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The search for life in the Universe is a fundamental problem of astrobiology and modern science. The current progress in the detection of terrestrial-type exoplanets has opened a new avenue in the characterization of exoplanetary atmospheres and in the search for biosignatures of life with the upcoming ground-based and space missions. To specify the conditions favourable for the origin, development and sustainment of life as we know it in other worlds, we need to understand the nature of global (astrospheric), and local (atmospheric and surface) environments of exoplanets in the habitable zones (HZs) around G-K-M dwarf stars including our young Sun. Global environment is formed by propagated disturbances from the planet-hosting stars in the form of stellar flares, coronal mass ejections, energetic particles and winds collectively known as astrospheric space weather. Its characterization will help in understanding how an exoplanetary ecosystem interacts with its host star, as well as in the specification of the physical, chemical and biochemical conditions that can create favourable and/or detrimental conditions for planetary climate and habitability along with evolution of planetary internal dynamics over geological timescales. A key linkage of (astro)physical, chemical and geological processes can only be understood in the framework of interdisciplinary studies with the incorporation of progress in heliophysics, astrophysics, planetary and Earth sciences. The assessment of the impacts of host stars on the climate and habitability of terrestrial (exo)planets will significantly expand the current definition of the HZ to the biogenic zone and provide new observational strategies for searching for signatures of life. The major goal of this paper is to describe and discuss the current status and recent progress in this interdisciplinary field in light of presentations and discussions during the NASA Nexus for Exoplanetary System Science funded workshop ‘Exoplanetary Space Weather, Climate and Habitability’ and to provide a new roadmap for the future development of the emerging field of exoplanetary science and astrobiology.
The seasonality of individual influenza subtypes/lineages and the association of influenza epidemics with meteorological factors in the tropics/subtropics have not been well understood. The impact of the 2009 H1N1 pandemic on the prevalence of seasonal influenza virus remains to be explored. Using wavelet analysis, the periodicities of A/H3N2, seasonal A/H1N1, A/H1N1pdm09, Victoria and Yamagata were identified, respectively, in Panzhihua during 2006–2015. As a subtropical city in southwestern China, Panzhihua is the first industrial city in the upper reaches of the Yangtze River. The relationship between influenza epidemics and local climatic variables was examined based on regression models. The temporal distribution of influenza subtypes/lineages during the pre-pandemic (2006–2009), pandemic (2009) and post-pandemic (2010–2015) years was described and compared. A total of 6892 respiratory specimens were collected and 737 influenza viruses were isolated. A/H3N2 showed an annual cycle with a peak in summer–autumn, while A/H1N1pdm09, Victoria and Yamagata exhibited an annual cycle with a peak in winter–spring. Regression analyses demonstrated that relative humidity was positively associated with A/H3N2 activity while negatively associated with Victoria activity. Higher prevalence of A/H1N1pdm09 and Yamagata was driven by lower absolute humidity. The role of weather conditions in regulating influenza epidemics could be complicated since the diverse viral transmission modes and mechanism. Differences in seasonality and different associations with meteorological factors by influenza subtypes/lineages should be considered in epidemiological studies in the tropics/subtropics. The development of subtype- and lineage-specific prevention and control measures is of significant importance.
In indirect-drive inertial confinement fusion, the radiation symmetry must be controlled for the achievement of hotspot ignition. The radiation symmetry is of great importance. In this paper, we investigate the drive asymmetry of the M-band (2–5 keV) radiation emitted from an Au holhraum wall by using the three-dimensional view-factor code IRAD3D. Analysis of the M-band flux drive at the Shenguang-III laser facility shows that it is asymmetric and that the asymmetry varies with time. For a given cross section over the pole, the initial M-band flux asymmetries are P2 = 11.59, P4 = 1.41, and P6 = −0.64%. When the asymmetries are artificially added to a symmetric radiation drive, the position of the deuterium-tritium (DT) ice/gas interface is asymmetric for a National Ignition Facility capsule in 1D simulation. This means that M-band flux asymmetry can lead to implosion asymmetry even if the total radiation is symmetric. Pure CH and Si-doped CH capsules are considered. The results show that a mid-Z dopant can partly reduce the asymmetry. However, the asymmetry is still very large. Thus, it is necessary to study the M-band flux asymmetry and its influence on the implosion symmetry.
