bluuebunny/crossref_metadata_2025 huggingface dataset:
Inverse Suspension Polymerization of Partially Neutralized and Lightly Cross‐Linked Acrylic Acid: Effect of Reaction Parameters
Authors: Choudhary Manjeet S.
Published: March 2009

An inverse suspension polymerization was carried out in laboratory in one Liter Buchi glass reactor to produce superabsorbent polymers (SAPs) based on acrylic monomers for hygiene applications. Strongly water absorbing polymers, based on acrylic acid, sodium acrylate were prepared by copolymerization using potassium per sulfate as initiator and N‐N′ methylene‐bisacrylamide (MBA) as crosslinking agent.

The effect of varying monomer, crosslinker, initiator, dispersant concentration, time of reaction and degree of neutralization, on absorption capacities was investigated. In the present studies, the continuous hydrocarbon phase was taken as 50:50 mixture of n‐heptane and cyclohexane (aliphatic‐alicyclic) because the availability of crosslinker in the aqueous phase is controlled by the partition coefficient of the crosslinker between the aqueous phase and the continuous hydrocarbon phase. The SAPs were evaluated for their free absorption capacities in distilled water, saline (0.9% NaCl), and also absorption under load (AUL). The experimental results show that these SAPs have good absorbency both in water and NaCl solutions. It was observed that SAP synthesized from acrylic acid with about 70% degree of neutralization, containing 1% cross‐linker, and 0.5–1.0% initiator concentration with 10% dispersant exhibited absorption capacities in water, saline and AUL as 220 g/g, 70 g/g and 27 g/g respectively.
Development of Oligomeric Phthalonitrile Resins for Advanced Composite Applications
Authors: Selvakumar Palaniappan , Sarojadevi Muthusamy
Published: March 2009

Phthalonitrile endcapped oligomers containing aromatic ether and imide linkages have been synthesized and characterized. The phthalonitrile terminated oligomers were prepared in two step (one spot) method by the reaction of an excess amount of pyromellitc dianhydride (PMDA) with aromatic diamines, in a N,N‐dimethylacetamide (DMAc)/toluene solvent mixture to form anhydride terminated oligomeric intermediate that was terminated by the reaction with 4‐(aminophenoxy) phthaloitrile. The average molecular weights of the prepared oligomers were determined by GPC analysis. The oligomeric phthalonitrile monomers have been converted to network polymers using 4,4'‐diaminodiphenyl sulfone (DDS) (5.0 wt %) curing additive at elevated temperatures. Differential scanning calorimetric (DSC) analysis was used to follow the polymerization as the oligomeric phthalonitrile/diamine mixtures and prepolymers. An isothermal rheometric analysis was conducted to determine the complex viscosity of the prepolymers during polymerization reaction. Viscosity increases as a function of time due to crosslinking, which depends upon the concentration and reactivity of the curing agent. The TGA analysis of cured resins showed superior thermal and thermo‐oxidative stability. The temperature of 10% weight loss from TGA are in the range of 498‐511 °C in N2 and 448–461 °C in air atmosphere. Char yield at 800 °C is 41.7–50.2% in air and 70.6–83.1% in N2.
Photocurable Fluorinated Methacrylates: Synthesis and Polymerization
Authors: Shim Sang‐Yeon , Kim Eei Seok
Published: March 2009

A series of hydroxy fluoroalkyl methacrylates were synthesized in 50% yields by the esterification reaction of the methacryloyl chloride with fluoroalkyl diol. These fluorinated methacrylates undergo rapid photopolymerization using Igacure651 as a photoinitiator. Hydrogels were prepared from various molar ratios of 2‐hydroxyethylmethacrylate (HEMA), ethylene glycol dimethacrylate and fluorine containing monomers with a photoinitiator. Analyzing the water contents and contact angles of the hydrogels, we found that the content of fluorinate monomers increased, water contents decreased and contact angles increased.
Recent Advances and Applications of “Successive Self‐Nucleation and Annealing” (SSA) High Speed Thermal Fractionation
Authors: Müller Alejandro J. , Lorenzo Arnaldo T. , Arnal María L.
Published: March 2009

The Successive Self‐nucleation and Annealing (SSA) thermal fractionation technique is briefly reviewed to highlight recent advances such as the use of high speed DSC concepts to perform faster fractionation. Additionally, recent applications of SSA to characterize confined semi‐crystalline model polyethylenes in block copolymer nanophases and in situ prepared nanocomposites with carbon nanotubes are also reviewed. A novel result presented here deals with the use of a macromolecular plasticizer to improve the quality of SSA thermal fractionation.
Complete assignments of 1H and 13C NMR data for two new sesquiterpenes from Cyperus rotundus L.
Authors: Xu Yan , Zhang Hong‐Wu , Wan Xiao‐Chun , Zou Zhong‐Mei
Published: March 2009

Two new sesquiterpenes, epi‐guaidiol A (1) and sugebiol (3), together with four known sesquiterpenes, guaidiol A(2), sugetriol triacetate (4), cyperenoic acid (5), and cyperotundone (6) were isolated from the rhizomes of Cyperus rotundus L. Their structures were identified by MS and NMR experiments, and the complete assignments of 1H and 13C NMR data for two new sesquiterpenes were obtained by the aid of two‐dimensional (2D) NMR techniques, including HSQC, HMBC, 1H‐1HCOSY and nuclear overhauser enhancement spectroscopy(NOESY). Copyright © 2009 John Wiley & Sons, Ltd.
Improved pulse sequences for measurement of small long‐range couplings between heteronuclei (29Si13C) at natural abundance
Authors: Blechta Vratislav , Schraml Jan
Published: March 2009

