bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Treatment Effects on Pd-based Electrocatalysts for Oxygen Reduction in PEM Fuel Cells
Authors: Ramos-Sanchez Guadalupe , Vázquez-Huerta Gerardo , Delgado Manuel David , Collins Virginia M. , Solorza-Feria Omar
Published: December 2009

The catalytic activity of carbon supported PdNi and Pd0.5Ni0.45Se0.05 materials for the oxygen reduction reaction (ORR) in acid media at 25{degree sign}C was studied. The electrocatalysts were synthesized by a chemical from metallic precursors with NaBH4. Thermal treatment in hydrogen atmosphere was performed in a stainless steel reactor, to improve their catalytic properties. The X-Ray diffraction pattern showed an enhancement of the crystallinity as well as a grown of the crystallite size in comparison to those without heat treatment. Displacements of diffraction peaks towards more positive 2θ values were observed and associated to the incorporation of the elements inside a crystalline structure.The catalytic activity was studied by electrochemical hydrodynamic techniques; the mass transfer corrected Tafel plots showed a decreasing in ~50 mV in the overpotential of Pd0.5Ni0.45Se0.05 to reach the same PdNi current density. There is not a significant enhancement of the Pd0.5Ni0.45Se0.05 catalyst associated to the formation of new inactive-ORR phases.
Dye-sensitized Solar Cells Based on Perpendicularly-oriented Porphyrin Monolayers Obtained by Electrophoretic Deposition on Nanocrystalline TiO2 Electrodes
Authors: López-García Ulises M. , Castellanos Oscar A. , Moorefield Charles N. , Newkome George R. , Godínez Luis A. , Manriquez Juan
Published: December 2009

A study of the photovoltaic properties and performance for dye-sensitized solar cells using mesoporphyrin IX electrophoretically deposited on nanocrystalline TiO2 photoanodes is reported. Performance data obtained from these photovoltaic devices were compared with photocells having TiO2 films sensitized by dip-coating deposition in absence of electric field. Global conversion efficiencies achieved for the solar cells containing porphyrins electrophoretically deposited were 4 times higher than for cells containing porphyrins deposited by dip-coating. Preliminary results suggest that conversion efficiencies for these photovoltaic devices depend from the orientation acquired by the dye monolayers on the TiO2 surfaces.
Electrochemical Evaluation of MgO-CeO2 Coatings on AA6066 Aluminum Alloy by MOCVD
Authors: Torres-Huerta Aidé M. , Brachetti-Sibaja Silvia B. , Dominguez-Crespo Miguel A. , Ramirez-Meneses Esther , Arenas-Alatorre Jesus A.
Published: December 2009

The corrosion inhibition of AA6066 aluminum alloy due to the addition of MgO-CeO2 thin films using MOCVD has been investigated. The structure and morphology of the deposited coatings were also investigated on both polished quartz and AA6066 aluminum alloy substrates. The results from the different coating conditions show that under the best experimental conditions (Tp=230 ºC, Tsus=505 ºC and tdep=120 min), uniform and crack-free coatings with a mixture of oxides forming the film were obtained. The particle size of these coatings ranged from 130 nm to 1 µm with different morphologies according to the substrate. The electrochemical behavior of the MgO-CeO2 coatings caused a displacement to the cathodic direction due to the presence of an important amount of magnesium oxide; however, the passive film presented a truly protective nature in comparison with that of bare aluminum and those reported in the literature.
Effect of Pollution on the Corrosion of Galvanized Steel in Cunduacán, Tabasco
Authors: Del Angel Meraz Ebelia , Márquez Dora Maria F. , Calderon Richart F. , Gómez Felipe L. , Romero Juan José Rueda D.
Published: December 2009

Galvanized steel samples were exposed to open air on aluminum panels following the procedures established in norms ISO 8565 and ASTM G 50-76, in a humid tropical climate environment (Cunduacán, Tabasco). The rate of corrosion (loss of mass) was recorded at different time periods (February-July 2009), and it presented a C3 (medium) aggressiveness category according to norm ISO 9223:92. In accordance with norm ISO 9223, the deposition rate of the pollutant sulphur dioxide (SO2) corresponded to a low (Po) corrosive aggressiveness category, and that of sodium chloride (NaCl) corresponded to a low (S1) category. X ray analyses indicate the corrosion products that formed on the galvanized steel. These included Simonkoleite [Zn5(OH)8Cl2.H2O], Gordoite [Zn4Na(OH)6(SO4)Cl.(H2O)6] and pentahydrated zinc hydroxisulphate (Zn(OH)2)3(ZnSO4)(H2O)5. The results show the effect of the pollutants (NaCl and SO2) on the corrosion of galvanized steel in Cunduacán, Tabasco.
Corrosion of Steel in Concrete with Recycled Aggregate and Pozzolanic Materials
Authors: Corral Higuera Ramón , Arredondo Rea Susana P. , Almaral Sánchez Jorge L. , Castorena González José H. , Neri Flores Miguel &. , Martínez Villafañe Alberto , Almeraya Calderón Facundo
Published: December 2009

