bluuebunny/crossref_metadata_2025 huggingface dataset:
On Evaluating Efficiency of a Combined Power and Cooling Cycle
Authors: Vijayaraghavan Sanjay , Goswami D. Y.
Published: December 2003

A combined power and cooling cycle is being investigated. The cycle is a combination of the Rankine cycle and an absorption refrigeration cycle. Evaluating the efficiency of this cycle is made difficult by the fact that there are two different simultaneous outputs, namely power and refrigeration. An efficiency expression has to appropriately weigh the cooling component in order to allow comparison of this cycle with other cycles. This paper develops several expressions for the first law, second law and exergy efficiency definitions for the combined cycle based on existing definitions in the literature. Some of the developed equations have been recommended for use over others, depending on the comparison being made. Finally, some of these definitions have been applied to the cycle and the performance of the cycle optimized for maximum efficiency. A Generalized Reduced Gradient (GRG) method was used to perform the optimization. The results of these optimizations are presented and discussed.
Modeling Time-Dependent Pore Pressure Due to Capillary and Chemical Potential Effects and Resulting Wellbore Stability in Shales
Authors: Rahman M. K. , Chen Zhixi , Rahman Sheik S.
Published: December 2003

During drilling operations, the mud filtrate interacts with the pore fluid around the wellbore and changes pore pressure by capillary and chemical potential effects. Thus the change in pore pressure around borehole becomes time-dependent, particularly in extremely low permeability shaley formations. In this paper, the change in pore pressure due to capillary and chemical potential effects are investigated experimentally. Analytical models are also developed based on the experimental results. A wellbore stability analysis model incorporating the time-dependent change in pore pressure is applied to a vertical well in a shale formation under normal fault stress regime.
Evaluation of Energy, Environmental, and Economic Characteristics of Fuel Cell Combined Heat and Power Systems for Residential Applications
Authors: Gunes M. Burak , Ellis Michael W.
Published: December 2003

Residential combined heat and power (CHP) systems using fuel cell technology can provide both electricity and heat and can substantially reduce the energy and environmental impact associated with residential applications. The energy, environmental, and economic characteristics of fuel cell CHP systems are investigated for single-family residential applications. Hourly energy use profiles for electricity and thermal energy are determined for typical residential applications. A mathematical model of a residential fuel cell based CHP system is developed. The CHP system incorporates a fuel cell system to supply electricity and thermal energy, a vapor compression heat pump to provide cooling in the summer and heating in the winter, and a thermal storage tank to help match the available thermal energy to the thermal energy needs. The performance of the system is evaluated for different climates. Results from the study include an evaluation of the major design parameters of the system, load duration curves, an evaluation of the effect of climate on energy use characteristics, an assessment of the reduction in emissions, and a comparison of the life cycle cost of the fuel cell based CHP system to the life cycle costs of conventional residential energy systems. The results suggest that the fuel cell CHP system provides substantial energy and environmental benefits but that the cost of the fuel cell sub-system must be reduced to roughly $500/kWe before the system can be economically justified.
Exergy Analysis of Single- and Two-Stage Crude Oil Distillation Units
Authors: Al-Muslim Husain , Dincer Ibrahim , Zubair Syed M.
Published: December 2003

In a refinery distillation plant, there are many components of interest to be analyzed thermodynamically, e.g., the crude oil heating furnace, the distillation column and a network of heat exchangers. Previous studies showed that the highest exergy losses occur when there is a heat transfer process especially in the crude oil heating furnace where high quality fuel is used to heat the crude oil, which is a low quality duty, beside the high temperature difference. Therefore, it is proposed in this work to perform distillation in two stages rather than one to reduce heat duty of the heating furnace and thus reducing irreversible losses. In this paper, energy and exergy analyses of a traditional one-stage crude oil distillation unit and a newly proposed two-stage crude oil distillation unit are conducted to study energy and exergy efficiencies of these units and determine the exergy losses. The results are compared for both one- and two-stage distillation units. In this regard, a commercial software package, SimSci/PRO II program is used to carry out both energy and exergy calculations. It is found that the overall exergy efficiencies for single- and two-stage distillation units are 14.0% and 31.5%, respectively. The proposed two-stage distillation unit shows 43.8% decrease in the overall exergy losses and 125% increase in the overall exergy efficiency.
Facilitating high quality student practice in introductory physics
Authors: Johnson Molly
Published: December 2003

“Practice makes perfect, but only if you do it right.” Typical physics students practice extensively through the large quantities of homework they do. But research in introductory physics instruction shows that despite this practice, students often do not learn much in introductory physics. Students often do not focus their practice on the skills (such as concept interpretation, and generating a physical representation of a problem) that they need in order to solve physics problems flexibly and reliably. They often focus their practice instead on simply getting an answer. By omitting practice of important skills, it is likely that those skills will not be learned. This paper identifies communication difficulties between students and between students and instructors as important sources of barriers to achieving high-quality student practice. Some strategies to address communication difficulties in the context of small group in-class problem solving are proposed. A classroom peer-collaborative structure, Supervised Practice, that implements these strategies is described, and the impact of the classroom design on the quality of student practice is investigated.
Concentration analysis: A quantitative assessment of student states
Authors: Bao Lei , Redish Edward F.
Published: December 2003