The gradient pulse sequences for measurement of small long‐range couplings between heteronuclei (29Si13C) in natural abundance reported to date (INEPT‐(Si,C)gCOSY and INEPT‐(Si,C,Si)HMQC) suffer from significant signal loss when these nuclei (29Si, 13C) are coupled through one‐bond couplings to protons. This negative effect can be completely eliminated by using non‐gradient versions (INEPT‐(Si,C)COSY) or by switching proton decoupling off during gradient pulses (modified INEPT‐(Si,C,Si)gHMQC pulse sequence). The beneficial effects of these two approaches on the quality of the spectra are demonstrated here. Copyright © 2009 John Wiley & Sons, Ltd.
Immunocontraceptive potential of the Ig‐like domain of Izumo
Authors: Wang Min , Lv Zhengmei , Shi Jianli , Hu Yanqin , Xu Chen
Published: March 2009

To investigate whether the Ig‐like domain of sperm protein Izumo or the other part of the protein could be used as an immunocontraceptive antigen, three partially overlapping cDNA fragments (PA, PB, and PC), together covering entire mouse Izumo, were cloned, expressed, and purified. PB contains the whole Ig‐like domain of mouse Izumo. The anti‐PB antibody significantly inhibited the fusion of sperm with zona‐free mouse eggs with no effect on sperm motility, while anti‐PA and anti‐PC antibodies virtually had no effect on sperm–egg fusion at the same concentration. Furthermore, in the presence of anti‐PB antibody, the anti‐sperm reactivity could be competitively inhibited by recombinant PB protein. The PB‐specific antibody staining was restricted to the acrosome region in acrosome‐reacted mouse spermatozoa by indirect immunofluorescence. Active immunization with the PB antigen sharply raised the antibody titers in mouse that were enough to cause a significant reduction in fertility compared to the PA and PC immunized groups. In conclusion, our data indicate that the Ig‐like domain of Izumo plays an important role in the fertilization process, as verified by the dose‐dependent reduction in fertilization rates in mouse IVF trials and mouse mating assay. These results indicate that the Ig‐like domain of Izumo might be a new candidate for the development of a contraceptive vaccine. Mol. Reprod. Dev. 76: 794–801, 2009. © 2009 Wiley‐Liss, Inc.
Effects of culture medium and protein supplementation on mRNA expression of in vitro produced bovine embryos
Authors: Purpera M.N. , Giraldo A.M. , Ballard C.B. , Hylan D. , Godke R.A. , Bondioli K.R.
Published: March 2009

Numerous studies have reported aberrant gene expression levels attributed to suboptimal in vitro culture conditions. This study investigated the effects of different culture systems and protein sources on the developmental competence of in vitro production (IVP) embryos measured by cleavage and blastocyst rates, cell number, and relative abundance of POU5F1 (OCT4), nanog, GJA1 (connexin 43), and SLC2A1 (GLUT1) transcripts when compared to in vivo embryos. Experiment 1 compared IVP embryos cultured in either synthetic oviductal fluid (SOFaa) or potassium simplex optimized medium supplemented with amino acids (KSOMaa). Experiment 2 compared the same two culture systems with and without the addition of calf serum (CS). Results from both experiments indicated that despite similar developmental rates, significant differences were observed at the mRNA level. In Experiment 1, OCT4 was the only transcript to have a mean abundance level significantly higher in KSOMaa blastocysts when compared with both SOFaa and in vivo embryos. The same pattern of upregulation of OCT4 mRNA was noted in Experiment 2. There were no significant alterations of the ICM specific transcript nanog in either experiment. In contrast to reports by others, connexin 43 mRNA was not expressed at detectable levels in in vivo embryos analyzed in our studies. Blastocysts cultured in SOFaa with CS or KSOMaa had a significant upregulation of GLUT1 mRNA when compared with other treatments and in vivo embryos. Until differences between IVP and in vivo embryos are minimized, aberrations in IVP will continue to arise. Mol. Reprod. Dev. 76: 783–793, 2009. © 2009 Wiley‐Liss, Inc.
Guanidinoacetate methyltransferase (GAMT) deficiency diagnosed by proton NMR spectroscopy of body fluids
Authors: Engelke Udo F. H. , Tassini Maria , Hayek Joseph , de Vries Maaike , Bilos Appie , Vivi Antonio , Valensin Gianni , Buoni Sabrina , Zannolli Raffaella , Brussel Wim , Kremer Berry , Salomons Gajja S. , Veendrick‐Meekes Monique J. B. M. , Kluijtmans Leo A. J. , Morava Éva , Wevers Ron A.
Published: March 2009

