bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructure Analysis and Corrosion Study of Excimer Laser Modified AA2024-T351
Authors: Yuan Yudie , Aburas Zakria , Hashimoto Teruo , Liu Zhu , Skeldon Peter , Thompson George
Published: March 2008

Laser surface melting (LSM), using an excimer laser, has been employed to modify the near-surface microstructure of AA2024-T351 aluminium alloy. The microstructure and associated phases in the modified surface structure were analyzed by scanning, transmission electron microscopy and X-ray diffraction. The corrosion behavior was evelauted in the ASTM G34-01 EXCO test and by electrochemical polarization. LSM produced a thin, relatively uniform, melted layer relative to the unmelted substrate, leading to significant decrease in anodic and cathodic activities. The decrease of reactivity related mainly to the elimination of fine Al2CuMg dispersoids of the original alloy matrix within the melted layer. However, delamination of the laser melted layer from the underlying substrate was observed after the EXCO immersion test, which may be attributed to the formation of copper-rich bands at the melted layer/bulk alloy interface and the introduction of tensile residual stress in the melted region as a result of the LSM.
Spray Applied Amorphous/Nanocrystalline Aluminum Alloy Coatings as a Replacement for Aluminum Cladding
Authors: Gauthier Ben , Tailleart Nicole , Eidelman Shmuel , Book David , Scully J. R.
Published: March 2008

A high density, low porosity Al-Co-Ce metallic coating has been successfully applied to a AA-2024-T351 substrate using a new PTS process in thicknesses ranging from 100-600 μm. The three proposed modes of corrosion protection brought about by coating (e.g., a localized corrosion barrier, a sacrificial anode to supply sacrificial cathode protection of any exposed AA 2024-T351, and active inhibitor release and protection of AA 2024-T351) have been verified to function and the results are promising. Although XRD has identified nanocrystalline peaks in the as-sprayed deposit, the best PTS applied coating samples have approached the barrier properties of fully amorphous melt spun ribbons of similar composition with regard to resistance to pitting. However, high surface area PTS coatings produced superior capabilities for active inhibitor release
Electrolyte Ion Effects on the Formation of Nanoscale Structure in Aluminum's Passive Oxide Prior to Pit Initiation
Authors: Zavadil Kevin R. , Kotula Paul , Ohlhausen James
Published: March 2008

The impact of pH, chloride concentration, and the presence of an alternate, adsorbing anion on interfacial void formation in the passive oxide of aluminum are explored. Constant current, anodic polarization of a model passive oxide on Al(111) oriented thin films exhibits a characteristic signature that can be used to track void formation. Void formation is shown to be highly sensitive to pH, consistent with competition between vacancy pairing reaction that forms voids and a vacancy filling reaction that leads to oxide growth. A lack of sensitivity is observed for chloride concentration range of 50 to 200 mM, arguing for a concerted proton-chloride interaction where a critical chloride concentration may be sufficient to drive void formation. Borate, as an alternate adsorbing anion, is shown to displace chloride at the outer:inner layer interface and provides a path for estimating this critical chloride concentration.
Electron Microscopic Observations of Interfacial Voids in Aluminum Created by Alkaline Dissolution
Authors: Adhikari Saikat , Chumbley Scott , Chen Hongmin , Jean Yan C. , Geiculescu Corina , Hebert Kurt
Published: March 2008

We report evidence from electron microscopy and positron annihilation spectroscopy (PAS) for the formation by alkaline dissolution of nm-scale voids in aluminum near the metal-oxide interface. Imaging was carried out using transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and field emission scanning electron microscopy (FE-SEM). EM images supported the PAS finding that voids were found within tens of nm of the interface, and revealed that the void number density increased by at least 10 times due to dissolution. From TEM, void number densities were on the order of 108 cm-2. From TEM and SEM, voids appeared circular in cross-section and were ~ 20 nm in diameter.
Effect of Embedded Titanium-Containing Particles on the Corrosion of Particulate Alumina Reinforced Aluminum-Matrix Composite
Authors: Ding Hongbo , Hihara Lloyd H.
Published: March 2008

The microstructure and corrosion initiation sites of particulate alumina reinforced 6092 Al metal-matrix composite (MMC) were examined with scanning electron microscopy and energy dispersive X-ray analyses (EDXA). The MMC was embedded with a variety of Ti-containing micro-particles that were likely introduced into the Al matrix as impurities of the alumina reinforcements. When the MMC was immersed in either 0.5M Na2SO4 or 3.15wt% NaCl solution in open-circuit conditions, micro-crevices formed around the Ti-containing particles as well as Fe-Si-Al intermetallic particles. With the semi-quantitative EDXA technique, the Ti-containing particles that induced micro-crevices can be roughly divided into three categories: 1) titanium suboxides with compositions close to that of Ti6O, Ti3O, Ti2O and TiO; 2) Ti-Zr-Al oxides; and 3) TiO2. Although little is known about the electrical properties of the titanium suboxides and the Ti-Zr-Al oxides, the results suggested that these compounds were either electrically conducting or semi-conducting.
Metallic Micropatterns on Anodic Alumina: Laser-Assisted Exposure of Trapped Seeds for Metallization
Authors: Jha Himendra , Kikuchi Tatsuya , Sakairi Masatoshi , Takahashi Hideaki
Published: March 2008

