bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface‐Induced Polymer Crystallization in High Volume Fraction Aligned Carbon Nanotube–Polymer Composites
Authors: Zhang Shanju , Lin Wei , Yu Xinfei , Wong Ching‐Ping , Cheng Stephen Z. D. , Bucknall David G.
Published: March 2010

Surface‐induced crystallization of high‐density polyethylene in vertically aligned multiwalled carbon nanotube arrays has been investigated by means of scanning electron microscopy (SEM), wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). 1‐mm long nanotube arrays are infiltrated by polyethylene solutions and then the system is allowed to crystallize under controlled conditions. Periodic disk‐shaped polyethylene single crystals grow perpendicularly to the aligned nanotubes but do not completely fill the intertube spacing, forming oriented 3D porous structures. This unique morphology leads to low density, high nanotube mass fraction (up to 80 wt.‐%) composites. Microstructure (WAXD) analysis shows that the nanotubes act as both orientation templates as well as nucleating agents for polyethylene crystallization creating orthorhombic and monoclinic forms, although the overall crystal structure is dominated by the orthorhombic form. Thermal analysis (DSC) shows that the nanocomposite exhibits multiple phase transitions during heating and cooling with a weak superheating and supercooling dependence on different scanning rates. Three phase structures have been identified and a possible model is proposed to explain the observed phenomenon.

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Synthesis and Characterization of Red‐Emitting Poly(aryleneethynylene)s Based on 2,5‐Bis(2‐ethylhexyl)‐3,6‐di(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione (DPP)
Authors: Palai Akshaya K. , Mishra Sarada P. , Kumar Amit , Srivastava Ritu , Kamalasanan Modeeparampil N. , Patri Manoranjan
Published: March 2010

Synthesis and characterization of a series of PAEs containing DPP units in the main chain are described. $\overline M _{\rm w} $ of the polymers was in the range 10 800–111 900. The polymers formed a deep blue solution in chloroform with absorption maxima between 589 and 645 nm and optical band gaps ranging from 1.61 to 1.74 eV. When excited at the absorption maxima, the polymer solutions showed red fluorescence with emission maxima between 656 and 676 nm. The polymers exhibited quasi‐reversible oxidation process with HOMO energy levels between −5.60 and −6.17 eV. EL properties of three polymers were investigated with device configuration ITO/PEDOT:PSS/Polymer/LiF/Al. When appropriate bias voltage was applied, a red EL with a maximum brightness of 17.5–24 cd · m−2 could observe from the devices.

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Large Enhancement in Conductivity of Polyaniline Films by Cold Stretching
Authors: Xiao Hong‐Mei , Zhang Wei‐Dong , Lv Chen , Fu Shao‐Yun , Wan Mei‐Xiang , Mai Yiu‐Wing
Published: March 2010

The hot‐stretching method has been well accepted for enhancing the electrical conductivity of conducting polymer films. High temperature is the prerequisite to soften the polymer to highly align and elongate the polymeric molecular chains. In this study, the cold‐stretching method is proposed for the first time to enhance the conductivity of conducting polymeric films. Polyaniline (PANI) films are stretched at room temperature to different strain levels. It is observed that the applied strain has significant effects on the morphology, molecular chain structure, crystallinity, and crosslinking of the PANI films. As a result, the conductivity of PANI films is effectively increased by the cold‐stretching process. Particularly, a maximum conductivity with an 18.4‐fold increase in the direction parallel to the stretched direction is obtained when the elastic limit strain is applied. Compared to hot stretching, cold stretching is unique due to the extremely low dimensional change and very high efficiency achieved.

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Fabrication of Amino‐Terminated Multiwalled Carbon Nanotubes via Layer‐by‐Layer Self‐Assembly Approach
Authors: Zhang Peng , Huang Xiaobin , Fu Jianwei , Huang Yawen , Tang Xiaozhen
Published: March 2010

MWCNT‐based composites have been successfully synthesized via layer‐by‐layer self‐assembly of crosslinked polyphosphazene nanoparticles on the surface of MWCNTs. The amino‐terminated CNTs were characterized by XPS, FT‐IR spectroscopy, EDS, XRD and TEM. The degree of functionalization could be controlled by simply changing the mass of hexachlorocyclotriphosphazene with 4,4′‐diaminodiphenyl ether. The activity of the surface amino groups was confirmed by the reaction of these groups with HAuCl4. In addition, the effects of the mass of HCCP and ODA ratios on the content of the surface amino groups was also investigated.

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Creation of Hydrophobic Materials Fabricated from Soy Protein and Natural Rubber: Surface, Interface, and Properties
Authors: Tian Huafeng , Zhang Lina , Wu Qiangxian , Wang Xiaomei , Chen Yun
Published: March 2010

Hydrophobic materials were successfully prepared from SPI and NR by blending via freezing/lyophilizing. The interfacial interaction, surface properties, hydrophobicity, and mechanical properties, biodegradability as well as the biocompatibility were investigated. The blend sheets exhibited good interface adhesion and good optical transparency. Their hydrophobicity was significantly improved compared with pure soy protein sheets. XPS results proved the NR surface enrichment. Flexibility and toughness of the blend sheets were enhanced and phase inversion phenomena were observed. Furthermore, the blend sheets exhibited good biodegradability and biocompatibility capable of supporting cell adhesion and proliferation.

