bluuebunny/crossref_metadata_2025 huggingface dataset:
The Cooling Impact of a Pair of Opposed Unsteady Confined Impinging Air Jets
Authors: Chiriac Victor , Rosales Jorge L.
Published: April 2009

A numerical investigation was performed at two Reynolds numbers to analyze the flow-field and heat transfer characteristics for a pair of laminar jets impinging on opposite walls in a channel. The present study is a continuation of the authors’ earlier work [1] in which the jets flowing out normal to the top channel wall produce a large stagnant bubble between the two jets which greatly reduce the heat transfer removal from the lower wall. In this case, the lower Reynolds number jet flow of 300 produces a symmetric, steady flow hydrodynamic pattern with the jets being deflected laterally. By further increasing the Reynolds number to 750, a complex asymmetric and highly unsteady flow develops between the two jets due to the opposite jet flow interaction. The convective heat transfer coefficients and the unsteady flow development between the jets are studied for each case. The flow unsteadiness is also characterized by analyzing the stagnation point displacement on the channel walls. The complex vortex patterns resulting from the jet interaction at the higher Reynolds number is investigated and its impact on the chip/microelectronics component cooling is thoroughly documented.   This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.
MX2 Processor Module: Twice the Processors in Half the Volume
Authors: Belady Christian , Williams Gary , Harris Shaun
Published: April 2009

Computer manufacturer’s are constantly trying to tweek more performance out of their existing products by using the highest performing processors. Typically, manufacturers upgrade the platforms by simply replacing the old processor with the latest speed processor. Like other manufacturers, HP generally follows this practice with the exception ot HP’s innovative mx2 module. This unique module used two Itanium-2 “Madison” processors packaged in the same physical volume as a single Itanium-2 processor. In addition, the module plugs into a standard Itanium-2 motherboard socket and requires no additional power capacity. As a result, the development team was able get 50% more performance [1] from a socket without increasing power by actively managing the power to the two processors. Thus, the performance per watt was substantially improved. This paper will provide an overview of some of the key packaging and power innovations that made the processor module a reality such as: 1) mezzanine power for space savings. The standard Itanium 2 processor has a power converter adjacent to the processor. HP engineers chose to put power on top of the processor which provided more room but made cooling the processors a challenge. 2) high performance mechnical gap filler. One of the biggest issues in the module was to develop a thermal gap filler that absorbed 0.060” of tolerance between the two processors. The thermal resistance of this technology was an order of magnitude better than anything commercially available in the industry. 3) Power Aware Architecture. This newly developed power mangement technology actively controls power to the processors. When system (thermal and power) extremes were exceeded by worst case abnormal code, the performance was throttled down until the worst case scenario had past. The combination of these advancements has delivered an innovative solution for a highly challenging design problem. This module is now shipping as the mx2 processor module in HP’s Integrity Servers and has been viewed as an engineering marvel by HP executives.
Measurement and Analysis of Insertion Loss in an Optical Collimation System Designed for a 2D MEMS Optical Switch
Authors: Ikehara Tsuyoshi , Maeda Ryutaro , Shan Xue Chuan
Published: April 2009

A 2D optical switch system using two ball lenses as a collimator was theoretically analyzed with the objective of minimizing optical insertion loss. The lens diameters, lens material, path length, and alignment tolerance were optimized for use with small MEMS mirrors and a relatively long (> 10 mm) path length. The insertion loss was calculated by the ray tracing method. The optimum lens diameter was determined by a balance of lens aberration and beam diameter. Insertion loss measurements of the optical system were performed without the use of a MEMS mirror. Those measurement results exhibited tendencies similar to the calculations. Measurements using a MEMS mirror were also performed and the insertion loss is discussed regarding the involvement of the optical system and mirror surface.
A New Approach to Model Axial Fans in Commercial CFD Tools
Authors: Sadeghi Nader , Barez Fred , Shabany Younes
Published: April 2009

Most commercial CFD tools use fan curves to represent a fan. However, the presence of a blockage near inlet or exhaust of a fan and a restricted airflow direction will alter the fan performance, and the use of the original fan curve may result in erroneous results in these cases. A new approach to model fans will be presented in this paper. Using conservation of mass, momentum and energy, and the velocity triangles, this model relates velocity and pressure at fan exhaust to the corresponding values at fan inlet as well as fan geometry, rotational speed and fan blade lift and drag coefficients.
Electrical Simulation Design Technology of Silicon Through Substrate
Authors: Takano Takamasa , Yamaguchi Masataka , Nakayama Koichi , Maruyama Tomoko , Chujyo Shigeki , Kuramochi Satoru , Fukuoka Yoshitaka
Published: April 2009

