bluuebunny/crossref_metadata_2025_split huggingface dataset:
Methods for selecting hypervirulent biocontrol agents of weeds: why and how
Authors: Sands David C , Pilgeram Alice L 
Published: March 2009

AbstractA 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

AbstractTime‐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

AbstractIn 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

AbstractIn 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

AbstractReproducible 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

AbstractElectrochemical 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

AbstractSOI‐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

AbstractPorous 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

AbstractThe 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

AbstractThis 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

AbstractA 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

AbstractWe 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

AbstractIn 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

AbstractThe 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

AbstractThe 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

AbstractBackgroundDissemination 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.MethodsA 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.ResultsAll 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.ConclusionsThis 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

AbstractBackgroundEsophagorespiratory fistulas are serious complications of esophageal tumors. The main goal of this study was to reveal their characteristics.MethodsIn 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.ResultsIt 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).ConclusionsThese 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.