bluuebunny/crossref_metadata_2025 huggingface dataset:
Lateral earth pressures in expansive clay soils
Authors: Pufahl D. E. , Fredlund D. G. , Rahardjo H.
Published: July 2008

Lateral earth pressures produced by saturated clays with negative pore-water pressures and unsaturated expansive clays with positive matric suctions are considered from a theoretical standpoint. Simple earth pressure equations are formulated in terms of total stresses using the Mohr–Coulomb failure criteria and the assumptions consistent with the Rankine earth pressure theory.Conventional practice is to separate the pressure that the soil exerts on the wall into the pressure produced by the soil structure (effective stress) and that produced by the water (neutral stress). Since two stress state variables are required to describe the behavior of unsaturated soils, the expressions can no longer be separated into two distinct components.The change in lateral pressures resulting from decreases in pore-water pressure or increases in matric suction are quantified by considering a 6 m high wall for the active and passive cases. Tension cracks are shown to have little effect on the conditions shown.The magnitude of the lateral pressure generated due to changes in matric suction under conditions where walls are restrained from moving depends upon the ratio (KT) of horizontal to vertical stress and the matric suction of the backfill at the time that it is placed behind the wall. When structural members are cast directly against undisturbed clays, similar criteria govern the magnitude of the lateral pressures that may be generated due to changes in matric suction. The maximum pressure that can be developed in some cases will be equal to the passive pressure of the soil when it is saturated.An expression for the critical height of a vertical bank for the saturated and unsaturated cases is developed. The role of tension cracks is shown by computing the critical height of a vertical slope for a typical soil both in the absence and in the presence of tension cracks.In many instances it is apparent that methods devised to sustain the matric suction at or near its original value may result in a substantial savings in design or that they will ensure adequate performance standards for existing facilities. Keywords: Lateral earth pressure, active pressure, passive pressure, unsaturated soils, expansive soils, tension cracks, retaining walls, unsupported excavations.
The design and performance of heavily loaded piles in a high-risk earthquake zone
Authors: Watson George H. , Williams Richard S. , Yam Chun Chiu
Published: July 2008

Amoco International Oil Company and the government of Trinidad and Tobago have formed a consortium (FERTRIN) to construct and operate two ammonia plants. The site is located on the west coast of Trinidad some 32 km south of Port of Spain and is part of a major industrial development being planned by the government.Trinidad is located in one of the most seismically active regions of the Caribbean. Local building codes are still in the process of development, but local practice requires design specifications similar to the highest risk earthquake zones in California. As a result, piling under critical and heavy structures is often governed by the lateral rather than the vertical load requirements.This paper describes the choice, design, and performance of the piles tested for the FERTRIN ammonia plants. The design methods are evaluated and predictions of both lateral and vertical pile performance are compared with the load test results. Keywords: piles, lateral loads, axial loads, load tests, foundations, load transfer.
Slope stability analysis of riverbanks
Authors: Chugh Ashok K.
Published: July 2008

Practical considerations for the use of subsurface exploratory data and material strength data in slope stability calculations for estimating the factor of safety along potential slip surfaces in natural slopes are described and illustrated with a sample problem. An alternative form of the slope stability equations for the method of slices, using the limit equilibrium method and satisfying complete statics on each slice, is presented for plane problems. The shortcomings inherent in commonly available computer programs for the analysis of slope stability problems are discussed. Means to overcome some of the limitations are indicated and illustrated with a sample problem. It is suggested that the general purpose computer programs for slope stability analysis should use the complete form of the slope stability equations. The alternative form of the equations and the discussion of their solution are valid for slope stability analysis of natural slopes and embankment dams. Keywords: stability analysis, slope stability, riverbanks, lake banks, natural slopes, soil mechanics, embankments.
The bearing capacity of dykes and fills founded on soft soils of limited thickness
Authors: Silvestri V.
Published: July 2008

This paper analyzes the stability of dykes and fills founded on soft clay layers of limited depth and is divided into two sections.In the first section, the critical condition at which failure is impending is analyzed in terms of the bearing capacity in the soft clay foundation, instead of the conventional slope stability approach of the fill–clay foundation interaction. The theoretical approach is based upon the works of Jurgenson, Hill, Meyerhof, Mandel, and Salençon. The solutions obtained by these investigators are of considerable interest and may be easily applied to geotechnical engineering problems.In the second section, several case histories dealing with failures of fills on soft clays will be presented and analyzed by means of the present approach. It will be shown that the plasticity approach, when compared with the conventional slope stability analysis, is much easier to apply and is able to represent adequately the failure criterion of fills founded on layers of soft clays of limited depth. Keywords: bearing capacity, soft clays, plasticity, fills, limited thickness.
Analyse géostatistique d'un noyau de barrage tel que construit
Authors: Soulie Michel , Favre Marc , Konrad Jean-Marie
Published: July 2008