The kinetics of corrosion was evaluated and the deterioration of the reinforced concrete made with recycled aggregate and pozzolanic materials was inferred. Four series of cylindrical specimens were made with water-binder ratio of 0.48; the reference series was made with natural aggregate and 100% Compound Portland Cement, the second series was with recycled coarse aggregate (RA) and a 100% CPC, a third series was made with RA, 30% fly ash and 70% CPC and the fourth series was made with RA, 10% silica fume and 90% CPC. Test specimens of each mixture were exposed to a 3.5% NaCl aqueous solution and the corrosion current density was obtained using Electrochemical Impedance Spectroscopy (EIS). The results show that the system of concrete with recycled aggregate and with silica fume addition has more corrosion resistance, because it presented the highest values of Resistance of charge transfer of reinforcement
Effect of Flow and a Triazole Derivative Based Inhibitor on the Corrosion of API X52 Pipeline Steel Grade in CO2 Saturated Brine Solution
Authors: Olalde Roman , Genesca Juan
Published: December 2009

The effect of moving environments on the efficiency of corrosion inhibitors is a research topic that has been in continuous development over the recent years. The present work explores the effect of turbulent flow on the electrochemical behavior and efficiency of a triazole-based corrosion inhibitor (3-amino-1,2,4, triazole, aminotriazole or 3-AT) in a CO2 saturated NaCl solution, using the rotating cylinder electrode, RCE, as hydrodynamic control system. The influence of turbulent flow on the corrosion rate of X52 pipeline steel was investigated using polarization curves and polarization resistance, Rp, techniques. It was found that the inhibiting effect of the triazole is considerably increased by flow.
Electrochemical Oxidation of Ethanol Using Heterobimetallic Complexes as an Approach to DEFC Catalysts
Authors: Correia Marie , Moghieb Ahmed M. , Goforth Sarah , McElwee-White Lisa
Published: December 2009

Direct ethanol fuel cells (DEFCs) are an attractive alternative to their methanol analogues. A series of Ru/Pt, Ru/Pd and Ru/Au complexes was studied to determine the electrocatalytic activity of these complexes for the oxidation of ethanol. Cyclic voltammetry was performed to establish the affinity of these complexes towards ethanol oxidation. Constant potential (bulk) electrolysis was carried out and the liquid products of oxidation were identified and quantified by gas chromatography. Headspace gas samples were collected in a modified airfree cell and analyzed using a Fourier transform infrared spectrometer.
In-situ Observation of CO2 through the Self-purging in Alkaline Membrane Fuel Cell (AMFC)
Authors: Fukuta Kenji , Inoue Hiroshi , Watanabe Shin , Yanagi Hiroyuki
Published: December 2009

Alkaline membrane fuel cell (AMFC) performance was investigated comparing clean air and ambient air as oxidizing gases. Maximum power density was 120 mW/cm2 in the case of ambient air, and it was below 1/2 of that obtained with clean air. By analyzing anode exhaust gas with FT-IR or mass spectroscopy, released CO2 through the self-purging was directly observed for the first time. In the case of clean air, almost all HCO3- counter anion was released at the higher current density, to make the AMFC performance better.
A Covalently Cross-linked Polyetheretherketone Proton Exchange Membrane for DMFC
Authors: Luo Hongze , Vaivars Guntars , Modibedi Mmalewane , Mathe Mkhulu
Published: December 2009

The proton exchange membrane was prepared by covalent cross-linking sulfonated-sulfinated polyetheretherketone. The cross-linked membrane showed high proton conductivity (0.04 S/cm) with suitable water uptake, low methanol permeability (2.21 × 10-7 cm2/s) and good electrochemical stability. The results suggested that cross-linked polyetheretherketone membrane is particularly promising to be used as proton exchange membrane for the direct methanol fuel cell application.
Approaches to Improve Durability and Special Applications of FC MEAs
Authors: Tsou Yu-Min , Cao Lixin , Young Maria , Morse Jeffrey
Published: December 2009

Three approaches are presented to address the most commonly observed durability problems in low temperature and high temperature fuel cells: carbon corrosion. Carbon support corrosion problem is severe during shutdown/re-start-up periods when gas mixing occurs. Process mitigation is very costly. The first approach is using corrosion resistant carbon. Electrochemical carbon screening methodology is presented and successful examples are demonstrated. Unsupported catalyst is another attractive approach. Cell stack testing indicates the much better durability of gas diffusion electrode (GDEs) with unsupported catalysts (USC) in 3000-4000 hour experiments. GDEs with UNC also showed advantage in low humidity operation and fast break-in. Technology in optimizing the performance of GDEs with UNC is illustrated. Ion beam deposition (IBD) is demonstrated to afford anode GDEs with similar performance to conventional one with complete dry process and without incorporating ionomer for proton conductivity. Cathode IBAD GDEs exhibit mass transport problem. Roll-to-roll IBAD manufacture is demonstrated
Reduction of CO Poisoning in PEM Fuel Cell by Application of Optimal Pulse Control
Authors: Dhanda Abhishek , Pitsch Heinz
Published: December 2009

CO poisoning in PEM fuel cells can be reduced by pulsing either the voltage or the current. The pulsing parameters are often obtained by experiment iterations. Further the structure of the optimal signal is presumed to be a pulse. Here we use the electrochemical model of hydrogen oxidation in presence of CO on Pt electrodes and formulate the problem as parametric optimization problem. Optimized pulse signal is derived for different schemes with either current or resistive load as the control variable. Simulation results are presented to demonstrate the effectiveness of the proposed approach.
Effect of Operating Backpressure on PEM Fuel Cell Performance
Authors: Zhang Jianlu , Li Hui , Zhang Jiujun
Published: December 2009

