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Ion-induced leakage current degradation, and single-event burnout may be manifestestations of the same device mechanisms in both silicon carbide power diodes and MOSFETs. In all cases there is a migration of the electrical field from the front body-drain interface to the back epi-drain n+ interface, with a peak exceeding the critical electric field of silicon carbide, causing avalanche generation which enables high short-duration power densities during an approximate 20 psec window after the ion strike. The degradation effect in JBS SiC diodes seems to be independent of the length of the epitaxial region for different voltage-rated diodes.

The onset of ion-induced reverse leakage current in SiC Schottky diodes is shown to depend on material properties, ion linear energy transfer (LET), and bias during irradiation, but not the voltage rating of the parts. This is demonstrated experimentally for devices from multiple manufacturers with voltage ratings from 600 to 1700 V. Using a device with a higher breakdown voltage than required in the application does not provide increased robustness related to leakage current degradation, compared to using a device with a lower voltage rating.

Ion-induced degradation and catastrophic failures in high-voltage SiC junction barrier Schottky power diodes are investigated. The experimental results agree with earlier data showing discrete jumps in leakage current for individual ions and show that the boundary between leakage current degradation and a single-event-burnout-like effect is a strong function of linear energy transfer and reverse bias. TCAD simulations show high localized electric fields under the Schottky junction, and high temperatures generated directly under the Schottky contact, consistent with the hypothesis that the ion energy causes eutectic-like intermixture at the metal–semiconductor interface or localized melting of the silicon carbide lattice.

Further miniaturization of imaging systems is prevented by the prevalent, traditional bulky refractive optics today. Meta-optics have recently generated great interest in the visible wavelength as a replacement for refractive optics thanks to their low weight, small size, and amenability to high-throughput semiconductor manufacturing. Here, we extend these meta-optics to the long-wave infrared (LWIR) regime and demonstrate imaging with a 2 cm aperture f/1 all-silicon metalens under ambient thermal emission. We showed that even with the strongly chromatic nature of the metalenses, we can perform ambient light imaging, primarily due to the lack of wavelength discrimination in the sensor, as is the norm for an RGB-camera in the visible.

The single-event effect sensitivity of fourth-generation, 90 nm SiGe HBTs is investigated. Inverse-mode, ≥1.0 Gbps SiGe digital logic using standard, unoptimized, fourth-generation SiGe HBTs is demonstrated and the inverse-mode shift register exhibited a reduction in bit-error cross section across all ion-strike LETs. Ion-strike simulations on dc calibrated, 3-D TCAD SiGe HBT models show a reduction in peak current transient magnitude and a reduction in overall transient duration for bulk SiGe HBTs operating in inverse mode. These improvements in device-level SETs are attributed to the electrical isolation of the physical emitter from the subcollector-substrate junction and the high doping in the SiGe HBT base and emitter, suggesting that SiGe BiCMOS technology scaling will drive further improvements in inverse-mode device and circuit-level SEE. Two-photon absorption experiments at NRL support the transient mechanisms described in the device-level TCAD simulations. Fully-coupled mixed-mode simulations predict large improvements in circuit-level SEU for inverse-mode SiGe HBTs in multi-Gbps, inverse-mode digital logic.

Objective Titin gene (TTN) mutations have been described in eight families with hereditary myopathy with early respiratory failure (HMERF). Some of the original patients had features resembling myofibrillar myopathy (MFM), arguing that TTN mutations could be a much more common cause of inherited muscle disease, especially in presence of early respiratory involvement. Methods We studied 127 undiagnosed patients with clinical presentation compatible with MFM. Sanger sequencing for the two previously described TTN mutations in HMERF (p.C30071R in the 119th fibronectin-3 (FN3) domain, and p.R32450W in the kinase domain) was performed in all patients. Patients with mutations had detailed review of their clinical records, muscle MRI findings and muscle pathology. Results We identified five new families with the p.C30071R mutation who were clinically similar to previously reported cases, and muscle pathology demonstrated diagnostic features of MFM. Two further families had novel variants in the 119th FN3 domain (p.P30091L and p.N30145K). No patients were identified with mutations at position p.32450. Conclusions Mutations in TTN are a cause of MFM, and titinopathy is more common than previously thought. The finding of the p.C30071R mutation in 3.9% of our study population is likely due to a British founder effect. The occurrence of novel FN3 domain variants, although still of uncertain pathogenicity, suggests that other mutations in this domain may cause MFM, and that the disease is likely to be globally distributed. We suggest that HMERF due to mutations in the TTN gene be nosologically classified as MFM-titinopathy.

