bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of Masticatory Function Using Bite Force Measurements in Patients Treated for Mandibular Fractures
Authors: Sybil Deborah , Gopalkrishnan K.
Published: February 2014

Bite force measurements are excellent criteria for assessment of masticatory efficiency. The purpose of this study was to assess the effect of mandibular fractures on the bite forces of patients treated for such fractures. Patients who were surgically treated for isolated mandibular fractures in the Department of Oral and Maxillofacial Surgery from January 2006 to December 2007 were included in the study. Patients were asked to bite on a bite force transducer on the first, fourth, sixth, and ninth postoperative weeks. The bite force values were compared with those of age, sex, and weight-matched controls. A total of 60 patients were included in the study. It was found that maximum bite forces in patients were significantly less than in controls for several weeks after surgery. After the ninth postoperative week, the maximum bite force measured < 65% the normal in patients with isolated angle fractures and > 80% the normal in patients with isolated parasymphysis fractures. The same values reduced to < 60% in patients with fractures of angle and parasymphysis and < 70% in patients with fractures of parasymphysis and condylar complex. An inverse relationship was found between the bite force values and the number of fractures of the mandible. We also found lower bite forces and longer period for normalization in patients who had fractures in those regions of the mandible which are more significantly associated with the masticatory apparatus for example angle or condyle of the mandible.
Branching Pattern of the Extraosseous Mental Nerve in a Kenyan Population
Authors: Loyal PoonamjeetKaur , Butt Fawzia , Ogeng'o JuliusAlexander
Published: February 2014

Knowledge of the branching pattern of the mental nerve is an important consideration during placement of tooth implants and reconstructive plates. It is known to display population variations and data for the same is scarce form the sub-Saharan region. With the recent increase in surgical interventions in the mandibular region in Kenya, a detailed description of mental nerve is warranted. A total of 64 mental nerves were dissected and branching pattern was noted. Single mental nerve was present in 60 (93.7%) cadavers while double mental nerves occurred in 3 (4.7%) and accessory in 1(1.6%). Most common pattern was bifurcation (39%) followed by trifurcation (34%), single (19%), and quadrification (8%). The double and triple branches were seen to further divide into two to three subbranches with diverse patterns. Side symmetry in branching was seen in four (6.25%). These are important anatomical considerations during placement of reconstructive plates for mandibular trauma and administration of mental nerve blocks.
A Novel Quantitative Method for Evaluating Surgical Outcomes in Craniosynostosis: Pilot Analysis for Metopic Synostosis
Authors: Weathers William M. , Khechoyan David , Wolfswinkel Erik M. , Mohan Kriti , Nagy Andrew , Bollo Robert J. , Buchanan Edward P. , Hollier Larry H.
Published: February 2014

Objective assessment of head shape has been an elusive goal in the management of craniosynostosis patients. Clinical judgment, craniometric indices, and computed tomography scans are the primary means through which a surgeon assesses this patient population. The purpose of this study was to examine and discuss the utility of the STARscanner for evaluation of surgical outcomes in metopic synostosis patients. A retrospective chart review of patients with metopic synostosis who underwent fronto-orbital advancement with pre- and postoperative STARscanner imaging at Texas Children's Hospital was performed. Two patients were identified and evaluation and discussion of the data produced by the STARscanner was undertaken. A novel symmetry index created by the authors, called the anterior–posterior volume ratio (APVR), was discussed for use in metopic synostosis patients. The postoperative growth metrics demonstrated an interval increase compared with the preoperative data. The anterior symmetry ratio, posterior symmetry ratio, overall symmetry ratio, cranial vault volumes, cranial vault asymmetry index, and cephalic ratio were not found to be useful in evaluating resolution of dysmorphology after fronto-orbital advancement in metopic synostosis. The APVR does not characterize dysmorphology, but may help show degree of expansion of the anterior cranial vault after fronto-orbital advancement. The STARscanner imaging device does not appear to have significant utility in characterizing head shape for surgical outcomes assessment in metopic synostosis. The minor utility of this device may be that it is a safe and fast way to derive growth parameters for both short-term and long-term follow-up of cranial vault remodeling.
Myositis Ossificans of the Left Medial Pterygoid Muscle: Case Report and Review of the Literature of Myositis Ossificans of Masticatory Muscles
Authors: Boffano Paolo , Zavattero Emanuele , Bosco Giovanni , Berrone Sid
Published: February 2014

Myositis ossificans is a disease that is characterized by nonneoplastic, heterotopic bone formation within a muscle. Myositis ossificans traumatica, also called myositis ossificans circumscripta, is a disease in which muscles are ossified presumably following acute trauma, burns, surgical manipulation, or repeated injury. It is often remitted after surgical excision though some patients have repeated recurrences. Myositis ossificans traumatica of masticatory muscles is not frequently reported in the literature, with the most common clinical finding being a progressive limitation of motion in the mandible. The aim of this article is to present and discuss a case of myositis ossificans traumatica of the left medial pterygoid muscle and to review the literature of myositis ossificans of the masticatory muscles.
Use of a Three-Dimensional Model to Optimize a MEDPOR Implant for Delayed Reconstruction of a Suprastructure Maxillectomy Defect
Authors: Echo Anthony , Wolfswinkel Erik M. , Weathers William , McKnight Aisha , Izaddoost Shayan
Published: February 2014

