bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Curve Tracking Algorithm for Efficient Computation of Stability Boundaries of Cutting Processes
Authors: Henninger Christoph , Eberhard Peter
Published: August 2007

Dynamic stability of cutting processes such as milling and turning is mainly restricted by the phenomenon of the regenerative effect, causing self-excited vibration, which is well known as machine-tool chatter. With the semidiscretization method for periodic delay-differential equations, there exists an appropriate method for determining the stability boundary curve in the domain of technological parameters. The stability boundary is implicitly defined as a level set of a function on the parameter domain, which makes the evaluation computationally expensive when using complete enumeration. In order to reduce computational cost, we first investigate two types of curve tracking algorithms finding them not appropriate for computing stability charts as they may get stuck at cusp points or near-branch zones. We then present a new curve tracking method, which overcomes these difficulties and makes it possible to compute stability boundary curves very efficiently.
Dynamics of a Nonlinear Electromechanical Device With a Pendulum Arm
Authors: Mogo J. B. , Woafo P.
Published: August 2007

This paper considers the dynamics of an electromechanical device with a pendulum arm. Conditions under which the pendulum does not experience a complete rotation are obtained. Various types of nonlinear behaviors including chaos are observed.
Rounding Spatial G-Code Tool Paths Using Pythagorean Hodograph Curves
Authors: Šír Zbyněk , Wings Elmar , Jüttler Bert
Published: August 2007

We describe and analyze a new algorithm for rounding standard G-code tool paths. The joints of circular/linear elements are replaced by small segments of Pythagorean hodograph (PH) curves so that the final curve is globally C2 continuous. The PH segments are produced via a second order Hermite interpolation. We discuss some implementation details and investigate the error introduced by replacing a part of G-code by a PH curve segment. We also report results of tests within an industrial environment that demonstrate an increase in path velocity while decreasing peak acceleration.
Challenges and Choices in the Specification and Implementation of the STEP-NC AP-238 Standard
Authors: Hardwick Martin , Loffredo David
Published: August 2007

STEP-NC AP-238 is the result of a ten-year effort to replace the RS274D (ISO 6983) M and G code standard with a modern associative language that connects CAD design data to CAM process data. STEP-NC builds on previous work to develop a neutral data standard for CAD data and uses the modern geometric constructs of that standard to define device-independent tool paths, and CAM-independent volume removal features. This paper describes four key factors, or challenges, that had to be addressed to extend STEP-NC AP-238 functionality beyond that offered by other CNC standards. The four factors are difficulties inherent in all CAD/CAM integration projects and can be summarized as follows: the information complexity of geometry, the volume of attributes defined for manufacturing processes, the difficulties of integrating models that span CAD and CAM, and the requirement for easy implementation. We describe an advanced CNC application that uses these four factors and show how STEP-NC AP-238 enhances CNC machining and measurement.
Die-Casting Feature Recognition for Automated Parting Direction and Parting Line Determination
Authors: Madan J. , Rao P. V. M. , Kundra T. K.
Published: August 2007

Determining parting direction and parting line for die-cast parts is a nontrivial task that not only depends upon shape and topology of the part, but also on many process related factors. Normally, a die-casting expert decides parting direction and parting line, intuitively taking into account a large number of factors, and this process can be time consuming and cumbersome in many cases. This study addresses automated determination of parting direction and parting line for a die-cast part from part CAD model. The proposed methodology takes STEP file of the part as input for extracting die-casting features, which consists of protrusion or depression regions of the part. These features are classified into those with single, double, or multiple withdrawal directions. Geometric reasoning is used for feature recognition, which includes nested and interacting features. Global visibility instead of local visibility is used for planning withdrawal direction, which makes the decision arrived by present system closer to industrial practice. Parting line is determined based on selected candidate parting direction considering process constraints and priorities. The contribution of this paper is in terms of development of an automated parting direction and parting line determination system, which is more comprehensive and overcomes limitations of the previous work. Results of this system have been validated with those arrived at by experts from the die-casting industry.
Influence of Inoculum Size on the Selection of Resistant Mutants of
Escherichia coli
in Relation to Mutant Prevention Concentrations of Marbofloxacin
Authors: Ferran Aude , Dupouy Véronique , Toutain Pierre-Louis , Bousquet-Mélou Alain
Published: August 2007

We demonstrate using an in vitro pharmacodynamic model that the likelihood of selection of
Escherichia coli
mutants resistant to a fluoroquinolone was increased when the initial size of the bacterial population, exposed to fluoroquinolone concentrations within the mutant selection window, was increased.
In Vitro Antimycobacterial Spectrum of a Diarylquinoline ATP Synthase Inhibitor
Authors: Huitric Emma , Verhasselt Peter , Andries Koen , Hoffner Sven E.
Published: August 2007

The diarylquinoline R207910 is in clinical development for tuberculosis treatment. The MIC
50
for 41 drug-susceptible and 44 multidrug-resistant
Mycobacterium tuberculosis
clinical isolates was 0.032 μg/ml. Out of 20 additional mycobacterial species, three were found to be naturally resistant to R207910 and were shown to exhibit a polymorphism in their
atpE
genes.
The Macrolide Resistance Genes
erm
(B) and
mef
(E) Are Carried by Tn
2010
in Dual-Gene
Streptococcus pneumoniae
Isolates Belonging to Clonal Complex CC271
Authors: Del Grosso Maria , Northwood John G. E. , Farrell David J. , Pantosti Annalisa
Published: August 2007

