Passive mode-locked cesium diode-pumped alkali laser.

A first, to the best of our knowledge, demonstration of passive mode-locking in diode-pumped alkali laser (DPAL) is reported in this paper. An intracavity cesium vapor cell, buffered by atmospheric pressure methane, is used to passively mode lock a continuously pumped cesium DPAL with a static gain medium. A train of short pulses with duration less than 460 ps was observed using a 2.0-GHz bandwidth detector that limited the real time duration measurements. The calculated minimum duration for these pulses is 57 ps.

AMON: annotation of metabolite origins via networks to integrate microbiome and metabolome data.

BACKGROUND: Untargeted metabolomics of host-associated samples has yielded insights into mechanisms by which microbes modulate health. However, data interpretation is challenged by the complexity of origins of the small molecules measured, which can come from the host, microbes that live within the host, or from other exposures such as diet or the environment. RESULTS: We address this challenge through development of AMON: Annotation of Metabolite Origins via Networks. AMON is an open-source bioinformatics application that can be used to annotate which compounds in the metabolome could have been produced by bacteria present or the host, to evaluate pathway enrichment of host verses microbial metabolites, and to visualize which compounds may have been produced by host versus microbial enzymes in KEGG pathway maps. CONCLUSIONS: AMON empowers researchers to predict origins of metabolites via genomic information and to visualize potential host:microbe interplay. Additionally, the evaluation of enrichment of pathway metabolites of host versus microbial origin gives insight into the metabolic functionality that a microbial community adds to a host:microbe system. Through integrated analysis of microbiome and metabolome data, mechanistic relationships between microbial communities and host phenotypes can be better understood.

Vapour-liquid-solid growth of ZnO-ZnMgO core-shell nanowires by gold-catalysed molecular beam epitaxy.

Nanowire heterostructures, combining multiple phases within a single nanowire, modify functional properties and offer a platform for novel device development. Here, ZnO/ZnMgO core-shell nanowires are grown by molecular beam epitaxy. At growth temperatures above 750 °C, Mg diffuses into ZnO making heterostructure growth impossible; at lower shell-growth temperatures (500 °C), the core-shell structure is retained. Even very thin ZnMgO shells show increased intensity photoluminescence (PL) across the ZnO band-gap and a suppression in defect-related PL intensity, relative to plain ZnO nanowires. EDX measurements on shell thickness show a correlation between shell thickness and core diameter which is explained by a simple growth model.

Beam quality measurement of a static-cell cesium DPAL with a stable resonator.

We performed a measurement of the beam quality of an optimized moderate power cesium Diode Pumped Alkali Laser (DPAL). The DPAL used a stable resonator and operated in continuous wave mode using a static cell filled with metallic cesium and a mixture of methane and helium at 200 and 400 torr respectively. In this work, we characterized the spatial quality of the DPAL output beam. As a result of these experiments we determined the output beam quality was excellent (M2 < 1.2) in the whole range of pump power used (up to 11.5W) and pump intensities reaching 1.5 kW/cm2. The optical conversion efficiency of this laser was 51% and the slope efficiency was 61%.

Narrowband diode laser pump module for pumping alkali vapors.

We describe a method of line narrowing and frequency-locking a diode laser stack to an alkali atomic line for use as a pump module for Diode Pumped Alkali Lasers. The pump module consists of a 600 W antireflection coated diode laser stack configured to lase using an external cavity. The line narrowing and frequency locking is accomplished by introducing a narrowband polarization filter based on magneto-optical Faraday effect into the external cavity, which selectively transmits only the frequencies that are in resonance with the 62S1/2 → 62P3/2 transition of Cs atoms. The resulting pump module has demonstrated that a diode laser stack, which lases with a line width of 3 THz without narrowbanding, can be narrowed to 10 GHz. The line narrowed pump module produced 518 Watts that is 80% of the power generated by the original broadband diode laser stack.

Symposium review: Building a better cow-The Australian experience and future perspectives.