The use of a three-dimensional (3-D) model has been well described for craniomaxillofacial reconstruction, especially with the preoperative planning of free fibula flaps. This article reports the application of an innovative 3-D model approach for the calculation of the exact contours, angles, length, and general morphology of a prefabricated MEDPOR 2/3 orbital implant for reconstruction of a suprastructure maxillectomy defect. The 3-D model allowed intraoperative modification of the MEDPOR implant which decreased the risk of iatrogenic harm, contamination while also improving aesthetic results and function. With the aid of preoperative 3-D models, porous polypropylene facial implants can be contoured efficiently intraoperatively to precisely reconstruct complex craniomaxillofacial defects.
Treatment of Edentulous Mandibular Fractures with Rigid Internal Fixation: Case Series and Literature Review
Authors: Franciosi Edgardo , Mazzaro Eduardo , Larranaga Juan , Rios Alfredo , Picco Pedro , Figari Marcelo
Published: February 2014

The aim of the study is to analyze the effectiveness of rigid internal fixation (RIF) for treating edentulous mandibular fractures. Because of the low incidence of fractures in edentulous mandible, there is no consensus of the optimal treatment for it. This study included all edentulous patients with mandibular fracture diagnosis, who were treated with internal fixation at the Hospital Italiano de Buenos Aires from November 1991 to July 2011. Data such as age, gender, etiology and location of fracture, surgical approach, type of osteosynthesis used, and postoperative complications were analyzed. A total of 18 patients, 76.2 years mean age, 12 females (66.6%), presented a total of 35 mandibular fractures. The mandibular body was the most common localization of the fractures. Twenty-five fractures received surgical treatment with RIF, mainly approached extraorally. Reconstruction plates were the most common type of fixation used. Fracture reduction was considered satisfactory in 96.5%, with 22.2% of complications and 11.1% of reoperations needed. Open reduction and RIF demonstrated to be a reliable method for treating edentulous mandibular fractures. Nevertheless, there is lack of high-level recommendation publication to support this.
Local Foreign-Body Reaction to Commercial Biodegradable Implants: An in Vivo Animal Study
Authors: Xue Amy S. , Koshy John C. , Weathers William M. , Wolfswinkel Erik M. , Kaufman Yoav , Sharabi Safa E. , Brown Rodger H. , Hicks M.John , Hollier Larry H.
Published: February 2014

Biodegradable plates have been used extensively in fracture fixation since the 1960s. They rarely cause stress-protection atrophy or problems requiring secondary plate removal, common complications seen with metallic plates. However, aseptic foreign-body reactions have been reported, sometimes years after the original implantation. Both inadequate polymer degradation and debris accumulation have been implicated as causes. The current generation of commercial biodegradable plates is formulated to minimize this complication by altering the ratio of polylactic and polyglycolic acids. This in vivo study compares the degree of local foreign-body reaction of two commercially available resorbable plates in rabbits. Two types of biodegradable plates were examined: poly(D/L)lactide acid (PDLLA) and polylactide-co-glycolide acid (PLGA). Each plate was placed into a periosteal pericalvarial pocket created beneath the anterior or posterior scalp of a rabbit. Humane killing occurred at 3, 6, and 12 months postoperatively. Foreign-body reaction was evaluated histologically. The PDLLA plates demonstrated marked local foreign-body reactions within the implant capsule as early as 3 months after implantation, with presence of inflammatory cells and granulomatous giant cells in close association with the implant material. All local foreign-body reactions were subclinical with no corresponding tissue swelling requiring drainage. PLGA plates did not demonstrate any signs of inflammatory reactions. In addition, the PLGA plates did not appear to resorb or integrate at 12 months. Neither PDLLA nor PLGA plates demonstrated inflammation of the soft tissue or adjacent bone outside the implant capsule. In our study, the PDLLA plates demonstrated histological evidence of foreign-body reaction that is confined within the implant capsule, which was not seen with the PLGA plates. This finding may be attributable to the lack of significant resorption seen in the PLGA plates. Both PDLLA and PLGA plates were biocompatible with the rabbit tissue environment and should be considered for continued use in craniofacial, maxillofacial, and orthopedic reconstruction.
A Simple Method for the Repair of Frontal Sinus Fracture: The Bone Mesh Pull-Up Technique
Authors: Robiony Massimo , Della Pietra Lorenzo , Bertossi Dario , Albanese Massimo , Fresku Arsa
Published: February 2014

Accurate reduction and stable fixation are important in the treatment of frontal sinus fracture. In this article, we introduce a rapid and simple method for the treatment of frontal fractures and restoration of normal forehead contour, named the “bone mesh pull-up technique” (BMPUT). We describe our experience with this technique in frontal trauma cases, with emphasis on the technical aspects and clinical results of this simple method. Postoperative computed tomography scans showed adequate reduction of displaced bone fragments in all cases. Esthetic results were satisfactory and no complications related to this procedure, such as uncontrollable sinus bleeding, infection, and posterior table and brain injuries, were observed. Follow-ups ranged from 1 to 24 months, with an average of 12 months. Contour deformities were effectively restored and cosmetic results were very good. The BMPUT is a safe procedure that can be performed with minimal morbidity and offers, good access, and excellent esthetic results.
Rapid Prototyping Technology in Orbital Floor Reconstruction: Application in Three Patients
Authors: Lim Christopher G. T. , Campbell Duncan I. , Clucas Don M.
Published: February 2014