The genetic elements carrying macrolide resistance genes in
Streptococcus pneumoniae
isolates belonging to CC271 were investigated. The international clone Taiwan
19F
-14 was found to carry Tn
2009
, a Tn
916
-like transposon containing
tet
(M) and
mef
(E). The dual
erm
(B)
mef
(E) isolates carried Tn
2010
, which is similar to Tn
2009
with the addition of a putative new transposon, the
erm
(B) genetic element.
TEM-158 (CMT-9), a New Member of the CMT-Type Extended-Spectrum β-Lactamases
Authors: Robin Frédéric , Delmas Julien , Brebion Amélie , Dubois Damien , Constantin Jean-Michel , Bonnet Richard
Published: August 2007

TEM-158 was found to include the substitutions previously observed for TEM-12 and TEM-35. This enzyme presented hydrolytic activity against ceftazidime and a high level of resistance against clavulanate, which can alter its detection. Its discovery highlights the need for accurate detection methods.
Molecular and Epidemiological Evidence for Spread of Multiresistant Methicillin-Susceptible
Staphylococcus aureus
Strains in Hospitals
Authors: Donnio Pierre-Yves , Février Frédéric , Bifani Pablo , Dehem Marie , Kervégant Christèle , Wilhelm Nathalie , Gautier-Lerestif Anne-Lise , Lafforgue Nathalie , Cormier Michel , Le Coustumier Alain
Published: August 2007

The excision of the staphylococcal chromosomal cassette
mec
(SCC
mec
) from methicillin-resistant
Staphylococcus aureus
(MRSA) strains results in methicillin-susceptible
S. aureus
(MSSA) strains. In order to determine the proportion and diversity of multidrug-resistant MSSA (MR-MSSA) strains derived from MRSA strains, 247
mecA
-negative isolates recovered in 60 French hospitals between 2002 and 2004 were characterized. The
spa
types of all strains were determined, and a subset of the strains (
n
= 30) was further genotyped by multilocus sequence typing. The IDI-MRSA assay was used to test the isolates for the presence of the SCC
mec
element, which was detected in 68% of all isolates analyzed. Molecular analysis of the samples suggested that 92% of the MR-MSSA isolates were derived from MRSA clones of diverse genetic backgrounds, of which the clone of sequence type 8 and SCC
mec
type IV
A
accounted for most of the samples. High variations in incidence data and differences in the molecular characteristics of the isolates from one hospital to another indicate that the emergence of MR-MSSA resulted from independent SCC
mec
excisions from epidemic MRSA isolates, as well as the diffusion of methicillin-susceptible strains after the loss of SCC
mec
. MR-MSSA could constitute a useful model for the study of the respective genetic and environmental factors involved in the dissemination of
S. aureus
in hospitals.
Mycobacterium tuberculosis-Induced Gamma Interferon Production by Natural Killer Cells Requires Cross Talk with Antigen-Presenting Cells Involving Toll-Like Receptors 2 and 4 and the Mannose Receptor in Tuberculous Pleurisy
Authors: Schierloh Pablo , Yokobori Noemí , Alemán Mercedes , Landoni Verónica , Geffner Laura , Musella Rosa M. , Castagnino Jorge , Baldini Matias , Abbate Eduardo , de la Barrera Silvia S. , Sasiain María C.
Published: August 2007

Tuberculous pleurisy allows the study of human cells at the site of activeMycobacterium tuberculosisinfection. In this study, we found that among pleural fluid (PF) lymphocytes, natural killer (NK) cells are a major source of early gamma interferon (IFN-γ) uponM. tuberculosisstimulation, leading us to investigate the mechanisms and molecules involved in this process. We show that the whole bacterium is the best inducer of IFN-γ, although a high-molecular-weight fraction of culture filtrate proteins fromM. tuberculosisH37Rv and the whole-cell lysate also induce its expression. The mannose receptor seems to mediate the inhibitory effect of mannosylated lipoarabinomannan, and Toll-like receptor 2 and 4 agonists activate NK cells but do not induce IFN-γ likeM. tuberculosisdoes. Antigen-presenting cells (APC) and NK cells bindM. tuberculosis, and although interleukin-12 is required, it is not sufficient to induce IFN-γ expression, indicating that NK cell-APC contact takes place. Indeed, major histocompatibility complex class I, adhesion, and costimulatory molecules as well as NK receptors regulate IFN-γ induction. The signaling pathway is partially inhibited by dexamethasone and sensitive to Ca2+flux and cyclosporine. Inhibition of p38 and extracellular-regulated kinase mitogen-activated protein kinase pathways reduces the number of IFN-γ+NK cells. Phosphorylated p38 (p-p38) is detected in ex vivo PF-NK cells, andM. tuberculosistriggers p-p38 in PF-NK cells at the same time that binding between NK andM. tuberculosisreaches its maximum value. Thus, interplay betweenM. tuberculosisand NK cells/APC triggering IFN-γ would be expected to play a beneficial role in tuberculous pleurisy by helping to maintain a type 1 profile.
Nucleotide-Binding Oligomerization Domain Protein 2-Deficient Mice Control Infection with
Mycobacterium tuberculosis
Authors: Gandotra Sheetal , Jang Sihyug , Murray Peter J. , Salgame Padmini , Ehrt Sabine
Published: August 2007