In patients with guanidinoacetate methyltransferase (GAMT) deficiency several parameters may point towards the diagnosis of GAMT deficiency. These include the low levels of creatine and creatinine in urine, the high concentration of guanidinoacetic acid (GAA) in urine and the low levels of creatine and creatinine in the cerebrospinal fluid (CSF). In this study, body fluids from 10 GAMT deficient patients were analysed using 1H NMR spectroscopy. The urine 1D 1H NMR spectra of all the patients showed a doublet resonance at 3.98 ppm (pH 2.50) derived from GAA present in high concentration. For this compound, a good recovery and good correlation was found between an LC‐MS/MS method and 1H NMR spectroscopy. In CSF NMR spectra of these patients, the singlet resonances of creatine and creatinine (3.05 and 3.13 ppm, respectively) were absent (normally always present in 1H NMR spectra of CSF). Due to overlap by other resonances, the doublet of GAA could not be observed. Our data demonstrate that 1H NMR spectroscopy of urine and CSF can be used to diagnose patients with GAMT deficiency. Copyright © 2009 John Wiley & Sons, Ltd.
Thermal history dependence of polymorphic transformation of polyamide 6/silicate nanocomposites
Authors: Zhao Xiong‐yan
Published: March 2009

BACKGROUND: Although much research has been devoted to nanocomposites of polyamide 6 (PA6) with inorganic nanoparticles, most research has mainly focused on the effects of clay and annealing temperature on the crystallization behavior of the PA6 matrix, but the effect of annealing on the thermal behavior of PA6/clay nanocomposites remains an interesting subject which requires further investigation. This paper focuses on the effects of thermal history on the polymorphic transformation of PA6 and PA6/layered silicate nanocomposites (PA6LSN).

RESULTS: It was found that PA6 and PA6LSN exhibit a similar polymorphic behavior when they were annealed at 190 °C. As the annealing temperature was elevated to 230 and 250 °C, significant differences in polymorphic transformation and thermal behavior between PA6 and PA6LSN could be observed. For example, the γ phase became the dominant crystalline phase for PA6LSN samples while the α crystal was still the predominant phase in neat PA6. Furthermore, a higher temperature endothermic peak observed at around 236 °C in all PA6LSN modulated differential scanning calorimetry scans was also found to be strongly dependent on the cooling rate and annealing temperature.

CONCLUSION: The thermal history has a strong influence on the polymorphic transformation of PA6 and PA6LSN. For the first time, the effect of thermal history on the high‐temperature endothermic peak of PA6LSN was investigated and it was observed that this peak is also strongly dependent on the thermal history. Copyright © 2009 Society of Chemical Industry
Measurement and simulation of low‐density polyethylene extrudate swell through a circular die
Authors: Mu Yue , Zhao Guoqun , Li Huiping , Liu Jie , Xu Xingming , Mu Wenbo , Chen Anbiao
Published: March 2009

BACKGROUND: Extrudate swell is a common phenomenon in polymer processing. The investigation of its mechanism is of both scientific and industrial interest.

RESULTS: The rheological parameters of a material described by the viscoelastic PTT (Phan‐Thien–Tanner) constitutive model are obtained by fitting the distributions of material functions detected with a strain‐controlled rheometer. The swelling ratios of low‐density polyethylene (LDPE) under different volume flow rates are indirectly obtained using a photographic technique. A mathematical model of extrudate swell is established and its finite element model is derived. A penalty method is employed to solve the extrudate swell problem with a decoupled algorithm. Computation stability is improved by using the discrete elastic‐viscous split stress algorithm incorporating the inconsistent streamline‐upwind scheme.

CONCLUSION: The swell phenomenon of LDPE through a circular die is investigated using both experimental measurement and numerical simulation. The swelling ratios obtained from the simulation are compared with those measured: they agree well with each other. The essential flow characteristics of polymer melts are predicted and the mechanism of the swell phenomenon is further discussed. Copyright © 2009 Society of Chemical Industry
n‐Type multicrystalline silicon wafers prepared from plasma torch refined upgraded metallurgical feedstock
Authors: Martinuzzi S. , Périchaud I. , Trassy C. , Degoulange J.
Published: March 2009

n‐Type silicon wafers present some definite advantages for the photovoltaic industry, mainly due to the low capture cross sections of minority carriers for most metallic impurities. This peculiarity is beneficial for multicrystalline silicon (mc‐Si) wafers in which the interaction between crystallographic defects and impurities is the main source of recombination centres. Most importantly, this peculiarity could be of a great interest when mc‐Si ingots are produced directly from upgraded and purified metallurgical silicon feedstock. It is of a paramount importance to verify if the advantages of conventional n‐type silicon also characterizes n‐type wafers provided by a direct metallurgical route. It is found, in raw wafers, that minority carrier diffusion lengths are three times higher in n‐type than in p‐type wafers, when the wafers are cut from the same ingot, where the bottom is p‐type and the top is n‐type, due to the difference in the segregation coefficients of doping elements (boron and phosphorus). After different processing steps and gettering treatments the minority carrier diffusion lengths are always neatly larger in n‐type than in p‐type wafers The results confirm the interest for n‐type silicon. Copyright © 2009 John Wiley & Sons, Ltd.
Sunrise to sunset optimization of thin film antireflective coatings for encapsulated, planar silicon solar cells
Authors: Boden S. A. , Bagnall D. M.
Published: March 2009