Microscale metallic patterns are fabricated on the anodic alumina by demonstrating a novel technique. The porous anodic alumina was colored in organic dye solution containing small amounts of palladium acetate and then hydro-thermally sealed. Such coloring and pore-sealing of porous anodic alumina enhanced the absorption of laser beam by the film, facilitating the laser ablation on the film surface. The palladium ions, impregnated during coloring, were trapped underneath the crystalline hydroxide layer that had formed during the hydrothermal treatment. Removing the surface layer with the help of laser beam exposed the palladium on the surface, which acts as seeds for the subsequent electroless plating. Various metallic micro-patterns with thickness of about 2μm were fabricated on the anodic alumina. The metallic patterns were free from cracks or defects, and can be fabricate with high precision.
The Open-Circuit Potential of a Polarizable and Reactive Electrode
Authors: Chen Zhan
Published: March 2008

The open-circuit potential (OCP) of a polarizable and reactive electrode is modeled by the combination of the mixed potential theory and the Frumkin effect. The product of surface oxidation reaction alters the electrolyte double layer structures at the interface, which conversely affects the surface reaction rate. Tribo-electrochemical experiments were carried out with a tungsten rotating disc electrode in a series of diluted KIO3 solutions at pH 2.00. The OCP change with time during the passivation of the electrode surface is fitted based on the model. All the fitting results can provide coherent and reasonable physical meanings, and the apparent surface reaction rate of 1.1*10^4 (mol/L)^-1*sec^-1 of the tungsten electrode surface by KIO3 is thus obtained.
Inhibitive Effect of Seawater on the Corrosion of Particulate-Reinforced Aluminum-Matrix Composites
Authors: Ding Hongbo , Hawthorn George A. , Hihara Lloyd H.
Published: March 2008

The corrosion rates of particulate 6092-T6 Al metal-matrix composites (MMCs) reinforced with 20 vol. % of B4C, SiC, and Al2O3 in ASTM seawater and real seawater were lower than those in 3.15 wt% NaCl or 0.5 M Na2SO4 solutions. Scanning electron microscopy revealed that precipitates consisting of agglomerated whiskers formed on the surfaces of the MMCs after prolonged immersion in either ASTM seawater or real seawater. The precipitates were tentatively ascribed to be Al-Mg hydrotalcite-like compounds based on energy-dispersive X-ray and X-ray diffraction analyses. Accordingly, the precipitation was proposed to follow an induced hydrolysis process that requires a relatively low pH close to that of seawater. It was postulated that the corrosion of the MMCs was inhibited both by precipitates that impede the diffusion of oxygen to cathodic sites and by the buffering effect of seawater, which attenuates pH fluctuations near the MMC surfaces.
Water Transport in Multilayer Organic Coatings
Authors: Allahar Kerry N. , Hinderliter Brian R. , Tallman Dennis , Bierwagen Gordon
Published: March 2008

Protective multilayer coatings are designed with each layer providing distinctive features to reduce the transport of water, ions, and oxygen from the environment to the substrate. The topcoat provides the barrier against the environment whereas the basecoat/primer provides adhesion to the substrate and additional protection such as galvanic or passivation. The change in the coating capacitance during the ingress or egress of water is associated with the change in the dielectric property of the coating due to the large difference between the relative dielectrics of water and coating. The coating capacitance during wetting and drying can be monitored using the electrochemical impedance spectroscopy response of a high frequency signal applied to the coating. The evolution of water uptake during wetting and water loss during drying associated with a two-layer coating is presented. Embedded electrodes were used to access the primer and a hydrophil ic room temperature ionic liquid was used to simulate drying while maintaining a non-aqueous electrical contact to the coating. The wetting and drying behaviors of epoxy, urethane, and epoxy primer/urethane topcoat coatings were experimentally measured. Mathematical models were developed based on Fick's second law for water transport in single-layer and two-layer coatings. Comparison of measured and simulated water uptake demonstrated that the assumptions used in the single-layer model were appropriate while the assumptions used for transport across the interface between the layers in the two- layer coating were inadequate.
Reason of Inhibiting the Iron Anodic Dissolution in Acid Sulfate Electrolyte by Tetrabutylammonium Cations
Authors: Maleeva Marina , Nenasheva Tatyana , Rybkina Aleftina , Marshakov Andrey
Published: March 2008

Hydrogen surface coverage (ΘH) is calculated for iron electrode as a function of tetrabutylammonium cations surface coverage and the hydrogen concentration in the metal (CH). It is shown that the effect of the organic corrosion inhibitor on the iron dissolution rate is due to the increase in the ΘH / CH ratio.
Initial Electroless NiP Coating Behavior On Mg - Al - Zn Alloy AZ91
Authors: Anik Mustafa , Korpe Erhan
Published: March 2008

Alloys represent the α and β phases of Alloy AZ91 were designed and the hypophosphite-reduced electroless nickel coating characteristics on them in both uncoupled and coupled conditions were analyzed. Galvanic coupling of β phase to the matrix phase in the coating bath was observed to decelerate the deposition rate on the matrix phase. This behavior was attributed to the effective cathodic action of β phase in the coating bath as a result of the catalytic cathodic reactions on it.
Hot Corrosion Behavior of Newly Developed Nickel based Superalloy and Comparison with other Alloys
Authors: Injeti Gurrappa , Alasdair Wilson , Hailiang Du , Burnell-gray Jim , Datta Santu
Published: March 2008

