bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulmonary Tuberculosis and Disease-Related Pulmonary Apical Fibrosis in Ankylosing Spondylitis
Authors: HO HUEI-HUANG , LIN MENG-CHIH , YU KUANG-HUI , WANG CHIN-MAN , WU YEONG-JIAN JAN , CHEN JI-YIH
Published: May 2009

Objective.

We investigated the etiological association and clinical characteristics of apical pulmonary fibrosis in ankylosing spondylitis (AS).

Methods.

We reviewed medical records of 2136 consecutive patients diagnosed with AS at a tertiary medical center. Clinical and radiographic characteristics were analyzed for evidence of apical lung fibrosis on chest radiographs.

Results.

Of 2136 patients with AS, 63 (2.9%) developed apical lung fibrosis, of which chronic infections were the cause in 41 and AS inflammation predisposed the fibrosis in 22 patients. Tuberculosis (TB) infection was considered to be the cause of apical lung fibrosis in 40 patients (63.5%) including 19 with bacteriologically-proven TB and 21 with chest radiographs suggestive of TB. Two were identified as having non-TB mycobacterial infection and one asAspergillusinfection. Lung cavity lesion appeared to be a crucial differentiator (p = 0.009, odds ratio 7.4, 95% CI 1.5–36.0) between TB infection and AS inflammation-induced apical fibrosis.

Conclusion.

Our study suggests that TB, instead ofAspergillus, is the most common pulmonary infection in patients with AS presenting with apical lung fibrosis. AS-associated apical lung fibrosis may mimic pulmonary TB infection. Thus, bacteriological survey and serial radiological followup of lung fibrocavitary lesions are critical for accurate diagnosis and treatment.
The Observation of the C–H···O Hydrogen Bond in Trisialic Acid Lactone and Its Implications for Cooperative Lactonization
Authors: Chen Chien‐Sheng , Yu Yi‐Ping , Lin Bo‐Chao , Gervay‐Hague Jacquelyn , Fang Jim‐Min , Hsu Chao‐Ping , Wu Shih‐Hsiung
Published: May 2009

The C–H···O hydrogen bond in trisialic acid lactones has been examined by using long‐range COSY (LRCOSY) and ab initio calculations. From an analysis of the LRCOSY spectra, 3J correlations of BH9ax/AH8 and CH9ax/BH8 confirmed the existence of hydrogen‐bond connections of x+1C9–x+1H9ax···xO8. The theoretical bond energy of the hydrogen bond was estimated to be 1.0 or 1.6 kcal/mol by using two models. The acid‐catalyzed cooperative lactonization of oligosialic acids can be understood in terms of the additional C–H···O stabilization in the lactone product. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Cultivating the Passion to Build Heterocycles from 1,2‐Diaza‐1,3‐dienes: the Force of Imagination
Authors: Attanasi Orazio A. , De Crescentini Lucia , Favi Gianfranco , Filippone Paolino , Mantellini Fabio , Perrulli Francesca R. , Santeusanio Stefania
Published: May 2009

The present microreview summarizes our progresses over the last years in the chemistry of 1,2‐diaza‐1,3‐dienes. Beyond the findings reported here, the main target of this microreview is to outline some of the reactive peculiarities that make this class of compounds powerful tools in heterocyclic chemistry. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Synthesis of Calystegine A3 from Glucose by the Use of Ring‐Closing Metathesis
Authors: Monrad Rune Nygaard , Pipper Charlotte Bressen , Madsen Robert
Published: May 2009

A synthesis of the nortropane alkaloid calystegine A3 is described from D‐glucose. The key step employs a zinc‐mediated tandem reaction where a benzyl‐protected methyl 6‐iodo glucoside is fragmented to give an unsaturated aldehyde, which is then transformed into the corresponding benzylimine and allylated in the same pot. The functionalized nona‐1,8‐diene, thus obtained, is converted into the seven‐membered carbon skeleton in calystegine A3 by ring‐closing olefin metathesis. Subsequent deoxygenation by the Barton–McCombie protocol, hydroboration and oxidative workup followed by hydrogenolysis affords calystegine A3. The synthesis uses a total of 13 steps from glucose and confirms the absolute configuration of the natural product.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Lipase‐Catalyzed Regioselective One‐Step Synthesis of Penta‐O‐acetyl‐3‐hydroxylactal
Authors: Filice Marco , Vanna Renzo , Terreni Marco , Guisan Jose M. , Palomo Jose M.
Published: May 2009

A highly efficient regioselective enzymatic preparation ofpenta‐O‐acetyl‐1,5‐anhydro‐2‐deoxy‐3‐hydroxy‐4‐O‐β‐galactopyranosyl‐D‐arabinohex‐1‐enitol has been successfully performed for the first time. This product was obtained in >99 % conversion (>95 % overall yield) by hydrolysis of per‐O‐acetylated lactal catalyzed by the lipase from Rhizomucor miehei immobilized on octylagarose. This molecule could be a potential building block for efficient synthesis of oligosaccharides or glycoconjugates.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Influence of reaction mechanisms, grid spacing, and inflow conditions on the numerical simulation of lifted supersonic flames
Authors: Gerlinger P. , Nold K. , Aigner M.
Published: May 2009