We present an approach for the optimization of thin film antireflective coatings for encapsulated planar silicon solar cells in which the variations in the incident spectra and angle of incidence (AOI) over a typical day are fully considered. Both the angular and wavelength dependences of the reflectance from the surface, absorptance within the coating, and transmittance into the device are calculated for both single‐ and double‐layer antireflection coatings with and without thin silicon oxide passivation layers. These data are then combined with spectral data as a function of time of day and internal quantum efficiency to estimate the average short‐circuit current produced by a fixed solar cell during a day. This is then used as a figure of merit for the optimization of antireflective layer thicknesses for modules placed horizontally at the equator and on a roof in the UK. Our results indicate that only modest gains in average short‐circuit current could be obtained by optimizing structures for sunrise to sunset irradiance rather than AM1·5 at normal incidence, and fabrication tolerances and uniformities are likely to be more significant. However, we believe that this overall approach to optimization will be of increasing significance for new, potentially asymmetric, antireflection schemes such as those based on subwavelength texturing or other photonic or plasmonic technologies currently under development especially when considered in combination with modules fixed at locations and directions that result in asymmetric spectral conditions. Copyright © 2009 John Wiley & Sons, Ltd.
A hierarchical MS2/MS3 database search algorithm for automated analysis of phosphopeptide tandem mass spectra
Authors: Xu Hua , Wang Liwen , Sallans Larry , Freitas Michael A.
Published: March 2009

A novel hierarchical MS2/MS3 database search algorithm has been developed to analyze MS2/MS3 phosphopeptides proteomic data. The algorithm is incorporated in an automated database search program, MassMatrix. The algorithm matches experimental MS2 spectra against a supplied protein database to determine candidate peptide matches. It then matches the corresponding experimental MS3 spectra against those candidate peptide matches. The MS2 and MS3 spectra are used in concert to arrive at peptide matches with overall higher confidence rather than combining MS2 and MS3 data searched separately. Receiver operating characteristic analysis showed that hierarchical MS2/MS3 database searches with MassMatrix had better sensitivity and specificity than the two‐stage MS2/MS3 database searches obtained with MassMatrix, MASCOT, and X!Tandem. A greater number of true peptide matches at a given false rate were identified by use of this new algorithm for data collected on both LCQ and LTQ‐FTICR mass spectrometers. The additional MS3 spectral data also improved the overall reliability and the number of true positives (TPs) due to the fact that the TPs of the MS2/MS3 search results had higher scores than those of the MS2.
A combined experimental and theoretical study of the pH‐dependent binding mode of NAD+ by water‐soluble molecular clips
Authors: Polkowska Jolanta , Bastkowski Frank , Schrader Thomas , Klärner Frank‐Gerrit , Zienau Jan , Koziol Felix , Ochsenfeld Christian
Published: March 2009

The highly selective recognition process of NAD+ and NADH (as important cofactors of many redox enzymes) by molecular clips in aqueous solution is studied systematically by a combined experimental and quantum‐chemical approach. The strongly pH‐dependent complexation‐induced 1H NMR shifts of the guest molecule indicate that in buffered aqueous solution at pH = 7.2 the nicotinamide ring, the active site of NAD+, is preferentially bound inside the cavity of the molecular clip, whereas in pure water under slightly acidic conditions both units (the nicotinamide ring as well as the adenine moiety) are located outside the cavity. The latter finding is explained by a competing self‐aggregation of NAD+ which prohibits the recognition process. In addition, the investigation of the NAD+ fragments NMNA, NMN, and AMP as well as the comparison of measured and computed chemical shieldings provides information on possible binding modes. Under equal conditions the binding of NADH to the molecular clip is significantly weaker than that of NAD+, so that the oxidation states (NAD+/NADH) can be distinguished by the molecular clips. The nucleotides NMN and AMP are bound less strongly by the molecular clips than NAD+. The weaker binding indicates that multiple aromatic π−π and cation−π host–guest interactions only possible in NAD+ have a synergetic effect on the complex stability. In addition to the inhibition of the cofactor NAD+, a further implication is the development of sensors since a quenching of fluorescence is observed for specific molecular clips by the addition of NAD+. Copyright © 2009 John Wiley & Sons, Ltd.
Bromoxynil degradation in a Mississippi silt loam soil
Authors: Zablotowicz Robert M , Krutz L Jason , Accinelli Cesare , Reddy Krishna N
Published: March 2009

BACKGROUND: The objectives of these laboratory experiments were: (1) to assess bromoxynil sorption, mineralization, bound residue formation and extractable residue persistence in a Dundee silt loam collected from 0–2 cm and 2–10 cm depths under continuous conventional tillage and no‐tillage; (2) to assess the effects of autoclaving on bromoxynil mineralization and bound residue formation; (3) to determine the partitioning of non‐extractable residues; and (4) to ascertain the effects of bromoxynil concentration on extractable and bound residues and metabolite formation.

RESULTS: Bromoxynil Kd values ranged from 0.7 to 1.4 L kg−1 and were positively correlated with soil organic carbon. Cumulative mineralization (38.5% ± 1.5), bound residue formation (46.5% ± 0.5) and persistence of extractable residues (T1/2 < 1 day) in non‐autoclaved soils were independent of tillage and depth. Autoclaving decreased mineralization and bound residue formation 257‐fold and 6.0‐fold respectively. Bromoxynil persistence in soil was rate independent (T1/2 < 1 day), and the majority of non‐extractable residues (87%) were associated with the humic acid fraction of soil organic matter.

