The effects of plasma beta and anisotropy instabilities on the dynamics of reconnecting magnetic fields in the heliosheath

The plasma {\beta} (the ratio of the plasma pressure to the magnetic pressure) of a system can have a large effect on its dynamics as high {\beta} enhances the effects of pressure anisotropies. We investigate the effects of {\beta} in a system of stacked current sheets that break up into magnetic islands due to magnetic reconnection. We find significant differences between {\beta} 1. At low {\beta} growing magnetic islands are modestly elongated and become round as contraction releases magnetic stress and reduces magnetic energy. At high {\beta} the increase of the parallel pressure in contracting islands causes saturation of modestly elongated islands as island cores approach the marginal firehose condition. Only highly elongated islands reach finite size. The kinking associated with the Weibel and firehose instabilities prevents full contraction of these islands, leading to a final state of highly elongated islands in which further reconnection is suppressed. The results are directly relevant to reconnection in the sectored region of the heliosheath and possibly to saturation mechanisms of the magnetorotational instability in accretion flows

It Could Not Be Seen Because It Could Not Be Believed on June 30, 2013

Nineteen Prescott Fire Department, Granite Mountain Hot Shot (GMHS) wildland firefighters (WF) perished in Arizona in June 2013 Yarnell Hill Fire, an inexplicable wildland fire disaster. In complex wildland fires, sudden, dynamic changes in human factors and fire conditions can occur, thus mistakes can be unfortunately fatal. Individual and organizational faults regarding the predictable, puzzling, human failures that will result in future WF deaths are addressed. The GMHS were individually, then collectively fixated with abandoning their Safety Zone to reengage, committing themselves at the worst possible time, to relocate to another Safety Zone - a form of collective tunnel vision. Our goal is to provoke meaningful discussion toward improved wildland firefighter safety with practical solutions derived from a long-established wildland firefighter expertise/performance in a fatality-prone profession. Wildfire fatalities are unavoidable, hence these proposals, applied to ongoing training, can significantly contribute to other well-thought-out and validated measures to reduce them

Salt modulates the stability and lipid binding affinity of the adipocyte lipid-binding protein

Adipocyte lipid-binding protein (ALBP or aP2) is an intracellular fatty acid-binding protein that is found in adipocytes and macrophages and binds a large variety of intracellular lipids with high affinity. Although intracellular lipids are frequently charged, biochemical studies of lipid-binding proteins and their interactions often focus most heavily on the hydrophobic aspects of these proteins and their interactions. In this study, we have characterized the effects of KCl on the stability and lipid binding properties of ALBP. We find that added salt dramatically stabilizes ALBP, increasing its ΔG of unfolding by 3-5 kcal/mol. At 37 °C salt can more than double the stability of the protein. At the same time, salt inhibits the binding of the fluorescent lipid 1-anilino-naphthalene-8-sulfonate (ANS) to the protein and induces direct displacement of the lipid from the protein. Thermodynamic linkage analysis of the salt inhibition of ANS binding shows a nearly 1:1 reciprocal linkage: i.e. one ion is released from ALBP when ANS binds, and vice versa. Kinetic experiments show that salt reduces the rate of association between ANS and ALBP while simultaneously increasing the dissociation rate of ANS from the protein. We depict and discuss the thermodynamic linkages among stability, lipid binding, and salt effects for ALBP, including the use of these linkages to calculate the affinity of ANS for the denatured state of ALBP and its dependence on salt concentration. We also discuss the potential molecular origins and potential intracellular consequences of the demonstrated salt linkages to stability and lipid binding in ALBP

Is the magnetic field in the heliosheath laminar or a turbulent bath of bubbles?

