Impulsive, local, 3‐D reconnection is identified for the first time in a laboratory current sheet. The events observed in the Magnetic Reconnection Experiment are characterized by large local ...gradients in the third direction and cannot be explained by 2‐D models. Detailed measurements show that the ejection of flux rope structures from the current sheet plays a key role in these events. By contrast, even though electromagnetic fluctuations in the lower hybrid frequency range are also observed concurrently with the impulsive behavior, they are not the key physics responsible. A qualitative, 3‐D, two‐fluid model is proposed to explain the observations. The experimental results may be particularly applicable to space and astrophysical plasmas where impulsive reconnection occurs.
Key Points
First example of local, 3‐D impulsive reconnection in a lab current sheet
3‐D flux rope signatures identified; impulsive events due to flux rope ejection
Neither a 2‐D nor an anomalous resistivity model can explain the observations
Abstract Purpose This study describes the lifetime prevalence of teen dating violence (TDV) perpetration in a sample of middle school students from high-risk urban communities and examines the ...relation between TDV and related cognitive and behavioral risk factors. Methods Surveys were administered to 2,895 middle school students in four U.S. cities; 1,673 students (58%) reported having dated and were included in analyses. The sample was 52.3% female, 48.2% non-Hispanic black/African-American, 38.2% Hispanic, 4.8% non-Hispanic white, and 7.6% other race. Six types of TDV perpetration were assessed: threatening behaviors, verbal/emotional abuse, relational abuse, physical abuse, sexual abuse, and stalking. Results Of the students who had dated, 77% reported perpetrating verbal/emotional abuse, 32% reported perpetrating physical abuse, 20% reported threatening a partner, 15% reported perpetrating sexual abuse, 13% reported perpetrating relational abuse, and 6% reported stalking. Girls were more likely than boys to report perpetrating threatening behaviors, verbal/emotional abuse, and physical abuse, and boys were more likely to report perpetrating sexual abuse. Involvement in bullying positively predicted perpetration of TDV, albeit, in different ways for boys and girls. Other risk factors differed by sex. For instance, alcohol use and sex initiation predicted multiple forms of TDV perpetration for boys, whereas weapon carrying and emotional symptoms predicted several forms of TDV perpetration for girls. Conclusions The prevalence of TDV was high in our sample. Important sex differences in rates of perpetration and risk factors emerged. Comprehensive prevention programs that target TDV and related risk factors, such as bullying and other risk factors, seem warranted.
Abstract Purpose Peers and dates are common targets of adolescent violence. Prevention programs typically address either peer violence (PV) or dating violence (DV) but not both. However, if PV and DV ...share predictors, prevention strategies could target both behaviors, yielding economic and time efficiencies. Longitudinal data were examined to determine the extent to which physical PV and DV shared predictors. Guided by social learning and social control theories, both risk and protective factors were examined at multiple levels of the social ecology. Methods Adolescents in the eighth through 10th grades in three North Carolina counties completed self-administered questionnaires in school in the fall 2003 (Wave 1) and again in spring 2004 (Wave 2) (n = 4,227). The sample was 48% male; 55% white, 33% black, and 12% of other race/ethnicity. A generalized estimating equations approach used adjusted standard errors to account for the correlation between the two violence outcomes. Results For both boys and girls, anger, family conflict, and having models of deviant behavior in the school were shared risk factors, and holding prosocial beliefs was a shared protective factor. For girls, anxiety and having models of deviant behavior in the neighborhood were additional shared risk factors. For boys, heavy alcohol use was an additional shared risk factor and parental monitoring was an additional shared protective factor. Conclusions Findings can inform the development of comprehensive cross-cutting prevention strategies at multiple levels of the social ecology designed to prevent both types of violence.
In 1928, Dirac published an equation
that combined quantum mechanics and special relativity. Negative-energy solutions to this equation, rather than being unphysical as initially thought, represented ...a class of hitherto unobserved and unimagined particles-antimatter. The existence of particles of antimatter was confirmed with the discovery of the positron
(or anti-electron) by Anderson in 1932, but it is still unknown why matter, rather than antimatter, survived after the Big Bang. As a result, experimental studies of antimatter
, including tests of fundamental symmetries such as charge-parity and charge-parity-time, and searches for evidence of primordial antimatter, such as antihelium nuclei, have high priority in contemporary physics research. The fundamental role of the hydrogen atom in the evolution of the Universe and in the historical development of our understanding of quantum physics makes its antimatter counterpart-the antihydrogen atom-of particular interest. Current standard-model physics requires that hydrogen and antihydrogen have the same energy levels and spectral lines. The laser-driven 1S-2S transition was recently observed
in antihydrogen. Here we characterize one of the hyperfine components of this transition using magnetically trapped atoms of antihydrogen and compare it to model calculations for hydrogen in our apparatus. We find that the shape of the spectral line agrees very well with that expected for hydrogen and that the resonance frequency agrees with that in hydrogen to about 5 kilohertz out of 2.5 × 10
hertz. This is consistent with charge-parity-time invariance at a relative precision of 2 × 10
-two orders of magnitude more precise than the previous determination
-corresponding to an absolute energy sensitivity of 2 × 10
GeV.