To determine the optimal cut-offs of BMI for Malaysian adults.
Population-based, cross-sectional study. Receiver operating characteristic curves were used to determine the cut-off values of BMI with optimum sensitivity and specificity for the detection of three cardiovascular risk factors: diabetes mellitus, hypertension and hypercholesterolaemia. Gender-specific logistic regression analyses were used to examine the association between BMI and these cardiovascular risk factors.
All fourteen states in Malaysia.
Malaysian adults aged ≥18 years (n 32 703) who participated in the Third National Health and Morbidity Survey in 2006.
The optimal BMI cut-off value for predicting the presence of diabetes mellitus, hypertension, hypercholesterolaemia or at least one of these cardiovascular risk factors varied from 23·3 to 24·1 kg/m2 for men and from 24·0 to 25·4 kg/m2 for women. In men and women, the odds ratio for having diabetes mellitus, hypertension, hypercholesterolaemia or at least one cardiovascular risk factor increased significantly as BMI cut-off point increased.
Our findings indicate that BMI cut-offs of 23·0 kg/m2 in men and 24·0 kg/m2 in women are appropriate for classification of overweight. We suggest that these cut-offs can be used by health professionals to identify individuals for cardiovascular risk screening and weight management programmes.
Most of the convergence results appearing so far for delayed Lotka–Volterra-type systems require that undelayed negative feedback dominate both delayed feedback and interspecific interactions. Such a requirement is rarely met in real systems. In this paper we present convergence criteria for systems without instantaneous feedback. Roughly, our results suggest that in a Lotka–Volterra-type system if some of the delays are small, and initial functions are small and smooth, then the convergence of its positive steady state follows that of the undelayed system or the corresponding system whose instantaneous negative feedback dominates. In particular, we establish explicit expressions for allowable delay lengths for such convergence to sustain.
Laser structures with InGaAsP quantum well were grown on GaAs substrates in a solid source MBE system. Threshold current density Jth as low as 290A/cm2 and slope efficiency as high as 0.68W/A per facet were obtained for uncoated laser chips at 25°C. After 857 hours burn-in at 47A (corresponding to around 47W) at room temperature, power degradation rate was measured to be less than 3×10−6/h.
Surface plasmon resonance (SPR) biosensors are widely used in sensitive chemical, biological and environmental sensing. Recently, the studies of nano-plasmonics in metallic structures have shown that surface plasmons can also be excited by the metallic nanostructures films which can be used for high-throughput and chip-based SPR type sensing. We developed a class of plasmonic crystal-like structures consisting of a film with arrays of periodic nanoslit geometry. Because the engineered array ensures multiple resonance modes, we use the multispectral analysis to evaluate the refractive index sensing capability. Different from the common method monitoring a single peak shift, the multispectral analysis, observing all the peak shifts and intensity changes in the multiple plasmonic resonances in the spectra, can improve the signal-to-noise ratio of the system and enhance the sensing capabilities. In this investigation, we studied the best condition for the gold nanoslit arrays by testing their ability for refractive index sensing, and a high sensitivity of up to 28586 %T nm/RIU was obtained by multispectral analysis (RIU = refreactive index unit, and T= transmission).
VO2 is a material with reversible thermo-chromic properties. The reversible phase transition of a strain-free single-crystalline VO2, at a transition temperature (Tt) 68°C, is accompanied with changes in crystal structure, optical and electrical properties. With different processing conditions during thin film deposition, different transmittance loops will be resulted upon thermal cycling. The residual stress of the thin films with poor crystallinity, as determined from X-ray diffractometry, is found to be an important factor responsible for the Tt that increases with increasing residual stress. Residual stress affects the hysteresis span of the transmittance loop. The relationship between residual stress of as-deposited VO2 films and the relative positions between vanadium and oxygen under the residual stress are also delineated.
