bluuebunny/crossref_metadata_2025 huggingface dataset:
Fibulo‐scapho‐lunate arthrodesis after resection of the distal radius for giant‐cell tumor of the bone
Authors: Jaminet Patrick , Rahmanian‐Schwarz Afshin , Pfau Mathias , Nusche Andreas , Schaller Hans‐Eberhard , Lotter Oliver
Published: March 2012

Background:

Giant‐cell tumors of the distal radius are rare. They have a high‐risk of local recurrence and a risk of pulmonary metastasis. Curettage alone or combined with adjunctive agents is often associated with local recurrence.

Methods:

Three patients with giant‐cell tumor of the distal radius are presented. All patients showed Campanacci grade 3 lesions. All patients underwent complete distal radius resection and reconstruction with a vascularized fibular graft distally fused with the scaphoid and the lunate, allowing midcarpal motion.

Results:

The follow‐up period ranged from 6 to 60 months. For all three patients, emotional acceptance was excellent. The postoperative motion of the wrist was good, with a range of motion of 30‐0‐30°, 40‐0‐0°, and 30‐0‐10° (extension–flexion). There was neither tumor recurrence nor pulmonary metastasis.

Conclusion:

Fibulo‐scapho‐lunate fusion is an elegant method of distal radius reconstruction with good functional outcome and low risk of pulmonary metastasis. © 2012 Wiley Periodicals, Inc. Microsurgery, 2012.
Patch‐averaged assumed strain finite elements for stress analysis
Authors: Castellazzi G. , Krysl P.
Published: March 2012

A finite element model for linear‐elastic small deformation problems is presented. The formulation is based on a weighted residual that requires a priori the satisfaction of the kinematic equation. In this approach, an averaged strain‐displacement matrix is constructed for each node of the mesh by defining an appropriate patch of elements, yielding a smooth representation of strain and stress fields. Connections with traditional and similar procedure are explored. Linear quadrilateral four‐node and linear hexahedral eight‐node elements are derived. Various numerical tests show the accuracy and convergence properties of the proposed elements in comparison with extant finite elements and analytic solutions. Specific examples are also included to illustrate the ability to resist numerical locking in the incompressible limit and insensitive response in the presence of shape distortion. Furthermore, the numerical inf‐sup test is applied to a selection of problems to show the stability of the present formulation. Copyright © 2012 John Wiley & Sons, Ltd.
Extruded foams from microbial poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) and its blends with cellulose acetate butyrate
Authors: Liao Qi , Tsui Amy , Billington Sarah , Frank Curtis W.
Published: March 2012

Extrusion foaming of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) and two blends of PHBV with cellulose acetate butyrate (CAB) were studied using an azodicarbonamide (AZ) blowing agent and a single‐screw extruder. The concentration of the blowing agent was systematically varied from 0 to 4.0 phr to achieve maximum density reduction reaching 41%, as well as to obtain information on the dependence of cell growth on blowing agent concentration. Extruded foams were characterized in terms of their bulk densities and cellular morphologies. Stereological and statistical methods permitted full characterization of the three‐dimensional cell size distributions, assessing the average cell diameters (ranging from 58 to 290 μm) and cell densities (ranging from 650 to 180,000 cm−3). The variation in cellular morphology among foams consisting of different polymer matrix or blowing agent concentration was compared. The results were analyzed by considering the influence of viscoelastic properties of the polymer matrix on the bubble growth during foaming. Significantly higher melt viscosity and elasticity and reduced gas solubility of the PHBV/CAB blends are believed to retard cell coalescence and collapse during foam expansion, resulting in more uniform cell size distribution and better homogeneity of cellular morphology. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Real‐time crystalline orientation measurements during low‐density polyethylene blown film extrusion using wide‐angle X‐ray diffraction
Authors: Gururajan Giriprasath , Ogale Amod A.
Published: March 2012

Real‐time wide‐angle X‐ray diffraction studies were successfully used to investigate the effect of film blowing process parameter on the crystalline orientation development during the blown film extrusion of low‐density polyethylene. Azimuthal distribution scans showed the evolution of crystalline orientation in the bubble from an isotropic state to an oriented state as inferred from (110) and (200) planes. These real‐time X‐ray diffraction measurements in a blown film line are consistent with prior observations using polarized Raman spectroscopy (Gururajan and Ogale, J. Raman Spectrosc.,
40, 212 (2009)) and small‐angle light scattering (Bullwinkel et al., Int. Polym. Proc., 16, 41 (2001)) that significant molecular orientation takes place past the frost‐line height, even after the blown film diameter is locked into place. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Characterization of the viscoelastic properties of poly(ε‐caprolactone)–hydroxyapatite microcomposite and nanocomposite scaffolds
Authors: Leung Linus H. , Naguib Hani E.
Published: March 2012