In this paper, the effects of operating backpressure on PEM fuel cell performance were studied at 70 ºC, 100% RH, and backpressures ranging from 1.00 to 3.04 atm. AC impedance spectroscopy and cyclic voltammetry were employed to diagnose the backpressure effects. It was observed that increasing operating backpressure could improve fuel cell performance by enhancing the fuel cell thermodynamics, increasing the exchange current densities of the reactions, accelerating the electrode kinetics, and improving the mass transfer process. However, some negative effects, such as increased H2 crossover rate and membrane resistance, were also observed.
Preparation and Photocatalytic Activity Evaluation of Composite Photocatalyst Fe-TiO2/TiO2
Authors: Shifu Chen , Xiaoling Yu , Wei Liu
Published: December 2009

Fe-TiO2 photocatalyst was prepared by Sol-gel method using tetrabutyl titanate [Ti(OC4H9)4] as the titanium precursor. The relative p-n junction composite Fe-TiO2/TiO2 samples were prepared by ball milling method. The structure and properties of the samples were characterized by XRD, DRS, XPS and PL emission spectra. The results show that doping Fe3+ into TiO2 is more beneficial to improve the photocatalytic reduction activity of the sample compared with the photooxidation activity. The optimum doping amount is 0.05% (Fe/Ti molar ratio) for the Fe-TiO2 photocatalyst. After coupled between Fe-TiO2 and TiO2, both the photooxidation and photoreduction activities of the sample are enhanced. It is proposed that as the formation of relative p-n junction between the Fe-TiO2 and TiO2, the photo-excited holes and electrons are separated effectively, and the photocatalytic activity is enhanced.
Nanostructure Approaches for Photoelectrocatalysis
Authors: Muñoz A. G. , Skorupska K. , Lewerenz H. J.
Published: December 2009

Processes, relevant for light-induced fuel generation (water photoelectrolysis, CO2 reduction) are shortly reviewed. Stabilization strategies for development of efficient tandem cell structures that are based on non-oxidic semiconductors are presented. The recently introduced nanoemitter concept that involves surface passivation by a nanoporous film is described and first results on light-induced hydrogen generation with p-Si(100) and p-InP(100):2x4 thin films are given. Solar-to-hydrogen efficiencies reach 14% for homoepitaxial InP thin films covered with Rh nanoislands. In the pursuit to develop biologically inspired systems, successful enzyme immobilization at an electrochemically nanostructured Si surface that shows step bunching has been achieved as evidenced by tapping mode atomic force microscopy.
PGC-1α plays a functional role in exercise-induced mitochondrial biogenesis and angiogenesis but not fiber-type transformation in mouse skeletal muscle
Authors: Geng Tuoyu , Li Ping , Okutsu Mitsuharu , Yin Xinhe , Kwek Jyeyi , Zhang Mei , Yan Zhen
Published: December 2009

Endurance exercise stimulates peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) expression in skeletal muscle, and forced expression of PGC-1α changes muscle metabolism and exercise capacity in mice. However, it is unclear if PGC-1α is indispensible for endurance exercise-induced metabolic and contractile adaptations in skeletal muscle. In this study, we showed that endurance exercise-induced expression of mitochondrial enzymes (cytochrome oxidase IV and cytochrome c) and increases of platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31)-positive endothelial cells in skeletal muscle, but not IIb-to-IIa fiber-type transformation, were significantly attenuated in muscle-specific Pgc-1α knockout mice. Interestingly, voluntary running effectively restored the compromised mitochondrial integrity and superoxide dismutase 2 (SOD2) protein expression in skeletal muscle in Pgc-1α knockout mice. Thus, PGC-1α plays a functional role in endurance exercise-induced mitochondrial biogenesis and angiogenesis, but not IIb-to-IIa fiber-type transformation in mouse skeletal muscle, and the improvement of mitochondrial morphology and antioxidant defense in response to endurance exercise may occur independently of PGC-1α function. We conclude that PGC-1α is required for complete skeletal muscle adaptations induced by endurance exercise in mice.
Human hephaestin expression is not limited to enterocytes of the gastrointestinal tract but is also found in the antrum, the enteric nervous system, and pancreatic β-cells
Authors: Hudson David M. , Curtis Susan B. , Smith Valerie C. , Griffiths Tanya A. M. , Wong Ann Y. K. , Scudamore Charles H. , Buchan Alison M. J. , MacGillivray Ross T. A.
Published: December 2009

Hephaestin (Hp) is a membrane protein with ferroxidase activity that converts Fe(II) to Fe(III) during the absorption of nutritional iron in the gut. Using anti-peptide antibodies to predicted immunogenic regions of rodent Hp, previous immunocytochemical studies in rat, mouse, and human gut tissues localized Hp to the basolateral membranes of the duodenal enterocytes where the Hp was predicted to aid in the transfer of Fe(III) to transferrin in the blood. We used a recombinant soluble form of human Hp to obtain a high-titer polyclonal antibody to Hp. This antibody was used to identify the intracellular location of Hp in human gut tissue. Our immunocytochemical studies confirmed the previous localization of Hp in human enterocytes. However, we also localized Hp to the entire length of the gastrointestinal tract, the antral portion of the stomach, and to the enteric nervous system (both the myenteric and submucous plexi). Hp was also localized to human pancreatic β-cells. In addition to its expression in the same cells as Hp, ferroportin was also localized to the ductal cells of the exocrine pancreas. The localization of the ferroxidase Hp to the neuronal plexi and the pancreatic β cells suggests a role for the enzymatic function of Hp in the protection of these specialized cell types from oxidative damage.
Physical activity and heart rate variability measured simultaneously during waking hours
Authors: Hautala Arto J. , Karjalainen Jaana , Kiviniemi Antti M. , Kinnunen Hannu , Mäkikallio Timo H. , Huikuri Heikki V. , Tulppo Mikko P.
Published: December 2009

