bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards on‐line monitoring of cell growth in microporous scaffolds: Utilization and interpretation of complex permittivity measurements
Authors: Bagnaninchi Pierre‐Olivier , Dikeakos Maria , Veres Teodor , Tabrizian Maryam
Published: September 2003

Here we demonstrate the ability to characterize microporous scaffolds and evaluate cell concentration variation via the utilization and interpretation of complex permittivity measurements (CP), a direct and nondestructive method. Polymer‐based microporous scaffolds are of importance to tissue engineering, particularly in the promotion of cell adhesion, proliferation, and differentiation in predefined shapes. Chitosan gel scaffolds were seeded with increasing concentrations of macrophages to simulate cell growth. Complex permittivity measurements were performed using a dielectric probe and a vector network analyzer over a frequency ranging from 200 MHz to 2 GHz. An effective medium theory was applied to interpret the data obtained; respectively, Looyenga and Maxwell‐Wagner‐Hanai functions were used to retrieve the porosity and the variation of the cell concentration from the CP measurements. Calculated porosities were in agreement with experimental evaluation—porosity ranged from 81–96%. Changes in cell concentration inside the scaffolds upon injection of differing cell concentrations into the scaffold were detected distinguishably. Variations resulting from the cumulative injection of 400–1800 μL of 106 cells/mL solution into the scaffold were monitored. Results suggest that CP measurements in combination with an appropriate effective medium approximation can enable on‐line monitoring of cell growth within scaffolds. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 343–350, 2003.
Co‐expression of molecular chaperones does not improve the heterologous expression of mammalian G‐protein coupled receptor expression in yeast
Authors: Butz James A. , Niebauer Ronald T. , Robinson Anne Skaja
Published: September 2003

The limitations to high‐level expression of integral membrane proteins are not well understood. The human A2a adenosine receptor (A2a) and mouse Substance P receptor (SPR) were individually expressed in S. cerevisiae to identify potential cellular bottlenecks for G‐protein coupled receptors. In the yeast system, A2a was not N‐linked glycosylated but was functional and plasma membrane‐localized. A2a also contained an intramolecular disulfide bond. Substance P receptor was also not N‐linked glycosylated in yeast, but, unlike A2a, SPR was intracellularly retained, nonfunctional, and did not appear to contain an intramolecular disulfide bond. Since both receptors contain N‐linked glycosylation and disulfide bonds in mammalian systems, machinery responsible for interacting with these modifications was investigated—specifically, the potential interactions between the nascent receptor and ER‐resident proteins were explored. The chaperones calnexin and protein disulfide isomerase were co‐overexpressed with the GPCRs to determine the effect on total and active yields of A2a and SPR, as well as on receptor trafficking. The effect of co‐expressing the chaperone BiP on the total yields of A2a as well as intracellular fates of both receptors were determined. The co‐expression of ER resident proteins did not improve A2a yields nor did they restore SPR activity or improve SPR cell surface expression. Taken together, these results indicate that an ER‐folding bottleneck does not limit the expression of the mammalian receptors in yeast. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 292–304, 2003.
Tracking the acetate threshold using DO‐transient control during medium and high cell density cultivation of recombinant Escherichia coli in complex media
Authors: Johnston Wayne A. , Stewart Meredith , Lee Peter , Cooney Michael J.
Published: September 2003

DO‐transient nutrient controllers use the dissolved oxygen signal to attempt acetate threshold tracking during fed‐batch cultivation of recombinant E. coli. Here we apply DO‐transient control to the production of Jembrana disease virus protein in complex Super Luria medium and compare performance against a high‐limit pH‐stat controller. For induction at medium cell density (harvest between 31 and 32.5 g dcw L) a total productivity of 0.27 g L h was achieved as compared to 0.24 g L h with the high‐limit pH‐stat. For induction at high cell density (harvest at 60 g dcw L), decreased productivity (0.12 g L h) was attributed to the effect of acetate accumulation on recombinant protein formation and a concomitant lowering of the critical growth rate. Our results suggest that complex media provides a difficult environment for the application of acetate threshold tracking DO‐transient control because of difficulties in re‐oxidizing acetate, and apparent localized production of acetate below the production threshold (as detected by the DO‐transient controller as SPOURcrit). Configuring the DO‐transient controller to avoid aggressive threshold probing is suggested as a means to improve performance and reduce acetate accumulation in complex media. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 314–323, 2003.
Virus‐like particle production at low multiplicities of infection with the baculovirus insect cell system
Authors: Maranga Luis , Brazão Tiago F. , Carrondo Manuel J. T.
Published: September 2003

The baculovirus insect cell expression system (BEVS) was used for the production of self‐formingPorcine parvovirus‐like particles (VLPs) in serum‐free medium. A low multiplicity of infection (MOI) strategy was used to overcome an extra virus amplification step, undesirable in industrial production, and to minimize the virus passage effect. It was confirmed that the time of infection (TOI) and MOI are dependent variables. Higher cell densities were obtained at low MOIs, keeping a constant TOI; however, both volumetric and specific productivities were lower. In synchronous infection, at high MOI, the specific productivity decreased when the cells were infected in the late phase of growth. Product degradation due to cell lysis strongly influenced the optimal time of harvest (TOH). Time of harvest was found to be highly dependent on the MOI, and a direct relationship with the cell yield was obtained.

