bluuebunny/crossref_metadata_2025 huggingface dataset:
Two‐dimensional crystallization of rabbit C‐reactive protein on lipid monolayers
Authors: Sui Sen-fang , Liu Zheng , Li Wei , Xiao Caide , Wang Shaoxiong , Gao Qiufeng , Zhou Qingzhong
Published: July 2002

Two‐dimensional (2D) crystals of rabbit C‐reactive protein (CRP) have been obtained by protein binding on lipid monolayers at the air/water interface. Two different types of crystalline arrays of CRP were obtained, by specific binding and non‐specific adsorption to the lipids. Electron crystallographic analysis of the negatively stained specimens showed that the unit cell parameters of the CRP 2D crystals formed by specific binding were , and those formed by non‐specific adsorption were , both with the layer group p1. Projection maps were obtained at a resolution of 26 Å and 22 Å respectively. They showed that only the monomers of the CRP were packed in the 2D arrays and the orientations of the monomers on the lipid monolayers were different in the two types of crystals. By comparing the two projection maps, a preliminary shape of the CRP monomer has been derived. A model of the pentameric structure of the oligomeric CRP has been proposed.
Increased susceptibility of low‐density lipoprotein (LDL) to oxidation by γ‐radiolysis with age
Authors: Khalil Abdelouahed , Wagner J.Richard , Lacombe Guy , Dangoisse Vincent , Fülöp Tamàs
Published: July 2002

The susceptibility to oxidation of freshly isolated LDL from healthy normolipidemic individuals in three age groups was estimated by exposure of LDL to ionizing radiation followed by analyses of vitamin E, TBARS, conjugated dienes, and fluorescent products. The results clearly showed that LDL from elderly subjects was the most susceptible to oxidative damage in vitro. In particular, the greater susceptibility of LDL from elderly subjects in comparison to that from young subjects may be attributed to the much lower (4‐fold) concentration of LDL vitamin E in the elderly subjects. The present study reinforces the notion that the susceptibility of LDL to oxidation increases with age.
Acetyl‐l‐carnitine restores choline acetyltransferase activity in the hippocampus of rats with partial unilateral fimbria‐fornix transection
Authors: Piovesan Paola , Quatrini Gianni , Pacifici Licia , Taglialatela Giulio , Angelucci Luciano
Published: July 2002

Transection of the fimbria‐fornix bundle in adult rats results in degeneration of the septo‐hippocampal cholinergic pathway, reminiscent of that occurring in aging as well as Alzheimer disease. We report here a study of the effect of a treatment with acetyl‐l‐carnitine (ALCAR) in three‐month‐old Fischer 344 rats bearing a partial unilateral fimbria‐fornix transection. ALCAR is known to ameliorate some morphological and functional disturbances in the aged central nervous system (CNS). We used choline acetyltransferase (ChAT) and acetyl cholinesterase (AChE) as markers of central cholinergic function, and nerve growth factor (NGF) levels as indicative of the trophic regulation of the medio‐septal cholinergic system. ChAT and AChE activities were significantly reduced in the hippocampus (HIPP) ipsilateral to the lesion as compared to the contralateral one, while no changes were observed in the septum (SPT), nucleus basalis magnocellularis (NBM) or frontal cortex (FCX). ALCAR treatment restored ChAT activity in the ipsilateral HIPP, while AChE levels were not different from those of untreated animals, and did not affect NGF content in either SPT or HIPP.
Modulation of interleukin‐1 receptos in the neuro‐endocrine‐immune axis
Authors: Takao T. , Hashimoto K. , De Souza E.B.
Published: July 2002

Interleukin‐1 (IL‐1) receptors with kinetics, pharmacological and biochemical characteristics of type I IL‐1 receptors have been identified in the mouse neuro‐endocrine‐immune axis. In the present study, we examined the in‐vitro and in‐vivo modulation of IL‐1 receptors by stress and endotoxin treatment. The treatment of AtT‐20 mouse pituitary adenoma cells for 24 hr with neuro‐endocrine mediators of stress such as corticotropin releasing factor (CRF) and catecholamine (β2 adrenergic) receptor agonists produced a dose‐dependent increase in cAMP and [125I]IL‐1α binding. In contrast, somatostatin and dexamethasone significantly inhibited CRF‐stimulated cAMP production and decreased both basal and CRF‐mediated increase of [125I]IL‐1α binding. Furthermore, in keeping with the effects of stress mediators to upregulate IL‐1 receptors in AtT‐20 cells, ether‐laparotomy stress in mice resulted in a significant increase in [125I]IL‐1α binding in the pituitary with no significant alterations observed in the brain; in contrast, [125I]oCRF binding in the pituitary was significantly decreased after the ether‐laparotomy stress.