Heart rate (HR) variability (HRV) during ambulatory recordings may be affected by individual differences in daily physical activity (PA). However, the influence of various levels of PA on different measures of HRV is not exactly known. We examined the association between simultaneously measured HRV and objective PA data obtained with an accelerometer during waking hours among 45 healthy adults. Bouts of PA were identified from minute-by-minute accelerometer data as metabolic equivalent (METs) values and calculated as mean METs for 30 min. HRV was analyzed concurrently. Within-individual correlation analyses and sign tests were performed to study the relationships between various HRV indexes and PA. The mean PA time was 15:44 ± 1:01 h, and the mean MET was 1.91 ± 0.14. HR and sample entropy, but not the other measures of HRV, had a significant relationship with PA, as shown by both correlation analyses ( r = 0.64, P = 0.021, and r = −0.55, P = 0.022, respectively) and sign tests ( P < 0.0001 for both). Beat-to-beat R-R interval fluctuation expressed as SD1 also demonstrated a significant relation to PA according to the sign test ( P = 0.037) and a trend of association according to the correlation analysis ( r = −0.40, P = 0.129). The complexity measure of HRV, in addition to average HR and the short-term index of HRV (SD1), is significantly influenced by the level of PA during ambulatory conditions. Long-term HRV indexes remained relatively stable at various activity levels, making them the most robust indexes for the assessment of cardiac autonomic function during free-running ambulatory conditions.
Lower energy cost of skeletal muscle contractions in older humans
Authors: Tevald Michael A. , Foulis Stephen A. , Lanza Ian R. , Kent-Braun Jane A.
Published: December 2009

Recent studies suggest that the cost of muscle contraction may be reduced in old age, which could be an important mediator of age-related differences in muscle fatigue under some circumstances. We used phosphorus magnetic resonance spectroscopy and electrically elicited contractions to examine the energetic cost of ankle dorsiflexion in 9 young (Y; 26 ± 3.8 yr; mean ± SD) and 9 older healthy men (O; 72 ± 4.6). We hypothesized that the energy cost of twitch and tetanic contractions would be lower in O and that this difference would be greater during tetanic contractions at f50(frequency at 50% of peak force from force-frequency relationship) than at 25 Hz. The energy costs of a twitch (O = 0.13 ± 0.04 mM ATP/twitch, Y = 0.18 ± 0.06; P = 0.045) and a 60-s tetanus at 25 Hz (O = 1.5 ± 0.4 mM ATP/s, Y = 2.0 ± 0.2; P = 0.01) were 27% and 26% lower in O, respectively, while the respective force·time integrals were not different. In contrast, energy cost during a 90-s tetanus at f50(O = 10.9 ± 2.0 Hz, Y = 14.8 ± 2.1 Hz; P = 0.002) was 49% lower in O (1.0 ± 0.2 mM ATP/s) compared with Y (1.9 ± 0.2; P < 0.001). Y had greater force potentiation during the f50protocol, which accounted for the greater age difference in energy cost at f50compared with 25 Hz. These results provide novel evidence of an age-related difference in human contractile energy cost in vivo and suggest that intramuscular changes contribute to the lower cost of contraction in older muscle. This difference in energetics may provide an important mechanism for the enhanced fatigue resistance often observed in older individuals.
Recovery of Motoneuron Output Is Delayed in Old Men Following High-Intensity Fatigue
Authors: Dalton Brian H. , Harwood Brad , Davidson Andrew W. , Rice Charles L.
Published: December 2009

Despite an age-related slowing in the contractile properties of the triceps surae, inherently low maximal motor unit firing rates (MUFRs) in the soleus are unchanged. Fatigue following high-intensity contractions is characterized by contractile slowing in conjunction with a reduction in MUFRs in young adults. Here we exploit the ageing model of the soleus to assess changes in neuromuscular function during fatigue and short-term recovery. We hypothesize that a high-intensity sustained contraction will cause minimal reductions in MUFRs in young and old subjects but that recovery of MUFRs will be delayed in aged subjects. We compared the effects of a high-intensity sustained task on the MUFRs of the soleus and triceps surae contractile properties in six young (∼24 yr) and six old (∼75 yr) men. Various measures of the contractile function of the triceps surae were tested during two to six sessions via maximal voluntary isometric contractions (MVCs) and tibial nerve stimulation. Populations of MUFR trains were recorded from the soleus during brief (∼7 s) MVCs, a high-intensity (75% MVC) sustained fatiguing task, and brief MVCs following task failure at 1, 2, 5, and 10 min. Old men had greater time to task failure than the young (∼138 and ∼100 s, respectively). Voluntary activation was near maximal (>99%) for all subjects but at task failure, decreased to ∼89% in both groups. Maximal MUFRs, for both groups, were reduced by ∼44% and twitch contraction duration slowed by ∼30% following task failure. Contraction duration recovered equally for both groups within 2 min, but maximal MUFRs did not recover until 5 min in the old compared with 1 min for the young. The surprising fatigue-induced reduction in MUFRs was similar for both groups, but despite a similar recovery of contractile properties for both, recovery of MUFRs was impaired in the old subjects.
Targeting the Hepcidin-Ferroportin Axis in the Diagnosis and Treatment of Anemias
Authors: Nemeth Elizabeta
Published: December 2009

