bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Doped Transition Metal on Reversible Hydrogen Release/Uptake from NaAlH4
Authors: Liu Jianjun , Han You , Ge Qingfeng 
Published: December 2008

AbstractStorage facility: A dihydrogen complex formed in transition‐metal‐doped NaAlH4 was found to play important roles in hydrogen release/uptake (see figure). Electronic structure analysis revealed that the electron transfer between hydrogen and Al groups was mediated by the d orbitals of transition metals. Hydrogen release/uptake from the transition‐metal‐doped NaAlH4 was accompanied by an exchange of AlH and HH bond ligands through σ‐bond metathesis.magnified imagePeriodic density functional theory calculations with plane‐wave basis set and projector‐augmented wave potentials have been carried out to investigate the stability and hydrogen interaction in the NaAlH4(001) surfaces doped with 3d transition‐metal (TM) elements. A complex structure, TMAl3H12, in which the TM atom occupies the interstitial position formed from three AlH4− groups, is the most stable structure for TM=Sc to Co. The stability of the complex structure, as well as the hydrogen desorption energies from different positions of the complex structure, was found to follow the 18‐electron rule in general. The electron‐deficient TMAl3Hx tends to get more electrons by coordinating with the surrounding AlH bonds and HH bond, or by losing the “outside” hydrogen atoms. On the other hand, the electron‐rich complex loses its excess electrons easily by releasing AlHx, which resulted in the formation of a new catalytic center, or by desorbing H2. By cycling between the electron‐deficient and electron‐rich states, TMAl3Hx acted as an active center in reversible hydrogen release/uptake processes. Electronic structure analysis revealed that the electron transfer between hydrogen and Al groups mediated by the d orbitals of TMs played important roles in hydrogen release/uptake from alanate‐based materials. The exchange of ligands can be described as a σ‐bond metathesis process catalyzed by transition metals through a dihydrogen complex. Early transition metals are more efficient to reduce hydrogen desorption energy and break HH and AlH bonds as a result of balanced electron‐accepting/backdonating abilities, making them better candidates as catalysts. The present analyses are consistent with the experimental observations.
Bi2O3 Hierarchical Nanostructures: Controllable Synthesis, Growth Mechanism, and their Application in Photocatalysis
Authors: Zhou Lin , Wang Wenzhong , Xu Haolan , Sun Songmei , Shang Meng 
Published: December 2008

AbstractFlower power: Unique 3D flower‐like Bi2O3 hierarchical nanostructures were synthesized using a mild aqueous template‐free method (see figure). By introducing VO3− into the reaction system, which mediated the nucleation and growth of Bi2O3, the in situ self‐assembly of 3D hierarchitectures from 2D nanosheets has been realized.magnified imageBy introducing VO3− into the reaction system, uniform hierarchical nanostructures of Bi2O3 have been successfully synthesized by a template‐free aqueous method at 60–80 °C for 6 h. The as‐prepared hierarchitectures are composed of 2D nanosheets, which intercross with each other. Based on the electron microscope observations, the growth of such hierarchitectures has been proposed as an Ostwald ripening process followed by self‐assembly. The nucleation, growth, and self‐assembly of Bi2O3 nanosheets could be readily tuned, which brought different morphologies and microstructures to the final products. Pore‐size distribution analysis revealed that both mesopores and macropores existed in the product. UV‐vis spectroscopy was employed to estimate the band gap energies of the hierarchical nanostructures. The photocatalytic activities of as‐prepared Bi2O3 hierarchitectures were 6–10 times higher than that of the commercial sample, which was evaluated by the degradation of RhB dye under visible light irradiation (λ>420 nm).
Chemoselective Capture of Glycans for Analysis on Gold Nanoparticles: Carbohydrate Oxime Tautomers Provide Functional Recognition by Proteins
Authors: Thygesen Mikkel B. , Sauer Jørgen , Jensen Knud J. 
Published: December 2008

