bluuebunny/crossref_metadata_2025 huggingface dataset:
Photochemical gating of heterologous ion channels: Remote control over genetically designated populations of neurons
Authors: Zemelman Boris V. , Nesnas Nasri , Lee Georgia A. , Miesenböck Gero
Published: February 2003

Heterologous proteins capable of transducing physical or chemical stimuli into electrical signals can be used to control the function of excitable cells in intact tissues or organisms. Restricted genetically to circumscribed populations of cellular targets, these selectively addressable sources of depolarizing current can supply distributed inputs to neural circuits, stimulate secretion, or regulate force and motility. In an initial demonstration of this principle, we have used elements of a G protein coupled signaling system, the phototransduction cascade of the fruit fly, to sensitize generalist vertebrate neurons to light [Zemelman, B. V., Lee, G. A., Ng, M. & Miesenböck, G. (2002)
Neuron
33, 15–22]. We now describe the use of ectopically expressed ligand-gated ion channels as transducers of optical or pharmacological stimuli. When either the capsaicin receptor, TRPV1, the menthol receptor, TRPM8, or the ionotropic purinergic receptor P2X
2
was introduced into hippocampal neurons, the cells responded to pulsed applications of agonist with characteristic sequences of depolarization, spiking, and repolarization. Responses required cognate matches between receptor and agonist, peaked at firing frequencies of ≈40 Hz, initiated and terminated rapidly, and did not attenuate. Precise dose–response relationships allowed current amplitudes and firing frequencies to be tuned by varying the concentration of ligand. Agonist could be administered either pharmacologically or, in the cases of TRPV1 and P2X
2
, optically, through photorelease of the active compounds from the respective “caged” precursors, 4,5-dimethoxy-2-nitrobenzyl-capsaicin and
P
3
-[1-(4,5-dimethoxy-2-nitrophenyl)ethyl]-ATP.
Microbe forensics: Oxygen and hydrogen stable isotope ratios in
Bacillus subtilis
cells and spores
Authors: Kreuzer-Martin Helen W. , Lott Michael J. , Dorigan Janet , Ehleringer James R.
Published: February 2003

Bacillus subtilis
, a Gram-positive, endospore-forming soil bacterium, was grown in media made with water of varying oxygen (δ
18
O) and hydrogen (δD) stable isotope ratios. Logarithmically growing cells and spores were each harvested from the cultures and their δ
18
O and δD values determined. Oxygen and hydrogen stable isotope ratios of organic matter were linearly related with those of the media water. We used the relationships determined in these experiments to calculate the effective whole-cell fractionation factors between water and organic matter for
B. subtilis
. We then predicted the δ
18
O and δD values of spores produced in nutritionally identical media and local water sources for five different locations around the United States. Each of the measured δ
18
O and δD values of the spores matched the predicted values within a 95% confidence interval, indicating that stable isotope ratio analyses may be a powerful tool for tracing the geographic point-of-origin for microbial products.
Adenosine receptor blockade reverses hypophagia and enhances locomotor activity of dopamine-deficient mice
Authors: Kim Douglas S. , Palmiter Richard D.
Published: February 2003

Adenosine receptors modulate dopaminergic function by regulating dopamine release in presynaptic neurons and intracellular signaling in postsynaptic striatal neurons. To investigate how adenosine impinges on the action of dopamine in feeding and locomotion, genetically altered, dopamine-deficient mice were treated with adenosine receptor antagonists. Acute administration of the nonselective adenosine receptor antagonist, caffeine (5–25 mg/kg i.p.), reversed the hypophagia of mutant mice and induced hyperactivity in both control and mutant animals. However, caffeine treatment elicited much less hyperactivity in dopamine-deficient mice than did
l
-3,4-dihydroxyphenylalanine (
l
-dopa) administration, which partially restores dopamine content. Caffeine treatment enhanced feeding of
l
-dopa-treated mutants but, unexpectedly, it reduced their hyperlocomotion. Caffeine administration induced c-Fos expression in the cortex of dopamine-deficient mice but had no effect in the striatum by itself. Caffeine attenuated dopamine agonist-induced striatal c-Fos expression. An antagonist selective for adenosine A
2A
receptors induced feeding and locomotion in mutants much more effectively than an A
1
receptor antagonist.
l
-dopa-elicited feeding and hyperlocomotion were reduced in mutants treated with an A
1
receptor agonist, whereas an A
2A
receptor agonist decreased
l
-dopa-induced feeding without affecting locomotion. The observations suggest that the hypophagia and hypoactivity of mutants result not only because of the absence of dopamine but also because of the presence of A
2A
receptor signaling. This study of a genetic model of dopamine depletion provides evidence that A
2A
receptor antagonists could ameliorate the hypokinetic symptoms of advanced Parkinson's disease patients without inducing excessive motor activity.
Two Hsp70 family members expressed in atherosclerotic lesions
Authors: Han Zhihua , Truong Quynh A. , Park Shirley , Breslow Jan L.
Published: February 2003