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Probability Distribution Function of the Polymer End‐to‐End Molecule Vector after Retraction and its Application to Step Deformation
Authors: Kharlamov Alexander A. , Rolón‐Garrido Víctor H. , Filip Petr
Published: March 2010

The classical Doi‐Edwards model describes the dynamics of polymer strands between entanglements and predicts stress in linear polymers. This contribution considers the dynamics of whole molecules within the same tube picture. The probability distribution function of the end‐to‐end molecule vectors after deformation and retraction was calculated. The second moment of the distribution function coincides with that derived earlier by Doi and Edwards. The damping function shows considerably weaker thinning if the molecule end‐to‐end vector is considered as a Hookean spring. The present model describes one of the possible mechanisms leading to weaker damping exhibiting, e.g., by branched polymers.

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Molecular mechanisms of membrane transport of vitamin E
Authors: Takada Tappei , Suzuki Hiroshi
Published: March 2010

Vitamin E is an essential fat‐soluble micronutrient for higher mammals and functions as an antioxidant for lipids and also as a regulator of gene expression and a modulator of cell signaling and proliferation. To exert its physiological functions, vitamin E must achieve an appropriate disposition throughout the body via several processes, such as intestinal absorption, uptake and efflux in peripheral tissues and biliary secretion. In this review, we mainly discuss membrane proteins involved in these transport processes (ATP‐binding cassette transporter A1, scavenger receptor class B type I, Niemann‐Pick C1‐like 1 and multidrug resistance 3) and vitamin E‐mediated regulation of their expression.
Remission re‐induction chemotherapy with clofarabine, topotecan, thiotepa, and vinorelbine for patients with relapsed or refractory leukemia
Authors: Steinherz Peter G. , Shukla Neerav , Kobos Rachel , Steinherz Laurel
Published: March 2010

Background

We determined the maximum tolerated dose (MTD) of clofarabine when administered with topotecan, vinorelbine, thiotepa, and dexamethasone (TVTC) for children with relapsed or refractory acute leukemia, and observed the efficacy and toxicities of this therapy.

Procedure

Twelve patients with acute lymphoblastic or myeloblastic leukemia were given a 14‐day remission induction therapy. Clofarabine was administered at a dose of 30 or 40 mg/m2/day over 2 hr for five consecutive days in six patients each. Patients who achieved a remission proceeded to a stem cell transplant (HSCT). A second cycle could be administered prior to HSCT.

Results

Of the six patients at the 30 mg/m2 clofarabine dose, two achieved a complete response (CR) and one a PR and proceeded to BMT. Three patients had progressive disease. Five of the six patients at the 40 mg/m2 achieved a CR. Four proceeded to HSCT, and one relapsed prior to HSCT. One patient died on day 45 with marrow hypoplasia without evidence of leukemia. Hematologic and infectious adverse events were universal. The one dose limiting non‐infectious toxicity observed was prolonged marrow hypoplasia.

Conclusion

TVTC has significant anti‐leukemic activity in both acute lymphoblastic and myeloblastic leukemia. The MTD of clofarabine is 40 mg/m2/day in this combination. This is the recommended dose for the phase II study in patients with refractory or relapsed leukemia, a population which has limited therapeutic options. Pediatr Blood Cancer 2010;54:687–693. © 2010 Wiley‐Liss, Inc.
Immunogenicity of trivalent influenza vaccine in children with acute lymphoblastic leukemia during maintenance therapy
Authors: Shahgholi Elham , Ehsani Mohammad Ali , Salamati Payman , Maysamie Alipasha , Sotoudeh Kambiz , Mokhtariazad Talat
Published: March 2010

Purpose

The aim of this study was to assess the immune response of children with acute lymphoblastic leukemia (ALL) to influenza vaccine and to compare it with healthy controls.

Procedure

Thirty‐two children aged 1–18 years with ALL on maintenance therapy and 30 healthy sibling controls were enrolled in the study. All children were vaccinated with trivalent inactivated influenza vaccine. Hemagglutinin‐inhibition (HI) antibody titers were determined in sera of both patient and control groups just before and 4 weeks after vaccination. The ability of each group to mount a protective (≥40) and/or fourfold titer was measured.

Results

The protective response for virus subunits among patients and healthy controls were 43.4% versus 88% for H1N1 (P = 0.04), 63.3% versus 80% for H3N2 antigens (P = 0.06), and 26% versus 73% for B antigen (P = 0.001). Responses for H1N1 and B subunits were significantly lower in patients than controls. In the patient group, the significant response to each virus was demonstrated in the analysis of pre‐ and post‐vaccination geometric mean titer (GMT) (P = 0.001). The percentage of patients and controls with fourfold increase in HI titers were 56.2% versus 80% for H1N1 (P = 0.04), 40.6% versus 53.3% for H3N2 (P = 0.31), and 59.4% versus 83.3% for B (P = 0.038). Immune responses for H1N1 and B subunits were significantly lower in patients than controls.

Conclusions

Influenza vaccine is tolerated well in ALL patients with acceptable but limited immune response compared to healthy controls. These findings support the recommendation for annual influenza vaccination in children with ALL. Pediatr Blood Cancer 2010;54:716–720. © 2010 Wiley‐Liss, Inc.
Syndrome of inappropriate secretion of antidiuretic hormone as a leading cause of hyponatremia in children who underwent chemotherapy or stem cell transplantation
Authors: Lim Yeon‐Jung , Park Eun‐Kyoung , Koh Hyun‐Chul , Lee Young‐Ho
Published: March 2010

Background

Hyponatremia is a common metabolic disorder in cancer patients. However, little information is available for patients receiving chemotherapy or stem cell transplantation (SCT). We analyzed the frequency, characteristics, and various causes of hyponatremia including routine use of hypotonic fluids in children following chemotherapy or SCT.

