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  • Öğe
    An ecological restoration assessment integrating multi-criteria decision analysis with landscape sensitivity analysis for a hydroelectric power plant project: the Tokat-Niksar case
    (Springer Science and Business Media Deutschland GmbH, 2021) Demir, Sara; Demirel, Ö.; Okatan, A.
    Due to Turkey’s reliance on imported electricity, it has been using hydroelectric power plants (HPPs) to cover some of its electrical energy needs since 2011. However, HPP projects, which do not take landscape sensitivity into account, cause the ecological integrity of the basins and the ecosystem structure to deteriorate. This study presents the Tokat-Niksar HPP project field example in Turkey’s Central Black Sea region with its steep slopes, rich forest and creek vegetation, protected endemic plants and wildlife, cultural heritage dating back to 3000 BC agricultural activities, and long-established local culture. The study, in fact, aims to develop a landscape restoration plan that considers the sensitivity of landscapes in the HPP project area. For this purpose, a landscape sensitivity analysis consisting of water, habitat, visibility, erosion functions, and multi-criteria decision analysis (MCDA) determining priority of functions conducted with experts were performed. According to the results, the water function was found to have the highest, and the visibility the lowest priority in the ranking. Consequently, 1st, 2nd, 3rd, and 4th-degree sensitive areas with very high, high, and moderate landscape sensitivity were determined by weighted sum function by considering the priority of each landscape function, and accordingly, a five-stage landscape restoration model was developed including soil protection, areas to be protected, erosion control, vegetation screening, and creek reclamation. This study presents a framework for sustainable landscape restoration solutions in the town by combining landscape sensitivity analysis via MCDA.
  • Öğe
    Senkron relüktans motorun gözlemci tabanlı sensörsüz kontrolü
    (BTÜ, Fen Bilimleri Enstitüsü, 2021) Cebeci, Emre; Yaşa, Yusuf
    Senkron relüktans motorlar, relüktans momenti prensibiyle mekanik enerji üretebilen elektrik makineleridir. Rotorunda herhangi bir sargı ve mıknatıs bulundurmadığından dolayı ucuz ve sağlam yapıya sahiptir. Bu sebeplerden dolayı keşfi daha önceki zamanlara dayansa da güç elektroniği ve kontrol yöntemlerindeki gelişmelerden dolayı son zamanlarda popüler hâle gelmiştir. Senkron relüktans motor; asenkron motor gibi sabit hız uygulamaları için direkt şebekeye bağlanamamakta, motor sürücü devresi gerektirmektedir. Motor sürücü devresi, gerekli anahtarlamaları yapabilmesi için rotor açısal konumuna ihtiyaç duymaktadır. Kontrol yöntemleri konum sensörlü ve sensörsüz olmak üzere ikiye ayrılmaktadır. Bu tez çalışmasında sensörsüz olarak senkron relüktans motor kontrol edilmiştir. Sensörsüz kontrol yönteminde daha önce tüm alternatif akımlı makineler için önerilen aktif akı kavramının prensibi ile rotor açısal konumu tahmin edilmektedir. Aktif akı vektörü ile rotor konumu tahmininde daha önce önerilen yöntemlerden farklı olarak aktif akı vektörünü diferansiyel denklemlerine ayırarak durum uzay denklem kümesi oluşturulmuştur. Oluşturulan durum uzay denklemlerine uygun Kokusuz Kalman Filtresi (UKF) tasarlanmıştır. UKF sayesinde aktif akı vektör bileşenleri tahmin edilmiştir. Bileşenler sayesinde rotor açısal konumu tahmin edilmiştir. Diğer aktif akı ile rotor açısal konumu tahmin yöntemlerinden farkı, içeriğinde herhangi bir integrator veya Faz Kilitli Döngü (PLL) bulundurmamasıdır. UKF ile tahmin edilen rotor açısal konum değeri kullanılarak motor elektriksel parametreleri Park Dönüşümü ile dönen eksen takımına dönüştürülmektedir. Dönen eksen takımında oluşturulan senkron relüktans motor dinamik denklemleri için Genişletilmiş Kalman Filtresi (EKF) tasarlanmıştır. Tasarlanan EKF ile rotor açısal hızı ve yük torku tahmin edilebilmektedir. Tahmin edilen rotor açısal hızı, diğer tahmin yöntemlerindeki tahmin değerleri ile karşılaştırılmış, EKF ile tahmin edilen rotor açısal hız hatasının diğer yöntemlere göre %70 oranında daha az olduğu gözlemlenmiştir. Tahmin edilen rotor açısal konum, hız ve yük torku değerleri için alan yönlendirmeli kontrol yöntemleri uygulanarak senkron relüktans motor kontrol edilmiştir. Bahsedilen kontrol basamakları bilgisayar ortamında benzetim çalışması yapıldıktan sonra test düzeneğinde kontrol edilmiştir. Test düzeneğindeki sürücü kartında diğer güç anahtarlarına nazaran daha iyi performans sergileyen silisyum karbür (SiC) tip mosfetler kullanılmıştır. Bu Şekilde devre ve sistemin performansı artırılmıştır.
