Iterative wavefront optimization of ultrafast laser beams carrying orbital angular momentum.

Structured intense laser beams offer degrees of freedom that are highly attractive for high-field science applications. However, the performance of high-power laser beams in these applications is often hindered by deviations from the desired spatiotemporal profile. This study reports the wavefront optimization of ultrafast Laguerre-Gaussian beams through the synergy of adaptive optics and genetic algorithm-guided feedback. The results indicate that the intensity fluctuations along the perimeter of the target ring-shaped profile can be reduced up to ∼15%. Furthermore, the radius of the ring beam profile can be tailored to a certain extent by establishing threshold fitting criteria. The versatility of this approach is experimentally demonstrated in conjunction with different focusing geometries.

Chronic obstructive pulmonary disease in sub-Saharan Africa.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide and an important cause of death in sub-Saharan Africa (SSA). We conducted a systematic review and meta-analysis on the prevalence of and risk factors for COPD in SSA.METHODS: We conducted a protocol-driven systematic literature search in MEDLINE, EMBASE, CINAHL and Global Health, supplemented by a manual search of the abstracts from thoracic conference proceedings from 2017 to 2020. We did a meta-analysis of COPD prevalence and its association with current smoking.RESULTS: We identified 831 titles, of which 27 were eligible for inclusion in the review and meta-analysis. The population prevalence of COPD ranged from 1.7% to 24.8% (pooled prevalence: 8%, 95% CI 6-11). An increased prevalence of COPD was associated with increasing age, smoking and biomass smoke exposure. The pooled odds ratio for the effect of current smoking (vs. never smoked) on COPD was 2.20 (95% CI 1.62-2.99).CONCLUSION: COPD causes morbidity and mortality in adults in SSA. Smoking is an important risk factor for COPD in SSA, and this exposure needs to be reduced through the combined efforts of clinicians, researchers and policymakers to address this debilitating and preventable lung disease.

Single-shot, double-pulse determination of the detonation energy in nanosecond-laser ablation using the blast model.

We demonstrate a novel single-shot method to determine the detonation energy of laser-induced plasma and investigate its performance. This approach can be used in cases where there are significant shot-to-shot variations in ablation conditions, such as laser fluctuations, target inhomogeneity, or multiple filamentation with ultrashort pulses. The Sedov blast model is used to fit two time-delayed shadowgrams measured with a double-pulse laser. We find that the reconstruction of detonation parameters is insensitive to the choice of interpulse delay in double-pulse shadowgraphy. In contrast, the initial assumption of expansion dimensionality has a large impact on the reconstructed detonation energy. The method allows for a reduction in the uncertainties of blast wave energy measurements as a diagnostic technique employed in various laser ablation applications.

Optical emission from ultrafast laser filament-produced air plasmas in the multiple filament regime.

We perform optical emission spectroscopy of ultrafast laser filament-produced air plasmas in the multiple filament regime at driving wavelengths of 400 nm and 800 nm. The spatiotemporal structure of the emission from the plasmas are observed and the emission spectra are used to estimate plasma temperature and density for a range of laser parameters. Plasma temperatures are determined from the molecular nitrogen fluorescence, while the electron densities are estimated from Stark broadening of the oxygen-I 777.19-nm line. Electron temperatures are determined to be in the range of 5000-5200 K and they do not vary significantly along the length of the filament, nor are they sensitive to incident laser energy or wavelength. Electron densities are on order of 1016 cm-3 and show a greater variation with axial position, laser energy, and laser wavelength. We discuss mechanisms responsible for spatial localization of emitting species within the filament. Optical emission spectroscopy offers a simple, non-perturbing method to measure filament properties, that allows the information on the associated molecular transitions and excitation/ionization mechanisms to be extracted.

Ultrafast Laser Filament-induced Fluorescence Spectroscopy of Uranyl Fluoride.