Three-dimensional NanoTCAD simulations of a 45 nm SOI SRAM cell indicate that the contributions of charge generation and transport in the surrounding oxides have a potentially meaningful effect on the SEU response in nanotechnologies.

Single-event transients (SETs) are modeled in a SiGe voltage reference using compact model and full 3-D mixed-mode TCAD simulations. The effect of bias dependence and circuit loading on device-level transients is examined with regard to the voltage reference circuit. The circuit SET simulation approaches are benchmarked against measured data to assess their effectiveness in accurate modeling of SET in SiGe analog circuits. The mechanisms driving the SET of this voltage reference are then identified for the first time and traced back to the original device transients. These results enable the differences between the simulation results to be explained, providing new insight into best practices for the modeling circuit SET in different circuit topologies and device technologies.

Comprehensive 3-D mixed-mode simulations, including accurate modeling of parasitic elements present in the experimental setup, resulted in close agreement between simulated and experimentally-measured heavy-ion-induced transients in first-generation SiGe HBTs. We have identified the key factors affecting previous simulations and observed experimental differences. The approach employed is also applicable to other submicron, high-speed technologies. Furthermore, we present a plausible answer to the previously unexplained issue of higher collector currents in single-transistor SiGe HBT single-event transients under positive collector bias. The new observations and conclusions facilitate improved understanding and potential mitigation options.

Silicon-germanium heterojunction bipolar transistor (SiGe HBT) heavy ion-induced current transients are measured using Sandia National Laboratories' microbeam and high- and low-energy broadbeam sources at the Grand Acce?le?rateur National d'Ions Lourds, Caen, France, and the University of Jyva?skyla?, Finland. The data were captured using a custom broadband IC package and real-time digital phosphor oscilloscopes with at least 16 GHz of analog bandwidth. These data provide detailed insight into the effects of ion strike location, range, and LET.

We investigate the single-event transient (SET) response of bandgap voltage references (BGRs) implemented in SiGe BiCMOS technology through heavy ion microbeam experiments. The SiGe BGR circuit is used to provide the input reference voltage to a voltage regulator. SiGe HBTs in the BGR circuit are struck with 36-MeV oxygen ions, and the subsequent transient responses are captured at the output of the regulator. Sensitive devices responsible for generating transients with large peak magnitudes (more than 5% of the dc output voltage) are identified. To determine the effectiveness of a transistor-layout-based radiation hardened by design (RHBD) technique with respect to immunity to SETs at the circuit level, the BGR circuit implemented with HBTs surrounded by an alternate reverse-biased pn junction (n-ring RHBD) is also bombarded with oxygen ions, and subsequent SETs are captured. Experimental results indicate that the number of events causing transients with peak magnitude more than 5% above the dc level have been reduced in the RHBD version; however, with the inclusion of the n-ring RHBD, new locations for the occurrence of transients (albeit with smaller peak magnitude) are created. Transients at the transistor-level are also independently captured and are presented. It is demonstrated that while the transients are short at the transistor level (ns duration), relatively long transients are obtained at the circuit level (hundreds of nanoseconds). In addition, the impact of the SET response of the BGR on the performance of an ultra-high-speed 3-bit SiGe analog-to-digital converter (ADC) is investigated through simulation. It is shown that ion-induced transients in the reference voltage could eventually lead to data corruption at the output of the ADC.

We investigate transistor-level layout-based techniques for SEE mitigation in advanced SiGe HBTs. The approach is based on the inclusion of an alternate reverse-biased pn junction (n-ring) designed to shunt electron charge away from the sub-collector to substrate junction. The inclusion of the n-ring affects neither the DC nor AC performance of the SiGe HBT and does not compromise its inherent multi-Mrad TID tolerance. The effects of ion strike location and angle of incidence, as well as n-ring placement, area, and bias on charge collection are investigated experimentally using a 36 MeV O2 microbeam. The results indicate that charge shunting through the n-ring can result in up to a 90% reduction in collector collected charge for strikes outside the DT and a 18% reduction for strikes to the emitter center. 3-D transient strike simulations using NanoTCAD are used to verify the experimental observations, as well as shed insight into the underlying physical mechanisms. Circuit implications for this RHBD technique are discussed and recommendations made.