AbstractOpen or closed: N‐Glycosyl oxyamine versus open‐chain glycosyl oxime is the key to protein recognition on glyconanoparticles. Unprotected glycans are captured by oxime formation with a novel bifunctional reagent and the resulting glycan‐linker conjugates are anchored to gold nanoparticles (AuNPs). These glyconanoparticles maintain the structural integrity of glycans in the study of protein–carbohydrate interactions (see figure).magnified imageNanoparticles functionalized with glycans are emerging as powerful solid‐phase chemical tools for the study of protein–carbohydrate interactions using nanoscale properties for detection of binding events. Methods or reagents that enable the assembly of glyconanoparticles from unprotected glycans in two consecutive chemoselective steps with meaningful display of the glycan are highly desirable. Here, we describe a novel bifunctional reagent that 1) couples to glycans by oxime formation in solution, 2) aids in purification through a lipophilic trityl tag, and 3) after deprotection then couples to gold nanoparticles through a thiol. NMR studies revealed that these oximes exist as both the open‐chain and N‐glycosyl oxy‐amine tautomers. Glycan‐linker conjugates were coupled through displacement of ligands from preformed, citrate‐stabilized gold nanoparticles. Recognition of these glycans by proteins was studied with a lectin, concanavalin A (ConA), in an aggregation assay and with a processing enzyme and glucoamylase (GA). We demonstrate that the presence of the N‐glycosyl oxy‐amines clearly enables functional recognition in sharp contrast to the corresponding reduced oxy‐amines. This concept is then realized in a novel reagent, which should facilitate nanoglycobiology by enabling the operationally simple capture of glycans and their biologically meaningful display.
Stereoselective Hydrogenation of Olefins Using Rhodium‐Substituted Carbonic Anhydrase—A New Reductase
Authors: Jing Qing , Okrasa Krzysztof , Kazlauskas Romas J. 
Published: December 2008

AbstractOne useful synthetic reaction missing from nature's toolbox is the direct hydrogenation of substrates using hydrogen. Instead nature uses cofactors like NADH to reduce organic substrates, which adds complexity and cost to these reductions. To create an enzyme that can directly reduce organic substrates with hydrogen, researchers have combined metal hydrogenation catalysts with proteins. One approach is an indirect link where a ligand is linked to a protein and the metal binds to the ligand. Another approach is direct linking of the metal to protein, but nonspecific binding of the metal limits this approach. Herein, we report a direct hydrogenation of olefins catalyzed by rhodium(I) bound to carbonic anhydrase (CA‐[Rh]). We minimized nonspecific binding of rhodium by replacing histidine residues on the protein surface using site‐directed mutagenesis or by chemically modifying the histidine residues. Hydrogenation catalyzed by CA‐[Rh] is slightly slower than for uncomplexed rhodium(I), but the protein environment induces stereoselectivity favoring cis‐ over trans‐stilbene by about 20:1. This enzyme is the first cofactor‐independent reductase that reduces organic molecules using hydrogen. This catalyst is a good starting point to create variants with tailored reactivity and selectivity. This strategy to insert transition metals in the active site of metalloenzymes opens opportunities to a wider range of enzyme‐catalyzed reactions.
Bright, Color‐Tunable Fluorescent Dyes in the Vis/NIR Region: Establishment of New “Tailor‐Made” Multicolor Fluorophores Based on Borondipyrromethene
Authors: Umezawa Keitaro , Matsui Akihiro , Nakamura Yuki , Citterio Daniel , Suzuki Koji 
Published: December 2008

AbstractA new series of high‐performance fluorophores named Keio Fluors (KFL), which are based on borondipyrromethene (BODIPY), are reported. The KFL dyes cover a wide spectral range from the yellow (547 nm) to the near‐infrared (NIR, 738 nm) region, and their emission wavelength could be easily and subtly controlled based on simple molecular modifications only, without losing their optical properties. This “tailor‐made” synthetic strategy for tuning the emission wavelength enabled the creation of fourteen KFL dyes with well‐controlled emission colors (yellow, orange, red, far‐red, and NIR). Moreover, these KFL dyes also retain their excellent optical properties, such as spectral bands sharper than quantum dots, high extinction coefficients (140 000–316 000 M−1 cm−1), and high quantum yields (0.56–0.98), without any critical solvent polarity dependent decrease of their brightness. These advantageous characteristics make the KFL dyes potentially useful as new candidates of fluorescent standard dyes to substitute or to complement existing long‐wavelength fluorescent dyes, such as cyanines, oxazines, rhodamines, or other BODIPY dyes.
Effect of shaft eccentricity on the laminar mixing performance of a radial impeller
Authors: Cabaret F. , Fradette L. , Tanguy P.A. 
Published: December 2008