The simulation of supersonic combustion requires finite‐rate chemistry because chemical and fluid mechanical time scales may be of the same order of magnitude. The size of the chosen reaction mechanism (number of species and reactions involved) has a strong influence on the computational time and thus should be chosen carefully. This paper investigates several hydrogen/air reaction mechanisms frequently used in supersonic combustion. It is shown that at low flight Mach numbers of a supersonic combustion ramjet (scramjet), some kinetic schemes can cause highly erroneous results. Moreover, extremely fine computational grids are required in the lift‐off region of supersonic flames to obtain grid‐independent solutions. The fully turbulent Mach 2 combustion experiment of Cheng et al. (Comb. Flame 1994; 99: 157–173) is chosen to investigate the influences of different reaction mechanisms, grid spacing, and inflow conditions (contaminations caused by precombustion). A detailed analysis of the experiment will be given and errors of previous simulations are identified. Thus, the paper provides important information for an accurate simulation of the Cheng et al. experiment. The importance of this experiment results from the fact that it is the only supersonic combustion test case where temperature and species fluctuations have been measured simultaneously. Such data are needed for the validation of probability density function methods. Copyright © 2009 John Wiley & Sons, Ltd.
13C‐NMR spectra of santalol derivatives: a comparison of DFT‐based calculations and database‐oriented prediction techniques
Authors: Stappen Iris , Buchbauer Gerhard , Robien Wolfgang , Wolschann Peter
Published: May 2009

A systematic investigation of a series of santalol and epi‐santalol derivatives by means of ab initio and density functional theory (DFT) calculations together with database‐oriented prediction methods leads to a configurational reassignment within this compound class. The DFT calculations as well as the HOSE‐code and neural network‐based predictions allow deriving a general rule set for unambiguous assignment within this compound class. The methyl group in position 2′ serves as an indication for the configuration at this stereocenter allowing easy differentiation between santalol derivatives and their diastereomers belonging to the epi‐santalol series. Copyright © 2009 John Wiley & Sons, Ltd.
1H, 13C and 15N NMR spectral assignments for new triazapentalene derivatives
Authors: Palmas Pascal , Nyffenegger Coralie , Pasquinet Eric , Guillaumet Gérald
Published: May 2009

Mesomeric heteropentalene betaines are conjugated fused polyheterocyclic structures that represent interesting intermediates for organic synthesis. Five such structures, containing at least four nitrogen atoms and various substituents, have been characterized by 1H, 13C and 15N NMR. We report, apparently for the first time, nitrogen NMR data and coupling information on such systems. Inter‐ring long‐range correlations across five bonds with 15N (5JHN) and up to seven bonds with 13C (6JHC and 7JHC) were observed in HSQC experiments. The incorporation of an electron‐withdrawing substituent such as NO2 was observed to cause an increase in the magnitude of the remote couplings and deshielding of nearby protons, carbons and on all nitrogen atoms of the structure, including remote ones situated on other cycles. Copyright © 2009 John Wiley & Sons, Ltd.
Fabrication of poly(ethylene glycol)‐based hydrogels entrapping enzyme‐immobilized silica nanoparticles
Authors: Jang Eunji , Park Saemi , Park Sangphil , Lee Yeol , Kim Dae‐Nyun , Kim Bumsang , Koh Won‐Gun
Published: May 2009

In this study, we immobilized enzymes by combining covalent surface immobilization and hydrogel entrapment. A model enzyme, glucose oxidase (GOX), was first covalently immobilized on the surface of silica nanoparticles (SNPs) via 3‐aminopropyltriethoxysilane (APTES), and the resultant SNP‐immobilized enzyme was physically entrapped within photopolymerized hydrogels prepared from two different molecular weights (MWs) (575 and 8000 Da) of poly(ethylene glycol)(PEG). The hydrogel entrapment resulted in a decrease in reaction rate and an increase in apparent Km of SNP‐immobilized GOX, but these negative effects could be minimized by using hydrogel with a higher MW PEG, which provides higher water content and larger mesh size. The catalytic rate of the PEG 8000 hydrogel was about ten times faster than that of the PEG 575 hydrogel because of enhanced mass transfer. Long‐term stability test demonstrated that SNP‐immobilized GOX entrapped within hydrogel maintained more than 60% of its initial activity after a week, whereas non‐entrapped SNP‐immobilized GOX and entrapped GOX without SNP immobilization maintained less than 20% of their initial activity. Incorporation of SNPs into hydrogel enhanced the mechanical strength of the hydrogel six‐fold relative to bare hydrogels. Finally, a hydrogel microarray entrapping SNP‐immobilized GOX was fabricated using photolithography and successfully used for quantitative glucose detection. Copyright © 2009 John Wiley & Sons, Ltd.
Empirical vs natural weighting in random effects meta‐analysis
Authors: Shuster Jonathan J.
Published: May 2009

This article brings into serious question the validity of empirically based weighting in random effects meta‐analysis. These methods treat sample sizes as non‐random, whereas they need to be part of the random effects analysis. It will be demonstrated that empirical weighting risks substantial bias. Two alternate methods are proposed. The first estimates the arithmetic mean of the population of study effect sizes per the classical model for random effects meta‐analysis. We show that anything other than an unweighted mean of study effect sizes will risk serious bias for this targeted parameter. The second method estimates a patient level effect size, something quite different from the first. To prevent inconsistent estimation for this population parameter, the study effect sizes must be weighted in proportion to their total sample sizes for the trial. The two approaches will be presented for a meta‐analysis of a nasal decongestant, while at the same time will produce counter‐intuitive results for the DerSimonian–Laird approach, the most popular empirically based weighted method. It is concluded that all past publications based on empirically weighted random effects meta‐analysis should be revisited to see if the qualitative conclusions hold up under the methods proposed herein. It is also recommended that empirically based weighted random effects meta‐analysis not be used in the future, unless strong cautions about the assumptions underlying these analyses are stated, and at a minimum, some form of secondary analysis based on the principles set forth in this article be provided to supplement the primary analysis. Copyright © 2009 John Wiley & Sons, Ltd.
Reaction Pathways in the Formation of Intermetallic InPd3 Polymorphs
Authors: Kohlmann Holger , Ritter Clemens
Published: May 2009