Gene expression profiling was carried out comparing Con A elicited peritoneal macrophages from C57BL/6 and FVB/N wild-type and apolipoprotein (apo)E knockout mice. An EST,W20829, was expressed at higher levels in C57BL/6 compared with FVB/N mice.W20829mapped to an atherosclerosis susceptibility locus on chromosome 19 revealed in an intercross between atherosclerosis-susceptible C57BL/6 and atherosclerosis-resistant FVB/N apoE knockout mice. A combination of database search and Northern analysis confirmed thatW20829corresponded to 3′-UTR of a hitherto predicted gene, namedHspA12A. Blasting the National Center for Biotechnology Information database revealed a closely related homologue,HspA12B. HspA12A and -B have very close human homologues. TaqMan analysis confirmed the increasedHspA12Aexpression (2.6-fold) in elicited peritoneal macrophages from C57BL/6 compared with FVB/N mice. TaqMan analysis also revealed increasedHspA12AandHspA12Bexpression (87- and 6-fold, respectively) in lesional versus nonlesional portions of the thoracic aorta from C57BL/6 apoE knockout mice on a chow diet.In situhybridization confirmed that both genes were expressed within lesions but not within nonlesional aortic tissue. Blasting of HspA12A and HspA12B against the National Center for Biotechnology Information database (NR) revealed a hit with the Conserved Domain database for Hsp70 (pfam00012.5, Hsp70). Both genes appear to contain an atypical Hsp70 ATPase domain. The BLAST search also revealed that both genes were more similar to primitive eukaryote and prokaryote than mammalian Hsp70s, making these two genes distant members of the mammalian Hsp70 family. In summary, we describe two genes that code for a subfamily of Hsp70 proteins that may be involved in atherosclerosis susceptibility.
Biochemical characterization of the
Yersinia
YopT protease: Cleavage site and recognition elements in Rho GTPases
Authors: Shao Feng , Vacratsis Panayiotis O. , Bao Zhaoqin , Bowers Katherine E. , Fierke Carol A. , Dixon Jack E.
Published: February 2003

The Gram-negative bacterial pathogen
Yersinia
delivers six effector proteins into the host cells to thwart the host innate immune response. One of the effectors, YopT, causes the disruption of the actin cytoskeleton and contributes to the inhibition of phagocytosis of the pathogen. YopT functions as a cysteine protease to cleave Rho family GTPases. We have analyzed the YopT cleavage products of Rho GTPases by TLC and determined their chemical structure by MS. Amino acid labeling experiments were performed to locate the exact site in RhoA where the YopT cleavage occurs. Our data unambiguously demonstrate that YopT cleaves N-terminal to the prenylated cysteine in RhoA, Rac, and Cdc42 and that the cleavage product of the GTPases is geranylgeranyl cysteine methyl ester. YopT cleaves GTP- and GDP-bound forms of RhoA equally, suggesting that the cleavage does not depend upon the conformation status of the GTPases. YopT also cleaves both farnesylated and geranylgeranylated forms of RhoA. The polybasic sequence in the C terminus of RhoA is essential for YopT substrate recognition and cleavage.
Transcriptional and posttranscriptional control of hepatitis B virus gene expression
Authors: Uprichard Susan L. , Wieland Stefan F. , Althage Alana , Chisari Francis V.
Published: February 2003

Hepatitis B virus (HBV) infects humans and certain nonhuman primates. Viral clearance and acute disease are associated with a strong, polyclonal, multispecific cytotoxic T lymphocyte response. Infiltrating T cells, as well as other activated inflammatory cells, produce cytokines that can regulate hepatocellular gene expression. Using an HBV transgenic mouse model, our laboratory has previously demonstrated that adoptive transfer of HBV-specific cytotoxic T lymphocytes or injection of IL-2 can noncytopathically inhibit HBV gene expression by a posttranscriptional IFN-γ- and/or tumor necrosis factor α-dependent mechanism. Here, we report that HBV gene expression can also be controlled at the posttranscriptional level during persistent lymphocytic choriomeningitis virus infection. In contrast, it is controlled at the transcriptional level during acute murine cytomegalovirus infection or after repetitive polyinosinic-polycytidylic acid injection. Finally, we show that transcriptional inhibition of HBV is associated with changes in liver-specific gene expression. These results elucidate pathways that regulate the viral life cycle and suggest additional approaches for the treatment of chronic HBV infection.
A role for Mints in transmitter release: Mint 1 knockout mice exhibit impaired GABAergic synaptic transmission
Authors: Ho Angela , Morishita Wade , Hammer Robert E. , Malenka Robert C. , Südhof Thomas C.
Published: February 2003