Next, we investigated the modulation of IL‐1β levels and [125I]IL‐1α binding following endotoxin lipopolysaccharide (LPS) treatment. IL‐1β levels were dramatically increased in the peripheral tissues (pituitary, tests and spleen) at 2–6 hr after a single LPS injection (30 μg LPS/mouse) However, no significant changes were observed in brain (hippocampus and hypothalamus). [125I]IL‐1α binding in the pituitary gland, liver, spleen and testis was significantly decreased at 2 hr following a single administration of both low (30 μg LPS/mouse) and high (300 μg LPS/mouse) doses of endotoxin. [125I]IL‐1α binding in the hippocampus was not significantly altered at 2 hr by a low dose of LPS and was significantly decreased by high dose administration of LPS (300 μg/mouse). Following two LPS injections (at 0 and 12 hr), dramatic increases in IL‐1β concentrations in the hypothalamus, hippocampus, spleen and testis were observed at 2 hr after the second LPS injection; a small but statistically nonsignificant change was evident in the pituitary. Moreover, dramatic decreases in [125I]IL‐1α binding were seen after two injections of 30 μg LPS/mouse in both central and peripheral tissues. These data provide further support for a role for IL‐1 in co‐ordinating neuro‐endocrine‐immune responses to stress and infection.
Melanotrope dopamine D2 receptor isoform expression in the developing rat pituitary
Authors: Chronwall Bibie M. , Sands Scott A. , Dickerson Daniel S. , Sibley David R. , Gary Keith A.
Published: July 2002

This study measured melanotrope mRNA and protein expression for the dopamine D2 receptor, and its long isoform, in relation to the appearance of dopamine in axons of the postnatal rat pituitary intermediate lobe. At postnatal day 2, prior to the onset of dopaminergic innervation, D2 receptor (D2T) mRNA was expressed heterogeneously in a subpopulation of melanotropes which also expressed the long isoform (DL). The D2L mRNA appeared to be predominant during early postnatal development, since the D2T probe, which did not discriminate between the isoforms, and the D2L probe hybridized generally to the same cells, as demonstrated in serial sections. Immunohistochemical methods, using two different antisera for the D2T receptor, however, indicated a low level of protein in most melanotropes. Localization of D2L protein corresponded well to D2L receptor mRNA distribution. At day 10, representing a time when dopamine is present in axons throughout the lobe, both D2T receptor mRNA and protein were detected in a significantly larger population of melanotropes than those expressing D2L mRNA and protein. This suggests the appearance of detectable short isoform (D2S) mRNA in virtually all melanotropes and implicates dopamine as a possible signal for increasing D2S isoform mRNA expression.
Regional differences in in vitro growth of neural cell processes during development
Authors: Colombo J.A. , Napp M. , Medana A.
Published: July 2002

Primary cell cultures from cerebral cortex, striatum and ventral mesencephalon obtained from rat fetal (embryonic day 17, E17) or postnatal (day 2, PN2) donors were grown either in media conditioned by subcultured astroglia from the same regions, an artificial trophic medium, normal human amniotic fluid, or in normal human cerebrospinal fluid. To estimate the presence of neuronal‐like and non‐neuronal cells, cell morphology and immunocytochemistry against microtubule‐associated proteins and β‐tubulin were taken into consideration. The percentage of emitting neural cells and length of cell processes were determined after 24 hr in culture. Growth of cell processes in neuronal and non‐neuronal cells from prenatal striatum was minimal compared with that in cerebral cortex and ventral mesencephalon, regardless of the culture condition. Nerve growth factor, basic fibroblast growth factor or epidermal growth factor did not significantly modify cell growth in E17 cultures, except for epidermal growth factor, which reduced the number of emitting cells in striatal cultures and increased it in cerebral cortex ones. Cultures derived from postnatal striatum showed a significant increase in neurite length when grown in an astroglial conditioned medium as compared to cultures derived from prenatal (E17) striatum. Results suggest significant regional differences in the brain regarding growth of cell processes at age E17, and reversal of striatal ability to grow cell processes by postnatal day 2. Reduced growth of cell processes showed by E17 striatum cultures was rather independent of the culture media. This fact could suggest that such early regional differences would depend on characteristics of sublineages present at this developmental stage, which would modulate the organization of regional neuropils. The restricted growth of cell processes in cultures from E17 striatum, no longer present in postnatal striatum, suggests that inputs to the striatum may modify expression of cell lineages at later stages of development.
Identification of residues in the TPR domain of Ssn6 responsible for interaction with the Tup1 protein
Authors: Gounalaki Niki , Tzamarias Dimitris , Vlassi Metaxia
Published: July 2002

Ssn6, a yeast protein that comprises 10 tandem tetratricopeptide repeat (TPR) motifs, associates with Tup1 repressor protein and acts as a transcriptional corepressor. In this report we identify point mutations in the TPR1 of Ssn6 that disrupt Tup1 interaction. Furthermore, we construct a 3D model of the TPR domain of Ssn6, which is responsible for Tup1 binding, based on the known structure of protein phosphatase 5. According to this model all selected mutations reduce the ability of Ssn6 to interact with Tup1 by affecting the structural integrity of TPR1 and/or the correct spatial arrangement of TPR1 relative to TPR2 and TPR3.
Lectins and traffic in the secretory pathway
Authors: Hauri Hans-Peter , Appenzeller Christian , Kuhn Franziska , Nufer Oliver
Published: July 2002