The current paper explains the hot corrosion characteristics of newly developed super alloy at two different temperatures, which corresponds to type I and type II hot corrosion. The data was compared with other super alloys under similar experimental conditions in order to understand the nature of degradation mechanism of new super alloy. The results show that the new super alloy is highly susceptible to hot corrosion. The relevant reaction mechanisms that are responsible for its faster degradation under hot corrosion conditions were established and discussed. Based on the results obtained with different techniques, an electrochemical model was proposed to show that the hot corrosion of new super alloy is electrochemical in nature. Finally, it is stressed the necessity of application of high performance coatings for its protection against high temperature corrosion.
Gas Sensing Response in Nanostructured CoAl2O4 Spinel Prepared by Soft-Chemistry Methods
Authors: Michel Carlos R. , Martínez Alma H. , Lopez-Mena Edgar R.
Published: March 2008

Nanostructured CoAl2O4 powders with spinel-type structure were synthesized by three different approaches, with the goal of evaluating the effect of the preparation method on the microstructure and gas sensing behavior.
Electrodeposition of a Nanostructured Hybrid Copper Hexacyanoferrate/Polypyrrole Film Using Lyotropic Liquid Crystals and Colloidal Particles Templates. Application to H2O2 Detection.
Authors: Gonçales Vinicius R. , Salvador Renan P. , Alcântara Maria , Córdoba de Torresi Susana
Published: March 2008

The incorporation of nanostructured materials in biosensors is capable of optimizing the enzyme immobilization and can turn the transduction of the chemical signal more efficient. Lyotropic liquid crystalline phases and colloidal polystyrene particles have been used as templates in order to prepare a nanostructured hybrid copper hexacyanoferrate/polypyrrole (CuHCNFe/Ppy) mediator. The nanostructured material has achieved sensitivities 4.3 times higher than the bulk film during H2O2 detection. Besides, the methods are interesting because allow the deposition of a range of compounds with high surface area and thin pore walls.
High Voltage, Moderate Current Thin Film Transistor for Actuator Applications
Authors: Jamshidi-Roudbari Abbas , Kuo Po-Chin , Hatalis Miltiadis
Published: March 2008

An n-type multiple-gate laser-crystallized Poly-Silicon Thin Film Transistor (TFT) is introduced as a high voltage (Vg>30v, Vds>35v) moderate current (I=50mA) TFT structure for general purpose, matrix format actuator application on stainless steel substrate. The off-state performance of the device has been simulated and studied by the Silvaco software package and the performance of the structure has been compared with the commonly used High Voltage (HV) TFT structures.
Fabrication of Fiber-optic Sensors Based on Plasmon Resonances of Metallic Nanostructures
Authors: Dhawan Anuj , Gerhold Michael , Marinakos Stella , Leonard Donovan , Wang Hsin-Neng , Chilkoti Ashutosh , Russell Phil , Vo-Dihn Tuan
Published: March 2008

This paper describes the fabrication of portable and robust fiber optic sensors - mainly chemical and biological sensors - on standard communication grade optical fibers. Metallic nanostructures such as nanoparticles, nanopillars, nanorods, and nanoholes in optically thick metallic films were employed to precisely control the enhancement and absorption of light so as to form sensitive and specific optical sensors based on optical fibers. The fiber-optic sensors employ localized plasmon resonances (LSPRs) of metallic nanostructures formed on the fiber end-face as well as surface plasmon resonances assoc1ated with nanoholes in optically thick metallic films as a means of transducing the input optical signal. These metallic nanostructures were formed on the cleaved end-face of multimode and single mode optical fibers and were employed in both reflection and transmission modes. Metallic nanoparticles, nanorods, and nanopillars were formed on the tip or surface of the optical fiber by either employing chemical means or by first depositing a 10-100 nm layer of metallic film on the tip or surface of the fiber and then employing focused ion beam (FIB) milling to pattern out the metallic nanoparticles and nanopillars from the film. Ordered arrays of nanoholes were formed in optically thick (150-230 nm) metallic films by employing FIB milling. Gold (Au) nanostructures are chemically stable and result in plasmon resonance related peaks in the transmission spectrum in the visible spectral region. Hence, gold was selected as the material of choice for the fabrication of the plasmon resonance sensors.
Pyridoxine uptake by colonocytes: a specific and regulated carrier-mediated process
Authors: Said Zainab M. , Subramanian Veedamali S. , Vaziri Nosratola D. , Said Hamid M.
Published: March 2008

The water-soluble vitamin B6 (pyridoxine) is important for normal cellular functions, growth, and development. The vitamin is obtained from two exogenous sources: a dietary source, which is absorbed in the small intestine, and a bacterial source, where the vitamin is synthesized in significant quantities by the normal microflora of the large intestine. Evidence exists to suggest the bioavailability of the latter source of the vitamin, but nothing is known about the mechanism involved and its regulation. In this study, we addressed these issues using young adult mouse colonic epithelial (YAMC) cells and human colonic apical membrane vesicles (AMV) as models and using [3H]pyridoxine as the uptake substrate. The results showed the initial rate of [3H]pyridoxine uptake by YAMC cells to be 1) energy- and temperature- (but not Na-) dependent and to occur without metabolic alteration in the transported substrate; 2) saturable as a function of concentration with an apparent Km and Vmax of 2.1 ± 0.5 μM and 53.4 ± 4.3 pmol·mg protein−1·3 min−1, respectively; 3) cis-inhibited by unlabeled pyridoxine and its structural analogs, but not by the unrelated compounds theophylline, penicillamine, and isoniazid; 4) trans-stimulated by unlabeled pyridoxine; 5) amiloride sensitive; and 6) regulated by extracellular and intracellular factors. Uptake of pyridoxine by native human colonic AMV was also found to involve a carrier-mediated process. These studies demonstrate, for the first time, the functional existence of a specific and regulatable carrier-mediated process for pyridoxine uptake by mammalian colonocytes.
Zinc-induced G2/M blockage is p53 and p21 dependent in normal human bronchial epithelial cells
Authors: Wong Stephen H. K. , Shih Rita S. M. , Schoene Norberta W. , Lei Kai Y.
Published: March 2008

