteristics in stable versus unstable conditions.

Statistical mechanics of beam self-cleaning in GRIN multimode optical fibers.

Since its first demonstration in graded-index multimode fibers, spatial beam self-cleaning has attracted a growing research interest. It allows for the propagation of beams with a bell-shaped spatial profile, thus enabling the use of multimode fibers for several applications, from biomedical imaging to high-power beam delivery. So far, beam self-cleaning has been experimentally studied under several different experimental conditions. Whereas it has been theoretically described as the irreversible energy transfer from high-order modes towards the fundamental mode, in analogy with a beam condensation mechanism. Here, we provide a comprehensive theoretical description of beam self-cleaning, by means of a semi-classical statistical mechanics model of wave thermalization. This approach is confirmed by an extensive experimental characterization, based on a holographic mode decomposition technique, employing laser pulses with temporal durations ranging from femtoseconds up to nanoseconds. An excellent agreement between theory and experiments is found, which demonstrates that beam self-cleaning can be fully described in terms of the basic conservation laws of statistical mechanics.

Continuous spatial self-cleaning in GRIN multimode fiber for self-referenced multiplex CARS imaging.

We demonstrate how spatial beam self-cleaning and supercontinuum generation in graded-index multimode optical fibers can be directly applied in multiplex coherent anti-Stokes Raman Scattering (M-CARS) spectroscopy. Although supercontinuum generation causes pump depletion mainly in the center of the beam, the partial recovery of the pump brightness due to self-cleaning may enable self-referenced M-CARS, with no additional delay lines to synchronize pump and Stokes waves. As a proof-of-principle, we report examples of imaging of single chemical compounds and polystyrene beads. The new scheme paves the way towards simpler M-CARS systems based on multimode fiber sources.

Helical plasma filaments from the self-channeling of intense femtosecond laser pulses in optical fibers: publisher's note.

This publisher's note contains a correction to Opt. Lett.47, 1 (2022)10.1364/OL.445321.

Helical plasma filaments from the self-channeling of intense femtosecond laser pulses in optical fibers.

We experimentally and numerically study the ignition of helical-shaped plasma filaments in standard optical fibers. Femtosecond pulses with megawatt peak power with proper off-axis and tilted coupling in the fiber core produce plasma skew rays. These last for distances as long as 1000 wavelengths thanks to a combination of linear waveguiding and the self-channeling effect. Peculiar is the case of graded-index multimode fibers; here the spatial self-imaging places constraints on the helix pitch. These results may find applications for fabricating fibers with helical-shaped core micro-structuration as well as for designing laser components and three-dimensional optical memories.

Thermalization of Orbital Angular Momentum Beams in Multimode Optical Fibers.

We report on the thermalization of light carrying orbital angular momentum in multimode optical fibers, induced by nonlinear intermodal interactions. A generalized Rayleigh-Jeans distribution of asymptotic mode composition is obtained, based on the conservation of the angular momentum. We confirm our predictions by numerical simulations and experiments based on holographic mode decomposition of multimode beams. Our work establishes new constraints for the achievement of spatial beam self-cleaning, giving previously unforeseen insights into the underlying physical mechanisms.

Experimental observation of self-imaging in SMF-28 optical fibers.

Spatial self-imaging, consisting of the periodic replication of the optical transverse beam profile along the propagation direction, can be achieved in guided wave systems when all excited modes interfere in phase. We exploited material defects photoluminescence for directly visualizing self-imaging in a few-mode, nominal singlemode SMF-28 optical fiber. Visible luminescence was excited by intense femtosecond infrared pulses via multiphoton absorption processes. Our method permits us to determine the mode propagation constants and the cutoff wavelength of transverse fiber modes.

3D time-domain beam mapping for studying nonlinear dynamics in multimode optical fibers.

Characterization of the complex spatiotemporal dynamics of optical beam propagation in nonlinear multimode fibers requires the development of advanced measurement methods, capable of capturing the real-time evolution of beam images. We present a new space-time mapping technique, permitting the direct detection, with picosecond temporal resolution, of the intensity from repetitive laser pulses over a grid of spatial samples from a magnified image of the output beam. By using this time-resolved mapping, we provide, to the best of our knowledge, the first unambiguous experimental observation of instantaneous intrapulse nonlinear coupling processes among the modes of a graded index fiber.

Posterior dynamic neutralization and hybrid stabilization in degenerative spine diseases: long-term clinical and radiological outcomes.