As electronic product becomes smaller and lighter with an increasing number of function, the demand for high density and high integration becomes stronger. In other aspect, IT (information technology) products supported on broadband network communication technologies. It changes from the cable communication by the digital circuit to the wire less communication by analogue and mixed-signal technologies. We have researched requirements for the design of next generation system in packaging module from the several points of view which include line width, pad pitch, clock, frequency, interconnection delay and number of passive components. Based on this, we presented a new concept packaging module model. The new module, silicon through integration platform, has through interconnection via, fine wiring build up layers, and embedded passives. This paper reports the result, which focus on the various electrical characteristics of silicon through substrate, and electrical simulation design technology for system in package. We have tried very accurate impedance matching design using 2D electromagnetic simulation and TDR (Time Domain Refrectometry) measurement technology. To investigate high frequency characteristic of hi-speed transmission line and silicon through interconnection, we have tried 3D electromagnetic simulation and VNA (vector network analyser) measurement. Thus, we have obtained good performance of high frequency transmission line and optimal design rule for system in package.
Power Distribution Analysis of Multi-Layer Substrates With Power Decoupling Capacitors
Authors: Lu Albert Chee Wai , Jin Lin , Chua Kai M. , Fan Wei , Wai Lai L.
Published: April 2009

This paper describes power distribution design and analysis for multi-layer LTCC (low temperature co-fired ceramic) substrates intended for broadband digital applications. Both land side discrete capacitor (LSC, i.e. mounted on the bottom) and top side discrete capacitor (TSC, i.e. mounted on the top or the same side as the active device) configurations were compared in terms of impedance characteristics up to 3 GHz, with respect to different port locations for the active device. Full-wave electromagnetic modeling was carried out to study the impedance characteristics and good correlation with vector network analyzer measurements was achieved. At lower frequencies well below the self-resonant frequency of the intrinsic power plane, the effective impedance is dominated by the series effective inductance. It was observed that the LSC configuration achieves lower impedance due to a reduced series effective inductance since the TSC configuration results in a longer low frequency impedance path. At higher frequencies, however, the LSC configuration actually results in an impedance peak at a lower frequency due to the parallel resonance attributed to the power planes.
A Systematic Approach for Determining the Thermal Fatigue-Life of Plastic Ball Grid Array (PBGA) Lead-Free Solder Joints
Authors: Lau John , Lee Ricky , Dauksher Walter , Shangguan Dongkai , Song Fubin , Lau Dennis
Published: April 2009

Reliability of plastic ball grid array (PBGA) SnAgCu lead-free solder joints is investigated. Emphasis is placed on the design for reliability (DFR) of lead-free solder joints. In particular, the thermal-fatigue life of the lead-free solder joints of a PBGA package assembly is predicted and compared with thermal cycling test results.
Silicone Gel Thermal Interface Materials for High Heat Dissipation and Thermo-Mechanical Stress Management for Good Reliability Performance
Authors: Matayabas J. C. , LeBonheur Vassou
Published: April 2009

The recent trend in microprocessor architecture has been to increase the number of transistors (higher power), shrink processor size (smaller die), and increase clock speeds (higher frequency) in order to meet the market demand for high performance microprocessors. These have resulted in the escalation of power dissipation as well as the heat flux at the silicon die level. The Intel packaging technology development group has been challenged to develop packaging solutions that not only meet the package thermal targets but also the reliability requirements. As a result, an integrated heat spreading (IHS) package was developed, comprising a Cu based heat spreader and a first level thermal interface material (TIM) between the die and the heat spreader. Due to CTE mismatches between its different elements, the IHS package is subjected to high level of thermo-mechanical stresses which lead to severe failures post reliability testing. A significant amount of theoretical understanding of thermal resistance has been developed and applied to the development of TIM formulations, and it was found that the thermo-mechanical properties of the TIM material need to be optimized to mitigate the package reliability stresses. Several material and process solutions have been investigated using fundamental approaches, and, as a result of these efforts, low stress silicone gel TIM’s were developed. This paper provides an overview of the silicone gel TIM technologies investigated at Intel, and the key learnings from the fundamental material and package integration studies.
Thermal Characterization of Non-Raised Floor Air Cooled Data Centers Using Numerical Modeling
Authors: Iyengar Madhusudan , Schmidt Roger , Sharma Arun , McVicker Gerard , Shrivastava Saurabh , Sri-Jayantha Sri , Amemiya Yasuo , Dang Hien , Chainer Timothy , Sammakia Bahgat
Published: April 2009

Data center equipment almost always represents a high expenditure capital investment to the customer, and is often operated without any down time. Data com equipment is typically designed to operate at a rack air inlet temperature of between 10 and 35°C, and a violation of this specification can diminish electronic device reliability and even lead to failure in the field. Thus, it is of paramount importance, from a reliability perspective, to sufficiently understand these systems. A representative non-raised floor data center system was numerically modeled and the data generated from a parametric study was analyzed. The model constitutes a half symmetry section of a 40 rack data center that is arranged in a cold aisle-hot aisle fashion. The effect of several input variables, namely, rack heat load, rack flow rate, rack temperature rise, diffuser flow rate, diffuser location, diffuser height, diffuser pitch, ceiling height, hot exhaust air return vent location, and non-uniformity in rack heat load, was studied. Temperature data was collected at several locations at the inlet to the racks. Statistical analysis was carried out to describe trends in the data.
Utilizing the Novel Laser Spallation Technique to Measure Interfacial Strength in Microelectronic Packages
Authors: Raman Arun , Tian Jun , La Mar Alfred A. , Tandon Shalabh
Published: April 2009