Genomic selection has led to opportunities for developing new breeding values that rely on phenotypes in dedicated reference populations of genotyped cows. In Australia, it has been applied to 2 novel traits: feed efficiency, which was released in 2015 as feed saved breeding values, and heat tolerance genomic breeding values, released for the first time in 2017. Feed saved is already included in the national breeding objective, which is focused on profitability and designed to be in line with farmer preferences. Our future focus is on traits associated with animal health, either directly or in combination with predictor traits, such as mid-infrared spectral data and, into the future, automated data capture. Although it is common for many evaluated traits to have genomic reliabilities ranging between 60 and 75%, many new, genomic information-only traits are likely to have reliabilities of less than 50%. Pooling of phenotype data internationally and investing in maintenance of reference populations is one option to increase the reliability of these traits; the other is to apply improved genomic prediction methods. For example, advances in the use of sequence data, in addition to gene expression studies, can lead to improved persistence of genomic breeding values across breeds and generations and potentially lead to greater reliabilities. Lower genomic reliabilities of novel traits could reduce the overall index reliability. However, provided these traits contribute to the overall breeding objective (e.g., profit), they are worth including. Bull selection tools and personalized genetic trends are already available, but increased access to economic and automatic capture farm data may see even better use of data to improve farm management and selection decisions.

Measurements of the gain medium temperature in an operating Cs DPAL.

A Mach-Zehnder interferometer was used for contactless measurement of the temperature of the gain medium within a static cell of Cs DPAL. The maximum temperature recorded approached 700° C leading to a significant degradation of laser performance. This work also examined lasing and non-lasing heat deposition and has shown that as much as 85% of the heating in a DPAL gain medium can be attributed to quenching.

Avoiding artefacts during electron microscopy of silver nanomaterials exposed to biological environments.

Electron microscopy has been applied widely to study the interaction of nanomaterials with proteins, cells and tissues at nanometre scale. Biological material is most commonly embedded in thermoset resins to make it compatible with the high vacuum in the electron microscope. Room temperature sample preparation protocols developed over decades provide contrast by staining cell organelles, and aim to preserve the native cell structure. However, the effect of these complex protocols on the nanomaterials in the system is seldom considered. Any artefacts generated during sample preparation may ultimately interfere with the accurate prediction of the stability and reactivity of the nanomaterials. As a case study, we review steps in the room temperature preparation of cells exposed to silver nanomaterials (AgNMs) for transmission electron microscopy imaging and analysis. In particular, embedding and staining protocols, which can alter the physicochemical properties of AgNMs and introduce artefacts thereby leading to a misinterpretation of silver bioreactivity, are scrutinized. Recommendations are given for the application of cryogenic sample preparation protocols, which simultaneously fix both particles and diffusible ions. By being aware of the advantages and limitations of different sample preparation methods, compromises or selection of different correlative techniques can be made to draw more accurate conclusions about the data.

Heterogeneity and disparities in the use of exception scores in pediatric liver allocation.

Physicians apply for Model for End-Stage Liver Disease/Pediatric End-Stage Liver Disease exception points on a case-by-case basis to improve an individual patient's chances of receiving a liver transplant. This retrospective cohort study describes trends in the use of exceptions among the pediatric liver waitlist population with chronic liver disease. The cohort (n = 3728) included all children with a diagnosis of chronic liver disease listed in the United Network for Organ Sharing transplant database for first isolated liver transplant between February 27, 2002 and March 31, 2013. Exception score requests were common (34%); 90% of requests were approved. The rate of exception score requests in 2013 was five times that of 2002 (incident rate ratios [IRR] 5.25, 95% confidence interval [CI] 3.19-8.63, p < 0.01). Patients of non-White race had exception score request rates 13% lower than patients of White race (IRR 0.87, 95% CI 0.77-0.98, p = 0.02). Older patients had lower rates of exception score requests than younger patients (p = 0.03). Request rates varied by region. Time spent at an active exception status nearly tripled the hazard rate for transplantation (hazard ratio = 2.90, 95% CI 2.62-3.21, p < 0.01). There is disparity in use of exceptions by race that is not explained by clinical disease severity, diagnosis, geography or other demographic factors.

In situ non-perturbative temperature measurement in a Cs alkali laser.

The two-dimensional (2D) temperature profiles of an active-gain medium in a Cs + methane diode pumped alkali laser (DPAL) have been experimentally measured. This nonperturbative technique uses a Mach-Zehnder interferometer, which is longitudinally coupled into the cavity of an operating alkali laser to probe the distortion of the optical path length in the gain medium due to heating. The resulting interferograms are analyzed using the commercial program QuickFringe to quickly and accurately measure the distortion through which the temperature profile can be determined. For a 9 W Cs + methane DPAL being pumped with 20 W of resonant D2 light, a maximum temperature rise of 58°C is observed.

Unveiling the longitudinal association between short sleep duration and the incidence of obesity: the Penn State Cohort.

