bluuebunny/crossref_metadata_2025 huggingface dataset:
Spare parts supply modelling: application to a space station
Authors: Pérès François , Grenouilleau Jean‐Christophe
Published: March 2003

The work deals with the topic of spare parts management in a space system. The paper is divided into three parts. The first one is dedicated to the characterization of the system structure and presents the particularities related to the spare‐elements procurement. Modelling is the object of the second part. After having exposed the bases of the problem to be solved, a macro‐model is introduced. Each of the three elements of an orbital system, namely ground, flying and transport, is then described with a Petri net. Operation specificities of every element are then listed and integrated into the model. A concrete application of this modelling is given in the last part. It concerns the Columbus laboratory of the International Space Station. A representative function is selected and several supply strategies are evaluated.
Customer‐focused build‐in reliability: a case study
Authors: Ming Tan Cher
Published: March 2003

Build‐in reliability (BIR) is becoming an essential requirement for product development today. However, the task of BIR can be resource‐intensive since root causes identification is necessary. If a product is complex, the number of possible failure modes can be great, rendering BIR too large to be practical. In this work, an objective methodology for BIR is developed so that the task of BIR is customer focus, thus reducing the scope of BIR and maximizing its effectiveness. This is achieved through combining the failure mode and effect analysis (FMEA) with quality function deployment (QFD). The method is applied to an actual product in an actual industry, and with this method the FMEA becomes customer‐focused, and hence the prioritization of the corrective actions to all failure modes can be done objectively with customer focus. Therefore, limited resources can be effectively used to maximize customers’ satisfaction.
Technology leadership for the twenty‐first century principal
Authors: Flanagan Linda , Jacobsen Michele
Published: March 2003

This paper examines current issues related to technology integration and provides a contextual framework with which school principals can undertake new leadership responsibilities in this area. Selected examples of successful technology integration are provided to inform current technology leadership practices. The leadership goals, competencies and responsibilities needed in order to achieve this preferred future are described. In the final section, the authors draw on professional experiences as researcher and teacher/leader to build and expand on a five‐part leadership model currently in use by a large urban school district to interpret multiple dimensions of technology leadership for principals. Ways in which this framework can serve as a guide for school leaders as they develop technology competencies, implement professional growth plans, work with their community, and provide daily technology leadership, mentorship and advocacy for teachers in an elementary school are discussed.
ICT implementation and school leadership
Authors: Yuen Allan H.K. , Law Nancy , Wong K.C.
Published: March 2003

The Hong Kong Special Administrative Region (SAR) government launched a five‐year ICT strategy in schools in late 1998. This paper reports the findings of the analysis on models of change in 18 schools striving to integrate the use of ICT in teaching and learning across the school curriculum. The study shows that the strategy adopted by a school in instituting such change and the resulting variation of pedagogical practices using ICT is strongly dependent on the school leaders’ vision and understanding of the role and impact of ICT in the curriculum, their goals and objectives for ICT integration, as well as the history, culture and background of the school and its general vision and mission.
Working with ICT
Authors: Schiller John
Published: March 2003

Without the support of school leaders, particularly the principal, the educational potential of information and communications technology may not be realised. Principals need to assume a major responsibility for initiating and implementing school change through the use of information and communications technology and can facilitate complex decisions to integrate it into learning, teaching and school administration. However, little is known about its use by principals, their perceived competence in it and their preferred means of acquiring these skills and understandings. This paper will report on these issues from an initial analysis of baseline data gathered from a survey of all elementary and secondary principals in government, Catholic and independent schools in the coastal Hunter region of New South Wales, Australia. Findings indicate that there were considerable variations in the use of information and communications technology by principals and in their perceived competencies. Preferences for learning more about it and possible professional development strategies to cater for these variations are explored and recommendations made for the attention of decision makers and policy developers.
Managing technology integration into schools
Authors: Mentz Elsa , Mentz Kobus
Published: March 2003

In this article, an overview of the current status of technology in schools in developed countries is provided. This is followed by establishing what the current status of technology in schools in a province in South Africa is through interviews with principals. The findings of the empirical survey is put in the context of the need for technology in schools as a tool to improve a society as a whole. The recommendations given are based on the results of the empirical survey and the relevant literature, and are provided in table form, indicating the duties of the different role players.
The relative effects of environmental, internal and contextual factors on organizational learning: the case of Hong Kong schools under reforms
Authors: Jack Lam Y.L. , Nicholas Pang S.K.
Published: March 2003

In the context of rapid environmental changes under current school reform, the present paper attempts to locate an answer for a historical question related to the sources of organizational changes and for a prevailing question probing the relationships among external, internal and contextual factors affecting school organizational learning. Based on the information provided by 1,197 teaching staff from 67 Hong Kong government‐aided elementary and secondary schools, the present study confirms the proposition advanced by the “strategic choice school”, that it is leadership action which accounts for organizational adaptation. Moreover, through a series of path analyses, transformational leadership along with supportive culture and flexible structure are mainly accountable for organizational learning, while external and contextual conditions provide the additional incentives in dictating the extent of organizational learning that is taking place in schools.
Foundations for a learning organization: organization learning mechanisms
Authors: Armstrong Anona , Foley Patrick
Published: March 2003

