bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of esterification crosslinking structures of rayon fibers with 1,2,3,4‐butanetetracarboxylic acid on tensile properties
Authors: Wang Xiaqin , Zhou Xingping , Wu Lishun , Zhang Jingfang , Li Xuefeng 
Published: April 2011

Abstract1,2,3,4‐Butanetetracarboxylic acid (BTCA) was applied to crosslink amorphous regions of cotton‐type rayon fibers via anhydride‐mediated esterification for the purpose of a molecular‐level control over macroscopic properties. Formation of intrafiber crosslinked structures of the rayon fibers was a facile and efficient method to diminish swelling degree and enhance tensile properties. Crosslinking was conducted under a series of curing temperature and various dosages of BTCA with the presence of sodium hypophosphite as the catalyst for anhydride formation. It was found that crosslinking conditions, both the curing temperature and dosage of the crosslinking agent, made notable impacts on the crosslinking behaviors of the rayon fibers. The dry and wet tensile strength of the rayon fibers were optimized for both the dosage of the crosslinking agent and the curing temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Novel functional nitrile butadiene rubber/magnetite nano composites for NTCR thermistors application
Authors: Al‐Juaid Salih S. , El‐Mossalamy E. H. , M. Arafa H. , Al‐Ghamdi A. A. , Daiem A. M. Abdel , El‐Tantawy Farid 
Published: April 2011

AbstractA new negative temperature coefficient of resistor (NTCR) thermistors based on nitrile butadiene rubber/magnetite (NBR/Fe3O4) nanocomposites were successfully fabricated by conventional roll milling technique. X‐ray diffraction and transmission (TEM) analysis showed that the product is mainly magnetite nanoparticles with diameter of 10‐13 nm. The microstructure of (NBR/Fe3O4) nanocomposites were examined by scanning electron microscopy (SEM) and FTIR spectroscopy. The dispersion of magnetite nanoparticles in the NBR rubber matrix and interfacial bonding between them were rather good. The thermal stability of nanocomposites was also obviously improved with the inclusion of the magnetite nanoparticles. The thermal conductivity, thermal diffusivity and specific heat of nanocomposites were investigated. The electrical conductivity of the NBR/Fe3O4 increases with the rise in temperature exhibiting a typical negative temperature coefficient of resistance (NTCR) behavior like a semiconductor. The nature of the temperature variation of electrical conductivity and values of activation and hopping energy, suggest that the transport conduction process is controlled by hopping mechanism. Values of characteristics parameters of the thermistors like thermistor constant, thermistor sensitivity and thermistor stability is quite good for practical application as NTCR devices at high temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
The mechanism and energy of activation of the melting of poly (ε‐caprolactone) with and without prior treatment with span 80
Authors: Fraga‐López Francisco , Manuel Martínez‐Ageitos J. , Rodríguez‐Núñez Eugenio , Blanco‐Mendez José , Luzardo‐Álvarez Asteria , Calvo‐Carnota Emilio , Jiménez‐Carrillo Lisbeth 
Published: April 2011

AbstractDifferential scanning calorimetry (DSC) is used to determine the energy of activation and melting mechanism of PCL and of mixtures of PCL with the surfactant Span 80. The melting of poly(ε‐caprolactone) follows a nucleation and growth model with an Avrami exponent of 4. Addition of Span 80 reduces the energy of activation of this process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Synthesis of biodegradable material poly(lactic acid‐co‐aspartic acid) via direct melt polycondensation and its characterization
Authors: Ye Rui‐Rong , Wang Zhao‐Yang , Wang Qun‐Fang , Yang Kai , Luo Shi‐He 
Published: April 2011

