bluuebunny/crossref_metadata_2025 huggingface dataset:
Personal goals as predictors of intended classroom goals: Comparing elementary and secondary school pre‐service teachers
Authors: Daniels Lia M. , Frenzel Anne C. , Stupnisky Robert H. , Stewart Tara L. , Perry Raymond P.
Published: March 2012

Background and Aims. The literature documents fewer classroom mastery goal structures in secondary school compared to elementary. However, little is known about how personal achievement goals may influence classroom goal structures. This is especially true at the level of pre‐service teachers. Our objective was to investigate if pre‐service teachers’ personal goals predicted their intended classroom goal structures.

Sample. Participants were 125 elementary and 175 secondary school pre‐service teachers from two Western Canadian universities.

Method. Structural equation modelling was used to examine if the structural relationships and latent means of personal and intended classroom goal structures differed for elementary and secondary school pre‐service teachers.

Results. The results revealed that personal goals predicted the goal structures that pre‐service teachers intended to establish; however, the relationships and means differed between elementary and secondary school pre‐service teachers. Specifically, personal mastery‐approach goals positively predicted classroom mastery goals much more strongly at the elementary than the secondary level. Furthermore, elementary pre‐service teachers had significantly higher latent mean scores on personal mastery‐approach goals than their secondary counterparts.

Conclusions. It seems possible that the currently documented differences between classroom goal structures noted for elementary compared to secondary school may be based on the personal goals endorsed as pre‐service teachers. The results are further discussed in terms of alignment with research on practising teachers’ personal and classroom goals and implications for teacher education.
Data-Driven Prediction of Drug Effects and Interactions
Authors: Tatonetti Nicholas P. , Ye Patrick P. , Daneshjou Roxana , Altman Russ B.
Published: March 2012

Two new databases—one of drug effects and a second of drug-drug interaction side effects—permit identification of drug targets, prediction of drug indications, and discovery of drug class interactions.
The Pacemaker Goes Organic
Authors: Methe Heiko
Published: March 2012

Stem cell–derived cardiomyocytes may mark the starting point for the development of biological pacemakers.
The Brain Origin of Choice
Authors: Singh Manpreet
Published: March 2012

In vivo neuroimaging combined with advanced computational modeling can demonstrate dynamic decision-making in the brain.
Sepsis: Up Against the Clock
Authors: Yipp Bryan G.
Published: March 2012

The innate immune system is linked to circadian rhythms through the cyclical expression of TLR9, and this regulation impacts septic shock.
Death Is Associated with Complement C3 Depletion in Cerebrospinal Fluid of Patients with Pneumococcal Meningitis
Authors: Goonetilleke U. R. , Scarborough M. , Ward S. A. , Hussain S. , Kadioglu A. , Gordon S. B.
Published: March 2012

Pneumococcal meningitis can lead to death or serious neurological sequelae as a result of the host inflammatory response. We investigated the association between host response protein expression and outcome in patients with pneumococcal meningitis. Cerebrospinal fluid (CSF) was obtained from 80 patients with pneumococcal meningitis (40 nonsurvivors and 40 survivors) and 10 normal controls. Candidate proteins were analyzed for an association with survival. Complement C3 levels were 5-fold lower in nonsurvivors than in survivors (
P
< 0.05). This C3 reduction was not associated with lower levels in serum, indicating a compartmentalized CSF response. Transferrin levels were significantly higher in CSF (but not serum) from nonsurvivors than in CSF from survivors, suggestive of blood-brain barrier damage. Classical apoptosis proteins caspase 3 and apoptosis-inducing factor were not present in CSF. Expression of creatine kinase BB in clinically infected CSF suggested neuronal necrosis, but there was no clear association between level of expression and clinical outcome. Increased blood-brain barrier permeability and complement C3 depletion may have a role in determining outcome from bacterial meningitis. Therapeutic use of citicoline or caspase inhibitors is unlikely to have beneficial effects in patients with meningitis.