This paper outlines the results of research currently being carried out at Victoria University, Australia, into what is a learning organization, how organizations learn, and how to develop a learning organization. The objective of the present study was to identify the components that underpin the development and operation of a learning organization, i.e. the foundations, or organizational learning mechanisms, that support the development and maintenance of a learning organization. The study identified four facilitating mechanisms: the learning environment, identifying learning and development needs, meeting learning and development needs and applying learning in the workplace. Factor analysis of the learning environment questionnaire identified 12 scales that supported the structural hypotheses, 11 of which had minimum reliability coefficients of 0.70 and above. This research provides an instrument for systematically measuring and monitoring progress towards achieving a learning organization.
Preparing for organisational learning by HK infrastructure project joint ventures organisations
Authors: Walker Derek H.T. , Johannes Derick S.
Published: March 2003

Organisations often collaboratively seek ways such as partnerships, alliances and joint venture (JVs), to bridge gaps in their knowledge and capacity to provide goods or services. Infrastructure projects in Hong Kong often require clusters of resources, knowledge, skills and capabilities that are difficult to obtain in a single provider – it is often problematic for any single organisation to successfully complete these projects using only in‐house resources and knowledge. Thus, providers frequently form JVs and similar forms of relationships to undertake large‐scale infrastructure projects. While one motivation has been to spread financial and other risks, a strong motivation is to better capture learning, so that this hidden and intangible asset may be later applied to improve JV partners’ competitive advantage. Presents results from a pilot study that investigates the nature of the JV relationship, focusing upon the dimension of organisational learning intentions of JV representatives interviewed.
Hand-arm vibration syndrome in Swedish car mechanics
Authors: Barregard L , Ehrenström L , Marcus K
Published: March 2003

Aims:To assess the occurrence of hand-arm vibration syndrome (HAVS) in Swedish car mechanics, and the relation between HAVS and duration of exposure.

Methods:A total of 806 mechanics answered a questionnaire on vascular and neurological symptoms, and exposure to vibrations. Mechanics with symptoms, and some mechanics without symptoms, were invited to a clinical examination, including also a timed Allen test. Vascular and neurological symptoms were classified using the Stockholm Workshop scales. The mean daily exposure (mainly using nut-runners) was 14 minutes and the mean exposure duration, 12 years. Published data have shown vibration levels in nut-runners of about 3.5 m/s2.

Results:In the questionnaire, 24% reported cold induced white finger (WF), 25% persistent numbness, and 13%, reduced grip force. The clinical examination showed a prevalence of vibration induced white finger (VWF) of about 15%, mainly in stage 2, and after 20 years, of 25%. A survival analysis showed similar results. We found that the International Organisation for Standardisation (ISO) model underestimates the risk of VWF. The incidence after 1975 was 19 cases per 1000 person-years. Slow refill times in the timed Allen test were common (15% had a refill time of >20 seconds), and associated with the presence of VWF. The clinical examination revealed neurological symptoms in the hands in about 25% of subjects, mainly at stage 2. After 20 years, the prevalence was 40%. The questionnaire items on WF and numbness both showed likelihood ratios of 13.

Conclusion:HAVS is common among Swedish car mechanics in spite of short daily exposure times. This underlines the need for preventive measures.
Organochlorine compounds and concentrations of thyroid stimulating hormone in newborns: Table 1
Authors: Ribas-Fitó N , Sala M , Cardo E , Mazón C , de Muga M E , Verdú A , Marco E , Grimalt J O , Sunyer J
Published: March 2003

Aims:To assess the association between prenatal exposure to organochlorine compounds and thyroid status in newborns from an area with high levels of hexachlorobenzene (HCB).

Methods:A total of 98 mother-infant pairs (83.1% of all children born during the period 1997–99 in a specific area polluted with HCB) were recruited. Levels of organochlorine compounds were measured in 70 cord serum samples. Concentrations of thyroid stimulating hormone (TSH) were measured in plasma of all newborns three days after birth.

Results:All newborns had concentrations of TSH within the range of normal reference values (<25 mU/l). Dichlorodiphenyl dichloroethylene (p,p′DDE), beta-hexachlorocyclohexane (β-HCH), polychlorinated biphenyl (PCB) 138 and 118 were related to higher concentrations of TSH, although only significant for β-HCH. Levels of HCB were not associated with TSH.

Conclusions:Although this community is highly exposed to HCB, no association was found between this organochlorine and TSH concentrations at birth.
THE SPECTRAL SCALE AND THE NUMERICAL RANGE
Authors: AKEMANN CHARLES A. , ANDERSON JOEL
Published: March 2003

Suppose that c is an operator on a Hilbert Space H such that the von Neumann algebra N generated by c is finite. Let τ be a faithful normal tracial state on N and set b1= (c + c*)/2 and b2= (c - c*)/2i. Also write B for the spectral scale of {b1, b2} relative to τ. In previous work by the present authors, some joint with Nik Weaver, B has been shown to contain considerable spectral information about the operator c. In this paper we expand that information base by showing that the numerical range of c is encoded in B also.

We begin by proving that the k-numerical range of an arbitrary operator d in B(H) coincides with the numerical range of d when the von Neumann algebra generated by d contains no finite rank operators. Thus, the k-numerical range is not useful for most operators considered here.

