bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Different Phonon Transport Models for Predicting Heat Conduction in Silicon-on-Insulator Transistors
Authors: Narumanchi Sreekant V. J. , Murthy Jayathi Y. , Amon Cristina H.
Published: July 2005

The problem of self-heating in microelectronic devices has begun to emerge as a bottleneck to device performance. Published models for phonon transport in microelectronics have used a gray Boltzmann transport equation (BTE) and do not account adequately for phonon dispersion or polarization. In this study, the problem of a hot spot in a submicron silicon-on-insulator transistor is addressed. A model based on the BTE incorporating full phonon dispersion effects is used. A structured finite volume approach is used to solve the BTE. The results from the full phonon dispersion model are compared to those obtained using a Fourier diffusion model. Comparisons are also made to previously published BTE models employing gray and semi-gray approximations. Significant differences are found in the maximum hot spot temperature predicted by the different models. Fourier diffusion underpredicts the hot spot temperature by as much as 350% with respect to predictions from the full phonon dispersion model. For the full phonon dispersion model, the longitudinal acoustic modes are found to carry a majority of the energy flux. The importance of accounting for phonon dispersion and polarization effects is clearly demonstrated.
Optimized Heat Transfer for High Power Electronic Cooling Using Arrays of Microjets
Authors: Fabbri Matteo , Dhir Vijay K.
Published: July 2005

Electronic cooling has become a subject of interest in recent years due to the rapidly decreasing size of microchips while increasing the amount of heat flux that they must dissipate. Conventional forced air cooling techniques cannot satisfy the cooling requirements and new methods have to be sought. Jet cooling has been used in other industrial fields and has demonstrated the capability of sustaining high heat transfer rates. In this work the heat transfer under arrays of microjets is investigated. Ten different arrays have been tested using deionized water and FC40 as test fluids. The jet diameters employed ranged between 69 and 250μm and the jet Reynolds number varied from 73 to 3813. A maximum surface heat flux of 310W∕cm2 was achieved using water jets of 173.6μm diameter and 3mm spacing, impinging at 12.5m∕s on a circular 19.3mm diameter copper surface. The impinging water temperature was 23.1°C and the surface temperature was 73.9°C. The heat transfer results, consistent with those reported in the literature, have been correlated using only three independent dimensionless parameters. With the use of the correlation developed, an optimal configuration of the main geometrical parameters can be established once the cooling requirements of the electronic component are specified.
Solution of Transient Temperature Field for Thermographic NDT Under Joule Effect Heating
Authors: Li Zhuo Qiu , Zhang Xiong , Zhang Jiang Tao
Published: July 2005

Conducting infrared thermographic nondestructive testing (NDT) by the internal heat generated by Joule effect of components is a new heating approach for flaw detection. Due to the combination of electric field and thermal field, the irregular geometric boundary and the complicated internal heat source distribution, the theoretical solution of transient temperature field is very difficult. Nowadays numerical solution by FEM and FDM is mainly applied. By adopting certain assumptions, this paper presents a method to obtain the approximate temperature field by using Green’s function, and gives the solution of a two-dimensional rectangular field including a circular flaw. By contrast, the result tallies with the FEM results well.
Damage-Free Low Temperature Pulsed Laser Printing of Gold Nanoinks On Polymers
Authors: Chung Jaewon , Ko Seunghwan , Grigoropoulos Costas P. , Bieri Nicole R. , Dockendorf Cedric , Poulikakos Dimos
Published: July 2005

In this study, pulsed laser based curing of a printed nanoink (nanoparticle ink) combined with moderate and controlled substrate heating was investigated to create microconductors at low enough temperatures appropriate for polymeric substrates. The present work relies on (1) the melting temperature depression of nanoparticles smaller than a critical size, (2) DOD (drop on demand) jettability of nanoparticle ink, and (3) control of the heat affected zone induced by pulsed laser heating. In the experiments, gold nanoparticles of 3-7nm diameter dissolved in toluene solvent were used as ink. This nanoink was printed on a polymeric substrate that was heated to evaporate the solvent during or after printing. The overall morphology of the gold microline was determined by the printing process and controlled by changing the substrate temperature during jetting. In addition, the printed line width of about 140μm at the room temperature decreased to 70-80μm when the substrate is heated at 90°C. By employing a microsecond pulsed laser, the nanoparticles were melted and coalesced at low temperature to form a conductive microline which had just 3–4 times higher resistivity than the bulk value without damaging the temperature sensitive polymeric substrate. This gold film also survived after Scotch tape test. These are remarkable results, considering the fact that the melting temperature of bulk gold is 1064°C and the polymeric substrate can be thermally damaged at temperatures as low as 500°C.
Fluid Flow Around and Heat Transfer From an Infinite Circular Cylinder
Authors: Khan W. A. , Culham J. R. , Yovanovich M. M.
Published: July 2005

In this study, an integral approach of the boundary layer analysis is employed to investigate fluid flow around and heat transfer from an infinite circular cylinder. The Von Karman–Pohlhausen method is used to solve momentum integral equation and the energy integral equation is solved for both isothermal and isoflux boundary conditions. A fourth-order velocity profile in the hydrodynamic boundary layer and a third-order temperature profile in the thermal boundary layer are used to solve both integral equations. Closed form expressions are obtained for the drag and the average heat transfer coefficients which can be used for a wide range of Reynolds and Prandtl numbers. The results for both drag and heat transfer coefficients are in good agreement with experimental/numerical data for a circular cylinder.
Narrow-Band Based Multiscale Full-Spectrum k-Distribution Method for Radiative Transfer in Inhomogeneous Gas Mixtures
Authors: Wang Liangyu , Modest Michael F.
Published: July 2005