Evidence is accumulating that intracellular animal lectins play important roles in quality control and glycoprotein sorting along the secretory pathway. Calnexin and calreticulin in conjunction with associated chaperones promote correct folding and oligomerization of many glycoproteins in the endoplasmic reticulum (ER). The mannose lectin ERGIC‐53 operates as a cargo receptor in transport of glycoproteins from ER to Golgi and the homologous lectin VIP36 may operate in quality control of glycosylation in the Golgi. Exit from the Golgi of lysosomal hydrolases to endosomes requires mannose 6‐phosphate receptors and exit to the apical plasma membrane may also involve traffic lectins. Here we discuss the features of these lectins and their role in glycoprotein traffic in the secretory pathway.
Hydrogen peroxide in the human body
Authors: Halliwell Barry , Clement Marie Veronique , Long Lee Hua
Published: July 2002

Hydrogen peroxide (H2O2) is widely regarded as a cytotoxic agent whose levels must be minimized by the action of antioxidant defence enzymes. In fact, H2O2 is poorly reactive in the absence of transition metal ions. Exposure of certain human tissues to H2O2 may be greater than is commonly supposed: substantial amounts of H2O2 can be present in beverages commonly drunk (especially instant coffee), in freshly voided human urine, and in exhaled air. Levels of H2O2 in the human body may be controlled not only by catabolism but also by excretion, and H2O2 could play a role in the regulation of renal function and as an antibacterial agent in the urine. Urinary H2O2 levels are influenced by diet, but under certain conditions might be a valuable biomarker of ‘oxidative stress’.
An intronless gene encoding a poly(A) polymerase is specifically expressed in testis1
Authors: Lee Young Jae , Lee Younghoon , Chung Jae Hoon
Published: July 2002

Previous work demonstrated that a single pre‐mRNA could generate multiple forms of mammalian poly(A) polymerase mRNAs by alternative splicing or alternative polyadenylation. A cDNA encoding a testis‐specific poly(A) polymerase was isolated in this study. The transcription level of Papt in testis of a 2 weeks old mouse was much lower than that of the general poly(A) polymerase gene, Pap. However, the transcription ratio of Papt to Pap was reversed in testis of a 4 weeks old mouse. Transient expression analysis showed that GFP‐Papt fusion protein is present both in the nucleus and cytoplasm of HeLa cells. These results suggest that Papt is involved in polyadenylation of transcripts expressed during spermatogenesis.
The structure and nucleotide occupancy of bovine mitochondrial F1‐ATPase are not influenced by crystallisation at high concentrations of nucleotide
Authors: Menz R.Ian , Leslie Andrew G.W , Walker John E
Published: July 2002

Analysis of tryptophan mutants of F1‐ATPase from Escherichia coli [Löbau et al. (1997) FEBS Lett. 404, 15–18] suggested that nucleotide concentrations used to grow crystals for the determination of the structure of bovine F1‐ATPase [Abrahams et al. (1994) Nature 370, 621–628] would be sufficient to occupy only two catalytic sites, and that higher concentrations of nucleotide would result in all three sites being occupied. We have determined the structure of bovine F1‐ATPase at 2.9 Å resolution with crystals grown in the presence of 5 mM AMPPNP and 5 μM ADP. Similar to previous structures of bovine F1‐ATPase determined with crystals grown in the presence of lower nucleotide concentrations, only two β‐subunits have bound nucleotide and the third subunit remains empty.
The vaccinia virus F17R protein interacts with actin
Authors: Reckmann Inge , Higley Sidney , Way Michael
Published: July 2002

We have examined the possible role of the F17R protein in vaccinia virus‐induced rearrangements of the host actin cytoskeleton. F17R is localized to vaccinia‐induced actin tails late during infection. The recombinant vaccinia strain vRO11k is able to induce actin tails that are indistinguishable from controls in the absence of F17R expression. The association of vaccinia and myxoma virus F17R with the actin cytoskeleton in the absence of additional viral factors suggests a basic region in the N‐terminal half of the protein is important for this interaction. A peptide corresponding to this region efficiently bundles actin filaments in vitro, confirming that the protein interacts directly with actin. Our results show F17R is not required for actin tail formation and highlight the difficulty in discriminating functional actin‐binding proteins from those that associate by virtue of their basic nature.
Simultaneous production of the 34‐kDa and 40‐kDa proteins from Bacillus thuringiensis subsp. thompsoni is required for the formation of inclusion bodies
Authors: Rang Cécile , Bes Martine , Moar William J , Frutos Roger
Published: July 2002

Cooperation of two crystal proteins from Bacillus thuringiensis subsp. thompsoni. strain HnC was shown to be essential for the formation of inclusion bodies. Expression of the operon containing the 34‐kDa and 40‐kDa protein genes from HnC in a B. thuringiensis crystal minus strain resulted in the formation of inclusion bodies identical to those from strain HnC. Interruption of one of the genes in the operon led to the lack of inclusion body and to low production of the remaining protein. Absence of inclusion body and low rate of protein production were also observed when both genes were simultaneously expressed but on different vectors. To show a cooperative effect in the formation of the inclusion body, both proteins must be produced from the same transcript.
The bacterial pigment xanthomonadin offers protection against photodamage
Authors: Rajagopal Lakshmi , Sundari C.Sivakama , Balasubramanian D. , Sonti Ramesh V.
Published: July 2002