AbstractDirectly starting from L‐lactic acid (LA) and L‐aspartic acid (Asp), biodegradable material poly(lactic acid‐co‐aspartic acid) [P(LA‐co‐Asp)] was synthesized via melt polycondensation. The synthetic conditions, including type and dosage of catalyst, temperature, and time of copolymerization, and influence of molar feed ratio were discussed. The structure and properties of the copolymer were systematically characterized with FTIR, 1H‐NMR, GPC, DSC, and XRD. With the increase of Asp in the feed, [η] and Mw decreased, and the crystallinity of the copolymer disappeared gradually. Compared to the homopolymer, poly(L‐lactic acid) synthesized via melt polycondensation and the copolymer P(LA‐co‐Asp) had a higher glass‐transition temperature (Tg). The copolymer P(LA‐co‐Asp) with Mw of 4400–24300 Da was obtained, which could meet the demand as a drug‐delivery carrier material. Compared to the ring‐opening polymerization of the cyclic intermediates, including lactide, the novel direct copolycondensation method was a cheap and practical method for the synthesis of copolymer P(LA‐co‐Asp) as biomedical materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Dielectric properties of new fully conjugated 2H‐ and metal‐pyrazinoporphyrazine network polymers
Authors: Abdel‐Razik H. H. , El‐Sayed S. , Hassen A. 
Published: April 2011

Abstract2,7‐Di‐tert‐butylpyrene was oxidized to 2,7‐di‐tert‐butylpyrene‐4,5,9,10‐tetraone. The latter through condensation reaction with vicinal diamine such as diaminomaleodinitrile afforded heterocyclic monomer, 2,7‐di‐tert‐butyl pyrene[4,5][9,10]bis(2,3‐pyrazine‐5,6‐dinitrile), which was cyclotetramerized to the corresponding 2H‐ and metal‐pyrazinoporphyrazine‐based network polymers (2H‐PyzPz and M‐PyzPz, M = Co, Ni, Zn, or Cu). Elemental analytical results, Infrared, and NMR spectral data of the new prepared molecules are consistent with their assigned formulations. Molecular masses and metal contents of the synthesized polymers proved to be of high molecular masses, which confirm the efficiency of tetramerization polymerization and complexation reactions. Dielectric permittivity, ε′, loss tangent, tan δ, and ac conductivity, σac(ω), of 2H‐PyzPz and M‐PyzPz films were studied as a function of temperature and frequency. It was found that dielectric permittivity, ε′, decreases with the increase of frequency and increases with the increase in temperature. Ac conductivity, σac(ω), is found to vary as Bωs and the frequency exponent, s, is less than unity around room temperature indicating a dominant hopping process. On the other hand, σac(T) of all samples is thermally activated with low activation energies. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.
Synthesis, characterization, and properties of poly(amide‐imide)s from a new diimide‐diacid by direct polycondensation with various diamines
Authors: Ghaemy Mousa , Movagharnezhad Nasim , Khajeh Soheila 
Published: April 2011

AbstractA new diimide‐diacid, 2,2′‐(5‐(4‐(4‐(4,5‐diphenyil‐1H‐imidazol‐2‐yl)phenoxy)phenylcarbam‐oyl)‐1,3‐phenylenebis(1,3‐dioxoisoindoline‐5‐carboxylic‐acid)(DADA), was synthesized from the reaction between trimellitic anhydride and a new diamine, N‐(4‐(4‐(4,5‐diphenyl‐1H‐imidazole‐2‐yl)phenoxylphenyl)‐3,5‐diaminobenzamide(NIDA). The direct polycondensation of DADA with various diamines was carried out in NMP in the presence of triphenylposphite and pyridine as condensing agents. The resulting poly(amide‐imide)s (PAIs) were amorphous, readily soluble in many polar aprotic solvents and showed inherent viscosities of 0.35–0.47 dL/g. According to thermal analysis, these polymers exhibited glass transition temperatures (Tgs) in the range of 207–271°C, and their initial decomposition temperature (Ti) varied from 260 to 330°C and temperature of 10% weight loss (T10) from 325 to 520°C in N2. These polymers in NMP solution exhibited strong UV–vis absorption maxima at 320 nm and their fluorescence emission peaks appeared around 425–450 nm. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.
Semiconductor‐assisted self‐cleaning polymeric fibers based on zinc oxide nanoparticles
Authors: Moafi Hadi Fallah , Shojaie Abdollah Fallah , Zanjanchi Mohammad Ali 
Published: April 2011