Rapid prototyping entails the fabrication of three-dimensional anatomical models which provide an accurate and cost-effective method to visualize complex anatomical structures. Our unit has been using this to assist in the diagnosis, planning, and preoperative titanium plate adaptation for orbital reconstruction surgery following traumatic injury. The aim of this article is to demonstrate the potential clinical and cost-saving benefits of this technology.
Analyses of the plasma generated by laser irradiation on sputtered target for determination of the thickness used for plasma generation
Authors: Kumaki Masafumi , Ikeda Shunsuke , Fuwa Yasuhiro , Cinquegrani David , Sekine Megumi , Munemoto Naoya , Kanesue Takeshi , Okamura Masahiro , Washio Masakazu
Published: February 2014

In Brookhaven National Laboratory, laser ion source has been developed to provide heavy ion beams by using plasma generation with 1064 nm Nd:YAG laser irradiation onto solid targets. The laser energy is transferred to the target material and creates a crater on the surface. However, only the partial material can be turned into plasma state and the other portion is considered to be just vaporized. Since heat propagation in the target material requires more than typical laser irradiation period, which is typically several ns, only the certain depth of the layers may contribute to form the plasma. As a result, the depth is more than 500 nm because the base material Al ions were detected. On the other hand, the result of comparing each carbon thickness case suggests that the surface carbon layer is not contributed to generate plasma.
Investigation of TiOx barriers for their use in hybrid Josephson and tunneling junctions based on pnictide thin films
Authors: Döring S. , Monecke M. , Schmidt S. , Schmidl F. , Tympel V. , Engelmann J. , Kurth F. , Iida K. , Haindl S. , Mönch I. , Holzapfel B. , Seidel P.
Published: February 2014

We tested oxidized titanium layers as barriers for hybrid Josephson junctions with high IcRn-products and for the preparation of junctions for tunneling spectroscopy. For that we firstly prepared junctions with conventional superconductor electrodes, such as lead and niobium, respectively. By tuning the barrier thickness, we were able to change the junction's behavior from a Josephson junction to tunnel-like behavior applicable for quasi-particle spectroscopy. Subsequently, we transferred the technology to junctions using Co-doped BaFe2As2 thin films prepared by pulsed laser deposition as base electrode and evaporated Pb as counter electrode. For barriers with a thickness of 1.5 nm, we observe clear Josephson effects with IcRn≈90 μV at 4.2 K. These junctions behave SNS'-like (SNS: superconductor-normal conductor-superconductor) and are dominated by Andreev reflection transport mechanism. For junctions with barrier thickness of 2.0 nm and higher, no Josephson but SIS'- (SIS: superconductor-insulator-superconductor) or SINS'-like (SINS: superconductor-normal conductor-insulator-superconductor) behavior with a tunnel-like conductance spectrum was observed.
Frequency dependence of the characteristic temperatures in PbSc0.5Ta0.36Nb0.14O3 relaxor ferroelectrics crystals seen via acoustic emission
Authors: Dul'kin E. , Mihailova B. , Gospodinov M. , Roth M.
Published: February 2014

PbSc0.5Ta0.36Nb0.14O3 relaxor ferroelectrics crystals were investigated in a wide temperature range of 200–700 K using acoustic emission. The intermediate temperature T* as well as the Burns temperature Td were successfully detected at 480 K and 581 K, respectively. Another acoustic emission burst was detected at Tnl ∼ 211 K, which is below the temperature of the dielectric-permittivity maximum Tm ∼ 257 K but it is accompanied by a slight anomaly in the dielectric permittivity. Tnl is attributed to the low-temperature boundary of an incommensurately modulated antiferroelectric phase transition taking place over a temperature range. All characteristic temperatures exhibit frequency dispersion in the range of 0.1–10 kHz, which is considerably stronger for T* and Td than for Tm and Tnl. In addition, Tnl depends linearly on frequency, whereas both T* and Td resemble the non-linear frequency dependence of Tm typical of relaxors. The nature of the frequency dispersion of T* and Td is discussed from the viewpoint of complex behavior of low-energy polar modes intrinsic of relaxor ferroelectrics.
Nuclear astrophysics in the laboratory and in the universe
Authors: Champagne A. E. , Iliadis C. , Longland R.
Published: February 2014

Nuclear processes drive stellar evolution and so nuclear physics, stellar models and observations together allow us to describe the inner workings of stars and their life stories. This Information on nuclear reaction rates and nuclear properties are critical ingredients in addressing most questions in astrophysics and often the nuclear database is incomplete or lacking the needed precision. Direct measurements of astrophysically-interesting reactions are necessary and the experimental focus is on improving both sensitivity and precision. In the following, we review recent results and approaches taken at the Laboratory for Experimental Nuclear Astrophysics (LENA, http://research.physics.unc.edu/project/nuclearastro/Welcome.html).
Size-dependent training effect in exchange coupled NiFe2O4/NiO nanogranular systems
Authors: Tian Zhaoming , Zhu Changming , Liu Yong , Shi Jing , Ouyang Zhongwen , Xia Zhengcai , Du Guihuan , Yuan Songliu
Published: February 2014

