bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Generation and Transport in SOI and GOI Devices
Authors: Pop Eric
Published: April 2007

This paper surveys recent progress in our understanding of heat generation and transport in nanoscale transistors. Monte Carlo simulations show that under quasi-ballistic transport conditions, most Joule heat is generated in the device drain. Measurements and modeling find the device thermal resistance scales inversely with device size, reaching well over 100 K/mW for sub-100 nm transistors. This trend is partly also driven by decreased thermal conductivity of ultra-thin films, as well as the increased role of boundary thermal resistance. Somewhat surprisingly, the analysis shows that well-behaved GOI transistors ought to outperform SOI from a thermal viewpoint as well, highlighting the importance of electro-thermal co-design at device length scales approaching 10 nm.
Non-Contact Photoelectric Method For Thin SOI Characterization
Authors: Tsidilkovski Edward , Steeples Kenneth
Published: April 2007

A non-contact photoelectric measurement method for accurate and rapid determination of silicon film thickness in thin SOI has been developed. A simple model, which explains the measurements, is proposed. An excellent correlation of the measurement results to the data obtained with a standard optical technique has been demonstrated.
Analysis of Trench Gate Power LDMOS Transistors in Thin SOI Technology
Authors: Cortes Ignasi , Fernández-Martinez Pablo , Flores David , Hidalgo Salvador , Rebollo José
Published: April 2007

The on-state performance of conventional thin SOI power LDMOS transistors can be further improved by implementing a wide trench gate partially filled with polysilicon, leading to asymmetric oxide characteristics. The on-state resistance of the analyzed TGLDMOS structure is lower than that of the LDMOS counterpart, but the structure design has to be optimized to minimize the added contributions to the parasitic capacitances. For this purpose, a modified TGLDMOS is proposed to reduce the gate-drain capacitance and to increase the cut-off frequency. The trench is modeled and simulated in this work with special emphasis on the gate-drain capacitance. An extensive simulation study has corroborated the expected electrical performance improvements of both TGLDMOS and modified TGLDMOS power transistors for 80 V switching and amplifying applications.
Simple Analytical Model to Study the ZTC Bias Point in FinFETs
Authors: Bellodi Marcello , Camillo Luciano Mendes , Martino Joao Antonio A. , Simoen Eddy , Claeys Cor
Published: April 2007

In this work we present a simple analytical model to study the Zero Temperature Coefficient (ZTC) bias point in FinFETs operating from room temperature up to 573 K. Three-dimensional simulations are carried out and compared with experimental results to qualify the results.
Temperature Influences on FinFETs with Undoped Body
Authors: Pavanello Marcelo A. , Martino Joao Antonio A. , Simoen Eddy , Rooyackers Rita , Collaert Nadine , Claeys Cor
Published: April 2007

This work presents a study, based on DC measurements, of the temperature influence on the performance of nMOS triple-gate FinFETs with high-K dielectrics, TiN gate material and an undoped body. FinFETs show smaller threshold voltage variations with temperature than planar fully-depleted SOI MOSFETs. The subthreshold slope reduced with the temperature and approached the ideal value at lower temperatures. In the temperature range under study the mobility increases linearly as the temperature is reduced and the dominating mobility degradation factor is phonon scattering. The DIBL has been evaluated and no temperature dependence has been found. Finally, the series resistance has been also extracted and demonstrates a reduction as the temperature is reduced due to the mobility improvement.
Application of Double Gate Graded-Channel SOI in MOSFET-C Balanced Structures
Authors: Doria Rodrigo T. , Pavanello Marcelo A. , Cerdeira Antonio , Raskin Jean-Pierre , Flandre Denis
Published: April 2007

This work studies the linearity of conventional and Graded- Channel (GC) Gate-All-Around (GAA) devices when applied in 2- MOS and 4-MOS balanced structures operating as tunable resistors. The study has been performed through device characterization and two-dimensional process and device simulations. Total harmonic distortion (THD) and third order harmonic distortion (HD3) have been evaluated. When taking into account similar on-resistance, the use of the GC GAA transistors in both 2-MOS and 4-MOS structures improves the linearity. The use of GC GAA devices in 2-MOS balanced structures allows a reduction of the gate overdrive voltage of 22.5% without degrading THD and HD3. On the other hand, the use of GC GAA devices in 4-MOS structures leads to an improvement in both HD3 and THD by 7 dB for devices with similar channel length at the same gate voltage overdrive.
Strained Silicon Directly on Insulator (SSOI): Biaxial, Uniaxial, or Hybrid Strain?
Authors: Thean Aaron
Published: April 2007

This paper reviews the development of uniaxial and biaxial strain silicon technologies and how they may be combined through strain engineering of SSOI substrates. Through a novel method of selective biaxial-uniaxial strain hybridization, this work demonstrates a scalable enhanced SSOI CMOS technology. With this mixed-strain approach, nFET uniaxial strain can be amplified by the substrate strain platform while SSOI pFETs can be enhanced beyond conventional single unaxially-strained or biaxially-strained Si. This can be accomplished with minimal process complexity cost.
LEGO Process for Mixed Power Applications: Fabrication at Low Cost of Localized Thick SOI Layers
Authors: Bertrand Isabelle , Dilhac Jean-Marie R. , Renaud Philippe , Bafleur Marise , Ganibal Christian
Published: April 2007