The involvement of p53 and p21 signal pathway in the G2/M cell cycle progression of zinc-supplemented normal human bronchial epithelial (NHBE) cells was examined using the small interferring RNA (siRNA) approach. Cells were cultured for one passage in a different concentration of zinc: <0.4 μM (ZD) as zinc deficient; 4 μM as normal zinc level (ZN) in culture medium; 16 μM (ZA) as normal human plasma zinc level; and 32 μM (ZS) as the high end of plasma zinc attainable by oral supplementation. Nuclear p21 protein and mRNA levels as well as promoter activity in ZS cells, but not in ZD cells, were markedly elevated to almost twofold compared with ZN control cells. G2/M blockage in ZS cells was coupled with the observation of elevated p21 gene expression. In ZS cells, the abrogation of p21 protein induction by the transfection of p21 siRNA was shown to alleviate the G2/M blockage, demonstrating the positive linkage of p21 elevation and G2/M blockage. Abolishment of the increase in p53 protein in ZS cells with transfection of p53 siRNA normalized the elevated p21 protein to a similar level as in ZN control cells, which demonstrated that the p21 induction is p53 dependent. Furthermore, the normalization of p53 protein by siRNA treatment in ZS cells alleviated cell growth depression and G2/M blockage, which demonstrated that p53 was involved in the high zinc status-induced G2/M blockage and growth depression. Thus high zinc status in NHBE cells upregulates p53 expression which in turn elevates p21 that eventually induces G2/M blockage.
The vitamin D receptor agonist elocalcitol upregulates L-type calcium channel activity in human and rat bladder
Authors: Morelli Annamaria , Squecco Roberta , Failli Paola , Filippi Sandra , Vignozzi Linda , Chavalmane Aravinda K. , Fibbi Benedetta , Mancina Rosa , Luciani Giorgia , Gacci Mauro , Colli Enrico , Francini Fabio , Adorini Luciano , Maggi Mario
Published: March 2008

Human bladder contraction mainly depends on Ca2+ influx via L-type voltage-gated Ca2+ channels and on RhoA/Rho kinase contractile signaling, which is upregulated in overactive bladder (OAB). Elocalcitol is a vitamin D receptor agonist inhibiting RhoA/Rho kinase signaling in rat and human bladder. Since in the normal bladder from Sprague-Dawley rats elocalcitol treatment delayed the carbachol-induced contraction without changing maximal responsiveness and increased sensitivity to the L-type Ca2+ channel antagonist isradipine, we investigated whether elocalcitol upregulated L-type Ca2+ channels in human bladder smooth muscle cells (hBCs). In hBCs, elocalcitol induced a rapid increase in intracellular [Ca2+], which was abrogated by the L-type Ca2+ channel antagonist verapamil. Moreover, hBCs exhibited L-type voltage-activated Ca2+ currents ( ICa), which were selectively blocked by isradipine and verapamil and enhanced by the selective L-type agonist BAY K 8644. Addition of elocalcitol (10−7 M) increased L-type ICa size and specific conductance by inducing faster activation and inactivation kinetics than control and BAY K 8644, while determining a significant negative shift of the activation and inactivation curves, comparable to BAY K 8644. These effects were strengthened in long-term treated hBCs with elocalcitol (10−8 M, 48 h), which also showed increased mRNA and protein expression of pore-forming L-type α1C-subunit. In the bladder from Sprague-Dawley rats, BAY K 8644 induced a dose-dependent increase in tension, which was significantly enhanced by elocalcitol treatment (30 μg·kg−1·day−1, 2 wk). In conclusion, elocalcitol upregulated Ca2+ entry through L-type Ca2+ channels in hBCs, thus balancing its inhibitory effect on RhoA/Rho kinase signaling and suggesting its possible efficacy for the modulation of bladder contractile mechanisms.
Personal reminiscences about Morton Grossman and the founding of the Center for Ulcer Research and Education (CURE)
Authors: Guth Paul H. , Kaunitz Jonathan D.
Published: March 2008

The Center for Ulcer Research and Education (CURE) from its onset was primarily the work of one man: Professor Morton Grossman, or “Mort” as he was known and called by all. Mort's legacy includes a large body of scientific publications, the first National Institutes of Health Digestive Diseases Center (CURE), and, most importantly, a group of scientists who have become academic leaders and who have made important contributions in the fields of upper gastrointestinal (GI) tract secretion, hormones and receptors, mucosal defense mechanisms, the design and conduct of randomized clinical trials, and ulcer epidemiology. Indeed, Mort is considered to be a founding father of modern academic GI research. I was fortunate to have known and worked with Mort and would like to memorialize his contributions so that his memory can inspire the next generation of academicians.
Small-conductance, Ca2+-activated K+ channel 2 is the key functional component of SK channels in mouse urinary bladder
Authors: Thorneloe K. S. , Knorn A. M. , Doetsch P. E. , Lashinger E. S. R. , Liu A. X. , Bond C. T. , Adelman J. P. , Nelson M. T.
Published: March 2008