We next show that the boundary of the numerical range of c is exactly the set of radial complex slopes on B at the origin. Further, we show that points on this boundary that lie in the numerical range are visible as line segments in the boundary of B. Also, line segments on the boundary which lie in the numerical range show up as faces of dimension two in the boundary of B. Finally, when N is abelian, we prove that the point spectrum of c appears as complex slopes of 1-dimensional faces of B.
THE STRUCTURE OF SPIN SYSTEMS
Authors: ARVESON WILLIAM , PRICE GEOFFREY
Published: March 2003

A spin system is a sequence of self-adjoint unitary operators U1, U2, … acting on a Hilbert space H which either commute or anticommute, UiUj = ±UjUi for all i, j; it is called irreducible when {U1, U2, …} is an irreducible set of operators. There is a unique infinite matrix (cij) with 0, 1 entries satisfying [Formula: see text] Every matrix (cij) with 0, 1 entries satisfying cij = cji and cii = 0 arises from a nontrivial irreducible spin system, and there are uncountably many such matrices.

In cases where the commutation matrix (cij) is of "infinite rank" (these are the ones for which infinite dimensional irreducible representations exist), we show that the C*-algebra generated by an irreducible spin system is the CAR algebra, an infinite tensor product of copies of [Formula: see text], and we classify the irreducible spin systems associated with a given matrix (cij) up to approximate unitary equivalence.

That follows from a structural result. The C*-algebra generated by the universal spin system u1, u2, … of (cij) decomposes into a tensor product [Formula: see text], where X is a Cantor set (possibly finite) and [Formula: see text] is either the CAR algebra or a finite tensor product of copies of [Formula: see text]. We describe the nature of this decomposition in terms of the "symplectic" properties of the ℤ2-valued form [Formula: see text]x, y ranging over the free infninite dimensional vector space over the Galois field ℤ2.
PLURISUBHARMONIC VARIATION OF THE LEAFWISE POINCARÉ METRIC
Authors: BRUNELLA MARCO
Published: March 2003

This paper is concerned with a higher dimensional generalization of the main result of our previous paper [2]: we shall prove that the Poincaré metric on the leaves of a one-dimensional holomorphic foliation on a compact Kähler manifold has a plurisubharmonic variation.
Life history of a small form of the plethodontid salamander Desmognathus quadramaculatus
Authors: Beachy Christopher , Bruce Richard
Published: March 2003

We sampled Desmognathus quadramaculatus, one of the largest species of plethodontid salamanders in eastern North America, from a population exhibiting extremely small adult body sizes in the Bald Mountains of North Carolina (USA). In order to test the hypothesis that miniaturization in desmognathine salamanders is due to early metamorphosis and maturation, we estimated ages and sizes at metamorphosis and maturation. Analysis of size-frequency distributions suggests that most larvae metamorphose after 24 months, with the remainder metamorphosing after 36. The minimum age of sexually mature individuals in the summer months is estimated to be 4 years in males and 5 years in females; some may mature 1 year earlier. This is earlier than other reliable estimates of age at maturation in D. quadramaculatus, and appears to account for the small size of the species at this locality. Larval and juvenile growth rates are within the range of growth rates of other populations. As in other populations of D. quadramaculatus, males are smaller than females at maturation, but grow to larger sizes. Estimates of clutch sizes based on dissection of gravid females are relatively low. The other species of salamanders in this community do not appear to be miniaturized.
Intrapopulation variation in life history traits of Boa constrictor occidentalis in Argentina
Authors: Sironi Mariano , Chiaraviglio Margarita , Lucino Sergio , Bertona Miguel
Published: March 2003

We provide data on intrapopulation variation of life history traits of Boa constrictor occidentalis in the District of Pocho, Córdoba, Argentina. A total of 153 individuals were captured. The distribution of individuals among four size classes differed significantly among the five years of study. The proportion of mature individuals did not differ between sexes but it showed variation among years. Females were longer and heavier than males. The mean litter size of the species was 24 and there was a linear relationship between litter size and maternal snout-vent length. Most boas were captured during the dry season. There were no significant sex differences in the time of capture and air temperature in either the wet or the dry seasons. However, we found significant differences in the time of capture and air temperature between the seasons. The long-term monitoring of wild populations should be a priority for the development of conservation and management plans for this boid.
Estudio psicométrico sobre la percepción social de los riesgos. Efectos de la estrategia de análisis
Authors: Puy Ana
Published: March 2003

En este artículo se presenta un trabajo empírico sobre la percepción social de los riesgos en un contexto español urbano. Desde un enfoque psicométrico, se consideran dos estrategias diferentes de análisis de datos: una basada en la variabilidad entre fuentes de riesgo, y la otra, en la variabilidad entre sujetos. La discusión se centra principalmente en las implicaciones de cada perspectiva respecto al patrón de resultados y al tipo de información específica que cada una puede aportar.
Autoestima y depresión: relaciones directas versus indirectas
Authors: Herrero Juan , Musitu Gonzalo , Gracia Enrique
Published: March 2003

