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1.
Geophys Res Lett ; 49(9): e2021GL096986, 2022 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-35864893

RESUMO

We report observations of reconnection exhausts in the Heliospheric Current Sheet (HCS) during Parker Solar Probe Encounters 08 and 07, at 16 R s and 20 R s , respectively. Heliospheric current sheet (HCS) reconnection accelerated protons to almost twice the solar wind speed and increased the proton core energy by a factor of ∼3, due to the Alfvén speed being comparable to the solar wind flow speed at these near-Sun distances. Furthermore, protons were energized to super-thermal energies. During E08, energized protons were found to have leaked out of the exhaust along separatrix field lines, appearing as field-aligned energetic proton beams in a broad region outside the HCS. Concurrent dropouts of strahl electrons, indicating disconnection from the Sun, provide further evidence for the HCS being the source of the beams. Around the HCS in E07, there were also proton beams but without electron strahl dropouts, indicating that their origin was not the local HCS reconnection exhaust.

2.
Phys Rev E ; 104(6-2): 065206, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-35030942

RESUMO

Reconnection and turbulence are two of the most commonly observed dynamical processes in plasmas, but their relationship is still not fully understood. Using 2.5D kinetic particle-in-cell simulations of both strong turbulence and reconnection, we compare the cross-scale transfer of energy in the two systems by analyzing the generalization of the von Kármán Howarth equations for Hall magnetohydrodynamics, a formulation that subsumes the third-order law for steady energy transfer rates. Even though the large scale features are quite different, the finding is that the decomposition of the energy transfer is structurally very similar in the two cases. In the reconnection case, the time evolution of the energy transfer also exhibits a correlation with the reconnection rate. These results provide explicit evidence that reconnection dynamics fundamentally involves turbulence-like energy transfer.

3.
BMC Health Serv Res ; 20(1): 995, 2020 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-33129332

RESUMO

BACKGROUND: Healthy Homes and Neighbourhoods (HHAN) Integrated Care Initiative was established to improve the care of families with complex health and social needs who reside in Sydney Local Health District. HHAN seeks to provide long-term multi-disciplinary care coordination as well as enhance capacity building and promote integrated care. The critical realist study reported here is part of the longitudinal development and evaluation of complex integrated health and social care interventions in Sydney, Australia. METHODS: We describe the qualitative component of a critical realist pilot case study aimed at exploring, explaining and refining emerging HHAN programme theories in relation to care coordination. Qualitative interviews were undertaken with HHAN clients (n = 12), staff and other stakeholders (n = 21). Interviews and coding used a context (C), mechanism (M) and outcome (O) framework. Inductive, deductive, retroductive and abductive modes of reasoning were used with the CMO heuristic tool to inform the developing programme theory. RESULTS: The mechanisms underpinning effective engagement of clients by care coordinators included: building trust, leveraging other family, social and organisational relationships, meeting clients on their own terms, demonstrating staff effectiveness as quickly as possible, and client empowerment. Mechanisms for enhancing care integration included knowledge transfer activities and shared learning among collaborators, structural and cultural changes, enhancing mutual respect, co-location of multidisciplinary and/or interagency staff and cultivating faith in positive change among staff. CONCLUSIONS: Use of a critical realism case study approach served to elucidate the varied influences of contexts and mechanisms on programme outcomes, to highlight what works for whom and in what context. Findings supported the initial programme theory that engagement and trust building with clients, alongside enhanced collaboration and integration of services, improved outcomes for vulnerable families with complex needs. Further research is needed to explore the cost-effectiveness of integrated care initiatives, in view of the long term nature of service provision and the risk of staff burnout.


