bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Refrigeration and Freezing on the Electromechanical and Biomechanical Properties of Articular Cartilage
Authors: Changoor Adele , Fereydoonzad Liah , Yaroshinsky Alex , Buschmann Michael D.
Published: October 2010

In vitro electromechanical and biomechanical testing of articular cartilage provide critical information about the structure and function of this tissue. Difficulties obtaining fresh tissue and lengthy experimental testing procedures often necessitate a storage protocol, which may adversely affect the functional properties of cartilage. The effects of storage at either 4°C for periods of 6 days and 12 days, or during a single freeze-thaw cycle at −20°C were examined in young bovine cartilage. Non-destructive electromechanical measurements and unconfined compression testing on 3 mm diameter disks were used to assess cartilage properties, including the streaming potential integral (SPI), fibril modulus (Ef), matrix modulus (Em), and permeability (k). Cartilage disks were also examined histologically. Compared with controls, significant decreases in SPI (to 32.3±5.5% of control values, p<0.001), Ef (to 3.1±41.3% of control values, p=0.046), Em (to 6.4±8.5% of control values, p<0.0001), and an increase in k (to 2676.7±2562.0% of control values, p=0.004) were observed at day 12 of refrigeration at 4°C, but no significant changes were detected at day 6. A trend toward detecting a decrease in SPI (to 94.2±6.2% of control values, p=0.083) was identified following a single freeze-thaw cycle, but no detectable changes were observed for any biomechanical parameters. All numbers are mean±95% confidence interval. These results indicate that fresh cartilage can be stored in a humid chamber at 4°C for a maximum of 6 days with no detrimental effects to cartilage electromechanical and biomechanical properties, while one freeze-thaw cycle produces minimal deterioration of biomechanical and electromechanical properties. A comparison to literature suggested that particular attention should be paid to the manner in which specimens are thawed after freezing, specifically by minimizing thawing time at higher temperatures.
Development of a Model Based Method for Investigating Facet Articulation
Authors: Cook Daniel J. , Cheng Boyle C.
Published: October 2010

Reported investigations of facet articulation in the human spine have often been conducted through the insertion of pressure sensitive film into the joint space, which requires incision of the facet capsule and may alter the characteristics of interaction between the facet surfaces. Load transmission through the facet has also been measured using strain gauges bonded to the articular processes. While this method allows for preservation of the facet capsule, it requires extensive instrumentation of the spine, as well as strain-gauge calibration, and is highly sensitive to placement and location of the strain gauges. The inherently invasive nature of these techniques makes it difficult to translate them into medical practice. A method has been developed to investigate facet articulation through the application of test kinematics to a specimen-specific rigid-body model of each vertebra within a lumbar spine segment. Rigid-body models of each vertebral body were developed from CT scans of each specimen. The distances between nearest-neighboring points on each facet surface were calculated for specific time frames of each specimen’s flexion/extension test. A metric describing the proportion of each facet surface within a distance (2 mm) from the neighboring surface, the contact area ratio (CAR), was calculated at each of these time frames. A statistically significant difference (p<0.037) was found in the CAR between the time frames corresponding to full flexion and full extension in every level of the lumbar spine (L1–L5) using the data obtained from the seven specimens evaluated in this study. The finding that the contact area of the facet is greater in extension than flexion corresponds to other findings in the literature, as well as the generally accepted role of the facets in extension. Thus, a biomechanical method with a sufficiently sensitive metric is presented as a means to evaluate differences in facet articulation between intact and treated or between healthy and pathologic spines.
Evaluation by Fluid/Structure-Interaction Spinal-Cord Simulation of
the Effects of Subarachnoid-Space Stenosis on an Adjacent Syrinx
Authors: Bertram C. D.
Published: October 2010

A finite-element numerical model was constructed of the spinal cord, pia mater, filum terminale, cerebrospinal fluid in the spinal subarachnoid space (SSS), and dura mater. The cord was hollowed out by a thoracic syrinx of length 140 mm, and the SSS included a stenosis of length 30 mm opposite this syrinx. The stenosis severity was varied from 0% to 90% by area. Pressure pulse excitation was applied to the model either at the cranial end of the SSS, simulating the effect of cranial arterial pulsation, or externally to the abdominal dura mater, simulating the effect of cough. A very short pulse was used to examine wave propagation; a pulse emulating cardiac systole was used to examine the effects of fluid displacement. Additionally, repetitive sinusoidal excitation was applied cranially. Bulk fluid flow past the stenosis gave rise to prominent longitudinal pressure dissociation (“suck”) in the SSS adjacent to the syrinx. However, this did not proportionally increase the longitudinal motion of fluid in the syrinx. The inertia of the fluid in the SSS, together with the compliance of this space, gave a resonance capable of being excited constructively or destructively by cardiac or coughing impulses. The main effect of mild stenosis was to lower the frequency of this resonance; severe stenosis damped out to-and-fro motions after the end of the applied excitation. Syrinx fluid motion indicated the fluid momentum and thus the pressure developed when the fluid was stopped by the end of the syrinx; however, the tearing stress in the local cord material depended also on the instantaneous local SSS pressure and was therefore not well predicted by syrinx fluid motion. Stenosis was also shown to give rise to a one-way valve effect causing raised SSS pressure caudally and slight average cord displacement cranially. The investigation showed that previous qualitative predictions of the effects of suck neglected factors that reduced the extent of the resulting syrinx fluid motion and of the cord tearing stress, which ultimately determines whether the syrinx lengthens.
Design of Practical Liquid Metal Cooling Device for Heat Dissipation of High Performance CPUs
Authors: Deng Yueguang , Liu Jing
Published: October 2010