AbstractThe effects of impeller eccentricity and Reynolds number on the mixing performance were studied for Rushton turbine stirred tank systems operated in the laminar regime (Re < 10). A digital image analysis of an acid–base decolourization reaction was used to characterize the mixing efficiency. Results show that both parameters have remarkable effects on the destruction of the toroidal segregated regions surrounding the Rushton turbine in laminar flow. Criteria are given to prevent the formation of these segregated regions in a tank. It is also shown that shaft eccentricity does not impact on the impeller power consumption.
Synthesis of heterogeneous copper complex catalyst for oxidation of cyclohexane using molecular oxygen
Authors: Anisia K.S. , Kumar A. 
Published: December 2008

AbstractBinuclear macrocyclic copper complex was synthesized and bonded ionically to the montmorillonite clay to enhance thermal stability upto 600°C. The oxidation of cyclohexane using molecular oxygen in the absence of initiators, promoters and coreactants has been studied in the temperature range 145–190°C. The overall cyclohexane conversion was 21% at 180°C and cyclohexanone, the major product with 71% selectivity. The experimental data were analyzed against kinetic scheme proposed and the rate constants determined using Genetic Algorithm.
Notes on the issues of equilibrium in the Fischer–Tropsch synthesis
Authors: Norval Graeme W. 
Published: December 2008

AbstractThe product distribution for the Fischer–Tropsch synthesis is normally described using the kinetically derived (Anderson–Schultz–Flory) ASF model. Variations of the kinetic model have been proposed to explain deviations from the ASF distribution. The Fischer–Tropsch system can be equally well described using a pseudo‐element (CH2, H2, O) equilibrium approach. A one‐parameter equilibrium model is derived for the product distributions for alkenes, alkanes and alcohols.The Fischer–Tropsch system should be considered as three separate partial equilibria systems: the product homologous series; the water gas shift system, and the redox behaviour of the catalyst with the H2/O ratio of the gas. This approach correctly predicts the impacts of changes in a variety of parameters (temperature pressure, feed composition) on the ASF product distribution. In addition, the catalyst phase changes with gas composition and pressure, indicative of an equilibrium response. Equilibrium is of much greater importance to the Fischer–Tropsch system than previously thought, and the decision to use a complex kinetics‐based model rather than a simpler equilibrium based model should be taken with care.
Henry's law constant for hydrogen in high temperature water with dissolved lithium and boron
Authors: Giraudeau Franck , Lister Derek H. , Morris David R. , Setthanan Uncharat , Steward Frank R. , Yang Lei Tai 
Published: December 2008

AbstractThe results of measurement of the Henry's law constant are reported for solutions of H2 in H2O, with dissolved lithium and boron, at high temperature (220 to ∼300°C). The experimental procedure involved the use of a palladium/hydrogen electrical resistance sensor to determine the hydrogen gas pressure in equilibrium with the hydrogen dissolved in the water. Values of $K_{\rm H}^\infty$ for the above solutions were lower than values for the solute‐free H2/H2O solutions. For conditions typical of a Pressurized Water Reactor (PWR) the lowering amounted to about 3%.
Catalytic dehydration of lactic acid to acrylic acid over sulfate catalysts
Authors: Zhang Jinfeng , Lin Jianping , Cen Peilin 
Published: December 2008

AbstractThe production of acrylates from biomass‐originated lactic acid is of extraordinary importance to overcome the increasing worldwide shortage of petroleum. In this work, the catalytic dehydration of lactic acid to acrylic acid was carried out over calcium sulfate catalyst with cupric sulfate and phosphates as promoters. The mass ratio of m(CaSO4)/m(CuSO4)/m(Na2HPO4)/m(KH2PO4) is 150.0:13.8:2.5:1.2. In the dehydration of lactic acid, effects of carrier gas, calcination temperature for catalyst, concentration of lactic acid as well as contact time are discussed in detail. With carbon dioxide as carrier gas, the highest acrylic acid yield of 63.7% is achieved from 26 wt.% lactic acid at 330°C and 88 s contact time.
Measurement of sliding velocity and induction time of a single micro‐bubble under an inclined collector surface
Authors: Najafi Aref Seyyed , Xu Zhenghe , Masliyah Jacob 
Published: December 2008

