bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and Aggregation Behaviors of Well‐Defined Thermoresponsive Pentablock Terpolymers With Tunable LCST
Authors: Wu Yufeng , Liu Xingli , Wang Yu , Guo Zanru , Feng Yujun
Published: June 2012

A series of thermoresponsive pentablock terpolymers, poly(N‐isopropylacrylamide)‐b‐poly(ethylene oxide)‐b‐poly(propylene oxide)‐b‐poly(ethylene oxide)‐b‐poly(N‐isopropylacrylamide), is prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization. The effect of NIPAM and PPO block lengths on lower critical solution temperature (LCST), critical micelle concentration (cmc), and aggregation number (Nagg) is investigated via UV–Vis spectroscopy and steady‐state fluorescence spectroscopy. The results show that upon increasing the block lengths, LCST and cmc decrease, while Nagg increases. TEM observation shows that associated spherical‐like particles are evidenced below the LCST of the terpolymers, and regular or irregular spherical micelles or even intermicellar aggregates are observed above the LCST.
Compounding of MWCNTs with PS in a Twin‐Screw Extruder with Varying Process Parameters: Morphology, Interfacial Behavior, Thermal Stability, Rheology, and Volume Resistivity
Authors: Sathyanarayana Shyam , Olowojoba Ganiu , Weiss Patrick , Caglar Burak , Pataki Bernadeth , Mikonsaari Irma , Hübner Christof , Henning Frank
Published: June 2012

1, 2, 3, 5, and 7.5 wt% MWCNTs are incorporated into PS in a twin‐screw extruder at varying speeds, throughputs and extruder barrel temperatures. Increased SME at enhanced processing speeds seems to have the single largest effect in enhancing dispersion. A relative evaluation of PS/MWCNT interactions indicate an interfacial layer growth of 24% for 2 wt% MWCNT at 1100 rpm compared to 18% growth at 500 rpm. Raman analysis does not show an MWCNT peak shift but a constant increase in FWHM is observed irrespective of the MWCNT content. A significant enhancement of thermal stability occurs up to 2 wt% MWCNT loading while 1–2 wt% shows the rheological threshold. The volume resistivity decreases dramatically in a 2 wt% sample processed at 1100 rpm compared to those processed at 500 rpm.

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Use of NMR in fish processing optimization: a review of recent progress
Authors: Erikson Ulf , Standal Inger B , Aursand Ida G , Veliyulin Emil , Aursand Marit
Published: June 2012

The goal of this review is to give an overview of general trends in the application of the NMR related to fish processing and quality and to provide some viewpoints on the current situation. Three novel examples of the application of the methodologies magnetic resonance spectroscopy, magnetic resonance imaging, and low‐field NMR are also presented. The capability of these techniques to be utilized as a tool to optimize fish processing, and thereby improving product quality, as well as to confirm labelling information, are demonstrated. Copyright © 2012 John Wiley & Sons, Ltd.
Neuromuscular properties of the thigh muscles in patients with ehlers–danlos syndrome
Authors: Gerrits Karin H.L. , Voermans Nicol C. , de Haan Arnold , van Engelen Baziel G.
Published: June 2012

Introduction: Ehlers–Danlos syndrome (EDS), a connective tissue disorder, may lead to impaired contractile function of lower limb muscles. Methods: To test this hypothesis and to understand the possible mechanisms involved, isometric function of the thigh muscles was investigated at different joint angles (30°, 60°, and 90° of knee flexion) in 7 tenascin‐X (TNX)‐deficient EDS patients. Results: There was reduced maximal voluntary torque of the knee extensors (but not knee flexors) across all joint angles in the patients. Time to reach maximal rate of torque development was delayed, and voluntary activation capacity was reduced in patients compared with controls, particularly at 30°. Conclusions: EDS is associated with muscle weakness, most likely due to increased compliance of the series‐elastic component of muscle tissue and failure of maximal voluntary muscle activation. Further research is required to understand the influence of reduced voluntary activation on the severe fatigue reported by EDS patients. Muscle Nerve, 2013
Electrophysiological study of medial and lateral branches of the superficial radial nerve
Authors: Cappellari Alberto M. , Bona Alberto R. , Lukasova Katerina
Published: June 2012

Introduction: In this study we sought to establish a new technique for nerve conduction study (NCS) of medial and lateral branches of the superficial radial nerve (SRN). Methods: Antidromic NCS were performed on 60 healthy subjects, recording the sensory nerve action potential (SNAP) from the dorsomedial and dorsolateral aspects of the phalanx of the thumb. The main trunk of SRN was also investigated. Results: SNAPs were easily recorded in all subjects, and normative latency and amplitude data were collected. Conclusions: We propose a simple and reliable technique to investigate nerve conduction of the terminal branches of the SRN, which could be useful in some focal and systemic pathologies. Muscle Nerve, 2013
Near‐infrared spectroscopy during exercise and recovery in children with juvenile dermatomyositis
Authors: Habers G. Esther A. , De Knikker Rogier , Van Brussel Marco , Hulzebos Erik , Stegeman Dick F. , Van Royen Annet , Takken Tim
Published: June 2012

