bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effective Borel measurability and reducibility of functions
Authors: Brattka Vasco 
Published: November 2004

AbstractThe investigation of computational properties of discontinuous functions is an important concern in computable analysis. One method to deal with this subject is to consider effective variants of Borel measurable functions. We introduce such a notion of Borel computability for single‐valued as well as for multi‐valued functions by a direct effectivization of the classical definition. On Baire space the finite levels of the resulting hierarchy of functions can be characterized using a notion of reducibility for functions and corresponding complete functions. We use this classification and an effective version of a Selection Theorem of Bhattacharya‐Srivastava in order to prove a generalization of the Representation Theorem of Kreitz‐Weihrauch for Borel measurable functions on computable metric spaces: such functions are Borel measurable on a certain finite level, if and only if they admit a realizer on Baire space of the same quality. This Representation Theorem enables us to introduce a realizer reducibility for functions on metric spaces and we can extend the completeness result to this reducibility. Besides being very useful by itself, this reducibility leads to a new and effective proof of the Banach‐Hausdorff‐Lebesgue Theorem which connects Borel measurable functions with the Baire functions. Hence, for certain metric spaces the class of Borel computable functions on a certain level is exactly the class of functions which can be expressed as a limit of a pointwise convergent and computable sequence of functions of the next lower level. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of porous GaAs layers formed on n+‐type GaAs by electrochemical anodization in HF solution
Authors: Beji L. , Sfaxi L. , BenOuada H. , Maaref H. 
Published: November 2004

AbstractThe electrochemical etching of n+‐type GaAs in a hydrofluoric acid (HF) solution results in the formation of a porous layer. The current–potential characteristic I(V) of the n+‐type GaAs–HF electrolyte interface shows that pore formation started at a breakdown anodic potential of about 2.5 V independent of the HF concentration. In addition, it is also shown that an electropolishing of the semiconductor started over a critical anodic potential value. The morphology and photoluminescence (PL) of the porous samples were investigated. It has been shown that the porous layer surface morphology consists of arbitrarily shaped crystallites, the pores grow deeply in the substrate and, under some electrochemical conditions, etch pits can be formed. The porous layers exhibited an intense and broad PL band, compared to that of the starting GaAs, composed of elementary bands located below and above the band gap of the starting GaAs. The elementary bands located above the band gap were attributed to GaAs nanocrystals. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrochemical deposition and characterization of CoFe2O4 thin films
Authors: Sartale S. D. , Lokhande C. D. , Ganesan V. 
Published: November 2004

AbstractAn electrochemical deposition process, which is a combination of electrodeposition of CoFe2 alloy from an ethylene glycol bath followed by its anodization at ambient temperature, is used to deposit CoFe2O4 thin films on different conducting substrates. Various deposition conditions are studied and optimized. The films have spinel CoFe2O4 structure with crystallite size less than 50 nm. The films are adherent and covered the substrates well. The films are annealed in air at 500 °C for 1 h and the observed properties are reported. After annealing the films have smooth and compact surfaces with improved magnetic properties. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of non‐Cr‐based deoxidizers on Al alloy 7475‐T7651
Authors: Toh S.K. , Hughes A.E. , McCulloch D.G. , duPlessis J. , Stonham A. 
Published: November 2004

AbstractThe effects of three non‐chromate‐based deoxidizers, namely NaBrO3/HNO3, (NH4)4Ce(SO4)4/H2SO4 and Fe(III)/HF/HNO3, on the Al alloy 7475‐T7651 were investigated. Several analytical methods were employed, including SEM, AES, transmission electron microscopy (TEM), electron energy‐loss spectroscopy (EELS) and glow discharge optical emission spectrometry (GDOES), to study the effects on the surface of this alloy after each treatment compared with the as‐received and alkaline‐cleaned alloy surfaces. The untreated alloy was found to have a thick oxide of 200–320 nm, consisting mainly of MgO. Alkaline cleaning results in an etching effect that thins the oxide and also deposits a thin silicate layer on the surface. In the case of the deoxidizers, there is significant removal of the native oxide of the alloy by the NaBrO3/HNO3 deoxidizer. There is also evidence of intermetallic attack on the alloy. The (NH4)4Ce(SO4)4/H2SO4 deoxidizer, which is a low‐etch‐rate deoxidizer, resulted in a slight thinning of the oxide. However, the effect was not significantly greater than with alkaline cleaning alone. The most effective deoxidizer in reducing the oxide thickness of the alloy is Fe(III)/HF/HNO3, in which the etch rate was sufficiently high to remove completely the native oxide. In this case, equilibrium between oxide removal and the formation of new oxides on the alloy surface was achieved. Copyright © 2004 John Wiley & Sons, Ltd.
Supplementary analysis of probabilities at the termination of a group sequential phase II trial
Authors: Liu Aiyi , Wu Chengqing , Yu Kai F. , Gehan Edmund 
Published: November 2004

