Femtosecond x-ray absorption spectroscopy of spin and orbital angular momentum in photoexcited Ni films during ultrafast demagnetization

We follow for the first time the evolution of the spin and orbital angular momentum of a thin Ni film during ultrafast demagnetization, by means of x-ray magnetic circular dichroism. Both components decrease with a 130 +/- 40 fs time constant upon excitation with a femtosecond laser pulse. Additional x-ray absorption measurements reveal an increase in the spin-orbit interaction by 6 +/- 2 % during this process. This is the experimental demonstration quantifying the importance of spin-orbit mediated processes during the demagnetization

Electronic tuneability of a structurally rigid surface intermetallic and Kondo lattice: CePt5_5 / Pt(111)

We present an extensive study of structure, composition, electronic and magnetic properties of Ce--Pt surface intermetallic phases on Pt(111) as a function of their thickness. The sequence of structural phases appearing in low energy electron diffraction (LEED) may invariably be attributed to a single underlying intermetallic atomic lattice. Findings from both microscopic and spectroscopic methods, respectively, prove compatible with CePt$_5$ formation when their characteristic probing depth is adequately taken into account. The intermetallic film thickness serves as an effective tuning parameter which brings about characteristic variations of the Cerium valence and related properties. Soft x-ray absorption (XAS) and magnetic circular dichroism (XMCD) prove well suited to trace the changing Ce valence and to assess relevant aspects of Kondo physics in the CePt$_5$ surface intermetallic. We find characteristic Kondo scales of the order of 10$^2$ K and evidence for considerable magnetic Kondo screening of the local Ce $4f$ moments. CePt$_5$/Pt(111) and related systems therefore appear to be promising candidates for further studies of low-dimensional Kondo lattices at surfaces.Comment: 14 pages, 11 figure

Configuration development study of the X-24C hypersonic research airplane

Bottom line results were made of a three-phase study to determine the feasibility of designing, building, and operating, and maintaining an air-launched high performance aircraft capable of cruising at speeds up to Mach 8 for short durations. The results show that Lockalloy heat-sink structure affords the capability for a 'work-horse' vehicle which can serve as an excellent platform for this research. It was further concluded that the performance of a blended wing body configuration surpassed that of a lifting body design for typical X-24C missions. The cost of a two vehicle program, less engines, B-52 modification and contractor support after delivery, can be kept within $70M (in Jan. 1976 dollars)

Study of the depletion depth in a frontside biased CMOS pixel sensors

Depletion of the sensitive volume for semiconductor based detectors is a key to achieve high performance. It is for instance required for charged particle detection in highly radiative environment and for X-ray spectroscopy. PIPPER-2 is a CMOS pixel sensor featuring an architecture that allows the application of the reverse bias of the pn junction from the frontside (cathode), on the electronic side, without process modification. Biasing voltages up to 45 V have been applied to sensor prototypes fabricated on two different high resistivity substrates: a thin epitaxial layer (1 kΩ cm) and a 40 μm thick bulk substrate (600 Ω cm). Calculations from a simplified analytical model and 3D-TCAD simulations were conducted to predict the evolution of the depletion depth with the bias voltage. These expectations were compared to measurements of PIPPER-2 illuminated with two X-ray energies. We conclude that the frontside biasing method allows the full-depletion of the thin epitaxial layer. In contrast, depletion of the bulk substrate reaches about half-depth but X-rays are still detected over the full depth

Подземный сток в таёжной зоне Западной Сибири: многолетние изменения и их причины

Проведён расчёт среднемесячных и среднегодовых значений подземного стока в таёжной зоне Западной Сибири, выполнен статистический анализ полученных данных и материалов наблюдений за уровнями подземных вод верхней гидродинамической зоны на участках вне явного антропогенного влияния. Установлено, что в регионе в последние десятилетия происходило статистически значимое увеличение подземной составляющей речного стока и уровней подземных вод. Увеличение подземного стока удовлетворительно объясняется смещением сроков установления снегового покрова и снеготаяния, снижением испарения с поверхности водосборов при уменьшении температур воздуха в летний период и увеличением температуры в остальные месяцы года даже при отсутствии изменений годового атмосферного увлажнения. Calculation of monthly average and mid-annual values of a ground flow in a taiga zone of Western Siberia is carried out. The statistical analysis of the received data and materials of supervision over levels of ground waters of the top hydrodynamical zone on sites outside of obvious anthropogenous influence is executed. In region last decades there was statistically significant increase in a underground component of a river drain and levels of ground waters. The increase in a ground flow well speaks displacement of terms of an establishment of a snow cover and snow melting, decrease in evaporation from a surface of river basins at reduction of temperatures of air during the summer period and increase in temperature in other months of year even at absence of changes of annual atmospheric humidifying

Pulmonary siRNA Delivery with Sophisticated Amphiphilic Poly(Spermine Acrylamides) for the Treatment of Lung Fibrosis

RNA interference (RNAi) is an efficient strategy to post-transcriptionally silence gene expression. While all siRNA drugs on the market target the liver, the lung offers a variety of currently undruggable targets, which can potentially be treated with RNA therapeutics. To achieve this goal, the synthesis of poly(spermine acrylamides) (P(SpAA) is reported herein. Polymers are prepared via polymerization of N-acryloxysuccinimide (NAS) and afterward this active ester is converted into spermine-based pendant groups. Copolymerizations with decylacrylamide are employed to increase the hydrophobicity of the polymers. After deprotection, polymers show excellent siRNA encapsulation to obtain perfectly sized polyplexes at very low polymer/RNA ratios. In vitro 2D and 3D cell culture, ex vivo and in vivo experiments reveal superior properties of amphiphilic spermine-copolymers with respect to delivery of siRNA to lung cells in comparison to commonly used lipid-based transfection agents. In line with the in vitro results, siRNA delivery to human lung explants confirm more efficient gene silencing of protease-activated receptor 2 (PAR2), a G protein-coupled receptor involved in fibrosis. This study reveals the importance of the balance between efficient polyplex formation, cellular uptake, gene knockdown, and toxicity for efficient siRNA delivery in vitro, in vivo, and in fibrotic human lung tissue ex vivo

On-site correlation in valence and core states of ferromagnetic nickel

We present a method which allows to include narrow-band correlation effects into the description of both valence and core states and we apply it to the prototypical case of nickel. The results of an ab-initio band calculation are used as input mean-field eigenstates for the calculation of self-energy corrections and spectral functions according to a three-body scattering solution of a multi-orbital Hubbard hamiltonian. The calculated quasi-particle spectra show a remarkable agreement with photoemission data in terms of band width, exchange splitting, satellite energy position of valence states, spin polarization of both the main line and the satellite of the 3p core level.Comment: 14 pages, 10 PostScript figures, RevTeX, submitted to PR

Angular Momentum Flow During Ultrafast Demagnetization of a Ferrimagnet

One of the key processes setting the speed of the ultrafast magnetization phenomena is the angular momentum transfer from and into the spin system. However, the way the angular momentum flows during ultrafast demagnetization and magnetization switching phenomena remains elusive so far. We report on time resolved soft x ray magnetic circular dichroism measurements of the ferrimagnetic GdFeCo alloy allowing us to record the dynamics of elemental spin and orbital moments at the Fe and Gd sites during femtosecond laser induced demagnetization. We observe a complete transfer of spin and orbital angular momentum to the lattice during the first hundreds of femtoseconds of the demagnetization proces