Small-conductance Ca2+-activated K+ (SK) channels play an important role in regulating the frequency and in shaping urinary bladder smooth muscle (UBSM) action potentials, thereby modulating contractility. Here we investigated a role for the SK2 member of the SK family (SK1-3) utilizing: 1) mice expressing β-galactosidase (β-gal) under the direction of the SK2 promoter (SK2 β-gal mice) to localize SK2 expression and 2) mice lacking SK2 gene expression (SK2−/− mice) to assess SK2 function. In SK2 β-gal mice, UBSM staining was observed, but staining was undetected in the urothelium. Consistent with this, urothelial SK2 mRNA was determined to be 4% of that in UBSM. Spontaneous phasic contractions in wild-type (SK2+/+) UBSM strips were potentiated (259% of control) by the selective SK channel blocker apamin (EC50 = 0.16 nM), whereas phasic contractions of SK2−/− strips were unaffected. Nerve-mediated contractions of SK2+/+ UBSM strips were also increased by apamin, an effect absent in SK2−/− strips. Apamin increased the sensitivity of SK2+/+ UBSM strips to electrical field stimulation, since pretreatment with apamin decreased the frequency required to reach a 50% maximal contraction (vehicle, 21 ± 4 Hz, n = 6; apamin, 12 ± 2 Hz, n = 7; P < 0.05). In contrast, the sensitivity of SK2−/− UBSM strips was unaffected by apamin. Here we provide novel insight into the molecular basis of SK channels in the urinary bladder, demonstrating that the SK2 gene is expressed in the bladder and that it is essential for the ability of SK channels to regulate UBSM contractility.
High glucose-induced NF-κB activation occurs via tyrosine phosphorylation of IκBα in human glomerular endothelial cells: involvement of Syk tyrosine kinase
Authors: Yang Won Seok , Seo Jang Won , Han Nam Jeong , Choi Jung , Lee Ki-Up , Ahn Hanjong , Lee Sang Koo , Park Su-Kil
Published: March 2008

Activation of nuclear factor-κB (NF-κB) occurs by dissociation from IκB after serine or tyrosine phosphorylation of IκBα, but the way of NF-κB activation by high glucose has not been defined. High glucose is known to activate NF-κB via protein kinase C and reactive oxygen species (ROS). In this study, we investigated how high glucose activates NF-κB for CC chemokine ligand 2 production in cultured human glomerular endothelial cells. High glucose increased nuclear translocation of p65 and also increased NF-κB DNA binding activity. High glucose-induced NF-κB activation occurred without degradation of IκBα. In agreement with this, there was no increase in serine phosphorylation of IκBα, while tyrosine phosphorylation of IκBα was increased by high glucose. High glucose increased the generation of ROS, whereas both α-lipoic acid and N-acetylcysteine scavenged the ROS and decreased high glucose-induced tyrosine phosphorylation of IκBα, nuclear translocation of p65, and NF-κB DNA binding activity. Protein kinase C pseudosubstrate inhibited high glucose-induced ROS production, tyrosine phosphorylation of IκBα, and nuclear translocation of p65. Both BAY 61-3606, a specific inhibitor of Syk protein-tyrosine kinase, and small interfering RNA directed against Syk inhibited high glucose-induced tyrosine phosphorylation of IκBα as well as p65 nuclear translocation. High glucose increased tyrosine phosphorylation of Syk, while it was inhibited by α-lipoic acid and protein kinase C pseudosubstrate. In summary, high glucose-induced NF-κB activation occurred not by serine phosphorylation of IκBα. Our data suggest that ROS-mediated tyrosine phosphorylation of IκBα is the mechanism for high glucose-induced NF-κB activation, and Syk may play a role in tyrosine phosphorylation of IκBα.
Dynamic myogenic autoregulation in the rat kidney: a whole-organ model
Authors: Kleinstreuer N. , David T. , Plank M. J. , Endre Z.
Published: March 2008

A transient 1D mathematical model of whole-organ renal autoregulation in the rat is presented, examining the myogenic response on multiple levels of the renal vasculature. Morphological data derived from micro-CT imaging were employed to divide the vasculature via a Strahler ordering scheme. A previously published model of the myogenic response based on wall tension is expanded and adapted to fit the response of each level, corresponding to a distally dominant resistance distribution with the highest contributions localized to the afferent arterioles and interlobular arteries. The mathematical model was further developed to include the effects of in vivo viscosity variation and flow-induced dilation via endothelial nitric oxide production. Computer simulations of the autoregulatory response to pressure perturbations were examined and compared with experimental data. The model supports the hypothesis that change in circumferential wall tension is the catalyst for the myogenic response. The model provides a basis for examining the steady state and transient characteristics of the whole-organ renal myogenic response in the rat, as well as the modulatory influences of metabolic and hemodynamic factors.
A Modeling Study Suggesting a Possible Pharmacological Target to Mitigate the Effects of Ethanol on Reward-Related Dopaminergic Signaling
Authors: Migliore Michele , Cannia Claudio , Canavier Carmen C.
Published: March 2008