Conventional statistical analysis does not take into account the spatial coordinates of the control tests (water content, density, etc.). The geostatistical approach, by considering how the values of measured parameters vary from one location to another, takes into account both features: structure and randomness inherent in the core of the dam. This approach has been applied to the core of the LG-3 dam (James Bay project) built with glacial till. After obtaining the variograms, the problems of estimating the mean compaction degree of a given volume have been studied and the following questions have been analysed: What is the distribution of the degree of compaction of the control volume? What is the efficiency of the compaction control tests that were used during the construction of the dam? Is it possible to improve the efficiency of these tests? Keywords: earthfill, compaction test, quality control, statistical analysis.
Laboratory and field determination of preconsolidation pressures at Gloucester
Authors: Leroueil S. , Samson L. , Bozozuk M.
Published: July 2008

In recent literature several special test methods have been proposed to measure the preconsolidation pressure of a compressible clay soil. Five methods, in addition to the conventional oedometer test, were applied to the marine clays from the Gloucester test site. The preconsolidation pressures measured using these laboratory tests were compared with that mobilized in situ below the centre of a test embankment. The investigation showed that the preconsolidation pressure is directly related to the rate of strain and that special techniques such as constant rate of strain, controlled gradient, single-stage loading, and anisotropic triaxial consolidation tend to overestimate the in-situ preconsolidation pressure. The conventional oedometer test using a load increment ratio of 0.5 and a reloading schedule of 24 h applied to good-quality undisturbed samples produced preconsolidation pressures that compared best with the in-situ values. Keywords: preconsolidation pressure, laboratory, in situ, strain rate effects, disturbance.
Yield states and stress–strain relationships in a natural plastic clay
Authors: Graham J. , Noonan M. L. , Lew K. V.
Published: July 2008

Natural clays are commonly anisotropic due to their mode of deposition, and lightly overconsolidated because of a variety of subsequent geological processes. They exhibit marked changes in stiffness when they yield. Yield stresses from individual tests can be generalized into a yield surface for the clay if displacements during loading are taken into account by calculating specific volumes V = (1 + e) throughout the tests.This paper describes tests on 76 mm diameter triaxial samples of natural plastic Lake Agassiz clay from Winnipeg. The samples were carefully trimmed, reconsolidated to approximately their in-situ stresses, and loaded in stress controlled tests along various stress paths in p′,q stress space.The tests produced well-defined yield envelopes in p′,q; p′, V; and q, V plots, and in corresponding plots where the stresses were normalized with respect to the vertical preconsolidation pressure σvc′. Comparison of one-dimensional yielding states with results from K0-triaxial tests that were continued to large strains suggests that the clay is cemented. At stresses inside the yield surface, the clay exhibits substantially linear elastic behaviour which is transversely isotropic. Values of bulk modulus, shear modulus, and a cross modulus which can be used to link mean effective pressures with shear strains, and deviator stresses with volumetric strains, have been evaluated in normalized form using a least-squares solution. The directions of plastic strain increment vectors after yielding have been examined. Consideration of the results suggests that they are not normal to the yield surface, and are influenced by systematic effects. Plastic compliances vary markedly with stress path direction. Keywords: clay, yield, critical state, anisotropic elasticity, associated flow, plasticity.
Consolidation thermique par chaleur d'un sol non saturé
Authors: Saix C.
Published: July 2008

The thermal consolidation by heating of an unsaturated silty soil is studied by means of six tests performed in a thermal triaxial apparatus. The results show the importance of the temperature parameter and a clear similarity with the classical consolidation tests on saturated soils. A constitutive law is proposed for the thermal consolidation by heat that allows the definition of indices of thermal compression. This law is used to calculate the displacements in an unsaturated fill for heat storing. Key words: unsaturated soil, consolidation, heat, triaxial, modelling. [Translated by the Journal]
Mechanistic evaluation of mitigation of petroleum hydrocarbon contamination by soil medium
Authors: Yong Raymond N. , Rao Sudhakar M.
Published: July 2008