IMPORTANCE
We previously identified proteins associated with clinical outcome in patients diagnosed with pneumococcal meningitis in a pilot proteomics study of cerebrospinal fluid (CSF). In this article, we have quantitatively assayed specific proteins identified from this previous proteomics analysis along with proteins associated with cell death by using Western blotting.
Annexin A5 Binds to Lipopolysaccharide and Reduces Its Endotoxin Activity
Authors: Rand Jacob H. , Wu Xiao-Xuan , Lin Elaine Y. , Griffel Alexander , Gialanella Philip , McKitrick John C.
Published: March 2012

Annexin A5 (AnxA5) has a high affinity for phosphatidylserine. The protein is widely used to detect apoptotic cells because phosphatidylserine, a phospholipid that is normally present in the inner leaflets of cytoplasmic membranes, becomes translocated to the outer leaflets during programmed cell death. Here we report the novel observation that AnxA5 binds to Gram-negative bacteria via the lipid A domain of lipopolysaccharide (LPS). Binding of AnxA5 to bacteria was measured quantitatively, confirmed by fluorescence microscopy, and found to be inhibited by antibodies against lipid A. AnxA5 also bound to purified dot-blotted LPS and lipid A. Through ellipsometry, we found that the binding of AnxA5 to purified LPS was calcium dependent and rapid and showed a high affinity—characteristics similar to those of AnxA5 binding to phosphatidylserine. Initial functional studies indicated that AnxA5 can affect LPS activities. AnxA5 inhibited LPS-mediated gelation in the
Limulus
amebocyte lysate assay. Incubation of LPS with the protein reduced the quantity of tumor necrosis factor alpha (TNF-α) released by cultured monocytes compared to that released upon incubation with LPS alone. Initial
in vivo
experiments indicated that injection of mice with LPS preincubated with AnxA5 produced serum TNF-α levels lower than those seen after injection of LPS alone. These data demonstrate that AnxA5 binds to LPS and open paths to investigation of the potential biological and therapeutic implications of this interaction.

IMPORTANCE
AnxA5 is highly expressed in cells that have a barrier function—including, among others, vascular endothelium, placental trophoblasts, and epithelial cells lining bile ducts, renal tubules, mammary ducts, and nasal epithelium. The protein has been well characterized for its binding to phospholipid bilayers that contain phosphatidylserine. This report of a previously unrecognized activity of AnxA5 opens the door to investigation of the possibility that this binding may have biological and therapeutic ramifications. In view of the tissue expression of the protein, the present results suggest the possibility that AnxA5 plays a role in modulating the host defense against lipopolysaccharide at these anatomic sites, where cells may interface with microorganisms. These results also raise the intriguing possibility that AnxA5 or analogous proteins or peptides could provide novel approaches to addressing the difficult clinical problem of Gram-negative sepsis.
Angioarchitectural features associated with hemorrhagic presentation in pediatric cerebral arteriovenous malformations
Authors: Ellis Michael J , Armstrong Derek , Vachhrajani Shobhan , Kulkarni Abhaya V , Dirks Peter B , Drake James M , Smith Edward R , Scott R Michael , Orbach Darren B
Published: March 2012

Background and objective

To date, there have been few published studies examining the relationship between arteriovenous malformation (AVM) angioarchitecture and hemorrhagic presentation among children with cerebral AVMs. This study examines this relationship in this unique population, in whom symptomatic presentation of cerebral AVM is the norm rather than the exception.

Methods

A cohort of children with AVMs from 2000 to 2011 were included. Predictors studied included patient age, gender and angioarchitectural features, including AVM location, nidus size and morphology, venous drainage, presence of venous outflow lesions and associated aneurysms. Predictors of hemorrhagic presentation were assessed using multivariate logistic regression.

Results

135 children (70 males, mean age 10.1 years) were included. 86/135 (63.7%) children presented with hemorrhage, 18 (13.3%) with seizures, 17 (12.6%) with headaches or neurological deficits and 14 (10.4%) were asymptomatic. AVM location, morphology and the presence of associated aneurysm, venous ectasia, draining vein stenosis and single draining vein were not significantly associated factors. After multivariate analysis, AVM size (OR 0.57, 95% CI 0.43 to 0.77; p<0.01), exclusive deep venous drainage (OR 4.94, 95% CI 1.30 to 18.8; p=0.02) and infratentorial location (OR 9.94, 95% CI 1.71 to 51.76; p=0.01) were independently associated with hemorrhagic presentation.

