bluuebunny/crossref_metadata_2025 huggingface dataset:
Research on a new heat transfer model for liquid film convective evaporation in annular flow
Authors: Qin Wei , Li Yongguang , Cai Zhuhui
Published: October 2002

Based on the phenomenon of turbulence restraint in liquid‐vapor interface, an analytical model is proposed for annular flow with a velocity distribution. The liquid‐vapor interface affecting district mixing length model was amended, and a new liquid film convective evaporation heat transfer model at the annular flow was developed. Compared with the experimental data, the results show that the new model is better than the model based on full tube flow velocity distribution. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(7): 524–530, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10051
Relationship between serum hormone concentrations, reproductive history, alcohol consumption and genetic polymorphisms in pre‐menopausal women
Authors: García‐Closas Montserrat , Herbstman Julie , Schiffman Mark , Glass Andrew , Dorgan Joanne F.
Published: October 2002

Reproductive characteristics, alcohol intake and polymorphisms in genes encoding sex‐steroid metabolizing enzymes might influence the risk of hormone‐related cancers by changing circulating concentrations of sex hormones. The relationship between these factors and serum concentrations of estradiol, progesterone, androstenedione, testosterone and DHEA was evaluated in a cross‐sectional study of 218 pre‐menopausal women from Kaiser Permanente Health Plan in Portland, Oregon. Risk factor information was obtained from questionnaires and hormone serum concentrations were determined by radioimmunoassays. Genotypes for CYP11A 5′UTR(tttta)n, CYP17 5′‐UTR −34 T>C, CYP19 IVS4(ttta)n, CYP1B1 (L432V and S453N) and COMT (V158M) were determined from genomic DNA samples. Increasing number of full‐term pregnancies was associated with a significant decrease in late‐follicular progesterone levels (p‐trend = 0.03). Increasing alcohol consumption was associated with higher estradiol levels averaged through the menstrual cycle (p‐trend = 0.009) and higher progesterone levels during luteal phase (p‐trend = 0.04). Androstenedione and testosterone levels were higher among light to moderate drinkers compared to non‐drinkers, although we only observe a significant trend with increasing levels of alcohol consumption for androstenedione. Women heterozygous or homozygous for the CYP1B1 L432V or the S453N polymorphisms had increased luteal estradiol levels (p‐value = 0.04 for L432V and 0.04 for S453N). None of the other factors evaluated was significantly associated with serum concentration of hormones. In conclusion, results from this cross‐sectional study of pre‐menopausal women provide support for an association between light to moderate alcohol intake and elevated levels of estrogen and androgen levels. Our data suggest that circulating levels of progesterone might be related to parity and alcohol consumption, however the biological plausibility of the observed associations is unclear. We found little support for an influence of the evaluated genetic polymorphisms in the steroid synthesis and metabolism pathway on serum hormone levels, except for a possible effect of the CYP1B1 L432V and S453N polymorphisms on serum estradiol levels. © 2002 Wiley‐Liss, Inc.
Human papillomavirus type 16 is episomal and a high viral load may be correlated to better prognosis in tonsillar cancer
Authors: Mellin Hanna , Dahlgren Liselotte , Munck‐Wikland Eva , Lindholm Johan , Rabbani Hodjattallah , Kalantari Mina , Dalianis Tina
Published: October 2002

The aim of our study was to investigate the physical state and the viral load of HPV‐16 in tonsillar cancer and to correlate these findings with clinical outcome. To distinguish between integrated and episomal forms of HPV, 22 fresh‐frozen tonsillar cancer samples were analysed by a method based on restriction enzyme cleavage, ligation and PCR (rliPCR). HPV‐16 was detected in 11/22 and HPV‐33 in 1/22 of the cancers, hence 12/22 (55%) of the tumours were HPV positive. Only extrachromosomal forms of HPV‐16 were observed. Full‐length episomal HPV was detected exclusively in 7/11 of the cancers, whereas both full‐length and deleted forms of episomal HPV‐16 were found in parallel in 2 other tumours. In 1 tumour only a deleted episomal form of HPV‐16 was present. In the remaining HPV‐16 positive tumour both full‐length episomal as well as an 11 kbp PCR product were detected and if the 11 kbp product contained integrated HPV, or was off‐size linearised episomal could not be determined. In 2 cervical cancer controls, HPV‐16 was integrated and could be chromosome located. HPV‐16 was quantified by real‐time PCR and most tonsillar cancers contained between 10 to a few hundred copies of HPV per β‐actin. The 6 patients with tumour sections with ≥190 HPV‐16 copies/β‐actin remained tumour free (p = 0.026) and had a better survival rate (p = 0.039) when compared to the 5 patients with tumours sections with ≤60 HPV‐16 copies/β‐actin. In conclusion, HPV‐16 is mainly episomal in tonsillar cancer. The viral load showed a wide distribution and the clinical outcome in our study was better when the HPV load was higher. © 2002 Wiley‐Liss, Inc.
Characteristics of disturbances in the laminar–turbulent transition of spherical Couette flow. 2. New disturbances observed for a medium gap
Authors: Nakabayashi Koichi , Zheng Zhiming , Tsuchida Yoichi
Published: October 2002

