bluuebunny/crossref_metadata_2025 huggingface dataset:
Rh‐Catalyzed AldehydeAldehyde Cross‐Aldol Reaction under Base‐Free Conditions: In Situ Aldehyde‐Derived Enolate Formation through Orthogonal Activation
Authors: Lin Luqing , Yamamoto Kumiko , Matsunaga Shigeki , Kanai Motomu
Published: October 2013

The chemoselective generation of aldehyde‐derived enolates to realize an aldehydealdehyde cross‐aldol reaction is described. A combined Rh/dippf system efficiently promoted the isomerization/aldol sequence by using primary allylic, homoallylic, and bishomoallylic alcohols; secondary allylic and homoallylic alcohols; and trialkoxyboranes that were derived from primary allylic and homoallylic alcohols. The reaction proceeded at ambient temperature under base‐free conditions, thus giving cross‐aldol products with high chemoselectivity. Mechanistic studies, as well as its application to double‐aldol processes under protecting‐group‐free conditions, are also described.
Thermodynamic Phase Transition Through Crystal‐to‐Crystal Process of Photochromic 1,2‐Bis(5‐phenyl‐2‐propyl‐3‐thienyl)perfluorocyclopentene
Authors: Kitagawa Daichi , Kobatake Seiya
Published: October 2013

A photochromic diarylethene, 1,2‐bis(5‐phenyl‐2‐propyl‐3‐thienyl)perfluorocyclopentene (1a), was found to have two polymorphic crystal forms, α‐ and β‐crystals. From X‐ray crystallographic analysis, the space groups of α‐ and β‐crystals were determined to be P21/c and C2/c, respectively. The difference between two crystal forms is ascribed to the orientation of two of four molecules in the unit cell. The thermodynamic phase transition from α‐ to β‐forms occurred via a crystal‐to‐crystal process, as confirmed by differential scanning calorimetry measurements, optical microscopic observations in the reflection mode and under crossed Nicols, and powder X‐ray diffraction measurements. The movement of the molecules in the crystal was evaluated by analyzing the change of face indices before and after the phase transition.
Phase‐Transfer‐Catalyzed Asymmetric Synthesis of Axially Chiral Anilides
Authors: Liu Kun , Wu Xiangfei , Kan S. B. Jennifer , Shirakawa Seiji , Maruoka Keiji
Published: October 2013

Catalytic asymmetric synthesis of axially chiral o‐iodoanilides and o‐tert‐butylanilides as useful chiral building blocks was achieved by means of binaphthyl‐modified chiral quaternary ammonium‐salt‐catalyzed N‐alkylations under phase‐transfer conditions. The synthetic utility of axially chiral products was demonstrated in various transformations. For example, axially chiral N‐allyl‐o‐iodoanilide was transformed to 3‐methylindoline by means of radical cyclization with high chirality transfer from axial chirality to C‐centered chirality. Furthermore, stereochemical information on axial chirality in o‐tert‐butylanilides could be used as a template to control the stereochemistry of subsequent transformations. The transition‐state structure of the present phase‐transfer reaction was discussed on the basis of the X‐ray crystal structure of ammonium anilide, which was prepared from binaphthyl‐modified chiral ammonium bromide and o‐iodoanilide. The chiral tetraalkylammonium bromide as a phase‐transfer catalyst recognized the steric difference between the ortho substituents on anilide to obtain high enantioselectivity. The size and structural effects of the ortho substituents on anilide were investigated, and a wide variety of axially chiral anilides that possess various functional groups could be synthesized with high enantioselectivities. This method is the only general way to access a variety of axially chiral anilides in a highly enantioselective fashion reported to date.
Mechanistic study of stress corrosion cracking of carbon steel in ethanol
Authors: Torkkeli J. , Hirsi V. , Saukkonen T. , Hänninen H.
Published: October 2013

Mechanistic study of stress corrosion cracking of carbon steel in fuel‐grade ethanol was made using slow strain rate testing and constant tensile load testing at yield strength stress level of the steels. Characterization of the fracture surface was made using SEM and SEM–EDS. Selective dissolution of ferrite from pearlite phase was observed. Crack initiation took place preferably from pearlite phase. Corroded zones consisting of crystallographic pits were found from fracture surfaces.
Comparison study on anticorrosion performances of the epoxy coatings with two different nano‐polyanilines for Q235 steel
Authors: Hou W. P. , Liu Y. , Ge Z. Y. , Zhao W. Y.
Published: October 2013

Sulfuric acid doped nano‐polyaniline was prepared by direct mixed oxidation in two different systems. A novel approach for preparing polyaniline (PANI) in FeCl2/H2O2 system was developed. The PANI possessed an excellent dispensability. Corrosion protection of epoxy coatings containing two kinds of polyaniline (PANI) on Q235 steel was studied by electrochemical impendance spectroscopy (EIS) technique and Tafel polarization test in 3.5 wt% sodium chloride (NaCl) aqueous solution. The results indicated that the epoxy coating containing PANI obtained in FeCl2/H2O2 system had the best performance of the corrosion protection among three systems under investigation. The possible protective mechanism of PANI was discussed.
Significantly changed intergranular corrosion and exfoliation corrosion behavior of the ultra‐fine grained Al–5 mass% Cu alloy fabricated by ECAP
Authors: Song D. , Ma A. B. , Jiang J. H. , Lin P. H. , Lu F. M. , Zhang L. Y.
Published: October 2013