Dynamic spinal stabilization aims to reduce some of the problems inherent with traditional fusion. The aim of our study is to analyse clinical and radiological outcomes and to identify the causes of clinical failure in patients who underwent posterior dynamic neutralization or posterior hybrid stabilization because of degenerative lumbar spine diseases. We retrospectively analysed 80 patients at 7.1 years mean follow-up (Range: 5.1 - 8.3 years): 50 were treated with Dynamic Stabilization System (Dynesys) (mean age 47 years old) and 30 with Dynamic Transition Option (mean age 48 years old). We performed clinical pre-and post-operative evaluation using Visual Analogue Scale (VAS), Oswestry Low Back Pain Scale (ODI) and X-rays study. Results: we reported an important reduction of VAS from 7 to 2 (p<.001) and minimal disability in 65% of the patients, moderate disability in 18.2%, severe disability in 12.5% and crippling back pain in 4.3%. X-ray analysis showed a significative decrease of 3.5° with respect to the preoperative values, exactly 2° in neutral position postop, 1.2° in flexion postop and 2.5° in extension postop. Data showed greater reduction of extension than flexion in postoperative period. Dynamic neutralization limits more the extension than flexion. The correct preoperative planning, the careful selection of patients and the meticulous surgical technique are mandatory to avoid clinical failures. It is very important to identify the correct screw positioning and to avoid excessive pre-tensioning of the implant. Posterior dynamic neutralization and hybrid stabilization are valid alternative to spinal fusion in degenerative spine disease.

Measles immunity in an Italian teaching hospital.

BACKGROUND: Healthcare workers (HCWs) have an increased exposure risk to measles, which can put them, their patients and their relatives at risk of infection. In Italy, 4617 cases of measles were reported in 2017; 302 involving HCWs. According to the Italian National Immunization and Prevention Plan, all HCWs should have demonstrable evidence of immunity to measles. AIMS: To evaluate measles immunization status in HCWs at a large Italian teaching hospital. METHODS: We analysed clinical records and measles-specific IgG antibody titres of HCWs undergoing occupational health surveillance between 1 January and 31 August 2017. RESULTS: Among the 1532 HCWs (mean age 32.7 ± 10.4 years) included in the study, 87% (1328) had protective antibody titres. The proportion of protective titres was highest in those born before 1982. No significant gender differences in mean measles-specific IgG antibody titres were detected. CONCLUSIONS: Our study shows non-protective measles IgG antibody titres in a substantial percentage of HCWs, especially those born in the 1980s and 1990s. Due to the increased risk of measles transmission in the hospital environment, increased prevention strategies are required, including rigorous screening and prompt vaccination of non-immune workers.

Managing the risk of bacterial meningitis among healthcare workers.

BACKGROUND: Meningococcal disease is generally caused by A, B, C, W and Y subgroups of Neisseria meningitidis. In 2015, the Italian mass media focused on this disease due to the death of two nurses. This generated alarm in the general population, especially in healthcare workers (HCWs). The Occupational Medicine department of the Foundation PTV Polyclinic Tor Vergata (PTV) offered free MenACWY vaccine to HCWs and to students of the University of Rome Tor Vergata. AIMS: To analyse the prevalence of N. meningitidis in PTV, a large teaching hospital, and to evaluate preventive measures offered to individuals at risk (i.e. HCWs and students). METHODS: The Hospital Informatic Service provided data about patients admitted to PTV from January 2012 to December 2016. Hospital Discharge Registers were analysed and all cases of meningitis were selected. MenACWY vaccine administered to HCWs and students of PTV in 2017 was analysed. RESULTS: There was just one case of meningococcal disease in 2016. Of the 117 MenACWY vaccines administered, 42% were given to students, 32% to doctors, 8% to nurses, 2% to clerks and 16% to other healthcare professionals. CONCLUSIONS: International guidelines recommend MenACWY vaccine for microbiologists exposed to N. meningitidis isolates. The Italian Legislative Decree 81/2008, however, states that occupational physicians can adopt special protective measures such as vaccination programmes for HCWs. The response rate highlights how perceived risk may influence behaviour even in populations with a higher background knowledge than the general population.

Frailty screening and assessment tools: a review of characteristics and use in Public Health.