The particle size dependent training effect has been investigated on the exchange coupled NiFe2O4/NiO nanogranular systems, with average particle size (DNFO) of NiFe2O4 ranging from ∼3 nm to ∼55 nm. For all samples, analysis of the field cycles (n) dependence on exchange bias fields (HEB) suggests the existence of two distinct forms of training mechanism during training procedure. One is related to an athermal contribution leading to the abrupt single cycle training, the other is the conventional thermal activation mechanism responsible for the gradual reduction of HEB during the subsequent cycles. With the increase of particle size, the relative change of HEB and enhanced coercivity (△HC) after training display a nonmonotonic size-scaling behavior and reaches the maxima for DNFO ∼ 22 nm. In this system, this largest reduction reveals the weakest dynamic stability of the interfacial exchange coupling energy during field cycle process. Moreover, different decay rate of HEB and ΔHC with field cycles are observed supporting the dual behavior of the interfacial uncompensated spins. The interfacial frozen spins are suggested to account for the appearance of HEB, while the rotatable spins are linked to the ΔHC.
Effect of chemical substitutions on photo-switching properties of 3-hydroxy-picolinic acid studied by ab initio methods
Authors: Rode Michał F. , Sobolewski Andrzej L.
Published: February 2014

Effect of chemical substitutions to the molecular structure of 3-hydroxy-picolinic acid on photo-switching properties of the system operating on excited-state intramolecular double proton transfer (d-ESIPT) process [M. F. Rode and A. L. Sobolewski, Chem. Phys. 409, 41 (2012)] was studied with the aid of electronic structure theory methods. It was shown that simultaneous application of electron-donating and electron-withdrawing substitutions at certain positions of the molecular frame increases the height of the S0-state tautomerization barrier (ensuring thermal stability of isomers) and facilitates a barrierless access to the S1/S0 conical intersection from the Franck-Condon region of the S1 potential-energy surface. Results of study point to the conclusion that the most challenging issue for practical design of a fast molecular photoswitch based on d-ESIPT phenomenon are to ensure a selectivity of optical excitation of a given tautomeric form of the system.
Rationalization of the Hubbard U parameter in CeOx from first principles: Unveiling the role of local structure in screening
Authors: Lu Deyu , Liu Ping
Published: February 2014

The density functional theory (DFT)+U method has been widely employed in theoretical studies on various ceria systems to correct the delocalization bias in local and semi-local DFT functionals with moderate computational cost. We present a systematic and quantitative study, aiming to gain better understanding of the dependence of Hubbard U on the local atomic arrangement. To rationalize the Hubbard U of Ce 4f, we employed the first principles linear response method to compute Hubbard U for Ce in ceria clusters, bulks, and surfaces. We found that the Hubbard U varies in a wide range from 4.3 eV to 6.7 eV, and exhibits a strong correlation with the Ce coordination number and Ce–O bond lengths, rather than the Ce 4f valence state. The variation of the Hubbard U can be explained by the changes in the strength of local screening due to O → Ce intersite transitions.
Exchange integrals in magnetoelectric hexagonal ferrite (SrCo2Ti2Fe8O19): A density functional study
Authors: Feng Min , Shao Bin , Lu Yuan , Zuo Xu
Published: February 2014

The exchange integrals in magnetoelectric hexagonal ferrite SrCo2Ti2Fe8O19 have been calculated by using density functional theory. To get 10 inter-sublattice and 3 intra-sublattice exchange integrals, the electronic structures and total energies of 20 spin arrangements have been calculated with General Gradient Approximation (GGA) + U method. The dependence of exchange integrals on U has been studied. The comparison between the exchange integrals in SrFe12O19 and those in SrCo2Ti2Fe8O19 shows that substitution of Co and Ti decreases the most interactions involving the 12 k sites. The investigation based on our exchange integrals indicates that magnetic interaction between R and S blocks reduces significantly in SrCo2Ti2Fe8O19.
Modeling the construction of polymeric adsorbent media: Effects of counter-ions on ligand immobilization and pore structure
Authors: Riccardi Enrico , Wang Jee-Ching , Liapis Athanasios I.
Published: February 2014