Supercritical flow in spherical Couette system with a rotating inner sphere and a fixed outer sphere has been investigated for a medium gap of the clearance ratio 0.206 in terms of the structure, wave-number, fundamental, and rotational frequencies of disturbances. Consequently, ring vortices and traveling letter-x-like waves were found within the Ekman-type secondary flow as new disturbances, in addition to Stuart vortices and shear waves. Also, interior waves were found within toroidal Taylor–Görtler (TG) vortices as a new disturbance, in addition to twists. Further, the wavy outflow boundary at the equator of the turbulent basic flow was found. Each ring vortex occurring successively around the pole moves toward the pole for one wavelength in the meridian direction (θ=10°) while it rotates for one wavelength in the azimuthal direction (φ=90°), because it has four traveling waves. The rotational direction of Stuart vortices is opposite to that of the inner sphere. The wave speed (rotation frequency) of interior waves or twists is the same as that of oscillating inflow boundary between two toroidal TG vortex cells, and the wave speed of shear waves is the same as that of the oscillating outflow boundary between the toroidal TG vortex cell and the Ekman-type secondary flow. Also, the wave speed of the oscillating outflow boundary is about two times the oscillating inflow boundary.
The interaction of turbulence with shock waves: A basic model
Authors: Zank G. P. , Zhou Ye , Matthaeus W. H. , Rice W. K. M.
Published: October 2002

The interaction of turbulence and shock waves is considered self-consistently so that the back-reaction of the turbulence and its associated reaction on the turbulence is addressed. This approach differs from previous studies which considered the interaction of linear modes with a shock. The most basic model of hypersonic flow, described by the inviscid form of Burgers’ equation, is used. An energy-containing model which couples the turbulent energy density and correlation length of the flow with the mean flow is developed. Upstream turbulence interacting with a shock wave is found to mediate the shock by (1) increasing the mean shock speed, and (2) decreasing the efficiency of turbulence amplification at the shock as the upstream turbulence energy density is increased. The implication of these results is that the energy in upstream turbulent fluctuations, while being amplified at the shock, is also being converted into mean flow energy downstream. The variance in both the shock speed and position is computed, leading to the suggestion that, in an ensemble-averaged sense, the turbulence mediated shock will acquire a characteristic thickness given by the standard deviation of the shock position. Lax’s geometric entropy condition is used to show that as the upstream turbulent energy density increases, the shock is eventually destabilized, and may emit one or more shocks to produce a system of multiple shock waves. Finally, turbulence downstream of the shock is shown to decay in time t according to t−2/3.
The role of thermal sensitivity of fluid properties, centrifugal destabilization, and nonlinear disturbances on the viscous heating instability in Newtonian Taylor–Couette flow
Authors: White James M. , Muller Susan J.
Published: October 2002

A number of questions regarding the effects of viscous dissipation on the stability of Newtonian Taylor–Couette flows are addressed through flow visualization experiments. Studies with three types of fluids of varying thermal sensitivity reveal that the instability is caused by a coupling of centrifugal destabilization and thermally induced gradients in viscosity. These tests also demonstrate that the Nahme number is the appropriate variable with which to describe dissipative effects on the hydrodynamic stability. Additional tests are performed to elucidate the effects of centrifugal destabilization by varying the amount of outer and inner cylinder co-rotation with the Reynolds number and Nahme number fixed. Lastly, a small hysteresis loop in the critical conditions is revealed by performing ramp tests in which the instability is approached from either above or below the critical condition; this indicates that the instability is weakly subcritical.
Calculation of nuclear magnetic shieldings. XV. Ab initio zeroth-order regular approximation method
Authors: Fukui H. , Baba T.
Published: October 2002

An ab initio zeroth-order regular approximation (ZORA) theory for relativistic calculation of the nuclear magnetic shielding tensors is presented at the Hartree–Fock level. The nuclear magnetic shieldings tensors of hydrogen halides, HX (X=F, Cl, Br, and I), are calculated, and the results are compared to experimental values and other calculated results obtained using the Douglas–Kroll–Hess (DKH) transformation, the four-component random phase approximation (RPA), and the Dirac–Fock (DF) approaches. It is shown that the ZORA method underestimates the relativistic effects on the magnetic shieldings as compared to the four-component RPA results. However, as to the proton chemical shifts, the ZORA results are closer to the experimental proton shifts than those of the DKH and 4-RPA approaches.
Calculation of van der Waals coefficients in hydrodynamic approach to time-dependent density functional theory
Authors: Banerjee Arup , Harbola Manoj K.
Published: October 2002

In this paper we employ hydrodynamic formulation of time-dependent density-functional theory to obtain coefficient C6 of the long-range part of the van der Waals interaction between alkali-metal clusters of large sizes. Such a calculation becomes computationally very demanding in the orbital-based Kohn–Sham formalism, but is quite simple in the hydrodynamic approach. This is because in hydrodynamic formulation, electron density and current density, rather than the orbitals, are employed as basic variables. We show that for intercations between the clusters of same sizes, C6 scales as the sixth power of the cluster radius and approaches the classically predicted value for large size clusters.
Electronic structure and chemical bonding of B5− and B5 by photoelectron spectroscopy and ab initio calculations
Authors: Zhai Hua-Jin , Wang Lai-Sheng , Alexandrova Anastassia N. , Boldyrev Alexander I.
Published: October 2002

