bluuebunny/crossref_metadata_2025 huggingface dataset:
Opioid requirement, opioid receptor expression, and clinical outcomes in patients with advanced prostate cancer
Authors: Zylla Dylan , Gourley Brett L. , Vang Derek , Jackson Scott , Boatman Sonja , Lindgren Bruce , Kuskowski Michael A. , Le Chap , Gupta Kalpna , Gupta Pankaj
Published: October 2013

BACKGROUND

Preclinical studies show that opioids stimulate angiogenesis and tumor progression through the mu opioid receptor (MOR). Although MOR is overexpressed in several human malignancies, the effect of chronic opioid requirement on cancer progression or survival has not been examined in humans.

METHODS

We performed a retrospective analysis on 113 patients identified in the Minneapolis VA Tumor Registry (test cohort) and 480 patients from the national VA Central Cancer Registry (validation cohort) who had been diagnosed with stage IV prostate cancer between 1995 and 2010 to examine whether MOR expression or opioid requirement is associated with disease progression and survival. All opioids were converted to oral morphine equivalents for comparison. Laser scanning confocal microscopy was used to analyze MOR immunoreactivity in prostate cancer biopsies. The effects of variables on outcomes were analyzed in univariable and multivariable models.

RESULTS

In patients with metastatic prostate cancer, MOR expression and opioid requirement were independently associated with inferior progression‐free survival (hazard ratio [HR] 1.65, 95% confidence interval [CI] 1.33‐2.07, P<.001 and HR 1.08, 95% CI 1.03‐1.13, P<.001, respectively) and overall survival (HR 1.55, 95% CI 1.20‐1.99, P<.001 and HR 1.05, 95% CI 1.00‐1.10, P = .031, respectively). The validation cohort confirmed that increasing opioid requirement was associated with worse overall survival (HR 1.005, 95% CI 1.002‐1.008, P = .001).

CONCLUSION

Higher MOR expression and greater opioid requirement are associated with shorter progression‐free survival and overall survival in patients with metastatic prostate cancer. Nevertheless, clinical practice should not be changed until prospective randomized trials show that opioid use is associated with inferior clinical outcomes, and that abrogation of the peripheral activities of opioids ameliorates this effect. Cancer 2013;119:4103–4110. ©2013 American Cancer Society.
From multidisciplinary to personalized treatment of colorectal liver metastases: 4 reasons to consider RAS
Authors: Vauthey Jean‐Nicolas , Kopetz Scott E.
Published: October 2013

Recent studies point to the prognostic value of RAS mutations in patients undergoing resection of colorectal liver metastases. RAS mutation status now offers the option to predict outcome at presentation before response to chemotherapy. It is anticipated that molecular indicators of biological resectability will be increasingly recognized as a complement to the already well‐established criteria for technical resectability.
Periodic Homogenization of Green and Neumann Functions
Authors: Kenig Carlos , Lin Fanghua , Shen Zhongwei
Published: October 2013

For a family of second‐order elliptic operators with rapidly oscillating periodic coefficients, we study the asymptotic behavior of the Green and Neumann functions, using Dirichlet and Neumann correctors. As a result we obtain asymptotic expansions of Poisson kernels and the Dirichlet‐to‐Neumann maps as well as optimal convergence rates in Lp and W1,p for solutions with Dirichlet or Neumann boundary conditions. © 2014 Wiley Periodicals, Inc.
In vitro dissolution and in vivo bioequivalence evaluation of two brands of trimetazidine tablets
Authors: Helmy Sally A. , Mansour Noha O.
Published: October 2013

Trimetazidine is an effective anti‐anginal agent and anti‐ischaemic effect. The objective of this study was to assess the in vitro dissolution and to evaluate the bioavailability of two brands of trimetazidine dihydrochloride tablets. Prior to the in vivo PKs study, an in vitro comparative dissolution test was performed for 2 oral brands of trimetazidine dihydrochloride tablets (20 mg). In vivo PKs study was evaluated in 24 healthy male volunteers after a single dose oral administration in an open, randomized, two‐way crossover study with a washout period of 1 week. After an overnight fast, human volunteers were randomly allocated to receive a single dose of either test or reference product. Blood samples were collected over a 24‐hour period following drug administration and plasma was analyzed for trimetazidine concentrations using a validated high‐performance liquid chromatography assay method. The PK parameters Cmax, AUC0−t, AUC0−∞, tmax, and t1/2 were determined from plasma concentration‐time profiles. The 90% confidence intervals for the ratio of log transformed values of Cmax, AUC0−t, and AUCt−∞ of the test product over those of reference were within the acceptable range (0.8–1.25) for bioequivalence. As a result, the 2 trimetazidine formulations are considered bioequivalent and thus could be prescribed interchangeably in the medical practice based on its PK effect and biopharmaceutical performance.
Tin Oxide Nanoparticles and SnO2/SiO2 Hybrid Materials by Twin Polymerization Using Tin(IV) Alkoxides
Authors: Leonhardt Christian , Brumm Susann , Seifert Andreas , Cox Gerhard , Lange Arno , Rüffer Tobias , Schaarschmidt Dieter , Lang Heinrich , Jöhrmann Nathanael , Hietschold Michael , Simon Frank , Mehring Michael
Published: October 2013