Significantly changed intergranular corrosion (IGC) and exfoliation corrosion (EFC) behaviors of the equal‐channel‐angular‐pressed (ECAPed) Al–Cu alloy were discovered through immersion test, electrochemical measurements, and microstructure observation. The ECAPed alloys with ultra‐fine grained (UFG) α(Al) matrix and extremely refined θ‐phase particles displayed obvious decreased IGC sensitivity, but deteriorated susceptibility to EFC. The decreased IGC sensitivity of ECAPed alloys presented decreased IGC propagation depths in immersion test in NaCl + H2O2 solutions and increased polarization resistance in electrochemical impedance spectrum test in MIL‐H‐600 solution. The reason for the decreased IGC sensitivity was the breakage of the net structure of θ phase during ECAP process, which destroys the continuity of IGC propagation channel. The deteriorated susceptibility to EFC of ECAPed alloys in EXCO solution presented gradual evolution from serious IGC attack into obvious lamellar EFC, and finally complete dissolution of surface grains. Meanwhile, the EFC propagation depths were sharply decreased with the increasing ECAP passes. This phenomenon was caused by the aspects ratio evolution of deformed grains and the gradually decreased IGC sensitivity of the ECAPed alloys.
Influence of thermo‐mechanical processing on the microstructure, mechanical properties and corrosion behaviour of a new quaternary titanium alloy
Authors: Vasilescu C. , Moreno J. M. Calderon , Drob S. I. , Popa M.
Published: October 2013

A new quaternary Ti–20Nb–10Zr–5Ta alloy was thermo‐mechanically processed; applying a stress of 10 ton‐forces after heat treatment at 1000 °C it resulted a very homogeneous, fine microstructure characterized by the best mechanical properties: low Young's modulus (60 GPa) and high tensile strength and hardness. The corrosion behaviour of this processed alloy after long‐term soaking (5000 h) in simulated human fluid (Ringer solution) was studied. SEM micrographs of as‐cast and processed alloy after immersion proved that their surfaces were covered with a layer with a porous microstructure. EDX analysis detected Ca, P, and O as constituent elements of this porous layer. XPS determined the presence of the protective TiO2, Nb2O5, ZrO2, and Ta2O5oxides and of the hydroxyapatite deposited from solution. All electrochemical parameters exhibited more favourable values for the processed alloy indicating the beneficial influence of the applied treatment. Impedance parameters revealed a nobler behaviour of the processed alloy than of the as‐cast one. EIS spectra showed a passive film with two layers: a compact, inner, electronically conducting, barrier layer and an outer, porous layer.
Qualitative analysis of Zircaloy‐4 cladding air degradation in O2–N2 mixtures at high temperature
Authors: Lasserre M. , Peres V. , Pijolat M. , Coindreau O. , Duriez C. , Mardon J.‐P.
Published: October 2013

This article is devoted to the qualitative analysis of the Zircaloy‐4 degradation mechanism at 850 °C in oxygen/nitrogen partial pressure atmospheres. Thermogravimetry, optical microscopy, scanning electron microscopy, and energy dispersive X‐ray spectrometry, are used to provide some information regarding the oxidation kinetics and the various phases involved along the process. The kinetic curves reveal two stages: a pre‐transition and a post‐transition one. Oxide growth during the pre‐transition stage is controlled by oxygen vacancy diffusion in the oxide layer, since neither oxygen nor nitrogen partial pressure influences the kinetics. In the post‐transition stage, nitrogen has an accelerating effect in the corrosion reaction. The kinetic curves reveal two distinct behaviors after the transition according to the oxygen and nitrogen partial pressures: in the first case the corrosion rate rises substantially and leads to a rapid degradation of the metal at high oxygen and nitrogen partial pressures, in the second case the corrosion rate rises dramatically and reaches a plateau at low oxygen and nitrogen partial pressures. This paper describes the influence of both gases on the corrosion kinetics in relation with morphological observations, analyses the discrepancies found between high and low oxygen and nitrogen partial pressures; it also exhibits the complexity of the solid state transformations due to three distinct reactions that appear to take place during the corrosion process.
Kappaphycus alvarezii – A marine red alga as a green inhibitor for acid corrosion of mild steel
Authors: Kamal C. , Sethuraman M. G.
Published: October 2013

The anticorrosion potential of Kappaphycus alvarezii on mild steel in both 1 M HCl and H2SO4 media has been studied using weight loss method at three different temperatures, electrochemical measurements, and surface analyses. The results revealed the inhibitive effect of K. alvarezii. The inhibition efficiency was found to increase with increasing concentration of the algal extract but decreased with increase in temperature which is attributed to the physisorption. The adsorption of the extract on the mild steel surface obeys the Temkin adsorption isotherm. Further, scanning electron microscope (SEM) and atomic force microscope (AFM) analyses supported the inhibitive action of this red alga by the formation of protective layer over the mild steel surface.
Characterization and electrochemical corrosion properties of Sn and Al + Sn containing coatings on magnesium alloys prepared by laser surface treatment
Authors: Wang L.‐Q. , Zhou J.‐S. , Liang J. , Chen J.‐M.
Published: October 2013

Sn and Al + Sn containing coatings were prepared on the surface of AZ91D magnesium alloy by laser surface treatment. The microstructure and composition of specimens were analyzed by metallurgical microscope, scanning electron microscope (SEM), field emission scanning electron microscope (FESEM) equipped with energy‐dispersive spectroscopy (EDS), and X‐ray diffraction (XRD). The corrosion resistance of the as‐received and laser treated magnesium alloys were evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests. The effect of Sn and Al + Sn addition on the microstructure, composition and corrosion behavior of magnesium alloys was investigated. Results showed that the surface presents different phase composition. The corrosion resistance of magnesium alloys sharply decreased after laser surface cladding (LSC) of Al + Sn, for the galvanic corrosion between Al and Sn. Conversely, the corrosion resistance was improved by laser surface alloying (LSA) of Sn due to the refinement effect and the protection of Mg2Sn and SnO2 in the grain boundary to the α‐Mg matrix.
Ion‐induced surface modification combining the halogen and the reactive element‐effect for a Ni‐base superalloy
Authors: Zschau H.‐E. , Schütze M. , King F.
Published: October 2013