Laser spallation is a high strain rate adhesion measurement technique. Based on the principle of pulsed laser ablation, strain rates of the order of 105–106s−1 are achieved with laser spallation. At these strain rates, low strain rate losses such as due to plasticity or viscoelasticity get minimized and so the strength measurement from laser spallation will be close to the intrinsic strength of the interface. In addition, the high strain rates also enable an understanding of “shock” stress conditions. This work focuses on the application of laser spallation to understand two types of interfaces in flip chip microelectronic packages — BGA solder joints and copper-epoxy based dielectrics. The ability of laser spallation to differentiate samples on the basis of their adhesive strength is understood.
An Engineering Model for Moisture Degradation of Polymer/Metal Interfacial Fracture Toughness
Authors: Ferguson Timothy P. , Qu Jianmin
Published: April 2009

Based on interfacial fracture mechanics and the hydrophobicity of the interface, en engineering model was developed in this paper. Using this model, one can predicted the degradation of interfacial fracture toughness of a polymer/metal interface once the moisture concentration near the interface is known.
Development of 1D Optical Micro Scanner Driven by Piezoelectric Actuators
Authors: Kobayashi Takeshi , Tsaur Jiunnjye , Maeda Ryutaro
Published: April 2009

1D optical micro scanners driven by piezoelectric actuators have designed, simulated, fabricated and tested. The newly designed micro scanners have a structure that rotation bars, hinges and PZT cantilevers support a square mirror (1mm × 1mm). Flat-structured micro scanners have been fabricated from Pt/PZT/Pt/Ti/SiO2/SOI(Si/SiO2/Si) multi-layered structure through conventional MEMS micro fabrication technologies. The micro scanner driven at 10 V showed an optical scan angle of 1.5 degree for the static actuation (60 Hz) and of 13 degree for the resonant actuation (4825 Hz), respectively.
Thermodynamic Design of Compact Thermal Compressor for Sorption Assisted Cryogenic Cooling of Electronics
Authors: Suman Shivesh K. , Fedorov Andrei G. , Joshi Yogendra K.
Published: April 2009

During the past several decades, significant performance improvement of microprocessor chips has been obtained mainly by reduction of (transistor) device length scale. Beyond the International Technology Roadmap for Semiconductors (ITRS)-defined 50 nm technology node, the parasitic effects associated with reduction of the feature size (e.g., increase in leakage current) begin to outweigh the favorable effects of increased functionality and speed. One promising route for continued performance improvement is to exploit low temperature operation of microprocessors (also referred to as the temperature scaling [1]). This calls for development of compact, inexpensive, and quiet refrigeration/cryogenics technology, which can be interfaced with electronic components. In this work, we consider thermally driven sorption-assisted refrigeration technology for sub-ambient cooling of high performance electronics. In the past, sorption-based cryocoolers have been successfully developed for cryogenic cooling of sensors in space applications, targeting very low (mW-level) cooling loads. These cryocoolers are quiet, vibration free, reliable since they have no moving parts at high pressure, and therefore offer significant advantages over mechanical refrigeration. In addition, there is no refrigerant-lubricant interaction in sorption-based cryocoolers, which can potentially degrade the evaporator performance. This paper presents a thermodynamics-based analytical framework for the design of sorption compressors for cryogenic cooling of electronics. A sample case study is also presented to illustrate the approach.
Characterization of Heated Atomic Force Microscope Cantilevers in Air and Vacuum
Authors: Lee Jungchul , Wright Tanya L. , Abel Mark , Sunden Erik , Marchenkov Alexei , Graham Samuel , King William P.
Published: April 2009

This paper presents characterization of heated atomic force microscope (AFM) cantilevers in air and helium, both at atmospheric pressure and in a partially evacuated environment. The cantilevers are made of doped single-crystal silicon using a standard silicon-on-insulator cantilever fabrication process. The electrical measurements show the link between the cantilever temperature-dependant electrical characteristics, electrical resistive heating, and thermal properties of the heated AFM cantilever and its surroundings. Laser Raman thermometry measures temperature along the cantilever with resolution near 1 μm and 4°C. By modulating the gaseous environment surrounding the cantilever, it is possible to estimate the microscale thermal coupling between the cantilever and its environment. This work seeks to improve the calibration and design of heated AFM cantilevers.
Experimental Characterization of Bonded Microcoolers for Hot Spot Removal
Authors: Zhang Yan , Zeng Gehong , Hoffman Christine , Shakouri Ali , Wang Peng , Bar-Cohen Avram
Published: April 2009

In this paper we describe the experimental results of Si/SiGe superlattice microcoolers, which are used to cool the target hot spot on a 65μm-thick silicon substrate. The device areas under test range from 50×50 to 150×150 μm2. We measured the cooling temperature at the hot spot region versus the current supplied to the microcooler, as well as the thermal resistance, and the cooling power density (CPD, also defined as heat flux — the flow of heat per unit area in W/cm2) of these devices. The experimental results show the maximum cooling at the hot spot region approaches 1°C for device area 150×150μm2 at 80°C, and CPD up to ∼110W/cm2 for device area 50×50×2 μm2 (two 50×50μm2 device array, as illustrated in Figure 3) at 80°C. The two-chip bonded configuration will allow the integration of spot coolers and integrated circuit chips with minimum impact on the processing of microelectronic devices. Key parameters limiting the cooling performance at the hot spots are also discussed.
Bending Simulation of BGA SMT Assemblies and Application to System Level Drop Simulation
Authors: Carroll Doug , Zampino Marc , Jones Kinzy
Published: April 2009