Assuntos
Prestação Integrada de Cuidados de Saúde , Austrália , Família , Feminino , Promoção da Saúde , Humanos
4.
J Geophys Res Space Phys ; 125(7): e2019JA027410, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32999805

RESUMO

The Vlasiator hybrid-Vlasov code was developed to investigate global magnetospheric dynamics at ion-kinetic scales. Here we focus on the role of magnetic reconnection in the formation and evolution of magnetic islands at the low-latitude magnetopause, under southward interplanetary magnetic field conditions. The simulation results indicate that (1) the magnetic reconnection ion kinetics, including the Earthward pointing Larmor electric field on the magnetospheric side of an X-point and anisotropic ion distributions, are well-captured by Vlasiator, thus enabling the study of reconnection-driven magnetic island evolution processes, (2) magnetic islands evolve due to continuous reconnection at adjacent X-points, "coalescence" which refers to the merging of neighboring islands to create a larger island, "erosion" during which an island loses magnetic flux due to reconnection, and "division" which involves the splitting of an island into smaller islands, and (3) continuous reconnection at adjacent X-points is the dominant source of magnetic flux and plasma to the outer layers of magnetic islands resulting in cross-sectional growth rates up to + 0.3 RE 2/min. The simulation results are compared to the Magnetospheric Multiscale (MMS) measurements of a chain of ion-scale flux transfer events (FTEs) sandwiched between two dominant X-lines. The MMS measurements similarly reveal (1) anisotropic ion populations and (2) normalized reconnection rate ~0.18, in agreement with theory and the Vlasiator predictions. Based on the simulation results and the MMS measurements, it is estimated that the observed ion-scale FTEs may grow Earth-sized within ~10 min, which is comparable to the average transport time for FTEs formed in the subsolar region to the high-latitude magnetopause. Future simulations shall revisit reconnection-driven island evolution processes with improved spatial resolutions.

5.
Phys Rev Lett ; 125(26): 265102, 2020 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-33449730

RESUMO

Magnetic reconnection is of fundamental importance to plasmas because of its role in releasing and repartitioning stored magnetic energy. Previous results suggest that this energy is predominantly released as ion enthalpy flux along the reconnection outflow. Using Magnetospheric Multiscale data we find the existence of very significant electron energy flux densities in the vicinity of the magnetopause electron dissipation region, orthogonal to the ion energy outflow. These may significantly impact models of electron transport, wave generation, and particle acceleration.

6.
Nature ; 576(7786): 237-242, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31802007

RESUMO

During the solar minimum, when the Sun is at its least active, the solar wind1,2 is observed at high latitudes as a predominantly fast (more than 500 kilometres per second), highly Alfvénic rarefied stream of plasma originating from deep within coronal holes. Closer to the ecliptic plane, the solar wind is interspersed with a more variable slow wind3 of less than 500 kilometres per second. The precise origins of the slow wind streams are less certain4; theories and observations suggest that they may originate at the tips of helmet streamers5,6, from interchange reconnection near coronal hole boundaries7,8, or within coronal holes with highly diverging magnetic fields9,10. The heating mechanism required to drive the solar wind is also unresolved, although candidate mechanisms include Alfvén-wave turbulence11,12, heating by reconnection in nanoflares13, ion cyclotron wave heating14 and acceleration by thermal gradients1. At a distance of one astronomical unit, the wind is mixed and evolved, and therefore much of the diagnostic structure of these sources and processes has been lost. Here we present observations from the Parker Solar Probe15 at 36 to 54 solar radii that show evidence of slow Alfvénic solar wind emerging from a small equatorial coronal hole. The measured magnetic field exhibits patches of large, intermittent reversals that are associated with jets of plasma and enhanced Poynting flux and that are interspersed in a smoother and less turbulent flow with a near-radial magnetic field. Furthermore, plasma-wave measurements suggest the existence of electron and ion velocity-space micro-instabilities10,16 that are associated with plasma heating and thermalization processes. Our measurements suggest that there is an impulsive mechanism associated with solar-wind energization and that micro-instabilities play a part in heating, and we provide evidence that low-latitude coronal holes are a key source of the slow solar wind.