The hepatic peptide hormone hepcidin regulates dietary iron absorption, plasma iron concentrations, and tissue iron distribution. Hepcidin acts by causing the degradation of its receptor, the cellular iron exporter ferroportin. The loss of ferroportin decreases iron flow into plasma from absorptive enterocytes, from macrophages that recycle the iron of senescent erythrocytes, and from hepatocytes that store iron, thereby lowering plasma iron concentrations. Malfunctions of the hepcidin-ferroportin axis contribute to the pathogenesis of different anemias. Deficient production of hepcidin causes systemic iron overload in iron-loading anemias such as beta-thalassemia; whereas hepcidin excess contributes to the development of anemia in inflammatory disorders and chronic kidney disease, and may cause erythropoietin resistance. The diagnosis of different forms of anemia will be facilitated by improved hepcidin assays, and the treatment will be enhanced by the development of hepcidin agonists and antagonists.
Electrochemical Estimation of the Corrosion Rate of Magnesium/Aluminium Alloys
Authors: Pardo A. , Feliu S. , Merino M. C. , Arrabal R. , Matykina E.
Published: December 2009

The corrosion rate of AZ31, AZ80, and AZ91D magnesium/aluminium alloys immersed in 3.5 wt.% NaCl was determined comparing gravimetric and electrochemical measurements. The findings revealed that, for all investigated materials, a fraction of the metallic surface exposed to the corrosive medium did not reveal a normal electrochemical response to the applied signal. This may be associated with phenomena such as partial disintegration of specimens into fine metallic particles, electrochemical formation of ions, and/or anomalous chemical attack occurring simultaneously with the normal electrochemical corrosion attack. The abnormal electrochemical behaviour was more evident for lower amounts of aluminium in the bulk composition of the investigated materials. Thus, the electrochemical estimates of pure Mg and the AZ31 alloy were not reliable and tended to underestimate corrosion losses.
Maternal Genitourinary Infection Appears to Synergistically Increase the Risk of Epilepsy in Children of Women with Epilepsy
Authors: McDermott Suzanne , Mann Joshua R. , Wu Junlong
Published: December 2009

Background: Evidence indicates that maternal genitourinary infection during pregnancy is associated with increased risk of epilepsy in children and that children of women with epilepsy are substantially more likely to have epilepsy themselves. Research is lacking on whether maternal genitourinary infection has a different effect on children of women with epilepsy compared to children of women without epilepsy. Methods: We conducted a retrospective cohort study using Medicaid data for 127,540 pregnancies, from 1996 to 2002, and children’s data through 2008. Maternal epilepsy, genitourinary infections, and child epilepsy were identified. Epilepsy was diagnosed in 1.7% of the children in the cohort. Results: There was a statistically significant interaction between maternal genitourinary infection and maternal epilepsy. Maternal genitourinary infection was strongly associated with increased risk of epilepsy in children of women with epilepsy (hazard ratio = 3.74, 95% CI = 1.67–8.40). Infection was more weakly associated with increased risk of epilepsy in children of women without epilepsy (hazard ratio = 1.23, 95% CI = 1.12–1.34). Conclusions: There is a significant association between genitourinary infection and childhood epilepsy, and the impact appears to be greater in children of women with epilepsy. This finding has implications for prenatal care of women with epilepsy as well as for research on antenatal risk factors for child epilepsy.
Comparative Analysis of Gene Expression in Rat Liver Tissue and Monolayer- and Spheroid-Cultured Hepatocytes
Authors: Sakai Yusuke , Yamagami Seita , Nakazawa Kohji
Published: December 2009

A culture system with spherical multicellular aggregates (spheroids), which are formed by the rearrangement and compaction of cell aggregates, is reported to be more useful than the traditional monolayer culture system for the culture of primary hepatocytes. By performing real-time polymerase chain reaction, we analyzed the expression of genes encoding key molecules involved in liver-specific functions, namely, cell adhesion molecules (integrin 3, cadherin 1 and connexin 32), transcription factors (hepatic nuclear factor 4α and CCAAT/enhancer-binding protein β), protein and metabolic enzymes (albumin, glucose-6-phosphatase, tryptophan 2,3-dioxygenase, arginase 1 and cytochrome P450 7A1) and transporters (organic anion transporting peptide 1, multidrug resistance-associated protein 2 and bile salt export pump), in spheroids derived from rat hepatocytes. Further, we compared these expression levels with those in a hepatocyte monolayer and in liver tissue. Only the gene encoding glucose-6-phosphatase (required for sugar metabolism) was expressed at a similar level in both the monolayer culture and liver tissue for 10 days of culture; the expression of all the other genes in the monolayer culture either rapidly decreased or completely disappeared as the culture duration increased. Although the expression levels of all the genes in the spheroids tended to decrease gradually with culture time, they were consistently higher than those in the monolayer culture for at least 10 days of culture. These results suggest that hepatocyte spheroids acquire intercellular organization and largely maintain many intercellular metabolic functions. Thus, the hepatocyte spheroid culture system seems to be promising for various in vitro cell-based assays.
Unique Modulation of Cadherin Expression Pattern during Posterior Frontal Cranial Suture Development and Closure
Authors: Sahar David E. , Behr Björn , Fong Kenton D. , Longaker Michael T. , Quarto Natalina
Published: December 2009

