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Search Results: 1 - 10 of 464346 matches for " G. S. Jenkins "
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Space-borne observations link the tropical atlantic ozone maximum and paradox to lightning
G. S. Jenkins ,J.-H. Ryu
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2004,
Abstract: The potential enhancement of tropospheric column ozone values over the Tropical Atlantic Ocean on a seasonal basis by lightning is investigated using satellite derived ozone data, TRMM lightning data, ozonesonde data and NCEP reanalysis during 1998-2001. Our results show that the number of lightning flashes in Africa and South America reach a maximum during September, October and November (SON). The spatial patterns of winds in combination with lightning from West Africa, Central Africa and South America is likely responsible for enriching middle/upper troposphere ozone over the Tropical South Atlantic during SON. Moreover, lightning flashes are high in the hemisphere opposite to biomass burning during December, January, and February (DJF) and June, July and August (JJA). This pattern leads to an enrichment of ozone in the middle/upper troposphere in the Southern Hemisphere Tropics during DJF and the Northern Hemisphere Tropics during JJA. During JJA the largest numbers of lightning flashes are observed in West Africa, enriching tropospheric column ozone to the north of 5S in the absence of biomass burning. During DJF, lightning is concentrated in South America and Central Africa enriching tropospheric column ozone south of the Equator in the absence of biomass burning.
Linking horizontal and vertical transports of biomass fire emissionsto the tropical Atlantic ozone paradox during the Northern Hemisphere winter season: climatology
G. S. Jenkins ,J.-H. Ryu
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2004,
Abstract: During the Northern hemisphere winter season, biomass burning is widespread in West Africa, yet the total tropospheric column ozone values (<30DU) over much of the Tropical Atlantic Ocean (15°N-5°S) are relatively low. At the same time, the tropospheric column ozone values in the Southern Tropical Atlantic are higher than those in the Northern Hemisphere (ozone paradox). We examine the causes for low tropospheric column ozone values by considering the horizontal and vertical transport of biomass fire emissions in West Africa during November through March, using observed data which characterizes fires, aerosols, horizontal winds, precipitation, lightning and outgoing longwave radiation. We have found that easterly winds prevail in the lower troposphere but transition to westerly winds at pressure levels lower than 500hPa. A persistent anticyclone over West Africa at 700hPa is responsible for strong easterly winds, which causes a net outflow of ozone/ozone precursors from biomass burning in West Africa across the Atlantic Ocean towards South America. The lowest outgoing longwave radiation (OLR) and highest precipitation rates are generally found over the central Atlantic, some distance downstream of fires in West Africa making the vertical transport of ozone and ozone precursors less likely and ozone destruction more likely. However, lightning over land areas in Central Africa and South America can lead to enhanced ozone levels in the upper troposphere especially over the Southern tropical Atlantic during the Northern Hemisphere winter season.
Linking horizontal and vertical transports of biomass fire emissions to the Tropical Atlantic Ozone Paradox during the Northern Hemisphere winter season: climatology
G. S. Jenkins,J.-H. Ryu
Atmospheric Chemistry and Physics Discussions , 2003,
Abstract: During the Northern hemisphere winter season, biomass burning is widespread in West Africa, yet the total tropospheric column ozone values (<30 DU) over much of the Tropical Atlantic Ocean (15° N–5° S) are relatively low. At the same time, the tropospheric column ozone values in the Southern Tropical Atlantic are higher than those in the Northern Hemisphere (ozone paradox). We examine the causes for low tropospheric column ozone values by considering the horizontal and vertical transport of biomass fire emissions in West Africa during November through March, using observed data which characterizes fires, aerosols, horizontal winds, precipitation, lightning and outgoing longwave radiation. We have found that easterly winds prevail in the lower troposphere but transition to westerly winds at pressure levels lower than 500 hPa. A persistent anticyclone over West Africa at 700 hPa is responsible for strong easterly winds, which causes a net outflow of ozone/ozone precursors from biomass burning in West Africa across the Atlantic Ocean towards South America. The lowest outgoing longwave radiation (OLR) and highest precipitation rates are generally found over the central Atlantic, some distance downstream of fires in West Africa making the vertical transport of ozone and ozone precursors less likely and ozone destruction more likely. However, lightning over land areas in Central Africa and South America can lead to enhanced ozone levels in the upper troposphere especially over the Southern tropical Atlantic during the Northern Hemisphere winter season.