AbstractWe consider estimation of various probabilities after termination of a group sequential phase II trial. A motivating example is that the stopping rule of a phase II oncologic trial is determined solely based on response to a drug treatment, and at the end of the trial estimating the rate of toxicity and response is desirable. The conventional maximum likelihood estimator (sample proportion) of a probability is shown to be biased, and two alternative estimators are proposed to correct for bias, a bias‐reduced estimator obtained by using Whitehead's bias‐adjusted approach, and an unbiased estimator from the Rao–Blackwell method of conditioning. All three estimation procedures are shown to have certain invariance property in bias. Moreover, estimators of a probability and their bias and precision can be evaluated through the observed response rate and the stage at which the trial stops, thus avoiding extensive computation. Copyright © 2004 John Wiley & Sons, Ltd.
Statistical discrimination in the presence of selection effects
Authors: Hilliam R. M. 
Published: November 2004

AbstractDiscrimination between diseases is a complex task. Cases may present contradictory information and diseases can present with unusual or atypical symptoms. In many diagnostic problems the recorded diagnosis is either a true diagnosis, based on hard evidence, or a working diagnosis, not necessarily equivalent to the true underlying disease with an associated level of uncertainty. This problem is often confounded since the type of diagnosis given may be subjected to selection effects. Much medical data is categorical in nature, hence existing techniques for identifying selection effects are inappropriate. This paper provides a method of obtaining a single parameter modelling, the probability of giving a true diagnosis dependent on the nature of the true disease, thereby offering a simple measure for the presence of selection effects. When the size of the data is limited identifiability problems exist with calculating this parameter, however this paper shows how a sensitivity analysis based on the profile likelihood can be used to identify the presence of selection effects even in this difficult situation. Copyright © 2004 John Wiley & Sons, Ltd.
Where do capabilities come from and how do they matter? A study in the software services industry
Authors: Ethiraj Sendil K. , Kale Prashant , Krishnan M. S. , Singh Jitendra V. 
Published: November 2004

AbstractRecent years have witnessed a surge of interest in the notion of capabilities as an important source of competitive advantage. This recognition has, in turn, placed emphasis on the question of where and how these capabilities emerge and how they influence firm performance. The present paper is an attempt to address this question. Using a large sample of detailed project‐level data from a leading firm in the global software services industry, we attempt to empirically study the importance of capabilities. We find that two broad classes of capabilities are significant. The first class, which we label client‐specific capabilities, is a function of repeated interactions with clients over time and across different projects. This learning from repeated interactions with a given client reduces project execution costs and helps improve project contribution. The second class, termed project management capabilities, is acquired through deliberate and persistent investments in infrastructure and systems to improve the firm's software development process. Our empirical results suggest that the marginal returns to acquiring different capabilities may be different and an understanding of such trade‐offs can improve firm decisions to improve and/or acquire such capabilities. We discuss the key contributions of our paper and the implications for future research on capabilities. Copyright © 2004 John Wiley & Sons, Ltd.
Security issues in IEEE 802.11 wireless local area networks: a survey
Authors: Mishra Arunesh , Petroni Nick L. , Arbaugh William A. , Fraser Timothy 
Published: November 2004

AbstractIn the past few years, wireless networks, specifically those based on the IEEE 802.11 standard, have experienced tremendous growth. However, numerous security problems have dampened this growth. The IEEE and vendors sensitive to these issues began a wholesale redesign of the security architecture, while simultaneously producing measures for mitigating existing problems. In this paper, we describe the past and future security architectures as well as the problems and concerns with both. Copyright © 2004 John Wiley & Sons, Ltd.
Adapting physical carrier sensing to maximize spatial reuse in 802.11 mesh networks
Authors: Zhu Jing , Guo Xingang , Lily Yang L. , Steven Conner W. , Roy Sumit , Hazra Mousumi M. 
Published: November 2004

