bluuebunny/crossref_metadata_2025 huggingface dataset:
String interactions and discrete symmetries of the pp‐wave background
Authors: Chu C.‐S. , Petrini M. , Russo R. , Tanzini A.
Published: June 2003

Free string theory on the plane‐wave background displays a discrete Z2 symmetry exchanging the two transverse SO(4) groups. This symmetry should be respected also at the interacting level. We show that the zero mode structure proposed in hep‐th/0208148 can be completed to a full kinematical vertex, contrary to claims appeared in the previous literature. We also comment on the relation with recent works on the string‐bit formalism and on the comparison with the field theory side of the correspondence.
Extra dimensions and non‐linear equations
Authors: Fairlie D.B.
Published: June 2003

It is shown how integrable non‐linear equations of hydrodynamic type, which arise as continuations of Dirac‐Born‐Infeld equations to the case where the target space is of lower dimension than the base space, are associated with linear diffusion equations in a space of double the number of space co‐ordinates.
Intersecting branes, defect conformal theories and tensionless strings
Authors: Constable N. , Erdmenger J. , Guralnik Z. , Kirsch I.
Published: June 2003

The defect conformal field theory describing intersecting D3‐branes at a
\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$ \mathbb{C}^2 / \mathbb{Z}_k $\end{document} sorbifold is used to deconstruct the theory of intersecting M5‐branes, as well as M5‐branes wrapping the holomorphic curve xy = c. The possibility of a 't Hooft anomaly due to tensionless strings at the intersection is discussed.
Solving string field equations: new uses for old tools
Authors: Kling A. , Lechtenfeld O. , Popov A.D. , Uhlmann S.
Published: June 2003

It is argued that the (NS‐sector) superstring field equations are integrable, i.e. their solutions are obtainable from linear equations. We adapt the 25‐year‐old solution‐generating “dressing” method and reduce the construction of nonperturbative superstring configurations to a specific cohomology problem. The application to vacuum superstring field theory is outlined.
𝒩 = 1 SUSY inspired Whitham prepotentials and WDVV
Authors: Mironov A.
Published: June 2003

This brief review deals with prepotentials inspired by 𝒩 = 1 SUSY considerations due to Cachazo, Intrilligator, Vafa. These prepotentials associated with matrix models following Dijkgraaf and Vafa should be considered as given on an enlarged moduli space that includes Whitham times (couplings of the superpotential). This moduli space is nothing but the whole moduli space of (decorated) hyperelliptic curves. Corresponding prepotentials are logarithms of (quasiclassical) τ‐functions and satisfy the WDVV equations.
On permutation branes
Authors: Recknagel A.
Published: June 2003

We give a brief review of recent work on rational boundary states associated with gluing automorphisms from the permutation group. We sketch how the construction can be extended to Gepner models and show that there is a D0‐brane among the permutation branes on the quintic.
A recursive algorithm for fractional BPS multitrace fields of 𝒩 = 4 SYM4 from AdS/CFT
Authors: Leonhardt T. , Meziane A. , Rühl W.
Published: June 2003

We present a recursive construction of k‐trace operators from k chiral primaries in the twenty dimensional SO(6) irrep, which are quasiprimary and have protected conformal dimensions. Use is made of the known perturbatively calculated four‐point function of these chiral primaries.
Boundaries, defects and Frobenius algebras
Authors: Fuchs J. , Runkel I. , Schweigert C.
Published: June 2003

The interpretation of D‐branes in terms of open strings has lead to much interest in boundary conditions of two‐dimensional conformal field theories (CFTs). These studies have deepened our understanding of CFT and allowed us to develop new computational tools. The construction of CFT correlators based on combining tools from topological field theory and non‐commutative algebra in tensor categories, which we summarize in this contribution, allows e.g. to discuss, apart from boundary conditions, also defect lines and disorder fields.
ALTERNATIVES TO MUCUNA FOR SOIL FERTILITY MANAGEMENT IN SOUTHERN BÉNIN: FARMER PERCEPTION AND USE OF TRADITIONAL AND EXOTIC GRAIN LEGUMES
Authors: SCHULZ S. , HONLONKOU A. N. , CARSKY R. J. , MANYONG V. M. , OYEWOLE B. D.
Published: June 2003

In southern Bénin, the legume cover crop Mucuna pruriens var. utilis has been widely promoted for soil fertility improvement. Recent findings have shown, however, that the majority of farmers have not adopted it, and that alternative technologies are needed that are both attractive to farmers and beneficial in terms of soil fertility. A survey was carried out in southern Bénin to determine farmer perception and use of traditional grain legumes and to assess the adoption potential of new low-harvest-index grain legumes. Grain legumes were shown to be integral components of traditional cropping systems and constituted farmers' most important technology for soil fertility maintenance. More than 80% of respondents expressed interest in testing new, low-harvest-index varieties. Preferred grain characteristics and farmers' culinary preferences for grain legumes varied between locations and need to be taken into account if new germplasm is to be introduced. It is argued that farmers' interest and experience in legume cultivation provide an opportunity for the introduction of alternative legume-based technologies such as low-harvest-index grain legumes and techniques for the detoxification of mucuna seed. In addition, efforts should be made to increase the productivity of current legume production systems and to develop mucuna cultivars with reduced L-dopa content.
DEVELOPING IMPROVED DRYLAND CROPPING SYSTEMS FOR MAIZE IN SEMI-ARID TANZANIA. PART 1: EXPERIMENTAL EVIDENCE FOR THE BENEFITS OF RAINWATER HARVESTING
Authors: HATIBU N. , YOUNG M. D. B. , GOWING J. W. , MAHOO H. F. , MZIRAI O. B.
Published: June 2003