Procedure

We reviewed the clinical and laboratory data of 63 children who received chemotherapy or SCT at the Department of Pediatrics, Hanyang University Medical Center from July 2005 to July 2008.

Results

All 63 patients at admission received routine parenteral fluids of 0.25% or 0.45% NaCl and 82 episodes of hyponatremia were observed in 40 (63.5%) patients. Of these 82 episodes, 50 episodes of hyponatremia developed in 29 children following chemotherapy and 32 episodes in 16 children following SCT. Seventy‐six out of 82 episodes (92.7%) of hyponatremia developed in 37 patients receiving hypotonic fluids with NaCl concentrations between 30 and 150 mEq/L. The frequency of SIADH in the SCT setting was more frequent (14/21, 66.6%) than in the chemotherapy setting (18/58, 31.0%) (P = 0.02), even though the leading cause of hyponatremia was SIADH in both settings.

Conclusions

SIADH is a leading cause of hyponatremia in children following chemotherapy or SCT, and more frequent in SCT settings than in chemotherapy settings. Furthermore, the routine use of hypotonic fluids which could aggravate the development of hyponatremia for these patients should be avoided and then switched to isotonic fluids. Pediatr Blood Cancer 2010;54:734–737. © 2010 Wiley‐Liss, Inc.
Synthesis and characterization of multi‐block copolymers containing poly [(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] and poly(ethylene glycol)
Authors: Liu Qingsheng , Zhu Meifang , Chen Yanmo
Published: March 2010

Various problems, including high crystallinity, high melting temperature, poor thermal stability, hydrophobicity and brittleness, have impeded many practical applications of poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] (PHBV) as an environmentally friendly material and biomedical material. In the work reported here, multi‐block copolymers containing PHBV and poly(ethylene glycol) (PHBV‐b‐PEG) were synthesized with telechelic hydroxylated PHBV as a hard and hydrophobic segment, PEG as a soft and hydrophilic segment and 1,6‐hexamethylene diisocyanate as a coupling reagent to solve the problems mentioned above. PHBV and PEG blocks in PHBV‐b‐PEG formed separate crystalline phases with lower crystallinity levels and lower melting temperatures than those of phases formed in the precursors. The crystallite dimensions of the two blocks in PHBV‐b‐PEG were smaller than those of the corresponding precursors. Compared to values for the original PHBV, the maximum decomposition temperature of the PHBV block in PHBV‐b‐PEG was 16.0 °C higher and the water contact angle was 9° lower. In addition, the elongation at break was 2.8% for a pure PHBV fiber but 20.9% for a PHBV/PHBV‐b‐PEG fiber with a PHBV‐b‐PEG content of 30%. PHBV‐b‐PEGs can overcome some of the disadvantages of pure PHBV; it is possible that PHBV might be a good candidate for the formulation of environmentally friendly materials and biomedical materials. Copyright © 2010 Society of Chemical Industry
Polymerization of 1,3‐dienes containing functional groups: 8. Free‐radical polymerization of 2‐triethoxysilyl‐ 1,3‐butadiene
Authors: Takenaka Katsuhiko , Kawamoto Satomi , Miya Masamitsu , Takeshita Hiroki , Shiomi Tomoo
Published: March 2010

The presence of a bulky substituent at the 2‐position of 1,3‐butadiene derivatives is known to affect the polymerization behavior and microstructure of the resulting polymers. Free‐radical polymerization of 2‐triethoxysilyl‐1,3‐butadiene (1) was carried out under various conditions, and its polymerization behavior was compared with that of 2‐triethoxymethyl‐ and other silyl‐substituted butadienes. A sticky polymer of high 1,4‐structure ($E:Z \approx 8:2$) was obtained in moderate yield by 2,2′‐azobisisobutyronitrile (AIBN)‐initiated polymerization. A smaller amount of Diels–Alder dimer was formed compared with the case of other silyl‐substituted butadienes. The rate of polymerization (Rp) was found to be Rp = k[AIBN]0.5[1]1.2, and the overall activation energy for polymerization was determined to be 117 kJ mol−1. The monomer reactivity ratios in copolymerization with styrene were r1 = 2.65 and rst = 0.26. The glass transition temperature of the polymer of 1 was found to be −78 °C. Free‐radical polymerization of 1 proceeded smoothly to give the corresponding 1,4‐polydiene. The 1,4‐E content of the polymer was less compared with that of poly(2‐triethoxymethyl‐1,3‐butadiene) and poly(2‐triisopropoxysilyl‐1,3‐butadiene) prepared under similar conditions. Copyright © 2010 Society of Chemical Industry
Synthesis and characterization of organo‐soluble polyimides derived from a new spirobifluorene diamine
Authors: Jiang Guo‐Min , Jiang Xue , Zhu You‐Fu , Huang Dan , Jing Xiao‐Hui , Gao Wei‐Dong
Published: March 2010