Introduction: We hypothesized that microvascular disturbances in muscle tissue play a role in the reduced exercise capacity in juvenile dermatomyositis (JDM). Methods: Children with JDM, children with juvenile idiopathic arthritis (clinical controls), and healthy children performed a maximal incremental cycloergometric test from which normalized concentration changes in oxygenated hemoglobin (Δ[O2Hb]) and total hemoglobin (Δ[tHb]) as well as the half‐recovery times of both signals were determined from the vastus medialis and vastus lateralis muscles using near‐infrared spectroscopy. Results: Children with JDM had lower Δ[tHb] values in the vastus medialis at work rates of 25%, 50%, 75%, and 100% of maximal compared with healthy children; the increase in Δ[tHb] with increasing intensity seen in healthy children was absent in children with JDM. Other outcome measures did not differ by group. Conclusions: The results suggest that children with JDM may experience difficulties in increasing muscle blood volume with more strenuous exercise. Muscle Nerve, 2013
Gram‐Schmidt orthogonalization: 100 years and more
Authors: Leon Steven J. , Björck Åke , Gander Walter
Published: June 2012

In 1907, Erhard Schmidt published a paper in which he introduced an orthogonalization algorithm that has since become known as the classical Gram‐Schmidt process. Schmidt claimed that his procedure was essentially the same as an earlier one published by J. P. Gram in 1883. The Schmidt version was the first to become popular and widely used. An algorithm related to a modified version of the process appeared in an 1820 treatise by P. S. Laplace. Although related algorithms have been around for almost 200 years, it is the Schmidt paper that led to the popularization of orthogonalization techniques. The year 2007 marked the 100th anniversary of that paper. In celebration of that anniversary, we present a comprehensive survey of the research on Gram‐Schmidt orthogonalization and its related QR factorization. Its application for solving least squares problems and in Krylov subspace methods are also reviewed. Software and implementation aspects are also discussed. Copyright © 2012 John Wiley & Sons, Ltd.
Validation of three coding algorithms to identify patients with end‐stage liver disease in an administrative database
Authors: Goldberg D , Lewis JD , Halpern SD , Weiner Mark , Lo Re Vincent
Published: June 2012

Purpose

Use of administrative or population‐based databases for post‐marketing pharmacoepidemiology research in patients with end‐stage liver disease (ESLD) has been limited by the difficulty of accurately identifying such patients. Algorithms to identify patients with ESLD using ICD‐9‐CM codes have not been developed outside of the Veterans Affairs healthcare setting.

Methods

We queried electronic medical records at two tertiary care hospitals to identify patients with ICD‐9‐CM codes indicative of ESLD. Coding algorithms were developed to identify patients with confirmed ESLD, and these were tested to determine their positive predictive value (PPV).

Results

The presence of one inpatient or outpatient ICD‐9‐CM code for: (i) cirrhosis; (ii) chronic liver disease, and (iii) a hepatic decompensation event yielded a PPV of 85.2% (167/196; 95% CI: 79.4%–89.9%). The PPV increased to 89.3% (150/168; 95% CI: 83.6%–93.5%) when the algorithm required two or more ICD‐9‐CM codes for a hepatic decompensation. However, an algorithm requiring only one ICD‐9‐CM code for (i) cirrhosis and (ii) a hepatic decompensation event, in the absence of a chronic liver disease code, yielded a PPV of 85.7% (30/35; 95% CI: 69.7%‐95.2%).

Conclusions

A coding algorithm that includes at least one ICD‐9‐CM code for cirrhosis plus one ICD‐9‐CM code for a hepatic decompensation event has a high PPV for identifying patients with ESLD. The inclusion of at least two codes indicative of a hepatic decompensation event increased the PPV. This algorithm can be used in future epidemiologic studies to examine the outcomes of a variety of long‐term medical therapies in patients with ESLD. Copyright © 2012 John Wiley & Sons, Ltd.
Exploring large weight deletion and the ability to balance confounders when using inverse probability of treatment weighting in the presence of rare treatment decisions
Authors: Kilpatrick Ryan D. , Gilbertson Dave , Brookhart M. Alan , Polley Eric , Rothman Kenneth J. , Bradbury Brian D.
Published: June 2012

Purpose

When medications are modified in response to changing clinical conditions, confounding by indication arises that cannot be controlled using traditional adjustment. Inverse probability of treatment weights (IPTWs) can address this confounding given assumptions of no unmeasured confounders and that all patients have a positive probability of receiving all levels of treatment (positivity). We sought to explore these assumptions empirically in the context of epoetin‐alfa (EPO) dosing and mortality.

Methods

We developed a single set of IPTWs for seven EPO dose categories and evaluated achieved covariate balance, mortality hazard ratios, and confidence intervals using two levels of treatment model parameterization and weight deletion.

Results

We found that IPTWs improved covariate balance for most confounders, but was not optimal for prior hemoglobin. Including more predictors in the treatment model or retaining highly weighted individuals resulted in estimates closer to the null, although precision decreased.

Conclusion

We chose to evaluate weights and covariate balance at a single time‐point to facilitate an empirical analysis of model assumptions. These same assumptions are applicable to a time‐dependent analysis, although empirical examination is not straight forward in that case. We find that the inclusion of rare treatment decisions and the high weights that result is needed for covariate balance under the positivity assumption. Removal of these influential weights can result in bias in either direction relative to the original confounding. It is therefore important to determine the reason for these rare patterns and whether inference is possible for all treatment levels. Copyright © 2012 John Wiley & Sons, Ltd.
Predictors of recall certainty of dates of analgesic medication use in pregnancy
Authors: Radin Rose G. , Mitchell Allen A. , Werler Martha M.
Published: June 2012

Purpose

Recalled dates of medication use are difficult to validate, particularly for over‐the‐counter (OTC) medications. We evaluated mothers’ recall certainty as an approximation of the accuracy of their recalled exposures.