Analysis of the culture medium reveals that glutamine depletion occurs in the late phase of the growth. Supplementation of glutamine to uninfected cell cultures resulted in an increased cell yield. Its addition to cultures infected in the middle phase of the growth curve was also able to restore the productivity levels, but addition to cells in their stationary phase caused no observable effect on product expression. The study clearly shows that for a specific TOI it is not obvious what the correct MOI should be to obtain the best volumetric productivity. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 245–253, 2003.
Large‐scale transient transfection of serum‐free suspension‐growing HEK293 EBNA1 cells: Peptone additives improve cell growth and transfection efficiency
Authors: Pham Phuong Lan , Perret Sylvie , Doan Huyen Chau , Cass Brian , St‐Laurent Gilles , Kamen Amine , Durocher Yves
Published: September 2003

Large‐scale transient transfection of mammalian cells is a recent and powerful technology for the fast production of milligram amounts of recombinant proteins (r‐proteins). As many r‐proteins used for therapeutic and structural studies are naturally secreted or engineered to be secreted, a cost‐effective serum‐free culture medium that allows their efficient expression and purification is required. In an attempt to design such a serum‐free medium, the effect of nine protein hydrolysates on cell proliferation, transfection efficiency, and volumetric productivity was evaluated using green fluorescent protein (GFP) and human placental secreted alkaline phosphate (SEAP) as reporter genes. The suspension growing, serum‐free adapted HEK293SF‐3F6 cell line was stably transfected with an EBNA1‐expression vector to increase protein expression when using EBV oriP bearing plasmids. Compared to our standard serum‐free medium, concomitant addition of the gelatin peptone N3 and removal of BSA slightly enhanced transfection efficiency and significantly increased volumetric productivity fourfold. Using the optimized medium formulation, transfection efficiencies between 40–60% were routinely obtained and SEAP production reached 18 mg/L−1. To date, we have successfully produced and purified over fifteen r‐proteins from 1–14‐L bioreactors using this serum‐free system. As examples, we describe the scale‐up of two secreted his‐tagged r‐proteins Tie‐2 and Neuropilin‐1 extracellular domains (ED) in bioreactors. Each protein was successfully purified to >95% purity following a single immobilized metal affinity chromatography (IMAC) step. In contrast, purification of Tie‐2 and Neuropilin‐1 produced in serum‐containing medium was much less efficient. Thus, the use of our new serum‐free EBNA1 cell line with peptone‐enriched serum‐free medium significantly improves protein expression compared to peptone‐less medium, and significantly increases their purification efficiency compared to serum‐containing medium. This eliminates labor‐intensive and expensive chromatographic steps, and allows for the simple, reliable, and extremely fast production of milligram amounts of r‐proteins within 5 days posttransfection. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 332–342, 2003.
Use of a plant‐derived enzyme template for the production of the green‐note volatile hexanal
Authors: Schade Frank , Thompson John E. , Legge Raymond L.
Published: September 2003

Hexanal is a key organoleptic element of green‐note that is found in both fragrances and flavors. We report a novel process for the production of hexanal using immobilized enzyme templates extracted from different plant sources in combination with hollow‐fiber ultrafiltration for in situ separation. Enzyme templates, known to be responsible for the synthesis of hexanal from linoleic acid (18:2), were isolated from naturally enriched tissues including carnation petals, strawberry and tomato leaves. These templates were immobilized in an alginate matrix and used as a biocatalyst in a packed‐bed bioreactor. Continuous product recovery was achieved using a hollow‐fiber ultrafiltration unit. The effects of pH, reaction temperature, and substrate and enzyme concentrations were studied and their effects on hexanal generation identified and optimized. Utilizing optimized conditions, hexanal production 112‐fold higher than endogenous steady‐state levels in a corresponding amount of plant tissue could be achieved over a 30‐minute period. Based on the reactor studies, product inhibition also appears to be an important factor for bioreactor‐based hexanal production. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 265–273, 2003.
Comparison of theoretical and experimental data to evaluate substrate diffusional limitations for crown ether‐ and methyl‐β‐cyclodextrin‐activated serine protease subtilisin Carlsberg in tetrahydrofuran
Authors: Santos Angélica M. , González Maryliz , Pacheco Yamaris , Griebenow Kai
Published: September 2003