Farmers in the southern Kilimanjaro region of Tanzania have a strong preference for maize as their staple crop and have resisted attempts to introduce sorghum as an alternative in spite of the high drought risk associated with maize production. This paper presents the results of a seven-year period of field experiments to assess the benefits of a modified cropping system for maize, which aims to reduce drought risk through rainwater harvesting. In-situ, microcatchment and macrocatchment rainwater harvesting systems were tested against the local practice of flat cultivation as control. All were managed according to local extension recommendations, and the benefits were measured in terms of grain yield. In-situ rainwater harvesting provided no benefit. Microcatchment rainwater harvesting resulted in increased yield per unit area cultivated. On a total system area basis (i.e. including the uncropped catchment), however, production decreases were observed. A cost-benefit analysis, however, does show a benefit in the short rainy season. Macrocatchment rainwater harvesting provided increases in grain yield in both the short and the long rainy seasons.
DEVELOPING IMPROVED DRYLAND CROPPING SYSTEMS FOR MAIZE IN SEMI-ARID TANZANIA. PART II. USE OF A MODEL TO EXTRAPOLATE AND ADD VALUE TO EXPERIMENTAL RESULTS
Authors: GOWING J. W. , YOUNG M. D. B. , HATIBU N. , MAHOO H. F. , RWEHUMBIZA F. , MZIRAI O. B.
Published: June 2003

Dryland agriculture is critically important to food security and rural livelihoods in Tanzania, but crop production is seriously constrained throughout the semi-arid lowlands by the rainfall regime. A major challenge is to develop improved cropping systems to alleviate the moisture constraint. Experimental evidence indicates that adoption of rainwater harvesting systems can bring benefits, but the restricted spatial and temporal extent of the experimental work leads to difficulties in extrapolation. This paper shows how the PARCHED-THIRST model can add value to the experimental results and provide important insights into their transferability. The model is seen as an aid to researchers, planners and extensionists in interpreting experimental results and designing locally appropriate interventions. Simulation based on 30 years of daily meteorological data provides an opportunity for temporal extrapolation. The long-term simulation allows an objective assessment of the risks and benefits associated with alternative rainwater harvesting systems. Simulation for different soils and modified rainfall regimes permits objective analysis of spatial transferability of experimental results to any other site for which rainwater harvesting interventions might be considered. It is shown that macrocatchment rainwater harvesting reduces drought risk within the target area, but may bring a serious risk of erosion due to excessively high flow rates. The overall assessment of the twin-track approach (experimentation+simulation) is that rainwater harvesting has potential for increasing productivity and sustainability of maize cropping systems in semi-arid Tanzania provided that the innovations are properly matched to the site-specific environmental conditions.
SURVEY OF PHALARIS MINOR IN THE INDIAN RICE-WHEAT SYSTEM
Authors: FRANKE A. C. , McROBERTS N. , MARSHALL G. , MALIK R. K. , SINGH S. , NEHRA A. S.
Published: June 2003

A combination of agro-ecological and socioeconomic factors gave rise to the current weed epidemic of Phalaris minor, threatening the sustainability of wheat (Triticum aestivum) production and rural livelihoods across a large area of the Indo-Gangetic plains in northern India. This paper presents the results of a system audit describing the current status of the P. minor epidemic in Haryana State, India, in a broad agronomic and socioeconomic context. The audit showed that the P. minor epidemic is a major production constraint for many farmers, and seriously affects farm profitability. It suggests that the epidemic is closely entangled with geographic factors, as well as farm management systems and farmers' socioeconomic positions. Since the farmer community is not a homogeneous group with respect to P. minor management, nor in ability to change farm management practices, farmers are not equally receptive to technical innovations aimed at improving sustainability of wheat production.
THEORETICAL PEARLS
Authors: OKASAKI CHRIS
Published: June 2003

A combinator expression is flat if it can be written without parentheses, that is, if all applications nest to the left, never to the right. This note explores a simple method for flattening combinator expressions involving arbitrary combinators.
Equilibrium pollution and economic development in China
Authors: Wang Hua , Wheeler David
Published: June 2003

This paper develops and estimates a structural equilibrium pollution model, in which the price and quantity of industrial pollution are jointly determined by the intersection of environmental demand and supply functions. The industrial environmental demand function relates industrial pollution intensity to the local price of pollution, while controlling for characteristics such as sector, scale, and ownership. The local environmental supply function specifies the pollution price imposed by the host community as pollution rises. The model provides a good fit to available data on provincial variations in China's pollution levy, or industrial emissions charge. Our results also suggest that Chinese industry has reduced emissions significantly in response to the levy.
An economic analysis of using crop residues for energy in China
Authors: Wang Xiaoping , Mendelsohn Robert
Published: June 2003

This study examines the economics of using crop residues to replace coal burning for energy in China in order to mitigate carbon emissions. About 60 per cent of the available crop residues are now used by rural households in China to replace coal so that the residues are already making a major contribution to controlling China's potential carbon emissions. Using the crop residues more efficiently in village or centralized facilities, shifting to crops with more residues, or growing energy crops can all further reduce carbon emissions. However, accounting for the costs of collecting, transporting, drying and storing crop residues and the foregone crop revenue, the study estimates that the marginal cost to remove more carbon emissions with crop residues will be high.
Technical efficiency in the Malaysian gill net artisanal fishery
Authors: Squires Dale , Grafton R. Quentin , Alam Mohammed Ferdous , Omar Ishak Haji
Published: June 2003

