bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultra High Critical Heat Flux During Forced Flow Boiling Heat
Transfer With an Impinging Jet
Authors: Mitsutake Yuichi , Monde Masanori 
Published: November 2003

Abstract
An ultra high critical heat flux (CHF) was attempted using a highly subcooled liquid jet impinging on a small rectangular heated surface of length 5∼10mm and width 4 mm. Experiments were carried out at jet velocities of 5∼60m/s, a jet temperature of 20°C and system pressures of 0.1∼1.3MPa. The degree of subcooling was varied from 80 to 170 K with increasing system pressure. The general correlation for CHF is shown to be applicable for such a small heated surface under a certain range of conditions. The maximum CHF achieved in these experiments was 211.9 MW/m2, recorded at system pressure of 0.7 MPa, jet velocity of 35 m/s and jet subcooling of 151 K, and corresponds to 48% of the theoretical maximum heat flux proposed by Gambill and Lienhard.
The Optimum Height of Winglet Vortex Generators Mounted on Three-Row
Flat Tube Bank Fin
Authors: Gao S. D. , Wang L. B. , Zhang Y. H. , Ke F. 
Published: November 2003

Abstract
Winglet vortex generators can be used to enhance the heat transfer performance of finned flat tube bank fin. The effects of the height of vortex generators (VG) on local heat transfer were studied using the naphthalene sublimation method and the optimum height of winglet VG are screened by using JF, a dimensionless factor of the larger the better characteristics. In order to get JF, the local heat transfer coefficient obtained in experiments and a numerical method were used to get the heat transferred from the fin. For the configurations studied in this paper: for local characteristic, as increasing height of VG, heat transfer is enhanced, but the mostly enhanced region moves away from the tube wall; with increasing height of VG to certain degree, the width of enhanced region does not increase significantly; the effects of VG’s height on span-average Nusselt number (Nu) are more mixed on fin surface mounted with VGs and its back surface, with increasing height of VG, in some region heat transfer is worsened, and in other region heat transfer is enhanced; in real working condition, the heat transferred from fin surface mounted with VGs is larger than the heat transferred from the other surface of the fin; increasing the height of VG (H) increases average Nu and friction factor (f ), but with considering the fin efficiency, there is an optimum H to get best heat transfer performance; the optimum height of VG is dependent on the thickness of fin and its heat conductivity, for mostly used fin thickness and material, the optimum height of VG is 0.8 times of net fin spacing.
Investigation of Decisive Mixture Effects in Nucleate Boiling of
Binary Mixtures Using a Theoretical Model
Authors: Kern Jürgen , Stephan Peter 
Published: November 2003

Abstract
In the present paper an attempt is made to clarify the influence of mixture effects upon heat transfer in nucleate boiling of binary mixtures. The studies are based on a theoretical model that is briefly summarized. Evaluating heat and mass transfer around a single vapor bubble emphasizes a strong influence of the so-called micro region where the liquid-vapor phase interface approaches the wall. Due to the preferential evaporation of one component of the mixture, strong concentration gradients occur in the micro region. These microscale composition effects cause diffusive mass transfer, Marangoni convection, and a variation of the liquid-vapor phase equilibrium as well as a variation of the thermophysical properties. From a macroscopic point of view the bubble site density and the departure diameter vary with the composition of the liquid. By means of parameter studies decisive mixture effects are identified and their relevance in the nucleate boiling process is stated. The heat transfer coefficient crucially depends on the bubble site density and departure diameter. For increasing bubble site density, the influence of microscopic concentration gradients increases. But only the variation of liquid-vapor phase equilibrium becomes important, while diffusive mass transfer and Marangoni convection can be neglected.
Theoretical Model for Nucleate Boiling Heat and Mass Transfer of
Binary Mixtures
Authors: Kern Jürgen , Stephan Peter 
Published: November 2003

Abstract
A model is presented to calculate nucleate boiling heat transfer coefficients of binary mixtures. The model includes the governing physical phenomena, such as the variation of the phase interface curvature, the adhesion pressure between wall and liquid, the interfacial thermal resistance as well as the local variation of composition and liquid-vapor equilibrium. Marangoni convection is considered, too. The theoretical background of these phenomena is described and their implementation is explained. The model is verified by comparing calculated heat transfer coefficients of hydrocarbon mixtures with experimental data. Computational and experimental data are in good agreement. In the examples a considerable amount of the total heat flow passes through a tiny thin film area, called micro region, where the liquid-vapor phase interface is attached to the wall. Very high spatial gradients of heat flux and mixture concentration occur interacting with overall heat transfer performance.
Phonon Transport in Anisotropic Scattering Particulate Media
Authors: Prasher Ravi 
Published: November 2003