On the Fine-Scale Topography Regulating Changes in Atmospheric Hydrological Cycle and Extreme Rainfall over West Africa in a Regional Climate Model Projections
M. B. Sylla,A. T. Gaye,G. S. Jenkins
International Journal of Geophysics , 2012, DOI: 10.1155/2012/981649
Abstract: The ICTP-RegCM3 is used to downscale at 40 km projections from ECHAM5 over West Africa during the mid and late 21st Century. The results show that while ECHAM5 projects wetter climate along the Gulf of Guinea and drier conditions along the Sahel, RegCM3 produces contrasting changes for low-elevation (negative) and high-elevation (positive) terrains more marked during the second period. These wetter conditions in the uplands result from an intensification of the atmospheric hydrological cycle arising as a consequence of more frequent and denser rainy days and leading to larger intensity and more extreme events. Examination of the large-scale dynamics reveal that these conditions are mostly driven by increased low-level moisture convergence which produces elevated vertical motion above Cameroun’s mountainous areas favoring more atmospheric instability, moisture, and rainfall. This regulation of climate change signal by high-elevation terrains is feasible only in RegCM3 as the driving ECHAM5 is smoothing along all the Gulf of Guinea. This consolidates the need to use regional climate model to investigate the regional and local response of the hydrological cycle, the daily rainfall and extreme events to the increasing anthropogenic GHG warming for suitable impact studies specifically over region with complex topography such as West Africa.
On the Fine-Scale Topography Regulating Changes in Atmospheric Hydrological Cycle and Extreme Rainfall over West Africa in a Regional Climate Model Projections
M. B. Sylla,A. T. Gaye,G. S. Jenkins
International Journal of Geophysics , 2012, DOI: 10.1155/2012/981649
Abstract: The ICTP-RegCM3 is used to downscale at 40?km projections from ECHAM5 over West Africa during the mid and late 21st Century. The results show that while ECHAM5 projects wetter climate along the Gulf of Guinea and drier conditions along the Sahel, RegCM3 produces contrasting changes for low-elevation (negative) and high-elevation (positive) terrains more marked during the second period. These wetter conditions in the uplands result from an intensification of the atmospheric hydrological cycle arising as a consequence of more frequent and denser rainy days and leading to larger intensity and more extreme events. Examination of the large-scale dynamics reveal that these conditions are mostly driven by increased low-level moisture convergence which produces elevated vertical motion above Cameroun’s mountainous areas favoring more atmospheric instability, moisture, and rainfall. This regulation of climate change signal by high-elevation terrains is feasible only in RegCM3 as the driving ECHAM5 is smoothing along all the Gulf of Guinea. This consolidates the need to use regional climate model to investigate the regional and local response of the hydrological cycle, the daily rainfall and extreme events to the increasing anthropogenic GHG warming for suitable impact studies specifically over region with complex topography such as West Africa. 1. Introduction Climate change information is needed at the regional and local scales over West Africa for impacts assessment and development of suitable mitigation and adaptation plans. To date, most of the regional changes due to increasing anthropogenic greenhouse gas (GHG) concentrations are derived from coupled global climate models (GCMs). Kamga et al. [1] found that the Sahel region is wetter in the 21st century in association with increased atmospheric moisture. In contrast, Hulme et al. [2] projected large reduction of precipitation over the Sahel. Recently, Giannini et al. [3] stated that there is no agreement among GCMs about future changes of precipitation over West Africa [4, 5]. This highlights arising difficulties while simulating and analyzing the West African climate with GCMs. The reasons may be related to the existence of mesoscale convection systems (MSCs), coastlines, marked gradient of vegetation, and complex topography forcing precipitation over the region. To bridge the gap between these fine-scale processes and the resolution of climate models, regional climate modeling [6] is critical for West Africa. Regional climate models take the large-scale atmospheric circulation supplied by either
Simultaneous measurement of circular dichroism and Faraday rotation at terahertz frequencies using heterodyne detection
G. S. Jenkins,D. C. Schmadel,H. D. Drew
Physics , 2010, DOI: 10.1063/1.3480554
Abstract: A far-infrared system measures the full complex Faraday angle, rotation as well as ellipticity, with an unprecedented accuracy of 10\,$\mu$rad/T. The system operates on several far-infrared laser lines in the spectral range from 0.3 to 6 THz and produces results as a continuous function of temperature from 10 to 310K and applied fields between $\pm$ 8\,T. Materials successfully measured include GaAs 2-DEG heterostructures, various high temperature superconductors including Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$, Pr$_{2 - x}$Ce$_{x}$CuO$_4$, and La$_{2-x}$Sr$_x$CuO$_4$, and single crystals of the topological insulator Bi$_2$Se$_3$.