In bone tissue engineering, the mechanical properties of the scaffolds need to be sufficiently high to prevent material failure when bearing loads. To strengthen the scaffold, various composites have been proposed in the literature, including poly(ε‐caprolactone) with hydroxyapatite (HA). In this study, the processing of this composite using the gas foaming/salt leaching technique is examined. The control of scaffold properties by varying the processing parameters was first investigated. Then, the change in properties, with a focus on the viscoelastic properties, from the varying morphology was examined. Although an increase in scaffold density and pore size increased the scaffold modulus, it did not significantly affect the viscoelastic properties. Furthermore, the addition of HA decreased the scaffold modulus and increased the loss factor of the composite scaffolds. The more viscoelastic behavior is believed to be due to the more open structure that was created. When tested in a water bath to better simulate the physiological environment, the mechanical properties decreased by up to 85%, and the scaffolds also behaved more viscoelastically. The comparison of the scaffold properties shows the differing behavior of the scaffolds in dry and wet conditions. Hence, the environment of testing should be more carefully considered when designing experiments. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Effect of benzyl triethylammonium chloride on microstructure of bicomponent polymeric fibers during electrospinning
Authors: Lu Weili , Liu Xiwang , Zhao Shengling , Na Haining , Zhao Yunhui , Yuan Xiaoyan
Published: March 2012

Effect of benzyl triethylammonium chloride (BTEAC) on the microstructure of electrospun bicomponent fibers, i.e., polyvinylidene fluoride (PVDF)/polycarbonate (PC), polyacrylonitrile (PAN)/polyethylene glycol (PEG), and PAN/PVDF, was investigated in this article. The evolution of morphology and microstructure of the above bicomponent fibers were examined by scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy. The results showed that distinct core/shell structured fibers were successfully prepared from PVDF/PC and PAN/PVDF via introducing a small amount of BTEAC, whereas only cocontinuous structure was detected in the electrospun PAN/PEG fibers. This study could be an example of electrospun multipolymer dispersions influencing by an organic salt, and it could be extended to control the structure of carbon nanofibers via electrospinning. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Facile preparation of water‐dispersible graphene nanosheets by covalent functionalization with poly(3‐aminobenzene sulfonic acid)
Authors: Pham Tuan Anh , Kim Jong Su , Kim Don , Jeong Yeon Tae
Published: March 2012

The synthesis of water‐dispersilbe graphene nanosheets plays an important role in various practical applications. Herein, we have demonstrated an efficient method for the preparation of water‐dispersible graphene hybrid material from graphene oxide (GO) and a hydrophilic‐conducting polymer, namely, poly(3‐aminobenzene sulfonic acid) (PABS). First, the covalent functionalization process of GO with PABS was carried out via a simple amidation reaction between acyl chloride group located on GO surface and the amino group present in the polymer. Second, the GO‐polymer hybrid was chemically reduced into graphene‐polymer hybrid using sodium borohydride as a reducing agent. The resulting hybrid material was characterized using various analytical techniques. Electron microscopic studies were used to characterize the morphology and chemical structure of the resulting hybrids. Fourier transform infrared spectroscopy was used to investigate the initial changes in surface functionalities, while the thermal stability of hybrid material on heating was studied via thermogravimetric analysis. The digital images provided a vivid observation on the high‐dispersion stability of the hybrid material in distilled water. POLYM. ENG. SCI., 52:1854–1861, 2012. © 2012 Society of Plastics Engineers
Thermal, mechanical, and barrier properties of polyethylene terephthalate‐platelet nanocomposites prepared by in situ polymerization
Authors: Li Shigeng , Auddy Kausick , Barber Peter , Hansen Tara J. , Ma Jisheng , zur Loye Hans‐Conrad , Ploehn Harry J.
Published: March 2012

This study used in situ polymerization to prepare polyethylene terephthalate (PET) nanocomposites incorporating Ethoquad‐modified montmorillonite (eMMT), unmodified hectorite (HCT), or phenyl hectorite (phHCT) particles to study the impact of platelet surface chemistry and loading on thermal, mechanical, and gas barrier properties. eMMT platelets reduced the PET crystallization rate without altering the ultimate degree of crystallinity. In contrast, HCT and phHCT platelets accelerated the polymer's crystallization rate and increased its crystallinity. DMA results for thermally‐quenched samples showed that as T increased past glass transition temperature (Tg), HCT and phHCT nanocomposites (and control PET) manifested precipitous drops in G′ followed by increasing G′ due to cold crystallization; in contrast, eMMT nanocomposites had much higher G′ values around Tg. This provides direct evidence of eMMT reinforcement in thermally‐quenched eMMT nanocomposites. These results suggest that eMMT has a strong, favorable interaction with PET, possibly through Ethoquad‐PET entanglement. HCT and phHCT have a fundamentally different interaction with PET that increases crystallization rate and Tg by 11 to 17°C. Water barrier improvement in eMMT nanocomposites agrees with previously published oxygen barrier results and can be rationalized in terms of a tortuous path gas barrier model. POLYM. ENG. SCI., 52:1888–1902, 2012. © 2012 Society of Plastics Engineers
Surface modifications of polypropylene with nonylphenol ethoxylates melt additives
Authors: Datla V. , Shim E. , Pourdeyhimi B.
Published: March 2012

Nonylphenol ethoxylated (NPE) additives were melt blended in polypropylene (PP) films and characteristics of the modified films were investigated. It was found that melt blending of NPE additives improved hydrophilicity of PP films through additive surface segregation. Surface specific techniques, such as X‐ray photoelectron spectroscopy (XPS) and Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS) were used to study surface compositions of samples modified with NPE additives at different aging time after extrusion. We found that surface enrichment of additives lead to hydrophilic surfaces. Hydrophilic chain length in NPE affected surface composition and hydrophilicity of NPE containing PP polymer. The effect of water immersion and aging were also reported. POLYM. ENG. SCI., 52:1920–1927, 2012. © 2012 Society of Plastics Engineers
The protein gp74 from the bacteriophage HK97 functions as a HNH endonuclease
Authors: Moodley Serisha , Maxwell Karen L. , Kanelis Voula
Published: March 2012