Polyimides exhibit outstanding thermal and thermo‐oxidative stability, excellent solvent resistance, good mechanical and electrical properties and superior chemical resistance. However, their practical applications are frequently limited by their infusible and insoluble nature. Structural modifications of the polymer backbone have been utilized to modify polyimide properties, either by reducing the interaction or by reducing the stiffness of the polymer backbone. Novel organo‐soluble polyimides containing spirobifluorene units were synthesized by the polycondensation of 2,7‐bis‐amino‐2′,7′‐di‐t‐butyl‐9,9′‐spirobifluorene with three aromatic dianhydrides. The one‐step polymerization procedure was conducted at 200 °C in m‐cresol, and the structures of the resulting polyimides were confirmed using infrared and NMR spectroscopy. The weight‐average molecular weights and polydispersities of the resulting polymers were in the ranges 20 600–341 000 and 1.02–1.30, respectively. The glass transition temperatures of the polyimides were in the range 289–322 °C, and the 10% weight loss in nitrogen appeared at a temperature higher than 435 °C and the residual weight at 800 °C was above 58%. The spiro segment has been introduced into polyimides, resulting in amorphous polyimides, conferring on them an enhanced solubility and leading to a significant increase in both glass transition temperature and thermal stability. These types of materials have potential for many applications. Copyright © 2010 Society of Chemical Industry
Melt rheology of biodegradable poly[(butylene succinate)‐co‐adipate]: Experimental and model predictions
Authors: Eslami Hassan , Grmela Miroslav , Dubois Charles , Lafleur Pierre
Published: March 2010

Steady and transient nonlinear melt‐state viscoelastic properties of poly[(butylene succinate)‐co‐adipate] (PBSA), a biodegradable polyester, are investigated. Experimental data are compared with predictions of a rheological model developed by Ait‐Kadi et al. (J Rheol, 1999, 43, 51–72). The results show that the model predicts very well the steady state shear viscosity and the normal stress difference. A good agreement is observed also for start‐up and relaxation shear viscosity. A less satisfactory agreement between model predictions and experimental data is found for the transient normal stress difference. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 832–839, 2010
A new spectral memory of filled rubbers
Authors: Wang Xiaorong , Robertson Christopher G.
Published: March 2010

We recently discovered that shearing particle‐reinforced rubbers in oscillation at a frequency fa at a small strain γa (e.g., ∼1% strain) for time ta can often produce a spectrum hole or drop in the strain‐dependent dissipation spectra of the materials. The location of the hole (or localized perturbation in the loss modulus or loss tangent) depends on the aging strain amplitude γa. The depth of this hole is influenced by both the oscillatory aging frequency fa and the aging duration ta, and follows a simple power relationship of the product of fa and ta. The exponent for the power relationship is a function of filler concentration. These attributes of the spectral hole in filled rubbers are not sensitive to the frequency used to postanalyze the hole. This new memory effect occurs at very small strains and involves material stiffening during the strain aging, and both of those features are quite different from the Mullins effect in filled elastomers. We interpret this newly discovered memory character of filled rubbers from a much broader concept of structure pinning in a condensed frustrated system and consider that the agglomeration of filler particles in rubber matrix shares common physics with granular materials and glass‐forming materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 859–869, 2010
Preparation, structure, and property of polyoxymethylene/carbon nanotubes thermal conducive composites
Authors: Zhao Xiaowen , Ye Lin
Published: March 2010

Polyoxymethylene (POM)/multiwalled carbon nanotubes (MWNTs) nanocomposites were prepared through a simple solution‐evaporation method assisted by ultrasonic irradiation. To enhance the dispersion of MWNTs in POM, MWNTs were chemically functionalized with PEG‐substituted amine (MWNT‐g‐PEG), which exhibited strong affinity with POM due to their similar molecular structure. The thermal conductivity and the mechanical properties of the composites were investigated, which showed that the thermal conductive properties of POM were improved remarkably in the presence of MWNTs, whereas reduced by using MWNT‐g‐PEG due to the heat transport barrier of the grafted‐PEG‐substituted amine chain. A nonlinear increase of the thermal conductivity was observed with increasing MWNTs content, and the Maxwell‐Eucken model and the Agari model were used for theoretical evaluation. The relatively high effective length factor of the composite predicted with mixture equation indicated that there were few entangles of MWNTs for the samples of MWNT‐g‐PEG in the composites. The mechanical strength of the composites can be improved remarkably by using suitable content of such functionalized MWNTs, and with the increase of the aliphatic chain length of PEG‐substituted amine, the toughness of the composites can be enhanced. Transmission electron microscope result indicated that MWNT‐g‐PEG exhibited strong affinity with POM and a good dispersion of MWNTs was achieved in POM matrix. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 905–912, 2010
Objective burden, resources, and other stressors among informal cancer caregivers: a hidden quality issue?
Authors: van Ryn Michelle , Sanders Sara , Kahn Katherine , van Houtven Courtney , Griffin Joan M. , Martin Michelle , Atienza Audie A. , Phelan Sean , Finstad Deborah , Rowland Julia
Published: March 2010

A great deal of clinical cancer care is delivered in the home by informal caregivers (e.g. family, friends), who are often untrained. Caregivers' context varies widely, with many providing care despite low levels of resources and high levels of additional demands.

Background: Changes in health care have shifted much cancer care to the home, with limited data to inform this transition. We studied the characteristics, care tasks, and needs of informal caregivers of cancer patients.