Familial hemiplegic migraine (FHM) is a rare autosomal-dominant subtype of migraine with aura, associated with hemiparesis during the aura. Here we describe a unique FHM family in which two novel allelic missense mutations in the Na,K-ATPase gene ATP1A2 segregate in the proband with hemiplegic migraine. Both mutations show reduced penetrance in family members of the proband. Cellular survival assays revealed Na,K-ATPase dysfunction for both ATP1A2 mutants, indicating that both mutations are disease causative. This is the first case of compound heterozygosity for any of the known FHM genes.

Improvements to solar cell efficiency and radiation hardness that are compatible with low cost, high volume manufacturing processes are critical for power generation applications in future long-term NASA and DOD space missions. In this paper, we provide the results of numerical simulation of the radiation effects in a novel, ultra-thin (UT), Si photovoltaic cell technology that combines enhanced light trapping (LT) and absorption due to nanostructured surfaces, separation of photogenerated carriers by carrier selective contacts (CSC), and increased carrier density due to multiple exciton generation (MEG). Such solar cells have a potential to achieve high conversion efficiencies while shown to be rad-hard, lightweight, flexible, and low–cost, due to the use of Si high volume techniques.

The off-state drain current leakage characteristics of 130 nm CMOS technology are investigated using x-ray irradiation and operating temperature as variables. Radiation-induced interface traps in the gate oxide to gate-drain overlap region strongly enhance the off-state leakage as a function of gate bias. Due to the thin gate oxide in these 130 nm devices, we find that drain-edge direct tunneling is more plausible than conventional gate-induced-drain-leakage in explaining the observed increase in drain leakage. Radiation-induced traps in the shallow trench isolation oxide create parasitic channels in the p-well and produce another source of off-state drain leakage with increasing total dose. The drain current increase from both the gate overlap region and the shallow trench edge are enhanced with increasing total dose and suppressed by cooling

A new approach for modeling the radiation-induced charge distribution in shallow-trench isolation (STI) structures shows that much less charge is trapped near the top of the trench. We found that charges inside the STI oxide are pushed down by the vertical electric field coming from the positive gate bias, leaving much less total-dose-induced charge close to the top of trench. This nonuniformity significantly affects the measured leakage current.

The present work considers electrothermal simulation of LDMOS devices and associated nonequilibrium effects. Simulations have been performed on three kinds of LDMOS: bulk Si, partial SOI and full SOI. Differences between equilibrium and nonequilibrium modeling approaches are examined. The extent and significance of thermal nonequilibrium is determined from phonon temperature distributions obtained using a common electronic solution and three different heating models (Joule heating, electron/lattice scattering, phonon scattering). The results indicate that, under similar operating conditions, nonequilibrium behavior is more significant in the case of full SOI devices, where the extent of nonequilibrium is estimated to be twice that of the partial SOI device and four times that of the bulk device. Time development of acoustic phonon and lattice temperatures in the electrically active region indicates that nonequilibrium effects are significant for times less than 10 ns.

Space exploration missions and space electronic equipment require improvements in solar cell efficiency and radiation hardness. Triple-junction photovoltaic (TJ PV) cell is one of the most widely used PV for space missions due to it high efficiency. A proper models and simulation techniques are needed to speed-up the development on novel solar cell devices and reduce the related expenses. In this paper we have developed a detailed 3D TCAD model of a TJ PV cell, and calibrated the various (not accurately known) physical parameters to match experimental data, such as dark and light JV, external quantum efficiency (EQE) . A detailed model of triple-junction InGaP/GaAs/Ge solar cell has been developed and implemented in CFDRC’s 3D NanoTCAD simulator. The model schematic, materials, layer thicknesses, doping levels and meshing are discussed. This triple-junction model is based on the experimental measurements of a Spectrolab triple-junction cell by [1] with material layer thicknesses provided by Rochester Institute of Technology [2]. This model of the triple-junction solar cell is primarily intended to simulate the external quantum efficiency, JV and other characteristics of a physical cell. Simulation results of light JV characteristics and EQE are presented. The calculated performance parameters compare well against measured experimental data [1]. Photovoltaic performance parameters (Jsc, Voc, Jm, Vm, FF, and Efficiency) can also be simulated using the presented model. This TCAD model is to be used to design an enhanced TJ PV with increased efficiency and radiation tolerance. Keywords: photovoltaic cell, triple-junction, numerical modeling, TCAD, dark and light JV.

