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We analyze constant-voltage isotropic and non-isotropic scaling issues for phase change memory (PCM) based on electrothermal physics. Various analytical and simulation models of general and typical PCM cells that support the analysis is also provided. The analysis shows that the maximum temperature in the PCM cell, which is a key parameter for PCM operation, is independent of geometrical sizes and depends only on the voltage and material properties. This leads to the minimum programming voltage concept, which is determined by material properties of the phase change material. Constant-voltage scaling, electrothermal modeling, ovonic unified memory (OUM), phase change memory (PCM, phase change random access memory, PRAM), proximity disturbance, thermal disturbance.

Anacetrapib is a potent and selective CETP inhibitor and is undergoing phase III clinical trials for the treatment of dyslipidemia. A simple and sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the quantification of anacetrapib in rat plasma was developed and validated using an easily purchasable compound, chlorpropamide, as an internal standard (IS). A minimal volume of rat plasma sample (20 μL) was prepared by a single-step deproteinization procedure with 80 μL of acetonitrile. Chromatographic separation was performed using Kinetex C18 column with a gradient mobile phase consisting of water and acetonitrile containing 0.1% formic acid at a flow rate of 0.3 mL/min. Mass spectrometric detection was performed using selected reaction monitoring modes at the mass/charge transitions m/z 638 → 283 for anacetrapib and m/z 277 → 175 for IS. The assay was validated to demonstrate the selectivity, linearity, precision, accuracy, recovery, matrix effect and stability. The lower limit of quantification was 5 ng/mL. This LC-MS/MS assay was successfully applied in the rat plasma protein binding and pharmacokinetic studies of anacetrapib. The fraction of unbound anacetrapib was determined to be low (ranging from 5.66 to 12.3%), and the absolute oral bioavailability of anacetrapib was 32.7%.

Phase change memory (PCRAM) is an ideal embedded memory due to its simple BEOL process and low voltage operation. Industrial and automotive applications of PCRAM, however, have not been realized because of poor high temperature properties of the conventional Ge 2 Sb 2 Te 5 phase-change material [1–3]. We have previously reported a special Ge x Sb y Te z material along the Ge and Sb 2 Te 3 tie line that showed superior high temperature performance. In this work we have further enhanced our previous “golden” material by incorporating nitrogen and engineering the Ge/N concentration. In order to rapidly explore a range of new materials a fast method to test retention behavior by laser melt-quenching is adopted which yields retention data on blanket films consistent with device results. A new material with special Ge/N concentration with excellent high temperature retention is discovered. The new material demonstrated nearly 100% yield in a 256 Mb test chip after 160 oC, 84 hrs baking, with projected 10-year retention at 120 oC. (> 9,000 years at 85 oC.)

The oral (po) bioavailability of gemifloxacin mesylate in rats and its possible association with efflux transporters was investigated. The apparent permeabilities (Papp) of gemifloxacin across the Caco-2 cell monolayer were 1.20 ± 0.09 × 10(-5) cm/s for apical to basal (absorptive) transport, and 2.13 ± 0.6 × 10(-5) cm/s for basal to apical (secretory) transport for a 5-500 μM concentration range, suggesting the involvement of a carrier-mediated efflux in the secretory transport. The secretory transport in Caco-2 cells was significantly decreased by MRP2 (MK571) and BCRP (Ko143) inhibitors. The secretory transport was distinct in MDCKII/P-gp, MDCKII/MRP2 and MDCKII/BCRP cells, and the affinity was highest for MRP2, followed by BCRP and P-gp. The efflux was significantly decreased by verapamil and Ko143, but not significantly by MK571. The comparative po bioavailability in rats was increased by the preadministration of Ko143 (four-fold), MK571 (two-fold) and verapamil (two-fold). Efflux transporters appeared to significantly limit the bioavailability of gemifloxacin in rats, suggesting their possible contribution to the low bioavailability of the drug in the human (70%).

We study the effect of programming current on the endurance failure of phase change memory and propose a general scheme of optimizing programming currents for the most endurance cycles. We consider two major endurance failure modes, stuck-SET and open failure. We show that higher current does not necessarily cause, and even prevents the earlier open failure and attribute it to phase-dependent open-failure mechanisms. As for the stuck-SET failure, RESET current is optimized to balance material segregation effect and RESET current margin. The overall programming conditions are optimized by combining open and stuck-SET failure characteristic curves.

