bluuebunny/crossref_metadata_2025 huggingface dataset:
Stacked Microchannel Heat Sinks for Liquid Cooling of Microelectronics
Authors: Wei Xiaojin , Joshi Yogendra , Patterson Michael K.
Published: April 2008

Stacked microchannels provide larger flow passages, so that for a fixed heat load the required pressure drop is significantly reduced. One unique feature of the stacked microchannel heat sink is that individual layers populated with parallel microchannels or distributing manifolds can be bonded into one stack with independent flow path. As a beneficial result, flexible control over the flow direction and flow rate can be harnessed to achieve better temperature uniformity and the low junction temperature. In the present work, stacked microchannels with different flow arrangement have been fabricated on silicon wafers using micromachining techniques. Platinum thin film heaters are deposited on the backside of the stacked structure to provide heating. In a close-loop setup, water is pumped through the microchannels to carry the heat from the heaters to a remote liquid-liquid heat exchanger rejecting the heat to a recirculating chiller. Wall temperature along the flow direction is measured at nine locations using platinum resistive temperature detectors deposited at the same time as the heaters. Good overall cooling performance (0.09°C/(W/cm2)) for the stacked microchannel heat sink has been shown in the experiments. It has also been identified that over the tested flow rate range counter-flow arrangement provides better temperature uniformity, while parallel flow has the best performance in reducing the peak temperature.
Dynamic Flow of Micro-Channels in a Ceramic Heat Exchanger
Authors: Cutts James , Wilson Merrill , Ponyavin Valery
Published: April 2008

This poster presents a comparison of flow between four possible designs for ceramic high temperature heat exchanger that is used as a sulfuric acid decomposer which may be used for hydrogen production within the sulfur iodine thermo-chemical cycle. The decomposer is manufactured using fused ceramic layers that allow creation of tailored micro-channels with dimensions below one millimeter. The baseline design uses parallel straight channels with rectangular cross sections. This design will be compared with other proposed designs where varying cross sections and serpentine flow paths can improve the heat transfer with minimal effects on the pressure drop. Measurements have been taken using a dynamic pressure mat that has been calibrated to allow for precise measurements of the flow data. Results of this research are used as a basis for investigation optimal design of the decomposer that can provide maximum thermal performance while maintaining low pressure drops and thermo-mechanical stresses within system.
DNA from Pre-Clovis Human Coprolites in Oregon, North America
Authors: Gilbert M. Thomas P. , Jenkins Dennis L. , Götherstrom Anders , Naveran Nuria , Sanchez Juan J. , Hofreiter Michael , Thomsen Philip Francis , Binladen Jonas , Higham Thomas F. G. , Yohe Robert M. , Parr Robert , Cummings Linda Scott , Willerslev Eske
Published: April 2008

The timing of the first human migration into the Americas and its relation to the appearance of the Clovis technological complex in North America at about 11,000 to 10,800 radiocarbon years before the present (
14
C years B.P.) remains contentious. We establish that humans were present at Paisley 5 Mile Point Caves, in south-central Oregon, by 12,300
14
C years B.P., through the recovery of human mitochondrial DNA (mtDNA) from coprolites, directly dated by accelerator mass spectrometry. The mtDNA corresponds to Native American founding haplogroups A2 and B2. The dates of the coprolites are >1000
14
C years earlier than currently accepted dates for the Clovis complex.
ROS-Generating Mitochondrial DNA Mutations Can Regulate Tumor Cell Metastasis
Authors: Ishikawa Kaori , Takenaga Keizo , Akimoto Miho , Koshikawa Nobuko , Yamaguchi Aya , Imanishi Hirotake , Nakada Kazuto , Honma Yoshio , Hayashi Jun-Ichi
Published: April 2008

Mutations in mitochondrial DNA (mtDNA) occur at high frequency in human tumors, but whether these mutations alter tumor cell behavior has been unclear. We used cytoplasmic hybrid (cybrid) technology to replace the endogenous mtDNA in a mouse tumor cell line that was poorly metastatic with mtDNA from a cell line that was highly metastatic, and vice versa. Using assays of metastasis in mice, we found that the recipient tumor cells acquired the metastatic potential of the transferred mtDNA. The mtDNA conferring high metastatic potential contained G13997A and 13885insC mutations in the gene encoding NADH (reduced form of nicotinamide adenine dinucleotide) dehydrogenase subunit 6 (
ND6
). These mutations produced a deficiency in respiratory complex I activity and were associated with overproduction of reactive oxygen species (ROS). Pretreatment of the highly metastatic tumor cells with ROS scavengers suppressed their metastatic potential in mice. These results indicate that mtDNA mutations can contribute to tumor progression by enhancing the metastatic potential of tumor cells.
Fine Structure Constant Defines Visual Transparency of Graphene
Authors: Nair R. R. , Blake P. , Grigorenko A. N. , Novoselov K. S. , Booth T. J. , Stauber T. , Peres N. M. R. , Geim A. K.
Published: April 2008

There are few phenomena in condensed matter physics that are defined only by the fundamental constants and do not depend on material parameters. Examples are the resistivity quantum, h/e2 (h is Planck's constant and e the electron charge), that appears in a variety of transport experiments and the magnetic flux quantum, h/e, playing an important role in the physics of superconductivity. By and large, sophisticated facilities and special measurement conditions are required to observe any of these phenomena. We show that the opacity of suspended graphene is defined solely by the fine structure constant, a = e2/hc � 1/137 (where c is the speed of light), the parameter that describes coupling between light and relativistic electrons and that is traditionally associated with quantum electrodynamics rather than materials science. Despite being only one atom thick, graphene is found to absorb a significant (pa = 2.3%) fraction of incident white light, a consequence of graphene's unique electronic structure.
Running economy in early and late maturing youth soccer players does not differ
Authors: Segers V , Clercq D De , Janssens M , Bourgois J , Philippaerts R
Published: April 2008

Purpose:

The aim of this study was to investigate the influence of maturity on running economy in a population of young soccer players.

