Photo-induced magnetization enhancement in two-dimensional weakly anisotropic Heisenberg magnets

By comparing the photo-induced magnetization dynamics in simple layered systems we show how light-induced modifications of the magnetic anisotropy directly enhance the magnetization. It is observed that the spin precession in (CH3NH3)2CuCl4, initiated by a light pulse, increases in amplitude at the critical temperature TC. The phenomenon is related to the dependence of the critical temperature on the axial magnetic anisotropy. The present results underline the possibility and the importance of the optical modifications of the anisotropy, opening new paths toward the control of the magnetization state for ultrafast memories.Comment: 5 pages, 3 figures, supplementary info as SIr.pd

Sophorolipids: A review on production and perspectives of application in agriculture

Sophorolipids are bioactive molecules that have gained a lot of attention in the recent decades due to their unique functional properties of reducing surface and interfacial tension, emulsification and solubilization. They are mainly produced by the yeast Candida bombicola and are composed of a sugar moiety linked to a fatty acid chain. Sophorolipids are non-toxic, highly efficient and stable at extreme conditions and possess environmentally friendly characteristics over the chemical surfactants. This review is focused on the main characteristics of sophorolipids, fermentation processes, and their utilization in the agricultural field. In this context, sophorolipids are very suitable for use in agriculture, as enhancers of solubility and mobility of plant nutrients, which could result in increased plant biomass, root size and fruit yield. In addition, they could be used for biodegradation of oils, bioremediation of heavy metals in contaminated soils, and as potential biopesticides, to control phytopathogenic microorganisms in agriculture. The extensive use of chemical pesticides has led to widespread insecticide resistance and to hazards to human health and the environment due to their high toxicity. Thus, the introduction of a new biomolecule to control plant diseases and increase crop yield has become an interesting alternative. As a result of the demonstrated antimicrobial activity towards phytopathogenic bacteria and fungi, sophorolipids could be extensively explored in the agriculture field, as a sustainable and natural multifunctional agent for plant crops and soils

Low-frequency Raman study of the ferroelectric phase transition in a layered CuCl4-based organic-inorganic hybrid

The ferroelectric phase transition at TC = 340 K in (C6H5CH2CH2NH3)2CuCl4 is studied by means of temperature-dependent low-frequency Raman scattering, focusing on the coupling of a low-energy librational mode to the order parameter of the transition. Analysis of the symmetry and characteristics of this mode links the dipolar order to the tilt angle of the organic cations. The thermal evolution of the Raman spectrum demonstrates the displacive component of the phase transition in combinationwith order-disorder phenomena and the importance of the organic-inorganic interplay to the physical properties of the compound. The ferroelectric properties investigated here can be generalized to the family of layered organic-inorganic hybrids.

High-Power Targets: Experience and R&D for 2 MW

High-power particle production targets are crucial elements of future neutrino and other rare particle beams. Fermilab plans to produce a beam of neutrinos (LBNE) with a 2.3 MW proton beam (Project X). Any solid target is unlikely to survive for an extended period in such an environment - many materials would not survive a single beam pulse. We are using our experience with previous neutrino and antiproton production targets, along with a new series of R&D tests, to design a target that has adequate survivability for this beamline. The issues considered are thermal shock (stress waves), heat removal, radiation damage, radiation accelerated corrosion effects, physics/geometry optimization and residual radiation

A Survey for Large Separation Lensed FIRST Quasars

Little is known about the statistics of gravitationally lensed quasars at large (7''-30'') image separations, which probe masses on the scale of galaxy clusters. We have carried out a survey for gravitationally-lensed objects, among sources in the FIRST 20cm radio survey that have unresolved optical counterparts in the digitizations of the Palomar Observatory Sky Survey. From the statistics of ongoing surveys that search for quasars among FIRST sources, we estimate that there are about 9100 quasars in this source sample, making this one of the largest lensing surveys to date. Using broad-band imaging, we have isolated all objects with double radio components separated by 5''-30'', that have unresolved optical counterparts with similar BVI colours. Our criteria for similar colours conservatively allow for observational error and for colour variations due to time delays between lensed images. Spectroscopy of these candidates shows that none of the pairs are lensed quasars. This sets an upper limit (95% confidence) on the lensing fraction in this survey of 3.3x10^-4, assuming 9100 quasars. Although the source redshift distribution is poorly known, a rough calculation of the expected lensing frequency and the detection efficiencies and biases suggests that simple theoretical expectations are of the same order of magnitude as our observational upper limit. Our procedure is novel in that our exhaustive search for lensed objects does not require prior identification of the quasars in the sample as such. Characterization of the FIRST-selected quasar population will enable using our result to constrain quantitatively the mass properties of clusters.Comment: 10 pages, accepted for publication in MNRA