AlGaN/GaN HFETs have demonstrated excellent RF performance, but the devices still suffer from a reliability problem. The decrease of the dc current and RF output power over time is attributed to gate tunneling which is determined by the magnitude of electric field at the gate edge. In this work, in order to improve the reliability of AlGaN/GaN HFETs, a 2D drift-diffusion tool is used to explore the relationship between the magnitude of electric field and different device structures through modifications of the 2DEG sheet charge density, AlGaN barrier layer thickness, AlGaN doping concentration and gate to drain spacing. The effect of field plates is also investigated. It was found that decreasing 2DEG sheet charge density results in much improved reliability, although the current and output power are somewhat reduced.
Familial caregivers are providing increasing amounts of care to advanced cancer patients. Increased understanding of caregivers’ needs is vital in providing necessary support to lessen caregiver burden and morbidity. Current literature has identified caregiver and patient needs at broad stages of the cancer trajectory; however, such broad stages may be too general to inform a practice of targeting specific interventions when they have the greatest utility. This study examines a variety of particular needs across a number of more discrete illness-related transition experiences specifically in the advanced cancer disease trajectory.
One hundred fifty-nine female informal caregivers of people with advanced cancer completed a needs assessment survey.
Analyses of these cross-sectional retrospective-report data reveal that cancer caregiver needs vary across specific key experiences occurring within the broader stages of illness identified by current literature. Furthermore, caregivers have unique needs during bereavement.
Significance of results:
Although the sample characteristics are demographically limited, this study provides preliminary evidence that the broad stages are not specific enough increments for effectively examining caregiver needs and supports the need for more precise distribution of cancer-related information at more discrete times in the illness course.
To rapidly establish a temporary isolation ward to handle an unexpected sudden outbreak of severe acute respiratory syndrome (SARS) and to evaluate the implementation of exposure control measures by healthcare workers (HCWs) for SARS patients.
Rapid creation of 60 relatively negative pressure isolation rooms for 196 suspected SARS patients transferred from 19 hospitals and daily temperature recordings of 180 volunteer HCWs from 6 medical centers.
A military hospital.
Of the 196 patients, 34 (17.3%) met the World Health Organization criteria for probable SARS with positive results of serologic testing for SARS-associated coronavirus (SARS-CoV), reverse transcriptase polymerase chain reaction (RT-PCR) from nasopharyngeal or throat swabs for SARS-CoV, or both. Seventy-four patients had suspected SARS based on unprotected exposure to SARS patients; three of them had positive results on RT-PCR but negative serologic results. The remaining 88 patients did not meet the criteria for a probable or suspected SARS diagnosis. Of the 34 patients with probable SARS, 13 were transferred to medical centers to receive mechanical ventilation due to rapid deterioration of chest x-ray results, and three patients died of SARS despite intensive therapy in medical centers. During the study period, one nurse developed probable SARS due to violation of infection control measures, but there was no evidence of cross-transmission to other HCWs.
Despite the use of full personal protection equipment, the facility failed to totally prevent exposures of HCWs to SARS but minimized the risk of nosocomial transmission. Better training and improvements in infection control infrastructure may limit the impact of SARS.
This paper deals with the convergence aspect of diffusive delay Lotka-Volterra systems with infinite delays. It is well known that such a system has a globally asymptotically stable steady state if the negative feedbacks of the intraspecific competitions are dominant and instantaneous. It is shown here that such a globally asymptotically stable steady state continues to exist even if the instantaneous assumption is removed, provided that solutions of the system are eventually uniformly bounded and the delays involved in the intraspecific competitions are small. This work generalises several recent related ones.
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