Present in situ chemical treatment technologies for mitigation of petroleum hydrocarbon contamination are in the developmental stage or being tested. To devise efficient strategies for restricting the movement of petroleum hydrocarbon (PHC) molecules in the contaminated soil, it is proposed to utilize the sorption–interaction relationships between the petroleum contaminants and the soil substrate. The basic questions addressed in this paper are as follows (i) What are the prominent chemical constituents of the various petroleum fractions that interact with the soil substrate? (ii) What are the functional groups of a soil that interact with the contaminants? (iii) What are the bonding mechanisms possible between the soil functional groups and the PHC contaminants? (iv) What are the consequent changes brought about the soil physical properties on interaction with PHC's? (v) What are the factors influencing the interactions between PHC molecules and clay particles of the soil substrate? (vi) What is the possibility of improving the soil's attenuation ability for PHC's? The development of answers to the basic questions reveal that petroleum hydrocarbons comprise a mixture of nonpolar alkanes and aromatic and polycyclic hydrocarbons, that have limited solubility in water. The bonding mechanism between the nonpolar PHC's and the clay surface is by way of van der Waals attraction. The adsorption of the nonpolar hydrocarbons by the clay surface occurs only when their (i.e., the hydrocarbon molecules) solubility in water is exceeded and the hydrocarbons exist in the micellar form. Dilute solutions of hydrocarbons in water, i.e., concentrations of hydrocarbons at or below the solubility limit, have no effect on the hydraulic conductivity of clay soils. Permeation with pure hydrocarbons invariably influences the clay hydraulic conductivity. To improve the attenuation ability of soils towards PHC's, it is proposed to coat the soil surface with "ultra" heavy organic polymers. Adsorption of organic polymers by the clay surface may change the surface properties of the soil from highly hydrophilic (having affinity for water molecules) to organophilic (having affinity for organic molecules). The organic polymers attached to the clay surface are expected to attenuate the PHC molecules by van der Waals attraction, by hydrogen bonding, and also by adsorption into interlayer space in the case of soils containing swelling clays. Key words: petroleum hydrocarbons (PHC's), bonding mechanisms, functional groups, PHC-soil interaction, permeation, hydraulic conductivity, attenuation, van der Waals, organic polymers, organophilic.
Amélioration des mesures des propriétés de consolidation au laboratoire à l'aide du montage perméamétrique
Authors: Morin Pierre
Published: July 2008

The readings of the settlement of a sample during a standard oedometer step loading test provide the values of the parameters of compressibility and indirectly of the permeability. The present article shows how a very simple permeability device available in most laboratories can be used to determine the modulus, the permeability, and the consolidation properties of the soils. The described procedure shortens the duration of the test and prevents the interruption of the loading required to carry out the traditional permeability tests. Four experimental examples allow the assessment of the merits of the simulation by computer of the test procedure. Key words: consolidation, oedometer test, falling head permeameter, permeability, oedometric modulus, laboratory test. [Translated by the Journal]
Analysis of ground-probing radar data: predictive deconvolution
Authors: Lafleche P. T. , Todoeschuck J. P. , Jensen O. G. , Judge A. S.
Published: July 2008

Recent advances in ground-probing radar instrumentation have allowed the collection of large volumes of digital data. Such data sets are amenable to modern data-processing techniques both to increase geological resolution and to enhance data presentation. The close similarity between ground-radar data and seismic data suggests that processing techniques that have been used in the seismic industry could be applied to radar data. As an example, a ground probing radar profile is deconvolved using the common prediction-error filter, which assumes a white power spectrum for the reflections, and a filter that assumes a spectrum proportional to spatial frequency. With the prediction-error filter we find three of four buried pipes which are not visible in the undeconvolved section; all four are found with the second filter. Key words: ground-penetrating radar, deconvolution, scaling geology, frozen-core dams, permafrost, containment dams, mill waste, Contwoyto Lake.
Engineering geology of nearshore areas off Richards Island, N.W.T.: a comparison of stable and actively eroding coastlines
Authors: Kurfurst P J , Dallimore S. R.
Published: July 2008

Nearshore areas off northern Richards Island can be expected to show considerable variability in lithology, strengths, and geothermal setting both in a temporal and a spatial sense. Drilling and laboratory studies carried out along onshore–offshore transects at a stable coastal site and an actively eroding coastal site have identified six major stratigraphic units of Holocene and pre-Holocene (Wisconsinan) age. The main factors controlling the geotechnical properties of these sediments and their distribution are the occurrence of shallow permafrost beneath areas seasonally covered by landfast sea ice, rapid degradation of permafrost in areas farther offshore, ice content of thawing pre-Holocene sediments, and variability in coastal processes. Key words: nearshore deposits, engineering geology, permafrost, physical properties, acoustic properties.
The pressure of clay backfill against retaining structures
Authors: Clayton C. R. I. , Symons I. F. , Hiedra-Cobo J. C.
Published: July 2008

This paper investigates the pressures exerted by clay backfills against retaining structures. The lateral pressures are developed during three main phases: placement, compaction, and burial; horizontal total stress reduction at constant moisture content; and swelling or consolidation under approximately constant vertical stress. Experimental data from laboratory and pilot-scale studies, using clays of intermediate and high plasticity, are presented and used to assess the magnitude of the pressure changes in each phase. The process of compaction is examined and it is concluded that previously developed theories for assessing the pressures on retaining walls developed by compaction of granular soils are inapplicable for cohesive soils. The factors controlling the swelling of cohesive backfill are reviewed and results from a preliminary numerical study are used to provide an indication of the likely effects of plasticity and placement moisture content. Key words: earth pressure, retaining walls, clay, compaction, swelling.
Deep-seated consolidation settlements in the Fraser River delta
Authors: Crawford C. B. , McCammon N. R. , Butler R. C.
Published: July 2008