The last gene in the genome of the bacteriophage HK97 encodes the protein gp74. We present data in this article that demonstrates, for the first time, that gp74 possesses HNH endonuclease activity. HNH endonucleases are small DNA binding and digestion proteins characterized by two His residues and an Asn residue. We demonstrate that gp74 cleaves lambda phage DNA at multiple sites and that gp74 requires divalent metals for its endonuclease activity. We also present intrinsic tryptophan fluorescence data that show direct binding of Ni2+ to gp74. The activity of gp74 in the presence of Ni2+ is significantly decreased below neutral pH, suggesting the presence of one or more His residues in metal binding and/or DNA digestion. Surprisingly, this pH‐dependence of activity is not seen with Zn2+, suggesting a different mode of binding of Zn2+ and Ni2+. This difference in activity may result from binding of a second Zn2+ ion by a putative zinc finger in gp74 in addition to binding of a Zn2+ ion by the HNH motif. These studies define the biochemical function of gp74 as an HNH endonuclease and provide a platform for determining the role of gp74 in life cycle of the bacteriophage HK97.
Manufacture and characterisation of thin flat and curved auxetic foam sheets
Authors: Alderson Kim , Alderson Andrew , Ravirala Naveen , Simkins Virginia , Davies Philip
Published: March 2012

A new method for the production of thin flat and curved auxetic foam sheets by uniaxial compression is reportted in this paper. Detailed optical microscopy and Poisson's ratio measurement by videoextensometry has revealed that the auxetic behaviour is due to a crumpling of the pores through the foam thickness, caused by a uniaxial compression of 40–60% in combination with shear for the curved foams. Poisson's ratio values of up to −3 have been recorded for the curved foams and −0.3 for the flat sheets.
Application of Statistical Techniques and Neural Networks in Condition‐Based Maintenance
Authors: Prajapati Ashok , Ganesan Subra
Published: March 2012

In this paper, we have evaluated five prediction approaches from two disciplines for condition‐based maintenance. It also includes a case study for vehicle tire pressure monitoring as an example application. Main focus of this paper is on two widely used areas in prediction: (i) statistics, (ii) neural networks. It is well known that these two areas have wide applications in forecasting. Statistical and neural network techniques are very powerful for predicting the future states based on current and previous states of the system or subsystem. Application of ARAR and Holt‐Winters (HW) in CBM has been presented from the statistics point of view. On the other hand, application of focused time delay, linear predictor, and backpropagation neural network has also been presented to prove the robustness of statistical approaches. Paper presents detailed comparative simulation study to show the suitability and feasibility of all the techniques. We assumed that the sensors are directly mounted on tires externally and report the current tire pressure to control or analysis. The control unit performs tire pressure analysis and reports the decision to operator or intended group about current pressure as well as the impending pressure conditions. Finally, investigation ends with conclusion that HW is best suited among these five approaches for tire pressure prediction and could be useful to design a CBM application for any system. Copyright © 2012 John Wiley & Sons, Ltd.
Reliability‐based Design for Damping Behavior of Inner Mass Single‐unit Impact Dampers
Authors: Afsharfard Aref , Kolahan Farhad
Published: March 2012

In this paper, the dynamic response of a vibratory system equipped with a single‐unit impact damper is analyzed. The reliability behavior of this system is investigated when the stress and strength are distributed lognormally. The standard deviation of lognormal stress is realistically calculated by applying external noise and an uncertainty parameter in the simulated model. Variations of the damping inclination and the reliability of the system, with respect to the coefficient of restitution, are obtained. Finally, damping inclination, safety factor and system reliability are presented in a user‐oriented diagram. Such reliable systems equipped with impact dampers can strongly suppress the undesired vibrations. Copyright © 2012 John Wiley & Sons, Ltd.
Adaptive Coding and Modulation‐enabled satellite triple play over DVB‐S2 (Digital Video Broadcasting ‐ Satellite ‐ Second Generation): a techno‐economic study
Authors: Anastasiadou N. , Gardikis G. , Nikiforiadis A. , Pangalos S.
Published: March 2012

This article looks at the techno‐economic perspectives of the use of DVB‐S2 (Digital Video Broadcasting ‐ Satellite ‐ Second Generation) and its unique feature, Adaptive Coding and Modulation (ACM) in the provision of satellite triple play. For this study, current market economic data were used, in conjunction with technical results derived within the European Union‐funded IST IMOSAN project. IMOSAN (Integrated Multi‐Layer Optimisation in DVB‐S2 Satellite Networks) succeeded in realising the provision of satellite triple play over an interactive DVB‐S2/DVB‐RCS (Return Channel via Satellite) platform. The ACM feature of DVB‐S2 was exploited, yielding increased spectrum efficiency and thus decreasing service cost. One‐user‐per‐terminal scenarios are examined, as well as terrestrial redistribution of satellite services to a group of users via WiMAX. Copyright © 2012 John Wiley & Sons, Ltd.
Toward early warning against Internet worms based on critical‐sized networks
Authors: Magkos Emmanouil , Avlonitis Markos , Kotzanikolaou Panayiotis , Stefanidakis Michalis
Published: March 2012