Simple co‐lyophilization of serine protease subtilisin Carlsberg with [12]‐crown ether‐4 (12‐crown‐4) or methyl‐β‐cyclodextrin (MβCD) drastically increases its catalytic activity in organic solvents. We investigated whether the improved activity would cause substrate diffusional limitations. To experimentally assess the issue, the enzyme was inactivated with PMSF. Different amounts of active and inactive subtilisin were codissolved in 10 mM phosphate buffer (pH 7.8) followed by lyophilization with or without 12‐crown‐4 or MβCD. Initial rates for the transesterification reaction of N‐acetyl‐L‐phenylalanine ethyl ester and 1‐propanol in anhydrous THF were plotted vs. the amount of active enzyme present in the formulations. For all three enzyme formulations a linear relationship was observed and the results clearly show that activation of subtilisin Carlsberg by crown ethers and MβCD did not cause diffusional limitations. This was somewhat surprising because theoretical models predicted such diffusional limitations for the activated formulations. However, investigation of the protein powder particles obtained after co‐lyophilization with 12‐crown‐4 and MβCD revealed a drastically reduced particle size for these formulations when suspended in THF. The particle micronization afforded by the excipients prevented substrate diffusional limitations, a factor that should be taken into account when designing improved enzyme formulations for synthetic applications in organic solvents. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 324–331, 2003.
On the dynamics of a spherical scaffold in rotating bioreactors
Authors: Ramirez L. E. S. , Lim E. A. , Coimbra C. F. M. , Kobayashi M. H.
Published: September 2003

We analyze the dynamics of a spherical scaffold in rotating bioreactors (or clinostats). The idealized clinostat environment consists of a purely rotational flow that is perpendicular to a gravitational field. We confirm through a detailed analytical study that lift effects considerably alter the position of the equilibrium point reached by the scaffolds in the (vertical) direction collinear to the gravitational field. This result holds for small particle and shear Reynolds numbers. Our analysis shows that the inertial lift effect is negligible in the horizontal direction. We show that for all rotations of practical interest, and for the range of particle Reynolds number smaller than unity, the vertical coordinate of the equilibrium point is strongly affected by consideration of lift effects. For light (heavy) particles, inclusion of lift in the formation forces the equilibrium position to be below (above) the horizontal plane that contains the axis of rotation. The equilibrium point for light particles is stable and therefore is observable experimentally. The equilibrium point for heavy particles is unstable. We also estimate the stress level applied to the scaffold and derive an algebraic expression that indicates that the stress level acting on the scaffold decreases with increasing shear Reynolds number. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 382–389, 2003.
Inducible expression of green fluorescent protein in porcine tracheal epithelial cells by the bovine tracheal antimicrobial peptide promoter
Authors: Dyce Paul W. , Devries Robert J. , Walton John , Hacker Roger R. , Li Julang
Published: September 2003

Tracheal antimicrobial peptides (TAP) are expressed primarily in respiratory epithelial cells of cattle. The TAP expression is inducible upon challenge with bacteria and bacterial lipopolysaccharide (LPS). In pigs, a promoter that can be activated by bacterial infection has yet to be identified. The objective of this study was to use green fluorescent protein (GFP) as a reporter gene to determine the function and inducibility of the bovine TAP promoter in porcine primary tracheal epithelial cells. Thus, evaluating the feasibility of using this promoter to direct transgene expression in porcine cells.

The percentage of GFP expressing cells increased in response to LPS challenge in both a dose‐dependent and time‐dependent manner (p< 0.05). Moreover, when the intensity of the GFP fluorescence was measured, it was observed that the percentage of cells that have a high intensity of GFP fluorescence, also increased gradually as LPS dose increased, the difference between the unchallenged (control) and challenged group become statistically significant at the concentration of 100 ng/mL after 36 h LPS challenge (p< 0.05). The level of induced‐expression driven by the TAP promoter was 67.8 ±12.2% that of the cytomegalovirus (CMV) promoter. The intensity of GFP fluorescence by the TAP promoter was 39.8 ± 7.6% when compared to the expression driven by the CMV promoter. These data suggest the TAP promoter functions at a lower, but comparable, level to the strong CMV promoter.

Our data demonstrated that the bovine TAP promoter was functional in porcine primary tracheal epithelial cells. The ability of the TAP promoter to control gene expression in an inducible manner in the porcine respiratory tract presents an important application potential in transgenic animal studies. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 374–381, 2003.
Parental influences and social modelling of youth lottery participation
Authors: Felsher Jennifer R. , Derevensky Jeffrey L. , Gupta Rina
Published: September 2003

Objective

The present study sought to investigate the relationship between perceived parental lottery involvement and the bearing this has upon youth lottery participation.

Participants

One thousand seventy(two youth, 10–18 years of age participated from 20 elementary and nine high schools throughout the province of Ontario, Canada.

Measurements

Measuring Youth Lottery Participation and Playing Behaviour Questionnaire and the DSM(IV(MR(J Revised to screen for youth pathological gambling.

Findings

Youth reported playing all forms of lottery tickets with 77% reporting that their parents purchase scratch tickets, lottery draws (50%), and sports tickets (23%) for them. Parental purchases of lottery tickets for their children increased by level of gambling severity. Participants with significant gambling problems perceived higher parental participation in the lottery compared to non(gamblers and social gamblers. The majority of participants reported that their parents were aware of their lottery involvement and were not afraid of getting caught purchasing lottery tickets in spite of legal prohibitions.