Methods: Caregivers of seven geographically and institutionally defined cohorts of newly diagnosed colorectal and lung cancer patients completed self‐administered questionnaires (n = 677). We combined this information with patient survey and chart abstraction data and focused on caregivers who reported providing, unpaid, at least 50% of the patient's informal cancer care.

Results: Over half of caregivers (55%) cared for a patient with metastatic disease, severe comorbidity, or undergoing current treatment. Besides assisting with activities of daily living, caregivers provided cancer‐specific care such as watching for treatment side effects (68%), helping manage pain, nausea or fatigue (47%), administering medicine (34%), deciding whether to call a doctor (30%), deciding whether medicine was needed (29%), and changing bandages (19%). However, half of caregivers reported not getting training perceived as necessary. In addition, 49% of caregivers worked for pay, 21% reported poor or fair health, and 21% provided unpaid care for other individuals. One in four reported low confidence in the quality of the care they provided.

Conclusions: Much assistance for cancer patients is delivered in the home by informal caregivers, often without desired training, with a significant minority having limited resources and high additional demands. Future research should explore the potentially high yield of addressing caregiver needs in improving quality of cancer care and both survivors' and caregivers' outcomes. Copyright © 2010 John Wiley & Sons, Ltd.
Dose rate effects on the performance of MWCVD diamond films as TL gamma radiation dosimeter
Authors: Cruz‐Zaragoza E. , Gastélum S. , Meléndrez R. , Chernov V. , Barboza‐Flores M.
Published: March 2010

Dose rate effects on the thermoluminescence (TL) properties of undoped and 750 ppm nitrogen doped microwave chemical vapor deposition (MWCVD) diamond films were analyzed. The diamond samples were exposed to 2.4–20.67 Gy/min dose rates from a 60Co source. The TL glow curve of undoped sample showed no apparent dose rate effects. The doped diamond film exhibited dose rate effects consisting in a 10–30% integrated TL increase as the dose rate increased. The TL response as a function of dose rates showed a nonlinear behavior for the doped sample contrary to the undoped diamond film. The dose rate effects were evaluated through the determination of the kinetics parameters by fitting of the TL glow curves. The results indicate that chemical vapor deposition (CVD) diamond may present some dose rate effects on the TL properties in a given dose range, implying that some care should be exercised in order to use CVD diamond films in radiation dose assessments.
Electrical resistance variation of carbon‐nanotube networks due to surface modification of glass substrate
Authors: Jang Eui Yun , Seo Dong Kyun , Jung Seoho , Kim Taewoo , Kang Tae June , Kim Yong Hyup
Published: March 2010

This study presents the effect of the wettability between a glass substrate and carbon‐nanotube (CNT) colloidal solution on the density of CNT networks in a dip‐coating process. The surface roughness and the density of functional groups of the glass substrate were modified by using an oxygen‐plasma treatment, and then we observed the density of CNT networks with respect to different surface conditions due to the surface modification. It is confirmed that the surface chemical property and the surface morphology of the glass substrate determines the density of CNT networks formed by the dip‐coating method. The change of surface free energy induced by hydroxylation and hydration enhances the wettability between a glass substrate and CNT colloidal solution. Moreover, the effective area on which silanol groups can be formed is dependent on the roughness of the surface of the substrate. Eventually, the change of the surface free energy due to the hydroxylation, hydration, and surface roughness effect on the density of the coated CNTs, which determines the sheet resistance of CNT networks.
Plasmonic effects and optical properties of InN composites with In nanoparticles
Authors: Shubina T. V.
Published: March 2010

Nanocomposites comprising metallic nanoparticles (MNPs) inside a semiconductor matrix are promising materials for plasmonics suggesting a new concept of light manipulation and generation. Optical properties of the nanocomposites are controlled by localized plasmons (Mie resonances) in the MNPs. The basic properties of the nanocomposites have been studied using InN/In with In clusters formed both spontaneously and by the periodic deposition of In insertions. In the specially designed nanocomposites, the spots of intense cathodoluminescence are strongly correlated with the agglomerations of the In MNPs due to plasmon‐induced enhancement. Furthermore, a strong difference is discovered between the onsets of thermally detected absorption and photocurrent. This feature is a key to distinguish InN/In from pure InN. To simulate the plasmonic effects in the nanocomposites a model has been proposed, which considers the clusters as spheroids of random shapes and orientations. The calculated dependences are in reasonable agreement with obtained optical data.
Investigation of InN layers grown by molecular beam epitaxy on GaN templates
Authors: Vilalta‐Clemente A. , Mutta G. R. , Chauvat M. P. , Morales M. , Doualan J. L. , Ruterana P. , Grandal J. , Sánchez‐García M. A. , Calle F. , Valcheva E. , Kirilov K.
Published: March 2010

An investigation of InN layers grown on GaN templates by molecular beam epitaxy (MBE) has been carried out by X‐ray diffraction (XRD), Raman spectroscopy (RS) and photoluminescence (PL). A good correlation is noticed between their crystalline quality and optical properties. The best samples exhibit a PL emission between 0.6 and 0.7 eV. The surface structure was quite different from one sample to the other, pointing out to a critical role of the growth conditions, which probably need to be tightly optimized for a good reproducibility.
Scanning X‐ray excited optical luminescence microscopy of multi‐crystalline silicon
Authors: Vyvenko O. , Arguirov T. , Seifert W. , Zizak I. , Trushin M. , Kittler M.
Published: March 2010

