bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase change memory cell with an upper amorphous nitride silicon germanium heating layer
Authors: Rao Feng , Song Zhitang , Wu Liangcai , Zhong Min , Feng Songlin , Chen Bomy
Published: August 2007

The advanced phase change memory (PCM) cell with an amorphous nitride silicon germanium (SiGexNy) upper heating layer was fabricated. Applying a proper height of reset voltage pulse to the cell, the amorphous SiGexNy heating layer was crystallized along with the melt of the Ge1Sb2Te4 layer. Then the SiGexNy heating layer preserved its crystalline state during the successive programming cycles. With this crystalline SiGexNy heating layer, the set and reset threshold voltage values were reduced, which enhanced the heat efficiency and decreased the power consumption of the PCM cell. Meanwhile, the PCM cell showed good endurance characteristics.
Short-term changes in soil properties under tillage systems and their effect on sweet potato (Ipomea batatas L.) growth and yield in an Ultisol in south-eastern Nigeria
Authors: Anikwe M. A. N. , Ubochi J. N.
Published: August 2007

Tillage influences soil quality via its effects on soil physical, chemical, and biological properties, which in turn affect crop productivity. This study evaluates the effects of conventional (CT) and no-till (NT) systems on (1) soil temperature, bulk density, soil gravimetric water content (GWC), saturated hydraulic conductivity (Ksat), soil organic carbon content (SOC), and total nitrogen (N), and (2) growth and yield of 3 sweet potato (Ipomoea batatas) (L) Lam varieties (87/00/87, ex-Igbariam, and 8164). A field experiment was conducted in 2005 and 2006 on a Typic paleudult in south-eastern Nigeria. The experimental plots comprised 6 treatments (CT 87/00/87 variety, CT ex-Igbariam, CT 8164, NT 87/00/87 variety, NT ex-Igbariam, NT 8164 variety) laid out in the field using randomised complete block design replicated 3 times. Soil temperature was 1–2°C higher in CT plots during early stages of crop development. CT plots had significantly lower soil dry bulk density (1.30–1.35 Mg/m3) than NT plots. Soil GWC was higher, whereas Ksat was lower, in NT plots than CT plots at 35 and 65 days after planting (DAP) for both planting seasons. NT plots had a 0.22–0.26-fold increase in SOC and 16–27% higher N content compared with CT plots at 35 and 65 DAP. The 3 varieties of sweet potato used did not significantly influence soil properties at the different times after planting. Sweet potato yield obtained in CT 87/00/87 variety (21.7–24.9 Mg/ha) for both seasons was higher (P < 0.05) than sweet potato tuber yield obtained from NT ex-Igbariam plots (which had the lowest yield) by about 88%. For each variety, CT plots has significantly higher yield than NT plots. This study showed that although NT practices conserved soil moisture, decreased soil temperature, reduced water infiltration, and increased SOC and soil total N content when compared to CT plots, the reduction in soil compaction at the early stages of crop development (0–65 DAP) in CT plots had a more positive impact on tuber yield and masked the positive effect of other soil productivity parameters for this crop.
Nucleosome hopping and sliding kinetics determined from dynamics of single chromatin fibers in
Xenopus
egg extracts
Authors: Ranjith Padinhateeri , Yan Jie , Marko John F.
Published: August 2007

Chromatin function
in vivo
is intimately connected with changes in its structure: a prime example is occlusion or exposure of regulatory sequences via repositioning of nucleosomes. Cell extracts used in concert with single-DNA micromanipulation can control and monitor these dynamics under
in vivo
-like conditions. We analyze a theory of the assembly–disassembly dynamics of chromatin fiber in such experiments, including effects of lateral nucleosome diffusion (“sliding”) and sequence positioning. Experimental data determine the force-dependent on- and off-rates as well as the nucleosome sliding diffusion rate. The resulting theory simply explains the very different nucleosome displacement kinetics observed in constant-force and constant-pulling velocity experiments. We also show that few-piconewton tensions comparable to those generated by polymerases and helicases drastically affect nucleosome positions in a sequence-dependent manner and that there is a long-lived structural “memory” of force-driven nucleosome rearrangement events.
The interaction of DiaA and DnaA regulates the replication cycle in E. coli by directly promoting ATP–DnaA-specific initiation complexes
Authors: Keyamura Kenji , Fujikawa Norie , Ishida Takuma , Ozaki Shogo , Su’etsugu Masayuki , Fujimitsu Kazuyuki , Kagawa Wataru , Yokoyama Shigeyuki , Kurumizaka Hitoshi , Katayama Tsutomu
Published: August 2007