This paper will examine the displacement and strain behavior of solder joints during static and dynamic bending. Simulation has shown that four point dynamic bending test result in a higher accumulation of plastic strain than static bending at equivalent board strains. This is important as the yielding and failure of lead-free solder joints occurs primarily at the joint package interface. Solder joint strains are on the order of magnitude higher than printed circuit board (PCB) bending strains at the edge of the package. Additionally, a method for using solder joint stretch has been developed for measuring joint response. Utilizing the concept of solder stretch, a technique for using equivalent beam models for the solder joints in a system level drop will be introduced. Results for three different beam model strategies will be given. The results show these techniques are valid and their use will greatly increase the ability to determine package impact reliability during the design stages.
Thermal Based Optimization of Functional Block Distributions in a Non-Uniformly Powered Die
Authors: Kaisare Abhijit , Agonafer Dereje , Haji-Sheikh A. , Chrysler Greg , Mahajan Ravi
Published: April 2009

Microprocessors continue to grow in capabilities, complexity and performance. The current generation of microprocessors integrates functional components such as logic and level two (L2) cache memory into the microprocessor architecture. The functional integration of the microprocessor has resulted in better performance of the microprocessor as the clock speed has increased and the instruction execution time has decreased. However, the integration has introduced a layer of complexity to the thermal design and management of microprocessors. As a direct result of function integration, the power map on a microprocessor is highly non-uniform and the assumption of a uniform heat flux across the chip surface is not valid. The objective of this paper is to minimize the thermal resistance of the package by optimizing the distribution of the uniformly powered functional blocks. In order to model the non-uniform power dissipation on the silicon chip, the chip surface area is divided into a 4 × 4 and 6×6 matrix with a matrix space representing a distinct functional block with a constant heat flux. Finally, using a FEM code, an optimization of the positioning of the functional blocks relative to each other was carried out in order to minimize the junction temperature Tj. This analysis has no constraints placed on the redistribution of functional blocks. The best possible Tjmax reduction could thus be found. In reality (and at a later date) constraints must be placed regarding the maximum separation of any 2 (or more) functional blocks to satisfy electrical timing and compute performance requirements. Design guidelines are then suggested regarding the thermal based optimal distribution for any number of functional blocks. The commercial finite element code ANSYS® is used for this analysis.
Thermal and Mechanical Properties of Silicone Thermal Interface Materials With Varying Cross-Link Densities
Authors: Gowda Arun , Zhong Annita , Tonapi Sandeep , Nagarkar Kaustubh , Srihari K.
Published: April 2009

Thermal Interface Materials (TIMs) play a key role in the thermal management of microelectronics by providing a path of low thermal impedance between the heat generating devices and the heat dissipating components (heat spreader/sink). In addition, TIMs need to reliably maintain this low thermal resistance path throughout the operating life of the device. Currently, several different TIM material solutions are employed to dissipate heat away from semiconductor devices. Thermal greases, adhesives, gels, pads, and phase change materials are among these material solutions. Each material system has its own advantages and associated application space. While thermal greases offer excellent thermal performance, their uncured state makes them susceptible to pump-out and other degradation mechanisms. On the other hand, adhesives offer structural support but offer a higher heat resistance path. Gels are designed to provide a level of cross-linking to allow the thermal performance of greases and prevent premature degradation. However, the degree of crosslinking can have a significant effect of the behavior of gels. In this research, TIMs with varying cross-linking densities are studied and their thermal and mechanical properties reported. The base resin systems and fillers were maintained constant, while slight compositional alternations were made to induce different degrees of cross-linking.
Comparison between two super‐resolution implementations in PET imaging
Authors: Chang Guoping , Pan Tinsu , Qiao Feng , Clark John W. , Mawlawi Osama R.
Published: March 2009

Super‐resolution (SR) techniques are used in PET imaging to generate a high‐resolution image by combining multiple low‐resolution images that have been acquired from different points of view (POV). In this article, the authors propose a novel implementation of the SR technique whereby the required multiple low‐resolution images are generated by shifting the reconstruction pixel grid during the image reconstruction process rather than being acquired from different POVs. The objective of this article is to compare the performances of the two SR implementations using theoretical and experimental studies. A mathematical framework is first provided to support the hypothesis that the two SR implementations have similar performance in current PET/CT scanners that use block detectors. Based on this framework, a simulation study, a point source study, and a NEMA/IEC phantom study were conducted to compare the performance of these two SR implementations with respect to contrast, resolution, noise, and SNR. For reference purposes, a comparison with a native reconstruction (NR) image using a high‐resolution pixel grid was also performed. The mathematical framework showed that the two SR implementations are expected to achieve similar contrast and resolution but different noise contents. These results were confirmed by the simulation and experimental studies. The simulation study showed that the two SR implementations have an average contrast difference of 2.3%, while the point source study showed that their average differences in contrast and resolution were 0.5% and 1.2%, respectively. Comparisons between the SR and NR images for the point source study showed that the NR image exhibited averages of 30% and 8% lower contrast and resolution, respectively. The NEMA/IEC phantom study showed that the three images (two SR and NR) exhibited different noise structures. The SNR of the new SR implementation was, on average, 21.5% lower than the original implementation largely due to an increase in background noise, while the NR image had averages of 18.5% and 8% lower SNR and contrast, respectively, versus the two SR images. The new SR implementation can potentially replace the original SR approach in current PET scanners that use block detectors while maintaining similar contrast and resolution, but at a relatively lower SNR. A major advantage of the new SR implementation is its shorter overall scan duration which results in an increase in scanner throughput and a reduction in patient motion.
The effect of x‐ray beam quality and geometry on radiation utilization efficiency in multidetector CT imaging
Authors: Perisinakis Kostas , Papadakis Antonios E. , Damilakis John
Published: March 2009