INTRODUCTION: Frailty screening and assessment are a fundamental issue in Public Health in order to plan prevention programs and services. METHODOLOGY: By a narrative review of the literature employing the International Narrative Systematic Assessment tool, the authors aims to develop an updated framework for the main procedures and measurement tools to assess frailty in older adults, paying attention to the use in the primary care setting. RESULTS: The study selected 10 reviews published between January 2010 and December 2016 that define some characteristics of the main tools used to measure the frailty. Within the selected reviews only one of the described tools met all the criteria (multidimensionality, quick and easy administration, accurate risk prediction of negative outcomes and high sensitivity and specificity) necessary for a screening tool. CONCLUSION: Accurate risk prediction of negative outcomes could be the appropriate and sufficient criteria to assess a tool aimed to detect frailty in the community-dwelling elderly population. A two-step process (a first short questionnaire to detect frailty and a second longer questionnaire to define the care demand at individual level) could represent the appropriate pathway for planning care services at community level.

Formoterol and fluticasone propionate combination improves histone deacetylation and anti-inflammatory activities in bronchial epithelial cells exposed to cigarette smoke.

BACKGROUND: The addition of long-acting beta2-agonists (LABAs) to corticosteroids improves asthma control. Cigarette smoke exposure, increasing oxidative stress, may negatively affect corticosteroid responses. The anti-inflammatory effects of formoterol (FO) and fluticasone propionate (FP) in human bronchial epithelial cells exposed to cigarette smoke extracts (CSE) are unknown. AIMS: This study explored whether FP, alone and in combination with FO, in human bronchial epithelial cellline (16-HBE) and primary bronchial epithelial cells (NHBE), counteracted some CSE-mediated effects and in particular some of the molecular mechanisms of corticosteroid resistance. METHODS: 16-HBE and NHBE were stimulated with CSE, FP and FO alone or combined. HDAC3 and HDAC2 activity, nuclear translocation of GR and NF-κB, pERK1/2/tERK1/2 ratio, IL-8, TNF-α, IL-1ß mRNA expression, and mitochondrial ROS were evaluated. Actin reorganization in neutrophils was assessed by fluorescence microscopy using the phalloidin method. RESULTS: In 16-HBE, CSE decreased expression/activity of HDAC3, activity of HDAC2, nuclear translocation of GR and increased nuclear NF-κB expression, pERK 1/2/tERK1/2 ratio, and mRNA expression of inflammatory cytokines. In NHBE, CSE increased mRNA expression of inflammatory cytokines and supernatants from CSE exposed NHBE increased actin reorganization in neutrophils. FP combined with FO reverted all these phenomena in CSE stimulated 16-HBE cells as well as in NHBE cells. CONCLUSIONS: The present study provides compelling evidences that FP combined with FO may contribute to revert some processes related to steroid resistance induced by oxidative stress due to cigarette smoke exposure increasing the anti-inflammatory effects of FP.

Observation of polarization-maintaining light propagation in depoled compositionally disordered ferroelectrics.

We investigate the evolution of the state of polarization of light propagating through bulk depoled composite ferroelectrics below the Curie temperature. In contrast to standard depoled ferroelectrics, where random birefringence causes depolarization and scattering, light is observed to suffer varying degrees of depolarization and remains fully polarized when linearly polarized along the crystal principal axes. The effect is found to be supported by the formation of polarized speckles organized into a spatial lattice and occurs as the ferroelectric settles into a spontaneous super-crystal, a three-dimensional coherent mosaic of ferroelectric clusters. The polarization lattices gradually disappear as the ferroelectric state reduces to a disordered distribution of polar nanoregions above the critical point.

Electric Dipole-Magnetic Dipole Polarizability and Anapole Magnetizability of Hydrogen Peroxide as Functions of the HOOH Dihedral Angle.

The trace of tensors that account for chiroptical response of the H2O2 molecule is a function of the HO-OH dihedral angle. It vanishes at 0° and 180°, due to the presence of molecular symmetry planes, but also for values in the range 90-100° of this angle, in which the molecule is unquestionably chiral. Such an atypical effect is caused by counterbalancing contributions of diagonal tensor components with nearly maximal magnitude but opposite sign, determined by electron flow in open or closed helical paths, and associated with induced electric and magnetic dipole moments and anapole moments. For values of dihedral angle external to the 90-100° interval, the helical paths become smaller in size, thus reducing the amount of cancellation among diagonal components. Shrinking of helical paths determines the appearance of extremum values of tensor traces approximately at 50° and 140° dihedral angles.