Escherichia coli DiaA is a DnaA-binding protein that is required for the timely initiation of chromosomal replication during the cell cycle. In this study, we determined the crystal structure of DiaA at 1.8 Å resolution. DiaA forms a homotetramer consisting of a symmetrical pair of homodimers. Mutational analysis revealed that the DnaA-binding activity and formation of homotetramers are required for the stimulation of initiation by DiaA. DiaA tetramers can bind multiple DnaA molecules simultaneously. DiaA stimulated the assembly of multiple DnaA molecules on oriC, conformational changes in ATP–DnaA-specific initiation complexes, and unwinding of oriC duplex DNA. The mutant DiaA proteins are defective in these stimulations. DiaA associated also with ADP–DnaA, and stimulated the assembly of inactive ADP–DnaA–oriC complexes. Specific residues in the putative phosphosugar-binding motif of DiaA were required for the stimulation of initiation and formation of ATP–DnaA-specific–oriC complexes. Our data indicate that DiaA regulates initiation by a novel mechanism, in which DiaA tetramers most likely bind to multiple DnaA molecules and stimulate the assembly of specific ATP–DnaA–oriC complexes. These results suggest an essential role for DiaA in the promotion of replication initiation in a cell cycle coordinated manner.
Collective Marketing Arrangements for Geographically Differentiated Agricultural Products: Welfare Impacts and Policy Implications
Authors: Lence Sergio H. , Marette Stéphan , Hayes Dermot J. , Foster William
Published: August 2007

We examine the incentives of atomistic producers to differentiate and collectively market products. We analyze market and welfare effects of alternative producer organizations, discuss circumstances under which they will evolve, and describe implications for the ongoing debate between the EU and the United States. As fixed costs of development and marketing increase and the anticipated market size falls, it becomes essential to increase the producer organization's ability to control supply to cover the fixed costs associated with the introduction of differentiated products. Counterintuitively, stronger property right protection for producer organizations may enhance welfare even after a differentiated product has been developed.
Welfare Impacts of Cross‐Country Spillovers in Agricultural Research
Authors: Lence Sergio H. , Hayes Dermot J.
Published: August 2007

The welfare implications of intellectual property protection (IPP) for private sector agricultural research are analyzed, focusing on the realistic cases where countries provide different IPP levels, technology spills over across countries, and the public sector is involved in research. A model is developed to determine who benefits from, and who should pay for, the associated research. The article contains some interesting results on the implications of a harmonization of IPP policies through multilateral agreements or via technology that allows research firms to prevent the copying of plants and animals that express traits that have emerged from their research.
Quantification of biofilm in microtiter plates: overview of testing conditions and practical recommendations for assessment of biofilm production by staphylococci
Authors: STEPANOVIĆ SRDJAN , VUKOVIĆ DRAGANA , HOLA VERONIKA , BONAVENTURA GIOVANNI DI , DJUKIĆ SLOBODANKA , ĆIRKOVIĆ IVANA , RUZICKA FILIP
Published: August 2007

The details of all steps involved in the quantification of biofilm formation in microtiter plates are described. The presented protocol incorporates information on assessment of biofilm production by staphylococci, gained both by direct experience as well as by analysis of methods for assaying biofilm production. The obtained results should simplify quantification of biofilm formation in microtiter plates, and make it more reliable and comparable among different laboratories.
Immunohistochemical and mutational analysis of FLASH in gastric carcinomas
Authors: JEONG EUN GOO , LEE SUNG HAK , LEE HAE WOO , SOUNG YOUNG HWA , YOO NAM JIN , LEE SUG HYUNG
Published: August 2007

FLASH was initially identified as a pro‐apoptotic protein that transmits an apoptosis signal during death receptor‐induced apoptosis. Additionally, diverse biologic roles of FLASH, including TNF‐induced NF‐κB activation, cell‐cycle progression and cell division, have been identified. Although such functions are important in cancer pathogenesis, little is known about the alterations of FLASH gene and FLASH protein expression in human cancers. In this study, we analyzed the expression of FLASH protein in 60 gastric adenocarcinomas by immunohistochemistry. We furthermore analyzed mutation of FLASH in exon 8, where two polyadenine tracts ((A)8 and (A)9) are present, by single‐strand conformation polymorphism (SSCP) assay in 184 gastric adenocarcinomas. By immunohistochemistry, FLASH protein expression in cancer cells was detected positively in 42 gastric carcinoma tissues (70%), whereas its expression in epithelial cells of normal gastric mucosa was shown as no or very weak intensity. Mutational analysis detected one FLASH mutation in the gastric carcinomas (0.5%). The increased expression of FLASH in the malignant gastric epithelial cells compared to the normal mucosal epithelial cells suggests that FLASH expression may play a role in gastric tumorigenesis. Also, the data suggest that somatic mutation of FLASH is a rare event in gastric carcinomas.
Enzyme‐linked immunosorbent assay using multimers of the 16th non‐collagenous domain of the BP180 antigen for sensitive and specific detection of pemphigoid autoantibodies
Authors: Sitaru Cassian , Dähnrich Cornelia , Probst Christian , Komorowski Lars , Blöcker Inga , Schmidt Enno , Schlumberger Wolfgang , Rose Christian , Stöcker Winfried , Zillikens Detlef
Published: August 2007