This study has the following objectives: To measure the geometric efficiency (GE) of a multidetector CT (MDCT) system and investigate its dependence on several exposure parameters and to correlate GE with radiation dose burden of patients undergoing MDCT imaging. Dose profiles for all available beam collimations, tube voltage values, focal spot sizes, and modes of operation were determined for a modern MDCT scanner using an array of thermoluminescent chip dosimeters positioned side by side. Dose profiles measured free‐in‐air and at the center and periphery of the standard polymethyl methacrylate (PMMA) phantoms were used to estimate GE. The standard free‐in‐air and a new measure of GE determined using the standard PMMA phantoms were correlated with volume computed tomography dose index normalized to the ‐axis coverage per rotation which is directly related to patient radiation dose burden. GE was found to be from 30% to 88% as beam collimation was changed from 1.2 to 24 mm, with thin beam collimations corresponding to higher “wasted” dose. For the same tube voltage and beam collimation, the use of small focal spot was associated with higher GE compared to the large focal spot. Besides, beam quality was found to have a much weaker effect on the GE value. In comparison to free‐in‐air, a weighted GE determined using the standard PMMA phantoms was found to have significantly better correlation with patient radiation burden . Overbeaming strongly depends on the beam collimation and focal spot size, while the impact of beam quality on GE is less pronounced. Thin beam collimations are associated with a GE of as low as 30%.
Apicomplexan Parasites Co-Opt Host Calpains to Facilitate Their Escape from Infected Cells
Authors: Chandramohanadas Rajesh , Davis Paul H. , Beiting Daniel P. , Harbut Michael B. , Darling Claire , Velmourougane Geetha , Lee Ming Yeh , Greer Peter A. , Roos David S. , Greenbaum Doron C.
Published: April 2009

Let Me Out

Apicomplexan parasites like
Plasmodium falciparum
, which causes malaria, and
Toxoplasma gondii
, which cause toxoplasmosis, replicate inside animal host cells. In order for infections to spread successfully within the host from cell to cell, daughter parasites after replication need to be able to escape from their incubator cell. In the course of studies intended to elucidate the functions of proteases during parasite infection,

Chandramohanadas
et al.

(p.
794
, published online 2 April) noted that host cell calpain is the only protease present at the right time and place to facilitate the egress of malaria parasites from infected red blood cells. Parasite egress from infected resealed erythrocytes was prevented when calpain was removed. Moreover,
T. gondii
was unable to escape efficiently from murine fibroblast knockouts lacking a calpain regulatory subunit.
Electrochemical processes of adsorbed chlorobenzene and fluorobenzene on a platinum polycrystalline electrode
Authors: Musilová-Kebrlová Natálie , Janderka Pavel , Trnková Libuše
Published: April 2009

The electrode processes of chlorobenzene (CB) and fluorobenzene (FB) on polycrystalline platinum (Pt-pc) electrode in sulfuric acid were studied by differential electrochemical mass spectrometry (DEMS). Contrary to the oxidation of adsorbed benzene on Pt surface, the oxidation of adsorbed CB and FB in the oxygen adsorption region does not provide solely CO2 as the final product. At negative polarization potentials CB and FB were desorbed under dehalogenation. While in the case of FB only benzene was detected, CB gave intermediates besides benzene. The final product of stepwise hydrogenation of these species was cyclohexane.
Soft lodgement till deposition and syndepositional deformation, Anielinek, the Polish Lowlands
Authors: Ruszczyńska-Szenajch Hanna , Trzciński Jerzy
Published: April 2009

The paper presents a case study of sediment, termed soft lodgement till (a product of subglacial deposition by active ice), described previously on the basis of macro-evidence from Poland and Canada but not yet studied in detail in one particular site. The till at Anielinek (about 7 m thick) was examined by macroscopic observation, thin section description, and qualitative and quantitative scanning electron microscopy (SEM) analyses. It shows a macroscopic massive structure and overlies a flat top of glaciolacustrine sediments. These sediments form upward intrusions within the till—owing to the existence of reversed density gradients among the deposits—and the upper parts of the intrusions are tilted in consistent directions within the successive parts of the till. Moreover, SEM images also record uniformly oriented microintrusions within this diamictic material. The occurrence of these macro- and microstructures within the successive parts of the till point to an almost continuous process of intrusion during ongoing deposition of the till and to water saturation of the subglacial environment. Such conditions reduced friction of the glacier bed against its substratum, and glacial debris must have been mainly melt-released from the moving glacier base. This process was responsible for deposition of sediment (soft lodgement till) that was immediately and continuously deformed by glacial stress during the ongoing accretion of debris from the glacier base.
A NEW FORMULATION AND RELAXATION OF THE SIMPLE PLANT LOCATION PROBLEM
Authors: SHARMA R. R. K. , MURALIDHAR A.
Published: April 2009