All the current global models of the heliosphere are based on the assumption that the magnetic field in the heliosheath, in the region close to the heliopause is laminar. We argue that in that region the heliospheric magnetic field is not laminar but instead consists of magnetic bubbles. Recently, we proposed that the annihilation of the "sectored" magnetic field within the heliosheath as it is compressed on its approach to the heliopause produces the anomalous cosmic rays and also energetic electrons. As a product of the annihilation of the sectored magnetic field, densely-packed magnetic islands/bubbles are produced. These magnetic islands/bubbles will be convected with the ambient flows as the sector region is carried to higher latitudes filling the heliosheath. We further argue that the magnetic islands/bubbles will develop upstream within the heliosheath. As a result, the magnetic field in the heliosheath sector region will be disordered well upstream of the heliopause. We present a 3D MHD simulation with very high numerical resolution that captures the north-south boundaries of the sector region. We show that due to the high pressure of the interstellar magnetic field a north-south asymmetry develops such that the disordered sectored region fills a large portion of the northern part of the heliosphere with a smaller extension in the southern hemisphere. We suggest that this scenario is supported by the following changes that occur around 2008 and from 2009.16 onward: a) the sudden decrease in the intensity of low energy electrons detected by Voyager 2; b) a sharp reduction in the intensity of fluctuations of the radial flow; and c) the dramatic differences in intensity trends between GCRs at V1 and 2. We argue that these observations are a consequence of V2 leaving the sector region of disordered field during these periods and crossing into a region of unipolar laminar field.Comment: 36 pages, 15 figures, submitted to Ap

Interplay between the Weibel instability and the Biermann battery in realistic laser-solid interactions

Our setup allows the Weibel instability and its interplay with the Biermann battery to be probed in laser-driven collisionless plasmas. Ab initio particle-in-cell simulations of the interaction of short ( ≤ 1 ps ) intense ( a 0 ≥ 1 ) laser pulses with overdense plasma targets show observable Weibel generated magnetic fields. This field strength surpasses that of the Biermann battery, usually dominant in experiments, as long as the gradient scale length is much larger than the local electron inertial length; this is achievable by carefully setting the appropriate gradients in the front of the target, e.g., by tuning the delay between the main laser pulse and the prepulse

Extreme Free Energy Stabilization of Taq DNA Polymerase

We have examined the chemical denaturations of the Klentaq and Klenow large-fragment domains of the Type 1 DNA polymerases from Thermus aquaticus (Klentaq) and Escherichia coli (Klenow) under identical solution conditions in order to directly compare the stabilization energetics of the two proteins. The high temperature stability of Taq DNA polymerase is common knowledge, and is the basis of its use in the polymerase chain reaction. This study, however, is aimed at understanding the thermodynamic basis for this high-temperature stability. Chemical denaturations with guanidine hydrochloride report a folding free energy (ΔG) for Klentaq that is over 20 kcal/mol more favorable than that for Klenow under the conditions examined. This difference between the stabilization free energies of a homologous mesophilic-thermophilic protein pair is significantly larger than generally observed. This is due in part to the fact that the stabilization free energy for Klentaq polymerase, at 27.5 kcal/ol, is one of the largest ever determined for a monomeric protein. Large differences in the chemical midpoints of the unfolding (Cm) and the dependences of the unfolding free energy on denaturant concentration in the transition region (m-value) between the two proteins are also observed. Measurements of the sedimentation coefficients of the two proteins in the native and denatured states report that both proteins approximately double in hydrodynamic size upon denaturation, but that Klentaq expands somewhat more than Klenow. © 2004 Wiley-Liss, Inc

Anisotropic heating and magnetic field generation due to Raman scattering in laser-plasma interactions

We identify a mechanism for magnetic field generation in the interaction of intense electromagnetic waves and underdense plasmas. We show that Raman scattered plasma waves trap and heat the electrons preferentially in their propagation direction, resulting in a temperature anisotropy. In the trail of laser pulse, we observe magnetic field growth that matches the Weibel mechanism due to the temperature anisotropy. We discuss the role of the initial electron temperature in our results. The predictions are confirmed with multidimensional particle-in-cell simulations. We show how this configuration is an experimental platform to study the long-time evolution of the Weibel instabilityinfo:eu-repo/semantics/publishedVersio