Este trabajo analiza la relación entre la autoestima y la depresión. Debido a que la formación de la autoestima reside fundamentalmente en procesos de interacción social (Cooley, 1902; Baldwin, 1908; Mead, 1934), la configuración de la autoestima se realiza en función de los distintos ámbitos o contextos en los que interactúa el individuo, creando de este modo diferentes aspectos o dimensiones de autoevaluación. Desde nuestra orientación teórica, la relación de la autoestima con la depresión depende de la dimensión que se analice: se observará una relación directa en aquellos aspectos del self muy vinculados al rol social preferente mientras que se observará una relación indirecta -mediada por otras variables relacionadas con la depresión: apoyo social y estrés- en aquellos aspectos más genéricos o distantes de ese rol social preferente. Para comprobar esta relación, se ha analizado una muestra de 405 estudiantes universitarios de la ciudad de Valencia, obteniéndose una medición de las siguientes variables: autoestima social e intelectual, participación e integración comunitaria, número de eventos vitales no deseables y depresión. Los resultados obtenidos confirman la hipótesis de la relación directa/indirecta en función del rol social preferente: la autoestima intelectual de los estudiantes universitarios -rol social preferente- se relaciona de forma directa con la depresión mientras que la autoestima social se relaciona de forma indirecta con la depresión.
Efectos de la discrepancia de estatus sobre el comportamiento intergrupal
Authors: Montalbán Francisco Manuel , Gómez Luis
Published: March 2003

Este estudio se centra en los efectos del estatus grrupal, estatus individual y estabilidad social percibida sobre el comportamiento intergrupal ampliamente conceptualizado. A partir de una variante del Paradigma de Grupo Mínimo, los sujetos (N=100) eran categorizados en grupos que variaban en su estatus (alto, bajo), la estabilidad percibida de esta diferencia (alta, baja) y el estatus personal de cada individuo como miembro (alto, bajo). Las variables dependientes iban dirigidas a la valoración de los productos de ambos grupos, la percepción de homogeneidad intragrupal y la identificación con el endogrupo. Los resultados mostraron un efecto principal para el estatus del grupo y la discrepancia de estatus individual vs. grupal. La pertenencia al grupo de alto estatus y la discrepancia de estatus, bajo estatus individual y alto grupal, posibilitaba una identidad social positiva a través de estrategias de discriminación y sobreestimación de la homogeneidad endogrupal en dimensiones (estereo)típicas. Cuando las diferencias de estatus se percibían como inestables, los efectos de la discriminación se incrementaban. Por otra parte, los miembros del grupo de bajo estatus reconocían su inferioridad y elegían fórmulas alternativas a la competición para superar su identidad social negativa. Los miembros pertenecientes al grupo de alto estatus pero con bajo estatus personal mostraban los niveles más elevados de identificación endogrupal. En el apartado conclusiones recogemos las implicaciones que estos datos sugieren a la Teoría de la Identidad Social.
Dimensionalidad de las causas percibidas en situaciones de éxito y fracaso escolar
Authors: Manassero M.a Antonia , Vázquez Ángel
Published: March 2003

Se estudian las causas de las calificaciones escolares en Matemáticas y Física y Química y su dimensionalidad autoatribuida sobre 5 dimensiones causales (Lugar de Causalidad, Estabilidad, Controlabilidad, Intencionalidad, y Globalidad) con alumnos de bachillerato y COU en una situación de logro escolar real. Las medias dimensionales de cada causa exhiben una tendencia sesgada a agruparse en una zona limitada del rango de puntuaciones en cada dimensión, en lugar de distribuirsepor toda la escala. Se analizan las diferencias entre grupos por sexo (no significativas), éxito/fracaso objetivo y éxito/fracaso percibido e intensidad positiva/negativa de las causas (las tres significativas). La tabulación cruzada del éxito y fracaso objetivo y percibido muestra un patrón asimétrico: numerosos resultados de éxito se perciben como fracaso, pero no al revés, y esta asimetría también se refleja entre la causalidad positiva o negativa atribuida en éxito o fracaso. Las puntuaciones de dimensiones causales muestran una utilidad taxonómica mayor para discriminar las polaridades de las causas singulares, en cada dimensión, que para clasificar causas.
NF-κB-dependent lymphocyte hyperadhesiveness to synovial fibroblasts by hypoxia and reoxygenation: potential role in rheumatoid arthritis
Authors: Han Myung-Kwan , Kim Jong-Suk , Park Byung-Hyun , Kim Jung-Ryul , Hwang Byung-Yun , Lee Hak-Yong , Song Eun-Kyung , Yoo Wan-Hee
Published: March 2003

Hypoxia/reoxygenation has been incriminated as a major factor in the pathogenesis of ischemia/reperfusion injury in various ischemic diseases such as rheumatoid arthritis (RA). In this study, we have investigated the effect of hypoxia/reoxygenation on the expression of intercellular adhesion molecule-1 (ICAM-1) in synovial fibroblasts and adherence of lymphocytes to synovial fibroblasts. Hypoxia/reoxygenation strongly activated nuclear factor-κB (NF-κB) in synovial fibroblasts to the levels produced by phorbol 12-myristate 13-acetate and caused lymphocyte hyperadhesiveness to synovial fibroblasts as well as up-regulation of ICAM-1, both of which were completely blocked by a NF-κB antagonist (pyrrolidine dithiocarbamate). These results indicate that hypoxia/reoxygenation has a major role in sequestration of inflammatory cells to synovium mediated by the activation of NF-κB. Our data suggest that hypoxia/reoxygenation could be an important target for the development of new, therapeutic strategies in RA.
Creating conditions similar to those that occur during exposure of cells to microgravity induces apoptosis in human lymphocytes by 5-lipoxygenase-mediated mitochondrial uncoupling and cytochrome c release
Authors: Maccarrone Mauro , Battista Natalia , Meloni Mariantonia , Bari Monica , Galleri Grazia , Pippia Proto , Cogoli Augusto , Finazzi-Agrò Alessandro
Published: March 2003