Xanthomonas oryzae pv. oryzae is a bacterial pathogen that causes leaf blight, a serious disease of rice. Most members of the genus Xanthomonas produce yellow, membrane bound, brominated aryl polyene pigments called xanthomonadins whose functional role is unclear. We find that pigment‐deficient mutants of X. oryzae pv. oryzae exhibit hypersensitivity to photobiological damage. A clone containing the xanthomonadin biosynthetic gene cluster alleviates the hypersensitivity of the pigment‐deficient mutant. Extracts containing xanthomonadin provide protection against photodynamic lipid peroxidation in liposomes. These results lead us to suggest a role for the pigment, namely protection against photodamage.
Cloning, sequencing and expression of the genes encoding the sodium translocating N5‐methyltetrahydromethanopterin:coenzyme M methyltransferase of the methylotrophic archaeon Methanosarcina mazei Gö1
Authors: Lienard Tanja , Gottschalk Gerhard
Published: July 2002

The N
5‐methyltetrahydromethanopterin:coenzyme M methyltransferase of Methanosarcina mazei Gö1 is a membrane‐associated, corrinoid‐containing protein that uses a transmethylation reaction to drive an energy‐conserving sodium ion pump. The eight open reading frames encoding the eight different subunits of the methyltransferase were identified and sequenced. All of these subunits are shown to be heterologously expressed in minicells of the Escherichia coli mutant DK6. Sequence comparisons with the methyltransferases of thermophilic and hypothermophilic methanogenic archaea are presented. The participation of the gene product of mtrD in sodium ion translocation as well as a consensus sequence of a corrinoid binding motif in MtrA are discussed.
cDNA cloning and mRNA distribution of a mouse very long‐chain acyl‐CoA synthetase
Authors: Berger Johannes , Truppe Christina , Neumann Heidemarie , Forss-Petter Sonja
Published: July 2002

The interaction of the adrenoleukodystrophy protein (ALDP), mutated in the peroxisomal disorder X‐linked adrenoleukodystrophy, and the very long‐chain acyl‐CoA synthetase (VLACS), the enzyme whose function is missing in this disease, remains obscure. As a first step to studying this interaction in wild type versus ALDP‐deficient mice, we have cloned a VLACS cDNA from mouse liver. The 1860 bp open reading frame encodes a 620 amino acid protein with a predicted molecular mass of 70.3 kDa. By Northern blot analysis, a 2.6 kbp VLACS mRNA was highly abundant in liver and kidney and present at low levels in brain and testes. By RT‐PCR VLACS mRNA was also detected in heart and lung but remained undetectable in skeletal muscle and spleen. In contrast to the peroxisomal β‐oxidation marker acyl‐CoA oxidase, whose mRNA level steadily increases during brain development, the VLACS transcript was found at a constant low level from embryo through adulthood, suggesting that additional isoforms may exist in brain.
On the expression of cytosolic calcium‐independent phospholipase A2 (88 kDa) in immature and mature myeloid cells and its role in leukotriene synthesis in human granulocytes
Authors: Larsson Forsell Pontus K.A. , Runarsson Gudmundur , Ibrahim Mirna , Björkholm Magnus , Claesson Hans-Erik
Published: July 2002

The human calcium‐independent phospholipase A2 (iPLA2; 88 kDa) has recently been cloned (Larsson, P.K.A., Claesson, H.‐E. and Kennedy, B.P. (1998) J. Biol. Chem. 272, 207–214). Here we demonstrate the expression of the human iPLA2 mRNA and its splice variants in blood progenitor cells, immature leukemic cells and mature granulocytes. Chromatographical resolvable iPLA2 activity was found in the cytosolic fraction of granulocytes and the activity was inhibited by the iPLA2 inhibitor bromoenol lactone. This drug also inhibited leukotriene synthesis in human granulocytes, induced by low concentration of calcium ionophore A23187 (0.10–0.15 μM) or opsonized zymosan. These results suggest that iPLA2 is involved in the regulation of the pool of arachidonic acid destined for leukotriene synthesis in human granulocytes.
An ABC transporter homologous to TAP proteins
Authors: Yamaguchi Yoko , Kasano Miki , Terada Tomoyuki , Sato Ryuichiro , Maeda Masatomo
Published: July 2002

Polymerase chain reaction amplification of cDNA from rat intestine revealed the expression of a novel ABC transporter, TAPL (TAP‐like). Subsequently, the protein sequence was deduced from the nucleotide sequence of cDNA carrying the entire coding region. TAPL is transcribed ubiquitously in various rat tissues. The protein, with 762 amino acid residues, has potential transmembrane domains, and an ATP‐binding domain in its amino and carboxyl terminal regions, respectively, and is highly homologous to TAP1 and TAP2 (transporters associated with antigen presentation/processing): pairwise comparisons with TAPL demonstrated 39 and 41% of the residues are identical, respectively. These numerical values are essentially the same as that for TAP1 and TAP2 (39%), and the hydropathy profiles of TAPL, TAP1 and TAP2 are quite similar. The similarity among these three proteins suggests that they could be derived from a common ancestral gene. Furthermore, we found that there is a potential splicing isoform, sharing the amino terminal 720 amino acid residues of TAPL.
An in vivo assay for the identification of target proteases which cleave membrane‐associated substrates
Authors: Steiner Harald , Pesold Brigitte , Haass Christian
Published: July 2002

