bluuebunny/crossref_metadata_2025_split huggingface dataset:
Incidence and mortality of tuberculosis before and after initiation of antiretroviral therapy: an HIV cohort study in India
Authors: Alvarez‐Uria Gerardo , Pakam Raghavakalyan , Midde Manoranjan , Naik Praveen K 
Published: December 2014

IntroductionIndia has the highest burden of tuberculosis (TB) in the world, but the epidemiology of HIV‐associated TB is not well known.MethodsWe describe the incidence and the mortality of TB from HIV diagnosis to antiretroviral therapy (ART) initiation (pre‐ART group) and after ART initiation (on‐ART group) in an HIV cohort study in Anantapur, India. Multivariable analysis of factors associated with TB was performed using competing risk regression and restricted cubic spline methods.ResultsA total of 4590 patients and 3133 person‐years (py) of follow‐up were included in the pre‐ART group, and 3784 patients and 4756 py were included in the on‐ART group. In the pre‐ART group, the incidence of TB was high during the first month after HIV diagnosis and dropped nearly four times soon after. In the on‐ART group, the incidence of TB increased after ART initiation reaching a peak in the third month. The probability of having TB within 30 months was 22.3% (95% confidence interval [CI], 21.1–23.6) in the pre‐ART group and 17.8% (95% CI, 16.3–19.3) in the on‐ART group. In a multivariable analysis, women had a lower risk of TB in both groups. Poor socio‐economical conditions were associated with an increased risk of TB in the pre‐ART group, but not in the group on‐ART. While the association between low CD4 counts and TB was strong in the pre‐ART group, this association was weaker in the on‐ART group, and the highest risk of TB was seen in those patients with CD4 counts around 110 cells/mm3. The cumulative incidence of mortality at 12 months in patients with TB was 29.6% (95% CI, 26.9–32.6) in pre‐ART TB and 34.9% (95% CI, 31–39.1) in on‐ART TB. Half deaths before ART initiation and two thirds of deaths after ART initiation occurred in patients with TB.ConclusionsThe high incidence and mortality of TB seen in this study underscore the urgent need to improve the prevention and diagnosis of HIV‐associated TB in India. We found substantial differences between TB before and after ART initiation.
Quake clamps down on slow slip
Authors: Wallace Laura M. , Bartlow Noel , Hamling Ian , Fry Bill 
Published: December 2014

AbstractUsing continuous GPS (cGPS) data from the Hikurangi subduction zone in New Zealand, we show for the first time that stress changes induced by a local earthquake can arrest an ongoing slow slip event (SSE). The cGPS data show that the slip rate in the northern portion of the 2013/2014 Kapiti SSE decreased abruptly following a nearby intraslab earthquake. We suggest that deceleration of the Kapiti SSE in early 2014 occurred due to a tenfold increase in the normal stress relative to shear stress in the SSE source, induced by the nearby Mw 6.3 earthquake, consistent with expectations of rate and state friction. Our observation of an abrupt halting/slowing of the SSE in response to stress changes imposed by a local earthquake has implications for the strength of fault zones hosting SSEs and supports the premise that static stress changes are an important ingredient in triggering (or delaying) fault slip.
Solar wind electron precipitation into the dayside Martian upper atmosphere through the cusps of strong crustal fields
Authors: Xu Shaosui , Liemohn Michael W. , Mitchell David L. 
Published: December 2014

AbstractMeasurements made by the magnetometer/electron reflectometer on board the Mars Global Surveyor spacecraft have shown spatially localized enhancements in electron fluxes over the strong crustal fields on both the dayside and night, which are used to identify the cusps in between the closed magnetic fields. This paper provides a comprehensive statistical study on the occurrence rate of dayside solar wind/magnetosheath precipitation over the strong crustal fields. Also, the occurrence rate's dependence on the magnetic elevation angles and the solar zenith angle is presented. A seasonal variation of the precipitation is also expected and found, due to both the tilt and the orbital eccentricity of Mars. The maximum occurrence rate is 40%, when the solar zenith angles are small and the magnetic fields are nearly vertical. Finally, the energy flux deposition of the solar wind electrons is calculated as well, which is 0.1%–2% of solar EUV flux input.
The interplay of Kappa and core populations in the solar wind: Electromagnetic electron cyclotron instability
Authors: Lazar M. , Poedts S. , Schlickeiser R. 
Published: December 2014