Mints (also called X11-like proteins) are adaptor proteins composed of divergent N-terminal sequences that bind to synaptic proteins such as CASK (Mint 1 only) and Munc18-1 (Mints 1 and 2) and conserved C-terminal PTB- and PDZ-domains that bind to widely distributed proteins such as APP, presenilins, and Ca
2+
channels (all Mints). We find that Mints 1 and 2 are similarly expressed in most neurons except for inhibitory interneurons that contain selectively high levels of Mint 1. Using knockout mice, we show that deletion of Mint 1 does not impair survival or alter the overall brain architecture, arguing against an essential developmental function of the Mint 1–CASK complex. In electrophysiological recordings in the hippocampus, we observed no changes in short- or long-term synaptic plasticity in excitatory synapses from Mint 1-deficient mice and detected no alterations in the ratio of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) to
N
-methyl-
d
-aspartate (NMDA) receptor-mediated synaptic currents. Thus the Mint 1–CASK complex is not required for AMPA- and NMDA-receptor functions or for synaptic plasticity in excitatory synapses. In inhibitory synapses, however, we uncovered an ≈3-fold increase in presynaptic paired-pulse depression, suggesting that deletion of Mint 1 impairs the regulation of γ-aminobutyric acid release. Our data indicate that Mints 1 and 2 perform redundant synaptic functions that become apparent in Mint 1-deficient mice in inhibitory interneurons because these neurons selectively express higher levels of Mint 1 than Mint 2.
Extensive and specific responses of a eukaryote to bacterial quorum-sensing signals
Authors: Mathesius Ulrike , Mulders Susan , Gao Mengsheng , Teplitski Max , Caetano-Anollés Gustavo , Rolfe Barry G. , Bauer Wolfgang D.
Published: February 2003

Many bacteria use
N
-acyl homoserine lactone (AHL) signals to coordinate the behavior of individual cells in a local population. The successful infection of eukaryotic hosts by bacteria seems to depend particularly on such AHL-mediated “quorum-sensing” regulation. We have used proteome analysis to show that a eukaryotic host, the model legume
Medicago truncatula
, is able to detect nanomolar to micromolar concentrations of bacterial AHLs from both symbiotic (
Sinorhizobium meliloti
) and pathogenic (
Pseudomonas aeruginosa
) bacteria, and that it responds in a global manner by significant changes in the accumulation of over 150 proteins, 99 of which have been identified by peptide mass fingerprinting. The accumulation of specific proteins and isoforms depended on AHL structure, concentration, and time of exposure. AHLs were also found to induce tissue-specific activation of β-glucuronidase (
GUS
) reporter fusions to an auxin-responsive and three chalcone synthase promoters, consistent with AHL-induced changes in the accumulation of auxin-responsive and flavonoid synthesis proteins. In addition, exposure to AHLs was found to induce changes in the secretion of compounds by the plants that mimic quorum-sensing signals and thus have the potential to disrupt quorum sensing in associated bacteria. Our results indicate that eukaryotes have an extensive range of functional responses to AHLs that may play important roles in the beneficial or pathogenic outcomes of eukaryote–prokaryote interactions.
The budding yeast Ipl1/Aurora protein kinase regulates mitotic spindle disassembly
Authors: Buvelot Stéphanie , Tatsutani Sean Y. , Vermaak Danielle , Biggins Sue
Published: February 2003

Ipl1p is the budding yeast member of the Aurora family of protein kinases, critical regulators of genomic stability that are required for chromosome segregation, the spindle checkpoint, and cytokinesis. Using time-lapse microscopy, we found that Ipl1p also has a function in mitotic spindle disassembly that is separable from its previously identified roles. Ipl1–GFP localizes to kinetochores from G1 to metaphase, transfers to the spindle after metaphase, and accumulates at the spindle midzone late in anaphase. Ipl1p kinase activity increases at anaphase, and ipl1 mutants can stabilize fragile spindles. As the spindle disassembles, Ipl1p follows the plus ends of the depolymerizing spindle microtubules. Many Ipl1p substrates colocalize with Ipl1p to the spindle midzone, identifying additional proteins that may regulate spindle disassembly. We propose that Ipl1p regulates both the kinetochore and interpolar microtubule plus ends to regulate its various mitotic functions.
Developmental morphology of normal and atypical flowers ofPhilodendron insigne(Araceae): a new case of homeosis
Authors: Barabé Denis , Lacroix Christian , Jeune Bernard
Published: February 2003

The early stages of development of the inflorescence of Philodendron insigne were examined using scanning electron microscopy. Pistillate flowers are initiated on the lower portion of the inflorescence and staminate flowers are initiated on the distal portion. The male flowers have three to five stamens. The female flowers have a multilocular ovary consisting of three to five locules. A transition zone consisting of sterile male flowers and atypical bisexual flowers with fused or free carpels and staminodes is located between the male and female floral zones. Generally, the portion of the bisexual flower facing the male zone forms stamens, and the portion facing the female zone develops one or two carpels. In P. insigne, the incomplete separation of staminodes from the gynoecial portion of the whorl shows that the staminodes and carpels belong to the same whorl. The atypical bisexual flowers of P. insigne are believed to be a case of homeosis where carpels have been replaced by sterile stamens on the same whorl. However, there is no regularity in the number of organs involved in the homeotic transformation taking place in atypical bisexual flowers. The presence of atypical bisexual flowers may correspond to a morphogenetic gradient at the level of the inflorescence as a whole.Key words: flower, development, gradient, inflorescence.
Contrasting seed germination patterns for intracontinental disjuncts of Heuchera (Saxifragaceae) in North America: the eastern temperate H. parviflora and western montane H. cylindrica
Authors: Hidayati Siti N , Walck Jeffrey L
Published: February 2003