This paper describes the settlements of three heavy silo structures at two cement plants located along the south arm of the Fraser River delta. In this area, it has not been possible to obtain sufficiently undisturbed samples for reliable consolidation tests, and it has been necessary therefore to employ in situ tests and site improvement techniques such as preloading and vibrocompaction for the design of foundations. In some cases, piles were used to redistribute heavy loads. Observations during the past 35 years have shown that most of the consolidation settlement has occurred in a deep layer of marine sediments and that it is largely completed within 10 years of the loading. Key words: case record, consolidation, foundation performance, in situ tests, preloading, settlements, site improvement.
Experimental and theoretical studies on installation torque of screw anchors
Authors: Ghaly Ashraf , Hanna Adel
Published: July 2008

Experimental and theoretical studies on the torque required to install screw anchors in sand are presented. Tests were conducted on five models of screw anchors with different geometry to study the effect of the shape of the screw element on the performance of the anchor during installation. Anchors were installed into prepared layers of dense, medium, and loose sand. An experimental setup was instrumented to allow the measurement of the total pullout load, the upward displacement, the sand surface deflection, installation torque value, and the stress development in the sand layer during all phases of the testing procedure. Special tests were conducted on coloured-layered sand to examine the effect of the installation procedure on the sand deposit and to define the sand wedge involved in resisting the installation of the screw anchor. Based on the results of the experimental investigation, the factors affecting the value of the installation torque were identified. A theoretical model was developed, from which the required installation torque value can be predicted. A torque factor was established in terms of the parameters affecting the torque value, and a correlation between this factor and the uplift capacity factor was proposed. From this correlation, the uplift capacity of a screw anchor can be determined from the measured installation torque value. A comparison between theoretical and experimental results showed good agreement. Also, reasonable agreement was observed when the present theoretical results were compared with the available field results from other investigations. Key words: anchorages, anchors, bearing capacity, helical anchors, models, sand, screw anchors, screw helical anchors, soil mechanics, torque, uplift capacity.
The collapse behavior of a compacted soil during inundation
Authors: Tadepalli Rambabu , Fredlund D. G.
Published: July 2008

The collapse behavior of a compacted, uncemented soil is studied within a theoretical context consistent with the concepts of unsaturated soil mechanics. Experimental data are presented relating the initial matric suction of a compacted soil to its volume decrease during inundation. The laboratory results indicate a unique relationship between the changes in matric suction (i.e., Δ(ua − uw), where ua is the pore-air pressure and uw is the pore-water pressure) of the compacted soil and the resulting volume reduction during inundation. Changes in the matric suction and total volume with respect to time were modelled using the theory of transient flow through an unsaturated soil. The predicted results show reasonable agreement with the experimental observations. The comparisons between the simulated results and the experimental data indicate that the coefficient of consolidation of the soil varies linearly with matric suction during the inundation process. Key words: unsaturated soil, matric suction, collapsible soils, negative pore-water pressures.
Generalized finite-element algorithm for laterally loaded piles in permafrost in comparison with measurements
Authors: Foriero A. , Ladanyi B.
Published: July 2008

This paper introduces an elasto-viscoplastic approach for the problem of a single laterally loaded pile in permafrost. The method requires the knowledge of a subgrade modulus k, a creep modulus kr, a yield strength qy, a displacement hardening parameter H* (for an ice-rich soil this amounts to a pure creep problem, thus qy and H* are reduced to zero), and creep parameters n, b, and γ. Finally, the validity of the proposed method is checked against the results of model pile tests that have been carried out at the Northern Engineering Centre of École Polytechnique. Key words: pile, lateral load, laboratory testing, elasto-viscoplastic soil, transient creep law.
A simplified version of the Bishop and Morgenstern slope-stability charts
Authors: Barnes G. E.
Published: July 2008

More critical values of the slope-stability coefficients, m and n, for effective stress analysis are given for a wide range of slope inclinations and values of the parameter c′/γH. The approach is also simplified by eliminating the need to choose from fixed depth factors. Key words: effective stress, slope stability, design charts.
Effects of frost on the mechanical behaviour of Champlain Sea clays
Authors: Leroueil S. , Tardif J. , Roy M. , Rochelle P. La , Konrad J.-M.
Published: July 2008

This paper presents the mechanical behaviour of Champlain Sea clays when subjected to one cycle of freeze-thaw. It appears that most of the characteristics, namely, the undrained shear strength, the thaw consolidation volume change, and the strength after consolidation, are related to the initial liquidity index and can thus be easily predicted. Results also show that frozen–thawed Champlain Sea clays present a dilatant behaviour very similar to that of granular materials. Key words: sensitive clays, frost, laboratory, strength, compressibility.
Static and cyclic liquefaction potential of Fraser Delta sand in simple shear and triaxial tests
Authors: Vaid Y P , Sivathayalan S
Published: July 2008

The potential for static and cyclic liquefaction of the sand that underlies the highly seismic Fraser Delta is assessed under simple shear test conditions, typical of an earthquake shaking. A comparison of liquefaction potential is also made between simple shear and conventional triaxial stress conditions. It is shown that the liquefaction potential of sand is profoundly influenced by the stress path. The reduction factors currently applied to the cyclic triaxial resistance for representing simple shear response may involve a large degree of conservatism in design. A direct measurement of soil behaviour under stress conditions typical of earthquake loading may thus have large economic benefits.