Methods

We used data from the Slone Epidemiology Center Birth Defects Study collected by retrospective interview of women about pregnancy medication use. For each medication reported, women were asked to report the dates of their use and how certain they were of their reported dates. For this analysis, 32 107 reports from 14 577 analgesic users were categorized as “high” or “low” recall certainty if they considered a reported date as exact or estimated, respectively. Patterns of analgesic use, maternal demographics, and health behaviors were explored as predictors of high recall certainty of dates of analgesic use. We used log‐binomial regression with the generalized estimating equations extension to account for multiple reports per subject in estimating prevalence ratios (PR) and 95% confidence intervals.

Results

Relative to episodes of short‐term routine use (≥4 times/week for ≤30 days), high recall certainty was more likely for episodes of a single dose (prescription PR = 1.92 (1.61, 2.27); OTC PR = 3.65 (3.03, 4.40)) and less likely for episodes of occasional use (prescription PR = 0.10 (0.05, 0.18); OTC PR = 0.65 (0.53, 0.79)). The association of chronic routine use with high recall certainty was inverse among prescription analgesics and positive among OTC analgesics (prescription PR = 0.56 (0.40, 0.80); OTC PR = 2.46 (1.92, 3.42)).

Conclusions

Some characteristics that were associated with recall accuracy in previous studies were also associated with recall certainty in this study. Copyright © 2012 John Wiley & Sons, Ltd.
Assessing the effect of vaccine on spontaneous abortion using time‐dependent covariates Cox models
Authors: Xu Ronghui , Luo Yunjun , Chambers Christina
Published: June 2012

Purpose

In studying the safety of vaccine for influenza A (H1N1) given during pregnancy, spontaneous abortion (SAB) is one of the important points to consider. Because women may receive the vaccine any time during their pregnancy, evaluation of the effect of the vaccine on SAB should only take place after vaccination and in the risk window for SAB, that is, the first 20 weeks of gestation. In addition, when such studies are conducted through pregnancy registries where recruitment occurs after pregnancy recognition, the accrued subjects are left truncated in the sense that they are not followed from the start of pregnancy.

Methods

As previously reported, left truncation needs to be properly handled using survival analysis methods to avoid bias. In the context of time‐dependent vaccine exposure, a time‐dependent covariate Cox model can be used to simultaneously take into account the left truncation and the vaccine exposure timing.

Results

In this communication, we illustrate the approach using the Vaccine and Medication in Pregnancy Surveillance System data. We explain in details how the model is fitted using different software.

Conclusions

We recommend survival analysis methods together with collection of necessary data to study the effects of vaccine on SAB. Copyright © 2012 John Wiley & Sons, Ltd.
Reporting of irradiance modeling relative prediction errors
Authors: Hoff Thomas E. , Perez Richard , Kleissl Jan , Renne David , Stein Joshua
Published: June 2012

Metrics used in assessing irradiance model accuracy, such as root mean square error and mean absolute error, are precisely defined. Their relative (%) counterpart, however, can be subject to interpretation and may cover a wide range of values for a given set of data depending on reporting practice. This note evaluates different approaches for the reporting of relative metrics quantifying the dispersion accuracy of a model and formulates recommendations for the most appropriate approach. Copyright © 2012 John Wiley & Sons, Ltd.
Unusual effect of molecular weight and concentration on thermoresponsive behaviors of well‐defined water‐soluble semirigid polymers
Authors: Liu Peng , Xie Helou , Tang Haoyu , Zhong Guanqun , Zhang Hailiang
Published: June 2012

A series of water‐soluble semirigid thermoresponsive polymers with well‐defined molecular weights based on mesogen‐jacketed liquid crystal polymers (MJLCPs), poly[bis(N‐hydroxyisopropyl pyrrolidone) 2‐vinylterephthalate] (PHIPPVTA) have been synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization. Dynamic light scattering (DLS) revealed that the novel monomer and polymers have thermoresponsive properties with cloud point in the range between 10 and 90 °C. The cloud point was increased by 56.2 °C when the polymer molecular weight increased from 0.47 × 104 g mol−1 to 3.69 × 104 g mol−1. In addition, the cloud point of PHIPPVTA was decreased by 18.8 °C with the increase of polymer concentration from 5 to 10 mg mL−1. A slight increase (0.1–3.5 °C) of cloud point has been observed after knocking off the end‐groups of PHIPPVTA. Moreover, the cloud point of polymer increased with increasing of its molecular weight with or without the trithiocarbonate end‐groups, which showed the opposite trend comparing with other thermoresponsive polymers with flexible backbones. These polymers show a dramatic solvent isotopic effect that the cloud point in D2O was lower than in H2O. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Improving the control of styrene polymerization at 60 °C using a dialkylated α‐hydrogenated nitroxide
Authors: Guillaneuf Yohann , Lamps Jean‐Philippe , Catala Jean‐Marie , Gigmes Didier , Drockenmuller Eric
Published: June 2012

A new dialkylated α‐hydrogenated linear nitroxide and the corresponding 1‐phenylethyl alkoxyamine were synthesized in two and three steps, respectively. The alkoxyamine was involved in the polymerization of styrene at 60 °C, and the in situ concentration of nitroxide was monitored by electron spin resonance spectroscopy. The enhanced characteristics of these new alkylated alkoxyamine and nitroxide (k = 1.5 × 10−4 s−1 and k = 5.7 × 104 L mol−1 s−1) yielded a monomer consumption one order of magnitude higher than styrene thermal polymerization. This resulted in well‐defined polystyrenes up to 70,000 g mol−1 and the observation of a control occurring through the establishment of the radical persistent effect, that is, ln([M]0/[M]) = t2/3. Experimentally determined kinetic constants were involved in PREDICI modelings to investigate the influence of temperature and initial alkoxyamine concentration on the kinetics as well as on the livingness and the controlled character of the polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Segmented block copolyesters using click chemistry
Authors: June Stephen M. , Bissel Philippe , Long Timothy E.
Published: June 2012