Heuchera parviflora var. parviflora grows primarily in southeastern North America and Heuchera cylindrica var. cylindrica in northwestern North America. Seeds of H. parviflora were collected in Kentucky in November 1995 and 1996 during the dispersal stage of the life cycle, and those of H. cylindrica were collected in Washington in August 1996. The purpose of the study was to compare the germination patterns of these two intracontinental disjunct species of Heuchera. During 212 weeks of incubation over a range of thermoperiods (15:6, 20:10, 25:15, 30:15, 35:20°C (12 h : 12 h)) that simulated habitat temperatures, fresh H. parviflora seeds germinated to 6287% at 20:10  30:15°C in light. Cold stratification at 5°C effectively broke conditional dormancy in H. parviflora seeds: 7696% germination took place during 2 weeks of incubation at 15:6  35:20°C in light following 12 weeks of cold stratification in light. In contrast, fresh H. cylindrica seeds germinated to 6994% at 15:6  25:15°C in light during 212 weeks of incubation in light, but cold stratification at 5°C did not improve germination. Peak germination of H. parviflora seeds sown in November 1996 in an ambient-temperature greenhouse occurred in early March 1997, whereas that of H. cylindrica seeds sown in September 1996 occurred in late October 1996. Adaptive divergence of these species apparently has occurred with respect to their seed germination ecology. Their dormancy and germination characteristics are similar to the many other species growing in the same vegetation types.Key words: adaptive divergence, Heuchera cylindrica, Heuchera parviflora, physiological dormancy, Saxifragaceae, seed germination.
Differential nectar production between male and female flowers in a wild cucurbit: Cucurbita maxima ssp. andreana (Cucurbitaceae)
Authors: Ashworth Lorena , Galetto Leonardo
Published: February 2003

In dioecious and monoecious plants that depend on animal vectors for reproduction, pollinators have to be attracted to male and female flowers for pollination to be effective. In the monoecious Cucurbita maxima ssp. andreana, male flowers are produced in greater quantity, are spatially more exposed to pollinators and offer pollen in addition to nectar as floral rewards. Nectar traits were compared between male and female flowers to determine any differences in the characteristics of the main reward offered to pollinators. Nectar chemical composition and sugar proportions were similar between flower types. Total nectar sugar production per female flower was threefold higher than per male flower, and nectar removal did not have any effect on total nectar production in both flower morphs. Pollinators reduced nectar standing crops to similar and very scarce amounts in both flower types. Results indicate indirectly that pollinators are consuming more nectar from female flowers, suggesting that the higher nectar production in female flowers may be a reward-based strategy to achieve the high female reproductive output observed in this species.Key words: Cucurbitaceae, Cucurbita maxima ssp. andreana, nectar production, nectar sugar composition, removal effects, standing crop.
Setomelanomma holmii (Pleosporales, Phaeosphaeriaceae) on living spruce twigs in Europe and North America
Authors: Rossman Amy Y , Farr David F , Castlebury Lisa A , Shoemaker Robert , Mengistu Alemu
Published: February 2003

Setomelanomma holmii M. Morelet, previously known only from the type specimen in France, was discovered in the U.S.A. (Kansas and Wisconsin) and Canada (Ontario) on living twigs of spruce (Picea pungens and Picea glauca). This fungus was grown from ascospores and compared with the ex-holotype culture. Morphology and ITS rDNA sequence similarities indicate that S. holmii belongs in the Pleosporales, Phaeosphaeriaceae. Sequence analysis of the SSU nrDNA places S. holmii in a clade containing members of the Leptosphaeriaceae and Phaeosphaeriaceae. Setomelanomma holmii is redescribed and illustrated based on the holotype and North American specimens.Key words: Loculoascomycetes, Phaeosphaeriaceae, Picea, Pleosporales, needle chlorosis.
Caractérisation en laboratoire du potentiel expansif de granulats de remblais de fondation
Authors: Bellaloui Achour , Nkurunziza Gilbert , Ballivy Gérard
Published: February 2003

Pyritic aggregates coming from sedimentary rocks may be subject to expansions when used in subbases, and, in certain cases, may then cause heaving or expansion of concrete slabs with consequences on the structures. This situation occurs in areas where the lack of prime aggregates requires the use of local materials. Swellings are observed and are basically related to the oxidation of sulphides such as pyrite, pyrrhotite, and chalcopyrite, which are present in aggregates. As a result of this oxidation, sulphuric acid is formed and reacts to produce gypsum, which is responsible for the increase of volume. This paper is a contribution to a better understanding of this topical phenomenon and also includes the procedure of characterization used for four aggregates to determine their expansive potential by using an experimental device developed at the laboratory. Different reactivity modes take place involving processes such as swelling and sulphate attack or even the combination of the two modes, which are corroborated by the intrinsic properties of the aggregates used in this study.Key words: subbase, aggregates, pyrite, oxidation, gypsum, swelling.
Probabilistic neural network for evaluating seismic liquefaction potential
Authors: Goh Anthony TC
Published: February 2003