Broad societal needs have focused attention on technologies that can effectively dissipate huge amount of heat from high power density electronic devices. Liquid metal cooling, which has been proposed in recent years, is fast emerging as a novel and promising solution to meet the requirements of high heat flux optoelectronic devices. In this paper, a design and implementation of a practical liquid metal cooling device for heat dissipation of high performance CPUs was demonstrated. GaInSn alloy with the melting point around 10°C was adopted as the coolant and a tower structure was implemented so that the lowest coolant amount was used. In order to better understand the design procedure and cooling capability, several crucial design principles and related fundamental theories were demonstrated and discussed. In the experimental study, two typical prototypes have been fabricated to evaluate the cooling performance of this liquid metal cooling device. The compared results with typical water cooling and commercially available heat pipes show that the present device could achieve excellent cooling capability. The thermal resistance could be as low as 0.13°C/W, which is competitive with most of the latest advanced CPU cooling devices in the market. Although the cost (about 70 dollars) is still relatively high, it could be significantly reduced to less than 30 dollars with the optimization of flow channel. Considering its advantages of low thermal resistance, capability to cope with extremely high heat flux, stability, durability, and energy saving characteristic when compared with heat pipe and water cooling, this liquid metal cooling device is quite practical for future application.
Digital Moiré Subtraction Interferometry (DMS) for Electronics Cooling Applications in Enclosures
Authors: Newport David , Forno Colin , Whelan Maurice
Published: October 2010

Optical noninvasive temperature measurement techniques, such as interferometry, are particularly advantageous in obtaining temperature information noninvasively from enclosed low velocity flows induced by thermal sources, as commonly arise in electronic systems. The single greatest restriction in the application of interferometry as a standard measurement methodology has been the enormous cost associated with the optical equipment required. This cost is due to the quality of the optics required, which exhibits an exponential dependence on size. Digital Moiré subtraction is a technique, which removes the restriction on the use of high quality optics, thereby, enabling reasonably large fields of view. In this paper, a digital Moiré subtraction interferometer configuration is presented with a 140 mm field of view. First, the ability of the interferometer to accurately measure the free convection temperature field about an isothermal horizontal cylinder is examined through a comparison with measurements from literature using classical interferometry. The technique is then applied to the thermal interaction between 2D components representing BGAs mounted on a vertical printed circuit board (PCB). Qualitative and quantitative evaluation of the interferograms show the significant influence of in-plane PCB conductivity on the temperature field about the PCB. The spacing to length ratio above, which upstream components on a PCB experience enhanced cooling, is reduced from 4 to 3 for a PCB with a high effective in-plane conductivity (15 W/m K).
The Constructal Law and the Design of the Biosphere: Nature and Globalization
Authors: Bejan Adrian , Lorente Sylvie
Published: October 2010

“Design in nature” is a topic of growing interest throughout science. The constructal law is the physics law of design generation and evolution in nature: “for a flow system to persist in time (to live), it must evolve such that it provides easier and easier access to its currents.” In this paper, we show how the constructal law accounts for the main features of the design of the biosphere: global movement of mass as the action of constructal engines (geophysical, animal, and human made) that dissipate their power into brakes, animal locomotion, vision, cognition, and hierarchy. The architecture and hierarchy of vegetation results from the constructal tendency to generate designs that facilitate the flow of water and “the flow of stresses” (i.e., mechanical strength per unit volume). Natural porous media have multiple scales because their flows are also configured as trees. The paper concludes with the oneness of design in nature, global design, and science and technology evolution—all as manifestations of the natural tendency captured by the constructal law and unified constructal theory of evolution.
Optimal Drug-Aerosol Delivery to Predetermined Lung Sites
Authors: Kleinstreuer Clement , Zhang Zhe
Published: October 2010

This review summarizes computer simulation methodologies of air-particle flow, results of drug-aerosol transport/deposition in models of the human respiratory system, as well as aspects of drug-aerosol targeting and associated inhalation devices. After a brief introduction to drug delivery systems in general, the required modeling and simulation steps for optimal drug-aerosol delivery in the lung are outlined. Starting with medical imaging and file conversion of patient-specific lung-airway morphologies, the air-particle transport phenomena are numerically solved for a representative inhalation flow rate of Qtotal=30 l/min. Focusing on microspheres and droplets, the complex airflow and particle dynamics, as well as the droplet heat and mass transfer are illustrated. With this foundation as the background, an overview of present inhaler devices is presented, followed by a discussion of the methodology and features of a new smart inhaler system (SIS). With the SIS, inhaled drug-aerosols can be directly delivered to any predetermined target area in the human lung.
Modeling Bidirectional Transport of New and Used Organelles in Fast Axonal Transport in Neurons
Authors: Kuznetsov A. V.
Published: October 2010