In this paper, we build on a recent worm propagation stochastic model, in which random effects during worm spreading were modeled by means of a stochastic differential equation. On the basis of this model, we introduce the notion of the critical size of a network, which is the least size of a network that needs to be monitored, in order to correctly project the behavior of a worm in substantially larger networks. We provide a method for the theoretical estimation of the critical size of a network in respect to a worm with specific characteristics. Our motivation is the requirement in real systems to balance the needs for accuracy (i.e., monitoring a network of a sufficient size in order to reduce false alarms) and performance (i.e., monitoring a small‐scale network to reduce complexity). In addition, we run simulation experiments in order to experimentally validate our arguments. Finally, based on notion of critical‐sized networks, we propose a logical framework for a distributed early warning system against unknown and fast‐spreading worms. In the proposed framework, propagation parameters of an early detected worm are estimated in real time by studying a critical‐sized network. In this way, security is enhanced as estimations generated by a critical‐sized network may help large‐scale networks to respond faster to new worm threats. Copyright © 2012 John Wiley & Sons, Ltd.
Study of dynamic stability of simply supported beams on Pasternak foundation considering the effect of first transition foundation parameter
Authors: Ratnam B.S. , Rao G.V. , Janardhana G.R.
Published: March 2012

The dynamic stability behavior of simply supported beams on the Pasternak foundation, with emphasis on the effect of the transition foundation parameter, subjected to a concentrated end axial periodic load, is presented in this paper. The energy method, using a single term exact trigonometric admissible function to represent the lateral deflection, is employed to obtain the dynamic instability regions. These regions are presented in the graphical form, for the first and second foundation parameters of the Pasternak foundation. The effect of the transition foundation parameter, which can be exactly evaluated for the simply supported beams on the Pasternak foundation, on the dynamic instability behavior of the simply supported beams, is investigated. The existence of the master dynamic instability curves is established in the present study by using the specific non‐dimensional parameters for the applied periodic load and its radian frequency.
Analytical solution of torsion vibration of a finite cylindrical cavity in a transversely isotropic half‐space
Authors: Eskandari‐Ghadi M. , Mahmoodian M. , Pak R.Y.S. , Ardeshir‐Behrestaghi A.
Published: March 2012

A transversely isotropic linear elastic half‐space with depth wise axis of material symmetry containing a cylindrical cavity of finite length is considered to be under the effect of a time‐harmonic torsion force applied on a ring at an arbitrary depth on the surface of the cylindrical cavity. With the aid of cosine transforms, the boundary value problem for the fundamental solution is reduced to a generalized Cauchy singular integral equation. The Cauchy integral equation involved in this paper is analytically investigated and the final equation is numerically solved with an in‐depth attention. Integral representation of the stress and displacement are obtained, and is shown that their degenerated form to the static problem of isotropic material is coincide with existing solutions in the literature. To investigate the effect of material anisotropy, the results are numerically evaluated and illustrated.
Metabolic flexibility of d-ribose producer strain of Bacillus pumilus under environmental perturbations
Authors: Srivastava Rajesh K , Maiti Soumen K , Das Debasish , Bapat Prashant M , Batta Kritika , Bhushan Mani , Wangikar Pramod P
Published: March 2012

The metabolic reaction rate vector is a bridge that links gene and protein expression alterations to the phenotypic endpoint. We present a simple approach for the estimation of flux distribution at key branch points in the metabolic network by using substrate uptake, metabolite secretion rate, and biomass growth rate for transketolase (tkt) deficient Bacillus pumilus ATCC 21951. We find that the glucose-6-phosphate (G6P) and pseudo catabolic/anabolic branch points are flexible in the d-ribose-producing tkt deficient strain of B. pumilus. The normalized flux through the pentose phosphate pathway (PPP) varied from 1.5 to 86 % under different growth conditions, thereby enabling substantial extracellular accumulation of d-ribose under certain conditions. Interestingly, the flux through PPP was affected by the extracellular phosphate concentration and dissolved oxygen concentration. This metabolic flexibility may have been the underlying reason for this strain being selected from thousands of others in a screening for d-ribose producers conducted in the 1970s.
Methods for analysis of the cancer microenvironment and their potential for disease prediction, monitoring and personalized treatments
Authors: Clausson Carl-Magnus , Grundberg Ida , Weibrecht Irene , Nilsson Mats , Söderberg Ola
Published: March 2012

A tumor does not consist of a homogenous population of cancer cells. Therefore, to understand cancer, the tumor microenvironment and the interplay between the different cell types present in the tumor has to be taken into account, and how this regulates the growth and survival of the cancer cells. To achieve a full picture of this complex interplay, analysis of tumor tissue should ideally be performed with cellular resolution, providing activity status of individual cells in this heterogeneous population of different cell-types. In addition, in situ analysis provides information on the architecture of the tissue wherein the cancer cells thrive, providing information of the identity of neighboring cells that can be used to understand cell-cell communication. Herein we describe how padlock probes and in situ PLA can be used for visualization of nucleic acids and protein activity, respectively, directly in tissue sections, and their potential future role in personalized medicine.
Parental psychological control and dysfunctional separation–individuation: A tale of two different dynamics
Authors: Kins Evie , Soenens Bart , Beyers Wim
Published: March 2012

