bluuebunny/crossref_metadata_2025_split huggingface dataset:
Propagation and evolution of electric fields associated with solar wind pressure pulses based on spacecraft and ground‐based observations
Authors: Takahashi N. , Kasaba Y. , Nishimura Y. , Shinbori A. , Kikuchi T. , Hori T. , Ebihara Y. , Nishitani N. 
Published: July 2017

AbstractWe investigate spatial and temporal evolution of large‐scale electric fields in the magnetosphere and ionosphere associated with sudden commencements (SCs) using multipoint equatorial magnetospheric (THEMIS, RBSP, and GOES) and ionospheric (C/NOFS) satellites with radars (SuperDARN). A distinct SC event on 17 March 2013 shows that the magnetospheric electric field in the equatorial plane propagates from dayside toward nightside as a fast‐mode wave. The ionospheric electric field responds ~41 s after the onset of dayside magnetospheric electric field, which can be explained by the propagation of the Alfvén wave along magnetic field lines. The wavelet analysis shows that the Alfvén wave is dominant in the plasmasphere. Poynting fluxes toward the ionosphere support these propagations. From a statistical analysis of response time, tailward propagation speed is estimated at about 1000–1100 km/s. We also statistically derive a spatial distribution and time evolution of the magnetospheric electric field in the dawn‐dusk direction (Ey). Our result shows that negative Ey (dawnward) propagates from noon toward the magnetotail, followed by positive Ey (duskward). The propagation characteristics of electric fields in the equatorial plane depend on magnetic local time. At noon, negative Ey lasts for about 1 min, and positive Ey becomes dominant about 2 min after the SC onset. Negative Ey soon attenuates in the nightside region, while the positive Ey propagates fairly well to the premidnight or postmidnight regions while maintaining a certain amplitude. The enhancement of positive Ey is due to the enhancement of magnetospheric convection associated with the main impulse of SCs.
Current‐driven flare and CME models
Authors: Melrose D. B. 
Published: July 2017

AbstractRoles played by the currents in the impulsive phase of a solar flare and in a coronal mass ejection (CME) are reviewed. Solar flares are magnetic explosions: magnetic energy stored in unneutralized currents in coronal loops is released into energetic electrons in the impulsive phase and into mass motion in a CME. The energy release is due to a change in current configuration effectively reducing the net current path. A flare is driven by the electromotive force (EMF) due to the changing magnetic flux. The EMF drives a flare‐associated current whose cross‐field closure is achieved by redirection along field lines to the chromosphere and back. The essential roles that currents play are obscured in the “standard” model and are described incorrectly in circuit models. A semiquantitative treatment of the energy and the EMF is provided by a multicurrent model, in which the currents are constant and the change in the current paths is described by time‐dependent inductances. There is no self‐consistent model that includes the intrinsic time dependence, the EMF, the flare‐associated current, and the internal energy transport during a flare. The current, through magnetic helicity, plays an important role in a CME, with twist converted into writhe allowing the kink instability plus reconnection to lead to a new closed loop and with the current‐current force accelerating the CME through the torus instability.
Nearly identical cycles of the quasi‐biennial oscillation in the equatorial lower stratosphere
Authors: Dunkerton T. J. 
Published: July 2017

AbstractAs a nonlinear dynamical system with limit cycles but subject to periodic forcings associated with the seasonal cycle, the quasi‐biennial oscillation (QBO) displays seasonal modulation such that phase transitions are more likely to occur in certain months than in others. Modulation is distinct from seasonal synchronization, defined as quantized QBO periods and identical cycles. Instead, nearly identical QBO cycles can be identified in the data having similar period, internal structure, and (optionally) timing with respect to the calendar year. Four such categories are found using a spectral phase method based on the 2‐D phase space of the leading rotated principal components (RPCs) of near‐equatorial monthly mean zonal wind in the layer 70–10 hPa. The most prominent category, containing as many as 15 cycles of the 28 observed thus far, is “nearly biennial” with period slightly greater than 24 months. All results, prior to the recent QBO anomaly in Cycle 28, are demonstrated to be statistically stationary in the sense that the RPCs are temporally invariant and insensitive to the inclusion of data to 100 hPa and with higher vertical resolution. Inclusion of Cycle 28 has no effect on the rotated empirical orthogonal functions but a microscopic change in the long‐term average, since strong easterlies are missing in the anomalous cycle. For objective definition of QBO cycles in physical space‐time, westerly onsets in the 40–53 hPa layer are least likely to stall and provide unambiguous starting times. Half of these onsets cluster in April–May, consistent with the seasonal modulation obtained with the spectral phase method.
Investigating the contribution of secondary ice production to in‐cloud ice crystal numbers
Authors: Sullivan S. C. , Hoose C. , Nenes A. 
Published: July 2017