Midbrain dopaminergic neurons are involved in several critical brain functions controlling goal-directed behaviors, reinforcing/reward processes, and motivation. Their dysfunctions alter dopamine release and contribute to a vast range of neural disorders, from Parkinson's disease to schizophrenia and addictive behaviors. These neurons have thus been a natural target of pharmacological treatments trying to ameliorate the consequences of several neuropathologies. From this point of view, a clear experimental link has been recently established between the increase in the pacemaker frequency of dopaminergic neurons in vitro after acute ethanol application and a particular ionic current ( Ih). The functional consequences in vivo, however, are not clear and they are very difficult to explore experimentally. Here we use a realistic computational model of dopaminergic neurons in vivo to suggest that ethanol, through its effects on Ih, modifies the temporal structure of the spiking activity. The model predicts that the dopamine level may increase much more during bursting than during pacemaking activity, especially in those brain regions with a slow dopamine clearance rate. The results suggest that a selective pharmacological remedy could thus be devised against the rewarding effects of ethanol that are postulated to mediate alcohol abuse and addiction, targeting the specific HCN genes expressed in dopaminergic neurons.
Whisker Movements Evoked by Stimulation of Single Motor Neurons in the Facial Nucleus of the Rat
Authors: Herfst Lucas J. , Brecht Michael
Published: March 2008

The lateral facial nucleus is the sole output structure whose neuronal activity leads to whisker movements. To understand how single facial nucleus neurons contribute to whisker movement we combined single-cell stimulation and high-precision whisker tracking. Half of the 44 stimulated neurons gave rise to fast whisker protraction or retraction movement, whereas no stimulation-evoked movements could be detected for the remainder. Direction, speed, and amplitude of evoked movements varied across neurons. Protraction movements were more common than retraction movements ( n = 16 vs. n = 4), had larger amplitudes (1.8 vs. 0.3° for single spike events), and most protraction movements involved only a single whisker, whereas most retraction movements involved multiple whiskers. We found a large range in the amplitude of single spike-evoked whisker movements (0.06–5.6°). Onset of the movement occurred at 7.6 (SD 2.5) ms after the spike and the time to peak deflection was 18.2 (SD 4.3) ms. Each spike reliably evoked a stereotyped movement. In two of five cases peak whisker deflection resulting from consecutive spikes was larger than expected when based on linear summation of single spike-evoked movement profiles. Our data suggest the following coding scheme for whisker movements in the facial nucleus. 1) Evoked movement characteristics depend on the identity of the stimulated neuron (a labeled line code). 2) The facial nucleus neurons are heterogeneous with respect to the movement properties they encode. 3) Facial nucleus spikes are translated in a one-to-one manner into whisker movements.
Contributions of Online Visual Feedback to the Learning and Generalization of Novel Finger Coordination Patterns
Authors: Liu Xiaolin , Scheidt Robert A.
Published: March 2008

We explored how people learn new ways to move objects through space using neuromuscular control signals having more degrees of freedom than needed to unambiguously specify object location. Subjects wore an instrumented glove that recorded finger motions. A linear transformation matrix projected joint angle signals (a high-dimensional control vector) onto a two-dimensional cursor position on a video monitor. We assessed how visual information influences learning and generalization of novel finger coordination patterns as subjects practiced using hand gestures to manipulate cursor location. Three groups of test subjects practiced moving a visible cursor between different sets of screen targets. The hand-to-screen transformation was designed such that the different sets of targets (which we called implicit spatial cues) varied in how informative they were about the gestures to be learned. A separate control group practiced gesturing with explicit cues (pictures of desired gestures) without ongoing cursor feedback. Another control group received implicit spatial cueing and feedback only of final cursor position. We found that test subjects and subjects provided with explicit cues could learn to produce desired gestures, although training efficacy decreased as the amount of task-relevant feedback decreased. Although both control groups learned to associate screen targets with specific gestures, only subjects provided with online feedback of cursor motion learned to generalize in a manner consistent with the internal representation of an inverse hand-to-screen mapping. These findings suggest that spatial learning and generalization require dynamic feedback of object motion in response to control signal changes; static information regarding geometric relationships between controller and endpoint configurations does not suffice.
On the Importance of Static Nonlinearity in Estimating Spatiotemporal Neural Filters With Natural Stimuli
Authors: Sharpee Tatyana O. , Miller Kenneth D. , Stryker Michael P.
Published: March 2008

