Reconnecting Magnetic Flux Tubes as a Source of In Situ Acceleration in Extragalactic Radio Sources

Many extended extragalactic radio sources require a local {\it in situ\/} acceleration mechanism for electrons, in part because the synchrotron lifetimes are shorter than the bulk travel time across the emitting regions. If the magnetic field in these sources is localized in flux tubes, reconnection may occur between regions of plasma \be (ratio of particle to magnetic pressure) $<<1$, even though $\beta$ averaged over the plasma volume may be \gsim 1. Reconnection in low $\beta$ regions is most favorable to acceleration from reconnection shocks. The reconnection X-point regions may provide the injection electrons for their subsequent non-thermal shock acceleration to distributions reasonably consistent with observed spectra. Flux tube reconnection might therefore be able to provide $in\ situ$ acceleration required by large scale jets and lobes.Comment: 14 pages, plain TeX, accepted to Ap.J.Let

Distinguishing Solar Flare Types by Differences in Reconnection Regions

Observations show that magnetic reconnection and its slow shocks occur in solar flares. The basic magnetic structures are similar for long duration event (LDE) flares and faster compact impulsive (CI) flares, but the former require less non-thermal electrons than the latter. Slow shocks can produce the required non-thermal electron spectrum for CI flares by Fermi acceleration if electrons are injected with large enough energies to resonate with scattering waves. The dissipation region may provide the injection electrons, so the overall number of non-thermal electrons reaching the footpoints would depend on the size of the dissipation region and its distance from the chromosphere. In this picture, the LDE flares have converging inflows toward a dissipation region that spans a smaller overall length fraction than for CI flares. Bright loop-top X-ray spots in some CI flares can be attributed to particle trapping at fast shocks in the downstream flow, the presence of which is determined by the angle of the inflow field and velocity to the slow shocks.Comment: 15 pages TeX and 2 .eps figures, accepted to Ap.J.Let

Personality Types and Emotional Intelligence as Predictors of Academic Achievement in Students at Kashan University of Medical Sciences

Background: Type of personality and emotional intelligence affects a person’s mental function and capabilities, which can influence academic achievement. Objectives: This study was designed to evaluate the relationship between emotional intelligence, type of character and academic achievement. Materials and Methods: This is a cross-sectional study on students of Kashan University of Medical Sciences in 2012. In total 221 students participated in the study. In addition to demographic information, a Five Factor Personality Questionnaire and Emotional Quotient Inventory were used. Participants completed questionnaires in their classrooms. Data were analyzed using SPSS software version 16. Descriptive statistics were calculated and analysis of variance and regression analysis were used. Results: Students in the various disciplines were not statistically different in terms of personality. Students with different grade point averages were significantly different in relation to: problem-solving, happiness, self-actualization, optimism, self-respect, flexibility and total emotional quotient (EQ) scores (P < 0.05). However, no statistically significant differences were observed between personality types in students with different grade point average. All variables (EQ, agreeableness, extroversion, openness, consciousness) except neuroticism were excluded from the regression model. Conclusions: Some components of personality types and emotional intelligence are predictors of academic achievement. Therefore, attention to these issues in students is needed to ensure the best achievement gains

Chewing activity, metabolic profile and performance of high- producing dairy cows fed conventional forages, wheat straw or rice straw

In this study, production and physiological responses of high-producing dairy cows fed wheat (WS) or rice (RS) straw, as a partial forage replacement for the conventional forages lucerne hay (LH) and maize silage (MS ), were investigated. The straws were treated under dry alkaline conditions, adjusted pH (pH ~12), and then ensiled. Twelve lactating Holstein cows were used in a replicated (n = 4) 3 × 3 Latin square design experiment with three periods of 21 days. Cows were offered one of three diets that differed in their forage sources: 1) 20% LH and 20% MS (control); 2) 12.8% LH, 12.8% MS; and 12.8% WS; and 3) 12.8% LH, 12.8% MS and 12.8% RS. Diet 1 had 60% concentrate, and diets 2 and 3 had 61.6% concentrate. Diets were iso-nitrogenous and iso-energetic. Supplemental buffer (NaHCO3) was omitted from the straw diets. However, straw diets contained greater sodium and dietary cation-anion difference (DCAD) compared with the control diet. Cows fed the WS had significantly greater apparent dry matter (DM) (69.7 versus 63.9%) and neutral detergent fibre (NDF) (55.4 versus 42.4%) digestibility than cows fed the control. Additionally, feeding either WS or RS significantly increased dry matter intake (DMI) (27.5 versus 25.6 kg/d ) and milk production (48.4 versus 45.6 kg/d) compared with control, but milk components were unaffected by treatments. Plasma minerals and metabolites concentrations and ruminal, urinary and faecal pH were similar across treatments. Feeding WS and RS resulted in lower time spent chewing per kg DMI compared with the control ( P = 0.01 ). Although there were no significant differences in performance between WS and RS, nutrient digestibility (DM, OM, and CP) was significantly higher while total chewing was lower for the WS diet than the RS diet. Partial inclusion of dry treated straw in lactating diets (12.8% DM basis) led to increases in sodium and DCAD levels and improved digestibility, DMI and milk yield without negative effects. Keywords: Cation and anion difference, cereal straw dietary sodium, lactating [email protected]