A predictive computational approach that limits use of DLTS experiments is presented, developed using the experimental data and proposed physics based models. Three-dimensional NanoTCAD simulations are used for physicsbased prediction of space radiation effects in III-V solar cells, and validated with experimentally measured characteristics of a p+n GaAs solar cell with AlGaAs window. The computed dark and illuminated I-V curves as well as corresponding performance parameters matched very well experimental data for 2 MeV proton irradiation at various fluences. We analyze the role of majority vs. minority and deep vs. shallow carrier traps in the solar cell performance degradation. The traps/defects parameters used in the simulations were derived from Deep Level Transient Spectroscopy (DLTS) data obtained at NRL. It was noticed that the degradation caused by deep traps observed in single-trap numerical tests exhibit a very similar trend to the degradation caused by a full spectrum of defect traps, but to a lesser degree. This led to the development of a method to accurately simulate the degradation of a solar cell by using only a single deep level defect whose density is calculated by the Stopping and Range of Ions in Matter (SRIM) code. Using SRIM, we calculated the number of vacancies produced by 2 MeV proton irradiation for fluences ranging from 6x1010 cm-2 to 5x1012 cm-2. Based on the SRIM results, we applied trap models in NanoTCAD and performed full I-V simulations from which the amount of degradation of performance parameters (Isc, Voc, Pmax) was calculated. The physics-based models using SRIM allowed obtaining good match with experimental data.

We present a predictive computational approach that may reduce the need for extensive inputs from Deep Level Transient Spectroscopy (DLTS) experiments. Three-dimensional NanoTCAD simulations are used for physics-based prediction of space radiation effects in a p + n GaAs solar cell with AlGaAs window, and validated with experimental data. The computed dark and illuminated I-V curves, as well as corresponding performance parameters, matched experimental data very well for 2 MeV proton irradiation at various fluence levels. We analyze the role of majority vs. minority and deep vs. shallow carrier traps in the solar cell performance degradation. The defects level parameters used in the simulations were taken from DLTS data obtained at NRL. It was determined from numerical simulations that the degradation of the photovoltaic parameters could be modeled and showed similar trends when a only a single deep level defect was considered compared to a spectrum of defect levels. This led to the development of an alternate method to simulate the degradation of a solar cell by using only a single deep level defect whose density is calculated by the Stopping and Range of Ions in Matter (SRIM) code. Using SRIM, we calculated the number of vacancies produced by 2 MeV proton irradiation for fluence levels ranging from 6x10 10 cm -2 to 5x10 12 cm -2 . Based on the SRIM results, we applied trap models in NanoTCAD and performed I-V simulations from which the degradation of the photovoltaic parameters (I sc , V oc , FF, P max ) was calculated. The simulations using SRIM-derived defect concentrations showed reasonable agreement with simulations using parameters determined from DLTS.

We present the radiation effect models for solar cells used in NanoTCAD device simulator and provide comparison with experimentally measured on solar cell performance. The device modeled is a p+ n GaAs solar cell. Dark, Light IV curves and corresponding performance parameters are simulated and compared with experimental results for 2 MeV protons at varying fluence. Majority carrier defect introduction rates for n-type GaAs used in the NanoTCAD simulations were taken from deep level transient spectroscopy (DLTS) data provided by the Naval Research Lab (NRL). Results show a good match between simulations and experimental results.

Detailed, physics-based three-dimensional (3D) technology computer-aided-design (TCAD) device model, coupled in mixed-mode with external load circuit and parasitics, enabled accurate simulation of single-event effects (SEEs) in nonplanar silicon-on-insulator (SOI) Multi-Gate Field Effect Transistors (MuGFETs) or FinFETs. We show the importance of correct device physics models, including mobility in different crystal planes of strained silicon — validated with experimental data — for correct computation of both steady-state and transient characteristics of FinFETs. Mixed-mode coupling of a realistic load circuit, including experimental parasitics, with the 3D TCAD device model, is critical to be able to compute single-event transient current waveforms and charge collection characteristics that reflect well experimental results.