Copper(I) catalyzed azide‐alkyne 1,3‐Huisgen cycloaddition reaction afforded the synthesis of triazole‐containing polyesters and segmented block copolyesters at moderate temperatures. Triazole‐containing homopolyesters exhibited significantly increased (∼40 °C) glass transition temperatures (Tg) relative to high temperature, melt synthesis of polyesters with analogous structures. Quantitative synthesis of azido‐terminated poly(propylene glycol) (PPG) allowed for the preparation of segmented polyesters, which exhibited increased solubility and mechanical ductility relative to triazole‐containing homopolyesters. Differential scanning calorimetry demonstrated a soft segment (SS) Tg near −60 °C for the segmented polyesters, consistent with microphase separation. Tensile testing revealed Young's moduli ranging from 7 to 133 MPa as a function of hard segment (HS) content, and stress at break values approached 10 MPa for 50 wt % HS segmented click polyesters. Dynamic mechanical analysis demonstrated an increased rubbery plateau modulus with increased HS content, and the Tg's of both the SS and HS did not vary with composition, confirming microphase separation. Atomic force microscopy also indicated microphase separated and semicrystalline morphologies for the segmented click polyesters. This is the first report detailing the preparation of segmented copolyesters using click chemistry for the formation of ductile membranes with excellent thermomechanical response. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Design, synthesis, photophysical, and electrochemical properties of DCM‐based conjugated polymers for light‐emitting devices
Authors: Vanjinathan Mahalingam , Lin Hong‐Cheu , Nasar A. Sultan
Published: June 2012

A series of conjugated hyperbranched polymers, hyperbranched copolymers, and linear polymers containing 2‐pyran‐4‐ylidenemalononitrile (acceptor) and triphenylamine/fluorene (donor) units were synthesized and characterized by FTIR, 1H NMR, thermogravimetric analyses, differential scanning calorimetry, gel permeation chromatography, UV–visible, photoluminescence, and cyclic voltammetry measurements. All the polymers show red‐light emission in the range of 566–656 nm both in solution and in solid state. The quantum efficiency of the polymers was in the range of 56–82%. Among the six polymers synthesized, only polymers containing fluorene units show Tg and polymers based on triphenylamine not exhibit Tg. The band gap of these polymers were found to be reasonably low; hyperbranched copolymer containing fluorene unit shows lowest band gap of 2.18 eV due to the stabilization of LUMO energy level by the electron withdrawing CN groups. The thermal and solubility behavior of the polymers were found to be good. All the EL spectra of the devices (indium‐tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)/polymer/2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline/tris(8‐hydroxyquinoline)aluminum)/LiF/Al) show red‐light emission, and the device fabricated with P3 and P4 shows maximum luminance and luminous efficiency of 4104 cd m−2 and 0.55 cd Å−1 and 3696 cd m−2 and 0.47 cd Å−1, respectively, indicates that they had the best carrier balance. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Synthesis and properties of hyperbranched poly(ether sulfone)s prepared by self‐polycondensation of novel AB2 monomer
Authors: Jikei Mitsutoshi , Uchida Daisuke , Haruta Yuuki , Takahashi Yuuki , Matsumoto Kazuya
Published: June 2012

Hyperbranched poly(ether sulfone)s were prepared by the self‐polycondensation of the novel AB2 monomer, 4‐(3,5‐hydroxyphenoxy)‐4′‐fluorodiphenylsulfone. The high‐molecular‐weight polymers were isolated in good yields. The degree of branching (DB) of the resulting polymers was investigated by the preparation of dendritic and linear model compounds. The DB determined by gated decoupling 13C NMR measurements was in the range 0.17–0.41 and was dependent on the base used for the self‐polycondensation. It was found that cesium fluoride was an effective base to form the polymer having the DB of 0.41. The resulting hyperbranched poly(ether sulfone)s showed good solubility in organic solvents. The solubility and the glass transition temperature of the polymers were influenced by the terminal functional groups. The unique thermal crosslinking phenomenon was observed during the DSC measurements of the hydroxyl‐terminated hyperbranched poly(ether sulfone) under air condition. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Efficient polymer passivation of ligand‐stripped nanocrystal surfaces
Authors: Duong Jennifer T. , Bailey Mark J. , Pick Teresa E. , McBride Patrick M. , Rosen Evelyn L. , Buonsanti Raffaella , Milliron Delia J. , Helms Brett A.
Published: June 2012

