bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical study of the geometries and dissociation energies of molecular water on neutral aluminum clusters Aln (n = 2–25)
Authors: Liu Yiliang , Hua Yawen , Jiang Ming , Jiang Gang , Chen Jun
Published: February 2012

Geometries and dissociation energies of water molecules on Aln (n = 2–25) clusters were investigated using density functional theory with all electron relativistic spin-polarized calculations under the generalized gradient approximation. An extensive structure search was performed to identify the low-energy conformations of AlnH2O complexes for each size. Optimal adsorption sites were assigned for low-energy isomers of the clusters. Size and site specific dependences were studied for the AlnH2O complexes in stabilities, geometries, adsorption energies, dissociation energies, Al–O bond lengths, and other characteristic quantities. The stabilities and geometries revealed that H atom in H2O is not inclined to bond with Al atoms. The most stable AlnH2O configurations for each size tend to correspond to the most stable bare Aln cluster except of Al6 and Al24 clusters. The HO bond lengths increase generally 0.01 Å with respect to the isolated H2O in all of the adsorption complexes. The dissociation energy of an isolated H2O into HO and H was 5.39 eV, which decreased about two-thirds to the energy range of 0.83–2.12 eV with the help of Aln clusters. In spite of the fluctuations, the dissociation energies of AlnH2O complexes rise with the size increasing as a whole. In addition, we also found that the bare Aln clusters with high vertical ionization potentials usually have high dissociation energies of H2O in the corresponding adsorption models. The energetically preferred spin-multiplicity of all the odd-n AlnH2O complexes is doublet, and it is singlet for all the even-n complexes with exception of Al2H2O which is triplet.
Measurement of probe displacement to the thermal resolution limit in photonic force microscopy using a miniature quadrant photodetector
Authors: Pal Sambit Bikas , Haldar Arijit , Roy Basudev , Banerjee Ayan
Published: February 2012

A photonic force microscope comprises of an optically trapped micro-probe and a position detection system to track the motion of the probe. Signal collection for motion detection is often carried out using the backscattered light off the probe–however, this mode has problems of low S/N due to the small backscattering cross sections of the micro-probes typically used. The position sensors often used in these cases are quadrant photodetectors. To ensure maximum sensitivity of such detectors, it would help if the detector size matched with the detection beam radius after the condenser lens (which for backscattered detection would be the trapping objective itself). To suit this condition, we have used a miniature displacement sensor whose dimensions makes it ideal to work with 1:1 images of micrometer-sized trapped probes in the backscattering detection mode. The detector is based on the quadrant photo-integrated chip in the optical pick-up head of a compact disc player. Using this detector, we measured absolute displacements of an optically trapped 1.1 \documentclass[12pt]{minimal}\begin{document}$\rm \mu$\end{document}μm probe with a resolution of ∼10 nm for a bandwidth of 10 Hz at 95% significance without any sample or laser stabilization. We characterized our optical trap for different sized probes by measuring the power spectrum for each probe to 1% accuracy, and found that for 1.1 μm diameter probes, the noise in our position measurement matched the thermal resolution limit for averaging times up to 10 ms. We also achieved a linear response range of around 385 nm with cross talk between axes ≃4% for 1.1 μm diameter probes. The detector has extremely high bandwidth (few MHz) and low optical power threshold–other factors that can lead to its widespread use in photonic force microscopy.
Viscous exchange flows
Authors: Matson Gary P. , Hogg Andrew J.
Published: February 2012

Gravitationally driven exchange flows of viscous fluids with different densities are analysed theoretically and investigated experimentally within a horizontal channel. Following initiation from rest when there is a vertical boundary dividing the two fluids, the denser fluid slumps under the less dense along the underlying boundary, while the less dense fluid intrudes along the upper boundary. The motion is driven by the pressure gradients associated with the density differences between the two fluids, resisted by viscous stresses, and mathematically modelled by a similarity solution that depends on the ratio of the viscosities of the two fluids. When the viscosity of the less dense fluid is much smaller than the viscosity of the denser fluid, the shape of the interface between the fluids varies rapidly close to the upper boundary and depends weakly on the viscosity ratio within the interior of the flow. Matched asymptotic expansions are employed in this regime to determine the shape of the interface and the rates of its propagation along the boundaries. The similarity solutions are shown to be linearly stable and thus are expected to represent the intermediate asymptotics of the flow. Experiments confirm the similarity form of solutions and demonstrate close agreement with the theoretical predictions when the viscosities of the fluids are comparable, but exhibit some discrepancies when the viscosities differ more substantially. It is suggested that these discrepancies may be due to mixing between the fluids close to the boundaries, which is induced by the no-slip boundary condition. Exchange flows within porous domains are also investigated to determine the shape of the interface as a function of the ratio of the viscosities of the two fluids and using asymptotic analysis, this shape is determined when this ratio is much larger, or smaller, than unity.
Space charge effects in ultrafast electron diffraction and imaging
Authors: Tao Zhensheng , Zhang He , Duxbury P. M. , Berz Martin , Ruan Chong-Yu
Published: February 2012