The atomic order in InPd3 was determined by neutron powder diffraction on a series of samples synthesized under various conditions. While annealing at temperature T ≥ 800 K yields a fourfold superstructure of a cubic closest packing (ccp) of the ZrAl3 type (space group I4/mmm (No. 139), a = 406.196(5) pm, c = 1520.31(2) pm, Z = 4), short reaction times at T ≤ 750 K produce InPd3 in a twofold ccp superstructure of the TiAl3 type (space group I4/mmm (No. 139), a = 409.96(2) pm, c = 747.59(5) pm, Z = 2). Crystallographic group‐subgroup relationships in terms of a Bärnighausen symmetry tree for a series of ccp superstructures reveal the simple formula n = 2m·3p for the domain size n, indicating the number of like layers in the stacking sequence An Bn, where m and p are the number of e2 and e3 transitions within the space group types P4/mmm and I4/mmm, respectively. From the factors governing the appearance and structural details of ccp superstructures atomic size seems to play a major role in determining the c/a ratio in MPd3 compounds with M being a main group metal. Thermal analysis, X‐ray and neutron powder diffraction suggest that the formation of InPd3 by an iodine catalyzed reaction starting from the elements procedes by the pathway: In + 3 Pd → 2 (In0.5Pd0.5)Pd [AuCu type] → InPd3 [TiAl3 type] → InPd3 [ZrAl3 type].
The Utility of Genetic Counseling Prior to Offering First Trimester Screening Options
Authors: Hafen L. Brent , Hulinsky Rebecca S. , Ellis Simonsen Sara , Wilder Stephanie , Rose Nancy C.
Published: May 2009

In order to evaluate the utility of genetic counseling at the time of first trimester screening in patients with no previously identified genetic concerns, we reviewed family history data for 700 women seen for genetic counseling in Utah during 2005‐2006. The mean maternal age was 35 years (Range: 16–47 years). The majority of patients seen were non‐Jewish Caucasians (90.8%, 634/700). A three‐generation pedigree was obtained from each woman by one of two certified genetic counselors and subsequently classified as “negative” (no birth defects/genetic disorders); “positive” (birth defect or genetic condition with a minimal/low risk of recurrence; additional evaluation/genetic testing during pregnancy not indicated); or “significant” (birth defect or genetic condition with an increased risk of recurrence; additional evaluation/genetic testing during the pregnancy indicated). About 72% (501/700) of the histories were negative, 19% (134/700) were positive, and about 9% (65/700) were significant. Among patients with significant family histories, 66% (n = 43) were women less than 35 years of age. We conclude that assessing a patient's family history at the time of first trimester serum screening is a valuable resource for pregnancy management.
Comparison of articaine and lidocaine for infiltration anaesthesia in patients undergoing bone marrow aspiration and biopsy
Authors: Kuivalainen Anna‐Maria , Niemi‐Murola Leila , Widenius Tom , Elonen Erkki , Rosenberg Per H.
Published: May 2009

Infiltration anaesthesia with articaine, a local anaesthetic able to penetrate bone, may relieve procedural pain better than lidocaine in bone marrow aspiration and biopsy. This randomised, double‐blind study comprised 150 patients with suspected or known haematologic disease. Either articaine 20 mg/ml (50 patients), articaine 40 mg/ml (49 patients) or lidocaine 20 mg/ml (51 patients), all with adrenaline 5 μg/ml, was infiltrated in volume of 6 ml (sternal manubrium), 8 ml (sternal body) or 10 ml (iliac crest) 2 min before puncture. Numeral rating scale score (median, range) at injection of local anaesthetic was 3.0 (0–10), at bone puncture 2.0 (0–8), at aspiration 3.5 (0–10) and at biopsy (48 patients) 3.0 (0–10). Pre‐procedural anxiety, rated on a verbal scale, correlated significantly with experienced pain (P < 0.01). Very anxious patients had fewer previous bone marrow examinations (P < 0.01) and they experienced more pain during aspiration (P < 0.05). In the post‐interview 42 patients reported appearance of pain (median 2.0, range 1–7) after 6.2 h, on average, and 15 patients needed oral analgesics. No parameter differed significantly between the groups.

In conclusion, the quality of infiltration anaesthesia for bone marrow punctures and aspiration with articaine and lidocaine was similarly poor. Several patients experienced strong pain which correlated with the degree of anxiety.
Phase equilibria testing of a multiple pulse mechanism for origin of mafic–ultramafic intrusions: a case example of the Shiant Isles Main Sill, NW Scotland
Authors: LATYPOV RAIS , CHISTYAKOVA SOFYA
Published: May 2009