Operation impact on endurance performance in GST-based phase change memory is investigated from small arrays to large test chips. SET operation induced electromigration and phase segregation are observed. For the first time, the RESET melting healing effect is proposed to partially repair the SET induced damage and further extend the endurance. This concept can be easily implemented by accordingly designing the control circuits.

Historically, transition of memory technologies has been enabled by not only disruptive new features of the memory technology but also new applications which proved the core value of those new features. As improvement of prevalent memory technologies is becoming more challenging, many resources have been devoted to development of emerging memory technologies. In this regard, characteristics of emerging memory technologies such as PCM, STT-MRAM, and RRAM will be reviewed to evaluate its potential of becoming transformational memory technology.

Application of phase change memory (PCM) has been limited by the high power required to reset the device (changing from crystalline to amorphous state by melting the phase change material). Utilizing the poor thermal and electrical conductivity of TaN we have designed a simple structure that thermally insulates the bottom electrode and thus drastically reduces the heat loss. A 39nm bottom electrode with a TaN thermal barrier and 1.5nm of TiN conductor has demonstrated 30µA reset current, representing a 90% reduction. The benefit of thermal insulation is understood through electrothermal simulation, and the benefit is demonstrated in a 256Mb test chip. The low reset current also improves the reliability and excellent cycling endurance >1E9 is observed. This low power device is promising for expanding the application for PCM.

The increasing demand for high-capacity non volatile memories in the electronic portable and media applications has required continuous scaling of the conventional FLASH memory technology beyond perceived limits. At the same time, system designers envision the use of novel memory technology may revolutionalize the organization of the memory hierarchy of processors and the design of SoC and SiP. This has resulted in the exploration of many alternate memory technologies like PCM, RRAM, STTRAM. In this paper we discuss some of our recent works on understanding the various aspects of PCM and RRAM.

We report the thickness and phase dependent thermal properties of Ge 2 Sb 2 Te 5 (GST) films using electrical Joule heating thermometry (3ω method) and validate the data with optical thermometry. The intrinsic thermal conductivity of GST increases from 0.26 W/mK for the amorphous phase to 0.57 W/mK for the crystalline phase. The thermal boundary resistance between GST and Si 3 N 4 films decreases from 134×10−9 m2KW−1 to 25×10−9 m2KW−1 after the phase change. The effective thermal resistance of GST shows a nonlinear dependence on the film thickness that infers the presence of microstructural defects. We separate the contributions of defects from intrinsic thermal transport and summarize possible causes for their thickness dependent behavior. An electrothermal simulation of PCM cell estimates the potential impact of the measured properties. This work improves the quality of PCM simulations by offering detailed knowledge of the distribution of thermal resistances.

In this paper, we study thermal disturbance and its impact on reliability using a novel measurement structure - the micro-thermal stage (MTS). The small thermal time constant of the MTS extends the time-scale of temperature dependence measurement to ∼100 µs. The reliability of phase-change memory (PCM) is evaluated in terms of data retention and variation of the high resistance (RESET) state resistance (R RESET ) and the threshold switching voltage (V th ). We experimentally show how the impact of thermal disturbances on retention is accumulated and its dependence on the electric field. The thermal disturbance effect on RR RESET variation changes with time and it is the largest for the shortest time delay after RESET programming. Thermal disturbance can cause at least 25 and 100% variation for RR RESET and V th respectively in the given thermal disturbance scenario. We propose an effective method to exploit thermal disturbance to make multi-bit operation more robust.

1D thickness scaling study on a-GST has been successfully demonstrated without the help of ultra-fine lithography. V th linearly scales down to ∼0.65 V at 6 nm scale, showing that stable read operation is possible at elevated temperature (70 °C). Reset R drift shows no dependency on the a-GST thickness up to 6 nm regime. Thin a-GST shows enhanced thermal stability compared to thick a-GST.

