On the stabilization of ion sputtered surfaces

The classical theory of ion beam sputtering predicts the instability of a flat surface to uniform ion irradiation at any incidence angle. We relax the assumption of the classical theory that the average surface erosion rate is determined by a Gaussian response function representing the effect of the collision cascade and consider the surface dynamics for other physically-motivated response functions. We show that although instability of flat surfaces at any beam angle results from all Gaussian and a wide class of non-Gaussian erosive response functions, there exist classes of modifications to the response that can have a dramatic effect. In contrast to the classical theory, these types of response render the flat surface linearly stable, while imperceptibly modifying the predicted sputter yield vs. incidence angle. We discuss the possibility that such corrections underlie recent reports of a ``window of stability'' of ion-bombarded surfaces at a range of beam angles for certain ion and surface types, and describe some characteristic aspects of pattern evolution near the transition from unstable to stable dynamics. We point out that careful analysis of the transition regime may provide valuable tests for the consistency of any theory of pattern formation on ion sputtered surfaces

Indentation of ultrathin elastic films and the emergence of asymptotic isometry

We study the indentation of a thin elastic film floating at the surface of a liquid. We focus on the onset of radial wrinkles at a threshold indentation depth and the evolution of the wrinkle pattern as indentation progresses far beyond this threshold. Comparison between experiments on thin polymer films and theoretical calculations shows that the system very quickly reaches the Far from Threshold (FT) regime, in which wrinkles lead to the relaxation of azimuthal compression. Furthermore, when the indentation depth is sufficiently large that the wrinkles cover most of the film, we recognize a novel mechanical response in which the work of indentation is transmitted almost solely to the liquid, rather than to the floating film. We attribute this unique response to a nontrivial isometry attained by the deformed film, and discuss the scaling laws and the relevance of similar isometries to other systems in which a confined sheet is subjected to weak tensile loads.Comment: 5 pages, close to published versio

Polarization memory in single Quantum Dots

We measured the polarization memory of excitonic and biexcitonic optical transitions from single quantum dots at either positive, negative or neutral charge states. Positive, negative and no circular or linear polarization memory was observed for various spectral lines, under the same quasi-resonant excitation below the wetting layer band-gap. We developed a model which explains both qualitatively and quantitatively the experimentally measured polarization spectrum for all these optical transitions. We consider quite generally the loss of spin orientation of the photogenerated electron-hole pair during their relaxation towards the many-carrier ground states. Our analysis unambiguously demonstrates that while electrons maintain their initial spin polarization to a large degree, holes completely dephase.Comment: 6 pages, 4 figure

Small Volume Resuscitation in Hemorrhagic Shock: Historical and Scientific Background

Exsanguination is the primary cause of death in trauma. The mortality can be prevented if bleeding can be stopped and blood loss can be replaced with fluid. Fluid resuscitation has been proven to improve tissue perfusion and reverse the cellular injury and swelling in state of hemorrhage. Fluid resuscitation can also depress the cytokines that could lead to multiple organ failure in hemorrhagic shock. The method of fluid resuscitation widely used nowadays refers to guideline by American College of Surgeon. Despite its wide application, some studies reported the guideline may be harmful and addressed the lack of its scientific basis. These studies introduced another strategy called small volume fluid resuscitation. Although studies were limited to animal model and some small clinical trials, they showed promising result for small volume fluid resuscitation. Small volume fluid resuscitation could reduce the additional blood loss due to continued bleeding or re-bleeding and lower mortality rate. Small volume fluid is an appropriate option in resuscitating patients especially those with uncontrolled hemorrhage

Analisis Kelayakan Ekonomis Cloud Computing Pada Lembaga Keuangan Mikro Di Indonesia Dengan Metode Ranti's Generic Is/it Business Value Dan Economic Value Added: Studi Kasus Pada Bank Perkreditan Rakyat Di Jakarta