Abstract:  Bullous pemphigoid (BP) and pemphigoid gestationis (PG) are acquired autoimmune subepidermal blistering diseases characterized by autoantibodies against the hemidesmosomal proteins BP180/type XVII collagen and BP230. In the vast majority of BP and PG patients, these autoantibodies bind to epitopes clustered within the 16th non‐collagenous domain of BP180. An ELISA system for the detection of these autoantibodies was developed and evaluated using 16th non‐collagenous domain (NC16A) tetramers instead of monomers. In contrast to antigens fused to large proteins used in the past for the detection of autoantibodies against type XVII collagen, tetrameric antigen fragments bearing a small hexahistidine tag allow for high expression levels without the need to cleave off the fusion partner. Using tetrameric BP180 NC16A, positive reactions were found in 106 (89.8%) of 118 randomly selected BP sera and in all of 20 (100%) randomly selected PG sera, whereas only 2.2% of a large cohort of control subjects were positive in this assay, including patients with rheumatoid arthritis (two of 107), progressive systemic sclerosis (two of 50), systemic lupus erythematosus (one of 72), and healthy blood donors (10 of 494). Thus, the sensitivity and specificity of the new anti‐tetrameric NC16A ELISA were 89.9% and 97.8% respectively. Levels of circulating autoantibodies against BP180 paralleled disease activity in the pemphigoid patients. In conclusion, the use of tetrameric NC16A in ELISA results in a sensitive and specific tool for diagnosis and monitoring of BP and PG.
A transient unresponsive state of self‐scratching behaviour is induced in mice by skin‐scratching stimulation
Authors: Yamaoka Junichi , Kawana Seiji
Published: August 2007

Abstract: When mice were scratched with brushes on their dorsal skins, they began to scratch themselves with their hind paws. Thus, self‐scratching behaviour was induced in mice in response to skin‐scratching stimulation. If the second skin‐scratching stimulation was given within a few days, the induction of the second self‐scratching behaviour was significantly suppressed compared with the first one. Thereafter, mice gradually recovered from this unresponsive state within a week. Thus, a transient unresponsive state of self‐scratching behaviour is induced by skin‐scratching stimulation. Pretreatment with a tachykinin receptor NK‐1R antagonist L‐703606 or capsaicin significantly suppressed self‐scratching behaviour, while pretreatment with a neutral endopeptidase inhibitor phosphoramidon significantly enhanced it. Pretreatment with a calcitonin gene‐related peptide (CGRP) receptor antagonist CGRP8–37did not affect the following self‐scratching behaviour. From these results, it is suggested that substance P (SP) signalling through its receptor NK‐1R at least in part mediates the induction of self‐scratching behaviour. After skin‐scratching stimulation, immunoreactivity of SP both in the peripheral nerve fibres and in the dorsal root ganglion (DRG) neurons was significantly decreased and was well‐correlated with suppression of self‐scratching behaviour. From these findings, it is suggested that the induction of unresponsive states of self‐scratching behaviour may be at least in part caused by the depleted states of SP in peripheral nerve fibres and/or in DRG neurons. The induction of a transient unresponsive state after skin‐scratching may possibly happen also in patients with pruritus. Thus, further studies to elucidate the precise mechanisms are required.
Probiotics: contributions to oral health
Authors: Meurman JH , Stamatova I
Published: August 2007

Probiotics have been extensively studied for their health‐promoting effects. The main field of research has been in the gastrointestinal tract. However, in the past few years probiotics have also been investigated in the oral health perspective, which is the topic of the present review. We discuss the mechanisms of bacterial adhesion, potential of probiotics in oral cavity colonization, interspecies interactions, and possible effects on immunomodulation, and means of probiotic administration. We suggest that probiotic treatment of diseases other than dental caries and periodontal disease should also be systematically investigated. In general, hardly any randomized controlled trials have been conducted in this area and the studies on probiotics vs oral health are still in their cradle. Hence, much more investigations are called for before any evidence‐based conclusions can be drawn: if or not probiotic therapy can be recommended for oral health purposes.
Price Dynamics in U.S. Grain and Freight Markets
Authors: Yu Tun‐Hsiang (Edward) , Bessler David A. , Fuller Stephen W.
Published: August 2007

This paper studies the spatial price linkages in U.S. grain and transportation markets using cointegration analysis and algorithms of inductive causation on directed acyclic graphs. Transport costs and prices from alternative transportation modes are considered to provide a relatively comprehensive view of the interaction between grain and freight markets over time. Dynamic relationship among corn prices in selected U.S. markets and freight rates, extending from January 1990 to December 2002, are explored. Results suggest the Mississippi Gulf (lower Mississippi River port area) is the most dominant corn market among evaluated export and domestic markets. Also, grain barge rates on the upper Mississippi/Illinois Rivers influence domestic corn markets in contemporaneous time. In the longer‐run, significant dynamic relationships among prices in domestic and export corn markets and freight rates are observed; perturbations in transportation rates affect the variation in corn prices considerably.