Twin polymerization was used to prepare composite materials composed of SnO2 nanoparticles entrapped in a polymer matrix. Novel, well‐defined tin‐containing molecular precursors, so‐called twin monomers, were synthesized by transesterification starting from Sn(OR)4 (R=tBu, tAm) to give Sn(OCH2C4H3O)4 (1), [Sn(OCH2C4H3S)4⋅HOCH2C4H3S]2 (2), [Sn(OCH2‐2‐OCH3C6H4)4⋅HOCH2‐2‐OCH3C6H4]2 (3), [Sn(OCH2‐2,4‐(OCH3)2C6H3)4⋅HOCH2‐2,4‐(OCH3)2C6H3]2 (4), 2,2′‐spirobi[4H‐1,3,2‐benzodioxastannine] (5), 2,2′‐spirobi[6‐methylbenzo(4H‐1,3,2)‐dioxastannine] (6), and 2,2′‐spirobi[6‐methoxybenzo(4H‐1,3,2)dioxastannine] (7). 13C and 119Sn NMR spectroscopy in the solid state and in solution as well as IR spectroscopy and elemental analysis were used to characterize the tin alkoxides. The molecular structures of compounds 2 and 3 were determined by single‐crystal X‐ray diffraction analysis. The moisture sensitivity of the tin(IV) alkoxides was demonstrated by the formation of the tin oxocluster [Sn3(μ3‐O)(μ2‐OH)(μ2‐OCH2C4H3S)3(OCH2C4H3S)6(HOCH2C4H3S)]2 (2 a), a hydrolysis product of compound 2. Polymerization reactions in the melt (for 1 and 5) and in solution (for 2–4) resulted in cross‐linked nanocomposites of the type polymer/SnO2. Subsequent oxidation of the composites gave SnO2 with BET surface areas up to 178 m2 g−1. Simultaneous twin polymerization of compounds 5–7 with the silicon derivative 2,2′‐spirobi[4H‐1,3,2‐benzodioxasiline] resulted in the formation of polymer/SnO2/SiO2 hybrid materials. Oxidation gave porous materials with SnO2 nanoparticles embedded in a silica network with BET surface areas up to 378 m2 g−1. The silica acts as a crystal growth inhibitor, which prevents sintering of the SnO2 nanoparticles 20–32 nm in size.
Shape‐Controlled Ceria‐based Nanostructures for Catalysis Applications
Authors: Qiao Zhen‐An , Wu Zili , Dai Sheng
Published: October 2013

Among oxide catalysts, ceria is a technologically important material because of its wide applications as a promoter in three‐way catalysts for the elimination of toxic exhaust gases, low‐temperature water–gas‐shift reaction, oxygen sensors, oxygen permeation membrane systems, and fuel cells. The catalytic activities of cerium oxide are highly dependent on interfacial structures and nanocrystal morphologies. This Minireview highlights the recent progress in the research of ceria nanoshapes as both catalysts and catalyst supports, including the synthesis, structure characterization, catalytic properties, surface chemistry, as well as reaction mechanisms. Insights from in situ spectroscopy study and theoretical modeling of nanostructured ceria‐based materials have shed light on the origin of the ceria shape effect. It is suggested that the surface structure of ceria controls the catalytic activity and selectivity through structure‐dependent surface‐site geometry, surface vacancy formation energy, defect sites, and coordinatively unsaturated sites on ceria. The morphology‐dependent catalysis in ceria has offered a new strategy to finely tune the catalytic activity and selectivity through shape control without altering the catalyst composition. A brief summary and an outlook on this research field will be presented at the end.
The Effect of Lattice Strain on the Catalytic Properties of Pd Nanocrystals
Authors: Kuo Chun‐Hong , Lamontagne Leo K. , Brodsky Casey N. , Chou Lien‐Yang , Zhuang Jia , Sneed Brian T. , Sheehan Margaret K. , Tsung Chia‐Kuang
Published: October 2013

The effect of lattice strain on the catalytic properties of Pd nanoparticles is systematically studied. Synthetic strategies for the preparation of a series of shape‐controlled Pd nanocrystals with lattice strain generated from different sources has been developed. All of these nanocrystals were created with the same capping agent under similar reaction conditions. First, a series of Pd nanoparticles was synthesized that were enclosed in {111} surfaces: Single‐crystalline Pd octahedra, single‐crystalline AuPd core–shell octahedra, and twinned Pd icosahedra. Next, various {100}‐terminated particles were synthesized: Single‐crystalline Pd cubes and single‐crystalline AuPd core–shell cubes. Different extents of lattice strain were evident by comparing the X‐ray diffraction patterns of these particles. During electrocatalysis, decreased potentials for CO stripping and increased current densities for formic‐acid oxidation were observed for the strained nanoparticles. In the gas‐phase hydrogenation of ethylene, the activities of the strained nanoparticles were lower than those of the single‐crystalline Pd nanoparticles, perhaps owing to a larger amount of cetyl trimethylammonium bromide on the surface.
Exposed Surfaces on Shape‐Controlled Ceria Nanoparticles Revealed through AC‐TEM and Water–Gas Shift Reactivity
Authors: Agarwal Shilpa , Lefferts Leon , Mojet Barbara L. , Ligthart D. A. J. Michel , Hensen Emiel J. M. , Mitchell David R. G. , Erasmus Willem J. , Anderson Bruce G. , Olivier Ezra J. , Neethling Johannes H. , Datye Abhaya K.
Published: October 2013

Aberration‐corrected transmission electron microscopy and high‐angle annular dark field imaging was used to investigate the surface structures and internal defects of CeO2 nanoparticles (octahedra, rods, and cubes). Further, their catalytic reactivity in the water–gas shift (WGS) reaction and the exposed surface sites by using FTIR spectroscopy were tested. Rods and octahedra expose stable (111) surfaces whereas cubes have primarily (100) facets. Rods also had internal voids and surface steps. The exposed planes are consistent with observed reactivity patterns, and the normalized WGS reactivity of octahedra and rods were similar, but the cubes were more reactive. In situ FTIR spectroscopy showed that rods and octahedra exhibit similar spectra for OH groups and that carbonates and formates formed upon exposure to CO whereas for cubes clear differences were observed. These results provide definitive information on the nature of the exposed surfaces in these CeO2 nanostructures and their influence on the WGS reactivity.
Size matters: Filamentous bacteria drive interstitial vortex formation and colony expansion in Paenibacillus vortex
Authors: Vallotton Pascal
Published: October 2013

