bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetite Nanocrystal Clusters with Ultra‐High Sensitivity in Magnetic Resonance Imaging
Authors: Xu Fangjie , Cheng Changming , Chen Du‐Xing , Gu Hongchen 
Published: November 2011

AbstractMagnetic iron oxide particles are widely used as contrast agents to improve the sensitivity of magnetic resonance imaging (MRI). Their efficiency in MRI is usually quantified by transverse relaxivity (r2) in solution. Herein, we synthesized a series of magnetite nanocrystal clusters (MNCs) with ultra‐high transverse relaxivity by a polyol process and studied the relationship between r2 and size of the MNCs. The sizes of MNCs can be tuned over a wide range from 13 to 179 nm. The r2 of MNC suspensions as a function of the size of the cluster was analyzed and compared with a theoretical model. We found that MNCs of 64 nm had an r2 value of 650 mM−1 s−1, which was more than three times that of the commercial contrast agent and was among the highest reported for iron oxide materials. Compared with the theoretical model, the r2 value of the MNC suspension is approximately 0.93 of the theoretical prediction. Imaging of the MNC suspensions was performed in a clinical 1.5 T MRI instrument and a comparison was made between MNCs and commercial contrast agents. MRI indicated that the decrease of signal intensity induced by MNCs was in proportion to the r2 value, which was in accordance with theoretical predictions. These results demonstrate that MNCs with ultra‐high transverse relaxivity and tunable size are promising candidates for molecular imaging and clinical diagnosis in MRI.
Formic Acid Catalyzed Gas‐Phase Reaction of H2O with SO3 and the Reverse Reaction: A Theoretical Study
Authors: Long Bo , Long Zheng‐wen , Wang Yi‐bo , Tan Xing‐feng , Han Yu‐hua , Long Chao‐yun , Qin Shui‐jie , Zhang Wei‐jun 
Published: November 2011

AbstractThe formic acid catalyzed gas‐phase reaction between H2O and SO3 and its reverse reaction are respectively investigated by means of quantum chemical calculations at the CCSD(T)//B3LYP/cc‐pv(T+d)z and CCSD(T)//MP2/aug‐cc‐pv(T+d)z levels of theory. Remarkably, the activation energy relative to the reactants for the reaction of H2O with SO3 is lowered through formic acid catalysis from 15.97 kcal mol−1 to −15.12 and −14.83 kcal mol−1 for the formed H2O⋅⋅⋅SO3 complex plus HCOOH and the formed H2O⋅⋅⋅HCOOH complex plus SO3, respectively, at the CCSD(T)//MP2/aug‐cc‐pv(T+d)z level. For the reverse reaction, the energy barrier for decomposition of sulfuric acid is reduced to −3.07 kcal mol−1 from 35.82 kcal mol−1 with the aid of formic acid. The results show that formic acid plays a strong catalytic role in facilitating the formation and decomposition of sulfuric acid. The rate constant of the SO3+H2O reaction with formic acid is 105 times greater than that of the corresponding reaction with water dimer. The calculated rate constant for the HCOOH+H2SO4 reaction is about 10−13 cm3 molecule−1 s−1 in the temperature range 200–280 K. The results of the present investigation show that formic acid plays a crucial role in the cycle between SO3 and H2SO4 in atmospheric chemistry.
Inhibited Phenol Ionization in Reverse Micelles: Confinement Effect at the Nanometer Scale
Authors: Silva O. Fernando , Fernández Mariana A. , Silber Juana J. , de Rossi Rita H. , Correa N. Mariano 
Published: November 2011

AbstractWe found that the absorption spectra of 2‐acetylphenol (2‐HAP), 4‐acetylphenol (4‐HAP), and p‐nitrophenol (p‐NPh) in water/sodium 1,4‐bis(2‐ethylhexyl)sulfosuccinate (AOT)/n‐heptane reverse micelles (RMs) at various W0 (W0=[H2O]/[surfactant]) values studied changed with time if −OH ions were present in the RM water pool. There is an evolution of ionized phenol (phenolate) bands to nonionized phenol absorption bands with time and this process is faster at low W0 values and with phenols with higher bulk water pKa values. That is, in bulk water and at the hydroxide anion concentration used, only phenolate species are observed, whereas in AOT RMs at this fixed hydroxide anion concentration, ionized phenols convert into nonionized phenol species over time. Furthermore, we demonstrate that, independent of the −OH concentration used to prepare the AOT RMs, the nonionized phenols are the more stable species in the RM media. We explain our results by considering that strong hydrogen‐bonding interactions between phenols and the AOT polar head groups result in the existence of only nonionized phenols at the AOT RM interface. The situation is quite different when the phenols are dissolved in cationic benzyl‐n‐hexadecyldimethylammonium chloride RMs. Therein, only phenolates species are present at the −OH concentrations used. The results clearly demonstrate that the classical definition of pH does not apply in a confined environment, such as in the interior of RMs and challenge the general idea that pH can be determined inside RMs.
Influence of defects and impurities on the deteriorated border region in multicrystalline silicon ingots
Authors: Wu Shanshan , Wang Lei , Li Xiaoqiang , Wang Peng , Yang Deren , You Da , Du Jiabin , Zhang Tao , Wan Yuepeng 
Published: November 2011