This study examined associations between psychologically controlling parenting and two possible manifestations of problematic separation–individuation (i.e., dysfunctional dependence and dysfunctional independence). To explain these associations, it has been argued that psychological control is an inherently independence‐stifling parenting dimension that gives rise to a dysfunctional dependent orientation. In this study, it was argued that psychological control may relate to dysfunctional dependence and dysfunctional independence, depending on whether parents’ use of psychological control is driven by issues of interpersonal closeness (i.e., dependency‐oriented psychological control) or by issues of achievement (i.e., achievement‐oriented psychological control). A Belgian sample of 232 emerging adults, involved in the process of home leaving, and their parents completed self‐report questionnaires. Regression analyses indicated that domain‐specific expressions of psychological control were related differentially to dysfunctional dependent and dysfunctional independent manifestations of problematic separation–individuation. Emerging adults’ residential status did not moderate these associations. Implications and directions for future research are discussed.
The Cultural Divide in Europe: Migration, Multiculturalism, and Political Trust
Authors: McLaren Lauren M.
Published: March 2012

One of the defining features of modern states is their incorporation of notions of political and social community based on shared language, history, and myths. However, large numbers of citizens in modern states have come to believe their national communities are under threat from several modern forces, including immigration. Using the European Social Survey (2002–9), this article explores the extent to which perceived threats posed by large-scale immigration undermine national political communities by reducing trust in national politicians and political institutions. The findings indicate that even after controlling for other predictors of trust in the political system, concerns about the effect of immigration on the national community have an impact on trust in politics. Moreover, having a lengthy postwar history with mass immigration mediates this effect, while the potentially mobilizing effects of far-right parties on the relationship between concern about immigration and political distrust are somewhat limited.
Scott's Induced Subdivision Conjecture for Maximal Triangle-Free Graphs
Authors: BOUSQUET NICOLAS , THOMASSÉ STÉPHAN
Published: March 2012

Scott conjectured in [6] that the class of graphs with no induced subdivision of a given graph is χ-bounded. We verify his conjecture for maximal triangle-free graphs.
Transient severe aortic regurgitation and left ventricular dysfunction due to a stuck leaflet in a patient undergoing percutaneous transcatheter aortic valve implantation
Authors: Hamid Tahir , Hasan Ragheb , Mahadevan Vaikom S.
Published: March 2012

We report the case of a 78-year-old patient who underwent transcatheter aortic valve implantation. During the deployment, the leaflets of the implanted valve appeared to be stuck in calcium protruding from the native aortic leaflets, resulting in transient severe aortic regurgitation leading to cardiac arrest with successful cardiac resuscitation. Transient severe aortic regurgitation secondary to the mechanical failure of the deployed valve can lead to serious clinical consequences.
Calibration of Piezoelectric Positioning Actuators Using a Reference Voltage-to-Displacement Transducer Based on Quartz Tuning Forks
Authors: Castellanos-Gomez Andres , Arroyo Carlos R. , Agraït Nicolás , Rubio-Bollinger Gabino
Published: March 2012

We use a piezoelectric quartz tuning fork to calibrate the displacement of ceramic piezoelectric scanners that are widely employed in scanning probe microscopy. We measure the static piezoelectric response of a quartz tuning fork and find it to be highly linear, nonhysteretic and with negligible creep. These performance characteristics, close to those of an ideal transducer, make quartz transducers superior to ceramic piezoelectric actuators. Furthermore, quartz actuators in the form of a tuning fork have the advantage of yielding static displacements comparable to those of local probe microscope scanners. We use the static displacement of a quartz tuning fork as a reference to calibrate the three axis displacement of a ceramic piezoelectric scanner. Although this calibration technique is a nontraceable method, it can be more versatile than using calibration grids because it enables characterization of the linear and nonlinear response of a piezoelectric scanner in a broad range of displacements, spanning from a fraction of a nanometer to hundreds of nanometers. In addition, the creep and the speed dependent piezoelectric response of ceramic scanners can be studied in detail.
Alphavirus replicon vaccines
Authors: Vander Veen Ryan L. , Harris D. L. Hank , Kamrud Kurt I.
Published: March 2012

The alphavirus replicon technology has been utilized for many years to develop vaccines for both veterinary and human applications. Many developments have been made to the replicon platform recently, resulting in improved safety and efficacy of replicon particle (RP) vaccines. This review provides a broad overview of the replicon technology and safety features of the system and discusses the current literature on RP and replicon-based vaccines.
HiCIRF: A high‐fidelity HF channel simulation
Authors: Nickisch L. J. , St. John Gavin , Fridman Sergey V. , Hausman Mark A. , Coleman C. J.
Published: March 2012

A high‐fidelity HF channel simulation has been developed that is suitable for Over‐the‐Horizon Radar (OTHR) and HF communication system design studies and test planning. The simulation capability is called HiCIRF, for High‐frequency Channel Impulse Response Function. HiCIRF provides simulated HF signals corresponding to transmissions from individual transmitter array elements to individual receiver array elements for propagation through the naturally disturbed or undisturbed ionospheric channel. Both one‐way link geometries and two‐way radar geometries can be simulated. HiCIRF incorporates numerical ray tracing and stochastic signal structure computations to realistically simulate signal scatter by small‐scale ionization structure. Stochastic signal generation is employed to generate signal realizations that can be used for OTHR array design and advanced signal processing studies.
Wind‐induced reorganization of the Bering shelf circulation
Authors: Danielson S. , Hedstrom K. , Aagaard K. , Weingartner T. , Curchitser E.
Published: March 2012