7.
Case Rep Womens Health ; 24: e00154, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31709158

RESUMO

When advising a pregnant patient who has previously had a cesarean section about the risks of trial of labor, it is important to explain the risk of uterine rupture. Subjective symptoms of abdominal pain or objective findings of non-reassuring fetal status and loss of fetal station are often indicative of this disease process, which most commonly is caused by a defect on the uterus from the cesarean delivery. Any uterine surgical intervention (myomectomy, for example) is the leading risk factor for uterine rupture. This case report presents a patient who had no such history. However, the maternal and fetal clinical status rapidly deteriorated and required emergency cesarean delivery, at which point a complete uterine rupture was diagnosed. Low suspicion for rare occurrences such as uterine rupture in an unscarred uterus can delay diagnosis, with increased likelihood of fetal and maternal morbidity and mortality.

8.
Nature ; 569(7757): E9, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31073227

RESUMO

Change history: In this Letter, the y-axis values in Fig. 3f should go from 4 to -8 (rather than from 4 to -4), the y-axis values in Fig. 3h should appear next to the major tick marks (rather than the minor ticks), and in Fig. 1b, the arrows at the top and bottom of the electron-scale current sheet were going in the wrong direction; these errors have been corrected online.

9.
Eur J Cardiovasc Nurs ; 18(7): 569-576, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31088306

RESUMO

BACKGROUND: Young black women have an increased risk of cardiovascular disease, and thus identifying innovative prevention strategies is essential. A potential preventive strategy is mobile health; however, few studies have tested this strategy in young black women. AIM: The purpose of this study was to assess the feasibility of a mobile health intervention through a digital application to reduce cardiovascular disease risk factors in young black women, and identify benefits and barriers to participation. METHODS: Forty black women aged 25-45 years completed four sessions of cardiovascular disease risk reduction education and a six-month smartphone cardiovascular disease risk reduction monitoring and coaching intervention, targeting heart-healthy behavior modifications. At follow-up, women responded to a semi-qualitative online survey assessing the user-friendliness and perceived helpfulness of the intervention. RESULTS: Of 40 women, 38 completed the follow-up survey. Sixty per cent of participants reported that the applications were easy or very easy to maintain, 90% reported that the application was easy or very easy to use. Over 60% observed that their family's nutrition improved "a lot" or "a medium amount," and many participants noted positive changes in their children's diets. Only 8% of participants cited time or cost required to prepare healthy foods as barriers to implementing dietary changes. CONCLUSIONS: The m-Health intervention was feasible as a means of cardiovascular disease risk reduction for young black women. In addition, we found that targeting women provided indirect benefits for other family members, especially children. Most of the participants did not encounter systemic barriers to participation, suggesting that mobile health interventions can be effective tools to improve health behaviors in vulnerable populations.


Assuntos
Negro ou Afro-Americano/educação , Doenças Cardiovasculares/prevenção & controle , Promoção da Saúde/métodos , Estilo de Vida Saudável , Participação do Paciente/psicologia , Comportamento de Redução do Risco , Telemedicina/métodos , Adulto , Negro ou Afro-Americano/psicologia , Negro ou Afro-Americano/estatística & dados numéricos , Idoso , Idoso de 80 Anos ou mais , Estudos de Viabilidade , Feminino , Humanos , Pessoa de Meia-Idade , Educação de Pacientes como Assunto/métodos , Participação do Paciente/estatística & dados numéricos , Inquéritos e Questionários
10.
Science ; 362(6421): 1391-1395, 2018 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-30442767

RESUMO

Magnetic reconnection is an energy conversion process that occurs in many astrophysical contexts including Earth's magnetosphere, where the process can be investigated in situ by spacecraft. On 11 July 2017, the four Magnetospheric Multiscale spacecraft encountered a reconnection site in Earth's magnetotail, where reconnection involves symmetric inflow conditions. The electron-scale plasma measurements revealed (i) super-Alfvénic electron jets reaching 15,000 kilometers per second; (ii) electron meandering motion and acceleration by the electric field, producing multiple crescent-shaped structures in the velocity distributions; and (iii) the spatial dimensions of the electron diffusion region with an aspect ratio of 0.1 to 0.2, consistent with fast reconnection. The well-structured multiple layers of electron populations indicate that the dominant electron dynamics are mostly laminar, despite the presence of turbulence near the reconnection site.