Uranyl fluoride (UO2F2) is a compound which forms in the reaction between water and uranium hexafluoride, a uranium containing gas widely used for uranium enrichment. Uranyl fluoride exhibits negligible natural background in atmosphere; as a result, its observation implies the presence and active operation of nearby enrichment facilities and could be used as a tracer for treaty verification technologies. Additionally, detection of UO2F2 has a potential application in guiding remediation efforts around enrichment facilities. Laser-induced fluorescence (LIF) has been proposed in the past as a viable technique for the detection and tracking of UO2F2. We demonstrate that ultrafast laser filamentation coupled with LIF extends the capabilities of standard LIF to enable remote detection of UO2F2. An intense femtosecond laser pulse propagated in air collapses into a plasma channel, referred to as a laser filament, allowing for the extended delivery of laser energy. We first investigate the luminescence of UO2F2 excited by the second harmonic of an ultrafast Ti:sapphire laser and subsequently excite it using the conical emission that accompanies ultrafast laser filamentation in air. We measure the decay rates spanning 4.3-5.6 × 104 s-1 and discuss the characteristics of the luminescence for both ultrafast- and filament-excitation. Larger decay rates than those observed using standard LIF are caused by a saturated component of prompt decay from annihilation of dense excited states upon excitation with an ultrafast source. The reproducibility of such decay rates for the given range of incident laser intensities 1.0-1.6 × 1011 W cm-2 is promising for the application of this technique in remote sensing.

Cementum structure in Beluga whale teeth.

A large fraction of the volume of Beluga whale (Delphinapterus leucas) teeth consists of cementum, a mineralized tissue which grows throughout the life of the animal and to which the periodontal ligaments attach. Annular growth bands or growth layer groups (GLGs) form within Beluga cementum, and this study investigates GLG structure using X-ray fluorescence mapping and X-ray diffraction mapping with microbeams of synchrotron radiation. The Ca and Zn fluorescent intensities and carbonated hydroxyapatite (cAp) diffracted intensities rise and fall together and match the light-dark bands visible in transmitted light micrographs. Within the bands of maximum Ca and Zn intensity, the ratio of Zn to Ca is slightly higher than in the minima bands. Further, the GLG cAp, Ca and Zn modulation is preserved throughout the cementum for durations >25year. STATEMENT OF SIGNIFICANCE: Cementum is an important tooth tissue to which the periodontal ligaments attach and consists primarily of carbonated apatite mineral and collagen. In optical microscopy of cementum thin sections, light/dark bands are formed annually, and age at death is determined by counting these bands. We employ synchrotron X-ray diffraction and X-ray fluorescence mapping to show the bands in Beluga whale cementum result from differences in mineral content and not from differences in collagen orientation as was concluded by others. Variation in Zn fluorescent intensity was found to be very sensitive indicator of changing biomineralization and suggest that Zn plays an important role this process.

Markers to differentiate between Kaposi's sarcoma and tuberculous pleural effusions in HIV-positive patients.

BACKGROUND: Kaposi's sarcoma (KS) and tuberculosis (TB) commonly cause pleural effusions in high human immunodeficiency virus (HIV) burden resource-limited countries. Differentiating between them is challenging, as pleural biopsy and TB culture are rarely available. OBJECTIVES: To identify markers to differentiate between TB effusions and KS effusions in HIV-positive patients, and to compare liquid culture and Xpert MTB/RIF in pleural fluid. METHODS: Fifty HIV-positive patients with pleural effusions recruited in Malawi underwent pleural ultrasound and aspiration. Fluid visual inspection, cell count, bacterial culture, glucose/protein, solid and liquid TB culture and Xpert were performed. RESULTS: The mean age of the patients was 32 years; 30/50 (60%) were male and 29 (58%) had cutaneous/oral KS. Thirteen (26%) pleural fluid samples were liquid culture-positive for TB, while 9/13 (69%) were Xpert-positive. Three (10.3%) KS patients had culture-positive TB effusions; 17 (58.6%) had KS effusions. The relative risk of TB in KS patients increased with limited KS, loculated fluid and low glucose. Eleven (52.3%) non-KS patients had culture-positive TB effusions associated with male sex, straw-coloured fluid and fibrin stranding on ultrasound. CONCLUSIONS: KS patients were most likely to have KS effusion, but TB should be considered. Most non-KS patients had TB, supporting the use of World Health Organization guidelines. Xpert identified two thirds of liquid culture-positive results.