AbstractEquation of phonon radiative transport (EPRT) is rewritten to include anisotropic scattering by a particulate media by including an acoustic phase function and an inscattering term which makes EPRT exactly same as equation of radiative transport (ERT). This formulation of EPRT is called generalized EPRT (GEPRT). It is shown that GEPRT reduces to EPRT for isotropic scattering and is totally consistent with phonon transport theory, showing that transport cross section is different from the scattering cross section. GEPRT leads to same formulation for transport cross section as given by phonon transport theory. However GEPRT shows that transport cross section formulations as described by phonon transport theory are only valid for acoustically thick medium. Transport cross section is different for the acoustically thin medium leading to the conclusion that mean free path (m.f.p) is size dependant. Finally calculations are performed for two types of scatterers for acoustic waves without mode conversion: (1) acoustically hard Rayleigh sphere; and (2) large sphere in the geometrical scattering regime. Results show that the scattering from these particles is highly anisotropic. It is also shown that for geometrical scattering case isotropic scattering leads to the conclusion of total internal reflection at the particle/medium interface.
An Improved Quasi-Steady Analysis for Solving Freezing Problems in a Plate, a Cylinder and a Sphere
Authors: Lin Sui , Jiang Zheng 
Published: November 2003

AbstractFreezing processes taking place in a plate, a cylinder and a sphere are investigated by using the improved quasi-steady analysis model developed in the present study. In the improved quasi-steady analysis, an additional term is added to the temperature profile to simulate the transient effect on the temperature distribution in the solid phase. This additional term is based on the ratio of the heat flux at the phase boundary to that at the cooling surface, and physically, presents the thermal capacity effect in the frozen region. The maximum relative error of the moving phase front location obtained from the improved quasi-steady analysis is about 3% in comparison with that obtained from the exact solution of the freezing process in a plate. Since there is no exact solution available for the freezing process taking place in a cylinder or a sphere, the results obtained from the improved quasi-steady analysis are compared with results from references. The maximum relative errors of the improved quasi-steady analysis for the cylindrical and spherical cases are less than 4% while the maximum relative errors of the quasi-steady approximation are higher than 42%. It is evident that the improved quasi-steady analysis developed in the present study maintains the simplicity of the quasi-steady approximation while greatly increasing its accuracy.
Plasmodium falciparum
Is Able To InvadeErythrocytes through a Trypsin-Resistant Pathway Independent ofGlycophorinB
Authors: Gaur Deepak , Storry Jill R. , Reid Marion E. , Barnwell John W. , Miller Louis H. 
Published: November 2003

ABSTRACT

Plasmodium
falciparum
invades erythrocytes through multiple ligand-receptor
interactions, with redundancies in each pathway. One such alternate
pathway is the trypsin-resistant pathway that enables
P.
falciparum
to invade trypsin-treated erythrocytes. Previous
studies have shown that this trypsin-resistant pathway is dependent on
glycophorin B, as
P. falciparum
strains invade
trypsin-digested glycophorin B-deficient erythrocytes at a highly
reduced efficiency. Furthermore, in a recent study, the
P.
falciparum
7G8 strain did not invade glycophorin B-deficient
erythrocytes, a finding that was not confirmed in the present study. To
analyze the degree of dependence on glycophorin B for invasion by
P. falciparum
through the trypsin-resistant pathway, we have
studied the invasion phenotypes of five parasite strains, 3D7, HB3,
Dd2, 7G8, and Indochina I, on trypsin-treated normal and glycophorin
B-deficient erythrocytes. Invasion was variably reduced in glycophorin
B-deficient erythrocytes. Four strains, 3D7, HB3, Dd2, and Indochina I,
invaded trypsin-treated erythrocytes, while invasion by the 7G8 strain
was reduced by 90%. Among the four strains, invasion by 3D7,
HB3, and Dd2 of trypsin-digested glycophorin B-deficient erythrocytes
was further reduced. However, Indochina I invaded trypsin-digested
glycophorin B-deficient erythrocytes at the same efficiency as its
invasion of trypsin-digested normal erythrocytes. This strongly
suggests that the Indochina I strain of
P. falciparum
is not
dependent on glycophorin B to invade through a trypsin-resistant
pathway as are the strains 3D7, HB3, and Dd2. Thus,
P.
falciparum
is able to invade erythrocytes through a glycophorin
B-independent, trypsin-resistant
pathway.
Listeria monocytogenesMutants That Fail To Compartmentalize Listerolysin O Activity Are Cytotoxic, Avirulent, and Unable To Evade Host Extracellular Defenses
Authors: Glomski Ian J. , Decatur Amy L. , Portnoy Daniel A. 
Published: November 2003