  • Öğe
    Gas phase polymerization of ethylene towards UHMWPE
    (2020) Geçim, Gözde; Erkoç, Ertuğrul
    For the first time, ultra-high molecular weight polyethylene (UHMWPE) was produced in gas phase process with a new fluidized bed concept where the solids are dispersed phase and the gas is bulk phase as opposed to conventional fluidized bed reactors (FBRs). With this concept, UHMWPE with average molecular weights about 1-6,9 × $10^6$ g moles ?1 were produced with a commercial supported Ziegler-Natta catalyst by using a gas phase mini semibatch reactor system. Additionally, optimum conditions of gas phase polymerization for the best results of productivity, catalyst activity, molecular weight and crystallinity were determined by Taguchi experimental design and catalyst stability at the optimum condition was tested by video microscopy polymerization. The characterization of products was carried out experimentally by TGA, DSC, FTIR, and NMR.
  • Öğe
    Selected Persistent Organic Pollutants in Ambient Air in Turkey: Regional Sources and Controlling Factors
    (American Chemical Society, 2021) Gungormus, E.; Sofuoglu, A.; Celik, H.; Gedik, K.; Mulder, M.D.; Lammel, G.; Birgül, Aşkın
    As a result of its unique location, Turkey receives air masses from Europe, Russia, Middle East, and Africa, making it an important place in terms of long-range atmospheric transport (LRT) of contaminants. Atmospheric levels of 22 organochlorine pesticides (OCPs), 45 polychlorinated biphenyls (PCBs), and 14 polybrominated diphenyl ethers (PBDEs) were measured in two metropolitan cities, Istanbul and Izmir, on a weekly basis from May 2014 to May 2015. Dichlorodiphenyltrichloroethane (DDT) and its derivatives were dominant OCP species, followed by isomers of hexachlorocyclohexane (HCH) at both sites. The annual mean concentration of ?DDX (sum of o,p?-DDT, p,p?-DDT, o,p?-DDD, p,p?-DDD, o,p?-DDE, and p,p?-DDE) was 82 pg/m3 for Istanbul and 89 pg/m3 for Izmir, while these levels were about 46 pg/m3 for ?HCHs (sum of ?-, ?-, ?-, and ?-HCH) at both of the sites. At both stations, tri- and tetra-PCBs and tetra- and penta-PBDEs were dominant congeners. The temperature dependence indicates that both LRT and local contaminated areas contribute to the elevated levels. A Lagrangian particle dispersion model (FLEXPART) showed a few potential source regions in northern Africa and Middle East, southern-southwestern and eastern Europe including Russia, as well as from local domestic metropolitan areas. © 2021 American Chemical Society.