Methods:

13 boys (mean age 14.3 years) active in soccer were divided into two groups: 6 early and 7 late maturers. Anthropometrical characteristics, respiratory exchange ratio, heart rate and maximal oxygen uptake were measured. Running economy was assessed at three submaximal running speeds (8, 9.5 and 11 km/h). Allometric coefficients were calculated and used to diminish the effect of body mass. In addition, running style was analysed biomechanically (stride length and meaningful kinematic values).

Results:

There was no significant difference in the running economy of early and late maturing soccer players, nor any significant differences in mass adjusted physiological values. Therefore physiological differences cannot explain why late maturers succeed in keeping up with early maturers. Late maturing boys take longer relative strides, and have more anteversion of the thigh at heel contact, a smaller knee-angle during swing-phase and a lower mass moment of inertia.

Conclusion:

Running style seems to be an important determinant in running economy of children.
Gender differences in plantar loading during three soccer-specific tasks
Authors: Sims E L , Hardaker W M , Queen R M
Published: April 2008

Objective:

Examine the effect of gender on plantar loading during three football-specific tasks.

Design:

Thirty-four athletes (17 men, 17 women) ran an agility course five times while wearing the Nike Vitoria hard ground cleat. Plantar loading data were recorded during a side cut, a cross-over cut and a forward acceleration task using Pedar-X insoles.

Setting:

Controlled laboratory study.

Participants:

No history of lower extremity injury in the past 6 months, no previous foot or ankle surgery, not currently wearing foot orthotics and play a cleated sport at least two times per week.

Main outcome measurements:

Contact area, maximum force and the force-time integral (FTI) in the medial and lateral midfoot, medial, middle and lateral forefoot as well as the hallux. A univariate ANCOVA (α = 0.05) was performed on each dependent variable (covariate was course speed).

Results:

Significant gender differences existed in the force and force-time integral beneath the lateral midfoot and forefoot during the cross-over cut task as well as in the middle forefoot during the side cut task with the men demonstrating an increased force. No significant differences existed in the loading on the medial side of the foot during any tasks.

Conclusions:

The results of this study indicate that the increase in plantar loading on the lateral portion of the midfoot and forefoot in men could be one possible explanation for the increased incidence of fifth metatarsal stress fractures in men. Gender differences in loading patterns need to be considered when comparing different movements as well as different footwear conditions.
Functional assessment of knee joint position sense following anterior cruciate ligament reconstruction
Authors: Mir S M , Hadian M-R , Talebian S , Nasseri N
Published: April 2008

Context:

The anterior cruciate ligament (ACL) has both mechanical and proprioceptive (sensory) functions. Knee-joint proprioception has been assessed using either reproduction of position or threshold to detect passive motion in non-weight-bearing positions. It has been suggested that a more functional and dynamic/active assessment of proprioception might clarify the effects of injury and reconstruction on the proprioceptive function of ACL at the knee joint.

Objective:

To assess knee joint position sense (JPS) following ACL reconstruction in functional positions.

Subjects:

Twelve male patients who had undergone ACL reconstruction and 12 male healthy control subjects participated in the study.

Methods and main outcome measures:

JPS was evaluated by reproduction of the angles in weight-bearing position with limb movement into flexion and extension. The dominant knee of healthy subjects and both (reconstructed and uninjured) knees of the patients were tested. Absolute angular error was used as a dependent variable.

Results:

There was no significant difference between the operated and uninjured knees of patients or between patients and healthy controls (p⩾0.05). These results were measured during two tasks of limb movement into flexion and extension.

Conclusion:

We found no evidence of impaired JPS in weight-bearing positions in subjects with ACL reconstruction at a mean follow-up of 11 months after surgery compared with subjects with healthy knees.
Reproductive biology ofVaccinium cylindraceum(Ericaceae), an endemic species of the Azores archipelago
Authors: Pereira M. J.
Published: April 2008

The reproductive biology of Vaccinium cylindraceum Smith, an endemic species confined to the islands of the Azores archipelago, was studied in populations from seven islands. Data indicate that the breeding system of the species is facultative xenogamy with spontaneous autogamy playing a minor role in fruit development. Stigma–anther distance was correlated with style length. Species of microlepidoptera were the most frequent floral visitors, and are possibly important pollinator taxa. Variation in flower, fruit, and seed morphology, as well as seed germination was significant among populations from the islands. The time each island has been available for colonization–evolution, as well as bird-assisted colonization of the Azores archipelago through transport of seeds from the South, likely play a role in floral and other characteristics of V. cylindraceum populations. The central group of islands is the centre of maximum differentiation of populations.
Cell wall architecture of Physcomitrella patens is revealed by atomic force microscopy
Authors: Wyatt Haley D.M. , Ashton Neil W. , Dahms Tanya E.S.
Published: April 2008