We present a simple framework for considering the variability of the eastern Bering Sea shelf circulation as a response to changes in wind direction. Both observations and numerical integrations show that much of the shelf flow reverses between northwesterly and southeasterly winds. While southeasterly winds are less frequent, they are associated with large on‐shelf transport across most of the shelfbreak, and in October–April they are also accompanied by a reversal of the normally eastward flow near Cape Navarin. In contrast, northwesterly winds promote off‐shelf transport across most of the shelfbreak, along with increased eastward transport near Cape Navarin. The westward‐intensified flow in the Gulf of Anadyr adjusts to changes both in the flux across the long (∼1000 km) shelfbreak and in the Bering Strait throughflow. These results also hold under the more stratified summer conditions (May–September), but weaker summer winds drive smaller flows across the shelf break, and the majority of the on‐shelf transport is directly into the Gulf of Anadyr.
Involvement of TSSA (trypomastigote small surface antigen) in Trypanosoma cruzi invasion of mammalian cells
Authors: Cánepa Gaspar E. , Degese Maria Sol , Budu Alexandre , Garcia Celia R. S. , Buscaglia Carlos A.
Published: March 2012

TSSA (trypomastigote small surface antigen) is a polymorphic mucin-like molecule displayed on the surface of Trypanosoma cruzi trypomastigote forms. To evaluate its functional properties, we undertook comparative biochemical and genetic approaches on isoforms present in parasite stocks from extant evolutionary lineages (CL Brener and Sylvio X-10). We show that CL Brener TSSA, but not the Sylvio X-10 counterpart, exhibits dose-dependent and saturable binding towards non-macrophagic cell lines. This binding triggers Ca2+-based signalling responses in the target cell while providing an anchor for the invading parasite. Accordingly, exogenous addition of either TSSA-derived peptides or specific antibodies significantly inhibits invasion of CL Brener, but not Sylvio X-10, trypomastigotes. Non-infective epimastigote forms, which do not express detectable levels of TSSA, were stably transfected with TSSA cDNA from either parasite stock. Although both transfectants produced a surface-associated mucin-like TSSA product, epimastigotes expressing CL Brener TSSA showed a ~2-fold increase in their attachment to mammalian cells. Overall, these findings indicate that CL Brener TSSA functions as a parasite adhesin, engaging surface receptor(s) and inducing signalling pathways on the host cell as a prerequisite for parasite internalization. More importantly, the contrasting functional features of TSSA isoforms provide one appealing mechanism underlying the differential infectivity of T. cruzi stocks.
Self-similarity in (∂M/∂T)H curves for magnetocaloric materials with ferro-to-paramagnetic phase transitions
Authors: Jin Y. , Gu S. , Bennett L. H. , Della Torre E. , Provenzano V. , Zhao Q.
Published: March 2012

A temperature scaling methodology to obtain a self-similar field dependence (∂M/∂T)H curve for metamagnetic material exhibiting first-order ferro-to-paramagnetic transitions is presented. The methodology extends Franco’s transformation by (i) performing the scaling methodology on the (∂M/∂T)H curve instead of the ΔSM(T,H) curve and (ii) redefining the arbitrary temperature references, Tr1 and Tr2, used by Franco, by employing the physical constants TFM and TPM, which can be determined from the (∂2M/∂T2)H curves. (∂M/∂T)H of the metamagnetic material, Gd5Si2Ge2, exhibiting first-order ferro-to-paramagnetic transition is shown as an example. Applying the new modified Franco’s transformation, Gd5Si2Ge2’s (∂M/∂T)H curves collapse onto a self-similar curve with a low index of dispersion. The collapsed curve is asymmetrical with a negative skewness, which reflects the intrinsic transition differences in the mixed-state region.
Contact characterization by photoemission and device performance in P3HT based organic transistors
Authors: Scheinert S. , Grobosch M. , Paasch G. , Hörselmann I. , Knupfer M. , Bartsch J.
Published: March 2012

The operation of organic devices as organic field-effect transistors (OFET) depends critically on the contact between the organic layer and the material for source/drain electrodes. Small barriers for carrier injection are required for efficient operation. In order to support the understanding of organic devices, photoemission spectroscopy has been used to determine the properties of metal/organic interfaces. Values for the hole injection barrier determined in the last decade by different groups are frequently of the order of 0.5–1 eV. It is not clear whether barrier lowering due to the image charge is sufficient to make contacts with such barriers efficient for carrier injection. Indeed, no results have been reported where the preparation of the samples for the photoemission study and for the devices are the same. Here we present results of such an investigation for OFETs with gold source/drain contacts. The measured hole barrier at the gold contact of 0.6 eV results from the Au work function of 4.6 eV. Taking into account the dependencies of the mobility on the carrier concentration and on the field for the Gaussian density of states (DOS) of disordered organics, measured OFET current characteristics cannot be described well with such contacts but rather for work functions of 4.7 eV or larger. Considering the method in determining the barrier from photoemission data and the Gaussian DOS of the hopping transport states, we present a quantitative connection between the barrier as determined from photoemission and the barrier as used in the device simulation.
Energy levels of exciton traps in yttrium aluminum garnet single crystals
Authors: Varney C. R. , Mackay D. T. , Pratt A. , Reda S. M. , Selim F. A.
Published: March 2012

