bluuebunny/crossref_metadata_2025_split huggingface dataset:
Damage Mechanisms in Duplex Treated Hot Work Tool Steel under Thermal Cycling
Authors: Pellizzari M. , Molinari A. , Straffelini G. 
Published: April 2003

Duplex treatments are becoming increasingly interesting in several technological applications through which complex forms of stresses act during service. In pressure die casting, for example, corrosion and erosion by molten metal and oxidation contribute, together with thermal fatigue, to excessive degradation of the dies and inserts. While the benefits introduced by combining nitriding and PVD coating have been assessed in counteracting soldering and wear problems, the resistance of such duplex systems with respect to thermal fatigue has not yet been established. In this work, the role of plasma nitriding, PVD coating (CrN, ZrN), and duplex treatment in counteracting thermal cracking, i.e. heat checking, of hot work tool steel is considered. Thermal fatigue tests carried out on a laboratory scale, highlight the negative role of coatings, although this result has to be partially ascribed to an unsuitable prenitriding treatment and heavy oxidation.
Centrally Administered Tuberoinfundibular Peptide of 39 Residues Inhibits Arginine Vasopressin Release in Conscious Rats
Authors: Sugimura Yoshihisa , Murase Takashi , Ishizaki Seiji , Tachikawa Kazushige , Arima Hiroshi , Miura Yoshitaka , Usdin Ted B. , Oiso Yutaka 
Published: April 2003

AbstractTuberoinfundibular peptide of 39 residues (TIP39) is a recently discovered neuropeptide identified on the basis of its ability to activate the PTH2 receptor, and it is thought to be the brain PTH2 receptor’s endogenous ligand. The PTH2 receptor is highly expressed in the hypothalamus, suggesting a role in the modulation of neuroendocrinological functions. PTHrP, which also belongs to the PTH-related peptides family, stimulates arginine vasopressin (AVP) release. In the present study, therefore, we investigated the effect of centrally administered TIP39 on AVP release in conscious rats. Intracerebroventricular administration of TIP39 (10–500 pmol/rat) significantly suppressed the plasma AVP concentration in dehydrated rats, and the maximum effect was obtained 5 min after administration (dehydration with 100 pmol/rat TIP39, 4.32 ± 1.17 pg/ml; vs. control, 8.21 ± 0.70 pg/ml). The plasma AVP increase in response to either hyperosmolality [ip injection of hypertonic saline (HS), 600 mosmol/kg] or hypovolemia [ip injection of polyethylene glycol (PEG)] was also significantly attenuated by an intracerebroventricular injection of TIP39 (HS with 100 pmol/rat TIP39, 2.65 ± 0.52 pg/ml; vs. HS alone, 4.69 ± 0.80 pg/ml; PEG with 100 pmol/rat TIP39, 4.10 ± 0.79 pg/ml; vs. PEG alone, 6.19 ± 0.34 pg/ml). Treatment with naloxone [1.5 mg/rat, sc injection], a nonselective opioid receptor antagonist, significantly reversed the inhibitory effects of TIP39 on AVP release. These results suggest that central TIP39 plays an inhibitory role in the osmoregulation and baroregulation of AVP release and that intrinsic opioid systems are involved in its mechanism.
Spectroscopic Implications for Magnetic Interactions in Metal Complexes with Nitroxide Radicals
Authors: Kaizaki Sumio 
Published: April 2003

Abstract
The influence of the magnetic interaction between a paramagnetic metal ion and a radical ligand upon the spectroscopic (UV-vis and/or NMR) properties will be described and discussed mainly for the mixed ligand complexes, M(L)(X) (M = Ni(II), Cr(III); L = nitroxide radicals such as NIT2py (2-(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-3-oxide-1-oxyl) or IM2py (2-(2-(pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxy), X = β-diketonates). For the Ni(II) and Cr(III) complexes, the spin-forbidden d–d bands demonstrated some intensity enhancement and the charge transfer band from the d orbital to the SOMO π* newly appeared in the visible region. Their variable temperature UV-vis spectra substantiated the antiferromagnetic and ferromagnetic interactions as revealed by the magnetic susceptibility measurements. The spectroscopic behaviors with variation of the β-diketonates is examined in connection with magnetic interaction constant J values, exhibiting the coligand effect, e.g., in terms of the exchange mechanism. For the Mn(II), Co(II), Ni(II), and Ln(III) complexes with the NIT2py and/or IM2py or their derivatives and for the Cr(III) and diamagnetic Co(III) complexes with monodentate NIT3- or 4py and IM3- or 4py, the spectroscopic properties are also found to be influenced to the d orbitals from the coordinated nitroxides.
Copper(I) Ion Mediated Self-Assembly of Triple-Stranded Helicates from Oligo(2-ethynylpyridines): Synthesis, Structure, and Properties
Authors: Kawano Tomikazu , Kato Takahiro , Du Chong-Xu , Ueda Ikuo 
Published: April 2003