Creating conditions similar to those that occur during exposure of cells to microgravity induced a sixfold increase of apoptotic bodies and DNA fragments in human lymphocytes, paralleled by an early (within 2 h) fourfold increase in 5-lipoxygenase (5-LOX) activity and a fivefold decrease in mitochondrial membrane potential and increase in cytochrome c release (within 4 and 8 h, respectively). Similar membrane potential and cytochrome c release were observed in isolated mitochondria treated with physiological amounts of 5-LOX and were enhanced by creating conditions similar to those that occur during exposure of cells to microgravity. 5-LOX inhibitors, 5,8,11,14-eicosatetraynoic acid and caffeic acid, completely prevented apoptosis, whereas the phospholipase A2 inhibitor methyl-arachidonoyl fluorophosphonate and the 5-LOX activating protein inhibitor MK886 reduced it to 65–70%. The intracellular calcium chelator EGTA-acetoxymethylester reduced 5-LOX activity and apoptosis to 30–40% of controls, whereas the p38 mitogen-activated protein kinase inhibitor SB203580 was ineffective. The caspase-3 and caspase-9 inhibitors Z-Asp(OCH3)-Glu(OCH3)-Val-Asp(OCH3)-fluoromethylketone (FMK) and Z-Leu-Glu(OCH3)-His-Asp(OCH3)-FMK reduced apoptotic bodies to 25–30% of the control cells. Finally, creating conditions similar to those that occur during exposure of cells to microgravity did not induce apoptosis in human lymphoma U937 cells, which did not express an active 5-LOX.
Arachidonic acid activates phospholipase D in human neutrophils; essential role of endogenous leukotriene B4 and inhibition by adenosine A2A receptor engagement
Authors: Grenier Sonya , Flamand Nicolas , Pelletier Julie , Naccache Paul H , Borgeat Pierre , Bourgoin Sylvain G
Published: March 2003

We report in human neutrophils (PMN) that phospholipase D (PLD) was stimulated by micromolar concentrations of arachidonic acid (AA) and nanomolar concentrations of leukotriene B4 (LTB4), and eicosapentaenoic acid was inactive. The stimulatory effect of AA occurred only when adenosine was eliminated from PMN suspensions or when PMN were incubated with adenosine A2A receptor antagonists. The mechanism of AA-induced PLD activation was investigated. The results show that AA- and LTB4-induced PLD activation were inhibited by the LTB4 receptor 1 (BLTR1) antagonist CP 105,696, whereas the LTA4 hydrolase inhibitor SC57461A and the LT biosynthesis inhibitor MK-0591 inhibited AA- but not LTB4-mediated PLD activation. The AA-induced ARF1 and RhoA translocation to PMN membranes was inhibited by CP 105,696 and SC57461A. These results provide evidence of a requirement for an autocrine-stimulatory loop involving LTB4 and BLTR1 in the translocation of small GTPases to membranes and the activation of PMN PLD by AA.
Differential sensitivity of human monocytes and macrophages to ANP: a role of intracellular pH on reactive oxygen species production through the phospholipase involvement
Authors: Baldini P M , De Vito P , Martino A , Fraziano M , Grimaldi C , Luly P , Zalfa F , Colizzi V
Published: March 2003

Atrial natriuretic peptide (ANP), a cardiovascular hormone, elicits different biological actions in the immune system. The aim of the present work was to study the effect of ANP on the intracellular pH (pHi) of human monocytes and macrophages and to investigate whether pHi changes could play a role on phospholipase activities and reactive oxygen species (ROS) production. Human macrophages isolated by peripheral blood mononuclear cells and THP-1 monocytes, which were shown to express all three natriuretic peptide receptors (NPR-A, NPR-B, and NPR-C), were treated with physiological concentrations of ANP. A significant decrease of pHi was observed in ANP-treated macrophages with respect to untreated cells; this effect was paralleled by enhanced phospholipase activity and ROS production. Moreover, all assessed ANP effects seem to be mediated by the NPR-C. In contrast, no significant effect on pHi was observed in THP-1 monocytes treated with ANP. Treatment of macrophages or THP-1 monocytes with 5-(N-ethyl-N-isopropyl)amiloride, a specific Na+/H+ antiport inhibitor, decreases pHi in macrophages and monocytes. Our results indicate that only macrophages respond to ANP in terms of pHi and ROS production, through diacylglycerol and phosphatidic acid involvement, pointing to ANP as a new modulator of ROS production in macrophages.
Accelerated wound closure in neutrophil-depleted mice
Authors: Dovi Julia V , He Li-Ke , DiPietro Luisa A
Published: March 2003