A Very Intense Neutrino Super Beam Experiment for Leptonic CP Violation Discovery based on the European Spallation Source Linac: A Snowmass 2013 White Paper

Very intense neutrino beams and large neutrino detectors will be needed in order to enable the discovery of CP violation in the leptonic sector. We propose to use the proton linac of the European Spallation Source currently under construction in Lund, Sweden to deliver, in parallel with the spallation neutron production, a very intense, cost effective and high performance neutrino beam. The baseline program for the European Spallation Source linac is that it will be fully operational at 5 MW average power by 2022, producing 2 GeV 2.86 ms long proton pulses at a rate of 14 Hz. Our proposal is to upgrade the linac to 10 MW average power and 28 Hz, producing 14 pulses/s for neutron production and 14 pulses/s for neutrino production. Furthermore, because of the high current required in the pulsed neutrino horn, the length of the pulses used for neutrino production needs to be compressed to a few $\mu$s with the aid of an accumulator ring. A long baseline experiment using this Super Beam and a megaton underground Water Cherenkov detector located in existing mines 300-600 km from Lund will make it possible to discover leptonic CP violation at 5 $\sigma$ significance level in up to 50% of the leptonic Dirac CP-violating phase range. This experiment could also determine the neutrino mass hierarchy at a significance level of more than 3 $\sigma$ if this issue will not already have been settled by other experiments by then. The mass hierarchy performance could be increased by combining the neutrino beam results with those obtained from atmospheric neutrinos detected by the same large volume detector. This detector will also be used to measure the proton lifetime, detect cosmological neutrinos and neutrinos from supernova explosions. Results on the sensitivity to leptonic CP violation and the neutrino mass hierarchy are presented.Comment: 28 page

Skyrmion Hall Effect Revealed by Direct Time-Resolved X-Ray Microscopy

Magnetic skyrmions are highly promising candidates for future spintronic applications such as skyrmion racetrack memories and logic devices. They exhibit exotic and complex dynamics governed by topology and are less influenced by defects, such as edge roughness, than conventionally used domain walls. In particular, their finite topological charge leads to a predicted "skyrmion Hall effect", in which current-driven skyrmions acquire a transverse velocity component analogous to charged particles in the conventional Hall effect. Here, we present nanoscale pump-probe imaging that for the first time reveals the real-time dynamics of skyrmions driven by current-induced spin orbit torque (SOT). We find that skyrmions move at a well-defined angle {\Theta}_{SH} that can exceed 30{\deg} with respect to the current flow, but in contrast to theoretical expectations, {\Theta}_{SH} increases linearly with velocity up to at least 100 m/s. We explain our observation based on internal mode excitations in combination with a field-like SOT, showing that one must go beyond the usual rigid skyrmion description to unravel the dynamics.Comment: pdf document arxiv_v1.1. 24 pages (incl. 9 figures and supplementary information

The Merit(nTOF-11) High Intensity Liquid Mercury Target Experiment at the CERN PS

The MERIT(nTOF-11) experiment is a proof-ofprinciple test of a target system for a high power proton beam to be used as front-end for a neutrino factory or a muon collider. The experiment took data in autumn 2007 with the fast-extracted beam from the CERN Proton Synchrotron (PS) to a maximum intensity of $30 × 10^{12}$ per pulse. The target system, based on a free mercury jet, is capable of intercepting a 4-MW proton beam inside a 15-T magnetic field required to capture the low energy secondary pions as the source for intense muon beams. Partice detectors installed around the target setup measure the secondary particle flux out of the target and can probe cavitation effects in the mercury jet when excited by an intense proton beam.Preliminary results of the data analysis will be presented here