bluuebunny/crossref_metadata_2025 huggingface dataset:
Examination of ‘lipotoxicity’ in skeletal muscle of high‐fat fed and ob/ob mice
Authors: Turpin S. M. , Ryall J. G. , Southgate R. , Darby I. , Hevener A. L. , Febbraio M. A. , Kemp B. E. , Lynch G. S. , Watt M. J.
Published: February 2009

Excess lipid accumulation resulting from an elevated supply of plasma fatty acids is linked to the pathogenesis of the metabolic syndrome and heart disease. The term ‘lipotoxicity’ was coined to describe how lipid accumulation leads to cellular dysfunction and death in non‐adipose tissues including the heart, pancreas and liver. While lipotoxicity has been shown in cultured skeletal muscle cells, the degree of lipotoxicity in vivo and the functional consequences are unresolved. We studied three models of fatty acid overload in male mice: 5 h Intralipid® and heparin infusion, prolonged high fat feeding (HFF) and genetic obesity induced by leptin deficiency (ob/ob mice). Markers of apoptosis, proteolysis and autophagy were assessed as readouts of lipotoxicity. The Intralipid® infusion increased caspase 3 activity in skeletal muscle, demonstrating that enhancing fatty acid flux activates pro‐apoptotic pathways. HFF and genetic obesity increased tissue lipid content but did not influence apoptosis. Gene array analysis revealed that HFF reduced the expression of 31 pro‐apoptotic genes. Markers of autophagy (LC3β and beclin‐1 expression) were unaffected by HFF and were associated with enhanced Bcl2 protein expression. Proteolytic activity was similarly unaffected by HFF or in ob/ob mice. Thus, contrary to our previous findings in muscle culture in vitro and in other non‐adipose tissues in vivo, lipid overload did not induce apoptosis, autophagy or proteolysis in skeletal muscle. A broad transcriptional suppression of pro‐apoptotic proteins may explain this resistance to lipid‐induced cell death in skeletal muscle.
Gonadotropin inhibitory hormone inhibits basal forebrain vGluT2‐gonadotropin‐releasing hormone neurons via a direct postsynaptic mechanism
Authors: Wu Min , Dumalska Iryna , Morozova Elena , Van Den Pol Anthony N. , Alreja Meenakshi
Published: February 2009

The novel hypothalamic peptides avian gonadotropin inhibitory hormone (GnIH) and its mammalian analogue RFRP‐3, are emerging as key negative regulators of reproductive functions across species. GnIH/RFRP‐3 reduces gonadotropin release and may play an inhibitory role in ovulation and seasonal reproduction, actions opposite to that of the puberty‐promoting kisspeptins. GnIH directly inhibits gonadotropin release from the anterior pituitary in birds. GnIH/RFRP‐3‐immunoreactive fibres also abut the preoptic‐septal gonadotropin‐releasing hormone (GnRH) neurons, suggesting an additional site of action that has not been studied at the cellular level. Using anatomical labelling and electrophysiological recordings in septal brain slices from GnRH‐GFP, vGluT2‐GFP and GAD67‐GFP mice, we report inhibitory actions of GnIH/RFRP‐3 on kisspeptin‐activated vGluT2 (vesicular glutamate transporter 2)‐GnRH neurons as well as on kisspeptin‐insensitive GnRH neurons, but not on cholinergic or GABAergic neurons (n= 531). GnIH and RFRP‐3 produced a strikingly similar non‐desensitizing hyperpolarization following brief 15 s applications (GnIH: 9.3 ± 1.9 mV; RFRP‐3: 9.0 ± 0.9 mV) with IC50 values of 34 and 37 nm, respectively. The inhibitory effect was mediated via a direct postsynaptic Ba2+‐sensitive K+ current mechanism and could prevent or interrupt kisspeptin‐induced activation of vGluT2‐GnRH neurons. GnIH‐immunoreactive fibres were in apparent contact with vGluT2‐GFP neurons. Thus, GnIH/RFRP‐3 could reduce GnRH and glutamate release in target brain regions and in the median eminence via a direct inhibition of vGluT2‐GnRH neurons. This in turn could suppress gonadotropin release, influence reproductive development and alter sex behaviour.
Stimulation of orexin/hypocretin neurones by thyrotropin‐releasing hormone
Authors: González J. Antonio , Horjales‐Araujo Emilia , Fugger Lars , Broberger Christian , Burdakov Denis
Published: February 2009

Central orexin/hypocretin neurones are critical for sustaining consciousness: their firing stimulates wakefulness and their destruction causes narcolepsy. We explored whether the activity of orexin cells is modulated by thyrotropin‐releasing hormone (TRH), an endo‐genous stimulant of wakefulness and locomotor activity whose mechanism of action is not fully understood. Living orexin neurones were identified by targeted expression of green fluorescent protein (GFP) in acute brain slices of transgenic mice. Using whole‐cell patch‐clamp recordings, we found that TRH robustly increased the action potential firing rate of these neurones. TRH‐induced excitation persisted under conditions of synaptic isolation, and involved a Na+‐dependent depolarization and activation of a mixed cation current in the orexin cell membrane. By double‐label immunohistochemistry, we found close appositions between TRH‐immunoreactive nerve terminals and orexin‐A‐immunoreactive cell bodies. These results identify a new physiological modulator of orexin cell firing, and suggest that orexin cell excitation may contribute to the arousal‐enhancing actions of TRH.
Inositol‐1,4,5‐trisphosphate receptor‐mediated Ca2+ waves in pyramidal neuron dendrites propagate through hot spots and cold spots
Authors: Fitzpatrick John S. , Hagenston Anna M. , Hertle Daniel N. , Gipson Keith E. , Bertetto‐D'Angelo Lisa , Yeckel Mark F.
Published: February 2009