  • Öğe
    Author Correction: Demonstration of Container Efects on Recognition Process of Liquids Using a RingResonator Measurement Method
    (Nature Research, 2020) Öztürk, Turgut
    The Acknowledgements section in this Article was omitted. The Acknowledgements section should read: “The author thanks İlhami Ünal and Aysun Sayıntı for providing the measurement data made at Marmara Research Center of TUBITAK.” © 2020, The Author(s).
  • Öğe
    Antibacterial activity of combination of synthetic and biopolymer non-woven structures
    (Walter de Gruyter GmbH, 2015) Bhullar, Sukhwinder Kaur; Özsel Kaya, Burçak; Yadav, R.; Kaur, G.; Chintamaneni, M.; Buttar, H.S.
    Background: Fibrous structures and synthetic polymer blends offer potential usages in making biomedical devices, textiles used in medical practices, food packaging, tissue engineering, environmental applications and biomedical arena. These products are also excellent candidates for building scaffolds to grow stem cells for implantation, to make tissue engineering grafts, to make stents to open up blood vessels caused by atherosclerosis or narrowed by blood clots, for drug delivery systems for micro- to nano-medicines, for transdermal patches, and for healing of wounds and burn care. The current study was designed to evaluate the antimicrobial activity of woven and non-woven forms of nano- and macro-scale blended polymers having biocompatible and biodegradable characteristics. Methods: The antimicrobial activity of non-woven fibrous structures created with the combination of synthetic and biopolymer was assessed using Gram-negative, Gram-positive bacteria, such as Staphylococcus aureus, Proteus vulgaris, Escherichia coli and Enterobacter aerogenes using pour plate method. Structural evaluation of the fabricated samples was performed by Fourier transform infrared spectroscopy. Results: Broad spectrum antibacterial activities were found from the tested materials consisting of polyvinyl alcohol (PVA) with chitosan and nylon-6 combined with chitosan and formic acid. Conclusions: The combination of PVA with chitosan was more bactericidal or bacteriostatic than that of nylon-6 combined with chitosan and formic acid. PVA combination with chitosan appears to be a broad-spectrum antimicrobial agent. © 2015 by De Gruyter 2015.
  • Öğe
    An alginate-poly(acrylamide) hydrogel with TGF-?3 loaded nanoparticles for cartilage repair: Biodegradability, biocompatibility and protein adsorption
    (Elsevier B.V., 2021) Saygili, E.; Kaya, E.; Ilhan-Ayisigi, E.; Saglam-Metiner, P.; Alarcin, E.; Kazan, Aslıhan; Girgic, E.
    Current implantable materials are limited in terms of function as native tissue, and there is still no effective clinical treatment to restore articular impairments. Hereby, a functionalized polyacrylamide (PAAm)-alginate (Alg) Double Network (DN) hydrogel acting as an articular-like tissue is developed. These hydrogels sustain their mechanical stability under different temperature (+4 °C, 25 °C, 40 °C) and humidity conditions (60% and 75%) over 3 months. As for the functionalization, transforming growth factor beta-3 (TGF-?3) encapsulated (NPTGF-?3) and empty poly(lactide-co-glycolide) (PLGA) nanoparticles (PLGA NPs) are synthesized by using microfluidic platform, wherein the mean particle sizes are determined as 81.44 ± 9.2 nm and 126 ± 4.52 nm with very low polydispersity indexes (PDI) of 0.194 and 0.137, respectively. Functionalization process of PAAm-Alg hydrogels with ester-end PLGA NPs is confirmed by FTIR analysis, and higher viscoelasticity is obtained for functionalized hydrogels. Moreover, cartilage regeneration capability of these hydrogels is evaluated with in vitro and in vivo experiments. Compared with the PAAm-Alg hydrogels, functionalized formulations exhibit a better cell viability. Histological staining, and score distribution confirmed that proposed hydrogels significantly enhance regeneration of cartilage in rats due to stable hydrogel matrix and controlled release of TGF-?3. These findings demonstrated that PAAm-Alg hydrogels showed potential for cartilage repair and clinical application. © 2021 Elsevier B.V.