The infiltration of neutrophils into injured tissue is known to protect wounds from invading pathogens. However, more recent studies suggest that neutrophils might inhibit the wound repair process. To investigate the role of neutrophils in wounds, mice were neutrophil-depleted by injection with rabbit anti-mouse neutrophil serum. Remarkably, epidermal healing, measured by wound closure, proceeded significantly faster in neutropenic than control mice (77.7+14.2% vs. 41.2+0.9%, P<0.02 at day 2). Dermal healing was not affected by neutrophil depletion, as neither collagen deposition nor wound-breaking strength was significantly different between neutropenic and control mice. As the delayed repair of diabetic individuals exhibits robust inflammation, the effect of neutrophil depletion on diabetic wound healing was investigated. Similar to the observations in wild-type mice, wound closure was accelerated by nearly 50% in neutropenic, diabetic mice. The results suggest that although neutrophils may provide protection against infection, they may retard wound closure.
Peritoneal dialysis solutions inhibit the differentiation and maturation of human monocyte-derived dendritic cells: effect of lactate and glucose-degradation products
Authors: Puig-Kröger Amaya , Muñiz-Pello Oscar , Selgas Rafael , Criado Gabriel , Bajo M-Auxiliadora , Sánchez-Tomero Jose A , Alvarez Vicente , del Peso Gloria , Sánchez-Mateos Paloma , Holmes Clifford , Faict Dirk , López-Cabrera Manuel , Madrenas Joaquín , Corbí Angel L
Published: March 2003

Peritoneal dialysis (PD) is a well-established therapy for end-stage renal failure, but its efficiency is limited by recurrent peritonitis. As PD solutions impair local inflammatory responses within the peritoneal cavity, we have analyzed their influence on the in vitro maturation of human monocyte-derived dendritic cells (MDDC). Evaluation of MDDC maturation parameters [expression of adhesion and costimulatory molecules, receptor-mediated endocytosis, allogeneic T cell activation, production of tumor necrosis factor α, interleukin (IL)-6 and IL-12 p70, and nuclear factor (NF)-κB activation] revealed that currently used PD solutions differentially inhibit the lipopolysaccharide (LPS)-induced maturation of MDDC, an inhibition that correlated with their ability to impair the LPS-stimulated NF-κB activation. Evaluation of PD components revealed that sodium lactate and glucose-degradation products impaired the acquisition of maturation parameters and NF-κB activation in a dose-dependent manner. Moreover, PD solutions impaired monocyte-MDDC differentiation, inhibiting the acquisition of DC markers such as CD1a and DC-specific intercellular adhesion molecule-3 grabbing nonintegrin (CD209). These findings have important implications for the initiation of immune responses under high lactate conditions, such as those occurring within tumor tissues or after macrophage activation.
Indirect capture augments leukocyte accumulation on P-selectin in flowing whole blood
Authors: St. Hill Catherine A , Alexander Shelia R , Walcheck Bruce
Published: March 2003

Leukocytes are captured directly by E- and P-selectin on activated endothelium and by indirect means, which includes attached leukocytes capturing free-flowing leukocytes. However, controversy exists as to whether the latter mechanism occurs in the presence of red blood cells. We analyzed leukocyte capture mechanisms on P-selectin under circulatory hydrodynamics using whole blood. The selective disruption of leukocyte–leukocyte interactions with an L-selectin monoclonal antibody reduced leukocyte accumulation by >50% under various stringencies (substrate concentrations and shear stresses). In addition, a direct analysis of leukocyte capture events revealed that 69% were indirect. Our data indicate that in the presence of red blood cells, P-selectin-attached leukocytes, individually and as a monolayer, augment leukocyte accumulation by indirect capture. This mechanism may contribute to increasing the density of leukocytes on discrete areas of activated endothelial cells at sites of inflammation. These findings are significant since L-selectin accounts for the majority of the leukocyte rolling flux in small venules at diverse inflammatory settings. Yet, the primary mechanism by which L-selectin mediates leukocyte accumulation remains unresolved.
Concurrent evolution and resolution in an acute inflammatory model of rat carrageenin-induced pleurisy
Authors: Murai Naoki , Nagai Kiyohito , Fujisawa Hideyuki , Hatanaka Ko , Kawamura Michiko , Harada Yoshiteru
Published: March 2003

Granulocyte apoptosis and subsequent clearance by phagocytes are critical for the resolution of inflammation. However, no studies have addressed how the resolution proceeds in the inflammatory site. We studied the time course of neutrophil apoptosis and the following ingestion by mononuclear leukocytes in rat carrageenin-induced pleurisy, detecting DNA fragmentation by the deoxyuridine triphosphate-biotin nick-end labeling (TUNEL) method, by acridine orange staining, and from the DNA ladder pattern on electrophoresis. Neutrophil accumulation started 3–5 h after carrageenin injection and then maintained a plateau until 24 h. Neutrophils decreased steeply between days 1 and 3. Mononuclear leukocytes started to accumulate at 5 h and reached a peak at day 2. TUNEL-positive bodies and acridine orange-positive bodies first became detectable in the cytoplasm of the mononuclear leukocytes from 24 h and 9 h, respectively. Both methods indicated that mononuclear leukocytes containing fragmented DNA increased rapidly on days 1 and 2 and reached a peak at day 3. The characteristic ladder pattern of neutrophil DNA was observed from 5 h. Tumor necrosis factor α was detectable on the start, and the levels of interleukin-10 and transforming growth factor-β1 rose together with signs of neutrophil apoptosis and the following ingestion by mononuclear leukocytes. These results indicate that neutrophils start to undergo apoptosis just after the beginning of their accumulation in the inflammation site. Thus, evolution and resolution processes may proceed concurrently in acute inflammation.
Fever-like thermal conditions regulate the activation of maturing dendritic cells
Authors: Tournier Jean-Nicolas , Hellmann Anne Quesnel , Lesca Gaëtan , Jouan Alain , Drouet Emmanuel , Mathieu Jacques
Published: March 2003