In this paper, we present the low cost fabrication process of a partial and thick silicon-on-insulator (SOI) substrate for mixed power integration (low and high voltage devices on the same chip). It is based on the Lateral Epitaxial Growth over Oxide process (LEGO). It is shown that the proposed process provides a crystalline quality compatible with a CMOS technology and high voltages devices.
Strained Silicon-On-Insulator - Fabrication and Characterization
Authors: Reiche Manfred , Himcinschi C. , Gösele U. , Christiansen S. , Mantl S. , Buca D. , Zhao Q.T. , Feste S. , Loo R. , Nguyen D. , Buchholtz W. , Wei A. , Horstmann M. , Feijoo D. , Storck P.
Published: April 2007

SSOI substrates were successfully fabricated using He+ ion implantation and annealing to relax thin (< 500nm) SiGe buffer layers, bonding and layer transfer processes to realize strained-Si layers onto oxide layers. The reduced thickness of the SiGe buffer possess numerous advantages such as reduced process costs for epitaxy and for reclaim of the handle wafer if the layer splitting is initiated in the SiGe/Si interface. The electron mobilities in the fabricated SSOI layers were measured using transistors with different gate lengths. An electron mobility of ~530 cm2 /Vs was extracted, being much higher than in non-strained SOI substrates. Furthermore, an 80% drive current (IDSAT) improvement has been measured for long channel devices.
Impact of Phonon-Limited Mobility Superiority in Double-Gate or Fin FET with a (111) Si and (001) Ge Surface Channel on Device Scaling
Authors: Yamamura Tsuyoshi , Sato Shingo , Omura Y.
Published: April 2007

1D self-consistent calculations and relaxation time approximations are used to study the phonon-limited electron mobility of the inversion layer at room temperature for ultra- thin Si (111), Ge (001) and Ge (111) layers in single-gate (SG) and double-gate (DG) MOSFET's. Assuming a 5-nm-thick SOI layer, it is shown that intra-valley phonon scattering in the DG SOI MOSFET inversion layer is strongly suppressed within a range of medium Eeff value; DG devices have higher phonon- limited electron mobility than SG devices. The suppression of intra-valley phonon scattering in a 5-nm TSOI DG device primarily stems from the reduction of the form factor (F00) value within medium Eeff values. Similar aspects of electron mobility expected for SG and DG GOI MOSFET's are also discussed.
Dislocation-Free Growth of III-V-N Alloys on Si and its Application to Monolithic OEICs
Authors: Yonezu Hiroo , Furukawa Yuzo , Wakahara Akihiro
Published: April 2007

Structural defect-free GaPN and InGaPN layers were grown on a Si substrate. LEDs and Si MOSFETs, which are elemental devices for OEICs, were monolithically merged in a single chip with a Si layer and an InGaPN/GaPN double hetereostructure layer grown on a Si substrate. The developed processing flow was based on a conventional MOSFET processing flow. It was confirmed that light emission from the LED was modulated by switching the MOSFET. The growth and fabrication process technologies are effective for the realization of monolithic OEICs.
Optoelectronic Properties for ZnO and Related Semiconductors in Various Nanoscale Geometries
Authors: Yang Jianyong , Yamanaka Takayuki , Sun Ke , Stroscio Michael A. , Dutta Mitra , Zhong Jian , Chen Hanhong , Saraf Gaurav , Lu Yicheng
Published: April 2007

Zinc oxide, ZnO, is a direct wide bandgap semiconductor, with a large exciton binding energy (60 meV). Many of its properties promise great potential for many optoelectronic device applications. In order to explore the nanoscale device applications and gain more understanding of the ZnO material, our research has focused on the optical characterization of several ZnO samples including both films and nanorods (nanotips) grown on different substrates. We will present experimental results of photoluminescence (PL) as a function of temperature and Raman scattering data at room temperature (RT). The spontaneous polarization in ZnO and GaN will be modeled and compared for these two similar wurtzite wide band gap materials. Finally, we will present the calculations of the electron and hole transmission mini bands in a three dimensional matrix of colloidal ZnO quantum dots and conductive polymers also a promising material in optoelectronic device applications.
Mechanism of Interlayer Dielectric Penetration Caused by Al Interconnection and Preventive Measures
Authors: Tanimoto Satoshi , Oohashi Hiromichi , Arai Kazuo
Published: April 2007

A reaction mechanism is proposed for the interlayer dielectric erosion that occurs in Al interconnect 4H-SiC DMOS devices at 500{degree sign}C. Based on this mechanism, three countermeasures are devised and implemented in various combinations. It is shown that the medium time to failure can be improved by two orders of magnitude.
Effects of RTA-treated ZnO/Quartz Thin Films on the Structural and Optical Properties
Authors: Hu Sheng-Yao , Lee Yueh-Chien , Water Walter , Huang Jen-Ching , Lee Jyh-Wei , Shen Ji-Lin , Tan Shih-Wei
Published: April 2007

ZnO thin films have been successfully grown on the quartz substrate by RF magnetron sputtering technique. The effects of rapid thermal annealing (RTA) on the structural and optical properties has been investigated by means of X-ray diffraction (XRD), atomic force microscopy (AFM) and photoluminescence (PL) measurements. The structural defects of ZnO thin films were reduced during the RTA processes and the crystallinity was improved after the RTA treatments. It is also found out that RTA treatments can remarkably improve the ZnO crystallinity and enhance the UV emission in the wavelength range of 335 - 450 nm over the annealing temperature range of 600 - 800 degree.
Low Temperature GaN Epitaxy Using Ga(mDTC)3 Precursor
Authors: Park Chinho , Kim Do-Hoon , Yoon Deoksun , Jung Woo-Sik , Joo Hyeong Uk , Umme Farva
Published: April 2007