Understanding space charge effects is central for the development of high-brightness ultrafast electron diffraction and microscopy techniques for imaging material transformation with atomic scale detail at the fs to ps timescales. We present methods and results for direct ultrafast photoelectron beam characterization employing a shadow projection imaging technique to investigate the generation of ultrafast, non-uniform, intense photoelectron pulses in a dc photo-gun geometry. Combined with N-particle simulations and an analytical Gaussian model, we elucidate three essential space-charge-led features: the pulse lengthening following a power-law scaling, the broadening of the initial energy distribution, and the virtual cathode threshold. The impacts of these space charge effects on the performance of the next generation high-brightness ultrafast electron diffraction and imaging systems are evaluated.
Promoter effect of BaO on CO oxidation on PdO surfaces
Authors: Hirvi Janne T. , Kallinen Kauko , Kinnunen Toni-Jani J. , Suvanto Mika , Pakkanen Tapani A.
Published: February 2012

The effect of bulk BaO promoter on CO oxidation activity of palladium oxide phase was studied by density functional calculations. A series of BaO(100) supported PdxOy thin layer models were constructed, and energy profiles for CO oxidation on the films were calculated and compared with corresponding profiles for the most stable PdO bulk surfaces PdO(100) and PdO(101). The most stable of the thin films typically exhibit the same PdO(100) and PdO(101) surface planes; the PdO(100) dominates already with double layer thickness. The supporting promoter improves the CO oxidation activity of the PdxOy phase via a direct electronic effect and introduced structural strain and corrugation. Changes in CO adsorption strength are reflected in oxidation energy barriers, and the promoting effect of even 0.3 eV can be seen locally. Easier oxygen vacancy formation may partially facilitate the reaction.
Thermoelectric prospects of nanomaterials with spin-orbit surface bands
Authors: Huber T. E. , Owusu K. , Johnson S. , Nikolaeva A. , Konopko L. , Johnson R. C. , Graf M. J.
Published: February 2012

Nanostructured composites and nanowire arrays of traditional thermoelectrics, like Bi, Bi1-xSbx, and Bi2Te3, have metallic Rashba surface spin-orbit bands featuring high mobilities rivaling that of the bulk for which topological insulator behavior has been proposed. Nearly pure surface electronic transport has been observed at low temperatures in Bi nanowires, with diameter around the critical diameter, 50 nm, for the semimetal-to-semiconductor transition. The surface contributes strongly to the thermopower, actually dominating for temperatures T < 100 K in these nanowires. The surface thermopower was found to be –1 T μV/K2, a value that is consistent with theory. We show that surface electronic transport together with boundary phonon scattering leads to enhanced thermoelectric performance at low temperatures of Bi nanowire arrays. We compare with bulk n-BiSb alloys, optimized CsBi4Te6, and optimized Bi2Te3. Surface dominated electronic transport can be expected in nanomaterials of the other traditional thermoelectrics.
Magnetic properties of few nanometers ɛ-Fe2O3 nanoparticles supported on the silica
Authors: Yakushkin S. S. , Dubrovskiy A. A. , Balaev D. A. , Shaykhutdinov K. A. , Bukhtiyarova G. A. , Martyanov O. N.
Published: February 2012

Magnetic properties of ɛ-Fe2O3 nanoparticles supported on silica with the average size of few nanometers, narrow size distribution and no admixture of any other iron oxide polymorphs are investigated. The investigation of the temperature behavior of magnetization within the temperature range from 4.2 to 1000 K revealed the presence of several magnetic subsystems in the species under study. The temperatures’ behavior of the magnetic moment value indicates ferrimagnetic ordering in the ɛ-Fe2O3 nanoparticles with a Curie temperature of about 800 K and points to the existence of a significant paramagnetic contribution becoming apparent at low temperatures. According to the electron spin resonance data, the particles possess superparamagnetic behavior at temperature higher ∼120 K. The model of the magnetic structure of monophase system of few nanometers ɛ-Fe2O3 nanoparticles supported on silica is proposed.
Cross-waves induced by the vertical oscillation of a fully immersed vertical plate
Authors: Moisy Frédéric , Michon Guy-Jean , Rabaud Marc , Sultan Eric
Published: February 2012

Capillary waves excited by the vertical oscillation of a thin elongated plate below an air-water interface are analyzed using time-resolved measurements of the surface topography. A parametric instability is observed above a well defined acceleration threshold, resulting in a so-called cross-wave, a staggered wave pattern localized near the wavemaker and oscillating at half the forcing frequency. This cross-wave, which is stationary along the wavemaker but propagative away from it, is described as the superposition of two almost anti-parallel propagating parametric waves making a small angle of the order of 20o with the wavemaker edge. This contrasts with the classical Faraday parametric waves, which are exactly stationary because of the homogeneity of the forcing. Our observations suggest that the selection of the cross-wave angle results from a resonant mechanism between the two parametric waves and a characteristic length of the surface deformation above the wavemaker.
Large exchange bias obtainable through zero-field cooling from an unmagnetized state in Ni-Mn-Sn alloys
Authors: Wang B. M. , Liu Y. , Xia B. , Ren P. , Wang L.
Published: February 2012