Nucleotide-binding oligomerization domain proteins (NODs) are modular cytoplasmic proteins implicated in the recognition of peptidoglycan-derived molecules. NOD2 has recently been shown to be important for host cell cytokine responses to
Mycobacterium tuberculosis
, to synergize with Toll-like receptor 2 (TLR2) in mediating these responses, and thus to serve as a nonredundant recognition receptor for
M. tuberculosis
. Here, we demonstrate that macrophages and dendritic cells from NOD2-deficient mice were impaired in the production of proinflammatory cytokines and nitric oxide following infection with live, virulent
M. tuberculosis
. Mycolylarabinogalactan peptidoglycan (PGN), the cell wall core of
M. tuberculosis
, stimulated macrophages to release tumor necrosis factor (TNF) and interleukin-12p40 in a partially NOD2-dependent manner, and
M. tuberculosis
PGN required NOD2 for the optimal induction of TNF. However, NOD2-deficient mice were no more susceptible to infection with virulent
M. tuberculosis
than wild-type mice: they controlled the replication of
M. tuberculosis
in lung, spleen, and liver as well as wild-type mice, and both genotypes displayed similar lung pathologies. In addition, mice doubly deficient for NOD2 and TLR2 were similarly able to control an
M. tuberculosis
infection. Thus, NOD2 appears to participate in the recognition of
M. tuberculosis
by antigen-presenting cells in vitro yet is dispensable for the control of the pathogen during in vivo infection.
Role of CD14 in Responses to Clinical Isolates ofEscherichia coli: Effects of K1 Capsule Expression
Authors: Metkar Shalaka , Awasthi Shanjana , Denamur Erick , Kim Kwang Sik , Gangloff Sophie C. , Teichberg Saul , Haziot Alain , Silver Jack , Goyert Sanna M.
Published: August 2007

Severe bacterial infections leading to sepsis or septic shock can be induced by bacteria that utilize different factors to drive pathogenicity and/or virulence, leading to disease in the host. One major factor expressed by all clinical isolates of gram-negative bacteria is lipopolysaccharide (LPS); a second factor expressed by someEscherichia colistrains is a K1 polysaccharide capsule. To determine the role of the CD14 LPS receptor in the pathogenic effects of naturally occurringE. coli, the responses of CD14−/−and CD14+/+mice to three different isolates ofE. coliobtained from sepsis patients were compared; two isolates express both smooth LPS and the K1 antigen, while the third isolate expresses only LPS and is negative for K1. An additional K1-positive isolate obtained from a newborn with meningitis and a K1-negative isogenic mutant of this strain were also used for these studies. CD14−/−mice were resistant to the lethal effects of the K1-negative isolates. This resistance was accompanied by significantly lower levels of systemic tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) in these mice than in CD14+/+mice, enhanced clearance of the bacteria, and significantly fewer additional gross symptoms. In contrast, CD14−/−mice were as sensitive as CD14+/+mice to the lethal effects of the K1-positive isolates, even though they had significantly lower levels of TNF-α and IL-6 than CD14+/+mice. These studies show that different bacterial isolates can use distinctly different mechanisms to cause disease and suggest that new, nonantibiotic therapeutics need to be directed against multiple targets.
Bacillus anthracis
Exosporium Protein BclA Affects Spore Germination, Interaction with Extracellular Matrix Proteins, and Hydrophobicity
Authors: Brahmbhatt Trupti N. , Janes Brian K. , Stibitz E. Scott , Darnell Stephen C. , Sanz Patrick , Rasmussen Susan B. , O'Brien Alison D.
Published: August 2007

Bacillus collagen-like protein of anthracis (BclA) is the immunodominant glycoprotein on the exosporium of
Bacillus anthracis
spores. Here, we sought to assess the impact of BclA on spore germination in vitro and in vivo, surface charge, and interaction with host matrix proteins. For that purpose, we constructed a markerless
bclA
null mutant in
B. anthracis
Sterne strain 34F2. The growth and sporulation rates of the Δ
bclA
and parent strains were nearly indistinguishable, but germination of mutant spores occurred more rapidly than that of wild-type spores in vitro and was more complete by 60 min. Additionally, the mean time to death of A/J mice inoculated subcutaneously or intranasally with mutant spores was lower than that for the wild-type spores even though the 50% lethal doses of the two strains were similar. We speculated that these in vitro and in vivo differences between mutant and wild-type spores might reflect the ease of access of germinants to their receptors in the absence of BclA. We also compared the hydrophobic and adhesive properties of Δ
bclA
and wild-type spores. The Δ
bclA
spores were markedly less water repellent than wild-type spores, and, probably as a consequence, the extracellular matrix proteins laminin and fibronectin bound significantly better to mutant than to wild-type spores. These studies suggest that BclA acts as a shield to not only reduce the ease with which spores germinate but also change the surface properties of the spore, which, in turn, may impede the interaction of the spore with host matrix substances.
The Surface Protein Srr-1 of
Streptococcus agalactiae
Binds Human Keratin 4 and Promotes Adherence to Epithelial HEp-2 Cells
Authors: Samen Ulrike , Eikmanns Bernhard J. , Reinscheid Dieter J. , Borges Frédéric
Published: August 2007