11.
Nature ; 557(7704): 202-206, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29743689

RESUMO

Magnetic reconnection in current sheets is a magnetic-to-particle energy conversion process that is fundamental to many space and laboratory plasma systems. In the standard model of reconnection, this process occurs in a minuscule electron-scale diffusion region1,2. On larger scales, ions couple to the newly reconnected magnetic-field lines and are ejected away from the diffusion region in the form of bi-directional ion jets at the ion Alfvén speed3-5. Much of the energy conversion occurs in spatially extended ion exhausts downstream of the diffusion region 6 . In turbulent plasmas, which contain a large number of small-scale current sheets, reconnection has long been suggested to have a major role in the dissipation of turbulent energy at kinetic scales7-11. However, evidence for reconnection plasma jetting in small-scale turbulent plasmas has so far been lacking. Here we report observations made in Earth's turbulent magnetosheath region (downstream of the bow shock) of an electron-scale current sheet in which diverging bi-directional super-ion-Alfvénic electron jets, parallel electric fields and enhanced magnetic-to-particle energy conversion were detected. Contrary to the standard model of reconnection, the thin reconnecting current sheet was not embedded in a wider ion-scale current layer and no ion jets were detected. Observations of this and other similar, but unidirectional, electron jet events without signatures of ion reconnection reveal a form of reconnection that can drive turbulent energy transfer and dissipation in electron-scale current sheets without ion coupling.

12.
Sol Phys ; 293(3): 52, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29568139

RESUMO

The magnetic field structures of two interplanetary coronal mass ejections (ICMEs), each observed by a pair of spacecraft close to radial alignment, have been analysed. The ICMEs were observed in situ by MESSENGER and STEREO-B in November 2010 and November 2011, while the spacecraft were separated by more than 0.6 AU in heliocentric distance, less than 4° in heliographic longitude, and less than 7° in heliographic latitude. Both ICMEs took approximately two days to travel between the spacecraft. The ICME magnetic field profiles observed at MESSENGER have been mapped to the heliocentric distance of STEREO-B and compared directly to the profiles observed by STEREO-B. Figures that result from this mapping allow for easy qualitative assessment of similarity in the profiles. Macroscale features in the profiles that varied on timescales of one hour, and which corresponded to the underlying flux rope structure of the ICMEs, were well correlated in the solar east-west and north-south directed components, with Pearson's correlation coefficients of approximately 0.85 and 0.95, respectively; microscale features with timescales of one minute were uncorrelated. Overall correlation values in the profiles of one ICME were increased when an apparent change in the flux rope axis direction between the observing spacecraft was taken into account. The high degree of similarity seen in the magnetic field profiles may be interpreted in two ways. If the spacecraft sampled the same region of each ICME (i.e. if the spacecraft angular separations are neglected), the similarity indicates that there was little evolution in the underlying structure of the sampled region during propagation. Alternatively, if the spacecraft observed different, nearby regions within the ICMEs, it indicates that there was spatial homogeneity across those different regions. The field structure similarity observed in these ICMEs points to the value of placing in situ space weather monitors well upstream of the Earth.

13.
Geophys Res Lett ; 45(10): 4569-4577, 2018 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-31031447

RESUMO

Magnetospheric Multiscale observations are used to probe the structure and temperature profile of a guide field reconnection exhaust ~100 ion inertial lengths downstream from the X-line in the Earth's magnetosheath. Asymmetric Hall electric and magnetic field signatures were detected, together with a density cavity confined near 1 edge of the exhaust and containing electron flow toward the X-line. Electron holes were also detected both on the cavity edge and at the Hall magnetic field reversal. Predominantly parallel ion and electron heating was observed in the main exhaust, but within the cavity, electron cooling and enhanced parallel ion heating were found. This is explained in terms of the parallel electric field, which inhibits electron mixing within the cavity on newly reconnected field lines but accelerates ions. Consequently, guide field reconnection causes inhomogeneous changes in ion and electron temperature across the exhaust.