AbstractSelf‐cleaning polymeric fibers have been successfully prepared by depositing ZnO nanoparticle onto wool and polyacrylonitrile (PAN) fibers with good compatibility and significant photocatalytic self‐cleaning activity using the sol‐gel process at ambient temperature. scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, diffuse reflectance spectroscopy, X‐ray diffraction, Brunauer‐Emmett‐Teller surface area analysis, and thermogravimetric analysis have been adopted as the characterization techniques. Transmission electron microscopy studies revealed presence of zinc oxide nanoparticles with 10–15 nm in size. Brunauer‐Emmett‐Teller measurement showed surface area of 48 m2/g for the ZnO nanoparticles. Photocatalytic activity of the self‐cleaning materials were tested by measuring the photo‐assisted degradation of methylene blue (MB) and eosin yellowish (EY) under ultraviolet‐visible illumination. The results indicate that both of the ZnO‐coated polyacrylonitrile and ZnO‐coated wool fibers acquire photocatalytic activity toward dyes degradation. The photocatalytic activity of the treated fibers is maintained upon several numbers of photodegradation cycles. This facile and cheap preparation technique can be also applied to new polymeric fabrics to produce self‐cleaning materials for industrial application. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Focal fat lesions at vertebral corners on magnetic resonance imaging predict the development of new syndesmophytes in ankylosing spondylitis
Authors: Chiowchanwisawakit Praveena , Lambert Robert G. W. , Conner‐Spady Barbara , Maksymowych Walter P. 
Published: April 2011

AbstractObjectiveFocal fat infiltration is frequently visible on magnetic resonance imaging (MRI) of the spine in patients with ankylosing spondylitis (AS) and likely reflects postinflammatory tissue metaplasia. To support the concept of coupling between inflammation and new bone formation, we tested the hypothesis that focal fat infiltration at a vertebral corner is more likely to evolve into a de novo syndesmophyte.MethodsMRI scans were obtained at baseline and radiographs were obtained at baseline and 2 years in 100 AS patients from 2 cohorts: a clinical trial cohort (n = 38) and an observational cohort (n = 62). In the clinical trial cohort, patients were randomized to receive anti–tumor necrosis factor (anti‐TNF) therapy or placebo for 12–24 weeks and then open‐label treatment for 2 years. In the observational cohort, patients received either standard therapy (n = 36) or anti‐TNF therapy (n = 26) for 2 years. Vertebral corner inflammation and fat infiltration were assessed independently by pairs of readers who were blinded with regard to the radiographic findings.ResultsNew syndesmophytes developed significantly more frequently in vertebral corners with fat in both the clinical trial (10.2%) and the observational (6.5%) cohort as compared to those without either feature on baseline MRI (3.1% [P = 0.008] and 1.4% [P = 0.0002], respectively). Adjusting for within‐patient variations in baseline syndesmophytes/ankylosis, vertebral corners that were fat‐positive/inflammation‐positive significantly predicted new syndesmophytes, with an odds ratio (OR) of 7.6 (95% confidence interval [95% CI] 1.5–38.5 [P = 0.01]), while a model that included baseline variations in both fat and inflammation showed an OR of 5.8 (95% CI 2.2–15.3 [P < 0.001]) for inflammation and an OR of 1.9 (95% CI 0.9–4.1 [P = 0.1]) for fat.ConclusionOur data lend support to the hypothesis that inflammatory lesions evolve into new bone through a process of tissue metaplasia that includes fat infiltration.
Hypoxia induces mitochondrial mutagenesis and dysfunction in inflammatory arthritis
Authors: Biniecka Monika , Fox Edward , Gao Wei , Ng Chin Teck , Veale Douglas J. , Fearon Ursula , O'Sullivan Jacintha 
Published: April 2011