The oxidation resistance of Ni‐base superalloys with Al‐contents of 2–5 wt% is commonly improved by the use of Al‐rich coatings. An alternative way has been proposed by using the halogen effect. In this case, the Al activity on the alloy surface is increased by the transport of Al via gaseous Al‐halides. Fluorine was chosen because of the good results obtained in the case of TiAl. The fluorine was applied by ion implantation. After oxidation at 1050 °C a dense protective alumina scale was formed on the surface of the alloy IN738. The fluorine effect was combined with the reactive element effect to improve the adherence of the alumina scale.
Photophysics and morphology of a polyfluorene donor–acceptor triblock copolymer for solar cells
Authors: Yan Chao , Cadby Ashley J. , Parnell Andrew J. , Tang Weihua , Skoda Maximilian W. A. , Mohamad David , King Simon P. , Reynolds Luke X. , Haque Saif A. , Wang Tao , Parnell Steven R. , Holmes Andrew B. , Jones Richard A. L. , Jones David J.
Published: October 2013

We present a study of the optical, structural and device properties of a polyfluorene (PFM)‐based (PFM‐F8BT‐PFM) donor–acceptor triblock copolymer for use in an organic solar cell. Neutron reflectivity is employed to probe the vertical composition profile before and after thermal annealing while the crystallinity was examined using grazing incidence wide‐angle X‐ray. The absorption spectra and photoluminescence emission for the triblock and analogous blend of PFM with F8BT reveal a greater degree of intermixing in the triblock. However, the triblock copolymer exhibits exciplex emission, which necessitates a geminate polar pair; long‐lived exciplex states are detrimental in organic photovoltaic devices. The triplet yield in the triblock and the blend is estimated using photoinduced absorption, with the triblock copolymer generating a triplet population 20 times that of the blend. This is far from ideal as triplets are wasted states in organic photovoltaic devices and they can also act as scavengers of polarons reducing the efficiency even more. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2013,51, 1705–1718
Rapid dislocation‐density mapping of as‐cut crystalline silicon wafers
Authors: Needleman David Berney , Choi1 Hyunjoo , Powell1 Douglas M. , Buonassisi Tonio
Published: October 2013

Rapid quantification of structural defects, especially dislocations, is desired for characterization of semiconductor materials. Herein, we outline and validate a low‐cost approach for dislocation‐density quantification in silicon, involving a high‐resolution commercial dark‐field imaging device, a flatbed scanner. This method requires minimal surface preparation and can be performed on as‐cut 15.6 × 15.6 cm2wafers in less than 5 minutes. The method has been tested at a spatial resolution down to 250 µm. At 1 mm resolution, the average root mean square of the normalized error was 0.39.

magnified image

Flatbed scanner image of a defect‐etched 15.6 × 15.6 cm2silicon wafer (left) and the corresponding dislocation‐density map obtained using our technique (right).

(© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sonographic prediction of vaginal delivery in prolonged labor: a two‐center study
Authors: Eggebø T. M. , Hassan W. A. , Salvesen K. Å. , Lindtjørn E. , Lees C. C.
Published: October 2013

Objective

To investigate whether head–perineum distance (HPD) measured by transperineal ultrasound is predictive of vaginal delivery and time remaining in labor in nulliparous women with prolonged first stage of labor and to compare the predictive value with that of angle of progression (AoP).

Methods

This was a prospective observational study at Stavanger University Hospital, Norway and Addenbrooke's Hospital, Cambridge, UK from January 2012 to April 2013, of nulliparous women with singleton pregnancies with cephalic presentation at term with prolonged first stage of labor. We used transperineal ultrasound to measure HPD (shortest distance between the outer bony limit of the fetal skull and the perineum) and AoP (angle between a line through the long axis of the symphysis and the tangent to the fetal head) and transabdominal ultrasound to classify fetal head position. The main outcomes were vaginal delivery and time remaining in labor.

Results

Of 150 women enrolled, 39 underwent delivery by Cesarean section. The area under the receiver–operating characteristics curve for the prediction of vaginal delivery was 81% (95% CI, 73–89%) using HPD as the test variable and 72% (95% CI, 63–82%) using AoP. HPD was ≤ 40 mm in 84 (56%) women, of whom 77 (92%; 95% CI, 84–96%) delivered vaginally. HPD was > 40 mm in the other 66 (44%) women, of whom 34 (52%; 95% CI, 40–63%) delivered vaginally. AoP was ≥ 110° in 84 of the 145 (58%) in whom this was available and, of these, 74 (88%; 95% CI, 79–93%) delivered vaginally. AoP was < 110° in the other 61 (42%) women, of whom 35 (57%; 95% CI, 45–69%) delivered vaginally. Multivariable logistic regression analysis showed that HPD ≤ 40 mm (odds ratio (OR), 4.92; 95% CI, 1.54–15.80), AoP ≥ 110° (OR, 3.11; 95% CI, 1.01–9.56), non‐occiput posterior position (OR, 3.36; 95% CI, 1.24–9.12) and spontaneous onset of labor (OR, 4.44; 95% CI, 1.42–13.89) were independent predictors for vaginal delivery. Both ultrasound methods were predictive for the time remaining in labor.