We studied inositol‐1,4,5‐trisphosphate (IP3) receptor‐dependent intracellular Ca2+ waves in CA1 hippocampal and layer V medial prefrontal cortical pyramidal neurons using whole‐cell patch‐clamp recordings and Ca2+ fluorescence imaging. We observed that Ca2+ waves propagate in a saltatory manner through dendritic regions where increases in the intracellular concentration of Ca2+ ([Ca2+]i) were large and fast (‘hot spots’) separated by regions where increases in [Ca2+]i were comparatively small and slow (‘cold spots’). We also observed that Ca2+ waves typically initiate in hot spots and terminate in cold spots, and that most hot spots, but few cold spots, are located at dendritic branch points. Using immunohistochemistry, we found that IP3 receptors (IP3Rs) are distributed in clusters along pyramidal neuron dendrites and that the distribution of inter‐cluster distances is nearly identical to the distribution of inter‐hot spot distances. These findings support the hypothesis that the dendritic locations of Ca2+ wave hot spots in general, and branch points in particular, are specially equipped for regenerative IP3R‐dependent internal Ca2+ release. Functionally, the observation that IP3R‐dependent [Ca2+]i rises are greater at branch points raises the possibility that this novel Ca2+ signal may be important for the regulation of Ca2+‐dependent processes in these locations. Futhermore, the observation that Ca2+ waves tend to fail between hot spots raises the possibility that influences on Ca2+ wave propagation may determine the degree of functional association between distinct Ca2+‐sensitive dendritic domains.
Activation of neurokinin 3 receptor increases Nav1.9 current in enteric neurons
Authors: Copel Carine , Osorio Nancy , Crest Marcel , Gola Maurice , Delmas Patrick , Clerc Nadine
Published: February 2009

The intrinsic primary afferent neurons (IPANs) of the guinea pig enteric nervous system express Nav1.9 sodium channels that produce a persistent TTX‐resistant current having a low activation threshold and slow gating kinetics. These neurons receive slow EPSPs induced mainly by the activation of neurokinin 3 receptors (NK3r). Here, we demonstrate that senktide, a specific NK3r agonist, potentiates the Nav1.9 current (INav1.9) in IPANs. Using whole‐cell patch‐clamp recordings from IPANs in duodenum longitudinal muscle/myenteric plexus preparations, we show that short (1–5 s) and long (up to 1 min) applications of senktide, increase the INav1.9 peak current up to 13‐fold. The effect, blocked by a NK3r antagonist SB235375 is transient, lasting ∼2 min and is due to a negative shift of the activation voltage by ∼20 mV and of fast inactivation by ∼10 mV. As a consequence, the window current resulting from the product of the activation and fast inactivation curves is shifted and enlarged. The transient effect of senktide is likely to be due to the fast desensitization of NK3r. Protein kinase C (PKC) activation with phorbol or oleoyl acetylglycerol also increases INav1.9, although persistently, by inducing similar voltage‐dependent changes. Current‐clamp experiments showed that INav1.9 modulation by senktide lowers action potential threshold and increases excitability. The increase in INav1.9 by NK3r activation is also likely to amplify slow EPSPs generated in the IPANs. These changes in excitability potentially have a profound effect on the entire enteric synaptic circuit and ultimately on gut motility and secretion.
Antimicrobial Activity of Curcumin against
Helicobacter pylori
Isolates from India and during Infections in Mice
Authors: De Ronita , Kundu Parag , Swarnakar Snehasikta , Ramamurthy T. , Chowdhury Abhijit , Nair G. Balakrish , Mukhopadhyay Asish K.
Published: February 2009

Treatment failure is a major cause of concern for the
Helicobacter pylori
-related gastroduodenal diseases like gastritis, peptic ulcer, and gastric cancer. Curcumin, diferuloylmethane from turmeric, has recently been shown to arrest
H. pylori
growth. The antibacterial activity of curcumin against 65 clinical isolates of
H. pylori
in vitro and during protection against
H. pylori
infection in vivo was examined. The MIC of curcumin ranges from 5 μg/ml to 50 μg/ml, showing its effectiveness in inhibiting
H. pylori
growth in vitro irrespective of the genetic makeup of the strains. The nucleotide sequences of the
aroE
genes, encoding shikimate dehydrogenase, against which curcumin seems to act as a noncompetitive inhibitor, from
H. pylori
strains presenting differential curcumin MICs showed that curcumin-mediated growth inhibition of Indian
H. pylori
strains may not be always dependent on the shikimate pathway. The antimicrobial effect of curcumin in
H. pylori
-infected C57BL/6 mice and its efficacy in reducing the gastric damage due to infection were examined histologically. Curcumin showed immense therapeutic potential against
H. pylori
infection as it was highly effective in eradication of
H. pylori
from infected mice as well as in restoration of
H. pylori
-induced gastric damage. This study provides novel insights into the therapeutic effect of curcumin against
H. pylori
infection, suggesting its potential as an alternative therapy, and opens the way for further studies on identification of novel antimicrobial targets of curcumin.
Paracoccidioides brasiliensis
Vaccine Formulations Based on the gp43-Derived P10 Sequence and the
Salmonella enterica
FliC Flagellin
Authors: Braga Catarina J. M. , Rittner Glauce M. G. , Muñoz Henao Julian E. , Teixeira Aline F. , Massis Liliana M. , Sbrogio-Almeida Maria E. , Taborda Carlos P. , Travassos Luiz R. , Ferreira Luís C. S.
Published: February 2009