Streptococcus agalactiae
is frequently the cause of bacterial sepsis and meningitis in neonates. In addition, it is a commensal bacterium that colonizes the mammalian gastrointestinal tract. During its commensal and pathogenic lifestyles,
S. agalactiae
colonizes and invades a number of host compartments, thereby interacting with different host proteins. In the present study, the serine-rich repeat protein Srr-1 from
S. agalactiae
was functionally investigated. Immunofluorescence microscopy showed that Srr-1 was localized on the surface of streptococcal cells. The Srr-1 protein was shown to interact with a 62-kDa protein in human saliva, which was identified by matrix-assisted laser desorption ionization-time-of-flight analysis as human keratin 4 (K4). Immunoblot and enzyme-linked immunosorbent assay experiments allowed us to narrow down the K4 binding domain in Srr-1 to a region of 157 amino acids (aa). Furthermore, the Srr-1 binding domain of K4 was identified in the C-terminal 255 aa of human K4. Deletion of the
srr-1
gene in the genome of
S. agalactiae
revealed that this gene plays a role in bacterial binding to human K4 and that it is involved in adherence to epithelial HEp-2 cells. Binding to immobilized K4 and adherence to HEp-2 cells were restored by introducing the
srr-1
gene on a shuttle plasmid into the
srr-1
mutant. Furthermore, incubation of HEp-2 cells with the K4 binding domain of Srr-1 blocked
S. agalactiae
adherence to epithelial cells in a dose-dependent fashion. This is the first report describing the interaction of a bacterial protein with human K4.
Quantitation of endorhizal fungi in High Arctic tundra ecosystems through space and time: the value of herbarium archives
Authors: Ormsby Alana , Hodson Emily , Li Yang , Basinger James , Kaminskyj Susan
Published: August 2007

Mycorrhizal fungi are widespread in temperate and tropical regions, but generally are thought to be relatively depauperate at high latitudes. The potential impact of global warming on the polar ecosystems has renewed interest in research into tundra soil microbiota. Although logistical impediments limit field access, herbarium accessions are a potential resource for surveying mycorrhizal distribution. We present: (i) a method for examining fungi in roots of herbarium specimens that provides morphological preservation comparable to formalin fixation; and (ii) a multiple quantitation method to assess diverse morphotypes. Arbuscular mycorrhizae, fine endophytes, and septate endophytes were widespread in Asteraceae roots from Axel Heiberg and Ellesmere islands, Arctic Canada, during 2004. Roots from the same species collected from this region since 1982, stored in our herbarium, consistently contained abundant endorhizal fungi. Although 2004 was one of the coolest growing seasons in the survey, mycorrhizal abundance was highest in that year. Endorhizal fungi are likely to be important for plant survival and soil-forming processes in High Arctic tundra environments, and may be sensitive to climate variation.
Genetic structure of rheophytic and nonrheophytic populations of Farfugium japonicum on Yaeyama Islands, Japan
Authors: Nomura Naofumi , Setoguchi Hiroaki , Yasuda Keiko , Takaso Tokushiro
Published: August 2007

Farfugium japonicum (L.f.) Kitam., a facultative rheophyte occupying both dryland and riparian habitats within the species range, exhibits various shapes of leaves ranging from stenophyllous to round. The present study assesses variability in leaf morphology (five leaf characters) and genetics (305 AFLP markers) for populations from dryland and riparian habitats on Yaeyama Islands, Japan. Results from the two datasets produced somewhat different patterns indicating that selection for habitat type is effective on leaf shape attributes, while lack of differentiation was observed for neutral markers caused by extensive gene flow. Leaf-shape attributes were clustered into three groups: shade (round), sun (round), and narrow (stenophyllous) leaves. Narrow leaves were only found in riparian populations, indicating that flood intensity acts as a selective agent for this attribute. Although high within-population variation was demonstrated by AMOVA, the populations were distinct enough to be classified in separate groups irrespective of habitat type. However, Nei’s genetic diversity index (H) was low; suggesting lack of barriers to gene flow among individuals and selection for narrow leaves may act on the survivorship of young seedling.
Sea-level forcing of carbon isotope excursions in epeiric seas: implications for chemostratigraphy
Authors: Fanton K C , Holmden C
Published: August 2007

Five new δ13C excursions are reported from the Upper Ordovician Galena Group of Iowa. The δ13Ccarb and δ13Corg trends are compared to sea-level trends based on conventional sedimentological and novel chemostratigraphic (εNd) methods. It is found that rising δ13C values occur during rising sea level, peak-magnitude δ13C values are coincident with inferred peak flooding, and declining δ13C values occur with declining sea levels. The relationship to sea level is explained by a simple model of episodic flooding of the Galena platform by cool, oxygen-depleted, nutrient-rich, bottom waters originating from the Sebree Trough, which was itself connected to the nearby Iapetus Ocean. Flooding of the inner Galena shelf during sea-level transgressions caused local changes in the carbon isotope balance of inner shelf waters due to (1) locally increased primary productivity and organic carbon burial, (2) locally increased exchange of 13C-enriched dissolved inorganic carbon (DIC) with surrounding epeiric sea water masses and the surface ocean, and (3) locally decreased 12C-weathering fluxes from the Transcontinental Arch. A sea-level driver of local C-cycle perturbations complicates the use of carbon isotopes as a chemostratigraphic tool because local and eustatic controls on sea level may combine to create different secular records of relative sea-level change in stratigraphically equivalent deposits of epeiric seas.
Fluid chemistry and evolution of hydrothermal fluids in an Archaean transcrustal fault zone network: the case of the Cadillac Tectonic Zone, Abitibi greenstone belt, Canada
Authors: Neumayr P , Hagemann S G , Banks D A , Yardley B WD , Couture J -F , Landis G P , Rye R
Published: August 2007