This work measures both the out-of-plane and the inplane thermal conductivities of Ge 2 Sb 2 Te 5 (GST) films in the amorphous (a), face-centered-cubic (c), and hexagonal close packed (h) phases using the 3ω method. The out-of-plane thermal conductivity, k z , is first measured from a wide heater. The data include 0.17 W/mK for a-GST, 0.55 W/mK and 1.01 W/mK for c-GST of annealing temperature 150 °C and 200 °C respectively, and 2.85 W/mK for h-GST. The GST film is rf-sputtered with film thickness nearly 600 nm to capture significant lateral spreading from a narrow heater. The measured out-of-plane thermal conductivity is used in the multi-layer heat diffusion equation to deduce the in-plane thermal conductivity, k r . The measurements from the varying heater width reveal that the anisotropy ratio (η = k r /k z ) to be 1 for amorphous GST and ∼0.6 for different forms of crystalline GST. Electrothermal simulation demonstrates that the thermal conductivity anisotropy possesses potential impact on the designs of novel phase change memory that are based on lateral structure.

The distributed file system (DFS) provides a mechanism where a file can be stored across several physical computer nodes ensuring replication transparency and failure transparency. In order to achieve this, one important feature of DFS's data structure is to employ a proper way to organize the large scale data and file namespaces to provide a fast access speed. In order to analyze file namespace issue, we present the comparison among three major data structures, AVL, Red-Black (RB) and B trees which are popular for organizing file namespace for DFS. This paper also presents significant results obtained from our intensive experiments. From the results collected, we conduct a precise vision about the performance comparison of these data structures and propose that AVL tree is the most appropriate solution.

In a distributed file system, operations such as read, write, send and receive should be efficient and must increase the overall performance of the system. Especially every remote read and write operation we encounter network and secondary storage latencies. In order to reduce this latency time and improve the performance of distributed file system, we analyze the problem of selecting application-level buffer size for the network communication and disk input/output operations. A number of experiments were carried out to identify the optimal size for our application-level buffer.

Applications that process large volumes of data (such as, search engines, grid computing applications, data mining applications, etc.) require a backend infrastructure for storing data. The distributed file system is the central component for storing data infrastructure. There have been many projects focused on network computing that have designed and implemented distributed file systems with a variety of architectures and functionalities. In this paper, we develop a comprehensive taxonomy for describing distributed file system architectures and use this taxonomy to survey existing distributed file system implementations in very large-scale network computing systems such as Grids, Search Engines, etc. We use the taxonomy and the survey results to identify architectural approaches that have not been fully explored in the distributed file system research.

We demonstrate a novel phase change memory cell utilizing doped Ge nanowire pn-junction diode both as a bottom electrode and a memory cell selection device. This memory cell can be used for a cross-point memory array with diode selection. Using selective growth of isolated vertical nanowires in each cell, we have minimized the contact area below the lithography limit. A very low SET programming current of 10's of muA was achieved. RESET/SET resistance ratio of 100x was obtained. The diode provides 100x isolation between forward and reverse bias in the SET state.

Background: The purpose was to determine the cumulative longitudinal effects of upper extremity distributed practice with variable treatment protocols involving EMG-triggered neuromuscular stimulation and coupled bilateral movements. Methods: Sixteen chronic stroke subjects were randomly selected to complete 5 effective upper extremity treatment protocols over 12 months. The subjects were randomly assigned to 1 of 2 treatment orders. Consistent across the orders and protocols, the participants completed 90 min of training per day for 4 days during separate 2-week rehabilitation periods. Results: Data for the 5 primary outcome measures were analyzed in separate mixed design ANOVAs (treatment order × test session: 2 × 6). The analyses revealed distinct cumulative treatment evidence later in training in comparison to the baseline motor capabilities: (1) higher number of blocks moved; (2) higher percentage of blocks moved by the impaired hand; (3) faster motor reaction time (peripheral component), and (4) faster total reaction time. Conclusions: These chronic stroke patients displayed robust cumulative motor improvement effects from the longitudinally distributed practice of active neuromuscular stimulation and coupled bilateral movements.