Multiple-choice tests such as the Force Concept Inventory (FCI) provide useful instruments to probe the distribution of student difficulties on a large scale. However, traditional analysis often relies solely on scores (number of students giving the correct answer). This ignores what can be significant and important information: the distribution of wrong answers given by the class. In this paper we introduce a new method, concentration analysis, to measure how students’ responses on multiple-choice questions are distributed. This information can be used to study if the students have common incorrect models or if the question is effective in detecting student models. When combined with information obtained from qualitative research, the method allows us to identify cleanly what FCI results are telling us about student knowledge.
Student understanding of time in special relativity: Simultaneity and reference frames
Authors: Scherr Rachel E. , Shaffer Peter S. , Vokos Stamatis
Published: December 2003

This article reports on an investigation of student understanding of the concept of time in special relativity. A series of research tasks are discussed that illustrate, step-by-step, how student reasoning of fundamental concepts of relativity was probed. The results indicate that after standard instruction students at all academic levels have serious difficulties with the relativity of simultaneity and with the role of observers in inertial reference frames. Evidence is presented that suggests many students construct a conceptual framework in which the ideas of absolute simultaneity and the relativity of simultaneity harmoniously co-exist.
Using two models in optics: Students’ difficulties and suggestions for teaching
Authors: Colin P. , Viennot L.
Published: December 2003

This paper focuses on difficulties linked to situations in physics involving two models: geometrical optics and wave optics. The starting point is an investigation of university-level students’ difficulties. Excerpts from textbooks are given, to illustrate potential difficulties. A content analysis is then presented, underlining two important features required for dealing with such situations: awareness of the status of the drawings, and the “backward selection” of paths of light. These features could provide some guidelines for the designing of innovative teaching strategies.
Surveying students’ conceptual knowledge of electricity and magnetism
Authors: Maloney David P. , O’Kuma Thomas L. , Hieggelke Curtis J. , Van Heuvelen Alan
Published: December 2003

The Conceptual Survey of Electricity and Magnetism (CSEM) was developed to assess students’ knowledge about topics in electricity and magnetism. The survey is a 32-question, multiple-choice test that can be used as both a pretest and posttest. During four years of testing and refinement, the survey has been given in one form or another to more than 5000 introductory physics students at 30 different institutions. Typical pretest results are that students in calculus-based courses get 31% of the questions correct and student’s in algebra/trigonometry-based courses average 25% correct. Posttest correct results only rise to 47% and 44%, respectively. From analysis of student responses, a number of student difficulties in electricity and magnetism are indicated.
Helping physics students learn how to learn
Authors: Elby Andrew
Published: December 2003

Students’ “epistemological” beliefs—their views about the nature of knowledge and learning—affect how they approach physics courses. For instance, a student who believes physics knowledge to consist primarily of disconnected facts and formulas will study differently from a student who views physics as an interconnected web of concepts. Unfortunately, previous studies show that physics courses, even ones that help students learn concepts particularly well, generally do not lead to significant changes in students’ epistemological beliefs. This paper discusses instructional practices and curricular elements, suitable for both college and high school, that helped students develop substantially more sophisticated beliefs about knowledge and learning, as measured by the Maryland Physics Expectations Survey and by the Epistemological Beliefs Assessment for Physical Science.
A geometric algebra reformulation of geometric optics
Authors: Sugon Quirino M. , McNamara Daniel J.
Published: December 2003

We present a tutorial on the Clifford (geometric) algebra Cl3,0 and use it to reformulate the laws of geometric optics. This algebra is essentially a Pauli algebra, with the Pauli sigma matrices interpreted as unit rays or vectors. In this algebra, the exponentials of imaginary vectors act as vector rotation operators. This property lets us rewrite the laws of reflection and refraction of light in geometric optics in exponential form. The reformulated laws allow easy translation of symbols to words and to diagrams. They also are shown to be equivalent to standard vector formulations. These coordinate-free laws can be shown to simplify the analysis of geometric optics problems such as the tracing of meridional and skew rays in lenses and optical fibers.
Growth Phase-Dependent Regulation and Stringent Control of
fis
Are Conserved Processes in Enteric Bacteria and Involve a Single Promoter (
fis
P) in
Escherichia coli
Authors: Mallik Prabhat , Pratt Timothy S. , Beach Michael B. , Bradley Meranda D. , Undamatla Jayanthi , Osuna Robert
Published: December 2003

The intracellular concentration of the
Escherichia coli
factor for inversion stimulation (Fis), a global regulator of transcription and a facilitator of certain site-specific DNA recombination events, varies substantially in response to changes in the nutritional environment and growth phase. Under conditions of nutritional upshift,
fis
is transiently expressed at very high levels, whereas under induced starvation conditions,
fis
is repressed by stringent control. We show that both of these regulatory processes operate on the chromosomal
fis
genes of the enterobacteria
Klebsiella pneumoniae
,
Serratia marcescens
,
Erwinia carotovora
, and
Proteus vulgaris
, strongly suggesting that the physiological role of Fis is closely tied to its transcriptional regulation in response to the nutritional environment. These transcriptional regulatory processes were previously shown to involve a single promoter (
fis
P) preceding the
fis
operon in
E. coli
. Recent work challenged this notion by presenting evidence from primer extension assays which appeared to indicate that there are multiple promoters upstream of
fis
P that contribute significantly to the expression and regulation of
fis
in
E. coli
. Thus, a rigorous analysis of the
fis
promoter region was conducted to assess the contribution of such additional promoters. However, our data from primer extension analysis, S1 nuclease mapping, β-galactosidase assays, and in vitro transcription analysis all indicate that
fis
P is the sole
E. coli fis
promoter in vivo and in vitro. We further show how certain conditions used in the primer extension reactions can generate artifacts resulting from secondary annealing events that are the likely source of incorrect assignment of additional
fis
promoters.
Diversifying Selection at theBacillusQuorum-Sensing Locus and Determinants of Modification Specificity during Synthesis of the ComX Pheromone
Authors: Ansaldi M. , Dubnau D.
Published: December 2003