Water‐dispersible, polymer‐wrapped nanocrystals are highly sought after for use in biology and chemistry, from nanomedicine to catalysis. The hydrophobicity of their native ligand shell, however, is a significant barrier to their aqueous transfer as single particles. Ligand exchange with hydrophilic small molecules or, alternatively, wrapping over native ligands with amphiphilic polymers is widely employed for aqueous transfer; however, purification can be quite cumbersome. We report here a general two‐step method whereby reactive stripping of native ligands is first carried out using trialkyloxonium salts to reveal a bare nanocrystal surface. This is followed by chemically directed immobilization of a hydrophilic polymer coating. Polyacrylic acids, with side‐chain grafts or functional end groups, were found to be extremely versatile in this regard. The resulting polymer‐wrapped nanocrystal dispersions retained much of the compact size of their bare nanocrystal precursors, highlighting the unique role of monomer side‐chain functionality to serve as effective, conformal ligation motifs. As such, they are well poised for applications where tailored chemical functionality at the nanocrystal's periphery or improved access to their surfaces is desirable. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Group 4 complexes bearing alkoxide functionalized N‐heterocyclic carbene ligands as catalysts in the polymerization of olefins
Authors: Costabile Chiara , Bocchino Carmen , Napoli Mariagrazia , Longo Pasquale
Published: June 2012

Novel octahedral zirconium complexes bearing alkoxide functionalized N‐heterocyclic carbene ligands have been synthesized and characterized. NMR analysis showed that more than one species was obtained during synthesis. The synthesized complexes were able to polymerize ethylene and propylene giving rise to a linear polyethylene with high Mw and polydispersity index often bimodal with molecular weight distribution (MDI) > 2, and highly isotactic polypropylene together with an atactic fraction. Density functional theory (DFT) studies on the complex stability indicate the possible species active during the polymerization reaction. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Factors reported to influence fear of recurrence in cancer patients: a systematic review
Authors: Crist Jade V. , Grunfeld Elizabeth A.
Published: June 2012

Objective

Fear of cancer recurrence (FCR) is a significant psychological problem for cancer survivors. Some survivors experience FCR, which is both persistent and highly distressing. The aim of this systematic review was to identify the key factors associated with fear of recurrence among cancer patients.

Methods

A comprehensive literature search using keywords was performed with three databases, followed by an organic search to identify additional relevant articles. Included studies had a quantitative methodology presenting empirical findings focussed on adult cancer patients. A methodological quality assessment was performed for each study, and the strength of evidence was defined by the consistency of results.

Results

Forty‐three studies met the inclusion criteria and are presented in this review. The most consistent predictor of elevated FCR was younger age. There was strong evidence for an association between physical symptoms and fear of cancer recurrence. Additional factors moderately associated with increased FCR included treatment type, low optimism, family stressors and fewer significant others. Inconsistent evidence was found for socio‐demographic factors.

Conclusions

Fear of cancer recurrence is a complex issue influenced by a multitude of factors, including demographic, clinical and psychological factors. However, some studies have reported contradictory evidence, and FCR has been measured using a range of scales, which can hamper comparison across studies. Further research is needed to clarify inconsistencies in the current published research. Copyright © 2012 John Wiley & Sons, Ltd.
Characterization of 4,6‐Diazido‐N‐nitro‐1,3,5‐triazine‐2‐amine
Authors: Musil Tomáš , Matyáš Robert , Lyčka Antonín , Růžička Aleš
Published: June 2012

4,6‐Diazido‐N‐nitro‐1,3,5‐triazine‐2‐amine (DANT) was prepared with a 35 % yield from cyanuric chloride in a three step process. DANT was characterized by IR and NMR spectroscopy (1H, 13C, 15N), single‐crystal X‐ray diffraction, and DTA. The crystal density of DANT is 1.849 g cm−3. The cyclization of one azido group and one nitrogen atom of the triazine group giving tetrazole was observed for DANT in a dimethyl sulfoxide solution using NMR spectroscopy. An equilibrium exists between the original DANT molecule and its cyclic form at a ratio of 7 : 3. The sensitivity of DANT to impact is between that for PETN and RDX, sensitivity to friction is between that for lead azide and PETN, and sensitivity to electric discharge is about the same as for PETN. DANT′s heat of combustion is 2060 kJ mol−1.
Explosive Strength and Impact Sensitivity of Several PBXs Based on Attractive Cyclic Nitramines
Authors: Elbeih Ahmed , Jungová Marcela , Zeman Svatopluk , Vávra Pavel , Akštein Zbyněk
Published: June 2012

Plastic explosives based on different cyclic nitramines with different polymeric matrices were prepared and studied. The used polymeric matrices were fabricated on the basis of polyisobutylene (PIB), acrylonitrile‐butadiene rubber (ABR), Viton A, and polydimethyl‐siloxane as binders, whereas the nitramines named RDX (1,3,5‐trinitroperhydro‐1,3,5‐triazine), β‐HMX (β‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine), BCHMX (cis‐1,3,4,6‐tetranitrooctahydroimidazo‐[4,5‐d]imidazole) and ε‐HNIW (ε‐2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane) were used as explosive fillers. Commercial Semtex 10, based on pentaerythritol tetranitrate (PETN), was used for comparison. Impact sensitivity, loading density, ρ, detonation velocity, D, and relative explosive strength (RS) measured by ballistic mortar were determined. It was concluded that plastic BCHMX based on Viton A or PIB‐matrix exhibits higher RS compared with PBXs based on RDX and HMX. Correlations between RS and the impact sensitivity, the ρD2 term and the square of the detonation velocity were studied and discussed. The results confirm the well‐known fact that increasing the performance is usually accompanied by an increase in the sensitivity of the explosives. In this connection, Viton A enables achieving a high RS, but with a relatively high sensitivity of the PBXs, whereas the polydimethyl‐siloxane matrix should perhaps give PBXs with optimum explosive strength and sensitivity parameters.
Predicting Maximum Attainable Detonation Velocity of CHNOF and Aluminized Explosives
Authors: Keshavarz Mohammad Hossein
Published: June 2012