The Bionanoprobe: hard X-ray fluorescence nanoprobe with cryogenic capabilities.

Hard X-ray fluorescence microscopy is one of the most sensitive techniques for performing trace elemental analysis of biological samples such as whole cells and tissues. Conventional sample preparation methods usually involve dehydration, which removes cellular water and may consequently cause structural collapse, or invasive processes such as embedding. Radiation-induced artifacts may also become an issue, particularly as the spatial resolution increases beyond the sub-micrometer scale. To allow imaging under hydrated conditions, close to the `natural state', as well as to reduce structural radiation damage, the Bionanoprobe (BNP) has been developed, a hard X-ray fluorescence nanoprobe with cryogenic sample environment and cryo transfer capabilities, dedicated to studying trace elements in frozen-hydrated biological systems. The BNP is installed at an undulator beamline at sector 21 of the Advanced Photon Source. It provides a spatial resolution of 30 nm for two-dimensional fluorescence imaging. In this first demonstration the instrument design and motion control principles are described, the instrument performance is quantified, and the first results obtained with the BNP on frozen-hydrated whole cells are reported.

Chronic obstructive pulmonary disease in sub-Saharan Africa: a systematic review.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a major global health problem. Although COPD is the sixth most common cause of mortality in low- and middle-income countries, most research comes from high-income countries. We set out to systematically review existing published research on COPD in sub-Saharan Africa to identify knowledge gaps and opportunities for further research. METHODS: A literature search of MEDLINE, EMBASE and CINAHL (Cumulative Index to Nursing and Allied Health Literature) databases, published reviews, reference lists from included publications and abstracts from major thoracic medicine conference proceedings within the previous 2 years was performed using a protocol-driven search strategy. Texts were screened for inclusion by two independent reviewers. Studies were included if they met the following criteria: 1) COPD was an outcome, and 2) the population included people from sub-Saharan Africa. There were no language restrictions. FINDINGS: Our search identified 688 studies: 41 were duplicates, 638 were excluded, and 9 met our inclusion criteria. Included studies were all cross-sectional, and included 3673 people from four sub-Saharan African countries. Estimates of COPD prevalence varied between 4% and 25%. Only one study used population-based representative sampling and an adequate case definition. Assessment of risk factors was limited. CONCLUSIONS: There is little existing research on COPD in sub-Saharan Africa. Prevalence estimates varied, reflecting the range of populations studied, inconsistent diagnostic criteria and variable methods and methodological quality. Population-representative studies using appropriate case definitions are needed to define the epidemiology of COPD in sub-Saharan Africa and to inform the development of prevention and management strategies for the future.

X-ray fluorescence microscopy for investigation of archival tissues.

Several recent efforts in the radiation biology community worldwide have amassed records and archival tissues from animals exposed to different radionuclides and external beam irradiation. In most cases, these samples come from lifelong studies on large animal populations conducted in national laboratories and equivalent institutions throughout Europe, North America, and Japan. While many of these tissues were used for histopathological analyses, much more information may still be obtained from these samples. A new technique suitable for imaging of these tissues is x-ray fluorescence microscopy (XFM). Following development of third generation synchrotrons, XFM has emerged as an ideal technique for the study of metal content, speciation, and localization in cells, tissues, and organs. Here the authors review some of the recent XFM literature pertinent to tissue sample studies and present examples of XFM data obtained from tissue sections of beagle dog samples, which show that the quality of archival tissues allows XFM investigation.

The National Stroke Strategy - is it achievable?