Detailed fluid geochemistry studies on hydrothermal quartz veins from the Rouyn-Noranda and Val-d'Or areas along the transcrustal Cadillac Tectonic Zone (CTZ) indicate that unmineralized (with respect to gold) sections of the CTZ contained a distinct CO2-dominated, H2S-poor hydrothermal fluid. In contrast, both gold mineralized sections of the CTZ (e.g., at Orenada #2) and associated higher order shear zones have a H2O–CO2 ± CH4–NaCl hydrothermal fluid. Their CO2/H2S ratios indicate H2S-rich compositions. The Br/Cl compositions in fluid inclusions trapped in these veins indicate that hydrothermal fluids have been equilibrated with the crust. Oxygen isotope ratios from hydrothermal quartz veins in the CTZ are consistently 2 more enriched than those of associated higher order shear zones, which are interpreted to be a function of greater fluid/rock ratios in the CTZ and lower fluid/rock ratios, and more efficient equilibration of the hydrothermal fluid with the wall rock, in higher order shear zones. An implication from this study is that the lower metal endowment of the transcrustal CTZ, when compared with the higher metal endowment in higher order shear zones (ratio of about 1 : 1000), may be the result of the lack of significant amounts of H2O–H2S rich fluids in most of the CTZ. In contrast, gold mineralization in the higher order shear zones appear to be controlled by the high H2S activity of the aqueous fluids, because gold was likely transported in a bisulfide complex and was deposited during sulfidation reactions in the wall rock and phase separation in the quartz veins.
Luminescence dating of mid- to Late Wisconsinan aeolian sand as a constraint on the last advance of the Laurentide Ice Sheet across the Tuktoyaktuk Coastlands, western Arctic Canada
Authors: Murton Julian B , Frechen Manfred , Maddy Darrel
Published: August 2007

Luminescence dating of pre-glacial sand in the Tuktoyaktuk Coastlands, Northwest Territories, discounts an Early Wisconsinan age for the last Laurentide glaciation to cross the Arctic Coastal Plain and supports a Late Wisconsinan age. Aeolian dune sand from the Kittigazuit Formation near Cliff Point, on the southern shore of Liverpool Bay, predates till deposited during the Toker Point Stade. Potassium-rich feldspar from three stratigraphic sections ~35 km up-ice from the Toker Point glacial limit provides thermoluminescence age estimates that range from 18.7 ± 2.0 to 9.1 ± 1.0 ka and infrared stimulated luminescence age estimates of 23.8 ± 5.1 to 11.0 ± 2.1 ka. Quartz from four of the same samples provides optically stimulated luminescence age estimates of 16.5 ± 1.0 to 13.7 ± 0.9 ka. Collectively, these estimates reject the Early Wisconsinan age for the Toker Point Stade glaciation inferred hitherto from radiocarbon dating. A review of pre-glacial and post-glacial age estimates from the region indicates that during the Toker Point Stade ice advanced across the Tuktoyaktuk Coastlands no earlier than ~30 ka, and probably not before ~22 ka. Deglaciation had certainly commenced by 14.3 ka, and probably by ~16 ka. The Toker Point glaciation, therefore, dates approximately to the last glacial maximum, reinforcing the interpretation of the late rebuild up of the Laurentide Ice Sheet that characterized many parts of its margin.
Study of hadrons emission in 4.5A GeV/c32Sinteractions with emulsion
Authors: Abdelsalam A , Badawy B M , EL-Falaky E
Published: August 2007

An experimental study of the forward and backward emission of relativistic and fast hadrons in the interactions of 4.5 A,GeV/c 32S with emulsion was carried out. The study supports the conclusion that a collective mechanism is responsible for the production of particles in the backward hemisphere (which is restricted beyond the kinematics limit). The backward emission of both shower and grey particles can be described by an exponential decay law independent of the projectile size. The experimental results suggest that the backward particles result from the decay of the system in a latter stage of the interaction. While the average multiplicities of the shower particles emitted in the forward hemisphere are strongly dependent on the projectile size and incident momentum, the average values of those emitted into the backward hemisphere are found to be only a function of the target size (i.e., impact parameter). Thus, the backward particle production can be considered as a yield of a highly excited target system, in its rest frame.PACS Nos.: 25.75.–q, 25.75.Dw, 25.75.Gz, 25.75.Ld, 25.70.Mn, 25.70.Pq,41.75.Ak, 41.75.Cn, 29.40.Rg, 07.68.+m
From Schwarzschild to Kerr under de Sitter background due to blackhole tunnelling
Authors: Xiao K , Liu W
Published: August 2007

When a particle with angular momentum tunnels across the event horizon of Schwarzschild–de Sitter black hole, the black hole will change into a Kerr–de Sitter one. Considering Hawking radiation as a process of quantum tunnelling near a black-hole horizon, the emission rate of the particles with angular momentum is calculated under energy and angular momentum conservation, and the result is consistent with an underlying unitary theory.PACS Nos.: 97.60.Lf, 04.70.Dy, 03.65.Pm
Evidence of rigid triaxiality in some xenon nuclei
Authors: Singh M , Bihari C , Singh Y , Gupta D , Varshney A K , Gupta K K , Gupta D K
Published: August 2007