Conclusion

Transperineal ultrasound measurement of HPD and AoP provide important information about the likelihood of vaginal delivery and the time remaining in labor in nulliparous women with prolonged labor. Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd.
The sonopartogram: a novel method for recording progress of labor by ultrasound
Authors: Hassan W. A. , Eggebø T. , Ferguson M. , Gillett A. , Studd J. , Pasupathy D. , Lees C. C.
Published: October 2013

Linked Comment: Ultrasound Obstet Gynecol 2014; 43: 137–138
Investigating Factors Affecting Water‐In‐Diesel Fuel Nanoemulsions
Authors: Noor El‐Din Mahmoud R. , El‐Hamouly Sabrnal H. , Mohamed Hamed M. , Mishrif Marwa R. , Ragab Ahmad M.
Published: September 2013

In this work, water‐in‐diesel fuel nanoemulsions were prepared with mixed nonionic surfactants. Several mixtures of sorbitan monooleate and polyoxyethylene (20) sorbitan monooleate, with different Hydrophilic–Lipophilic Balance (HLB) values (9.6, 9.8, 10, 10.2 and 10.4) were prepared to achieve the optimal HLB value. Three mixed surfactant concentrations were prepared at 6, 8 and 10 wt% to identify the optimum concentration. Five emulsions with different water contents: 5, 6, 7, 8 and 9 % (wt/wt) were prepared using a high energy method under the optimum conditions (HLB = 10 and mixed surfactant concentration = 10 %). The effect of the HLB value, mixed surfactant concentration and water content on the droplet size has been studied. The interfacial tension and thermodynamic properties of the individual and the blended emulsifiers were investigated. Droplet size of the prepared nanoemulsions was determined by dynamic light scattering and the nanoemulsion stability was assessed by measuring the variation of the droplet size as a function of time. From the results obtained, it was found that the mean droplet size was formed between 49.5 and 190 nm depending on the HLB value, surfactant concentration and water content of the blended emulsifiers.
Production of Canolol from Canola Meal Phenolics via Hydrolysis and Microwave‐Induced Decarboxylation
Authors: Khattab Rabie Y. , Eskin Michael N. A. , Thiyam‐Hollander Usha
Published: September 2013

A potent antioxidant, anti‐inflammatory and anti‐mutagenic agent; 4‐vinyl‐2,6‐dimethoxyphenol (canolol) was obtained from canola meal in a significant yield via alkaline (NaOH)/enzymatic (ferulic acid esterase) hydrolysis followed by microwave‐assisted decarboxylation. The hydrolysis was carried out either through using canola meal directly as a substrate or by using the 70 % aqueous methanolic extract filtrates. The hydrolyzed extracts underwent RP‐HPLC analysis which showed that 81.0 and 94.8 % of the total phenolics were hydrolyzed to sinapic acid after the alkaline hydrolysis of the meal and the methanolic extracts, respectively. The enzymatic hydrolysis showed lower conversion rates (49.5 and 58.3 %). The hydrolyzed extracts were consequently decarboxylated using 8‐diazabicyclo[5.4.0]undec‐7‐ene under microwave irradiation at different conditions. The HPLC profiling of decarboxylated extracts showed that using microwave at 300 W of microwave power for 12 min brought the highest sinapic acid conversion to canolol (58.3 %) yielding 4.2 mg canolol from each gram of canola meal suggesting that the process could be commercially economical.
Zur Objektivität und Validität des Einschätzbogens „Sprache und Literacy bei deutschsprachig aufwachsenden Kindern – SELDAK“
Authors: Mayr† Toni , Gsottschneider Julia
Published: October 2013

SELDAK ist in deutschen Kindertageseinrichtungen ein weit verbreitetes Einschätzverfahren zur Erfassung von Sprache und Literacy. In drei Studien wurden Objektivität und Validität des Verfahrens untersucht. Die Überprüfung der Objektivität ergab insgesamt hohe bis sehr hohe Bobachterübereinstimmungen sowohl auf Item- als auch auf Skalen-Ebene. In der ersten Validitätsstudie wurden die SELDAK-Werte von drei Gruppen verglichen: (1) Kita-Kinder ohne heilpädagogische Förderung, (2) Kita-Kinder mit ambulanter heilpädagogischer Förderung und (3) Kinder, die eine Einrichtung für sprachbehinderte Kinder besuchen. Gruppe 1 schnitt bei allen neun SELDAK-Skalen signifikant besser ab als Gruppe 2 und Gruppe 3. In der zweiten Validitätsstudie konnte gezeigt werden, dass die neun SELDAK-Skalen substantiell mit den Sprach-Subtests „Arbeitsgedächtnis für Nichtwörter“ (SSV), „Grammatik“ (PET) und „Aktiver Wortschatz“ (KISTE) korrelieren. Multiple Regressionen mit den Subtests als Prädiktoren und dem SELDAK-Gesamtscore (R2 = .62) und der SELDAK-Skala „Aktive Sprachkompetenz“ (R2 = .47) als Kriterien zeigen auch multivariat hohe Zusammenhänge.
Modeling Alzheimer's Disease Progression Using Disease Onset Time and Disease Trajectory Concepts Applied to CDR‐SOB Scores From ADNI
Authors: Delor I , Charoin J‐E , Gieschke R , Retout S , Jacqmin P ,   For the Alzheimer's Disease Neuroimaging Initiative
Published: October 2013

Disease‐onset time (DOT) and disease trajectory concepts were applied to derive an Alzheimer's disease (AD) progression population model using the clinical dementia rating scale—sum of boxes (CDR‐SOB) from the AD neuroimaging initiative (ADNI) database. The model enabled the estimation of a DOT and a disease trajectory for each patient. The model also allowed distinguishing fast and slow‐progressing subpopulations according to the functional assessment questionnaire, normalized hippocampal volume, and CDR‐SOB score at study entry. On the basis of these prognostic factors, 81% of the mild cognitive impairment (MCI) subjects could correctly be assigned to slow or fast progressers, and 77% of MCI to AD conversions could be predicted whereas the model described correctly 84% of the conversions. Finally, synchronization of the biomarker‐time profiles on estimated individual DOT virtually expanded the population observation period from 3 to 8 years. DOT‐disease trajectory model is a powerful approach that could be applied to many progressive diseases.

