Normal and pathological NCAT image and phantom data based on physiologically realistic left ventricle finite-element models

The four-dimensional (4-D) NURBS-based cardiac-torso (NCAT) phantom, which provides a realistic model of the normal human anatomy and cardiac and respiratory motions, is used in medical imaging research to evaluate and improve imaging devices and techniques, especially dynamic cardiac applications. One limitation of the phantom is that it lacks the ability to accurately simulate altered functions of the heart that result from cardiac pathologies such as coronary artery disease (CAD). The goal of this work was to enhance the 4-D NCAT phantom by incorporating a physiologically based, finite-element (FE) mechanical model of the left ventricle (LV) to simulate both normal and abnormal cardiac motions. The geometry of the FE mechanical model was based on gated high-resolution X-ray multislice computed tomography (MSCT) data of a healthy male subject. The myocardial wall was represented as a transversely isotropic hyperelastic material, with the fiber angle varying from -90 degrees at the epicardial surface, through 0 degrees at the midwall, to 90 degrees at the endocardial surface. A time-varying elastance model was used to simulate fiber contraction, and physiological intraventricular systolic pressure-time curves were applied to simulate the cardiac motion over the entire cardiac cycle. To demonstrate the ability of the FE mechanical model to accurately simulate the normal cardiac motion as well as the abnormal motions indicative of CAD, a normal case and two pathologic cases were simulated and analyzed. In the first pathologic model, a subendocardial anterior ischemic region was defined. A second model was created with a transmural ischemic region defined in the same location. The FE-based deformations were incorporated into the 4-D NCAT cardiac model through the control points that define the cardiac structures in the phantom which were set to move according to the predictions of the mechanical model. A simulation study was performed using the FE-NCAT combination to investigate how the differences in contractile function between the subendocardial and transmural infarcts manifest themselves in myocardial Single photon emission computed tomography (SPECT) images. The normal FE model produced strain distributions that were consistent with those reported in the literature and a motion consistent with that defined in the normal 4-D NCAT beating heart model based on tagged magnetic resonance imaging (MRI) data. The addition of a subendocardial ischemic region changed the average transmural circumferential strain from a contractile value of -0.09 to a tensile value of 0.02. The addition of a transmural ischemic region changed average circumferential strain to a value of 0.13, which is consistent with data reported in the literature. Model results demonstrated differences in contractile function between subendocardial and transmural infarcts and how these differences in function are documented in simulated myocardial SPECT images produced using the 4-D NCAT phantom. Compared with the original NCAT beating heart model, the FE mechanical model produced a more accurate simulation for the cardiac motion abnormalities. Such a model, when incorporated into the 4-D NCAT phantom, has great potential for use in cardiac imaging research. With its enhanced physiologically based cardiac model, the 4-D NCAT phantom can be used to simulate realistic, predictive imaging data of a patient population with varying whole-body anatomy and with varying healthy and diseased states of the heart that will provide a known truth from which to evaluate and improve existing and emerging 4-D imaging techniques used in the diagnosis of cardiac disease.     

Exploiting Macrodiversity with Distributed Antennas in Micro-Cellular CDMA Systems

We consider the use of distributed antennas to increase the capacity and peak data rate achievable in a microcellular CDMA system with limited bandwidth. In additon to the diversity against Rayleigh fading achievable by use of microdiversity among nearly co-located transmit or receive antennas, we exploit macrodiversity against shadow fading that more widely separated antennas permit. We report on antenna configurations for both directional and omni-directional antennas that provide the most uniform signal-to-interference ratio coverage, averaged over a large number of position vectors drawn from a spatially uniform distribution of mobiles. Call capacities and peak transmission rates are determined for an integrated system carrying traffic at different constant rates, where processing gain and the transmission rate are selected to satisfy a common chip rate. For the downlink a 5.5 dB capacity gain can be achieved for 64 kb/s calls using four antennas located on the diagonals of each square cell. A bandwidth of 5 MHz allows two or more calls to be simultaneously supported at data rates up to 512 kb/s, as opposed to only 128 kb/s for three co-located antennas. On the uplink we distinguish between the computationally simpler equal-gain combining of the antenna signals and the possibly more complex maximum-ratio combining. With equal gain combining we achieve a peak data rate of 128 kb/s and a capacity gain of 2.5 dB relative to equal gain combining of three nearly co-located antenna signals. With maximum ratio combining the peak uplink rate can be as high as 512 kb/s and the capacity is increased by 2.0 dB relative to the maximum-ratio combining of three co-located antennas.     

