Electromagnetic and semiconductor device simulation usinginterpolating wavelets

A MESFET and a two-dimensional cavity enclosing a cylinder are simulated using a nonuniform mesh generated by an interpolating wavelet scheme. A self-adaptive mesh is implemented and controlled by the wavelet coefficient threshold. A fine mesh can therefore be used in domains where the unknown quantities are varying rapidly and a coarse mesh can be used where the unknowns are varying slowly. It is shown that good accuracy can be achieved while compressing the number of unknowns by 50% to 80% during the whole simulation. In the case of the MESFET, the I-V characteristics are obtained and the accuracy is compared with the basic finite difference scheme. A reduction of 83% in the number of discretization points at steady state is obtained with 3% error on the drain current. The performance of the scheme is investigated using different values of threshold and two types of interpolating wavelet, namely, the second-order and fourth-order wavelets. Due to the specific problem analyzed, a tradeoff appears between good compression, accuracy, and order of the wavelet. This represents the ongoing effort toward a numerical technique that uses wavelets to solve both Maxwell's equations and the semiconductor equations. Such a method is of great interest to deal with the multiscale problem that is the full-wave simulation of active microwave circuits     

Time-domain optical response of an electrooptic modulator usingFDTD

A time-domain analysis of an LiNbO₃ electrooptic modulator using the finite-difference time-domain (FDTD) technique is performed. This allows for the calculation of optical modulation and the time-domain optical response of an electrooptic modulator. The electromagnetic fields computed by FDTD are coupled to standard electrooptic relations that characterize electrooptic interactions inside the embedded Ti diffused LiNbO₃ optical waveguides. The electric field-dependent change in the index of refraction inside these optical waveguides and resulting minute phase shifts imparted to optical signals propagating along the device are determined in time, allowing for the simulation of optical intensity modulation. This novel approach to LiNbO₃ electrooptic modulators using a coupled FDTD technique allows for previously unattainable investigations into device operating bandwidth and data transmission speed     

Using Kestrel and XMPP to Support the STAR Experiment in the Cloud

This paper presents the results and experiences of adapting and improving the Many-Task Computing (MTC) framework Kestrel for use with bag of tasks applications and the STAR experiment in particular. Kestrel is a lightweight, highly available job scheduling framework for Virtual Organization Clusters (VOCs) constructed in the cloud. Kestrel uses the Extensible Message and Presence Protocol (XMPP) for increasing MTC platform scalability and mitigating faults in Wide Area Network (WAN) communications. Kestrel’s architecture is based upon pilot job frameworks used extensively in Grid computing, with fault-tolerant communications inspired by command-and-control botnets. The extensibility of XMPP has allowed development of protocols for identifying manager nodes, discovering the capabilities of worker agents, and for distributing tasks. Presence notifications provided by XMPP allow Kestrel to monitor the global state of the pool and to perform task dispatching based on worker availability. Since its inception, Kestrel has been modified based on its performance managing operational scientific workloads from the STAR group at Brookhaven National Laboratories. STAR provided a virtual machine image with applications for simulating proton collisions using PYTHIA and GEANT3. A Kestrel-based Virtual Organization Cluster, created on top of Clemson University’s Palmetto cluster, CERN, and Amazon EC2, was able to provide over 400,000 CPU hours of computation over the course of a month using an average of 800 virtual machine instances every day, generating nearly seven terabytes of data and the largest PYTHIA production run that STAR has achieved to date.     

nanoMOS 2.5: A two-dimensional simulator for quantum transport in double-gate MOSFETs

A program to numerically simulate quantum transport in double gate metal oxide semiconductor field effect transistors (MOSFETs) is described. The program uses a Green's function approach and a simple treatment of scattering based on the idea of so-called Buttiker probes. The double gate device geometry permits an efficient mode space approach that dramatically lowers the computational burden and permits use as a design tool. Also implemented for comparison are a ballistic solution of the Boltzmann transport equation and the drift-diffusion approaches. The program is described and some examples of the use of nanoMOS for 10 nm double gate MOSFETs are presented.     

Virtual distributed environments in a shared infrastructure

We have developed a middleware system that integrates and extends virtual machine and virtual network technologies to support mutually isolated virtual distributed environments in shared infrastructures like the grid and the PlanetLab overlay infrastructure. Integrating virtual network and on-demand virtual machine creation and customization technologies makes virtual distributed environments a reality. The Violin-based middleware system integrates and enhances such technologies to create virtual distributed environments.     