  • Öğe
    A test of improved force field parameters for urea: molecular-dynamics simulations of urea crystals
    (Springer, 2012) Altınbaş Özpınar, Gül; Beierlein, Frank R.; Peukert, Wolfgang; Zahn, Dirk; Clark, Timothy
    Molecular-dynamics (MD) simulations of urea crystals of different shapes (cubic, rectangular prismatic, and sheet) have been performed using our previously published force field for urea. This force field has been validated by calculating values for the cohesive energy, sublimation temperature, and melting point from the MD data. The cohesive energies computed from simulations of cubic and rectangular prismatic urea crystals in vacuo at 300 K agreed very well with the experimental sublimation enthalpies reported at 298 K. We also found very good agreement between the melting points as observed experimentally and from simulations. Annealing the crystals just below the melting point leads to reconstruction to form crystal faces that are consistent with experimental observations. The simulations reveal a melting mechanism that involves surface (corner/edge) melting well below the melting point, and rotational disordering of the urea molecules in the corner/edge regions of the crystal, which then facilitates the translational motion of these molecules.
  • Öğe
    A DFT study on the [VO](1+)-ZSM-5 cluster: direct methanol oxidation to formaldehyde by N2O
    (Royal Soc Chemistry, 2013) Fellah, Mehmet Ferdi; Onal, Isik
    The mechanism of direct oxidation of methanol to formaldehyde by N2O has been theoretically investigated by means of density functional theory over an extra framework species in ZSM-5 zeolite represented by a [(SiH3)(4)AlO4](1) [V-O](1+) cluster model. The catalytic reactivity of these species is compared with that of mononuclear (Fe-O)(1+) sites in ZSM-5 investigated in our earlier work at the same level of theory (J. Catal. 2011, 282, 191). The [V-O](1+) site in ZSM-5 zeolite shows an enhanced catalytic activity for the reaction. The calculated vibrational frequencies for grafted species on vanadium sites on the surface are in good agreement with the experimental values. According to the theoretical results obtained in this study the [V-O](1+) site in the ZSM-5 catalyst has an important role in the direct catalytic oxidation of methanol to formaldehyde by N2O.
  • Öğe
    Radiation transmission of colemanite, tincalconite and ulexite for 6 and 18 MV X-rays by using linear accelerator
    (Pergamon-Elsevier Science Ltd, 2013) Demir, Faruk; Un, Adem
    Tincalconite, ulexite and colemanite are boron ores. Since these ores include boron, hydrogen and many other elements, these boron ores may be used as shielding materials instead of Pb metal and paraffin wax. In this study, measurements have been made to determine radiation transmission of tincalconite, ulexite and colemanite by transmission method for 6 and 18 MV using linear accelerator (LINAC) with ionization chamber. The experimental results were compared to the results of WinXCom X-ray computer program's. In pair production region, ores such as colemanite, ulexite and tincalconite can be preferred as shielding materials to prevent photon and neutron particle radiations. (C) 2012 Elsevier Ltd. All rights reserved.
  • Öğe
    Determination of mass attenuation coefficients, effective atomic numbers and effective electron numbers for heavy-weight and normal-weight concretes
    (Pergamon-Elsevier Science Ltd, 2013) Un, Adem; Demir, Faruk
    Total mass attenuation coefficients, effective atomic numbers and effective electron numbers values for different 16 heavy-weight and normal-weight concretes are calculated in the energy range from 1 keV to 100 GeV. The values of mass attenuation coefficients used in calculations are taken from the WinXCom computer program. The obtained results for heavy-weight concretes are compared with the results for normal-weight concretes. The results of heavy-weight concretes fairly differ from results for normalweight concretes. (C) 2013 Elsevier Ltd. All rights reserved.