AbstractRecently, a realistic parameterization was proposed for the kinetic anisotropy and the resulting instabilities in the solar wind plasma. This parameterization is based on observations of the particle velocity distribution, which always comprises a Maxwellian population at low energies, viz. the core, and a suprathermal halo in the tail of the distribution which is best described by the Kappa (power law) models. The cyclotron instability, driven by an anisotropic electron halo, was found to be inhibited by the finite thermal spread in the core, and this effect is highly dependent on the halo‐core relative density. In this paper, the interplay between the Kappa and Maxwellian populations is further investigated for more complex (less idealized) situations when both the core and halo temperatures are anisotropic. Growth of this instability is markedly stimulated by the core anisotropy. The wave numbers that are stable for an isotropic core become unstable even for small anisotropies of this population. Just a modest increase of the core anisotropy from Ac=T⊥/T∥=1.2 to 2 causes the growth rates to enhance by 1 order of magnitude, and the range of unstable wave numbers to extend considerably. When the anisotropies in the core and halo are comparable, the growth rate exhibits two distinct peaks, the first driven by the halo at lower wave numbers and the second driven by the core. However, the first peak is inhibited by the suprathermal populations, while the second peak is sustained, suggesting a more intricate connection between the core and Kappa populations.
Effects of tidal forcing, conductivity gradient, and active seeding on the climatology of equatorial spread F over Kwajalein
Authors: Tsunoda Roland T. , Nguyen Trang T. , Le Minh Huy 
Published: December 2014

AbstractPlasma structure in nighttime equatorial F layer, referred to as equatorial spread F (ESF), displays climatology whose seasonal variation depends on longitude. At longitudes where ESF favors equinoxes, times when maxima occur can be predicted in terms of the day of year, when E region sunset is simultaneous in conjugate hemispheres (i.e., “sunset nodes”). Aside from occurrences around equinoxes, there are only three longitudes where ESF also occurs during a solstice; one is the central Pacific region. Here ESF activity is strong during the June solstice, when solar activity is high. To understand this puzzling behavior, ESF climatology over the Kwajalein Atoll was compared with properties of the postsunset rise (PSSR) of the F layer and seeding activity in the troposphere. The key findings are as follows: (1) Maxima in PSSR velocity (VPSSR) are better aligned with equinoxes than with sunset nodes; hence, seasonal pattern of VPSSR, not only sunset nodes, should be included in interpretation of ESF climatology. (2) The source of VPSSR during solstice appears to differ from that during equinoxes. (3) Equinoctial maxima in VPSSR could be related to a semiannual variation in equatorial electrojet strength and its contribution to polarization of the F region dynamo current. (4) Enhanced VPSSR during the June solstice is interpreted in terms of tidal forcing with a wave number of 2. (5) Displacements of maxima in ESF climatology from maxima in VPSSR are shown to be consistent with deep convective activity.
Microseisms and its impact on the marine‐controlled source electromagnetic signal
Authors: Bhatt Kaushalendra M. 
Published: December 2014

AbstractThe marine‐controlled source electromagnetic method (mCSEM) is employed for studying the electrical characteristics and fluid contents of sedimentary reservoirs. However, the success rate of the method can be improved significantly by finding the sources of electromagnetic noise and addressing the challenge posed by them at larger offsets where the reservoir signal is often weak. I have studied the mCSEM data and reporting an electromagnetic noise. The strength of the noise is observed 1600 times stronger than the seafloor mCSEM signal at 0.1 Hz. Moreover, the noise and the transmitted mCSEM signals are found coherent in interstation recordings. These readings suggest the severity of the noise. The source investigation presuming the observed noise as an infragravity wave failed to match the response. Then, the role of microseisms is investigated. Microseism causes oscillation of the seafloor and produces electromagnetic disturbances by the dynamics of water. I have used various conditions for a proper discrimination of the noise as microseisms. This mechanism is clearly illustrated with the help of a conceptual diagram. The role of the directionality is part of the study, which is argued for having a significant role in the generation of microseisms. In this paper, a new algorithm is presented and is used for calculating the coherency. The algorithm helps in mapping the coherency value simultaneously in time and frequency domains.
Probabilistic short‐term volcanic hazard in phases of unrest: A case study for tephra fallout
Authors: Selva Jacopo , Costa Antonio , Sandri Laura , Macedonio Giovanni , Marzocchi Warner 
Published: December 2014