Conclusion

The results suggest youths' perception of parental involvement with the lottery plays an important role in the initiation and maintenance of lottery participation for youth. Given that youth report receiving lottery tickets from their parents, it is clear that the lottery is perceived as an innocuous form of gambling. Public awareness programmes and education of this issue is critical. Copyright © 2003 John Wiley & Sons, Ltd.
Effects of gender and sexuality on judgements of victim blame and rape myth acceptance in a depicted male rape
Authors: Davies Michelle , McCartney Samantha
Published: September 2003

Relatively few studies have investigated judgements towards male rape, and no published studies have investigated gay men's judgements towards this offence. The current study investigated the effects of gender and sexuality on victim blame and male rape myth acceptance in the depicted rape of a gay man. It was predicted that heterosexual men would make the most anti‐victim judgements, while gay men would make the most pro‐victim judgements. One hundred and fifty members of the UK population read a scenario that depicted a male rape, and then completed a questionnaire that measured blame and rape myths. As predicted, heterosexual men endorsed more rape myths and blamed the victim more than heterosexual women or gay men. Gay men made the most pro‐victim judgements overall. Results are discussed in relation to homophobia and traditional gender roles. Copyright © 2003 John Wiley & Sons, Ltd.
Narrating the negative consequences of elder care and familial obligation in Atlantic Canada
Authors: Hodgetts D. , Pullman D. , Goto A.
Published: September 2003

At a time when renewed emphasis is being placed on the role of the family in providing care for elderly people, shifts in family structures and the demographic profile of societies such as Atlantic Canada are impacting on community structures foundational to familial caregiving practices. Research shows that family members who attempt to provide familial care without adequate support risk negative health and interpersonal consequences. Hence many find it necessary to reflect upon their familial obligations. This article investigates the storytelling processes through which caregivers, aged between 45 and 55 years (N = 26), make sense of their efforts to provide care. We explore the ways in which participants in four focus groups and 12 interviews refer to negative consequences of caring in order to navigate dilemmas arising from their enactment of familial obligations in the absence of adequate support. Copyright © 2003 John Wiley & Sons, Ltd.
Human capital, acculturation and social identity: Bosnian refugees in Australia
Authors: Colic‐Peisker Val , Walker Iain
Published: September 2003

This article explores the processes of acculturation and identity among refugees from Bosnia and Herzegovina who resettled in the Australian cities of Perth and Sydney during the 1990s. We start from the idea that refugees, through the process of forced migration, lose aspects of their identities that were embedded in their former communities, jobs, skills, language, and culture. Upon arrival in a new society, they seek to reconstruct their identity, and we argue that this happens in the context of the process of acculturation. We use two social psychological perspectives, social identity theory and acculturation theory, and the sociological theory of the migration of human capital, to examine our data collected by qualitative research methods from refugees and Australian professionals who work in the government‐funded refugee resettlement programme. Our data highlight the loss of identity experienced in forced migration, difficulties in refugee acculturation and identity reconstruction, and collective and individual strategies in acculturation and identity adaptation. We see our perspective as essentially interdisciplinary, and take an interactional view of the acculturation and identity processes, as the characteristics of both the host society and the immigrants affect them. Copyright © 2003 John Wiley & Sons, Ltd.
Children and regeneration: setting an agenda for community participation and integration
Authors: Matthews Hugh
Published: September 2003

Unlike other marginalised groups children are often not in a position to enter into dialogue with adults about their community needs and environmental concerns. Despite the current emphasis on involving communities in the regeneration of their own neighbourhoods, young people are still seemingly invisible in decision‐making processes. This paper looks at recent attempts to increase public participation in local decision‐making, proposes a typology of community action that recognises the different ways in which children may be drawn into the process of neighbourhood renewal and offers a set of recommendations that, if taken up, provide an agenda that will strengthen the active social commitment of young people in general. Copyright © 2002 John Wiley & Sons, Ltd.
Having a say in health: involving young people with a chronic illness or physical disability in local health services development
Authors: Lightfoot Jane , Sloper Patricia
Published: September 2003

Increasing attention is being paid to involving users in local NHS service development, and to involving young people as users in their own right. However, we know little about the views and experiences of young participants, especially those with a chronic illness or physical disability, which could inform more effective approaches to their involvement. The paper reports on research investigating the views of young patients and staff who have taken part in NHS service development projects, and suggests a range of issues for consideration when involving young patients in future. Copyright © 2002 John Wiley & Sons, Ltd.
Evaluating the impact of betrayal for children exposed in photographs
Authors: Zurbriggen Eileen L. , Pearce Gale E. , Freyd Jennifer J.
Published: September 2003