We report a large unusual exchange bias effect occurred after zero-field cooling from an unmagnetized state (ZEB) in Ni-Mn-Sn alloys, in which the maximum ZEB field is about twice as large as that observed in Ni-Mn-In alloys at moderate field range (< 40 kOe). The ZEB field can be tuned by tuning the magnitude of the initial magnetization fields and its sign is strongly dependent on the direction of the initial magnetization fields. Furthermore, the ZEB effect only exists in alloys with volume fraction of superparamagnetic domains less than the percolation limitation in three-dimensional system (∼16%). The present results confirm the universality of this unusual ZEB effect and suggest that NiMn-based alloys provide a platform to obtain this unusual ZEB effect. Such ZEB effect may also exist in other systems with similar magnetic properties.
Thermal-magnetic-electric oscillator based on spin-valve effect
Authors: Kadigrobov A. M. , Andersson S. , Park Hee Chul , Radić D. , Shekhter R. I. , Jonson M. , Korenivski V.
Published: February 2012

A thermal-magnetic-electric valve with the free layer of exchange-spring type and inverse magnetoresistance is investigated. The structure has S-shaped current-voltage characteristics and can exhibit spontaneous oscillations when integrated with a conventional capacitor within a resonator circuit. The frequency of the oscillations can be controlled from essentially dc to the GHz range by the circuit capacitance.
Correlation of current drop, filling gas pressure, and ion beam emission in a low energy Mather-type plasma focus device
Authors: Behbahani R. A. , Aghamir F. M.
Published: February 2012

The behavior of current drop and its correlation with ion beam emission during the radial phase of a high inductance low energy Mather type plasma focus device have been studied. The study includes two ranges of filling gas pressure, namely the low range of 0.2–0.8 mbar and the high range of 0.8–1.5 mbar. Two different current simulation processes were performed to aid the interpretation of the experimental results. Within the low range of operating pressure, an acceptable match between the computed and experimental current signals was achieved when the effects of anomalous resistances were contemplated. While in the high range of pressure, the computed and experimental current traces were in line even without considering the effects of anomalous resistances. The analysis shows that by decreasing the filling gas pressure the effects of instabilities are intensified. The computed and experimental current traces, along with ion beam signals gathered from a faraday cup, show that there is a strong correlation between the intensity of ion beam and its duration with the current drop during the radial phase.
Similarities and differences among the models proposed for real electrodes in the Poisson-Nernst-Planck theory
Authors: Barbero G. , Scalerandi M.
Published: February 2012

The ionic distribution induced by an external field is investigated by means of the Poisson-Nernst-Planck model, by taking into account the non-blocking properties of the limiting electrodes. Three types of models proposed for the description of real electrodes are considered. The first two assume an ionic current on the electrodes proportional to the variation of the bulk density of ions and to the surface electric field, respectively. The third model assumes that the sample is limited by perfectly blocking electrodes with a true resistance in parallel to the cell. Here we show that the first two models are equivalent, in the sense that it is possible to find a phenomenological parameter by means of which the predictions of the two models, for what concerns the spectra of the real and imaginary parts of the impedance of the cell, are the same. On the contrary, the third model is equivalent to the others only if the conduction current across the electrodes is small with respect to the displacement current.
Modeling resistance of nanofibrous superhydrophobic coatings to hydrostatic pressures: The role of microstructure
Authors: Bucher T. M. , Emami B. , Tafreshi H. Vahedi , Gad-el-Hak M. , Tepper G. C.
Published: February 2012

In this paper, we present a numerical study devised to investigate the influence of microstructural parameters on the performance of fibrous superhydrophobic coatings manufactured via dc and ac electrospinning. In particular, our study is focused on predicting the resistance of such coatings against elevated hydrostatic pressures, which is of crucial importance for submersible applications. In our study, we generate 3D virtual geometries composed of randomly or orthogonally oriented horizontal fibers with bimodal diameter distributions resembling the microstructure of our electrospun coatings. These virtual geometries are then used as the computational domain for performing full morphology numerical simulations to establish a relationship between the coatings’ critical pressure (pressure beyond which the surface may depart from the Cassie state) and their microstructures. For coatings with ordered microstructures, we have also derived analytical expressions for the critical pressure based on the balance of forces acting on the water–air interface. Predictions of our force balance analysis are compared with those of our FM simulations as well as the equations proposed by Tuteja et al. [Proc. Natl. Acad. Sci. U.S.A. 105, 18200 (2008)]10.1073/pnas.0804872105, and discussed in detail. Our numerical simulations are aimed at providing useful information with regards to the tolerance of fibrous superhydrophobic coatings against elevated pressures, and helping with the design and optimization of the coatings’ microstructures. Our results show considerably higher pressure tolerance for the case of coatings with orthogonally oriented fibers as compared to those with randomly laid fibers when other microstructural parameters are held constant. Moreover, it is demonstrated that thickness of the coating has less influence on performance in the case of orthogonal microstructures. Coatings’ responses to other variations favor those that yield smaller-sized inter-fiber spaces. Studies are also performed investigating the effect of subtle permutations in the layer configurations of our ac-electrospun coatings, as well as the use of a hybrid coating that utilizes advantages from both dc and ac electrospinning.
Descriptive analysis of a mode transition of the flow over an open cavity
Authors: Farkas B. , Paál G. , Szabó K. G.
Published: February 2012