AbstractIn‐cloud measurements of ice crystal number concentration can be orders of magnitude higher than the precloud ice nucleating particle number concentration. This disparity may be explained with secondary ice production processes. Several such processes have been proposed, but their relative importance and even the exact physics are not well known. In this work, a six‐hydrometeor‐class parcel model is developed to investigate the ice crystal number enhancement, both its bounds and its value for different cloud states, from rime splintering and breakup upon graupel‐graupel collision. The model also includes ice aggregation and droplet coalescence, ice hydrometeor nonsphericity, and a time delay formulation for hydrometeor growth. Conditions to maximize the breakup contribution, as well as the effects of nonsphericity and turbulence, are discussed. We find that the largest enhancement of ice crystal number occurs for “intermediate” conditions, characterized by moderate updrafts and activation and nucleation rates. In this case, vertical motion is strong enough, and new hydrometeor formation limited enough, to sustain supersaturation as hydrometeors grow to larger sizes. After these larger hydrometeors form at sufficient number concentrations, the ice crystal number can be enhanced by a factor of 104 in some cases relative to the number generated by primary ice nucleation alone. Excluding ice hydrometeor nonsphericity limits secondary production significantly, and the parcel updraft can modulate it by about an order of magnitude.
A climatology of Rossby wave generation in the middle atmosphere of the Southern Hemisphere from MERRA reanalysis
Authors: Rodas Claudio , Pulido Manuel 
Published: July 2017

AbstractA climatological characterization of Rossby wave generation events in the middle atmosphere of the Southern Hemisphere is conducted using 20 years of Modern‐Era Retrospective Analysis for Research and Applications (MERRA) reanalysis. An automatic detection technique of wave generation events is developed and applied to MERRA reanalysis. The Rossby wave generation events with wave period of 1.25 to 5.5 days and zonal wave number from one to three dominate the Eliassen‐Palm flux divergence around the stratopause at high latitudes in the examined 20 year period. These produce an eastward forcing of the general circulation between May and mid‐August in that region. Afterward from mid‐August to the final warming date, Rossby wave generation events are still present but the Eliassen‐Palm flux divergence in the polar stratopause is dominated by low‐frequency Rossby waves that propagate from the troposphere. The Rossby wave generation events are associated with potential vorticity gradient inversion, and so they are a manifestation of the dominant barotropic/baroclinic unstable modes that grow at the cost of smearing the negative meridional gradient of potential vorticity. The most likely region of wave generation is found between 60° and 80°S and at a height of 0.7 hPa, but events were detected from 40 hPa to 0.3 hPa (which is the top of the examined region). The mean number of events per year is 24, and its mean duration is 3.35 days. The event duration follows an exponential distribution.
Rapid transport of ash and sulfate from the 2011 Puyehue‐Cordón Caulle (Chile) eruption to West Antarctica
Authors: Koffman Bess G. , Dowd Eleanor G. , Osterberg Erich C. , Ferris David G. , Hartman Laura H. , Wheatley Sarah D. , Kurbatov Andrei V. , Wong Gifford J. , Markle Bradley R. , Dunbar Nelia W. , Kreutz Karl J. , Yates Martin 
Published: July 2017