Elements of betrayal trauma theory (Freyd, 1996 ) are used to evaluate potential negative and positive consequences for children who serve as artistic models, particularly those who model for their artist parents. Several dimensions are considered in evaluating the likelihood of harm: nudity, motives of the artist, consent, external vulnerability, and objectification. Recommendations to artists include appointing an advocate for the child, discussing photographic sessions and allowing observers, and going beyond standard release procedures. Similarities to the domains of creative writing and research psychology are considered. Copyright © 2002 John Wiley & Sons, Ltd.
Promoting children's interest in health: an evaluation of the child health profile
Authors: Hill Malcolm , Morton Peter
Published: September 2003

The child health profile was developed as an extension for older children of the personal child health record, which has normally been kept by mothers. The profile was introduced in three health board areas in Scotland. A questionnaire survey of young people revealed a mixed response concerning the usage and value of the profile. A small number had used it fully as a means of recording or communicating about personal health‐related matters, but a majority had not actively used the profile and two fifths said they had lost their copy. Children reported that doctors and nurses rarely asked to see the profile. Many respondents wanted more extensive and detailed health information. Copyright © 2002 John Wiley & Sons, Ltd.
Postnatal development of pre‐ and postsynaptic GABA markers at chandelier cell connections with pyramidal neurons in monkey prefrontal cortex
Authors: Cruz Dianne A. , Eggan Stephen M. , Lewis David A.
Published: September 2003

The protracted postnatal maturation of the primate prefrontal cortex (PFC) is associated with substantial changes in the number of excitatory synapses on pyramidal neurons, whereas the total number of inhibitory synapses appears to remain constant. In this study, we sought to determine whether the developmental changes in excitatory input to pyramidal cells are paralleled by changes in functional markers of inhibitory inputs to pyramidal neurons. The chandelier subclass of γ‐aminobutyric acid (GABA) neurons provides potent inhibitory control over pyramidal neurons by virtue of their axon terminals, which form distinct vertical structures (termed cartridges) that synapse at the axon initial segment (AIS) of pyramidal neurons. Thus, we examined the relative densities, laminar distributions, and lengths of presynaptic chandelier axon cartridges immunoreactive for the GABA membrane transporter 1 (GAT1) or the calcium‐binding protein parvalbumin (PV) and of postsynaptic pyramidal neuron AIS immunoreactive for the GABAA receptor α2 subunit (GABAA α2) in PFC area 46 of 38 rhesus monkeys (Macaca mulatta). From birth through 2 years of age, the relative densities and laminar distributions of these three markers exhibited different trajectories, suggesting developmental shifts in the weighting of at least some factors that determine inhibition at the AIS. In contrast, from 2 to 4 years of age, all three markers exhibited similar declines in density and length that paralleled the periadolescent pruning of excitatory synapses to pyramidal neurons. Across development, the predominant laminar location of PV‐labeled cartridges and GABAA α2‐immunoreactive AIS shifted from the middle to superficial layers, whereas the laminar distribution of GAT1‐positive cartridges did not change. Together, these findings suggest that the maturation of inhibitory inputs to the AIS of PFC pyramidal neurons is a complex process that may differentially affect the firing patterns of subpopulations of pyramidal neurons at specific postnatal time points. J. Comp. Neurol. 465:385–400, 2003. © 2003 Wiley‐Liss, Inc.
Perinatal and early postnatal changes in the expression of monocarboxylate transporters MCT1 and MCT2 in the rat forebrain
Authors: Baud Olivier , Fayol Laurence , Gressens Pierre , Pellerin Luc , Magistretti Pierre , Evrard Philippe , Verney Catherine
Published: September 2003

In addition to glucose, monocarboxylates including lactate represent a major source of energy for the brain, especially during development. We studied the immunocytochemical expression of the monocarboxylate transporters MCT1 and MCT2 in the rat brain between embryonic day (E) 16 and postnatal day (P) 14. At E16–18, MCT1‐like immunoreactivity was found throughout the cortical anlage, being particularly marked medially in the hippocampal anlage next to the ventricle. In a complementary pattern, MCT2‐like immunoreactivity was expressed along the medial and ventral border of the ventricle in the medial septum and habenula before birth. The hypothalamic area exhibited MCT2 and MCT1 positive areas from E18 on. These transient labelings revealed four main sites of monocarboxylate and/or glucose exchange: the brain parenchyma, the epithelial cells, the ependymocytes, and the glia limitans. During the first postnatal week, MCT1 immunoreactivity extended massively to the vessel walls and moderately to the developing astrocytes in the cortex. In contrast, MCT2 immunoreactivity was faint in blood vessels but massive in developing astrocytes from P3 to P7. Neither MCT2 nor MCT1 colocalized with neuronal, microglial, or oligodendrocytic markers during the first postnatal week. At P14, a part of the scattered punctate MCT2 staining could be associated with astrocytes and postsynaptic dendritic labeling. The transient pattern of expression of MCTs throughout the perinatal period suggests a potential relationship with the maturation of the blood‐brain barrier. J. Comp. Neurol. 465:445–454, 2003. © 2003 Wiley‐Liss, Inc.
Constitutive expression of p55TNFR mRNA and mitogen‐specific up‐regulation of TNFα and p75TNFR mRNA in mouse brain
Authors: Bette Michael , Kaut Oliver , Schäfer Martin K.‐H. , Weihe Eberhard
Published: September 2003