In this paper we examine the role of multiple emplacement of sills into partly solidified rocks (an intrusive mechanism ‘liquid into solid’) as a possible explanation for some textural and compositional ‘anomalies’ of single-cyclic mafic intrusions. As a case study we used the Shiant Isles Main Sill that is widely regarded as a classical example of a multiple, picrite–picrodolerite–crinanite alkaline sill. This sill is currently interpreted as having been formed by several olivine phenocryst-rich pulses of magma, which were successively emplaced into their almost solidified predecessors. Such an intrusive mechanism is a random process in which many parameters vary independently and unpredictably. Among them are: the number, relative volume and bulk composition of magma pulses, and their place, sequence and timing of emplacement, as well as modal abundance, phase composition and distribution of intratelluric phenocrysts in magmas upon emplacement. In terms of these variables, one can envisage countless different profiles through alkaline sills produced from only three randomly intruded magma pulses of picritic, picrodoleritic and crinanitic composition. Such multiple sills can readily be distinguished from simple ones formed from a single pulse of magma by anomalous compositional profiles with several prominent breaks in crystallization and compositional sequences. The compositional profile of the Shiant Isles Main Sill is remarkably similar to an M-shaped profile expected from fractional crystallization of a single pulse of olivine-saturated magma along a crystallization path Ol+Sp+L (picrite), Ol+Pl±Sp+L (picrodolerite = troctolite), Ol+Pl+Cpx+L (crinanite). The probability of the accidental formation of such a compositional profile by multiple intrusion ‘liquid into solid’ is exceedingly small, even for the single case of the Shiant Isles Main Sill. The probability approaches zero when considering that exactly the same sequence of intrusive events must have been repeated in about 20 neighbouring alkaline sills with similar compositional profiles. This can only be achieved by some universally operating differentiation process. The best candidate for this is the classical fractional crystallization of magma constrained by liquidus phase equilibria. This suggests that the Shiant Isles Main Sill can be best interpreted and modelled as a simple sill that crystallized from one large pulse of magma, with possible involvement of minor refilling events. Further progress in our knowledge of intrachamber magma fractionation processes will probably enable us to interpret many ‘anomalous’ textural and compositional features of mafic–ultramafic intrusions in the frame of a single magma pulse model.
Cancer in the older person
Authors: Stephens Peter
Published: May 2009

The challenges of treating malignant disease in the older population are gaining greater prominence. In the last 10 years the European Organisation for Research and Treatment of Cancer (EORTC) has established a task force to examine challenges of managing older cancer patients. As an indication of their importance, the American Society of Clinical Oncology (ASCO) specifically addressed the issues raised by older patients at their annual conference in 2004.
Regional TEC mapping using neural networks
Authors: Yilmaz A. , Akdogan K. E. , Gurun M.
Published: May 2009

Characterization and modeling of ionospheric variability in space and time is very important for communications and navigation. To characterize the variations, the ionosphere should be monitored, and the sparsity of the measurements has to be compensated by interpolation algorithms. The total electron content (TEC) is a major parameter that can be used to obtain regional ionospheric maps. In this study, neural networks (NNs), specifically multilayer perceptrons (MLPs) and radial basis function networks (RBFN), are investigated for the merits of their nonlinear modeling capability. In order to assess the performance of MLP and RBFN structures with respect to mapping and ionospheric parameters, these algorithms are applied to synthetically generated TEC surfaces representing various ionospheric states. Synthetic TEC data are sampled homogenously and randomly for a varying number of data points. The reconstruction errors show that the performance improves significantly when homogenous sampling is preferred to random station distribution. The best MLP and RBFN structures for any possible realistic scenario are determined by examining the performance parameters for all possible cases. It is also observed that RBFN with local receptive fields relies more on the number of training data points. In contrast to RBFN, MLP as a global approximator depends strongly on ionospheric trends. Finally, chosen MLP and RBFN models are applied to a set of real GPS‐TEC values obtained from central Europe, and their performances are compared with well known Global Ionospheric Maps produced by the International GNSS Service. The resolution and interpolation quality of the generated maps indicate that NNs offer a powerful and reliable alternative to the conventional TEC mapping algorithms.
Local high‐slope effects on sediment transport and fluvial bed form dynamics
Authors: Francalanci Simona , Solari Luca , Toffolon Marco
Published: May 2009

We investigate the morphodynamic evolution of an arbitrarily tilted, coarse, mobile bed under the action of a free surface water flow. The analysis is based on the experimental observations of the evolution of a mobile bed from its initial, laterally tilted configuration to the final laterally flat state, due to the presence of a lateral component of bed load transport. Measurements of the bed topography at different times allow one to reconstruct the flattening process. The experimental observations are interpreted by means of a three‐dimensional numerical hydromorphodynamic model employing different relationships, linear and nonlinear, to evaluate bed load intensity and direction. The analysis shows that the inclusion of nonlinear gravitational effects in the description of the bed load leads to a more satisfactory description of the bed evolution. This finding opens important issues on how the inclusion of the nonlinear gravitational effects on the bed load can affect the morphodynamic evolution of complex bed topography occurring in natural rivers. To investigate this point, an application to the evolution of river bars is presented.
Apparent stress and corner frequency variations in the 1999 Taiwan (Chi‐Chi) sequence: Evidence for a step‐wise increase at Mw ∼ 5.5
Authors: Mayeda Kevin , Malagnini Luca
Published: May 2009