GaN thin film growth using vapor-phase epitaxy is a well- studied process that typically requires growth temperatures in the range of 950~1000{degree sign}C. Tris(N,N- dimethyldithiocarbamato)- gallium(III) (Ga(mDTC)3) was investigated in this study, a new precursor material for the GaN film deposition by hot-wall VPE technique, in an effort to reduce the growth temperature. TMGa, HCl and NH3 were used as gas source precursors. Parametric growth studies were performed to optimize the growth temperature and the distance between the gas outlet and the substrate (z-position) using this process. The optimal growth temperature was found to be 850 {degree sign}C, and the optimal z- position was determined to be in the range of 12.5 to 15 cm. XRD studies showed that this growth method produces high- crystalline GaN thin films at relatively lower deposition temperature compared to existing growth techniques.
High Density Inductively Coupled Plasma Etching of Zinc-Oxide(ZnO) and Indium-Zinc Oxide(IZO)
Authors: Lim Wantae , Stafford Luc , Gila Brent , Norton David , Pearton Steve , Ren Fan , Song Ju-Il , Park Jae-Soung , Heo Young-Woo , Lee Joon-Hyung , Kim Jeong-Joo
Published: April 2007

The dry etching characteristics of bulk single-crystal zinc- oxide (ZnO) and RF-sputtered indium-zinc-oxide (IZO) films have been investigated using an inductively coupled high- density plasma in Ar/IBr and Ar/BI3. In both plasma chemistries, the etch rate of ZnO is very similar to that of IZO, which indicates that zinc and indium atoms are driven by a similar plasma etching dynamics. IBr and BI3-based plasmas show no enhancement of the etch rate over pure physical sputtering under the same experimental conditions. Also, CH4/H2 -based discharges are attractive for dry etching of single crystal ZnO because of their non-corrosive nature. The C2H6/H2/Ar mixture provides a strong enhancement over pure Ar sputtering, in sharp contrast to the case of CH4/H2/Ar. The etched surface morphologies were smooth, independent of the chemistry and the Zn/O ratio in the near-surface region was unchanged within experimental error after etching with all chemistries.
Influence of Base Passivation on the Optical Performance of Dual-Emitter Heterojunction Phototransistors
Authors: Tan Shih-Wei , Chen Wei-Tien , Chen Hong-Rung , Hsu Meng-Kai , Chiu Shao-Yen , Lour Wen S.
Published: April 2007

N-p-n InGaP/GaAs Dual-Emitter heterojunction phototransistor (DEPT) with/without InGaP-passivation layer have been fabricated to investigate the influence of surface leakage on the device optical performance. The comparison between DEPT with a voltage-biased emitter and HPT with a voltage-biased base is also included. There are four (three) operating regions appearing in the optical characteristics of the DEPT (HPT): negative-saturation, negative-tuning, positive-tuning, and positive-saturation (cut-off, tuning, and saturation) regions. The InGaP-passivated DEPT with the extrinsic base surface passivated by InGaP, exhibits the maximum optical gains of 46.57, 46.86 and 47.39 while the non-passivated one shows those of 32.02, 33.55 and 33.57 under the optical powers of 8.62, 13.2 and 17.5 μW, respectively. However, the optical gains are only in the range of 0.93~2.0 (0.83~1.64) for the InGaP- passivated HPT (non-passivated HPT) for all the illuminating conditions.
Robust Detection of Hydrogen Using Differential AlGaN/GaN High Electron Mobility Transistor Sensing Diodes
Authors: Wang Hung-Ta , Anderson Travis , Ren Fan , Li Changzhi , Low Zhen-Ning , Lin Jenshan , Gila Brent , Pearton Steve , Dabiran Amir , Osinsky Andrei
Published: April 2007

The use of AlGaN/GaN High Electron Mobility Transistor differential sensing diodes is shown to provide robust detection of 1% H2 in air at 25{degree sign}C.The active device in the differential pair is coated with 10 nm of Pt to enhance catalytic dissociation of molecular hydrogen, while the reference diode is coated with Ti/Au. The active diode in the pair shows an increase in forward current of several mA at a bias voltage of 2.5V when exposed to 1%H2 in air. The use of the differential pair removes false alarms due to ambient temperature variations. A wireless module is demonstrated to successfully detect hydrogen leakage.
Understanding and Controlling Pore Etching in Semiconductors
Authors: Foell Helmut , Carstensen Juergen , Foca Eugen , Leisner Malte
Published: April 2007

The paper first compares pore formation in semiconductors, and then turns to some common features found in all semiconductors. In particular, the appearance of some kind of self- organization, expressed as pattern formation in time (e.g. self- induced current oscillations) or in space (e.g. pore crystal formation), will be discussed. A stochastic model of the electrode dissolution via oxidation, implemented in a Monte- Carlo algorithm, can reproduce some of these phenomena quite closely, and the paper will give some new results. For a deeper understanding of pore etching as well as for some control of etching parameters over etching time, it is necessary to have some in-situ measurements that contain data about what is going on at the pore tips deep inside the sample. It will be shown that Fast-Fourier Transform (FFT) impedance spectroscopy (IS) is principally suited to the task. The method gains even more power if photo impedance , i.e. modulation of the backside or frontside illumination and monitoring the current response, is used in conjunction with suitable theoretical models. Extending FFTIS to other semiconductor like InP or to basic processes like anodic oxidation provides new insights; this will be demonstrated for the case of anodic oxidation in a range of organic electrolytes often used for pore etching in p-type semiconductors.
Electrophoretic Deposition of Template-Free ZnO Nanorod Films
Authors: Hara Yukihiro , Brownson Jeffrey R. , Anderson Marc A.
Published: April 2007