The full-spectrum k-distribution (FSK) method has become the most promising model for radiative transfer in participating media since its introduction a few years ago. It achieves line-by-line (LBL) accuracy for homogeneous media with only a tiny fraction of LBL’s computational cost. Among the variants of the FSK method for dealing with inhomogeneous media, the multiscale FSK (MSFSK) method not only provides a strategy to treat the inhomogeneity problem by introducing an overlap coefficient, it also accommodates a solution to the so-called mixing problem (mixing of k-distributions for different gas species). The evaluation of MSFSK parameters, however, is tedious and excludes the MSFSK method from practical applications. In this paper a new scheme of evaluating k-distributions and overlap coefficients from a database of narrow-band k-distributions is formulated, treating each gas specie as a single scale. The new scheme makes the MSFSK method efficient and convenient for practical applications, and ready to accommodate nongray absorbing particles (such as soot) in the medium. The method virtually eliminates errors caused by uncorrelatedness due to independently varying species concentrations. It was also found that, in addition, breaking up a gas mixture into gas scales reduces the error caused by temperature inhomogeneities. The mathematical development of the new scheme is described and validated; the concept and the implication of the overlap coefficient are discussed. Sample calculations for inhomogeneous media with step changes in species mole fraction and temperature are performed to demonstrate the accuracy of the new scheme by comparison with LBL calculations.
Measurement of Air Film Damping Effectiveness
Authors: Mathison R. M. , Dunn M. G. , Weaver M. M. , Dushko A.
Published: July 2005

Air film damping systems have attracted considerable interest within the gas turbine industry because of their effectiveness at controlling modes of vibration without environmental limitations. Though still in the early stages of development, air film dampers have promise for improving the high cycle fatigue characteristics of solid gas turbine airfoils. This study used experimental methods to compare the vibrational response of a solid flat plate with the response of an identically sized plate that incorporated an air film damper. It also investigated the influence of elevated pressures on air film damping effectiveness, the impact of the damper on the various vibration modes, and the relative strain levels of the air film cover plate to the solid backing. The results show that the air film damper is very effective in controlling the two-stripe mode for which it was designed. Increasing the surrounding air pressure makes the damper more effective and shifts the resonant frequencies lower.
Experimental Investigation of the Aerothermal Performance of a High Blockage Rib-Roughened Cooling Channel
Authors: Casarsa Luca , Arts Tony
Published: July 2005

The present study deals with a detailed experimental investigation of the turbulent flow inside a rib-roughened turbine blade cooling channel. The measurements are carried out in a stationary straight channel with high blockage ribs installed on one wall. The main objective is to enhance the understanding and deepen the analysis of this complex flow field with the help of highly resolved particle image velocimetry measurements. A quasi-three-dimensional view of the flow field is achieved, allowing the identification of the main time-averaged coherent structures. The combined analysis of the present aerodynamic results with available heat transfer data emphasizes the role of the mean and fluctuating flow features in the heat transfer process. In particular, the stream wise/normal to the wall component of the Reynolds stress tensor is shown to be strictly related to the heat transfer rate on the channel surfaces. A correlation to estimate the heat transfer field from the aerodynamic data is presented for the high blockage rib roughened channel flow.
Toward Intra-Row Gap Optimization for One and Half Stage Transonic Compressor
Authors: Li H. D. , He L.
Published: July 2005

Multistage effects on both aerodynamics and aeromechanics have been identified as significant. Thus, design optimizations for both aerodynamic performance and aeromechanical stability should be done in the unsteady multistage environment. The key issue preventing such a procedure to be carried out is the enormous computing time cost of multistage unsteady simulations. In this paper, a methodology based on the single-passage shape-correction method integrated with an interface disturbance truncation technique has been developed. The capability, efficiency, and accuracy of the developed methodology have been demonstrated for a one and a half stage quasi-three-dimensional transonic compressor with realistic blade counts. Furthermore, the interface disturbance truncation technique enables us to separate multirow interaction effects from the upstream and the downstream, which makes it possible to superimpose different rotor upstream gap effects and rotor downstream gap effects on the middle row rotor aerodynamic damping. In addition, a gap influence coefficient approach has been developed for investigation of all the possible gap spacing combinations of M upstream stator-rotor gaps and N downstream rotor-stator gaps. Then the number of cases that need to be computed has been reduced from M×N to M+N, which saved substantial computing time. The optimization analysis shows significant damping variation (∼300%) within the chosen intrarow gap design space. The intrarow gap spacing could have either stabilizing or destabilizing effects so that the stabilizing axial spacing could be utilized to increase flutter-free margin in aeromechanical designs. The current approach also can be used for setting aeromechanical constraints for aerodynamic performance optimizations.
Development and Experimental Validation of a Compressor Dynamic Model
Authors: Venturini M.
Published: July 2005

In recent years, transient response analysis of energy systems is becoming more and more important in optimizing plant operation and control. Furthermore, dynamic analyses are also used to integrate steady-state diagnostic analyses, since they allow the detection of malfunctions characterized by time-dependent effects. The paper deals with the development of a nonlinear modular model for compressor dynamic simulation. After developing the compressor mathematical model through a physics-based approach (laws of conservation and thermal balances), the model is implemented through the MATLAB® SIMULINK® tool. Then, a sensitivity analysis is carried out to evaluate the influence of model parameters on the model response. Finally, the model is calibrated on a multistage axial-centrifugal small size compressor running in the test facility of the University of Ferrara (Italy) and validated through experimental data taken on the compressor under investigation.
A Numerical and Experimental Investigation of the Slot Film-Cooling Jet With Various Angles
Authors: Jia Rongguang , Sundén Bengt , Miron Petre , Léger Bruno
Published: July 2005