Artisanal fishing communities include some of the ‘poorest of the poor’. Using data from gill net fishers in Malaysia, the paper presents the first technical efficiency study of an artisanal fishery and finds that artisanal fishers are poor, but enjoy a high level of technical efficiency. If the relatively high levels of technical efficiency found in the Malaysian gill net fishery existed in other artisanal fisheries, it suggests that targeted development assistance that has traditionally been focussed on the harvesting sector may be better directed to other priorities in artisanal fishing communities.
Eco-labels for credence attributes: the case of shade-grown coffee
Authors: Larson Bruce A.
Published: June 2003

Using the case of shade-grown coffee, this paper examines the market impacts of ‘eco-labels’ for credence attributes. First, the Mattoo and Singh (1994) test is conducted for the case of shade-grown coffee to investigate the market impacts of a shade label. This analysis in section 2 shows that a shade label could ‘pass’ the test, but the market impacts are likely to be minor. Section 2 also shows how to use estimates of supply, potential demand, and price elasticities of demand and supply to predict eco-label premiums in the post-label equilibrium. And second, given the importance of consumer demands for eco-label impacts, and since the theoretical foundations of demand for eco-labeled items are not well developed in the literature, Section 3 takes a closer look at the microeconomics of labels and consumer demand. A nested constant-elasticity-of-substitution preference structure is used to derive theoretically consistent Marshallian demands for shade and non-shade coffee. A numerical simulation shows how relative prices and consumer preferences for the credence attribute and variety are both important factors in demand creation of labeled items.
Characterization of human palmitoyl-acyl transferase activity using peptides that mimic distinct palmitoylation motifs
Authors: VARNER Amanda S. , DUCKER Charles E. , XIA Zuping , ZHUANG Yan , DE VOS Mackenzie L. , SMITH Charles D.
Published: June 2003

The covalent attachment of palmitate to proteins commonly occurs on cysteine residues near either N-myristoylated glycine residues or C-terminal farnesylated cysteine residues. It therefore seems likely that multiple palmitoyl-acyl transferase (PAT) activities exist to recognize and modify these distinct palmitoylation motifs. To evaluate this possibility, two synthetic peptides representing these palmitoylation motifs, termed MyrGCK(NBD) and FarnCNRas(NBD), were used to characterize PAT activity under a variety of conditions. The human tumour cell lines MCF-7 and Hep-G2 each demonstrated high levels of PAT activity towards both peptides. In contrast, normal mouse fibroblasts (NIH/3T3 cells) demonstrated PAT activity towards the myristoylated substrate peptide but not the farnesylated peptide, while ras-transformed NIH/3T3 cells were able to palmitoylate the FarnCNRas(NBD) peptide. The kinetic parameters for PAT activity were determined using membranes from MCF-7 cells, and indicated that the Km values for palmitoyl-CoA were identical for PAT activity towards the two substrate peptides; however, the Km for MyrGCK(NBD) was 5-fold lower than the Km for FarnCNRas(NBD). PAT activity towards the two substrate peptides was dose-dependently inhibited by 2-bromopalmitate and 3-(1-oxo-hexadecyl)oxiranecarboxamide (16C; IC50 values of approx. 4 and 1.3 μM, respectively); however, 2-bromopalmitate was found to be uncompetitive with respect to palmitoyl-CoA, whereas 16C was competitive. To seek additional evidence for multiple PATs, the effects of altering the assay conditions on the palmitoylation of MyrGCK(NBD) and FarnCNRas(NBD) were compared. PAT activity towards the two peptide substrates was modulated similarly by changing the ionic strength or incubation temperature, or by the addition of dithiothreitol. In contrast, the enzymic palmitoylation of the two peptides was differentially affected by N-ethylmaleimide and thermal denaturation. Overall, these data demonstrate that the enzymic palmitoylation of farnesyl- and myristoyl-containing peptide substrates can be differentiated, suggesting that multiple motif-specific PATs exist.
MEKK3 interacts with the PA28gamma regulatory subunit of the proteasome
Authors: HAGEMANN Carsten , PATEL Rajnikant , BLANK Jonathan L.
Published: June 2003

The proteasome is a multisubunit proteolytic enzyme comprising activator complexes bound to the 20 S catalytic core. The functions of the proteasomal activator (PA) 700 in ubiquitin/ATP-dependent protein degradation and of the PA28α/β activators in antigen presentation are well defined. However, the function of a third PA, PA28γ, remains elusive. We now show that mitogen-activated protein kinase (MAPK)/extracellular-signal-regulated kinase (ERK) kinase kinase 3 (MEKK3), a MAPK kinase kinase (MAPKKK) involved in MAPK kinase 7 (MKK7)–c-Jun N-terminal kinase (‘JNK’) and MKK6–p38 signalling, can bind PA28γ but not PA28α. In contrast, B-Raf, a MAPKKK specific for the MAPK/ERK kinase (‘MEK’)–ERK module, binds PA28γ and α. The PA28γ-binding domain of MEKK3 is located within its N-terminal regulatory domain (amino acids 1–178). Expression of MEKK3 in Cos-7 cells led to an increase in endogenous and co-expressed PA28γ protein levels, whereas kinase-deficient MEKK3 had no effect on PA28γ expression. Furthermore, in vitro assays indicated that PA28γ was a MEKK3 substrate. MEKK3 represents the first protein kinase capable of binding and phosphorylating a PA, and provides a potential mechanism to link stress-activated protein kinase signalling with the PA28γ-dependent proteasome.
Purification, cloning and sequencing of an enzyme mediating the reductive dechlorination of 2,4,6-trichlorophenol from Desulfitobacterium frappieri PCP-1
Authors: BOYER Annie , PAGÉ-BÉLANGER Rachel , SAUCIER Maude , VILLEMUR Richard , LÉPINE Francois , JUTEAU Pierre , BEAUDET Réjean
Published: June 2003