This paper describes a simple method to predict the detonation velocity of pure and mixed CHNOF explosives as well as aluminized explosives at their maximum nominal density as one of the most important detonation properties. The new correlation uses the contribution of some structural parameters to apply for a wide range of ideal and non‐ideal explosives. Aluminized explosives have non‐ideal behavior and the ChapmanJouguet detonation velocities significantly differ from those expected from existing thermodynamic computer codes for equilibrium and steady state calculations. With the presented method, there is no need to use any assumed detonation products, heat of formation and experimental data. Detonation velocities at maximum nominal density of explosives predicted by this procedure show good agreement with respect to experimental values. They are more reliable compared to the calculated results of well‐known empirical methods and computed outputs using BKWS equation of state for CHNOF and aluminized explosives.
Aminonitrocyclopropanes as Possible High‐Energy Materials. Quantum Chemical Calculations
Authors: Halstead Joshua M. , Whittaker Jessica N. , Ball David W.
Published: June 2012

The structures, vibrational spectra, and thermodynamic properties of three cyclopropane derivatives with amino and nitro substitutions were evaluated using standard density functional calculations. Calculations of thermodynamic properties show that the energy content per unit mass of these compounds is higher than current high energy materials. The actual density of these substances may be higher than that calculated because of expected intermolecular interactions between adjacent NH2 and NO2 groups.
Role of aluminium oxide in the structure of heavy metal oxide borosilicate glasses
Authors: Monika  , Falconieri M. , Baccaro S. , Sharma G. , Thind K. S. , Singh D. P.
Published: June 2012

Lead borosilicate and bismuth borosilicate glasses with and without aluminium oxide of varying compositions were prepared by conventional melt‐quench method. Raman spectroscopy was used to analyze the influence of Al2O3 incorporation in the heavy metal oxide borosilicate glass network. The compositions of glasses were chosen in a way that Al2O3 is added at expenses of PbO and Bi2O3 in lead borosilicate and bismuth borosilicate glasses, respectively.
Energy harvesting using multilayer structure based on La‐doped PMN‐PT electrostrictive ceramics
Authors: Huang Hualin , Li Guorong , Huang Lizhu , Ruan Wei , Cheng Lihong , Zeng Jiangtao , Wen Baosong
Published: June 2012

Electrostrictive materials exhibit high induced strain under dc electric fields and this effect is important in generator application. This paper studied the energy‐harvesting performances of La‐doped PMN‐PT electrostrictive ceramics that have rarely been reported. A multilayer structured electrostrictive energy harvester with high dielectric constant and electrostrictive coefficient is proposed. With a strain Sm = 7 × 10−5 (m/m), a peak current value of 630 µA is obtained across a small matched resistance of 450 Ω under a dc electrical field of 1.5 V/µm. The working principle of the device is reviewed and improved to predict the current and power generated by the harvester. Experimental results are compared to the theoretic behaviors of the improved model. A good agreement is observed by the two sets of data. The study on the efficiency of the energy conversion showed that a positive balance between the consumed power and the harvested power was presented by the device. The result demonstrates the potential perspective of the electrostrictive device in energy harvesting applied to low‐power electronics.
Sulfurization of near‐stoichiometric CuIn precursor and the influence of low‐temperature slopes on morphology and structural quality
Authors: Dombrowa A. , Lehmann C. , Pettenkofer C.
Published: June 2012

Polycrystalline CuInS2 (CIS) films are prepared by sulfurization of CuIn metallic precursors with Cu/In = 1.2 on Mo substrates. Variation of the rapid thermal processing (RTP) parameters adjusted to the low copper surplus yielded near stoichiometric CIS films with considerably less CuSx precipitation at the surface. A start temperature and low temperature slopes were introduced to guarantee crystal quality and large grain size. XPS/UPS, X‐ray diffraction measurement, and scanning electron microscopy data show the distinct properties of the chalcopyrite phase and its morphological structure in comparison to the standard sulfurization process. A considerable improvement has been achieved by variation of the temperature profiles. The proposed process modules obtain near stoichiometric CIS films for industrial solar cell production.
Many electrons on a mesoscopic cylinder in a threading magnetic field: Persistent current and magnetization
Authors: Onorato P.
Published: June 2012

The behavior of Ne interacting electrons confined in a mesoscopic “quantum” cylinder, QC, threaded by an Aharonov–Bohm (AB) flux ϕ is carefully analyzed by using a Hartree–Fock approximation. The ground state energies of the QC as a function of the magnetic field, B, and the electron–electron repulsion strength, U, are obtained. A phase diagram is presented indicating a rich variety of ground states and the spin and orbital magnetization responses to the magnetic field's variations are discussed. The behavior of persistent current is investigated and a significant change in current amplitude is observed when the strength of the electron–electron repulsion increases.
Anti‐inflammatory Activities of Eleven Centaurea Species Occurring in the Carpathian Basin
Authors: Csupor Dezső , Widowitz Ute , Blazsó Gábor , Laczkó‐Zöld Eszter , Tatsimo Joel S. N. , Balogh Ágnes , Boros Klára , Dankó Balázs , Bauer Rudolf , Hohmann Judit
Published: June 2012