Simplified techniques based on in situ testing methods are commonly used to assess seismic liquefaction potential. Many of these simplified methods are based on finding the liquefaction boundary separating two categories (the occurrence or non-occurrence of liquefaction) through the analysis of liquefaction case histories. As the liquefaction classification problem is highly nonlinear in nature, it is difficult to develop a comprehensive model taking into account all the independent variables, such as the seismic and soil properties, using conventional modeling techniques. Hence, in many of the conventional methods that have been proposed, simplified assumptions have been made. In this study, a probabilistic neural network (PNN) approach based on the Bayesian classifier method is used to evaluate seismic liquefaction potential based on actual field records. Two separate analyses are performed, one based on cone penetration test data and one based on shear wave velocity data. The PNN model effectively explores the relationship between the independent and dependent variables without any assumptions about the relationship between the various variables. Through the iterative presentation of the data (the learning phase), this study serves to demonstrate that the PNN can "discover" the intrinsic relationship between the seismic and soil parameters and the liquefaction potential. Comparisons indicate that the PNN models perform far better than the conventional methods in predicting the occurrence or non-occurrence of liquefaction.Key words: cone penetration test, neural networks, prediction, probabilistic neural network, sand, seismic liquefaction, shear wave velocity.
A new elastic viscoplastic model for time-dependent behaviour of normally and overconsolidated clays: theory and verification
Authors: Yin Jian-Hua , Zhu Jun-Gao , Graham James
Published: February 2003

This paper presents a new three-dimensional elastic viscoplastic (3D EVP) constitutive model for the time-dependent stressstrain behaviour of both normally consolidated and overconsolidated clays. There are two major new developments in the 3D EVP model: (i) incorporation of a nonlinear creep function with a limit for the creep volume strain under isotropic stressing conditions; (ii) adoption of a new loading surface function with a smooth shape on the π plane. Based on the "equivalent time" concept of Yin and Graham, the formulation of the new 3D EVP model is derived using the new nonlinear creep function and loading surface function. A new approach to determining all model parameters is presented. The 3D EVP model is calibrated using data from one conventional isotropic stress creep test and consolidated-undrained triaxial tests on soft Hong Kong marine deposits (HKMD). The model is verified by comparing model results with those from both normally and overconsolidated triaxial tests on HKMD and a mixture of kaolin and bentonite.Key words: creep, time-dependent, viscoplastic, equivalent time, stressstrain, constitutive model, verification, clay.
Variation of evaporative and shear strength parameters along a tailings delta
Authors: Rassam Daud W
Published: February 2003

Following their disposal into storage impoundments, mine tailings form a sloping delta along which hydraulic sorting of the particles occurs. The sorting process has a major effect on the engineering properties of the tailings which are relevant to future rehabilitation procedures. In this paper, the variation of the evaporative and shear strength parameters of tailings along a delta is described. It is demonstrated numerically that the sorting process has a significant effect on the critical evaporation rate, which dictates the maximum steady-state matric suctions that might be attained in tailings above a water table. The sorting process also has a pronounced impact on the magnitude of both the matric suctions above the water table and the unsaturated shear strength along the tailings delta. These two effects together contribute significantly to the shear strength of finer tailings. A 10 year simulation of the seasonal water table fluctuations along the tailings delta defined an upper-bound shear strength gain profile following a prolonged dry period and a lower-bound shear strength gain profile following a wet period.Key words: tailings, evaporation, critical evaporation rate, matric suction, unsaturated shear strength.
Effect of ageing on stiffness of very loose sand
Authors: Howie J A , Shozen T , Vaid Y P
Published: February 2003

The paper presents the results of laboratory triaxial compression tests to study the stiffness of very loose Fraser River sands. The stiffness has been shown to be very dependent on the time of confinement prior to shearing and the stress ratio at which the sample is aged. Higher stress ratios resulted in very low initial moduli with no ageing, but the moduli increased by several hundred percent during the first 1000 min of ageing. For ageing at a stress ratio of 1.0 (i.e., isotropic ageing), the initial moduli were higher than those for ageing at high stress ratios, but the stiffness increased by only about 60% during the first 1000 min of ageing. The rate of stiffness increase was approximately linear with the logarithm of time up to ageing times of 10 000 min (>1 week). Ageing at any stress ratio resulted in reduced contractive volumetric strain during subsequent shearing, reflecting a change in soil structure during ageing. The dεv/dεaratio under triaxial compression loading decreased as the ageing stress ratio increased. The results suggest that close attention must be paid to the age of laboratory samples prepared to study the stressstrain response of sands at strains up to about 0.1%, particularly in studies on loose sand.Key words: sands, ageing, creep, modulus.
An equation of state for unsaturated soils
Authors: Murray Edward J
Published: February 2003

The enthalpy within a soil system under equilibrium conditions is investigated theoretically. Terzaghi's effective stress equation for a saturated soil is first examined and the approach extended to determine the enthalpy associated with the air, water, and solid phases, and the interactions between the phases, in an unsaturated soil. An equation of state is developed which links the stress state variables (p  ua) and (ua uw) to the specific volume (v) and specific water volume (vw) and thus to the volumes of the phases. The equation is shown to provide a logical interpretation of the average volumetric "coupling" stress p'cwithin unsaturated soils which highlights the significance of the dual stress regime and bimodal structure. The new equation is compared with previously reported experimental data on kaolin and a lateritic gravel. The agreement is good and it provides insight into unsaturated soil strength and deformation behaviour and clarifies various previously identified anomalies.Key words: partial saturation, unsaturated soils, thermodynamics, effective stress, equation of state, critical state.
Submarine landslides: advances and challenges
Authors: Locat Jacques , Lee Homa J
Published: February 2003