The electronic structure and chemical bonding of B5− and B5 were investigated using anion photoelectron spectroscopy and ab initio calculations. Vibrationally resolved photoelectron spectra were obtained for B5− and were compared to theoretical calculations performed at various levels of theory. Extensive searches were carried out for the global minimum of B5−, which was found to have a planar C2v structure with a closed-shell ground state (1A1). Excellent agreement was observed between ab initio detachment energies and the experimental spectra, firmly establishing the ground-state structures for both B5− and B5. The chemical bonding in B5− was investigated and compared to that in Al5−. While both B5− and Al5− have a similar C2v planar structure, their π-bonding orbitals are different. In Al5−, a π-bonding orbital was previously observed to delocalize over only the three central atoms in the C2v ground-state structure, whereas a similar π orbital (1b1) was found to completely delocalize over all five atoms in the C2v B5−. This π bonding in B5− makes it more rigid towards butterfly out-of-plane distortions relative to Al5−.
Light emission from the shadows: Surface plasmon nano-optics at near and far fields
Authors: Hohng S. C. , Yoon Y. C. , Kim D. S. , Malyarchuk V. , Müller R. , Lienau Ch. , Park J. W. , Yoo K. H. , Kim J. , Ryu H. Y. , Park Q. H.
Published: October 2002

When light illuminates a thick metal film perforated with small holes, shadows appear. At the nanoscopic level, however, light can be emitted predominantly from the metal surfaces between the holes—shadows can be indeed brighter than the lighted holes. The symmetry of the near-field emission pattern is determined by the symmetry of the surface plasmon waves. Surprisingly, these nanoscopic emission patterns from the metal can be preserved to the far-field region, where the pattern becomes sinusoidal. This unusual behavior of light emission from the shadows is explained by efficient wave vector selection.
Carrier diffusion and radiative recombination in CdTe thin films
Authors: Romero Manuel J. , Gessert Timothy A. , Al-Jassim Mowafak M.
Published: October 2002

We employed cathodoluminescence spectroscopy and imaging to investigate the carrier diffusion and radiative recombination in CdTe thin films. We observed that carriers excited by the electron beam diffuse by excitons or by free electrons via donor states at low temperatures. The distribution and concentration of these states in the CdTe films were estimated from the dependence on the excitation level of the donor-to-acceptor radiative recombination.
Dependence of ferroelectric performance of sol–gel-derived Pb(Zr,Ti)O3 thin films on bottom-Pt-electrode thickness
Authors: Lim Ji-Eun , Park Dong-Yeon , Jeong Jae Kyeong , Darlinski Gregor , Kim Hyeong Joon , Hwang Cheol Seong , Kim Seung-Hyun , Koo Chang-Young , Woo Hyun-Jung , Lee Dong-Su , Ha Jowoong
Published: October 2002

Pb ( Zr,Ti ) O 3 (PZT) thin films were deposited on Pt/Ti and Pt/IrO2 electrode stacks with various Pt thicknesses (30–200 nm) by a sol–gel process. The sputter-deposited Pt films showed a (111)-preferred texture irrespective of the thickness. However, a high-resolution x-ray diffraction study of the Pt films showed that the films were composed of three kinds of grains with slightly different lattice parameters. The grains with a bulk-like lattice parameter grew with increasing Pt thickness, which was accompanied with an improvement in the crystalline quality. Accordingly, the crystallization and ferroelectric behavior of the 100-nm-thick PZT films improved with increasing Pt film thickness. However, the PZT films on the Pt/IrO2 electrode showed a deteriorated ferroelectric performance due to the outward diffusion of the Ir (O) onto the Pt surface, which increases the depolarizing field and amount of charge injection by the formation of a conducting phase.
Remote detection of human electroencephalograms using ultrahigh input impedance electric potential sensors
Authors: Harland C. J. , Clark T. D. , Prance R. J.
Published: October 2002

In this letter, we demonstrate the use of very high performance, ultrahigh impedance, electric potential probes in the detection of electrical activity in the brain. We show that these sensors, requiring no electrical or physical contact with the body, can be used to monitor the human electroencephalogram (EEG) revealing, as examples, the α and β rhythms and the α blocking phenomenon. We suggest that the advantages offered by these sensors compared with the currently used contact (Ag/AgCl) electrodes may act to stimulate new developments in multichannel EEG monitoring and in real-time electrical imaging of the brain.
Activation of melanocortin type 3 receptor as a molecular mechanism for adrenocorticotropic hormone efficacy in gouty arthritis
Authors: Getting Stephen J. , Christian Helen C. , Flower Roderick J. , Perretti Mauro
Published: October 2002

Objective

To test the hypothesis that local activation of melanocortin receptor(s) by adrenocorticotropic hormone (ACTH) could be responsible, at least in part, for its efficacy in human gouty arthritis.

Methods

Monosodium urate monohydrate (MSU) crystals were administered into rat knee joints either alone or with ACTH or a selective melanocortin type 3 receptor (MC3‐R) agonist. Neutrophil migration, arthritis score, increases in joint size, and cytokine levels were measured over time. MC3‐R expression on rat knee joint macrophages was monitored by electron microscopy and intracellular accumulation of cyclic adenosine monophosphate.

Results

MSU crystals produced a knee joint inflammation that was time dependent and was characterized by cell influx and cytokine release that was sensitive to treatment with classic anti‐arthritic drugs (indomethacin, colchicine, dexamethasone). Local, but not systemic, ACTH had an antiinflammatory effect in normal rats, a dose that did not alter circulating corticosterone (5 μg). This treatment was also effective in adrenalectomized rats. Rat knee joint macrophages expressed functional MC3‐R. The MC3‐R antagonist (SHU9119, 10 μg) blocked ACTH antiinflammatory actions, whereas antiinflammatory activity was retained with a selective MC3‐R agonist (γ2‐melanocyte–stimulating hormone).