Incompressible flow computations have been performed on a cavity with a length to depth ratio of 2. Depending on the Reynolds number, three qualitatively different unsteady flow regimes have been identified. In the first (regular) regime the second Rossiter mode dominates the spectrum, in the second (transitional) regime two incommensurable frequencies compete with each other via mode switching, and finally, in the third (suppressed) regime a lower frequency dominates. The various forms of appearance of these regimes in the flow field are identified and discussed. Among others, the relative importance of the upstream and downstream vortices, the spatial concentration of certain frequency components, and the amplitude of the instability waves all change radically with the change of regime. In search of the hydrodynamic causes for the qualitative changes in the flow field it has become necessary to identify vortices more precisely than usual. We critically evaluate the conditions of applicability of the Truesdell–Okubo–Weiss vortex detection criterion. We propose a new vortex identification scheme by including terms describing both the local and the convective acceleration. This scheme is more accurate than that of Hua and Klein by being truly first order. The results justify the additional effort; vortical structures are more clearly identifiable with the new criterion.
A Laplace pressure based microfluidic trap for passive droplet trapping and controlled release
Authors: Simon Melinda G. , Lin Robert , Fisher Jeffrey S. , Lee Abraham P.
Published: February 2012

Here, we present a microfluidic droplet trap that takes advantage of the net Laplace pressure force generated when a droplet is differentially constricted. Mathematical simulations were first used to understand the working range of the component; followed by finite element modeling using the CFD software package to further characterize the behavior of the system. Controlled release of the trapped droplets is also demonstrated through both a mechanical method and a chemical method that manipulates the total pressure exerted on the trapped droplet. The unique design of this trapping device also provides the capability for selection of a single droplet from a train, as well as droplet fusion.
Wind power potential assessment for seven buoys data collection stations in Aegean Sea using Weibull distribution function
Authors: Bagiorgas Haralambos S. , Mihalakakou Giouli , Rehman Shafiqur , Al-Hadhrami Luai M.
Published: February 2012

This paper utilizes three hourly measured values of wind speed and direction from seven buoys data collection stations in Aegean Sea to study the wind speed and power characteristics applying the Weibull shape and scale parameters. Specifically, the site dependent, annual and monthly mean patterns of mean wind speed, Weibull parameters, frequency distribution, most probable wind speed, maximum energy carrying wind speed, wind power density and wind energy density characteristics have been studied. The Weibull distribution was found to represent the wind speed distribution with more than 90% accuracy in most of the cases. Slightly decreasing trends were observed in annual mean wind speed values at Lesvos and increasing at Mykonos. The mean values of wind speed, scale parameter, most probable wind speed, maximum energy carrying wind speed, wind power and wind energy density values showed higher values during winter time and lower in summer time. Mykonos was found to be the best site from wind power harnessing point of view. Moreover, the correlation between the percentages of times the wind speed was above cut-in-speed and the measured mean wind speed for the three selected sites and the correlation between the aforementioned percentages and the scale parameter c were examined and were found linear.
B segregation to grain boundaries and diffusion in polycrystalline Si with flash annealing
Authors: Jin S. , Jones K. S. , Law M. E. , Camillo-Castillo R.
Published: February 2012

Three-dimensional atom probe tomography was used to characterize the segregation of B dopant atoms to grain boundaries in polycrystalline Si after flash-assisted rapid thermal annealing. Tomographic reconstructions allowed direct measurement of segregation coefficients, which were found to be greater at lower flash temperatures with thermal budgets that limit grain growth. Hall measurements confirmed the deactivation of B at the grain boundaries, while secondary ion mass spectrometry was used to measure B diffusion in the film. Experimental parameters were then simulated in a diffusion model which accurately predicts the diffusion of B in polycrystalline Si at flash temperatures of 1150 °C, 1250 °C, and 1350 °C, as well as with conventional rapid thermal annealing.
Small molecular phosphorescent organic light-emitting diodes using a spin-coated hole blocking layer
Authors: Zhao Yan , Duan Lian , Zhang Deqiang , Hou Liudong , Qiao Juan , Wang Liduo , Qiu Yong
Published: February 2012

Small molecular green phosphorescent organic light-emitting diodes (OLEDs) have been studied using a solution processed polyethyleneoxide (PEO) hole blocking layer (HBL) and a Cs2CO3/Al cathode. PEO is soluable in alcoholic solvents and allows the fabrication of multilayer OLEDs by successive spin-coating. The current efficiency of the optimized OLED with the PEO HBL increases from 18.8 cd/A to 32.1 cd/A, and the turn-on voltage reduces from 4.8 V to 3.4 V, compared with the device without the PEO HBL. Photovoltaic measurements indicate that the injection barrier for electron is reduced by inserting the PEO layer. X-ray photoelectron spectroscopy measurements further reveal that improvement in device performance is due to the partial penetration of Cs into the PEO layer.
Micro-fabricated channel with ultra-thin yet ultra-strong windows enables electron microscopy under 4-bar pressure
Authors: Alan Tuncay , Yokosawa Tadahiro , Gaspar João , Pandraud Gregory , Paul Oliver , Creemer Fredrik , Sarro Pasqualina M. , Zandbergen Henny W.
Published: February 2012