Le présent article examine les relations d'arbitrage spatial entre les prix pour les marchés des céréales et du transport aux États‐Unis à l'aide d'une analyse de cointégration et d'algorithmes utilisant la notion de causalité inductive sur des graphiques acycliques orientés. Les coûts et les prix de divers modes de transport sont examinés afin de fournir un tableau assez complet de l'interaction entre le marché des céréales et le marché du fret au fil du temps. Nous avons exploré la relation dynamique entre les prix du maïs sur des marchés états‐uniens sélectionnés et les taux de fret, entre janvier 1990 et décembre 2002. Les résultats indiquent que le golfe du Mississippi (zone portuaire du Mississippi inférieur) est le marché de maïs le plus important parmi les marchés intérieurs et extérieurs évalués. Les frais de transport des céréales par barge sur le cours supérieur du Mississippi et la rivière Illinois influencent les marchés intérieurs du maïs à l'heure actuelle. À long terme, des liens dynamiques importants entre les prix sur les marchés du maïs intérieur et extérieurs et les frais de transport sont observés. Des changements de frais de transport affectent considérablement la variation des prix du maïs.
Potential for Sample Bias Due to NAPL Partitioning
Authors: Soutter Douglas , McBean Edward
Published: August 2007

Tetrachloroethene, trichloroethene, dichloroethenes, and vinyl chloride are collectively known as chlorinated ethenes. Chlorinated ethenes are some of the most prevalent organic ground water contaminants in North America and may develop large ground water plumes. If areas of free‐phase petroleum are present within the boundaries of a chlorinated ethene plume, consideration must be given to the interpretation of ground water samples due to interactions between chlorinated ethenes and the petroleum. Chlorinated ethene concentrations in ground water samples may be significantly greater than concentrations immediately upgradient of the free‐phase petroleum zone if any of the free‐phase petroleum is entrained in the sample due to turbidity or a sheen/layer of product. This occurs because a significant mass of chlorinated ethenes can partition into the petroleum. The bias due to the entrainment of petroleum in a ground water sample becomes significant if a visible thickness of petroleum or oily sediment occurs in the sample.
Ten Years of Pesticide Monitoring in Norwegian Ground Water
Authors: Haarstad K. , Ludvigsen G. H.
Published: August 2007

Pesticides in Norwegian ground water have been monitored since 1995. Here, we report data including 2004. The monitoring has focused on shallow ground water near agricultural fields (4 locations), on farm wells (22 locations), and on public waterworks (38 locations) 450 samples were analyzed for a total of 62 pesticide compounds and metabolites, and the result was 514 detections of single compounds. Altogether 27 pesticides and metabolites were detected: 2 insecticides, 9 fungicides, and 16 herbicides. Herbicides were most frequently detected (in 79% of the samples), followed by fungicides (20%) and insecticides (1%). Pesticide concentration was generally low, although high concentrations also occurred, for example, 33 μg/L of metribuzine in shallow ground water near agricultural fields and 20 μg/L of bentazon in a farm well. Some water soluble pesticides occurred both frequently and with relatively high concentrations in shallow ground water near agricultural fields. The results show that local ground water near farms is vulnerable for contamination of pesticides and needs further monitoring. Efforts should be made to minimize contamination of wells in farming areas through education on pesticide use, monitoring, and well positioning. Few pesticides were detected in ground water from waterworks and the concentrations were low. Monitoring of waterworks ended in 2002. The data show that there is a continuous need to monitor pesticides as well as selected metabolites in shallow ground water and wells near agricultural fields in Norway.
REDUCING THE RISK OF FISHERY RESOURCE DISASTERS: A BIOECONOMIC APPROACH TO SUSTAINABLE RESOURCE MANAGEMENT1
Authors: Levy Jason K. , Kilgour D. Marc , Hipel Keith W;
Published: August 2007

Abstract: Recognition is growing that fisheries must be both ecologically and commercially sustainable. The bioeconomic models proposed herein constitute an analytic framework capable of integrating the ethics and Societal values associated with fisheries preservation. Specifically, we focus on the normalized optimal (equilibrium) fish population, z*, a dimensionless variable representing biomass as a proportion of environmental capacity. We model z* as a function of (a) the dimensionless “bionomic growth ratio”, γ, which is the ratio of the discount rate to the intrinsic population growth rate, and (b) the preservation coefficient, Ω, which is the ratio of the preservation value (a measure of Society's value for the stock) to price, assuming that the population growth rate and intrinsic growth rate are fixed. It is shown that increasing Ω significantly impacts z*, particularly for moderate values of γ (2 γ 4). Finally, stochastic population models are used to analyze the risk of a fish stock collapse due to harvesting pressures. The bioeconomic models and simulations herein described improve the accuracy and reliability of maximum sustainable yield management.
The effect of quadriceps muscle fatigue on position matching at the knee
Authors: Givoni Nathan J. , Pham Tuan , Allen Trevor J. , Proske Uwe
Published: August 2007

This is a report of the effects of exercise on position matching at the knee. Young adult subjects were required to step down a set of stairs (792 steps), representing eccentric‐biased exercise of the quadriceps muscle, or step up them, concentric‐biased exercise. Immediately after eccentric exercise subjects showed a mean force drop of 28% (± 6%, s.e.m.) of the control value in their exercised quadriceps muscle, which was accompanied by 4.8 deg (± 0.8 deg) of error between reference and matching legs in a position matching task at the knee. Similarly concentric exercise was followed by a force drop of 15% (± 3%) and matching errors of 3.7 deg (± 0.4 deg). These effects were significant. The direction of the errors suggested that subjects perceived their exercised muscles to be longer that they actually were. This finding was not consistent with the hypothesis that the increase in effort required to support the leg after fatigue from exercise was responsible for the errors. It is hypothesized that position sense in an unsupported leg arises, in part, from operation of an internal forward model. When the motor command is increased to compensate for the effects of fatigue, the comparison between predicted and actual feedback from quadriceps leads to the impression that the muscle is longer than it actually is. The exercise effects on proprioception may have implications for sports injuries and for evaluation of the factors leading to falls in the elderly.
Defective interaction between dual oscillators for respiratory rhythm generation in Na+,K+‐ATPase α2 subunit‐deficient mice
Authors: Onimaru Hiroshi , Ikeda Keiko , Kawakami Kiyoshi
Published: August 2007