Conclusion

This research provides evidence for a separate mechanism of action of ACTH in experimental gouty arthritis and points to a novel antiinflammatory target (selective agonists at MC3‐R) for clinical management of human gouty arthritis and possibly other chronic inflammatory conditions.
Uncoupling of type II collagen synthesis and degradation predicts progression of joint damage in patients with knee osteoarthritis
Authors: Garnero Patrick , Ayral Xavier , Rousseau Jean‐Charles , Christgau S. , Sandell Linda J. , Dougados Maxime , Delmas Pierre D.
Published: October 2002

Objective

The hallmark of osteoarthritis (OA) is the loss of articular cartilage. This loss arises from an imbalance between cartilage synthesis and cartilage degradation over a variable period of time. The aims of this study were to investigate the rates of these processes in patients with knee OA using two new molecular markers and to investigate whether the combined use of these markers could predict the progression of joint damage evaluated by both radiography and arthroscopy of the joints during a period of 1 year.

Methods

Seventy‐five patients with medial knee OA (51 women, 24 men; mean ± SD age 63 ± 8 years, mean ± SD disease duration 4.8 ± 5.2 years) were studied prospectively. At baseline, we measured serum levels of N‐propeptide of type IIA procollagen (PIIANP) and urinary excretion of C‐terminal crosslinking telopeptide of type II collagen (CTX‐II) as markers of type II collagen synthesis and degradation, respectively. Joint space width (JSW) on radiography and medial chondropathy at arthroscopy (assessed using a 100‐mm visual analog scale [VAS]) were measured in all patients at baseline and in 52 patients at 1 year. Progression of joint destruction was defined as a decrease of ≥0.5 mm in JSW on radiography and as increased chondropathy (an increase in the VAS score of >8.0 units) between the baseline and 1‐year evaluations.

Results

At baseline, compared with 58 healthy age‐ and sex‐matched controls, patients with knee OA had decreased serum levels of PIIANP (20 ng/ml versus 29 ng/ml; P < 0.001) and increased urinary excretion of CTX‐II (618 ng/mmole creatinine [Cr] versus 367 ng/mmole Cr; P < 0.001). The highest discrimination between OA patients and controls was obtained by combining PIIANP and CTX‐II in an uncoupling index (Z score CTX‐II − Z score PIIANP), which yielded a mean Z score of 2.9 (P < 0.0001). Increased baseline values in the uncoupling index were associated with greater progression of joint damage evaluated either by changes in JSW (r = −0.46, P = 0.0016) or by VAS score (r = 0.36, P = 0.014). Patients with both low levels of PIIANP (less than or equal to the mean − 1 SD in controls) and high levels of CTX‐II (greater than or equal to the mean + 1 SD in controls) had an 8‐fold more rapid progression of joint damage than other patients (P = 0.012 and P < 0.0001 as assessed by radiography and arthroscopy, respectively) and had relative risks of progression of 2.9 (95% confidence interval [95% CI] 0.80–11.1) and 9.3 (95% CI 2.2–39) by radiography and arthroscopy, respectively.

Conclusion

Patients with knee OA are characterized by an uncoupling of type II collagen synthesis and degradation which can be detected by assays for serum PIIANP and urinary CTX‐II. The combination of these two new markers could be useful for identifying knee OA patients at high risk for rapid progression of joint damage.
Therapeutic cancer targeting peptides
Authors: Aina Olulanu H. , Sroka Thomas C. , Chen Man‐Ling , Lam Kit S.
Published: October 2002

Antitumor monoclonal antibodies have shown clinical promise as cancer cell surface targeting agents. More tumor targeting antibodies are likely to be approved by the FDA in the next few years. However, there are two major limitations in antibody‐targeted therapy: large size and nonspecific uptake of the antibody molecules by the liver and the reticuloendothelial system. These result in poor tumor penetration of antibody pharmaceuticals and dose‐limiting toxicity to the liver and bone marrow. Peptides are excellent alternative targeting agents for human cancers, and they may alleviate some of the problems with antibody targeting. In the last decade, several investigators have successfully used combinatorial library methods to discover cell surface binding peptides that may be useful for cancer targeting. The phage‐display library technique and the “one‐bead one‐compound” combinatorial library method are the two approaches that have been used. Cancer cell surface receptors or endothelial cell surface receptors of the neovasculature are the two popular therapeutic targets for cancer. Results from preclinical studies with some peptides are encouraging in their targeting potential. © 2002 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 66: 184–199, 2002
Probabilistic seismic demand analysis of controlled steel moment‐resisting frame structures
Authors: Barroso Luciana R. , Winterstein Steven
Published: October 2002