AbstractThe origin of the lower minority carrier lifetime in the border region of multicrystalline silicon (mc‐Si) ingots was investigated. Based on minority carrier lifetime measurements and chemical analyses, distributions of defects and impurities were studied. It is found that the content of oxygen, carbon and other metal impurities in the border region were almost at the same level as that in the bulk, while the concentration of Fe‐B pairs is significantly higher. More interestingly, the dislocation density in the border region was observed to be much lower than that in the adjacent part. It is elucidated that the lower dislocation density in the border region leads to more iron existing in the form of Fe‐B pairs, which could be responsible for the low lifetime. In addition, it is shown that the low minority carrier lifetime in the border region can be improved effectively by phosphorous gettering. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Assembling Nanostructures for Effective Catalysis: Supported Palladium Nanoparticle Multicores Coated by a Hollow and Nanoporous Zirconia Shell
Authors: Wang Yanfei , Biradar Ankush V. , Asefa Tewodros 
Published: November 2011

AbstractWe report the synthesis and catalytic activities of highly stable, hollow nanoreactors, called SiO2/Pd/h‐ZrO2, which consist of silica microsphere (SiO2)‐supported Pd nanoparticle multicores (Pd) that are encapsulated with a hollow and nanoporous ZrO2 shell (h‐ZrO2). The SiO2/Pd/h‐ZrO2 nanoreactors are fabricated by first synthesizing SiO2/Pd/SiO2/ZrO2 microspheres, and then etching the inner SiO2 shell with dilute NaOH solution. The hollow and nanoporous ZrO2 shell of the nanoreactors serves two important functions: 1) it provides reactants direct access to the Pd nanoparticle multicores inside the SiO2/Pd/h‐ZrO2 nanoreactors during catalysis, and 2) it stabilizes the Pd nanoparticles or protects them from aggregation/sintering. The fabrication of such structures capable of protecting the Pd nanoparticles from aggregation/sintering is of particular interest considering the fact that Pd nanoparticles generally have a high tendency to aggregate because of their high surface energies. Furthermore, the structures are interesting because the Pd nanoparticles are designed and synthesized here to have ‘naked’ surfaces or no organic surface‐passivating ligands—that are often necessary to stabilize metallic nanoparticles—in order to increase their catalytic efficiency. The resulting SiO2/Pd/h‐ZrO2 nanoreactors show excellent catalytic activity, as shown in the hydrogenation of olefins and nitro groups, even at room temperature under moderate hydrogen pressure. This stems from the SiO2/Pd/h‐ZrO2 microspheres’ high surface area and their small, stable, and bare Pd nanoparticles. Furthermore, the SiO2/Pd/h‐ZrO2 nanoreactor catalysts remain fairly stable after reaction and can be recycled multiple times without losing their high catalytic activities.
Olive oil protects against 2,4‐dichlorophenoxyacetic acid‐induced oxidative renal dysfunction in adult rats
Authors: Nakbi Amel , Tayeb Wafa , Dabbou Samia , Chargui Issam , Issaoui Manel , Ferih Ameur , Ali Zohra Ben , Alsaif Mohammed A. , Hammami Mohamed 
Published: November 2011