This paper develops a model for simulating transport of newly synthesized material from the neuron body toward the synapse of the axon as well as transport of misfolded and aggregated proteins back to the neuron body for recycling. The model demonstrates that motor-assisted transport, much similar to diffusion, can occur due to a simple concentration difference between the cell body and the synapse; organelles heading to the synapse do not need to attach preferably to plus-end-directed molecular motors, same as organelles heading to the neuron body for recycling do not need to attach preferably to minus-end-directed molecular motors. The underlying mechanics of molecular-motor-assisted transport is such that organelles would be transported to the right place even if new and used organelles had the same probability of attachment to plus-end-directed (and minus-end-directed) motors. It is also demonstrated that the axon with organelle traps and a region with a reversed microtubule polarity would support much smaller organelle fluxes of both new and used organelles than a healthy axon. The flux of organelles is shown to decrease as the width of organelle traps increases.
Human Eye Response to Thermal Disturbances
Authors: Shafahi Maryam , Vafai Kambiz
Published: October 2010

Human eye is one of the most sensitive parts of the body when exposed to a thermal heat flux. Since there is no barrier (such as skin) to protect the eye against the absorption of an external thermal wave, the external flux can readily interact with cornea. The modeling of heat transport through the human eye has been the subject of interest for years, but the application of a porous media model in this field is new. In this study, a comprehensive thermal analysis has been performed on the eye. The iris/sclera section of the eye is modeled as a porous medium. The primary sections of the eye, i.e., cornea, anterior chamber, posterior chamber, iris/sclera, lens, and vitreous are considered in our analysis utilizing a two-dimensional finite element simulation. Four different models are utilized to evaluate the eye thermal response to external and internal disturbances. Results are shown in terms of temperature profiles along the pupillary axis. Effects of extreme ambient conditions, blood temperature, blood convection coefficient, ambient temperature, sclera porosity, and perfusion rate on different regions of the eye are investigated. Furthermore, the role of primary thermal transport mechanisms on the eye subject to different conditions is analyzed.
Metabolic Mass Transfer in Monotonic Growth of Microorganisms
Authors: Vadasz Peter , Vadasz Alisa S.
Published: October 2010

Microorganism growth and reproduction have been traditionally modeled independently of the direct effect of the metabolic process. The latter caused inconsistencies between the modeling results and experimental data. A major inconsistency was linked to the experimentally observed lag phase in the growth process. Attempts to associate the lag phase to delay processes have been recently proven incorrect. The only other alternative is the existence of unstable stationary states resulting from the explicit inclusion of the metabolic mass transfer process via the resource consumption and utilization. The proposed theory that accounts for the latter is presented, analyzed, and compared with experimental data both qualitatively as well as quantitatively.
Investigation of the behavior of serum and plasma in a microfluidics system
Authors: Henderson J. Caroline , Yacopucci Michele , Chun ChangJu , Lenghaus Keith , Sommerhage Frank , Hickman James J.
Published: October 2010

There are common problems with adsorption of analytes on the surfaces of microfluidic systems with physiological samples such as blood serum, plasma, and urine. The authors’ investigation involves the interaction of serum components with fused-silica surfaces under various flow regimes in microcapillaries. Their focus will include the individual components of serum as well as fresh whole serum. The authors studied the whole serum components in our microfluidic system to uncover the responses of proteins in capillary and microchannel surfaces when influenced by the highly variable serum constituents. They have observed the whole serum with a total protein assay by using the bicinchoninic acid assay in combination with a characterization method, such as SDS polyacrylamide gel electrophoresis, and repeated observations for any change of flow rate in fused-silica capillaries (50 μm inside diameter) under continuous flow. The authors’ preliminary results contradict anecdotal evidence that proteins and other components of serum clog or prevent flow at steady low flow rates.
Evidence for a Collective Intelligence Factor in the Performance of Human Groups
Authors: Woolley Anita Williams , Chabris Christopher F. , Pentland Alex , Hashmi Nada , Malone Thomas W.
Published: October 2010

Meeting of Minds

The performance of humans across a range of different kinds of cognitive tasks has been encapsulated as a common statistical factor called
g
or general intelligence factor. What intelligence actually is, is unclear and hotly debated, yet there is a reproducible association of
g
with performance outcomes, such as income and academic achievement.

Woolley
et al.

(p.
686
, published online 30 September) report a psychometric methodology for quantifying a factor termed “collective intelligence” (
c
), which reflects how well groups perform on a similarly diverse set of group problem-solving tasks. The primary contributors to
c
appear to be the
g
factors of the group members, along with a propensity toward social sensitivity—in essence, how well individuals work with others.
Lung function loss in relation to silica dust exposure in South African gold miners
Authors: Ehrlich R I , Myers J E , te Water Naude J M , Thompson M L , Churchyard G J
Published: October 2010

Objective

To estimate exposure-response relationships between respirable dust, respirable quartz and lung function loss in black South African gold miners.

Methods

520 mineworkers aged >37 years were enrolled in a cross-sectional study. Gravimetric dust measurements were used to calculate cumulative respirable dust and quartz exposures. Excess lung function loss was defined as predicted minus observed forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). The association between excess loss and exposure was estimated, adjusting for smoking, tuberculosis and silicosis.