ABSTRACTListeria monocytogenesis a facultative intracellular bacterial pathogen that escapes from a phagosome and grows in the host cell cytosol. Escape of the bacterium from the phagosome to the cytosol is mediated by the bacterial pore-forming protein listeriolysin O (LLO). LLO has multiple mechanisms that optimize activity in the phagosome and minimize activity in the host cytosol. Mutants that fail to compartmentalize LLO activity are cytotoxic and have reduced virulence. We sought to determine why cytotoxic bacteria have attenuated virulence in the mouse model of listeriosis. In this study, we constructed a series of strains with mutations in LLO and with various degrees of cytotoxicity. We found that the more cytotoxic the strain in cell culture, the less virulent it was in mice. Induction of neutropenia increased the relative virulence of the cytotoxic strains 100-fold in the spleen and 10-fold in the liver. The virulence defect was partially restored in neutropenic mice by adding gentamicin, an antibiotic that kills extracellular bacteria. Additionally,L. monocytogenesgrew more slowly in extracellular fluid (mouse serum) than within tissue culture cells. We concluded thatL. monocytogenescontrols the cytolytic activity of LLO to maintain its nutritionally rich intracellular niche and avoid extracellular defenses of the host.
Modulation of Polymorphonuclear Cell Interleukin-8 Secretion by Human Monoclonal Antibodies to Type 8 Pneumococcal Capsular Polysaccharide
Authors: Burns Tamika , Zhong Zhaojing , Steinitz Michael , Pirofski Liise-anne 
Published: November 2003

ABSTRACTPneumococcal capsular polysaccharide (PS) vaccines induce type-specific immunoglobulin M (IgM), IgG, and IgA. Type-specific IgG to the PS is sufficient to confer protection against the homologous serotype of the pneumococcus, but the efficacies of type-specific IgM and IgA are less well understood. We examined the in vitro activities and efficacies in mice of two human monoclonal antibodies (MAbs) to type 8 PS, NAD (IgA) and D11 (IgM). MAb-mediated opsonophagocytic killing was evaluated after coculture of type 8 pneumococci with human polymorphonuclear cells (PMNs), type-specific or control MAbs, and human complement sources. The effects of the MAbs on PMN interleukin-8 (IL-8) and IL-6 secretion were determined in supernatants from cocultures containing pneumococci and PMNs by enzyme-linked immunosorbent assay. MAb efficacy was determined in an intratracheal model of type 8 infection in mice with classical complement pathway deficiency. Both MAbs were protective in 100% of infected mice. Neither MAb promoted a significant amount of killing of type 8 pneumococci compared to its isotype control MAb. Both type-specific MAbs mediated complement-dependent modulation of PMN IL-8 secretion, with increased secretion at effector/target (E:T) ratios of 500:1 and 50:1 and reduced secretion at 1:5. Trypan blue staining revealed that PMNs cocultured with D11 were less viable at an E:T ratio of 1:5 than PMNs cocultured with the control MAb. PMN IL-6 secretion was increased by both type-specific and control MAbs. These results suggest that certain type-specific IgM and IgAs might contribute to host defense by modulation of the inflammatory response to pneumococci.
Functional Analysis of the
Mycobacterium tuberculosis
MprAB Two-Component SignalTransductionSystem
Authors: Zahrt Thomas C. , Wozniak Christopher , Jones Denise , Trevett Andrea 
Published: November 2003