In X‐ray beam induced current (XBIC) in combination with X‐ray fluorescence (XRF) and X‐ray absorption (XAS) microscopy techniques is now widely used as a powerful tool for the investigation of transition metal (TM) behavior in Si. The aim of this work was to replace XBIC with a new recombination‐sensitive, but contactless technique, that is, scanning X‐ray beam excited optical luminescence microscopy (µ‐SXEOL). We report for the first time the successful realization of µ‐SXEOL to register the spatial distribution of band–band luminescence in silicon in a reasonable time of 1 s/pixel with X‐ray flux of 1011/s. Results of simultaneous µ‐SXEOL/XBIC/µ‐XRF measurements on multi‐crystalline silicon are presented. A correlation between XBIC and µ‐SXEOL maps of the same sample as well as significant differences are found. The magnitude of µ‐SXEOL signal is shown to anti‐correlate with the averaged amount of copper detected by µ‐XRF.
Theoretical investigations of defects in a Si‐based digital ferromagnetic heterostructure – a spintronic material
Authors: Fong C. Y. , Shauhgnessy M. , Snow R. , Yang L. H.
Published: March 2010

We investigate the effects of two different forms of defects on the half‐metallic properties of the Mn/Si digital ferromagnetic heterostructure (DFH) (PRL 96, 027211 (2006)) using first principles algorithm based on density functional theory. The half metallicity is retained when the δ‐layer of the Mn atoms has 25% imperfection and even a vacancy. The cruci al properties of the DFH are robust against 25% defects (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Performance of amorphous and microcrystalline silicon pin solar cells under variable light intensity
Authors: Nath M. , Chakraborty S. , Kim K. H. , Johnson E. V. , Roca i Cabarrocas P. , Chatterjee P.
Published: March 2010

We have studied the solar cell behaviour under variable light intensity (VLI) of a standard a‐Si:H pin solar cell with a wide band gap a‐SiC:H emitter layer, and microcrystalline (μc)‐Si:H solar cells of different degrees of crystallinity, using experiments in conjunction with detailed electrical‐optical modelling. Both experiments and modelling reveal that whereas the fill factor (FF) of the a‐Si:H pin cell decreases with increasing light intensity, starting from a low applied light bias, that of the μc‐Si:H cells increases with light intensity over a major part of this range. This fact enables one to attain the maximum of the open‐circuit voltage ‐ fill factor product (Voc x FF) at 1 to 2 suns intensity for the latter case; however this is not achieved for the a‐Si:H cell. Using modelling we try to understand this difference in behaviour of the FF under VLI for the two types of cells. We also predict under what conditions it would be possible to shift the (Voc x FF)max for the a‐Si:H cell towards one sun intensity. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The influence of Si precursor on poly‐Si crystallized by YAG laser
Authors: Yao Ying , Li Juan , Wang Shuo , Meng Zhiguo , Wu Chunya , Xiong Shaozhen
Published: March 2010

The influence of the Si‐based crystallization precursor on the quality of the resulted poly‐Si crystallized by 2ω YAG laser was investigated in this paper. Based on the simulation analysis, we suggested that the H content in crystallization precursor maybe one of main effect factors. It has been found that the lower H content in Si‐based precursor, the better crystallinity of the resulted poly‐Si is. By using the low H content Si‐based film as the precursor, the poly Silicon with the grain size of about 500 nm crystallized by 2ω YAG was obtained at the relatively optimal crystallization conditions. Meanwhile, a dehydrogenation process before laser crystallization also could be omitted. It would be beneficial to lower cost of crystallization of a‐Si (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low‐temperature deposition of high quality β‐FeSi2 films by co‐sputtering of Fe and Si for β‐FeSi2/Si heterojunction solar cell
Authors: Hou Guofu , Yu Cao , Liu Fang , Sun Jian , Geng Xinhua , Zhao Ying
Published: March 2010

Single‐phase β‐FeSi2 films have been prepared by Fe‐Si mixed targets in a facing target sputtering (FTS) system. Compared with depositing iron on silicon, co‐sputtering of Fe and Si atoms in as‐deposited samples guarantees that Fe and Si atoms only need relative low energy via short distance migration to form iron silicide during the annealing process, which helps decreasing annealing temperature and reducing annealing time. Then pure single‐phase β‐FeSi2 films can be obtained at a low annealing temperature 600 °C in this instance. By adjusting the sputtering areas of Fe and Si targets, it’s convenient to control the Fe/Si atom ratios in as‐deposited samples and thus p‐type and n‐type films can be obtained easily. The best n‐type β‐FeSi2 film on Si(111) substrate shows an electron concentration of 1.7×1016 cm‐3 and a Hall mobility of 488cm2/Vs, respectively. An n‐β‐FeSi2/p‐Si(111) heterojunction solar cell has been fabricated with a conversion efficiency 0.54% (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First principles structure modeling for amorphous Si‐rich transition metal silicides
Authors: Miyazaki Takehide , Uchida Noriyuki , Kanayama Toshihiko
Published: March 2010

We present a first‐principles theoretical study for the atomic and electronic structures of amorphous Si‐rich transition metal silicides (a‐MxSiy, where M is the transition metal). For M =Mo and y /x =12 (a‐MoSi12), we found that each Mo atom is encapsulated by nine Si atoms while Si atoms form the network similar to that in amorphous Si (a‐Si). We also found that Mo atoms terminate the Si dangling bonds (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of hydrogen dilution on surface roughness development of a‐Si:H thin films grown by remote plasma deposition
Authors: Wank M. A. , Illiberi A. , Tichelaar F. D. , van Swaaij R. A. C. M. M. , van de Sanden M. C. M. , Zeman M.
Published: March 2010

Hydrogenated amorphous silicon (a‐Si:H) films are grown at different hydrogen dilutions. For high dilutions we observe a discrepancy in the surface roughness analysis between real‐time spectroscopic ellipsometry (RTSE) and atomic force microscopy (AFM) measurements. With RTSE a much higher roughness layer thickness is measured than with AFM. Additionally we observe what appears to be a strong roughening phase in the first 30‐50 nm of film growth for all conditions. A mechanism that involves the formations of a hydrogenrich overlayer and etching of higher hydrides in this overlayer is suggested.