Apparent stress and corner frequencies are measured for the Chi‐Chi, Taiwan sequence beginning with the Mw 7.6 mainshock on 20 September 1999. Using the coda source ratio method, we obtained stable source ratio estimates using broadband stations on Taiwan. We find the following: (1) For the mainshock and 3 of the larger aftershocks, apparent stress is clustered around 0.8 MPa (±0.1 MPa); (2) Events below ∼Mw 5.5 exhibit lower apparent stress with larger scatter, ranging between ∼0.08 and 0.8 MPa and are spatially variable; 3) The Brune [1970a, 1970b] omega‐square source model fits the spectral shape for events 4.7 < Mw < 7.6, however a step‐wise break in self‐similarity exists at ∼Mw 5.5. We hypothesize that larger events are subject to the regional state‐of‐stress, whereas smaller aftershocks are sensitive to the local state‐of‐stress from stress‐field redistribution following the mainshock and/or fault zone lubrication that affects only larger events.
Water velocity and the nature of critical flow in large rapids on the Colorado River, Utah
Authors: Magirl Christopher S. , Gartner Jeffrey W. , Smart Graeme M. , Webb Robert H.
Published: May 2009

Rapids are an integral part of bedrock‐controlled rivers, influencing aquatic ecology, geomorphology, and recreational value. Flow measurements in rapids and high‐gradient rivers are uncommon because of technical difficulties associated with positioning and operating sufficiently robust instruments. In the current study, detailed velocity, water surface, and bathymetric data were collected within rapids on the Colorado River in eastern Utah. With the water surface survey, it was found that shoreline‐based water surface surveys may misrepresent the water surface slope along the centerline of a rapid. Flow velocities were measured with an ADCP and an electronic pitot‐static tube. Integrating multiple measurements, the ADCP returned velocity data from the entire water column, even in sections of high water velocity. The maximum mean velocity measured with the ADCP was 3.7 m/s. The pitot‐static tube, while capable of only point measurements, quantified velocity 0.39 m below the surface. The maximum mean velocity measured with the pitot tube was 5.2 m/s, with instantaneous velocities up to 6.5 m/s. Analysis of the data showed that flow was subcritical throughout all measured rapids with a maximum measured Froude number of 0.7 in the largest measured rapids. Froude numbers were highest at the entrance of a given rapid, then decreased below the first breaking waves. In the absence of detailed bathymetric and velocity data, the Froude number in the fastest‐flowing section of a rapid was estimated from near‐surface velocity and depth soundings alone.
Characterization of (Pt2 nm/Co0.4 nm)3/Ptx/IrMn7 nm multilayers by tomographic atom probe: On the role of a Pt spacer
Authors: Zarefy A. , Lardé R. , Lechevallier L. , Cuvilly F. , Le Breton J. M. , Baltz V. , Rodmacq B. , Dieny B.
Published: May 2009

Structural investigation of Ta3 nm/[(Pt2 nm/Co0.4 nm)3/Ptx/IrMn7 nm]7/Pt10 nm multilayers without (x=0 nm) and with (x=0.4 nm) a Pt spacer has been performed by laser-assisted tomographic atom probe. Without a Pt spacer a strong intermixing is observed at the Co/IrMn interface. In the multilayer containing a Pt spacer the Co/Pt/IrMn interface is very weakly intermixed. It thus appears that the Pt spacer acts as a diffusion barrier that prevents the Ir and Mn atoms from diffusing into the Co layer. The consequences of this effect on the magnetic properties are discussed. The exchange bias field and the anisotropy direction of these two multilayers are analyzed and correlated with the structural investigation.
Electron tomography using a geometric surface-tangent algorithm: Application to atom probe specimen morphology
Authors: Petersen T. C. , Ringer S. P.
Published: May 2009

To adapt electron tomography for the specific study of specimen morphology, a novel reconstruction algorithm is proposed which treats strong intensity gradients in images as arising from the projected edges of surfaces. Images portraying scattering interfaces arising from absorption, elastic, or Fresnel diffraction processes are used to identify edge maps that define the abscissa of projected surface tangents. Differential geometry is used to calculate the shape of these surfaces by considering smooth variations of measured tangent abscissa to infer local tangent intersections. The approach outlined here is not restricted to convex shapes and is designed for cases where morphology is more important than retrieval of the three-dimensional scattering density. The proposed algorithm is tested on simulated data, experimental benchmark specimens of MgO nanoparticles and is then applied to a nanosized atom probe tip, for which the approach here was specifically developed.
Formation and material analysis of plasma polymerized carbon nitride nanoparticles
Authors: Kovačević E. , Berndt J. , Stefanović I. , Becker H.-W. , Godde C. , Strunskus Th. , Winter J. , Boufendi L.
Published: May 2009

This paper deals with the analysis of nanoparticles polymerized in nitrogen/acetylene and argon/acetylene gas mixtures in low temperature rf discharges. The polymerization process was monitored by means of mass spectroscopy. The chemical characteristics of the material were obtained in situ by infrared absorption spectroscopy and ex situ by means of near edge x-ray absorption fine structure spectroscopy. These data were supported by complimentary elemental analyses such as deuteron induced gamma emission, Rutherford backscattering, and nuclear reaction analysis. Although morphology showed no differences, further material analysis shows clearly nitrogen incorporation in the nanoparticles, mostly by multiple bonds. In comparison with the nanoparticles from argon/acetylene plasma, the amount of carbon in carbon-nitride nanoparticles remains unchanged, whereas hydrogen content strongly decreases. The results of mass spectroscopy on neutrals and ions lead to the assumption that carbon-nitride nanoparticles are formed by copolymerization of two kinds of precursors: hydrocarbon and nitrogen containing hydrocarbon species.
On the capacitance-boost of ionic polymer metal composites due to electroless plating: Theory and experiments
Authors: Aureli Matteo , Lin Weiyang , Porfiri Maurizio
Published: May 2009