The present study deals with a topic of current interest, getting clear evidence for triaxiality in the 120–130 Xe nuclei near A = 130. The odd–even staggering in a so-called gamma-vibrational band may be treated using the asymmetric rotor model (ARM) on employing the Lipas parameter. The Hilbert space is too limited to describe the full variation of the moment of inertia and, therefore, the Lipas Ansatz ismade to correct the ARM energies, which conserve the good result for B(E2) values.PACS Nos.: 21.10.Re, 21.60.Ev, 27.60.+j
Higher derivative fermionic field equation in the first-orderformalism
Authors: Kruglov S I
Published: August 2007

The generalized Dirac equation of the third order, describing particles with spin 1/2 and three mass states, is analyzed. We obtain the first-order generalized Dirac equation in the 24-dimensional matrix form. The mass and spin projection operators are found that extract solutions of the wave equation corresponding to pure spin states of particles. The density of the electromagnetic current is obtained, and minimal and nonminimal(anomalous) electromagnetic interactions of fermions are considered by introducing three phenomenological parameters. The Hamiltonian form of the first-order equation is obtained.PACS Nos.: 03.65.Pm, 11.10.Ef; 12.10.Kt
Time-domain reflectometry measurements and soil-water characteristic curves of coarse granular materials used in road pavements
Authors: Ekblad Jonas , Isacsson Ulf
Published: August 2007

Coarse granular materials are used extensively in road construction. Bearing capacity can be affected by the water content in the layers of these materials. The ability to estimate water content and to infer water movements is therefore important. The purpose of the work described herein was to determine soil-water characteristic curves and the relationship between relative apparent permittivity and volumetric water content for coarse (maximum particle size 90 mm) granular materials having various gradations. The relative apparent permittivity was measured with the aid of time-domain reflectometry (TDR), and the concurrent matric suction was measured with a tensiometer. Samples were prepared in a steel box and were heavily compacted, and TDR probes and a tensiometer cup were buried within the matrix. The variation in volumetric water content with apparent relative permittivity was found to deviate from the Topp et al. relationship. Soil-water characteristic curves were described using the Brooks–Corey and van Genuchten models. A pronounced hysteresis between wetting and drying paths was observed. For the low water retention coarse materials, measurements of water content might, in general, require correction because of the nonlinear distribution of water in the sample.Key words: pavement, time-domain reflectometry, soil-water characteristic curve, granular material.
FieldP–ycurves in weathered rock
Authors: Cho Kook Hwan , Gabr Mohammed A , Clark Shane , Borden Roy H
Published: August 2007

In weathered and decomposed rock profiles, the lack of an acceptable analysis procedure for estimating lateral load–displacement response of drilled shafts is compounded by the unavailability of weathered material properties, including the material's lateral subgrade reaction modulus. Such deficiency often leads to the overdesign of the drilled shaft foundation. Six field tests were conducted on drilled shafts to investigate the shape and magnitude of P–y curves in weathered rock material at three locations in North Carolina. The tested shafts were instrumented using dial gages, strain gages, and continuous vertical inclinometers. The measured load versus deflection data are used to study the stiffness response of weathered rock. Measured lateral responses are compared with the results estimated based on a "weak rock" model and a stiff clay model. The comparison shows that Reese's weak rock model overestimated the resistances of the tested shafts while the stiff clay model consistently underestimated the measured shaft resistances. The measured and computed results are analyzed and discussed.Key words: drilled shaft, weathered rock P–y curve, subgrade modulus, ultimate resistances in weathered rock, verification tests.
Seismic liquefaction, lateral spreading, and flow slides: a numerical investigation into void redistribution
Authors: Seid-Karbasi Mahmood , Byrne Peter M
Published: August 2007

Experience from past earthquakes indicates that seismically induced large lateral spreads and flow slides in alluvial sand deposits have taken place in coastal and river areas in many parts of the world. The ground slope in these slides was often not very steep, gentler than a few percent. Recent research indicates that the presence of low-permeability silt or clay sublayers within the sand deposits is responsible for this behaviour. Such layers form a barrier to upward flow of water associated with earthquake-generated pore pressures. This causes an accumulation of pore water at the base of the layers, resulting in greatly reduced strength and possible slope instability. This paper uses an effective stress coupled stress-flow dynamic analyses procedure to demonstrate the effects of a low-permeability barrier layer on ground deformations from an earthquake event. The analyses show that an expansion zone develops at the base of barrier layers in stratified soil deposits under seismic loading which can greatly reduce shear strength and result in large deformations and flow failure. Without such a layer or layers, the slope may undergo significant displacements, but not a flow slide. Slopes with a barrier layer can be stabilized by drains.Key words: liquefaction, lateral spreads, stratification, flow failure, dynamic analysis, UBCSAND model, drain.
Behaviour of geocell-reinforced sand beds under strip loading
Authors: Dash Sujit Kumar , Rajagopal K , Krishnaswamy N R
Published: August 2007