This mechanism explains the difference in RTSE roughness layer thickness evolution. At higher hydrogen dilutions, we obtain a thicker overlayer dominated by lower hydrides. RTSE interprets this overlayer as additional surface roughness and consequently overestimates the surface roughness for higher dilutions. The initial strong roughening phase is related to the built‐up of this over‐layer. In this phase, we obtain much denser films compared to the bulk film. The presence of columnar growth at higher dilutions is attributed to reduced surface mobility under these conditions (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
N‐type hydrogenated amorphous silicon oxide containing a microcrystalline silicon phase as an intermediate reflector in silicon thin film solar cells
Authors: Grundler Thomas , Lambertz Andreas , Finger Friedhelm
Published: March 2010

To decrease the extent of degradation of a‐Si:H/μc‐Si:H tandem solar cells it is important to reduce the thickness of the a‐Si:H component cell. A silicon oxide intermediate reflector between top and bottom cell reflects the light back into the a‐Si:H top cell and thus increases its current. For this purpose the reflector material has to fulfill certain optical and electrical requirements. Phosphorous doped silicon oxide films (a‐SiOx:H) with a certain volume fraction of microcrystalline silicon (μc‐Si:H) are used for this purpose and the trade‐off between the material's optical and electrical properties is studied in detail. A suitable intermediate reflector is implemented in a tandem solar cell resulting in an increase in top cell current density by 1.3 mA/cm2 with similar FF and Voc compared to cells without intermediate reflector. An efficiency of 11.5% is achieved at a top cell absorber layer thickness of only 250 nm (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bioremediation of TCE in a fractured limestone aquifer using a novel horizontal passive biobarrier
Authors: Riis Charlotte E. , Christensen Anders G. , Mortensen Annette P. , Jannerup Henrik
Published: March 2010

This article discusses a project demonstrating the successful use of a novel horizontal biobarrier approach to protect a fractured limestone aquifer from continuing contamination while passive bioremediation of the overlying clay till source area is in progress. The emplacement of the biobarrier has significantly reduced the concentrations of chlorinated ethenes and dechlorination activity in the limestone aquifer, promoting complete reductive dechlorination of the trichloroethene plume. The biobarrier strategy has thus met the challenge of protecting the limestone from the overlying overburden. Direct GeoProbe injections performed in the source area, which consist of a clay till overburden, have also reduced the contaminant concentrations in the clay till due to enhanced dechlorination activity; however, repeat injections may be required to address the areas of the till in which the injectate has not yet been distributed. The time frame for remediating the source area in the till is expected to be on the order of a decade. © 2010 Wiley Periodicals, Inc.
Plant selection for a pilot phytoremediation study at a former skeet range
Authors: Kuzovkina Yulia A. , Zhivotovsky Olena P. , Schulthess Cristian P. , Pettinelli Dawn
Published: March 2010

A pilot phytoremediation project was conducted at the Mukluk site in Sprague, Connecticut, formerly a private skeet shooting range. A series of experiments was conducted to investigate if any plants can be effective lead phytoextractors for this site that has very high soil lead concentrations and low soil pH. Greenhouse screening of plants for lead resistance and accumulation using field soil was implemented as the initial step before the field installation. Herbaceous plant species with known lead phytoextraction capabilities included Indian mustard and blue fescue; a few willow clones with purported heavy metal resistance were also tested. Based on the results of the greenhouse experiments, blue fescue appeared to be sensitive to high lead concentration in soil, and only willows and Indian mustard along with various soil amendments were selected for the field installation. Indian mustard grew poorly in most of the treatments at the site except in the compost and lime treatment. Lead accumulation by this species was low in all treatments. In contrast, willows showed tolerance to very high lead concentrations present in the soil and were able to uptake and translocate lead into aboveground tissues. However, lead content in aerial tissues was low, and no change in soil lead concentration at the site was recorded post‐harvest after one growing season. It appeared that highly unfavorable soil characteristics at the Mukluk site complicated the species selection, and no effective phytoextractors have been found for this location. These suggest that the feasibility of phytostabilization and possible production of biofuel from willow biomass on these types of sites should be further investigated. © 2010 Wiley Periodicals, Inc.
Visual and nondestructive evaluation inspection of live gas mains using the Explorer™ family of pipe robots
Authors: Schempf Hagen , Mutschler Edward , Gavaert Alan , Skoptsov George , Crowley William
Published: March 2010