Paracoccidioidomycosis (PCM) is a systemic granulomatous disease caused by the dimorphic fungus
Paracoccidioides brasiliensis
. Anti-PCM vaccine formulations based on the secreted fungal cell wall protein (gp43) or the derived P10 sequence containing a CD4
+
T-cell-specific epitope have shown promising results. In the present study, we evaluated new anti-PCM vaccine formulations based on the intranasal administration of
P. brasiliensis
gp43 or the P10 peptide in combination with the
Salmonella enterica
FliC flagellin, an innate immunity agonist binding specifically to the Toll-like receptor 5, in a murine model. BALB/c mice immunized with gp43 developed high-specific-serum immunoglobulin G1 responses and enhanced interleukin-4 (IL-4) and IL-10 levels. On the other hand, mice immunized with recombinant purified flagellins genetically fused with P10 at the central hypervariable domain, either flanked or not by two lysine residues, or the synthetic P10 peptide admixed with purified FliC elicited a prevailing Th1-type immune response based on lung cell-secreted type 1 cytokines. Mice immunized with gp43 and FliC and intratracheally challenged with
P. brasiliensis
yeast cells had increased fungal proliferation and lung tissue damage. In contrast, mice immunized with the chimeric flagellins and particularly those immunized with P10 admixed with FliC reduced
P. brasiliensis
growth and lung damage. Altogether, these results indicate that
S. enterica
FliC flagellin modulates the immune response to
P. brasiliensis
P10 antigen and represents a promising alternative for the generation of anti-PCM vaccines.
Molecular Characterization of Human Clinical Isolates ofYersinia enterocoliticaBioserotype 1B/O8 in Poland: Emergence and Dissemination of Three Highly Related Clones
Authors: Gierczyński Rafał , Szych Jolanta , Rastawicki Waldemar , Wardak Sebastian , Jagielski Marek
Published: February 2009

Thirty-three clinical isolates of the highly pathogenicYersinia enterocoliticabioserotype 1B/O8 were collected from sporadic cases in Poland from January 2004 to July 2008. The isolates carried major virulence markers and were strongly clonal. This is the first report of the emergence and dissemination of highly related clones ofY. enterocolitica1B/O8 in Europe.
Variable Nucleotide Tandem-Repeat Analysis Revealing a Unique Group ofLeptospira interrogansSerovar Pomona Isolates Associated with California Sea Lions
Authors: Zuerner Richard L. , Alt David P.
Published: February 2009

Leptospira interrogansserovar Pomona isolates were compared by variable nucleotide tandem-repeat typing. Most cattle isolates grouped together, while isolates from pigs and wildlife were distributed across several groups. Significantly, California sea lion isolates formed a unique group, providing evidence that these animals are maintenance hosts of serovar Pomona.
Identification of Spirochetes Associated with Contagious Ovine Digital Dermatitis
Authors: Sayers G. , Marques P. X. , Evans N. J. , O'Grady L. , Doherty M. L. , Carter S. D. , Nally J. E.
Published: February 2009

Spirochetes of the genus
Treponema
were cultured from 7 of 10 cases of digital dermatitis in sheep. Two cultures comprised
Treponema phagedenis
-like and
Treponema medium/Treponema vincentii
-like spirochetes, respectively, while the remaining cultures comprised mixed populations of
Treponema medium/Treponema vincentii
-like,
Treponema phagedenis
-like, and
Treponema denticola/Treponema putidum
-like organisms.
Collapse behavior of sand
Authors: Sasitharan S. , Robertson P.K. , Sego D.C. , Morgenstern N.R.
Published: February 2009

Loose cohesionless materials can collapse during either static or dynamic loading, resulting in a rapid buildup of pore pressure and associated reduction in shear resistance. As the cohesionless material collapses, it rapidly looses resistance until the acting shear stress decreases to the available residual or steady-state strength. Specially designed stress-path testing has been performed on sand to investigate this collapse process. Results from this test program and previously published data show that a state boundary can be defined when a cohesionless material moves from peak to steady state along a constant void ratio stress path regardless of whether it is loaded drained or undrained. Further, it is demonstrated that the state boundary represents a surface in the effective mean normal stress–deviator stress–void ratio space. Hence, flow slides and liquefaction can be initiated when the stress path followed during either drained or undrained loading attempts to cross this state boundary surface. Key wordy : sand, collapse, liquefaction, stress path, state boundary, triaxial test.
Design of a composite soil cover for an experimental waste rock pile near Newcastle, New Brunswick, Canada
Authors: Yanful Ernest K. , Bell Alan V. , Woyshner Mark R.
Published: February 2009