In this paper, we analyze the effect of electrode surface roughness on ionic polymer metal composite (IPMC) capacitance. We use the linearized Poisson–Nernst–Planck model to describe the charge and electric potential distribution in response to a small voltage applied across the IPMC electrodes. We use perturbation methods to develop a comprehensive understanding of the interplay among the scale of the electrode roughness, the Debye screening length, and the IPMC nominal dimensions on the electrical behavior of IPMCs. We derive a closed-form expression of the IPMC capacitance per unit nominal surface area in terms of the Debye screening length, the IPMC nominal thickness, and physically relevant statistical properties of the rough landscape. We find that IPMC capacitance is largely dictated by the effective electrode surface area when the Debye screening length is considerably smaller than the polymer thickness. In this case, the diffuse charge layers that form at the polymer-electrode interface closely follow the rough electrodes profile. As the Debye screening length increases, diffuse layers do not completely adhere to the electrode profile, and local curvature changes and additional geometric factors contribute to the overall IPMC capacitance. We specialize our findings to different electrode models, including fractal electrodes that have been recently observed in IPMC morphological studies. We corroborate our theoretical findings with experimental data on the capacitance of in-house fabricated IPMCs.
Degradation mechanisms of electron mobility in metal-oxide-semiconductor field-effect transistors with LaAlO3 gate dielectric
Authors: Chang Ingram Yin-ku , You Sheng-wen , Chen Main-gwo , Juan Pi-chun , Chen Chun-heng , Lee Joseph Ya-min
Published: May 2009

LaAlO 3 is a promising candidate of gate dielectric for future very large scale integration devices. In this work, metal-oxide-semiconductor capacitors and transistors with LaAlO3 gate dielectric were fabricated and the electron mobility degradation mechanisms were studied. The LaAlO3 films were deposited by radio frequency magnetron sputtering. The LaAlO3 films were examined by x-ray diffraction, secondary ion mass spectroscopy, and x-ray photoelectron spectroscopy. The temperature dependence of metal-oxide-semiconductor field-effect transistors characteristics was studied from 11 K to 400 K. The rate of threshold voltage change with temperature (ΔVT/ΔT) is −1.51 mV/K. The electron mobility limited by surface roughness is proportional to Eeff−0.66 in the electric field of 0.93 MV/cm<Eeff<2.64 MV/cm at 300 K and the phonon scattering is proportional to T−5.6 between 300 and 400 K. Soft optical phonon scattering was used to explain the extra source of phonon scattering in LaAlO3-gated n-channel metal-oxide-semiconductor field-effect transistors.
Equilibrium spin current in ferromagnetic graphene junction
Authors: Gu Y. , Yang Y. H. , Wang J. , Chan K. S.
Published: May 2009

We report a theoretical study of the equilibrium spin current (ESC) flowing in a ferromagnet/ferromagnet (FM/FM) graphene junction with noncollinear magnetizations, in which the FM correlation in graphene is induced by depositing an FM insulator on it. Using the scattering matrix method, we derived an analytical expression of the ESC which is formally the same as that of a normal FM/FM junction. The ESC comes from the exchange coupling between the two FM magnetizations. Owing to the linear dispersion of graphene, the ESC disappears in the one-dimensional case, while it exists in the two-dimensional case. It exhibits damped oscillations with change in the Fermi energy, the layer length between the two FM regions, and the FM exchange splitting. It is also found that ESC in FM/FM graphene junctions has electron-hole inversion symmetry whereas it has electron-hole inversion antisymmetry in normal FM/FM junctions.
Current and field dependent proximity effects in the Nd0.43Sr0.57MnO3/YBa2Cu3O7 heterostructure
Authors: Mani Awadhesh , Kumary T. Geetha , Hsu Daniel , Lin J. G.
Published: May 2009

Proximity effects of superconductivity and antiferromagnetism are investigated in an Nd0.43Sr0.57MnO3/YBa2Cu3O7 (NSMO/YBCO) heterostructure through the measurements of resistivity, magnetization, and magnetoresistivity. The evolution of superconducting transition temperature (Tc) and antiferromagnetic transition temperature (TN) with applied current density (J) and magnetic field (H) mark the profound influences of spin injection on destructing the superconductivity as well as the magnetic orders, which is reflected from the fact that both Tc and TN reduce significantly with increasing J.
Experimental study on electromagnetic wave transparency for coated metallic cylinders
Authors: Cai Xiaobing , Deng Qibo , Hu Gengkai
Published: May 2009

In this work, coated metallic cylinders transparent to electromagnetic waves are designed based on the neutral inclusion method; they are then verified experimentally by measuring the reflection coefficient and total scattering fields. The dynamic effective permittivity of a composite made of coated metallic cylinders is first derived by setting the effective permittivity of the composite equals to that of air; the necessary dielectric constant of the coating layer as function of the geometry of the coated cylinder is obtained. We choose the mixture of carbon nanotube (CNT) and rubber for the coating material, its dielectric constant can be tuned by adjusting the content of CNT to reach the value necessary for realizing the transparency. The reflection coefficients and the total scattering electric fields are measured for the carefully designed coated and bare copper cylinders, respectively, significant reductions of the reflection coefficient and total scattering fields are observed for the coated cylinders, which confirms the proposed design method.
Real-time in situ spectroscopic ellipsometry of GaSb nanostructures during sputtering
Authors: Nerbø I. S. , Le Roy S. , Kildemo M. , Søndergård E.
Published: May 2009