Proteases not only play a fundamental role in numerous physiological processes, but are also involved in several human diseases including Alzheimer's disease (AD). A key protease implicated in AD is the so far unidentified γ‐secretase, which cleaves the membrane‐bound β‐amyloid precursor protein (βAPP) at the C‐terminus of its amyloid domain within the membrane to release the neurotoxic amyloid β‐peptide. In order to allow the isolation of proteases, which specifically cleave membrane‐bound substrates within or in the vicinity of a transmembrane domain, we developed a reporter gene assay in Saccharomyces cerevisiae. This assay may allow the identification of genes encoding target proteases that specifically cleave membrane bound substrates by transforming expression libraries.
Concurrent engineering and its consequences
Authors: Koufteros Xenophon , Vonderembse Mark , Doll William
Published: July 2002

Technology and market changes introduce uncertainty and equivocality in the product development arena, and firms are considering various structural relationships to help them cope with these changes. Concurrent engineering (CE) is a mechanism that can reduce uncertainty and equivocality and improve an organization’s competitive capabilities. CE is typically manifested through concurrent work‐flows, product development teams, and early involvement of constituents. It enables information to flow through the organization quickly and effectively thereby, reducing uncertainty. At the same time, it enables debate, clarification, and enactment which are essential elements in combating equivocality. CE practices are also purported to have significant effects on product innovation, quality, and premium price capabilities.

This research carefully defines CE and creates a valid and reliable instrument to assess it. It reports on the development and testing of a model that relates CE to some of its most salient consequences. Half of the sample of 244 firms is used for exploratory purposes and half for confirmatory work and hypotheses testing. Results indicate that firms that experience a high technological and product change in their environment are using more CE practices. In addition, results suggest that CE practices have significant direct effects on product innovation. However, only the indirect effects of CE on quality and premium pricing are statistically significant. Firms with higher levels of product innovation have higher levels of quality. Firms with higher levels of product innovation do exhibit premium pricing capabilities but only if they affect quality capabilities. Firms that display elevated quality levels excel in their premium pricing capabilities.
The rediscovery of postponement a literature review and directions for research
Authors: van Hoek R.I
Published: July 2002

The concept of postponement is increasingly drawing the attention of researchers and practitioners. Postponement means delaying activities in the supply chain until customer orders are received with the intention of customizing products, as opposed to performing those activities in anticipation of future orders. This paper reviews the literature on postponement dating back to 1965, and puts it in a systematic framework. In light of the classification of the literature developed, opportunities are identified for integration and cross‐fertilization between research papers in disciplines such as logistics and operations management and between the variety of research methods used. Some directions for research (in terms of content and methodology) are then formulated. For instance, the development of a more integrated supply chain perspective on postponement, and the application of triangulation rather than single methods. Specific research activities to meet these challenges are suggested in the paper.
E‐services: operating strategy—a case study and a method for analyzing operational benefits
Authors: Boyer Kenneth K. , Hallowell Roger , Roth Aleda V.
Published: July 2002

The Internet’s influence in creating e‐services has been revolutionary for providers and their customers. Unfortunately, there has been a wide gap between inspiring applications of the Internet that help increase service customization while maintaining or even improving delivery efficiency, and downright flops in which companies that have made bold promises have failed to deliver on even a portion of their pledges. This paper provides an examination of e‐services utilizing three approaches in order to provide guidance on how to fly rather than flop. First, we develop a model of the e‐service customer retention. Second, we offer a case study of Sothebys.com to illustrate how a well‐known, but not typically technologically adventurous, company can utilize e‐services to expand its offerings and streamline its services. Finally, we offer a profiling technique for analyzing the benefits and challenges of e‐services for particular industries.
Evaluating and classifying POM journals
Authors: Goh Chon‐Huat , Holsapple Clyde W. , Johnson Linda Ellis , Tanner John R.
Published: July 2002

A multitude of journals impact the production and operations management (POM) discipline. POM researchers, practitioners, and students all need objective means of rating these journals' impacts on the field. By applying an established multifaceted citation‐based methodology, journals are assigned to categories (elite and major) along each of four dimensions (breadth, consistency, trend, and intensity of recognition) and subsequently organized into distinct tiers of importance to the production and operations management field. The data underlying this study consist of 13,992 periodical citations that appeared in three prominent POM journals over a recent five‐year period.
The impact of quality on learning
Authors: Li George , Rajagopalan S
Published: July 2002

The strategic importance of learning curves has been recognized for a long time both in industry and in academia, but little is known about the huge difference in rates at which different firms learn. Recent theoretical studies and anecdotal evidence from Japanese manufacturing firms suggest that quality‐related activities may be one major factor explaining the difference in learning rates. When the impact of quality on learning is considered, three important questions arise: (1) How well does cumulative output of defective or good units explain learning curve effects? (2) Do defective units explain learning curve effects better than good units? (3) How should cumulative experience be represented in the learning curve model when the quality level may have an impact on learning effects? This paper presents, to our knowledge, the first empirical study addressing these questions. Using time series data from two manufacturing firms, we find that cumulative output of defective or good units is statistically significant in explaining learning curve benefits. However, defective and good units do not explain learning curve effects equally as is implicitly assumed in traditional learning curve models. In particular, defective units are statistically more significant than good units in explaining learning curve effects.
Assessing production and operations management related journals: the European perspective
Authors: Soteriou Andreas C. , Hadjinicola George C. , Patsia Kalia
Published: July 2002