The moss Physcomitrella patens (Hedw.) Bruch & Schimp. in B.S.G. serves as a nonvascular plant model system suitable for studying many plant developmental phenomena. The tip-growing filamentous protonemal stage of its life cycle exhibits polarized growth and various tropic responses. Conventional staining and light microscopy (LM) were used to provide the first direct evidence that protonemal cells of P. patens lack a cuticle. Atomic force microscopy (ATM) images reveal detailed surface structures identified by scanning electron microscopy (SEM). The cell wall ultrastructure is characterized by rounded protrusions that are uniformly distributed along each caulonemal filament, and longer fibrillar structures, which are disorganized at the apex, but become oriented in longitudinal arrays parallel to the growth axis in more proximal regions of caulonemal apical cells. The subapical cells are characterized by a polylamellated texture. There was no difference in gross surface ultrastructure between light-grown and dark-grown filaments, but the dimensions of the rounded protrusions at the apices of caulonemata cultured in the light and in darkness were significantly different. The convex and concave cell wall surfaces of a curved, gravitropically responding dark-grown caulonema appear structurally different. This investigation is the first to use AFM to probe the cell wall ultrastructure of a bryophyte. The data further elaborate a simple model of cell wall development in the caulonemata of P. patens that was proposed for other tip-growing filamentous plants.
Genetic differentiation and admixture amongFestuca idahoensis,F. roemeri, andF. ovinadetected in AFLP, ITS, and chloroplast DNA
Authors: Jones Thomas A. , Larson Steven R. , Wilson Barbara L.
Published: April 2008

North American forms of the Festuca ovina L. complex, Festuca idahoensis Elmer and Festuca roemeri (Pavlick) E.B. Alexeev, are distributed broadly east and narrowly west of the Cascade Mountains, respectively. The psbA-trnH and rps16-trnK chloroplast DNA intergenic sequences, 18S-5.8S-26S nuclear ribosomal DNA internal transcribed spacer (ITS) sequences, and six AFLP primer combinations were used to investigate genetic relatedness and differences among 327 plant samples from 24 F. idahoensis and 33 F. roemeri natural-source germplasm accessions, two multiple-origin F. idahoensis × F. roemeri cultivars, one apparently admixed F. ovina × F. idahoensis accession, four naturalized populations or cultivars of Eurasian-source F. ovina s. l., and several Festuca arizonica Vasey, Festuca occidentalis Hooker, and Festuca rubra L. reference accessions. The AFLP profiles of individual plants were unique, but distance-based and Bayesian model-based clustering separated AFLP genotypes into groups corresponding to taxa. Approximately 15.9% of the AFLP variation was apportioned between F. idahoensis and F. roemeri, with the remaining 61.2% and 22.9% variation maintained within and among natural-source accessions, respectively. Genetic admixture between F. idahoensis, F. roemeri, and F. ovina was detectable and DNA sequence divergence was very low in the chloroplast and ITS regions. These three taxa are genetically differentiated, but capable of hybridization.
Herbivores and pathogens onAlnus viridissubsp.fruticosain Interior Alaska: effects of leaf, tree, and neighbour characteristics on damage levels
Authors: Mulder Christa P.H. , Roy Bitty A. , Güsewell Sabine
Published: April 2008

Parasite damage strongly affects dynamics of boreal forests. Damage levels may be affected by climate change, either directly or indirectly through changes in properties of host trees. We examined how herbivore and pathogen damage in Alnus viridis subsp. fruticosa (Rupr.) Nym. depend on leaf morphology and chemistry, tree size, and tree neighborhood. Damage and tree properties were measured in 2003 and 2004 on eight trees at each of 20 sites in Interior Alaska. Damage varied significantly among sites and among trees within sites, but Cartesian distances between sites were not correlated with similarity in damage levels. Compared with middle leaves, terminal leaves experienced less damage from phloem-feeding insects and pathogens, whereas leaf-roller damage was largely confined to terminal leaves. Summer drought in 2004 strongly reduced damage from phloem-feeding insects, while damage from chewing insects increased. Overall, herbivore damage was best explained by leaf morphology and chemistry, and pathogen damage by the proximity of other trees; the two damage types were not correlated with each other. Reproduction was negatively correlated with herbivore damage, but positively with pathogen damage. The contrasting relationships found for individual feeding guilds suggest that they must be studied separately in assessing impacts of climate change on parasite damage.
Effect of Shape and Volume on the Capacity of Model Piles in Sand
Authors: Robinsky E I , Sagar W L , Morrison C F
Published: April 2008

This report presents load test results on instrumented model piles, both straight-sided and tapered, driven into Standard Ottawa sand in both loose and medium dense states. The distribution of load between pile points and walls, as well as the over-all pile capacities at various depths of embedment, was studied. Tests revealed continuous changes in the intensity of unit load transfer through the walls as the piles were advanced. These changes, as well as the limited ability of the straight-sided piles to transfer large loads through their walls, are presumed to be the result of the development of a system of arching in the sand surrounding the piles. The most interesting and as yet unexplained results obtained in these tests revealed that for all piles straight-line relationships exist between embedded pile volumes and their capacities.
Failure of an Oil Storage Tank Founded on a Sensitive Marine Clay
Authors: Brown J D , Paterson W G
Published: April 2008