The current concept regarding the respiratory centre in mammals is that it is composed of two distinct rhythm‐generating neuronal networks in the ventrolateral medulla. These two rhythm generators can be active independently but are normally coupled in newborn and juvenile rats. Detailed characteristics of each generator and the neuronal mechanisms of coupling during development remain to be elucidated. Here, we report a knockout mouse (Na+,K+‐ATPase α2 subunit gene (Atp1a2) knockout) that may be defective in functional coupling between the two respiration‐related rhythm generators. We investigated respiration‐related neuron activity in an en bloc brainstem–spinal cord preparation isolated from embryonic day 18.5 Atp1a2−/− mouse fetuses. In the presence of adrenaline, two different types of rhythm generators were identified. One produced inspiratory burst activity that correlated with C4 inspiratory activity and was thought to be the inspiratory rhythm generator on the basis of its location and sensitivity to a μ‐opiate receptor agonist, [d‐Ala2, N‐Me‐Phe4, Gly5‐ol]‐enkephalin (DAMGO). The other was presumed to be the preinspiratory rhythm generator because it was insensitive to DAMGO and correlated with facial nerve activity. Coupling between these rhythm generators did not function in the normal manner in Atp1a2−/− mice, as shown by disruption of the linkage between the preinspiratory burst and the inspiratory burst. Coupling was partially restored by repeated activation of the neurons within the networks, suggesting the involvement of an activity‐dependent process in the prenatal development of this coupling.
Measurement of Solid Oxide Fuel Cell System Flow Rate by Tracer Gas Method
Authors: Amano Masatsugu , Kato Tohru , Negishi Akira , Kato Ken , Nozaki Ken , Momma Akihiko , Honda Takeo , Takano Kiyonami , Kashihara Toshinori , Kobayasi Miwako , Iimura Yoko , Yoshiharai Miki
Published: August 2007

A high-precision method to measure efficiency of fuel cells with a 0.1% margin of error is proposed. This method is principally divided into two procedures: determining the composition of fuel gas to be fed into a fuel cell system and measuring the flow rate of the fuel gas. The composition of the fuel gas is determined by an FTIR (Fourier transform infrared spectrometer) and/or a QMS (quadrapole mass spectrometer) with a built-in sonic nozzle sampling system. The flow rate was measured by the tracer gas method; that is, a given amount of tracer gas, such as one of the noble gases, was introduced into the line of the fuel gas, then, the mixed gas was sampled at the point where the tracer gas had been well mixed, and the concentration of the tracer gas was determined by the QMS. In this paper, a gravimetric calibration method using a highly sensitive balance is also proposed for flow control of the tracer gas. Also proposed are calibration of the FTIR and the QMS to establish the required low uncertainty or high accuracy of the measurement of the efficiency.
Study of an Electrochemical Alcohol Concentration Sensor: Optimization of the Anode Structure
Authors: Sgroi Mauro , Bollito Gianluca , Innocenti Gianfranco , Saracco Guido , Specchia Stefania , Icardi Ugo Andrea
Published: August 2007

Micro power sources have a wide potential market for consumer electronics and portable applications, such as weather stations, medical devices, signal units, APU (auxiliary power units), gas sensors, and security cameras. A micro power source could be the direct methanol fuel cell system (DMFC). An important aspect of this system is the precise control of the concentration of the alcohol-water solution fed to the anode. Different detection principles were taken into consideration: electrochemical, infrared spectroscopy, gas chromatography, refractometry, density measurements, ultraviolet absorption. The present work is devoted to the study of an electrochemical amperometric sensor. The device is based on the electro-oxidation of methanol to carbon dioxide on platinum catalyst into a polymeric-membrane fuel cell operated as a galvanic cell. The alcohol-water solution under examination is fed to the anode (positive side) of a polymeric membrane fuel cell, where it reacts with water to produce carbon dioxide, protons, and electrons. Protons diffuse through the electrolyte material and recombine with electrons on the cathode catalyst (negative side). At high potentials (>0.7V) mass transfer of methanol to the electrode solution interface controls the observed current. Therefore, it is possible to correlate the solution concentration to the observed limiting current. This method was successfully applied to relatively diluted solutions (concentration <1M). The application of this principle to more concentrate solutions (up to 2M) requires an optimization of the anode structure to enhance the influence of mass transport limitation. Moreover, during continuous operation of the sensor, a decay of the signal was observed: the absence of a steady-state current value hinders the application of the sensor. An explanation of this phenomenon and a possible solution strategy are proposed.
Squiggle Ball Capture: A Simple, Visual Kinetic Theory Experiment
Authors: Gfroerer Tim , Rathbun Ken
Published: August 2007