Novel nanomaterials and devices based on them offer significant advantages over traditional technologies in terms of light-weight and efficiency for applications in satellite and space systems. Examples of such novel devices include quantum dot (QD) based solar cells and photodetectors. However, the radiation effects modeling tools are not yet available for these devices, and the response to radiation are not well understood (Figure 1). Review of numerical models and experimental investigation of radiation effects in quantum dot based solar cells are provided. Although some studies have been conducted on degradation of solar cells in high-radiation environment of space and test data on the performance of solar cells in a radiation environment are collected, the mechanisms of radiation-induced degradation of QD solar cells has yet to be established. We develop the Nanoscale Technology Computer Aided Design (NanoTCAD) simulation software for simulation of radiation effects in QD-based photovoltaic (PV), and use conducted proton irradiation experiments to develop models and perform a direct comparison of radiation hardness of quantum dot based cells and regular solar cells. These NanoTCAD tools are based on advanced drift-diffusion and quantum models for the simulation of QD based devices and materials.

The latest enhancements to NanoTCAD mixed-mode software package, combining 3D physics-based nano-scale device models and unique mixed-mode interface to the Cadence Spectre circuit simulator, have enabled simulations and in-operation analysis of ionizing radiation single event effects (SEEs) in modern high-speed SiGe BiCMOS technologies and integrated circuits. Additionally, the NanoTCAD new, automated interface to Geant4 radiation models and the 3D solver capability to model very low temperature behavior, enable a comprehensive and accurate modeling of radiation effects in nano-scale systems, in the extreme radiation and temperature environments of space. Example simulations of SEEs affecting digital output of a 7.2GHz mixed-signal circuit are presented. Our mixed-mode modeling results compare very well with experimental data.

For applications in space systems, devices based on novel nanomaterials offer significant advantages over traditional technologies in terms of light-weight and efficiency. Examples of such novel devices include quantum dot (QD) based solar cells and photodetectors. However, the response of these devices to radiation effects is not well understood, and radiation effects modeling tools are not yet available. In this paper we review our numerical models and experimental investigation of radiation effects in quantum dot based solar cells. In the natural, high-radiation environment of space all solar cells suffer from degradation. Although some studies have been conducted, and test data collected, on the performance of solar cells in a radiation environment, the mechanisms of radiation-induced degradation of quantum dot superlattices (QDS) has yet to be established. We have conducted proton irradiation experiments to provide a direct comparison of radiation hardness of quantum dot based cells and regular solar cells. An approach to the development of Nano-scale Technology Computer Aided Design (NanoTCAD) simulation software for simulation of radiation effects in QDS-based photovoltaic (PV) devices is presented. The NanoTCAD tools are based on classical drift-diffusion and quantum-mechanical models for the simulation of QD PV cells.

For applications in satellite systems, devices based on novel nanomaterials offer significant advantages over traditional technologies in terms of light-weight and efficiency. Examples of such novel devices include quantum dot (QD) based solar cells and photodetectors. However, the response of these devices to radiation effects is not well understood, and radiation effects modeling tools are not yet available. In this paper we review our numerical models and experimental investigation of radiation effects in quantum dot based solar cells. In the natural, high-radiation environment of space all solar cells suffer from degradation. Although some studies have been conducted, and test data collected, on the performance of solar cells in a radiation environment, the mechanisms of radiation-induced degradation of quantum dot superlattices (QDS) has yet to be established. We have conducted proton irradiation experiments to provide a direct comparison of radiation hardness of quantum dot based cells and regular solar cells. An approach to the development of Nano-scale Technology Computer Aided Design (NanoTCAD) simulation software for simulation of radiation effects in QDS-based photovoltaic (PV) devices is presented. The NanoTCAD tools are based on classical drift-diffusion and quantum-mechanical models for the simulation of QD PV cells.