  • Öğe
    Cycloartane glycosides from Astragalus plumosus var. krugianus and evaluation of their antioxidant potential
    (Elsevier, 2014) Denizli, Nilufer; Horo, Ibrahim; Gulcemal, Derya; Masullo, Milena; Festa, Michela; Koz, Ömer
    The methanol extracts of Astragalus plumosus var. krugianus Chamb. & Matthews afforded sixteen cycloartane glycosides among which krugianoside A, was never reported before. All compounds were evaluated for their cytotoxic activity in human skin fibroblast WS1 cells. For compounds exhibiting no significant effect on WS1 viability, the antioxidant potential was examined. Compounds 1 and 8 prevented elevation of ROS induced by t-BOOH, suggesting the potential activity of these compounds to protect fibroblasts from oxidative stress. (C) 2013 Elsevier B.V. All rights reserved.
  • Öğe
    Enzymatic hydrolysis of autohydrolyzed wheat straw followed by refining to produce fermentable sugars
    (Elsevier Sci Ltd, 2014) Ertaş, Murat; Han, Qiang; Jameel, Hasan; Chang, Hou-min
    Wheat straw was pretreated using an autohydrolysis process with different temperatures (160-200 degrees C) and times (10-20 min) in order to allow the recovery of hemicellulose in the filtrate and help open up the structure of the biomass for improved accessibility of enzymes during enzymatic hydrolysis. Autohydrolysis at 190 degrees C for 10 min provided the highest overall sugar (12.2/100 g raw wheat straw) in the autohydrolysis filtrate and recovered 62.3% of solid residue. Before enzymatic hydrolysis, the pulps obtained from each pretreatment condition were subjected to a refining post-treatment to improve enzyme accessibility. Enzymatic hydrolysis was performed for all the pretreated solids with and without refining post-treatment at the enzyme loadings of 4 and 10 FPU/g oven dry substrate for 96 h. A total of 30.4 g sugars can be recovered from 100 g wheat straw at 180 degrees C for 20 min with 4 FPU/g enzyme charge. (C) 2013 Elsevier Ltd. All rights reserved.
  • Öğe
    Quantum chemical modeling of the inhibition mechanism of monoamine oxidase by oxazolidinone and analogous heterocyclic compounds
    (Taylor & Francis Ltd, 2014) Erdem, Safiye Sag; Altınbaş Özpınar, Gül; Boz, Umut
    Monoamine oxidase (MAO, EC 1.4.3.4) is responsible from the oxidation of a variety of amine neurotransmitters. MAO inhibitors are used for the treatment of depression or Parkinson's disease. They also inhibit the catabolism of dietary amines. According to one hypothesis, inactivation results from the formation of a covalent adduct to a cysteine residue in the enzyme. If the adduct is stable enough, the enzyme is inhibited for a long time. After a while, enzyme can turn to its active form as a result of adduct breakdown by beta-elimination. In this study, the proposed inactivation mechanism was modeled and tested by quantum chemical calculations. Eight heterocyclic methylthioamine derivatives were selected to represent the proposed covalent adducts. Activation energies related to their beta-elimination reactions were calculated using ab initio and density functional theory methods. Calculated activation energies were in good agreement with the relative stabilities of the hypothetical adducts predicted in the literature by enzyme inactivation measurements.
  • Öğe
    First Report of Diplodia pinea on Pseudotsuga menziesii in Turkey
    (Amer Phytopathological Soc, 2014) Kaya, A. G. A.; Lehtijaervi, Asko Tapio; Kaya, O.; Dogmus-Lehtijarvi, T.
  • Öğe
    First Report of Phytophthora syringae on Cedrus libani in Turkey
    (Amer Phytopathological Soc, 2014) Dogmus-Lehtijarvi, T.; Kaya, A. G. Aday; Lehtijaervi, Asko Tapio; Jung, T.
