bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Noble‐Metal‐Free System for Photocatalytic Hydrogen Production from Water
Authors: Mejía Esteban , Luo Shu‐Ping , Karnahl Michael , Friedrich Aleksej , Tschierlei Stefanie , Surkus Annette‐Enrica , Junge Henrik , Gladiali Serafino , Lochbrunner Stefan , Beller Matthias 
Published: October 2013

AbstractA series of heteroleptic copper(I) complexes with bidentate $\widehat{PP}$ and $\widehat{NN}$ chelate ligands was prepared and successfully applied as photosensitizers in the light‐driven production of hydrogen, by using [Fe3(CO)12] as a water‐reduction catalyst (WRC). These systems efficiently reduces protons from water/THF/triethylamine mixtures, in which the amine serves as a sacrificial electron donor (SR). Turnover numbers (for H) up to 1330 were obtained with these fully noble‐metal‐free systems. The new complexes were electrochemically and photophysically characterized. They exhibited a correlation between the lifetimes of the MLCT excited state and their efficiency as photosensitizers in proton‐reduction systems. Within these experiments, considerably long excited‐state lifetimes of up to 54 μs were observed. Quenching studies with the SR, in the presence and absence of the WRC, showed that intramolecular deactivation was more efficient in the former case, thus suggesting the predominance of an oxidative quenching pathway.
Preparation of Excitation‐Independent Photoluminescent Graphene Quantum Dots with Visible‐Light Excitation/Emission for Cell Imaging
Authors: Chen Shuai , Hai Xin , Xia Chang , Chen Xu‐Wei , Wang Jian‐Hua 
Published: October 2013

AbstractWe report the first pyrrole‐ring surface‐functionalized graphene quantum dots (p‐GQDs) prepared by a two‐step hydrothermal approach under microwave irradiation in an ammonia medium. The most distinct feature of the functionalized GQDs is that both the excitation and emission wavelengths fall into the visible‐light region. The p‐GQDs are excited by visible light at λex 490 nm (2.53 eV) to emit excitation‐independent photoluminescence at a maximum wavelength of λem 550 nm. This is thus far the longest emission wavelength reported for GQDs. Stable photoluminescence is achieved at pH 4–10 with an ionic strength of 1.2 mol L−1 KCl. These features make the p‐GQDs excellent probes for bio‐imaging and bio‐labeling, which is demonstrated by imaging live HeLa cells.
Spin‐Crossover Complex on Au(111): Structural and Electronic Differences Between Mono‐ and Multilayers
Authors: Gopakumar Thiruvancheril G. , Bernien Matthias , Naggert Holger , Matino Francesca , Hermanns Christian F. , Bannwarth Alexander , Mühlenberend Svenja , Krüger Alex , Krüger Dennis , Nickel Fabian , Walter Waldemar , Berndt Richard , Kuch Wolfgang , Tuczek Felix 
Published: October 2013

AbstractSubmono‐, mono‐ and multilayers of the Fe(II) spin‐crossover (SCO) complex [Fe(bpz)2(phen)] (bpz=dihydrobis(pyrazolyl)borate, phen=1,10‐phenanthroline) have beenprepared by vacuum deposition on Au(111) substrates and investigated with near edge X‐ray absorption fine structure (NEXAFS) spectroscopy and scanning tunneling microscopy (STM). As evidenced by NEXAFS, molecules of the second layer exhibit a thermal spin crossover transition, although with a more gradual characteristics than in the bulk. For mono‐ and submonolayers of [Fe(bpz)2(phen)] deposited on Au(111) substrates at room temperature both NEXAFS and STM indicate a dissociation of [Fe(bpz)2(phen)] on Au(111) into four‐coordinate complexes, [Fe(bpz)2], and phen molecules. Keeping the gold substrate at elevated temperatures ordered monolayers of intact molecules of [Fe(bpz)2(phen)] are formed which can be spin‐switched by electron‐induced excited spin‐state trapping (ELIESST).
Design and Synthesis of Lipidic Organoalkoxysilanes for the Self‐Assembly of Liposomal Nanohybrid Cerasomes with Controlled Drug Release Properties
Authors: Liang Xiaolong , Li Xiaoda , Jing Lijia , Xue Peng , Jiang Lingdong , Ren Qiushi , Dai Zhifei 
Published: October 2013