Background: Curcumin (CUR) is a polyphenolic component derived from an herbal remedy and dietary spice turmeric (Curcuma longa). Objective: The aim of this study was to investigate inhibitory effects of CUR on in vitro cytochrome P450 (CYP) activity and in vivo pharmacokinetic consequences of single CUR dose in rats. Materials and Methods: An in vitro CYP inhibition study in rat liver microsomes (RLM) was conducted using probe substrates for CYPs. Then, an in vivo pharmacokinetics of intravenous buspirone (BUS), a probe substrate for CYP3A, was studied with the concurrent administration of oral CUR in rats. Results: In the in vitro CYP inhibition study, CUR inhibited the CYP3A-mediated metabolism of testosterone (TES) with a half maximal inhibitory concentration of 11.0 ± 3.3 μM. However, the impact of a single oral CUR dose on the pharmacokinetics of BUS in rats is limited, showing that CUR cannot function as an inhibitor for CYP3A-mediated drug metabolism in vivo. Conclusion: To the best of our knowledge, our results are the first reported data regarding the inhibition of in vitro CYP3A-mediated metabolism of TES and the in vivo impact of a single CUR dose on the pharmacokinetics of BUS in rats. Further study is required to draw a confirmative conclusion on whether CUR can be a clinically relevant CYP3A4 inhibitor. SUMMARY CUR can inhibit the in vitro CYP3A-mediated metabolism of TES in RLM. However, the impact of a single oral CUR dose on the pharmacokinetics of BUS in rats is limited, showing that CUR cannot function as an inhibitor for CYP3A-mediated drug metabolism in vivo.

Random Access Channel (RACH) of WCDNIA system is the common uplink channel that can be used to send call request message or short packet data. However, RACH could be the interference source against traffic channels. The amount of interference power generated by RACH depends on the setting of RACH parameters such as the target Signal to Interference Ratio (SIR) of preamble and the ramp step size. When the target SIR becomes higher, RACH performance, such as access success ratio, gets improved. However, the interference caused by RACH is getting severe and can degrade the quality of traffic channels. If the target SIR becomes lower, the retransmissions of preamble can occur frequently to obtain a desirable RACH performance, and then the interference level can be increased by the retransmissions. In this paper, we analyze the uplink traffic channel capacity for a level of RACH performance in WCDMA system. The retransmission probabilities of preamble on the fast fading environment are derived by a simulation developed. The simulation results are applied to the Erlang capacity formula of uplink traffic channel. Then we drive the capacity as functions of RACH parameters. Results show that the uplink traffic channel capacity can be maximized by setting the RACH parameters carefully.

In this paper, we present a generalized scaling analysis for phase change memory in analytical forms which are verified by 3D finite-element electrothermal modeling. Our analytical solutions provide insights into the key device parameters that control the maximum temperature of the phase change memory cell and the minimum required programming voltage

Computer modeling is reported about the creation and pinning of a magnetic vortex-antivortex (V-AV) pair in a superconducting thin film, due to the magnetic field of a vertical magnetic dipole above the film, and two antidot pins inside the film. For film thickness $= 0.1\xi$, $\kappa = 2$, and no pins, we find the film carries two V-AV pairs at steady state in the imposed flux range $2.10\Phi_0 < \Phi^+ < 3.0\Phi_0$, and no pairs below. With two antidot pins suitably introduced into the film, a single V-AV pair can be stable in the film for $\Phi^+ \ge 1.3\Phi_0$. At pin separation $\ge 17\xi$, we find the V-AV pair remains pinned after the dipole field is removed, and, so can represent a 1 for a nonvolatile memory., Comment: 8 pages, 6 figures

Motor improvements in chronic stroke recovery accrue from coupled protocols of bilateral movements and active neuromuscular stimulation. This experiment investigated coupled protocols and within-limb transfer between distal and proximal joint combinations. The leading question focused on within-limb transfer of coupled protocols on distal joints to a bimanual aiming task that involved proximal joints. Twenty-six volunteers completed one of three motor recovery protocols according to group assignments: (1) coupled bilateral involved concurrent wrist/finger movements on the unimpaired limb coupled with active stimulation on the impaired limb; (2) unilateral/active stimulation involved neuromuscular electromyogram-triggered stimulation on the impaired wrist/fingers; and (3) no protocol (control group). During the pretest and posttest, subjects performed transverse plane target aiming movements (29 cm) with vision available. The coupled bilateral group showed positive intralimb transfer post-treatment when both arms moved simultaneously. During the posttest, the coupled bilateral group displayed improved movement time, higher peak limb velocity, less variability in peak velocity, and less percentage of total movement time in the deceleration phase than during the pretest. The evidence confirms that within-limb transfer from distal joint training to proximal joint combinations is viable and generalizable in chronic stroke rehabilitation. Moreover, these intralimb transfer findings extend the evidence favoring motor improvements for coupled bilateral protocols during chronic stroke.