OBJECTIVE: Several epidemiologic, longitudinal studies have reported that short sleep duration is a risk factor for the incidence of obesity. However, the vast majority of these studies used self-reported measures of sleep duration and did not examine the role of objective short sleep duration, subjective sleep disturbances and emotional stress. DESIGN: Longitudinal, population-based study. SUBJECTS: We studied a random sample of 815 non-obese adults from the Penn State Cohort in the sleep laboratory for one night using polysomnography (PSG) and followed them up for a mean of 7.5 years. Subjective and objective measures of sleep as well as emotional stress were obtained at baseline. Obesity was defined as a body mass index (BMI) ≥30 kg/ m(-2). RESULTS: The incidence of obesity was 15% and it was significantly higher in women and in individuals who reported sleep disturbances, shorter sleep duration and higher emotional stress. Significant mediating effects showed that individuals with subjective sleep disturbances who developed obesity reported the shortest sleep duration and the highest emotional stress, and that subjective sleep disturbances and emotional stress were independent predictors of incident obesity. Further analyses revealed that the association between short sleep duration, subjective sleep disturbances and emotional stress with incident obesity was stronger in young and middle-age adults. Objective short sleep duration was not associated with a significantly increased risk of incident obesity. CONCLUSION: Self-reported short sleep duration in non-obese individuals at risk of developing obesity is a surrogate marker of emotional stress and subjective sleep disturbances. Objective short sleep duration is not associated with a significant increased risk of incident obesity. The detection and treatment of sleep disturbances and emotional stress should become a target of our preventive strategies against obesity.

Examining the Quasi-Static Uniaxial Compressive Behaviour of Commercial High-Performance Epoxy Matrices.

Four commercial high-performance aerospace aromatic epoxy matrices, CYCOM®890, CYCOM®977-2, PR520, and PRISM EP2400, were cured to a standardised 2 h, 180 °C cure cycle and evaluated in quasi-static uniaxial compression, as well as by dynamic scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The thermoplastic toughened CYCOM®977-2 formulation displayed an overall increase in true axial stress values across the entire stress-strain curve relative to the baseline CYCOM®890 sample. The particle-toughened PR520 sample exhibited an overall decrease in true axial stress values past the yield point of the material. The PRISM EP2400 resin, with combined toughening agents, led to true axial stress values across the entire plastic region of the stress-strain curve, which were in line with the stress values observed with the CYCOM®890 material. Interestingly, for all formulations, the dilation angles (associated with the volume change during plastic deformation), recorded at 0.3 plastic strain, were close to 0°, with the variations reflecting the polymer structure. Compression data collected for this series of commercial epoxy resins are in broad agreement with a selection of model epoxy resins based on di- and tetra-functional monomers, cured with polyamines or dicarboxylic anhydrides. However, the fully formulated resins demonstrate a significantly higher compressive modulus than the model resins, albeit at the expense of yield stress.

Association between serum retinol-binding protein 4 concentrations and clinical indices in subjects with type 2 diabetes: a meta-analysis.

BACKGROUND: Retinol-binding protein (RBP4) is an adipokine that may be important in type 2 diabetes. Previous studies have examined the association between serum RBP4 concentrations and clinical indices in patients with type 2 diabetes, although the results obtained have been inconsistent. We conducted a meta-analysis aiming to investigate the association between serum RBP4 concentrations and clinical indicators of diabetes, renal function, metabolic syndrome and obesity in subjects with type 2 diabetes. METHODS: MEDLINE, EMBASE and CINAHL databases were searched from 2005 through November 2011, and the search identified 21 clinical variables from seven studies (total n = 1406). For each variable, summary correlation coefficients (r(s) ) were estimated using a random-effects meta-analysis. RESULTS: None of the diabetes markers were correlated with serum RBP4 concentrations in subjects with type 2 diabetes, whereas all of the renal function markers and many metabolic syndrome markers were significantly correlated. Summary correlation coefficients and 95% confidence intervals (CIs) were -0.36 (95% CI = -0.51 to -0.18) for creatinine clearance, -0.39 (95% CI = -0.44 to -0.33) for estimated glomerular filtration rate and 0.53 (95% CI = 0.30-0.71) for creatinine concentration. In addition, plasma triglyceride concentrations (r(s) = 0.22; 95% CI = 0.11-0.32), plasma total cholesterol concentrations [r(s) = 0.14 (95% CI = 0.05-0.23)] and low-density lipoprotein cholesterol level (r(s) = 0.14; 95% CI = 0.02-0.25) were positively correlated with serum RBP4 concentrations. CONCLUSIONS: The results obtained in the present study suggest that serum RBP4 concentrations in patients with type 2 diabetes may be associated with diabetes-related renal dysfunction and imbalances in lipid metabolism.