Molecular dynamics modeling and simulations are employed to study the effects of counter-ions on the dynamic spatial density distribution and total loading of immobilized ligands as well as on the pore structure of the resultant ion exchange chromatography adsorbent media. The results show that the porous adsorbent media formed by polymeric chain molecules involve transport mechanisms and steric resistances which cause the charged ligands and counter-ions not to follow stoichiometric distributions so that (i) a gradient in the local nonelectroneutrality occurs, (ii) non-uniform spatial density distributions of immobilized ligands and counter-ions are formed, and (iii) clouds of counter-ions outside the porous structure could be formed. The magnitude of these counter-ion effects depends on several characteristics associated with the size, structure, and valence of the counter-ions. Small spherical counter-ions with large valence encounter the least resistance to enter a porous structure and their effects result in the formation of small gradients in the local nonelectroneutrality, higher ligand loadings, and more uniform spatial density distributions of immobilized ligands, while the formation of exterior counter-ion clouds by these types of counter-ions is minimized. Counter-ions with lower valence charges, significantly larger sizes, and elongated shapes, encounter substantially greater steric resistances in entering a porous structure and lead to the formation of larger gradients in the local nonelectroneutrality, lower ligand loadings, and less uniform spatial density distributions of immobilized ligands, as well as substantial in size exterior counter-ion clouds. The effects of lower counter-ion valence on pore structure, local nonelectroneutrality, spatial ligand density distribution, and exterior counter-ion cloud formation are further enhanced by the increased size and structure of the counter-ion. Thus, the design, construction, and functionality of polymeric porous adsorbent media will significantly depend, for a given desirable ligand to be immobilized and represent the adsorption active sites, on the type of counter-ion that is used during the ligand immobilization process. Therefore, the molecular dynamics modeling and simulation approach presented in this work could contribute positively by representing an engineering science methodology to the design and construction of polymeric porous adsorbent media which could provide high intraparticle mass transfer and adsorption rates for the adsorbate biomolecules of interest which are desired to be separated by an adsorption process.
Dynamics of polymers: A mean-field theory
Authors: Fredrickson Glenn H. , Orland Henri
Published: February 2014

We derive a general mean-field theory of inhomogeneous polymer dynamics; a theory whose form has been speculated and widely applied, but not heretofore derived. Our approach involves a functional integral representation of a Martin-Siggia-Rose (MSR) type description of the exact many-chain dynamics. A saddle point approximation to the generating functional, involving conditions where the MSR action is stationary with respect to a collective density field ρ and a conjugate MSR response field ϕ, produces the desired dynamical mean-field theory. Besides clarifying the proper structure of mean-field theory out of equilibrium, our results have implications for numerical studies of polymer dynamics involving hybrid particle-field simulation techniques such as the single-chain in mean-field method.
A stochastic model for kinesin bidirectional stepping
Authors: Yao Xiaojun , Zheng Yujun
Published: February 2014

In this paper, a hand-over-hand stochastic model for the dynamics of the conventional kinesin is constructed. In the model, both forward and backward motions are taken into consideration. First passage time distributions, average velocities, dwell times, and forward/backward step ratios are investigated based on the model. A good agreement between the results of the model and experimental data is achieved under a variety of external loads.
Mass effect on the Soret coefficient in n-alkane mixtures
Authors: Alonso de Mezquia David , Mounir Bou-Ali M. , Madariaga J. Antonio , Santamaría Carlos
Published: February 2014

We have determined the Soret coefficient of different equimolar and non equimolar n-alkane mixtures from measurements of the molecular diffusion and thermal diffusion coefficients. It is shown that equimolar mixtures behave as isotopic-like mixtures in which only the mass effect contributes to the Soret effect. In non equimolar mixtures, a small linear dependence with the molar fraction is observed. Finally, we have obtained a new correlation, which allows the determination of the Soret coefficient of n-alkane mixtures using the data of viscosity, the thermal expansion coefficient of the pure components, and the density of the equimolar mixture.
Hyperspectral imaging with in-line interferometric femtosecond stimulated Raman scattering spectroscopy
Authors: Dobner Sven , Fallnich Carsten
Published: February 2014

We present the hyperspectral imaging capabilities of in-line interferometric femtosecond stimulated Raman scattering. The beneficial features of this method, namely, the improved signal-to-background ratio compared to other applicable broadband stimulated Raman scattering methods and the simple experimental implementation, allow for a rather fast acquisition of three-dimensional raster-scanned hyperspectral data-sets, which is shown for PMMA beads and a lipid droplet in water as a demonstration. A subsequent application of a principle component analysis displays the chemical selectivity of the method.
Towards a systematic way to correct density functional approximations
Authors: Savin Andreas
Published: February 2014

In order to simulate the exact universal density functional, approximations are nowadays constructed by permitting more flexibility in its ansatz. In view of the difficulty of defining a systematically improvable form for it, this paper argues that an alternative way could be considered. It falls within the class of hybrid functionals with multi-determinant wave functions. The parameter controlling the hybridization is considered as variable. The invariance of the exact result with respect to changes in this variable is used to introduce information about the system under consideration, and to correct the density functional result. The construction considered in this paper accelerates convergence from the model system to the physical one, in the vicinity of the latter. The method, at the present level of implementation, should be seen as a starting point for further development, and not necessarily as a computationally advantageous tool.
A self-interaction-free local hybrid functional: Accurate binding energies vis-à-vis accurate ionization potentials from Kohn-Sham eigenvalues
Authors: Schmidt Tobias , Kraisler Eli , Makmal Adi , Kronik Leeor , Kümmel Stephan
Published: February 2014