The beautiful patterns formed by motile bacteria have always intrigued the curious (Ben‐Jacob et al., Eur. Phys. J. B 2008;65:315–322). The mechanisms underlying their formation are believed to play a role in a range of natural phenomena, including embryogenesis, animal behavior, and economics. There has been significant effort to develop tools for characterizing the behavior of individual cells within large populations of migrating bacteria; a prerequisite for studying self‐organization in this context (Garner, Mol. Micro. 2011;80:577–579). Here, I apply powerful computer vision methods to study P. vortex interstitial colony expansion. Quantitative observations show how exceptionally long bacteria play a catalytic role—both in vortex formation, which had to date remained somewhat mysterious—and in facilitating colony expansion. This highlights the functional importance of bacterial morphology in bridging the microscopic and macroscopic scales, and it reshapes our understanding of vortex‐forming bacteria. © 2013 International Society for Advancement of Cytometry
Improvement of robust smart‐card‐based password authentication scheme
Authors: Jiang Qi , Ma Jianfeng , Li Guangsong , Li Xinghua
Published: October 2013

Smart‐card‐based password authentication scheme is one of the commonly used mechanisms to prevent unauthorized service and resource access and to remove the potential security threats over the insecure networks and has been investigated extensively in the last decade. Recently, Chen et al. proposed a smart‐card‐based password authentication scheme and claimed that the scheme can withstand offline password guessing attacks even if the information stored in the smart card is extracted by the adversary. However, we observe that the scheme of Chen et al. is insecure against offline password guessing attacks in this case. To remedy this security problem, we propose an improved authentication protocol, which inherits the merits of the scheme of Chen et al. and is free from the security flaw of their scheme. Compared with the previous schemes, our improved scheme provides more security guarantees while keeping efficiency. Copyright © 2013 John Wiley & Sons, Ltd.
Are food restriction and pressure‐to‐eat parenting practices associated with adolescent disordered eating behaviors?
Authors: Loth Katie A. , MacLehose Richard F. , Fulkerson Jayne A. , Crow Scott , Neumark‐Sztainer Dianne
Published: October 2013

Objective

To examine associations between parental pressure‐to‐eat and food restriction and adolescent disordered eating behaviors, within a sample of parent–adolescent pairs.

Method

Adolescents (N = 2,231) and their parents (N = 3,431) participated in two, coordinated, population‐based studies designed to examine factors associated with weight and weight‐related behaviors in adolescents.

Results

Overall, higher levels of pressure‐to‐eat or food restriction were significantly and positively associated with use of disordered eating behaviors among boys. For every one unit increase [Scale Range: 1 (low control) to 4 (high control)] in mothers' food restriction, boys were twice as likely to engage in extreme weight control behaviors (p ≤ .01). Examination of the association between food‐related parenting practices and disordered eating behaviors among girls revealed fewer significant associations. However, analyses revealed that for every one unit increase in mothers' food restriction, girls were 1.33 times more likely to engage in extreme weight control behaviors (p = .04).

Discussion

Study findings provide evidence of an association between controlling food‐related parenting practices and adolescent disordered eating behaviors, particularly in boys. Future longitudinal research is needed to establish directionality of observed associations. © 2013 Wiley Periodicals, Inc. (Int J Eat Disord 2014; 47:310–314)
Mitochondrial DNA inference between European populations of Tanymastix stagnalis and their glacial survival in Scandinavia
Authors: Arukwe Augustine , Langeland Arnfinn
Published: October 2013

The early observation from 1914 of Tanymastix stagnalis in Norway was not repeated recently, showing a rare and restricted distribution of this species. All four sampled localities were concentrated in the same area of the Trollheimen Mountains with altitudes of 900–1244 m above sea level. In March 2002, a new population of T. stagnalis was observed at about 50 km north of Madrid at an altitude of 1350 m. In general, all habitats with T. stagnalis were fishless shallow ponds and varied in size from 1 to about 300 m2. Natural variability of the global temperature is well accepted, but recent climate models have predicted increases in global average temperature. Based on the new biogeographical distribution, diurnal temperature variations, and biological evidence (inference with the analysis of mitochondria DNA), the immigration history of T. stagnalis was considered on the basis of two opposing immigration theories and in relation to the implications of global climate change. Two immigration theories, namely – the Tabula rasa and Nunatak, have prevailed in explaining the present distribution of plants and animals in Scandinavia. It was concluded that the rare occurrence of T. stagnalis in Norway fits into the Nunatak theory and that the species probably survived, at least, the last glaciation on Nunataks or coast refuges located in central northwestern Norway at Møre mountain and coast areas.
Possible combined effects of climate change, deforestation, and harvesting on the epiphyte Catopsis compacta: a multidisciplinary approach
Authors: del Castillo Rafael F. , Trujillo‐Argueta Sonia , Rivera‐García Raul , Gómez‐Ocampo Zaneli , Mondragón‐Chaparro Demetria
Published: October 2013

Climate change, habitat loss, and harvesting are potential drivers of species extinction. These factors are unlikely to act on isolation, but their combined effects are poorly understood. We explored these effects in Catopsis compacta, an epiphytic bromeliad commercially harvested in Oaxaca, Mexico. We analyzed local climate change projections, the dynamics of the vegetation patches, the distribution of Catopsis in the patches, together with population genetics and demographic information. A drying and warming climate trend projected by most climate change models may contribute to explain the poor forest regeneration. Catopsis shows a positive mean stochastic population growth. A PVA reveals that quasi‐extinction probabilities are not significantly affected by the current levels of harvesting or by a high drop in the frequency of wet years (2%) but increase sharply when harvesting intensity duplicates. Genetic analyses show a high population genetic diversity, and no evidences of population subdivision or a past bottleneck. Colonization mostly takes place on hosts at the edges of the fragments. Over the last 27 years, the vegetation cover has being lost at a 0.028 years−1 rate, but fragment perimeter has increased 0.076 years−1. The increases in fragment perimeter and vegetation openness, likely caused by climate change and logging, appear to increase the habitat of Catopsis, enhance gene flow, and maintain a growing and highly genetically diverse population, in spite of harvesting. Our study evidences conflicting requirements between the epiphytes and their hosts and antagonistic effects of climate change and fragmentation with harvesting on a species that can exploit open spaces in the forest. A full understanding of the consequences of potential threatening factors on species persistence or extinction requires the inspection of the interactions of these factors among each other and their effects on both the focus species and the species on which this species depends.
A bioturbation classification of European marine infaunal invertebrates
Authors: Queirós Ana M. , Birchenough Silvana N. R. , Bremner Julie , Godbold Jasmin A. , Parker Ruth E. , Romero‐Ramirez Alicia , Reiss Henning , Solan Martin , Somerfield Paul J. , Van Colen Carl , Van Hoey Gert , Widdicombe Stephen
Published: October 2013