RAFT I: Discovery of new planetary candidates and updated orbits from archival FEROS spectra
M. G. Soto,J. S. Jenkins,M. I. Jones
Physics , 2015,
Abstract: A recent reanalysis of archival data has lead several authors to arrive at strikingly different conclusions for a number of planet-hosting candidate stars. In particular, some radial velocities measured using FEROS spectra have been shown to be inaccurate, throwing some doubt on the validity of a number of planet detections. Motivated by these results, we have begun the Reanalysis of Archival FEROS specTra (RAFT) program and here we discuss the first results from this work. We have reanalyzed FEROS data for the stars HD 11977, HD 47536, HD 70573, HD 110014 and HD 122430, all of which are claimed to have at least one planetary companion. We have reduced the raw data and computed the radial velocity variations of these stars, achieving a long-term precision of $\sim$ 10 m/s on the known stable star tau Ceti, and in good agreement with the residuals to our fits. We confirm the existence of planets around HD 11977, HD 47536 and HD 110014, but with different orbital parameters than those previously published. In addition, we found no evidence of the second planet candidate around HD 47536, nor any companions orbiting HD 122430 and HD 70573. Finally, we report the discovery of a second planet around HD 110014, with a minimum mass of 3.1 Mjup and a orbital period of 130 days. Analysis of activity indicators allow us to confirm the reality of our results and also to measure the impact of magnetic activity on our radial velocity measurements. These results confirm that very metal-poor stars down to [Fe/H]$\sim$ -0.7 dex, can indeed form giant planets given the right conditions.
Transcriptome Analysis of Ten Days Post Anthesis Elongating Fiber in the Upland Cotton (Gossypium hirsutum) Chromosome Substitution Line CS-B25  [PDF]
Chuan-Yu Hsu, Mark A. Arick II, Qing Miao, Sukumar Saha, Johnie N. Jenkins, Mirzakamol S. Ayubov, Ibrokhim Y. Abdurakhmonov, Daniel G. Peterson, Din-Pow Ma
American Journal of Plant Sciences (AJPS) , 2018, DOI: 10.4236/ajps.2018.96098
Abstract: A chromosome substitution line, CS-B25, was developed by the substitution of chromosome pair 25 of Gossypium hirsutum TM-1 with the homologous pair of chromosome 25 from G. barbadense, a double haploid Pima 3-79 line. CS-B25 has improved fiber traits compared to its parent TM-1. To explore the molecule mechanisms underlying improved fiber traits, deep sequencing of total RNA was used to compare gene expression in fibers of CS-B25 and TM-1 at 10 days post anthesis (10-DPA). A total of 1872 differentially expressed genes (DEGs) were detected between the two lines, with 1175 up-regulated and 697 down-regulated in CS-B25. Gene Ontology (GO) enrichment analysis of the expression data by Generally Applicable Gene-set Enrichment (GAGE) and ReviGO indicated that the most prevalent Biological Process GO terms associated with DEGs included DNA-templated transcription, response to oxidative stress, and cellulose biosynthesis. Enriched Molecular Function GO terms included structural constituents of cytoskeleton, peroxidase activity, cellulose synthase (UDP-forming) activity, and transcription regulatory region sequence-specific DNA binding factors. GAGE was also used to find enriched KEGG pathways, and the highly represented pathways were Biosynthesis of Amino Acids, Starch and Sucrose Metabolism, Phenylpropanoid Biosynthesis, Protein Processing in Endoplasmic Reticulum, and Plant Hormone Signal Transduction. Many of the identified DEGs are involved in cytoskeleton and cell wall metabolism. The results of gene expression data have provided new insight into the molecular mechanisms of fiber development during the fiber elongation stage and would offer novel candidate genes that may be utilized in cotton fiber quality improvement.