We present and test a new approximation for the exchange-correlation (xc) energy of Kohn-Sham density functional theory. It combines exact exchange with a compatible non-local correlation functional. The functional is by construction free of one-electron self-interaction, respects constraints derived from uniform coordinate scaling, and has the correct asymptotic behavior of the xc energy density. It contains one parameter that is not determined ab initio. We investigate whether it is possible to construct a functional that yields accurate binding energies and affords other advantages, specifically Kohn-Sham eigenvalues that reliably reflect ionization potentials. Tests for a set of atoms and small molecules show that within our local-hybrid form accurate binding energies can be achieved by proper optimization of the free parameter in our functional, along with an improvement in dissociation energy curves and in Kohn-Sham eigenvalues. However, the correspondence of the latter to experimental ionization potentials is not yet satisfactory, and if we choose to optimize their prediction, a rather different value of the functional's parameter is obtained. We put this finding in a larger context by discussing similar observations for other functionals and possible directions for further functional development that our findings suggest.
The effect of film tensile stress on crystallite nucleation and growth in thermally annealed a-Si:H
Authors: Mahan A. H. , Dabney M. S. , Molina Piper D. , Nemeth W.
Published: February 2014

The influence of stress in thin films appears to be a widespread issue when such films are thermally annealed to facilitate crystallite nucleation and growth. It is therefore of interest to examine on a fundamental level how stress influences crystallite nucleation and growth in a thermally annealed thin film system that has been extensively studied and well characterized. This article reports crystallite nucleation rates, growth rates and activation energies for nucleation and growth in different spatial regions of a thermally annealed a-Si:H film. The rates far from a cleaved film edge are representative of a film region that is under high tensile stress, while rates near a cleaved film edge are representative of a film region that has undergone stress relief. The existence of or reduction in film stress is supported by μ-Raman measurements. It is shown that film stress increases the film nucleation rate and decreases the crystallite growth rate, resulting in significantly smaller crystallite sizes in the fully crystallized stressed film areas compared to those observed in the stress relieved areas. By combining the activation energy data for nucleation and growth, it is shown how film stress affects two fundamental structural parameters that control crystallization, the height of the amorphous-crystalline energy barrier and the critical crystallite size.
Channel drop filters in woodpile-heterostructures
Authors: Feng Zhifang , Zhang Dandan , Yasin Akhtar Raja M.
Published: February 2014

Channel drop-filter is essential building blocks of transceivers that are the workhorse of Gbps communication and enable the emerging 100 Gb/s technology. Using finite difference time domain method, heterostructures based channel drop filter in microwave region involving resonant system (in woodpile structure) are designed, analyzed, and simulated. Our simulations using hetero-woodpile-structures show that the resonant modes can be effectively adjusted in various ways, such as only changing the distance of two cavities or changing the lattice constants in the core woodpile. When bus/drop waveguides and resonant systems are located in different layers, we find that there is a resonant band.
Effect of annealing on the temperature dependence of inelastic tunneling contributions vis-à-vis tunneling magnetoresistance and barrier parameters in CoFe/MgO/NiFe magnetic tunnel junctions
Authors: Bhusan Singh Braj , Chaudhary Sujeet
Published: February 2014

The effect of annealing on the changes in the inelastic tunneling contributions in tunneling conductance of ion beam sputtered CoFe/MgO/NiFe magnetic tunnel junctions (MTJs) is investigated. The inelastic contributions are evaluated using hopping conduction model of Glazman and Matveev in the temperature range of 25–300 K. The hopping through number of series of localized states present in the barrier due to structural defects increases from 9 (in as deposited MTJ) to 18 after annealing (at 200 °C/1 h); although no changes in the interface roughness of CoFe-MgO and MgO-NiFe interfaces are observed as revealed by the x-ray reflectance studies on planar MTJs. The bias dependence of tunneling magnetoresistance (TMR) at 25 K is found to get improved after annealing as revealed by the value V1/2 (the bias value at which the TMR reaches to half of its value at nearly zero bias); which is 78 mV (in MTJ annealed at 200 °C/1 h) 2.5 times the value of 33 mV (in as deposited MTJ). At 25 K the inelastic tunneling spectra revealed the presence of zero bias anomaly and magnon excitations in the range of 10–15 mV. While the barrier height exhibited a strong temperature dependence with nearly 100% increase from the value at 300 K to 25 K, the temperature dependence of TMR becomes steep after annealing.
Structural and magnetic properties of Ti4+/Co2+ co-substituted cobalt ferrite
Authors: Nlebedim I. C. , Dennis K. W. , McCallum R. W. , Jiles D. C.
Published: February 2014

The variations in the structural magnetic properties of cobalt ferrite due to Ti4+/Co2+ co-substitution for 2Fe3+ are presented. The non-linear relation in the variation of the lattice parameter agrees with a previous study on cation distribution, which showed that the rate of substitution of cations into the A-sites and B-sites varies with Ti-concentration. Such variation in the rate of substitution into the cation sites was also observed in the magnetization, coercive field, and susceptibility data. The coercive field and differential susceptibility are inversely related. Although the coercive field of the Ti-substituted cobalt ferrite generally decreased compared to the un-substituted cobalt ferrite, magnetic susceptibility was higher at higher Ti-concentrations.
Effective three-dimensional superhydrophobic aerogel-coated channel for high efficiency water-droplet transport
Authors: Kim Aeree , Kim Hyungmo , Lee Chan , Kim Joonwon
Published: February 2014