AbstractThis study was aimed to evaluate the protective effect of extra virgin olive oil (EVOO) and its fractions (hydrophilic (HF) and lipophilic (LF)) treatment on 2,4‐dichlorophenoxiacetic acid (2,4‐D)‐induced nephrotoxicity in rats. The Wistar rats (n = 80, 210–230 g) were divided into eight groups having ten animals, i.e., control group (C), (2,4‐D) group that received 2,4‐D (5 mg/kg b.w.), (2,4‐D/EVOO) group was treated with 2,4‐D plus EVOO, (2,4‐D/olive oil hydrophilic fraction, OOHF) group that received 2,4‐D plus HF, (2,4‐D/olive oil lipophilic fraction, OOLF) group was treated with 2,4‐D plus LF, (EVOO) group that received only EVOO, (OOHF) group was given HF and (OOLF) group was treated with the LF. These components were administered daily by gavage for 4 wk. 2,4‐D administration affected plasma urea and creatinine levels, which increased while uric acid significantly decreased. A marked increase of malondialdehyde level and with a significant decrease in enzymatic antioxidant's activities, were also observed in 2,4‐D treated rats. The co‐administration of EVOO and its fractions along with 2,4‐D resulted in a reversal of 2,4‐D induced biochemical changes in kidney accompanied by a significant decrease in lipid peroxidation and an increase in the level of the antioxidant defence system. Light microscopy investigations revealed that 2,4‐D exposure induced numerous histopathological alterations in the kidney. EVOO administration with 2,4‐D severely reduced the toxicity of 2,4‐D and preserved the normal histological architecture of the renal tissue. However, a milder histopathological improvement was observed in animals co‐treated with HF or LF plus 2,4‐D. In conclusion, the present study suggest that the nephroprotective potential of EVOO against 2,4‐D toxicity might be due to the synergic effect of the two fractions, which could be useful for achieving optimum effects in 2,4‐D‐induced renal damage.
Beta‐cell injury in Ncb5or‐null mice is exacerbated by consumption of a high‐fat diet
Authors: Guo Ying , Xu Ming , Deng Bin , Frontera Jennifer R. , Kover Karen L. , Aires Daniel , Ding Helin , Carlson Susan E. , Turk John , Wang WenFang , Zhu Hao 
Published: November 2011

AbstractNADH‐cytochrome b5 oxidoreductase (Ncb5or) in endoplasmic reticulum (ER) is involved in fatty acid metabolism, and Ncb5or−/− mice fed standard chow (SC) are insulin‐sensitive but weigh less than wild‐type (WT) littermates. Ncb5or−/− mice develop hyperglycemia at about age 7 wk due to β‐cell dysfunction and loss in association with saturated fatty acid (SFA) accumulation and manifestations of ER and oxidative stress. Here we report that when Ncb5or−/− mice born to heterozygous mothers fed a high fat (HF) diet continue to ingest HF, they weigh as much as SC‐fed WT at age 5 wk. By age 7 wk, diabetes mellitus develops in all HF‐fed versus 68% of SC‐fed Ncb5or−/− mice. Islet β‐cell content in age 5‐wk Ncb5or−/− mice fed HF for 7 days is lower (53%) than for those fed SC (63%), and both are lower than for WT (75%, SC, vs. 69%, HF). Islet transcript levels for markers of mitochondrial biogenesis (PGC‐1α) and ER stress (ATF6α) are higher in Ncb5or−/− than WT mice but not significantly affected by diet. Consuming a HF diet exacerbates Ncb5or−/− β‐cell accumulation of intracellular SFA and increases the frequency of ER distention from 11% (SC) to 47% (HF), thus accelerates β‐cell injury in Ncb5or−/− mice.Practical applications: Lipid‐induced beta‐cell injury plays a key role in the etiology of diabetes but its mechanism is poorly understood. We have established a lean diabetes mouse model lacking Ncb5or, a redox enzyme that functions in cellular fatty acid metabolism. Ncb5or‐null mice develop early‐onset diabetes as a result of beta‐cell dysfunction and loss, which is associated with intracellular accumulation of saturated free fatty acids and elevated markers of ER and oxidative stress in beta‐cells. Consumption of a high fat diet partially restores body weight of Ncb5or‐null mice but accelerates onset of diabetes by exacerbating beta‐cell lipid overload and ER stress. This mouse model allows us to elucidate the role of fatty acid metabolism in beta‐cell function and maintenance.
Electrocatalytic Performance of Pd Nanoparticles Supported on SiC Nanowires for Methanol Oxidation in Alkaline Media
Authors: Tong X. , Dong L. , Jin G. , Wang Y. , Guo X.‐Y. 
Published: November 2011