Results

Mean service length was 21.8 years, mean respirable dust 0.37 mg/m3and mean respirable quartz 0.053 mg/m3. After adjustment, 1 mg-yr/m3increase in cumulative respirable dust exposure was associated with 18.7 ml mean excess loss in FVC [95% confidence interval (CI) 0.3, 37.1] and 16.2 ml in FEV1 (95% CI -0.3, 32.6). Mean excess loss with silicosis was 224.1 ml in FEV1 and 123.6 ml in FVC; with tuberculosis 347.4 ml in FEV1 and 264.3 ml in FVC.

Conclusion

Despite a healthy worker effect, lung function loss was demonstrable whether due to silicosis, tuberculosis or an independent effect of dust. A miner working at a respirable dust intensity of 0.37 mg/m3for 30 years would lose on average an additional 208 ml in FVC (95% CI 3, 412) in the absence of other disease, an impact greater than that of silicosis and comparable to that of tuberculosis. Improved dust control on the South African gold mines would reduce the risk of silicosis, tuberculosis and lung function impairment.
Reduction of cooking oil fume exposure following an engineering intervention in Chinese restaurants
Authors: Pan Chih-Hong , Shih Tung-Sheng , Chen Chiou-Jong , Hsu Jin-Huei , Wang Shun-Chih , Huang Chien-Ping , Kuo Ching-Tang , Wu Kuen-Yuh , Hu Howard , Chan Chang-Chuan
Published: October 2010

Background

A new engineering intervention measure, an embracing air curtain device (EACD), was used to increase the capture efficiency of cooker hoods and reduce cooking oil fume (COF) exposure in Chinese restaurants.

Methods

An EACD was installed in six Chinese restaurants where the cooks complained of COF exposure. Before- and after-installation measurements were taken to compare changes in particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) in kitchen air, and changes in levels of urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) and malondialdehyde (MDA). The association between PM and PAHs in air and 8-OHdG and MDA in urine was evaluated by linear mixed-effects regression analysis.

Results

Results showed that geometric mean kitchen air levels of PM10, PM2.5, PM1.0and total particulate PAHs were significantly reduced after the EACDs were introduced. Urinary levels of 8-OHdG and MDA in cooks were also significantly lower after EACD instalment. PM2.5, PM1.0and benzo(a)pyrene (BaP) levels were positively associated with urinary 8-OHdG levels after adjusting for key personal covariates. Urinary MDA levels in cooks were also positively associated with BaP levels after adjusting for key personal covariates.

Conclusion

This study demonstrates that the EACD is effective for reducing COF and oxidative stress levels in cooks working in Chinese kitchens.
Retrospective cohort study of the risk of obesity among shift workers: findings from the Industry-based Shift Workers' Health study, Japan
Authors: Kubo Tatsuhiko , Oyama Ichiro , Nakamura Takehiro , Shirane Kiyoyumi , Otsuka Hirotake , Kunimoto Masamizu , Kadowaki Koji , Maruyama Takashi , Otomo Hajime , Fujino Yoshihisa , Matsumoto Tetsuro , Matsuda Shinya
Published: October 2010

Objectives

The authors investigated the effect of shift working on the risk of obesity using data from the Industry-based Shift Workers' Health (IbSH) study, a retrospective cohort study based on a health care database system belonging to a manufacturing corporation in Japan.

Methods

The study database contains data on annual health check-ups and work schedules for every worker in the corporation in Japan since 1981. Study subjects consisted of 9912 male employees (8892 daytime workers and 920 rotating three-shift workers; mean age at first check-up was 23.7 years) whose work schedules were consistent during the follow-up period. Obesity was defined as a body mass index ≥25.0.

Results

3319 cases of obesity were recorded over the 27.5 years of retrospective follow-up. Kaplan–Meier survival analysis visually demonstrated an increased risk of obesity among shift workers. The risk becomes particularly obvious after 10 years of follow-up. Cox proportional-hazards model analysis revealed a significantly increased risk among shift workers (RR 1.14, 95% CI 1.01 to 1.28).

Conclusion

The risk of obesity among male shift workers was visually and statistically demonstrated.
The impact of deployment length on the health and well-being of military personnel: a systematic review of the literature
Authors: Buckman Joshua E J , Sundin Josefin , Greene Talya , Fear Nicola T , Dandeker Christopher , Greenberg Neil , Wessely Simon
Published: October 2010

To determine the current state of knowledge regarding the effects of deployment length and a ‘mismatch’ between the expected and actual length of deployments on the health and well-being of military personnel in order to draw relevant conclusions for all organisations that deploy personnel to conflict zones. A systematic review was conducted of studies measuring deployment length to theatres of operations and the issue of ‘mismatch’ between expected and actual tour lengths. The nine studies included were rated for quality. Of the nine studies reviewed, six were rated as high quality, two as moderate quality and one as low quality. Seven of these studies found adverse effects of longer deployments on health and well-being. The two studies that measured ‘mismatch’ found adverse effects on mental health and well-being when deployments lasted longer than personnel expected. There are a limited number of studies which have assessed the effects of deployment length and very few that have assessed the effects of ‘mismatch’ on health and well-being. However, this review suggests that, as deployment length increases, the potential for personnel to suffer adverse health effects also increases. Further research is required to investigate the effects of spending prolonged periods of time away from family and friends, especially when deployment lasts longer than expected by personnel. These results are important not only for the Armed Forces, but also for other organisations that place employees in similar working conditions. Taking account of these findings may allow better preparation for the potentially harmful effects that deployments can have on employees' health and well-being.
Outdoor work and risk for Parkinson's disease: a population-based case–control study
Authors: Kenborg Line , Lassen Christina F , Ritz Beate , Schernhammer Eva S , Hansen Johnni , Gatto Nicole M , Olsen Jørgen H
Published: October 2010