AbstractObjectiveTo assess the levels and spectrum of mitochondrial DNA (mtDNA) point mutations in synovial tissue from patients with inflammatory arthritis in relation to in vivo hypoxia and oxidative stress levels.MethodsRandom Mutation Capture assay was used to quantitatively evaluate alterations of the synovial mitochondrial genome. In vivo tissue oxygen levels (tPO2) were measured at arthroscopy using a Licox probe. Synovial expression of lipid peroxidation (4‐hydroxynonenal [4‐HNE]) and mitochondrial cytochrome c oxidase subunit II (CytcO II) deficiency were assessed by immunohistochemistry. In vitro levels of mtDNA point mutations, reactive oxygen species (ROS), mitochondrial membrane potential, and markers of oxidative DNA damage (8‐oxo‐7,8‐dihydro‐2′‐deoxyguanine [8‐oxodG]) and lipid peroxidation (4‐HNE) were determined in human synoviocytes under normoxia and hypoxia (1%) in the presence or absence of superoxide dismutase (SOD) or N‐acetylcysteine (NAC) or a hydroxylase inhibitor (dimethyloxalylglycine [DMOG]). Patients were categorized according to their in vivo tPO2 level (<20 mm Hg or >20 mm Hg), and mtDNA point mutations, immunochemistry features, and stress markers were compared between groups.ResultsThe median tPO2 level in synovial tissue indicated significant hypoxia (25.47 mm Hg). Higher frequency of mtDNA mutations was associated with reduced in vivo oxygen tension (P = 0.05) and with higher synovial 4‐HNE cytoplasmic expression (P = 0.04). Synovial expression of CytcO II correlated with in vivo tPO2 levels (P = 0.03), and levels were lower in patients with tPO2 <20 mm Hg (P < 0.05). In vitro levels of mtDNA mutations, ROS, mitochondrial membrane potential, 8‐oxo‐dG, and 4‐HNE were higher in synoviocytes exposed to 1% hypoxia (P < 0.05); all of these increased levels were rescued by SOD and DMOG and, with the exception of ROS, by NAC.ConclusionThese findings demonstrate that hypoxia‐induced mitochondrial dysfunction drives mitochondrial genome mutagenesis, and antioxidants significantly rescue these events.
Synthesis and luminescence properties of Ca3Ga2Si3O12:RE3+ (RE = Eu/Tb) powder phosphors
Authors: Bhushana Reddy M. , Sailaja S. , Vemasevana Raju K. , Nageswara Raju C. , Giridhar P. , Vengala Rao B. , Sudhakar Reddy B. 
Published: April 2011

ABSTRACTRare earth ions (Eu3+ or Tb3+)‐activated Ca3 Ga2 Si3O12 (CaGaSi) phosphors were synthesized by using a sol–gel method. Photoluminescence spectra of Eu3+:CaGaSi phosphors exhibited five emission bands at 578, 592, 612, 652 and 701 nm, which were assigned to the transitions (5D0 → 7F0, 7F1, 7F2, 7F3 and 7F4), respectively, with an excitation wavelength of λexci = 392 nm. Among these, the transition 5D0 → 7F2 (612 nm) displayed bright red emission. In the case of Tb3+:CaGaSi phosphors, four emission bands were observed at 488 (5D4 → 7F6), 543 (5D4 → 7F5), 584 (5D4 → 7F4) and 614 nm (5D4 → 7F3) from the measurement of PL spectra with λexci = 376 nm. Among these, the transition 5D4 → 7F5 at 543 nm displayed bright green emission. The structure and morphology of the phosphors were studied from the measurements of X‐ray diffraction (XRD), scanning electron microscopy (SEM) and energy‐dispersive X‐ray analysis (EDAX) results. Copyright © 2011 John Wiley & Sons, Ltd.
Sodium azide as a specific quencher of singlet oxygen during chemiluminescent detection by luminol andCypridinaluciferin analogues
Authors: Bancirova Martina 
Published: April 2011