When particles move about randomly in the presence of traps, how long does it take for them to be captured? Well, it depends on the average speed of the particles and the dimensions and distribution of the traps. For example, when neutrons are generated in nuclear fission reactions, they must be captured by other fissionable nuclei in order to sustain a chain reaction. But we learn in introductory physics that these energetic neutrons are traveling at enormous speeds and must be slowed to increase the time that they spend in the vicinity of the nuclei. While the capture of “thermal” particles into lower energy states is an important physical process, it is difficult to simulate macroscopically. For example, where do you get a collection of macroscopic objects that have the means to sustain random motion? Enter Squiggle Balls™—inexpensive spherical cat toys that use a battery-powered motor and asymmetric rotor to roll and tumble happily about.1 Put a few on a bounded, elevated platform with several circular holes, and you have an ideal macroscopic system for exploring the world of capture.
Where Is the Center of Mass of Florida?
Authors: Greenslade Thomas B.
Published: August 2007

An attention-grabbing center-of-mass demonstration uses the map of a state mounted on a sheet of heavy cardboard and cut out along the boundaries.1 The two-dimensional object is hung from a hole punched into a city near the edge, and a string with a pendulum bob attached to it passes through the center of mass. The process is repeated with a different city, and the center of mass is determined uniquely. I did this regularly with a map of the state of Ohio, and the geographic center of the state reliably came out to be the nearby village of Centerburg.
PSEUDO-COMPLEX FIELD THEORY
Authors: HESS PETER O. , GREINER WALTER
Published: August 2007

A new formulation of field theory is presented, based on a pseudo-complex description. An extended group structure is introduced, implying a minimal scalar length, rendering the theory regularized a la Pauli–Villars. Cross sections are calculated for the scattering of an electron at an external Coulomb field and the Compton scattering. Deviations due to a smallest scalar length are determined. The theory also permits a modification of the minimal coupling scheme, resulting in a generalized dispersion relation. A shift of the Greisen–Zatsepin–Kuzmin (GZK) limit of the cosmic ray spectrum is the consequence.
THE ESCAPE WIDTHS AND STRENGTH OF ISOSCALAR GIANT DIPOLE RESONANCE IN 208Pb
Authors: LEITE T. N. , TERUYA N. , DIAS H.
Published: August 2007

The structure of the isoscalar giant dipole resonance (ISDGR) in 208Pb has been investigated by using the continuum Randon Phase Aproximation (RPA). The main properties (strength function and escape widths) of the ISDGR are calculated and compared with recent available experimental data.
EDITORIAL
Authors: KROC JIŘÍ
Published: August 2007

This special journal issue of Advances in Complex Systems presents a collection of papers describing current research delivered by recognized researchers actively working in various corners of the field of modeling of complex systems by cellular automata and related methods. All included papers are self-contained and present the latest developments in the areas where the authors work. Hence, all papers can be read independently, but it is strongly recommended to study the issue as a whole to get a general overview of the various methods and techniques from the field. The main aim of this special issue is to provide researchers from neighboring fields with sufficient information and vital examples of how to design models in complex systems. The whole issue is organized in such a way that common features occurring repeatedly in most models of complex systems are highlighted.
SWARM INTELLIGENCE SYSTEMS USING GUIDED SELF-ORGANIZATION FOR COLLECTIVE PROBLEM SOLVING
Authors: RODRÍGUEZ ALEJANDRO , GRUSHIN ALEXANDER , REGGIA JAMES A.
Published: August 2007

Drawing inspiration from social interactions in nature, the field of swarm intelligence has presented a promising approach to the design of complex systems consisting of numerous, usually homogeneous, simple parts, to solve a wide variety of problems. Like cellular automata, swarm-intelligence systems involve highly parallel computations across space, based heavily on self-organization, the emergence of global behavior through local interactions of components, and the absence of centralized or global control. However, this has a disadvantage as the desired behavior of a system becomes hard to predict or design based on its local interaction rules. In our ongoing research, we propose to provide greater control over a system, and potentially more useful, goal-oriented behavior, by introducing layered, hierarchical controllers in the particles or components. The layered controllers allow each particle to extend their reactive behavior in a more goal-oriented style, while keeping the locality of the interactions and the general simplicity of the system. In this paper, we present three systems designed using this approach: a competitive foraging system, a system for the collective transport and distribution of goods, and a self-assembly system capable of creating complex structures in a 3D world. Our simulation results show that in all three cases it was possible to guide the self-organization process at different levels of the designated task, suggesting that the self-organizing behavior of swarm-intelligence systems may be extendable to support problem solving in various contexts, such as coordinated robotic teams.
PROPERTIES OF SELF-REPLICATING CELLULAR AUTOMATA SYSTEMS DISCOVERED USING GENETIC PROGRAMMING
Authors: PAN ZHIJIAN , REGGIA JAMES , GAO DONGHONG
Published: August 2007