The Heath Steele Waste Rock Project was initiated in 1989 under Canada's Mine Environment Neutral Drainage (MEND) Program to develop and test strategies for managing acid-generating waste rock. The multiphase project involved the identification and selection of a few waste rock piles for field evaluation at the Heath Steele mine site located at about 50 km northeast of Newcastle, New Brunswick. As part of the evaluation, a 0.25-ha acid-generating pile, pile 7/12, was relocated and reconstructed on an impermeable synthetic membrane by end dumping from the perimeter and pushing into the middle section. The pile, which contains about 14 000 t of mine waste rock, has been producing an acidic seepage characterized by high dissolved iron (3.5–13.5 g/L) and sulphate (12.7–43.4 g/L) concentrations. Following the definition of the baseline acid-generating characteristics of the pile and laboratory investigation of potential soil cover materials in the vicinity of the site, a three-layer cover design is proposed. The design calls for a 60 cm thick saturated impermeable cover sandwiched between a 30 cm thick sand base and a 30 cm thick, overlying granular layer. The principal objectives of the design are to obtain a low gas diffusion coefficient to minimize oxygen fluxes and, also, to attain a low hydraulic conductivity to reduce infiltration into the pile. Both objectives can be achieved by compacting the impermeable cover at a density of 95% of Modified Proctor or greater and a water content slightly higher than the optimum value. The design of the cover and the anticipated resulting low gaseous-oxygen fluxes are confirmed by one-dimensional diffusion modelling. The potential for the impermeable layer to remain nearly fully saturated, even under an evaporative flux, is demonstrated by flow modelling. It is noted that the assessment of the durability of the cover with respect to variable climatic conditions (drying, freezing, and thawing) is a critical component of the performance evaluation. Key words : acid rock drainage, soil cover, capillary barrier, oxygen flux, infiltration.
Construction and monitoring of a composite soil cover on an experimental waste-rock pile near Newcastle, New Brunswick, Canada
Authors: Yanful Ernest K. , Riley Michael D. , Woyshner Mark R. , Duncan Jim
Published: February 2009

A 130 cm thick composite soil cover was constructed on an experimental waste-rock pile at the Heath Steele mine site near Newcastle, New Brunswick. The cover consisted of a 30 cm thick sand base, a 60 cm thick compacted glacial till, a 30 cm thick granular layer, and a final 10 cm thick gravel layer for erosion protection. The till was compacted on the sand base in three finished lifts each of 20 cm thickness. Results of a preconstruction pad test indicated six passes of a 5-t vibratory compactor were required to attain the design specifications of 95% of the Modified Proctor maximum dry density at a moulding water content of 2–3% wet of the optimum. These compaction specifications also ensure that the till has a degree of water saturation of at least 95%, which is required to reduce oxygen and acid fluxes in the underlying pile. Quality control measures were taken during the construction to ensure the specifications were followed. Monitoring instrumentation was installed during the construction of the cover. Results indicate a reduction in gaseous oxygen concentrations in the pile from 20% before cover to about 3% after cover placement. The decreased oxygen penetration implies reduced oxygen flux and acid production. Volumetric water contents averaged about 32% in the till both immediately following cover installation and 7 months later. The water-content data are corroborated by soil-suction measurements. Temperatures in the pile have decreased following cover installation but appear to be more influenced by climatic variability than by a decrease in heat production and hence sulphide mineral oxidation. Observed discharge from two lysimeters, installed below the cover, indicates infiltration of 2–2.5% of precipitation during a 55-day period when rainfall was heavy. The quality of seepage from the pile has not changed since cover installation. Further monitoring will be required to confirm the reduction in acid production. Key words : waste-rock pile, acid generation, soil cover, suction, oxygen flux, percolation.
The assessment of rockfall hazard at the base of talus slopes
Authors: Evans S.G. , Hungr O.
Published: February 2009

Fragmental rockfall is characterized by the independent movement of individual rock fragments after detachment from a rock face. The continued operation of the process leads to the accumulation of talus slopes. On talus slopes the rockfall shadow extends beyond the base of the talus and consists of scattered boulders that have run out beyond the base of the slope. The landing probability of boulders in the shadow is examined; return periods of the order of 1000 years relative to a house site are typical. Rockfall behaviour particularly with respect to run out into the shadow can be assessed using geological evidence, empirical methods, physical modelling, and computer-based analytical models. An empirical minimum shadow angle of 27.5° (i.e., the angle between the distal limit of the shadow and the top of the talus slope) is suggested and would be useful in rockfall vulnerability studies at the base of talus slopes as a first approximation to shadow limits. It is preferable to the use of the rockfall fahrböschung as proposed by several authors. A random collision lumped mass model (ROCKFALL) is outlined, ROCKFALL uses two restitution coefficients and a transition to rolling criterion, ROCKFALL is used to analyse two fatal rockfall accidents in southern British Columbia, at Hedley in 1939 and Sunnybrae in 1983, which are documented in detail. An additional nonfatal incident is also analysed (Barnhartvale in 1974). Results based on an initial calibration were encouraging. Documentation of the three rockfall incidents shows that, in each case, rockfall fragments impacted on homes at equivalent shadow angles of 30° or more. This would suggest that a review of existing development within rockfall shadow areas at the base of talus slopes may be in order. Key words : rockfall, dynamics, talus slopes, landslides, British Columbia
The coefficient of earth pressure at rest
Authors: Mesri G. , Hayat T.M.
Published: February 2009