Abstract
The reaction of oligo(2-ethynylpyridines) (L1–L8) with copper(I) ions proceeded smoothly to afford tri-, tetra-, and pentanuclear triple-stranded helicates (CL1–CL8) in good yields. If a chiral ligand was used, the stereoselective self-assembly of chiral helicates with one particular chirality was achieved in the solid state. Racemization of copper(I) helicates was also observed in solution.
Does the Hydroperoxo Species of Cytochrome P450 Participate in Olefin Epoxidation with the Main Oxidant, Compound I? Criticism from Density Functional Theory Calculations
Authors: Kamachi Takashi , Shiota Yoshihito , Ohta Takehiro , Yoshizawa Kazunari 
Published: April 2003

Abstract
Ethylene epoxidation by an iron(III)-hydroperoxo model of cytochrome P450 Fe(OOH)(C20N4H12)(SCH3) is investigated with the B3LYP density functional theory (DFT) method to look at whether or not the iron(III)–hydroperoxo species can participate in olefin epoxidation with the iron(IV)–oxo species (compound I). The answer is negative. There are two possible entrance channels in the epoxidation reaction, a proximal oxygen transfer mechanism and a distal oxygen transfer mechanism, both mechanisms being stepwise processes involving radical intermediates. In the proximal oxygen transfer mechanism, the homolytic cleavage of the Fe–O bond of the iron(III)–hydroperoxo species initially occurs with a change in the Fe atomic charge from +3 to +2. The proximal oxygen transfer mechanism involves an energetically less stable radical •CH2CH2(OOH). In contrast, in the initial stages of the distal oxygen transfer mechanism, the O–O bond of the hydroperoxo ligand is homolytically cleaved, and the iron(IV)–oxo complex thus formed retains a weak interaction with the hydroxy group of the resultant radical intermediate involving •CH2CH2(OH). This mechanism is more realistic, but the activation energy of the transition state of the O–O bond cleavage is comparable to that of the corresponding transition state by hydrogen peroxide. The present result suggests that the mechanism and energetics of ethylene epoxidation remain unchanged by the involvement of the iron–porphyrin complex. The epoxidation of ethylene by a compound I model is also calculated to increase our understanding of olefin epoxidation by P450. The mechanism and energetics of olefin epoxidation by iron(III)–hydroperoxo species are less plausible than epoxidation by compound I.
A Subsidy-Surplus Model and the Skorokhod Problem in an Orthant
Authors: Ramasubramanian S. 
Published: April 2003

We consider the deterministic Skorokhod problem in an orthant of the form [Formula: see text] with (Yw)i(·) nondecreasing, and (Yw)i(·) not increasing while (Zw)i(·) > 0. This can be viewed as a subsidy-surplus model in an interdependent economy. Existence of a unique solution is established under fairly general conditions (viz. with R(·, ·, ·) satisfying a uniform spectral radius condition). Comparison result for (SP) vis-a-vis the usual partial order on the orthant is studied; we show that the more “inward looking” the reflection vectors and the drift, the larger the values of Yw will be but the values of Zw will be smaller. In addition to showing that the Leontief-type output is a feasible subsidy, connection between (SP) and “minimality” of feasible subsidies is discussed (consequently it is suggested that (SP) may be taken as a continuous time feedback-form analogue of open Leontief model). In the stochastic case, (Y(t), Z(t)) turns out to be a strong Markov process if w(·) arises from aLevy process. Relevance of the comparison result to recurrence/positive recurrence of Z(·) process is pointed out.
The Optimal Performance of the Global Firm: Formalizing and Extending the Integration- Responsiveness Framework
Authors: Devinney Timothy M. , Midgley David F. , Venaik Sunil 
Published: April 2003