Thermionic Emission as a Tool to Study Transport in Undoped nFinFETs

Thermally activated subthreshold transport has been investigated in undoped triple-gate MOSFETs. The evolution of the barrier height and of the active cross-sectional area of the channel as a function of gate voltage has been determined. The results of our experiments and of the tight-binding simulations we have developed are both in good agreement with previous analytical calculations, confirming the validity of the thermionic approach to investigate transport in FETs. This method provides an important tool for the improvement of device characteristics.      

Learning contextual relationships in mammograms using a hierarchical pyramid neural network

This paper describes a pattern recognition architecture, which we term hierarchical pyramid/neural network (HPNN), that learns to exploit image structure at multiple resolutions for detecting clinically significant features in digital/digitized mammograms. The HPNN architecture consists of a hierarchy of neural networks, each network receiving feature inputs at a given scale as well as features constructed by networks lower in the hierarchy. Networks are trained using a novel error function for the supervised learning of image search/detection tasks when the position of the objects to be found is uncertain or ill defined. We have evaluated the HPNN's ability to eliminate false positive (FP) regions of interest generated by the University of Chicago's (UofC) Computer-aided diagnosis (CAD) systems for microcalcification and mass detection. Results show that the HPNN architecture, trained using the uncertain object position (UOP) error function, reduces the FP rate of a mammographic CAD system by approximately 50% without significant loss in sensitivity. Investigation into the types of FPs that the HPNN eliminates suggests that the pattern recognizer is automatically learning and exploiting contextual information. Clinical utility is demonstrated through the evaluation of an integrated system in a clinical reader study. We conclude that the HPNN architecture learns contextual relationships between features at multiple scales and integrates these features for detecting microcalcifications and breast masses.     

Influence of metal gate and capping film stress on TANOS cell performance

In this work it is shown that film stress in the gate stack of TANOS NAND memories plays an important role for cell device performance and reliability. Tensile stress induced by a TiN metal gate deteriorates TANOS cell retention compared to TaN gate material. However, the erase saturation level as well as cell endurance is improved by the use of a TiN gate. This trade-off between retention and erase saturation for TANOS cells is elaborated in detail.     

Nth order current mode universal filter using MOCCCIIs

This article presents a new current mode single-input-multiple-output nth order universal filter. The proposed circuit employs (n + 1) number multiple output second generation current conveyors and n number grounded capacitors only. Presented circuits can realize current mode low pass, high pass, band pass, notch and all pass responses simultaneously at different high output impedance terminals. The current mode filter circuit provides low input impedance by selecting the proper value of bias current and also has high output impedance, which is suitable for cascading. The circuit offers some important features such as resistor less realization, no passive component matching constraints, low sensitivity, electronic tunability and active-C realization. The functionality of the proposed filter circuit is tested with the PSPICE simulation, which is found to agree well with the proposed theory.     

Solid-state intermetallic compound layer growth between copper and 95.5Sn-3.9Ag-0.6Cu solder