Electronic defects and exciton traps were studied in yttrium aluminum garnet (YAG) single crystals by wavelength and temperature resolved thermoluminescence (TL). Measurements were carried out from room temperature to 400 °C on a number of rare earth (RE) doped and undoped YAG crystals, and the trap parameters were determined. Although the TL emission spectrum is characteristic of the RE ion, the main trap levels are found to be characteristic of the undoped host crystal. Nevertheless, the thermal activation energies of the traps are slightly modified by doping. The trap kinetics are found to be of the first order in both undoped and Ce doped YAG single crystals indicating the absence of retrapping, which suggests that the traps and recombination centers exhibit a close spatial correlation. The effect of annealing on TL response suggests that some of the major traps are associated with oxygen vacancies.
Role of dual-laser ablation in controlling the Pb depletion in epitaxial growth of Pb(Zr0.52Ti0.48)O3 thin films with enhanced surface quality and ferroelectric properties
Authors: Mukherjee Devajyoti , Hyde Robert , Mukherjee Pritish , Srikanth Hariharan , Witanachchi Sarath
Published: March 2012

Pb depletion in Pb(Zr0.52Ti0.48)O3 (PZT) thin films has remained as a major setback in the growth of defect-free PZT thin films by pulsed laser ablation techniques. At low excimer (KrF) laser fluences, the high volatility of Pb in PZT leads to non-congruent target ablation and, consequently, non-stoichiometric films, whereas, at high laser fluences, the inherent ejection of molten droplets from the target leads to particulate laden films, which is undesirable in heterostructure growth. To overcome these issues, a dual-laser ablation (PLDDL) process that combines an excimer (KrF) laser and CO2 laser pulses was used to grow epitaxial PZT films on SrTiO3 (100) and MgO (100) substrates. Intensified-charge-coupled-detector (ICCD) images and optical emission spectroscopy of the laser-ablated plumes in PLDDL revealed a broader angular expansion and enhanced excitation of the ablated species as compared to those for single-laser ablation (PLDSL). This led to the growth of particulate-free PZT films with higher Pb content, better crystallinity, and lower surface roughness as compared to those deposited using PLDSL. For FE measurements, PZT capacitors were fabricated in situ using the latticed-matched metallic oxide, La0.7Sr0.3MnO3, as the top and bottom electrodes. PZT films deposited using PLDDL exhibited enhanced polarization for all driving voltages as compared to those deposited using PLDSL. A highest remanent polarization (Pr) of ∼91 μC/cm2 and low coercive field of ∼40 kV/cm was recorded at 9 V driving voltage. Fatigue characterization revealed that PZT films deposited using PLDDL showed unchanging polarization, even after 109 switching cycles.
On the origin of the redshift in the emission wavelength of InGaN/GaN blue light emitting diodes grown with a higher temperature interlayer
Authors: Ju Z. G. , Tan S. T. , Zhang Z.-H. , Ji Y. , Kyaw Z. , Dikme Y. , Sun X. W. , Demir H. V.
Published: March 2012

A redshift of the peak emission wavelength was observed in the blue light emitting diodes of InGaN/GaN grown with a higher temperature interlayer that was sandwiched between the low-temperature buffer layer and high-temperature unintentionally doped GaN layer. The effect of interlayer growth temperature on the emission wavelength was probed and studied by optical, structural, and electrical properties. Numerical studies on the effect of indium composition and quantum confinement Stark effect were also carried out to verify the experimental data. The results suggest that the redshift of the peak emission wavelength is originated from the enhanced indium incorporation, which results from the reduced strain during the growth of quantum wells.
Effects of alignment, pH, surfactant, and solvent on heat transfer nanofluids containing Fe2O3 and CuO nanoparticles
Authors: Younes Hammad , Christensen Greg , Luan Xinning , Hong Haiping , Smith Pauline
Published: March 2012

In this paper, the effects of alignment, pH, surfactant and solvent on heat transfer nanofluids containing Fe2O3 and CuO nanoparticles are studied and analyzed. The microscope images show that Fe2O3 could form some kind of alignment spontaneously in water even without external magnetic field. With the addition of external magnetic field, the alignment is strengthened. In water, the magnetic particle agglomeration to larger size occurs easily, which makes the directional alignment much faster and easier. Ethylene glycol solvent and chemical surfactant sodium dodecyl benzene sulfonate, NaDDBS could separate the Fe2O3 and CuO nanoparticles well in the fluids and avoid possible aggregation. Therefore, magnetic alignments are hard to observe. The measured thermal conductivities of each individual sample coincide with the microscope images and assumptions. In addition, pH values of Fe2O3 and CuO nanoparticles are measured and it has been determined that at those pH values, thermal conductivities of those nanoparticles would not be influenced according to the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. The highlight of this paper is that our microscope images could well explain most of the literature data and conclusions and may open new door to better understanding fundamental nature of nanofluids.
The quasi-periodic solutions of mixed KdV equations
Authors: Xia Baoqiang
Published: March 2012