Understanding neural responses with natural stimuli has increasingly become an essential part of characterizing neural coding. Neural responses are commonly characterized by a linear–nonlinear (LN) model, in which the output of a linear filter applied to the stimulus is transformed by a static nonlinearity to determine neural response. To estimate the linear filter in the LN model, studies of responses to natural stimuli commonly use methods that are unbiased only for a linear model (in which there is no static nonlinearity): spike-triggered averages with correction for stimulus power spectrum, with or without regularization. Although these methods work well for artificial stimuli, such as Gaussian white noise, we show here that they estimate neural filters of LN models from responses to natural stimuli much more poorly. We studied simple cells in cat primary visual cortex. We demonstrate that the filters computed by directly taking the nonlinearity into account have better predictive power and depend less on the stimulus than those computed under the linear model. With noise stimuli, filters computed using the linear and LN models were similar, as predicted theoretically. With natural stimuli, filters of the two models can differ profoundly. Noise and natural stimulus filters differed significantly in spatial properties, but these differences were exaggerated when filters were computed using the linear rather than the LN model. Although regularization of filters computed under the linear model improved their predictive power, it also led to systematic distortions of their spatial frequency profiles, especially at low spatial and temporal frequencies.
Long-term Epigenetic Therapy with Oral Zebularine Has Minimal Side Effects and Prevents Intestinal Tumors in Mice
Authors: Yoo Christine B. , Chuang Jody C. , Byun Hyang-Min , Egger Gerda , Yang Allen S. , Dubeau Louis , Long Tiffany , Laird Peter W. , Marquez Victor E. , Jones Peter A.
Published: March 2008

Recent successes in the application of epigenetic drugs for the treatment of myelodysplastic syndrome have raised questions on the safety of long-term administration of DNA methylation inhibitors. We treated preweaned cancer prone ApcMin/+ (Min) mice continuously with the DNA methylation inhibitor zebularine in their drinking water to determine the effects of the drug on normal mouse development as well as cancer prevention. Zebularine caused a tissue-specific reduction in DNA methylation at B1 short interspersed nucleotide elements in the small and large intestines of female Min mice but not in other organs examined after chronic oral treatment. No significant difference in the average weights of mice was observed during the treatment. In addition, analysis of global gene expression of colonic epithelial cells from the females indicated that only 3% to 6% of the genes were affected in their expression. We did not detect toxicity and abnormalities from the histopathologic analysis of liver and intestinal tissues. Lastly, we tested whether prevention of tumorigenesis can be achieved with chronic oral administration of zebularine in Min mice. The average number of polyps in Min females decreased from 58 to 1, whereas the average polyp number remained unaffected in Min males possibly due to differential activity of aldehyde oxidase. Taken together, our results show for the first time that long-term oral administration of zebularine causes a gender-specific abrogation of intestinal tumors while causing a tissue-specific DNA demethylation. Importantly, prolonged treatment of mice with epigenetic drugs resulted in only minor developmental and histologic changes.
Escitalopram Regulates Expression of TRH and TRH-Like Peptides in Rat Brain and Peripheral Tissues
Authors: Sattin Albert , Pekary Albert E. , Blood James
Published: March 2008

Background: Escitalopram (eCIT) is a highly selective serotonin reuptake inhibitor (SSRI) that can be an effective treatment for a number of neuropsychiatric disorders including major depression. We, and others, have previously reported that thyrotropin-releasing hormone (TRH, pGlu-His-Pro-NH2) and TRH-like peptides with the general structure pGlu-X-Pro-NH2, where ‘X’ can be any amino acid residue, have neuroprotective, antidepressant, analeptic, arousal, and anti-epileptic effects that could mediate the neuropsychiatric and therapeutic effects of a variety of neurotropic agents. The present work explores the possible mediation of the therapeutic effects of eCIT by TRH and TRH-like peptides. Methods: In order to extend our understanding of the range of neurotransmitter systems that are modulated by and, in turn, influence the expression of TRH and TRH-like peptides, 16 male Sprague-Dawley rats were injected i.p. with eCIT (24 mg/kg BW) and the brain levels of TRH and TRH-like peptides in various brain regions involved in mood regulation and peripheral tissues with serotonergic innervation were measured 0, 2, 4, and 6 h later by combined HPLC and RIA. Results and Conclusion: Remarkable 3- to 25-fold increases in TRH and TRH-like peptide levels were observed 2 h after i.p. eCIT in the epididymis. This reproductive tissue has the highest level of serotonin found in most mammals. The acute (2 h) effect of eCIT in brain regions involved in mood regulation, particularly the nucleus accumbens and medulla oblongata, cerebellum, and striatum was to increase the levels of TRH-like peptides, most consistently Phe-TRH. An important exception was a decrease in the level of TRH in the nucleus accumbens. These responses, in general, were the opposite of those we have previously observed after acute restraint stress in this same rat strain. We conclude that some of the therapeutic effects of inhibition of serotonin reuptake are mediated by altered release of TRH and TRH-like peptides.
Notch1, Jagged1, and HES5 Are Abundantly Expressed in Osteoarthritis
Authors: Karlsson C. , Brantsing C. , Egell S. , Lindahl A.
Published: March 2008

Background: Notch signalling controls differentiation and proliferation in various cell types and is associated with several diseases. We investigated the localization and regulation of several Notch markers in human osteoarthritic (OA) cartilage as well as identified genes controlled by Notch signalling. Methods: Immunolocalization and real-time PCR analysis of Notch markers in healthy and OA articular cartilage were performed. Genes regulated by Notch signalling were studied using microarray. Cytokine-induced transcription of Notch markers was analyzed using real-time PCR and its effect on cellular localization of the intracellular domain of Notch1 (NICD1) was investigated using immunohistochemistry, subcellular fractionation, and transfection. The effect of NFĸB activation on HES5 transcription was studied using the NFĸB inhibitor pyrrolidine dithiocarbamate. Results: Notch signalling was activated in OA cartilage and Notch1, Jagged1, and HES5 were abundantly expressed compared to healthy cartilage. Notch signalling regulated the expression of several genes associated with OA, like interleukin-8, lubricin, CD10, matrix metalloproteinase-9, and bone morphogenetic protein-2. Cytokines significantly affected the expression of several Notch markers and repressed expression of HES5, but did not affect the cellular localization of NICD1. Conclusion: Notch signalling is dysregulated in OA, inducing and repressing transcription of genes that could potentially partly contribute to the OA phenotype.
The Eye of the Camera
Authors: van Rompay Thomas J. L. , Vonk Dorette J. , Fransen Marieke L.
Published: March 2008