ZnO nanorods were synthesized by hydrothermal coarsening of quantum dots. The length of the nanorods and degree of asymmetry increased with higher Zn and LiOH concentrations. Particles were deposited by cathodic electrophoresis on transparent conductive oxide substrates from isopropanolic suspensions. As particle asymmetry increased, homogeneous films were deposited with preferred horizontal orientation. Commercially available ZnO nanopowders yielded inhomogeneous films and showed no preferred orientation with electrophoretic deposition.
PbTe - PbSe Superlattice Formation by Electrochemical Atomic Layer Deposition
Authors: Stickney J. , Banga Dhego
Published: April 2007

We report on an investigation of the formation of PbTe - PbSe superlattices using electrochemical atomic layer deposition (ALD). Characterization involves glancing incident X-ray diffraction, using a Scintag PAD V equipped with a thin film attachment, and using Cu Kα radiation. This report describes changes in the X-ray diffraction pattern resulting from adjustment of the superlattice period. The period is defined by the number of ALD cycles of PbTe and PbSe, performed for the deposition. Adjustment of the period results in expected changes in the positions of satellite peaks in the XRD pattern, adjacent to the (111) peak. Deposits were found to be essentially stoichiometric, as determined using electron probe micro analysis. In addition, the ratio of PbTe to PbSe cycles followed the relative numbers of cycles.
A Significant Anodic Passivation of n and p-InP Surfaces in Liquid Ammonia: First Evidence of Stable Phosphorus-Nitrogen Bonds
Authors: Goncalves Anne-Marie , Seitz Oliver , Eb Alexandra , Mathieu Charles , Herlem Michel , Etcheberry A.
Published: April 2007

The anodic electrochemical treatment in liquid ammonia of InP (n- and p-) leads to a simultaneous oxidation of both semiconductor and solvent. The oxidation of InP takes place through a passivating layer revealed as well by electrochemistry as by XPS. The chemical composition of InP surface is therefore gradually modified according the anodic charge. The composition of the film layer is supposed to be close to HN=P-NH2, a promising compound stable as well in liquid ammonia as in water.
In-situ IR Spectroscopy to Study Anodic Oxidation of Si(111) in KOH Solution
Authors: Philipsen Harold , Chazalviel Jean-Noel , Allongue Philippe , Ozanam François
Published: April 2007

Fourier Transform Infrared (FTIR) spectroscopy was used to study in-situ the anodic oxidation of n-type Si(111) in KOH solution. Changes in surface chemistry were followed during oxide growth. The results are considered on the basis of a model developed from electrochemical measurements.
Characterization and Modeling of Dye-Sensitized Solar Cells
Authors: Peter Laurence
Published: April 2007

The physical and chemical processes taking place in the dye- sensitized nanocrystalline solar cell (DSC) are reviewed and related to cell performance. Modeling of the steady-state and transient response of the DSC is developed within the framework of the generation/collection/recombination problem. Experimental methods for DSC characterization are described, and models for interfacial electron transfer and electron transport manuscript are outlined. The discussion is illustrated by selected experimental examples.
Electrochemical Deposition of Copper onto Silicon
Authors: daRosa Calvin P. , Iglesia Enrique , Maboudian Roya
Published: April 2007

The open-circuit deposition of copper onto silicon rotating disks has been studied to determine the deposition mechanism and the effects of deposition conditions on the properties of the resulting copper films. Cu2+ reduction limits the rate when HF is present in large excess, and Si oxidation and dissolution limit the rate at lower ratios of [HF] to [CuSO4]. The rate-limiting process strongly affects the resulting film properties, as the Cu films are smoother and more reflective when Cu2+ reduction limits the rate. Deposition rates increased with increasing rotating speed, and Cu2+ was found to be the diffusion- limited species over a wide range of CuSO4 (0.001- 0.04 M) and HF (0.02-0.4 M) concentrations. Open circuit potential measurements confirmed that Cu2+ was the species responsible for diffusion limitations through the external boundary layer.
Inhibition of cytochromeP-450 C17 enzyme by a GnRH agonist in ovarian follicles from gonadotropin-stimulated rats
Authors: Irusta Griselda , Parborell Fernanda , Tesone Marta
Published: April 2007

Our objective was to study the direct action of a GnRH-I agonist, leuprolide acetate (LA), on ovarian steroidogenesis in preovulatory follicles obtained from equine chorionic gonadotropin (eCG)-treated rats. Previously, we have demonstrated an inhibitory effect of LA on steroidogenesis and follicular development. In this study, we tested the hypothesis that gonadotropin-releasing hormone (GnRH) exerts its negative effect on follicular development by inhibiting thecal cytochrome P-450 C17 (P450C17) α-hydroxylase expression and, consequently, androgen synthesis. Studies were carried out in prepubertal female rats injected with either eCG (control) or eCG plus LA (LA) and killed at different time points. Immunohistochemical studies indicated that LA induced steroidogenic acute regulatory protein (StAR) expression mainly in theca cells of preantral and antral follicles. In addition, serum progesterone levels increased significantly ( P < 0.05), whereas those of androsterone decreased ( P < 0.05) after 8 h of LA treatment. This inhibition caused by LA seemed to be a consequence of the decreased expression of follicular P450C17 α-hydroxylase, as demonstrated by Western blot and RT-PCR techniques. In vitro studies using follicles isolated from 48-h-eCG-treated rats and cultured with LA showed a significant ( P < 0.05) inhibition of FSH-induced androsterone follicular content as well as P450C17 α-hydroxylase protein levels, as determined by Western analysis. However, LA increased StAR protein expression in these follicles without significant changes in P450scc enzyme levels. Taking all these findings into account, we suggest that GnRH-I exerts a direct inhibitory action on gonadotropin-induced follicular development by decreasing the temporal expression of the P450C17 enzyme and, consequently, androgen production, thus reducing the supply of estrogens available to developing follicles.
Pathogenic angiogenesis in IBD and experimental colitis: new ideas and therapeutic avenues
Authors: Chidlow John H. , Shukla Deepti , Grisham Matthew B. , Kevil Christopher G.
Published: April 2007