This paper describes a proposed methodology, referred to as probabilistic seismic control analysis, for the development of probabilistic seismic demand curves for structures with supplemental control devices. The resulting curves may be used to determine the probability that any response measure, whether for a structure or control device, exceeds a pre‐determined allowable limit. This procedure couples conventional probabilistic seismic hazard analysis with non‐linear dynamic structural analyses to provide system specific information. This method is performed by evaluating the performance of specific controlled systems under seismic excitations using the SAC Phase II structures for the Los Angeles region, and three different control‐systems: (i) base isolation; (ii) linear viscous brace dampers; and (iii) active tendon braces. The use of a probabilistic format allows for consideration of structural response over a range of seismic hazards. The resulting annual hazard curves provide a basis for comparison between the different control strategies. Results for these curves indicate that no single control strategy is the most effective at all hazard levels. For example, at low return periods the viscous system has the lowest drift demands. However, at higher return periods, the isolation system becomes the most effective strategy. Copyright © 2002 John Wiley & Sons, Ltd.
Experimental analysis of seismic torsional ground motion recorded by the LSST‐Lotung array
Authors: Laouami Nasser , Labbe Pierre
Published: October 2002

The purpose of this study was to perform an experimental analysis of the amplitude of full‐scale spatial variability of seismic motions with regard to earthquake engineering. The LSST‐Lotung array in Taiwan provides a good set of records for this type of study. Of interest are the free‐field torsional seismic components induced by the spatial variability of seismic motions. In this study, three events have been considered: LSST‐06, LSST‐07 and LSST‐16. In time domain analysis, the experimental results obtained show that when the separation distance increases, the induced torsion decreases, and the normalized differential motion parameter increases. Also, the results show that the stronger the event, in terms of maximum PGA, the larger the induced torsional amplitude and the smaller the induced normalized differential motion parameter. Copyright © 2002 John Wiley & Sons, Ltd.
Analysis of the polymorphic CAG repeat length in the androgen receptor gene in patients with testicular germ cell cancer
Authors: Rajpert‐De Meyts Ewa , Leffers Henrik , Daugaard Gedske , Andersen Charlotte B. , Petersen Peter M. , Hinrichsen Jane , Pedersen Lene G. , Skakkebæk Niels E.
Published: October 2002

Changes in the length of a polymorphic trinucleotide (CAG) repeat in the androgen receptor (AR) gene, which may lead to altered transactivation of the AR gene, have been implicated to play a role in the pathogenesis of several forms of endocrine cancer and certain reproductive disorders. Subjects with reproductive disorders that are associated with a relative deficiency of androgen function carry an increased risk for testicular cancer, therefore we have examined the (CAG)n in the AR gene in DNA isolated from peripheral blood cells of 102 patients diagnosed with testicular germ cell neoplasia and compared them with a control group of 110 healthy men with proven fertility. All patients and control subjects underwent comprehensive andrological examination that included reproductive hormone profiles and the analysis of the (CAG)n in the AR gene that was done by means of PCR and DNA sequencing. There was no difference in the distribution of (CAG)n between the subjects and controls, no association of (CAG)n and the tumor type and no association with severity of the disease. We conclude that the high risk of testicular germ cell cancer in the Danish population is not associated with the (CAG)n polymorphism in the AR gene. © 2002 Wiley‐Liss, Inc.
Sonic hedgehog is involved in osteoblast differentiation by cooperating with BMP‐2
Authors: Yuasa Takahito , Kataoka Hiroko , Kinto Naoki , Iwamoto Masahiro , Enomoto‐Iwamoto Motomi , Iemura Shun‐ichiro , Ueno Naoto , Shibata Yasuaki , Kurosawa Hisashi , Yamaguchi Akira
Published: October 2002

The roles of Sonic hedgehog (Shh) and Bone morphogenetic protein‐2 (Bmp‐2) in osteoblast differentiation were investigated using in vitro cell systems. Recombinant amino‐terminal portion of SHH (rSHH‐N) dose dependently stimulated ALP activity in C3H10T1/2 and MC3T3‐E1 cells. rSHH‐N induced expression of Osteocalcin mRNA in C3H10T1/2 cells. A soluble form of the receptor for type IA BMP receptor antagonized rSHH‐N‐induced ALP activity in C3H10T1/2 and MC3T3‐E1 cells, indicating that BMPs are involved in SHH‐induced osteoblast differentiation. Simultaneous supplement with rSHH‐N and BMP‐2 synergistically induced ALP activity and expression of Osteocalcin mRNA in C3H10T1/2 cells. Pretreatment with rSHH‐N for 6 h enhanced the response to BMP‐2 by increasing ALP activity in C3H10T1/2 and MC3T3‐E1 cells. Stimulatory effects of rSHH‐N and additive effects with rSHH‐N and BMP‐2 on ALP activity were also observed in mouse primary osteoblastic cells. Transplantation of BMP‐2 (1 μg) into muscle of mice induced formation of ectopic bone, whereas transplantation of r‐SHH‐N (1–5 μg) failed to generate it. These results indicate that Shh plays important roles in osteoblast differentiation by cooperating with BMP. © 2002 Wiley‐Liss, Inc.
Bone morphogenetic protein‐2 modulation of chondrogenic differentiation in vitro involves gap junction‐mediated intercellular communication
Authors: Zhang Wei , Green Colin , Stott N. Susan
Published: October 2002