Idiopathic intracranial hypertension (IIH) is defined as increased intracranial pressure in the absence of intracranial mass or obstructive hydrocephalus. Over 80% of patients are overweight women. IIH is usually encountered in the neurology and ophthalmology practise as headaches, visual disturbance and papilloedema are the characteristic features of this syndrome. Patients with IIH also experience tinnitus, hearing loss, balance disturbance, cerebrospinal fluid (CSF) otorrhoea or rhinorrhoea and in some cases these otorhinological symptoms can be presenting features of this syndrome. IIH is also associated with obstructive sleep apnoea. Otolaryngologists should be familiar with this important condition as it can manifest a variety of symptoms that are more frequently seen in their clinics. Sometimes otolaryngologists may be involved in the surgical management of this condition, such as repair of CSF rhinorrhoea or otorrhoea or endoscopic optic nerve decompression. The aim of this review article is to familiarise the otolaryngologists with the important features of this unusual syndrome which may remain unrecognised in the otolaryngology practice.

A multi-scale modeling approach is proposed and employed to investigate thermal issues and to enable "thermally aware" design of radio-frequency (RF) integrated circuits (ICs). Thermal analysis from full-chip scale down to the single transistor level was made possible with the development of this approach using the finite volume three-dimensional (3D) numerical technique. We have developed new tools that import GDSII layout of entire IC and, for the purpose of generating full-chip 3D thermal model, automatically eliminate the minuscule layout elements that do not affect thermal results. We present here our approach and examples of using equivalent thermal conductivity blocks in place of "forest of vias" typical in modern ICs. Our method and tools are demonstrated on a couple of RF ICs based on a high performance SiGe BiCMOS technology. The tool provides a 3D temperature map that can show thermal gradients across a chip, as well as local temperature distribution (hot spots) down to single transistor level. This allows introducing temperature back into design process. The multi-scale modeling is verified with infrared temperature measurements.

This paper describes the new CFDRC mixed-mode simulator which combines multiscale 3D Technology Computer Aided Design (TCAD) device models (fluid carrier transport and nuclear ion track impact), and advanced compact transistors models. Key features include an interface and 3D adaptive meshing to allow simulations of single event radiation effects with nuclear reactions and secondary particles computed by Vanderbilt's MRED/Geant4 tools.

The authors have implemented a robust CNSPACK-based linear equation solver in an in-house TCAD tool. This solver is enhanced with efficient matrix pre-conditioning algorithms to enable accurate handling of a wide scale of floating-point numbers. Sample results are shown for very low temperature radiation response of a 0.12-mum NMOSFET and I-V curves of 0.13-mum SiGe HBT. The solution is very stable. However, the match against corresponding experimental data is not good due to inaccuracy of physical models (ongoing work).

Single event transient (SET) pulses produced from heavy ion irradiation in digital integrated circuits (ICs) are modeled and analyzed using a mixed-mode approach, that is, three-dimensional (3-D) semiconductor device simulation coupled with a circuit solver. In this paper, we analyze the factors affecting the generation and propagation of digital SET pulses in fast CMOS ICs. Our mixed-mode simulations of various ion strike locations allowed to obtain agreement with measured data and explain the earlier published wide distribution of SET pulse widths created by heavy ion radiation in digital CMOS ICs at a given linear energy transfer (LET) value, which was observed experimentally, but not fully understood. We also indicate that the transient charge-collection current pulse (width and shape) on the struck device node is not directly related to the SET voltage pulse that will propagate through a logic circuit, and therefore current pulses alone should not be treated as a measure of DSET.

Early onset familial Alzheimer's disease (EOFAD) has been associated with mutations in three genes, of which presenilin 1 (PSEN1) mutations are the most frequent. Several families with an association of progressive dementia and spastic paraplegia caused by PSEN1 mutations have been described. Here we described a novel PSEN1 mutation that was associated with dementia and spastic paraplegia in a family with 5 affected individuals in three generations. The proband was a 44-year-old woman who presented with 5 years history of progressive difficulties in walking, cognition and visuospatial impairment. Her maternal grandmother, mother and two maternal aunts also had similar neurological presentation. Molecular genetic analysis showed a missense mutation predicted to substitute an arginine residue for a serine residue at position 278 in the PSEN1 polypeptide (Arg278Ser). The novel PSEN1 mutation identified in this patient adds to the diverse list of existing mutations causing EOFAD associated with spastic paraparesis.