Key words: sand, liquefaction, static, cyclic, triaxial, simple shear.
Influence des propriétés du milieu poreux sur la durabilité au gel des roches calcaires
Authors: Bellanger Michel , Remy Jean-Michel , Homand Françoise
Published: July 2008

The frost susceptibility is a limiting factor for calcarous materials used as aggregates (pavements, concrete) or as rockfill. Its evaluation is made difficult by the complexity of the porous medium for these materials that are very often out of the range of present standard tests. The analysis of water freezing mechanisms at the pore scale and the determination of the resulting stresses has been coupled with laboratory experiments (freezing conditions have been simulated in a thermally controlled room, and the damage has been monitored by ultrasonic wave damping measurements). A physical model is proposed for the freezing behaviour of calcarous rocks that depends on the geometry of the porous constituents. The comparaison of this model with test results either normalized or recommended for aggregates and rockfill shows that the latter are too severe for calcarous materials. Test procedures should be modified to better represent the conditions of saturation and temperature prevailing in structures that includes this type of material and to take into account the complexity of the calcarous porous medium.

Key words: frost, calcarous rock, porous medium, aggregates, rockfill.[Journal Translation]
Joint cluster analysis of attribute data and relationship data
Authors: Ge Rong , Ester Martin , Gao Byron J. , Hu Zengjian , Bhattacharya Binay , Ben-Moshe Boaz
Published: July 2008

Attribute data and relationship data are two principal types of data, representing the intrinsic and extrinsic properties of entities. While attribute data have been the main source of data for cluster analysis, relationship data such as social networks or metabolic networks are becoming increasingly available. It is also common to observe both data types carry complementary information such as in market segmentation and community identification, which calls for a joint cluster analysis of both data types so as to achieve better results. In this article, we introduce the novel Connected
k
-Center (
CkC
) problem, a clustering model taking into account attribute data as well as relationship data. We analyze the complexity of the problem and prove its NP-hardness. Therefore, we analyze the approximability of the problem and also present a constant factor approximation algorithm. For the special case of the
CkC
problem where the relationship data form a tree structure, we propose a dynamic programming method giving an optimal solution in polynomial time. We further present NetScan, a heuristic algorithm that is efficient and effective for large real databases. Our extensive experimental evaluation on real datasets demonstrates the meaningfulness and accuracy of the NetScan results.
An Implementation and Evaluation of the AMLS Method for Sparse Eigenvalue Problems
Authors: Gao Weiguo , Li Xiaoye S. , Yang Chao , Bai Zhaojun
Published: July 2008

We describe an efficient implementation and present a performance study of an automated multi-level substructuring (AMLS) method for sparse eigenvalue problems. We assess the time and memory requirements associated with the key steps of the algorithm, and compare it with the shift-and-invert Lanczos algorithm. Our eigenvalue problems come from two very different application areas: accelerator cavity design and normal-mode vibrational analysis of polyethylene particles. We show that the AMLS method, when implemented carefully, outperforms the traditional method in broad application areas when large numbers of eigenvalues are sought, with relatively low accuracy.
Thar's gold in them thar constructs
Authors: Barki Henri
Published: July 2008

Conceptualization and measurement of constructs provide many opportunities for contributing to information systems research and practice by providing a better understanding and explanation of interesting and important phenomena. To assist researchers in such endeavors, this paper describes four approaches to construct conceptualization and illustrates them with examples from past research. The paper also suggests directions for future research by identifying examples of constructs that stand to benefit from the application of the four approaches.
The Emergence of iSCSI
Authors: Goldner Jeffrey S.
Published: July 2008

When most IT pros think of SCSI, images of fat cables with many fragile pins come to mind. Certainly, that’s one manifestation. But modern SCSI, as defined by the SCSI-3 Architecture Model, or SAM, really considers the cable and physical interconnections to storage as only one level in a larger hierarchy. By separating the instructions or commands sent to and from devices from the physical layers and their protocols, you arrive at a more generic approach to storage communication
Bacterial Quorum Sensing: Signals, Circuits, and Implications for Biofilms and Disease
Authors: Jayaraman Arul , Wood Thomas K.
Published: July 2008

Communication between bacteria, belonging to the same species or to different species, is mediated through different chemical signals that are synthesized and secreted by bacteria. These signals can either be cell-density related (autoinducers) or be produced by bacteria at different stages of growth, and they allow bacteria to monitor their environment and alter gene expression to derive a competitive advantage. The properties of these signals and the response elicited by them are important in ensuring bacterial survival and propagation in natural environments (e.g., human oral cavity) where hundreds of bacterial species coexist. First, the interaction between a signal and its receptor is very specific, which underlies intraspecies communication and quorum sensing. Second, when multiple signals are synthesized by the same bacterium, the signaling circuits utilized by the different signals are coordinately regulated with distinct overall circuit architecture so as to maximize the overall response. Third, the recognition of a universal communication signal synthesized by different bacterial species (interspecies communication), as well that of signals produced by eukaryotic cells (interkingdom communication), is also integral to the formation of multispecies biofilm communities that are important in infection and disease. The focus of this review is on the principles underlying signal-mediated bacterial communication, with specific emphasis on the potential for using them in two applications—development of synthetic biology modules and circuits, and the control of biofilm formation and infection.
Slow Light with Photonic Crystals for On‐Chip Optical Interconnects
Authors: Anderson Sean P. , Shroff Ashutosh R. , Fauchet Philippe M.
Published: July 2008