Objectives

Sunlight is the main contributor to vitamin D in humans. Since inadequate levels of vitamin D have been linked to increased risks for neurodegenerative diseases, we examined whether outdoor work is associated with a reduced risk for Parkinson's disease in a population-based case–control study of Danish men.

Methods

We identified 3819 men with a primary diagnosis of Parkinson's disease in the period 1995–2006 in the Danish National Hospital Register and selected 19 282 age- and sex-matched population controls at random from the Central Population Register. Information on work history was ascertained from the Danish Supplementary Pension Fund and the Central Population Register. Based on trade grouping codes and job titles, we evaluated the extent of outdoor work of study subjects as a proxy of exposure to sunlight.

Results

Relying on trade grouping codes, we estimated ORs for study subjects with moderate, frequent and maximal outdoor work compared with exclusive indoor work of 0.90 (95% CI 0.78 to 1.02), 0.86 (95% CI 0.75 to 0.99) and 0.72 (95% CI 0.63 to 0.82), respectively, for Parkinson's disease. Reduced risks were also found for Parkinson's disease among outdoor workers based on study subjects' job titles.

Conclusions

Our findings suggest that men working outdoors have a lower risk for Parkinson's disease. Further studies of measured vitamin D levels in outdoor workers are warranted to clarify a potential inverse association between vitamin D and the risk for Parkinson's disease.
TIME-PROJECTION-CHAMBERS WITH OPTICAL READOUT FOR DARK MATTER, DOUBLE BETA DECAY, AND NEUTRON MEASUREMENTS
Authors: AHLEN S. P.
Published: October 2010

In recent years, there have been impressive advances in the technology of cameras using charged coupled devices (CCD's) and electron multiplying charged coupled devices (EMCCD's) that make possible a number of applications for the detection of ionizing radiation. The new cameras have quantum efficiencies exceeding 90%, effective noise levels less than one electron per pixel, and can be made to detect light ranging from the ultraviolet to the infrared. When combined with photomultiplier tubes (PMT's), and when used with Time-Projection-Chambers (TPC's) that contain narrow gap mesh charge amplification stages and scintillating gas compositions, these cameras can be used to provide three-dimensional images of particle tracks. There are many applications for such devices, including direction sensitive searches for dark matter, measurements of thermal and fast neutrons, and searches for double-beta-decay. I will describe the operation of optical TPC's and their various applications in this review article.
SPIKY STRINGS AND GAUGE THEORY PARTONS
Authors: DOREY NICK , LOSI MANUEL
Published: October 2010

We propose a correspondence between strings with cusps which approach the boundary in AdS and energetic partons in the dual gauge theory on S3. In particular, the momenta of individual quanta on S3 are identified with certain collective coordinates associated with the cusps. We check the correspondence by studying the known exact string solutions, as well as a large class of approximate solutions, in the limit of large AdS angular momentum.
MODELING THE FLYBY ANOMALIES WITH DARK MATTER SCATTERING
Authors: ADLER STEPHEN L.
Published: October 2010

We continue our exploration of whether the flyby anomalies can be explained by scattering of spacecraft nucleons from dark matter gravitationally bound to the earth. We formulate and analyze a simple model in which inelastic and elastic scatterers populate shells generated by the precession of circular orbits with normals tilted with respect to the earth's axis. Good fits to the data published by Anderson et al. are obtained.
MASS OPERATOR OF THE INTERACTING ELECTRONS IN FORMALISM OF PERMUTATION GROUP THEORY
Authors: TOVSTYUK CORNELIA
Published: October 2010

Double permutation (DP) method is developed here for designing Feynman diagrams for mass operator (MO) of interacting electrons in high orders of perturbation theory (PT). The derived expression allows finding the Young diagrams for the class of permutations corresponding to disconnect Feynman diagrams. The classification of DPs, carried out before, allows to identify the permutations corresponding to disconnected, singly connected (improper) diagrams and to derive expressions for intolerant cycles of permutations. Ordering the nonprimed digits in natural order in the cycles of DP, we avoid the permutations, corresponding to the Feynman diagrams of the same topology because of other numbering of nodes. Thus, the numbers of considered permutations is sufficiently reduced: (from 24 to 6 and from 720 to 42) in the second and the third orders of PT. All 414 expressions (diagrams) for MO in the fourth order of PT were designed using this method. The use of group theory allows us to conclude that no more Feynman diagrams can be designed. The developed method can be used as algorithm for Feynman diagrams designing for MO of interacting electrons (one sort fermions) in higher orders of PT.
NEW POSSIBILITIES FOR OBTAINING STEEPLY NONLINEAR CURRENT–VOLTAGE CHARACTERISTICS IN SOME SEMICONDUCTOR STRUCTURES
Authors: SHEKA D. I. , TRETYAK O. V. , KOROL A. M. , SEN A. K. , MOOKERJEE A.
Published: October 2010