Angiogenesis is now understood to play a major role in the pathology of chronic inflammatory diseases and is indicated to exacerbate disease pathology. Recent evidence shows that angiogenesis is crucial during inflammatory bowel disease (IBD) and in experimental models of colitis. Examination of the relationship between angiogenesis and inflammation in experimental colitis shows that initiating factors for these responses simultaneously increase as disease progresses and correlate in magnitude. Recent studies show that inhibition of the inflammatory response attenuates angiogenesis to a similar degree and, importantly, that inhibition of angiogenesis does the same to inflammation. Recent data provide evidence that differential regulation of the angiogenic mediators involved in IBD-associated chronic inflammation is the root of this pathological angiogenesis. Many factors are involved in this phenomenon, including growth factors/cytokines, chemokines, adhesion molecules, integrins, matrix-associated molecules, and signaling targets. These factors are produced by various vascular, inflammatory, and immune cell types that are involved in IBD pathology. Moreover, recent studies provide evidence that antiangiogenic therapy is a novel and effective approach for IBD treatment. Here we review the role of pathological angiogenesis during IBD and experimental colitis and discuss the therapeutic avenues this recent knowledge has revealed.
Hierarchy of individual calibration levels for heart rate and accelerometry to measure physical activity
Authors: Brage Søren , Ekelund Ulf , Brage Niels , Hennings Mark A. , Froberg Karsten , Franks Paul W. , Wareham Nicholas J.
Published: April 2007

Combining accelerometry with heart rate (HR) monitoring may improve precision of physical activity measurement. Considerable variation exists in the relationships between physical activity intensity (PAI) and HR and accelerometry, which may be reduced by individual calibration. However, individual calibration limits feasibility of these techniques in population studies, and less burdensome, yet valid, methods of calibration are required. We aimed to evaluate the precision of different individual calibration procedures against a reference calibration procedure: a ramped treadmill walking-running test with continuous measurement of PAI by indirect calorimetry in 26 women and 25 men [mean (SD): 35 ( 9 ) yr, 1.69 (0.10) m, 70 ( 14 ) kg]. Acceleration (along the longitudinal axis of the trunk) and HR were measured simultaneously. Alternative calibration procedures included treadmill testing without calorimetry, submaximal step and walk tests with and without calorimetry, and nonexercise calibration using sleeping HR and gender. Reference accelerometry and HR models explained >95% of the between-individual variance in PAI ( P < 0.001). This fraction dropped to 73 and 81%, respectively, for accelerometry and HR models calibrated with treadmill tests without calorimetry. Step-test calibration captured 62–64% (accelerometry) and 68% (HR) of the variance between individuals. Corresponding values were 63–76% and 59–61% for walk-test calibration. There was only little benefit of including calorimetry during step and walk calibration for HR models. Nonexercise calibration procedures explained 54% (accelerometry) and 30% (HR) of the between-individual variance. In conclusion, a substantial proportion of the between-individual variance in relationships between PAI, accelerometry, and HR is captured with simple calibration procedures, feasible for use in epidemiological studies.
Sustained contraction at very low forces produces prominent supraspinal fatigue in human elbow flexor muscles
Authors: Smith Janette L. , Martin Peter G. , Gandevia Simon C. , Taylor Janet L.
Published: April 2007

During sustained maximal voluntary contractions (MVCs), most fatigue occurs within the muscle, but some occurs because voluntary activation of the muscle declines (central fatigue), and some of this reflects suboptimal output from the motor cortex (supraspinal fatigue). This study examines whether supraspinal fatigue occurs during a sustained submaximal contraction of 5% MVC. Eight subjects sustained an isometric elbow flexion of 5% MVC for 70 min. Brief MVCs were performed every 3 min, with stimulation of the motor point, motor cortex, and brachial plexus. Perceived effort and pain, elbow flexion torque, and surface EMGs from biceps and brachioradialis were recorded. During the sustained 5% contraction, perceived effort increased from 0.5 to 3.9 (out of 10), and elbow flexor EMG increased steadily by ∼60–80%. Torque during brief MVCs fell to 72% of control values, while both the resting twitch and EMG declined progressively. Thus the sustained weak contraction caused fatigue, some of which was due to peripheral mechanisms. Voluntary activation measured by motor point and motor cortex stimulation methods fell to 90% and 80%, respectively. Thus some of the fatigue was central. Calculations based on the fall in voluntary activation measured with cortical stimulation indicate that about two-thirds of the fatigue was due to supraspinal mechanisms. Therefore, sustained performance of a very low-force contraction produces a progressive inability to drive the motor cortex optimally during brief MVCs. The effect of central fatigue on performance of the weak contraction is less clear, but it may contribute to the increase in perceived effort.
Influence of noninvasive peripheral arterial blood pressure measurements on assessment of dynamic cerebral autoregulation
Authors: Sammons Emily L. , Samani Nilesh J. , Smith Stephen M. , Rathbone Wendy E. , Bentley Steve , Potter John F. , Panerai Ronney B.
Published: April 2007