Cranial suture development involves coordinated expression of multiple genes and tissue contribution from neural crest cells and paraxial mesoderm for timely sutural morphogenesis. Transcription factors, growth factors, and neural crest determinant genes play critical roles in calvarial growth ensuring normal development of the underlying brain. In vitro studies have implicated cell-cell adhesion molecules as a driving force behind suture closure. We performed cDNA microarray to study differential expression of adhesion molecules during the timing of suture closure in a mouse model where only the posterior frontal (PF) suture closes. Our results indicate increased expression of E-cadherin during the period of PF suture closure. Quantitative RT-PCR analysis of E- and N-cadherin in PF closing suture revealed a biphasic expression of N-cadherin, the first phase coinciding with cellular condensation preceding chondrogenesis followed by a second phase coinciding with E-cadherin co-expression and suture closure. Furthermore, expression analysis of the N-cadherin and E-cadherin transcriptional repressors Wnt7a and Snail indicate a specific temporal regulation of these genes, suggesting their potential role as regulators of both E- and N-cadherin during the PF suture development and closure. Finally, given the in vitro evidence of fibroblast growth factor (FGF)-2 as a potential regulator of E- and N-cadherin we investigated the expression of E-cadherin during PF suture closure in Fgf-2 deficient mice. In contrast to in vitrodata previously reported, E-cadherin expression is normal in these animals, and PF suture closure occurs properly, probably due to potential redundancy of FGF ligands ensuring normal temporal expression of E-cadherin and PF suture closure.
Bioinformatic Analysis of Gene Sets Regulated by Ligand-Activated and Dominant-Negative Peroxisome Proliferator–Activated Receptor γ in Mouse Aorta
Authors: Keen Henry L. , Halabi Carmen M. , Beyer Andreas M. , de Lange Willem J. , Liu Xuebo , Maeda Nobuyo , Faraci Frank M. , Casavant Thomas L. , Sigmund Curt D.
Published: December 2009

Objective—

Drugs that activate peroxisome proliferator–activated receptor (PPAR) γ improve glucose sensitivity and lower blood pressure, whereas dominant-negative mutations in PPARγ cause severe insulin resistance and hypertension. We hypothesize that these PPARγ mutants regulate target genes opposite to those of ligand-mediated activation, and we tested this hypothesis on a genomewide scale.

Methods and Results—

We integrated gene expression data in aorta specimens from mice treated with the PPARγ ligand rosiglitazone with data from mice containing a globally expressed knockin of the PPARγ P465L dominant-negative mutation. We also integrated our data with publicly available data sets containing the following: (1) gene expression profiles in many human tissues, (2) PPARγ target genes in 3T3-L1 adipocytes, and (3) experimentally validated PPARγ binding sites throughout the genome. Many classic PPARγ target genes were induced by rosiglitazone and repressed by dominant-negative PPARγ. A similar pattern was observed for about 90% of the gene sets regulated by both rosiglitazone and dominant-negative PPARγ. Genes exhibiting this pattern of contrasting regulation were significantly enriched for nearby PPARγ binding sites.

Conclusion—

These results provide convincing evidence that the PPARγ P465L mutation causes transcriptional effects that are opposite to those mediated by PPARγ ligand, thus validating mice carrying the mutation as a model of PPARγ interference.
Hypoxia Triggers Subcellular Compartmental Redox Signaling in Vascular Smooth Muscle Cells
Authors: Waypa Gregory B. , Marks Jeremy D. , Guzy Robert , Mungai Paul T. , Schriewer Jacqueline , Dokic Danijela , Schumacker Paul T.
Published: December 2009

Rationale
:

Recent studies have implicated mitochondrial reactive oxygen species (ROS) in regulating hypoxic pulmonary vasoconstriction (HPV), but controversy exists regarding whether hypoxia increases or decreases ROS generation.

Objective
:

This study tested the hypothesis that hypoxia induces redox changes that differ among subcellular compartments in pulmonary (PASMCs) and systemic (SASMCs) smooth muscle cells.

Methods and Results
:

We used a novel, redox-sensitive, ratiometric fluorescent protein sensor (RoGFP) to assess the effects of hypoxia on redox signaling in cultured PASMCs and SASMCs. Using genetic targeting sequences, RoGFP was expressed in the cytosol (Cyto-RoGFP), the mitochondrial matrix (Mito-RoGFP), or the mitochondrial intermembrane space (IMS-RoGFP), allowing assessment of oxidant signaling in distinct intracellular compartments. Superfusion of PASMCs or SASMCs with hypoxic media increased oxidation of both Cyto-RoGFP and IMS-RoGFP. However, hypoxia decreased oxidation of Mito-RoGFP in both cell types. The hypoxia-induced oxidation of Cyto-RoGFP was attenuated through the overexpression of cytosolic catalase in PASMCs.