The effect of guide field on magnetic reconnection is quantitatively studied by systematically varying an applied guide field in the Magnetic Reconnection Experiment (MRX). The quadrupole field, a ...signature of two-fluid reconnection at zero guide field, is altered by a finite guide field. It is shown that the reconnection rate is significantly reduced with increasing guide field, and this dependence is explained by a combination of local and global physics: locally, the in-plane Hall currents are reduced, while globally guide field compression produces an increased pressure both within and downstream of the reconnection region.
The observation of hyperfine structure in atomic hydrogen by Rabi and co-workers and the measurement of the zero-field ground-state splitting at the level of seven parts in 10
are important ...achievements of mid-twentieth-century physics. The work that led to these achievements also provided the first evidence for the anomalous magnetic moment of the electron, inspired Schwinger's relativistic theory of quantum electrodynamics and gave rise to the hydrogen maser, which is a critical component of modern navigation, geo-positioning and very-long-baseline interferometry systems. Research at the Antiproton Decelerator at CERN by the ALPHA collaboration extends these enquiries into the antimatter sector. Recently, tools have been developed that enable studies of the hyperfine structure of antihydrogen-the antimatter counterpart of hydrogen. The goal of such studies is to search for any differences that might exist between this archetypal pair of atoms, and thereby to test the fundamental principles on which quantum field theory is constructed. Magnetic trapping of antihydrogen atoms provides a means of studying them by combining electromagnetic interaction with detection techniques that are unique to antimatter. Here we report the results of a microwave spectroscopy experiment in which we probe the response of antihydrogen over a controlled range of frequencies. The data reveal clear and distinct signatures of two allowed transitions, from which we obtain a direct, magnetic-field-independent measurement of the hyperfine splitting. From a set of trials involving 194 detected atoms, we determine a splitting of 1,420.4 ± 0.5 megahertz, consistent with expectations for atomic hydrogen at the level of four parts in 10
. This observation of the detailed behaviour of a quantum transition in an atom of antihydrogen exemplifies tests of fundamental symmetries such as charge-parity-time in antimatter, and the techniques developed here will enable more-precise such tests.
Abstract Purpose The negative impact on adolescents of being a victim of violence is well documented, but the impact of being a perpetrator of violence is less well known. Knowing the negative ...outcomes of being a perpetrator could inform clinical interactions with adolescents, development of violence prevention strategies, and estimates of the societal burden of violence. This longitudinal study examined the effects of physical dating violence (DV) and peer violence (PV) perpetration on internalizing symptoms, relationships with friends and family, academic aspirations and grades, and substance use. Methods The four-wave longitudinal study (N = 3,979), conducted in two North Carolina counties over 2½ years, spanned grades 8–12. Generalized linear mixed models were used to examine prospective lagged effects of each type of violence perpetration on each outcome and sex and grade as moderators of effects. Results Perpetrating DV significantly predicted lower college aspirations and greater likelihood of marijuana use. The effect of DV perpetration on increased family conflict was moderated by school grade; the effect decreased in significance across grades. Perpetrating PV significantly predicted greater likelihood of cigarette and marijuana use. The effects of PV perpetration on increased internalizing symptoms and alcohol intensity and decreased college aspirations were moderated by school grade; effects decreased in significance across grades. Neither type of perpetration predicted changes in number of reciprocated friendships, social status, or academic grades, and no effects varied by sex. Conclusions These detrimental outcomes for the perpetrator need to be considered in clinical interactions with adolescents and violence prevention programming.
The photon-the quantum excitation of the electromagnetic field-is massless but carries momentum. A photon can therefore exert a force on an object upon collision
. Slowing the translational motion of ...atoms and ions by application of such a force
, known as laser cooling, was first demonstrated 40 years ago
. It revolutionized atomic physics over the following decades
, and it is now a workhorse in many fields, including studies on quantum degenerate gases, quantum information, atomic clocks and tests of fundamental physics. However, this technique has not yet been applied to antimatter. Here we demonstrate laser cooling of antihydrogen
, the antimatter atom consisting of an antiproton and a positron. By exciting the 1S-2P transition in antihydrogen with pulsed, narrow-linewidth, Lyman-α laser radiation
, we Doppler-cool a sample of magnetically trapped antihydrogen. Although we apply laser cooling in only one dimension, the trap couples the longitudinal and transverse motions of the anti-atoms, leading to cooling in all three dimensions. We observe a reduction in the median transverse energy by more than an order of magnitude-with a substantial fraction of the anti-atoms attaining submicroelectronvolt transverse kinetic energies. We also report the observation of the laser-driven 1S-2S transition in samples of laser-cooled antihydrogen atoms. The observed spectral line is approximately four times narrower than that obtained without laser cooling. The demonstration of laser cooling and its immediate application has far-reaching implications for antimatter studies. A more localized, denser and colder sample of antihydrogen will drastically improve spectroscopic
and gravitational
studies of antihydrogen in ongoing experiments. Furthermore, the demonstrated ability to manipulate the motion of antimatter atoms by laser light will potentially provide ground-breaking opportunities for future experiments, such as anti-atomic fountains, anti-atom interferometry and the creation of antimatter molecules.