AbstractPd nanoparticles (NPs) with a mean size of 10–12 nm are dispersed on the surface of SiC nanowires (NWs) by a cyclic voltammetric deposition method, and employed as an electrocatalyst for methanol oxidation. The high dispersion and small size of supported Pd NPs enable the catalyst to have an electrochemical active surface area of 49.5 m2 g–1, which is larger than that of carbon nanotube supported Pd NPs (38.6 m2 g–1), and that of non‐supported Pd NPs (29.9 m2 g–1). Methanol oxidation measurements show that the supported Pd NPs possess a high electrocatalytic activity and an excellent stability. These results indicate that SiC NWs have great potentials as an advantageous supporting material in alcohol fuel cells.
Sulfonated Aromatic Polyethers Containing Pyridine Units as Electrolytes for High Temperature Fuel Cells
Authors: Kalamaras I. , Daletou M. K. , Gregoriou V. G. , Kallitsis J. K. 
Published: November 2011

AbstractNovel sulfonated copolymers bearing main chain pyridine units have been synthesized for use as electrolytes in high temperature proton exchange membrane fuel cells (PEMFCs). The aim was to combine the excellent thermomechanical properties and high conductivity values after doping with phosphoric acid of these materials with the ability of the sulfonic groups to absorb and retain water and finally to examine the effect on the proton conduction ability. The resulted copolymers showed excellent film forming properties, mechanical integrity, and high glass transition temperatures (Tg > 300 °C). The Tg of the sulfonated copolymers is strongly affected by the sulfonated group content in the polymer backbone due to the acid base interactions of the pyridine and sulfonated groups. Furthermore, the membranes exhibited remarkable oxidative stability and presented proton conductivities in the range of 10–2 S cm–1.
Homozygosity mapping identifies a bile acid biosynthetic defect in an adult with cirrhosis of unknown etiology
Authors: Molho-Pessach Vered , Rios Jonathan J. , Xing Chao , Setchell Kenneth D.R. , Cohen Jonathan C. , Hobbs Helen H. 
Published: November 2011

Abstract

The most common inborn error of bile acid metabolism is 3β-hydroxy-Δ5-C27-steroid oxidoreductase (3β-HSD) deficiency, a disorder that usually presents in early childhood with hepatic dysfunction. Timely diagnosis of this disorder is crucial because it can be effectively treated with primary bile acid replacement. Here we describe a 24-year-old woman from Iran with cirrhosis of unknown etiology. Her sister and a first cousin died of cirrhosis (ages 19 and 6 years) and another 32-year-old first cousin had a self-limited liver disorder in childhood that resolved at age 9 years. The family history suggested that the affected family members were homozygous for a mutant allele inherited identical-by-descent. A genome-wide analysis of 2.4 million single nucleotide polymorphisms was performed to identify regions of homozygosity that were present in the proband and the 32-year-old first cousin, but not in a healthy relative. One of these regions contained the gene encoding 3β-HSD (HSD3B7). Sequence analysis of HSD3B7 revealed that the proband and her 32-year-old cousin were homozygous for a frameshift mutation (c.45_46del AG, p.T15Tfsx27) in exon 1. The diagnosis of 3β-HSD deficiency was confirmed by documenting high levels of 3β-hydroxy-Δ5 bile acids in the serum of the proband and the 32-year-old first cousin using mass spectrometry. To our knowledge, the 32-year-old relative in this family represents the oldest asymptomatic patient with this disorder. Conclusion: This study highlights the clinical utility of homozygosity mapping in diagnosing autosomal recessive metabolic disorders. This family illustrates the wide variation in expressivity that occurs in 3β-HSD deficiency and underscores the need to consider a bile acid synthetic defect as a possible cause of liver disease in adults. (Hepatology 2012)
Hepatic ratio of phosphatidylcholine to phosphatidylethanolamine predicts survival after partial hepatectomy in mice
Authors: Ling Ji , Chaba Todd , Zhu Lin-Fu , Jacobs René L. , Vance Dennis E. 
Published: November 2011