Laboratory experiments on undisturbed specimens of a large number of soft clay deposits, as well as previous measurements on clays and granular soils, were used to examine and explain the magnitude and behavior of the coefficient of earth pressure at rest, K0: (i) after sedimentation – primary consolidation, (ii) during secondary-compression aging, (iii) after active or passive preshearing away from the laterally constrained condition, (iv) during a decrease in effective vertical stress, and (v) during an increase in effective vertical stress in the recompression or compression range, in terms of [Formula: see text], the slope of the effective horizontal [Formula: see text] versus effective vertical[Formula: see text] stress path. The behavior of K0 is explained using the concept of mobilized angle of friction in laterally constrained deformation condition. The Jaky equation provides, in terms of the angle of internal friction, a good estimate of K0 of sedimented, normally consolidated young clays and granular soils, as well as of [Formula: see text] of presheared clays and sands, and of densified granular soils that are subjected to laterally constrained compression from [Formula: see text]. Empirical equations provide reasonable estimates of K0 for clays and granular soils after secondary-compression aging, after preconsolidation by unloading, and for soft clay deposits that display a preconsolidation pressure [Formula: see text] greater than in situ effective vertical stress [Formula: see text]. Proposed empirical equations and methods successfully predict K0 of presheared clays. Key words: coefficient of earth pressure at rest, soft clays, granular soils, presheared soils, sampling and laboratory testing.
Evaluation of a compacted till liner test pad constructed over a granular subliner contingency layer
Authors: Rowe R. Kerry , Caers Chris J. , Chan Cliff
Published: February 2009

The construction and evaluation of a compacted clayey till test pad constructed over a stone layer are described. The evaluation of the clayey liner involved (i) excavation of six test pits through the liner, followed by careful visual inspection for defects in the liner; (ii) sampling of the liner using standard 75 mm diameter Shelby tubes, a 150 mm diameter piston sampler, and block sampling; (iii) triaxial hydraulic conductivity tests on samples of liner material consolidated to a number of stress levels relevant to the proposed design; and (iv) diffusion tests on samples of liner material. Based on the results it is concluded that it was possible to construct a low-permeability liner (hydraulic conductivity less than 1.4 × 10−8 cm/s under expected field stress conditions). Geotextiles from above and below the compacted liner were carefully exhumed and subjected to a series of laboratory tests to examine (i) the effect of construction damage on the geotextile's strength; (ii) the effectiveness of the geotextile to minimize intrusion of the clay liner through the geotextile and into the stone layer(s) under expected field stress conditions; (iii) the effectiveness of the geotextile as a filter for the compacted liner material under high upward gradient conditions; and (iv) the friction angle between the geotextile and clay, and geotextile and stone. The geotextiles exhumed from the test liner showed some evidence of construction damage; however, based on the field observations and subsequent laboratory tests, it is concluded that they performed adequately. Key words : waste disposal, clay liners, geotextiles, field performance, hydraulic conductivity, landfills.
Parameters for stress and deformation analysis of rockfill dams
Authors: Saboya Jr. F. , Byrne P.M.
Published: February 2009

Stress–strain parameters for modelling the response of rockfill dams to construction and reservoir filling are examined. Parameters from both laboratory tests and back analysis of existing dams are considered. The influence of physical properties of the material, such as mineral composition, grading curves, grain shape, and grain size, is also examined. The results of the study were applied to Foz do Areia dam in Brazil. Finite element analyses were carried out using selected material parameters to predict the response of the dam for both construction and reservoir-filling stages. The predicted and observed results were found to be in good agreement during the construction stage. During reservoir filling, measurements indicated that the dam initially behaved in a much suffer manner than during construction. The stiffer response results from an initial unloading of stress ratio caused by the water load on the face. Under increased reservoir loading, the stress ratio increases again, activating the softer normal loading modulus, leading to substantially larger movements. The predicted results for both construction and reservoir filling are in good agreement with the measurements, provided a stress ratio criterion is used to specify the appropriate tangent moduli. Key words : rockfill, dams, deformations, finite element analysis, field measurements.
Effet de l'inclinaison de la charge et stabilité latérale de pieux flottants dans la glace ou le pergélisol
Authors: Morin Pierre
Published: February 2009

The numerical modeling of the displacements of a pile in frozen soil adds to the analytical partial solutions and allows for a better understanding of the various parameters involved. The present paper analyses the influence of an axial load on a floating pile also subjected to lateral loading. The frozen soil is simulated by a rheological model calibrated from available data from the literature. Two circular piles of different flexibility have been considered. The significance of the lateral stability for such piles is discussed. Key words : piles, lateral displacement, creep, frozen soil, buckling, stability.
Energy-efficient encoding techniques for off-chip data buses
Authors: Suresh Dinesh C. , Agrawal Banit , Yang Jun , Najjar Walid
Published: February 2009

Reducing the power consumption of computing devices has gained a lot of attention recently. Many research works have focused on reducing power consumption in the off-chip buses as they consume a significant amount of total power. Since the bus power consumption is proportional to the switching activity, reducing the bus switching is an effective way to reduce bus power. While numerous techniques exist for reducing bus power in address buses, only a handful of techniques have been proposed for data-bus power reduction, where frequent value encoding (FVE) is the best existing scheme to reduce the transition activity on the data buses.