14.
Space Weather ; 15(7): 955-970, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28983209

RESUMO

We present an advance toward accurately predicting the arrivals of coronal mass ejections (CMEs) at the terrestrial planets, including Earth. For the first time, we are able to assess a CME prediction model using data over two thirds of a solar cycle of observations with the Heliophysics System Observatory. We validate modeling results of 1337 CMEs observed with the Solar Terrestrial Relations Observatory (STEREO) heliospheric imagers (HI) (science data) from 8 years of observations by five in situ observing spacecraft. We use the self-similar expansion model for CME fronts assuming 60° longitudinal width, constant speed, and constant propagation direction. With these assumptions we find that 23%-35% of all CMEs that were predicted to hit a certain spacecraft lead to clear in situ signatures, so that for one correct prediction, two to three false alarms would have been issued. In addition, we find that the prediction accuracy does not degrade with the HI longitudinal separation from Earth. Predicted arrival times are on average within 2.6 ± 16.6 h difference of the in situ arrival time, similar to analytical and numerical modeling, and a true skill statistic of 0.21. We also discuss various factors that may improve the accuracy of space weather forecasting using wide-angle heliospheric imager observations. These results form a first-order approximated baseline of the prediction accuracy that is possible with HI and other methods used for data by an operational space weather mission at the Sun-Earth L5 point.

15.
Risk Anal ; 37(2): 206-218, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-28230267

RESUMO

Space weather describes the way in which the Sun, and conditions in space more generally, impact human activity and technology both in space and on the ground. It is now well understood that space weather represents a significant threat to infrastructure resilience, and is a source of risk that is wide-ranging in its impact and the pathways by which this impact may occur. Although space weather is growing rapidly as a field, work rigorously assessing the overall economic cost of space weather appears to be in its infancy. Here, we provide an initial literature review to gather and assess the quality of any published assessments of space weather impacts and socioeconomic studies. Generally speaking, there is a good volume of scientific peer-reviewed literature detailing the likelihood and statistics of different types of space weather phenomena. These phenomena all typically exhibit "power-law" behavior in their severity. The literature on documented impacts is not as extensive, with many case studies, but few statistical studies. The literature on the economic impacts of space weather is rather sparse and not as well developed when compared to the other sections, most probably due to the somewhat limited data that are available from end-users. The major risk is attached to power distribution systems and there is disagreement as to the severity of the technological footprint. This strongly controls the economic impact. Consequently, urgent work is required to better quantify the risk of future space weather events.

16.
Phys Rev Lett ; 117(18): 185102, 2016 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-27835012

RESUMO

Observations made using the Wind spacecraft of Hall magnetic fields in solar wind reconnection exhausts are presented. These observations are consistent with the generation of Hall fields by a narrow ion inertial scale current layer near the separatrix, which is confirmed with an appropriately scaled particle-in-cell simulation that shows excellent agreement with observations. The Hall fields are observed thousands of ion inertial lengths downstream from the reconnection X line, indicating that narrow regions of kinetic dynamics can persist extremely far downstream.

17.
Geophys Res Lett ; 43(10): 4716-4724, 2016 05 28.
Artigo em Inglês | MEDLINE | ID: mdl-27635105

RESUMO

New Magnetospheric Multiscale (MMS) observations of small-scale (~7 ion inertial length radius) flux transfer events (FTEs) at the dayside magnetopause are reported. The 10 km MMS tetrahedron size enables their structure and properties to be calculated using a variety of multispacecraft techniques, allowing them to be identified as flux ropes, whose flux content is small (~22 kWb). The current density, calculated using plasma and magnetic field measurements independently, is found to be filamentary. Intercomparison of the plasma moments with electric and magnetic field measurements reveals structured non-frozen-in ion behavior. The data are further compared with a particle-in-cell simulation. It is concluded that these small-scale flux ropes, which are not seen to be growing, represent a distinct class of FTE which is generated on the magnetopause by secondary reconnection.