We recently formulated an approach to representing structures in cellular automata (CA) spaces, and the rules that govern cell state changes, that is amenable to manipulation by genetic programming (GP). Using this approach, it is possible to efficiently generate self-replicating configurations for fairly arbitrary initial structures. Here, we investigate the properties of self-replicating systems produced using GP in this fashion as the initial configuration's size, shape, symmetry, allowable states, and other factors are systematically varied. We find that the number of GP generations, computation time, and number of resulting rules required by an arbitrary structure to self-replicate are positively and jointly correlated with the number of components, configuration shape, and allowable states in the initial configuration, but inversely correlated with the presence of repeated components, repeated sub-structures, and/or symmetric sub-structures. We conclude that GP can be used as a "replicator factory" to produce a wide range of self-replicating CA configurations, and that the properties of the resulting replicators can be predicted in part a priori. The rules controlling self-replication that are created by GP generally differ from those created manually in past CA studies.
PERFORMANCE AND ROBUSTNESS OF CELLULAR AUTOMATA COMPUTATION ON IRREGULAR NETWORKS
Authors: DARABOS CHRISTIAN , GIACOBINI MARIO , TOMASSINI MARCO
Published: August 2007

We investigate the performances of collective task-solving capabilities and the robustness of complex networks of automata using the density and synchronization problems as typical cases. We show by computer simulations that evolved Watts–Strogatz small-world networks have superior performance with respect to several kinds of scale-free graphs. In addition, we show that Watts–Strogatz networks are as robust in the face of random perturbations, both transient and permanent, as configuration scale-free networks, while being widely superior to Barabási–Albert networks. This result differs from information diffusion on scale-free networks, where random faults are highly tolerated by similar topologies.
The potentially latent dominance of groundwater in ground engineering
Authors: Rowe P.W.
Published: August 2007

Examples are given of unforeseen damage or difficulties arising during or after construction of buildings, wharves, foundations, tunnels, in-ground storage, pipe lines, and embankments. The underlying potentially latent mechanisms of groundwater are classified into four groups, namely water pressure changes, physical changes, erosion, and affects of earthworks, in order to assist early identification of some of the types of change in ground properties which may be induced by site operations and may lead to damage. It is concluded that otherwise unforeseen damage is more likely to be averted by a greater degree of investigation during construction into the consequences of the construction sequences, method and plant used.
Investigations into the role of groundwater in promoting floor heave in coal mine gateroads
Authors: Hart P.A.
Published: August 2007

The geological environment of two South Wales collieries at which site investigations were carried out is summarised. This is followed by a review of identified geological parameters and their effects on floor heave under the headings of discontinuities, mineralogy, and groundwater. Methods of underground site investigation, laboratory testing, and data treatment are summarised. The effect of an increase of groundwater content on mechanical parameter values was quantified for laboratory tested rock cores, and
in situ
interbedded strata sections. The extent to which groundwater affects floor heave was found to be controlled by the mineralogical and structural nature of the floor strata.
Site investigations techniques used to assess the likely hydrological impact of a proposed landfill site
Authors: Whittle J.H. , Swanson A.C.S.
Published: August 2007

The construction of a landfill site is proposed at Dalinlongart, near Dunoon, Argyllshire. The site forms an unspoilt and secluded area within the hills and glens of the Cowal Peninsula on the Clyde Estuary and lies to the north of the nearby Highland Boundary Fault.

A development of this type has to satisfy the rigid constraints on the emission of pollutants and in this respect it was necessary to assess the likely impact of such a development on the existing hydrological conditions.

To obtain information for the design and subsequent operation of the landfill site, a site investigation was carried out involving a variety of techniques, both within the site and its environs. The merits and limitations of the differing investigation methods are described and discussed with respect to providing the required hydrogeological data in the context of this site.

This paper illustrates the benefits of a desk study, in particular the aerial photograph interpretation, in assessing the hydrogeology of the site area and in the economic planning of the subsequent ground investigation. The advantages of mapping techniques and deep trial pits to expose the structure of soil and rock strata are outlined together with the requirement to carry out water quality analyses before, during and after the construction of the landfill site. Boreholes were required not only to confirm the ground conditions indicated by other works, but also to provide permeability data and install standpipes and piezometers for the continued monitoring of groundwater conditions.
Dynamic sampling of groundwater for dispersion and corrosion investigations
Authors: Watkins D.C.
Published: August 2007

Principles of sampling groundwater for the determination of its
in situ
inorganic and organic composition are described in the context of purpose and accuracy required. Two examples of techniques developed and used by Hydraulics Research are presented. Sampling of groundwater in a natural gradient regime containing artificial contamination by a tracer species is described. Special pneumatic piezometers were installed and employed to produce micro samples. Methods of installing, commissioning and monitoring these for extended periods are explained. Dynamic sampling of groundwater in a laminated glacial lake formation is also illustrated. Data were needed to define the corrosion and incrustation potential of the native groundwater on, for example, well screens. A method was devised which enabled a rapid assessment of relevant parameters using hand-portable equipment. Dynamic measurement of EC, pH, Eh and O
2
were accomplished. Samples were also taken for off-site chemical and bacterialogical analyses.
The measurement, interpretation and use of permeability values with specific reference to fissured aquifers
Authors: Walthall S. , Campbell J.E.
Published: August 2007