Transistor scaling alone can no longer be relied upon to yield the exponential speed increases
we have come to expect from the microprocessor industry. The principle reason for this is the
interconnect bottleneck, where the electrical connections between and within microprocessors are becoming, and in some cases have already become, the limiting factor in overall microprocessor performance. Optical interconnects have the potential to address this shortcoming directly, by providing an inter‐ and intrachip communication infrastructure that has both greater bandwidth and lower latency than electrical interconnects, while remaining safely within size and power constraints. In this paper, we review the requirements that a successful optical interconnect must meet, as well as some of the recent work in our group in the area of slow‐light photonic crystal devices for on‐chip optical interconnects. We show that slow‐light interferometric optical modulators in photonic crystal can have not only high bandwidth, but also extremely compact size. We also introduce the first example of a multichannel slow light platform, upon which a new class of ultracompact optical devices can be built.
Lack of Disease Specificity Limits the Usefulness of In Vitro Costimulation in HIV- and HCV-Infected Patients
Authors: Kuerten Stefanie , Schlingmann Tobias R. , Rajasalu Tarvo , Angelov Doychin N. , Lehmann Paul V. , Tary-Lehmann Magdalena
Published: July 2008

Measurements of antigen-specific T cell responses in chronic diseases are limited by low frequencies of antigen-specific cells in the peripheral blood. Therefore, attempts have been made to add costimulatory molecules such as anti-CD28 or IL-7/IL-15 to ELISPOT assays to increase sensitivity. While this approach has been successful under certain circumstances, results are often inconsistent. To date, there are no comprehensive studies directly comparing the in vitro effects of multiple costimulatory molecules in different disease settings. Therefore, in the present study we tested the effects of IL-7/IL-15, IFN-α, anti-ICOS, and anti-CD28 on antigen-specific T cell responses in patients infected with HCV or HIV versus healthy individuals. Our data show that none of the aforementioned molecules could significantly increase ELISPOT sensitivity, neither in HCV nor in HIV. Moreover, all of them caused false-positive responses to HCV and HIV antigens in healthy individuals. Our results question the broad use of in vitro costimulation.
Meeting Report: Sixth Annual AACR International Conference on Frontiers in Cancer Prevention Research
Authors: Girnun Geoffrey D. , Howe Louise R. , Manne Sharon , Mao Jenny T. , Reid Mary E. , Szabo Eva
Published: July 2008

Recent progress in understanding key events in carcinogenesis, early cancer detection, therapeutic interventions to prevent cancer, public policy, and biobehavioral approaches toward cancer control was the subject of the 6th Annual AACR International Conference on Frontiers in Cancer Prevention Research held on December 5 to 8, 2007, in Philadelphia, PA. Abundant preclinical and clinical data show that invasive cancer is preventable, yet clinical strategies to decrease society's cancer burden through prevention, early detection, and lifestyle modification are still in the early phases of development and implementation. The conference explored the multiple facets of cancer prevention and provided an update on the progress and challenges in this rapidly developing field.
Increased Cardiac Myocyte Progenitors in Failing Human Hearts
Authors: Kubo Hajime , Jaleel Naser , Kumarapeli Asangi , Berretta Remus M. , Bratinov George , Shan Xiaoyin , Wang Hongmei , Houser Steven R. , Margulies Kenneth B.
Published: July 2008

Background—

Increasing evidence, derived mainly from animal models, supports the existence of endogenous cardiac renewal and repair mechanisms in adult mammalian hearts that could contribute to normal homeostasis and the responses to pathological insults.

Methods and Results—

Translating these results, we isolated small c-kit
+
cells from 36 of 37 human hearts using primary cell isolation techniques and magnetic cell sorting techniques. The abundance of these cardiac progenitor cells was increased nearly 4-fold in patients with heart failure requiring transplantation compared with nonfailing controls. Polychromatic flow cytometry of primary cell isolates (<30 μm) without antecedent c-kit enrichment confirmed the increased abundance of c-kit
+
cells in failing hearts and demonstrated frequent coexpression of CD45 in these cells. Immunocytochemical characterization of freshly isolated, c-kit–enriched human cardiac progenitor cells confirmed frequent coexpression of c-kit and CD45. Primary cardiac progenitor cells formed new human cardiac myocytes at a relatively high frequency after coculture with neonatal rat ventricular myocytes. These contracting new cardiac myocytes exhibited an immature phenotype and frequent electric coupling with the rat myocytes that induced their myogenic differentiation.