With the increasing globalization of business, there has been growing interest in how to create and manage a successful international enterprise. Although researchers and practitioners have grappled with the issue of globalization for some time, there is no one model that encompasses the range of phenomena we observe in the global economy, nor have those models that do exist been precisely formalized. This paper provides an expanded approach to thinking about the organizational forms and linkages that exist in international business operations. Building on the popular integration-responsiveness framework of international strategic orientation, we develop a more expansive approach that is better able to account for the diversity of organizational forms and strategic choices open to managers. By adding a third set of environmental pressures, incorporating the beliefs of managers, and by employing the idea of efficient frontiers, we reformulate the integration-responsiveness framework, making it more consistent with modern economic models of the firm. Our integration-responsiveness-completeness (IRC) model argues that global firms can respond to these fundamental and competing pressures by configuring themselves in a variety of ways—rather than normatively prescribing that the transnational form is optimal. In addition, our model has methodological ramifications. Its formal structure suggests that empirical techniques that focus on the best rather than average performance are necessary to adequately investigate the performance differences among alternative organizational forms. This may explain the paradoxical lack of empirical support for a link between organizational form and performance.
Prader‐Willi syndrome and the evolution of human childhood
Authors: Haig David , Wharton Robert 
Published: April 2003

AbstractThe kinship theory of genomic imprinting predicts that imprinted genes have effects on asymmetric kin (relatives with different degrees of matrilineal and patrilineal relatedness). The most important interaction with such a relative is a child's interaction with its mother. Therefore, the study of imprinted genes and their phenotypic effects promises to provide insights into the evolution of mother–child relations. Prader‐Willi syndrome (PWS) is caused by the absence of expression of genes at 15q11–q13 that are normally expressed only when paternally derived. The kinship theory predicts that children with PWS will fail to express behaviors that have increased mothers' costs of child‐rearing. Our analysis focuses on aspects of the PWS phenotype that affect appetite and feeding. Immediately after birth, children with PWS have little appetite and are usually unable to suckle, but at some stage (usually within the first 2 years) they develop a voracious appetite and an obsession with food. We conjecture that this change in appetite reflects evolutionary forces associated with weaning. Immediately after birth, when a child is completely dependent on the breast, poor appetite reduced maternal costs. However, once a child was able to consume supplemental foods, maternal costs would have been reduced by children with increased, nonfastidious appetites. Am. J. Hum. Biol. 15:320–329, 2003. © 2003 Wiley‐Liss, Inc.
Early Developmental conditions and reproductive success in humans: Downstream effects of prenatal famine, birthweight, and timing of birth
Authors: Lummaa Virpi 
Published: April 2003

AbstractGrowth, survival, and breeding success of individuals in populations of wild mammals are influenced by the climatic and nutritional conditions that individuals experience during their early development. Recent findings have shown that early conditions also have consequences for subsequent survival and reproductive performance in humans. Environmental conditions which affect early development of individuals, such as the quality and quantity of nutrition received in utero and infancy, predict the onset of many chronic diseases in adulthood, affect longevity and may also influence a range of measures of reproductive performance in both food‐limited and contemporary Western human populations. These associations are proposed to result from foetal programming, where a stimulus or insult during a critical period early in life may permanently affect body structure, physiology, and metabolism. Here I review studies showing how birthweight, season of birth, or exposure to prenatal starvation affect different aspects of an individual's subsequent reproductive success in humans and the growth, survival, and reproductive performance of the offspring produced. I show that early maternal and environmental conditions can have a large impact on human reproductive strategies and fitness that can span across generations. Am. J. Hum. Biol. 15:370–379, 2003. © 2003 Wiley‐Liss, Inc.
Validation of expert assessment of occupational exposures
Authors: Fritschi Lin , Nadon Louise , Benke Geza , Lakhani Ramzan , Latreille Benoit , Parent Marie‐Elise , Siemiatycki Jack 
Published: April 2003