Transmission electron microscopy (TEM) of (de-)hydrogenation reactions is crucial to characterize efficiency of hydrogen storage materials. The nanoreactor, a micromachined channel with 15-nm-thick windows, effectively confines the gas flow to an electron-transparent chamber during TEM of reactions. Realistic experiments require very high pressures to be sustained by the device. Nanomechanical bulge tests and simulations show that due to a very strong size effect, ultra-thin device components can reliably withstand tensile stresses as high as 19.5 GPa enabling high pressure operation. We use the device to characterize Pd particles under a 4-bar H2 pressure within the ultra-high-vacuum of the TEM.
Whispering gallery mode selection in optical bottle microresonators
Authors: Ding Ming , Senthil Murugan Ganapathy , Brambilla Gilberto , Zervas Michalis N.
Published: February 2012

We demonstrated a method to excite selected whispering gallery modes in optical bottle microresonators (BMR) by inscribing microgroove scars on their surface by focused ion beam milling. Substantial spectral clean-up is obtained in appropriately scarred BMRs, providing the potential for high performance sensors and other optical devices.
Phonon spectrum and bonding properties of Bi2Se3: Role of strong spin-orbit interaction
Authors: Wang Bao-Tian , Zhang Ping
Published: February 2012

Phonon dispersions of one typical three-dimensional topological insulator Bi2Se3 have been studied within density functional theory. The soft modes of two acoustic branches along the Z – F and Γ-F directions within the pure local density approximation will transit to show imaginary frequency oscillating after including the spin-orbit interaction (SOI). Similar phenomenon has also been observed for Bi2Te3. Besides, we have found that the weak van der Waals forces between two Se1 layers in Bi2Se3 are strengthened by turning on the spin-orbit interaction.
Communication: Identical temperature dependence of the time scales of several linear-response functions of two glass-forming liquids
Authors: Jakobsen Bo , Hecksher Tina , Christensen Tage , Olsen Niels Boye , Dyre Jeppe C. , Niss Kristine
Published: February 2012

The frequency-dependent dielectric constant, shear and adiabatic bulk moduli, longitudinal thermal expansion coefficient, and longitudinal specific heat have been measured for two van der Waals glass-forming liquids, tetramethyl-tetraphenyl-trisiloxane (DC704) and 5-polyphenyl-4-ether. Within the experimental uncertainties the loss-peak frequencies of the measured response functions have identical temperature dependence over a range of temperatures, for which the Maxwell relaxation time varies more than nine orders of magnitude. The time scales are ordered from fastest to slowest as follows: Shear modulus, adiabatic bulk modulus, dielectric constant, longitudinal thermal expansion coefficient, and longitudinal specific heat. The ordering is discussed in light of the recent conjecture that van der Waals liquids are strongly correlating, i.e., approximate single-parameter liquids.
Magnetic-field and temperature dependence of the energy gap in InN nanobelt
Authors: Aravind K. , Su Y. W. , Chung D. S. , Kuo Watson , Wu C. S. , Chang-Liao K. S. , Chen K. H. , Chen L. C. , Chen C. D.
Published: February 2012

We present tunneling measurements on an InN nanobelt which shows signatures of superconductivity. Superconducting transition takes place at temperature of 1.3K and the critical magnetic field is measured to be about 5.5kGs. The energy gap extrapolated to absolute temperature is about 110μeV. As the magnetic field is decreased to cross the critical magnetic field, the device shows a huge zero-bias magnetoresistance ratio of about 400%. This is attributed to the suppression of quasiparticle subgap tunneling in the presence of superconductivity. The measured magnetic-field and temperature dependence of the superconducting gap agree well with the reported dependences for conventional metallic superconductors.
The p53 cofactor Strap exhibits an unexpected TPR motif and oligonucleotide-binding (OB)–fold structure
Authors: Adams Cassandra J. , Pike Ashley C. W. , Maniam Sandra , Sharpe Timothy D. , Coutts Amanda S. , Knapp Stefan , La Thangue Nicholas B. , Bullock Alex N.
Published: February 2012

Activation of p53 target genes for tumor suppression depends on the stress-specific regulation of transcriptional coactivator complexes. Strap (stress-responsive activator of p300) is activated upon DNA damage by ataxia telangiectasia mutated (ATM) and Chk2 kinases and is a key regulator of the p53 response. In addition to antagonizing Mdm2, Strap facilitates the recruitment of p53 coactivators, including JMY and p300. Strap is a predicted TPR-repeat protein, but shows only limited sequence identity with any protein of known structure. To address this and to elucidate the molecular mechanism of Strap activity we determined the crystal structure of the full-length protein at 2.05 Å resolution. The structure of Strap reveals an atypical six tetratricopeptide repeat (TPR) protein that also contains an unexpected oligonucleotide/oligosaccharide-binding (OB)-fold domain. This previously unseen domain organization provides an extended superhelical scaffold allowing for protein-protein as well as protein-DNA interaction. We show that both of the TPR and OB-fold domains localize to the chromatin of p53 target genes and exhibit intrinsic regulatory activity necessary for the Strap-dependent p53 response.
Effects of Freezing on the Bactericidal Activity of Human Milk
Authors: Takci Sahin , Gulmez Dolunay , Yigit Sule , Dogan Ozlem , Dik Kezban , Hascelik Gulsen
Published: February 2012

Objectives:

Storage of human milk by freezing has been recommended for long‐term storage. The present study analyzed the bactericidal activity of human milk on Escherichia coli and Pseudomonas aeruginosa and determined the changes in bactericidal activity following freezing at −20°C and −80°C for 1 month and 3 months.