A new membrane-associated 2,4,6-trichlorophenol reductive dehalogenase from Desulfitobacterium frappieri PCP-1 was isolated. Initial characterization of the crude preparation showed that the dechlorinating activity was sensitive to oxygen, and its optimum pH was 7.0. Its dechlorinating activity was not inhibited by sulphate, was completely inhibited by 1 mM sulphite, and partially inhibited by 5 mM sodium azide and by more than 5 mM nitrate. Several polychlorophenols were dechlorinated in the ortho position with respect to the hydroxy group. A dehalogenase was purified to apparent homogeneity. SDS gel electrophoresis revealed a single protein band with a molecular mass of 37 kDa. However, after two-dimensional gel electrophoresis, this band was composed of three isoforms. MS analyses showed that the three isoforms were from the same protein and the molecular mass of the most abundant isoform is 33800 Da. A mixture of iodopropane and titanium citrate caused a light-reversible inhibition of the dechlorinating activity, suggesting the involvement of a corrinoid cofactor. The apparent Km value for 2,4,6-trichlorophenol and pentachlorophenol were 18.3±2.8 μM and 26.8±2.9 μM respectively, at a methyl viologen concentration of 2 mM. The N-terminal amino acid sequence and an internal tryptic peptide sequence were determined. One open reading frame (ORF) was found in the Desulfitobacterium hafniense genome containing these peptides sequences. The corresponding ORF in D. frappieri PCP-1 was cloned and sequenced. This ORF, that we designated crdA, showed no homology with any known dehalogenase, suggesting a distinct reductive dehalogenase.
Acetylcholinesterase active centre and gorge conformations analysed by combinatorial mutations and enantiomeric phosphonates
Authors: KOVARIK Zrinka , RADIĆ Zoran , BERMAN Harvey A. , SIMEON-RUDOLF Vera , REINER Elsa , TAYLOR Palmer
Published: June 2003

A series of eight double and triple mutants of mouse acetylcholinesterase (AChE; EC 3.1.1.7), with substitutions corresponding to residues found largely within the butyrylcholinesterase (BChE; EC 3.1.1.8) active-centre gorge, was analysed to compare steady-state kinetic constants for substrate turnover and inhibition parameters for enantiomeric methylphosphonate esters. The mutations combined substitutions in the acyl pocket (Phe295→Leu and Phe297→Ile) with the choline-binding site (Tyr337→Ala and Phe338→Ala) and with a side chain (Glu202→ Gln) N-terminal to the active-site serine, Ser203. The mutations affected catalysis by increasing Km and decreasing kcat, but these constants were typically affected by an order of magnitude or less, a relatively small change compared with the catalytic potential of AChE. To analyse the constraints on stereoselective phosphonylation, the mutant enzymes were reacted with a congeneric series of SP- and RP-methylphosphonates of known absolute stereochemistry. Where possible, the overall reaction rates were deconstructed into the primary constants for formation of the reversible complex and intrinsic phosphonylation. The multiple mutations greatly reduced the reaction rates of the more reactive SP-methylphosphonates, whereas the rates of reaction with the RP-methylphosphonates were markedly enhanced. With the phosphonates of larger steric bulk, the enhancement of rates for the RP enantiomers, coupled with the reduction of the SP enantiomers, was sufficient to invert markedly the enantiomeric preference. The sequence of mutations to enlarge the size of the AChE active-centre gorge, resembling in part the more spacious gorge of BChE, did not show an ordered conversion into BChE reactivity as anticipated for a rigid template. Rather, the individual aromatic residues may mutually interact to confer a distinctive stereospecificity pattern towards organophosphates.
Synthetic peptides derived from the prosegments of proprotein convertase 1/3 and furin are potent inhibitors of both enzymes
Authors: BASAK Ajoy , LAZURE Claude
Published: June 2003

Proprotein convertases (PCs) are Ca2+-dependent serine proteases of the subtilisin/kexin family which are known specifically to cleave propeptide and proprotein substrates at the C-terminal of R-X-(K/R)-R↓ to generate the relevant biologically active peptides. PCs are initially synthesized as enzymically inactive proenzyme forms where the prosegments play an important inhibitory role to the respective enzymes. Here we investigated whether synthetic peptides derived from the pro-region could also represent specific and potent inhibitors. Based upon sequence alignment, secondary structure analysis and hydrophilicity plot, a number of peptides ranging from 8 to 33 residues were selected. These included segments encompassing residues 55–62, 50–62, 39–62, 50–83, 55–83, 64–83 and 74–83 in the pro-mouse PC1/3 sequence and residues 54–62, 48–62 and 39–62 of the pro-human furin sequence. All peptides were prepared by solid-phase FastMoc chemistry, purified by reversed-phase HPLC and characterized by MS and amino acid analysis. These peptides were tested in vitro for inhibitory activity towards recombinant mouse PC1/3 and human furin. Progress-curve and end-time kinetic analysis demonstrated that a number of these peptides, particularly those containing both the primary and the secondary processing sites, displayed strong inhibition of both enzymes with inhibition constants (Ki) in the high nanomolar range. Unlike the whole propeptide, these small synthetic peptide inhibitors exhibited either true competitive or mixed competitive inhibition, depending on the sequence. Our data revealed further the critical role of the last two basic amino acid residues (e.g. Lys82-Arg83 for the mouse PC1/3 sequence) of the prodomain in imparting a strong anti-convertase activity. The study also establishes the inhibitory potential of certain regions contained within the prosegment of the two convertases.
Evidence for the interaction of the hereditary haemochromatosis protein, HFE, with the transferrin receptor in endocytic compartments
Authors: DAVIES Paige S. , ZHANG An-Sheng , ANDERSON Emily L. , ROY Cindy N. , LAMPSON Michael A. , McGRAW Timothy E. , ENNS Caroline A.
Published: June 2003

