Field-reversed bubble in deep plasma channels for high quality electron acceleration

We study hollow plasma channels with smooth boundaries for laser-driven electron acceleration in the bubble regime. Contrary to the uniform plasma case, the laser forms no optical shock and no etching at the front. This increases the effective bubble phase velocity and energy gain. The longitudinal field has a plateau that allows for mono-energetic acceleration. We observe as low as 10^{-3} r.m.s. relative witness beam energy uncertainty in each cross-section and 0.3% total energy spread. By varying plasma density profile inside a deep channel, the bubble fields can be adjusted to balance the laser depletion and dephasing lengths. Bubble scaling laws for the deep channel are derived. Ultra-short pancake-like laser pulses lead to the highest energies of accelerated electrons per Joule of laser pulse energy

Twenty‐year study of in‐hospital and postdischarge mortality following emergency general surgical admission

We are grateful to Lizzie Nicholson, and the team at the Information Services Division, Scotland for their support in providing us with these data and the Data Safehaven Department of the University of Aberdeen for its storage. The authors would also like to thanks Dr Neil Scott and Dr Rute Vieira of the Department of Medical Statistics, University of Aberdeen for their advice in conducting this research.Peer reviewedPublisher PD

Numerical stability of the AA evolution system compared to the ADM and BSSN systems

We explore the numerical stability properties of an evolution system suggested by Alekseenko and Arnold. We examine its behavior on a set of standardized testbeds, and we evolve a single black hole with different gauges. Based on a comparison with two other evolution systems with well-known properties, we discuss some of the strengths and limitations of such simple tests in predicting numerical stability in general.Comment: 16 pages, 12 figure

Magnetic properties of PdAs2O6: a dilute spin system with an unusually high N\'eel temperature

The crystal structure and magnetic ordering pattern of PdAs2O6 were investigated by neutron powder diffraction. While the magnetic structure of PdAs2O6 is identical to the one of its isostructural 3d-homologue NiAs2O6, its N\'{e}el temperature (140 K) is much higher than the one of NiAs2O6 (30 K). This is surprising in view of the long distance and indirect exchange path between the magnetic Pd$^{2+}$ ions. Density functional calculations yield insight into the electronic structure and the geometry of the exchange-bond network of both PdAs2O6 and NiAs2O6, and provide a semi-quantitative explanation of the large amplitude difference between their primary exchange interaction parameters

The Benefish consortium reports on the influence of system water refreshment rates on realized feed load, weight development, fish physiology and behaviour in turbot

Farmers with recirculation aquaculture systems (RAS) have a greater necessity and capacity to control the culture conditions of their farms than farmers with other aquaculture systems. Water quality is one of the factors that is closely monitored and managed in order to maintain the optimal levels of oxygen, ammonia, temperature, pH, and CO2. Effects of these parameters on growth and health are well studied and almost immediately noticeable. In RAS it often occurs that, although water quality conditions seem to be optimal, the feed intake of the fish might suddenly diminishes, thus reflecting a situation of sub optimal welfare of the animals. This phenomenon is particular relevant in marine RAS where these situations of reduced feed intake occur even though the normally monitored water quality parameters and husbandry conditions appear to be optimal. Similar phenomena also occur in other aquaculture culture systems, such as flow through systems, where feed intake fluctuates whilst the reasons are not always known, although there is typically less control and monitoring compared with RAS. It is therefore necessary to actively monitor deviation of expected feed intake, in combination with the monitoring of culture conditions and farm management on pilot-scale level. Only through this intermediate level experimental work and farm observations for the assumed relationship between deviation of expected feed intake and fish welfare can be validated. It is furthermore necessary to provide refinements to causative relationships expected to be found on commercial farms, where it is often claimed that e.g. lower system water refreshment rates or more closed RAS are leading to growth retardation and lower feed intake in fish and thus lower production. The present study is, therefore, intending to prove the hypothesis that changes in feed intake can be associated with changed fish welfare status, using turbot as model species. It is furthermore hypothesized that this changed fish welfare status is caused by different system water refreshment rates and fish and system management. As a final result, feed intake should relate by same efficiency to lower fish growth in closed RAS compared to flow through systems. The objectives are therefore to validate the relationships between deviation from expected feed intake and fish welfare, and their causative factors on the commercial farms interpreting data on feed intake, behavior, endocrinology and immune patterns as welfare indicators

Causes of death after emergency general surgical admission : population cohort study of mortality

Funding: This study was funded by the NHS Highland Endowments fund.Peer reviewedPublisher PD

Analisa Gelombang Kejut Terhadap Karakteristik Arus Lalu Lintas Di Jalan Walanda Maramis Bitung