The investigation of the failure of an oil storage tank founded on a sensitive, soft-to-firm clay is described. The history of the failure and the geotechnical properties of the clay are reported. Failure occurred during first loading, and an analysis in terms of total stresses has been carried out. The applicability of bearing capacity theories to foundations on this type of clay has been examined, particularly the propositions that either the bearing capacity factor, or the measured strength of the clay, should be reduced to allow for local shear or progressive failure effects.The results of the analysis indicate that the Skempton-Meyerhof bearing capacity factor for circular loaded areas, Nc = 6.2, may be used, and that the full measured strength of the clay is mobilized.
Deformations and pore pressures in the vicinity of a precast, segmented, concrete-lined tunnel in clay
Authors: Palmer J. H. L. , Belshaw D. J.
Published: April 2008

During construction of a 2.16 m diameter tunnel in a soft to firm clay deposit in Thunder Bay, Ontario, an initial array of instrumentation to provide data indicating overall performance and a second array to provide detailed spatial deformation and pore-water pressure distribution were installed. The tunnel lining consisted of unbolted rings composed of four trapezoidal, unreinforced concrete sections assembled within the tailpiece of the tunnel boring machine.This paper presents and discusses detailed observations of soil deformation, pore-water pressure changes, and total pressure on the lining obtained from the second array of instrumentation. The soil stratigraphy was similar to that at the first array and the data obtained are compared with the earlier data. Monitoring of the instruments is continuing and data from the first year of observations are presented.
Groundwater and drawdown in a large earth excavation
Authors: Debidin F. , Lee C. F.
Published: April 2008

In deep excavations below the water table, the transient and steady state drawdown conditions are often of interest. Particularly in moderately pervious soils, the stability of the slopes, the excavation methods, and equipment are affected by the groundwater response in the excavation. The extent of the drawdown in the area beyond the excavation must also be determined.For a site under construction by Ontario Hydro, a test excavation to determine the drawdown response in the irregularly stratified soils is described. Analyses of the data by the finite element method and by the theory of aquifer tests are presented. The effect of recharge on the steady state and transient drawdown is discussed.For the main excavation, approximate methods to determine the rate of drawdown, the quantity of seepage, and the steady state drawdown position with recharge from infiltration or deep seepage are outlined.
Behaviour of friction piles in soft sensitive clays
Authors: Blanchet R. , Tavenas F. , Garneau R.
Published: April 2008

During the construction of heavy structures, such as bridges and overpasses, on soft clays on the north shore of the St. Lawrence Valley, a detailed load test program on friction piles was performed to establish the characteristics of the most suitable type of pile and to study its long-term behaviour. Three types of piles, timber, steel pipe with closed end, and precast concrete Herkules H-420 piles, were tested. Four timber piles driven in a group and submitted to a 712 kN load served to study the long-term settlement of a small group of piles. Three deep settlement gauges were installed in the centre of this group for measuring settlements in clay at various depths.This test program was completed by the instrumentation of two bridge piers in order to verify the behaviour of larger groups of piles.The paper presents the results of the test piles, the long-term behaviour (4 years) of the bridge pier foundations resting on friction piles in soft clay, and the interpretation of the results.This study shows that the pore pressures induced by pile driving are related to the pre-consolidation of the clay and that they are much larger for tapered piles. It is demonstrated that the effective stress analysis method proposed in 1976 by Meyerhof determines adequately the ultimate pile bearing capacity, but that the effect of the timber pile taper doubles the skin friction.The settlement analysis of pile groups shows that settlements are due to the reconsolidation of the clay and shear creep deformations in the clay close to the pile wall.
Design charts for ultimate bearing capacity of foundations on sand overlying soft clay
Authors: Hanna A. M. , Meyerhof G. G.
Published: April 2008

It is often the case that the base of a footing rests in a foundation material consisting of more than one layer. Problems of this type have been under investigation by the authors for the last few years, and the results of these studies were reported for footings on two layers of soil and for footings on three layers of sand. This paper is an attempt to extend the authors' previous theory to cover the case of footings resting on a subsoil consisting of a dense layer of sand overlying a soft clay deposit. The results of this analysis are presented in the form of design charts.
Considerations on the use of cast-in-place piles in permafrost
Authors: Weaver J. S. , Morgenstern N. R.
Published: April 2008

Conventional cements have proven to be unsuitable for subsurface concreting in permafrost and as a result cast-in-place piles have seldom been used in arctic regions. The petroleum industry has developed a gypsum-based cement that has been satisfactorily used to grout well casings through permafrost.Laboratory studies have been undertaken to evaluate the suitability of this cement for subsurface concreting in permafrost. It is concluded that this cement does have an adverse effect on the adfreeze bond strength and hence should not be used for cylindrical friction piles. However, it appears from this preliminary study that the cement does have potential for use as a construction material for cast-in-place belled and tapered piles.
THE OBLIQUE CORRECTIONS FROM HEAVY SCALARS IN IRREDUCIBLE REPRESENTATIONS
Authors: ZHANG HONG-HAO , YAN WEN-BIN , LI XUE-SONG
Published: April 2008

The contributions to S, T and U from heavy scalars in any irreducible representation of the electroweak gauge group SU (2)L × U (1)Y are obtained. We find that in the case of a heavy scalar doublet, there is a slight difference between the S parameter we have obtained and that in previous works.
INHOMOGENEOUS QUANTUM GROUP GENERALIZATION OF IO(2n,ℂ) AND ISp(2n,ℂ)
Authors: ALTINTAṢ AZMI ALI , ARIK METIN
Published: April 2008