Optimizing the placement of electronics packages to minimize thermal loads in large systems (e.g., power electronics modules in vehicles), and prediction of overall system thermal performance, is typically a very complex problem. Physical prototyping of each permutation during design cycles is time-intensive and expensive. Use of full-scale computational fluid dynamics (CFD) solvers may be impractical for system-level analyses because of: (a) typically large manual efforts needed for grid generation; and (b) long simulation times. There is a need, therefore, for simulation and design tools based on reduced models that will enable rapid, system-level, thermal-fluidic analyses. In this paper, we describe a multi-resolution flow-thermal simulation approach and prototype software tool for thermal management of electronics packages in large systems. This method offers higher efficiency than CFD analyses in terms of computational resources and time. Our demonstration example is related to flow-thermal analysis of a simple vehicle model containing multiple electronics packages. Artificial neural networks (ANNs) are used for rapid modeling of the electronics components and subsystems. The tool is capable of performing fully-resolved (CFD), mixed-resolution (CFD-ANN), and reduced-model (ANN) flow-thermal simulations. Coupled CFD-ANN simulations are a powerful method for design and thermal management of electronics packages and other electrical-mechanical components in large multi-component systems

Three-dimensional (3D) stacked integrated circuits (ICs) can significantly improve circuit performance and offer the promise of integrating various technologies (memory, logic, RF, mixed-signal, optoelectronics) within a single block. Lack of 3D design tools and heat dissipation from vertically stacked multiple layers are the crucial problems in their development. To address these issues, CFD Research Corporation (CFDRC) is developing methodologies and tools to analyze and assess coupled electrical and thermal performance of 3D ICs, including calculation of realistic full-chip thermal distributions and determining from them signal delay/distortion. Due to the stacking technology, extensive localized heating can occur. Analysis to minimize these hot spots using thermal vias is demonstrated. Our Python-script based framework allows to drive and control all the aspects of the 3D model building (directly from layouts), thermal simulations, and results extraction/post-processing. Hence, it is a good basis for coupling with Electronic Design Automation (EDA) systems. We present results of automated, fast, but detailed thermal simulations of 3D stacked integrated circuits. In addition, procedures for automatic extraction of reduced and compact thermal-resistance-based 3D models have been implemented. These techniques greatly reduce required computational time, and allow for very fast parametric modeling analysis of 3D IC design configurations and temperature extraction. From these thermal resistance models, equivalent SPICE netlists may be generated and used for independent or coupled thermal analysis.

This paper presents full-chip scale detailed thermal simulations of three-dimensional (3D) integrated circuit (IC) stacks. The inter-layer dielectric (ILD) and inter-metal dielectric (IMD) materials inside 3D IC stacks may cause extensive localized heating. The influence of multiple layers of dielectrics on heat trapping inside the 3D stack is analyzed. Different methods to minimize such localized heating are studied. It is shown that the use of thermal vias is very effective in heat dissipation from the hot spots. Comparisons are made between several 3D IC configurations to verify these conclusions.Copyright © 2003 by ASME

The present work considers electro-thermal simulation of LDMOS devices and associated non-equilibrium effects. Simulations have been performed on three kinds of LDMOS i.e. bulk Si, partial SOI and full SOI. From the analysis, the extent of thermal non-equilibrium is determined from phonon temperature contours and electron energies in each case. The results indicate that, under similar operating conditions, non-equilibrium is more significant in the case of full SOI devices. Time development of acoustic phonon and lattice temperatures, obtained using two different heat source terms, was studied. This study provided insight into the difference between localized device heating in the electrically active region. The variation of optical and acoustic phonon temperatures with time is presented, and is used to identify time scales where thermal non-equilibrium would be significant.

In this article, British neurologists share their experiences of neurology in Malawi - as educators and researchers. Malawi is a resource-poor country in Central Africa. The spectrum of neurological illnesses is varied and primarily related to HIV and neuroinfections. Structured overseas training programmes for residents can lead to aca- demic exchange with mutual benefit. New links can be established which can then be used to launch international health initiatives. Such visits can also lead to the develop- ment of institutional links, the fostering of which can have a role in the achievement of the global health agenda.