CPT: Pharmacometrics & Systems Pharmacology (2013) 2, e78; doi:10.1038/psp.2013.54; advance online publication 2 October 2013
Design of a reduced‐order non‐linear observer for vehicle velocities estimation
Authors: Guo Hongyan , Chen Hong , Cao Dongpu , Jin Weiwei
Published: October 2013

This study presents a novel reduced‐order non‐linear observer for vehicle velocities estimation based on vehicle dynamics and Unified Exponential tire model. Yaw rate is chosen to construct the reduced‐order observer since it can be conceived as the function of vehicle velocities. The observer is designed such that the error dynamics system is input‐to‐state stability (ISS), where model errors including mass and CoG variation, and estimation or measurement error of the maximum tire–road friction coefficient are considered as additive disturbance inputs. Then, the condition of the observer gain satisfied is obtained by the ISS analysis and the lower observer gain is obtained through the convex optimisation described by the linear matrix inequalities. The proposed observer requires fewer tuning parameters and thus indicates an easier implementation compared with the existing extended Kalman filter. Simulation results demonstrate the effectiveness of the proposed reduced‐order non‐linear observer, which is also validated through experimental data from Hongqi vehicle HQ430. Furthermore, its computational efficiency is shown based on the laboratory Field Programmable Gate Array and System on a Programmable Chip testing platform.
Diffracted X-ray tracking for monitoring intramolecular motion in individual protein molecules using broad band X-ray
Authors: Ichiyanagi Kouhei , Sekiguchi Hiroshi , Hoshino Masato , Kajiwara Kentaro , Hoshisashi Kentaro , Jae-won Chang , Tokue Maki , Matsushita Yufuku , Nishijima Masaki , Inoue Yoshihisa , Senba Yasunori , Ohashi Haruhiko , Ohta Noboru , Yagi Naoto , Sasaki Yuji C.
Published: October 2013

Diffracted X-ray tracking (DXT) enables the tilting and twisting motions of single protein molecules to be monitored with micro- to milliradian resolution using a highly brilliant X-ray source with a wide energy bandwidth. We have developed a technique to monitor single molecules using gold nanocrystals attached to individual protein molecules using the BL28B2 beamline at SPring-8. In this paper we present the installation of a single toroidal X-ray mirror at BL28B2 to focus X-rays in an energy range of 10–20 keV (△E/E = 82% for an X-ray with a wide energy bandwidth). With this beamline we tracked diffraction spots from gold nanocrystals over a wide angle range than that using quasi-monochromatic X-rays. Application of the wide angle DXT technique to biological systems enabled us to observe the on-site motions of single protein molecules that have been functionalized in vivo. We further extend the capability of DXT by observing the fractional tilting and twisting motions of inner proteins under various conditions. As a proof of this methodology and to determine instrumental performance the intramolecular motions of a human serum albumin complex with 2-anthracenecarboxylic acid was investigated using the BL28B2 beamline. The random tilting and twisting intramolecular motions are shown to be directly linked to the movement of individual protein molecules in the buffer solution.
General implementation of the resolution-of-the-identity and Cholesky representations of electron repulsion integrals within coupled-cluster and equation-of-motion methods: Theory and benchmarks
Authors: Epifanovsky Evgeny , Zuev Dmitry , Feng Xintian , Khistyaev Kirill , Shao Yihan , Krylov Anna I.
Published: October 2013

We present a general implementation of the resolution-of-the-identity (RI) and Cholesky decomposition (CD) representations of electron repulsion integrals within the coupled-cluster with single and double substitutions (CCSD) and equation-of-motion (EOM) family of methods. The CCSD and EOM-CCSD equations are rewritten to eliminate the storage of the largest four-index intermediates leading to a significant reduction in disk storage requirements, reduced I/O penalties, and, as a result, improved parallel performance. In CCSD, the number of rate-determining contractions is also reduced; however, in EOM the number of operations is increased because the transformed integrals, which are computed once in the canonical implementation, need to be reassembled at each Davidson iteration. Nevertheless, for large jobs the effect of the increased number of rate-determining contractions is surpassed by the significantly reduced memory and disk usage leading to a considerable speed-up. Overall, for medium-size examples, RI/CD CCSD calculations are approximately 40% faster compared with the canonical implementation, whereas timings of EOM calculations are reduced by a factor of two. More significant speed-ups are obtained in larger bases, i.e., more than a two-fold speed-up for CCSD and almost five-fold speed-up for EOM-EE-CCSD in cc-pVTZ. Even more considerable speedups (6-7-fold) are achieved by combining RI/CD with the frozen natural orbitals approach. The numeric accuracy of RI/CD approaches is benchmarked with an emphasis on energy differences. Errors in EOM excitation, ionization, and electron-attachment energies are less than 0.001 eV with typical RI bases and with a 10−4 threshold in CD. Errors with 10−2 and 10−3 thresholds, which afford more significant computational savings, are less than 0.04 and 0.008 eV, respectively.
Simulation study of type-II Ge/Si quantum dot for solar cell applications
Authors: Hu Weiguo , Maksudur Rahman Mohammad , Lee Ming-Yi , Li Yiming , Samukawa Seiji
Published: September 2013