We consider an extension of orthogonal and symplectic inhomogeneous groups into quantum groups with noncommuting inhomogeneous parameters. The quantum subgroups of these quantum groups are investigated.
THE RHIC AZIMUTH QUADRUPOLE: "PERFECT LIQUID" OR GLUONIC RADIATION?
Authors: TRAINOR THOMAS A.
Published: April 2008

Large elliptic flow at RHIC seems to indicate that ideal hydrodynamics provides a good description of Au – Au collisions, at least at the maximum RHIC energy. The medium formed has been interpreted as a nearly perfect (low-viscosity) liquid, and connections have been made to gravitation through string theory. Recently, claimed observations of large flow fluctuations comparable to participant eccentricity fluctuations seem to confirm the ideal hydro scenario. However, determination of the azimuth quadrupole with 2D angular autocorrelations, which accurately distinguish "flow" (quadrupole) from "nonflow" (minijets), contradicts conventional interpretations. Centrality trends may depend only on the initial parton geometry, and methods used to isolate flow fluctuations are sensitive instead mainly to minijet correlations. The results presented in this paper suggest that the azimuth quadrupole may be a manifestation of gluonic multipole radiation.
COMMENTS ON D-BRANES ON ORBIFOLDS AND K-THEORY
Authors: KRIZ IGOR , PANDO ZAYAS LEOPOLDO A. , QUIROZ NORMA
Published: April 2008

We systematically revisit the description of D-branes on orbifolds and the classification of their charges via K-theory. We include enough details to make the results accessible to both physicists and mathematicians interested in these topics. The minimally charged branes predicted by K-theory in ℤN orbifolds with N odd are only BPS. We confirm this result using the boundary state formalism for ℤ3. For ℤN × ℤN orbifolds with N odd, in the untwisted case and with discrete torsion whose class is a generator of H3(ℤ/N × ℤ/N,ℤ), we show that the K-theory classification of charges agrees with the boundary state approach, largely developed by Gaberdiel and collaborators, including the types of representation on the Chan–Paton factors.
EFFECT OF MOTT TRANSITION WITH DIFFERENT DIELECTRIC FUNCTIONS IN LOW-DIMENSIONAL SEMICONDUCTOR SYSTEMS
Authors: PETER A. JOHN
Published: April 2008

Ionization energies of a GaAs/Ga 1-x Al x As superlattice system with finite and infinite barriers are investigated with different dielectric screening functions within the effective mass approximation. Within the one-electron approximation the occurrence of Mott transition is seen when the binding energy of a donor vanishes. While the Thomas–Fermi screening function does not admit the Mott transition below a well-width around 60 Å,1,2 the Hartree–Fock screening function with exchange and correlation effects included pushes the critical well-width to a value around 20 Å. The Lindhard screening function also gives the same results. The effects of Anderson localization and exchange and correlation in the Hubbard model are included in our model. It is found that the ionization energy (i) decreases as well-width increases, (ii) decreases when well-width increases and (iii) the critical concentration at which the metal-insulator transition occurs is lowered when well dimensions are reduced. All the calculations have been carried out with finite and infinite barriers and the results are compared with available data in the literature.
NOISE EFFECT ON INTRACELLULAR CALCIUM OSCILLATIONS IN A MODEL WITH DELAYED COUPLING
Authors: JI LIN , XU WEIGUO , LI QIANSHU
Published: April 2008

The cooperation of noise and the delayed coupling is investigated in a calcium model. Simulation results show that the constructive noise effect, like the coherence resonance (CR) and the optimization of signal regularity, can be significantly adjusted by the delayed coupling. Besides, the coupling may also play the constructive role to strengthen the signal by producing CR-like phenomenon under weak noise influence. When the noise is strong, the increase of coupling strength can decrease the adverse noise effect on the signal regularity.
WAVE-BASED APPROACH FOR MICROWAVE NOISE CHARACTERIZATION
Authors: CHEN C. H. , WANG Y. L. , BAKR M. H.
Published: April 2008

The noise behavior of a two-port is usually described through the conventional set of noise parameters Fmin, Rn, and the complex Yopt. However, noise parameters developed using wave-based techniques also have their merit as they could offer different insights to a two-port's noise behavior. Unlike the conventional noise parameters, these wave-based noise parameters could be terminal-invariant and describe only the intrinsic noise behavior of a two-port. In this paper, several important noise parameters derived from wave-based approaches are reviewed. The derivation of each set of parameters is discussed and illustrated. The measurement approach of each set of parameters is also briefly covered.
HYBRID NANOPATTERNING USING COLLOIDAL LITHOGRAPHY AND NANOIMPRINT FOR THE FABRICATION OF NANOTEMPLATE
Authors: CHOI DAE-GEUN , JEONG JUN-HO , LEE EUNG-SUG
Published: April 2008

In this work, various 2D nano- and micropatterns with the feature resolution from micrometer to nanometer scale by using colloidal self-assembly and nanoimprint lithography (or micromolding) for the fabrication of patterned catalyst pattern are fabricated. To control size and shape of colloidal templates and patterned catalyst metals, colloidal self-assembly based on bottom-up approach and dry etching conditions were deliberately controlled.
EPR STUDY OF NANOSTRUCTURED ZINC FERRITE
Authors: SINGH JITENDRA PAL , SRIVASTAVA R. C. , AGRAWAL H. M. , KUSHWAHA R. P. S. , CHAND PREM , KUMAR RAVI
Published: April 2008