Conclusions—

Despite the increased abundance and cardiac myogenic capacity of cardiac progenitor cells in failing human hearts, the need to replace these organs via transplantation implies that adverse features of the local myocardial environment overwhelm endogenous cardiac repair capacity. Developing strategies to improve the success of endogenous cardiac regenerative processes may permit therapeutic myocardial repair without cell delivery per se.
Predictors of Outcome in Patients With Suspected Myocarditis
Authors: Kindermann Ingrid , Kindermann Michael , Kandolf Reinhard , Klingel Karin , Bültmann Burkhard , Müller Thomas , Lindinger Angelika , Böhm Michael
Published: July 2008

Background—

The objective of this study was to identify the prognostic indicators in patients with suspected myocarditis who underwent endomyocardial biopsy.

Methods and Results—

Between 1994 and 2007, 181 consecutive patients (age, 42±15 years) with clinically suspected viral myocarditis were enrolled and followed up for a mean of 59±42 months. Endomyocardial biopsies were studied for inflammation with histological (Dallas) and immunohistological criteria. Virus genome was detected by polymerase chain reaction. The primary end point was time to cardiac death or heart transplantation. In 38% of the patients (n=69), the Dallas criteria were positive. Immunohistological signs of inflammation were shown in 50% (n=91). Genomes of cardiotropic virus species were detected in 79 patients (44%). During follow-up, 22% of the patients (n=40) reached the primary end point. Three independent predictors were identified for the primary end point, namely New York Heart Association class III or IV at entry (hazard ratio, 3.20; 95% confidence interval, 1.36 to 7.57;
P
=0.008), immunohistological evidence of inflammatory infiltrates in the myocardium (hazard ratio, 3.46; 95% confidence interval, 1.39 to 8.62;
P
=0.008), and β-blocker therapy (hazard ratio, 0.43; 95% confidence interval, 0.21 to 0.91;
P
=0.027). Ejection fraction, left ventricular end-diastolic pressure, and left ventricular end-diastolic dimension index were predictive only in univariate, not in multivariate, analysis. Neither the Dallas criteria nor the detection of viral genome was a predictor of outcome.

Conclusions—

For patients with suspected myocarditis, advanced New York Heart Association functional class, immunohistological signs of inflammation, and lack of β-blocker therapy, but not histology (positive Dallas criteria) or viral genome detection, are related to poor outcome.
Prevention of Ventricular Arrhythmias With Sarcoplasmic Reticulum Ca
2+
ATPase Pump Overexpression in a Porcine Model of Ischemia Reperfusion
Authors: Prunier Fabrice , Kawase Yoshiaki , Gianni Davide , Scapin Cristina , Danik Stephan B. , Ellinor Patric T. , Hajjar Roger J. , del Monte Federica
Published: July 2008

Background—

Ventricular arrhythmias are life-threatening complications of heart failure and myocardial ischemia. Increased diastolic Ca
2+
overload occurring in ischemia leads to afterdepolarizations and aftercontractions that are responsible for cellular electric instability. We inquired whether sarcoplasmic reticulum Ca
2+
ATPase pump (SERCA2a) overexpression could reduce ischemic ventricular arrhythmias by modulating Ca
2+
overload.

Methods and Results—

SERCA2a overexpression in pig hearts was achieved by intracoronary gene delivery of adenovirus in the 3 main coronary arteries. Homogeneous distribution of the gene was obtained through the left ventricle. After gene delivery, the left anterior descending coronary artery was occluded for 30 minutes to induce myocardial ischemia followed by reperfusion. We compared this model with a model of permanent coronary artery occlusion. Twenty-four–hour ECG Holter recordings showed that SERCA2a overexpression significantly reduced the number of episodes of ventricular tachycardia after reperfusion, whereas no significant difference was found in the occurrence of sustained or nonsustained ventricular tachycardia and ventricular fibrillation in pigs undergoing permanent occlusion.

Conclusions—

We show that Ca
2+
cycling modulation using SERCA2a overexpression reduces ventricular arrhythmias after ischemia-reperfusion. Strategies that modulate postischemic Ca
2+
overload may have clinical promise for the treatment of ventricular arrhythmias.
Acute Inhibition of Guanosine Triphosphate Cyclohydrolase 1 Uncouples Endothelial Nitric Oxide Synthase and Elevates Blood Pressure
Authors: Wang Shuangxi , Xu Jian , Song Ping , Wu Yong , Zhang Junhua , Chul Choi Hyoung , Zou Ming-Hui
Published: July 2008

