Modified Steels for Cold-Forming U-Bolts Used In Leaf Springs Systems

In this work, a low alloy steel and a fabrication process were developed to produce U-Bolts for commercial vehicles. Thus, initially five types of no-heat treated steel were developed with different additions of chrome, nickel, and silicon to produce strain hardening effect during cold-forming processing of the U-Bolts, assuring the required mechanical properties. The new materials exhibited a fine perlite and ferrite microstructure due to aluminum and vanadium additions, well known as grain size refiners. The mechanical properties were evaluated in a servo-hydraulic test machine system-MTS 810 according to ASTM A370-03; E739 and E08m-00 standards. The microstructure and fractography analyses of the cold-formed steels were performed by using optical and scanning electronic microscope techniques. To evaluate the performance of the steels and the production process, fatigue tests were carried out under load control (tensile-tensile), R = 0.1 and f = 30 Hz. The Weibull statistic methodology was used for the analysis of the fatigue results. At the end of this work the 0.21% chrome content steel, Alloy 2, presented the best fatigue performance.

Using the ultrasound and instrumented indentation techniques to measure the elastic modulus of engineering materials

Currently, the acoustic and nanoindentation techniques are two of the most used techniques for material elastic modulus measurement. In this article fundamental principles and limitations of both techniques are shown and discussed. Last advances in nanoindentation technique are also reviewed. An experimental study in ceramic, metallic, composite and single crystals was also done. Results shown that ultrasonic technique is capable to provide results in agreement with those reported in literature. However, ultrasonic technique does not allow measuring the elastic modulus of some small samples and single crystals. On the other hand, the nanoindentation technique estimates the elastic modulus values in reasonable agreement with those measured by acoustic methods, particularly in amorphous materials, while in some policristaline materials some deviation from expected values was obtained.

LOCAL HEAD LOSS OF NON-COAXIAL EMITTERS INSERTED IN POLYETHYLENE PIPE

The design of a lateral line for drip irrigation requires accurate evaluation of head losses in not only the pipe but in the emitters as well. A procedure was developed to determine localized head losses within the emitters by the formulation of a mathematical model that accounts for the obstruction caused by the insertion point. These localized losses can be significant when compared with tire total head losses within the system due to the large number of emitters typically installed along the lateral line. Air experiment was carried out by altering flow characteristics to create Reynolds numbers (R) from 7,480 to 32,597 to provide turbulent flow and a maximum velocity of 2.0 m s(-1). The geometry of the emitter was determined by an optical projector and sensor An equation was formulated to facilitate the localized head loss calculation using the geometric characteristics of the emitter (emitter length, obstruction ratio, and contraction coefficient). The mathematical model was tested using laboratory measurements on four emitters. The local head loss was accurately estimated for the Uniram (difference of +13.6%) and Drip Net (difference of +7.7%) emitters, while appreciable deviations were found for the Twin Plus (-21.8%) and Tiran (+50%) emitters. The head loss estimated by the model was sensitive to the variations in the obstruction area of the emitter However, the variations in the local head loss did not result in significant variations in the maximum length of the lateral lines. In general, for all the analyzed emitters, a 50% increase in the local head loss for the emitters resulted in less than an 8% reduction in the maximum lateral length.

Survival and Neuronal Differentiation of Mesenchymal Stem Cells Transplanted into the Rodent Brain Are Dependent upon Microenvironment

Introduction: The successful integration of stem cells in adult brain has become a central issue in modern neuroscience. In this study we sought to test the hypothesis that survival and neurodifferentiation of mesenchymal stem cells (MSCs) may be dependent upon microenvironmental conditions according to the site of implant in the brain. Methods: MSCs were isolated from adult rats and labeled with enhanced-green fluorescent protein (eGFP) lentivirus. A cell suspension was implanted stereotactically into the brain of 50 young rats, into one neurogenic area (hippocampus), and into another nonneurogenic area (striatum). Animals were sacrificed 6 or 12 weeks after surgery, and brains were stained for mature neuronal markers. Cells coexpressing NeuN (neuronal specific nuclear protein) and GFP (green fluorescent protein) were counted stereologically at both targets. Results: The isolated cell population was able to generate neurons positive for microtubule-associated protein 2 (MAP2), neuronal-specific nuclear protein (NeuN), and neurofilament 200 (NF200) in vitro. Electrophysiology confirmed expression of voltage-gated ionic channels. Once implanted into the hippocampus, cells survived for up to 12 weeks, migrated away from the graft, and gave rise to mature neurons able to synthesize neurotransmitters. By contrast, massive cell degeneration was seen in the striatum, with no significant migration. Induction of neuronal differentiation with increased cyclic adenosine monophosphate in the culture medium before implantation favored differentiation in vivo. Conclusions: Our data demonstrated that survival and differentiation of MSCs is strongly dependent upon a permissive microenvironment. Identification of the pro-neurogenic factors present in the hippocampus could subsequently allow for the integration of stem cells into nonpermissive areas of the central nervous system.