The competence quorum-sensing system ofBacillus subtilisconsists of two-component regulatory proteins, ComP (histidine kinase) and the response regulator, ComA, an extracellular pheromone (ComX), and a protein that is needed for the proteolytic cleavage and modification of pre-ComX (ComQ). ComQ and pre-ComX are both necessary and sufficient for the production of active pheromone, which is released as an isoprenylated peptide. Laboratory strain 168 and a number of natural isolates of bacilli differ in the primary sequences of their pheromones as well as in the masses of their isoprenyl adducts. We have shown that ComX, ComQ, and the membrane-localized sensor domain of ComP are highly polymorphic in natural isolates of bacilli all closely related to the laboratory strain ofB. subtilis. In this study, we used two statistical tests (the ratio of synonymous and nonsynonymous substitution rates and the TajimaDtest) to demonstrate that these polymorphic sequences evolved by diversifying selection rather than by neutral drift. We show that the choice of isoprenyl derivative is determined by the C-terminal (mature) sequence of pre-ComX rather than by the ComQ protein. The implications of these findings for the evolution of the quorum-sensing system and for the protein-protein interactions involved in determining specificity are discussed.
pH-Dependent Catabolic Protein Expression during Anaerobic Growth of
Escherichia coli
K-12
Authors: Yohannes Elizabeth , Barnhart D. Michael , Slonczewski Joan L.
Published: December 2003

During aerobic growth of
Escherichia coli
, expression of catabolic enzymes and envelope and periplasmic proteins is regulated by pH. Additional modes of pH regulation were revealed under anaerobiosis.
E. coli
K-12 strain W3110 was cultured anaerobically in broth medium buffered at pH 5.5 or 8.5 for protein identification on proteomic two-dimensional gels. A total of 32 proteins from anaerobic cultures show pH-dependent expression, and only four of these proteins (DsbA, TnaA, GatY, and HdeA) showed pH regulation in aerated cultures. The levels of 19 proteins were elevated at the high pH; these proteins included metabolic enzymes (DhaKLM, GapA, TnaA, HisC, and HisD), periplasmic proteins (ProX, OppA, DegQ, MalB, and MglB), and stress proteins (DsbA, Tig, and UspA). High-pH induction of the glycolytic enzymes DhaKLM and GapA suggested that there was increased fermentation to acids, which helped neutralize alkalinity. Reporter
lac
fusion constructs showed base induction of
sdaA
encoding serine deaminase under anaerobiosis; in addition, the glutamate decarboxylase genes
gadA
and
gadB
were induced at the high pH anaerobically but not with aeration. This result is consistent with the hypothesis that there is a connection between the
gad
system and GabT metabolism of 4-aminobutanoate. On the other hand, 13 other proteins were induced by acid; these proteins included metabolic enzymes (GatY and AckA), periplasmic proteins (TolC, HdeA, and OmpA), and redox enzymes (GuaB, HmpA, and Lpd). The acid induction of NikA (nickel transporter) is of interest because
E. coli
requires nickel for anaerobic fermentation. The position of the NikA spot coincided with the position of a small unidentified spot whose induction in aerobic cultures was reported previously; thus, NikA appeared to be induced slightly by acid during aeration but showed stronger induction under anaerobic conditions. Overall, anaerobic growth revealed several more pH-regulated proteins; in particular, anaerobiosis enabled induction of several additional catabolic enzymes and sugar transporters at the high pH, at which production of fermentation acids may be advantageous for the cell.
Inactivation ofompXCauses Increased Interactions of Type 1 FimbriatedEscherichia coliwith Abiotic Surfaces
Authors: Otto Karen , Hermansson Malte
Published: December 2003

During the initial steps of biofilm formation, bacteria have to adapt to a major change in their environment. The adhesion-induced phenotypic changes in a type 1 fimbriatedEscherichia colistrain included reductions in the levels of several outer membrane proteins, one of which was identified as OmpX. Here, the phenotypes of mutant strains that differ at theompXlocus were studied with regard to adhesion, cell surface properties, and resistance to stress and antimicrobial compounds. The kinetics of adhesion were measured online by an extended quartz crystal microbalance technique for wild-type and mutant strains with a fimbriated or nonfimbriated background. Deletion ofompXled to significantly increased cell-surface contact in fimbriated strains but to decreased cell-surface contact in a nonfimbriated strain. Phenotypic characterization of theompXmutant demonstrated thatompXinterferes with proper regulation of cell surface structures that play a key role in mediating firm contact of the cell with a surface (i.e., type 1 fimbriae, flagellae, and exopolysaccharides). These phenotypic changes were accompanied by increased tolerance to several antibiotic compounds and sodium dodecyl sulfate. Based on these results, we propose that changes in the composition of outer membrane proteins during fimbria-mediated adhesion may be part of a coordinated adaptive response to the attached mode of growth.
Identification of Residues of the Kid Toxin Involved in Autoregulation of the
parD
System
Authors: Lemonnier Marc , Santos-Sierra Sandra , Pardo-Abarrio Consolación , Díaz-Orejas Ramón
Published: December 2003