Electronic processes in a semiconductor system consisting of some resonant tunneling structures, built in the depletion region of a Schottky barrier, are investigated. It is shown that the Schottky barrier can block or unblock the resonant tunneling current effectively. Tunneling processes do reveal the coherent character. Sharply nonlinear current–voltage characteristics are observed for both the forward and the reverse branches.
MAGNETIC CLUSTER EXCITATIONS
Authors: FURRER ALBERT
Published: October 2010

Magnetic cluster systems can be considered as nanomagnets consisting of a small number of interacting spins that are magnetically isolated from the neighboring clusters of the compound by nonmagnetic ligands. Inelastic neutron scattering is a powerful experimental tool for the study of magnetic clusters, since it provides direct access to energy splittings. The present work provides an overview on this subject. The underlying concepts are presented and illustrated for some representative examples such as single-molecule magnets, diluted magnets, magnetic polarons, and dimer based compounds associated with quantum phase transitions and Bose–Einstein condensation as well as spin-Peierls dimerization. It is shown that — besides the dominant Heisenberg interaction — anisotropic and higher-order exchange terms are often needed to rationalize the experimental data.
MODIFIED EXP-FUNCTION METHOD AND VARIABLE-COEFFICIENT KORTEWEG–DE VRIES MODEL FROM BOSE–EINSTEIN CONDENSATES
Authors: CAI KE-JIE , ZHANG CHENG , XU TAO , ZHANG HUAN , TIAN BO
Published: October 2010

The amplitude of nonlinear excitations in BECs with inhomogeneities is governed by a generalized variable-coefficient Korteweg–de Vries model. With symbolic computation, the Exp-function method is modified to obtain analytical nontraveling solitary-wave and periodic-wave solutions. Through the qualitative analysis and graphical illustration, the inhomogeneous propagation features of solitary waves are discussed, and some observable effects for BEC dynamic in the presence of external potentials are provided. The modified Exp-function method is also applicable to other variable-coefficient nonlinear evolution equations.
A GRADIENT-LIKE NONAUTONOMOUS EVOLUTION PROCESS
Authors: CARABALLO TOMÁS , LANGA JOSÉ A. , RIVERO FELIPE , CARVALHO ALEXANDRE N.
Published: October 2010

In this paper we consider a dissipative damped wave equation with nonautonomous damping of the form [Formula: see text] in a bounded smooth domain Ω ⊂ ℝn with Dirichlet boundary conditions, where f is a dissipative smooth nonlinearity and the damping β : ℝ → (0, ∞) is a suitable function. We prove, if (1) has finitely many equilibria, that all global bounded solutions of (1) are backwards and forwards asymptotic to equilibria. Thus, we give a class of examples of nonautonomous evolution processes for which the structure of the pullback attractors is well understood. That complements the results of [Carvalho & Langa, 2009] on characterization of attractors, where it was shown that a small nonautonomous perturbation of an autonomous gradient-like evolution process is also gradient-like. Note that the evolution process associated to (1) is not a small nonautonomous perturbation of any autonomous gradient-like evolution processes. Moreover, we are also able to prove that the pullback attractor for (1) is also a forwards attractor and that the rate of attraction is exponential.
RANDOM ATTRACTORS FOR STOCHASTIC EQUATIONS DRIVEN BY A FRACTIONAL BROWNIAN MOTION
Authors: GARRIDO-ATIENZA M. J. , MASLOWSKI B. , SCHMALFUß B.
Published: October 2010

In this paper, the asymptotic behavior of stochastic differential equations driven by a fractional Brownian motion with Hurst parameter H > 1/2 is studied. In particular, it is shown that the corresponding solutions generate a random dynamical system for which the existence and uniqueness of a random attractor is proved.
ON THE SUPERCRITICALITY OF THE FIRST HOPF BIFURCATION IN A DELAY BOUNDARY PROBLEM
Authors: ARRIETA J. M. , CONSUL N. , OLIVA S. M.
Published: October 2010

The goal of this paper is to analyze the character of the first Hopf bifurcation (subcritical versus supercritical) that appears in a one-dimensional reaction–diffusion equation with nonlinear boundary conditions of logistic type with delay. We showed in the previous work [Arrieta et al., 2010] that if the delay is small, the unique non-negative equilibrium solution is asymptotically stable. We also showed that, as the delay increases and crosses certain critical value, this equilibrium becomes unstable and undergoes a Hopf bifurcation. This bifurcation is the first one of a cascade occurring as the delay goes to infinity. The structure of this cascade will depend on the parameters appearing in the equation. In this paper, we show that the first bifurcation that occurs is supercritical, that is, when the parameter is bigger than the delay bifurcation value, stable periodic orbits branch off from the constant equilibrium.
Identification of low-level point radioactive sources using a sensor network
Authors: Chin Jren-Chit , Rao Nageswara S. V. , Yau David K. Y. , Shankar Mallikarjun , Yang Yong , Hou Jennifer C. , Srivathsan Srinivasagopalan , Iyengar Sitharama
Published: October 2010