In this paper a new formulation of the simple plant location problem (SPLP) is given that uses the style of Sharma and Sharma (European Journal of Operational Research, 122(3), 37–48). When the integer restrictions are relaxed, it results in a new relaxation of SPLP that is different from the already well known "strong" and "weak" relaxation of SPLP. It is shown that the bound given by the new relaxation is worse than the bound given by "strong relaxation" of SPLP. However, a numerical example illustrates that the bound given by the new relaxation can at times be better than the bound given by "weak relaxation" (already known) of SPLP. In this paper a new proof [which is different from the one given by Bilde and Krarup (Annals of Discrete Mathematics, 1, 79–97)] is given to establish relative strengths of various relaxations of SPLP.
ANALYSIS OF A MULTI-SERVER QUEUE WITH MARKOVIAN ARRIVALS AND SYNCHRONOUS PHASE TYPE VACATIONS
Authors: CHAKRAVARTHY SRINIVAS R.
Published: April 2009

We study a MAP/M/c queueing system in which a group of servers take a simultaneous phase type vacation. The queueing model is studied as a QBD process. The steady-state analysis of the model including the waiting time distribution is presented. Interesting numerical results are discussed.
A NOTE ON DIFFERENCES BETWEEN (4+1)- AND (5+1)-DIMENSIONAL ANISOTROPIC COSMOLOGY IN THE PRESENCE OF THE GAUSS–BONNET TERM
Authors: PAVLUCHENKO S. A. , TOPORENSKY A. V.
Published: March 2009

We investigate a flat anisotropic (5+1)-dimensional cosmological model in the presence of the Gauss–Bonnet (GB) contribution in addition to the usual Einstein term in the action. We compared it with (4+1)-dimensional case and found a substantial difference in the corresponding cosmological dynamics. This difference is manifested in the probability of the model to have smooth transition from GB-term-dominated to Einstein-term-dominated phases — this probability in a reasonable measure on the initial condition space is almost zero for (4+1) case and about 60% for (5+1) case. We discuss this difference as well as some features of the dynamics of the considered model.
AN EFFECTIVE GEOMETRY TREATMENT OF GENERAL-RELATIVISTIC RADIATIVE TRANSFER INSIDE STELLAR PHOTOSPHERES
Authors: FUMERON S.
Published: April 2009

The aim of this paper is to determine how the gravitational field inside a massive star affects the propagation of photons, and to investigate the consequences for the radiation field. The chosen approach consists in modeling the curved metric by an effective refractive medium: from this very simple perspective, the energy transport problem is investigated and the new form of the radiative transfer is derived. Then, the main effects of curvature on the energy balance are discussed and, in particular, it is shown that these effects influence the radiative flux emitted by the star.
SIMULATED SHEWHART CONTROL CHART FOR MONITORING VARIANCE COMPONENTS
Authors: TSAI TZONG-RU , HSIEH YI-WEI
Published: April 2009

Shewhart control charts based on the simulation method are proposed for monitoring separate variance components of the single-factor random effect model. Monte Carlo simulation results show that the proposed control charts have competitive performance relative to the approximate Shewhart regression control charts (ARSCCs) proposed by Chang and Gan2 in terms of the average run length (ARL). Compared with the ARSCCs, our control charts can be constructed easily with less sample resources. The application of our proposed method is illustrated with two examples.
ENHANCING SAFETY IN SHIP'S CRITICAL SYSTEMS USING MARKOV MODELING
Authors: MENNIS EVANGELOS , PLATIS AGAPIOS , NIKITAKOS NIKITAS , FONTAINE JEAN GUY
Published: April 2009

The current study uses reliability models for the improvement of the operation of a ship's "bilge — water separator" system. A "bilge-water separator" is a mechanism which cleans and inspects the ship's bilge water before it is discharged into the sea. Homogeneous continuous time Markov models have been used to record and estimate possible hazards and system failures in two different operational scenarios. If the photocell unit of the system fails, the ship may cause severe sea pollution. This study attempts to estimate the probability of sea pollution based on empirical data. In addition, the results of the model are compared with those of a system in which a second metering unit is added in an effort to to find out if this alteration improves the systems' efficiency.
South Caspian to Central Iran basins: introduction
Authors: Brunet Marie-Françoise , Granath James W. , Wilmsen Markus
Published: April 2009