The electronic structure, miniband formation conditions, and required process parameters of type-II Ge/Si quantum dots are calculated using a 3D finite element method. We further estimate the device conversion efficiency and optimize the appropriate operation conditions. By using the crystalline silicon as the matrix, the explored intermediate band solar cell (IBSC) may not be suitable for 1 sun application, but it is a great value under concentration application. By considering an appropriate H-passivation treatment on amorphous silicon, the type II Ge/Si IBSC can achieve 44.0% conversion efficiency under 1 sun application.
Broadband dynamics in neat 4-methyl-3-heptanol and in mixtures with 2-ethyl-1-hexanol
Authors: Bauer S. , Wittkamp H. , Schildmann S. , Frey M. , Hiller W. , Hecksher T. , Olsen N. B. , Gainaru C. , Böhmer R.
Published: October 2013

The relatively small dielectric Debye-like process of the monohydroxy alcohol 4-methyl-3-heptanol (4M3H) was found to depend slightly on the intramolecular conformation. Proton and deuteron nuclear magnetic resonance demonstrate that the hydroxyl dynamics and the overall molecular dynamics take place on similar time scales in contrast to the situation for the structural isomer 2-ethyl-1-hexanol (2E1H) [S. Schildmann et al., J. Chem. Phys. 135, 174511 (2011)]. This indicates a very weak decoupling of Debye-like and structural relaxation which was further probed using volume expansivity experiments. Shear viscosity as well as diffusometry measurements were performed and the data were analyzed in terms of the Debye-Stokes-Einstein equations. In mixtures of 4M3H with 2E1H the Debye-like process becomes much stronger and for 2E1H mole fraction of more than 25% the behavior of this alcohol is rapidly approached. This finding is interpreted to indicate that the ring-like supramolecular structures in 4M3H become energetically unfavorable when adding 2E1H, an alcohol that tends to form chain-like molecular aggregates. The concentration dependence of the Kirkwood factor in these mixtures displays a high degree of similarity with experimental results on monohydroxy alcohols in which the pressure or the location of the OH group within the molecular structure is varied.
Conservation laws and conversion efficiency in ultraintense laser-overdense plasma interactions
Authors: Levy M. C. , Wilks S. C. , Tabak M. , Baring M. G.
Published: October 2013

Particle coupling to the oscillatory and steady-state nonlinear force of an ultraintense laser is studied through analytic modeling and particle-in-cell simulations. The complex interplay between these absorption mechanisms—corresponding, respectively, to “hot” electrons and “hole punching” ions—is central to the viability of many ultraintense laser applications. Yet, analytic work to date has focused only on limiting cases of this key problem. In this paper, we develop a fully relativistic model in 1-D treating both modes of ponderomotive light absorption on equitable theoretical footing for the first time. Using this framework, analytic expressions for the conversion efficiencies into hole punching ions and into hot electrons are derived. Solutions for the relativistically correct hole punching velocity and the hot electron Lorentz factor are also calculated. Excellent agreement between analytic predictions and particle-in-cell simulations is demonstrated, and astrophysical analogies are highlighted.
Branching points in the low-temperature dipolar hard sphere fluid
Authors: Rovigatti Lorenzo , Kantorovich Sofia , Ivanov Alexey O. , Tavares José Maria , Sciortino Francesco
Published: October 2013

In this contribution, we investigate the low-temperature, low-density behaviour of dipolar hard-sphere (DHS) particles, i.e., hard spheres with dipoles embedded in their centre. We aim at describing the DHS fluid in terms of a network of chains and rings (the fundamental clusters) held together by branching points (defects) of different nature. We first introduce a systematic way of classifying inter-cluster connections according to their topology, and then employ this classification to analyse the geometric and thermodynamic properties of each class of defects, as extracted from state-of-the-art equilibrium Monte Carlo simulations. By computing the average density and energetic cost of each defect class, we find that the relevant contribution to inter-cluster interactions is indeed provided by (rare) three-way junctions and by four-way junctions arising from parallel or anti-parallel locally linear aggregates. All other (numerous) defects are either intra-cluster or associated to low cluster-cluster interaction energies, suggesting that these defects do not play a significant part in the thermodynamic description of the self-assembly processes of dipolar hard spheres.
Application of maximum likelihood methods to laser Thomson scattering measurements of low density plasmas
Authors: Washeleski Robert L. , Meyer Edmond J. , King Lyon B.
Published: October 2013

Laser Thomson scattering (LTS) is an established plasma diagnostic technique that has seen recent application to low density plasmas. It is difficult to perform LTS measurements when the scattered signal is weak as a result of low electron number density, poor optical access to the plasma, or both. Photon counting methods are often implemented in order to perform measurements in these low signal conditions. However, photon counting measurements performed with photo-multiplier tubes are time consuming and multi-photon arrivals are incorrectly recorded. In order to overcome these shortcomings a new data analysis method based on maximum likelihood estimation was developed. The key feature of this new data processing method is the inclusion of non-arrival events in determining the scattered Thomson signal. Maximum likelihood estimation and its application to Thomson scattering at low signal levels is presented and application of the new processing method to LTS measurements performed in the plume of a 2-kW Hall-effect thruster is discussed.
Experimental study of drop spreading on textured superhydrophilic surfaces
Authors: Kim Seong Jin , Kim Jungchul , Moon Myoung-Woon , Lee Kwang-Ryeol , Kim Ho-Young
Published: September 2013