CONCLUSIONS: Irrespective of tillage or depth, bromoxynil half‐life in native soil is less than 1 day owing to rapid incorporation of the herbicide into non‐extractable residues. Bound residue formation is governed principally by biochemical metabolite formation and primarily associated with soil humic acids that are moderately bioavailable for mineralization. These data indicate that the risk of off‐site transport of bromoxynil residues is low owing to rapid incorporation into non‐extractable residues. Published 2009 by John Wiley & Sons, Ltd
A sterile‐female technique proposed for control of Striga hermonthica and other intractable weeds: advantages, shortcomings and risk management
Authors: Rector Brian G
Published: March 2009

Weeds have posed intractable challenges to farmers since the dawn of agriculture. This article describes in detail a proposed control strategy based on the introduction of genes conferring female sterility into the genome of an intractable target weed. Spread of these genes through target populations via pollen would be facilitated by their incorporation within active transposable elements. Advantages (e.g. self‐dissemination, self‐proliferation, target specificity) and shortcomings (e.g. high cost, long project incubation period, limited range of possible targets) of this strategy are discussed in depth, as are assessment and management of its attendant biological and ecological risks, such as the risk of introduced genes spreading to non‐target species. The parasitic weed Striga hermonthica (Del.) Benth. is examined as a potential target. Published 2009 by John Wiley & Sons, Ltd
Methods for selecting hypervirulent biocontrol agents of weeds: why and how
Authors: Sands David C , Pilgeram Alice L
Published: March 2009

A considerable number of plant pathogens have been studied for their possible use in weed control. Some have proven virulent enough to control weed species and to compete commercially with chemical herbicides. However, most pathogens of weeds are not useful in their wild form because they are not sufficiently host‐specific and/or virulent. The authors believe that these barriers can be overcome. The present research has focused on the inhibitory effects of certain amino acids on the growth and development of specific plants. Pathogens that overproduce these selected amino acids can be easily selected from a pool of spontaneous mutants. Such mutants can have increased pathogenicity to their target weed and enhanced field performance as biocontrol agents. Enhancement of biocontrol efficacy in three separate pathogen–host systems, two with Fusarium and one with Pseudomonas, has already been reported. It is proposed to use the same technology to enhance the biocontrol efficacy of the two species of Fusarium that are host‐specific pathogens of the broomrape group of parasitic weeds. The stepwise approach outlined can lead to obtaining enhanced biocontrol agents capable of producing inhibitory levels of selected amino acids in situ. It is proposed that these approaches, in combination with other methods of virulence enhancement, will lead to sustainable systems of biological control of parasitic weeds. Copyright © 2009 Society of Chemical Industry
Excitonic transitions in silicon nanostructures probed by time‐resolved photoluminescence spectroscopy
Authors: Dovrat M. , Shalibo Y. , Arad N. , Popov I. , Lee S.‐T. , Sa'ar A.
Published: March 2009

Time‐resolved photoluminescence spectroscopy has been utilized to reveal excitonic transitions in silicon nanowires and silicon nanocrystals. While previous works on porous silicon and silicon nanocrystals have shown a two‐level splitting, e.g., singlet‐triplet states, our measurements reveal the fine structure of the excitons including three semi‐bright states and a ground dark excitonic state. Surprisingly, for silicon nanowires we have found the slowest semi‐dark exciton to fall above the faster semi‐bright excitonic state as opposed to silicon nanocrystals. The results are analyzed in terms of spin and orbital selection rules showing that the interchange in the level's hierarchy corresponds to a swap between spin‐forbidden and orbitally‐allowed states. We assign this surprising phenomenon to the relationship between the exchange interaction and the direct Coulomb interaction, which is affected by the dimensionality of the exciton. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A porous silicon intermediate reflector in thin film epitaxial silicon solar cells as a gettering site of impurities
Authors: Kuzma‐Filipek Izabela , Duerinckx Filip , Van Nieuwenhuysen Kris , Beaucarne Guy , Poortmans Jef , Mertens Robert
Published: March 2009

In this work, we study the gettering properties of a porous silicon (Psi) intermediate reflector. This type of reflector is used currently in the thin film epitaxial silicon solar cell approach. The porous layers are electrochemically etched into low‐cost, highly contaminated UMG (Upgraded Metallurgical Grade) Si in order to investigate the influence of impurity diffusion to the active layer due to the high thermal budget during epitaxial growth. When implemented into a solar cell, a porous silicon (Psi) multilayer stack consisting of layers with alternating porosities can serve as a gettering site for impurities that originate from the substrate. This statement is confirmed in our present work by several techniques such as SIMS (Secondary Ion Mass Spectrometry) and TXRF (Total Reflection X‐Ray Fluorescence). Additionally to these experiments, solar cell results are presented, for which the active layer is grown with two different growth rates on top of porous silicon (Psi) multilayer stack and on two different types of multicrystalline silicon substrates: UMG (Upgraded Metallurgical Grade) and OFFSPEC (Out‐of spec silicon material treated as a waste from Integrated Circuits industry). (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Role of the buffer porous layer and dysprosium doping in GaInP‐porGaAs‐GaAs heterostructures
Authors: Domashevskaya E. P. , Seredin P. V. , Gordienko N. N. , Glotov A. V. , Arsentyev I. N. , Shishkov M. V.
Published: March 2009

In the samples with porous buffer layer the residual internal stresses caused by the difference in lattice parameters between the surface layer of ternary GaInP alloy and GaAs substrate are redistributed into the porous layer, which in this case plays a role of a “sponge” and completely removes the internal stresses. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron structure of porous silicon obtained without the use of HF acid
Authors: Kashkarov Vladimir , Nazarikov Igor , Lenshin Alexander , Terekhov Vladimir , Turishchev Sergey , Agapov Boris , Pankov Konstantin , Domashevskaya Evelina
Published: March 2009