AbstractIn this study, interactions between a gas bubble and a flat solid surface were investigated by determining two dynamic parameters, bubble sliding velocity underneath an inclined solid surface and induction time of the gas bubble attaching to the solid surface in aqueous solutions. A single micro‐bubble was allowed to move vertically toward an inclined solid surface. After reaching its terminal velocity, the bubble approaches the inclined solid surface and slides underneath it. Complete trajectory of the bubble movement was monitored and recorded by a high‐speed CCD video imaging system.Various types of gas bubbles (CO2, air, H2, and O2) and solid surfaces such as bitumen‐coated Teflon, hydrophobized and hydrophilic silica were used in sliding velocity and induction time measurements. The effect of water chemistry (industrial process water and de‐ionized water) and surface heterogeneity on bubble sliding velocity and induction time was investigated. The results showed that the sliding velocity of micro‐bubbles under an inclined solid surface is a strong function of water chemistry, gas type, temperature and hydrophobicity of the solid surface. This study provides relevant information on bubble–solid interactions that would assist in the understanding of bubble–solid attachment under diverse conditions.
Steam fingering at the edge of a steam chamber in a heavy oil reservoir
Authors: Gotawala Dharmesh R. , Gates Ian D. 
Published: December 2008

AbstractThe steam‐assisted gravity drainage (SAGD) process is one of the key in situ recovery processes being used today to recover heavy oil and bitumen. In this process, steam injected through a horizontal well, flows convectively towards the outer edges of a depletion chamber. At the edges of the depletion chamber, the steam releases its latent heat to the cool oil sand and raises its temperature. The heated oil is mobile and flows under the action of gravity to a horizontal production well located several metres below the injection well. It remains unclear what is the exact mechanism of chamber growth. Some have suggested that in addition to heat conduction, it is by convective steam flow in the form of pointed fingers at the edges of the chamber which penetrate the oil sand. In theory published by Butler [Butler, J. Can. Petroleum Technol. 1987;26(3):70–75], it was determined that the fingers can be as long as 6 m for Athabasca bitumen reservoirs. In this research, a new theory is derived and provides predictions of the rise rate which compare better to estimates derived from field thermocouple data and physical model experimental observations than values obtained from Butler's theory. The results suggest that in the absence of mobile water, heat conduction rather than steam fingers at the chamber edge is the dominant heat transfer mechanism.
Twenty‐four‐month postradiation prostate biopsies are strongly predictive of 7‐year disease‐free survival
Authors: Crook Juanita M. , Malone Shawn , Perry Gad , Eapen Libni , Owen Julie , Robertson Susan , Ludgate Charles , Fung Sharon , Lockwood Gina 
Published: December 2008

AbstractBACKGROUND:The objective of this study was to evaluate the predictive value of prostate biopsies that were obtained 24 months after the completion of radiotherapy (RT) with respect to disease‐free survival (DFS) in a randomized trial that compared 3 months versus 8 months of neoadjuvant hormone therapy before conventional dose external RT.METHODS:From February 1995 to June 2001, 378 men were randomized to receive either 3 months or 8 months of combined flutamide and goserelin before they received 66 Gray of RT at 4 participating centers. By risk group, 26% of patients were categorized as low risk, 43% were categorized as intermediate risk, and 31% were categorized as high risk. The 2 treatment arms were balanced in terms of age, Gleason score, clinical tumor classification, risk group, and presenting prostate‐specific antigen level. The median follow‐up for the patients who remained alive was 6.6 years (range, 1.6‐10.1 years). Of 361 evaluable patients, 290 patients remained alive. Post‐RT prostate biopsies were performed between 24 and 30 months after the completion of RT in 3 of the 4 centers. Biopsies that had residual tumor with severe treatment effect were considered indeterminate, and biopsies that had minimal or no treatment effect were considered positive.RESULTS:The 5‐year rate of actuarial freedom from any failure for the 3‐month arm versus the 8‐month arm was 72% versus 75% (P = .18). The DFS for patients who had negative and indeterminate biopsies was similar. Two‐year post‐treatment biopsy status was a strong predictor of 5‐year DFS rate (82% and 83% for negative and indeterminate biopsies, respectively, vs 27% for positive biopsies; P < .0001). Multivariate analysis indicated that biopsy status (P < .0001) and Gleason score (P < .0001) were the strongest determinates of biochemical DFS.CONCLUSIONS:Two‐year post‐RT prostate biopsies were strongly predictive of subsequent DFS. Biopsies with severe treatment effect were considered negative. Cancer 2009. © 2008 American Cancer Society.
Prevention of postoperative hypocalcemia with routine oral calcium and vitamin D supplements in patients with differentiated papillary thyroid carcinoma undergoing total thyroidectomy plus central neck dissection
Authors: Roh Jong‐Lyel , Park Jae‐Yong , Park Chan‐Il 
Published: December 2008