Serum tumor necrosis factor (TNF) functions as a mediator of the immune‐to‐brain axis. Numerous TNF receptor‐mediated effects on the nervous system are described but the knowledge about the regional and cellular expression of TNF receptor p55TNFR and p75TNFR in vivo is far from being complete. It is unclear whether TNF mediates its neuroimmune effects alone or in combination with other factors, e.g., bacterial mitogens. Here, we investigated the distribution of TNFα, p55TNFR, and p75TNFR in normal mouse brain and examined the stimulus‐specific effects of lipopolysaccharide (LPS) and staphylococcal enterotoxin B (SEB) on the expression of the cerebral TNF system. Both mitogens caused enhanced TNFα serum levels and induced c‐fos mRNA in the paraventricular nucleus but exhibited different effects on the cerebral gene expression of the TNF system. LPS but not SEB rapidly induced TNFα mRNA in circumventricular organs (CVOs) followed by spreading of TNFα mRNA into brain parenchyma close to the CVOs. The p55TNFR gene was constitutively expressed in many neurons with high levels in brainstem motor nuclei and in neurons of the sensory mesencephalic trigeminal nucleus. Moderate levels of p75TNFR mRNA were seen in single cells scattered throughout the brain in a pattern resembling microglia. Neither LPS nor SEB modulated the p55TNFR gene expression in any region or cell type of the brain, and LPS but not SEB induced p75TNFR mRNA in the CVOs. Thus, enhanced TNF serum levels able to stimulate c‐fos mRNA expression in the paraventricular nucleus did not necessarily result in a modulation of the cerebral TNF system. J. Comp. Neurol. 465:417–430, 2003. © 2003 Wiley‐Liss, Inc.
Upper bound on the coarsening rate for an epitaxial growth model
Authors: Kohn Robert V. , Yan Xiaodong
Published: September 2003

We study a specific example of energy‐driven coarsening in two space dimensions. The energy is ∫|∇∇u|2 + (1 ‐ | ∇u|2)2; the evolution is the fourth‐order PDE representing steepest descent. This equation has been proposed as a model of epitaxial growth for systems with slope selection. Numerical simulations and heuristic arguments indicate that the standard deviation of u grows like t1/3, and the energy per unit area decays like t‐1/3. We prove a weak, one‐sided version of the latter statement: The time‐averaged energy per unit area decays no faster than t‐1/3. Our argument follows a strategy introduced by Kohn and Otto in the context of phase separation, combining (i) a dissipation relation, (ii) an isoperimetric inequality, and (iii) an ODE lemma. The interpolation inequality is new and rather subtle; our proof is by contradiction, relying on recent compactness results for the Aviles‐Giga energy. © 2003 Wiley Periodicals, Inc.
Purely nonlinear instability of standing waves with minimal energy
Authors: Comech Andrew , Pelinovsky Dmitry
Published: September 2003

We consider Hamiltonian systems with U(1) symmetry. We prove that in the generic situation the standing wave that has the minimal energy among all other standing waves is unstable, in spite of the absence of linear instability. Essentially, the instability is caused by higher algebraic degeneracy of the zero eigenvalue in the spectrum of the linearized system. We apply our theory to the nonlinear Schrödinger equation. © 2003 Wiley Periodicals, Inc.
Gauged harmonic maps, Born‐Infeld electromagnetism, and magnetic vortices
Authors: Lin Fanghua , Yang Yisong
Published: September 2003

We study maps from a 2‐surface into the standard 2‐sphere coupled with Born‐Infeld geometric electromagnetism through an Abelian gauge field. Such a formalism extends the classical harmonic map model, known as the σ‐model, governing the spin vector orientation in a ferromagnet allows us to obtain the coexistence of vortices and antivortices characterized by opposite, self‐excited, magnetic flux lines. We show that the Born‐Infeld free parameter may be used to achieve arbitrarily high local concentration of magnetic flux lines that the total minimum energy is an additive function of these quantized flux lines realized as the numbers of vortices antivortices. In the case where the underlying surface, or the domain, is compact, we obtain a necessary sufficient condition for the existence of a unique solution representing a prescribed distribution of vortices antivortices. In the case where the domain is the full plane, we prove the existence of a unique solution representing an arbitrary distribution of vortices and antivortices. Furthermore, we also consider the Einstein gravitation induced by these vortices, known as cosmic strings, establish the existence of a solution representing a prescribed distribution of cosmic strings cosmic antistrings under a necessary sufficient condition that makes the underlying surface a complete surface with respect to the induced gravitational metric. © 2003 Wiley Periodicals, Inc.
The scattering support
Authors: Kusiak Steven , Sylvester John
Published: September 2003