AbstractSpatial reuse in a mesh network can allow multiple communications to proceed simultaneously, hence proportionally improve the overall network throughput. To maximize spatial reuse, the MAC protocol must enable simultaneous transmitters to maintain the minimal separation distance that is sufficient to avoid interference. This paper demonstrates that physical carrier sensing enhanced with a tunable sensing threshold is effective at avoiding interference in 802.11 mesh networks without requiring the use of virtual carrier sensing. We present an analytical model for deriving the optimal sensing threshold given network topology, reception power and data rate. A distributed adaptive scheme is also presented to dynamically adjust the physical carrier sensing threshold based on periodic estimation of channel conditions in the network. Simulation results are shown for large‐scale 802.11b and 802.11a networks to validate both the analytical model and the adaptation scheme. It is demonstrated that the enhanced physical carrier sensing mechanism effectively improves network throughput by maximizing the potential of spatial reuse. With dynamically tuned physical carrier sensing, the end to end throughput approaches 90% of the predicted theoretical upper‐bound assuming a perfect MAC protocol, for a regular chain topology of 90 nodes. Copyright © 2004 John Wiley & Sons, Ltd.
COLONY AND FRUSTULE MORPHOLOGY OF THREE TUBE‐DWELLING DIATOMS FROM EASTERN CANADA1
Authors: Lobban Christopher S. 
Published: November 2004

ABSTRACTThree species of Navicula are described from light and scanning electron microscopy. Navicula bottnica Grunow, has not previously been illustrated at the SEM level, nor has it previously been reported to form colonies, but the cells appear to be identical to Schizonema smithii C. Agardh (sensu van Heurck) and the name is amended to Navicula smithii (C. Ag.) van Heurck. The colonies are irregularly branched, the cells within forming strands which frequently appear braided. Material of N. delognei van Heurck differs in several points from typical material and a new form, elliptica is proposed. Observations on the third species, N. pseudocomoides corroborate recent work by Cox in Britain.
THE OCCURRENCE OF CHLOROPHYLLS C1 AND C2 IN THE CHRYSOPHYCEAE1
Authors: Andersen Robert A. , Mulkey Timothy J. 
Published: November 2004

ABSTRACTWe analyzed 34 strains representing 25 species of Chrysophyceae for chlorophylls c1 and c2 using thin‐layer chromatography. Most organisms had both chlorophylls c1 and c2 in addition to chlorophyll a but 17 strains of 9 species of Synura and Mallomonas possessed only chlorophylls a and c1. These are the first chlorophyll c‐bearing algae which lack chlorophyll c2. We postulate that at least some of the silica‐scaled algae including Mallomonas and Synura may be distinct from other Chrysophyceae based upon pigmentation and other characters described in the literature.
DIATOM MINERALIZATION OF SILICIC ACID. VII. INFLUENCE OF MICROTUBULE DRUGS ON SYMMETRY AND PATTERN FORMATION IN VALVES OF NAVICULA SAPROPHILA DURING MORPHOGENESIS1
Authors: Blank Gregory S. , Sullivan Cornelius W. 
Published: November 2004

ABSTRACTMicrotubule involvement in diatom valve symmetry and pattern formation was investigated using cells synchronized subsequent to mitosis and cytokinesis but prior to cell wall formation. Two analog drug pairs, each consisting of an active and an inactive microtubule drug, were used to distinguish inhibitory effects related or unrelated to microtubule disruption. The active anti‐microtubule drug of each analog pair produced significantly higher percentages of aberrant valves than did the respective inactive analogs. High frequencies of aberrant valves also were caused by N‐isophenlpropylcarbamate, which disorganizes rather than disrupts microtubules. Valves could be placed into different classes based upon characteristic aberrations. Formation of these classes was not random but was instead a function of both the drug and the drug concentration. The central nodule and the raphe were the principal valve components affected by anti‐microtubule drugs. Stria alterations appeared as a secondary result of alterations in the central nodule/raphe. Valve aberrations occurred at very low drug concentrations in the range 1 × 10−6 to 1 × 10−9M.
LIGHT AND NUTRIENT DEPENDENCE OF PHOTOSYNTHESIS BY ALGAE1
Authors: Smith Val H. 
Published: November 2004