Numerical simulations coupled with laser Doppler velocimetry (LDV) experiments were carried out to investigate a slot jet issued into a cross flow, which is relevant in the film cooling of gas turbine combustors. The film-cooling fluid injection from slots or holes into a cross flow produces highly complicated flow fields. In this paper, the time-averaged Navier-Stokes equations were solved on a collocated body-fitted grid system with the shear stress transport k−ω, V2F k−ϵ, and stress-ω turbulence models. The fluid flow and turbulent Reynolds stress fields were compared to the LDV experiments for three jet angles, namely, 30, 60, and 90 deg, and the jet blowing ratio is ranging from 2 to 9. Good agreement was obtained. Therefore, the present solution procedure was also adopted to calculations of 15 and 40 deg jets. In addition, the temperature fields were computed with a simple eddy diffusivity model to obtain the film-cooling effectiveness, which, in turn, was used for evaluation of the various jet cross-flow arrangements. The results show that a recirculation bubble downstream of the jet exists for jet angles larger than 40 deg, but it vanishes when the angle is <30deg, which is in good accordance with the experiments. The blowing ratio has a large effect on the size of the recirculation bubble and, consequently, on the film cooling effectiveness. In addition, the influence of boundary conditions for the jet and cross flow are also addressed in the paper.
THE ELECTRON–ANTINEUTRINO ANGULAR CORRELATION IN FREE NEUTRON DECAY
Authors: WIETFELDT F. E.
Published: July 2005

Free neutron beta decay is the simplest nuclear beta decay and the prototype charged-current semileptonic decay. It has some theoretical advantage over other nuclear decay systems in that there are no nuclear structure corrections, and it is the only mixed Fermi/Gamow–Teller beta decay for which the relative matrix elements can be directly calculated. The status of the electron–antineutrino angular correlation (a-coefficient) in neutron beta decay and its role in elucidating fundamental properties of the weak interaction are reviewed, with an emphasis on experiments. A new generation of experiments intended to reduce the uncertainty in the a-coefficient to less than 1% is described.
THE EFFECTS OF NON-UNIVERSAL EXTRA DIMENSIONS ON THE $\tau\rightarrow\mu\bar\nu_i\nu_i$ DECAY
Authors: ILTAN E. O.
Published: July 2005

We study [Formula: see text], i = e, μ, τ decays in the two-Higgs doublet model, with the inclusion of one and two spatial non-universal extra dimensions. We observe that the branching ratio is sensitive to two extra dimensions in contrary to a single extra dimension.
GLUONS AT FINITE TEMPERATURE IN LANDAU GAUGE YANG–MILLS THEORY
Authors: MAAS AXEL
Published: July 2005

The infrared behavior of Yang–Mills theory at finite temperature provides access to the role of confinement. In this review recent results on this topic from lattice calculations and especially Dyson–Schwinger studies are discussed. These indicate persistence of a residual confinement even in the high-temperature phase. The confinement mechanism is very similar to the one in the vacuum for the chromomagnetic sector. In the chromoelectric sector screening occurs at the soft scale g2T, although not leading to a perturbative behavior.
WIDTH OF θ-PENTAQUARKS IN RELATIVISTIC QUARK MODEL
Authors: GERASYUTA S. M. , KOCHKIN V. I.
Published: July 2005

The relativistic generalization of Faddeev–Yakubovsky approach is constructed in the form of the dispersion relations. The five-quark amplitudes for the low-lying pentaquarks including the u-, d-, s-quarks are calculated. The poles of these amplitudes determine the masses and widths of θ-pentaquarks.
REDOX REGULATION BY INTRINSIC SPECIES AND EXTRINSIC NUTRIENTS IN NORMAL AND CANCER CELLS
Authors: McEligot Archana Jaiswal , Yang Sun , Meyskens, Jr. Frank L.
Published: July 2005

▪ Abstract  Cells in multicellular organisms are exposed to both endogenous oxidative stresses generated metabolically and to oxidative stresses that originate from neighboring cells and from other tissues. To protect themselves from oxidative stress, cells are equipped with reducing buffer systems (glutathione/GSH and thioredoxin/thioredoxin reductase) and have developed several enzymatic mechanisms against oxidants that include catalase, superoxide dismutase, and glutathione peroxidase. Other major extrinsic defenses (from the diet) include ascorbic acid, β-carotene and other carotenoids, and selenium. Recent evidence indicates that in addition to their antioxidant function, several of these redox species and systems are involved in regulation of biological processes, including cellular signaling, transcription factor activity, and apoptosis in normal and cancer cells. The survival and overall well-being of the cell is dependent upon the balance between the activity and the intracellular levels of these antioxidants as well as their interaction with various regulatory factors, including Ref-1, nuclear factor-κB, and activating protein-1.
DIETARY FIBER: How Did We Get Where We Are?
Authors: Eastwood Martin , Kritchevsky David
Published: July 2005