A numerical scheme to study the mixed states in a mesoscopic type-II superconducting cylinder is described. Steady-state configurations and transient behavior of the magnetic vortices for various values of the applied magnetic field H are presented. Transitions between different multi-vortex states as H is changed is demonstrated by contour plots and jumps in the B vs H plot. Evolving a uniformly-superconducting initial state using the simplest set of relaxation equations shows that the system passes through nearly metastable intermediate configurations, while seeking the final minimum-energy, steady state consistent with the square symmetry of the sample. An efficient scheme to determine the equilibrium vortex configuration in a mesoscopic system at any given applied field, not limited to the symmetry of the system, is devised and demonstrated., 10 pages, 6 figures, 1 table. Submitted to Physical Review B

This paper presents hierarchical cell deployment strategies for high-speed data CDMA systems. The hierarchical cell structure has been considered as a method to improve the quality of service and increase the system capacity. We evaluate the performance of the hierarchical system with one embedded micro-cell. We show that the system capacity is dependent on the location of the micro-cell site and its transmission power. Then, two different deployment strategies for hierarchical systems with multiple micro-cells are proposed and compared. The analysis results show that the cell throughput can be maximized by co-locating micro and macro-cell site with different frequency bands. On the other hand, it is shown that both the fairness of the QoS and the cell throughput is improved by deploying a micro-cell at the edges of the macro-cell.

This paper presents the design and impementation of MPI_Rejoin() for MPICH-GF, a grid-enabled fault tolerant MPICH implementation. To provide fault tolerance to the MPI applications, it is mandatory for a failed process to recover and continue execution. However, current MPI implementations do not support dynamic process management and it is not possible to restore the information regarding communication channels. The ‘rejoin’ operation allows the restored process to rejoin the existing group by updating the corresponding entries of the channel table with the new physical address. We have verified that our implementation can correctly reconstruct the MPI communication structure by running NPB applications. We also report on the cost of ‘rejoin’ operation.

This paper presents the performance of a double dwell acquisition system with a continuous integration detector. In the acquisition system, the first dwell output is combined with the second dwell output to yield the final decision variable. The mean acquisition time is derived and analyzed for the acquisition system.

Since so many potentials of QoS degradation, it is difficult to predict the QoS degradation of VBR MPEG video application under high-speed network environment. The general procedure of the call admission requires the QoS contract between the users and the network. But, various statistical properties of the source traffic and its hard estimation make it difficult to satisfy the QoS contract. In this paper, we propose the measurement-based cell-rate autocorrelation function as the criterion of estimation on QoS degradation. The analysis of the power spectrum of MPEG video with P-MMBBP traffic modeling is ventured. Simulation results show that QoS degradation of the input traffic, particularly delay is closely related to the power spectrum. Furthermore, a new method of the pricing scheme based on the power spectral analysis is proposed and analyzed.

Background and Purpose —After stroke, many individuals have chronic unilateral motor dysfunction in the upper extremity that severely limits their functional movement control. The purpose of this study was to determine the effect of electromyography-triggered neuromuscular electrical stimulation on the wrist and finger extension muscles in individuals who had a stroke ≥1 year earlier. Methods —Eleven individuals volunteered to participate and were randomly assigned to either the electromyography-triggered neuromuscular stimulation experimental group (7 subjects) or the control group (4 subjects). After completing a pretest involving 5 motor capability tests, the poststroke subjects completed 12 treatment sessions (30 minutes each) according to group assignments. Once the control subjects completed 12 sessions attempting wrist and finger extension without any external assistance and were posttested, they were then given 12 sessions of the rehabilitation treatment. Results —The Box and Block test and the force-generation task (sustained muscular contraction) revealed significant findings ( P Conclusions —Two lines of evidence clearly support the use of the electromyography-triggered neuromuscular electrical stimulation treatment to rehabilitate wrist and finger extension movements of hemiparetic individuals ≥1 year after stroke. The treatment program decreased motor dysfunction and improved the motor capabilities in this group of poststroke individuals.