First Observations of a Foreshock Bubble at Earth: Implications for Magnetospheric Activity and Energetic Particle Acceleration

Earth?s foreshock, which is the quasi-parallel region upstream of the bow shock, is a unique plasma region capable of generating several kinds of large-scale phenomena, each of which can impact the magnetosphere resulting in global effects. Interestingly, such phenomena have also been observed at planetary foreshocks throughout our solar system. Recently, a new type of foreshock phenomena has been predicted: foreshock bubbles, which are large-scale disruptions of both the foreshock and incident solar wind plasmas that can result in global magnetospheric disturbances. Here we present unprecedented, multi-point observations of foreshock bubbles at Earth using a combination of spacecraft and ground observations primarily from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission, and we include detailed analysis of the events? global effects on the magnetosphere and the energetic ions and electrons accelerated by them, potentially by a combination of first and second order Fermi and shock drift acceleration processes. This new phenomena should play a role in energetic particle acceleration at collisionless, quasi-parallel shocks throughout the Universe

On the size-Ramsey number of cycles

For given graphs $G_1,\ldots,G_k$, the size-Ramsey number $\hat{R}(G_1,\ldots,G_k)$ is the smallest integer $m$ for which there exists a graph $H$ on $m$ edges such that in every $k$-edge coloring of $H$ with colors $1,\ldots,k$, $H$ contains a monochromatic copy of $G_i$ of color $i$ for some $1\leq i\leq k$. We denote $\hat{R}(G_1,\ldots,G_k)$ by $\hat{R}_{k}(G)$ when $G_1=\cdots=G_k=G$. Haxell, Kohayakawa and \L{}uczak showed that the size-Ramsey number of a cycle $C_n$ is linear in $n$ i.e. $\hat{R}_{k}(C_{n})\leq c_k n$ for some constant $c_k$. Their proof, however, is based on the regularity lemma of Szemer\'{e}di and so no specific constant $c_k$ is known. In this paper, we give various upper bounds for the size-Ramsey numbers of cycles. We provide an alternative proof of $\hat{R}_{k}(C_{n})\leq c_k n$, avoiding the use of the regularity lemma, where $c_k$ is exponential and doubly-exponential in $k$, when $n$ is even and odd, respectively. In particular, we show that for sufficiently large $n$ we have $\hat{R}(C_{n},C_{n}) \leq 10^5\times cn,$ where $c=6.5$ if $n$ is even and $c=1989$ otherwise

Characterization of radio active aerosols in Tehran research reactor containment

The objectives of this research were to determine the levels of radioactivity in the Tehran research reactor containment and to investigate the mass-size distribution, composition, and concentration of radio nuclides during operation of the reactor. A cascade impactor sampler was used to determine the size-activity distributions of radioactive aerosols in each of the sampling stations. Levels of α and β activities were determined based on a counting method using a liquid scintillation counter and smear tests. The total average mass fractions of fine particles (particle diameter dp &lt;1 µm) in all of the sampling stations were approximately 26.75 , with the mean and standard deviation of 52.15 ± 19.75 µg/m3. The total average mass fractions of coarse particles were approximately 73.2, with the mean and standard deviation of 71.34 ± 24.57 µg/m3. In addition to natural radionuclides, artificial radionuclides, such as 24Na,91Sr,131I,133I,103Ru,82Br, and 140La, may be released into the reactor containment structure. Maximum activity was associated with accumulation-mode particles with diameters less than 400 nm. The results obtained from liquid scintillation counting suggested that the mean specific activity of alpha particles in fine and coarse-modes were 89.7 and 10.26 , respectively. The mean specific activity of beta particles in fine and coarse-modes were 81.15 and 18.51 , respectively. A large fraction ofthe radionuclides' mass concentration in the Tehran research reactor containment was associated with coarse-mode particles, in addition, a large fraction of the activity in the aerosol particles was associated with accumulation-mode particles. © 2015, Vinca Inst Nuclear Sci. All rights reserved