The toxin-antitoxin system
parD
(
kis kid
) of plasmid R1 is coregulated by the coordinated action of its two gene products. Here we describe the isolation and the in vivo characterization of three single-amino-acid changes in the Kid toxin, G4E, C74Y, and E91K, that affect the coregulatory activity but preserve the toxicity of the protein.
Necessity of Meningococcal γ-Glutamyl Aminopeptidase for
Neisseria meningitidis
Growth in Rat Cerebrospinal Fluid (CSF) and CSF-Like Medium
Authors: Takahashi Hideyuki , Hirose Kenji , Watanabe Haruo
Published: December 2003

The growth of a γ-glutamyl aminopeptidase (GGT)-deficient
Neisseria meningitidis
strain was much slower than that of the parent strain in rat cerebrospinal fluid (CSF) and in a synthetic CSF-mimicking medium, and the growth failure was suppressed by the addition of cysteine. These results suggested that, in the environment of cysteine shortage, meningococcal GGT provided an advantage for meningococcal multiplication by supplying cysteine from environmental γ-glutamyl-cysteinyl peptides.
Cysteinyl-tRNA
Cys
Formation in
Methanocaldococcus jannaschii
: the Mechanism Is Still Unknown
Authors: Ruan Benfang , Nakano Hiroaki , Tanaka Masashi , Mills Jonathan A. , DeVito Joseph A. , Min Bokkee , Low K. Brooks , Battista John R. , Söll Dieter
Published: December 2003

Most organisms form Cys-tRNA
Cys
, an essential component for protein synthesis, through the action of cysteinyl-tRNA synthetase (CysRS). However, the genomes of
Methanocaldococcus jannaschii
,
Methanothermobacter thermautotrophicus
, and
Methanopyrus kandleri
do not contain a recognizable
cysS
gene encoding CysRS. It was reported that
M. jannaschii
prolyl-tRNA synthetase (C. Stathopoulos, T. Li, R. Longman, U. C. Vothknecht, H. D. Becker, M. Ibba, and D. Söll, Science
287:
479-482, 2000; R. S. Lipman, K. R. Sowers, and Y. M. Hou, Biochemistry
39:
7792-7798, 2000) or the
M. jannaschii
MJ1477 protein (C. Fabrega, M. A. Farrow, B. Mukhopadhyay, V. de Crécy-Lagard, A. R. Ortiz, and P. Schimmel, Nature
411:
110-114, 2001) provides the “missing” CysRS activity for in vivo Cys-tRNA
Cys
formation. These conclusions were supported by complementation of temperature-sensitive
Escherichia coli cysS
(Ts) strain UQ818 with archaeal
proS
genes (encoding prolyl-tRNA synthetase) or with the
Deinococcus radiodurans
DR0705 gene, the ortholog of the MJ1477 gene. Here we show that
E. coli
UQ818 harbors a mutation (V27E) in CysRS; the largest differences compared to the wild-type enzyme are a fourfold increase in the

K
m

for cysteine and a ninefold reduction in the
k
cat
for ATP. While transformants of
E. coli
UQ818 with archaeal and bacterial
cysS
genes grew at a nonpermissive temperature, growth was also supported by elevated intracellular cysteine levels, e.g., by transformation with an
E. coli cysE
allele (encoding serine acetyltransferase) or by the addition of cysteine to the culture medium. An
E. coli cysS
deletion strain permitted a stringent complementation test; growth could be supported only by archaeal or bacterial
cysS
genes and not by archaeal
proS
genes or the
D. radiodurans
DR0705 gene. Construction of a
D. radiodurans
DR0705 deletion strain showed this gene to be dispensable. However, attempts to delete
D. radiodurans cysS
failed, suggesting that this is an essential
Deinococcus
gene. These results imply that it is not established that
proS
or MJ1477 gene products catalyze Cys-tRNA
Cys
synthesis in
M. jannaschii
. Thus, the mechanism of Cys-tRNA
Cys
formation in
M. jannaschii
still remains to be discovered.
Flavin Mononucleotide-Binding Flavoprotein Family in the Domain
Archaea
Authors: Ding Yan-Huai R. , Ferry James G.
Published: December 2003

The protein (AfpA, for archaeoflavoprotein) encoded by AF1518 in the genome of
Archaeoglobus fulgidus
was produced in
Escherichia coli
and characterized. AfpA was found to be a homodimer with a native molecular mass of 43 kDa and containing two noncovalently bound flavin mononucleotides (FMNs). The cell extract of
A. fulgidus
catalyzed the CO-dependent reduction of AfpA that was stimulated by the addition of ferredoxin. Ferredoxin was found to be a direct electron donor to purified AfpA, whereas rubredoxin was unable to substitute. Neither NADH nor NADPH was an electron donor. Ferricyanide, 2,6-dichlorophenolindophenol, several quinones, ferric citrate, bovine cytochrome
c
, and O
2
accepted electrons from reduced AfpA, whereas coenzyme F
420
did not. The rate of cytochrome
c
reduction was enhanced in the presence of O
2
suggesting that superoxide is a product of the interaction of reduced AfpA with O
2
. Although AF1518 was previously annotated as encoding a decarboxylase involved in coenzyme A biosynthesis, the results establish that AfpA is an electron carrier protein with ferredoxin as the physiological electron donor. The genomes of several diverse
Archaea
contained
afpA
homologs clustered with open reading frames annotated as homologs of genes encoding reductases involved in the oxidative stress response of anaerobes from the domain
Bacteria
. A potential role for AfpA in coupling electron flow from ferredoxin to the putative reductases is discussed. A search of the databases suggests that AfpA is the prototype of a previously unrecognized flavoprotein family unique to the domain
Archaea
for which the name archaeoflavoprotein is proposed.
PERTURBATIVELY DEFINED EFFECTIVE CLASSICAL POTENTIAL IN CURVED SPACE
Authors: KLEINERT H. , CHERVYAKOV A.
Published: December 2003