Bioturbation, the biogenic modification of sediments through particle reworking and burrow ventilation, is a key mediator of many important geochemical processes in marine systems. In situ quantification of bioturbation can be achieved in a myriad of ways, requiring expert knowledge, technology, and resources not always available, and not feasible in some settings. Where dedicated research programmes do not exist, a practical alternative is the adoption of a trait‐based approach to estimate community bioturbation potential (BPc). This index can be calculated from inventories of species, abundance and biomass data (routinely available for many systems), and a functional classification of organism traits associated with sediment mixing (less available). Presently, however, there is no agreed standard categorization for the reworking mode and mobility of benthic species. Based on information from the literature and expert opinion, we provide a functional classification for 1033 benthic invertebrate species from the northwest European continental shelf, as a tool to enable the standardized calculation of BPc in the region. Future uses of this classification table will increase the comparability and utility of large‐scale assessments of ecosystem processes and functioning influenced by bioturbation (e.g., to support legislation). The key strengths, assumptions, and limitations of BPc as a metric are critically reviewed, offering guidelines for its calculation and application.
Adaptive divergence along environmental gradients in a climate‐change‐sensitive mammal
Authors: Henry P. , Russello M. A.
Published: October 2013

In the face of predicted climate change, a broader understanding of biotic responses to varying environments has become increasingly important within the context of biodiversity conservation. Local adaptation is one potential option, yet remarkably few studies have harnessed genomic tools to evaluate the efficacy of this response within natural populations. Here, we show evidence of selection driving divergence of a climate‐change‐sensitive mammal, the American pika (Ochotona princeps), distributed along elevation gradients at its northern range margin in the Coast Mountains of British Columbia (BC), Canada. We employed amplified‐fragment‐length‐polymorphism‐based genomic scans to conduct genomewide searches for candidate loci among populations inhabiting varying environments from sea level to 1500 m. Using several independent approaches to outlier locus detection, we identified 68 candidate loci putatively under selection (out of a total 1509 screened), 15 of which displayed significant associations with environmental variables including annual precipitation and maximum summer temperature. These candidate loci may represent important targets for predicting pika responses to climate change and informing novel approaches to wildlife conservation in a changing world.
The purinergic P2×7 receptor is expressed on monocytes in Behçet's disease and is modulated by TNF‐α
Authors: Castrichini Monica , Lazzerini Pietro Enea , Gamberucci Alessandra , Capecchi Pier Leopoldo , Franceschini Rossella , Natale Mariarita , Hammoud Mohamed , Moramarco Antonio , Zimbone Stefania , Gianchecchi Elena , Montilli Cinzia , Ricci Gianluca , Selvi Enrico , Cantarini Luca , Galeazzi Mauro , Laghi‐Pasini Franco
Published: October 2013

The P2×7 receptor (P2×7r) is expressed in innate immune cells (e.g. monocyte/macrophages), playing a key role in IL‐1β release. Since innate immune activation and IL‐1β release seem to be implicated in Behçet's disease (BD), a systemic immune‐inflammatory disorder of unknown origin, we hypothesized that P2×7r is involved in the pathogenesis of the disease. Monocytes were isolated from 18 BD patients and 17 healthy matched controls. In BD monocytes, an increased P2×7r expression and Ca2+ permeability induced by the selective P2×7r agonist 2′‐3′‐O‐(4‐benzoylbenzoyl)ATP (BzATP) was observed. Moreover, IL‐1β release from LPS‐primed monocytes stimulated with BzATP was markedly higher in BD patients than in controls. TNF‐α‐incubated monocytes from healthy subjects almost reproduced the findings observed in BD patients, as demonstrated by the increase in P2×7r expression and BzATP‐induced Ca2+ intake. Our results provide evidence that in BD monocytes both the expression and function of the P2×7r are increased compared with healthy controls, as the possible result, at least in part, of a positive modulating effect of TNF‐α on the receptor. These data indicate P2×7r as a new potential therapeutic target for the control of BD, further supporting the rationale for the use of anti‐TNF‐α drugs in the treatment of the disease.
Thy1+Sca1+ innate lymphoid cells infiltrate the CNS during autoimmune inflammation, but do not contribute to disease development
Authors: Mair Florian , Becher Burkhard
Published: October 2013

IL‐23 is absolutely crucial for the development of T‐cell driven autoimmune disease in mice. Even though IL‐23 is widely held to be involved in the stabilization of IL‐17‐secreting T cells, naïve T cells lack the IL‐23 receptor. Thus, the primary cellular target of IL‐23 in the context of autoimmunity is a subject of some debate. Innate lymphoid cells (ILCs) are a recently discovered family of lymphocytes being involved in early host defense, particularly at mucosal epithelial surfaces. Given the fact that RORγt‐dependent ILCs (group 3 ILCs) constitutively express the IL‐23‐receptor, and that they have been implicated in intestinal autoimmunity, we hypothesized that ILCs could contribute to the early development of autoimmune neuroinflammation. Through systematic analysis, we detected a sizable population of Thy1+ Sca1+ ILCs in the inflamed CNS tissue. CNS‐infiltrating ILCs were characterized by expression of the IL‐7‐receptor and production of proinflammatory IL‐17 and IFN‐γ. Furthermore, genetic fate‐mapping revealed their dependence on the transcription factor RORγt. However, upon specific in vivo ablation of this cell population, we found that they do not influence the course of the disease.
Application of Pulse Radiolysis to Mechanistic Investigations of Water Oxidation Catalysis
Authors: Polyansky Dmitry E. , Hurst James K. , Lymar Sergei V.
Published: October 2013