A series of laboratory model tests have been performed to study the behaviour of geocell-reinforced sand beds under strip loading. The strain in geocell walls, pressure transmitted to the subgrade soil, and deformations in the subgrade were measured during the tests to develop an understanding of the mechanism of geocell reinforcement. The pattern of strain variation in the geocell walls indicates that the geocell mattress behaves as a composite beam supported by the subgrade soil. The load dispersion in the geocell mattress is found to be governed by factors such as geometry of the geocell layer and its placement position under the footing.Key words: soil reinforcement, geocell, sand, behaviour, strip loading.
MAINTAINING VISIBILITY INFORMATION OF PLANAR POINT SETS WITH A MOVING VIEWPOINT
Authors: DEVILLERS OLIVIER , DUJMOVIĆ VIDA , EVERETT HAZEL , HORNUS SAMUEL , WHITESIDES SUE , WISMATH STEVE
Published: August 2007

Given a set of n points in the plane, we consider the problem of computing the circular ordering of the points about a viewpoint q and efficiently maintaining this ordering information as q moves. In linear space, and after O(n log n) preprocessing time, our solution maintains the view at a cost of O( log n) amortized time (resp.O( log 2 n) worst case time) for each change. Our algorithm can also be used to maintain the set of points sorted according to their distance to q .
COMPUTATIONAL GEOMETRY COLUMN 48
Authors: O'ROURKE JOSEPH
Published: August 2007

A new class of art gallery -like problems inspired by wireless localization is discussed.
ON A MICROSCOPIC MODEL OF VISCOUS FRICTION
Authors: CAPRINO SILVIA , CAVALLARO GUIDO , MARCHIORO CARLO
Published: August 2007

We consider a body moving along the x-axis under the action of an external force E and immersed in an infinitely extended perfect gas. We assume the gas to be described by the mean-field approximation and interacting elastically with the body. In this setup, we discuss the following statement: "Let V0 be the initial velocity of the body and V∞ its asymptotic velocity, then for |V0 - V∞| small enough it results |V(t) - V∞| ≈ C t-d-2 for t large, where V(t) is the velocity of the body at time t, d the dimension of the space and C is a positive constant depending on the medium and on the shape of the body". The reason for the power law approach to the stationary state instead of the exponential one (usually assumed in viscous friction problems), is due to the long memory of the dynamical system.

In a recent paper by Caprino, Marchioro and Pulvirenti,3 the case of E constant and positive, with 0 < V0 < V∞, for a disk orthogonal to the x-axis has been discussed. Here we complete the analysis in the cases E > 0 with V0 > V∞ and E = 0. We also approach the problem of an x-dependent external force, by choosing E of harmonic type. In this case we obtain the power-like asymptotic time behavior for the body position X(t). The investigation is done in detail for a disk orthogonal to the x-axis and then, by a sketched proof, extended to a body with a general convex shape.
HOMOGENIZATION OF A SINGLE PHASE FLOW THROUGH A POROUS MEDIUM IN A THIN LAYER
Authors: AMAZIANE B. , PANKRATOV L. , PIATNITSKI A.
Published: August 2007

The paper deals with homogenization of stationary and non-stationary high contrast periodic double porosity type problem stated in a porous medium containing a 2D or 3D thin layer. We consider two different types of high contrast medium. The medium of the first type is characterized by the asymptotically vanishing volume fraction of fractures (highly permeable part). The medium of the second type has uniformly positive volume fraction of fracture part. In both cases we construct the homogenized models and prove the convergence results. The techniques used in this work are based on a special version of the two-scale convergence method adapted to thin structures. The resulting homogenized problems are dual-porosity type models that contain terms representing memory effects.
MALLIAVIN CALCULUS FOR THE ESTIMATION OF TIME-VARYING REGRESSION MODELS USED IN FINANCIAL APPLICATIONS
Authors: ABUTALEB AHMED , PAPAIOANNOU MICHAEL G.
Published: August 2007

The paper introduces a new method for the estimation of time-varying regression coefficients employed in financial modeling. We use Malliavin calculus (stochastic calculus of variations) to estimate the time-varying regression coefficients that appear in linear regression models, and the generalized Clark–Ocone formula to derive a closed-form solution for the estimates of the time-varying coefficients. While this approach can be applied to any signal model, we present its application to signals modeled as a Brownian motion and an Ornstein–Uhlenbeck process. Simulation results prove the superiority of the proposed method, as compared to conventional methods.
QUADRATIC HEDGING FOR THE BATES MODEL
Authors: HUBALEK FRIEDRICH , SGARRA CARLO
Published: August 2007

In the present paper we give some preliminary results for option pricing and hedging in the framework of the Bates model based on quadratic risk minimization. We provide an explicit expression of the mean-variance hedging strategy in the martingale case and study the Minimal Martingale measure in the general case.
ON THE ASYMPTOTICS OF FAST MEAN-REVERSION STOCHASTIC VOLATILITY MODELS
Authors: SOUZA MAX O. , ZUBELLI JORGE P.
Published: August 2007

We consider the asymptotic behavior of options under stochastic volatility models for which the volatility process fluctuates on a much faster time scale than that defined by the riskless interest rate. We identify the distinguished asymptotic limits and, in contrast with previous studies, we deal with small volatility-variance (vol-vol) regimes. We derive the corresponding asymptotic formulae for option prices, and find that the first order correction displays a dependence on the hidden state and a non-diffusive terminal layer. Furthermore, this correction cannot be obtained as the small variance limit of the previous calculations. Our analysis also includes the behavior of the asymptotic expansion, when the hidden state is far from the mean. In this case, under suitable hypothesis, we show that the solution behaves as a constant volatility Black–Scholes model to all orders. In addition, we derive an asymptotic expansion for the implied volatility that is uniform in time. It turns out that the fast scale plays an important role in such uniformity. The theory thus obtained yields a more complete picture of the different asymptotics involved under stochastic volatility. It also clarifies the remarkable independence on the state of the volatility in the correction term obtained by previous authors.
A BIPARAMETRIC FAMILY OF CARDINALITY-BASED FUZZY SIMILARITY MEASURES
Authors: BOSTEELS KLAAS , KERRE ETIENNE E.
Published: August 2007