Methods:

Forty‐eight milk samples were collected from 48 lactating mothers. Each sample was divided into 10 aliquots. Two of the samples were processed immediately and the others were stored at both −20°C and −80°C until analysis after 1 month and 3 months of freezing.

Results:

All of the fresh milk samples showed bactericidal activity against E coli and P aeruginosa. Freezing at −20°C for 1 month did not cause statistically significant alteration in bactericidal activity (P > 0.017), whereas storage for 3 months lowered the degree of bactericidal activity significantly (P < 0.017) against E coli. Bactericidal activity was protected when the samples were stored at −80°C. There was no statistically significant difference in the bactericidal activity of human milk against E coli between freezing at −20°C and −80°C for 1 month (P > 0.017); however, when milk was stored for 3 months, −80°C was significantly more protective (P < 0.017). Freezing at −20°C and −80°C for 1 month and 3 months did not cause any significant change in bactericidal activity against P aeruginosa (P > 0.05).

Conclusions:

Storage by freezing at −80°C is more appropriate to keep bactericidal capacity of stored human milk >1 month if affordable and available, especially in intensive care settings.
Endoscopic Diagnosis of Pediatric Acute Gastrointestinal Graft‐Versus‐Host Disease
Authors: Sultan Mutaz , Ramprasad Jonathan , Jensen M. Kyle , Margolis David , Werlin Steven
Published: February 2012

Background and Objectives:

Acute graft‐versus‐host disease (GVHD) is a major cause of morbidity and mortality in the first 100 days following allogeneic hematopoietic progenitor stem cell transplant. The best diagnostic endoscopic strategy for gastrointestinal (GI) GVHD is a matter of debate. Our aim in the present study was to compare the relative contribution of the endoscopic appearance and biopsies from upper endoscopy and flexible sigmoidoscopy in children with suspected acute GVHD.

Methods:

The present study was designed as single‐center retrospective chart review cohort study. We reviewed the charts of all of the patients younger than 18 years with suspected acute GI GVHD who had endoscopic evaluation within the first 100 days after stem cell transplant between 1999 and 2009.

Results:

A total of 48 patients were included. The most common symptoms prompting endoscopic evaluation were diarrhea (70%) and a combination of nausea and vomiting (67%). GVHD was diagnosed in at least 1 biopsy site in 40 of 48 patients (83%). Twenty‐two of 40 (55%) patients with GVHD had simultaneous upper and lower endoscopic biopsies, 11 patients had only upper endoscopy, and 7 had only lower endoscopy. The most common endoscopic finding was normal mucosa. The sensitivity for diagnosing GVHD was 77% for both rectosigmoid and upper endoscopic biopsies. Thirty‐three of 40 patients had upper endoscopy with biopsies; 28 (85%) had GVHD. The sensitivities and negative predictive value of gastric biopsies were 85% and 63%, whereas for duodenal biopsies they were 50% and 57%, respectively.

Conclusions:

Rectosigmoid and combined upper endoscopic biopsies are equally sensitive for the diagnosis of acute GI GVHD in children. Flexible sigmoidoscopy can be done unsedated in appropriate patients at the bedside without anesthesia; it can be performed first to identify GI GVHD.
A Revised Architecture of Primary Cell Walls Based on Biomechanical Changes Induced by Substrate-Specific Endoglucanases
Authors: Park Yong Bum , Cosgrove Daniel J.
Published: February 2012

Xyloglucan is widely believed to function as a tether between cellulose microfibrils in the primary cell wall, limiting cell enlargement by restricting the ability of microfibrils to separate laterally. To test the biomechanical predictions of this “tethered network” model, we assessed the ability of cucumber (Cucumis sativus) hypocotyl walls to undergo creep (long-term, irreversible extension) in response to three family-12 endo-β-1,4-glucanases that can specifically hydrolyze xyloglucan, cellulose, or both. Xyloglucan-specific endoglucanase (XEG from Aspergillus aculeatus) failed to induce cell wall creep, whereas an endoglucanase that hydrolyzes both xyloglucan and cellulose (Cel12A from Hypocrea jecorina) induced a high creep rate. A cellulose-specific endoglucanase (CEG from Aspergillus niger) did not cause cell wall creep, either by itself or in combination with XEG. Tests with additional enzymes, including a family-5 endoglucanase, confirmed the conclusion that to cause creep, endoglucanases must cut both xyloglucan and cellulose. Similar results were obtained with measurements of elastic and plastic compliance. Both XEG and Cel12A hydrolyzed xyloglucan in intact walls, but Cel12A could hydrolyze a minor xyloglucan compartment recalcitrant to XEG digestion. Xyloglucan involvement in these enzyme responses was confirmed by experiments with Arabidopsis (Arabidopsis thaliana) hypocotyls, where Cel12A induced creep in wild-type but not in xyloglucan-deficient (xxt1/xxt2) walls. Our results are incompatible with the common depiction of xyloglucan as a load-bearing tether spanning the 20- to 40-nm spacing between cellulose microfibrils, but they do implicate a minor xyloglucan component in wall mechanics. The structurally important xyloglucan may be located in limited regions of tight contact between microfibrils.
High-pressure phase transitions and equations of state in NiSi. I.Ab initiosimulations
Authors: Vočadlo Lidunka , Wood Ian G. , Dobson David P.
Published: February 2012