Gelombang kejut didefinisikan sebagai gerakan atau perjalanan pada sebuah Perubahan kerapatan dan arus lalu lintas. Pada keadaan arus bebas, kendaraan-kendaraan akan melaju dengan kecepatan tertentu. Apabila pada arus tersebut diberikan suatu hambatan, maka akan terjadi pengurangan arus yang dapat melewati lokasi hambatan tersebut. Pengurangan arus ini mengakibatkan kerapatan kendaraan pada daerah sebelum lokasi hambatan menjadi tinggi yang pada akhirnya kecepatan kendaraan turun atau bahkan terjadi antrian. Hambatan pada arus lalu lintas tersebut dapat berupa penutupan sebagian atau seluruh lajur jalan misalnya akibat terjadinya kecelakaan, perbaikan jalan, atau dapat juga terjadi karena adanya lampu lalu lintas.Penelitian dilakukan di Jalan Walanda Maramis Bitung (4 lajur 2 arah tidak terpisah lebih khusus untuk jalur arah Pusat Kota ke Wangurer), dengan menggunakan 3 metode yaitu: Greenshield, Greenberg, dan Underwood, kemudian dipilih model yang terbaik. Hasil analisa menunjukkan bahwa untuk arah Pusat Kota Bitung ke Wangurer didapatkan model Greenshield dengan R2 sebesar = 0,883. Arus maksimum yang didapat dari model greenshield adalah sebesar = 917.751 smp/jam. Dengan menggunakan skenario insiden yang terjadi ketika volume kendaraan sebesar 720 smp/jam mengakibatkan satu lajur dari 2 lajur jalan arah pusat kota ke Wangurer harus ditutup karena terjadi insiden. Dari hasil analisa gelombang kejut, didapatkan total waktu pembukaan jalur dengan waktu kendaraan terakhir memasuki antrian yaitu = 1,935 menit. Total waktu dari pembukaan jalur ke kondisi normal = 2,013 menit, dengan panjang antrian 1,11 km

Transient behavior in Single-File Systems

We have used Monte-Carlo methods and analytical techniques to investigate the influence of the characteristics, such as pipe length, diffusion, adsorption, desorption and reaction rates on the transient properties of Single-File Systems. The transient or the relaxation regime is the period in which the system is evolving to equilibrium. We have studied the system when all the sites are reactive and when only some of them are reactive. Comparisons between Mean-Field predictions, Cluster Approximation predictions, and Monte Carlo simulations for the relaxation time of the system are shown. We outline the cases where Mean-Field analysis gives good results compared to Dynamic Monte-Carlo results. For some specific cases we can analytically derive the relaxation time. Occupancy profiles for different distribution of the sites both for Mean-Field and simulations are compared. Different results for slow and fast reaction systems and different distribution of reactive sites are discussed.Comment: 18 pages, 19 figure

Adaptive mesh refinement approach to construction of initial data for black hole collisions

The initial data for black hole collisions is constructed using a conformal-imaging approach and a new adaptive mesh refinement technique, a fully threaded tree (FTT). We developed a second-order accurate approach to the solution of the constraint equations on a non-uniformly refined high resolution Cartesian mesh including second-order accurate treatment of boundary conditions at the black hole throats. Results of test computations show convergence of the solution as the numerical resolution is increased. FTT-based mesh refinement reduces the required memory and computer time by several orders of magnitude compared to a uniform grid. This opens up the possibility of using Cartesian meshes for very high resolution simulations of black hole collisions.Comment: 13 pages, 11 figure

Fowler-Nordheim-like local injection of photoelectrons from a silicon tip

Tunneling between a photo-excited p-type silicon tip and a gold surface is studied as a function of tip bias, tip/sample distance and light intensity. In order to extend the range of application of future spin injection experiments, the measurements are carried out under nitrogen gas at room temperature. It is found that while tunneling of valence band electrons is described by a standard process between the semiconductor valence band and the metal, the tunneling of photoelectrons obeys a Fowler-Nordheim-like process directly from the conduction band. In the latter case, the bias dependence of the photocurrent as a function of distance is in agreement with theoretical predictions which include image charge effects. Quantitative analysis of the bias dependence of the dark and photocurrent spectra gives reasonable values for the distance, and for the tip and metal work functions. For small distances image charge effects induce a vanishing of the barrier and the bias dependence of the photocurrent is exponential. In common with many works on field emission, fluctuations in the tunneling currents are observed. These are mainly attributed to changes in the prefactor for the tunneling photocurrent, which we suggest is caused by an electric-field-induced modification of the thickness of the natural oxide layer covering the tip apex.Comment: 12 pages, 11 figures. Submitted to Phys. Rev.