Undifferentiated mesenchymal cells in the limb bud integrate a complex array of local and systemic signals during the process of cell condensation and chondrogenic differentiation. To address the relationship between bone morphogenetic protein (BMP) signaling and gap junction‐mediated intercellular communication, we examined the effects of BMP‐2 and a gap junction blocker 18 alpha glycyrrhetinic acid (18α‐GCA) on mesenchymal cell condensation and chondrogenic differentiation in an in vitro chondrogenic model. We find that connexin43 protein expression significantly correlates with early mesenchymal cellular condensation and chondrogenesis in high‐density limb bud cell culture. The level of connexin43 mRNA is maximally upregulated 48 h after treatment with recombinant human BMP‐2 with corresponding changes in protein expression. Inhibition of gap junction‐mediated intercellular communication with 2.5 μM 18α‐GCA decreases chondrogenic differentiation by 50% at 96 h without effects on housekeeping genes. Exposure to 18α‐GCA for only the first 24–48 h after plating does not affect condensation or later chondrogenic differentiation suggesting that gap junction‐mediated intercellular communication is not critical for the initial phase of condensation but is important for the onset of differentiation. 18α‐GCA can also block the chondrogenic effects of BMP‐2 without effects on cell number or connexin43 expression. These observations demonstrate 18α‐GCA‐sensitive regulation of intercellular communication in limb mesenchymal cells undergoing chondrogenic differentiation and suggest that BMP‐2 induced chondrogenic differentiation may be mediated in part through the modulation of connexin43 expression and gap junction‐mediated intercellular communication. J. Cell. Physiol. 193: 233–243, 2002. © 2002 Wiley‐Liss, Inc.
Gene expression in peripheral arterial chemoreceptors
Authors: Gauda Estelle B.
Published: October 2002

The peripheral arterial chemoreceptors of the carotid body participate in the ventilatory responses to hypoxia and hypercapnia, the arousal responses to asphyxial apnea, and the acclimatization to high altitude. In response to an excitatory stimuli, glomus cells in the carotid body depolarize, their intracellular calcium levels rise, and neurotransmitters are released from them. Neurotransmitters then bind to autoreceptors on glomus cells and postsynaptic receptors on chemoafferents of the carotid sinus nerve. Binding to inhibitory or excitatory receptors on chemoafferents control the electrical activity of the carotid sinus nerve, which provides the input to respiratory‐related brainstem nuclei. We and others have used gene expression in the carotid body as a tool to determine what neurotransmitters mediate the response of peripheral arterial chemoreceptors to excitatory stimuli, specifically hypoxia. Data from physiological studies support the involvement of numerous putative neurotransmitters in hypoxic chemosensitivity. This article reviews how in situ hybridization histochemistry and other cellular localization techniques confirm, refute, or expand what is known about the role of dopamine, norepinephrine, substance P, acetylcholine, adenosine, and ATP in chemotransmission. In spite of some species differences, review of the available data support that 1) dopamine and norepinephrine are synthesized and released from glomus cells in all species and play an inhibitory role in hypoxic chemosensitivity; 2) substance P and acetylcholine are not synthesized in glomus cells of most species but may be made and released from nerve fibers innervating the carotid body in essentially all species; 3) adenosine and ATP are ubiquitous molecules that most likely play an excitatory role in hypoxic chemosensitivity. Microsc. Res. Tech. 59:153–167, 2002. © 2002 Wiley‐Liss, Inc.
Regulation of gene expression for neurotransmitters during adaptation to hypoxia in oxygen‐sensitive neuroendocrine cells
Authors: Paulding Waltke R. , Schnell Phillip O. , Bauer Amy L. , Striet Justin B. , Nash James A. , Kuznetsova Anna V. , Czyzyk‐Krzeska Maria F.
Published: October 2002

Reduced oxygen tension (hypoxia) in the environment stimulates oxygen‐sensitive cells in the carotid body (CB). Upon exposure to hypoxia, the CB immediately triggers a reflexive physiological response, thereby increasing respiration. Adaptation to hypoxia involves changes in the expression of various CB genes, whose products are involved in the transduction and modulation of the hypoxic signal to the central nervous system (CNS). Genes encoding neurotransmitter‐synthesizing enzymes and receptors are particularly important in this regard. The cellular response to hypoxia correlates closely with the release and biosynthesis of catecholamines. The gene expression of tyrosine hydroxylase (TH), the rate‐limiting enzyme for catecholamine biosynthesis, is regulated by hypoxia in the CB and in the oxygen‐sensitive cultured PC12 cell line. Recently, genomic microarray studies have identified additional genes regulated by hypoxia. Patterns of gene expression vary, depending on the type of applied hypoxia, e.g., intermittent vs. chronic. Construction of a hypoxia‐regulated, CB‐specific, subtractive cDNA library will enable us to further characterize regulation of gene expression in the CB. Microsc. Res. Tech. 59:178–187, 2002. © 2002 Wiley‐Liss, Inc.
Oxidation of small alkenes at high temperature
Authors: Heyberger Barbara , Belmekki Najib , Conraud Valérie , Glaude Pierre‐Alexandre , Fournet René , Battin‐Leclerc Frédérique
Published: October 2002

If the mechanism of formation of alkenes, the main primary products of the combustion of alkanes above 1000 K, is now well understood, their ways of degradation have been much less studied. Following a previous modeling of the oxidation of propene in a static and a jet‐stirred reactors by using an automatically generated mechanism, the present paper shows new validations of the same mechanism for ignition delays in a shock tube. It also describes the extension of the rules used for the automatic generation to the case of 1‐butene. The predictions of the mechanism produced for the oxidation of 1‐butene are compared successfully with two sets of experimental results: the first obtained in a jet‐stirred reactor between 900 and 1200 K; the second being new measurements of ignitions delays behind reflected shock waves for temperatures from 1200 up to 1670 K, pressures from 6.6 to 8.9 atm, equivalence ratios from 0.5 to 2, and with argon as bath gas. Flux and sensitivity analyses show that the role of termination reactions involving the very abundant allylic radicals is less important for 1‐butene than for propene. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 666–677, 2002
Gas‐phase reactions of Cl atoms with propane, n‐butane, and isobutane
Authors: Sarzynski Dariusz , Sztuba Barbara
Published: October 2002