Photoionization in alkali lasers.

We have calculated photoionization rates in alkali lasers. The photoionization of alkali atoms in the gain medium of alkali lasers can significantly degrade the laser performance by reducing the neutral alkali density and with it the gain. For a ten atmosphere Rb laser and a Cs exciplex laser, the photoionization induced alkali atom loss rates are greater than 10(5) sec(-1). These high loss rates will quickly deplete the neutral alkali density, reducing gain, and may require fast, possibly, supersonic flow rates to sufficiently replenish the neutral medium for CW operation.

Cs laser with unstable cavity transversely pumped by multiple diode lasers.

We have demonstrated a Cs vapor laser with an unstable resonator transversely pumped by 15 narrowband laser diode arrays. A slope efficiency of 43%, a total optical efficiency of 31% and a maximum output power 49 W were obtained with a pump power of 157 Watts.

Biogeography of the Megazoo: Biogeographic studies suggest organizing principles for a future system of wild lands.

A system of primary wildland reserves may be required to ensure a diversity of plant and animal species in the future. A strategy for locating such reserves involves considerations of their location, number, size, and linkage. The equilibrium theory of island biogeography is a useful analytical tool for predicting future biogeographies according to the dynamics of present plant and animal distributions. Existing reserves in the United States are inadequate in size and number and are clumped in one geographic region. In a planned network there might be several levels of reserves, starting with first- and second-order watersheds of large enough size to support a stable population of large carnivores. Reserves should be distributed so that they include a maximum of the world's biological diversity. Lower-order reserves might serve as stepping-stones among which a supply of species might move as a kind of distributed storage and reintroduce themsleves when local instabilities occur. This would maintain a high immigration rate to balance an extinction rate which can only increase as human settlements expand.

Escape from self-produced rates of brain stimulation.

Rats were allowed to self-stimulate while their responses were being recorded on tape. Subsequently, prerecorded patterns of their brain stimulation were "played back" to them. All subjects learned to escape brain stimulation delivered in exactly the same manner as they had previously elected to receive it.

The relationship between race, cigarette smoking and carotid intimal medial thickness in systemic lupus erythematosus.

Racial differences are known to account for a higher incidence of systemic lupus erythematosus (SLE), as well as increased disease severity and mortality. The purpose of this study was to determine whether there are any race-specific risk factors that affect measures of subclinical atherosclerosis in SLE patients. Traditional and SLE-related cardiovascular disease (CVD) risk factors were assessed in 106 female SLE patients. Carotid medial intimal medial thickness (mIMT) and coronary artery calcification (CAC) were measured on all subjects. Differences were evaluated between races for all clinical, serologic, and CVD risk factors and the racial interactions with all covariables. Outcomes included mIMT and CAC. There were no significant differences between races with regard to mIMT or CAC. Significant covariables in the final model for mIMT included age, triglycerides, glucose, and race-age and race-smoking interactions. A prediction model with fixed significant covariables demonstrated that Black subjects with a smoking history had a significantly higher mIMT than Blacks who had never smoked, an effect not seen in Whites. There were no differences between having CAC or with the CAC scores between the races. In the final model for CAC, age and SLE disease duration were significant covariables impacting CAC. When controlling for other significant CVD covariables and interactions, Black women, but not White, with SLE with a history of smoking have higher mIMT measurements than those who have never smoked. This is the first report documenting the race-specific effect of smoking on subclinical measures of CVD in SLE.

Frequency-doubling of a high power cesium vapor laser using a PPKTP crystal.

447.3 nm blue light generation was demonstrated through direct frequency doubling a continuous-wave Cesium vapor lasers 894.6 nm output using a PPKTP nonlinear crystal. The diode-pumped Cs vapor laser has an output power as large as 10 W with a very narrow emission linewidth less than 10 GHz. The PPKTP crystal is about 30 mm long and has a moderate acceptance wavelength bandwidth. The second harmonic wave generation efficiency achieved is about 4.4 %/W. Power depletion in second harmonic pulses, which relates to the absorption related thermal effects, was observed when using high pump power, long pulse duration, or high repetition rate.

Extended tuning of an injection-locked diode laser.

We have investigated the application of an electronic feedback technique recently reported by Repasky et al. [Appl. Opt. 45, 9013 (2006)] to an injection-locked semiconductor diode laser. We find that without electronic feedback, the injection-locked slave laser will only follow the master for less than 1 GHz, but once the electronic feedback is applied, the slave laser is capable of following for more than 20 GHz, corresponding to the full scan range of the master laser.