Radiolysis is a powerful technique capable of generating both inorganic and organic strong one‐electron oxidants over a wide range of aqueous medium conditions. Accordingly, current pulse radiolysis methods are quite advanced and have been productively used to study dynamics of many types of redox reactions for several decades. Nonetheless, despite its apparent usefulness for gaining mechanistic insights into water oxidation catalysis through probing normally inaccessible oxidation states of the catalysts, pulse radiolysis has only infrequently been applied to this purpose. In this paper, we identify those oxidizing radicals deemed most suited to these types of studies and describe methods for their radiolytic generation, review the scant literature on pulse radiolysis studies of both heterogeneous and homogeneous water oxidation catalysts, and discuss results of our own investigations of two dimeric and one monomeric ruthenium‐based catalysts, each of which appears to oxidize water by a distinct pathway. The optical spectra and redox dynamics of transient species determined have in each case provided information central to evaluating proposed catalytic mechanisms. Moreover, quantitative “over‐oxidation” by generating a stoichiometric excess amount of radicals has permitted investigation of an intermediate formed from a highly reactive precursor, demonstrating the unique capability of the pulse radiolysis method. As illustrated by these examples, this technique is broadly applicable to investigations of catalyzed water oxidation, which has the potential to become a method of choice for detecting and characterizing reaction transients.
Donor Behaviour of Anionic and Asymmetric Phosphanido Derivatives of Platinum and Palladium
Authors: Arias Andersson , Forniés Juan , Fortuño Consuelo , Martín Antonio , Mastrorilli Piero , Gallo Vito , Latronico Mario , Todisco Stefano
Published: October 2013

The reactions of [Ag(OClO3)(PPh3)] with [NBu4][(C6F5)2Pt(μ‐PPh2)2M(hq)], [NBu4][(C6F5)2Pt(μ‐PPh2)2M(bq)], [NBu4][(C6F5)2Pt(μ‐PPh2)2M(pic)] and [NBu4][(C6F5)2Pt(μ‐PPh2)2Pt(C6F5)(tht)] (M = Pt, Pd; hq = 8‐hydroxyquinolinate, bq = benzoquinolinate, pic = picolinate, tht = tetrahydrothiophene) afford the corresponding neutral adducts [(C6F5)2Pt(μ‐PPh2)2(μ‐AgPPh3)M(bq)] (M = Pt, 1; Pd, 2), [(C6F5)2Pt(μ‐PPh2)2(μ‐AgPPh3)M(hq)] (M = Pt, 3; Pd, 4) [(C6F5)2Pt(μ‐PPh2)2(μ‐AgPPh3)Pt(C6F5)(tht)] (5) and [(C6F5)2Pt(μ‐PPh2)2M(pic‐AgPPh3)] (M = Pt, 6; Pd, 7) as yellow solids. The XRD structures of 1–5, in which a [AgPPh3]+ moiety bridges the metal centres, were confirmed in solution at low temperature. At room temperature, a dynamic process for the [AgPPh3]+ moiety, which passes from the top to the bottom part of the molecules 1–5, was ascertained. For 6 and 7, the XRD analyses revealed structures in which the [AgPPh3]+ moiety is linked to the picolinate oxygen atom bonded to the M centre; however, although such a structure was confirmed in solution for the Pt–Pd species 7, the stable form of the Pt–Pt species 6 in solution is that with the [AgPPh3]+ moiety bridging the metal centres.
Synthesis, Structure, and Magnetic Study of Two Tridecanuclear Planar Cobalt Clusters with Unique Core Geometries
Authors: Peng Yan , Tian Chong‐Bin , Lan Yan‐Hua , Magnani Nicola , Li Qi‐Peng , Zhang Hua‐Bin , Powell Annie K. , Du Shao‐Wu
Published: October 2013

The reaction of Co(NO3)2·6H2O with N,N‐diethanolamine (H2L1) in the presence of sodium acetate, using triethylamine as a base, leads to a tridecanuclear mixed‐valent cobalt cluster [CoII9CoIII4(OH)6(H2O)2(L1)8(OAc)4](NO3)4·24H2O (1). Similar reaction with a newly designed hydroxy‐ and nitrogen‐rich chelating ligand 2‐[bis(pyridin‐2‐ylmethyl)amino]‐2‐(hydroxymethyl)propane‐1,3‐diol (H2L2) gives a mixed‐valent Co13 cluster [CoII7CoIII6(OH)12(L2)6](NO3)8·10H2O (2). The cobalt ions in both 1 and 2 are nearly coplanar, forming a novel shieldlike configuration for 1 and a unique hexagram structure for 2, both of which have not been observed for the polynuclear cobalt clusters. The magnetic susceptibility investigation showed that complexes 1 and 2 exhibited ferromagnetic coupling between CoII ions. Further magnetic studies revealed a slight frequency dependence of 2, which suggests that 2 might be a single‐molecule magnet.
Direct Synthesis of Ag Nanoparticles Incorporated on a Mesoporous Hybrid Material as a Sensitive Sensor for the Simultaneous Determination of Dihydroxybenzenes Isomers
Authors: Canevari Thiago C. , Raymundo‐Pereira Paulo A. , Landers Richard , Machado Sérgio A. S.
Published: October 2013