The quasi-periodic solutions of mixed KdV equations are constructed. To derive the solutions, we introduce the mixed finite-dimensional integrable Hamiltonian systems (FDIHS), which are linearized on the Jacobi variety of the associated hyperelliptic curve. A relation between the FDIHS and the mixed KdV equations is revealed. Based on this relation, we construct the quasi-periodic solutions for the mixed KdV equations with aid of the Riemann theta function. The quasi-periodic solutions for the KdV6 equation and the negative order KdV equation are obtained as special members of the mixed KdV equations.
The effect of pressure on the hydration structure around hydrophobic solute: A molecular dynamics simulation study
Authors: Sarma Rahul , Paul Sandip
Published: March 2012

Molecular dynamics simulations are performed to study the effects of pressure on the hydrophobic interactions between neopentane molecules immersed in water. Simulations are carried out for five different pressure values ranging from 1 atm to 8000 atm. From potential of mean force calculations, we find that with enhancement of pressure, there is decrease in the well depth of contact minimum (CM) and the relative stability of solvent separated minimum over CM increases. Lower clustering of neopentane at high pressure is also observed in association constant and cluster-structure analysis. Selected site-site radial distribution functions suggest efficient packing of water molecules around neopentane molecules at elevated pressure. The orientational profile calculations of water molecules show that the orientation of water molecules in the vicinity of solute molecule is anisotropic and this distribution becomes flatter as we move away from the solute. Increasing pressure slightly changes the water distribution. Our hydrogen bond properties and dynamics calculations reveal pressure-induced formation of more and more number of water molecules with five and four hydrogen bond at the expense of breaking of two and three hydrogen bonded water molecules. We also find lowering of water-water continuous hydrogen bond lifetime on application of pressure. Implication of these results for relative dispersion of hydrophobic molecules at high pressure are discussed.
Spontaneous emission control of single quantum dots in bottom-up nanowire waveguides
Authors: Bulgarini Gabriele , Reimer Michael E. , Zehender Tilman , Hocevar Moïra , Bakkers Erik P. A. M. , Kouwenhoven Leo P. , Zwiller Valery
Published: March 2012

Nanowire waveguides with controlled shape are promising for engineering the collection efficiency of quantum light sources. We investigate the exciton lifetime in individual InAsP quantum dots, perfectly positioned on-axis of InP nanowire waveguides. We demonstrate control over the quantum dot spontaneous emission by varying the nanowire diameter in e-beam patterned arrays, which modifies the coupling efficiency of the emitter to the fundamental waveguide mode. The spontaneous emission rate is inhibited by a factor of 12 in thin nanowires compared to nanowires with optimized waveguide diameter. From the measured inhibition factor, we determine a high radiative yield exceeding 92% in bottom-up grown nanowires.
Emission stability enhancement of a tip-type carbon-nanotube-based field emitter via hafnium interlayer deposition and thermal treatment
Authors: Kim Jong-Pil , Chang Han-Beet , Kim Bu-Jong , Park Jin-Seok
Published: March 2012

Carbon nanotubes (CNTs) were deposited on a tip-type tungsten substrate via electrophoretic deposition, in which a hafnium thin film was used as an interlayer. The long-term (up to 24 h) emission stability of the CNT-based field emitter was remarkably enhanced when the hafnium interlayer was coated and thermally treated. This is attributed to the enhanced adhesion between the substrate and the CNTs. An x-ray photoelectron spectroscopy study and nano-scratch measurement provided a convincing evidence of the increase in the adhesive force.
A detailed test study of barrier heights for the HO2 + H2O + O3 reaction with various forms of multireference perturbation theory
Authors: Viegas Luís P. , Varandas António J. C.
Published: March 2012

We report an ab initio multireference perturbation theory investigation of the HO2 + H2O + O3 reaction, with particular emphasis on the barrier heights for two possible reaction mechanisms: oxygen abstraction and hydrogen abstraction, which are identified by two distinct saddle points. These saddle points and the corresponding pre-reactive complexes were optimized at the CASSCF(11,11) level while the single point energies were calculated with three different MRPT2 theories: MRMP, CASPT2, and SC-NEVPT2. Special attention has been drawn on the “intruder state” problem and the effect of its corrections on the relative energies. The results were then compared with single reference coupled-cluster methods and also with our recently obtained Kohn-Sham density functional theory (KS-DFT) calculations [L. P. Viegas and A. J. C. Varandas, Chem. Phys.,10.1016/j.chemphys.2011.04.022 (2011)]. It is found that the relative energies of the pre-reactive complexes have a very good agreement while the MRPT2 classical barrier heights are considerably higher than the KS-DFT ones, with the SC-NEVPT2 calculations having the highest energies between the MRPT2 methods. Possible explanations have been given to account for these differences.
Corrigenda and addenda to “Fundamentality of a cubic unit 𝑢 for ℤ[𝕦]”
Authors: Beers J. , Henshaw D. , McCall C. , Mulay S. , Spindler M.
Published: March 2012

Due to a certain ambiguity present in section 3 of [E. Thomas, Fundamental units for orders in certain cubic number fields, J. Reine Angew. Math. 310 (1979), 33-55], it became necessary to amend a crucial definition and a few proofs appearing in our article Fundamentality of a cubic unit

u
u

for

Z

[
u
]

\mathbb {Z}[u]

. Here, the necessary corrections are provided.