The partition function of a quantum statistical system in flat space can always be written as an integral over a classical Boltzmann factor exp [-βV eff cl (x0)], where V eff cl (x0) is the so-called effective classical potential containing the effects of all quantum fluctuations. The variable of integration is the temporal path average [Formula: see text]. We show how to generalize this concept to paths qμ(τ) in curved space with metric gμν(q), and calculate perturbatively the high-temperature expansion of V eff cl (q0). The requirement of independence under coordinate transformations qμ(τ)→ q′μ(τ) introduces subtleties in the definition and treatment of the path average [Formula: see text], and covariance is achieved only with the help of a suitable Faddeev–Popov procedure.
ANALYTIC INVARIANT CHARGE IN QCD
Authors: NESTERENKO A. V.
Published: December 2003

This paper gives an overview of recently developed model for the QCD analytic invariant charge. Its underlying idea is to bring the analyticity condition, which follows from the general principles of local Quantum Field Theory, in perturbative approach to renormalization group (RG) method. The concrete realization of the latter consists in explicit imposition of analyticity requirement on the perturbative expansion of β function for the strong running coupling, with subsequent solution of the corresponding RG equation. In turn, this allows one to avoid the known difficulties originated in perturbative approximation of the RG functions. Ultimately, the proposed approach results in qualitatively new properties of the QCD invariant charge. The latter enables one to describe a wide range of the strong interaction processes both of perturbative and intrinsically nonperturbative nature.
Quartic exercises
Authors: Knus Max-Albert , Tignol Jean-Pierre
Published: December 2003

A correspondence between quartic étale algebras over a
field and quadratic étale extensions of cubic étale
algebras is set up and investigated. The basic
constructions are laid out in general
for sets with a profinite group action and for torsors,
and translated in terms of étale algebras and Galois
algebras. A parametrization of cyclic
quartic algebras is given.
Inhibition of Intimal Thickening in the Rat Carotid Artery Injury Model by a Nontoxic Ras Inhibitor
Authors: George Jacob , Sack Jessica , Barshack Iris , Keren Pnina , Goldberg Iris , Haklai Roni , Elad-Sfadia Galit , Kloog Yoel , Keren Gad
Published: December 2003

Background—

Neointimal formation with and without previous vascular injury is common after balloon dilation and in transplant arteriosclerosis. It involves proliferation and migration of medial smooth muscle cells and inflammation, processes that are regulated by Ras proteins and their down-stream effectors. Farnesylthiosalicylate (FTS) is a Ras inhibitor that interferes with Ras membrane anchorage and affects Ras proteins in their active state. In the present study, we tested the hypothesis that systemic administration of FTS will suppress intimal thickening in the rat carotid injury model.

Methods and Results—

The effects of FTS on rat vascular smooth muscle cells (VSMC) and splenocytes proliferation were evaluated in vitro. The in vivo effects of FTS on the neointima of balloon-injured male Wistar rats, treated daily for 2 weeks with FTS (5 mg/kg weight, intraperitoneally) were evaluated by determination of Ras, Ras-GTP, and active ERK levels (3 days after injury), and by quantitative determination of the extent of intimal thickening and immunohistochemistry for Ras, iNOS, NFkB, and Ki-67 (2 weeks after injury). FTS inhibited VSMC and splenocyte proliferation as well as interferon-γ secretion by splenocytes in a dose-dependent manner. Compared with controls, FTS treatment resulted in a strong decrease in Ras-GTP and active ERK, and it significantly reduced intimal thickening after the injury. Ras expression appeared predominantly at areas of neointima regardless of the treatment group. NFkB and iNOS-positive cell numbers were reduced in sections of FTS treated rats.

Conclusion—

FTS appears to act as a potent inhibitor of intimal thickening in a model of experimental arterial injury.
High ω-3 Fatty Acid Content in Alpine Cheese
Authors: Hauswirth Christa B. , Scheeder Martin R.L. , Beer Jürg H.
Published: December 2003

Background—

α-Linolenic acid (ALA) may protect from cardiovascular disease. Because fresh alpine grass contains high amounts of ALA, we hypothesized that the levels of ω-3 fatty acids would concentrate to nutritional relevance in the cheese of milk from cows with alpine grass feeding compared with cheese from silage and concentrate feeding; the newly available cheese produced from cows fed with linseed supplementation should contain even higher ALA concentrations.

Methods and Results—

Forty different cheeses were analyzed by gas chromatography for their fatty acid profile: (1) 12 from well-defined alpine regions around Gstaad, Switzerland; (2) 7 commercially available English cheddar cheeses; (3) 6 cheeses from cows fed with linseed supplementation; (4) 7 industrial-type Emmentals; and (5) 8 alpine cheeses with partial silage feeding. The alpine cheese contained 4 times more linolenic acid (C18:3ω-3) compared with cheddar, more total ω-3 fatty acids, and showed a significantly lower n-6:ω-3 ratio. Conjugated linoleic acid (C18:2 c9/t11) was 3-fold higher, whereas the amount of palmitic acid was 20% lower. The Emmental reached 40% of the ALA content compared with alpine cheese, and surprisingly, cheese from linseed-supplemented cows contained only 49% of that of the alpine cheese (
P
<0.001 for each trait in the 5 cheese groups).