Two formation channels of ultra-compact dwarf galaxies in Hickson compact groups

Context. The formation of ultra-compact dwarf galaxies (UCDs) is believed to be driven by interaction, and UCDs are abundant in the cores of galaxy clusters, environments that mark the end-point of galaxy evolution. Nothing is known about the properties of UCDs in compact groups of galaxies, environments where most of galaxy evolution and interaction is believed to occur and where UCDs in an intermediate stage in their evolution may be expected. Aims. The main goal of this study is to detect and characterize, for the first time, the UCD population of compact groups of galaxies. For that, two nearby groups in different evolutionary stages, HCG22 and HCG90, were targeted. Methods. We selected about 40 UCD candidates from pre-existing photometry of both groups, and obtained spectra of these candidates using the VLT FORS2 instrument in MXU mode. Archival HST/ACS imaging was used to measure their structural parameters. Results. We detect 16 and 5 objects belonging to HCG22 and HCG90, respectively, covering the magnitude range -10.0 > M(R) > -11.5 mag. Their integrated colours are consistent with old ages covering a broad range in metallicities (metallicities confirmed by the spectroscopic measurements). Photometric mass estimates put 4 objects in HCG90 and 9 in HCG22 in the mass range of UCDs (> 2 x 10(6) M(circle dot)) for an assumed age of 12Gyr. These UCDs are on average 2-3 times larger than the typical size of Galactic GCs, covering a range of 2 less than or similar to r(h) less than or similar to 21 pc. The UCDs in HCG22 are more concentrated around the central galaxy than in HCG90, at the 99% confidence level. They cover a broad range in [alpha/Fe] abundances from sub-to super-solar. The spectra of 3 UCDs (2 in HCG22, 1 in HCG90) show tentative evidence of intermediate age stellar populations. The clearest example is the largest and most massive UCD (similar to 10(7) M(circle dot)) in our sample, which is detected in HCG22. Its properties are most consistent with a stripped dwarf galaxy nucleus. We calculate the specific frequency (S(N)) of UCDs for both groups, finding that HCG22 has about three times higher S(N) than HCG90. Conclusions. The ensemble properties of the detected UCDs supports two co-existing formation channels: a star cluster origin (low-luminosity, compact sizes, old ages, super-solar alpha/Fe), and an origin as tidally stripped dwarf nuclei (more extended and younger stellar populations). Our results imply that the UCDs detected in both groups do not, in their majority, originate from relatively recent galaxy interactions. Most of the detected UCDs have likely been brought into the group along with their host galaxies.

PARTITIONED ANALYSIS FOR DIMENSIONALLY-HETEROGENEOUS HYDRAULIC NETWORKS

In this work an iterative strategy is developed to tackle the problem of coupling dimensionally-heterogeneous models in the context of fluid mechanics. The procedure proposed here makes use of a reinterpretation of the original problem as a nonlinear interface problem for which classical nonlinear solvers can be applied. Strong coupling of the partitions is achieved while dealing with different codes for each partition, each code in black-box mode. The main application for which this procedure is envisaged arises when modeling hydraulic networks in which complex and simple subsystems are treated using detailed and simplified models, correspondingly. The potentialities and the performance of the strategy are assessed through several examples involving transient flows and complex network configurations.

Hadronic resonance production in d+Au collisions at root S(NN) = 200 GeV measured at the BNL Relativistic Heavy Ion Collider

We present the first measurements of the rho(770)(0),K(*)(892),Delta(1232)(++),Sigma(1385), and Lambda(1520) resonances in d+Au collisions at s(NN)=200 GeV, reconstructed via their hadronic decay channels using the STAR detector (the solenoidal tracker at the BNL Relativistic Heavy Ion Collider). The masses and widths of these resonances are studied as a function of transverse momentum p(T). We observe that the resonance spectra follow a generalized scaling law with the transverse mass m(T). The < p(T)> of resonances in minimum bias collisions are compared with the < p(T)> of pi,K, and p. The rho(0)/pi(-),K(*)/K(-),Delta(++)/p,Sigma(1385)/Lambda, and Lambda(1520)/Lambda ratios in d+Au collisions are compared with the measurements in minimum bias p+p interactions, where we observe that both measurements are comparable. The nuclear modification factors (R(dAu)) of the rho(0),K(*), and Sigma(*) scale with the number of binary collisions (N(bin)) for p(T)> 1.2 GeV/c.