While atomic vibrations dominate thermal conduction in the amorphous and face-centered cubic phases of Ge2Sb2Te5, electrons dominate in the hexagonal closed-packed (hcp) phase. Here we separate the electron and phonon contributions to the interface and volume thermal resistances for the three phases using time-domain thermoreflectance and electrical contact resistance measurements. Even when electrons dominate film-normal volume conduction (i.e., 70% for the hcp phase), their contribution to interface heat conduction is overwhelmed by phonons for high-quality interfaces with metallic TiN.

We analyze the controlled behavior of light propagation in a stratified Kerr-nonlinear medium with its photonic band structure tuned by applying an external electric field. The transmittance T of light is significantly influenced by nonlinear effects induced by both the external field and the incident light. Transmission resonance (T = 1) is induced by two mechanisms, band-edge resonance and gap soliton resonance. The T?Eex graph has two turning points and consists of three solution branches. One unstable branch is located between the turning points, and connected with a stable solution branch at each turning point. As Eex increases and then decreases through the region of the turning points, the transition between the stable states on different branches produces optical bistability and hysteresis. As input light intensity grows, the upper stable solution branch separates itself from the unstable branch at the turning point, and both branches extend down to the ordinate axis at Eex = 0. We have greatly enhanced single-envelope solitons on the upper stable branch from the separation point to the line of zero external field.

We report on the stability of high-permittivity (high-k) TiO2 films incorporated in metal-oxide-silicon capacitor structures with a TiN metal gate electrode, focusing on oxygen migration. Titanium oxide films are deposited by either Ti sputtering [physical vapor deposition (PVD)] followed by radical shower oxidation or by plasma-enhanced atomic layer deposition (PEALD) from titanium isopropoxide (Ti{OCH(CH3)2}4) and O2 plasma. Both PVD and PEALD films result in near-stoichiometric TiO2 prior to high-temperature annealing. We find that dopant activation anneals of TiO2-containing gate stacks at 1000 °C cause 5 A or more of additional SiO2 to be formed at the gate-dielectric/Si-channel interface. Furthermore, we demonstrate for the first time that oxygen released from TiO2 diffuses through the TiN gate electrode and oxidizes the poly-Si contact. The thickness of this upper SiO2 layer continues to increase with increasing TiO2 thickness, while the thickness of the regrown SiO2 at the gate-dielectric/Si inter...

A computational study of the second-harmonic generation in one-dimensional photonic crystals made of GaAs and AlAs with quadratic optical nonlinearity and material dispersion is presented. The computational approach uses a shooting method to solve nonlinear wave equations for coupled fundamental and second-harmonic fields and the invariant imbedding method to obtain the linear transmittance and group index spectra. The photonic crystal is built with an elementary cell consisting of four sublayers whose thicknesses are systematically varied. Doubly-resonant second harmonic generation with high conversion efficiency is achieved by choosing the geometrical parameters of the elementary cell optimally and controlling the band structure.

Thermal conduction in GeSbTe films strongly influences the writing energy and time for phase change memory (PCM) technology. This study measures the thermal conductivity of Ge2Sb2Te5 between 25 and 340°C for layers with thicknesses near 60, 120, and 350nm. A strong thickness dependence of the thermal conductivity is attributed to a combination of thermal boundary resistance (TBR) and microstructural imperfections. Stoichiometric variations significantly alter the phase transition temperatures but do not strongly impact the thermal conductivity at a given temperature. This work makes progress on extracting the TBR for Ge2Sb2Te5 films, which is a critical unknown parameter for PCM simulations.

Second harmonic generation efficiency in one-dimensional photonic crystals with material dispersion is calculated. The computational approach uses a shooting method to solve the wave equation for fundamental and second harmonic fields.