Three-dimensional superhydrophobic surfaces have been used effectively to optimize droplet transport efficiency in diverse fluidic systems. However, the fabrication methods for superhydrophobic surfaces applicable to fluidic devices usually involve complicated process. Herein, we report a simple but effective method of fabricating a superhydrophobic surface using organically modified silica aerogel. Superhydrophobic aerogel thin film having highly porous micro/nanostructured surface with methyl groups was realized inside a 3D channel by coating it. To demonstrate that the aerogel-coated surface effectively facilitates movement of water droplets, the droplet-based flow characteristics regarding the triple line were conducted.
Giant electrocaloric effect in asymmetric ferroelectric tunnel junctions at room temperature
Authors: Liu Yang , Infante Ingrid C. , Lou Xiaojie , Dkhil Brahim
Published: February 2014

Room-temperature electrocaloric properties of Pt/BaTiO3/SrRuO3 ferroelectric tunnel junctions (FTJs) are studied by using a multiscale thermodynamic model. It is found that there is a divergence in the adiabatic temperature change ΔT for the two opposite polarization orientations. This difference under a typical writing voltage of 3 V can reach over 1 K as the barrier thickness decreases. Thanks to the ultrahigh external stimulus, a giant electrocaloric effect (1.53 K/V) with ΔT being over 4.5 K can be achieved at room temperature, which demonstrates the perspective of FTJs as a promising solid-state refrigeration.
Diffusion injected multi-quantum well light-emitting diode structure
Authors: Riuttanen L. , Kivisaari P. , Nykänen H. , Svensk O. , Suihkonen S. , Oksanen J. , Tulkki J. , Sopanen M.
Published: February 2014

The attention towards light-emitting diode (LED) structures based on nanowires, surface plasmon coupled LEDs, and large-area high-power LEDs has been increasing for their potential in increasing the optical output power and efficiency of LEDs. In this work we demonstrate an alternative way to inject charge carriers into the active region of an LED, which is based on completely different current transport mechanism compared to conventional current injection approaches. The demonstrated structure is expected to help overcoming some of the challenges related to current injection with conventional structures. A functioning III-nitride diffusion injected light-emitting diode structure, in which the light-emitting active region is located outside the pn-junction, is realized and characterized. In this device design, the charge carriers are injected into the active region by bipolar diffusion, which could also be utilized to excite otherwise challenging to realize light-emitting structures.
Measurement of the Clausius-Mossotti factor of generalized dielectrophoresis
Authors: Lo Y. J. , Lin Y. Y. , Lei U. , Wu M. S. , Yang P. C.
Published: February 2014

The force and torque of generalized dielectrophoresis, including conventional dielectrophoresis, electrorotation, and travelling wave dielectrophoresis, depend on the real and imaginary parts of the Clausius-Mossotti factor, Kr and Ki, which are unknown for biological cells, yet seldom measured in the literature. Methods are proposed and validated for measuring Kr and Ki of spherical particles, based on the force balances in an approximate radial and a travelling wave electric field, respectively, inside designed micro channels. The methods were demonstrated by measuring Kr and Ki spectra of three human cancer cells, which also provide quantitative results for cell manipulation and characterization.
Synthesis and magnetic properties of size-tunable MnxFe3−xO4 ferrite nanoclusters
Authors: Choi Young Soo , Young Yoon Ha , Sung Lee Ji , Hua Wu Jun , Keun Kim Young
Published: February 2014

We report the synthesis and characterization of size-tunable MnxFe3−xO4 ferrite nanoclusters of different sizes ranging from ∼30 to ∼120 nm. The nanoclusters synthesized via a hydrothermal polyol process show high crystallinity and a narrow size distribution. The magnetic properties of the nanoclusters demonstrate well-behaved magnetization and low-coercivity characteristics, ferrimagnetically at a large size, and superparamagnetically at a small size.
Wafer-scale solution-derived molecular gate dielectrics for low-voltage graphene electronics
Authors: Sangwan Vinod K. , Jariwala Deep , Everaerts Ken , McMorrow Julian J. , He Jianting , Grayson Matthew , Lauhon Lincoln J. , Marks Tobin J. , Hersam Mark C.
Published: February 2014

Graphene field-effect transistors are integrated with solution-processed multilayer hybrid organic-inorganic self-assembled nanodielectrics (SANDs). The resulting devices exhibit low-operating voltage (2 V), negligible hysteresis, current saturation with intrinsic gain >1.0 in vacuum (pressure < 2 × 10−5 Torr), and overall improved performance compared to control devices on conventional SiO2 gate dielectrics. Statistical analysis of the field-effect mobility and residual carrier concentration demonstrate high spatial uniformity of the dielectric interfacial properties and graphene transistor characteristics over full 3 in. wafers. This work thus establishes SANDs as an effective platform for large-area, high-performance graphene electronics.
Semicircular Rashba arc spin polarizer
Authors: Bin Siu Zhuo , Jalil Mansoor B. A. , Ghee Tan Seng
Published: February 2014