Conclusion

Smaller AVM size, exclusive deep venous drainage and infratentorial location are specific angioarchitectural factors independently associated with initial hemorrhagic presentation in children with AVMs.
EFFECT OF RANDOM LINK MALFUNCTIONS TO SYNCHRONIZATION OF HODGKIN–HUXLEY NEURONS IN A LATTICE NETWORK
Authors: PANG JAMES CHRISTOPHER S. , BANTANG JOHNROB Y. , MONTEROLA CHRISTOPHER P.
Published: March 2012

We study the synchronization of Hodgkin–Huxley (HH) neurons connected in a directed lattice network under the influence of varying coupling strength (g) and random link malfunctions in the form of probabilistic deletion (probability q) and link direction flipping (p). We quantify the extent of synchronization of the neurons in the network by averaging the fraction of firing neurons that produce action potentials (exceeding a threshold potential of V th ) across the entire observation time. By extensively scanning over the values of g, synchronization of this network type can be enhanced by increasing g until it reaches a threshold value wherein synchronization will deteriorate abruptly due to suppression of neural firings. We also extensively probe the interplay of p and q and show that there are certain combinations for which the synchronization will improve, defying negative notions of how we perceive random malfunctions.
CAPACITY INVESTMENT, PRICING, AND PRODUCTION ALLOCATION ACROSS INTERNATIONAL MARKETS WITH EXCHANGE RATE UNCERTAINTY
Authors: AHMED ANAS , ERKOC MURAT , CHO SOHYUNG
Published: March 2012

In this paper, we investigate joint optimal capacity investment, pricing and production decisions for a multinational manufacturer who faces exchange rate uncertainties. We consider a manufacturer who sells its product in both domestic and foreign markets over a multiperiod season. Because of long-lead times, the capacity investment must be committed before the selling season begins. The exchange rate between the two countries fluctuates across periods and the demand in both markets are price dependent. Our model considers three scenarios: (1) early commitment to price and quantity with central sourcing, (2) postponement of prices and quantities with central sourcing, and (3) local sourcing. We derive the optimal capacity and the optimal prices for each scenario, and investigate the impact of the exchange rate parameters and the length of the selling season. We observe that while the price and production decisions in the domestic market are independent of the exchange rate under early commitment and local sourcing scenarios, the exchange rate between two countries directly impacts these decisions under the postponement setting. We identify thresholds and gain insights on capacity and production costs, exchange rate movement, and selling season length for the choice of entering a foreign market under all scenarios.
SPACE-CHARGE EFFECT IN UNINTENTIONALLY N-DOPED SILICON
Authors: CONG KANKAN , JI YANG
Published: March 2012

We report experimental results on current–voltage characteristics of Au-Ti/n-Si/Au-Ti devices made on unintentionally n-doped silicon, which depend dramatically on temperature and external magnetic field. While such devices show Ohmic behavior in the temperature range 154–300 K, space-charge effect dominates at high bias voltages in the temperature range 77–154 K. In the later case, external magnetic field may increase its breakdown voltage, thus inducing large positive magnetoresistance similar to those reported by other groups.
FINITE DIFFERENCE METHODS FOR FRACTIONAL DIFFERENTIAL EQUATIONS
Authors: LI CHANGPIN , ZENG FANHAI
Published: March 2012

In this review paper, the finite difference methods (FDMs) for the fractional differential equations are displayed. The considered equations mainly include the fractional kinetic equations of diffusion or dispersion with time, space and time-space derivatives. In some way, these numerical methods have similar form as the case for classical equations, some of which can be seen as the generalizations of the FDMs for the typical differential equations. And the classical tools, such as the von Neumann analysis method, the energy method and the Fourier method are extended to numerical methods for fractional differential equations accordingly. At the same time, the techniques for improving the accuracy and reducing the computation and storage are also introduced.
GENERALIZED FRACTIONAL ORDER BLOCH EQUATION WITH EXTENDED DELAY
Authors: BHALEKAR SACHIN , DAFTARDAR-GEJJI VARSHA , BALEANU DUMITRU , MAGIN RICHARD
Published: March 2012

The fundamental description of relaxation (T1 and T2) in nuclear magnetic resonance (NMR) is provided by the Bloch equation, an integer-order ordinary differential equation that interrelates precession of magnetization with time- and space-dependent relaxation. In this paper, we propose a fractional order Bloch equation that includes an extended model of time delays. The fractional time derivative embeds in the Bloch equation a fading power law form of system memory while the time delay averages the present value of magnetization with an earlier one. The analysis shows different patterns in the stability behavior for T1 and T2 relaxation. The T1 decay is stable for the range of delays tested (1 μsec to 200 μsec), while the T2 relaxation in this extended model exhibits a critical delay (typically 100 μsec to 200 μsec) above which the system is unstable. Delays arise in NMR in both the system model and in the signal excitation and detection processes. Therefore, by adding extended time delay to the fractional derivative model for the Bloch equation, we believe that we can develop a more appropriate model for NMR resonance and relaxation.
CHAOS IN FRACTIONAL-ORDER POPULATION MODEL
Authors: PETRÁŠ IVO
Published: March 2012