Using the relative kinetic method, rate coefficients have been determined for the gas‐phase reactions of chlorine atoms with propane, n‐butane, and isobutane at total pressure of 100 Torr and the temperature range of 295–469 K. The Cl2 photolysis (λ = 420 nm) was used to generate Cl atoms in the presence of ethane as the reference compound. The experiments have been carried out using GC product analysis and the following rate constant expressions (in cm3 molecule−1 s−1) have been derived: (7.4 ± 0.2) × 10−11 exp [‐(70 ± 11)/ T], Cl + C3H8 → HCl + CH3CH2CH2; (5.1 ± 0.5) × 10−11 exp [(104 ± 32)/ T], Cl + C3H8 → HCl + CH3CHCH3; (7.3 ± 0.2) × 10−11 exp[−(68 ± 10)/ T], Cl + n‐C4H10 → HCl + CH3 CH2CH2CH2; (9.9 ± 2.2) × 10−11 exp[(106 ± 75)/ T], Cl + n‐C4H10 → HCl + CH3CH2CHCH3; (13.0 ± 1.8) × 10−11 exp[−(104 ± 50)/ T], Cl + i‐C4H10 → HCl + CH3CHCH3CH2; (2.9 ± 0.5) × 10−11 exp[(155 ± 58)/ T], Cl + i‐C4H10 → HCl + CH3CCH3CH3 (all error bars are ± 2σ precision). These studies provide a set of reaction rate constants allowing to determine the contribution of competing hydrogen abstractions from primary, secondary, or tertiary carbon atom in alkane molecule. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 651–658, 2002
Composition cascade control for chemical reactors
Authors: Alvarez‐Ramirez Jose , Valencia Jesus , Morales America
Published: October 2002

Eventhough the composition control of chemical reactors is an old, widely studied, and still relevant problem in chemical process control, it still presents some aspects that remain unexplored or unresolved. For instance, a unifying approach is needed to systematize the existing ad hoc controller constructions, to rigorously explain their remarkable robustness property, and to explore the possibility of improving their construction and functioning. In this paper, some aspects of these control problems are addressed by resorting to recently developed approaches in constructive non‐linear control, yielding a systematic controller construction coupled to a simple tuning scheme that can be executed with standard tuning rules, a closed‐loop stability criterion, and an explanation of the closed‐loop dynamics behaviour. Specifically, a linear cascade (master/slave) control configuration is proposed, which leads to global internal stability of the controlled system with asymptotic regulation of the output‐stream composition about a given desired setpoint. A simulation example is used to illustrate the results. Copyright © 2002 John Wiley & Sons, Ltd.
A small-angle neutron scattering investigation of the structure of highly swollen block copolymer micelles
Authors: Castelletto V. , Hamley I. W. , Pedersen J. S.
Published: October 2002

The structure of highly swollen micelles of an amphiphilic poly(oxyethylene)–poly(oxybutylene) diblock copolymer with a lengthy hydrophilic poly(oxyethylene) block has been investigated by small-angle neutron scattering (SANS). The density profile of the tethered polymer brush is obtained by fitting the SANS data using analytical expressions for the form factor of a micelle with a spherical core and self-avoiding chains. The decrease in coronal chain radius of gyration with increasing temperature, and the decrease in water content in the poly(oxybutylene) core lead to an increase in association number, in good agreement with previous light scattering experiments. The increase in polymer volume fraction close to the core on increasing temperature is related to the increase in fractional surface coverage and reduction in interfacial curvature.
Viscous effects in control of near-wall turbulence
Authors: Chang Yong , Collis S. Scott , Ramakrishnan Srinivas
Published: October 2002

Prior studies of wall bounded turbulence control have utilized direct numerical simulation (DNS) which has limited investigations to low Reynolds numbers where viscous effects may play an important role. The current paper utilizes large eddy simulation (LES) with the dynamic subgrid-scale model to explore the influence of viscosity on one popular turbulence control strategy, opposition control, that has been extensively studied using low Reynolds number DNS. Exploiting the efficiency of LES, opposition control is applied to fully developed turbulent flow in a planar channel for turbulent Reynolds numbers in the range Reτ=80–720. At Reτ=80, opposition control completely suppresses turbulent fluctuations returning the flow to the laminar state. For higher Reynolds numbers, the flow remains turbulent and the predicted drag reduction drops from 26% at Reτ=100 to 19% at Reτ=720. Furthermore, the ratio of power saved to power input drops by more than a factor of 4 when Reynolds number increases over this range, indicating that the drag reduction mechanism in opposition control is both less effective and less efficient at higher Reynolds numbers.
On the existence of non-nuclear maxima in simple metals
Authors: Madsen Georg K. H. , Blaha Peter , Schwarz Karlheinz
Published: October 2002