Fever is one of the most frequent clinical signs encountered in pathology, especially with respect to infectious diseases. It is currently thought that the role of fever on immunity is limited to activation of innate immunity; however, its relevance to activation of adaptive immunity remains unclear. Dendritic cells (DCs) that behave as sentinels of the immune system provide an important bridge between innate and adaptive immunity. To highlight the role of fever on adaptive immunity, we exposed murine bone marrow-derived lipopolysaccharide (LPS)- or live bacteria-maturing DCs over a 3-h period to 37°C or to fever-like thermal conditions (39°C or 40°C). At these three temperatures, we measured the kinetics of cytokine production and the ability of DCs to induce an allogeneic mixed lymphocyte reaction. Our results show that short exposure of DCs to temperatures of 39°C or 40°C differentially increased the secretion of interleukin (IL)-12p70 and decreased the secretion of IL-10 and tumor necrosis factor α by maturing DCs. These fever-like conditions induced a regulation of cytokine production at the single-cell level. In addition, short-term exposed LPS-maturing DCs to 39°C induced a stronger reaction with allogeneic CD4+ T cells than maturing DCs incubated at 37°C. These results provide evidence that temperature regulates cytokine secretion and DC functions, both of which are of particular importance in bacterial diseases.
A PI-3 kinase-dependent, Stat1-independent signaling pathway regulates interferon-stimulated monocyte adhesion
Authors: Navarro Angels , Anand-Apte Bela , Tanabe Yoshinari , Feldman Gerald , Larner Andrew C
Published: March 2003

Type I interferon (IFN)-α/β and type II IFN-γ induce the expression of early response genes through activation of the Janus tyrosine kinase/signal transducer and activator of transcription (Stat) pathway. Although IFNs regulate a variety of other signaling cascades, little is known about how they contribute to the biological activities of these cytokines. In this study, we demonstrate that IFN-β or IFN-γ induces the phosphorylation of the serine/threonine kinase Akt in primary human peripheral blood monocytes. Abrogation of the IFN-stimulated Akt activation by phosphatidylinositol-3 kinase (PI-3K) inhibitors prevents IFN-induced adhesion in these cells, and IFN activation of the Stat1-dependent guanylate-binding protein (GBP) gene is not affected. Importantly, Stat1-deficient bone marrow macrophages displayed a similar level of IFN-γ-stimulated adhesion compared with macrophages derived from wild-type littermates. These findings demonstrate for the first time that IFN stimulation of a PI-3K signaling cascade modulates the ability of these cytokines to regulate monocyte adhesion, and this process does not require the expression of Stat1, a primary mediator of IFN-γ signaling.
Sky luminance and radiance distributions: a comparison based on data from Bahrain, Israel, Japan and Europe
Authors: Muneer T , Fairooz F , Zhang X
Published: March 2003

Predictive models of building performance are increasingly being based on sky luminance and radiance distributions. These, though, tend to exist as separate records and the word-wide coverage is not complete: sky luminance, in particular, has been recorded at relatively few locations. It is important in practice to ensure that luminance and radiation values are consistent with each other and that radiation measurements are used to supplement the illumination records. The paper compares data from the authors’ research in several climatic regions and shows that an anisotropic model of the sky distribution can be significantly more accurate than an isotropic function. This is discussed with particular reference to shadow band correction.
Attenuation of diffuse daylight due to dust deposition on glazing in a tropical urban environment
Authors: Ullah MB , Kurniawan Julius Tan , Poh Lam Khee , Wai Tham Kwok , Tregenza PR
Published: March 2003

Transmittance of diffuse daylight by horizontal and vertical glazing was measured in a model placed in an exposed outdoor environment in Singapore for 41 weeks. Correction factors for sensor location were developed, and associations between transmittance and rainfall, wind speed and wind directional frequency were analysed. The paper discusses the interplay of forces for adhesion, resuspension and cleaning.
Air-clad optical rod daylighting system
Authors: Callow JM , Shao L
Published: March 2003

A novel daylighting system is proposed in which a set of ‘light rods’ is used to transport light from the exterior of a building into dull or unlit rooms within the building. These rods are sufficiently small to be fitted into most existing buildings without structural modification. During testing, rods were found to have a transmittance equal to that of a light pipe which had an aspect ratio six times smaller. Rods would collect both direct and diffuse light throughout the year, with high collection efficiency. Building occupants would benefit from natural light and the reduction of pollution and expense associated with the use of electric lights.
Why Don't Prices Rise During Periods of Peak Demand? Evidence from Scanner Data
Authors: Chevalier Judith A , Kashyap Anil K , Rossi Peter E
Published: March 2003