Bank Perkreditan Rakyat (BPR) sebagai salah satu pemain terbesar dalam bisnis keuangan mikro di Indonesia telah meningkatkan penggunaan Sistem Informasi/Teknologi Informasi (SI/TI) untuk mendukung bisnis mereka. Namun, hanya sedikit dari mereka yang menyadari isu-isu seputar investasi TI. Ada kekhawatiran tentang tidak tersedianya sumber daya yang cukup untuk membeli, memelihara, dan mengamankan SI/TI mereka sendiri. Di sisi lain, investasi yang besar diperlukan dan akhirnya menjadi momok bagi BPR yang paling menerapkan SI/TI untuk mendukung pengembangan bisnis mereka. Penelitian ini menganalisis nilai ekonomi dari penerapan komputasi awan di BPR. Analisis dilakukan, pertama dengan mengidentifikasi dan mengukur relevansi manfaat SI/TI menggunakan Ranti's IS/IT Generic Business Values dan kedua dengan menempatkan nilai-nilai yang diukur atau manfaat pada metode Economic Value Added (EVA), untuk melakukan analisis keuangan. Komputasi awan mampu memberikan solusi bagi masalah yang dihadapi oleh BPR seperti dapat dilihat dari nilai EVA positif. Oleh karena itu, komputasi awan merupakan pendekatan yang berharga bagi BPR untuk bergerak maju. Resiko investasi SI/TI dapat ditransfer ke penyedia komputasi awan, dengan kata lain, tidak ada waktu untuk berpikir tentang teknologi USAng sebelum Return of Investment (ROI) tercapai. Bank Perkreditan Rakyat (BPR) as one of the biggest players in Indonesia's microfinance business has increased their use of Information Systems/Information Technology (IS/IT) to support their business. However, only few of them are aware of issues around IT investment. There are concerns about the unavailability of sufficient resource to purchase, maintain, and secure their own IS/IT. On the other hand, a large investment is needed and it eventually becomes the scourge for most rural banks to apply IS/IT to support their business development. This research analyzes the economic value of implementing cloud computing in BPR. Analysis is done, firstly by identifying and quantifying the relevant IS/IT benefits using Ranti's IS/IT Generic Business Values and, secondly by putting the quantified values or benefits into Economic Value Added (EVA) method to do the financial analysis. Cloud computing is able to provide solutions for problems faced by BPR as can be seen from the positive EVA value. Hence, the cloud computing is a valuable approach for BPR to move forward. IS/IT investment risk can be transferred to cloud computing providers, in other words, there is no time to think about outdated technology before Return of Investment (ROI) is achieved

Effect of strain rate on the yielding mechanism of amorphous metal foam

Stochastic amorphous Pd_(43)Ni_(10)Cu_(27)P_(20) foams were tested in quasistatic and dynamic loading. The strength/porosity relations show distinct slopes for the two loading conditions, suggesting a strain-rate-induced change in the foam yielding mechanism. The strength/porosity correlation of the dynamic test data along with microscopy assessments support that dynamic foam yielding is dominated by plasticity rather than elastic buckling, the mechanism previously identified to control quasistatic yielding. The strain-rate-induced shift in the foam yielding mechanism is attributed to the rate of loading approaching the rate of sound wave propagation across intracellular membranes, thereby suppressing elastic buckling and promoting plastic yielding

Moving boundary approximation for curved streamer ionization fronts: Solvability analysis

The minimal density model for negative streamer ionization fronts is investigated. An earlier moving boundary approximation for this model consisted of a "kinetic undercooling" type boundary condition in a Laplacian growth problem of Hele-Shaw type. Here we derive a curvature correction to the moving boundary approximation that resembles surface tension. The calculation is based on solvability analysis with unconventional features, namely, there are three relevant zero modes of the adjoint operator, one of them diverging; furthermore, the inner/outer matching ahead of the front has to be performed on a line rather than on an extended region; and the whole calculation can be performed analytically. The analysis reveals a relation between the fields ahead and behind a slowly evolving curved front, the curvature and the generated conductivity. This relation forces us to give up the ideal conductivity approximation, and we suggest to replace it by a constant conductivity approximation. This implies that the electric potential in the streamer interior is no longer constant but solves a Laplace equation; this leads to a Muskat-type problem.Comment: 22 pages, 6 figure

Two-photon- photoluminescence excitation spectroscopy of single quantum-dots

We present experimental and theoretical study of single semiconductor quantum dots excited by two non-degenerate, resonantly tuned variably polarized lasers. The first laser is tuned to excitonic resonances. Depending on its polarization it photogenerates a coherent single exciton state. The second laser is tuned to biexciton resonances. By scanning the energy of the second laser for various polarizations of the two lasers, while monitoring the emission from the biexciton and exciton spectral lines, we map the biexciton photoluminescence excitation spectra. The resonances rich spectra of the second photon absorption are analyzed and fully understood in terms of a many carrier theoretical model which takes into account the direct and exchange Coulomb interactions between the quantum confined carriers.Comment: Accepted for publication in PR