This paper describes the synthesis, characterization, and applications of a mesoporous silica/ multiwalled carbon nanotube (SiO2/MWCNT) hybrid material, which was obtained by a sol–gel process and decorated with silver nanoparticles (AgNPs) ranging in size from 5 to 8 nm. The AgNPs were prepared directly on the surface of the SiO2/MWCNTs material by using N,N‐dimethylformamide (DMF) as the reducing agent, and the resulting material was designated Ag/SiO2/MWCNT. The Ag/SiO2/MWCNT material was characterized by scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDS), high‐resolution transmission electron microscopy (HR‐TEM), and X‐ray photoelectron spectroscopy (XPS). A glassy carbon electrode, modified with the Ag/SiO2/MWCNT material, was used in the development of a sensitive electrochemical sensor for the determination of hydroquinone and catechol in the presence of resorcinol by squarewave voltammetry. Well‐defined and separate oxidation peaks were observed in phosphate buffer solution (PBS) at pH 7. The Ag/SiO2/MWCNT‐modified electrode exhibited high sensitivity for the simultaneous determination of hydroquinone and catechol in the presence of resorcinol, and the limits of detection for hydroquinone and catechol are 0.0117 and 0.0121 μM, respectively. No significant interference was seen for 2,6‐dichloroindophenol, phenol, 4‐nitrophenol, and nitrite ions in the detection of dihydroxybenzenes. Our study demonstrates that the resultant Ag/SiO2/MWCNT‐modified electrode can be used for hydroquinone and catechol detection in the presence of resorcinol and other potentially interfering materials in river water samples.
NaRb7(Si4–xGex)2 – Soluble Zintl Phases Containing Heteroatomic Tetrahedral ­[Si4–xGex]4– Clusters
Authors: Waibel Markus , Pecher Oliver , Mausolf Bernhard , Haarmann Frank , Fässler Thomas F.
Published: October 2013

The quaternary phases NaRb7(Si4–xGex)2 (x = 1–3) crystallize with an NaRb7Ge8‐type structure and contain tetrahedral four‐atom clusters that consist of Si and Ge atoms. The quaternary phases possess larger cell volumes with increasing Ge amount. The formation of heteroatomic [Si4–xGex]4– clusters is indicated by chemically different Si environments, which were analyzed by means of solid‐state 29Si MAS (magic‐angle spinning) NMR spectroscopy of a 29Si‐enriched NaRb7(Si4–xGex)2 sample with x = 0.5 as well as quantum chemical calculations of the NMR coupling parameters. NaRb7(Si4–xGex)2 represents another rare example of a phase with exclusively tetrahedral clusters that readily dissolves in liquid ammonia. The nature of the heteroatomic clusters was further investigated by dissolution of NaRb7(Si4–xGex)2 with x = 2 in liquid ammonia. In the presence of MesCu (Mes = mesityl) and 18‐crown‐6 as a sequestering agent, crystals with the composition [Rb(18‐crown‐6)]2Rb2[(MesCu)2(Si4–xGex)](NH3)11 were isolated with x = 2.2(1). [(MesCu)2(Si4–xGex)]4– represents another isomer of a MesCu‐stabilized tetrahedral anion and supports the observation that Zintl phases, which contain solely tetrahedranide subunits, represent a new class of soluble Zintl phases.
Strong Solid‐State Phosphorescence of 1,2‐Telluraplatinacycles Incorporated into Rigid Dibenzobarrelene and Triptycene Skeletons
Authors: Yamaguchi Yuki , Nakata Norio , Ishii Akihiko
Published: October 2013

Four‐ and five‐membered 1,2‐telluraplatinacycles incorporated into dibenzobarrelene and triptycene skeletons were synthesized by the reaction of bis(dibenzobarrelenyl) ditelluride and bis(triptycyl) ditelluride, respectively, with [Pt(η2‐norbornene)(PPh3)2] in the presence of PPh3. These complexes emit strong, orange phosphorescence in the solid state at room temperature (λem = 622–676 nm). Ligand‐exchange reactions of a five‐membered telluraplatinacycle with bidentate phosphine ligands gave a series of derivatives that emitted a range of colors (blue to orange, λem = 507–596 nm) with high emission quantum yields (max. ΦF = 0.93) in the solid state at room temperature, for which vapoluminescence was observed.
Synthesis of a Cn–Cn+6 Building Block Common to Important Polyol,Polyene Antibiotics from a Divinylcarbinol by a Desymmetrizing Sharpless Epoxidation
Authors: Nachbauer Luc , Brückner Reinhard
Published: October 2013

A stereocontrolled synthesis of the enantiomerically pure epoxide 7b from propargyl ether 15 has been realized in 15 steps. Epoxide 7b represents a building block for the “eastern” moieties of the title compounds. Key steps in our approach were a desymmetrizing Sharpless epoxidation (→ anti,cis‐16), the selective processing of the bis‐enolate of the bis(tert‐butyl alkoxyacetate) 11 through a diastereoselective [2,3]‐Wittig rearrangement (→ syn,syn‐9), and a stereo‐ and chemoselective iodolactonization (→ 35). The CO2H groups of dicarboxylic acid 37 were differentiated in a one‐pot bis‐oxidation reaction. The latter entailed the novel transformation of HO2CCH2‐O‐alkyl into AcOCH2‐O‐alkyl.
Stereocontrolled Synthesis of a Cn–Cn+6Building Block for the Unnatural Enantiomers of Important Polyol,Polyene Antibiotics from an Epoxy Alcohol by a Reduction/Conjugate Addition/Hydroxylation Sequence
Authors: Kramer Rainer , Brückner Reinhard
Published: October 2013

Epoxy alcoholanti‐10, derived from a desymmetrizing Sharpless epoxidation (up to 97 %ee) of divinylcarbinol9, provided the unsaturated 1,3‐diolsyn‐11upon treatment with RedAl®;syn‐11was converted into the α,β‐unsaturated esters (E)‐ or (Z)‐7bin three steps. Cu‐promoted 1,4‐addition of vinylmagnesium halides to the (E)‐ester proceeded with diastereoselectivities of up to 91 % and Cu‐catalyzed 1,4‐additions with diastereoselectivities of up to 82 %. The potassium enolate of the major vinylation productsyn‐22bwas hydroxylated by the Davis oxaziridine with perfect but unprecedented diastereoselectivity. The resulting hydroxy ester,α,βsyn,β,γsyn‐32, furnished the “eastern moiety” building block6of the title compounds in three steps.
Gold‐Catalyzed Cascade Oxidative Cyclization and Arylation of Allenoates
Authors: Zhang Rui , Xu Qin , Chen Kai , Gu Peng , Shi Min
Published: October 2013