▪ Abstract  Dietary fiber has been a topic of considerable interest among nutritionists and clinicians for the past 50 years. Many studies on fiber have concentrated on fiber isolates, resulting in findings that have ignored fiber as a component of fruits, vegetables, nuts, cereals, and legumes in the general diet. The principle actions of fiber are to alter the nature of the contents of the gastrointestinal tract and to modify the absorption of other nutrients and chemicals. Fiber is but one component of plant food, and to neglect the other components—be they proteins, lipids, vitamins, minerals, antioxidants, or the secondary metabolites—is to seriously limit our understanding. Much of the effort expended in defining fiber and studying the fiber isolate would have been better focused using this whole-plant-food approach. Greater progress in our understanding of the relevance of fiber in the etiology of disease would have been achieved if a more holistic approach had been followed.
UPTAKE, LOCALIZATION, AND NONCARBOXYLASE ROLES OF BIOTIN
Authors: Zempleni Janos
Published: July 2005

▪ Abstract  Evidence is emerging that biotin participates in processes other than classical carboxylation reactions. Specifically, novel roles for biotin in cell signaling, gene expression, and chromatin structure have been identified in recent years. Human cells accumulate biotin by using both the sodium-dependent multivitamin transporter and monocarboxylate transporter 1. These transporters and other biotin-binding proteins partition biotin to compartments involved in biotin signaling: cytoplasm, mitochondria, and nuclei. The activity of cell signals such as biotinyl-AMP, Sp1 and Sp3, nuclear factor (NF)-κB, and receptor tyrosine kinases depends on biotin supply. Consistent with a role for biotin and its catabolites in modulating these cell signals, greater than 2000 biotin-dependent genes have been identified in various human tissues. Many biotin-dependent gene products play roles in signal transduction and localize to the cell nucleus, consistent with a role for biotin in cell signaling. Posttranscriptional events related to ribosomal activity and protein folding may further contribute to effects of biotin on gene expression. Finally, research has shown that biotinidase and holocarboxylase synthetase mediate covalent binding of biotin to histones (DNA-binding proteins), affecting chromatin structure; at least seven biotinylation sites have been identified in human histones. Biotinylation of histones appears to play a role in cell proliferation, gene silencing, and the cellular response to DNA repair. Roles for biotin in cell signaling and chromatin structure are consistent with the notion that biotin has a unique significance in cell biology.
PDK2: the missing piece in the receptor tyrosine kinase signaling pathway puzzle
Authors: Dong Lily Q. , Liu Feng
Published: July 2005

Activation of members of the protein kinase AGC (cAMP dependent, cGMP dependent, and protein kinase C) family is regulated primarily by phosphorylation at two sites: a conserved threonine residue in the activation loop and a serine/threonine residue in a hydrophobic motif (HM) near the COOH terminus. Although phosphorylation of these kinases in the activation loop has been found to be mediated by phosphoinositide-dependent protein kinase-1 (PDK1), the kinase(s) that catalyzes AGC kinase phosphorylation in the HM remains uncharacterized. So far, at least 10 kinases have been suggested to function as an HM kinase or the so-called “PDK2,” including mitogen-activated protein (MAP) kinase-activated protein kinase-2 (MK2), integrin-linked kinase (ILK), p38 MAP kinase, protein kinase Cα (PKCα), PKCβ, the NIMA-related kinase-6 (NEK6), the mammalian target of rapamycin (mTOR), the double-stranded DNA-dependent protein kinase (DNK-PK), and the ataxia telangiectasia mutated (ATM) gene product. However, whether any or all of these kinases act as a physiological HM kinase remains to be established. Nonetheless, available data suggest that multiple systems may be used in cells to regulate the activation of the AGC family kinases. It is possible that, unlike activation loop phosphorylation, phosphorylation of the HM site in the different AGC family kinases is mediated by distinct kinases. In addition, phosphorylation of the AGC family kinase at the HM site could be cell type, signaling pathway, and substrate specific. Identification and characterization of the bonafide HM kinase(s) will be essential to verify these hypotheses.
Maintenance of the postabsorptive plasma glucose concentration: insulin or insulin plus glucagon?
Authors: Raju Bharathi , Cryer Philip E.
Published: July 2005

The prevalent view is that the postabsorptive plasma glucose concentration is maintained within the physiological range by the interplay of the glucose-lowering action of insulin and the glucose-raising action of glucagon. It is supported by a body of evidence derived from studies of suppression of glucagon (and insulin, among other effects) with somatostatin in animals and humans, immunoneutralization of glucagon, defective glucagon synthesis, diverse mutations, and absent or reduced glucagon receptors in animals and glucagon antagonists in cells, animals, and humans. Many of these studies are open to alternative interpretations, and some lead to seemingly contradictory conclusions. For example, immunoneutralization of glucagon lowered plasma glucose concentrations in rabbits, but administration of a glucagon antagonist did not lower plasma glucose concentrations in healthy humans. Evidence that the glycemic threshold for glucagon secretion, unlike that for insulin secretion, lies below the physiological range, and the finding that selective suppression of insulin secretion without stimulation of glucagon secretion raises fasting plasma glucose concentrations in humans underscore the primacy of insulin in the regulation of the postabsorptive plasma glucose concentration and challenge the prevalent view. The alternative view is that the postabsorptive plasma glucose concentration is maintained within the physiological range by insulin alone, specifically regulated increments and decrements in insulin, and the resulting decrements and increments in endogenous glucose production, respectively, and glucagon becomes relevant only when glucose levels drift below the physiological range. Although the balance of evidence suggests that glucagon is involved in the maintenance of euglycemia, more definitive evidence is needed, particularly in humans.
Stimulation characteristics that determine arteriolar dilation in skeletal muscle
Authors: Murrant Coral L.
Published: July 2005