A study of the existence of non-nuclear maxima (NNM) in the electron density of simple metals is presented. The calculations are based on density functional theory and the linearized augmented plane wave method in which the basis set quality can be systematically improved. We find that only lithium and beryllium exhibit NNM at calculated and experimental equilibrium volumes. The existence of NNM is found to be caused by a relatively small extension of their core densities. The NNM appear in both the local density and generalized gradient approximations. The use of the latter favors the existence of NNM and at the same time improves the agreement with measured structure factors and lattice constants. Therefore, we argue that it is very likely that NNM would also appear for the exact functional.
Capillary condensation of nitrogen in MCM-41 and SBA-15
Authors: Morishige Kunimitsu , Ito Masataka
Published: October 2002

We performed measurements of a series of adsorption–desorption isotherms of nitrogen into MCM-41 and SBA-15 mesoporous molecular sieves with different pore sizes in a wide temperature range between a bulk triple point (Tt) and a bulk critical point (Tc). The hysteresis loop shrinks with increasing temperature and eventually disappears at the hysteresis critical temperature (Tch), in accord with the appearance of metastable states in a single pore. We estimated the exact pore sizes of our samples from comparing the experimental equilibrium pressure at 77 K with the NLDFT isotherms, where the condensation pressures at 77 K were determined by extrapolating a plot of the equilibrium pressure versus temperature measured above Tch. The pore critical temperature (Tcp) was also determined from the inflection point in a plot of the inverse slope of the adsorption step against temperature. Tch is always lower than Tcp. Both plots of (Tc−Tch)/Tc versus d/rp and (Tc−Tcp)/Tc versus d/rp form straight lines passing through the origin, where d is the molecular diameter, although the former plot deviate from the linear relationship at large pores; Tch approaches Tcp in large pores. This strongly suggests that in large pores the energy barrier from the metastable state to the stable state is too large to be overcome within the period of observations even at the high temperatures just below Tcp.
The stretching of an electrified non-Newtonian jet: A model for electrospinning
Authors: Feng J. J.
Published: October 2002

Electrospinning uses an external electrostatic field to accelerate and stretch a charged polymer jet, and may produce ultrafine “nanofibers.” Many polymers have been successfully electrospun in the laboratory. Recently Hohman et al. [Phys. Fluids, 13, 2201 (2001)] proposed an electrohydrodynamic model for electrospinning Newtonian jets. A problem arises, however, with the boundary condition at the nozzle. Unless the initial surface charge density is zero or very small, the jet bulges out upon exiting the nozzle in a “ballooning instability,” which never occurs in reality. In this paper, we will first describe a slightly different Newtonian model that avoids the instability. Well-behaved solutions are produced that are insensitive to the initial charge density, except inside a tiny “boundary layer” at the nozzle. Then a non-Newtonian viscosity function is introduced into the model and the effects of extension thinning and thickening are explored. Results show two distinct regimes of stretching. For a “mildly stretched” jet, the axial tensile force in the fiber resists stretching, so that extension thinning promotes stretching and thickening hinders stretching. For a “severely stretched” jet, on the other hand, the tensile force enhances stretching at the beginning of the jet and suppresses it farther downstream. The effects of extensional viscosity then depend on the competition between the upstream and downstream dynamics. Finally, we use an empirical correlation to simulate strain hardening typical of polymeric liquids. This generally steepens the axial gradient of the tensile stress. Stretching is more pronounced at the beginning but weakens later, and ultimately thicker fibers are produced because of strain hardening.
On the electrical double layer contribution to the interfacial tension of protein crystals
Authors: Sear R. P. , Warren P. B.
Published: October 2002

We study the electrical double layer at the interface between a protein crystal and a salt solution or a dilute solution of protein, and estimate the double layer’s contribution to the interfacial tension of this interface. This contribution is negative and decreases in magnitude with increasing salt concentration. We also consider briefly the interaction between a pair of protein surfaces.
Template-directed convective assembly of three-dimensional face-centered-cubic colloidal crystals
Authors: Zhang J. , Alsayed A. , Lin K. H. , Sanyal S. , Zhang F. , Pao W.-J. , Balagurusamy V. S. K. , Heiney P. A. , Yodh A. G.
Published: October 2002

We demonstrate that square two-dimensional grating templates can drive the growth of three-dimensional, face-centered-cubic (fcc) colloidal crystals by convective assembly. The square symmetry [i.e., (100) planes parallel to the substrate] of the underlying template was transferred to the colloidal crystal and maintained throughout its growth of ∼50 layers. We characterized crystals grown on flat and on templated substrates using electron microscopy and small-angle x-ray scattering (SAXS). SAXS measurements of the templated samples clearly show fourfold diffraction patterns that arise from fcc domains without stacking faults.
Chemical structure of Al/LiF/Alq interfaces in organic light-emitting diodes
Authors: Grozea D. , Turak A. , Feng X. D. , Lu Z. H. , Johnson D. , Wood R.
Published: October 2002

Al/LiF cathode/organic is known to form an excellent interface for electron injection into the organic active layer, resulting in excellent performing organic light-emitting diodes (OLEDs). Here, the chemical structure of the interface between the Al/LiF bilayer cathode and tris (8-hydroxyquinoline) aluminum (Alq) of working OLED devices was investigated by using x-ray photoelectron spectroscopy (XPS). Using a in situ peel-off technique, we are able to characterize the buried interface structure without disturbing the chemical states of each element probed. The data show that there are two types of F at the interface; one is attributed to LiF and the other to F attached to the Alq. This F-doped Alq layer could induce a downshift in molecular orbital levels and thus leads to a reduced electron injection barrier. XPS depth profile results show significant O diffusion through Al layer to the interface, and the diffusion of O ends abruptly at the Al/LiF interface.