Conclusions—

Cheese made of milk from cows grazed on alpine pastures had a more favorable fatty acid profile than all other cheese types. Alpine cheese may be a relevant source of ALA and other cardioprotective fatty acids.
Intracellular Localization and Functional Effects of P
21
-Activated Kinase-1 (Pak1) in Cardiac Myocytes
Authors: Ke Yunbo , Wang Lynn , Pyle W. Glen , de Tombe Pieter P. , Solaro R. John
Published: December 2003

We investigated intracellular localization and substrate specificity of P
21
-activated kinase-1 (Pak1) in rat cardiac myocytes. Pak1 is a serine/threonine protein kinase that is activated by Rac1/Cdc42 and important in signaling of stress responses. Yet the localization and in vivo function of Pak1 in heart cells is poorly understood. Studies reported here indicate that Pak1 physically interacts with protein phosphatase 2a and localizes to the Z-disk, cell membrane, intercalated disc, and nuclear membrane of adult rat heart myocytes. We compared levels of phosphorylation of cardiac troponin I (cTnI) in control myocytes with phosphorylation of cTnI and myosin binding protein C (C-protein) in myocytes with increased Pak1 activity. The increase in activity was induced by infection of myocytes with a recombinant adenovirus (AdPak1) containing cDNA for a constitutively active Pak1. Control cells were infected with a virus (AdLacZ) containing LacZ. Basal levels of phosphorylation of cTnI and C-protein were relatively high in the myocytes infected with AdLacZ. However, phosphorylation of cTnI and C-protein in cells expressing constitutively active Pak1 was significantly reduced compared with those expressing LacZ. Measurement of Ca
2+
tension relations in single myocytes demonstrated that this reduction in phosphorylation of cTnI and C-protein was associated with the predicted increase in sensitivity to Ca
2+
. Our data provide evidence for a novel pathway of phosphatase regulation in cardiac myocytes.
Decreased Levels of Plasma Vitamin C and Increased Concentrations of Inflammatory and Oxidative Stress Markers After Stroke
Authors: Sánchez-Moreno Concepción , Dashe John F. , Scott Tammy , Thaler David , Folstein Marshal F. , Martin Antonio
Published: December 2003

Background and Purpose—

Inflammatory response is a critical component of the complex pathophysiological response to stroke. Vitamin C has been shown to have important roles in cell performance and vascular function. In this study, we compared the nutritional status and levels of inflammatory markers between stroke cases and controls and assessed which antioxidant was associated with levels of inflammatory markers and oxidative stress among cases and controls.

Methods—

We evaluated the nutritional status and measured plasma levels of vitamins C and E, uric acid, serum levels of C-reactive protein (CRP), the cytokines tumor necrosis factor-α and interleukin-1β, intercellular adhesion molecule-1 (ICAM-1) and chemokine monocyte chemoattractant protein-1 (MCP-1), prostaglandins PGE2 and PGI2, and 8-isoprostanes (8-
epi
PGF
2α
) for 15 patients with ischemic stroke within 2 to 5 days after stroke onset and for 24 control subjects.

Results—

Stroke patients had significantly lower plasma levels of vitamin C than did controls. Among stroke patients, CRP was significantly elevated, as were the ICAM-1, MCP-1, and 8-
epi
PGF
2α
, but the prostaglandins PGE2 and PGI2 were significantly reduced. Interestingly, vitamin C concentration was significantly inversely correlated with the levels of CRP and 8-
epi
PGF
2α
among stroke patients, and 8-
epi
PGF
2α
was significantly associated with the levels of CRP. Uric acid was also elevated among stroke patients.

Conclusions—

Lower vitamin C concentration, higher serum levels of inflammatory (CRP, ICAM-1, MCP-1) and oxidative stress (8-
epi
PGF
2α
) markers, and lower PGI2 and PGE2 concentrations among stroke patients indicate the presence of an inflammatory response associated with stroke.
Influence of Arterial Input Function on Hypoperfusion Volumes Measured With Perfusion-Weighted Imaging
Authors: Thijs Vincent N. , Somford Diederik M. , Bammer Roland , Robberecht Wim , Moseley Michael E. , Albers Gregory W.
Published: December 2003

Background and Purpose—

The arterial input function (AIF) is critical in determining hemodynamic parameters quantitatively with bolus-tracking MRI. We studied the effect of varying the location of measurement of AIF on the volume of hypoperfusion. We compared the volumes of hypoperfusion obtained with different AIFs with the final ischemic lesion volume.

Methods—

We included 13 patients with acute cerebral ischemia in the anterior circulation who underwent diffusion- (DWI) and perfusion (PWI)-weighted imaging within 8 hours after symptom onset and exhibited DWI lesion expansion between baseline and follow-up. AIF was measured at 4 locations: near both middle cerebral arteries (MCAs), in MCA branches adjacent to the largest DWI abnormality, and at the same level on the opposite hemisphere. Hypoperfusion lesion volumes were compared with the DWI volume at follow-up.

Results—

Large variations in PWI lesion size were found with different AIF locations. The largest PWI lesions were found when AIF was measured at the contralateral MCA. Smaller PWI lesions were found when AIF was measured in the other locations. There was no significant difference between PWI lesion area at baseline and follow-up DWI lesion when AIF was measured at the contralateral MCA. The other PWI lesions significantly underestimated follow-up DWI lesion size.