To determine the skeletal muscle stimulation parameters that are most important in establishing vasodilation in the microvasculature, I tested whether arteriolar diameter during 2 min of repetitive, short-duration, tetanic skeletal muscle contractions increased with changes in stimulus frequency, stimulation train duration, and contraction frequency. To test this, the diameter of transverse arterioles approximately perpendicular to small bundles of cremaster muscle fibers in situ of anesthetized Golden Syrian hamsters was used as a bioassay system. Arteriolar diameter was measured before and during different stimulation patterns that consisted of a contraction frequency [6, 12, or 24 contractions per minute (cpm)], a stimulation train duration (250, 500, or 750 ms) and a stimulus frequency (4, 8, 10, 15, 20, 30, 40, 60, and 80 Hz). The magnitude of the dilation significantly increased with stimulus frequency but not in a simple linear manner. The average rate of increase was 0.32 ± 0.02 μm/Hz from 4 to 20 Hz and 0.09 ± 0.02 μm/Hz from 30 to 80 Hz. The magnitude of the dilation increased significantly with the contraction frequency where the dilation at 6 cpm was significantly smaller than the dilation at 24 cpm across all stimulus frequencies. Changing the train duration from 250 to 750 ms did not significantly affect the magnitude of the dilation. These observations suggest that stimulation parameters are important in determining the magnitude of the microvascular dilation and that the magnitude of the dilation was dependent on both the contraction frequency and stimulus frequency but was independent of train duration.
Expression of nitric oxide synthase isoforms is reduced in late-gestation ovine fetal brainstem
Authors: Wood Charles E. , Chen Gin-Fu , Keller-Wood Maureen
Published: July 2005

Fetal baroreflex responsiveness increases in late gestation. An important modulator of baroreflex activity is the generation of nitric oxide in the brainstem nuclei that integrate afferent and efferent reflex activity. The present study was designed to test the hypothesis that nitric oxide synthase (NOS) isoforms are expressed in the fetal brainstem and that the expression of one or more of these enzymes is reduced in late gestation. Brainstem tissue was rapidly collected from fetal sheep of known gestational ages (80, 100, 120, 130, 145 days gestation and 1 day and 1 wk postnatal). Neuronal (nNOS), inducible (iNOS), and endothelial (eNOS) mRNA was measured using real-time PCR methodology specific for ovine NOS isoforms. The three enzymes were measured at the protein level using Western blot methodology. In tissue prepared for histology separately, the cellular pattern of immunostaining was identified in medullae from late-gestation fetal sheep. Fetal brainstem contained mRNA and protein of all three NOS isoforms, with nNOS the most abundant, followed by iNOS and eNOS, respectively. nNOS and iNOS mRNA abundances were highest at 80 days' gestation, with statistically significant decreases in abundance in more mature fetuses and postnatal animals. nNOS and eNOS protein abundance also decreased as a function of developmental age. nNOS and eNOS were expressed in neurons, iNOS was expressed in glia, and eNOS was expressed in vascular endothelial cells. We conclude that all three isoforms of NOS are constitutively expressed within the fetal brainstem, and the expression of all three forms is reduced with advancing gestation. We speculate that the reduced expression of NOS in this brain region plays a role in the increased fetal baroreflex activity in late gestation.
Growth regulation of the vascular system: an emerging role for adenosine
Authors: Adair Thomas H.
Published: July 2005

The importance of metabolic factors in the regulation of angiogenesis is well understood. An increase in metabolic activity leads to a decrease in tissue oxygenation causing tissues to become hypoxic. The hypoxia initiates a variety of signals that stimulate angiogenesis, and the increase in vascularity that follows promotes oxygen delivery to the tissues. When the tissues receive adequate amounts of oxygen, the intermediate effectors return to normal levels, and angiogenesis ceases. An emerging concept is that adenosine released from hypoxic tissues has an important role in driving the angiogenesis. The following feedback control hypothesis is proposed: AMP is dephosphorylated by ecto-5′-nucleotidase, producing adenosine under hypoxic conditions in the extracellular space adjacent to a parenchymal cell (e.g., cardiomyocyte, skeletal muscle fiber, hepatocyte, etc.). Extracellular adenosine activates A2receptors, which stimulates the release of vascular endothelial growth factor (VEGF) from the parenchymal cell. VEGF binds to its receptor (VEGF receptor 2) on endothelial cells, stimulating their proliferation and migration. Adenosine can also stimulate endothelial cell proliferation independently of VEGF, which probably involves modulation of other proangiogenic and antiangiogenic growth factors and perhaps an intracellular mechanism. In addition, hemodynamic factors associated with adenosine-induced vasodilation may have a role in the development and remodeling of the vasculature. Once a new capillary network has been established, and the diffusion/perfusion capabilities of the vasculature are sufficient to supply the parenchymal cells with adequate amounts of oxygen, adenosine and VEGF as well as other proangiogenic and antiangiogenic growth factors return to near-normal levels, thus closing the negative feedback loop. The available data indicate that adenosine might be an essential mediator for up to 50–70% of the hypoxia-induced angiogenesis in some situations; however, additional studies in intact animals will be required to fully understand the quantitative importance of adenosine.
Fixed point theorems for the class Q(X, Y)
Authors: Chen Chi-Ming , Yen Chi-Lin
Published: July 2005

We study a new family of functions
Q(X, Y), research its properties, and get some fixed point
theorems about this family.
Convex separable minimization problems with a linearconstraint and bounded variables
Authors: Stefanov Stefan M.
Published: July 2005