Our study aimed at the identification of anti‐inflammatory activities of different fractions of C. sadleriana extract after per os administration in rats, the identification of the active compounds of the plant and the investigation of the in vitro anti‐inflammatory activities of Centaurea species native to or cultivated in the Carpathian Basin. The aerial parts of Centaurea sadleriana Janka have been used in Hungarian folk medicine to treat the wounds of sheep. Methanol extract of C. sadleriana was fractioned by solvent‐solvent partitioning. The n‐hexane fraction was further fractionated and the anti‐inflammatory activities of certain subfractions were confirmed in vivo in rats. The n‐hexane and chloroform fraction of the methanol extract of C. sadleriana exhibited remarkable COX‐1 and COX‐2 inhibiting effects in vitro. Chromatographic separation of the fractions led to the identification of the active subfractions and 11 compounds (α‐linolenic acid, γ‐linolenic acid, stigmasterol, β‐sitosterol, campesterol, vanillin, pectolinarigenin, salvigenin, hispidulin, chrysoeriol and apigenin). The in vitro screening for anti‐inflammatory activities of further Centaurea species occurring in the Carpathian Basin (C. adjarica, C. bracteata, C. cataonica, C. cynaroides, C. dealbata, C. indurata, C. macrocephala, C. melitensis, C. nigrescens, C. ruthenica) revealed considerable COX‐1 and COX‐2 inhibitory activities. Because C. sadleriana is an endangered species native only to the Carpathian Basin, the investigation of more prevalent species is reasonable. Copyright © 2012 John Wiley & Sons, Ltd.
Stability and bonding in the borane–H2complexes
Authors: Méndez Mariano , Cedillo Andrés
Published: June 2012

The ability of substituted boranes, XnBH3−n, to form stable complexes with the hydrogen molecule is analyzed by making use of computational chemistry and local reactivity parameters. In these complexes, the hydrogen molecule acts as a Lewis base while the borane moiety is the Lewis acid. Electronegative groups (X = CF3, F, OH) are selected to increase the acidity of the borane and it is found that the energetic stability of the complexes is only increased for the trifluoromethyl‐substituted Lewis acids, at the MP2/6‐311++g(3df, 3pd) level. It is also found that the BLYP density functional underestimates the adduct stability of these species. On the other hand, fluoroboranes and hydroxyboranes do not form donor–acceptor adducts with the hydrogen molecule; instead, we find weakly bounded van der Waals complexes. Additional features on the intrinsic reactivity of boranes are analyzed with the molecular electrostatic potential and the acceptor Fukui function. The nature of the interaction among the boranes and the hydrogen molecule is explored by using the topological analysis of the electron density through the Bader's Atoms‐in‐Molecules theory. © 2012 Wiley Periodicals, Inc.
Finite‐time formation control of multiagent systems via dynamic output feedback
Authors: Du Haibo , Li Shihua , Lin Xiangze
Published: June 2012

Finite‐time formation control of multiple second‐order agents via dynamic output feedback is investigated in this paper. Under the assumption that the velocities of all agents cannot be measured, a continuous consensus algorithm is first proposed such that the states of all agents will reach an agreement in finite time. Then, the consensus algorithm is applied to the finite‐time formation control, including stationary formation and moving formation, respectively. Rigorous proof shows that all agents will converge to the desired formation pattern in finite time. Finally, an example is given to verify the efficiency of the proposed method. Copyright © 2012 John Wiley & Sons, Ltd.
State‐saturatedH∞filtering with randomly occurring nonlinearities and packet dropouts: the finite‐horizon case
Authors: Ding Derui , Wang Zidong , Shen Bo , Shu Huisheng
Published: June 2012

This paper deals with theH∞filtering problem for a class of discrete time‐varying systems with state saturations, randomly occurring nonlinearities as well as successive packet dropouts. Two mutually independent sequences of random variables that obey the Bernoulli distribution are employed to describe the random occurrence of the nonlinearities and packet dropouts. The purpose of the addressed problem is to design a time‐varying filter such that theH∞disturbance attenuation level is guaranteed, over a given finite‐horizon, for the filtering error dynamics in the presence of saturated states, randomly occurring nonlinearities, and successive packet dropouts. By introducing a free matrix with its infinity norm less than or equal to 1, the error state is bounded by a convex hull so that some sufficient conditions obtained via solving a certain set of recursive nonlinear matrix inequalities. Furthermore, the obtained results are extended to the case when state saturations are partial. Two numerical simulation examples are provided to demonstrate the effectiveness and applicability of the proposed filter design approach. Copyright © 2012 John Wiley & Sons, Ltd.
How is Flow Experienced and by Whom? Testing Flow among Occupations
Authors: Llorens Susana , Salanova Marisa , Rodríguez Alma Mª
Published: June 2012

The aims of this paper are to test (1) the factorial structure of the frequency of flow experience at work; (2) the flow analysis model in work settings by differentiating the frequency of flow and the frequency of its prerequisites; and (3) whether there are significant differences in the frequency of flow experience depending on the occupation. A retrospective study among 957 employees (474 tile workers and 483 secondary school teachers) using multigroup confirmatory factorial analyses and multiple analyses of variance suggested that on the basis of the flow analysis model in work settings, (1) the frequency of flow experience has a two‐factor structure (enjoyment and absorption); (2) the frequency of flow experience at work is produced when both challenge and skills are high and balanced; and (3) secondary school teachers experience flow more frequently than tile workers. Copyright © 2012 John Wiley & Sons, Ltd.
Small‐Sized Carbon Nanohorns Enabling Cellular Uptake Control
Authors: Zhang Minfang , Zhou Xin , Iijima Sumio , Yudasaka Masako
Published: June 2012