GTP cyclohydrolase 1 (GTPCH1) is the rate-limiting enzyme in de novo synthesis of tetrahydrobiopterin (BH4), an essential cofactor for endothelial NO synthase (eNOS) dictating, at least partly, the balance of NO and superoxide produced by this enzyme. The aim of this study was to determine the effect of acute inhibition of GTPCH1 on BH4, eNOS function, and blood pressure (BP) in vivo. Exposure of bovine or mouse aortic endothelial cells to GTPCH1 inhibitors (2,4-diamino-6-hydroxypyrimidine or
N
-acetyl-serotonin) or GTPCH1 small-interference RNA (siRNA) significantly reduced BH4 and NO levels but increased superoxide levels. This increase was abolished by sepiapterin (BH4 precursor) or
N
G
-nitro-
l
-arginine methyl ester (nonselective NOS inhibitor). Incubation of isolated murine aortas with 2,4-diamino-6-hydroxypyrimidine or
N
-acetyl-serotonin impaired acetylcholine-induced endothelium-dependent relaxation but not endothelium-independent relaxation. Aortas from GTPCH1 siRNA-injected mice, but not their control-siRNA injected counterparts, also exhibited impaired endothelium-dependent relaxation. BH4 reduction induced by GTPCH1 siRNA injection was associated with increased aortic levels of superoxide, 3-nitrotyrosine, and adhesion molecules (intercellular adhesion molecule 1 and vascular cell adhesion molecule 1), as well as a significantly elevated systolic, diastolic, and mean BP in C57BL6 mice. GTPCH1 siRNA was unable to elicit these effects in eNOS
−/−
mice. Sepiapterin supplementation, which had no effect on high BP in eNOS
−/−
mice, partially reversed GTPCH1 siRNA–induced elevation of BP in wild-type mice. In conclusion, GTPCH1 via BH4 maintains normal BP and endothelial function in vivo by preserving NO synthesis by eNOS.
Surface Morphology Effects on High-Rate Fracture of an Aluminum/Epoxy Interface
Authors: Chul Jin Syn  , Chen Weinong W.
Published: July 2008

Crack initiation and propagation along interfaces are influenced by interface morphology under quasi-static loading conditions. In this article, the loading rate and surface topography effects on energy dissipation during dynamic fracture of an aluminum/epoxy interface were experimentally investigated. Four-point bending specimens with a precrack on the interface were dynamically loaded at high rates with stress waves. The aluminum side of the interface on the specimen had four surface roughness levels. The study of surface morphology effects at high rates is the original contribution of this research. The results indicate that surface morphology significantly affect the energy dissipation during the dynamic fracture of the interface. At a specific roughness, fracture toughness and energy dissipation increase with increasing loading rates.
Culpable Control and Counterfactual Reasoning in the Psychology of Blame
Authors: Alicke Mark D. , Buckingham Justin , Zell Ethan , Davis Teresa
Published: July 2008

Many counterfactual reasoning studies assess how people ascribe blame for harmful actions. By itself, the knowledge that a harmful outcome could easily have been avoided does not predict blame. In three studies, the authors showed that an outcome's mutability influences blame and related judgments when it is coupled with a basis for negative evaluations. Study 1 showed that mutability influenced blame and compensation judgments when a physician was negligent but not when the physician took reasonable precautions to prevent harm. Study 2 showed that this finding was attenuated when the victim contributed to his own demise. In Study 3, whether an actor just missed arriving on time to see his dying mother or had no chance to see her influenced his blameworthiness when his reason for being late provided a basis for negative evaluations but made no difference when there was a positive reason for the delay. These findings clarify the conditions under which an outcome's mutability is likely to influence blame and related attributions.
Action and thought in cello playing: an investigation of children's practice and performance
Authors: Lisboa Tânia
Published: July 2008

This article presents a longitudinal case study investigation of three young cellists' self-directed preparation of a new piece of music for an informal performance. The investigation considers how musical understanding starts to emerge in children's practice and performance. It explores practice at early stages of learning and examines the children's thoughts and action through a comparison between what they say and what they are able to demonstrate through playing. The participants were filmed both in practice sessions and in informal performances. A multi-method approach was used in which detailed analysis of the children's playing, semi-structured interviews and the children's own appraisal five years after the research were combined. The results show that when left to their own devices, the children developed an internal representation of the music that incorporated rhythm and pitch mistakes of which they were unaware. The participants' appraisal five years later confirmed that they all adopted a mainly technical approach to the piece, through repetitive practice strategies, with no focus on musical matters and, therefore, no particular understanding of the structure of the piece. Overall, their interpretation was limited by their technical and conceptual difficulties and there were only a few signs of musical expression.
Music activity reports by music teachers with varying training in Orff Schulwerk
Authors: Sogin David W. , Wang Cecilia Chu
Published: July 2008

The purpose of this study was to examine music activities occurring in the music classroom of teachers who received different levels of training in Orff Schulwerk. The subjects ( N = 49) were teachers participating in three training levels at a summer Orff Schulwerk certification program in a university in the USA. Teachers were asked to report the types and amount of musical activities in their own classroom. A questionnaire modeled after one used in a published research study was used to obtain the data. Results from the selfreport of participants indicate that there were similarities as well as differences among music teachers of three levels of Orff training. Similarities were found in the amount of time devoted to reading, listening, and singing. The impact of the Orff Schulwerk was detected in increased amount in playing, creating and moving for teachers with advanced training. It appears that with increased training teachers increase the amount of activities with the children without replacing any of the activities. There was also an increase in student participation in decision making for teachers with more advanced Orff training.