AbstractThe Volcanic Explosivity Index 5 eruption of the Puyehue‐Cordón Caulle volcanic complex (PCC) in central Chile, which began 4 June 2011, provides a rare opportunity to assess the rapid transport and deposition of sulfate and ash from a midlatitude volcano to the Antarctic ice sheet. We present sulfate, microparticle concentrations of fine‐grained (~5 μm diameter) tephra, and major oxide geochemistry, which document the depositional sequence of volcanic products from the PCC eruption in West Antarctic snow and shallow firn. From the depositional phasing and duration of ash and sulfate peaks, we infer that transport occurred primarily through the troposphere but that ash and sulfate transport were decoupled. We use Hybrid Single‐Particle Lagrangian Integrated Trajectory back trajectory modeling to assess atmospheric circulation conditions in the weeks following the eruption and find that conditions favored southward air parcel transport during 6–14 June and 4–18 July 2011. We suggest that two discrete pulses of cryptotephra deposition relate to these intervals, and as such, constrain the sulfate transport and deposition lifespan to the ~2–3 weeks following the eruption. Finally, we compare PCC depositional patterns to those of prominent low‐ and high‐latitude eruptions in order to improve multiparameter‐based efforts to identify “unknown source” eruptions in the ice core record. Our observations suggest that midlatitude eruptions such as PCC can be distinguished from explosive tropical eruptions by differences in ash/sulfate phasing and in the duration of sulfate deposition, and from high‐latitude eruptions by differences in particle size distribution and in cryptotephra geochemical composition.
On the aliasing of the solar cycle in the lower stratospheric tropical temperature
Authors: Kuchar Ales , Ball William T. , Rozanov Eugene V. , Stenke Andrea , Revell Laura , Miksovsky Jiri , Pisoft Petr , Peter Thomas 
Published: July 2017

AbstractThe double‐peaked response of the tropical stratospheric temperature profile to the 11 year solar cycle (SC) has been well documented. However, there are concerns about the origin of the lower peak due to potential aliasing with volcanic eruptions or the El Niño–Southern Oscillation (ENSO) detected using multiple linear regression analysis. We confirm the aliasing using the results of the chemistry‐climate model (CCM) SOCOLv3 obtained in the framework of the International Global Atmospheric Chemisty/Stratosphere‐troposphere Processes And their Role in Climate Chemistry‐Climate Model Initiative phase 1. We further show that even without major volcanic eruptions included in transient simulations, the lower stratospheric response exhibits a residual peak when historical sea surface temperatures (SSTs)/sea ice coverage (SIC) are used. Only the use of climatological SSTs/SICs in addition to background stratospheric aerosols removes volcanic and ENSO signals and results in an almost complete disappearance of the modeled solar signal in the lower stratospheric temperature. We demonstrate that the choice of temporal subperiod considered for the regression analysis has a large impact on the estimated profile signal in the lower stratosphere: at least 45 consecutive years are needed to avoid the large aliasing effect of SC maxima with volcanic eruptions in 1982 and 1991 in historical simulations, reanalyses, and observations. The application of volcanic forcing compiled for phase 6 of the Coupled Model Intercomparison Project (CMIP6) in the CCM SOCOLv3 reduces the warming overestimation in the tropical lower stratosphere and the volcanic aliasing of the temperature response to the SC, although it does not eliminate it completely.
Technical Note: Using k‐means clustering to determine the number and position of isocenters in MLC‐based multiple target intracranial radiosurgery
Authors: Yock Adam D. , Kim Gwe‐Ya 
Published: July 2017

AbstractPurposeTo present the k‐means clustering algorithm as a tool to address treatment planning considerations characteristic of stereotactic radiosurgery using a single isocenter for multiple targets.MethodsFor 30 patients treated with stereotactic radiosurgery for multiple brain metastases, the geometric centroids and radii of each met were determined from the treatment planning system. In‐house software used this as well as weighted and unweighted versions of the k‐means clustering algorithm to group the targets to be treated with a single isocenter, and to position each isocenter. The algorithm results were evaluated using within‐cluster sum of squares as well as a minimum target coverage metric that considered the effect of target size. Both versions of the algorithm were applied to an example patient to demonstrate the prospective determination of the appropriate number and location of isocenters.ResultsBoth weighted and unweighted versions of the k‐means algorithm were applied successfully to determine the number and position of isocenters. Comparing the two, both the within‐cluster sum of squares metric and the minimum target coverage metric resulting from the unweighted version were less than those from the weighted version. The average magnitudes of the differences were small (−0.2 cm2 and 0.1% for the within cluster sum of squares and minimum target coverage, respectively) but statistically significant (Wilcoxon signed‐rank test, P < 0.01).ConclusionsThe differences between the versions of the k‐means clustering algorithm represented an advantage of the unweighted version for the within‐cluster sum of squares metric, and an advantage of the weighted version for the minimum target coverage metric. While additional treatment planning considerations have a large influence on the final treatment plan quality, both versions of the k‐means algorithm provide automatic, consistent, quantitative, and objective solutions to the tasks associated with SRS treatment planning using a single isocenter for multiple targets.
Prevalence of Sacroiliitis in Inflammatory Bowel Disease Using a Standardized Computed Tomography Scoring System
Authors: Chan Jonathan , Sari Ismail , Salonen David , Silverberg Mark S. , Haroon Nigil , Inman Robert D. 
Published: July 2017