An AuI/AuIII catalytic system was found to be effective for the cascade oxidative arylation and cyclization of allenoates with arylboronic acids to give the corresponding cyclic adducts in moderate yields. This reaction system constitutes a new method for the synthesis of β‐aryl‐γ‐butenolides under mild conditions. Based on the previous mechanistic studies, a proposed AuI/AuIII redox catalytic cycle has been outlined.
Fluorocarbon and Hydrocarbon N‐Heterocyclic (C5–C7) Difluorooxymethylene‐Bridged Liquid Crystals
Authors: Chen Hongren , Liu Peilian , Li Huijuan , Zhang Hong , Daniel Stelck , Zeng Zhuo
Published: October 2013

A series of new fluorocarbon and hydrocarbon N‐heterocyclic (C5–C7) difluorooxymethylene‐bridged liquid crystals have been prepared. The impact of ring (C5–C7) as end group was investigated. Compounds with terminal N‐heterocyclic 5‐ or 6‐membered rings such as 3,4‐difluoropyrrole, pyrrolidine, or pyridine, exhibited nematic phases (N). Whereas the terminal 3,3,4,4‐tetrafluoropyrrolidine and 3,3,4,4,5,5‐hexafluoropiperidine derivatives exhibited smectic C and B phases; the mesomorphic behavior weakened with increasing ring size. These new compounds also exhibited promising physicochemical and electro‐optical properties. Modification of the ring size with different length alkyl groups and variation of the chains from alkyl to polyfluoroalkyl markedly changed the properties of these compounds. It is possible that these N‐heterocycles (C5–C7) could replace fluorobenzene as terminal groups to form valuable difluorooxymethylene‐bridged liquid crystals. Compounds with 3,4‐difluoropyrrole as terminal group showed strongly positive dielectric anisotropy (Δϵ), moderate birefringence (Δn), and relatively low viscosity (γ1), thus meeting the criterion for high‐performance liquid‐crystalline materials.
Stereoselective Synthesis of a Bicyclic Norsesquiterpene Backbone – A Possible Route to Nardosinane Derivatives
Authors: Selaïmia‐Ferdjani Ouassila , Kar Anirban , Chavan Sambhaji P. , Horeau Maxime , Viault Guillaume , Pouessel Jacky , Guillory Xavier , Blot Virginie , Tessier Arnaud , Planchat Aurelien , Jacquemin Denis , Dubreuil Didier , Pipelier Muriel
Published: October 2013

We have developed an efficient diastereoselective synthetic route towards a nardosinane sesquiterpene scaffold. The strategy used a key bicyclic diene intermediate 11a, and allowed access to valuable polyoxygenated sesquiterpenes 21 and 22, which may be regarded as analogues of the natural sesquiterpenes laevinol B and fulvol acetate, respectively.
Iridium‐Catalyzed Direct Dehydroxylation of Alcohols
Authors: Huang Jian‐Lin , Dai Xi‐Jie , Li Chao‐Jun
Published: October 2013

Iridium‐catalyzed direct dehydroxylation of alcohols with hydrazine was developed through a combination of the oxidation of alcohols and the Wolff–Kishner reduction. This protocol is simple to perform and highly efficient for a series of primary, benzylic and allylic alcohols.
Chitosan/Ionic Liquid Composite Electrode for Electrochemical Monitoring of the Surface‐Confined Interaction Between Mitomycin C and DNA
Authors: Eksin Ece , Muti Mihrican , Erdem Arzum
Published: October 2013

In the present study a chitosan/ionic liquid modified pencil graphite electrode (CHIT‐IL‐PGEs) was developed for the first time for enhanced electrochemical monitoring of nucleic acid, and the interaction of the anticancer drug Mitomycin C (MC) and calf thymus double stranded DNA (dsDNA) by measuring the oxidation signals of MC and guanine in the same voltammetric scale. Differential pulse voltammetry, cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to evaluate the performance of the CHIT‐IL based biosensor on electrochemical monitoring of DNA, and drug‐DNA interaction. The experimental parameters, IL, dsDNA and MC concentration and the interaction time were then optimized.
Direct Electrodeposition of Graphene‐Gold Nanocomposite Films for Ultrasensitive Voltammetric Determination of Mercury(II)
Authors: Ding Liang , Liu Yuping , Zhai Jianping , Bond Alan M. , Zhang Jie
Published: October 2013

Graphene‐gold nanocomposite (rGO‐Au) modified glassy carbon electrodes (GCE) have been fabricated by a one‐step electrodeposition method. The nanocomposites were characterized by scanning electron microscopy, energy dispersive X‐ray spectroscopy, Raman spectra as well as electrochemical methods, and were utilized for mercury(II) detection via anodic stripping voltammetry. The peak stripping current was linearly dependent on the concentration of Hg(II) over the range of 1.0 to 150.0 nM and high selectivity and sensitivity (limit of detection 0.6 nM) and excellent stability/reusability were achieved. The applicability to environmental samples was successfully demonstrated by the direct determination of Hg(II) in tap water samples with minimal sample pretreatment.
The Influence of Graphene on the Electrical Communication Through Organic Layers on Graphite and Gold Electrodes
Authors: Zong Xidan , Kong Na , Liu Jingquan , Yang Wenrong , Cao Mengmei , Gooding J. Justin
Published: October 2013