AbstractBACKGROUND:Routine oral calcium and vitamin D supplementation may prevent hypocalcemic crisis, but its efficacy has not been studied in patients undergoing thyroidectomy plus central neck dissection (CND). The authors therefore prospectively evaluated the clinical usefulness of routine oral calcium and vitamin D supplementation for prevention of hypocalcemia after total thyroidectomy and CND.METHODS:Of 197 patients with differentiated papillary thyroid carcinoma, 49 underwent total thyroidectomy alone, and 148 underwent total thyroidectomy plus CND. The latter were randomized to oral calcium (3 g/day) plus vitamin D (1 mg/day) (Group A, n = 49), calcium alone (Group B, n = 49), or no supplements (Group C, n = 50). Hypocalcemic symptoms, serum calcium, and parathyroid hormone (PTH) levels were compared among the groups.RESULTS:Group C had significantly higher incidences of symptomatic (26.0% vs 6.1%; P < .015) and laboratory (44.0% vs 14.3%; P < .015) hypocalcemia than the group without CND. The incidences of symptomatic and laboratory hypocalcemia were significantly decreased in Groups A (2.0% and 8.2%, respectively) and B (12.2% and 24.5%, respectively) (P < .05). Serum calcium levels decreased in most patients after surgery, but recovered earliest in Group A. Hypercalcemia and PTH inhibition did not occur in gs A and B.CONCLUSIONS:Compared with total thyroidectomy alone, CND significantly increases the rate of postoperative hypocalcemia, which can be prevented by routine postoperative supplementation with oral calcium and vitamin D. Cancer 2009. © 2009 American Cancer Society.
Benign breast lesions at risk of developing cancer—A challenging problem in breast cancer screening programs
Authors: Manfrin Erminia , Mariotto Renata , Remo Andrea , Reghellin Daniela , Falsirollo Francesca , Dalfior Daniela , Bricolo Paola , Piazzola Elena , Bonetti Franco 
Published: December 2008

AbstractBACKGROUND:Cytology and core‐needle biopsies are not always sufficient to exclude malignancy in benign breast lesions (BBL) that are at risk of developing cancer, and open biopsy often is mandatory. In screening programs, open biopsies performed for lesions that are at risk of developing malignancy are considered benign. The authors of this report evaluated the impact of the screen‐detected BBL at risk of developing cancer that were counted in the quota of benign breast open biopsies in the Breast Cancer Screening Program of Verona.METHODS:Benign open biopsies were subdivided into 4 groups according to their risk of developing cancer: Histo1, normal histology; Histo2, ‘pure’ BBL (fibroadenoma, fibrocystic disease, mastitis, adenosis); Histo3, BBL with a low risk of developing cancer (radial scar, papilloma, papillomatosis, phyllodes tumor, mucocele‐like lesion); and Histo4, BBL with a high risk of developing cancer (atypical columnar cell hyperplasia, atypical ductal hyperplasia, atypical lobular hyperplasia).RESULTS:Of 510 open biopsies, 83 biopsies were benign, and the ratio of benign to malignant biopsies was 1:5. Histo1 was observed in 4.8% of all benign open biopsies, Histo2 was observed in 37.4%, Histo3 was observed in 31.3%, and Histo4 was observed 26.5%.CONCLUSIONS:BBL at risk of developing cancer may be numerous in screening programs. It is inappropriate to include BBL at risk of developing cancer in the overall benign open biopsy rate. The authors propose separating pure BBL from lesions at higher risk of developing cancer. To date, there is no evidence to support the premise that detecting high‐risk proliferative lesions leads to benefits in terms of reduced mortality; however, these lesions need to be counted separately for future evaluations. Cancer 2009. © 2008 American Cancer Society.