Multicenter evaluation of the BD max enteric bacterial panel PCR assay for rapid detection of Salmonella spp., Shigella spp., Campylobacter spp. (C. jejuni and C. coli), and Shiga toxin 1 and 2 genes.

Diarrhea due to enteric bacterial pathogens causes significant morbidity and mortality in the United States and worldwide. However, bacterial pathogens may be infrequently identified. Currently, culture and enzyme immunoassays (EIAs) are the primary methods used by clinical laboratories to detect enteric bacterial pathogens. We conducted a multicenter evaluation of the BD Max enteric bacterial panel (EBP) PCR assay in comparison to culture for the detection of Salmonella spp., Shigella spp., Campylobacter jejuni, and Campylobacter coli and an EIA for Shiga toxins 1 and 2. A total of 4,242 preserved or unpreserved stool specimens, including 3,457 specimens collected prospectively and 785 frozen, retrospective samples, were evaluated. Compared to culture or EIA, the positive percent agreement (PPA) and negative percent agreement (NPA) values for the BD Max EBP assay for all specimens combined were as follows: 97.1% and 99.2% for Salmonella spp., 99.1% and 99.7% for Shigella spp., 97.2% and 98.4% for C. jejuni and C. coli, and 97.4% and 99.3% for Shiga toxins, respectively. Discrepant results for prospective samples were resolved with alternate PCR assays and bidirectional sequencing of amplicons. Following discrepant analysis, PPA and NPA values were as follows: 97.3% and 99.8% for Salmonella spp., 99.2% and 100% for Shigella spp., 97.5% and 99.0% for C. jejuni and C. coli, and 100% and 99.7% for Shiga toxins, respectively. No differences in detection were observed for samples preserved in Cary-Blair medium and unpreserved samples. In this large, multicenter study, the BD Max EBP assay showed superior sensitivity compared to conventional methods and excellent specificity for the detection of enteric bacterial pathogens in stool specimens.

Free-space optical communications research and demonstrations at the U.S. Naval Research Laboratory.

Free-space optical communication can allow high-bandwidth data links that are hard to detect, intercept, or jam. This makes them attractive for many applications. However, these links also require very accurate pointing, and their availability is affected by weather. These challenges have limited the deployment of free-space optical systems. The U.S. Naval Research Laboratory has, for the last 15 years, engaged in research into atmospheric propagation and photonic components with a goal of characterizing and overcoming these limitations. In addition several demonstrations of free-space optical links in real-world Navy applications have been conducted. This paper reviews this work and the principles guiding it.

Reduction of scintillation in optical modulating retro-reflector links.

Optical modulating retro-reflectors enable free-space optical links that have greatly reduced pointing requirements and do not require a laser at one end of the link. However, these types of links can exhibit very high optical scintillation due to the double passage of the beam through the atmosphere. This high scintillation causes fades and surges that can lead to packet errors in the link. It is shown that scintillation can be greatly reduced through a combination of techniques including retro-reflector diversity, aperture averaging and bistatic optical interrogation. Improvements of 20 dB in link performance are demonstrated.

Multi-center evaluation of the VITEK® MS system for mass spectrometric identification of non-Enterobacteriaceae Gram-negative bacilli.

Studies have demonstrated that matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a rapid, accurate method for the identification of clinically relevant bacteria. The purpose of this study was to evaluate the performance of the VITEK MS v2.0 system (bioMérieux) for the identification of the non-Enterobacteriaceae Gram-negative bacilli (NEGNB). This multi-center study tested 558 unique NEGNB clinical isolates, representing 18 genera and 33 species. Results obtained with the VITEK MS v2.0 were compared with reference 16S rRNA gene sequencing and when indicated recA sequencing and phenotypic analysis. VITEK MS v2.0 provided an identification for 92.5 % of the NEGNB isolates (516 out of 558). VITEK MS v2.0 correctly identified 90.9 % of NEGNB (507 out of 558), 77.8 % to species level and 13.1 % to genus level with multiple species. There were four isolates (0.7 %) incorrectly identified to genus level and five isolates (0.9 %), with one incorrect identification to species level. The remaining 42 isolates (7.5 %) were either reported as no identification (5.0 %) or called "mixed genera" (2.5 %) since two or more different genera were identified as possible identifications for the test organism. These findings demonstrate that the VITEK MS v2.0 system provides accurate results for the identification of a challenging and diverse group of Gram-negative bacteria.