Identification of a low-level point radioactive source amidst background radiation is achieved by a network of radiation sensors using a two-step approach. Based on measurements from three or more sensors, a geometric difference triangulation method or an
N
-sensor localization method is used to estimate the location and strength of the source. Then a sequential probability ratio test based on current measurements and estimated parameters is employed to finally decide: (1) the presence of a source with the estimated parameters, or (2) the absence of the source, or (3) the insufficiency of measurements to make a decision. This method achieves specified levels of false alarm and missed detection probabilities, while ensuring a close-to-minimal number of measurements for reaching a decision. This method minimizes the ghost-source problem of current estimation methods, and achieves a lower false alarm rate compared with current detection methods. This method is tested and demonstrated using: (1) simulations, and (2) a test-bed that utilizes the scaling properties of point radioactive sources to emulate high intensity ones that cannot be easily and safely handled in laboratory experiments.
Localized spanner construction for ad hoc networks with variable transmission range
Authors: Peleg David , Roditty Liam
Published: October 2010

This article presents an algorithm for constructing a spanner for ad hoc networks whose nodes have
variable
transmission range. Almost all previous spanner constructions for ad hoc networks assumed that all nodes in the network have the same transmission range. This allowed a succinct representation of the network as a unit disk graph, serving as the basis for the construction. In contrast, when nodes have variable transmission range, the ad hoc network must be modeled by a general disk graph. Whereas unit disk graphs are undirected, general disk graphs are directed. This complicates the construction of a spanner for the network, since currently there are no efficient constructions of low-stretch spanners for general directed graphs. Nevertheless, in this article it is shown that the class of disk graphs enjoys (efficiently constructible) spanners of quality similar to that of unit disk graph spanners. Moreover, it is shown that the new construction can be performed in a localized fashion. Our results use only simple packing arguments, hence all algorithms work for every metric space of constant doubling dimension.
Analysis of power-aware buffering schemes in wireless sensor networks
Authors: Ling Yibei , Chen Chung-Min , Chen Shigang
Published: October 2010

We study the power-aware buffering problem in battery-powered sensor networks, focusing on the fixed-size and fixed-interval buffering schemes. The main motivation is to address the yet poorly understood size variation-induced effect on power-aware buffering schemes. Our theoretical analysis elucidates the fundamental differences between the fixed-size and fixed-interval buffering schemes in the presence of data-size variation. It shows that data-size variation has detrimental effects on the power expenditure of the fixed-size buffering in general, and reveals that the size variation induced effects can be either mitigated by a positive skewness or promoted by a negative skewness in size distribution. By contrast, the fixed-interval buffering scheme has an obvious advantage of being eminently immune to the data-size variation. Hence the fixed-interval buffering scheme is a risk-averse strategy for its robustness in a variety of operational environments. In addition, based on the fixed-interval buffering scheme, we establish the power consumption relationship between child nodes and parent node in a static data-collection tree, and give an in-depth analysis of the impact of child bandwidth distribution on the parent's power consumption.

This study is of practical significance: it sheds new light on the relationship among power consumption of buffering schemes, power parameters of radio module and memory bank, data arrival rate, and data-size variation, thereby providing well-informed guidance in determining an optimal buffer size (interval) to maximize the operational lifespan of sensor networks.
Force-directed approaches to sensor localization
Authors: Efrat Alon , Forrester David , Iyer Anand , Kobourov Stephen G. , Erten Cesim , Kilic Ozan
Published: October 2010

As the number of applications of sensor networks increases, so does the interest in sensor network localization, that is, in recovering the correct position of each node in a network of sensors from partial connectivity information such as adjacency, range, or angle between neighboring nodes. In this article, we consider the anchor-free localization problem in sensor networks that report possibly noisy range information and angular information about the relative order of each sensor's neighbors. Previously proposed techniques seem to successfully reconstruct the original positions of the nodes for relatively small networks with nodes distributed in simple regions. However, these techniques do not scale well with network size and yield poor results with nonconvex or nonsimple underlying topology. Moreover, the distributed nature of the problem makes some of the centralized techniques inapplicable in distributed settings. To address these problems we describe a multiscale dead-reckoning (MSDR) algorithm that scales well for large networks, can reconstruct complex underlying topologies, and is resilient to noise. The MSDR algorithm takes its roots from classic force-directed graph layout computation techniques. These techniques are augmented with a multiscale extension to handle the scalability issue and with a dead-reckoning extension to overcome the problems arising with nonsimple topologies. Furthermore, we show that the distributed version of the MSDR algorithm performs as well as, if not better than, its centralized counterpart, as shown by the quality of the layout, measured in terms of the accuracy of the computed pairwise distances between sensors in the network.
Personal fabrication
Authors: Stemp-Morlock Graeme
Published: October 2010

Open source 3D printers could herald the start of a new industrial revolution.
Victorian data processing
Authors: Campbell-Kelly Martin
Published: October 2010

Reflections on the first payment systems.
Version aversion
Authors: Neville-Neil George V.
Published: October 2010