HFE, the protein mutated in hereditary haemochromatosis type 1, is known to interact with the transferrin receptor (TfR) on the cell surface and during endocytosis [Gross, Irrinki, Feder and Enns (1998) J. Biol. Chem. 273, 22068–22074; Roy, Penny, Feder and Enns (1999) J. Biol. Chem. 274, 9022–9028]. However, whether they are capable of interacting with each other once inside the cell is not known. In the present study we present several lines of evidence that they do interact in endosome compartments. Cells expressing a chimaera of HFE protein with the cytoplasmic domain of lysosomal-associated membrane protein 1 (LAMP1) in place of its own (HFE–LAMP) show a decrease in the half-life of the TfR. This implies that the interaction between HFE and TfR in endosomes targets the TfR to lysosomal compartments. The interaction between TfR and HFE–LAMP was confirmed by immunoprecipitation, in addition to immunofluorescence studies. Addition of transferrin (Tf) to HFE–LAMP-expressing cells competes with HFE for binding to the TfR, thereby increasing the half-life of TfR and confirming that the HFE–LAMP–TfR complex reaches the cell surface prior to entering the endosomal vesicles and trafficking to the lysosome. These results raise the possibility that interaction of HFE and TfR in intracellular vesicles may play an important role in determining the function of HFE in iron homoeostasis, which is still unknown. Analysis of endosomal pH and the iron content of internalized Tf indicated that HFE does not appear to alter the unloading of iron from Tf in the endosome.
beta-Sheet is the bioactive conformation of the anti-angiogenic anginex peptide
Authors: DINGS Ruud P. M. , ARROYO Monica M. , LOCKWOOD Nathan A. , van EIJK Loes I. , HASEMAN Judy R. , GRIFFIOEN Arjan W. , MAYO Kevin H.
Published: June 2003

Anginex is a designed peptide 33mer that functions as a cytokine-like agent to inhibit angiogenesis. Although this short linear peptide has been shown by NMR and CD to form a nascent β-sheet conformation in solution, the actual bioactive structure formed upon binding to its receptor on the surface of endothelial cells could be quite different. By using a series of double-cysteine disulphide-bridged analogues, we provide evidence in the present study that the β-sheet is in fact the bioactive conformation of anginex. CD and NMR spectral analysis of the analogues indicate formation of a β-sheet conformation. Three functional assays, endothelial cell proliferation, apoptosis and in vitro angiogenesis, were performed on all analogues. As long as the placement of disulphide bonds preserved the β-strand alignment, as in the proposed bioactive conformation, bioactivities were preserved. Knowledge of the bioactive conformation of anginex will aid in the design of smaller molecule mimetics of this potent anti-angiogenic peptide.
Angiotensin II and tubular development
Authors: Wolf Gunter
Published: June 2003

Accumulating evidence suggests that angiotensin II (ANG II) plays an important role in the complex affair of renal organogenesis. The renin–angiotensin system (RAS) is up-regulated during renal development and in the perinatal period. On the other hand, inhibition of the RAS, for example by angiotensin-converting enzyme (ACE) inhibitors, may produce specific renal abnormalities including abnormal renal vessels, failure to develop a renal pelvis and tubular atrophy associated with expansion of the interstitium. AT2 receptors are expressed abundantly during fetal development and are down-regulated markedly after birth, whereas the abundance of AT1 receptors increases as maturation proceeds. Mice with targeted deletions of genes for angiotensinogen or ACE revealed severe renal abnormalities. In contrast, AT1A, AT1B and AT2 receptor knockout animals exhibited milder abnormalities of the kidney. These findings suggest that AT1 and AT2 receptors are both involved in the development of the nephron, and that ANG II provides signals through both receptors. ANG II exerts in vitro growth-stimulatory effects on tubular cells. Moreover, ANG II induces synthesis of collagen type IV in tubular cells, a necessary prerequisite for successful basement membrane formation. These effects are mediated through AT1 receptors. Thus, it is feasible that blockade of the RAS during kidney organogenesis leads to a decrease in the growth factor ANG II that may be pivotal for tubular growth and differentiation. On the other hand, ANG II's growth-stimulatory effects through AT1 receptors may be counterbalanced by AT2 receptor-mediated apoptosis and growth inhibition. Therefore, alterations in AT2 receptor signalling may alter the delicate balance between growth stimulation and inhibition, leading to alterations in tubular formation.
POWER LAW DISTRIBUTION IN EDUCATION: EFFECT OF ECONOMICAL, TEACHING, AND STUDY CONDITIONS IN UNIVERSITY ENTRANCE EXAMINATION
Authors: GUPTA HARI M. , CAMPANHA JOSÉ R. , CHAVARETTE FÁBIO R.
Published: June 2003