AbstractThis paper reports the facile design and synthesis of a series of lipidic organoalkoxysilanes with different numbers of triethoxysilane headgroups and hydrophobic alkyl chains linked by glycerol and pentaerythritol for the construction of cerasomes with regulated surface siloxane density and controlled release behavior. It was found that the number of triethoxysilane headgroups affected the properties of the cerasomes for encapsulation efficiency, drug loading capacity, and release behavior. For both water‐soluble doxorubicin (DOX) and water‐insoluble paclitaxel (PTX), the release rate from the cerasomes decreased as the number of triethoxysilane headgroups increased. The slower release rate from the cerasomes was attributed to the higher density of the siloxane network on the surface of the cerasomes, which blocks the drug release channels. In contrast to the release results with DOX, the introduction of one more hydrophobic alkyl chain into the cerasome‐forming lipid resulted in a slower release rate of PTX from the cerasomes due to the formation of a more compact cerasome bilayer. An MTT viability assay showed that all of these drug‐loaded cerasomes inhibited proliferation of the HepG2 cancer cell line. The fine tuning of the chemical structure of the cerasome‐forming lipids would foster a new strategy to precisely regulate the release rate of drugs from cerasomes.
ZnSe Etching of Zn‐Rich Cu2ZnSnSe4: An Oxidation Route for Improved Solar‐Cell Efficiency
Authors: López‐Marino Simón , Sánchez Yudania , Placidi Marcel , Fairbrother Andrew , Espindola‐Rodríguez Moisés , Fontané Xavier , Izquierdo‐Roca Víctor , López‐García Juan , Calvo‐Barrio Lorenzo , Pérez‐Rodríguez Alejandro , Saucedo Edgardo 
Published: October 2013

AbstractCu2ZnSnSe4 kesterite compounds are some of the most promising materials for low‐cost thin‐film photovoltaics. However, the synthesis of absorbers for high‐performing devices is still a complex issue. So far, the best devices rely on absorbers grown in a Zn‐rich and Cu‐poor environment. These off‐stoichiometric conditions favor the presence of a ZnSe secondary phase, which has been proved to be highly detrimental for device performance. Therefore, an effective method for the selective removal of this phase is important. Previous attempts to remove this phase by using acidic etching or highly toxic organic compounds have been reported but so far with moderate impact on device performance. Herein, a new oxidizing route to ensure efficient removal of ZnSe is presented based on treatment with a mixture of an oxidizing agent and a mineral acid followed by treatment in an aqueous Na2S solution. Three different oxidizing agents were tested: H2O2, KMnO4, and K2Cr2O7, combined with different concentrations of H2SO4. With all of these agents Se2− from the ZnSe surface phase is selectively oxidized to Se0, forming an elemental Se phase, which is removed with the subsequent etching in Na2S. Using KMnO4 in a H2SO4‐based medium, a large improvement on the conversion efficiency of the devices is observed, related to an improvement of all the optoelectronic parameters of the cells. Improvement of short‐circuit current density (Jsc) and series resistance is directly related to the selective etching of the ZnSe surface phase, which has a demonstrated current‐blocking effect. In addition, a significant improvement of open‐circuit voltage (Voc), shunt resistance (Rsh), and fill factor (FF) are attributed to a passivation effect of the kesterite absorber surface resulting from the chemical processes, an effect that likely leads to a reduction of nonradiative‐recombination states density and a subsequent improvement of the p–n junction.
Organic Chemistry of Graphene: The Diels–Alder Reaction
Authors: Denis Pablo A. 
Published: October 2013

AbstractHerein, by using dispersion‐corrected density functional theory, we investigated the Diels–Alder chemistry of pristine and defective graphene. Three dienes were considered, namely 2,3‐dimethoxy‐1,3‐butadiene (DMBD), 9‐methylanthracene (9MA), and 9,10‐dimethylanthracene (910DMA). The dienophiles that were assayed were tetracyanoethylene (TCNE) and maleic anhydride (MA). When pristine graphene acted as the dienophile, we found that the cycloaddition products were 47–63 kcal mol−1 less stable than the reactants, thus making the reaction very difficult. The presence of Stone–Wales translocations, 585 double vacancies, or 555‐777 reconstructed double vacancies did not significantly improve the reactivity because the cycloaddition products were still located at higher energy than the reactants. However, for the addition of 910DMA to single vacancies, the product showed comparable stability to the separated reactants, whereas for unsaturated armchair edges the reaction was extremely favorable. With regards the reactions with dienophiles, for TCNE, the cycloaddition product was metastable. In the case of MA, we observed a reaction product that was less stable than the reactants by 50 kcal mol−1. For the reactions between graphene as a diene and the dienophiles, we found that the most‐promising defects were single vacancies and unsaturated armchair edges, because the other three defects were much‐less reactive. Thus, we conclude that the reactions with these above‐mentioned dienes may proceed on pristine or defective sheets with heating, despite being endergonic. The same statement also applies to the dienophile maleic anhydride. However, for TCNE, the reaction is only likely to occur onto single vacancies or unsaturated armchair edges. We conclude that the dienophile character of graphene is slightly stronger than its behavior as a diene.
Spiropyran Photoswitches in the Context of DNA: Synthesis and Photochromic Properties
Authors: Brieke Clara , Heckel Alexander 
Published: October 2013