ABSTRACTThe validity of a recent nutrient‐based modal of algal photosynthesis was tested using phosphorus‐limited semi‐continuous cultures of the green alga, Scenedesmus quadricauda. The data suggest that light‐saturate photosynthesis (P opt, mg C · mg chla−1· h−1) is a hyperbolic function of cellular phosphorus quota (Qp), whether Qp is expressed per unit cellular chlorophyll a, per unit dry weight, or per cell number. Furthermore, the light availability during growth appears to have little effect on these hyperbolic relationships over the range of light intensities studied here (65–110 μE · m−2· s−1). These data, and data presented from other published studies, suggest that the cell quota model is a valid empirical description of the photosynthetic behavior of nutrient‐limited cells.
DIATOM COLONIZATION ON ARTIFICIAL SUBSTRATA IN POOL AND RIFFLE ZONES STUDIED BY LIGHT AND SCANNING ELECTRON MICROSCOPY1
Authors: Korte Virginia L. , Blinn Dean W. 
Published: November 2004

ABSTRACTLight and scanning electron microscopy were utilized to quality diatom colonization in Oak Creek, Arizona. Aluminum SEM stubs with and without plexiglass discs were anchored into rocks. Early colonization on five stub microzones was examined at hourly intervals; weekly intervals of up to 3 wk were employed to record community development in pool find riffle. Plexiglass was more suitable for microbial colonization than aluminum. Organic matter and bacteria were important surface pre‐conditioning agents while fungi were instrumental in trap/ting cells during early stages of colonization in the riffle. Diatom colonization was initialed within 1 h on the upstream side of substrata in riffles, while the tap face was colonized first in pools. Colonization moved rapidly to the perimeter in each system. Early colonization of‐side microzones was considerably more asymmetric in the riffle than, pool. At Idler stages (2 wk) diatoms with their associated mucilage and algal filaments contributed to the stability of the microbial communities. Horizontally positioned species(Achnanthes, Cocconeis)were early colonizers in both systems while vertically positioned species(Gomphonema, Nitzschia)were more important in later successional stages (3 wk) in the riffle. Horizontally positioned species remained dominant throughout the 3 wk period in the pool. After 3 wk, diversity was normally greater in the pool while density was higher in the riffle. Detrital microcosms containing viable microbiol assemblages frequently collected on tin‐upstream face of substrata in the riffle. The random nature by which these detrital microcoms contact downstream substrata greatly contribute to the spatial variation of periphyton in streams. These detrital microcosms expedite repeated colonization in lotic systems.
VALVE AND BAND MORPHOLOGY OF SOME FRESHWATER DIATOMS. IV. OUTER SURFACE MUCILAGE OF NAVICULA CONFERVACEA VAR. CONFERVACEA1
Authors: Rosowski James R. , Hoagland Kyle D. , Roemer Stephen C. 
Published: November 2004

ABSTRACTThe development of the mucilage on the outer surface of Navicula confervacea (Kütz.) Grun., a raphed, filamentous diatom, was studied with scanning electron microscopy. This nonstructural cell wall material, present on the surface after critical‐point drying and absent after acid cleaning, was of two types: strands and papillae. Strands were associated with the raphe system, areolae, elongated pores of the mantle, and all girdle sutures. Organic papillae were a common feature of valves, valvo‐copulae and pleurae, but their origin and distribution could not be explained since they often occurred between the obvious openings in the frustule. Strands from the raphe and areolae may function in attaching terminal cells to a substrate and adjacent cells to each other. Other strands of the girdle arise from sutures during cell enlargement and continue to lengthen and intertwine until the individual frustules within a filament are obscured. Strands from sutures might originate from the advalvar row of pores of the girdle bands since these pores lie along the suture, but direct observation of this was not made. Secretion between, the bands also cannot be ruled out. Although mucilaginous papillae may sometimes occur at random on the entire surface of frustules, there is also a distinct, narrow multiseriate row of them around the edge of valves without marginal spines.
SEASONAL PHOTOSYNTHETIC PERFORMANCE OF MACROCYSTIS INTEGRIFOLIA (PHAEOPHYCEAE)1
Authors: Smith Ronald G. , Wheeler William N. , Srivastava Lalit M. 
Published: November 2004