Abstract

A major predictor of failed liver resection and transplantation is nonalcoholic fatty liver disease (NAFLD). NAFLD is linked to a wide spectrum of diseases including obesity and diabetes that are increasingly prevalent in Western populations. Thus, it is important to develop therapies aimed at improving posthepatectomy outcomes in patients with NAFLD, as well as to improve the evaluation of patients slated for hepatic surgery. Decreased hepatic phosphatidylcholine (PC) content and decreased ratio of hepatic PC to phosphatidylethanolamine (PE) have previously been linked to NAFLD. To determine if decreased hepatic PC/PE could predict survival after hepatectomy, we used mouse models lacking key enzymes in PC biosynthesis, namely, phosphatidylethanolamine N-methyltransferase and hepatic-specific CTP:phosphocholine cytidylyltransferase α. These mice were fed a high-fat diet to induce NAFLD. We then performed a 70% partial hepatectomy and monitored postoperative survival. We identified hepatic PC/PE to be inversely correlated with the development of steatosis and inflammation in the progression of NAFLD. Decreased hepatic PC/PE before surgery was also strongly associated with decreased rates of survival after partial hepatectomy. Choline supplementation to the diet increased hepatic PC/PE in Pemt
−/− mice with NAFLD, decreased inflammation, and increased the survival rate after partial hepatectomy. Conclusion: Decreased hepatic PC/PE is a predictor of NAFLD and survival following partial hepatectomy. Choline supplementation may serve as a potential therapy to prevent the progression of NAFLD and to improve postoperative outcome after liver surgery. (Hepatology 2012)
Lysine acetylation induced by chronic ethanol consumption impairs dynamin-mediated clathrin-coated vesicle release
Authors: Shepard Blythe D. , Tuma Dean J. , Tuma Pamela L. 
Published: November 2011

Abstract

The liver is the major site of ethanol metabolism and thus sustains the most injury from chronic alcohol consumption. Ethanol metabolism by the hepatocyte leads to the generation of reactive metabolites and oxygen radicals that can readily adduct DNA, lipids, and proteins. More recently, it has become apparent that ethanol consumption also leads to increased post-translational modifications of the natural repertoire, including lysine hyperacetylation. Previously, we determined that alcohol consumption selectively impairs clathrin-mediated internalization in polarized hepatocytes. However, neither the step at which the block occurs nor the mechanism responsible for the defect have been identified. To identify the specific step at which clathrin-mediated internalization is impaired, we examined the distributions, levels, and assembly of selected components of the clathrin machinery in control and ethanol-treated cells. To determine whether the impairment is caused by ethanol-induced lysine acetylation, we also examined the same coat components in cells treated with trichostatin A (TSA), a deacetylase inhibitor that leads to protein hyperacetylation in the absence of ethanol. Conclusion: We determined that both ethanol and TSA impair internalization at a late stage before vesicle fission. We further determined that this defect is likely the result of decreased dynamin recruitment to the necks of clathrin-coated invaginations resulting in impaired vesicle budding. These results also raise the exciting possibility that agents that promote lysine deacetylation may be effective therapeutics for the treatment of alcoholic liver disease. (Hepatology 2012)
Hepatitis C viral kinetics with the nucleoside polymerase inhibitor mericitabine (RG7128)
Authors: Guedj Jeremie , Dahari Harel , Shudo Emi , Smith Patrick , Perelson Alan S. 
Published: November 2011

Abstract

Mericitabine (RG7128) is a nucleoside polymerase inhibitor (NPI), which requires intracellular uptake and phosphorylation to two active triphosphates. Mathematical modeling has provided important insights for characterizing hepatitis C virus (HCV) RNA decline and estimating in vivo effectiveness of antiviral agents; however, it has not been used to characterize viral kinetics with NPIs. HCV RNA was frequently measured in 32 treatment-experienced patients infected with HCV genotype 1 during and after mericitabine monotherapy for 14 days with 750 mg or 1500 mg administered once (qd) or twice daily (bid). The initial decline of HCV RNA was typically slower than with interferon-α or protease inhibitors, and 12 patients presented a novel pattern of HCV RNA kinetics characterized by a monophasic viral decline. Viral kinetics could be well fitted by assuming that the effectiveness in blocking viral production gradually increased over time to reach its final value, ε2, consistent with previous accumulation time estimates of intracellular triphosphates. ε2 was high with bid dosing (mean 750 mg and 1500 mg: 98.0% and 99.8%, respectively; P = 0.018) and significantly higher than in patients treated qd (mean qd versus bid: 90% versus 99%, P < 10−7). Virus rebounded rapidly upon drug discontinuation, which was attributed to the elimination of active drug and the subsequent decline of drug effectiveness, with mean t1/2 = 13.9 hours in the bid regimens. Conclusion: The observed slower initial decline likely represents the time needed to accumulate intracellular triphosphates and is consistent with in vitro data. When administered bid, mericitabine reached a high, dose-dependent, final effectiveness in blocking viral production that rapidly dropped upon treatment cessation. Understanding HCV RNA kinetics with mericitabine could provide valuable insights for combining it with other direct-acting antiviral agents. (Hepatology 2012)