AbstractBackgroundAssessment by experts may be the best method available for retrospective occupational exposure measurement in community‐based studies. This study was undertaken to examine the validity of occupational exposure assessment by comparing the ratings of experienced raters with previously recorded industrial hygiene measurements.MethodsWe obtained 50 measurements from industrial hygiene records, covering a variety of jobs and substances and created 47 job descriptions around these measurements. Three raters were asked to assess exposure to a checklist of 19 substances (including those substances which had been measured). We estimated the sensitivity of the raters in correctly detecting those substances known to have been present.ResultsUsing a liberal criterion for the ratings, the average sensitivity among the raters was 90%. Using a more stringent criterion, the average sensitivity was 73%. Among substances coded as present, the raters were quite accurate in rating the relative concentration and frequency of exposure.ConclusionsThis trial demonstrated that a team of experienced raters could successfully characterize jobs in which important exposures occurred. Am. J. Ind. Med. 43:519–522, 2003. © 2003 Wiley‐Liss, Inc.
Individual and combined impacts of biomechanical and work organization factors in work‐related musculoskeletal symptoms
Authors: Huang Grant D. , Feuerstein Michael , Kop Willem J. , Schor Kenneth , Arroyo Freya 
Published: April 2003

AbstractBackgroundInvestigations of work‐related low back (LB) and upper extremity (UE) disorders have increasingly utilized multivariable models that include biomechanical/physical and work organization factors. However, the nature of any interactive effects is not well understood.MethodsUsing questionnaires, high and low exposure groups for biomechanical/physical factors, cognitive demands, cognitive processing, interpersonal demands, participatory management, skill discretion, and time pressure for 289 individuals (U.S. Marines) were identified. Musculoskeletal symptom status was also determined by questionnaire. Individual and biomechanical–psychosocial combinations were examined in adjusted multivariable logistic regression analyses.ResultsTime pressure was associated with both LB and UE symptoms (odds ratio(s) (OR) range = 2.13–3.09), while higher biomechanical exposures were risk factors for LB symptoms (OR = 2.07; 95% confidence intervals (CI): 1.00–4.35) and concurrent LB and UE symptoms (OR = 2.80; CI: 1.35–5.83). Greater risks for concurrent LB and UE symptoms were indicated for combinations involving higher biomechanical exposure and: time pressure (OR = 2.21; CI: 1.19–4.10); cognitive demands (OR = 2.25; CI: 1.23–4.09); cognitive processing (OR = 2.08; CI: 1.16–3.75); interpersonal demands (OR = 2.44; CI: 1.35–4.41); participatory management (OR = 2.50; CI: 1.30–4.81). Results did not suggest any interaction between biomechanical and work organization factors.ConclusionsWhile no synergism was indicated, the present findings emphasize the need to consider both biomechanical factors and specific work organization factors, particularly time pressure, in reducing musculoskeletal‐related morbidity. Am. J. Ind. Med. 43:495–506, 2003. Published 2003 Wiley‐Liss, Inc.
Physical properties of high molecular weight acetal resins
Authors: Linton W. H. , Goodman H. H. 
Published: April 2003

AbstractInformation is presented on those physical properties where measurement is greatly facilitated by thermal stability greater than previously known in polyoxymethylenes, and properties of a mechanical nature characteristic of high molecular weight polymeric materials. The high molecular weight polyoxymethylenes studied possess the characteristic properties of a semicrystalline material in the high molecular weight range. The melting point, stiffness, and tensile strength of these materials substantially exceed those for linear polyethylene, which suggests that the effective chain interactions are enhanced by ease of close packing of the chains. High density and high crystallinity are in accord with this picture.
Condensation polymers containing fluorine. II. Physical characterization of linear polyesters from hexafluoropentanediol
Authors: Gouinlock E. V. , Verbanic C. J. , Schweiker G. C. 
Published: April 2003