Engineering interactions for quasiperfect transfer of polariton states through nonideal bosonic networks of distinct topologies

We present a scheme for quasiperfect transfer of polariton states from a sender to a spatially separated receiver, both composed of high-quality cavities filled by atomic samples. The sender and the receiver are connected by a nonideal transmission channel -the data bus- modelled by a network of lossy empty cavities. In particular, we analyze the influence of a large class of data-bus topologies on the fidelity and transfer time of the polariton state. Moreover, we also assume dispersive couplings between the polariton fields and the data-bus normal modes in order to achieve a tunneling-like state transfer. Such a tunneling-transfer mechanism, by which the excitation energy of the polariton effectively does not populate the data-bus cavities, is capable of attenuating appreciably the dissipative effects of the data-bus cavities. After deriving a Hamiltonian for the effective coupling between the sender and the receiver, we show that the decay rate of the fidelity is proportional to a cooperativity parameter that weighs the cost of the dissipation rate against the benefit of the effective coupling strength. The increase of the fidelity of the transfer process can be achieved at the expense of longer transfer times. We also show that the dependence of both the fidelity and the transfer time on the network topology is analyzed in detail for distinct regimes of parameters. It follows that the data-bus topology can be explored to control the time of the state-transfer process.

Reverse engineering in many-body quantum physics: Correspondence between many-body systems and effective single-particle equations

The mapping, exact or approximate, of a many-body problem onto an effective single-body problem is one of the most widely used conceptual and computational tools of physics. Here, we propose and investigate the inverse map of effective approximate single-particle equations onto the corresponding many-particle system. This approach allows us to understand which interacting system a given single-particle approximation is actually describing, and how far this is from the original physical many-body system. We illustrate the resulting reverse engineering process by means of the Kohn-Sham equations of density-functional theory. In this application, our procedure sheds light on the nonlocality of the density-potential mapping of density-functional theory, and on the self-interaction error inherent in approximate density functionals.

Intracellular Ca(2+) Regulation During Neuronal Differentiation of Murine Embryonal Carcinoma and Mesenchymal Stem Cells

Changes in intracellular Ca(2+) concentration ([Ca(2+)](i)) play a central role in neuronal differentiation. However, Ca(2+) signaling in this process remains poorly understood and it is unknown whether embryonic and adult stem cells share the same signaling pathways. To clarify this issue, neuronal differentiation was analyzed in two cell lines: embryonic P19 carcinoma stem cells (CSCs) and adult murine bone-marrow mesenchymal stem cells (MSC). We studied Ca(2+) release from the endoplasmic reticulum via intracellular ryanodine-sensitive (RyR) and IP(3)-sensitive (IP(3)R) receptors. We observed that caffeine, a RyR agonist, induced a [Ca(2+)](i) response that increased throughout neuronal differentiation. We also demonstrated a functional coupling between RyRs and L-but not with N-, P-, or Q-type Ca(v)1 Ca(2+) channels, both in embryonal CSC and adult MSC. We also found that agonists of L-type channels and of RyRs increase neurogenesis and neuronal differentiation, while antagonists of these channels have the opposite effect. Thus, our data demonstrate that in both cell lines RyRs control internal Ca(2+) release following voltage-dependent Ca(2+) entry via L-type Ca(2+) channels. This study shows that both in embryonal CSC and adult MSC [Ca(2+)](i) is controlled by a common pathway, indicating that coupling of L-type Ca(2+) channels and RyRs may be a conserved mechanism necessary for neuronal differentiation.

Programmable diagnostic devices made from paper and tape

This paper describes three-dimensional microfluidic paper-based analytical devices (3-D mu PADs) that can be programmed (postfabrication) by the user to generate multiple patterns of flow through them. These devices are programmed by pressing single-use 'on' buttons, using a stylus or a ballpoint pen. Pressing a button closes a small space (gap) between two vertically aligned microfluidic channels, and allows fluids to wick from one channel to the other. These devices are simple to fabricate, and are made entirely out of paper and double-sided adhesive tape. Programmable devices expand the capabilities of mu PADs and provide a simple method for controlling the movement of fluids in paper-based channels. They are the conceptual equivalent of field-programmable gate arrays (FPGAs) widely used in electronics.