AbstractDuring volcanic crises, volcanologists estimate the impact of possible imminent eruptions usually through deterministic modeling of the effects of one or a few preestablished scenarios. Despite such an approach may bring an important information to the decision makers, the sole use of deterministic scenarios does not allow scientists to properly take into consideration all uncertainties, and it cannot be used to assess quantitatively the risk because the latter unavoidably requires a probabilistic approach. We present a model based on the concept of Bayesian event tree (hereinafter named BET_VH_ST, standing for Bayesian event tree for short‐term volcanic hazard), for short‐term near‐real‐time probabilistic volcanic hazard analysis formulated for any potential hazardous phenomenon accompanying an eruption. The specific goal of BET_VH_ST is to produce a quantitative assessment of the probability of exceedance of any potential level of intensity for a given volcanic hazard due to eruptions within restricted time windows (hours to days) in any area surrounding the volcano, accounting for all natural and epistemic uncertainties. BET_VH_ST properly assesses the conditional probability at each level of the event tree accounting for any relevant information derived from the monitoring system, theoretical models, and the past history of the volcano, propagating any relevant epistemic uncertainty underlying these assessments. As an application example of the model, we apply BET_VH_ST to assess short‐term volcanic hazard related to tephra loading during Major Emergency Simulation Exercise, a major exercise at Mount Vesuvius that took place from 19 to 23 October 2006, consisting in a blind simulation of Vesuvius reactivation, from the early warning phase up to the final eruption, including the evacuation of a sample of about 2000 people from the area at risk. The results show that BET_VH_ST is able to produce short‐term forecasts of the impact of tephra fall during a rapidly evolving crisis, accurately accounting for and propagating all uncertainties and enabling rational decision making under uncertainty.
Multimodel simulations of Arctic Ocean sea surface height variability in the period 1970–2009
Authors: Koldunov Nikolay V. , Serra Nuno , Köhl Armin , Stammer Detlef , Henry Olivier , Cazenave Anny , Prandi Pierre , Knudsen Per , Andersen Ole Baltazar , Gao Yongqi , Johannessen Johnny 
Published: December 2014

AbstractThe performance of several numerical ocean models is assessed with respect to their simulation of sea surface height (SSH) in the Arctic Ocean, and the main patterns of SSH variability and their causes over the past 40 years (1970–2009) are analyzed. In comparison to observations, all tested models broadly reproduce the mean SSH in the Arctic and reveal a good correlation with both tide gauge data and SSH anomalies derived from satellite observations. Although the models do not represent the positive Arctic SSH trend observed over the last two decades, their interannual‐to‐decadal SSH variability is in reasonable agreement with available measurements. Focusing on results from one of the models for a detailed analysis, it is shown that the decadal‐scale SSH variability over shelf areas and deep parts of the Arctic Ocean have pronounced differences that are determined mostly by salinity variations. A further analysis of the three time periods 1987–1992, 1993–2002, and 2003–2009, corresponding to the transition times between cyclonic and anticyclonic regimes of the atmospheric circulation over the Arctic, revealed an unusual increase of SSH in the Amerasian basin during 2003–2009. Results from this model support the recent finding that the increase is caused mainly by changes in freshwater content brought about by the freshwater export through the Canadian Arctic Archiplago and increased Ekman pumping in the Amerasian basin and partly by lateral freshwater transport changes, leading to a redistribution of low‐salinity shelf water. Overall, we show that present‐day models can be used for investigating the reasons for low‐frequency SSH variability in the region.
Adaptive observation in the South China Sea using CNOP approach based on a 3‐D ocean circulation model and its adjoint model
Authors: Li Yineng , Peng Shiqiu , Liu Duanling 
Published: December 2014