ObjectiveThere is an increasing emphasis on the early identification and treatment of ankylosing spondylitis (AS) of which the hallmark is sacroiliitis. Patients with inflammatory bowel disease (IBD) are at increased risk of AS and often receive computed tomography (CT) scans of their abdomen, affording clinicians the opportunity to determine the presence of sacroiliitis. Previous studies using CT have relied only on the radiologist's gestalt or a nonvalidated adaptation of the modified New York criteria. Our aim is to assess the prevalence of sacroiliitis in IBD using a validated screening tool and to determine how frequently these patients are referred for rheumatologic evaluation.MethodsPatients with IBD were recruited from an IBD clinic. Control patients were recruited from a urology clinic and were confirmed to be without back pain, spondylitis, psoriasis, colitis, or uveitis by chart review. CT scans were read by 2 blinded readers and sacroiliitis was defined by the presence of ankylosis or a total erosion score of ≥3.ResultsCT scans were available in 233 Crohn's disease (CD) patients, 83 ulcerative colitis (UC) patients, and 108 control patients, and sacroiliitis was seen in 15%, 16.9%, and 5.6% of patients, respectively. The prevalence was higher in patients with IBD than in controls (P = 0.007), with no significant difference between CD and UC patients. Of the 49 IBD patients found to have sacroiliitis by CT scan, only 5 had been referred to a rheumatologist.ConclusionThere is a 3‐fold higher prevalence of sacroiliitis in IBD compared with controls. Despite a growing awareness of this increased prevalence, many patients are not referred to a rheumatologist.
Bisphosphine‐Ligated Nickel Pre‐catalysts in C(sp2)–N Cross‐Couplings of Aryl Chlorides: A Comparison of Nickel(I) and Nickel(II)
Authors: Lavoie Christopher M. , McDonald Robert , Johnson Erin R. , Stradiotto Mark 
Published: July 2017

AbstractThe influence of ancillary ligand and nickel oxidation state in the nickel‐catalyzed C(sp2)–N cross‐coupling of aryl chlorides is examined by use of experimental and DFT methods for the first time, focusing on (L)NiCl and (L)Ni(o‐tolyl)Cl pre‐catalysts (PAd‐DalPhos, L1; dppf, L2). Whereas Ni(II) pre‐catalysts generally out‐performed Ni(I) species in our study, the viability and in some cases superiority of Ni(I) pre‐catalysts in challenging aminations is established. Computational analyses support the viability of Ni(0)/Ni(II) cycles featuring rate‐limiting C–N reductive elimination, as well as parallel Ni(I)/Ni(III) mechanisms involving rate‐limiting C–Cl oxidative addition.magnified image
High‐Performance Bottom‐Contact Organic Thin‐Film Transistors by Improving the Lateral Contact
Authors: Zhang Xiaodong , Wang Zi , Zhou Xu , Wang Zhifang , Huang Lizhen , Chi Lifeng 
Published: July 2017

AbstractOne of the main challenges to achieve high‐performance bottom‐contact transistors involves the organic/electrodes contacts. This study provides a simple approach to address the contact issue by incorporating an inducing layer prior to the organic semiconductor deposition. The molecules of the inducing layer nucleate into lamellar grains from the edge to the channel, resulting in a good morphological contact to the bottom electrodes. The following active layer maintains nearly layer‐by‐layer growth mode and yields uniformed terraced‐like films both on the electrode edges and in the channels. With the inducing layer, pentacene thin‐film bottom‐contact transistors are obtained with a hole mobility exceeding 1 cm2 V−1 s−1.
Phenyl Derivative of Dibenzothiopheno[6,5‐b:6′,5′‐f]Thieno[3,2‐b]Thiophene (DPh‐DBTTT): High Thermally Durable Organic Semiconductor for High‐Performance Organic Field‐Effect Transistors
Authors: Lee Eun‐Kyung , Lee Moo Yeol , Choi Ajeong , Kim Joo‐Young , Kweon O. Young , Kim Jung‐Hwa , Jung Ji Young , Shin Tae‐Joo , Oh Joon Hak , Park Jeong‐Il , Lee Sang Yoon 
Published: July 2017