Assessment of dynamic cerebral autoregulation (CA) requires continuous recording of arterial blood pressure (ABP). In humans, noninvasive ABP recordings with the Finapres device have often been used for this purpose. We compared estimates of dynamic CA derived from Finapres with those from invasive recordings in the aorta. Measurements of finger noninvasive ABP (Finapres), intra-aortic ABP (Millar catheter), surface ECG, transcutaneous CO2, and bilateral cerebral blood flow velocity (CBFV) in the middle cerebral arteries were simultaneously and continuously recorded in 27 patients scheduled for percutaneous coronary interventions. Phase, gain, coherence, and CBFV step response from both the Finapres and intra-arterial catheter were estimated by transfer function analysis. A dynamic autoregulation index (ARI) was also calculated. For both hemispheres, the ARI index and the CBFV step response recovery at 4 s were significantly greater for the Finapres-derived estimates than for the values obtained from aortic pressure. The transfer function gain for frequencies <0.1 Hz was significantly smaller for the Finapres estimates. The phase frequency response was significantly greater for the Finapres estimates at frequencies >0.1 Hz, but not at lower frequencies. The Finapres gives higher values for the efficiency of dynamic CA compared with values derived from aortic pressure measurements, as indicated by biases in the ARI index, CBFV step response, gain, and phase. Despite the significance of these biases, their relatively small amplitude indicates a good level of agreement between indexes of CA derived from the Finapres compared with corresponding estimates obtained from invasive measurements of aortic ABP.
Ischemic preconditioning does not protect via blockade of electron transport
Authors: Tanaka-Esposito Christine , Chen Qun , Moghaddas Shadi , Lesnefsky Edward J.
Published: April 2007

Ischemic preconditioning (IPC) before sustained ischemia decreases myocardial infarct size mediated in part via protection of cardiac mitochondria. Reversible blockade of electron transport at complex I immediately before sustained ischemia also preserves mitochondrial respiration and decreases infarct size. We proposed that IPC would attenuate electron transport from complex I as a potential effector mechanism of cardioprotection. Isolated, Langendorff-perfused rat hearts underwent IPC (3 cycles of 5-min 37°C global ischemia and 5-min reperfusion) or were perfused for 40 min without ischemia as controls. Subsarcolemmal (SSM) and interfibrillar (IFM) populations of mitochondria were isolated. IPC did not decrease ADP-stimulated respiration measured in intact mitochondria using substrates that donate reducing equivalents to complex I. Maximally expressed complex I activity measured as rotenone-sensitive NADH:ubiquinone oxidoreductase in detergent-solubilized mitochondria was also unaffected by IPC. Thus the protection of IPC does not occur as a consequence of a partial decrease in complex I activity leading to a decrease in integrated respiration through complex I. IPC and blockade of electron transport both converge on mitochondria as effectors of cardioprotection; however, each modulates mitochondrial metabolism during ischemia by different mechanisms to achieve cardioprotection.
Role of the altitude level on cerebral autoregulation in residents at high altitude
Authors: Jansen Gerard F. A. , Krins Anne , Basnyat Buddha , Odoom Joseph A. , Ince Can
Published: April 2007

Cerebral autoregulation is impaired in Himalayan high-altitude residents who live above 4,200 m. This study was undertaken to determine the altitude at which this impairment of autoregulation occurs. A second aim of the study was to test the hypothesis that administration of oxygen can reverse this impairment in autoregulation at high altitudes. In four groups of 10 Himalayan high-altitude dwellers residing at 1,330, 2,650, 3,440, and 4,243 m, arterial oxygen saturation (SaO2), blood pressure, and middle cerebral artery blood velocity were monitored during infusion of phenylephrine to determine static cerebral autoregulation. On the basis of these measurements, the cerebral autoregulation index (AI) was calculated. Normally, AI is between zero and 1. AI of 0 implies absent autoregulation, and AI of 1 implies intact autoregulation. At 1,330 m (SaO2 = 97%), 2,650 m (SaO2 = 96%), and 3,440 m (SaO2 = 93%), AI values (mean ± SD) were, respectively, 0.63 ± 0.27, 0.57 ± 0.22, and 0.57 ± 0.15. At 4,243 m (SaO2 = 88%), AI was 0.22 ± 0.18 ( P < 0.0005, compared with AI at the lower altitudes) and increased to 0.49 ± 0.23 ( P = 0.008, paired t-test) when oxygen was administered (SaO2 = 98%). In conclusion, high-altitude residents living at 4,243 m have almost total loss of cerebral autoregulation, which improved during oxygen administration. Those people living at 3,440 m and lower have still functioning cerebral autoregulation. This study showed that the altitude region between 3,440 and 4,243 m, marked by SaO2 in the high-altitude dwellers of 93% and 88%, is a transitional zone, above which cerebral autoregulation becomes critically impaired.
Usefulness of the Comprehensive Geriatric Assessment in Older Patients with Upper Gastrointestinal Bleeding: A Two-Year Follow-Up Study
Authors: Pilotto Alberto , Ferrucci Luigi , Scarcelli Carlo , Niro Valeria , Di Mario Francesco , Seripa Davide , Andriulli Angelo , Leandro Gioacchino , Franceschi Marilisa
Published: April 2007