We present a systematic way of constructing and analyzing fuzzy similarity measures based on cardinality. This is achieved by introducing a general form for such measures, that depends on two parameters. We demonstrate that this general form includes several existing families of fuzzy similarity measures. Moreover, we show that certain properties can be ensured by imposing simple constraints on the parameters. In particular, we present constraints that ensure several forms of restrictability, which allow to reduce the calculation time in practical implementations. To conclude, we illustrate the presented technique by using it to analyze some well-known fuzzy similarity measures.
ON PASSIVITY ANALYSIS OF STOCHASTIC DELAYED NEURAL NETWORKS WITH RANDOM ABRUPT CHANGES
Authors: LOU XU-YANG , CUI BAO-TONG
Published: August 2007

The passivity conditions for stochastic neural networks with time-varying delays and random abrupt changes are considered in this paper. Sufficient conditions on passivity of stochastic neural networks with time-varying delays and random abrupt changes are developed in the linear matrix inequality (LMI) setting. The results obtained in this paper improve and extend some of the previous results.
A FUZZY ALGORITHM FOR SCHEDULING SOFT PERIODIC TASKS IN PREEMPTIVE REAL-TIME SYSTEMS
Authors: SABEGHI MOJTABA , NAGHIBZADEH MAHMOUD , RAZAVIZADEH TOKTAM TAGHVI
Published: August 2007

Most researches concerning real-time system scheduling assume scheduling constraint to be precise. However, in the real world, scheduling is a decision making process which involves vague constraints and uncertain data. Fuzzy constraints are particularly well suited for dealing with imprecise data. This paper proposes a fuzzy scheduling approach to real-time system scheduling in which the scheduling parameters are treated as fuzzy variables. A simulation is also performed and the results are compared with both EDF and LLF scheduling algorithms. The latter two algorithms are the most commonly used algorithms for scheduling real-time processes. It is concluded that the proposed fuzzy approach is very promising and it has the potential to be considered for future research.
COMPOSITION LINEAR CONTROL IN STIRRED TANK CHEMICAL REACTORS
Authors: MÉNDEZ A. REGALADO , ÁLVAREZ-RAMÍREZ J.
Published: August 2007

This work studies loop control composition in continuous chemical reactors with simple structures, due to its large acceptance in chemical industry. A linear cascade composition control (master/slave) is proposed, designed with basic control structures based on Laplace tools. Two configurations are designed, which were evaluated in a dynamic model of continuous stirred tank. From a stability analysis it is noted that, for such configurations, system assent time is 7 to 8 times reduced if compared to the assent time without loop control. Besides, the system shows a good performance when coming to the asked reference. Implementation of such control configurations can solve the problem of loop control composition.
Evolutionary Endocrinology: The Developing Synthesis between Endocrinology and Evolutionary Genetics
Authors: Zera Anthony J. , Harshman Lawrence G. , Williams Tony D.
Published: August 2007

A productive synthesis of endocrinology and evolutionary genetics has occurred during the past two decades, resulting in the first direct documentation of genetic variation and correlation for endocrine regulators in nondomesticated animals. In a number of insect genetic polymorphisms (dispersal polymorphism in crickets, butterfly wing-pattern polymorphism), blood levels of ecdysteroids and juvenile hormone covary with morphology, development, and life history. Genetic variation in insulin signaling may underlie life history trade-offs in Drosophila. Vertebrate studies identified variation in brain neurohormones, bone-regulating hormones, and hormone receptor gene sequences that underlie ecologically important genetic polymorphisms. Most work to date has focused on genetically variable titers (concentrations) of circulating hormones and the activities of titer regulators. Continued progress will require greater integration among (a) traditional comparative endocrine approaches (e.g., titer measures); (b) molecular studies of hormone receptors and intracellular signaling pathways; and (c) fitness studies of genetically variable endocrine traits in ecologically appropriate conditions.
Understanding the Effects of Marine Biodiversity on Communities and Ecosystems
Authors: Stachowicz John J. , Bruno John F. , Duffy J. Emmett
Published: August 2007

There is growing interest in the effects of changing marine biodiversity on a variety of community properties and ecosystem processes such as nutrient use and cycling, productivity, stability, and trophic transfer. We review published marine experiments that manipulated the number of species, genotypes, or functional groups. This research reveals several emerging generalities. In studies of primary producers and sessile animals, diversity often has a weak effect on production or biomass, especially relative to the strong effect exerted by individual species. However, sessile taxon richness did consistently decrease variability in community properties, and increased resistance to, or recovery from disturbance or invasion. Multitrophic-level studies indicate that, relative to depauperate assemblages of prey species, diverse ones (a) are more resistant to top-down control, (b) use their own resources more completely, and (c) increase consumer fitness. In contrast, predator diversity can either increase or decrease the strength of top-down control because of omnivory and because interactions among predators can have positive and negative effects on herbivores. Recognizing that marine and terrestrial approaches to understanding diversity-function relationships are converging, we close with suggestions for future research that apply across habitats.