Consider the minimization problem with a convex separable
objective function over a feasible region defined by linear
equality constraint(s)/linear inequality constraint of the form
“greater than or equal to” and bounds on the variables. A
necessary and sufficient condition and a sufficient condition are
proved for a feasible solution to be an optimal solution to these
two problems, respectively. Iterative algorithms of polynomial
complexity for solving such problems are suggested and convergence
of these algorithms is proved. Some convex functions, important
for problems under consideration, as well as computational results
are presented.
On an inequality of Diananda. Part II
Authors: Gao Peng
Published: July 2005

We extend the result in part I, 2003, of
certain inequalities among the generalized power means.
A weak periodicity condition for rings
Authors: Abu-Khuzam Hazar , Bell Howard E. , Yaqub Adil
Published: July 2005

A ring is called semi‐weakly periodic if each element which is not in the center or the Jacobson radical can be written as the sum of a potent element and a nilpotent element. After discussing some
basic properties of such rings, we investigate their commutativity behavior.
Determination of surfaces in three‐dimensional Minkowski andEuclidean spaces based on solutions of the Sinh‐Laplace equation
Authors: Bracken Paul
Published: July 2005

The relationship between solutions of the sinh‐Laplace
equation and the determination of various kinds of
surfaces of constant Gaussian curvature, both positive
and negative, will be investigated here. It is shown
that when the metric is given in a particular set
of coordinates, the Gaussian curvature is related to
the sinh‐Laplace equation in a direct way. The
fundamental equations of surface theory are found to
yield a type of geometrically based Lax pair for the system.
Given a particular solution of the sinh‐Laplace
equation, this Lax can be integrated to determine
the three fundamental vectors related to the surface.
These are also used to determine the coordinate vector
of the surface. Some specific examples of this procedure
will be given.
Application of uniform asymptotics method to analyzing theasymptotic behaviour of the general fourth Painlevé transcendent
Authors: Qin Huizeng , Lu Youmin
Published: July 2005

We use the uniform asymptotics method proposed by A. P. Bassom et
al. (1998) to study the general fourth Painlevé transcendent, find a
group of its asymptotics and the corresponding monodromic data,
and prove its existence and ”uniqueness.“
Groups with the same orders of Sylow normalizers as the Mathieu groups
Authors: Khosravi Behrooz , Khosravi Behnam
Published: July 2005

There exist many characterizations for the sporadic simple groups.
In this paper we give two new characterizations for the Mathieu
sporadic groups. Let M be a Mathieu group and let p be the
greatest prime divisor of |M|. In this paper, we prove that M is uniquely determined by |M| and |NM(P)|, where P ∈ Sylp(M). Also we prove that if G is a finite group, then
G≅M if and only if for every prime q, |NM(Q)| = |NG(Q′)|, where Q ∈ Sylq(M) and Q′ ∈ Sylq(G).
Generalizations of Hopfian and co‐Hopfian modules
Authors: Wang Yongduo
Published: July 2005

Let R be a ring and M a left R‐module. M which satisfies
DCC on essential submodules is GCH, and M which satisfies ACC on
small submodules is WH. If M[X] is GCH R[X]‐module, then M is GCH R‐module. Examples show that a GCH module need not be
co‐Hopfian and a WH module need not be Hopfian.
Angiotensin-Converting Enzyme Inhibitors and Calcium Channel Blockers for Coronary Heart Disease and Stroke Prevention
Authors: Verdecchia Paolo , Reboldi Gianpaolo , Angeli Fabio , Gattobigio Roberto , Bentivoglio Maurizio , Thijs Lutgarde , Staessen Jan A. , Porcellati Carlo
Published: July 2005

We investigated whether protection from coronary heart disease (CHD) and stroke conferred by angiotensin-converting enzyme inhibitors (ACEIs) and calcium channel blockers (CCBs) in hypertensive or high-risk patients may be explained by the specific drug regimen. We extracted summary statistics regarding CHD and stroke from 28 outcome trials that compared either ACEIs or CCBs with diuretics, β-blockers, or placebo for a total of 179 122 patients, 9509 incident cases of CHD, and 5971 cases of stroke. CHD included myocardial infarction and coronary death. In placebo-controlled trials, ACEIs decreased the risk of CHD (
P
<0.001), and CCBs reduced stroke incidence (
P
<0.001). There were no significant differences in CHD risk between regimens based on diuretics/β-blockers and regimens based on ACEIs (
P
=0.46) or CCBs (
P
=0.52). The risk of stroke was reduced by CCBs (
P
=0.041) but not by ACEIs (
P
=0.15) compared with diuretics/β-blockers. Because heterogeneity between trials was significant, we investigated potential sources of heterogeneity by metaregression. Examined covariates were the reduction in systolic blood pressure (BP), drug treatment (ACEIs versus CCBs), their interaction term, sex, age at randomization, year of publication, and duration of treatment. Prevention of CHD was explained by systolic BP reduction (
P
<0.001) and use of ACEIs (
P
=0.028), whereas prevention of stroke was explained by systolic BP reduction (
P
=0.001) and use of CCBs (
P
=0.042). These findings confirm that BP lowering is fundamental for prevention of CHD and stroke. However, over and beyond BP reduction, ACEIs appear superior to CCBs for prevention of CHD, whereas CCBs appear superior to ACEIs for prevention of stroke.
Impaired Heart Rate Baroreflex in Older Rats
Authors: Sakima Atsushi , Averill David B. , Gallagher Patricia E. , Kasper Sherry O. , Tommasi Ellen N. , Ferrario Carlos M. , Diz Debra I.
Published: July 2005