In this article, we propose improved frequent value data bus-encoding techniques aimed at reducing more switching activity and, hence, power consumption. We propose three new schemes and five new variations to exploit bit-wise temporal and spatial locality in the data-bus values. Our techniques just use one external control signal and capture bit-wise locality to efficiently encode data values. For all the embedded and SPEC applications we tested, the overall average switching reduction is 53% over unencoded data and 10% more than the conventional FVE scheme.
Throughput-driven synthesis of embedded software for pipelined execution on multicore architectures
Authors: Hashemi Matin , Ghiasi Soheil
Published: February 2009

We present a methodology for pipelined software synthesis of streaming applications. First, we develop a versatile task assignment algorithm capable of optimizing realistically-arbitrary cost functions for two cores. The algorithm is exact (i.e., theoretically optimal) contrary to existing heuristics. Second, our approximation technique provides an adjustable knob to trade solution quality with algorithm runtime and memory. Third, we develop a recursive heuristic for more cores. FPGA-based emulated experiments validate our theoretical results. The exact algorithm yields 1.7 × throughput improvement. The approximation method offers a range of tradeoff points (e.g., 3 × faster with 20 × less memory) while degrading the throughput only 1% to 5%.
Cross-layer customization for rapid and low-cost task preemption in multitasked embedded systems
Authors: Zhou Xiangrong , Petrov Peter
Published: February 2009

Preemptive multitasking is widely used in many low-cost and real-time embedded applications for its superior hardware utilization. The frequent and asynchronous context switches, however, require the preservation and restoration of the task state, thus resulting in a large number of memory transfer instructions. As a consequence, task responsiveness and application throughput can be significantly deteriorated. To address this problem we propose a cross-layer customization framework which through the close cooperation of compiler, OS, and hardware architecture achieves rapid and low-cost task switch. Application information extracted during compile-time regarding state liveness is exploited in order to preserve a minimal amount of task state on task preemption. We introduce two complementary techniques to implement the application-aware state preservation. The first technique utilizes compiler-generated custom routines which preserve/restore an extremely small live context at judiciously selected points in the application code. The second technique requires more sophisticated hardware support. It employs an OS-controlled register file mapping to achieve a rapid context switch. By mapping a small fraction of the register file in a single clock cycle, a context switch is achieved requiring no memory transfers for the majority of cases to preserve/restore the live state. The effect of aggressively replicated register files, where each task is given its own replica, is achieved with the hardware cost of only adding from 25% to 50% extra physical registers. Through the utilization of these novel mechanisms, a significant improvement on task response time is achieved as the context-switch cost is minimized.
A comparison of software platforms for wireless sensor networks
Authors: Mozumdar Mohammad Mostafizur Rahman , Lavagno Luciano , Vanzago Laura
Published: February 2009

Wireless sensor networks are characterized by very tight code size and power constraints and by a lack of well-established standard software development platforms such as Posix. In this article, we present a comparative study between a few fairly different such platforms, namely MANTIS, TinyOS, and ZigBee, when considering them from the application developer's perspective, that is, by focusing mostly on functional aspects, rather than on performance or code size. In other words, we compare both the tasking model used by these platforms and the API libraries they offer. Sensor network applications are basically event based, so most of the software platforms are also built on considering event handling mechanism, however some use a more traditional thread based model. In this article, we consider implementations of a simple generic application in MANTIS, TinyOS, and the Ember ZigBee development framework, with the goal of depicting major differences between these platforms, and suggesting a programming style aimed at maximizing portability between them.
Fault tolerance measures for large-scale wireless sensor networks
Authors: Ammari Habib M. , Das Sajal K.
Published: February 2009