Conclusions—

AIF is an important determinant of the size of hypoperfusion lesions measured with PWI. PWI lesion volumes determined with AIF from the contralateral MCA are associated with follow-up lesion volume.
Detection of Reversed Basilar Flow With Power-Motion Doppler After Acute Occlusion Predicts Favorable Outcome
Authors: Ribo Marc , Garami Zsolt , Uchino Ken , Song Joon , Molina Carlos A. , Alexandrov Andrei V.
Published: December 2003

Background and Purpose—

Power-motion transcranial Doppler PMD-TCD is a new method for simultaneous display of flow at multiple depths. We aimed to determine clinical significance of PMD-TCD demonstration of reversed basilar flow in patients with basilar artery (BA) occlusion.

Methods—

We prospectively evaluated patients with acute vertebrobasilar ischemia using PMD-TCD. Using a predefined set of TCD depth criteria and specific flow findings, occlusion was localized to the proximal, middle, or distal BA stem. The National Institutes of Health Stroke Scale was used to measure stroke severity and the modified Rankin Scale (mRS) to assess outcome at 3 months.

Results—

BA occlusion was diagnosed in 16 patients (3 women, mean age 65, median NIHSS 8, mean time from symptoms onset 8.5 hours). PMD-TCD diagnosis of BA occlusion was confirmed in 11 of 12 patients who underwent invasive angiography. Reversed BA flow on PMD-TCD was identified in 8 patients (50%). Angiography confirmed flow from carotid system in 6 of these 8 patients (κ=0.87). Patients with reversed BA flow showed lower NIHSS scores on admission (median 4 versus 15.5,
P
=0.009), on discharge (2 versus 21.5,
P
=0.03) and did not experience neurological deterioration during hospital stay (n=0 versus 4,
P
=0.05). There was a trend toward better outcome at 3 months (mRS 1 versus 4,
P
=0.07).

Conclusion—

Detection of reversed flow in the distal BA with PMD-TCD is associated with lower stroke severity and better outcome after acute basilar artery occlusion.
Antiplatelet Effect of Aspirin in Patients With Cerebrovascular Disease
Authors: Alberts Mark J. , Bergman Deborah L. , Molner Elise , Jovanovic Borko D. , Ushiwata Issei , Teruya Jun
Published: December 2003

Background and Purpose—

Aspirin is used commonly to prevent ischemic strokes and other vascular events. Although aspirin is considered safe and effective, it has limited efficacy with a relative risk reduction of 20% to 25% for ischemic stroke. We sought to determine if aspirin as currently used is having its desired antiplatelet effects.

Methods—

We ascertained patients with cerebrovascular disease who were taking only aspirin as an antiplatelet agent. Platelet function was evaluated using a platelet function analyzer (PFA-100). PFA test results were correlated with aspirin dose, formulation, and basic demographic factors.

Results—

We ascertained 129 patients, of whom 32% were taking an enteric-coated aspirin preparation and 32% were taking low-dose (≤162 mg/d) aspirin. For the entire cohort, 37% of patients had normal PFA-100 results, indicating normal platelet function. For the patients taking low-dose aspirin, 56% had normal PFAs compared with 28% of those taking ≥325 mg/d of aspirin, while 65% of patients taking enteric-coated aspirin had normal PFAs compared with 25% taking an uncoated preparation (
P
<0.01 for both comparisons). Similar results were obtained if PFA results were analyzed using mean closure times (low-dose aspirin, 183 sec; high-dose aspirin, 233 sec; enteric-coated, 173 sec; uncoated, 235 sec;
P
<0.01 for comparisons). Older patients and women were less likely to have a therapeutic response to aspirin, independent of aspirin dose or formulation.

Conclusions—

A significant proportion of patients taking low-dose aspirin or enteric-coated aspirin have normal platelet function as measured by the PFA-100 test. If these results correlate with clinical events, they have broad implications in determining how aspirin is used and monitored.
Na
+
/H
+
Exchanger Inhibitor, SM-20220, Is Protective Against Excitotoxicity in Cultured Cortical Neurons
Authors: Matsumoto Yuji , Yamamoto Seiji , Suzuki Yasuhiro , Tsuboi Takashi , Terakawa Susumu , Ohashi Naohito , Umemura Kazuo
Published: December 2003

Background and Purpose—

Recently, it has been reported that Na
+
/H
+
exchanger (NHE) inhibitors demonstrated protective effects on ischemia/reperfusion brain injury in animal models. However, the mechanisms by which the neurons were protected against ischemic insult remain unclear. To reveal the cellular mechanism of the NHE inhibitor on the neuronal death, we examined the effects of a selective NHE inhibitor, SM-20220 (
N
-[aminoiminomethyl]-1-methyl-1
H
-indole-2-carboxamide methanesulfonate), on glutamate-induced neuronal death in rat cortical culture.

Methods—

Cortical neurons were prepared from 1-day old rats, and cultured on the glass-based dishes. Glutamate-induced neuronal death was assessed by staining the cells with propidium iodide. Morphological changes in the neurons were observed with a video-enhanced contrast-differential interference contrast microscope. The intracellular calcium concentration ([Ca
2+
]
i
) and the intracellular pH (pH
i
) were measured by fluorescence imaging with a confocal laser microscope using fluo-3/acetoxymethylester (AM) and 2′, 7′-bis-2-carboxy-ethyl-5(6)-carboxyfluorescein (BCECF)/AM as a fluorescent dye, respectively.

Results—

SM-20220 (0.3 to 30 nmol/L) dose-dependently attenuated glutamate (300 μmol/L)-induced neuronal death over a period of 6 hours, and inhibited the acute cellular swelling following glutamate (500 μmol/L) exposure. Dual peaks of [Ca
2+
]
i
rise were observed at 5 and 12 minutes after glutamate (500 μmol/L) exposure, followed by a persistent rise. SM-20220 suppressed the persistent [Ca
2+
]
i
increase. SM-20220 inhibited intracellular acidification following glutamate (500 μmol/L) exposure. All of the events induced by glutamate were also inhibited by the
N
-methyl-
d
-aspartate receptor antagonist, MK-801, indicating the death process was excitotoxicity.