We discuss inverse problems for the Helmholtz equation at fixed energy, specifically the inverse source problem and the inverse scattering problem from a medium or an obstacle. We introduce the convex scattering support of a far field, a set which will be a subset of the convex hull of the support of any source which can produce it. We give several theorems which explain how to compute the convex scattering support and how to relate it to the actual support of a source, medium, or obstacle. © 2003 Wiley Periodicals, Inc.
One‐bit sigma‐delta quantization with exponential accuracy
Authors: Güntürk C. Si̇nan
Published: September 2003

One‐bit quantization is a method of representing bandlimited signals by ±1 sequences that are computed from regularly spaced samples of these signals; as the sampling density λ → ∞, convolving these one‐bit sequences with appropriately chosen filters produces increasingly close approximations of the original signals. This method is widely used for analog‐to‐digital and digital‐to‐analog conversion, because it is less expensive and simpler to implement than the more familiar critical sampling followed by fine‐resolution quantization. However, unlike fine‐resolution quantization, the accuracy of one‐bit quantization is not well‐understood. A natural error lower bound that decreases like 2−λ can easily be given using information theoretic arguments. Yet, no one‐bit quantization algorithm was known with an error decay estimate even close to exponential decay. In this paper, we construct an infinite family of one‐bit sigma‐delta quantization schemes that achieves this goal. In particular, using this family, we prove that the error signal for π‐bandlimited signals is at most O(2−.07λ). © 2003 Wiley Periodicals, Inc.
SCALEA: a performance analysis tool for parallel programs
Authors: Truong Hong‐Linh , Fahringer Thomas
Published: September 2003

Many existing performance analysis tools lack the flexibility to control instrumentation and performance measurement for code regions and performance metrics of interest. Performance analysis is commonly restricted to single experiments.

In this paper we present SCALEA, which is a performance instrumentation, measurement, analysis, and visualization tool for parallel programs that supports post‐mortem performance analysis. SCALEA currently focuses on performance analysis for OpenMP, MPI, HPF, and mixed parallel programs. It computes a variety of performance metrics based on a novel classification of overhead. SCALEA also supports multi‐experiment performance analysis that allows one to compare and to evaluate the performance outcome of several experiments. A highly flexible instrumentation and measurement system is provided which can be controlled by command‐line options and program directives. SCALEA can be interfaced by external tools through the provision of a full Fortran90 OpenMP/MPI/HPF frontend that allows one to instrument an abstract syntax tree at a very high‐level with C‐function calls and to generate source code. A graphical user interface is provided to view a large variety of performance metrics at the level of arbitrary code regions, threads, processes, and computational nodes for single‐ and multi‐experiment performance analysis. Copyright © 2003 John Wiley & Sons, Ltd.
Fairness in systems based on multiparty interactions
Authors: Ruiz David , Corchuelo Rafael , Toro Miguel
Published: September 2003

In the context of the Multiparty Interaction Model, fairness is used to insure that an interaction that is enabled sufficiently often in a concurrent program will eventually be selected for execution. Unfortunately, this notion does not take conspiracies into account, i.e. situations in which an interaction never becomes enabled because of an unfortunate interleaving of independent actions; furthermore, eventual execution is usually too weak for practical purposes since this concept can only be used in the context of infinite executions. In this article, we present a new fairness notion, k‐conspiracy‐free fairness, that improves on others because it takes finite executions into account, alleviates conspiracies that are not inherent to a program, and k may be set a priori to control its goodness to address the above‐mentioned problems. Copyright © 2003 John Wiley & Sons, Ltd.
Dynamic query scheduling in parallel data warehouses
Authors: Märtens Holger , Rahm Erhard , Stöhr Thomas
Published: September 2003

Parallel processing is a key to high performance in very large data warehouse applications that execute complex analytical queries on huge amounts of data. Although parallel database systems (PDBSs) have been studied extensively in the past decades, the specifics of load balancing in parallel data warehouses have not been addressed in detail.

In this study, we investigate how the load balancing potential of a Shared Disk (SD) architecture can be utilized for data warehouse applications. We propose an integrated scheduling strategy that simultaneously considers both processors and disks, regarding not only the total workload on each resource but also the distribution of load over time. We evaluate the performance of the new method in a comprehensive simulation study and compare it to several other approaches. The analysis incorporates skew aspects and considers typical data warehouse features such as star schemas with large fact tables and bitmap indices. Copyright © 2003 John Wiley & Sons, Ltd.
On the performance of TCP over a TDD‐TD/CDMA architecture
Authors: Casoni Maurizio
Published: September 2003

This paper determines the performance of TCP when it is employed over a TDD‐TD/CDMA architecture which supports different classes of subscribers and adopts an interference‐driven admission control policy. The blocking and the outage probability of the system users are evaluated under various traffic conditions as well as the TCP throughput that data users experience. Call blocking and TCP throughput are determined by means of a semi‐analytical approach. This work shows that when TCP is taken into account, many options come out for the system design in order to optimize radio resources. Resource assignment in the TDD‐TD/CDMA system can then be done as a function of the actual radio link quality with the goal both to serve as many users as possible and to keep the TCP throughput as high as possible. Copyright © 2003 John Wiley & Sons, Ltd.
Accurate and time efficient estimation of the probability of error in bursty channels
Authors: Berber M. Stevan
Published: September 2003