ABSTRACTReactive oxygen species (ROS) are presently thought to play important role in an increasing number of the physiological and pathological processes in living organisms. Various chemiluminescent (CL) compounds have been studied in order to find suitable and specific probes for the detection of particular ROS species. The CL of luminol is known to be non‐specific and can be induced by various oxidants. TwoCypridinaluciferin analogues, CLA and MCLA, have been used for the detection of ROSin vivo. CLAs are thought to emit light only when reacting with superoxide and singlet oxygen. It is possible to distinguish the particular ROS by using a specific quencher or scavenger, e.g. superoxide dismutase (SOD) or sodium azide (NaN3). The CL reactions of luminol (3‐aminophthalhydrazide), CLA [2‐methyl‐6‐phenyl‐3,7‐dihydroimidazo(1,2α) pyrazin‐3‐one] and MCLA [2‐methyl‐6‐(p‐methoxyphenyl)‐3,7‐dihydroimidazo(1,2α) pyrazin‐3‐one] were studied in three hydrogen peroxide decomposition systems (H2O2–HRP; H2O2–CuSO4; and H2O2–NaOCl). The measurements were carried out in phosphate buffer, pH 7.4, at 25 °C, using a luminometer (Fluoroskan Ascent FL and Sirius C). NaN3was used as the specific quencher of singlet oxygen. The results demonstrate that the proclaimed specifity of the CL ofCypridinaluciferin analogues towards singlet oxygen has to be discussed. Copyright © 2011 John Wiley & Sons, Ltd.
Filtration kinetics of chitosan separation by electrofiltration
Authors: Gözke Gözde , Kirschhöfer Frank , Heissler Stefan , Trutnau Mirko , Brenner‐Weiss Gerald , Ondruschka Jelka , Obst Ursula , Posten Clemens 
Published: April 2011

AbstractDownstream processing of chitosan requires several technological steps that contribute to the total production costs. Precipitation and especially evaporation are energy‐consuming processes, resulting in higher costs and limiting industrial scale production. This study investigated the filtration kinetics of chitosan derived from cell walls of fungi and from exoskeletons of arthropods by electrofiltration, an alternative method, thus reducing the downstream processing steps and costs. Experiments with different voltages and pressures were conducted in order to demonstrate the effect of both parameters on filtration kinetics. The concentration of the biopolymer was obtained by the average factor of 40 by applying an electric field of 4 V/mm and pressure of 4 bars. A series of analytical experiments demonstrated the lack of structural and functional changes in chitosan molecules after electrofiltration. These results, combined with the reduction of energy and processing time, define the investigated method as a promising downstream step in the chitosan production technology.
A single, selective and simple validated method for simultaneous estimation of amiloride and hydrochlorothiazide in human plasma by liquid chromatography–tandem mass spectrometry
Authors: Jangid Arvind G. , Tale Rajesh H. , Vaidya Vikas V. 
Published: April 2011