The spreading dynamics of a drop deposited on a superhydrophilic micropillar array are qualitatively different from those on a smooth surface in that a thin fringe layer rapidly wicks into microstructures while the bulk collapses in the center. Here we experimentally measure the temporal evolution of the shapes of water and silicone oil drops on the superhydrophilic surfaces, and find various power laws that describe the spreading dynamics. The bulk radius increases initially but shrinks in the late stages for drainage of its volume by wicking. The fringe film tends to grow diffusively for the entire timespan of spreading with the effective diffusivity being a function of surface tension, pillar height, viscosity, and surface roughness. The entire footprint is shown to grow like t1/4, t being time, for the entire time range, which allows us to estimate the time for complete drop spreading.
Electrical and magnetic properties of hot-deformed Nd-Fe-B magnets with different DyF3 additions
Authors: Sawatzki Simon , Dirba Imants , Schultz Ludwig , Gutfleisch Oliver
Published: October 2013

The effect of deformation and DyF3 additions on the electrical resistivity and the magnetic performance has been studied in hot-deformed Nd-Fe-B melt-spun ribbons and correlated with respective microstructures. Despite the nanocrystallinity of hot-compacted magnets, the specific electrical resistivity measured by four-point-method was shown to be comparable with that of sintered magnets. Die-upsetting reduces electrical resistivity within the magnetically hard plane because of an enhanced shape anisotropy of the grains. The addition of DyF3 overcompensates this reduction due to the presence of electrically insulating Dy-F rich inclusions and thus reduces eddy current losses within the magnet. Magnetic measurements reveal an increase in coercivity without a change in remanence for die-upset magnets with a total height reduction of 63% and 1.2 wt. % Dy (1.6 wt. %DyF3). Both properties, remanence and coercivity, demonstrate an effective reduction in heavy rare earth Dy for Nd-Fe-B magnets.
On the large interelectronic distance behavior of the correlation factor for explicitly correlated wave functions
Authors: Lesiuk Michał , Jeziorski Bogumił , Moszynski Robert
Published: October 2013

In currently most popular explicitly correlated electronic structure theories, the dependence of the wave function on the interelectronic distance rij is built via the correlation factor f (rij). While the short-distance behavior of this factor is well understood, little is known about the form of f (rij) at large rij. In this work, we investigate the optimal form of f (r12) on the example of the helium atom and helium-like ions and several well-motivated models of the wave function. Using the Rayleigh-Ritz variational principle, we derive a differential equation for f (r12) and solve it using numerical propagation or analytic asymptotic expansion techniques. We found that for every model under consideration, f (r12) behaves at large rij as \documentclass[12pt]{minimal}\begin{document}$r_{12}^\rho \,e^{B r_{12}}$\end{document}r12ρeBr12 and obtained simple analytic expressions for the system dependent values of ρ and B. For the ground state of the helium-like ions, the value of B is positive, so that f (r12) diverges as r12 tends to infinity. The numerical propagation confirms this result. When the Hartree-Fock orbitals, multiplied by the correlation factor, are expanded in terms of Slater functions rne−βr, n = 0,…,N, the numerical propagation reveals a minimum in f (r12) with depth increasing with N. For the lowest triplet state, B is negative. Employing our analytical findings, we propose a new “range-separated” form of the correlation factor with the short- and long-range r12 regimes approximated by appropriate asymptotic formulas connected by a switching function. Exemplary calculations show that this new form of f (r12) performs somewhat better than the correlation factors used thus far in the standard R12 or F12 theories.
Internal stress induced texture in Ni-Mn-Ga based glass-covered microwires
Authors: Rodionova V. , Ilyn M. , Granovsky A. , Perov N. , Zhukova V. , Abrosimova G. , Aronin A. , Kiselev A. , Zhukov A.
Published: September 2013

We have studied magnetic and structural properties of the composite microwires consisted of the metallic core and the outer glass shell. Nominal chemical composition of the core was Ni49.5Mn25.4Ga25.1, its diameter was 13.2 μm, and the total diameter of the glass-covered microwires was 26.4 μm. We have found out that at room temperature the core of the as-cast microwires was composed by two phases with tetragonal I4/mmm and cubic Fm3m crystal structures, but annealing rendered it single phase. Measurements of the magnetic properties have demonstrated substantial growth of the magnetic anisotropy with cooling, which we have attributed to the phase transition from the room-temperature austenitic to the low-temperature martensitic state. Magnetic easy axis was found to be perpendicular to the axis of the microwires at low temperatures. We believe that it is a result of the crystallographic texture induced in the martensite by high internal stress characteristic of the glass-covered magnetic microwires. Though rearrangement of the martensitic microstructure under external pressure was previously observed in the single crystal Ni2MnGa samples, in composite materials this effect is new and can be potentially useful for the applications.
Ion heating dynamics in solid buried layer targets irradiated by ultra-short intense laser pulses
Authors: Huang L. G. , Bussmann M. , Kluge T. , Lei A. L. , Yu W. , Cowan T. E.
Published: September 2013

We investigate bulk ion heating in solid buried layer targets irradiated by ultra-short laser pulses of relativistic intensities using particle-in-cell simulations. Our study focuses on a CD2-Al-CD2 sandwich target geometry. We find enhanced deuteron ion heating in a layer compressed by the expanding aluminium layer. A pressure gradient created at the Al-CD2 interface pushes this layer of deuteron ions towards the outer regions of the target. During its passage through the target, deuteron ions are constantly injected into this layer. Our simulations suggest that the directed collective outward motion of the layer is converted into thermal motion inside the layer, leading to deuteron temperatures higher than those found in the rest of the target. This enhanced heating can already be observed at laser pulse durations as low as 100 fs. Thus, detailed experimental surveys at repetition rates of several ten laser shots per minute are in reach at current high-power laser systems, which would allow for probing and optimizing the heating dynamics.
A direct density modulation cathode in magnetron
Authors: Li Wei , Zhang Jun , Liu Yong-gui , Yang Han-wu , Shu Ting
Published: September 2013