Reproducible technique for obtaining of porous silicon samples without the use of fluoric acid was elaborated. The main component for electrochemical etching of silicon is a concentrated aqueous solution of NH4F. The obtained samples are characterized by unusual pore morphology and the presence of corrugated “nanoribbons” of Si on the surface of porous layer. The density of occupied electron states in the samples determined by ultrasoft X‐ray emission spectroscopy shows practically complete absence of Si‐O bonds in the near‐surface layers of porous silicon (por‐Si). Analysis of the data of X‐ray absorption spectra and X‐ray photoelectron spectra demonstrates the presence of a great amount of Si‐O bonds just on the surface of the sample and an unusual abrupt decay in the absorption spectra near Si L2,3 edge of elementary silicon. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Self‐induced oscillation of the macropore diameter in n‐type silicon
Authors: Cojocaru Ala , Carstensen Jürgen , Leisner Malte , Föll Helmut , Tiginyanu Ion
Published: March 2009

Electrochemical etching of n‐type silicon in viscous‐electrolyte containing HF for macropore formation has been employed to obtain deep pores at high growth rates. Under certain conditions, a new kind of macropore growth has been observed. The macropore diameters show self‐induced anti‐phase oscillations during specific phases of pore growth. This remarkable structural feature is not only interesting by itself, it is also the manifestation of a steady state of pore growth, a feature which has not been observed in any kind of electrochemically grown pores in semiconductors so far. This conclusion is mainly based on in‐situ FFT (Fast Fourier Transform) voltage and illumination impedance spectroscopy measurements performed during the pore etching. Some voltage impedance data are presented here. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Buried porous SiNx layer in nitrogen‐implanted silicon
Authors: Bak‐Misiuk Jadwiga , Antonova Irina V. , Misiuk Andrzej , Formanek Petr , Romanowski Przemyslaw
Published: March 2009

SOI‐like structures produced by N2+ implantation (nitrogen doses, D = 1×1017 cm–2 and 8.5×1017 cm–2, energy 140 keV) into Czochralski grown silicon (Cz‐Si) and subsequent processing of Cz‐Si:N at up to 1520 K (HT) under atmospheric or enhanced hydrostatic pressure (H P, up to 1.4 GPa) were investigated. The main HT–HP induced effects in Si:N are following: formation of buried porous SiNx layer, decreased Si/SiNx interface roughness and improved uniformity of layer thickness, decreased concentration and / or dimensions of defects within the top silicon layer and the substrate, suppressed formation of exfoliation defects in the top silicon layer and decreased size of silicon nanocrystals at the Si/SiNx interface. Subsequent treatment of Si:N resulted in a creation of buried layers with interesting properties, especially in respect of formation of nano‐structured areas. Porosity of buried layer depends on nitrogen concentration and can be tuned by specific treatment conditions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparation and optical properties of porous silicon rugate‐type multilayers with different pore sizes
Authors: Salem M. S. , Sailor M. J. , Fukami K. , Sakka T. , Ogata Y. H.
Published: March 2009

Porous silicon rugate filters having different pore sizes were prepared by electrochemical anodization of silicon in hydrofluoric (HF) acid solution using a sinusoidal current density. The pore size was tuned by an appropriate choice of the anodization conditions, electrolyte composition, and the doping level of the starting silicon substrate. The anodization process of heavily doped silicon in HF acid produces a mesoporous filter. Whereas, a microporous filter can be formed by applying the same process to a lightly doped silicon substrate. A sinusoidal current signal with amplitude of 13 mAcm–2 was sufficient to form a mesoporous rugate filter with an index contrast of 0.39. However, a microporous filter prepared from lightly doped silicon with two times smaller index contrast needed a sinusoidal current amplitude four times larger than that applied for the mesoporous one prepared from heavily doped silicon. A rugate filter with pore diameter lying in the intermediate region between the meso and macro size range was formed on heavily doped silicon with the addition of oxidizing agents. The optical properties of the formed filters were compared and discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study and characterization of porous germanium for radiometric measurements
Authors: Akkari E. , Benachour Z. , Aouida S. , Touayar O. , Bessais B. , Benbrahim J.
Published: March 2009

The aim of this article is to study and realize a new detector based on a porous germanium (pGe) photodiode to be used as a standard for radiometric measurement in the wavelength region between 800 nm and 1700 nm. We present the development and characterization of a porous structure realized on a single‐crystal substrate of p‐type germanium (Ga doped) and of crystallographic orientation (100). The obtained structure allows, on the one hand, to trap the incident radiation, and on the other hand, to minimize the fluctuations of the front‐face reflection coefficient of the photodiode. The first studies thus made show that it is possible to optimize, respectively, the electrical current density and the electrochemical operation time necessary for obtaining exploitable porous structures. The obtained results show that for 50 mA/cm2 and 5 min as operational parameters, we obtain a textured aspect of the porous samples that present a pyramidal form. The reflectivity study of the front surface shows a constant value of around 38% in a spectral range between 800 nm and 1700 nm approximately. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Image processing for the characterization of porous silicon nanostructure
Authors: Ludurczak Willy , Garel Olivier , Berthoumieu Yannick , Babot Odile , Donias Marc , Dufour‐Gergam Elisabeth , Niang Fatimata , Pellet Claude , Toupance Thierry , Verjus Fabrice
Published: March 2009