ABSTRACT

The
mechanisms utilized by
Mycobacterium tuberculosis
to
establish, maintain, or reactivate from latent infection in the host
are largely unknown but likely include genes that mediate adaptation to
conditions encountered during persistence. Previously, a two-component
signal transduction system,
mprAB
, was found to be required in
M. tuberculosis
for establishment and maintenance of
persistent infection in a tissue- and stage-specific fashion. To begin
to characterize the role of this system in
M. tuberculosis
physiology and virulence, a functional analysis of the
mprA
and
mprB
gene products was initiated. Here, evidence is
presented demonstrating that sensor kinase MprB and response regulator
MprA function as an intact signal-transducing pair in vitro and in
vivo. Sensor kinase MprB can be autophosphorylated, can donate
phosphate to MprA, and can act as a phospho-MprA phosphatase in vitro.
Correspondingly, response regulator MprA can accept phosphate from MprB
or from small phosphodonors including acetyl phosphate. Mutagenesis of
residues His249 in MprB and Asp48 in MprA abolished the
ability of these proteins to be phosphorylated in vitro. Introduction
of these alleles into
Mycobacterium bovis
BCGattenuated virulence in macrophages in vivo. Together, these results
support a role for the
mprAB
two-component system in
M.
tuberculosis
physiology and pathogenesis. Characterization of
two-component signal transduction systems will enhance our
understanding of processes regulated by
M. tuberculosis
during
acute and/or persistent infection in the
host.
Disruptionof Cell Polarity by Enteropathogenic
Escherichia coli
EnablesBasolateral Membrane Proteins To Migrate Apically and ToPotentiate PhysiologicalConsequences
Authors: Muza-Moons Michelle M. , Koutsouris Athanasia , Hecht Gail 
Published: November 2003

ABSTRACT

Enteropathogenic
Escherichia coli
(EPEC) disrupts the structure and barrier
function of host intestinal epithelial tight junctions (TJs). The
impact of EPEC on TJ “fence function,” i.e.,
maintenance of cell polarity, has not been investigated. In polarized
cells, proteins such as β
1
-integrin and
Na
+
/K
+
ATPase are restricted to
basolateral (BL) membranes. The outer membrane EPEC protein intimin
possesses binding sites for the EPEC translocated intimin receptor
(Tir) and β
1
-integrin. Restriction ofβ
1
-integrin to BL domains, however, precludes
opportunity for interaction. We hypothesize that EPEC perturbs TJ fence
function and frees BL proteins such as β
1
-integrin
to migrate to apical (AP) membranes of host cells, thus allowing
interactions with bacterial adhesins such as intimin. The aim of this
study was to determine whether EPEC alters the polar distribution of BL
proteins, in particular β
1
-integrin, and if such
redistribution contributes to pathogenesis. Human intestinal epithelial
T84 cells and EPEC strain E2348/69 were used. Selective biotinylation
of AP or BL membrane proteins and confocal microscopy showed the
presence of β
1
-integrin and
Na
+
/K
+
ATPase on the AP membrane
following infection. β
1
-Integrin antibody afforded
no protection against the initial EPEC-induced decrease in
transepithelial electrical resistance (TER) but halted the progressive
decrease at later time points. While the effects of EPEC on TJ barrier
and fence function were Tir dependent, disruption of cell polarity by
calcium chelation allowed a
tir
mutant to be nearly as
effective as wild-type EPEC. In contrast, deletion of
espD
,
which renders the type III secretory system ineffective, had no effect
on TER even after calcium chelation, suggesting that the putativeβ
1
-integrin-intimin interaction serves to
provide intimate contact, like that of Tir and intimin, making
translocation of effector molecules more efficient. We conclude that
the initial alterations of TJ barrier and fence function by EPEC are
Tir dependent but that later disruption of cell polarity and
accessibility of EPEC to BL membrane proteins, such asβ
1
-integrin, potentiates the physiological
perturbations.
TheSiderophore Receptor IroN of Extraintestinal Pathogenic
Escherichia coli
Is a Potential VaccineCandidate
Authors: Russo Thomas A. , McFadden Catherine D. , Carlino-MacDonald Ulrike B. , Beanan Janet M. , Olson Ruth , Wilding Gregory E. 
Published: November 2003