Age-related baroreflex reductions in function may originate from central neural dysregulation as well as vascular structural/functional changes. We determined the role of 2 angiotensin (Ang) peptides at the nucleus tractus solitarii in age-related baroreflex impairment. Baroreflex sensitivity control of heart rate in response to increases in blood pressure was tested in younger (3 to 5 months) and older (16 to 20 months) anesthetized male Sprague-Dawley rats before and after bilateral solitary tract injections of the Ang II type 1 (AT
1
) receptor antagonist candesartan (24 pmol) or the Ang-(1–7) antagonist (
d
-Ala
7
)-Ang-(1–7) (144 fmol or 24 pmol). Basal reflex sensitivity of older rats was significantly lower than younger rats. In younger rats, the reflex was facilitated by bilateral candesartan injections and attenuated by bilateral (
d
-Ala
7
)-Ang-(1–7) injections. In older rats, the reflex was facilitated by AT
1
blockade; however, (
d
-Ala
7
)-Ang-(1–7) injected into the solitary tract nucleus had no effect. Neprilysin mRNA in the medulla was lower in older rats compared with younger rats, whereas angiotensin-converting enzyme (ACE), ACE2, and
mas
receptor mRNA levels of older rats did not differ from values of younger rats. Thus, opposing actions of endogenous Ang II and Ang-(1–7) in the solitary tract nucleus contribute to baroreflex function in response to increases in mean arterial pressure of younger rats. The attenuated counterbalancing effect of Ang-(1–7) on baroreflex function is lost in older rats, which may be attributable to diminished production of the peptide from neprilysin.
Obstructive Sleep Apnea Syndrome Affects Left Ventricular Diastolic Function
Authors: Arias Miguel A. , García-Río Francisco , Alonso-Fernández Alberto , Mediano Olga , Martínez Isabel , Villamor José
Published: July 2005

Background—

The purpose of this study was to determine the role of obstructive sleep apnea syndrome (OSAS) as an independent risk factor for the development of left ventricular diastolic abnormalities. Moreover, we tested the hypothesis that nasal continuous positive airway pressure (nCPAP) improves such alterations in OSAS patients by eliminating apneic events.

Methods and Results—

In this prospective, randomized, placebo-controlled, double-blind crossover study, 27 consecutive newly diagnosed middle-aged OSAS men with neither controllable factors nor conditions affecting left ventricular diastolic function and 15 healthy control subjects were selected. OSAS patients were randomized to 12 weeks on sham nCPAP and 12 weeks on effective nCPAP application. Echocardiographic parameters, blood pressure recordings, and urinary catecholamine levels were obtained at baseline and after both treatment modalities. At baseline, an abnormal left ventricular filling pattern was present in 15 of the 27 OSAS patients and only in 3 of the 15 control subjects (
P
=0.020). Impaired relaxation was by far the most common abnormal pattern in both groups (11 and 3 patients, respectively). In OSAS patients, 12 weeks on effective nCPAP induced a significant increase in E/A ratio (
P
<0.01), as well as reductions in mitral deceleration (
P
<0.01) and isovolumic relaxation (
P
<0.05) times.

Conclusions—

OSAS can affect left ventricular diastolic function independently of other possible factors. Chronic application of nCPAP could avoid the progression of diastolic abnormalities, and indeed, it might reverse these alterations, at least in the initial stages before severe structural changes can be developed.
Cardiospecific Overexpression of the Prostaglandin EP
3
Receptor Attenuates Ischemia-Induced Myocardial Injury
Authors: Martin Melanie , Meyer-Kirchrath Jutta , Kaber Gernot , Jacoby Christoph , Flögel Ulrich , Schrader Jürgen , Rüther Ulrich , Schrör Karsten , Hohlfeld Thomas
Published: July 2005

Background—

The generation of prostaglandin E
2
(PGE
2
) is significantly increased in acute myocardial ischemia and reperfusion. PGE
2
, in addition to other prostaglandins, protects the reperfused ischemic myocardium. It has been hypothesized that this cardioprotection is mediated by E-type prostaglandin receptors of the G
i
-coupled EP
3
subtype.

Methods and Results—

We tested this hypothesis by generating transgenic (tg) mice with cardiospecific overexpression of the EP
3
receptor. According to ligand binding, a 40-fold overexpression of the EP
3
receptor was achieved in membranes prepared from tg hearts compared with wild-type (wt) littermates. In isolated cardiomyocytes from tg mice, the forskolin-induced rise in cAMP was markedly attenuated, indicating coupling of the overexpressed EP
3
receptor to inhibitory G proteins (G
i
) with constitutive receptor activity. There was no evidence for EP
3
receptor coupling to G
q
-mediated protein kinase C signaling. Isolated hearts from tg and wt mice were subjected to 60 minutes of no-flow ischemia and 45 minutes of reperfusion. In tg hearts, ischemic contracture was markedly delayed compared with wt hearts, and the ischemia-induced increase in left ventricular end-diastolic pressure was reduced by 55%. Creatine kinase and lactate dehydrogenase release was significantly decreased by 85% and 73%, respectively, compared with wt hearts.