This paper presents a new method based on image processing (IP) for the characterization of porous silicon (PS) nanostructures. It was developed using porous silicon layers (PS1 and PS2) having different nanostructures. According to gravimetric measurements, these layers present the same porosity of 45%. First we characterized the PS layers by Barrett‐Joyner‐Halenda (BJH) theory applied to sorption data. Then applying BJH theory, we found that the mean pore diameter of PS1 and PS2 are 4.3 and 5.5 nm respectively. With Brunauer‐Emmet‐Teller (BET) theory, we found that PS1 has a specific area of 330 m2/g, and PS2 has a specific area of 223 m2/g. We obtained images of the PS layer surface by high resolution scanning electronic microscopy (HRSEM). The processing of these images leads to the estimation of mean pore diameter: 5.6 nm and 7.5 nm for PS1 and PS2 respectively, and to the representation of pore size distribution. According to a geometrical model, we estimated the porosity and found 55% and 48% for PS1 and PS2 respectively. The calculation of specific area according to the same model leads to the values of 343 m2/g and 217 m2/g for PS1 and PS2 respectively. The close agreement of results obtained by IP to those obtained by sorption theories shows the validity of our method. Advantages of images processing are discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of electrical characteristics of the In3Sb1Te2 ternary alloy for application in phase‐change memory
Authors: Kim Eun Tae , Lee Jeong Yong , Kim Yong Tae
Published: March 2009

A simple layered phase‐change random access memory (PRAM) cell was fabricated using the In3Sb1Te2 alloy. The overall resistance value of the reset state was about 70 times larger than that of the set state. The resistance difference between the amorphous and crystalline state was fairly well maintained after 102 cycles. Interestingly, the measured current–voltage (I –V) curve showed three obvious steps in the crystalline state. By means of high temperature X‐ray diffractometry (HTXRD) and differential scanning calorimetry (DSC) experiments, we confirmed that the current steps originate from successive structural transformations of the In3Sb1Te2 ternary alloy. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Green's function method in quantum chemistry: New numerical algorithm for the Dirac equation with complex energy and Fermi‐model nuclear potential
Authors: Glushkov A. V. , Malinovskaya S. V. , Khetselius O. Yu. , Loboda A. V. , Sukharev D. E. , Lovett L.
Published: March 2009

We present a new effective approach to construction of the electron Green function for the Dirac equation with a nonsingular central nuclear Fermi‐model potential and complex energy. We represent the radial Green function as a combination of two fundamental solutions of the Dirac equation. The approach proposed includes a procedure of generating the relativistic electron functions Ψ with performance of the gauge invariance principle. To reach the gauge invariance principle performance, we use earlier developed QED perturbation theory approach. In the fourth order of the QED perturbation theory (PT) there are diagrams, whose contribution into imaginary part of radiation width ImdE for the multielectron system accounts for many‐body correlation effects. A minimization of the functional ImdE leads to integral‐differential Kohn‐Sham‐like density functional equations. Further check for the gauge principle performance is realized by means of the Ward identities. In the numerical procedure we use the effective algorithm, within which a definition of the Dirac equation fundamental solutions is reduced to solving the single system of the differential equations. This system includes also the differential equations for the Fermi‐model nuclear potential and equations for calculating the integrals of the ∫ ∫ dr1dr2 type in the Mohr formula for definition of the self‐energy shift to atomic levels energies. Such an approach allows to compensate a main source of the errors, connected with numerical integration ∫dξ and summation on χ in the Mohr expressions during calculating the self‐energy radiative correction to the atomic levels energies. Some numerical illustrations of applying the approach within QED PT to calculate the intermediate and high‐Z Li‐like ions transitions energies are presented. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
False‐positive liquid chromatography/tandem mass spectrometric confirmation of sebuthylazine residues using the identification points system according to EU directive 2002/657/EC due to a biogenic insecticide in tarragon
Authors: Schürmann Andreas , Dvorak Veronika , Crüzer Claudio , Butcher Patrick , Kaufmann Anton
Published: March 2009

In pesticide residue analysis using liquid chromatography/tandem mass spectrometry (LC/MS/MS) the confirmation of a sebuthylazine finding in a tarragon (Artemisia dranunculus) sample was demonstrated to be false positive. A coeluting interfering matrix compound produced product ions in MS/MS analysis, perfectly corresponding to the multiple reaction monitoring (MRM) of two sebuthylazine transitions. Using the EU directive 2002/657/EC which regulates the confirmation of suspected positive findings would have resulted in a false‐positive finding. A third LC/MS/MS transition with a deviant ion ratio and a gas chromatography (GC)/MS/MS analysis revealed the false‐positive results. With optimized high resolving ultra‐performance liquid chromatography (UPLC) conditions it was possible to separate spiked sebuthylazine from the interfering matrix compound. Using its exact mass and isotope ratios from LC/time‐of‐flight (TOF) MS measurements, the compound was identified as nepellitorine, a – not surprising – endogenous alkamide in tarragon (Arthemisia dranunculus). False‐positive results, especially in heavy matrix samples such as herbs, can be dealt with by further confirmatory analysis, e.g. a third transition, GC analysis if possible or more advantageous by an orthogonal criterion like exact mass. Copyright © 2009 John Wiley & Sons, Ltd.
Passive and transpassive films formed on a nickel alloy in ammoniacal solution
Authors: Asselin E. , Alfantazi A. , Rogak S.
Published: March 2009