Connectivity
, primarily a graph-theoretic concept, helps define the
fault tolerance
of wireless sensor networks (WSNs) in the sense that it enables the sensors to communicate with each other so their sensed data can reach the sink. On the other hand,
sensing coverage
, an intrinsic architectural feature of WSNs plays an important role in meeting application-specific requirements, for example, to reliably extract relevant data about a sensed field. Sensing coverage and network connectivity are not quite orthogonal concepts. In fact, it has been proven that connectivity strongly depends on coverage and hence considerable attention has been paid to establish tighter connection between them although only loose lower bound on network connectivity of WSNs is known. In this article, we investigate connectivity based on the degree of sensing coverage by studying
k-covered
WSNs, where every location in the field is simultaneously covered (or sensed) by at least
k
sensors (property known as
k-coverage
, where
k
is the
degree of coverage
). We observe that to derive network connectivity of
k
-covered WSNs, it is necessary to compute the sensor spatial density required to guarantee
k
-coverage. More precisely, we propose to use a model, called the
Reuleaux Triangle
, to characterize
k
-coverage with the help of Helly's Theorem and the analysis of the intersection of sensing disks of
k
sensors. Using a deterministic approach, we show that the sensor spatial density to guarantee
k
-coverage of a convex field is proportional to
k
and inversely proportional to the sensing range of the sensors. We also prove that network connectivity of
k
-covered WSNs is higher than their sensing coverage
k
. Furthermore, we propose a new measure of fault tolerance for
k
-covered WSNs, called
conditional fault tolerance
, based on the concepts of
conditional connectivity
and
forbidden faulty sensor set
that includes all the neighbors of a given sensor. We prove that
k
-covered WSNs can sustain a large number of sensor failures provided that the faulty sensor set does not include a forbidden faulty sensor set.
Chowkidar
Authors: Bapat S. , Leal W. , Kwon T. , Wei P. , Arora A.
Published: February 2009

Wireless sensor network (WSN) testbeds are useful because they provide a way to test applications in an environment that makes it easy to deploy experiments, configure them statically or dynamically, and gather performance information. However, WSNs are typically composed of low-cost devices and tend to be unreliable, with failures a common phenomenon. Accurate knowledge of network health status, including nodes and links of each type, is critical for correctly configuring applications on WSN testbeds and for interpreting the data collected from them.

In this article we present a stabilizing protocol, Chowkidar, that provides accurate and efficient network health monitoring in WSNs. Our approach adapts the well-known problem of message-passing rooted spanning tree construction and its use in propagation of information with feedback (PIF) for the case of a WSN. The Chowkidar protocol is initiated upon demand; that is, it does not involve ongoing maintenance, and it terminates with accurate results, including detection of failure and restart during the monitoring process. Chowkidar is distinguished from others in two important ways. Given the resource constraints of WSNs, it is message-efficient in that it uses only a few messages per node. Also, it tolerates ongoing node and link failure and node restart, in contrast to requiring that faults stop during convergence.

We have implemented the Chowkidar protocol as part of enabling a network health status service that is tightly integrated with a remotely accessible wireless sensor network testbed, Kansei, at The Ohio State University. We present experimental results from this testbed that validate the correctness and performance of Chowkidar. We also report on initial experiences and lessons learnt from the integration of Chowkidar with Kansei, including feedback from both testbed users and administrators who have found Chowkidar to be a useful tool for improving the accuracy and efficiency of testbed experimentation and maintenance, and the need for well-defined policies to address issues such as minimizing interference with concurrently running experiments. Finally, we discuss extensions that enhance the functionality and usability of Chowkidar.
Light enabling snap-stabilization of fundamental protocols
Authors: Cournier Alain , Devismes Stephane , Villain Vincent
Published: February 2009

In this article, we show that some fundamental self- and snap-stabilizing wave protocols (e.g., token circulation,
PIF
, etc.) implicitly assume a very light property that we call
BreakingIn
. We prove that
BreakingIn
is strictly induced by self- and snap-stabilization. Combined with a transformer,
BreakingIn
allows to easily turn the non-fault-tolerant versions of those protocols into snap-stabilizing versions. Unlike the previous solutions, the transformed protocols are very efficient and work at least with the same daemon as the initial versions extended to satisfy
BreakingIn
. Finally, we show how to use an additional property of the transformer to design snap-stabilizing extensions of those fundamental protocols like Mutual Exclusion.
Sensor node lifetime analysis
Authors: Jung Deokwoo , Teixeira Thiago , Savvides Andreas
Published: February 2009

This article presents two lifetime models that describe two of the most common modes of operation of sensor nodes today, trigger-driven and duty-cycle driven. The models use a set of hardware parameters such as power consumption per task, state transition overheads, and communication cost to compute a node's average lifetime for a given event arrival rate. Through comparison of the two models and a case study from a real camera sensor node design we show how the models can be applied to drive architectural decisions, compute energy budgets and duty-cycles, and to preform side-by-side comparison of different platforms. Based on our models we present a MATLAB Wireless Sensor Node Platform Lifetime Prediction and Simulation Package (MATSNL). This demonstrates the use of the models using sample applications drawn from existing sensor node measurements.
On the lifetime of wireless sensor networks
Authors: Dietrich Isabel , Dressler Falko
Published: February 2009

Network lifetime has become the key characteristic for evaluating sensor networks in an application-specific way. Especially the availability of nodes, the sensor coverage, and the connectivity have been included in discussions on network lifetime. Even quality of service measures can be reduced to lifetime considerations. A great number of algorithms and methods were proposed to increase the lifetime of a sensor network—while their evaluations were always based on a particular definition of network lifetime. Motivated by the great differences in existing definitions of sensor network lifetime that are used in relevant publications, we reviewed the state of the art in lifetime definitions, their differences, advantages, and limitations. This survey was the starting point for our work towards a generic definition of sensor network lifetime for use in analytic evaluations as well as in simulation models—focusing on a formal and concise definition of accumulated network lifetime and total network lifetime. Our definition incorporates the components of existing lifetime definitions, and introduces some additional measures. One new concept is the ability to express the service disruption tolerance of a network. Another new concept is the notion of time-integration: in many cases, it is sufficient if a requirement is fulfilled over a certain period of time, instead of at every point in time. In addition, we combine coverage and connectivity to form a single requirement called connected coverage. We show that connected coverage is different from requiring noncombined coverage and connectivity. Finally, our definition also supports the concept of graceful degradation by providing means of estimating the degree of compliance with the application requirements. We demonstrate the applicability of our definition based on the surveyed lifetime definitions as well as using some example scenarios to explain the various aspects influencing sensor network lifetime.
A variational approach for automatic generation of panoramic maps
Authors: Degener Patrick , Klein Reinhard
Published: February 2009