Due to the recent development of well-integrated surveying techniques of the sea floor, significant improvements were achieved in mapping and describing the morphology and architecture of submarine mass movements. Except for the occurrence of turbidity currents, the aquatic environment (marine and fresh water) experiences the same type of mass failure as that found on land. Submarine mass movements, however, can have run-out distances in excess of 100 km, so their impact on any offshore activity needs to be integrated over a wide area. This great mobility of submarine mass movements is still not very well understood, particularly for cases like the far-reaching debris flows mapped on the Mississippi Fan and the large submarine rock avalanches found around many volcanic islands. A major challenge ahead is the integration of mass movement mechanics in an appropriate evaluation of the hazard so that proper risk assessment methodologies can be developed and implemented for various human activities offshore, including the development of natural resources and the establishment of reliable communication corridors.Key words: submarine slides, hazards, risk assessment, morphology, mobility, tsunami.
Assessment of the hydraulic characteristics of unsaturated base-course materials: a practical method for pavement engineers
Authors: Côté J , Konrad J -M
Published: February 2003

This paper presents the results of a comprehensive laboratory investigation program on the influence of the properties of fines particles on the hydraulic characteristics of granular base-courses. The soil-water characteristic curve and the hydraulic conductivity were determined for three types of well-graded crushed aggregates (granite, limestone, and schist) with different amounts of fines (3.512.5%). A porosity model that considers the uniform dispersion of fines is proposed for well-graded material. Empirical relationships have been developed between the hydraulic parameters (i.e., the saturated hydraulic conductivity, the air entry value, the pore-size distribution index, the fines fraction porosity) and their specific surface area. A methodology is proposed for the assessment of the saturated and unsaturated hydraulic characteristics of base-course materials.Key words: pavement, drainage, base-course, fines, soil-water characteristic curve, hydraulic conductivity.
Some experiences on the stabilization of Irish peats
Authors: Hebib Samir , Farrell Eric R
Published: February 2003

This paper presents the findings of a study into the engineering properties of two peats from the Irish Midlands that were mixed with various binders to form a stabilized soil. The study comprised an investigation of the increase in unconfined compressive strength over time achieved using different binders for both peats and a comprehensive series of triaxial and compression tests on one peat when mixed with cement. A stabilized structure (i.e., a stabilized surface layer and a stabilized column) was tested in a large testing chamber in Trinity College to compare the laboratory parameters with those interpreted from the results of the large-scale test. The study showed that the engineering properties of the peat were considerably improved when mixed with some binders, however the degrees of improvement were markedly different for the two peats that had similar organic content. The formation of the stabilized soil structure within the testing chamber significantly reduced the amount of settlement when compared with that interpreted for the untreated soil, and the rate of consolidation was accelerated. A finite element analysis of the recorded behaviour in the large testing chamber showed good agreement between the simulated and the experimental behaviour.Key words: peat, cement, stabilization, compressibility, column.
Time domain reflectrometry measurements of water content in coarse waste rock
Authors: Nichol Craig , Smith Leslie , Beckie Roger
Published: February 2003

Methods are presented to calibrate and implement a time domain reflectrometry (TDR) system to estimate the water content of coarse mine waste rock containing high solute concentrations in the pore water. High electrical conductivity of the pore water reduces the quality of TDR waveforms through the loss of signal amplitude. Zegelin-type probes with a resistive coating on the center conductor were used to obtain higher signal-to-noise waveforms. These probes must be calibrated prior to use. The TDR pulse travel-time measured in soils containing pore water with high solute concentrations increases systematically with solute concentration. Empirical calibrations are derived for waste rock with low and high electrical conductivity pore water. An ambient temperature correction is derived from observed diurnal fluctuations in the measured travel time to determine whether or not a detailed laboratory calibration for temperature effects is required. The variation of apparent dielectric permittivity with temperature is positively correlated with temperature at low water content and negatively correlated at high water content. This trend indicates the influence of water bound to mineral surfaces on the variation of apparent dielectric permittivity with temperature. Examination of our field data indicates that the effect of dissolved ions on the TDR calibration was great enough to justify a calibration that accounts for pore-water composition. The effect of ambient temperature was found to be small enough that an intensive laboratory calibration was not required.Key words: time domain reflectrometry, water content, mining.
Efficient Intelligent Backtracking Using Linear Programming
Authors: Davey Bruce , Boland Natashia , Stuckey Peter J.
Published: February 2003

Intelligent backtracking is a technique used in constraint programming for reducing search in solving combinatorial feasibility problems. The technique uses information derived from small sets of infeasible constraints discovered in one part of the search space to avoid searching other, similar, regions. It is often able to reduce the size of the search space significantly. For many problems, however, the computational effort required to achieve this reduction in search space is prohibitive. We introduce an algorithm that uses intelligent backtracking inside a linear-programming based branch-and-bound framework. We show that minimal infeasible sets can immediately be deduced from the dual extreme ray associated with the infeasible linear program. This allows us to obtain the reduction in search space associated with intelligent backtracking, without paying the large computational cost. We show the implementation of our intelligent backtracking approach as a branch-and-cut algorithm, and present computational results.
The Role of Integer Programming Techniques in Constraint Programming's Global Constraints
Authors: Milano Michela , Ottosson Greger , Refalo Philippe , Thorsteinsson Erlendur S.
Published: February 2003