The surface of alloy 625 (Ni‐22Cr‐9Mo) was characterized with XPS and AES depth profiling after exposure to mildly alkaline ammoniacal solution at open circuit and after potentiostatic treatments at various potentials. It was determined that the passive surface film was a Cr and Mo oxide that was depleted in Ni with respect to the bulk alloy. Increased solution temperatures or oxygen concentrations decreased the Ni to Cr ratio in the passive film. The alloy's transpassive film was characterized using SEM and EDX as well as XPS. The transpassive film was heavily depleted in Ni and Cr and consisted mainly of an oxide of Fe. Copyright © 2009 John Wiley & Sons, Ltd.
Size‐Dependent Cytotoxicity of Monodisperse Silica Nanoparticles in Human Endothelial Cells
Authors: Napierska Dorota , Thomassen Leen C. J. , Rabolli Virginie , Lison Dominique , Gonzalez Laetitia , Kirsch‐Volders Micheline , Martens Johan A. , Hoet Peter H.
Published: March 2009

The effect that monodisperse amorphous spherical silica particles of different sizes have on the viability of endothelial cells (EAHY926 cell line) is investigated. The results indicate that exposure to silica nanoparticles causes cytotoxic damage (as indicated by lactate dehydrogenase (LDH) release) and a decrease in cell survival (as determined by the tetrazolium reduction, MTT, assay) in the EAHY926 cell line in a dose‐related manner. Concentrations leading to a 50% reduction in cell viability (TC50) for the smallest particles tested (14‐, 15‐, and 16‐nm diameter) ranging from 33 to 47 µg cm−2 of cell culture differ significantly from values assessed for the bigger nanoparticles: 89 and 254 µg cm−2 (diameter of 19 and 60 nm, respectively). Two fine silica particles with diameters of 104 and 335 nm show very low cytotoxic response compared to nanometer‐sized particles with TC50 values of 1095 and 1087 µg cm−2, respectively. The smaller particles also appear to affect the exposed cells faster with cell death (by necrosis) being observed within just a few hours. The surface area of the tested particles is an important parameter in determining the toxicity of monodisperse amorphous silica nanoparticles.
Efficacy of Chlorhexidine Gluconate During Surgery for Hydatid Cyst
Authors: Topcu Omer , Sumer Zeynep , Tuncer Ersin , Aydin Cengiz , Koyuncu Ayhan
Published: March 2009

Background

Dissemination of protoscolices‐rich fluid during surgery for hydatid cyst disease is a major cause of recurrence. Instillation of a scolicidal agent into a hepatic hydatid cyst before opening is the most commonly employed measure to prevent this serious complication. In this clinical study, the efficacy of 0.04% chlorhexidine gluconate (Chx‐Glu) during hydatid cyst surgery was tested, and early‐term results were evaluated.

Methods

A total of 30 consecutive patients with 45 liver cysts were studied. Only type I and type II cysts were included. Cysts were punctured, and fluid was aspirated. The viability of protoscolices in this fluid was determined. Chx‐Glu 0.04% was instilled into the cyst cavity. After 5 minutes of exposure, the cyst fluid was reaspirated and evaluated for the viability of protoscolices. Imprints of the germinative membranes were determined for protoscolices viability.

Results

All protoscolices in 45 cysts evaluated were killed by 5 minutes of exposure to 0.04% Chx‐Glu. The whole of the germinative membrane imprints contained dead protoscolices. Chx‐Glu 0.04% did not cause any adverse effect on biliary tracts in communication with cysts. There was no recurrence during the 2‐year follow‐up period. There were also no mortality and no cavity‐related complications.

Conclusions

This study shows that intracystic injection of 0.04% Chx‐Glu is an effective measure against the dissemination of viable protoscolices. In addition, Chx‐Glu is the most convenient scolicidal agent as per the criteria defined by the World Health Organization. Therefore, it can be used safely during hydatid cyst surgery. However, there remains the need to perform advanced comparative clinical studies on the efficacy of Chx‐Glu and other scolicidal agents.
Characteristics of Esophagorespiratory Fistulas Resulting from Esophageal Cancers: A Single‐Center Study on 243 Cases in a 20‐Year Period
Authors: Balazs Akos , Galambos Zoltan , Kupcsulik Peter K.
Published: March 2009

Background

Esophagorespiratory fistulas are serious complications of esophageal tumors. The main goal of this study was to reveal their characteristics.

Methods

In the period between 1984 and 2004, 243 fistulas were diagnosed among the 1993 patients with esophageal cancer. Comparing the characteristic data of patients with and without fistula (demographics, symptoms, duration time of symptoms, morphologic features, histology, metastases, staging), multivariance analysis showed significant differences (P < 0.05). Patients with fistula were divided into two additional groups (I, n = 82; II, n = 161 cases) with cluster analysis. The difference between these two groups was also significant.

Results

It was possible to perform a palliative endoscopic intubation in 176 cases, while 62 patients could be treated only supportively. The average survival was 3.4 and 1.2 months, respectively. Fistula was a late complication of tumor in two thirds (66.3%) of the cases, while in 33.7% it was diagnosed in younger patients at the early stage of the disease, with a more aggressive, less differentiated histology. In these patients the weight loss, the grade of dysphagia, and the size of the tumor were smaller, the possibilities of treatment were fewer, and survival time was shorter (2.1 vs. 3.1 months).

Conclusions

These tumors seem to be specific forms of esophageal cancers. For a better quality of life and longer survival time for these patients, there should be earlier diagnosis and endoscopic intubation as the best palliative treatment should be performed.