AbstractThis study investigates the effect of adaptive (or targeted) observation on improving the midrange (30 days) forecast skill of ocean state of the South China Sea (SCS). A region associated with the South China Sea Western Boundary Current (SCSWBC) is chosen as the “target” of the adaptive observation. The Conditional Nonlinear Optimal Perturbation (CNOP) approach is applied to a three‐dimensional ocean model and its adjoint model for determining the sensitive region. Results show that the initial errors in the sensitive region determined by the CNOP approach have significant impacts on the forecast of ocean state in the target region; thus, reducing these initial errors through adaptive observation can lead to a better 30 day prediction of ocean state in the target region. Our results suggest that implementing adaptive observation is an effective and cost‐saving way to improve an ocean model's forecast skill over the SCS.
A neural network‐based four‐band model for estimating the total absorption coefficients from the global oceanic and coastal waters
Authors: Chen Jun , Cui Tingwei , Quan Wenting 
Published: December 2014

AbstractIn this study, a neural network‐based four‐band model (NNFM) for the global oceanic and coastal waters has been developed in order to retrieve the total absorption coefficients a(λ). The applicability of the quasi‐analytical algorithm (QAA) and NNFM models is evaluated by five independent data sets. Based on the comparison of a(λ) predicted by these two models with the field measurements taken from the global oceanic and coastal waters, it was found that both the QAA and NNFM models had good performances in deriving a(λ), but that the NNFM model works better than the QAA model. The results of the QAA model‐derived a(λ), especially in highly turbid waters with strong backscattering properties of optical activity, was found to be lower than the field measurements. The QAA and NNFM models‐derived a(λ) could be obtained from the MODIS data after atmospheric corrections. When compared with the field measurements, the NNFM model decreased by a 0.86–24.15% uncertainty (root‐mean‐square relative error) of the estimation from the QAA model in deriving a(λ) from the Bohai, Yellow, and East China seas. Finally, the NNFM model was applied to map the global climatological seasonal mean a(443) for the time range of July 2002 to May 2014. As expected, the a(443) value around the coastal regions was always larger than the open ocean around the equator. Viewed on a global scale, the oceans at a high latitude exhibited higher a(443) values than those at a low latitude.
Structural diagnostics of the tropopause inversion layer and its evolution
Authors: Gettelman A. , Wang T. 
Published: December 2014

AbstractThe Tropopause Inversion Layer (TIL) is marked by a peak in static stability directly above the tropopause. The TIL is quantitatively defined with new diagnostics using Global Positioning System Radio Occultation temperature soundings and reanalysis data. A climatology of the TIL is developed from reanalysis data (1980–2011) using diagnostics for the position, depth, and strength of the TIL based on the TIL peak in static stability. TIL diagnostics have defined relationships to the synoptic situation in the Upper Troposphere and Lower Stratosphere. The TIL is present nearly all the time. The TIL becomes hard to define in the subtropics where tropical air overlies midlatitude air, in a region of complex static stability profiles. The mean position of the subtropical TIL gradient is sharp and is co‐located with the subtropical tropopause break. Over the period 1980–2011 the TIL depth below the tropopause has decreased by 5% per decade and increased above the tropical tropopause by a similar percentage. Furthermore, the latitude of the abrupt change in the TIL from tropical to extratropical in the lower stratosphere appears to have shifted poleward in each hemisphere by ∼1° latitude per decade, depending on the diagnostic examined. Reanalysis trends should be treated with caution.
Aerosol transport over the western Mediterranean basin: Evidence of the contribution of fine particles to desert dust plumes over Alborán Island
Authors: Valenzuela A. , Olmo F. J. , Lyamani H. , Granados‐Muñoz M. J. , Antón M. , Guerrero‐Rascado J. L. , Quirantes A. , Toledano C. , Perez‐Ramírez D. , Alados‐Arboledas L. 
Published: December 2014