We demonstrate that real-time in situ spectroscopic ellipsometry can be used to measure the height evolution of nanostructures during low energy ion sputtering of GaSb. A graded anisotropic effective medium approximation is used to extract the height from the optical measurements. Two different growth regimes have been observed, first exponential then followed by a linear regime. The linear regime is not expected from the traditional sputtering theories. The in situ results correspond well to ex situ atomic force microscopy measurements.
Miscible viscous fingering in microgravity
Authors: Aubertin A. , Gauthier G. , Martin J. , Salin D. , Talon L.
Published: May 2009

To address the issue of miscible viscous fingering instability in buoyancy free conditions, experiments have been performed under microgravity conditions in parabolic flights. A Hele-Shaw cell, two parallel plates separated by a small gap, has been used with two miscible fluids of viscosity ratio 100 (the injected fluid is the less viscous). The influence of the initial thickness of the pseudointerface between the two fluids has been studied, using flow rates large enough to prevent further mixing during displacement. The selected wavelength, measured on the observed fingering pattern, does not depend on the initial front thickness: It is around three times the gap of the cell, i.e., significantly lower than the value of five, observed on earth. However, the initial thickness does control the displacement length required for the instability to occur. Our results are in reasonable agreement with existing and new numerical simulations.
Ab initio molecular dynamics calculations of ion hydration free energies
Authors: Leung Kevin , Rempe Susan B. , von Lilienfeld O. Anatole
Published: May 2009

We apply ab initio molecular dynamics (AIMD) methods in conjunction with the thermodynamic integration or “λ-path” technique to compute the intrinsic hydration free energies of Li+, Cl−, and Ag+ ions. Using the Perdew–Burke–Ernzerhof functional, adapting methods developed for classical force field applications, and with consistent assumptions about surface potential (ϕ) contributions, we obtain absolute AIMD hydration free energies (ΔGhyd) within a few kcal/mol, or better than 4%, of Tissandier et al.’s [J. Phys. Chem. A 102, 7787 (1998)] experimental values augmented with the SPC/E water model ϕ predictions. The sums of Li+/Cl− and Ag+/Cl− AIMD ΔGhyd, which are not affected by surface potentials, are within 2.6% and 1.2 % of experimental values, respectively. We also report the free energy changes associated with the transition metal ion redox reaction Ag++Ni+→Ag+Ni2+ in water. The predictions for this reaction suggest that existing estimates of ΔGhyd for unstable radiolysis intermediates such as Ni+ may need to be extensively revised.
Investigation of the C2H2–CO2 van der Waals complex in the overtone range using cw cavity ring-down spectroscopy
Authors: Lauzin C. , Didriche K. , Liévin J. , Herman M. , Perrin A.
Published: May 2009

A slit nozzle supersonic expansion containing acetylene [492 SCCM (SCCM denotes cubic centimeter per minute at STP)] and carbon dioxide (740 SCCM) seeded into Ar (837 SCCM) is investigated using cw-cavity ring-down spectroscopy, in the 1.5 μm range. The C2H2–CO2 van der Waals complex is observed around the ν1+ν3 acetylenic band. The rotational temperature is estimated to be close to 60 K from the comparison between observed and simulated spectra. The analysis of the main, perturbed B-type band centered near 6 549.280 cm−1, is performed. It is attributed to a dimer with the known planar, C2v geometry. The present overtone data, involving ground state levels with higher J/K states (J≤35 and Ka≤20) than previously reported, are combined to 3 μm data [D. G. Prichard, R. N. Nandi, J. S. Muenter, and B. J. Howard, J. Chem. Phys. 89, 1245 (1988); Z. S. Huang and R. E. Miller, Chem. Phys. 132, 185 (1989)] to determine improved ground state parameters. The major perturbations affecting the upper state are accounted for through C-type Coriolis resonances involving one dark state, whose symmetry must therefore be A1. Upper state constants are obtained for the bright and dark states. The dependence upon vibrational excitation is demonstrated to arise from excitation in the acetylene unit, only, for the former, but cannot be unravelled for the latter.
Numerical studies of vortex-induced extinction/reignition relevant to the near-field of high-Reynolds number jets
Authors: Venugopal Rishikesh , Abraham John
Published: May 2009

This work is motivated by the need to understand physical mechanisms governing near-field phenomena, such as flame lift-off, in high-Reynolds number jet flames. Numerical studies of vortex-induced flame extinction/reignition are performed for conditions representative of the near field of high-Reynolds number (∼100 000) jets under high pressure and temperature conditions. The governing equations for compressible, viscous, and reacting flows are solved along with a single-step irreversible chemical kinetic model for gaseous n-heptane oxidation. Extinction/reignition phenomena, influenced by unsteady and curvature effects, are observed. Unsteady flamelet/progress variable models are shown to accurately describe the flame response during extinction/reignition observed in the flame-vortex studies. Furthermore, while unsteady effects on extinction/reignition are found to diminish with weaker vortices and relatively strong flames, curvature effects are found to increase with relatively thicker flames. The observed flame-vortex interaction regimes are summarized on an outcome diagram, which is useful to understand the nature of localized flame dynamics in the near field of jet flames.
Rarefied gas flow in microtubes at different inlet-outlet pressure ratios
Authors: Yang Z. , Garimella S. V.
Published: May 2009