Efforts aimed at combining operations research and constraint programming have become increasingly prominent and successful in the last few years. It is now widely recognized that integration, e.g., inference in the form of constraint propagation and relaxation in the form of linear programming, can yield substantial results. In this paper, we argue the benefits of constraint programming's global constraints as a basis for such an integration and discuss the advantages along with some examples. We illustrate the integration on the global cardinality structure, on piecewise linear functions, on variable subscripts, on the cycle structure and on resource constraints. Each example is completed with a case study.
Nonparametric Efficiency Estimation In Stochastic Environments
Authors: Post Thierry , Cherchye Laurens , Kuosmanen Timo
Published: February 2003

This paper develops a new nonparametric model for efficiency estimation. In contrast to Data Envelopment Analysis (DEA), it does not impose debatable production assumptions like free disposability and convexity, and it does not assume that the data are measured without error. The estimators are asymptotically unbiased and have an asymptotic variance that is comparable to that of stochastic frontier estimators (provided the latter use a correct specification of the functional form for the production relationships). In addition, the estimators can be computed using a simple enumeration algorithm.
A Bi-Objective Median Location Problem With a Line Barrier
Authors: Klamroth Kathrin , Wiecek Margaret M.
Published: February 2003

The multiple objective median problem (MOMP) involves locating a new facility with respect to a given set of existing facilities so that a vector of performance criteria is optimized. A variation of this problem is obtained if the existing facilities are situated on two sides of a linear barrier. Such barriers, like rivers, highways, borders, or mountain ranges, are frequently encountered in practice. In this paper, theory of an MOMP with line barriers is developed. As this problem is nonconvex but specially structured, a reduction to a series of convex optimization problems is proposed. The general results lead to a polynomial algorithm for finding the set of efficient solutions. The algorithm is proposed for bicriteria problems with different measures of distance.
Deliberate Learning and the Evolution of Dynamic Capabilities
Authors: Zollo Maurizio , Winter Sidney G.
Published: February 2003

This paper investigates the mechanisms through which organizations develop dynamic capabilities, defined as routinized activities directed to the development and adaptation of operating routines. It addresses the role of (1) experience accumulation, (2) knowledge articulation, and (3) knowledge codification processes in the evolution of dynamic, as well as operational, routines. The argument is made that dynamic capabilities are shaped by the coevolution of these learning mechanisms. At any point in time, firms adopt a mix of learning behaviors constituted by a semiautomatic accumulation of experience and by deliberate investments in knowledge articulation and codification activities. The relative effectiveness of these capability-building mechanisms is analyzed here as contingent upon selected features of the task to be learned, such as its frequency, homogeneity, and degree of causal ambiguity. Testable hypotheses about these effects are derived. Somewhat counterintuitive implications of the analysis include the relatively superior effectiveness of highly deliberate learning processes such as knowledge codification at lower levels of frequency and homogeneity of the organizational task, in contrast with common managerial practice.
Smectite-Type Clay Minerals as Nanomaterials
Authors: Schoonheydt Robert A.
Published: February 2003

Dilute aqueous smectite suspensions are well suited to convert into functional nanofilms. The functionalization is performed by ion exchange of amphiphilic molecules carrying the desired functionality. A functionalized clay mineral nanofilm is obtained by the organization of the molecules at the clay surface and by the organization of the elementary clay platelets in the film. Two techniques are presented: self-assembling and Langmuir-Blodgett (LB). Self-assembling is a very simple experiment, but the organizational order of the clay mineral particles is low. Nevertheless, films with nonlinear optical properties which are able to generate frequency-doubled light have been produced. The drawback of disorder of the clay platelets in the film can be largely overcome with the LB technique. Well organized films are obtained. In the presence of amphiphilic ruthenium(II)-bipyridine complexes, nonlinear optical properties are measured. In the presence of two dyes, oxacarbocyanine and rhodamine B, simultaneously adsorbed, efficient energy transfer between the donor (oxacarbocyanine) and the acceptor (rhodamine B) is measured. Fundamental research into the organization of molecules at clay mineral platelets is necessary to optimize the materials for specific applications.
Benzene Vapor Sorption by Organobentonites From Ambient Air
Authors: Zhu Lizhong , Su Yuhong
Published: February 2003

A number of organobentonites were synthesized by exchanging the metal ions in bentonite with the cationic surfactant, cetyltrimethylammonium bromide. Samples of natural bentonite and organobentonites were analyzed for their organic carbon contents, examined by X-ray diffraction (XRD) for interlayer spacings, and viewed using a scanning electron microscope (SEM) for surface morphology. The sorption isotherm of benzene vapor from ambient air (relative humidity (RH) = 45 ± 5%) on natural bentonite was nonlinear; however, the isotherms of benzene from ambient air onto organobentonites were virtually linear over a large range of relative vapor concentrations. The sorption capacities of air-dried organobentonites were far greater than that of the natural bentonite. For air-dried organobentonites, the sorption coefficients correlated positively with the sample organic carbon contents and negatively with the sample BET-N2 surface areas. The heats of benzene vapor sorption onto air-dried organobentonites were less exothermic than the heat of benzene-vapor condensation. These findings suggest that benzene vapor sorption by air-dried organobentonites occurs essentially by vapor partition into the sample organic-matter fractions. This offers a potential application of organobentonites for the removal of organic vapors from flue gases and for assessing the efficiency of vapor removal.
Genesis, Mineralogy and Geochemistry of Kaolin Deposits of the Jari River, Amapá State, Brazil
Authors: Montes Célia R. , Melfi Adolpho J. , Carvalho Adilson , Vieira-Coelho Antonio C. , Formoso Milton L. L.
Published: February 2003