    Cedrus libani, commonly known as Lebanon cedar, is one of the most important coniferous tree species in Turkey. Its main distribution is in the Taurus Mountains in the Mediterranean Region. The total area of pure Taurus cedar forest covers 109,440 ha in Turkey, all located in the southwestern regions of the country. Due to its drought resistance, Taurus cedar has been commonly used for afforestations in these semi-arid areas (1). In September 2011, during surveys for Phytophthora spp. in forest nurseries in Adapazari and İzmir in eastern Turkey, initial symptoms such as death of fine roots, yellowing, and wilting of Taurus cedar seedlings were observed. Soil samples were collected from 10 symptomatic C. libani seedlings and isolation tests for Phytophthora species were carried out using leaflets from young Quercus suber, Azalea sp., and Rhodendron sp. saplings as baits floated over flooded soil. Necrotic baits were blotted dry, cut into small pieces, and placed on selective PARPNH carrot agar. Out growing colonies were subcultured on carrot agar and kept at 12°C for morphological and molecular identifications (2). In total, six Pythiaceous isolates were obtained from the C. libani soil samples. The isolates were investigated using a light microscope and grouped according to their morphological characteristics (3). DNA was extracted from two representative isolates using Qiagen DNeasy Plant Mini Kit following the manufacturer's instructions. PCR amplifications and sequencing of the internal transcribed spacer (ITS) region of rDNA and the β-tubulin gene were performed using ITS1 and ITS4 and Tub1 and Tub2 primer sets (4). Sequencing of the PCR products in both directions was conducted by IonTek Inc. (Istanbul, Turkey) in an ABI PRISM automated sequencer. The obtained sequences were compared with those in the GenBank and Phytophthora database using BLAST search. On the basis of morphological features and molecular analyses, the two isolates were identified as Phytophthora syringae. Morphological characteristics on carrot agar were identical with the description of P. syringae (2). At 20°C, colonies reached 7 cm in diameter after 1 week. Sporangia were semipapillate to non-papillate, ovoid, with average length of 59 μm (SD ± 2.8) (range 58 to 70 μm). Oogonia were 38 μm (SD ± 5.4) in diameter (range 30 to 47 μm) with paragynous antheridia. The morphological identification was confirmed by sequence comparison at GenBank with 99% homology for both ITS and β-tubulin. The ITS sequences of the two isolates were deposited in GenBank with the accession nos. KF430614 and KF944377. Under-bark inoculation tests with mycelia plugs were conducted with both isolates of P. syringae at 18°C in a growth chamber on a total of six 1-year-old shoots cut from two C. libani trees. Lesions with an average length of 19 mm (SD ± 6) developed after 10 days. P. syringae was consistently re-isolated from the margins of necrotic tissues. Control shoots remained symptomless. To our knowledge, this is the first report of damage caused by P. syringae on C. libani seedlings in forest nursery in Turkey.
  • Öğe
    Wave Propagation Analysis of Edge Cracked Circular Beams under Impact Force
    (Public Library Science, 2014) Akbaş, Şeref Doğuşcan
    This paper presents responses of an edge circular cantilever beam under the effect of an impact force. The beam is excited by a transverse triangular force impulse modulated by a harmonic motion. The Kelvin-Voigt model for the material of the beam is used. The cracked beam is modelled as an assembly of two sub-beams connected through a massless elastic rotational spring. The considered problem is investigated within the Bernoulli-Euler beam theory by using energy based finite element method. The system of equations of motion is derived by using Lagrange's equations. The obtained system of linear differential equations is reduced to a linear algebraic equation system and solved in the time domain by using Newmark average acceleration method. In the study, the effects of the location of crack, the depth of the crack, on the characteristics of the reflected waves are investigated in detail. Also, the positions of the cracks are calculated by using reflected waves.