ABSTRACTA single, simple and selective method for simultaneous estimation of amiloride and hydrochlorothiazide in human plasma was validated using triamterine and hydrochlorothiazide13C,d2 as internal standard. The compounds were separated on a reverse‐phase column with an isocratic mobile phase consisting of 2 mm ammonium acetate pH 3.0 and acetonitrile (30:70, v/v) and detected by tandem mass spectrometry with positive/negative ion mode. The analytes and internal standards were extracted from plasma using simple solid phase extraction. The ion transitions recorded in multiple reaction monitoring mode were m/z 230.1 → 116.0 for amiloride, m/z 254.1 → 237.1 for internal standard, triamterine in positive mode and m/z 296.1 → 204.9 for hydrochlorothiazide, m/z 299.2 → 205.8 for internal standard, hydrochlorothiazide13C,d2 in negative ion mode. Linearity in plasma was observed over the concentration range 0.1–10 ng/mL for amiloride and 5.0–500.0 ng/mL for hydrochlorothiazide. The mean recovery was 41.1 and 81.5% for amiloride and hydrochlorothiazide respectively. The coefficient of variation of the assay was less than 11.2 and 5.2% for amiloride and hydrochlorothiazide, respectively, and the accuracy was 89.0–98.1 and 96.6–102.9% for amiloride and hydrochlorothiazide, respectively. The validated method can be applied to the pharmacokinetic study of amiloride and hydrochlorothiazide. Copyright © 2011 John Wiley & Sons, Ltd.
Chemical Synthesis and Expression of the HIV‐1 Rev Protein
Authors: Siman Peter , Blatt Ofrah , Moyal Tal , Danieli Tsafi , Lebendiker Mario , Lashuel Hilal A. , Friedler Assaf , Brik Ashraf 
Published: April 2011

AbstractThe HIV‐1 Rev protein is responsible for shuttling partially spliced and unspliced viral mRNA out of the nucleus. This is a crucial step in the HIV‐1 lifecycle, thus making Rev an attractive target for the design of anti‐HIV drugs. Despite its importance, there is a lack of structural, biophysical, and quantitative information about Rev. This is mainly because of its tendency to undergo self‐assembly and aggregation; this makes it very difficult to express and handle. To address this knowledge gap, we have developed two new highly efficient and reproducible methods to prepare Rev in large quantities for biochemical and structural studies: 1) Chemical synthesis by using native chemical ligation coupled with desulfurization. Notably, we have optimized our synthesis to allow for a one‐pot approach for the ligation and desulfurization steps; this reduced the number of purification steps and enabled the obtaining of desired protein in excellent yield. Several challenges emerged during the design of this Rev synthesis, such as racemization, reduced solubility, formylation during thioester synthesis, and the necessity for using orthogonal protection during desulfurization; solutions to these problems were found. 2) A new method for expression and purification by using a vector that contained an HLT tag, followed by purification with a Ni column, a cation exchange column, and gel filtration. Both methods yielded highly pure and folded Rev. The CD spectra of the synthetic and recombinant Rev proteins were identical, and consistent with a predominantly helical structure. These advances should facilitate future studies that aim at a better understanding of the structure and function of the protein.
Supported Transition Metal Catalysts for Hydrodechlorination Reactions
Authors: Keane Mark A. 
Published: April 2011

AbstractAs halogenated waste is xenobiotic with no analogous compounds in nature, there is no natural means of ameliorating the negative environmental impact caused by halo‐organic emissions. The presence of organo‐halogens in effluent discharges is of increasing concern, owing to the mounting evidence of adverse stratospheric ozone, ecological effects, and the impact on public health. There is a pressing need, driven by legislative and financial imperatives, to develop robust and efficient treatment technologies. This Review considers the application of catalytic hydrodechlorination (HDC) as a progressive approach to the conversion and recycling of toxic chloro‐compounds. An overview of the existing treatment technologies is provided with an assessment of the benefits of catalytic HDC over separation/oxidation methodologies. Taking the transformation of chloro‐aromatics, the catalytic HDC of liquid and gas phase reactants is considered in turn with a critical analysis of the pertinent literature. Two “case studies” are considered in detail: i) the liquid phase HDC of chlorophenols over alumina supported palladium, focusing on the critical process and catalyst structural characteristics that influence HDC performance; ii) the gas phase conversion of a range of halogenated (Cl and Br) aromatics over silica supported nickel with an examination of the dehalogenation activity/selectivity response as a function of the nature of the aromatic reactant.