ABSTRACT

It
would be medically and economically desirable to prevent the millions
of annual extraintestinal infections and the thousands of associated
deaths due to
Escherichia coli
. Outer membrane
proteins are potential vaccine candidates for the prevention of these
infections. This study tested the hypotheses that the siderophore
receptor IroN is antigenic and that an IroN-specific antibody response
confers protection in vivo. Subcutaneous immunization with denatured
IroN resulted in a significant IroN immunoglobulin G (IgG)-specific
response in serum (
P
< 0.0001) but not a systemic or
mucosal IroN-specific IgA response. In a mouse model of ascending
urinary tract infection, subcutaneous immunization with denatured IroN
conferred significant protection against renal (
P
=
0.0135 and 0.0095 in two independent experiments), but not bladder,
infection. These data, together with the previously demonstrated role
of IroN in virulence, its expression in human biologic fluids, and its
prevalence among extraintestinal pathogenic
E. coli
strains, support further studies on the role of IroN as a vaccine
candidate.
Deletionof
Mycobacterium tuberculosis
Sigma Factor E Results inDelayed Time to Death with Bacterial Persistence in the Lungsof Aerosol-InfectedMice
Authors: Ando Masaru , Yoshimatsu Tetsuyuki , Ko Chiew , Converse Paul J. , Bishai William R. 
Published: November 2003

ABSTRACT

The
stress-induced extracytoplasmic sigma factor E (SigE) of
Mycobacterium tuberculosis
shows increased expression after
heat shock, sodium dodecyl sulfate treatment, and oxidative stress, as
well as after phagocytosis in macrophages. We report that deletion of
sigE
results in delayed lethality in mice without a
significant reduction of bacterial numbers in
lungs.
Functional BvgAS Virulence Control System in
Bordetella bronchiseptica
Is Necessary for Induction of Ca
2+
Transients in Ciliated Tracheal Epithelial Cells
Authors: Groathouse Nathan A. , Heinzen Robert A. , Boitano Scott 
Published: November 2003

ABSTRACT

To study initial
Bordetella bronchiseptica
-tracheal epithelial cell interactions, we coincubated
B. bronchiseptica
with rabbit tracheal explant cultures and assayed bacterial adherence and host cell Ca
2+
signaling. Wild-type
B. bronchiseptica
(RB50) preferentially adhered to cilia and induced ciliated host cell Ca
2+
transients within 2 min of coincubation, whereas coincubation with an avirulent strain (RB57) resulted in limited binding and Ca
2+
signaling. The described cell system allows for assessment of initial
B. bronchiseptica
-host cell interactions that can contribute to pathogenicity or to host cell defense.
Further Evidence that Papillomavirus Capsids Exist inTwo DistinctConformations
Authors: Selinka Hans-Christoph , Giroglou Tzenan , Nowak Thorsten , Christensen Neil D. , Sapp Martin 
Published: November 2003

ABSTRACT
Cell
surface heparan sulfate proteoglycans (HSPGs) serve as primary
attachment receptors for human papillomaviruses (HPVs). To demonstrate
that a biologically functional HPV-receptor interaction is restricted
to a specific subset of HSPGs, we first explored the role of HSPG
glucosaminoglycan side chain modifications. We demonstrate that HSPG O
sulfation is essential for HPV binding and infection, whereas
de-N-sulfated heparin interfered with VLP binding but not with HPV
pseudoinfection. This points to differences in VLP-HSPG and
pseudovirion-HSPG interactions. Interestingly, internalization kinetics
of VLPs and pseudovirions, as measured by fluorescence-activated cell
sorting analysis, also differ significantly with approximate half times
of 3.5 and 7.5 h, respectively. These data suggest that
differences in HSPG binding significantly influence postbinding events.
We also present evidence that pseudovirions undergo a conformational
change after cell attachment. A monoclonal antibody (H33.J3), which
displays negligible effectiveness in preattachment neutralization
assays, efficiently neutralizes cell-bound virions. However, no
difference in H33.J3 binding to pseudovirions and VLPs was observed in
enzyme-linked immunosorbent assay and virus capture assays. In contrast
to antibody H33.B6, which displays equal efficiencies in pre- and
postattachment neutralization assays, H33.J3 does not block VLP binding
to heparin, demonstrating that it interferes with steps subsequent to
virus binding. Our data strongly suggest that H33.J3 recognizes a
conformation-dependent epitope in capsid protein L1, which undergoes a
structural change after cell
attachment.