A method and a technique for the probability of error estimation in digital channels with memory are developed and demonstrated. The expressions for the mean and variance of a random variable, representing a block of bits transmission in a bursty channel (channel with memory), are derived. The influence of the memory is expressed by a parameter called the memory factor. It is shown that the traditional Monte Carlo method can be applied for the probability of error estimation. In order to control the accuracy and increase the time efficiency of estimation this method is modified and a new method, called the modified Monte Carlo method, is proposed. Based on this modified method a technique of estimation with controlled accuracy is developed and demonstrated using data obtained by simulation. According to this technique the sample size is adjusted in the course of estimating procedure to give an accurate estimate of the probability of error for a minimum required time of estimation. Copyright © 2003 John Wiley & Sons, Ltd.
Implicit bias in impression formation: associations influence the construal of individuating information
Authors: Gawronski Bertram , Geschke Daniel , Banse Rainer
Published: September 2003

The present research investigated the influence of group‐related evaluative associations on the process of impression formation. In particular, we expected the impact of a target's category membership on the construal of ambiguous behaviour to be moderated by perceivers' evaluative associations related to the target category. Associative strength was further expected to have an indirect effect on dispositional inference, mediated by its impact on behaviour identification. Results support both of these assumptions. Moreover, the influence of evaluative associations on impression formation was not moderated by perceivers' motivation to control prejudiced reactions. Rather, motivation to control moderated only the relation between evaluative associations and the explicit endorsement of prejudiced beliefs about the target group in general, such that explicit prejudice endorsement was correlated with evaluative associations only for perceivers low, but not for those high in motivation to control. Implications for prejudice control are discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Attitude‐behaviour consistency: the role of group norms, attitude accessibility, and mode of behavioural decision‐making
Authors: Smith Joanne R. , Terry Deborah J.
Published: September 2003

The interplay between two perspectives that have recently been applied in the attitude area—the social identity approach to attitude‐behaviour relations (Terry & Hogg, 1996) and the MODE model (Fazio, 1990a)—was examined in the present research. Two experimental studies were conducted to examine the role of group norms, group identification, attitude accessibility, and mode of behavioural decision‐making in the attitude‐behaviour relationship. In Study 1 (N = 211), the effects of norms and identification on attitude‐behaviour consistency as a function of attitude accessibility and mood were investigated. Study 2 (N = 354) replicated and extended the first experiment by using time pressure to manipulate mode of behavioural decision‐making. As expected, the effects of norm congruency varied as a function of identification and mode of behavioural decision‐making. Under conditions assumed to promote deliberative processing (neutral mood/low time pressure), high identifiers behaved in a manner consistent with the norm. No effects emerged under positive mood and high time pressure conditions. In Study 2, there was evidence that exposure to an attitude‐incongruent norm resulted in attitude change only under low accessibility conditions. The results of these studies highlight the powerful role of group norms in directing individual behaviour and suggest limited support for the MODE model in this context. Copyright © 2003 John Wiley & Sons, Ltd.
Self, in‐group, and out‐group evaluation: bond or breach?
Authors: De Vries Reinout E.
Published: September 2003

A number of studies have looked at causes of in‐group bias, but few studies have actually investigated whether the two components of in‐group bias, i.e. in‐group and out‐group evaluation, are related to each other and whether they have similar or different predictors. In the Fiji Islands, self‐, in‐group, and out‐group evaluations were obtained using within‐subject correlations from a sample of 336 indigenous and Indian Fijians. Self‐evaluation was positively related to in‐group evaluation, and both were positively related to out‐group evaluation, supporting a spillover model. After controlling for background variables and the other evaluation variables, regression analyses showed that in‐group identification was positively related to in‐group evaluation, and social distance and political ethnocentrism were negatively related to out‐group evaluation. Additionally, ethnicity interacted with collective self‐esteem in determining both in‐group favouritism and out‐group derogation. Copyright © 2003 John Wiley & Sons, Ltd.
Is politician A or politician B more persuasive? recipients' source preference and the direction of biased message processing
Authors: Ziegler René , Diehl Michael
Published: September 2003

Participants' preference for one of two politicians running for the post of Chancellor in Germany was measured. Under conditions conducive to effortful processing, participants were then presented with a persuasive message ascribed to one of these two sources. The message was either unambiguous strong, unambiguous weak, or ambiguous. Different from previous research on the role of message ambiguity for attitude change, the ambiguous message consisted of arguments rated as moderately convincing in a pretest rather than of a mixture of strong and weak arguments. The results were in line with predictions derived from the heuristic‐systematic model (HSM). Indicating unbiased systematic processing, an unambiguous strong message led to more agreement than an unambiguous weak message. In the case of an ambiguous message, in line with the HSM's bias hypothesis, more agreement was found among participants preferring the source politician as compared to participants preferring the other politician. Copyright © 2003 John Wiley & Sons, Ltd.