A direct Density Modulation Cathode (DMC) in magnetron is proposed in this paper. By removing the velocity modulation process, electron spokes corresponding to the dominant operating mode can be quickly formed when the DMC is used. Based on theoretical analysis, particle-in-cell simulations and experimental investigations are carried out for demonstration. The final results show that compared with conventional solid cathode and transparent cathode, the DMC can increase 68% and even 146% of relative microwave widths, respectively.
New solvable discrete-time many-body problem featuring several arbitrary parameters. II
Authors: Calogero F. , Leyvraz F.
Published: October 2013

A new solvable discrete-time many-body problem is identified. It extends a model treated in a previous paper by introducing in its equations of motion an additional free parameter. Hence, it features 6 parameters, 2 of which can be eliminated (say, replaced by unity) by appropriate rescalings. Assignments of these parameters are identified which entail that the many-body model is asymptotically isochronous, namely, that its generic solution—when the discrete-time variable ℓ diverges, ℓ → ∞—becomes completely periodic up to exponentially vanishing corrections, with a fixed period independent of the initial data.
Evidence for multifilamentary valence changes in resistive switching SrTiO3 devices detected by transmission X-ray microscopy
Authors: Koehl A. , Wasmund H. , Herpers A. , Guttmann P. , Werner S. , Henzler K. , Du H. , Mayer J. , Waser R. , Dittmann R.
Published: October 2013

Transmission X-ray microscopy is employed to detect nanoscale valence changes in resistive switching SrTiO3 thin film devices. By recording Ti L-edge spectra of samples in different resistive states, we could show that some spots with slightly distorted structure and a small reduction to Ti3+ are already present in the virgin films. In the ON-state, these spots are further reduced to Ti3+ to different degrees while the remaining film persists in the Ti4+ configuration. These observations are consistent with a self-accelerating reduction within pre-reduced extended growth defects.
Validation of transport models using additive flux minimization technique
Authors: Pankin A. Y. , Kruger S. E. , Groebner R. J. , Hakim A. , Kritz A. H. , Rafiq T.
Published: October 2013

A new additive flux minimization technique is proposed for carrying out the verification and validation (V&V) of anomalous transport models. In this approach, the plasma profiles are computed in time dependent predictive simulations in which an additional effective diffusivity is varied. The goal is to obtain an optimal match between the computed and experimental profile. This new technique has several advantages over traditional V&V methods for transport models in tokamaks and takes advantage of uncertainty quantification methods developed by the applied math community. As a demonstration of its efficiency, the technique is applied to the hypothesis that the paleoclassical density transport dominates in the plasma edge region in DIII-D tokamak discharges. A simplified version of the paleoclassical model that utilizes the Spitzer resistivity for the parallel neoclassical resistivity and neglects the trapped particle effects is tested in this paper. It is shown that a contribution to density transport, in addition to the paleoclassical density transport, is needed in order to describe the experimental profiles. It is found that more additional diffusivity is needed at the top of the H-mode pedestal, and almost no additional diffusivity is needed at the pedestal bottom. The implementation of this V&V technique uses the FACETS::Core transport solver and the DAKOTA toolkit for design optimization and uncertainty quantification. The FACETS::Core solver is used for advancing the plasma density profiles. The DAKOTA toolkit is used for the optimization of plasma profiles and the computation of the additional diffusivity that is required for the predicted density profile to match the experimental profile.
Towards artifact-free atomic-resolution elemental mapping with electron energy-loss spectroscopy
Authors: Zhu Y. , Soukiassian A. , Schlom D. G. , Muller D. A. , Dwyer C.
Published: October 2013

Atomic-resolution elemental maps of materials obtained using energy-loss spectroscopy in the scanning transmission electron microscope (STEM) can contain artifacts associated with strong elastic scattering of the STEM probe. We demonstrate how recent advances in instrumentation enable a simple and robust approach to reduce such artifacts and produce atomic-resolution elemental maps amenable to direct visual interpretation. The concept is demonstrated experimentally for a (BaTiO3)8/(SrTiO3)4 heterostructure, and simulations are used for quantitative analysis. We also demonstrate that the approach can be used to eliminate the atomic-resolution elastic contrast in maps obtained from lower-energy excitations, such as plasmon excitations.
Bifurcation analysis and dimension reduction of a predator-prey model for the L-H transition
Authors: Dam Magnus , Brøns Morten , Juul Rasmussen Jens , Naulin Volker , Xu Guosheng
Published: October 2013

The L-H transition denotes a shift to an improved confinement state of a toroidal plasma in a fusion reactor. A model of the L-H transition is required to simulate the time dependence of tokamak discharges that include the L-H transition. A 3-ODE predator-prey type model of the L-H transition is investigated with bifurcation theory of dynamical systems. The analysis shows that the model contains three types of transitions: an oscillating transition, a sharp transition with hysteresis, and a smooth transition. The model is recognized as a slow-fast system. A reduced 2-ODE model consisting of the full model restricted to the flow on the critical manifold is found to contain all the same dynamics as the full model. This means that all the dynamics in the system is essentially 2-dimensional, and a minimal model of the L-H transition could be a 2-ODE model.