  • Öğe
    Reliability Estimation for Single-unit Ceramic Crown Restorations
    (Sage Publications Inc, 2014) Lekesiz, Hüseyin
    The objective of this study was to evaluate the potential of a survival prediction method for the assessment of ceramic dental restorations. For this purpose, fast-fracture and fatigue reliabilities for 2 bilayer (metal ceramic alloy core veneered with fluorapatite leucite glass-ceramic, d.Sign/d.Sign-67, by Ivoclar; glass-infiltrated alumina core veneered with feldspathic porcelain, VM7/In-Ceram Alumina, by Vita) and 3 monolithic (leucite-reinforced glass-ceramic, Empress, and ProCAD, by Ivoclar; lithium-disilicate glass-ceramic, Empress 2, by Ivoclar) single posterior crown restorations were predicted, and fatigue predictions were compared with the long-term clinical data presented in the literature. Both perfectly bonded and completely debonded cases were analyzed for evaluation of the influence of the adhesive/restoration bonding quality on estimations. Material constants and stress distributions required for predictions were calculated from biaxial tests and finite element analysis, respectively. Based on the predictions, In-Ceram Alumina presents the best fast-fracture resistance, and ProCAD presents a comparable resistance for perfect bonding; however, ProCAD shows a significant reduction of resistance in case of complete debonding. Nevertheless, it is still better than Empress and comparable with Empress 2. In-Ceram Alumina and d.Sign have the highest long-term reliability, with almost 100% survivability even after 10 years. When compared with clinical failure rates reported in the literature, predictions show a promising match with clinical data, and this indicates the soundness of the settings used in the proposed predictions.
  • Öğe
    Acid-catalyzed autohydrolysis of wheat straw to improve sugar recovery
    (Elsevier Sci Ltd, 2014) Ertaş, Murat; Han, Qiang; Jameel, Hasan
    A comparison study of autohydrolysis and acid-catalyzed autohydrolysis of wheat straw was performed to understand the impact of acid addition on overall sugar recovery. Autohydrolysis combined with refining is capable of achieving sugar recoveries in the mid 70s. If the addition of a small amount of acid is capable of increasing the sugar recovery even higher it may be economically attractive. Acetic, sulfuric, hydrochloric and sulfurous acids were selected for acid-catalyzed autohydrolysis pretreatments. Autohydrolysis with no acid at 190 degrees C showed the highest total sugar in the prehydrolyzate. Enzymatic hydrolysis was performed for all the post-treated solids with and without refining at enzyme loadings of 4 and 10 FPU/g for 96 h. Acid-catalyzed autohydrolysis at 190 degrees C with sulfurous acid showed the highest total sugar recovery of 81.2% at 4 FPU/g enzyme charge compared with 64.3% at 190 degrees C autohydrolysis without acid. (C) 2014 Elsevier Ltd. All rights reserved.
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    One-Step Synthesis and Characterization of Polyaniline Nanofiber/Silver Nanoparticle Composite Networks as Antibacterial Agents
    (Amer Chemical Soc, 2014) Poyraz, Selcuk; Çerkez, İdris; Huang, Tung Shi; Liu, Zhen; Kang, Litao; Luo, Jujie
    Through a facile and effective seeding polymerization reaction via a one-step redox/complexation process, which took place in aqueous medium at ambient temperature, silver nanoparticles (Ag NPs) embedded polyaniline nanofiber (PANI NF) networks were synthesized as antibacterial agents. During the reaction, not only NF morphology formation of the resulting conducting polymers (CPs) but also amplification of the aqueous silver nitrate (AgNO3) solutions oxidative potentials were managed by vanadium pentoxide (V2O5) solgel nanofibers, which acted as well-known nanofibrous seeding agents and the auxiliary oxidative agent at the same time. The PANI/Ag nanocomposites were proven to exhibit excellent antibacterial property against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Antibacterial property performance and average life span of the nanocomposite network were optimized through the homogeneous distribution/embedment of Ag NPs within one-dimensional (1-D) PANI NF matrix. The antibacterial efficacy tests and nanocomposite material characterization results further indicated that the sole components of PANI/Ag have a synergistic effect to each other in terms of antibacterial property. Thus, this well-known catalytic seeding approach via a one-step oxidative polymerization reaction can be considered as a general methodology and a substantial fabrication tool to synthesize Ag NP decorated nanofibrillar PANI networks as advanced antibacterial agents.