Kaolin samples from the Jari deposit (Amazon region) were studied using various techniques to characterize its structural and crystallochemical aspects, and to establish its origin and evolution. A profile 60 m thick was selected in a kaolin mine (Morro do Felipe) located at the banks of the Jari river. Despite the great thickness of the deposit and the variety of kaolin types, the mineralogical composition is rather homogeneous and is mainly kaolinite associated with gibbsite and small amounts of quartz, anatase, goethite and hematite. The field observations and the morphological analysis indicate the existence of sedimentary features throughout the whole profile except for the upper aluminous clayey layer (Belterra Clay). This is evidence that the Rio Jari kaolin deposit originated from sedimentary material, the Alter do Chão Formation. The presence of alternating clay and sandy layers is explained by sedimentation processes with great depositional energy variation. Thus, the accumulation of thick clay layers was related to a low-energy phase, and during the high-energy phases, the deposition process led to the accumulation of sandy materials, constituted essentially of quartz and showing strong textural and structural variation. Later on, periods of hydromorphy were responsible for iron removal and consequently for the bleaching of the sedimentary formation. The crystallinity data show an increase of the structural disorder toward the surface associated with an increase in the amount of structural Fe in the kaolinite. The Rio Jari kaolin deposits should be considered as having originated from kaolinitic clay sediments of the Alter do Chão formation (protore) that was submitted to intensive lateritic weathering processes.
Kerolite in Carbonate-Rich Speleothems and Microbial Deposits From Basaltic Caves, Kauai, Hawaii
Authors: Léveillé Richard J. , Longstaffe Fred J. , Fyfe William S.
Published: February 2003

The occurrence of kerolite in association with various secondary Ca-Mg carbonate mineral deposits (speleothems) was identified in basaltic sea caves on the island of Kauai, Hawaii. Kerolite is the dominant clay mineral in the deposits. X-ray diffraction (XRD) peaks of the kerolite are characteristically broadened indicating its extremely poor crystallinity. Few changes were observed in the XRD patterns of this kerolite when it was subjected to various humidity, temperature and ethylene-glycol treatments. The crystals appear as flaky masses with irregular or jagged edges in scanning (SEM) and transmission electron microscopy (TEM). Electron probe and energy dispersive X-ray (EDX) microanalysis show that the clay material is dominated by Mg-Si-O, with minor amounts of Al and Ca in some samples. The chemical composition, thermal analysis and TEM observations suggest that smaller amounts of an amorphous serpentine-like phase are mixed with the kerolite. Kerolite is often the only mineral associated with poorly mineralized, actively-growing microbial mats in these caves and it is common in completely lithified microbial mats. The latter commonly have microstromatolitic structures with kerolite as a dominant phase. These features suggest that kerolite formation is at least in part a result of microbial activity. The abundant extracellular polymers of the mat-forming bacteria bind and concentrate ions (Mg2+, silica) from solution and serve as nucleation sites for kerolite precipitation. Conditions within the mats also probably lead to formation of Mg-Si-gels, amorphous Mg-silicate precursors and ultimately kerolite. Evaporation of the cave solutions may also contribute to kerolite formation.
Thickness Distribution of Illite Crystals in Shales. I: X-Ray Diffraction vs. High-Resolution Transmission Electron Microscopy Measurements
Authors: Dudek Teresa , Środoń Jan , Eberl Dennis D. , Elsass Françoise , Uhlik Peter
Published: February 2003

Two independent methods of crystal-size distribution analysis were compared: the Bertaut-Warren-Averbach XRD technique (MudMaster computer program) and high-resolution transmission electron microscopy (HRTEM). These techniques were used to measure thickness distributions of illite crystals (fundamental particles) from sets of illite-smectites from shales and bentonites that had expandabilities ranging from 86%S to 6%S. The illite-smectites were treated with a polymer (polyvinylopyrolidone, PVP) to separate them into fundamental particles for XRD and HRTEM investigations.

A systematic difference between XRD and HRTEM results was observed: XRD (area-weighted distributions) detected a larger fraction of thick (>4 nm) and a smaller fraction of thin crystals as compared to HRTEM (number-weighted distributions). As a result, XRD-determined distributions have larger mean thickness values and larger distribution parameters (α and β2). The measurements performed by the two techniques were verified by modeling XRD patterns of the PVP-illites, using the measured distributions as inputs. The modeling indicated that the XRD-determined distributions are very accurate. Selecting broader thickness distributions in MudMaster further improved the modeling results. The HRTEM measurements underestimate the proportion of coarse particles, in particular in shale samples, and this inaccuracy is attributed to the effect of using number-weighted (rather than area-weighted) distributions and to inaccurate counting statistics for thick crystals.