Visual inspection and nondestructive evaluation (NDE) of natural gas distribution mains is an important future maintenance cost‐planning step for the nation's gas utilities. These data need to be gathered at an affordable cost with the fewest excavations and maximum linear feet inspected for each deployment, with minimal to no disruption in service. Current methods (sniffing, direct assessment) are either postleak reactive or too unreliable to offer a viable and Department of Transportation–acceptable approach as a whole. Toward achieving the above goal, a consortium of federal and commercial sponsors funded the development of Explorer™. Explorer™ is a long‐range, untethered, self‐powered, and wirelessly controlled modular inspection robot for the visual inspection and NDE of 6‐ and 8‐in. natural gas distribution pipelines/mains. The robot is launched into the pipeline under live (pressurized flow) conditions and can negotiate diameter changes, 45‐ and 90‐deg bends and tees, as well as inclined and vertical sections of the piping network. The modular design of the system allows it to be expanded to include additional inspection and/or repair tools. The range of the robot is an order of magnitude higher (thousands of feet) than present state‐of‐the‐art inspection systems and will improve the way gas utilities maintain and manage their systems. Two prototypes, Explorer‐I and ‐II (X‐I and X‐II), were developed and field‐tested over a 3‐year period. X‐I is capable of visual inspection only and was field‐tested in 2004 and 2005. The next‐generation X‐II, capable of visual and NDE inspection [remote field eddy current (RFEC) and magnetic flux leakage (MFL)] was developed thereafter and had field trials in 2006 and late 2007. It was successfully deployed into low‐pressure (<125 psig) and high‐pressure (>500 psig) distribution and transmission natural gas mains, with multi‐1,000‐ft inspection runs under live conditions from a single excavation. This paper will describe the overall engineering design and functionality of the Explorer™ family of robots, as well as the results of the field trials for both platforms. It will highlight the importance of the various design and safety features of the in‐pipe crawler and showcase the value of data types and position‐tagged visual∼NDE data collected in working pipelines under live flow conditions. © 2010 Wiley Periodicals, Inc.
The influence of discharge and temperature on the ability of upstream migrant adult river lamprey (Lampetra fluviatilis) to pass experimental overshot and undershot weirs
Authors: Kemp Paul S. , Russon Iain J. , Vowles Andrew S. , Lucas Martyn C.
Published: March 2010

The efficiencies of fish passes specifically designed and constructed to facilitate the movement of a limited number of species and life‐stages past structural barriers are likely to decline as site‐specific conditions shift with a changing climate. There is a need to develop realistic fish passage criteria based on understanding swimming capability and behaviour of multiple species in relation to temperature and flow. The influence of temperature and discharge on behaviour and ability of groups of migrating adult river lamprey (Lampetra fluviatilis), a threatened species, to pass a small overshot or undershot weir at night was investigated using a large experimental flume. Lamprey approached the weirs less, and more often maintained station by using the oral disk to attach to structure, under high flows. Oral disk attachment was more commonly observed during tests employing the undershot weir. Upstream movement tended to be in close proximity to the channel walls and floor where, compared to the mid‐channel, velocities were generally lower and velocity vectors more likely to be in a direction other than the bulk flow. Upstream movement was positively related to temperature, and was higher for the overshot weir. Weir passage rate was higher for undershot than overshot weirs, and negatively related to the maximum velocity at the weir. Passage rate was low when maximum velocities at the weir exceeded 1.5 m s−1, although some fish passed at c. 1.7 m s−1. Passage efficiency, the number of weir passes as a percentage of the number of approaches, was also higher for the undershot weir, but was not affected by discharge because lamprey approached less frequently at high flows. This study provides fish passage criteria under realistic conditions for an infrequently studied anguilliform species of conservation concern and provides a methodological perspective by which to improve fishway suitability for a wider range of species subject to changing climate. Copyright © 2010 John Wiley & Sons, Ltd.

This article was published online on March 3, 2010. An error was subsequently identified in the Article title. This notice is included in the online and print versions to indicate that both have been corrected [April 12, 2010].
Papain‐gel degrades intact nonmineralized type I collagen fibrils
Authors: Bertassoni L. E. , Marshall G. W.
Published: March 2010

Papain‐gel has been utilized as a chemo‐mechanical material for caries removal due to its ability to preserve underlying sound dentin. However, little is known about the effect of the papain enzyme on intact type I collagen fibrils that compose the dentin matrix. Here we sought to define structural changes that occur in intact type I collagen fibrils after an enzymatic treatment with a papain‐gel. Intact and nonmineralized type I collagen fibrils from rat tail were obtained and treated with a papain‐gel (Papacarie) for 30 s, rinsed with water and imaged using an atomic force microscope (AFM). Additionally, polished healthy dentin specimens were also treated using the same protocol described above and had their elastic modulus (E) and hardness (H) measured by means of AFM‐based nanoindentation. AFM images showed that the papain‐gel induced partial degradation of the fibrils surface, yet no rupture of fibrils was noticed. The distinction between gap and overlap zones of fibrils vanished in most regions after treatment, and overlap zones appeared to be generally more affected. Mechanical data suggested a gradual decrease in E and H after treatments. A significant two‐fold drop from the values of normal dentin (E=20±1.9, H=0.8±0.08 GPa) was found after four applications (E=9.7±3.2, H=0.24±0.1 GPa) (P<0.001), which may be attributed to the degradation of proteoglycans of the matrix. In summary, this study provided novel evidence that intact nonmineralized type I collagen fibrils are partially degraded by a papain‐gel. SCANNING 31: 253–258, 2009. © 2010 Wiley Periodicals, Inc.