AbstractA number of fluorinated polyesters have been prepared by condensing hexafluoropentanediol with one or more dibasic acid chlorides, and melting and glass transition temperatures and rates of crystallization have been determined, largely by means of volume dilatometry. The relation between [η] in chloroform at 30° and M̄n for hexafluoropentylene adipate (HFPA) was found to be [η] = 3.20 × 10−5 M̄n. The melting point Tm was found to increase from 34.5° to 104° as the isophthalate content in a series of adipate copolyesters increased from 0 to 100 mole‐%. The glass transition Tg increases from −57° to −31° as isophthalate content increases from 0 to 50 mole‐%. Tg is raised about 6° by the crosslinking of the polyesters. Rates of crystallization were determined for two HFPA samples with M̄n's of 13,000 and 19,500. Maxima in these rates occurred at about ‐13° and ‐15°, respectively. Respective t½ values for (linear) HFPA, vulcanized HFPA, and a copolyester containing 20 mole‐% isophthalate are 48, 1140, and 27,200 min., respectively, at ‐10°. All the crystallization isotherms conform to Avrami's equation, (Vt − V∞)/(Vt − V∞) = exp {−αt″} for n = 6 over the initial stages of the process. At 1° both HFPA isotherms agree with the above equation over a large part of the process; however, as the isotherm temperature decreases, the equilibrium degree of crystallinity, as judged by the overall specific volume change, decreases and the isotherms diverge from Avrami's equation over progressively larger portions of the process. The product of the maximum rate of crystallization for each isotherm with either t½ or τi, the “induction time,” decreases with decreasing temperature, as would be expected in view of Avrami's equation. The value of 6 observed for n, a constant determined by the nucleation and growth mechanisms, is anomalous since only values of 1 to 4 are theoretically predictable. Values over the range of 1 to 4 have been observed experimentally by other workers for a variety of polymers.
Glass transition in polymers
Authors: Saito Shogo , Nakajima Tatsuji 
Published: April 2003

AbstractGlass transition phenomena in several polymers were studied by dielectric and dilatometric measurements. The dielectric measurements were made over the frequency range of 10−4 or 10−1 to 106 cycles/sec. and the temperature range of the glass transition. In the dilatometric study, volume relaxation curves and volume vs. temperature curve were obtained. The transition in three amorphous polymers, (polyvinyl acetate, polystyrene, and polymethyl methacrylate), depends upon frequency or rate of cooling and seems to be an apparent transition. In three crystallizable polymers, (vinylidene chloride‐vinyl chloride copolymer, polyethylene terephthalate, and polyacrylonitrile), the magnitude of the dielectric absorption decreases steeply with decreasing temperature in the transition range, and the transition by the volume expansion remains when equilibrium is attained. The transition in the three crystallizable polymers seems to be a real one. Temperature dependences of the activation energies of the dielectric relaxation processes have been described.
Determination of degree of crosslinking in natural rubber vulcanizates. Part IV. Stress‐strain behavior at large extensions
Authors: Mullins L. 
Published: April 2003

AbstractDepartures from behavior predicted by the statistical theory of rubberlike elasticity, which occur at high extensions, are ascribed to the finite extensibility of network chains. By use of a non‐Gaussian statistical theory, a relation is obtained between the extension ratio λ*, the extension at which departures are small but significant and the degree of crosslinking. Experimental results on the dependence of λ* on the degree of crosslinking and on the degree of swelling are in good agreement with theoretical predictions. It is shown that the additional determination of λ* permits the calculation of both the degree of crosslinking and the extent of network flaws due to chain ends, from a single simple extension stress‐strain curve. The calculation of these two basic parameters has hitherto been unattainable from measurements on vulcanized rubbers alone. This development provides a new technique of particular value in studies of the degradation of vulcanized networks.
Anisotropy in thermoplastic moldings and their impact strength
Authors: Keskkula Henno , Norton J. W. 
Published: April 2003

AbstractThe machanical anisotropy of several thermoplastic polymers has been investigated, and the relationship with a practical dart drop impact measurement has been explored. It has been shown that the unnotched Izod impact strength of a specimen taken perpendicular to flow orientation can be correlated with the dart drop impact strength. Further, the effect of several dart drop test variables, such as drop height, dart tip radius, and specimen size, have been investigated and reported. It has been concluded that the conventional strength measurement of injection‐molded specimens may lead to erroneous appraisal of the practical strength of a material. Testing at an orientation normal to flow or by multiaxial stressing as in a dart drop test is suggested.
The effect of radiation on the melt index of polyethylene
Authors: Harper B. G. 
Published: April 2003

AbstractFive different types of polyethylene were irradiated in air and their melt indices determined as a function of the radiation dose. A resonant transformer electron beam generator was the source of radiation, and cellophane dye dosimetry was used to determine the radiation dose. The melt index was found to change uniformly with dose, and a single empirical equation was derived which describes the curves for all five types of polyethylene. By using the melt index as a measure of crosslinking, it was shown that the effect of radiation intensity on crosslinking is negligible.