Conclusions—

Constitutive prostaglandin EP
3
receptor signaling exerts a protective effect on cardiomyocytes, which is probably G
i
mediated and results in a remarkable attenuation of myocardial injury during ischemia and reperfusion. Cardioprotective actions of E-type prostaglandins may be mediated by this receptor subtype.
Physiological Background of the Loss of Fractal Heart Rate Dynamics
Authors: Tulppo Mikko P. , Kiviniemi Antti M. , Hautala Arto J. , Kallio Mika , Seppänen Tapio , Mäkikallio Timo H. , Huikuri Heikki V.
Published: July 2005

Background—

Altered fractal heart rate (HR) dynamics occur during various disease states, but the physiological background of abnormal fractal HR behavior is not well known. We tested the hypothesis that the fractal organization of human HR dynamics is determined by the balance between sympathetic and vagal outflow.

Methods and Results—

A short-term fractal scaling exponent (α
1
) of HR dynamics, analyzed by the detrended fluctuation analysis (DFA) method, and the high-frequency (HF) and low-frequency (LF) spectral components of R-R intervals (0.15 to 0.4 Hz; n=13), along with muscle sympathetic nervous activity (MSNA) from the
peroneus
nerve (n=11), were assessed at rest and during cold face and cold hand immersion in healthy subjects. During cold face immersion, HF power increased (from 6.9±1.3 to 7.6±1.2 ln ms
2
,
P
<0.01), as did MSNA (from 32±17 to 44±14 bursts/100 heartbeats,
P
<0.001), and LF/HF ratio decreased (
P
<0.01). Cold hand immersion resulted in a similar increase in MSNA (from 34±17 to 52±19 bursts/100 heartbeats,
P
<0.001) but a decrease in HF spectral power (from 7.0±1.3 to 6.5±1.1 ln ms
2
,
P
<0.05) and an increase in the LF/HF ratio (
P
<0.05). The fractal scaling index α
1
decreased in all subjects (from 0.85±0.27 to 0.67±0.30,
P
<0.0001) during cold face immersion but increased during cold hand immersion (from 0.77±0.22 to 0.97±0.20,
P
<0.01).

Conclusions—

The fractal organization of human HR dynamics is determined by a delicate interplay between sympathetic and vagal outflow, with the breakdown of fractal HR behavior toward more random dynamics occurring during coactivation of sympathetic and vagal outflow.
Molecular Magnetic Resonance Imaging of Atrial Clots in a Swine Model
Authors: Spuentrup Elmar , Fausten Bernd , Kinzel Sylvia , Wiethoff Andrea J. , Botnar Rene M. , Graham Philip B. , Haller Stephan , Katoh Marcus , Parsons Edward C. , Manning Warren J. , Busch Thomas , Günther Rolf W. , Buecker Arno
Published: July 2005

Background—

The detection and differentiation of intracardiac masses is still challenging and may include neoplasms and thrombi. The aim of this study was the investigation of a targeted, fibrin-specific contrast agent (EP-2104R) for molecular targeted magnetic resonance imaging (MRI) of left atrial clots.

Methods and Results—

Chronic human thrombi were surgically implanted in the left atrial appendage of 5 swine. Molecular MRI was performed with a navigator-gated, free-breathing, cardiac-triggered 3D inversion-recovery, black-blood, gradient-echo sequence before and after systemic administration of 4 μmol/kg EP-2104R. MR images were analyzed by 2 investigators, and the contrast-to-noise ratio was calculated. Location of clots was confirmed by autopsy, and the gadolinium concentration in the clots was assessed. Before contrast agent administration, thrombi were not visible on black-blood MR images. After contrast administration, all atrial clots (n=5) were selectively visualized as white spots with a high contrast-to-noise ratio (clot/blood, 29.7±8.0). The gadolinium concentration in the clots averaged 74±45 μmol/L.

Conclusions—

The fibrin-specific MR contrast agent EP-2104R allows for selective and high-contrast visualization of left atrial clots by means of molecular targeted MRI.
Behavioral Versus Genetic Correlates of Lipoproteins and Adiposity in Identical Twins Discordant for Exercise
Authors: Williams Paul T. , Blanche Patricia J. , Krauss Ronald M.
Published: July 2005

Background—

Lipoprotein and weight differences between vigorously active and sedentary monozygotic (MZ) twins were used to (1) estimate the effects of training while controlling for genotype and (2) estimate genetic concordance (ie, similarity) in the presence of divergent lifestyles.

Methods and Results—

Thirty-five pairs of MZ twins (25 male, 10 female) were recruited nationally who were discordant for vigorous exercise (running distances differed by ≥40 km in male and ≥32 km in female twins). The active twins ran an average (mean±SD) of 63.0±20.4 km/wk, whereas the mostly sedentary twins averaged 7.0±13.5 km/wk. The active twins had significantly lower body mass index (difference±SE, −2.12±0.57 kg/m
2
,
P
=0.0007) and significantly higher HDL cholesterol (0.14±0.04 mmol/L,
P
=0.004), HDL
2
(2.71±1.04 U,
P
=0.01), and apolipoprotein (apo) A-I (0.10±0.03 g/L,
P
=0.004). Despite the difference in lifestyle, when adjusted for sex, the correlations between the discordant MZ twin pairs were significant (
P
<0.01) for HDL cholesterol (
r
=0.69), apoA-I (
r
=0.58), and HDL
2
(
r
=0.67). There was no significant MZ twin correlation for body mass index (
r
=0.17). None of the active twins having an overweight twin were themselves overweight.

Conclusions—

Behavior (vigorous exercise) may reduce genetic influences on body mass index. In contrast, genetics (or shared environment) substantially influences HDL cholesterol and HDL subclasses, even in the presence of extreme behavioral differences. There may be greater individual control over moderate degrees of obesity, whereas low HDL cholesterol may be largely predetermined and less effectively treated by vigorous exercise.