Bulk zinc ferrite has been studied in the past. In the bulk form zinc ferrite crystallizes in the normal spinel structure with all the zinc ions occupying the tetrahedral and all the iron occupying the octahedral sites, respectively. But, nanosize zinc ferrite is believed to crystallize in a different way. It is now well established that in a nanosize zinc ferrite there is partial inversion in the cation occupancy, leading to some kind of magnetic ordering in this system much above its Neel temperature of 10 K. Hence, there is ample scope of maneuvering the electrical and magnetic properties of this ferrite. In the present study nanosize zinc ferrite was prepared by a chemical reaction involving the nitrates of Zn and Fe and using the citric acid as the host. The sintering of the precursor was done for 1 h at various temperatures ranging from 300°C to 1000°C. These samples were characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), and electron paramagnetic resonance (EPR). The average particle sizes in these sintered samples measured by TEM are found to vary from ≈ 10 to 62 nm. The XRD measurements show the formation of single-phase spinel structure in all the samples. The X-band EPR spectrum of the precursor specimen at room temperature consists of two EPR signals: an intense signal at g eff = 2.02 having peak-to-peak line width △H PP = 425 Gauss and other a weak signal at g eff = 4.51 having an asymmetric line shape. As the samples are heat-treated at different temperatures, the EPR signal corresponding to the intense peak gets stabilized at g eff ≈ 2.03, whereas the weak signal gets suppressed progressively. The spin–spin relaxation time in these samples have values ≈ 3 × 10-10 s . The effect of sintering temperature on the properties of the nanostructured specimen of zinc ferrite and the underlying mechanism would be discussed.
SYNTHESIS, CHARACTERIZATION, AND ASSEMBLY OF CdSe QUANTUM DOT ARRAY
Authors: VIGNEASHWARI B. , DASH S. , TYAGI A. K. , SUTHANTHIRARAJ S. AUSTIN
Published: April 2008

CdSe semiconducting nanoparticles in the range of 6–7 nm in size were synthesized by a soft chemical procedure at room temperature. The particles were characterized by powder X-ray diffraction, UV–visible optical spectroscopy revealing nanocrystallization, and quantum mechanical electron confinement. Photoluminescence and Raman spectroscopy of these nanocrystalline powders indicated optical phonon confinement. Asymmetric line shapes revealed occurrence of nonzone center phonons. The particles could be successfully deposited on ITO substrate by electrophoresis to obtain self-organized quantum dot array. Scanning electron microscopy, high-resolution scanning electron microscopy, confocal fluorescence microscopy, and atomic force microscopy investigations revealed self-similar deposits.
ALTERNATE FIELD EVAPORATION AND KINK RELAXATION ON (001) AND (112) SURFACES OF TUNGSTEN NANOTIPS
Authors: WANDERKA N. , MIKHAILOVSKIJ I. M. , KSENOFONTOV V. A. , MAZILOVA T. I. , SADANOV E. V. , MAZILOV A. A.
Published: April 2008

Fine-scale field evaporation of stepped (001) and (112) surfaces of tungsten nanotips was studied by field ion microscopy. It was shown that some atoms at kinks and steps are anomalously stable against field evaporation. This effect is responsible for the observed alternate field evaporation near the kink and step sites. The phenomenon of alternate field evaporation could be used to determine an atomic relaxation at kinks on nanotip surface. Using the geometric method of analysis of field ion images, the normal to surface differential displacements of the kink-site atoms were estimated.
QUANTUM CONDUCTANCE AND ELECTRONIC PROPERTIES OF LOWER DIAMONDOID MOLECULES AND DERIVATIVES
Authors: XUE YONG , MANSOORI G. ALI
Published: April 2008

Diamondoids and their derivatives have found major applications as templates and as molecular building blocks in nanotechnology. An ab initio method we calculated the quantum conductance and the essential electronic properties of two lower diamondoids (adamantane and diamantane) and three of their important derivatives (amantadine, memantine and rimantadine). We also studies two artificial molecules that are built by substituting one hydrogen ion with one sodium ion in both adamantane and diamantane molecules. Most of our results are based on an infinite Au two-probe system constructed by ATK and VNL software, which comprise TRANSTA-C package. By changing various system structures and molecule orientations in linear Au and 2 × 2 Au probe systems, we found that although the conductance of adamantane and diamantane are very small, the derivatives of the lower diamondoids have considerable conductance at specific orientations and also showed interesting electronic properties. The quantum conductance of such molecules will change significantly by changing the orientations of the molecules, which approves that residues like nitrogen and sodium atoms have great effects on the conductance and electronic properties of single molecule. There are obvious peaks near Fermi energy in the transmission spectrums of artificial molecules, indicating the plateaus in I–V characteristics of such molecules.
From the Determination of Complex Reaction Mechanisms to Systems Biology
Authors: Ross John
Published: April 2008

This review presents several methods of determining complex chemical reaction mechanisms and their functions. One method is based on correlation functions of measured time series of concentrations of chemical species, another is on measurements of temporal responses of concentrations to various perturbations of arbitrary magnitude, the third deals with the analysis of oscillatory systems, and the fourth describes the use of genetic algorithms. All methods are applicable to chemical, biochemical, and biological reaction systems and to genetic networks. The methods depend on the design of appropriate experiments for the whole system and corresponding theories for interpretation that lead to information on the causal chemical connectivity of species, reaction pathways, reaction mechanisms, control centers in the system, and functions of the system. The first three methods require no assumption of a model or hypothesis, nor extensive calculations, unlike the interpretation of measurements made on a gene network at only one time. The methods offer advantageous approaches to systems biology.
Electronic Spectroscopy of Carbon Chains
Authors: Jochnowitz Evan B. , Maier John P.
Published: April 2008