The structurally and stratigraphically complex area of northern and central Iran holds the key to understanding the plate tectonic evolution of the South Caspian–Central Iran area. The closure of the Palaeotethys, the opening of the Neotethys, the rise and demise of the Cimmerian mountain chain, as well as the onset of Neotethys subduction and large-scale Neotethyan back-arc rifting all predated the formation of the more than 20 km-thick fill of the South Caspian Basin. This volume brings together work by specialists in different disciplines of the geosciences (tectonics, geophysics, sedimentology, stratigraphy, palaeontology, basin modelling and geodynamics) in order to elucidate the complex Late Palaeozoic–Cenozoic geodynamic history of the Iran area and the birth of the South Caspian Basin.
The Triassic stratigraphic succession of Nakhlak (Central Iran), a record from an active margin
Authors: Balini Marco , Nicora Alda , Berra Fabrizio , Garzanti Eduardo , Levera Marco , Mattei Massimo , Muttoni Giovanni , Zanchi Andrea , Bollati Irene , Larghi Cristiano , Zanchetta Stefano , Salamati Reza , Mossavvari Fathullah
Published: April 2009

An important, 2.4 km-thick Triassic succession is exposed at Nakhlak (central Iran). This succession was deformed during the Cimmerian orogeny and truncated by an angular unconformity with undeformed Upper Cretaceous sediments. This integrated stratigraphic study of the Triassic included bed-by-bed sampling for ammonoids, conodonts and bivalves, as well as limestone and sandstone petrographic analyses. The Nakhlak Group succession consists of three formations: Alam (Olenekian–Anisian), Bāqoroq (?Upper Anisian–Ladinian) and Ashin (Upper Ladinian). The Alam Formation records several shifts from carbonate to siliciclastic deposition, the Bāqoroq Formation consists of continental conglomerates and the Ashin Formation documents the transition to deep-sea turbiditic sedimentation.

Petrographic composition has been studied for sandstones and conglomerates. Provenance analysis for Alam and most of the Ashin samples suggests a volcanic arc setting, whereas the samples from the Bāqoroq Formation are related to exhumation of a metamorphic basement. The provenance data, together with the great thickness, the sudden change of facies, the abundance of volcaniclastic supply, the relatively common occurrence of tuffitic layers and the orogenic calc-alkaline affinity of the volcanism, point to sedimentation along an active margin in a forearc setting.

A comparison between the Triassic of Nakhlak and the Triassic succession exposed in the erosional window of Aghdarband (Koppeh Dag, NE Iran) indicates that both were deposited along active margins. However, they do not show the same type of evolution. Nakhlak and Aghdarband have quite different ammonoid faunal affinities during the Early Triassic, but similar faunal composition from the Bithynian to Late Ladinian. These results argue against the location of Nakhlak close to Aghdarband.
Inorganic Polyphosphate: Essential for Growth and Survival
Authors: Rao Narayana N. , Gómez-García María R. , Kornberg Arthur
Published: April 2009

Inorganic polyphosphate (Poly P) is a polymer of tens to hundreds of phosphate residues linked by “high-energy” phosphoanhydride bonds as in ATP. Found in abundance in all cells in nature, it is unique in its likely role in the origin and survival of species. Here, we present extensive evidence that the remarkable properties of Poly P as a polyanion have made it suited for a crucial role in the emergence of cells on earth. Beyond that, Poly P has proved in a variety of ways to be essential for growth of cells, their responses to stresses and stringencies, and the virulence of pathogens. In this review, we pay particular attention to the enzyme, polyphosphate kinase 1 (Poly P kinase 1 or PPK1), responsible for Poly P synthesis and highly conserved in many bacterial species, including 20 or more of the major pathogens. Mutants lacking PPK1 are defective in motility, quorum sensing, biofilm formation, and virulence. Structural studies are cited that reveal the conserved ATP-binding site of PPK1 at atomic resolution and reveal that the site can be blocked with minute concentrations of designed inhibitors. Another widely conserved enzyme is PPK2, which has distinctive kinetic properties and is also implicated in the virulence of some pathogens. Thus, these enzymes, absent in yeast and animals, are novel attractive targets for treatment of many microbial diseases. Still another enzyme featured in this review is one discovered in Dictyostelium discoideum that becomes an actin-like fiber concurrent with the synthesis, step by step, of a Poly P chain made from ATP. The Poly P–actin fiber complex, localized in the cell, lengthens and recedes in response to metabolic signals. Homologs of DdPPK2 are found in pathogenic protozoa and in the alga Chlamydomonas. Beyond the immediate relevance of Poly P as a target for anti-infective drugs, a large variety of cellular operations that rely on Poly P will be considered.
Proton-Coupled Electron Transfer in Biology: Results from Synergistic Studies in Natural and Model Systems
Authors: Reece Steven Y. , Nocera Daniel G.
Published: April 2009

Proton-coupled electron transfer (PCET) underpins energy conversion in biology. PCET may occur with the unidirectional or bidirectional transfer of a proton and electron and may proceed synchronously or asynchronously. To illustrate the role of PCET in biology, this review presents complementary biological and model systems that explore PCET in electron transfer (ET) through hydrogen bonds [azurin as compared to donor-acceptor (D-A) hydrogen-bonded networks], the activation of C–H bonds [alcohol dehydrogenase and soybean lipoxygenase (SLO) as compared to Fe(III) metal complexes], and the generation and transport of amino acid radicals [photosystem II (PSII) and ribonucleotide reductase (RNR) as compared to tyrosine-modified photoactive Re(I) and Ru(II) complexes]. In providing these comparisons, the fundamental principles of PCET in biology are illustrated in a tangible way.
Do corticotropin releasing factor-1 receptors influence colonic transit and bowel function in women with irritable bowel syndrome?
Authors: Sweetser Seth , Camilleri Michael , Linker Nord Sara J. , Burton Duane D. , Castenada Lorna , Croop Robert , Tong Gary , Dockens Randy , Zinsmeister Alan R.
Published: April 2009