First-principles calculations have been used to determine the equation of state and structural properties of NiSi up to pressures equivalent to that in the Earth's inner core. At atmospheric pressure, the thermodynamically stable phase is that with the MnP structure (as found experimentally). At high pressures, NiSi shows phase transformations to a number of high-pressure polymorphs. For pressures greater than ∼250 GPa, the thermodynamically stable phase of NiSi is that with the CsCl structure, which persists to the highest pressures simulated (∼500 GPa). At the pressures of the Earth's inner core, therefore, NiSi and FeSi will be isostructural and thus are likely to form a solid solution. The density contrast between NiSi and FeSi at inner-core pressures is ∼6%, with NiSi being the denser phase. Therefore, if a CsCl-structured (Fe,Ni)Si alloy were present in the inner core, its density (for the commonly assumed nickel content) might be expected to be ∼1% greater than that of pure FeSi.
Incommensurate modulation of calcium barium niobate (CBN28 and Ce:CBN28)
Authors: Graetsch Heribert A. , Pandey Chandra Shekhar , Schreuer Jürgen , Burianek Manfred , Mühlberg Manfred
Published: February 2012

The incommensurately modulated crystal structures of Ca0.28Ba0.72Nb2O6 (CBN28) and Ce0.02Ca0.25Ba0.72Nb2O6 (Ce:CBN28) were refined in the supercentred setting X4bm(AA0,−AA0) of the 3 + 2-dimensional superspace group P4bm(aa½,−aa½). Both compounds are isostructural with a tetragonal tungsten bronze-type structure. The modulation of CBN28 consists of a wavy distribution of Ba and Ca atoms as well as vacancies on the incompletely occupied Me2 site with 15-fold oxygen coordination. The occupational modulation is coupled with a modulation of the atomic displacement parameters and a very weak modulation of the positional parameters of Me2. The surrounding O atoms show strong displacive modulations with amplitudes up to ca 0.2 Å owing to the cooperative tilting of the rigid NbO6 octahedra. The Me1 site with 12-fold coordination and Nb atoms are hardly affected by the modulations. Only first-order satellites were observed and the modulations are described by first-order harmonics. In Ce:CBN28 cerium appears to be located on both the Me2 and Me1 sites. Wavevectors and structural modulations are only weakly modified upon substitutional incorporation of 0.02 cerium per formula unit of calcium.
On the structural integrity of the spinel block in the β"-alumina structure
Authors: Birnie Dunbar P.
Published: February 2012

The β′′-alumina structure is examined in detail and an analysis is presented of the three-dimensional integrity of the lattice. The layer structure that is responsible for the very high sodium conduction rate is the specific focus. Rigid layers that are derived from the cubic spinel structure are interleaved by more open honeycomb pathways where rapid ion diffusion takes place. The three-dimensional rigidity of the spinel block in this structure makes it possible to accurately quantify the conduction layer thickness based only on the hexagonal unit-cell dimensions, as suggested originally by Harbach [(1983), J. Mater. Sci.
18, 2437–2452]. His calculation is tested rigorously against the many single-crystal structure determinations that have been made on the β′′-alumina family compounds and excellent correlation is found.
Ab-initio crystal structure analysis and refinement approaches of oligo p-benzamides based on electron diffraction data
Authors: Gorelik Tatiana E. , van de Streek Jacco , Kilbinger Andreas F. M. , Brunklaus Gunther , Kolb Ute
Published: February 2012

Ab-initio crystal structure analysis of organic materials from electron diffraction data is presented. The data were collected using the automated electron diffraction tomography (ADT) technique. The structure solution and refinement route is first validated on the basis of the known crystal structure of tri-p-benzamide. The same procedure is then applied to solve the previously unknown crystal structure of tetra-p-benzamide. In the crystal structure of tetra-p-benzamide, an unusual hydrogen-bonding scheme is realised; the hydrogen-bonding scheme is, however, in perfect agreement with solid-state NMR data.
Structure of the inclusion complex of β-cyclodextrin with lipoic acid from laboratory powder diffraction data
Authors: Rácz Csaba-Pal , Borodi Gheorghe , Pop Mihaela Maria , Kacso Irina , Sánta Szabolcs , Tomoaia-Cotisel Maria
Published: February 2012