The measurement of permeability, or more correctly, hydraulic conductivity of an aquifer is of fundamental importance in the understanding of water movement within it and to the prediction of the behaviour of engineering works. A wide range of techniques is available to the hydrogeologist and engineering geologist, and includes: laboratory measurement, using both gas and water permeameters; pumping test, with and without observation boreholes; inflow and outflow packer tests; and numerical and analogue aquifer models. Each technique is described, and its practical problems and relative merits discussed. It is important to realise that some of the techniques measure the hydraulic properties of the borehole while others measure the properties of the surrounding aquifer. Care is needed to choose the appropriate methods for different problems. A brief case history is presented explaining the use of these techniques for the dewatering of a large civil engineering structure.
Analysis of an advanced dewatering scheme at an opencast coal site in Northumberland
Authors: Minett S.T. , Blythe D.A. , Hallam G.D. , Hughes D.B.
Published: August 2007

A triangular area of Coal Measures rocks bounded to the south by the major WSW-ENE trending Causey Park Dyke, to the north and west by the limit of outcrop and the east by the North Sea, has been extensively worked by opencast methods over the past twenty years. Due to the close concentration of opencast workings it has been feasible to maintain a regional dewatering scheme over a number of years from Hauxley Shaft. However, during prospecting operations for an opencast coal site it was found that substantial quantities of groundwater existed in old workings horizons, ponded against the Causey Park Dyke in a broad anticlinal structural trap.

It was decided by the Contractor that the area should be dewatered before excavations took place, to avoid the danger of flooding and water induced slope failures, and a submersible borehole pump was, thus, installed.

This provided an opportunity to undertake a pumping test in mining disturbed strata. Due to the high permeability of the old underground workings it was found that the data did not conform to any standard analysis methods. However, it was found that the system could be modelled by treating it as a lagoon of triangular wedge shape. A mass balance calculation was performed and it was predicted that it would take approximately 350 days to dewater the site. The field data conforms closely to the predicted drawdowns and it is concluded that this method may be applicable to many regions with a mining history.
Some aspects of groundwater control by the ground freezing and grouting methods
Authors: Harris J.S. , Pollard C.A.
Published: August 2007

Prior to the construction of a new mineshaft, hydrological and geophysical tests are performed on a shaft centreline borehole and the recovered core which permit water-bearing zones to be located, and potential shaft inflows to be estimated. An assessment of this information enables the most appropriate method of groundwater control to permit safe and controlled shaft sinking to be selected. The three methods discussed in this paper are grouting, freezing and pressure relief.

Grouting is the process of reducing the permeability of water-bearing strata by the injection of appropriate materials under pressure, thereby reducing the shaft inflow to an acceptable level.

The geometry of the injection hole pattern required to form a grout cover, and the selection and subsequent injection of a suitable grout are discussed. An in-shaft test, performed from the advancing shaft sump into the water bearing strata, is described. This test gives a final check on the local aquifer characteristics, and allows the grouting scheme to be modified as required. A similar test performed after grouting enables the efficacy of the treatment to be assessed.
Groundwater control in large scale slope excavations — five case histories from Hong Kong
Authors: McNicholl D.P. , Pump W.L. , Cho G.W.F.
Published: August 2007

Slopes in Hong Kong are usually long in relation to their height and, with large quantities of excavation, they commonly require periods of days or sometimes weeks to construct the slope from berm to berm. There is usually sufficient time to implement drainage remedial measures, such as counterfort drains, raking drains, caisson drains, etc. if stability is in doubt due to high groundwater levels or seepage flows. The paper describes five case histories of typical site formation and slope preventive works, which were constructed in different weathering grades and parent rocks. All the schemes entailed extensive excavation and slopeworks. Sketch details of the drainage measure are outlined together with their costs.
Modified activity-stress paradigm in an animal model of the female athlete triad
Authors: DiMarco Nancy M. , Dart Lyn , Sanborn Charlotte (Barney)
Published: August 2007

The exercising woman with nutritional deficits and related menstrual irregularities is at risk of compromising long-term bone health, i.e., the female athlete triad. There is no animal model of the female athlete triad. The purpose of this study was to examine long-term energy restriction in voluntary wheel-running female rats on estrous cycling, bone mineral content, and leptin levels. Twelve female Sprague-Dawley rats (age 34 days) were fed ad libitum and given access to running wheels during an initial 14-wk period, providing baseline and age-related data. Daily collection included dietary intake, body weight, estrous cycling, and voluntary running distance. At 4 mo, rats were randomized into two groups, six restrict-fed rats (70% of ad libitum intake) and six rats continuing as ad libitum-fed controls. Energy intake, energy expenditure, and energy availability (energy intake − energy expenditure) were calculated for each animal. Serum estradiol and leptin concentrations were measured by RIA. Femoral and tibial bone mineral density and bone mineral content (BMC) were determined by dual-energy X-ray absorptiometry. Restrict-fed rats exhibited a decrease in energy availability during Weight Loss and Anestrous phases ( P = 0.002). Compared with controls after 12 wk, restrict-fed rats showed reduced concentrations of serum estradiol ( P = 0.002) and leptin ( P = 0.002), lower ovarian weight ( P = 0.002), and decreased femoral ( P = 0.041) and tibial ( P = 0.05) BMC. Decreased energy availability resulted in anestrus and significant decreases in BMC, estrogen and leptin levels, and body weight. Finally, there is a critical level of energy availability to maintain estrous cycling.