Investigators have recorded the electronic spectra of assorted carbon-chain systems in the gas phase using a variety of methods, ranging from direct cavity ringdown absorption spectroscopy to photofragmentation techniques that utilize the cooling capabilities of an ion trap. We summarize the results from these studies and compare them with astronomical measurements of the diffuse interstellar band (DIB) absorptions. Although carbon chains comprising up to a handful of carbon atoms cannot be the carrier species, we explore which chains remain viable. In particular, the 1Σu+–X1Σg+ transitions of the odd-numbered carbon chains (n = 17,19,…) possess large oscillator strengths and lie in the 400–900-nm DIB range. The origin bands of larger bare carbon rings, such as C18, have also been observed, with striking similarities to some DIB measurements at high resolution, although at other wavelengths. Finally, we consider recently obtained electronic spectra of metal-containing carbon chains.
Functional Polymer Brushes in Aqueous Media from Self-Assembled and Surface-Initiated Polymers
Authors: Toomey Ryan , Tirrell Matthew
Published: April 2008

This review focuses on the behavior of single-component, water-soluble neutral and charged brushes. Selected examples illustrate how solvation effects, hydrophobic interactions, and electrostatic interactions create complex behaviors not easily captured in mean-field treatments. In particular, we distinguish between two classes of polymer brushes: those that can be described classically within the context of generalized van der Waals potentials and those that can be described by model-dependent potentials arising from specific interactions. In classical systems, only a few global parameters are needed to predict behavior. Nonclassical systems, in contrast, necessitate several local details, which do not necessarily lead to universal scaling laws. Although these nonclassical interactions present unique opportunities for engineering functional surfaces, they also present new challenges for designing well-defined systems with precise control over distributions in the degree of polymerization and tethering density.
Gene expression in human NAFLD
Authors: Greco Dario , Kotronen Anna , Westerbacka Jukka , Puig Oscar , Arkkila Perttu , Kiviluoto Tuula , Laitinen Saara , Kolak Maria , Fisher Rachel M. , Hamsten Anders , Auvinen Petri , Yki-Järvinen Hannele
Published: April 2008

Despite the high prevalence of nonalcoholic fatty liver disease (NAFLD), little is known of its pathogenesis based on study of human liver samples. By the use of Affymetrix GeneChips (17,601 genes), we investigated gene expression in the human liver of subjects with extreme steatosis due to NAFLD without histological signs of inflammation (liver fat 66.0 ± 6.8%) and in subjects with low liver fat content (6.4 ± 2.7%). The data were analyzed by using sequence-based reannotation of Affymetrix probes and a robust model-based normalization method. We identified genes involved in hepatic glucose and lipid metabolism, insulin signaling, inflammation, coagulation, and cell adhesion to be significantly associated with liver fat content. In addition, genes involved in ceramide signaling (MAP2K4) and metabolism (UGCG) were found to be positively associated with liver fat content. Genes involved in lipid metabolism (PLIN, ACADM), fatty acid transport (FABP4, CD36), amino acid catabolism (BCAT1), and inflammation (CCL2) were validated by real-time PCR and were found to be upregulated in subjects with high liver fat content. The data show that multiple changes in gene expression characterize simple steatosis.
Mouse heart valve structure and function: echocardiographic and morphometric analyses from the fetus through the aged adult
Authors: Hinton Robert B. , Alfieri Christina M. , Witt Sandra A. , Glascock Betty J. , Khoury Philip R. , Benson D. Woodrow , Yutzey Katherine E.
Published: April 2008

The purpose of this study is to provide standard echocardiographic and morphometric data for normal mouse valve structure and function from late fetal to aged adult stages. Cross-sectional, two-dimensional and Doppler transthoracic echocardiography was performed in C57BL6 mice anesthetized with 1% to 2% isoflurane at embryonic day 18.5 (late fetal), 10 days (neonate), 1 mo (juvenile), 2 mo (young adult), 9 mo (old adult), and 16 mo (aged adult). Normal annulus dimensions indexed to age or weight, and selected flow velocities, were established by echocardiography. After echocardiographic imaging, hearts were harvested and histological and morphometric analyses were performed. Morphometric analysis demonstrated a progressive valve thinning and elongation during the fetal and juvenile stages that plateaued during adult stages (ANOVA, P < 0.01); however, there was increased thickening of the hinge of the aortic valve with advanced age, reminiscent of human aortic valve sclerosis. There was no age-related calcification. The results of this study provide comprehensive echocardiographic and morphometric data for normal mouse valve structure and function from late fetal to aged adult stages and should prove useful as a reference standard for future studies using mouse models of progressive valve disease.
Oral tolerance attenuates changes in in vitro lung tissue mechanics and extracellular matrix remodeling induced by chronic allergic inflammation in guinea pigs
Authors: Nakashima Adriane S. , Prado Carla M. , Lanças Tatiana , Ruiz Viviane C. , Kasahara David I. , Leick-Maldonado Edna A. , Dolhnikoff Marisa , Martins Milton A. , Tibério Iolanda F. L. C.
Published: April 2008