Sirs: In a clinical setting, isolated thunderclap headache is commonly assumed to be benign in origin once subarachnoid haemorrhage (SAH) has been excluded [1]. However, cerebral venous sinus thrombosis (CVST) is an infrequent, alternative cause of sudden-onset headache and is not conclusively excluded by normal conventional CT and LP. CVST is also a recognised rare cause of SAH. Here, we report a case of CVST presenting with thunderclap headache and complicated by delayed SAH. A previously well 53-year-old woman presented with spontaneous, sudden-onset occipital headache as her sole symptom. Neurological examination including fundoscopy was normal, with no evidence of meningism. Acute head CT and subsequent LP performed 16 hours after onset were unremarkable (opening pressure 19 cm, CSF acellular with no bilirubin detectable on spectrophotometry). The headache resolved completely within 24 hours and the patient was discharged with a diagnosis of primary thunderclap headache. The following day, she represented with sudden-onset headache at rest accompanied by mild neck stiffness. Her symptoms resolved before a further suddenonset headache occurred two days later. Examination remained normal throughout. Repeat, unenhanced head CT demonstrated a small, high left frontal SAH along the cranial convexity without involvement of the basal cisterns (Fig. 1a). CT angiography detected no arterial aneurysm, but its venous phase showed changes suggestive of superior sagittal sinus thrombosis, which was confirmed on MR venography (Fig. 1b). Screening for secondary causes of thrombosis was negative. She was initially treated with intravenous unfractionated heparin to allow rapid reversal in case of rebleeding, before being warfarinised under cover from low molecular weight heparin. She remained well at follow-up six months later. Repeat MR angiography showed resolution of the superior sagittal sinus thrombosis, with no other vascular or brain parenchymal abnormalities. Thunderclap headache is an unusual presentation of CVST, perhaps seen in fewer than 20 % of cases [2]. Rarely, there may be no concomitant findings to suggest the presence of a CVST, such as focal neurological signs, seizures or features of raised intracranial pressure. Most patients with CVST have a raised opening pressure and abnormal CSF constituents, but absence of these features does not conclusively rule out the diagnosis. In a previous series of 38 cases, nine patients had both opening pressure and CSF constituents measured, and in one of them all parameters were normal [3]. SAH is a very rare complication of cerebral venous thrombosis, with only 30 cases reported to date. It has been suggested that venous intraparenchymal haemorrhages may rupture into the subarachnoid space, thus causing sudden-onset headache in CVST [2, 4]. However, we hypothesise that our patient’s first headache was caused by the CVST, as there was no evidence of SAH on initial brain CT and bilirubin was not detectable in the CSF. The second or third episode of headache may have been caused by SAH. LETTER TO THE EDITORS

Titin gene (TTN) mutations have been described in 8 families with hereditary myopathy with early respiratory failure (HMERF) a rare condition with features resembling myofibrillar myopathy (MFM). In order to verify if TTN mutations could be a cause of MFM, especially in presence of early respiratory involvement, we carried out a clinical and genetic analysis of 127 undiagnosed patients with a clinical presentation compatible with MFM. Sanger sequencing for the TTN mutations previously described in patients with HMERF (p.C30071R and p.R32450W) was performed in all patients. We identified 5 families with the p.C30071R mutation (3.9% of study population) likely due to a British founder effect. Affected subjects showed phenotypic features similar to previously reported cases, and muscle pathology demonstrated diagnostic features of MFM. Two further families had novel variants in the 119th FN3 domain (p.P30091L and p.N30145K). Although still with uncertain pathogenicity, these new variants suggest that other TTN mutations in this domain may cause MFM. Our results indicate that mutations in TTN gene cause MFM and titinopathy is more common than previously thought. We suggest that HMERF due to mutations in the TTN gene be nosologically classified as MFM-titinopathy.

Lactotransferrin is an iron-binding protein. It has been purified from buffalo colostrum. The purified lactotransferrin has been crystallized in 10% ethanol solution. The crystals are orthorhombic and the space group is P2(1)2(1)2(1) with unit cell dimensions a = 161.70 A, b = 155.75 A, c = 113.48 A. The asymmetric unit contains three molecules of the protein with a solvent content of about 59%. The crystals were stable in the X-ray beam and diffract beyond 3.5 A resolution. The native data have been collected and the structure determination is in progress.