In this work, we study the generation of spin polarized currents using curved arcs of finite widths, in which the Rashba spin orbit interaction (RSOI) is present. Compared to the 1-dimensional RSOI arcs with zero widths studied previously, the finite width presents charge carriers with another degree of freedom along the transverse width of the arc, in addition to the longitudinal degree of freedom along the circumference of the arc. The asymmetry in the transverse direction due to the difference in the inner and outer radii of the arc breaks the antisymmetry of the longitudinal spin z current in a straight RSOI segment. This property can be exploited to generate spin z polarized current output from the RSOI arc by a spin unpolarized current input. The sign of the spin current can be manipulated by varying the arc dimensions.
Multifunctional polymer nanocomposites with uniaxially aligned liquid crystal polymer fibrils and graphene nanoplatelets
Authors: Leung S. N. , Khan M. O. , Naguib H. , Dawson F.
Published: February 2014

Polymer nanocomposites have actively been studied to replace metals in different emerging applications because of their light weight, superior manufacturability, and low processing cost. For example, extensive research efforts have been made to develop advanced thermally conductive polymer nanocomposites, with good processability, for heat management applications. In this study, liquid crystal polymer (LCP)-based nanocomposites have shown to possess much higher effective thermal conductivity (keff) (i.e., as high as 2.58 W/m K) than neat polymers (i.e., ∼0.2–0.4 W/m K). The fibrillation of LCP in LCP-graphene nanoplatelet (GNP) nanocomposites also demonstrated more pronounced increase in keff than that of polyphenylene sulfide (PPS)-GNP nanocomposites. Furthermore, ultra-drawing of LCP-GNP nanocomposite led to additional increase in the nanocomposite's keff because of the alignments of LCP fibrils and the embedded GNP. Experimental results also revealed that, unlike keff, the electrical conductivity (σ) of nanocomposites was unaffected by the types of polymer matrix. This exhibited that the keff and σ were promoted by different mechanisms, suggesting a potential route to tailor polymer nanocomposite's keff and σ independently.
Enhanced dielectric and ferroelectric properties in the artificial polymer multilayers
Authors: Zhao X. L. , Wang J. L. , Liu B. L. , Tian B. B. , Zou Y. H. , Sun S. , Sun J. L. , Meng X. J. , Chu J. H.
Published: February 2014

Multilayers consisting of alternating ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer and relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofloroethylene) (P(VDF-TrFE-CFE)) terpolymer with different periodicities in thickness were prepared. A superlattice-like structure is shown in the polymer multilayer as the periodic thickness is lower than a critical value. The dielectric constant of the multilayer with a small periodic thickness is two times higher than that of the P(VDF-TrFE) copolymer over a temperature range between 300 K and 350 K. The multilayer also shows a good ferroelectricity in the same temperature range. The enhanced electrical properties of the multilayers are due to the long-range ferroelectric coupling.
Stress dependent oxidation of sputtered niobium and effects on superconductivity
Authors: David Henry M. , Wolfley Steve , Monson Todd , Clark Blythe G. , Shaner Eric , Jarecki Robert
Published: February 2014

We report on the suppression of room temperature oxidation of DC sputtered niobium films and the effects upon the superconductive transition temperature, Tc. Niobium was sputter-deposited on silicon dioxide coated 150 mm wafers and permitted to oxidize at room temperature and pressure for up to two years. Resistivity and stress measurements indicate that tensile films greater than 400 MPa resist bulk oxidation with measurements using transmission electron microscope, electron dispersive X-ray spectroscopy, x-ray photoelectric spectroscopy, and secondary ion mass spectrometry confirming this result. Although a surface oxide, Nb2O5, consumed the top 6–10 nm, we measure less than 1 at. % oxygen and nitrogen in the bulk of the films after the oxidation period. Tc measurements using a SQUID magnetometer indicate that the tensile films maintained a Tc approaching the dirty superconductive limit of 8.4 K after two years of oxidation while maintaining room temperature sheet resistance. This work demonstrates that control over niobium film stress during deposition can prevent bulk oxidation by limiting the vertical grain boundaries ability to oxidize, prolonging the superconductive properties of sputtered niobium when exposed to atmosphere.
Tailoring exchange coupling and phase separation in Fe-Co-Mn nanocomposites
Authors: Jiménez-Villacorta F. , McDonald I. , Heiman D. , Lewis L. H.
Published: February 2014

An intriguing pathway for the realization of metallic, rare-earth-free magnets is described. Creation of a so-called “exchange-bias” permanent magnet is contemplated that mimics the microstructure of Alnico magnets, comprised of FeCo-based precipitates that are separated by a metallic antiferromagnetic phase that replaces non-magnetic NiAl-rich phase of alnico. In this manner, the existing shape anisotropy is augmented by exchange-bias anisotropy through interphase coupling, providing enhanced coercivities. As a proof of concept, nanocomposite alloys have been fabricated from rapidly solidified Fe34Co33Mn33 ribbons that phase separate into an antiferromagnetic Mn-rich γ-phase and ferromagnetic α-FeCo nanoprecipitates upon post-solidification processing. A progressive enhancement of coercivity, remanence, and exchange bias at T < TN in the ferromagnetic-antiferromagnetic nanocomposite is noted upon annealing, with maximum properties realized at Tann ≈ 673 K for 30 min. Optimization of the microstructure of these Fe-Co-Mn-based alloys is anticipated to be accompanied by improved magnetic performance that could contribute to the development of next-generation permanent magnets.