AbstractPhenyl‐substituted heteroacene, diphenyl‐dibenzothiopheno[6,5‐b:6′,5′‐f]thieno[3,2‐b]thiophene (DPh‐DBTTT), is introduced as a thermally durable high‐performance organic semiconductor. The DPh‐DBTTT single crystals exhibit hole mobility up to 31.9 cm2 V−1 s−1, and the vacuum‐deposited DPh‐DBTTT thin‐film transistors show a maximum mobility of 6.32 cm2 V−1 s−1. X‐ray crystallographic analysis reveals that the small tilting angle between the phenyl substituent and the DBTTT core reduces the reorganization energy dramatically. The structure–property relationships are thoroughly investigated using atomic force microscopy, transmission electron microscopy, and grazing incidence X‐ray diffraction analyses, in addition to charge‐transport studies. The vacuum‐deposited DPh‐DBTTT thin‐film transistors show superior thermal durability compared to the core DBTTT, which is highly valuable for device processability.
Surface and Interface Engineering of Silicon‐Based Anode Materials for Lithium‐Ion Batteries
Authors: Luo Wei , Chen Xinqi , Xia Yuan , Chen Miao , Wang Lianjun , Wang Qingqing , Li Wei , Yang Jianping 
Published: July 2017

AbstractSilicon is one of the most promising anode materials for lithium‐ion batteries because of the highest known theoretical capacity and abundance in the earth' crust. Unfortunately, significant “breathing effect” during insertion/deinsertion of lithium in the continuous charge‐discharge processes causes the seriously structural degradation, thus losing specific capacity and increasing battery impedance. To overcome the resultant rapid capacity decay, significant achievements has been made in developing various nanostructures and surface coating approaches in terms of the improvement of structural stability and realizing the long cycle times. Here, the recent progress in surface and interface engineering of silicon‐based anode materials such as core‐shell, yolk‐shell, sandwiched structures and their applications in lithium‐ion batteries are reviewed. Some feasible strategies for the structural design and boosting the electrochemical performance are highlighted. Future research directions in the field of silicon‐based anode materials for next‐generation lithium‐ion batteries are summarized.
“Water‐in‐Salt” Electrolyte Makes Aqueous Sodium‐Ion Battery Safe, Green, and Long‐Lasting
Authors: Suo Liumin , Borodin Oleg , Wang Yuesheng , Rong Xiaohui , Sun Wei , Fan Xiiulin , Xu Shuyin , Schroeder Marshall A. , Cresce Arthur V. , Wang Fei , Yang Chongyin , Hu Yong‐Sheng , Xu Kang , Wang Chunsheng 
Published: July 2017

AbstractNarrow electrochemical stability window (1.23 V) of aqueous electrolytes is always considered the key obstacle preventing aqueous sodium‐ion chemistry of practical energy density and cycle life. The sodium‐ion water‐in‐salt electrolyte (NaWiSE) eliminates this barrier by offering a 2.5 V window through suppressing hydrogen evolution on anode with the formation of a Na+‐conducting solid‐electrolyte interphase (SEI) and reducing the overall electrochemical activity of water on cathode. A full aqueous Na‐ion battery constructed on Na0.66[Mn0.66Ti0.34]O2 as cathode and NaTi2(PO4)3 as anode exhibits superior performance at both low and high rates, as exemplified by extraordinarily high Coulombic efficiency (>99.2%) at a low rate (0.2 C) for >350 cycles, and excellent cycling stability with negligible capacity losses (0.006% per cycle) at a high rate (1 C) for >1200 cycles. Molecular modeling reveals some key differences between Li‐ion and Na‐ion WiSE, and identifies a more pronounced ion aggregation with frequent contacts between the sodium cation and fluorine of anion in the latter as one main factor responsible for the formation of a dense SEI at lower salt concentration than its Li cousin.