AbstractEight months (June 2011 to January 2012) of aerosol property data were obtained at the remote site of Alborán Island (35.95°N, 3.03°W) in the western Mediterranean basin. The aim of this work is to assess the aerosol properties according to air mass origin and transport over this remote station with a special focus on air mass transport from North Africa. For air masses coming from North Africa, different aerosol properties showed strong contributions from mineral dust lifted from desert areas. Nevertheless, during these desert dust intrusions, some atmospheric aerosol properties are clearly different from pure mineral dust particles. Thus, Angström exponent α(440–870) presents larger values than those reported for pure desert dust measured close to dust source regions. These results combine with α(440, 670) − α(670, 870) ≥ 0.1 and low single scattering albedo (ω(λ)) values, especially at the largest wavelengths. Most of the desert dust intrusions over Alborán can be described as a mixture of dust and anthropogenic particles. The analyses support that our results apply to North Africa desert dust air masses transported from different source areas. Therefore, our results indicate a significant contribution of fine absorbing particles during desert dust intrusions over Alborán arriving from different source regions. The aerosol optical depth data retrieved from Sun photometer measurements have been used to check Moderate Resolution Imaging Spectroradiometer retrievals, and they show reasonable agreement, especially for North African air masses.
Aircraft‐type dependency of contrail evolution
Authors: Unterstrasser S. , Görsch N. 
Published: December 2014

AbstractThe impact of aircraft type on contrail evolution is assessed using a large eddy simulation model with Lagrangian ice microphysics. Six different aircraft ranging from the small regional airliner Bombardier CRJ to the largest aircraft Airbus A380 are taken into account. Differences in wake vortex properties and fuel flow lead to considerable variations in the early contrail geometric depth and ice crystal number. Larger aircraft produce contrails with more ice crystals (assuming that the number of initially generated ice crystals per kilogram fuel is constant). These initial differences are reduced in the first minutes, as the ice crystal loss during the vortex phase is stronger for larger aircraft. In supersaturated air, contrails of large aircraft are much deeper after 5 min than those of small aircraft. A parameterization for the final vertical displacement of the wake vortex system is provided, depending only on the initial vortex circulation and stratification. Cloud resolving simulations are used to examine whether the aircraft‐induced initial differences have a long‐lasting mark. These simulations suggest that the synoptic scenario controls the contrail cirrus evolution qualitatively. However, quantitative differences between the contrail cirrus properties of the various aircraft remain over the total simulation period of 6 h. The total extinctions of A380‐produced contrails are about 1.5 to 2.5 times higher than those from contrails of a Bombardier CRJ.
Satellite‐based augmentation systems: A novel and cost‐effective tool for ionospheric and space weather studies
Authors: Sunda Surendra , Sridharan R. , Vyas B. M. , Khekale P. V. , Parikh K. S. , Ganeshan A. S. , Sudhir C. R. , Satish S. V. , Bagiya Mala S. 
Published: December 2014

AbstractSatellite‐Based Augmentation Systems (SBASes) are designed to provide additional accuracy and robustness to existing satellite‐based radio navigation systems for all phases of a flight. However, similar to navigation systems such as GPS which has proven its worth for the investigation of the ionosphere, the SBASes do have certain advantages. In the present paper, we propose and demonstrate SBAS applicability to ionospheric and space weather research in a novel and cost‐effective way. The recent commissioning of the Indian SBAS, named GPS Aided Geo Augmented Navigation (GAGAN), covering the equatorial and low‐latitude regions centered around the Indian longitudes provides the motivation for this approach. Two case studies involving different ionospheric behavior over low‐latitude regions vindicate the potential of SBAS over extended areas.
A decoupled adaptive control algorithm for global state feedback stabilization of a class of nonlinear systems
Authors: Liu Zhen‐Guo , Wu Yu‐Qiang 
Published: December 2014

SummaryA decoupled adaptive control algorithm, namely the combined dynamic gain and adaptive homogeneous domination approach, is introduced to solve the global state feedback stabilization problem for a class of uncertain nonlinear systems. Compared with the conventional adaptive backstepping/tuning functions approach, the algorithm differs in the way of constructing the estimator and handling the nonlinear drifts, and allows the adaptive control law that is decoupled via a dynamic gain to be designed only by choosing some appropriate constants. The proposed adaptive controller guarantees that all the states of the closed‐loop system are globally bounded and the system solutions converge to zero asymptotically. Both physical and academic examples are provided to demonstrate the validness of the theory. Copyright © 2014 John Wiley & Sons, Ltd.