18.
Phys Rev Lett ; 116(23): 235102, 2016 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-27341241

RESUMO

We report observations from the Magnetospheric Multiscale satellites of parallel electric fields (E_{∥}) associated with magnetic reconnection in the subsolar region of the Earth's magnetopause. E_{∥} events near the electron diffusion region have amplitudes on the order of 100 mV/m, which are significantly larger than those predicted for an antiparallel reconnection electric field. This Letter addresses specific types of E_{∥} events, which appear as large-amplitude, near unipolar spikes that are associated with tangled, reconnected magnetic fields. These E_{∥} events are primarily in or near a current layer near the separatrix and are interpreted to be double layers that may be responsible for secondary reconnection in tangled magnetic fields or flux ropes. These results are telling of the three-dimensional nature of magnetopause reconnection and indicate that magnetopause reconnection may be often patchy and/or drive turbulence along the separatrix that results in flux ropes and/or tangled magnetic fields.

19.
J Hum Hypertens ; 30(12): 778-782, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27334520

RESUMO

CYP3A5 (cytochrome P450, family 3, subfamily A, polypeptide 5) expression stimulates the sodium retentive actions of the mineralocorticoid receptor causative of hypertension, probably by means of its ability to substantially increase the level of 6ß-hydroxylase activity. Most Black individuals are functional CYP3A5 expressers, and this is a candidate gene for the high incidence of hypertension in Black populations. The study investigates whether CYP3A5 expression results in higher blood pressure in a Ghanaian population. Real-time PCR was used to genotype 898 DNA samples for the CYP3A5*3 and CYP3A5*6 single-nucleotide polymorphisms with technically adequate genotyping for 881 samples. Of these, 803 were genetic CYP3A5 expressers, 44 nonexpressers and 34 uncertain (CYP3A5*3/*6). Although there was a trend in the proportion of hypertensive individuals as CYP3A5 expression decreased, using a two-sided t-test, no statistically significant relationship was established between systolic or diastolic pressure and CYP3A5*3 or CYP3A5*6 genotypes, or their haplotypes (Systolic confidence interval: -8.44 to -7.70, P=0.93, Diastolic confidence interval: -4.89 to 4.85, P=0.99). We conclude, therefore, that there is either no association between CYP3A5 expression and blood pressure or, if there is a relationship, the strength of the association is very small.


Assuntos
População Negra/genética , Pressão Sanguínea/genética , Citocromo P-450 CYP3A/genética , Hipertensão/genética , Polimorfismo de Nucleotídeo Único , Adulto , Idoso , Feminino , Frequência do Gene , Estudos de Associação Genética , Predisposição Genética para Doença , Gana/epidemiologia , Haplótipos , Heterozigoto , Homozigoto , Humanos , Hipertensão/enzimologia , Hipertensão/etnologia , Hipertensão/fisiopatologia , Masculino , Pessoa de Meia-Idade , Fenótipo , Prevalência , Medição de Risco , Fatores de Risco
20.
Science ; 352(6290): aaf2939, 2016 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-27174677

RESUMO

Magnetic reconnection is a fundamental physical process in plasmas whereby stored magnetic energy is converted into heat and kinetic energy of charged particles. Reconnection occurs in many astrophysical plasma environments and in laboratory plasmas. Using measurements with very high time resolution, NASA's Magnetospheric Multiscale (MMS) mission has found direct evidence for electron demagnetization and acceleration at sites along the sunward boundary of Earth's magnetosphere where the interplanetary magnetic field reconnects with the terrestrial magnetic field. We have (i) observed the conversion of magnetic energy to particle energy; (ii) measured the electric field and current, which together cause the dissipation of magnetic energy; and (iii) identified the electron population that carries the current as a result of demagnetization and acceleration within the reconnection diffusion/dissipation region.

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