Following the evolution and growth of the field of production and operations management (POM), a number of studies have recently appeared which provide insights on the ranking of the research outlets of the field. These studies are US‐based and exclude non‐US researchers. In this study we present rankings of the publication outlets in the POM discipline as perceived by POM researchers in Europe. Perceived relevance and quality of POM related journals, and differences between the rankings obtained by our study and those obtained by existing studies are identified. An examination of the publication rate of European researchers in five highly ranked journals provides further insights and future research directions.
Ethical issues in international buyer–supplier relationships: a dyadic examination
Authors: Carter Craig R
Published: July 2002

The author combines extant literature with findings from focus group interviews and a set of surveys to identify the ethical issues involved in relationships of US purchasing managers and their non‐US suppliers. Survey data from matched sets (dyads) of buyers and suppliers is then used to examine the influence of unethical behavior on the satisfaction with the relationship and on supplier performance.
The theory of performance frontiers
Authors: Vastag Gyula
Published: July 2002

This paper seeks to illustrate how the basic theory of performance frontiers proposed by Schmenner and Swink [Schmenner, R.L., and Swink, M.L., 1998. On theory in operations management. Journal of Operations Management, 17, 97–113] can be extended to apply to a broader range of operations management issues. It extends the scope of the proposed theory to include a “between‐firm” level analysis which can be useful in assessing a firm's competitive position and for strategic decision making. In addition, this paper provides a link between the resource‐based view of organizations that has gained some prominence in the strategy literature and the proposed theory of performance frontiers. This paper argues that the operating frontiers of organizations represent unique resources and they are more important than the asset frontiers in achieving a competitive advantage because these unique resources are valuable, rare and specific to a given firm, and they are difficult to replicate. Future research directions and research methods focusing on the internal resources of competitive advantage are also discussed.
On the existence of a positive solution of semilinear elliptic equations in unbounded domains
Authors: Bahri Abbas , Lions Pierre-Louis
Published: July 2002

We prove here the existence of a positive solution, under general conditions, for semilinear elliptic equations in unbounded domains with a variational structure. The solutions we build cannot be obtained in general by minimization problems. And even if Palais-Smale condition is violated, precise estimates on the losses of compactness are obtained by the concentration-compactness method which enables us to apply the theory of critical points at infinity.

Nous prouvons dans cet article l’existence d’une solution positive, sous des conditions générales, pour des équations semilinéaires elliptiques dans les domaines non bornés avec une structure variationnelle. Les solutions obtenues ne peuvent être en général obtenues par des problèmes de minimisation. Bien que la condition de Palais-Smale n’ait pas lieu, des estimées précises sur les pertes de compacité sont déduites de la méthode de concentration-compacité et nous permettent d’appliquer la théorie des points critiques à l’infini.
Carbon filaments direct the growth of postlesional plastic axons after spinal cord injury
Authors: Chauhan Neelima B. , Figlewicz Helen M. , Khan Talat
Published: July 2002

The effect of implantation of carbon filaments and fetal tissues on the axonal regeneration following contusion injury in a rat model was investigated by in situ immunofluorescence. Female Sprague‐Dawley rats were subjected to severe contusion injury to the spinal cord at T9–T10. All animals were divided into 5 groups (N=5/group): normal controls, surgical controls, with carbon filament implants, with fetal tissue implants and with implants consisting of fetal tissue cocultured with carbon filaments. After a 10‐week survival period, the astroglial response was assessed by immunoreactive glial fibrillary acidic protein and the neuro‐axonal profile by immunoreactive phosphorylated and nonphosphorylated neurofilament proteins. The contusion injury resulted in: (a) dramatically increased immunoreactivity of glial fibrillary acidic protein indicating injury‐associated reactive astrogliosis, (b) increase in immunoreactive phosphorylated neurofilament protein indicating upregulated phosphorylation of neurofilament protein, (c) with no change in the highly differentiated nonphosphorylated neurofilament protein which normally occur in the nonregenerating mature neurons. Implantation of fetal tissues alone following contusion injury did not show any appreciable change with regard to the immunoreactivities for the glial and neuronal markers studied, compared to the injury controls. However, the implantation of carbon filaments alone or together with fetal tissues directed the growth of glial fibrillary acidic protein‐positive astroglia and phosphoneurofilament‐positive neurites along the carbon fibers, with no effect on nonphosphoneurofilament protein. In conclusion, implantation of carbon filaments appears to be critical for facilitating the attachment of astroglia forming a substrate and scaffolding that can further support and direct the growth of postlesional plastic axons across the lesion. In addition, carbon filament prostheses in combination with fetal tissue implants provides an improved combinational approach to promote regrowth of injured neurons following injury.
Thromboembolism in heart failure: who should be treated?
Authors: Diet Frank , Erdmann Erland
Published: July 2002