We studied the statistical distribution of student's performance, which is measured through their marks, in university entrance examination (Vestibular) of UNESP (Universidade Estadual Paulista) with respect to (i) period of study — day versus night period (ii) teaching conditions — private versus public school (iii) economical conditions — high versus low family income. We observed long ubiquitous power law tails in physical and biological sciences in all cases. The mean value increases with better study conditions followed by better teaching and economical conditions. In humanities, the distribution is close to normal distribution with very small tail. This indicates that these power law tails in science subjects are due to the nature of the subjects themselves. Further and better study, teaching and economical conditions are more important for physical and biological sciences in comparison to humanities at this level of study. We explain these statistical distributions through Gradually Truncated Power law distributions. We discuss the possible reason for this peculiar behavior.
SECONDARY RELAXATION IN A SUPERCOOLED BINARY MIXTURE
Authors: HARBOLA UPENDRA , DAS SHANKAR P.
Published: June 2003

We investigate the structural relaxation in a binary fluid over the time scales of β-relaxation regime. For this we have used a recently proposed self-consistent mode-coupling theory (MCT) formulated from the fluctuating nonlinear hydrodynamics approach. We have considered here both the hard sphere as well as the Kob–Andersen Lennard–Jones1binary mixtures. From the solution of the MCT equations obtained here the initial power law decay t-aappears to be very weak. For the later part of the β-relaxation regime, the density correlation functions follow von Schweidler (VS) power law decay tb. The validity of the so-called factorization property of the MCT over the β-relaxation is also analyzed. We find the exponent b to be in qualitative agreement with the findings from the computer simulations of the same system by Kob and Andersen.
GROWTH RATES OF TOTAL VARIATIONS OF SNAPSHOTS OF THE 1D LINEAR WAVE EQUATION WITH COMPOSITE NONLINEAR BOUNDARY REFLECTION RELATIONS
Authors: HUANG YU
Published: June 2003

The linear wave equation on an interval with a van der Pol nonlinear boundary condition at one end and an energy-pumping condition at the other end is a useful model for studying chaotic behavior in distributed parameter system. In this paper, we study the dynamics of the Riemann invariants (u, v) of the wave equation by means of the total variations of the snapshots on the spatial interval. Our main contributions here are the classification of the growth of total variations of the snapshots of u and v in long-time horizon, namely, there are three cases when a certain parameter enters a different regime: the growth

(i) remains bounded;

(ii) is unbounded (but nonexponential);

(iii) is exponential,

for a large class of initial conditions with finite total variations. In particular, case (iii) corresponds to the onset of chaos. The results here sharpen those in an earlier work [Chen et al., 2001].
EQUIVALENT CNN CELL MODELS AND PATTERNS
Authors: ITOH MAKOTO , CHUA LEON O.
Published: June 2003

In this paper, canonical isolated CNN cell models are proposed by using implicit differential equations. A number of equivalent but distinct CNN cell models are derived from these canonical models. Almost every known CNN cell model can be classified into one or more groups via constrained conditions. This approach is also applied to discrete-time CNN cell models. Pattern formation mechanisms are investigated from the viewpoint of equivalent templates and genetic algorithms. A strange wave propagation phenomenon in nonuniform CNN cells is also presented in this paper. Finally, chaotic associative memories are proposed.
REFINEMENTS TO MODEL SELECTION FOR NONLINEAR TIME SERIES
Authors: NAKAMURA TOMOMICHI , JUDD KEVIN , MEES ALISTAIR
Published: June 2003

Many models of the dynamics of nonlinear time series have large numbers of parameters and tend to overfit. This paper discusses algorithms for selecting the best basis functions from a dictionary for a model of a time series. Selecting the optimal subset of basis functions is typically an NP-hard problem which usually has to be solved by heuristic methods. In this paper, we propose a new heuristic that is a refinement of a previous one. We demonstrate with applications to artificial and real data. The results indicate that the method proposed in this paper is able to obtain better models in most cases.
STREAMLINE TOPOLOGY AND DILUTE PARTICLE DYNAMICS IN A KÁRMÁN VORTEX STREET FLOW
Authors: WU ZUO-BING
Published: June 2003

Three types of streamline topology in a Kármán vortex street flow are shown under the variation of spatial parameters. For the motion of dilute particles in the Kármán vortex street flow, there exist a route of bifurcation to a chaotic orbit and more attractors in a bifurcation diagram for the proportion of particle density to fluid density. Along with the increase of spatial parameters in the flow field, the bifurcation process is suspended, as well as more and more attractors emerge. In the motion of dilute particles, a drag term and gravity term dominate and result in the bifurcation phenomenon.
DYNAMICS BETWEEN ORDER AND CHAOS IN A SIMPLE REENTRANT MODEL OF PRODUCTION DYNAMICS
Authors: KATZORKE I. , PIKOVSKY A.
Published: June 2003

We consider a simple reentrant model of a manufacturing process, consisting of one machine at which two different types of items have to be processed. The model is completely deterministic: all delivery and processing times are fixed, and are generally incommensurate. Dependent on the arrival and processing times, a queue of waiting items grows, remains constant or disappears. We demonstrate that the dynamics of the system crucially depends on the queue type. Complexity is most observed for the case of growing queue. We characterize this dynamics between order and chaos with the T-entropy and the autocorrelation function.
INFLATION IN BIANCHI MODELS AND COSMIC NO-HAIR THEOREM IN EINSTEIN–CARTAN THEORY
Authors: CHAKROBORTY SUBENORY , CHAKRABARTI SULAGNA
Published: June 2003