The influence of graphene on the electrical communication through organic layers fabricated on graphite and gold electrodes is investigated. These layers were prepared by in situ reductive adsorption of 4‐aminobenzoic acid in the presence of NaNO2 and HCl to have surface bound carboxylic acid functionalities, followed by covalent attachment of 1‐aminopyrene via an amide coupling reaction to have surface bound pyrene groups for graphene immobilization via noncovalent ππ stacking interaction. The coverage of the layers created via reductive adsorption on graphite electrodes was found to be much higher than that on gold electrodes. It was revealed that graphene significantly enhances the electrical communication through the layers on graphite electrodes but on gold electrodes the enhancement effect through the layers was only minor. However, when gold electrodes were modified with a self‐assembled monolayer (SAM) of propanethiol the subsequent immobilization of graphene resulted in a significant enhancement of the electrical communication. It is also found that immobilization of graphene could affect the electron transfer between the redox probe, pyrene and the underlying electrodes. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to characterize the graphene sheets. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and X‐ray photoelectron spectroscopy (XPS) were also used to characterize the stepwise modified electrodes.
Carbon Black‐Modified Electrodes as Sensitive Tools for the Electrochemical Detection of Nitrite and Nitrate
Authors: Malha Seif Islam Rabie , Mandli Jihane , Ourari Ali , Amine Aziz
Published: October 2013

Both screen‐printed electrodes modified with a dispersion of carbon black (CB) and solid paste electrodes prepared using a nanostructured CB were developed and characterized. Indeed, increasing the peak currents and/or their shifting to negative potentials were observed, exhibiting efficient electrocatalytic activity towards nitrite oxidation with high sensitivity and low detection limit. Solid carbon paste electrodes (SCPEs) and solid carbon black paste electrodes (SCBPEs) were challenged in amperometric mode with nitrite since detection limit reached is 65 and 5 nM respectively. Nitrate was first reduced to nitrite in reductor column, then detected on SCBPEs. Nitrate and nitrite were determined in real samples.
Ultra Flexible Paper Based Electrochemical Sensors: Effect of Mechanical Contortion upon Electrochemical Performance
Authors: Foster Christopher W. , Metters Jonathan P. , Banks Craig E.
Published: October 2013

The influence of mechanical contortion upon the electrochemical performance of screen‐printed graphite paper‐based electroanalytical sensing platforms is evaluated and contrasted with traditionally employed polymeric based screen‐printed graphite sensors. Such a situation of implementation can be envisaged for the potential sensing of analytes on the skin where such sensors are based, for example in clothing where mechanical contortion, viz, bending will occur, and as such, its effect upon electrochemical sensors is of both fundamental and applied importance. The effect of mechanical contortion or stress upon electrochemical behaviour and performance is of screen printed sensors is explored. Comparisons are made between both paper‐ and polymeric‐ based sensing platforms that are evaluated towards the sensing of the well characterised electrochemical probes potassium ferrocyanide(II), hexaammine‐ruthenium(III) chloride and nicotinamide adenine dinucleotide (NADH). It is determined that the paper‐based sensors offer greater resilience in terms of electrochemical performance after mechanical stress. We gain insights into the role played by both the effect of the time of mechanical contortion and additionally the potentially detrimental effects of repeated contortion are explored. These unique paper‐based sensors hold promise for widespread applications where flexible and ultra‐low cost sensors are required such as applications into medical devices were ultra‐low cost sensors are a pre‐requisite, but also for utilisation within applications which require the implementation of ultra‐flexible electroanalytical sensing platforms such as in the case of wearable sensors, whilst maintaining useful electrochemical performances.
Environmentally Friendly Reduction of Graphene Oxide Using Tyrosine for Nonenzymatic Amperometric H2O2 Detection
Authors: Wang Qi , Li Musen , Szunerits Sabine , Boukherroub Rabah
Published: October 2013

Herein, we report on the simultaneous reduction and functionalization of graphene oxide (GO) with environmentally friendly tyrosine through the direct reaction of GO with tyrosine (Tyr) at 100 °C for 24 h. The resultant material (rGO/Tyr) has been characterized using UV‐vis spectrometry, FTIR spectroscopy, X‐ray photoelectron spectroscopy (XPS), and electrochemical measurements. The rGO/Tyr nanomaterial displayed good electrocatalytic activity for the detection of hydrogen peroxide (H2O2) with a wide linear range from 100 µM to 2.1 mM, a detection limit of 80 µM and a sensitivity of 69.07 µA mM−1 cm−2. In addition, the rGO/Tyr electrode showed good selectivity for H2O2 detection in the presence of uric acid, ascorbic acid, dopamine and glucose.
A periodic array of nano‐scale parallel slats for high‐efficiency electroosmotic pumping
Authors: Kung Chun‐Fei , Wang Chang‐Yi , Chang Chien‐Cheng
Published: October 2013

It is known that the eletroosmotic (EO) flow rate through a nano‐scale channel is extremely small. A channel made of a periodic array of slats is proposed to effectively promote the EO pumping, and thus greatly improve the EO flow rate. The geometrically simple array is complicated enough that four length scales are involved: the vertical period 2L, lateral period 2aL, width of the slat 2cL as well as the Debye length . The EO pumping rate is determined by the normalized lengths: a, c, or the perforation fraction of slats and the dimensionless electrokinetic width . In a nano‐scale channel, K is of order unity or less. EO pumping in both longitudinal and transverse directions (denoted as longitudinal EO pumping (LEOP) and transverse EO pumping (TEOP), respectively) is investigated by solving the Debye–Hückel approximation and viscous electro‐kinetic equation. The main findings include that (i) the EO pumping rates of LEOP for small K are remarkably improved (by one order of magnitude) when we have longer slats () and a large perforation fraction of slats (η > 0.7); (ii) the EO pumping rates of TEOP for small K can also be much improved but less significantly with longer slats and a large perforation fraction of slats. Nevertheless, it must be noted that in practice K cannot be made arbitrarily small as the criterion of for the reference potential at the channel center put lower bounds on K; in other words, there are geometrical limits for the use of the Poisson–Boltzmann equation.