The risk of thromboembolic complications in patients with heart failure and/or chronic left‐ventricular systolic dysfunction is increased. Nevertheless, anticoagulant therapy in these patients is still a subject of debate. Atrial fibrillation is the only prospectively evaluated, proven thromboembolic risk factor and patients with atrial fibrillation benefit from long term anticoagulant therapy. The significance of other proposed thromboembolic risk factors in heart failure and/or chronic left‐ventricular dysfunction such as gender, cause of myocardial disease, severity of heart failure, left‐ventricular ejection fraction, left‐ventricular thrombus, left ventricular aneurysm and history of previous thromboembolic event is less clear. This article summarizes key studies, assesses the incidence of thromboembolism, evaluates risk factors and proposes guidelines for anticoagulation of patients with heart failure and/or left ventricular systolic dysfunction.
Aquificales
Authors: Bonch‐Osmolovskaya Elizaveta
Published: October 2020

Based on 16S ribosomal ribonucleic acid (rRNA) genes sequence comparisons, the order Aquificales represents a phylum Aquificeae, a very deep phylogenetic branch within the bacterial domain. It consists of two families, Aquificaceae and Hydrogenothermaceae. Some Aquificales relatives have an upper temperature limit of growth at 95 °C. Together with members of the order Thermotogales, they represent bacteria with the highest growth temperatures known so far. However, unlike Thermotogales, most of the members of the order Aquificales are lithoautotrophs, using energy of molecular hydrogen, or of reduced sulfur compounds to support their growth. Some Aquificales are able to use other than oxygen electron acceptors and grow anaerobically reducing nitrate, ferric iron or arsenate. Representatives of Aquificales inhabit terrestrial, submarine and deep subsurface thermal environments where they play role of primary organic matter producers. More than 40 genomes of Aquificales have already been sequenced providing access to new genes encoding thermostable enzymes for bioindustry.

Key Concepts

Aquificales represent one of the most ancient lineages of Bacteria.

Aquificales are among the organisms having the highest growth temperatures among Bacteria.

Aquificales are lithoautotrophs utilising inorganic energy substrates of volcanic origin.

Aquificales are widely spread all over the Earth thriving in submarine and terrestrial thermal environments, as well as in subsurface biosphere.

In terrestrial hot springs, some Aquificales form visible biofilms and hair‐like ‘streamers’ utilising hydrogen sulfide and hydrogen dissolved in streaming water.
From Neural Induction in Frogs to Human Brains on Chips
Authors: De Santis R , Brivanlou Ali H
Published: October 2020

The entire nervous system of the vertebrate embryo is derived from an epithelium sheet called the neural plate, which is induced by the organizer/node at the onset of gastrulation. Dissection of the molecular network underlying the emergence of the neural plate, originally performed in
Xenopus
embryos, led to the discovery of the TGFβ double inhibition mechanism for neural induction, coined ‘the default model’. Years later, these developmental principles have been translated
in vitro
to instruct human pluripotent stem cells towards neural fate and to build brain organoids.

Key Concepts

The Spemann organizer is defined by the capability of a group of cells in a transplantation experiment to induce, in a non‐cell‐autonomous fashion, a secondary neural axis and to autonomously differentiate into axial and paraxial mesoderm derivatives.

Neural fate acquisition both
in vivo
in the embryo and
in vitro
from pluripotent stem cells is the result of blocking the ongoing TGFβ pathway, both Activin‐Nodal and BMP branches.

Embryonic stem cells are defined based on two basic properties: their ability to maintain their undifferentiated state (stemness) indefinitely and to be able to differentiate into cell types derived from the three embryonic germ layers (pluripotency).

Brain organoids are 3D
in vitro
structures that resemble several features of the developing human brain.

Human pluripotent stem cells cultured in confined geometry (micropattern) self‐organized into defined embryonic structures with standardised cytoarchitecture and distinct cell fates.
DrosophilaEmbryo: Homeotic Genes in Specification of the Anterior–Posterior Axis
Authors: Rogers Bryan T
Published: October 2020

Embryonic expression of homeotic genes inDrosophila melanogasterimparts the diversity of morphology and cell type along the anterior–posterior axis that is characteristic of its body plan. The homeotic genes encode a related set of nine transcription factors. Each homeotic gene has a unique, temporally dynamic expression pattern, battery of target genes and range of regulatory effects. Changes in any of these three aspects can have dramatic consequences due to the large number of target genes affected. These dramatic effects place the homeotic genes high in the regulatory gene hierarchy of developmental programmes and are sometimes referred to as ‘master regulators’ of identity. The combined action of all nine genes produces a unique cellular pattern of gene activation and repression across the embryo that changes throughout development. The result is the specification of the diverse cells and tissues typical of the animal body in the precise pattern that gives each segment or region its own identity.

Key Concepts

Mutations in Hox genes alter their modulation of underlying developmental programmes and produce homeotic transformations.

The Hox genes ofDrosophila melanogasterare organised into two complexes that arose from a single ancestral complex.

The variation among Hox genes limits the diversity of segment‐specific development.

HOX proteins are transcription factors that bind DNA via the homeodomain which is encoded by the homeobox.

Homeoboxes and homeodomain proteins form a superfamily of which the Hox genes are a small part.

Hox expression and segmentation are initiated by the same regulatory cascade, insuring proper domains of Hox expression.

An important aspect of Hox expression is that it is not static but continually changing during development.

Initiation of Hox expression requires different factors than their maintenance, which depends on the chromatin structure.

By regulating the expression of other regulators such as selector and signal transducing genes, Hox genes greatly magnify the number of genes under their control.