We have examined cosmic no-hair theorem for anisotropic Bianchi-models in Einstein–Cartan theory and it is possible to have inflationary solution with a scalar field. It has been noted that during the inflationary era, the evolution of the Universe does not depend on the form of the potential but the late time behaviour is dependent on the potential for the inflation field.
A MODEL OF 1PN QUASI-RIGID BODY FOR ROTATION OF CELESTIAL BODIES
Authors: TAO JIN-HE , XU CHONG-MING
Published: June 2003

Applying the Damour–Soffel–Xu framework of general-relativistic celestial mechanics, the theory of relativistic rigid body presented by Thorne and Gürsel is extended and developed in this paper. We successfully construct a quasi-rigid body model in the full post-Newtonian framework for the first time. This model has some simple properties in a similar way to the Newtonian rigid body, and it could be applied in geodynamics and astronomy, for example, to solve problems on rotation or precession of celestial bodies when relativistic effects are not negligible.
THE OPTICAL-X-RAY–GAMMA-RAY SPECTRAL ENERGY DISTRIBUTIONS OF GEV GAMMA-RAY LOUD BLAZARS AND CONNECTION AMONG LBLs, HBLs AND FSRQs
Authors: XIE G. Z. , DING S. X. , DAI H. , LIANG E. W. , LIU H. T.
Published: June 2003

In this paper, we introduce a new composite spectral indices αγxγ = αxγ - αγ, and prove [Formula: see text], that means αγxγ is intrinsic. We plot a αxox - αγxγ diagram for 25 Gev γ-ray blazars for which αx and αγ have been provided in the literature, where αxox = αox - αx which was introduced by Sambruna et al. (1996) and proved that it is intrinsic by our previous paper (Xie et al. 2001). Using this new composite color–color (αxox - αγxγ) diagram, we investigated the nature of the HBLs–LBLs relationship, and the BL Lacs–FSRQs relationship, in high-energy emission. The results show that the spectral energy distributions of three subclasses of Gev γ-ray loud blazars are different, but essentially continuous: HBLs and FSRQs occupy separated regions while LBLs bridge the gap between HBLs and FSRQs. The results are consistent with that derived from a low energy color–color(αxox - αoro) diagram by Sambruna et al. (1996) and Xie et al. (2001). However, on the αox - αxγ diagram, FSRQs, LBLs and HBLs occupy same region. Because both αγxγ and αxox are intrinsic, thus, the new connection among HBLs, LBLs and FSRQs obtained by us is intrinsic.
DYNAMICAL BEHAVIOR OF CONTINUOUS TICK DATA IN FUTURES EXCHANGE MARKET
Authors: KIM KYUNGSIK , YOON SEONG-MIN
Published: June 2003

We study the tick dynamical behavior of the bond futures in Korean Futures Exchange (KOFEX) market. Since the survival probability in the continuous-time random walk theory is applied to the bond futures transaction, the form of the decay function in our bond futures model is discussed from two kinds of Korean Treasury Bond (KTB) transacted recently in KOFEX. The decay distributions for survival probability are particularly displayed stretched exponential forms with novel scaling exponents β = 0.82 (KTB203) and 0.90 (KTB112), respectively, for our small time intervals. We obtain the scaling exponents for survival probability ∊ = 17 and 18 decayed rapidly in large time limit, and our results are compared with recent numerical calculations.
LANGUAGE AND CODIFICATION DEPENDENCE OF LONG-RANGE CORRELATIONS IN TEXTS
Authors: AMIT M. , SHMERLER Y. , EISENBERG E. , ABRAHAM M. , SHNERB N.
Published: June 2003

We study the long-range correlations in various translations of the Bible by mapping them onto a one dimensional random walk model. We show that the exponent α, which characterizes the algebraic decay law of these correlations depends on both the language and the codification. Some considerations concerning the origin of these correlations are suggested in terms of which a qualitative explanation of this dependence is presented.
DENDRITIC COMPLEXITY AND THE EVOLUTION OF CEREBELLAR PURKINJE CELLS
Authors: KRAUSS B. R. , SEROG B. J. , CHIALVO D. R. , APKARIAN A. V.
Published: June 2003

Cerebellar Purkinje cells have the most extensive dendritic arborization in the central nervous system. These neurons can be readily identified in most vertebrates. We reexamined a recently postulated relationship between phylogeny and fractal dimension of Purkinje cells' dendritic field (Takeda et al.1). The fractal dimension of Purkinje cells was measured, using a box-counting technique, from several species with diverging eras spanning 5.24 × 108 years. The linear correlation (y = mx + b) between phylogenetic placement and fractal dimension, for water creatures gave m = −0.057, r2 = 0.137 and for land creatures m = −0.096, r2 = 0.685. Regression analysis showed that the slope for the water creatures line was not significantly different from zero, but the slope for the land creatures was significant. These results only partially agree with the conclusions of Takeda et al. We also found that small variations in data collection and analysis can significantly change these results, including: quality and technique of cell reconstruction, criteria of selection of the scaling region, and tolerance on the power-law fit.
AN AMENDMENT TO THE FUNDAMENTAL LIMITS ON DIMENSION CALCULATIONS
Authors: HONG SHI-ZHONG , HONG SHI-MING
Published: June 2003

Fundamental limits on the minimum size of a data set is an important problem to estimate dimensions for practical objects, using the Grassberger–Procaccia algorithm. We amend the results previously given by Smith (1988) and Eckmann and Ruelle (1992) respectively, and establish a new inequality [Formula: see text].
PATTERN FORMATIONS IN CHEMICAL SYSTEMS
Authors: MASELKO JERZY
Published: June 2003