Carbon nanotubes perform well in preclinical tests for drug delivery and diagnostic imaging, but controlling the size at less than 100 nm to avoid nonspecific uptake by reticuloendothelial systems while targeting delivery to cells of interest via receptor‐mediated endocytosis is difficult, which currently limits their widespread use. Herein, 20–50‐nm graphene tubules, small‐sized single‐walled carbon nanohorns (S‐SWNHs), are obtained with a yield of 20% or higher by an oxidative exfoliation of 100 nm pristine SWNH aggregates. S‐SWNHs are highly hydrophilic and remarkably resistant to cellular uptake by macrophages (RAW 264.7 cells), tumor cells (HeLa or KB), or normal cells (FHs 173We). The nonstimulatory property to cell membranes therefore makes cellular uptake control of S‐SWNHs by functionalization easy. By attaching phospholipid polyethylene glycol, the cellular internalization of S‐SWNHs is almost completely inhibited in RAW 264.7 macrophages. When functionalized with tumor‐targeting folic acid (FA), FA‐S‐SWNHs are taken up by FA receptor‐overexpressing KB cells but not by normal human embryonic cells (FHs 173We), which do not express the FA receptor. With a high rate of stealth and targeting in vitro, S‐SWNHs are one of the most promising nanoparticles for medical use.
Patterning of Crystalline Organic Materials by Electro‐hydrodynamic Lithography
Authors: Goldberg‐Oppenheimer Pola , Kohn Peter , Langford Richard M. , Steiner Ullrich
Published: June 2012

The control of semi‐crystalline polymers in thin films and in micrometer‐sized patterns is attractive for (opto‐)electronic applications. Electro‐hydrodynamic lithography (EHL) enables the structure formation of organic crystalline materials on the micrometer length scale while at the same time exerting control over crystal orientation. This gives rise to well‐defined micro‐patterned arrays of uniaxially aligned polymer crystals. This study explores the interplay of EHL structure formation with crystal alignment and studies the mechanisms that give rise to crystal orientation in EHL‐generated structures.
pH‐Controlled Delivery of Doxorubicin to Cancer Cells, Based on Small Mesoporous Carbon Nanospheres
Authors: Zhu Jie , Liao Lei , Bian Xiaojun , Kong Jilie , Yang Pengyuan , Liu Baohong
Published: June 2012

Mesoporous carbon nanospheres (MCNs) with small diameters of ≈90 nm are developed as an efficient transmembrane delivery vehicle of an anticancer drug, doxorubicin (DOX). MCNs exhibit a high loading capacity toward DOX due to hydrophobic interactions and the supramolecular π stacking between DOX and the carbonaceous structures, on which the pH‐dependent drug release are successfully achieved. Specifically, DOX can be loaded onto MCNs in basic solution and in a physiological pH range, while release occurs in acidic solution in its ionized state. By effective passive and active targeting, MCNs can be readily internalized into HeLa cells, where the carried DOX can be efficiently released in the acidic microenvironment of the tumors for further therapy. The endocytosis and cytotoxicity of DOX@MCNs toward HeLa cells are investigated by confocal microscopy and MTT assay. This smart pH‐dependent drug loading and release property of DOX@MCNs makes it possible to reduce the cytotoxicity to normal tissues during circulation in the body since the normal physiological pH is ≈7.4.
Doxorubicin‐Conjugated Mesoporous Magnetic Colloidal Nanocrystal Clusters Stabilized by Polysaccharide as a Smart Anticancer Drug Vehicle
Authors: Li Dian , Tang Jing , Wei Chuan , Guo Jia , Wang Shilong , Chaudhary Deeptangshu , Wang Changchun
Published: June 2012

Fabrication of magnetic nanocarriers that demonstrate enhanced biocompatibility and excellent colloidal stability is critical for the application of magnetic‐motored drug delivery, and it remains a challenge. Herein, a novel approach to synthesize mesoporous magnetic colloidal nanocrystal clusters (MMCNCs) that are stabilized by agarose is described; these clusters demonstrate high magnetization, large surface area and pore volume, excellent colloidal stability, enhanced biocompatibility, and acid degradability. The hydroxyl groups of agarose, which cover the surface of the magnetic nanocrystals, are modified with vinyl groups, followed by click reaction with mercaptoacetyl hydrazine to form the terminal hydrazide (–CONHNH2). The anticancer agent doxorubicin (DOX) is then conjugated to MMCNCs through a hydrazone bond. The resulting hydrazone is acid cleavable, thereby providing a pH‐sensitive drug release capability. This novel carrier provides an important step towards the construction of a new family of magnetic‐motored drug‐delivery systems. The experimental results show that the release rate of DOX from the DOX‐conjugated MMCNCs (MMCNCs‐DOX) is dramatically improved at low pH (tumor cell: pH 4–5 in the late stage of endolysosome and pH 5–6 from the early to late endosome), while almost no DOX is released at neutral pH (blood plasma). The cell cytotoxicity of the MMCNCs‐DOX measured by MTT assay exhibits a comparable antitumor efficacy but lower cytotoxicity for normal cell lines, when measured against the free drug, thus achieving the aim of reducing side effects to normal tissues associated with controlled drug release.
A Controllable Chiral Molecular Machine: Movement on Molecular Level
Authors: Yang Wenlong , Li Yongjun , Zhang Jianhong , Chen Nan , Chen Songhua , Liu Huibiao , Li Yuliang
Published: June 2012

With the view to develop new chiral molecular switches, a new pH‐controlled bistable chiral [3]rotaxane with a binaphthalene as chiral moiety is synthesized and characterized. The movement of the macrocycle DB24C8 along the thread tunes the dihedral angle between the two naphthalene rings and supplies tunable circular dichroism output signals.