This paper presents a fractional-order population model which consists of the two-predators and one-prey scheme. For this new model, the numerical solution is derived and the simulations are performed for various sets of model parameters together with stability analysis for commensurate and incomensurate orders of the fractional-order population model. The results obtained via the simulations show that chaos can be observed in such population model.
A FRACTIONAL ORDER UNIVERSAL HIGH GAIN ADAPTIVE STABILIZER
Authors: LI YAN , CHEN YANGQUAN
Published: March 2012

In this paper, a fractional order universal high gain adaptive stabilizer is proposed which guarantees the Lp stability of fractional order multiple–input and multiple–output (MIMO) systems with finite control effort. The boundedness of the control gain for the fractional order universal adaptive strategy is discussed for fractional order MIMO systems, and an upper bound of the control gain is presented for fractional order single-input and single-output (SISO) systems. Some advantages of the discussed fractional order universal adaptive stabilizer are demonstrated in numerical simulations, such as the overshoots of system outputs can be efficiently reduced by decreasing the fractional order of the universal adaptive stabilizer without significantly increasing the system gains.
STOCHASTIC HOPF BIFURCATION OF QUASI-INTEGRABLE HAMILTONIAN SYSTEMS WITH FRACTIONAL DERIVATIVE DAMPING
Authors: HU F. , ZHU W. Q. , CHEN L. C.
Published: March 2012

The stochastic Hopf bifurcation of multi-degree-of-freedom (MDOF) quasi-integrable Hamiltonian systems with fractional derivative damping is investigated. First, the averaged Itô stochastic differential equations for n motion integrals are obtained by using the stochastic averaging method for quasi-integrable Hamiltonian systems. Then, an expression for the average bifurcation parameter of the averaged system is obtained and a criterion for determining the stochastic Hopf bifurcation of the system by using the average bifurcation parameter is proposed. An example is given to illustrate the proposed procedure in detail and the numerical results show the effect of fractional derivative order on the stochastic Hopf bifurcation.
FINITE DIFFERENCE SCHEMES FOR VARIABLE-ORDER TIME FRACTIONAL DIFFUSION EQUATION
Authors: SUN HONGGUANG , CHEN WEN , LI CHANGPIN , CHEN YANGQUAN
Published: March 2012

Variable-order fractional diffusion equation model is a recently developed and promising approach to characterize time-dependent or concentration-dependent anomalous diffusion, or diffusion process in inhomogeneous porous media. To further study the properties of variable-order time fractional subdiffusion equation models, the efficient numerical schemes are urgently needed. This paper investigates numerical schemes for variable-order time fractional diffusion equations in a finite domain. Three finite difference schemes including the explicit scheme, the implicit scheme and the Crank–Nicholson scheme are studied. Stability conditions for these three schemes are provided and proved via the Fourier method, rigorous convergence analysis is also performed. Two numerical examples are offered to verify the theoretical analysis of the above three schemes and illustrate the effectiveness of suggested schemes. The numerical results illustrate that, the implicit scheme and the Crank–Nicholson scheme can achieve high accuracy compared with the explicit scheme, and the Crank–Nicholson scheme claims highest accuracy in most situations. Moreover, some properties of variable-order time fractional diffusion equation model are also shown by numerical simulations.
DEALING WITH FRACTIONAL DYNAMICS OF IP NETWORK DELAYS
Authors: TEJADO INÉS , HOSSEINNIA S. HASSAN , VINAGRE BLAS M. , SONG XIAONA , CHEN YANGQUAN
Published: March 2012

The analysis of delay dynamics (DD) is the basic big picture in networked control systems (NCS) research since the knowledge of its behavior may improve the design of more robust controllers, and consequently, the system performance. However, the extreme complexity of modern communications and networks, coupled with their traffic characteristics, makes the characterization of their performance through analytical models a difficult task. Relying on fractional calculus (FC), this paper studies the dynamics of IP delays and attempts to clarify the most important features of network traffic, providing the reader some connections between traffic in communication networks and FC. Likewise, a fractional order model of DD is presented based on a survey of current network traffic models. Some simulations are given to validate the proposed model.
MEAN EXIT TIME AND ESCAPE PROBABILITY FOR A TUMOR GROWTH SYSTEM UNDER NON-GAUSSIAN NOISE
Authors: REN JIAN , LI CHUJIN , GAO TING , KAN XINGYE , DUAN JINQIAO
Published: March 2012