Influence of land-use change on near-surface hydrological processes: Undisturbed forest to pasture

Soil compaction that follows the clearing of tropical forest for cattle pasture is associated with lower soil hydraulic conductivity and increased frequency and volume of overland flow. We investigated the frequency of perched water tables, overland flow and stormflow in an Amazon forest and in an adjacent 25-year-old pasture cleared from the same forest. We compared the results with the frequencies of these phenomena estimated from comparisons of rainfall intensity and soil hydraulic conductivity. The frequency of perched water tables based on rainfall intensity and soil hydraulic conductivity was expected to double in pasture compared with forest. This corresponded closely with an approximate doubling of the frequency of stormflow and overland flow in pasture. In contrast, the stormflow volume in pasture increased 17-fold. This disproportional increase of stormflow resulted from overland flow generation over large areas of pasture, while overland flow generation in the forest was spatially limited and was observed only very near the stream channel. In both catchments, stormflow was generated by saturation excess because of perched water tables and near-surface groundwater levels. Stormflow was occasionally generated in the forest by rapid return flow from macropores, while slow return flow from a continuous perched water table was more common in the pasture. These results suggest that deforestation for pasture alters fundamental mechanisms of stormflow generation and may increase runoff volumes over wide regions of Amazonia. (C) 2009 Elsevier B.V. All rights reserved.

ABNORMAL EXPRESSION OF VOLTAGE-GATED SODIUM CHANNELS Nav1.7, Nav1.3 AND Nav1.8 IN TRIGEMINAL NEURALGIA

Voltage-gated sodium channels have been implicated in acute and chronic neuropathic pain. Among subtypes, Nav1.7 single mutations can cause congenital indifference to pain or chronic neuropathic pain syndromes, including paroxysmal ones. This channel is co-expressed with Nav1.8, which sustains the initial action potential; Nav1.3 is an embrionary channel which is expressed in neurons after injury, as in neuropathic conditions. Few studies are focused on the expression of these molecules in human tissues having chronic pain. Trigeminal neuralgia (TN) is an idiopathic paroxysmal pain treated with sodium channel blockers. The aim of this study was to investigate the expression of Nav1.3, Nav1.7 and Nav1.8 by RT-PCR in patients with TN, compared to controls. The gingival tissue was removed from the correspondent trigeminal area affected. We found that Nav1.7 was downregulated in TN (P=0.017) and Nav1.3 was upregulated in these patients (P=0.043). We propose a physiopathological mechanism for these findings. Besides vascular compression of TN, this disease might be also a channelopathy. (C) 2009 IBRO. Published by Elsevier Ltd. All rights reserved.

Obtaining and stability verification of superconducting phases of the Nb-Al and Nb-Sn systems by mechanical alloying and low-temperature heat treatments

The development of Nb(3)Al and Nb(3)Sn superconductors is of great interest for the applied superconductivity area. These intermetallics composites are obtained normally by heat treatment reactions at high temperature. Processes that allow formation of the superconducting phases at lower temperatures (<1000 degrees C), particularly for Nb(3)Al, are of great interest. The present work studies phase formation and stability of Nb(3)Al and Nb(3)Sn superconducting phases using mechanical alloying (high energy ball milling). Our main objective was to form composites near stoichiometry, which could be transformed into the superconducting phases using low-temperature heat treatments. High purity Nb-Sn and Nb-Al powders were mixed to generate the required superconducting phases (Nb-25at.%Sn and Nb-25at.%Al) in an argon atmosphere glove-box. After milling in a Fritsch mill, the samples were compressed in a hydraulic uniaxial press and encapsulated in evacuated quartz tubes for heat treatment. The compressed and heat treated samples were characterized using X-ray diffractometry. Microstructure and chemical analysis were accomplished using scanning electron microscopy and energy dispersive spectrometry. Nb(3)Al XRD peaks were observed after the sintering at 800 degrees C for the sample milled for 30 h. Nb(3)Sn XRD peaks could be observed even before the heat treatment. (C) 2009 Elsevier B.V. All rights reserved.

Flow boiling heat transfer of R134a and R245fa in a 2.3 mm tube

This paper presents new experimental flow boiling heat transfer results in micro-scale tubes. The experimental data were obtained in a horizontal 2.3 mm I.D stainless steel tube with heating length of 464 mm, R134a and R245fa as working fluids, mass velocities ranging from 50 to 700 kg m(-2) s(-1), heat flux from 5 to 55 kW m(-2), exit saturation temperatures of 22, 31 and 41 degrees C, and vapor qualities ranging from 0.05 to 0.99. Flow pattern characterization was also performed from images obtained by high-speed filming. Heat transfer coefficient results from 1 to 14 kW m(-2) K(-1) were measured. It was found that the heat transfer coefficient is a strong function of heat flux, mass velocity and vapor quality. The experimental data were compared against ten flow boiling predictive methods from the literature. Liu and Winterton [3], Zhang et al. [5] and Saitoh et al. [6] worked best for both fluids, capturing most of the experimental heat transfer trends. (C) 2010 Elsevier Ltd. All rights reserved.