AbstractA new design is presented for the incorporation of spiropyran photoswitches into nucleic acids by oligonucleotide solid phase synthesis. This design enables interaction of the 6‐nitrospirobenzopyran (NitroBIPS) photoswitch with the adjacent nucleobases and leaves the photochemical properties of NitroBIPS intact. UV/Vis spectroscopy and HPLC revealed that NitroBIPS incorporated into DNA consists of up to 40 % merocyanine in its thermal equilibrium and undergoes reversible switching between the photoisomeric spiropyran (SP) and merocyanin (MC) state by alternating excitation using visible light or heat for at least fifteen switching cycles. Exchanging the chromene part of NitroBIPS on the DNA level gives access to differently substituted spiropyran derivatives allowing the screening for spiropyrans with suitable properties in a straightforward manner. Thus, by incorporating the highly hydrolysis‐stable pyrido‐spiropyran derivative PyBIPS pure light‐triggered reversible switching of a spiropyran in DNA has been realized for the first time. Therefore, this design represents a new useful platform for investigating the photochromic behavior of different spiropyran photoswitches in a nucleic acid environment and for using spiropyrans to induce light‐ or heat‐triggered changes in conformations or in fluorescence quenching properties of oligonucleotides.
A Platinum(II) Terpyridine Metallogel with an L‐Valine‐Modified Alkynyl Ligand: Interplay of Pt⋅⋅⋅Pt, π–π and Hydrogen‐Bonding Interactions
Authors: Po Charlotte , Ke Zhihai , Tam Anthony Yiu‐Yan , Chow Hak‐Fun , Yam Vivian Wing‐Wah 
Published: October 2013

AbstractA series of platinum(II) terpyridine complexes with L‐valine‐modified alkynyl ligands has been synthesized. A complex with an unsubstituted terpyridine and one valine unit on the alkynyl is shown to be capable of gel formation, which is in sharp contrast to the gelation properties of the corresponding organic counterparts. Upon sol–gel transition, a drastic color change from yellow to red is observed, which is indicative of the involvement of Pt⋅⋅⋅Pt interactions. Through the concentration‐ and temperature‐dependent UV/Vis absorption, emission, circular dichroism, and 1H NMR studies, the contribution of hydrogen bonding, Pt⋅⋅⋅Pt and π–π stacking interactions as driving forces for gelation have been established, and the importance of maintaining a delicate balance between different intermolecular forces has also been illustrated.
Improving air permeability of paper with acrylic and melamine resins
Authors: Ma Jinxia , Zhou Xiaofan , Zhang Dan , Xiao Huining 
Published: October 2013

AbstractA novel approach was developed to fabricate structures with high bulk from curled cellulosic material and to eliminate the pulp loss occurring in conventional mercerising pulp processes. Cellulose fibres treated with acrylic resin and melamine resin were curled as a result of the cross‐linking and solidification of the resins. The curled fibres brought about incompact structures of cellulose fibres with high air permeability of paper. Various influencing factors were investigated to control the air permeability of the substrates, including pulp consistency, resin amount and solidification temperature. The results showed that when the pulps at 30% consistency were treated with 10% (wt. on dry fibre) resin and solidified at 140°C, the resulting paper had similar or even better air permeability than that made from the mercerised pulps.
Ladder‐type Diindenopyrazine Based Conjugated Copolymers for Organic Solar Cells with High Open‐circuit Voltages
Authors: Chen Shanci , Tang Changquan , Yin Zhigang , Ma Yunlong , Cai Dongdong , Ganeshan Dhanavel , Zheng Qingdong 
Published: October 2013