We examine retail and wholesale prices for a large supermarket chain over seven and one-half years. We find that prices fall on average during seasonal demand peaks for a product, largely due to changes in retail margins. Retail margins for specific goods fall during peak demand periods for that good, even if these periods do not coincide with aggregate demand peaks for the retailer. This is consistent with “loss-leader” models of retailer competition. Models stressing cyclical demand elasticities or cyclical firm conduct are less consistent with our findings. Manufacturer behavior plays a limited role in the countercyclicality of prices.
Stages of Diversification
Authors: Imbs Jean , Wacziarg Romain
Published: March 2003

This paper studies the evolution of sectoral concentration in relation to the level of per capita income. We show that various measures of sectoral concentration follow a U-shaped pattern across a wide variety of data sources: countries first diversify, in the sense that economic activity is spread more equally across sectors, but there exists, relatively late in the development process, a point at which they start specializing again. We discuss this finding in light of existing theories of trade and growth, which generally predict a monotonic relationship between income and diversification.
The Economic Costs of Conflict: A Case Study of the Basque Country
Authors: Abadie Alberto , Gardeazabal Javier
Published: March 2003

This article investigates the economic effects of conflict, using the terrorist conflict in the Basque Country as a case study. We find that, after the outbreak of terrorism in the late 1960's, per capita GDP in the Basque Country declined about 10 percentage points relative to a synthetic control region without terrorism. In addition, we use the 1998–1999 truce as a natural experiment. We find that stocks of firms with a significant part of their business in the Basque Country showed a positive relative performance when truce became credible, and a negative relative performance at the end of the cease-fire.
The Evolution of Human Life Expectancy and Intelligence in Hunter-Gatherer Economies
Authors: Robson Arthur J , Kaplan Hillard S
Published: March 2003

The economics of hunting and gathering must have driven the biological evolution of human characteristics, since hunter-gatherer societies prevailed for the two million years of human history. These societies feature huge intergenerational resource flows, suggesting that these resource flows should replace fertility as the key demographic consideration. It is then theoretically expected that life expectancy and brain size would increase simultaneously, as apparently occurred during our evolutionary history. The brain here is considered as a direct form of bodily investment, but also crucially as facilitating further indirect investment by means of learning-by-doing.
Gravity with Gravitas: A Solution to the Border Puzzle
Authors: Anderson James E , van Wincoop Eric
Published: March 2003

Gravity equations have been widely used to infer trade flow effects of various institutional arrangements. We show that estimated gravity equations do not have a theoretical foundation. This implies both that estimation suffers from omitted variables bias and that comparative statics analysis is unfounded. We develop a method that (i) consistently and efficiently estimates a theoretical gravity equation and (ii) correctly calculates the comparative statics of trade frictions. We apply the method to solve the famous McCallum border puzzle. Applying our method, we find that national borders reduce trade between industrialized countries by moderate amounts of 20–50 percent.
National Inventory of Hospital Trauma Centers
Authors: MacKenzie Ellen J. , Hoyt David B. , Sacra John C. , Jurkovich Gregory J. , Carlini Anthony R. , Teitelbaum Sandra D. , Teter Harry
Published: March 2003

Context

Trauma centers benefit thousands of injured individuals every day and play a critical role in responding to disasters. The last full accounting of the number and distribution of trauma centers identified 471 trauma centers in the United States in 1991.

Objective

To determine the number and configuration of trauma centers and identify gaps in coverage.

Design, Setting, and Subjects

Interviews with trauma center directors (September 2001 to April 2002), data from the American Hospital Association's Annual Survey of Hospitals (2000), and the US Health Resources Administration's Area Resource File (2001) were used to determine characteristics of trauma center hospitals and the geographic areas they serve in all 50 states and in the District of Columbia. Characteristics of trauma centers were examined by level of care and compared with nontrauma centers. Hospitals are designated or certified as trauma centers by a state or regional authority or verified as trauma centers by the American College of Surgeons Committee on Trauma. Trauma centers that treat only children (n = 31) were excluded.

Main Outcome Measure

Total number of trauma centers and number of trauma centers per million population.

Results

In 2002, there were 1154 trauma centers in the United States, including 190 level I centers and 263 level II centers. Several states have categorized every hospital with an emergency department at some level of trauma care while others have designated a limited number of level I and level II centers only. The number of level I and II centers per million population ranges from 0.19 to 7.8 by state. When compared with nontrauma center hospitals, trauma centers are larger, more likely to be teaching hospitals, and more likely to offer specialized services.

Conclusions

Although the availability of trauma centers has improved, challenges remain to ensure the optimal number, distribution, and configuration of trauma centers. These challenges must be addressed, especially in light of the recent emphasis on hospital preparedness and homeland security.
The Impact of United States Law on Medicine as a Profession
Authors: Rosenbaum Sara
Published: March 2003

The evolution of US law has had an enormous influence on medicine as a profession, and much of this legal evolution can be attributed to changes in the science and practice of medicine. This changing legal framework and its intersection with medicine has many facets. Three of the most important facets concern the evolution of the no duty-to-treat principle and the role of modern health care financing and civil rights law in altering this rule, the manner in which advances in medicine led courts and legislatures to change the standards against which professional medical liability is measured, and the basic loss of highly preferential treatment under US laws aimed at preventing anticompetitive conduct by businesses. However, despite the impact on the profession of an evolving legal system, concern over the integrity of medical professionalism continues to significantly influence both laws and lawmakers, including legislatures, regulatory agencies, and the courts.