Conclusions
:

These results indicate that hypoxia causes a decrease in nonspecific ROS generation in the matrix compartment, whereas it increases regulated ROS production in the IMS, which diffuses to the cytosol of both PASMCs and SASMCs.
Noggin Protects Against Ischemic Brain Injury in Rodents
Authors: Samanta Jayshree , Alden Tord , Gobeske Kevin , Kan Lixin , Kessler John A.
Published: December 2009

Background and Purpose—

Bone morphogenetic proteins and their receptors are expressed in adult brains, and their expression levels increase after cerebral ischemia. The brain also expresses an inhibitor of bone morphogenetic protein signaling, noggin, but the role of noggin in ischemic disease outcome has not been studied.

Methods—

We used transgenic mice overexpressing noggin to assess whether inhibition of bone morphogenetic protein signaling affects ischemic injury responses after permanent middle cerebral artery occlusion.

Results—

Transgenic mice overexpressing noggin mice had significantly smaller infarct volumes and lower motor deficits compared to wild-type mice. CD11b
+
and IBA1
+
microglia along with oligodendroglial progenitors were significantly increased in transgenic mice overexpressing noggin mice at 14 days after permanent middle cerebral artery occlusion.

Conclusions—

These results provide genetic evidence that overexpression of noggin reduces ischemic brain injury after permanent middle cerebral artery occlusion via enhanced activation of microglia and oligodendrogenesis.
A Bilateral Perspective on the Digital Divide in South Africa
Authors: Blignaut Pieter
Published: December 2009

There is an awareness of the need for “access to technology,” and there are several initiatives by government, non-governmental organizations and other community development programs to fulfill this demand. The digital divide is, however, not only a matter of access; the challenge is also to empower people to become proficient computer users, even those with general literacy backlogs. People should become actively involved in order to stay computer literate. Demographic aspects such as age, gender, education and socio-economic status affect usage patterns and the gratification gained from Internet usage. The long-term solution to solve the problem of the digital divide is to uplift the socio-economic standard of a community.
“Should a country's leaders apologize for its past misdeeds?” An analysis of the effects of both public apologies from a Belgian official and perception of Congolese victims' continued suffering on Belgians' representations of colonial action, support for reparation, and attitudes towards the Congolese
Authors: Lastrego Simona , Licata Laurent
Published: December 2009

This study sought to identify the conditions facilitating the recognition of a social group's past misdeeds among its members. Such recognition entails a threat to group members' social identity, potentially triggering defensive strategies, such as denying these misdeeds, not experiencing collective guilt and shame, opposing reparative actions, and derogating the victim group's members. As collective rituals, public apologies performed by an official representative should allow group members to acknowledge the harm done while maintaining a positive social identity, therefore alleviating the need for such defensive strategies. We carried out an experimental study based on a 2 (Apologies vs. No apologies) × 2 (Continued suffering vs. No continued suffering) + 1 (Control) design, with Belgian participants (N = 164). In all conditions, participants were reminded of the atrocities committed during the first years of the Belgian colonization of Congo. This description was followed by a short statement about the suffering that Congolese people still endured (Continued suffering condition) or none (No continued suffering), then by a transcript of public apologies pronounced by Belgium's Foreign Affairs Minister in the Apologies condition, or none (No apologies). Results revealed that Belgian participants' attitudes and behavioural intentions towards the Congolese were the most positive when both apologies and the victims' continued suffering were reunited. A mediation analysis further demonstrated that differences in levels of racism and in support for reparation were mediated by representations of the ingroup's past.
Psychosocial effects of forgiveness petition and “self-criticism” by the Basque Government and Parliament directed to the victims of collective violence
Authors: Bobowik Magdalena , Bilbao M. Ángeles , Momoitio Joana
Published: December 2009

This experimental study analyses the psychosocial effects of apologies directed to the victims of collective violence by the Basque Government and Parliament on Basque participants. It was expected that institutional apology would lead to an increase in collective guilt, shame and sorrow, while at the same time it would induce a more positive perception of emotional climate, as well as increasing positive beliefs and support for reparative actions towards the victims. As expected, when reminded of apology and past collective violence, participants reported higher shame and sorrow and agreed more with new reparations in comparison with the control condition, in which people were only reminded of past collective violence. Low identifiers exhibited a more positive perception of the social climate in the apology condition than in the control group, whereas high identifiers displayed the opposite pattern. In addition, high identifiers agreed more with defensive opinions related to past collective violence and reported lower agreement with reparations, although they did not express less collective guilt, or shame and sorrow.
Plantar Vein Thrombosis—Evaluation by Ultrasound and Clinical Outcome
Authors: Lins Barros Marcio Vinicius , Labropoulos Nicos
Published: December 2009

Objective: This study was designed to describe the characteristics and clinical outcome of patients diagnosed with plantar vein thrombosis. Methods: Patients presenting with sudden pain and/or swelling of the foot were evaluated by duplex scanning of the affected leg. All the main foot veins were imaged with high resolution multi-linear array transducers. The location and extent of thrombosis was recorded in detail. All patients were scheduled for clinical and ultrasound follow-up within a week from the diagnosis and at various intervals thereafter. Results: Acute thrombosis was found in the plantar veins in 11 patients of whom 7 were females. Pain was presented in all patients, swelling in 8 and the left foot was involved in 7. From the risk factors evaluated, the most common were recent surgery 4, use of contraceptive pills 3, followed by malignancy, airplane travel, HIV-AIDS infection, and past history of DVT in one each. Plantar veins were exclusively affected in 8, with lower segment of the posterior tibial veins in 2 and the great saphenous vein in 1. In the follow up, there was evidence of thrombosis extension in 3 patients. At six months partial recanalization was found in 9 and complete in 2. Conclusions: Pain and swelling of the foot can be caused by plantar vein thrombosis. Complete or partial recanalization occurs in these patients by 6 months. Thrombi in the plantar veins can progress more proximally with the possibility of postthrombotic events.
Leg Pain in an Infant
Authors: Haile Jennifer T. , Carroll Vanessa G. , Steele Russell W.
Published: December 2009