Background: The potential usefulness of standardized comprehensive geriatric assessment (CGA) in evaluating treatment and follow-up of older patients with upper gastrointestinal bleeding is unknown. Aim: To evaluate the usefulness of the CGA as a 2-year mortality multidimensional prognostic index (MPI) in older patients hospitalized for upper gastrointestinal bleeding. Materials and Methods: Patients aged ≧65 years consecutively hospitalized for acute upper gastrointestinal bleeding were included. Diagnosis of bleeding was based on clinical and endoscopic features. All patients underwent a CGA that included six standardized scales, i.e., Activities of Daily Living (ADL), Instrumental Activities of Daily Living (IADL), Short Portable Mental Status Questionnaire (SPMSQ), Mini Nutritional Assessment (MNA), Exton-Smith Score (ESS) and Comorbity Index Rating Scale (CIRS), as well as information on medication history and cohabitation, for a total of 63 items. A MPI was calculated from the integrated total scores and expressed as MPI 1 = low risk, MPI 2 = moderate risk, and MPI 3 = severe risk. The predictive value of the MPI for mortality over a 24-month follow-up was calculated. Results: 36 elderly patients (M 16/F 20, mean age 82.8 ± 7.9 years, range 70–101 years) were included in the study. A significant difference in mean age was observed between males and females (M 80.1 ± 4.8 vs. F 84.9 ± 9.3 years; p < 0.05). The causes of upper gastrointestinal bleeding were duodenal ulcer in 38.8%, gastric ulcer in 22.2%, and erosive gastritis in 16.6% of the patients, while 16.6% had gastrointestinal bleeding from unknown origin. The overall 2-year mortality rate was 30.5%. 18 patients (50%) were classified as having a low-risk MPI (mean value 0.18 ± 0.09), 12 (33.3%) as having a moderate-risk MPI (mean value 0.48 ± 0.08) and 6 (16.6%) as having a severe-risk MPI (mean value 0.83 ± 0.06). Higher MPI grades were significantly associated with higher mortality (grade 1 = 12.5%, grade 2 = 41.6%, grade 3 = 83.3%; p = 0.001). Adjusting for age and sex, the prognostic efficacy of MPI for mortality was confirmed and highly significant (odds ratio 10.47, 95% CI 2.04–53.6). Conclusion: CGA is a useful tool for calculating a MPI that significantly predicts the risk of 2-year mortality in older patients with upper gastrointestinal bleeding.
Liver Diseases in the Elderly: An Update
Authors: Floreani Annarosa
Published: April 2007

Although there are no liver diseases specific to advanced age, the clinical course and management of liver diseases in the elderly may differ in several aspects from those of younger adults. During the last decade an explosion of new knowledge in liver disease has provoked increasing enthusiasm among hepatologists. On the other hand, the development of new emerging conditions (e.g. non-alcoholic steatohepatitis) and novel therapeutic approaches has made it increasingly difficult to validate and assimilate information to be applied in clinical practice. Some liver diseases in the elderly need to be revisited, particularly non-alcoholic fatty liver disease, chronic hepatitis C, alcoholic liver disease, and hepatocellular carcinoma. Moreover, some therapeutic approaches, especially antiviral therapy and liver transplantation, should be discussed also in selected groups of elderly patients.
Fast Cognitive Decline at the Time of Dementia Diagnosis: A Major Prognostic Factor for Survival in the Community
Authors: Carcaillon Laure , Pérès Karine , Péré Jean-Jacques , Helmer Catherine , Orgogozo Jean-Marc , Dartigues Jean-François
Published: April 2007

Background/Aims: Current findings suggest the existence of a category of fast cognitive decliners with a poorer prognosis but better treatment response. Our study aimed at confirming the concept of fast decliners at the time of Alzheimer’s disease (AD) diagnosis which best predicts mortality, in an unselected sample. Methods: 245 incident cases of AD were selected from the French longitudinal cohort PAQUID. We investigated a different threshold of cognitive decline [measured by the annual loss of points in the Mini Mental State Examination (MMSE) score] to define when a subject could be considered as a fast decliner. We used Cox proportional hazards models to study the relation between cognitive decline and mortality. Results:The significant threshold of decline associated with a higher mortality rate was a loss of 3 points per year in the MMSE score. Among the 245 AD cases, 83 (33.9%) subjects were considered as fast decliners. Of them, 78.3% died during the follow-up compared with 63.0% of the slow decliners (RR = 1.7, 95% CI 1.2–2.5). Conclusion:These results constitute an empirical validation of the concept of fast decliners in community-based AD patients and justify the cutoff of 3 points for the definition of this condition.
Recalling Superior Mesenteric Artery Syndrome
Authors: Welsch Thilo , Büchler Markus W. , Kienle Peter
Published: April 2007

Background: Superior mesenteric artery syndrome is uncommon and characterized by postprandial epigastric pain, nausea, vomiting, anorexia and weight loss. The syndrome is caused by compression of the third part of the duodenum in the angle between the aorta and the superior mesenteric artery. This review updates etiology, epidemiology, diagnosis, treatment and outcome of the superior mesenteric artery syndrome. Methods: Review of the literature. Results: Frequently, predisposing medical conditions associated with catabolic states or rapid weight loss result in a decrease of the aortomesenteric angle and subsequent duodenal obstruction. External cast compression, anatomic variants and surgical alteration of the anatomy following spine surgery or ileoanal pouch anastomosis can also precipitate the syndrome. Once radiologic studies have established diagnosis, first-line treatment is usually conservative with jejunal or parenteral nutrition for restoration of the aortomesenteric fatty tissue. If conservative management fails, surgical options include open or laparoscopic duodenojejunostomy or duodenal mobilization and division of the ligament of Treitz. Conclusion: Superior mesenteric artery syndrome is clearly defined and frequently associated with a wide range of predisposing conditions and surgical procedures; clinicians have to consider this syndrome in such a setting. Larger studies are needed to better define the optimal treatment for this disease.
Inflammatory Fibroid Polyps of the Duodenum: A Review of the Literature
Authors: Wysocki A. Peter , Taylor Graeme , Windsor John A.
Published: April 2007