ABSTRACTThe seasonal photosynthetic performances of three age classes of blades of Macrocystis integrifolia Bory were estimated by studying their photosynthetic rate vs. irradiance curves and pigment contents for 15 months. All blade types were irradiance‐saturated between 25 and 70 μE · m−2· S−1. Young and mature blade tissues had higher photosynthetic maxima and initial slopes on an area basis than older blade tissue. The latter, however, had pigment concentrations similar to those in mature blade tissues. All these parameters varied on a seasonal basis. The photosynthetic maxima ranged from 0.1–0.8 μmol · C · cm−2· h−t and showed two peaks, one in late summer‐early fall and the other in late winter. Changes in initial slope and pigment concentrations in the blade tissues suggest that, changes in the size or efficiency of electron transfer in the photosynthetic unit occur. These data are discussed in relation to changes in seawater temperature and nitrate concentrations.
CARDIOPROTECTIVE FUNCTIONS OF ATRIAL NATRIURETIC PEPTIDE AND B‐TYPE NATRIURETIC PEPTIDE: A BRIEF REVIEW
Authors: Woods Robyn L 
Published: November 2004

SUMMARY1. If one was to design a hormone to protect the heart, it would have a number of features shown by the cardiac natriuretic peptides atrial natriuretic peptide (ANP) and B‐type natriuretic peptide (BNP). These hormones are made in cardiomyocytes and are released into the circulation in response to atrial and ventricular stretch, respectively. Atrial natriuretic peptide and BNP can reduce the preload and after‐load in normal and failing hearts. They reduce blood volume over the short term by sequestering plasma and over the longer term by promoting renal salt and water excretion and by antagonizing the renin–angiotensin–aldosterone system at many levels. Each of these actions affords indirect benefit to a volume‐ or pressure‐threatened heart.2. Recent studies have identified additional modes of action of the natriuretic peptides that may also confer cardioprotective benefits, especially in heart disease. The emerging findings are: (i) that ANP and BNP antagonize the cardiac hypertrophic action of angiotensin II and continue working under conditions where endothelial nitric oxide (NO) function is compromised, such as in the presence of high glucose in diabetes; (ii) they potentiate the bradycardia caused by inhibitory (‘autoprotective’) cardio‐cardiac reflexes; and, furthermore, (iii) BNP can suppress cardiac sympathetic nerve activity in humans, including those with heart failure. Thus, it appears that natriuretic peptides can shift sympathovagal balance in a beneficial direction (away from the sympathetic). The vagal reflex and antihypertrophic actions of the peptides are mediated by particulate guanylyl cyclase (pGC) natriuretic peptide receptors.3. The multiple synergistic actions of the natriuretic peptides make them and their pGC receptors attractive targets for therapy in heart disease. Encouragingly, exogenous natriuretic peptides remain effective even when endogenous peptide levels are raised, as is the case in heart failure. They also remain effective in disease states where other protective mechanisms, such as the NO system, have become ineffective, offering yet further encouragement for the therapeutic use of the natriuretic peptides.
Novel heat shock protein HspQ stimulates the degradation of mutant DnaA protein in Escherichia coli
Authors: Shimuta Toh‐ru , Nakano Kiyotaka , Yamaguchi Yoko , Ozaki Shogo , Fujimitsu Kazuyuki , Matsunaga Chika , Noguchi Kenji , Emoto Akiko , Katayama Tsutomu 
Published: November 2004

Escherichia coli DnaA protein initiates chromosomal replication and is an important regulatory target during the replication cycle. In this study, a suppressor mutation isolated by transposon mutagenesis was found to allow growth of the temperature‐sensitive dnaA508 and dnaA167 mutants at 40 °C. The suppressor consists of a transposon insertion in a previously annotated ORF, here termed hspQ, a novel heat shock gene whose promoter is recognized by the major heat shock sigma factor σ32. Expression of hspQ on a pBR322 derivative inhibits growth of the dnaA508 and dnaA167 mutants at 30 °C, whereas growth of dnaA46 and other dnaA mutants is insensitive to changes in the level of hspQ. Cellular DnaA508 protein is degraded rapidly at elevated temperature, but hspQ disruption impedes this process. In contrast, DnaA46 protein is rapidly degraded in an hspQ‐independent manner. Gel‐filtration and chemical cross‐linking experiments suggest that HspQ forms a stable homodimer in solution and can form homomultimers consisting of about four monomers. Heat‐shock induced proteases such as Clp contain homomultimers of subunit proteins. We propose that HspQ is a new factor involved in the quality control of proteins and that it functions by excluding denatured proteins.