The formation of complex patterns in chemical systems is discussed in the following cases: relations of pattern formation to thermodynamics theories; unusually complex pattern formation in very simple experimental chemical systems; and numerical simulation of patterns that develop in multicellular chemical systems. The paper concludes with a discussion on future technological applications.
APPLICATION OF CHEMICAL CHAOS TO ANALYTICAL CHEMISTRY
Authors: STRIZHAK PETER E.
Published: June 2003

A simple theoretical consideration of the possibility of using deterministic chaos for a quantitative determination of trace amounts of chemical compounds is analyzed in terms of return maps. This allows the development of a general approach to find a calibration plot for a chemical compound determination, i.e. to find a one-to-one correspondence between a measured value and the concentration of a substance to be determined. As experimental verification of these theoretical results, we present a study of the effect of copper (II) ions on the transient chaotic regime in the BZ reaction catalyzed by ferroin in batch as well as of the effect of vanadium (IV) on the deterministic chaotic regime in the BZ reaction catalyzed by ferroin in a CSTR. These studies show that it is possible to quantify the response of transient chaotic regimes to chemical compounds, i.e. to construct a calibration plot for chemical compound determination using their effect on the chaotic dynamics in the BZ reaction. Moreover, these studies shown that vanadium (IV) affects the chaotic regimes at concentration levels of the order of 10-12g/mL , which gives the best detection limit for the kinetic methods of trace analysis.
Hausdorff measure of the singular set of quasiregular maps on Carnot groups
Authors: Markina Irina
Published: June 2003

Recently, the theory of quasiregular mappings on Carnot groups has been developed intensively. Let ν stand for the homogeneous dimension of a Carnot group and let m be the index of the last vector space of the corresponding Lie algebra. We prove that the (ν − m − 1)‐dimensional Hausdorff measure of the image of the branch set of a quasiregular mapping on the Carnot group is positive. Some estimates of the local index of quasiregular mappings are also obtained.
Verbal and Visual Parallelism
Authors: Fahnestock Jeanne
Published: June 2003

This study investigates the practice of presenting multiple supporting examples in parallel form. The elements of parallelism and its use in argument were first illustrated by Aristotle. Although real texts may depart from the ideal form for presenting multiple examples, rhetorical theory offers a rationale for minimal, parallel presentation. The form for presenting data can also influence the way it is observed and selected, as the case of the Linnaean template for species grouping illustrates. Parallel presentation is not limited to verbal phrasing. Arranging data in tables, typical in scientific discourse, satisfies the same requirements for minimal, equivalent presentation of evidence. Arranging representational or iconic images in rows or arrays is yet another mode for the parallel presentation of evidence, although this mode has a recent history. A cognitive rationale can perhaps explain the use of parallelism to present multiple supporting examples.
The Myth of the “Turn” in Contrastive Rhetoric
Authors: Cahill David
Published: June 2003

Contrastive rhetoric scholarship researches rhetorical structures across languages to predict the difficulties experienced by students learning to write essays in a second language. The paradigmatic contrast is between Western languages (e.g., English) that are said to exemplify “linearity” and “directness” and Eastern languages (e.g., Chinese, Japanese) that are said to exemplify “nonlinearity” and “indirectness.” The prime examples in English-language contrastive rhetoric scholarship of Asian essay structure are the four-part Chinese qi cheng zhuan he and Japanese ki sho ten ketsu, whose third steps are said to represent a “turn.” The author's research into Chinese and Japanese-language scholarship on these two structures finds that the “turn” is not a rhetorical move of “circularity” or “digression” as commonly assumed but rather serves as the occasion to develop an essay further by alternative means. The implication for second-language writing is recognition of greater similarities in essayist literacy across these languages than previously supposed.
The Effects of Pre-exam Instruction on Students' Performance on an Effective Writing Exam
Authors: Saunders Paula , Scialfa Charles T.
Published: June 2003

The purpose of Study 1a was to determine the criteria that differentiate students who perform well and those who perform poorly on a standardized test of university-level writing. Discriminant function analysis revealed that measures of structure, sentencing, paragraphing, and grammar play the most important role in separating these two groups. These results were used in Study 1b to develop a tutorial attended by an independent group of students preparing to write a standardized writing exam. The intervention had a positive effect on their test performance. Participants reported the tutorial to be useful, committed fewer errors on most of the criteria, and had a higher probability of passing the exam. It was concluded that this type of tutorial is beneficial to students who are preparing for such exams and may have wider educational use for those seeking assistance with their writing skills.
Polyimides Prepared from 4,4′-(2-Diphenylphosphinyl-1,4-Phenylenedioxy)Diphthalic Anhydride for Potential Space Applications
Authors: Thompson C M , Smith J G , Connell J W
Published: June 2003

As part of an ongoing materials development activity to produce high performance polymers that are space environmentally stable, phosphine oxide containing polyimides were prepared by reacting a novel aromatic dianhydride, 4,4′-(2-diphenylphosphinyl-1,4-phenylenedioxy)diphthalic anhydride 3, with aromatic diamines. The dianhydride was prepared from 2,5-dihydroxyphenyldiphenylphosphine oxide in three steps in relatively good yield. In general, the polyimides exhibited physical and mechanical properties comparable to other wholly aromatic polyimides. Depending upon the diamine, nearly all of the polyimides formed near colorless to yellow films. The polyimides were amorphous and in most cases soluble in polar aprotic solvents. However, one polymer film prepared using 1,4-phenylenediamine exhibited some degree of ordering when prepared by chemical imidization. The chemistry, physical and mechanical properties of the polymers are discussed.