AbstractA ladder‐type diindenopyrazine (IPY) was synthesized and used as a building block for constructing conjugated copolymers. Three copolymers based on the IPY moiety were obtained via the Suzuki coupling reaction with different monomers, including 4,7‐dithien‐2‐yl‐2,1,3‐benzothiadiazole (DBT), 5,8‐dithien‐2‐yl‐2,3‐diphenylquinoxaline (DTQ), and 5,8‐dithien‐2‐yl‐2,3‐di(4‐fluorophenyl)quinoxaline (DFTQ). The obtained polymers were characterized by 1H NMR spectroscopy, UV‐Vis absorption spectroscopy, cyclic voltammetry, and gel permeation chromatography (GPC). Owing to the four solubilizing alkyl chains on the IPY unit, all the three copolymers have good solubility in common solvents. These polymers have deep‐lying HOMO energy levels in the range of −5.55–−5.60 eV, and exhibit ?eld‐effect mobilities as high as 0.006 cm2·V−1·s−1. Photovoltaic applications of these polymers as light‐harvesting and hole‐conducting materials were investigated in conjunction with [6,6]‐phenyl‐C61‐butyric acid methyl ester (PC61BM). Both conventional and inverted devices were fabricated based on these three polymers. A power conversion efficiency (PCE) of 2.53% and a high open‐circuit voltage of 1.00 V were obtained under simulated solar light AM 1.5 G (100 mW/cm2) from an inverted solar cell with an active layer containing 25 wt% ladder‐type IPY containing copolymer (PIPYDTQ) and 75 wt% PC61BM. Moreover, a high open‐circuit voltage of 1.02 V and a PCE of 2.40% were achieved from a conventional solar cell based on PIPYDTQ.
Study of K/Mn‐MgO Supported Fe Catalysts with Fe(CO)5 and Fe(NO3)3 as Precursors for CO Hydrogenation to Light Alkenes
Authors: Tang Liping , Song Chengli , Li Mengli , Yang Xiaolong , Hu Bin 
Published: October 2013

AbstractTwo K/Mn‐MgO supported catalysts were prepared by Fe(CO)5 and Fe(NO3)3 as precursor respectively. The obtained Fe‐K/Mn‐MgO catalysts were tested for CO hydrogenation to light alkenes and characterized by X‐ray powder diffraction (XRD), X‐ray photoelectron spectra (XPS), H2 temperature‐programmed reduction (H2‐TPR), H2, CO and CO2 temperature‐programmed desorption (H2, CO/CO2‐TPD) and transmission electron microscope (TEM). The results indicated that the catalyst with 10 wt% Fe loading prepared by Fe(CO)5 as precursor showed better performance in syngas to light alkenes than ones obtained from Fe(NO3)3 as precursor, where the CO conversion was 62.50% and the selectivity was 55.95% at 350°C, 1.5 MPa and 1000 hminus;1, respectively.
Synthesis of New Substituted 4‐Amino‐3,5‐dinitropyridine Derivatives
Authors: Ma Congming , Wang Yongbin , Hou Kehui , Liu Zuliang , Yao Qizheng 
Published: October 2013

AbstractFacile synthetic routes for the preparation of some new 4‐amino‐3,5‐dinitropyridine derivatives have been revealed. Nitration of 2‐chloropyridin‐4‐amine (1) as a starting material, in an unexpected one‐step reaction, to give dinitrated derivatives, followed by nucleophilic substitution reactions with sodium azide, potassium fluoride, ammonia, methylamine, and 4‐nitroimidazol, respectively, gave substituted 4‐amino‐3,5‐dinitropyridine derivatives. Meanwhile, its azide derivative underwent a ring closure conversion into 7‐amino‐6‐nitro‐[1,2,5]oxadiazolo[3,4‐b]pyridine‐1‐oxide. It is of significance that all of the nucleophilic substitution reactions were carried out under mild conditions.
Postdischarge International Normalized Ratio Testing and Long‐term Clinical Outcomes of Patients With Heart Failure Receiving Warfarin: Findings From the ADHERE Registry Linked to Medicare Claims
Authors: Qualls Laura G. , Greiner Melissa A. , Eapen Zubin J. , Fonarow Gregg C. , Mills Roger M. , Klaskala Winslow , Hernandez Adrian F. , Curtis Lesley H. 
Published: October 2013