Background/Aim: An inflammatory fibroid polyp (IFP) is a rare benign submucosal gastro-intestinal lesion with an uncertain origin and natural history. An IFP was first described in the stomach and is rare in the duodenum. Presenting signs and symptoms vary according to anatomical site. This systematic literature review was prompted by the recent presentation of a patient with biliary obstruction caused by a duodenal IFP. Methods: A review of all duodenal IFPs identified in the PubMed database from 1971 onwards is presented within the context of what is known about the lesion at other gastro-intestinal sites. Results: Of approximately 1,000 IFP cases identified, 70% were of gastric origin, and fewer than 1% occurred in the duodenum. Duodenal IFPs typically present with non-specific features, and no pre-operative diagnoses of lesions at this site have been made. Microscopy reveals spindle-shaped cells, prominent capillaries, and an inflammatory cell filtrate. Immunohistochemistry shows the lesions to be CD34 and vimentin positive, but CD117, S100, and factor VIII negative. Local recurrence is most unusual following complete resection. Conclusions: This rare benign entity in the duodenum should be included in the differential diagnosis of all peripancreatic masses. The advent of endoscopic ultrasound may allow pre-operative diagnosis of the lesion in the duodenum, enabling local resection and potentially avoiding unnecessary pancreatoduodenectomy.
Minimum Leakage Rate (0.5%) of Stapled Esophagojejunostomy with Sacrifice of a Small Part of the Jejunum after Total Gastrectomy in 390 Consecutive Patients
Authors: Hyodo M. , Hosoya Y. , Hirashima Y. , Haruta H. , Kurashina K. , Saito S. , Yokoyama T. , Arai W. , Zuiki T. , Yasuda Y. , Nagai H.
Published: April 2007

Background: The development of new surgical instruments and devices has facilitated the performance of esophagojejunostomy after total gastrectomy. However, total prevention of dehiscence of anastomoses remains difficult. We introduced a new procedure for esophagojejunostomy using a circular stapler, requiring sacrifice of only a small part of the jejunum. Methods: The study group comprised 390 consecutive patients who underwent reconstruction by Roux-en-Y esophagojejunostomy, performed with a circular stapler, sacrificing a small part of the jejunum after total gastrectomy. We assessed anastomotic leakage and anastomotic stenosis after surgery. Results: Only 2 patients (0.5%) had leakage and 4 (1.0%) had anastomotic stenosis after reconstruction. All the patients were cured by conservative therapy. Conclusions: Esophagojejunostomy performed with a circular stapler after total gastrectomy, with sacrifice of only a small part of the jejunum, is a useful and easy procedure, with a leakage rate of 0.5%.
Thin Filament Disinhibition by Restrictive Cardiomyopathy Mutant R193H Troponin I Induces Ca
2+
-Independent Mechanical Tone and Acute Myocyte Remodeling
Authors: Davis Jennifer , Wen Haitao , Edwards Terri , Metzger Joseph M.
Published: April 2007

Inherited restrictive cardiomyopathy (RCM) is a debilitating disease characterized by a stiff heart with impaired ventricular relaxation. Mutations in cardiac troponin I (cTnI) were identified as causal for RCM. Acute genetic engineering of adult cardiac myocytes was used to identify primary structure/function effects of mutant cTnI. Studies focused on R193H cTnI owing to the poor prognosis of this allele. Compared with wild-type cTnI, R193H mutant cTnI more effectively incorporated into the sarcomere, where it exerted dose-dependent effects on basal and dynamic contractile function. Under loaded conditions, permeabilized myocyte Ca
2+
sensitivity of tension was increased, whereas the passive tension–extension relationship was not altered by R193H cTnI. Normal rod-shaped myocyte morphology acutely transitioned to a “short-squat” phenotype in concert with progressive stoichiometric incorporation of R193H in the absence of altered diastolic Ca
2+
. The specific myosin inhibitor blebbistatin fully blocked this transition. Heightened Ca
2+
buffering by the R193H myofilaments, and not alterations in Ca
2+
handling by the sarcoplasmic reticulum, slowed the decay rate of the Ca
2+
transient. Incomplete mechanical relaxation conferred by R193H was exacerbated at increasing pacing frequencies independent of elevated diastolic Ca
2+
. R193H cTnI–dependent mechanical tone caused acute remodeling to a quasicontracted state not elicited by other Ca
2+
-sensitizing proteins and is a direct correlate of the stiff heart characteristic of RCM in vivo. These results point toward targets downstream of Ca
2+
handling, notably thin filament regulation and actin–myosin interaction, in designing therapeutic strategies to redress the primary cell morphological and mechanical underpinnings of RCM.
Platelet Receptor Proteolysis
Authors: Andrews Robert K. , Karunakaran Denuja , Gardiner Elizabeth E. , Berndt Michael C.
Published: April 2007

The platelet plasma membrane is literally at the cutting-edge of recent research into proteolytic regulation of the function and surface expression of platelet receptors, revealing new mechanisms for how the thrombotic propensity of platelets is controlled in health and disease. Extracellular proteolysis of receptors irreversibly inactivates receptor-mediated adhesion and signaling, as well as releasing soluble fragments into the plasma where they act as potential markers or modulators. Platelet-surface sheddases, particularly of the metalloproteinase-disintegrin (ADAM) family, can be regulated by many of the same mechanisms that control receptor function, such as calmodulin association or activation of signaling pathways. This provides layers of regulation (proteinase and receptor), and a higher order of control of cellular function. Activation of pathways leading to extracellular shedding is concomitant with activation of intracellular proteinases such as calpain, which may also irreversibly deactivate receptors. In this review, platelet receptor shedding will be discussed in terms of (1) the identity of proteinases involved in receptor proteolysis, (2) key platelet receptors regulated by proteolytic pathways, and (3) how shedding might be regulated in normal physiology or future therapeutics. In particular, a focus on proteolytic regulation of the platelet collagen receptor, glycoprotein (GP)VI, illustrates many of the key biochemical, cellular, and clinical implications of current research in this area.