This study addresses the effects of security cameras on prosocial behavior. Results from previous studies indicate that the presence of others can trigger helping behavior, arising from the need for approval of others. Extending these findings, the authors propose that security cameras can likewise trigger such approval-seeking behaviors by implying the presence of a watchful eye. Because people vary in the extent to which they strive for others' approval, it was expected that the effects of security cameras on prosocial behavior vary with participants' need for approval. To test these predictions, an experimental study was conducted with “presence of security camera” and “need for approval” as independent variables. Results showed that participants indeed offered more help in the presence of a security camera but only to the extent that this helping involved public or observable behavior. As expected, this effect was more pronounced for individuals high in need for approval. Practical implications and suggestions for future research are discussed.
An Urban Community-Based Intervention to Advance Social Interactions
Authors: Semenza Jan C. , March Tanya L.
Published: March 2008

Blighted urban environments can be detrimental to community life and result in alienation and isolation. An intervention was developed in 2003 in Portland, Oregon, to engage low- to moderate-income, urban communities in creating pleasant amenities in the public right-of-way, including ecologically built information kiosks, benches, trellises for hanging gardens, and interactive art features such as large street paintings and art walls. As part of a postintervention survey of 359 residents within a two-block radius at three project sites, 53% rated their neighborhood better than before and 44% or 53% rated their present neighborhood as an excellent or good place to live, respectively. In open-ended qualitative comments, 30% mentioned increased social interactions, 13% revealed an enhanced sense of place, 43% described neighborhood participation, and 20% discussed aesthetic aspects of their local environment. Community involvement in urban design can enrich social networks with direct benefits for social capital and well-being.
Packaging and Proenvironmental Consumption Behavior
Authors: van Birgelen Marcel , Semeijn Janjaap , Keicher Manuela
Published: March 2008

Understanding proenvironmental consumption behavior may enable companies to establish reputational and competitive advantages. This study generates new insights by analyzing consumer-related factors related to distinct but connected package-related behaviors regarding beverage consumption: purchase and postconsumption disposal. An online survey among 176 German respondents provides empirical support for all but one hypothesis. The results suggest that eco-friendly purchase and disposal decisions for beverages are related to the environmental awareness of consumers and their eco-friendly attitude. Furthermore, consumers are willing to trade off almost all product attributes in favor of environmentally friendly packaging of beverages, except for taste and price. The nonsupported hypothesis pertains to the expectation that believing in the positive effects of own eco-friendly disposal actions will guide ecological disposal behavior. Perceived behavioral control may thus not translate into actual disposal behavior. Underlying this may be the belief that individual actions are not enough to contribute to a greener world.
Behavioral Determinants of Household Participation in a Home Composting Scheme
Authors: Edgerton Eddie , McKechnie Jim , Dunleavy Karen
Published: March 2008

This article investigates the factors that influence the decision made by individuals to participate in home composting schemes promoted by two local authorities in Scotland. The research considers eight potential determinants of home composting behavior and applies logistic regression data analysis to assess the significance of these specific determinants. The results suggest that the most important variables for predicting whether individuals choose to participate in the home composting scheme include (a) having a favorable attitude toward what home composting involves, (b) being knowledgeable about home composting, (c) and the stage of the household in terms of the family life cycle. Variables such as general environmental concern, participation in other proenvironmental behaviors, social norms, social diffusion, and being a “gardener” were not significant predictors of the decision to participate. The implications of these findings for the promotion of home composting schemes are discussed.
Lessons From the Maafa
Authors: Wells-Wilbon Rhonda , Jackson Nigel D. , Schiele Jerome H.
Published: March 2008

The culture of hip-hop and the legacy of some artists have received much criticism during the past two decades. At the center of that controversy is one artist who is never forgotten, for better or worse, Tupac Amaru Shakur. Although the legacy of Tupac looms large in urban centers around the world among the popular culture of youth, there has been little attention paid to him as a central figure in the professional literature. This article explores his life and lyrics, placing his contributions and struggles on a cycle of the Maat, Maafa, Sankofa paradigm, challenging critics to rethink his legacy.
Explaining Employees' Experience of Work in Outsourced Call Centres: The Influence of Clients, Owners and Temporary Work Agencies
Authors: Kinnie Nicholas , Purcell John , Adams Mark
Published: March 2008

Third party call centres are growing as employers respond to market pressures. However, evidence shows their employees' experience of work is inferior compared to those working for in-house call centres. Drawing on research in two organizations we argue that the differences in employees' experiences can be explained by examining external influences on HR practices. These cases reveal a complex web of relationships involving clients, owners and Temporary Work Agencies. The strategic choice of HR practices is severely constrained by these important external parties and by the labour market making it difficult to develop effective, stable, mutually beneficial employment relationships. The impact of these external influences has implications for employee representation and legal protection in third-party call centres and for future research into the constraints on HR decision-making in these organizations.