Segmental identity is a consequence of a unique combination of Hox‐regulated events achieved by the dynamic and diverse temporal and spatial expression of Hox genes and the specific target recognition and regulation capabilities of each Hox protein.
A simple dosimetric approach to spatially fractionated GRID radiation therapy using the multileaf collimator for treatment of breast cancers in the prone position
Authors: Murphy Natasha L. , Philip Rino , Wozniak Matt , Lee Brian H. , Donnelly Eric D. , Zhang Hualin
Published: October 2020

The purpose of this study was to explore the treatment planning methods of spatially fractionated radiation therapy (SFRT), commonly referred to as GRID therapy, in the treatment of breast cancer patients using multileaf collimator (MLC) in the prone position. A total of 12 patients with either left or right breast cancer were retrospectively chosen. The computed tomography (CT) images taken for the whole breast external beam radiation therapy (WB‐EBRT) were used for GRID therapy planning. Each GRID plan was made by using two portals and each portal had two fields with 1‐cm aperture size. The dose prescription point was placed at the center of the target volume, and a dose of 20 Gy with 6‐MV beams was prescribed. Dose‐volume histogram (DVH) curves were generated to evaluate dosimetric properties. A modified linear‐quadratic (MLQ) radiobiological response model was used to assess the equivalent uniform doses (EUD) and therapeutic ratios (TRs) of all GRID plans. The DVH curves indicated that these MLC‐based GRID therapy plans can deliver heterogeneous dose distribution in the target volume as seen with the conventional cerrobend GRID block. The plans generated by the MLC technique also demonstrated the advantage for accommodating different target shapes, sparing normal structures, and reporting dose metrics to the targets and the organs at risks. All GRID plans showed to have similar dosimetric parameters, implying the plans can be made in a consistent quality regardless of the shape of the target and the size of volume. The mean dose of lung and heart were respectively below 0.6 and 0.7 Gy. When the size of aperture is increased from 1 to 2 cm, the EUD and TR became smaller, but the peak/valley dose ratio (PVDR) became greater. The dosimetric approach of this study was proven to be simple, practical and easy to be implemented in clinic.
Technical note: Generation of a Cerenkov scatter function convolution kernel for a primary proton beam
Authors: Thompson Steven A.
Published: October 2020

Purpose

To generate a Cerenkov scatter function (CSF) for a primary proton beam and to study the dependence of the CSF on the irradiated medium.

Materials and Methods

The MCNP 6.2 code was used to generate the CSF. The CSF was calculated for light‐pigmented, medium‐pigmented, and dark‐pigmented stratified skin, as well as for a homogeneous optical phantom, which mimics the optical properties of human tissue. CSFs were generated by binning all of the Cerenkov photons which escape the back end (end opposite beam incidence) of a 20 × 20 × 20 cm phantom. A 4 × 4 cm, 500 × 500 bin grid was used to create a histogram of the Cerenkov photon flux on the simulated medium’s back surface (surface opposite beam incidence). A triple Gaussian was then used to fit the data.

Results

From the triple Gaussian fit, the coefficients of the CSF for the four phantom materials was generated. The individual CSF fit coefficient errors, with respect to the Gaussian representation, were found to be between 0.92% and 4.11%. The R2 value for the fit was calculated to be 0.99. The phantom material was found to have a significant effect (63% difference between materials) on the CSF amplitude and full width at half maximum (195% difference between materials). The difference in these parameters for the three skin pigments was found to be small.

Conclusions

The CSF was obtained for a proton beam using the MCNP 6.2 code for a phantom constructed of light, medium, and dark stratified human skin, as well as for an optical phantom. The CSFs were then fit with a triple‐Gaussian function. The coefficients can be used to generate a radially symmetric CSF, which can then be used to deconvolve a measured Cerenkov image to obtain the dose distribution.
Most health apps not safe and effective: ATA
Authors: Knopf Alison
Published: October 2020

Health applications for phones have proliferated, especially since the pandemic. But 85% of them are not safe and effective, according to the American Telemedicine Association (ATA).
Laminate Squeeze Casting and Equibiaxial Bend Behavior of Carbon Fiber Fabric Reinforced Aluminum Matrix Composites
Authors: Tu Zhiqiang , Nganbe Michel
Published: October 2020

The 2D bend behavior of composites fabricated by the new laminate squeeze casting technique is studied. Particular focus is on effects of the initial alternating solid‐state laminate configuration of aluminum 6061 sheets and carbon fiber fabric. Equibiaxial pin‐on‐ring bend tests are performed. It is shown that hydrostatic pressures around 40 MPa are required, which is at the higher end of the range reported for conventional squeeze casting. This is primarily due to the oxide scale on the aluminum layers that can hinder infiltration and weaken the fiber–matrix interface. However, above the threshold squeeze pressure, flexural modulus, yield strength, and strain hardening modulus continuously increase by up to 11.65%, 90.12%, and 248.28%, respectively. The strong strain hardening behavior suggests initial plastic deformation as pre‐condition for full load transfer to the fibers, indicating that the composites are most efficient when pre‐deformed following casting. Moreover, the ultimate flexural strength improves by up to 322.23% at 3.74 vol% with a maximum value of 1050.95 MPa. The major property improvements are primarily due to the possibility offered by the laminate technique to selectively place the reinforcement at critical sections, in this case, close to the composite surfaces with the highest bend stresses.