Panoramic maps combine the advantages of both ordinary geographic maps and terrestrial images. While inheriting the familiar perspective of terrestrial images, they provide a good overview and avoid occlusion of important geographical features. The designer achieves this by skillful choice and integration of several views in a single image. As important features on the surface must be carefully rearranged to guarantee their visibility, the manual design of panoramic maps requires many hours of tedious and painstaking work.

In this article we take a variational approach to the design of panoramic maps. Starting from conventional elevation data and aerial images, our method fully automatically computes panoramic maps from arbitrary viewpoints. It rearranges geographic structures to maximize the visibility of a specified set of features while minimizing the deformation of the landscape's shape.
A tool to create illuminant and reflectance spectra for light-driven graphics and visualization
Authors: Bergner Steven , Drew Mark S. , Möller Torsten
Published: February 2009

Full spectra allow the generation of a physically correct rendering of a scene under different lighting conditions. In this article we devise a tool to augment a palette of given lights and material reflectances with constructed spectra, yielding specified colors or spectral properties such as metamerism or objective color constancy. We utilize this to emphasize or hide parts of a scene by matching or differentiating colors under different illuminations. These color criteria are expressed as a quadratic programming problem, which may be solved with positivity constraints. Further, we characterize full spectra of lights, surfaces, and transmissive materials in an efficient linear subspace model by forming eigenvectors of sets of spectra and transform them to an intermediate space in which spectral interactions reduce to simple component-wise multiplications during rendering. The proposed method enhances the user's freedom in designing photo-realistic scenes and helps in creating expressive visualizations. A key application of our technique is to use specific spectral lighting to scale the visual complexity of a scene by controlling visibility of texture details in surface graphics or material details in volume rendering.
An edge-based computationally efficient formulation of Saint Venant-Kirchhoff tetrahedral finite elements
Authors: Kikuuwe Ryo , Tabuchi Hiroaki , Yamamoto Motoji
Published: February 2009

This article describes a computationally efficient formulation and an algorithm for tetrahedral finite-element simulation of elastic objects subject to Saint Venant-Kirchhoff (StVK) material law. The number of floating point operations required by the algorithm is in the range of 15% to 27% for computing the vertex forces from a given set of vertex positions, and 27% to 38% for the tangent stiffness matrix, in comparison to a well-optimized algorithm directly derived from the conventional Total Lagrangian formulation. In the new algorithm, the data is associated with edges and tetrahedron-sharing edge-pairs (TSEPs), as opposed to tetrahedra, to avoid redundant computation. Another characteristic of the presented formulation is that it reduces to that of a spring-network model by simply ignoring all the TSEPs. The technique is demonstrated through an interactive application involving haptic interaction, being combined with a linearized implicit integration technique employing a preconditioned conjugate gradient method.
Display supersampling
Authors: Damera-Venkata Niranjan , Chang Nelson L.
Published: February 2009

Supersampling is widely used by graphics hardware to render anti-aliased images. In conventional supersampling, multiple scene samples are computationally combined to produce a single screen pixel. We consider a novel imaging paradigm that we calldisplay supersampling, where multiple display samples are physically combined via the superimposition of multiple image subframes. Conventional anti-aliasing and texture mapping techniques are shown inadequate for the task of rendering high-quality images on supersampled displays. Instead of requiring anti-aliasing filters, supersampled displays actually require alias generation filters to cancel the aliasing introduced by nonuniform sampling. We present fundamental theory and efficient algorithms for the real-time rendering of high-resolution anti-aliased images on supersampled displays. We show that significant image quality gains are achievable by taking advantage of display supersampling. We prove that alias-free resolution beyond the Nyquist limits of a single subframe may be achieved by designing a bank of alias-canceling rendering filters. In addition, we derive a practical noniterative filter bank approach to real-time rendering and discuss implementations on commodity graphics hardware.
Optimization-based interactive motion synthesis
Authors: Jain Sumit , Ye Yuting , Liu C. Karen
Published: February 2009

We present a physics-based approach to synthesizing motion of a virtual character in a dynamically varying environment. Our approach views the motion of a responsive virtual character as a sequence of solutions to the constrained optimization problem formulated at every time step. This framework allows the programmer to specify active control strategies using intuitive kinematic goals, significantly reducing the engineering effort entailed in active body control. Our optimization framework can incorporate changes in the character's surroundings through a synthetic visual sensory system and create significantly different motions in response to varying environmental stimuli. Our results show that our approach is general enough to encompass a wide variety of highly interactive motions.