The crystal structure of the inclusion complex of β-cyclodextrin with lipoic acid was determined from laboratory powder diffraction data. Thermogravimetric data was used to estimate the number of water molecules in the crystal structure. Lipoic acid is included in β-cyclodextrin through its primary face with the five-membered ring reaching the center plane of the cyclodextrin cavity and its fatty acid chain adopting a bent conformation. Lipoic acid and β-cyclodextrin form a channel-like packing which is stabilized by guest–host hydrogen bonding and close contacts, host–host intermolecular interactions and hydrogen bonding involving the water molecules.
Habitat restoration will help some functional plant types persist under climate change in fragmented landscapes
Authors: Renton Michael , Shackelford Nancy , Standish Rachel J.
Published: February 2012

In the next century, global climate change is predicted to have large influences on species' distributions. Much of the research in this area has focused on predicting the areas where conditions will be suitable for the species in future, and thus the potential distribution of the species. However, it is equally important to predict the relative abilities of species to migrate into new suitable areas as conditions shift, while accounting for dynamic processes, such as dispersal, maturation, mortality, and reproduction, as well as landscape characteristics, such as level of habitat fragmentation and connectivity. In this study, we developed a spatially explicit individual‐based model that addresses these factors. As a motivating case study, we based aspects of the model on southwest Australia, a global biodiversity hotspot, but stress that the results obtained are generalizable beyond this region. Using the model, we enhanced current understanding of climate change impacts by investigating how and to what extent the functional traits of plant species affect their ability to move with climate change across landscapes with various levels of fragmentation. We also tested the efficacy of strategic restoration, such as planting corridors to increase connectivity among fragments. We found that even if the landscape is fully intact, only an average of 34.2% of all simulated functional groups had a good chance of successfully tracking climate change. However, our study highlights the power of strategic restoration as a tool for increasing species persistence. Corridors linking fragments increased species persistence rates by up to 24%. The lowest persistence rates were found for trees, a functional group with high dispersal but also long generation times. Our results indicate that for trees intervention techniques, such as assisted migration might be required to prevent species losses.
Mesiobuccal root resection in endodontic–periodontal combined lesions
Authors: Oh S.‐L.
Published: February 2012

Oh S‐L. Mesiobuccal root resection in endodontic–periodontal combined lesions. International Endodontic Journal, 45, 660–669, 2012.

Aim  To present two successful cases involving management of endodontic–periodontal combined lesions with root resection and guided tissue regeneration (GTR) therapy.

Summary  Mesiobuccal resection surgery was performed concomitant with GTR therapy to manage endodontic–periodontal combined lesions on teeth 17 and 26. The increased mobility after the periodontal surgery gradually decreased during the healing period. At 15 and 20 month follow‐ups, respectively, the teeth showed no mobility, 2–3 mm pocket depths and no further bone loss.

Key learning points  • Treatment of periodontally involved maxillary teeth creates unique challenges, given the presence of furcations, root proximities and the maxillary sinus.

• Root resection combined with GTR therapy can enable tooth maintenance with a good long‐term prognosis.
Age and historical biogeography of the pantropically distributed Spathelioideae (Rutaceae, Sapindales)
Authors: Appelhans Marc S. , Keßler Paul J.A. , Smets Erik , Razafimandimbison Sylvain G. , Janssens Steven B.
Published: February 2012

Aim  The family Rutaceae (rue family) is the largest within the eudicot order Sapindales and is distributed mainly in the tropical and subtropical regions of both the New World and the Old World, with a few genera in temperate zones. The main objective of this study is to present molecular dating and biogeographical analyses of the subfamily Spathelioideae, the earliest branching clade (which includes eight extant genera), to interpret the temporal and spatial origins of this group, ascertaining possible vicariant patterns and dispersal routes and inferring diversification rates through time.

Location  Pantropics.

Methods  A dataset comprising a complete taxon sampling at generic level (83.3% at species level) of Spathelioideae was used for a Bayesian molecular dating analysis (beast). Four fossil calibration points and an age constraint for Sapindales were applied. An ancestral area reconstruction analysis utilizing the dispersal–extinction–cladogenesis model and diversification rate analyses was conducted.

Results  Dating analyses indicate that Rutaceae and Spathelioideae are probably of Late Cretaceous origin, after which Spathelioideae split into a Neotropical and a Palaeotropical lineage. The Palaeotropical taxa have their origin inferred in Africa, with postulated dispersal events to the Mediterranean, the Canary Islands, Madagascar and Southeast Asia. The lineages within Spathelioideae evolved at a relatively constant diversification rate. However, abrupt changes in diversification rates are inferred from the beginning of the Miocene and during the Pliocene/Pleistocene.

Main conclusions  The geographical origin of Spathelioideae probably lies in Africa. The existence of a Neotropical lineage may be the result of a dispersal event at a time in the Late Cretaceous when South America and Africa were still quite close to each other (assuming that our age estimates are close to the actual ages), or by Gondwanan vicariance (assuming that our age estimates provide minimal ages only). Separation of land masses caused by sea level changes during the Pliocene and Pleistocene may have been triggers for speciation in the Caribbean genus Spathelia.