Subtypes of posttraumatic psychopathology were replicated and extended in 254 female veterans with posttraumatic stress disorder (PTSD). Cluster analyses on Minnesota Multiphasic Personality ...Inventory‐2 and Personality Psychopathology Five scales (Harkness, McNulty, & Ben‐Porath, ) yielded internalizing and externalizing psychopathology dimensions, with a third low psychopathology group (simple PTSD). Externalizers were higher than the internalizers and the simple PTSD groups on the antisocial, substance, and aggression scales; internalizers were higher on depression and anxiety scales. Further validation included an independent measure of psychopathology to examine anger (Buss‐Durkee Hostility Inventory, BDHI; Buss & Durkee, ). Externalizers were higher on extreme behavioral anger scales (assault and verbal hostility); and externalizers and internalizers were higher than the simple PTSD subjects on other anger scales. Positive correlations between the BDHI scales and the PTSD symptom of “irritability and anger outbursts” were found across scales in the total sample (range: r = .19–.36), on the assault scale in externalizers (r = .59), and the verbal hostility scale in both internalizers (r = .30) and simple PTSD (r = .37) groups, suggesting the broad utility of the symptom in the diagnosis. The results demonstrate the generalizability of the internalizing/externalizing typology to the female veteran population and highlight clinically relevant distinctions in anger expression within PTSD.
抽象
Traditional and Simplified Chinese s by AsianSTSS
標題：創傷後精神病理學和憤怒表現的外化和內化類別。
撮要：在254名患有創傷後壓力症(PTSD)的女退役兵中重覆及延展創傷後精神病理學類別。群集分析了明民蘇達多相人格量表‐2和人格精神病理學五量表 (Harkness, McNulty, & Ben‐Porath,1995)，得出內化和外化精神病理學維度，及第三個低精神病理學組別(簡單PTSD)。外化者對比內化者和簡單PTSD組別，在反社會、物質濫用和暴力量度方面得分較高，而內化者則在抑鬱及焦慮方面得分較高。採用獨立精神病理學量度來驗證憤怒 (Buss‐Durkee敵意量表，BDHI；Buss & Durkee,1957)。外化者在極端行為憤怒量度更高 (襲擊和語言敵意)；而外化者和內化者對比簡單PTSD者都在其他憤怒量度更高。BDHI量表和PTSD的"易激和憤怒爆發"症狀呈正相連 (在所有樣本的量度中，值域 r=.19至.36)，與外化者襲擊量度 (r=.59) 呈正相連，亦在內化者 (r=.30) 和簡單PTSD (r=.37) 組別的語言敵意呈正相連。這顯示診斷中這症狀的廣泛使用性。結果指出在女退役軍人中外化/內化類別的概括性，及PTSD中憤怒表達的臨床相關區別的重要性。
标题：创伤后精神病理学和愤怒表现的外化和内化类别。
撮要：在254名患有创伤后压力症(PTSD)的女退役兵中重复及延展创伤后精神病理学类别。聚类分析了明民苏达多相人格量表‐2和人格精神病理学五量表 (Harkness, McNulty, & Ben‐Porath,1995)，得出内化和外化精神病理学维度，及第三个低精神病理学组别(简单PTSD)。外化者对比内化者和简单PTSD组别，在反社会、物质滥用和暴力量度方面得分较高，而内化者则在抑郁及焦虑方面得分较高。采用独立精神病理学量度来验证愤怒 (Buss‐Durkee敌意量表，BDHI；Buss & Durkee,1957)。外化者在极端行为愤怒量度更高 (袭击和语言敌意)；而外化者和内化者对比简单PTSD者都在其他愤怒量度更高。BDHI量表和PTSD的"易激和愤怒爆发"症状呈正相连 (在所有样本的量度中，值域 r=.19至.36)，与外化者袭击量度 (r=.59) 呈正相连，亦在内化者 (r=.30) 和简单PTSD (r=.37) 组别的语言敌意呈正相连。这显示诊断中这症状的广泛使用性。结果指出在女退役军人中外化/内化类别的概括性，及PTSD中愤怒表达的临床相关区别的重要性。
The properties of antihydrogen are expected to be identical to those of hydrogen, and any differences would constitute a profound challenge to the fundamental theories of physics. The most commonly ...discussed antiatom-based tests of these theories are searches for antihydrogen-hydrogen spectral differences (tests of CPT (charge-parity-time) invariance) or gravitational differences (tests of the weak equivalence principle). Here we, the ALPHA Collaboration, report a different and somewhat unusual test of CPT and of quantum anomaly cancellation. A retrospective analysis of the influence of electric fields on antihydrogen atoms released from the ALPHA trap finds a mean axial deflection of 4.1 ± 3.4 mm for an average axial electric field of 0.51 V mm(-1). Combined with extensive numerical modelling, this measurement leads to a bound on the charge Qe of antihydrogen of Q=(-1.3 ± 1.1 ± 0.4) × 10(-8). Here, e is the unit charge, and the errors are from statistics and systematic effects.
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