Indolent course as a relatively frequent presentation in T-prolymphocytic leukaemia. Groupe Fran?ais d'Hématologie Cellulaire

T-prolymphocytic leukaemia (T-PLL) is a rare disorder with a poor outcome. Presentation features were studied in 78 T-PLL cases. Although 53 patients (group A) presented with typical progressive disease including rapidly increasing leucocytosis. 25 patients (group B) experienced an initial indolent clinical course with stable moderate leucocytosis. The morphology and antigenic profile of abnormal cells were similar in both groups, except for a lower incidence of CD45RO+ CD45RA- pattern in group B. A high incidence of inv(14)(q11;q32), t(14;14)(q11;q32) and i(8)(q10) chromosomal abnormalities were found in both groups. After an initial indolent phase (median 33 months; 6-103 months), 16 group B patients progressed to an aggressive stage with clinical and laboratory features similar to group A. Moreover, median survival after progression was short in both groups. In conclusion, T-PLL may start as an indolent disease similar to that reported in ataxia telangectasia. In this rare genetic disorder, some patients develop stable T-cell clones which progress toward T-PLL-like leukaemia. Moreover, ATM gene mutations have been reported in T-PLL. Thus, both diseases are likely to be closely related.     

Autonomic Clouds on the Grid

Computational clouds constructed on top of existing Grid infrastructure have the capability to provide different entities with customized execution environments and private scheduling overlays. By designing these clouds to be autonomically self-provisioned and adaptable to changing user demands, user-transparent resource flexibility can be achieved without substantially affecting average job sojourn time. In addition, the overlay environment and physical Grid sites represent disjoint administrative and policy domains, permitting cloud systems to be deployed non-disruptively on an existing production Grid. Private overlay clouds administered by, and dedicated to the exclusive use of, individual Virtual Organizations are termed Virtual Organization Clusters. A prototype autonomic cloud adaptation mechanism for Virtual Organization Clusters demonstrates the feasibility of overlay scheduling in dynamically changing environments. Commodity Grid resources are autonomically leased in response to changing private scheduler loads, resulting in the creation of virtual private compute nodes. These nodes join a decentralized private overlay network system called IPOP (IP Over P2P), enabling the scheduling and execution of end user jobs in the private environment. Negligible overhead results from the addition of the overlay, although the use of virtualization technologies at the compute nodes adds modest service time overhead (under 10%) to computationally-bound Grid jobs. By leasing additional Grid resources, a substantial decrease (over 90%) in average job queuing time occurs, offsetting the service time overhead.     

A Science Driven Production Cyberinfrastructure��the Open Science Grid

This article describes the Open Science Grid, a large distributed computational infrastructure in the United States which supports many different high-throughput scientific applications, and partners (federates) with other infrastructures nationally and internationally to form multi-domain integrated distributed systems for science. The Open Science Grid consortium not only provides services and software to an increasingly diverse set of scientific communities, but also fosters a collaborative team of practitioners and researchers who use, support and advance the state of the art in large-scale distributed computing. The scale of the infrastructure can be expressed by the daily throughput of around seven hundred thousand jobs, just under a million hours of computing, a million file transfers, and half a petabyte of data movement. In this paper we introduce and reflect on some of the OSG capabilities, usage and activities.     

Myelodysplastic syndromes in childhood: is the FAB classification relevant? Report of 81 children from a French multicentre study. French Group of Cellular Hematology

We reviewed the peripheral blood and bone marrow smears of 81 children with myelodysplastic syndrome (MDS). The morphological FAB classification was applicable in 59 children (72.8%): RAEB and RAEBt were the most frequent, 32 cases (39.5%). CMML was observed in 15 cases (18.5%) and in 25% of them, serological evidence for a recent EBV infection was demonstrated. In 22 cases (27.2%), the FAB classification was not convenient. In some of these children, dysmyelopoiesis was associated with constitutional disorders. Among these various inherited conditions, Down syndrome in which myelodysplasia is the expression of an abnormal clonal hematopoiesis, and mitochondrial cytopathies in which MDS is the hematological expression of a polyclonal multi-organ disease. The FAB classification does not appear to be satisfactory for all the disorders included in the group of childhood MDS and should be modified for specific use in children.