Recent studies emphasize the presence of alveolar tissue inflammation in asthma. Immunotherapy has been considered a possible therapeutic strategy for asthma, and its effect on lung tissue had not been previously investigated. Measurements of lung tissue resistance and elastance were obtained before and after both ovalbumin and acetylcholine challenges. Using morphometry, we assessed eosinophil and smooth muscle cell density, as well as collagen and elastic fiber content, in lung tissue from guinea pigs with chronic pulmonary allergic inflammation. Animals received seven inhalations of ovalbumin (1–5 mg/ml; OVA group) or saline (SAL group) during 4 wk. Oral tolerance (OT) was induced by offering ad libitum ovalbumin 2% in sterile drinking water starting with the 1st inhalation (OT1 group) or after the 4th (OT2 group). The ovalbumin-exposed animals presented an increase in baseline and in postchallenge resistance and elastance related to baseline, eosinophil density, and collagen and elastic fiber content in lung tissue compared with controls. Baseline and post-ovalbumin and acetylcholine elastance and resistance, eosinophil density, and collagen and elastic fiber content were attenuated in OT1 and OT2 groups compared with the OVA group. Our results show that inducing oral tolerance attenuates lung tissue mechanics, as well as eosinophilic inflammation and extracellular matrix remodeling induced by chronic inflammation.
Aliskiren-Binding Increases the Half Life of Renin and Prorenin in Rat Aortic Vascular Smooth Muscle Cells
Authors: Batenburg Wendy W. , de Bruin René J.A. , van Gool Jeanette M.G. , Müller Dominik N. , Bader Michael , Nguyen Geneviève , Danser A. H. Jan
Published: April 2008

Objective—

Renin inhibition with aliskiren has been reported to cause a greater rise in renin than other types of renin-angiotensin system blockade, thereby potentially leading to angiotensin generation or stimulation of the human (pro)renin receptor (h(P)RR). Here we studied whether this rise in renin is attributable to an aliskiren-induced change in the prorenin conformation, allowing its detection in renin assays, or a change in renin/prorenin clearance. We also investigated whether aliskiren affects (pro)renin binding to its receptors, using rat aortic vascular smooth muscle cells (VSMCs) overexpressing the h(P)RR.

Methods and Results—

A 48-hour incubation with aliskiren at 4°C converted the prorenin conformation from “closed” to “open,” thus allowing its recognition in active site-directed renin assays. VSMCs accumulated (pro)renin through binding to mannose 6-phosphate receptors (M6PRs) and h(P)RRs. Aliskiren did not affect binding at 4°C. At 37°C, aliskiren increased (pro)renin accumulation up to 40-fold, and M6PR blockade prevented this. Aliskiren increased the intracellular half life of prorenin 2 to 3 times.

Conclusion—

Aliskiren allows the detection of prorenin as renin, and decreases renin/prorenin clearance. Both phenomena may contribute to the “renin” surge during aliskiren treatment, but because they depend on aliskiren binding, they will not result in angiotensin generation. Aliskiren does not affect (pro)renin binding to its receptors.
IP
3
Constricts Cerebral Arteries via IP
3
Receptor–Mediated TRPC3 Channel Activation and Independently of Sarcoplasmic Reticulum Ca
2+
Release
Authors: Xi Qi , Adebiyi Adebowale , Zhao Guiling , Chapman Kenneth E. , Waters Christopher M. , Hassid Aviv , Jaggar Jonathan H.
Published: April 2008

Vasoconstrictors that bind to phospholipase C–coupled receptors elevate inositol-1,4,5-trisphosphate (IP
3
). IP
3
is generally considered to elevate intracellular Ca
2+
concentration ([Ca
2+
]
i
) in arterial myocytes and induce vasoconstriction via a single mechanism: by activating sarcoplasmic reticulum (SR)-localized IP
3
receptors, leading to intracellular Ca
2+
release. We show that IP
3
also stimulates vasoconstriction via a SR Ca
2+
release–independent mechanism. In isolated cerebral artery myocytes and arteries in which SR Ca
2+
was depleted to abolish Ca
2+
release (measured using D1ER, a fluorescence resonance energy transfer–based SR Ca
2+
indicator), IP
3
activated 15 pS sarcolemmal cation channels, generated a whole-cell cation current (
I
Cat
) caused by Na
+
influx, induced membrane depolarization, elevated [Ca
2+
]
i
, and stimulated vasoconstriction. The IP
3
-induced
I
Cat
and [Ca
2+
]
i
elevation were attenuated by cation channel (Gd
3+
, 2-APB) and IP
3
receptor (xestospongin C, heparin, 2-APB) blockers. TRPC3 (canonical transient receptor potential 3) channel knockdown with short hairpin RNA and diltiazem and nimodipine, voltage-dependent Ca
2+
channel blockers, reduced the SR Ca
2+
release–independent, IP
3
-induced [Ca
2+
]
i
elevation and vasoconstriction. In pressurized arteries, SR Ca
2+
depletion did not alter IP
3
-induced constriction at 20 mm Hg but reduced IP
3
-induced constriction by ≈39% at 60 mm Hg. [Ca
2+
]
i
elevations and constrictions induced by endothelin-1, a phospholipase C–coupled receptor agonist, were both attenuated by TRPC3 knockdown and xestospongin C in SR Ca
2+
-depleted arteries. In summary, we describe a novel mechanism of IP
3
-induced vasoconstriction that does not occur as a result of SR Ca
2+
release but because of IP
3
receptor–dependent
I
Cat
activation that requires TRPC3 channels. The resulting membrane depolarization activates voltage-dependent Ca
2+
channels, leading to a myocyte [Ca
2+
]
i
elevation, and vasoconstriction.