AbstractBackgroundEffective warfarin thromboprophylaxis requires maintaining anticoagulation within the recommended international normalized ratio (INR) range. INR testing rates and associations between testing and outcomes are not well understood.HypothesisINR testing rates after hospitalization for acute decompensated heart failure are suboptimal, and testing is associated with lower risks of mortality and adverse clinical events.MethodsWe conducted a retrospective cohort study of patients who were long‐term warfarin users and were hospitalized for heart failure, had a medical history of atrial fibrillation or valvular heart disease, and were enrolled in fee‐for‐service Medicare. INR testing was defined as ≥1 outpatient INR test within 45 days after discharge. Using Cox proportional hazards models, we examined associations between testing and all‐cause mortality, all‐cause readmission, and adverse clinical events at 1 year.ResultsAmong 8558 patients, 7722 (90.2%) were tested. After 1 year, tested patients had lower all‐cause mortality (23.5% vs 32.6%; P < 0.001) and fewer myocardial infarctions (2.0% vs 3.3%; P = 0.02). These differences remained significant after multivariable adjustment with hazard ratios of 0.72 (95% confidence interval [CI]: 0.63‐0.84; P < 0.001) and 0.58 (95% CI: 0.41‐0.83; P = 0.003), respectively. Differences in all‐cause readmission, thromboembolic events, ischemic stroke, and bleeding events were not statistically significant.ConclusionsPostdischarge outpatient INR testing in patients with heart failure complicated by atrial fibrillation or valvular heart disease was high. INR testing was associated with improved survival and fewer myocardial infarctions at 1 year but was not independently associated with other adverse clinical events.
Significance of Aortic Valve Calcification in Patients With Low‐Gradient Low‐Flow Aortic Stenosis
Authors: Aksoy Olcay , Cam Akin , Agarwal Shikhar , Ige Mobolaji , Yousefzai Rayan , Singh Dhssraj , Griffin Brian P. , Schoenhagen Paul , Kapadia Samir R. , Tuzcu Murat E. 
Published: October 2013

AbstractBackgroundAssessment of patients with aortic stenosis (AS) and impaired left ventricular function remains challenging. Aortic valve calcium (AVC) scoring with computed tomography (CT) and fluoroscopy has been proposed as means of diagnosing and predicting outcomes in patients with severe AS.HypothesisSeverity of aortic valve calcification correlates with the diagnosis of true severe AS and outcomes in patients with low‐gradient low‐flow AS.MethodsEchocardiography and CT database records from January 1, 2000 to September 26, 2009 were reviewed. Patients with aortic valve area (AVA) < 1.0 cm2 who had ejection fraction (EF) ≤ 25% and mean valvular gradient ≤ 25 mmHg with concurrent noncontrast CT scans were included. AVC was evaluated using CT and fluoroscopy. Mortality and aortic valve replacement (AVR) were established using the Social Security Death Index and medical records. The role of surgery in outcomes was evaluated.ResultsFifty‐one patients who met the above criteria were included. Mean age was 75.1 ± 9.6 years, and 15 patients were female. Mean EF was 21% ± 4.6% with AVA of 0.7 ± 0.1 cm2. The peak and mean gradients were 35.5 ± 10.6 and 19.0 ± 5.1 mmHg, respectively. Median aortic valve calcium score was 2027 Agatston units. Mean follow‐up was 908 days. Patients with calcium scores above the median value were found to have increased mortality (P = 0.02). The benefit of surgery on survival was more pronounced in patients with higher valvular scores (P = 0.001). Fluoroscopy scoring led to similar findings, where increased AVC predicted worse outcomes (P = 0.04).ConclusionsIn patients with low‐gradient low‐flow AS, higher valvular calcium score predicts worse long‐term mortality. AVR is associated with improved survival in patients with higher valve scores.
Racial disparities in functional disability among older women with newly diagnosed nonmetastatic breast cancer
Authors: Owusu Cynthia , Schluchter Mark , Koroukian Siran M. , Mazhuvanchery Suzanne , Berger Nathan A. 
Published: October 2013

BACKGROUNDThis study sought to assess racial differences in functional disability among older women with nonmetastatic breast cancer.METHODSIn this cross‐sectional study, between April 2008 and December 2012, women aged ≥ 65 years with newly diagnosed stage I through III breast cancer were recruited from ambulatory oncology clinics at an academic center. Prior to receiving any adjuvant treatment, participants completed a comprehensive geriatric assessment. The primary outcome was functional disability, defined as dependency in any basic or instrumental activity of daily living, categorized as “yes” or “no.” Logistic regression analyses were undertaken.RESULTSThe study enrolled 190 women whose mean age was 75.0 years at diagnosis (standard deviation=7.0, range=65‐93 years). Thirty‐two percent were African American (AA), and 39% had functional disability. Controlling for age, participants with functional disability were more likely to be AA (versus non‐Hispanic white), odds ratio=4.19, 95% confidence interval=2.12‐8.27. Fifty‐nine percent of the racial difference in functional disability was explained by a higher prevalence of lower income and education among AAs. In addition, the higher prevalence of chronic medical conditions and obesity among AAs, after accounting for socioeconomic factors, further explained 40% of the black–white difference in functional disability.CONCLUSIONSAmong older women with newly diagnosed nonmetastatic breast cancer, functional disability is highly prevalent, and AAs are disproportionately affected. Interventions to optimize the functional status of at‐risk individuals, particularly AAs, during and after cancer treatment may improve treatment tolerance and overall survival outcomes. Cancer 2013;119:3839–3846. © 2013 American Cancer Society.