Corticotropin releasing factor (CRF), a mediator of stress response, alters gastrointestinal (GI) functions. Stress-related changes in colonic motility are blocked by selective CRF1receptor antagonists. Our aim was to assess whether modulation of central and peripheral CRF1receptors affects colonic transit and bowel function in female patients with diarrhea-predominant irritable bowel syndrome (D-IBS). This randomized, double-blind, placebo-controlled, 2-wk study evaluated the effects of oral pexacerfont (BMS-562086), a selective CRF1receptor antagonist, 25 and 100 mg qd, on GI and colonic transit of solids [by validated scintigraphy with primary end point colonic geometric center (GC) at 24 h] and bowel function (by validated daily diaries) in 39 women with D-IBS. The 100-mg dose was comparable to a dose that inhibited colonic motility in stressed rats. Treatment effects were compared by analysis of covariance with baseline colonic transit as covariate. The study had 80% power (α = 0.05) to detect clinically meaningful (26%) differences in colonic transit. Thirty-nine of 55 patients fulfilled eligibility criteria (9 screen failures, 5 baseline GC24 outside prespecified range). At baseline, three treatment groups had comparable age, body mass index, and GC 24 h. Significant effects of pexacerfont relative to placebo were not detected on colonic GC24 ( P = 0.53), gastric emptying, orocecal transit, ascending colon emptying half-time, and stool frequency, consistency, and ease of passage. No safety issues were identified. We conclude that in women with D-IBS, pexacerfont, 25 or 100 mg qd, does not significantly alter colonic or other regional transit or bowel function. The role of central and peripheral CRF1receptors in bowel function in D-IBS requires further study.
l-Arginine promotes angiogenesis in the chronically hypoxic lung: a novel mechanism ameliorating pulmonary hypertension
Authors: Howell K. , Costello C. M. , Sands M. , Dooley I. , McLoughlin P.
Published: April 2009

Chronic alveolar hypoxia, whether due to residence at high altitude or lung disease, leads to a sustained increase in pulmonary vascular resistance and pulmonary hypertension (PH). Strategies that augment endogenous nitric oxide production or activity, including l-arginine supplementation, attenuate the development of PH. This action has been attributed to inhibition of vessel wall remodeling, thus preventing structural narrowing of the vascular lumen. However, more recent evidence suggests that structural changes are not responsible for the elevated vascular resistance observed in chronic hypoxic PH, calling into question the previous explanation for the action of l-arginine. We examined the effect of dietary l-arginine supplementation on pulmonary vasoconstriction, structurally determined maximum vascular lumen diameter, and vessel length in rats during 2 wk of exposure to hypoxia. l-Arginine attenuated the development of hypoxic PH by preventing increased arteriolar resistance. It did not alter mean maximal vascular lumen diameter, nor did it augment nitric oxide-mediated vasodilatation, in chronically hypoxic lungs. However, the total length of vessels within the gas exchange region of the hypoxic lungs was significantly increased after l-arginine supplementation. These findings suggest that dietary l-arginine ameliorated hypoxic PH, but not by an effect on the structurally determined lumen diameter of pulmonary blood vessels. l-Arginine enhanced angiogenesis in the hypoxic pulmonary circulation, which may attenuate hypoxic PH by producing new parallel vascular pathways through the lung.
Local response to cold in rat tail after spinal cord transection
Authors: Kalincik Tomas , Jozefcikova Katarina , Waite Phil M. E. , Carrive Pascal
Published: April 2009

Subjects with severe chronic spinal cord injury (SCI) are prone to hypothermia when they are exposed to relatively low environmental temperatures that are normally well tolerated by healthy individuals. This impaired thermoregulation is presumably due to disconnection of territories below the SCI from supraspinal thermoregulatory centers. However, it is not known how these territories respond to low temperatures. Using a complete transection at T11 in rats, we examined the responses of the tail to cold (6–9°C) by measuring changes in tail blood flow and skin temperature weekly for 8 wk after SCI. Despite no significant change in baseline mean flow or temperature in the tail, the transection effectively removed the sympathetically mediated supraspinal control of the tail vasculature, since the amplitude of the pulse flow was markedly increased and the natural variations of the mean flow were almost abolished. As expected, the cold challenge before SCI caused a marked drop in mean flow, pulse amplitude, and temperature of the tail. Surprisingly, the drops in mean blood flow and temperature were observed after SCI, although the decrease in flow was slower and the pulse amplitude was not reduced. The results suggest that the cutaneous vasculature of the tail is sensitive to cold and will constrict, despite disconnection from supraspinal centers. This local effect is slow but may be sufficient to maintain some level of thermoregulation to cold. Without this vascular reaction, the effects of SCI on temperature regulation to cold would probably be much worse.