Long-term, solid-state intermetallic compound (IMC) layer growth was examined in 95.5Sn-3.9Ag-0.6Cu (wt.%)/copper (Cu) couples. Aging temperatures and times ranged from 70°C to 205°C and from 1 day to 400 days, respectively. The IMC layer thicknesses and compositions were compared to those investigated in 96.5Sn-3.5Ag/Cu, 95.5Sn-0.5Ag-4.0Cu/Cu, and 100Sn/Cu couples. The nominal Cu₃Sn and Cu₆Sn₅ stoichiometries were observed. The Cu₃Sn layer accounted for 0.4–0.6 of the total IMC layer thickness. The 95.5Sn-3.9Ag-0.6Cu/Cu couples exhibited porosity development at the Cu₃Sn/Cu interface and in the Cu₃Sn layer as well as localized “plumes” of accelerated Cu₃Sn growth into the Cu substrate when aged at 205°C and t>150 days. An excess of 3–5at.%Cu in the near-interface solder field likely contributed to IMC layer growth. The growth kinetics of the IMC layer in 95.5Sn-3.9Ag-0.6Cu/Cu couples were described by the equation x=x_o+Atⁿexp [−ΔH/RT]. The time exponents, n, were 0.56±0.06, 0.54±0.07, and 0.58±0.07 for the Cu₃Sn layer, the Cu₆Sn₅, and the total layer, respectively, indicating a diffusion-based mechanism. The apparent-activation energies (ΔH) were Cu₃Sn layer: 50±6 kJ/mol; Cu₆Sn₅ layer: 44±4 kJ/mol; and total layer: 50±4 kJ/mol, which suggested a fast-diffusion path along grain boundaries. The kinetics of Cu₃Sn growth were sensitive to the Pb-free solder composition while those of Cu₆Sn₅ layer growth were not so.     

Interdigitated back‐contact heterojunction solar cell concept for liquid phase crystallized thin‐film silicon on glass

We present an interdigitated back‐contact silicon heterojunction system designed for liquid‐phase crystallized thin‐film (~10 µm) silicon on glass. The preparation of the interdigitated emitter (a‐Si:H(p)) and absorber (a‐Si:H(n)) contact layers relies on the etch selectivity of doped amorphous silicon layers in alkaline solutions. The etch rates of a‐Si:H(n) and a‐Si:H(p) in 0.6% NaOH were determined and interdigitated back‐contact silicon heterojunction solar cells with two different metallizations, namely Al and ITO/Ag electrodes, were evaluated regarding electrical and optical properties. An additional random pyramid texture on the back side provides short‐circuit current density (j_SC) of up to 30.3 mA/cm² using the ITO/Ag metallization. The maximum efficiency of 10.5% is mainly limited by a low of fill factor of 57%. However, the high j_SC, as well as V_OC values of 633 mV and pseudo‐fill factors of 77%, underline the high potential of this approach. Copyright © 2015 John Wiley & Sons, Ltd.     

A Methodology for Architecture Exploration of Heterogeneous Signal Processing Systems

We present a methodology for the exploration of signal processing architectures at the system level. The methodology, named SPADE, provides a means to quickly build models of architectures at an abstract level, to easily map applications, modeled as Kahn Process Networks, onto these architecture models, and to analyze the performance of the resulting system by simulation. The methodology distinguishes between applications and architectures, and uses a trace-driven simulation technique for co-simulation of application models and architecture models. As a consequence, architecture models need not be functionally complete to be used for performance analysis while data dependent behavior is still handled correctly. We have used the methodology for the exploration of architectures and mappings of an MPEG-2 video decoder application.     

Co-RAM: combinational logic synthesis applied to softwarepartitions for mapping to a novel memory device

We introduce the application of current techniques for hardware synthesis of combinational logic blocks to large-scale software partitions for eventual implementation of these partitions in a novel memory device called "Co-RAM." The novelty of our approach is based upon the observation that a wide variety of largescale software functionality can be considered "stateless" by conventional hardware synthesis tools and so may be realized as combinational logic. By limiting the functions placed in memory to combinational functions, we eliminate conventional synchronization overhead associated with coprocessors. A significant aspect of Co-RAM is that it is a system design concept that inherently merges hardware and software design styles at the system level, impacting programming styles, system build approaches, and the programmer's view of the underlying machine. A direct consequence of viewing the functionality as combinational is that the system state is not partitioned with the tasks. By Considering Co-RAM functionality to be stateless with respect to system state, Co-RAM functionality is inlined around the advancement of effectively unpartitioned system state. The rules for procedural combinational logic synthesis are shown to apply to a wide variety of software partitions. Results of our investigation project speedups of 8× to 1000× for a range of algorithms of varying problem size and for projected devices ranging from conventional field programmable gate arrays (FPGAs) to highly specific combinational logic devices