Conclusions—

NHE inhibitor is neuroprotective through inhibition of both persistent [Ca
2+
]
i
increase and acidification in excitotoxicity.
LA COORDINATION DANS LA TRADITION GRAMMATICALE ARABE
Authors: Gharbia Abdeljabbar Ben
Published: December 2003

Nous avons essayé dans cet article de voir comment la Tradition Grammaticale Arabe a situé la coordination dans le système linguistique conçu pour rendre compte de l'architecture de la langue arabe. Nous avons montré comment l'emprise de la déclinaison, la division tripartite des parties du discours et la structure de constituance que les grammairiens arabes ont adoptées les ont conduits à marginaliser la coordination inter-phrastique, à s'intéresser essentiellement à la coordination des termes constituants de la phrase, notamment à celle des nominaux, et à étudier certains aspects de cette structure dans les chapitres consacrés aux particules et aux expansions du groupe nominal. En revanche, l'examen de certains aspects relatifs à la structure et à la sémantique de la coordination les ont amenés à soumettre la coordonnabilité des expressions à deux conditions fondamentales, à savoir l'homogénéité syntaxique et la compatibilité sémantique des conjoints. Ils ont, en outre, soulevé des questions intéressantes qui restent d'actualité, et qui concernent en particulier les coordonnants et la catégorisation.
HAND AND FOOT SYMBOLISMS: FROM ROCK ART TO THE QUR' ĀN
Authors: Achrati Ahmed
Published: December 2003

Wedded to creativity and spirituality since the dawn of humanity, the symbolisms of the hand and the foot have assumed many religious and artistic forms. This essay explores the artistic and religious significance of the hand and foot in the prehistoric rock art of North Africa and Arabia and examines their various ethnographic and mythological expressions in historical times. It then shows how these symbolisms were restructured in the Qur' n to fit a strictly iconoclastic monotheism. It is a multidisciplinary approach to a collective consciousness that finds its roots in an Afroasiatic substrate and its expression in the artistic and linguistic traditions of the eastern and southern coasts of the Mediterranean.
Justus von Liebig, FRS: creator of the world's first scientific research laboratory
Authors: Michaelis Anthony R.
Published: December 2003

The date 26 May 1824, when Justus von Liebig was made an ‘extraordinary professor’ of chemistry at the University of Giessen, is for me as momentous an occasion in the history of science as 16 July 1662, when the Charter of Incorporation of the Royal Society passed the Great Seal, making it the official date of that body's foundation. This year marks the two hundredth anniversary of Liebig's birth, and here I describe his long and interdisciplinary scientific career, and in particular his creation of the world's first scientific research and teaching laboratory at Giessen. This essay is in part a review of William H. Brock's biography, Justus von Liebig: The Chemical Gatekeeper.
The origins of A Scientific Theology
Authors: McGrath Alister E.
Published: December 2003

This paper sets out a new approach to Christian theology, which accentuates its interdisciplinary potential through a rigorous interaction with the natural sciences. The approach here developed treats the natural sciences as a dialogue partner in an intellectually rigorous engagement with reality. After exploring the origins and development of this approach, and clarifying its leading features, the paper engages with three major issues which arise froma ‘scientific theology': the implications of provisionality in the dialogue between science and religion; the critique of the concept of ‘nature’ as the basis of Christian theology; and the idea that a scientific theology represents a response to its distinctive object. It is argued that a unitary understanding of reality, such as that mandated by a Christian doctrine of creation, does not demand that all human intellectual disciplines should adopt identical methods for their tasks, but that they should accommodate themselves to the distinctive natures of those aspects of reality which they attempt to represent and depict.
An analysis of the present system of scientific publishing: what's wrong and where to go from here
Authors: Greenbaum Dov , Lim Joanna , Gerstein Mark
Published: December 2003

The internet has produced an unprecedented opportunity to provide free and unhindered access to the wealth of scientific information, the volume of which continues to grow at a furious pace. The current balkanised system of individual journals limits possibilities for powerful search tools and for an integrated repository of the whole body of scientific literature. This paper reviews the current publishing environment, commenting on its strong and weak points (for example peer review, which is both a strength and a weakness). It attempts to find a viable solution to the current issues that plague STM (scientific, technical, and medical) publishing in the introduction of a centralised repository of scientific literature. Related issues such as the question of long term archiving and the justified fears of STM publishers of becoming obsolete are also discussed.
Where the science–religion dialogue is going wrong
Authors: Haas Peter J.
Published: December 2003

In 1987, the John Templeton Foundation was established to ‘encourage a fresh appreciation … of the moral and spiritual dimensions of life’. Unfortunately the current science and religion dialogue has not taken shape in a helpful way; rather, it has become reductionist. For a start, many of the prominent writers in this field reduce ‘religion’ to a certain form of liberal Protestantism, and in the process secularise the mysterious and read the Bible as though it was about our contemporary understanding of Western science. The situation is in reality no better in the field of ethics. Here also the dialogue is reductionist, in that it assumes that there is a religious answer, or at least a religious approach, to the ethical issues that scientific and technological advances bring forth. For those of us who continue to think that Templeton style dialogue between religion and science is important, there is thus a strong need to extricate the conversation from the reductionist rut in which it has become snared.