A model is developed for rarefied gas flow in long microtubes with different inlet-outlet pressure ratios at low Mach numbers. The model accounts for significant changes in Knudsen number along the length of the tube and is therefore applicable to gas flow in long tubes encountering different flow regimes along the flow length. Predictions from the model show good agreement with experimental measurements of mass flow rate, pressure drop, and inferred streamwise pressure distribution obtained under different flow conditions and offer a better match with experiments than do those from a conventional slip flow model.
Thermal expansion of silver iodide-silver molybdate glasses at low temperatures
Authors: Mandanici A. , Raimondo A. , Cutroni M. , Ramos M. A. , Rodrigo J. G. , Vieira S. , Armellini C. , Rocca F.
Published: May 2009

Ionic glasses obtained combining silver iodide and silver molybdate are characterized by quite low values of the glass transition temperature Tg around 320–350 K, by high values of the dc ionic conductivity even at room temperature and by a peculiar behavior of the mechanical response at ultrasonic frequencies. In fact, at temperatures well below their glass transition temperature, these glasses exhibit an intense peak of acoustic attenuation well described by two different and almost overlapping relaxational contributions. Considering also that negative thermal expansion has been reported for some molybdate crystalline compounds, we have investigated in this work the thermal expansion of two silver iodomolybdate glasses (AgI)1−x(Ag2MoO4)x for x=0.25 and x=0.33 in a wide temperature range (4.2–300 K) from cryogenic temperatures up to some 20 K below Tg using a precision capacitance dilatometer aiming to understand whether the expansivity shows some possible fingerprint corresponding to the above-mentioned mechanical response. Two different measuring methods, a quasiadiabatic and a continuous one, have been used for the thermal expansion measurements. The results are discussed in comparison with the information obtained from previous investigations based on the extended x-ray absorption fine structure (EXAFS) technique and with the behavior of other ionic glasses.
Resistance switching at the Al/SrTiO3−xNy anode interface
Authors: Shkabko A. , Aguirre M. H. , Marozau I. , Lippert T. , Weidenkaff A.
Published: May 2009

The electroformation and resistance switching behavior of Al/SrTiO3−xNy/Al have been investigated. The resistance of Al/SrTiO3−xNy/Al irreversibly increases when voltages higher than a certain threshold voltage are applied. A bistable resistance switching develops at one of the Al electrodes that performs as the anode. The formation of stacking faults in SrTiO3−xNy during preparation by microwave plasma treatment is a prerequisite for the occurrence of switching as confirmed by site-specific high resolution transmission electron microscopy at the electrode interfaces. The resistance switching effect is discussed by considering the role of stacking fault defects in the oxygen/nitrogen diffusion at the anode metal-oxynitride interface.
Electronic and structural characteristics of Zr-incorporated Gd2O3 films on strained SiGe substrates
Authors: Baeck J. H. , Park S. A. , Lee W. J. , Jeong I. S. , Jeong K. , Cho M.-H. , Kim Y. K. , Min B. G. , Ko D. H.
Published: May 2009

Zr-incorporated Gd2O3 films were grown on various substrates as a function of Zr content. The extent of interfacial reactions was found to be critically dependent on both the incorporated Zr content and the substrate type. Specifically, the silicide layer was suppressed and the Gd2O3 phase was changed to ZrO2 on a Si substrate with increasing Zr content. Crystalline Gd2Ge2O7 was grown on a Ge substrate, as the result of interfacial reactions between Gd-oxide and the Ge substrate. However, interfacial reactions were not affected by the amount of Zr incorporated. On the SiGe/Si substrate, reactions between Gd-oxide and Si could be controlled effectively by the incorporation of Zr, while the extent of reactions with Ge was significantly enhanced as the Zr content increased. The formation of an interfacial layer between the film and the SiGe substrate resulted in a textured crystalline growth.
Induction of the ovulatory LH surge in Asian elephants (Elephas maximus): a novel aid in captive breeding management of an endangered species
Authors: Thitaram Chatchote , Pongsopawijit Pornsawan , Chansitthiwet Saran , Brown Janine L. , Nimtragul Kannikar , Boonprasert Khajhonpat , Homkong Pongpon , Mahasawangkul Sittidet , Rojanasthien Suvichai , Colenbrander Ben , van der Weijden Gysbert C. , van Eerdenburg Frank J. C. M.
Published: May 2009

A unique feature of the reproductive physiology of Asian elephants (Elephas maximus) is the occurrence of two LH surges before ovulation, instead of one. An anovulatory LH (anLH) surge, the function of which is unknown, occurs consistently 3 weeks before the ovulatory LH (ovLH) surge that induces ovulation. Thus, the ability to induce an ovLH surge would be useful for scheduling natural mating or artificial insemination. The present study tested the efficacy of a gonadotrophin-releasing hormone agonist (GnRH-Ag) to induce LH surges during the follicular phase of the oestrous cycle, which resulted in varied LH responses, but generally none were as high as previously documented natural surges. Thus, for the ovulation-induction trials, nine females were administered 80 μg GnRH-Ag intravenously at three time periods during the oestrous cycle, namely the anovulatory follicular phase, the ovulatory follicular phase and the luteal phase. During the late anovulatory follicular phase, nine of 10 females (90%) responded with an immediate LH surge followed 15–22 days later by an ovLH surge or a post-ovulatory increase in progestagens. In contrast, despite responding to the GnRH-Ag with an immediate increase in LH, none of the females treated during other periods of the oestrous cycle exhibited subsequent ovLH surges. One cow got pregnant from natural mating following the induced ovLH surge. In conclusion, ovLH induction is possible using a GnRH-Ag, but only during a specific time of the anovulatory follicular phase.