Dual-Task Interference: The Effects of Verbal Cognitive Tasks on Upright Postural Stability in Parkinson's Disease
J. D. Holmes,M. E. Jenkins,A. M. Johnson,S. G. Adams,S. J. Spaulding
Parkinson's Disease , 2010, DOI: 10.4061/2010/696492
Abstract: Although dual-task interference has previously been demonstrated to have a significant effect on postural control among individuals with Parkinson's disease, the impact of speech complexity on postural control has not been demonstrated using quantitative biomechanical measures. The postural stability of twelve participants with idiopathic Parkinson's disease and twelve healthy age-matched controls was evaluated under three conditions: (1) without a secondary task, (2) performing a rote repetition task and (3) generating a monologue. Results suggested a significant effect of cognitive load on biomechanical parameters of postural stability. Although both groups increased their postural excursion, individuals with Parkinson's disease demonstrated significantly reduced excursion as compared with that of healthy age-matched controls. This suggests that participants with Parkinson's disease may be overconstraining their postural adjustments in order to focus attention on the cognitive tasks without losing their balance. Ironically, this overconstraint may place the participant at greater risk for a fall. 1. Introduction Postural instability is a frequent and incapacitating symptom of Parkinson’s disease (PD) and is only modestly responsive to pharmacotherapy [1]. As a result, patients must often resort to the use of attentional strategies such as mentally rehearsing action sequences, or consciously attending to their balance, to maintain equilibrium [2, 3]. The role of attention in PD has often been investigated within a dual-task paradigm; a methodology which requires participants to perform a primary task (e.g., postural control) while simultaneously performing a secondary task, which may be cognitive (e.g., speech) or motoric (e.g., carrying an object). Despite the considerable research that has evaluated the impact of dual-task interference on gait and upper extremity performance [4], few studies have examined the effects of dual-task performance on posture, among individuals with PD. Early work in this area employed clinically relevant measurements, rather than biomechanical assessments. Smithson et al. [3] evaluated standing balance in a sample of individuals with PD, both with and without the addition of a motoric secondary task (self-initiated movements, including arm raise, functional reach, and bend reach). Results suggested that postural instability was greatest among individuals with PD and also that this instability increased with the addition of a secondary task. Morris et al. [5] measured the effect of dual-task interference on postural
Australian perspective regarding recommendations for physical activity and exercise rehabilitation in pulmonary arterial hypertension
Fowler R, Jenkins S, Maiorana A, Gain K, O'Driscoll G, Gabbay E
Journal of Multidisciplinary Healthcare , 2011, DOI: http://dx.doi.org/10.2147/JMDH.S26617
Abstract: ustralian perspective regarding recommendations for physical activity and exercise rehabilitation in pulmonary arterial hypertension Original Research (2255) Total Article Views Authors: Fowler R, Jenkins S, Maiorana A, Gain K, O'Driscoll G, Gabbay E Published Date December 2011 Volume 2011:4 Pages 451 - 462 DOI: http://dx.doi.org/10.2147/JMDH.S26617 Robin Fowler1–3, Sue Jenkins2,3,5, Andrew Maiorana2,4, Kevin Gain2,3,6,7, Gerry O'Driscoll7–9, Eli Gabbay1–3,7–9 1Advanced Lung Disease Program, Royal Perth Hospital, 2School of Physiotherapy and Curtin Health Innovation Research Institute, Curtin University, 3Lung Institute of Western Australia (LIWA), Centre for Asthma, Allergy and Respiratory Research, University of Western Australia, 4Advanced Heart Failure and Cardiac Transplant Service, Royal Perth Hospital, 5Physiotherapy Department, Sir Charles Gairdner Hospital, 6Respiratory Medicine Department, Royal Perth Hospital, 7School of Medicine, University of Western Australia, 8School of Medicine, University of Notre Dame, 9Heart and Lung Transplant Foundation of Western Australia, Perth, Western Australia, Australia Aim: To determine the opinion of health care professionals within Australia, regarding acceptable levels of exertion and symptoms, and referral for exercise rehabilitation in patients with pulmonary arterial hypertension (PAH). Method: In 2010, 76 health care professionals at a specialist pulmonary hypertension meeting in Australia were surveyed using a self-administered questionnaire. The questionnaire included case studies of patients with PAH in World Health Organization (WHO) functional classes II–IV. For each case study, respondents were asked to report their opinion regarding the acceptable level of exertion and symptoms during daily activities, and whether they would refer the patient for exercise rehabilitation. Three additional questions asked about advice in relation to four specific physical activities. Results: The response rate was 70% (n = 53). Overall, 58% of respondents recommended patients undertake daily activities 'as tolerated'. There was no consensus regarding acceptable levels of breathlessness or fatigue, but the majority of respondents considered patients should have no chest pain (73%) and no more than mild light-headedness (92%) during daily activities. Overall, 63% of respondents would have referred patients for exercise rehabilitation. There was little difference in opinion regarding the acceptable level of exertion or symptoms, or referral for exercise rehabilitation, according to functional class. However, the patients' functional class did influence the advice given regarding the specific physical activities. Conclusion: In 2010, there were inconsistencies between individual health care professionals within Australia regarding appropriate levels of physical exertion and acceptable symptoms during daily activities. Almost two-thirds of the respondents reported they would refer patients for exercise rehabil
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