The way you number your releases communicates more than you might think.
SCORE
Authors: Hicks Michael , Foster Jeffrey S.
Published: October 2010

Adapting agile software development methodology toward more efficient management of academic research groups.
Photoshop scalability
Authors: ACM Case Study
Published: October 2010

Clem Cole and Russell Williams discuss Photoshop's long history with parallelism, and what is now seen as the chief challenge.
A neuromorphic approach to computer vision
Authors: Serre Thomas , Poggio Tomaso
Published: October 2010

Neuroscience is beginning to inspire a new generation of seeing machines.
Difference engine
Authors: Gupta Diwaker , Lee Sangmin , Vrable Michael , Savage Stefan , Snoeren Alex C. , Varghese George , Voelker Geoffrey M. , Vahdat Amin
Published: October 2010

Virtual machine monitors (VMMs) are a popular platform for Internet hosting centers and cloud-based compute services. By multiplexing hardware resources among virtual machines (VMs) running commodity operating systems, VMMs decrease both the capital outlay and management overhead of hosting centers. Appropriate placement and migration policies can take advantage of statistical multiplexing to effectively utilize available processors. However, main memory is not amenable to such multiplexing and is often the primary bottleneck in achieving higher degrees of consolidation.

Previous efforts have shown that content-based page sharing provides modest decreases in the memory footprint of VMs running similar operating systems and applications. Our studies show that significant additional gains can be had by leveraging both subpage level sharing (through page patching) and incore memory compression. We build
Difference Engine
, an extension to the Xen VMM, to support each of these---in addition to standard copy-on-write full-page sharing---and demonstrate substantial savings across VMs running disparate workloads (up to 65%). In head-to-head memory-savings comparisons, Difference Engine outperforms VMware ESX server by a factor 1.6--2.5 for heterogeneous workloads. In all cases, the performance overhead of Difference Engine is less than 7%.
Q&A: Gray's paradigm
Authors: Hoffmann Leah
Published: October 2010

Tony Hey talks about Jim Gray and his vision of a new era of collaborative, data-intensive science.
SIGCSE
Authors: Johnson Julie
Published: October 2010

What is the impact of SIGCSE's global vision? When we interviewed the outgoing SIGCSE board for our June newsletter, we got an earful! Many past and present SIGCSE board members believe that broadening our international vision will be a key factor in the group's future success.
The art of paper categorization
Authors: Walker Henry
Published: October 2010

Authors of proposals to the SIGCSE symposia and ITiCSE conferences pick one to four subject areas for their work. Conference leaders use these categories to assign reviewers with appropriate expertise.
The New Ubiquity
Authors: Denning Peter J.
Published: October 2010

Ubiquity's new site will launch this month, marking a new editorial direction. Ubiquity is now a peer-reviewed online publication of ACM dedicated to the future of computing and the people who are creating it.
Stimulation of apical Cl−/HCO3−(OH−) exchanger, SLC26A3 by neuropeptide Y is lipid raft dependent
Authors: Saksena Seema , Tyagi Sangeeta , Goyal Sonia , Gill Ravinder K. , Alrefai Waddah A. , Ramaswamy K. , Dudeja Pradeep K.
Published: October 2010

Neuropeptide Y (NPY), an important proabsorptive hormone of the gastrointestinal tract has been shown to inhibit chloride secretion and stimulate NaCl absorption. However, mechanisms underlying the proabsorptive effects of NPY are not fully understood. The present studies were designed to examine the direct effects of NPY on apical Cl−/HCO3−(OH−) exchange activity and the underlying mechanisms involved utilizing Caco2 cells. Our results showed that NPY (100 nM, 30 min) significantly increased Cl−/HCO3−(OH−) exchange activity (∼2-fold). Selective NPY/Y1 or Y2 receptor agonists mimicked the effects of NPY. NPY-mediated stimulation of Cl−/HCO3−(OH−) exchange activity involved the ERK1/2 MAP kinase-dependent pathway. Cell surface biotinylation studies showed that NPY does not alter DRA (apical Cl−/HCO3−(OH−) exchanger) surface expression, ruling out the involvement of membrane trafficking events. Interestingly, DRA was found to be predominantly expressed in the detergent-insoluble (DI) and low-density fractions (LDF) of human colonic apical membrane vesicles (AMVs) representing lipid rafts. Depletion of membrane cholesterol by methyl-β-cyclodextrin (MβCD, 10 mM, 1 h) remarkably decreased DRA expression in the DI fractions. Similar results were obtained in Triton-X 100-treated Caco2 plasma membranes. DRA association with lipid rafts in the DI and LDF fractions of Caco2 cells was significantly enhanced (∼45%) by NPY compared with control. MβCD significantly decreased Cl−/HCO3−(OH−) exchange activity in Caco2 cells as measured by DIDS- or niflumic acid-sensitive36Cl−uptake (∼50%). Our results demonstrate that NPY modulates Cl−/HCO3−(OH−) exchange activity by enhancing the association of DRA with lipid rafts, thereby resulting in an increase in Cl−/HCO3−(OH−) exchange activity. Our findings suggest that the alteration in the association of DRA with lipid rafts may contribute to the proabsorptive effects of NPY in the human intestine.