INTRODUCTION: Timing of intervention in symptomatic carotid disease is critical. The UK Department of Health's National Stroke Strategy published in December 2007 recommends urgent carotid intervention within 48 h, in appropriate patients, who have suffered a transient ischaemic attack (TIA), amaurosis fugax or minor stroke. Despite the running of a rapid-access clinic for patients with symptoms of TIA, the time from symptom to surgery is rarely less than 2 weeks. To date, there has been little published research on the UK public response to the symptoms of TIA, and no study at all of the response of primary care to such patients. The aim of this study was to ascertain both these responses to see whether a 48-h target is achievable. PATIENTS AND METHODS: A total of 402 men attending our aortic aneurysm screening sessions were asked to complete a questionnaire requesting their most likely response to an episode of amaurosis fugax or TIA. All 45 GP practices in the hospital catchment area were asked how they would respond to patients requesting to be seen with the symptoms used in the questionnaire. RESULTS: Nearly one in six patients would ignore the symptom unless it recurred, approximately half would request a GP appointment and a third would see an optician if they had amaurosis fugax. The mean waiting time to see a GP was 2 days for a routine appointment and within 24 h for an emergency appointment. CONCLUSIONS: It is clear that a significant number of people would ignore the first symptom of carotid ischaemia; for those with amaurosis fugax, nearly a third would initially seek help from their optician. Those given a routine GP appointment would have to wait a minimum of 2 days. If the Department of Health is serious about reducing the incidence of stroke and introducing a target of 48 h from symptom to treatment, then there needs to be a wide-spread public and healthcare education programme, in particular alerting opticians and GP receptionists that these symptoms constitute a medical emergency.

Performance evaluation and testing of digital intra-oral radiographic systems.

Four digital intra-oral radiographic systems were tested and evaluated; three charge-coupled device (CCD) based systems from RVG, Visualix and Sidexis and a photostimulable phosphor (PSP) system from DenOptix. Image quality was assessed using three purpose-built phantoms to measure uniformity, low contrast detail detectability and signal-to-noise ratio (SNR). Limiting resolution was measured using a 20 lp mm(-1) bar pattern. Radiation output inaccuracies caused difficulties in achieving optimum doses for CCD systems. However, the accuracy was improved by using K-edge filters. SNR measurements proved to be a useful tool in assessing system performance. Each system has specific attributes: resolution was highest for the RVG system, the Visualix system measured the highest SNR and the lowest exposure settings were on the Sidexis system. Test methods and phantoms developed are suitable for acceptance testing and commissioning digital dental X-ray systems and for programming each system to produce an optimum level of image quality.

The impact of family history of breast cancer on women's health beliefs, salience of breast cancer family history, and degree of involvement in breast cancer issues.

Prior investigations have employed the Health Belief Model (HBM) to predict health care utilization and cancer screening behaviors. The HBM is expanded in the current investigation to include issue involvement with breast cancer and salience of breast cancer family history. Differences in the constructs of this expanded HBM, as they relate to mammography screening, between women with positive and negative family histories of breast cancer were assessed in 378 women. Perceived benefits and barriers were found to be similar for women with positive and negative family histories of breast cancer. However, susceptibility, cues to action, salience of family history, and issue involvement were found to be more relevant for women with a positive family history of breast cancer. These findings have implications for interventions directed at increasing compliance with recommendations for breast cancer screening.

What the mouth has to say about diabetes. Careful examinations can avert serious complications.

Periodontal disease is a major but preventable complication of diabetes mellitus. Patient education, good glycemic control, regular dental care, appropriate diet, and a team approach that involves physicians, dietitians, dentists, and other health professionals offer the best chance for optimum care for these patients. Other oral complications of diabetes include tooth decay, xerostomia, candidiasis, and oral peripheral neuropathy. The mouth may also reflect secondary causes of diabetes, and oral examination may provide clues to diseases that coexist with type 1 diabetes. Truly, the mouth has much to say about diabetes.

Epidemiology of reported syphilis among U.S. Navy and Marine Corps personnel, 1985-1987.

The authors analyzed four hundred fifty-six cases of syphilis reported via a passive disease surveillance system in the Navy and Marine Corps during 1985-1987. The annual incidence of all reported cases significantly increased during this time from approximately 16 out of 100,000 in 1985 to 23 out of 100,000 in 1987. Much of this increase is attributed to concurrent increased rates of primary syphilis and late latent syphilis. Incidence rates for all stages of syphilis combined increased significantly among men and blacks during these years. Cumulatively, most reported patients were male (422, 96.1%), aged 20-24 years (204, 55.1%), E-3 (junior) enlisted pay grade (101, 30.1%), and black (217, 53.8%). Sexual exposures were reported most frequently from the eastern U.S. coast and from western Pacific countries.