Nonaccidental trauma can be difficult to differentiate from osteogenesis imperfecta (OI), especially in the face of multiple fractures. When nonaccidental trauma is being considered, medical causes of injury must be ruled out. In this report, we discuss the case of an 11-month-old female infant who presented with a transverse femur fracture and was also found to have a healing transverse humeral fracture and rib fractures. Medical causes of the fractures were investigated by performing an analysis of urine organic acids, serum amino acids, vitamin D, parathyroid hormone, ceruloplasmin, copper, and blood sequencing for COL1A1 and COL1A2. A mutation of the gene COL1A1 was found, which is consistent with OI type I.
Building the Case for Delivering Health Promotion Services Within the Vocational Rehabilitation System
Authors: Ipsen Catherine , Seekins Tom , Ravesloot Craig
Published: December 2009

Research studies report a negative relationship between employment and secondary conditions. Access to health promotion programs to manage secondary conditions, however, is limited for people with disabilities due to employment, financial, and insurance barriers. Vocational rehabilitation (VR) is one possible delivery point to overcome these barriers and improve access. To build the case for VR delivery, this article compares VR clients to Living Well health promotion program participants, who successfully reduced their secondary conditions. At baseline,VR ( n = 162) and Living Well ( n = 188) participants reported similar health promoting lifestyle behavior ratings and similar severity ratings across many secondary conditions. In addition, the VR group experienced similar rates of limitation from secondary conditions over time, indicating that their health was not improving in the absence of a health promotion intervention. Because health promotion programs can reduce secondary conditions, this research supports continued exploration of health promotion delivery within the VR system.
The U.S. Movement in Solidarity with Chile in the 1970s
Authors: Power Margaret
Published: December 2009

The international movement in solidarity with Chile that developed and flourished in the 1970s first emerged when the Unidad Popular government of Salvador Allende (1970—1973) was still in power but gained strength after the Chilean military overthrew the government and imposed the military dictatorship that ruled that country from 1973 to 1990. The power of the movement stems from the historical context in which it arose, the tremendous appeal exerted by the Allende government, North Americans’ familiarity with and support for the UP government, the outrage and horror many felt at the atrocities committed by the dictatorship, and the presence of Chilean political refugees in the United States. The work that the solidarity movement engaged in ranged from securing entry for political refugees and direct action against the Chilean ship Esmeralda to raising funds for the Chilean resistance through cultural programs. While political tensions among the refugees undermined the movement to a degree, the presence of the refugees brought their experience into the lives of North Americans and inspired them to support the Chilean resistance.
Heirs of Sandino
Authors: Perla Héctor
Published: December 2009

The 1979 triumph of the Sandinista Revolution and the Sandinista National Liberation Front’s resistance of U.S. efforts to oust it from power inspired thousands of individuals from all over the world to support Nicaragua’s struggle for self-determination. One of the most important constituencies to take up the Sandinista cause was a significant portion of the U.S. public. What moved this collection of individuals and organizations to join a movement to oppose their own government’s policy and often even identify with the Sandinista cause? To date Latin Americanists have neglected this movement and the role that Nicaraguans, both in their home country and in the United States, played in its rise and success. A transnational approach to the movement’s origins and its relationship to Nicaraguan revolutionary social forces allows one to understand it as it really was: a transnational social movement in which U.S. and Nicaraguan citizens acted together for a common purpose.
Mapping Chicago, Imagining Metropolises: Reconsidering the Zonal Model of Urban Growth
Authors: Lewinnek Elaine
Published: December 2009

Chicago’s early boosters, realtors, and urban planners mapped their city as a series of concentric circles. In 1924, sociologist Ernest Burgess extrapolated from these maps to project a model for America’s urban and suburban growth. Despite the persuasive power of Burgess’s zonal model, his own students’ grounded, unpublished work offers a countermodel of more diverse and contested suburbanization, including suburban vice, industry, retail, and class variations. Their alternative maps reinsert human power dynamics into what Chicago’s urban ecologists had promoted as inevitable and homogeneous suburbanization.
Sex Buffers Intimates Against the Negative Implications of Attachment Insecurity
Authors: Little Katherine C. , McNulty James K. , Russell V. Michelle
Published: December 2009

Contextual models of relationships and recent theories of attachment system activation suggest that experiences that promote intimacy, such as sexual intercourse, may moderate the negative implications of attachment insecurity. In two independent studies, 207 couples reported their attachment insecurity, the frequency of their sexual intercourse over the past 30 days, their expectancies for their partner’s availability, and their marital satisfaction, and in a 7-day diary they reported their daily sexual and relationship satisfaction and their expectancies for how satisfied they would be with their partners’ availability the next day. Attachment avoidance was unrelated to marital satisfaction among spouses reporting more frequent sex, and attachment anxiety was unrelated to marital satisfaction among spouses reporting more daily sexual satisfaction. Both effects were mediated by expectancies for partner availability. These findings suggest that the effects of attachment insecurity are not immutable but vary according to the context of the relationship.