Effects of non-Gaussian α-stable Lévy noise on the Gompertz tumor growth model are quantified by considering the mean exit time and escape probability of the cancer cell density from inside a safe or benign domain. The mean exit time and escape probability problems are formulated in a differential-integral equation with a fractional Laplacian operator. Numerical simulations are conducted to evaluate how the mean exit time and escape probability vary or bifurcates when α changes. Some bifurcation phenomena are observed and their impacts are discussed.
THE FIRST "LOST" INTERNATIONAL CONFERENCE ON NONLINEAR OSCILLATIONS (I.C.N.O.)
Authors: GINOUX JEAN-MARC
Published: March 2012

From January 28 to 30, 1933, was held at the Institut Henri Poincaré (Paris) the first International Conference of Nonlinear Oscillations organized at the initiative of the Dutch physicist Balthazar Van der Pol and of the Russian mathematician Nikolaï Dmitrievich Papaleksi. The discovery of this forgotten event, whose virtually no trace remains, was made possible thanks to the report written by Papaleksi on his return to USSR. This document has revealed, both the list of participants who included French mathematicians — Alfred Liénard, Élie and Henri Cartan, Henri Abraham, Eugène Bloch, Léon Brillouin, Yves Rocard — and, the content of presentations and discussions. The analysis of the minutes of this conference presented here for the first time highlights the role and involvement of the French scientific community in the development of the theory of nonlinear oscillations.
HOMOLOGICALLY PERIPHERAL HYPERBOLIC LINKS WHICH ARE NOT PARTIALLY PERIPHERAL
Authors: IKEDA TORU
Published: March 2012

Partially peripheral 3-manifolds and homologically peripheral 3-manifolds are defined by generalizing the notion of totally peripheral 3-manifolds. The aim of this paper is to provide a method for constructing hyperbolic links in 3-manifolds whose exteriors are not partially peripheral but homologically peripheral, and to prove that the connected sum with a homology 3-sphere enables every closed connected orientable 3-manifold to contain infinitely many such hyperbolic links.
COLORING LINK DIAGRAMS BY ALEXANDER QUANDLES
Authors: BAE YONGJU
Published: March 2012

In this paper, we study the colorability of link diagrams by the Alexander quandles. We show that if the reduced Alexander polynomial ΔL(t) is vanishing, then L admits a non-trivial coloring by any non-trivial Alexander quandle Q, and that if ΔL(t) = 1, then L admits only the trivial coloring by any Alexander quandle Q, also show that if ΔL(t) ≠ 0, 1, then L admits a non-trivial coloring by the Alexander quandle Λ/(ΔL(t)).
RATIONAL POLYHEDRA AND PROJECTIVE LATTICE-ORDERED ABELIAN GROUPS WITH ORDER UNIT
Authors: CABRER LEONARDO , MUNDICI DANIELE
Published: March 2012

An ℓ-groupG is an abelian group equipped with a translation invariant lattice-order. Baker and Beynon proved that G is finitely generated projective if and only if it is finitely presented. A unital ℓ-group is an ℓ-group G with a distinguished order unit, i.e. an element 0 ≤ u ∈ G whose positive integer multiples eventually dominate every element of G. Unital ℓ-homomorphisms between unital ℓ-groups are group homomorphisms that also preserve the order unit and the lattice structure. A unital ℓ-group (G, u) is projective if whenever ψ : (A, a) → (B, b) is a surjective unital ℓ-homomorphism and ϕ : (G, u) → (B, b) is a unital ℓ-homomorphism, there is a unital ℓ-homomorphism θ : (G, u) → (A, a) such that ϕ = ψ ◦ θ. While every finitely generated projective unital ℓ-group is finitely presented, the converse does not hold in general. Classical algebraic topology (à la Whitehead) is combined in this paper with the Włodarczyk–Morelli solution of the weak Oda conjecture for toric varieties, to describe finitely generated projective unital ℓ-groups.
LOCALIZATION OF SOLUTIONS TO A DOUBLY DEGENERATE PARABOLIC EQUATION WITH A STRONGLY NONLINEAR SOURCE
Authors: MU CHUNLAI , ZHENG PAN , LIU DENGMING
Published: March 2012

In this paper, we investigate the localization of solutions of the Cauchy problem to a doubly degenerate parabolic equation with a strongly nonlinear source [Formula: see text] where N ≥ 1, p > 2 and m, l, q > 1. When q > l + m(p - 2), we prove that the solution u(x, t) has strict localization if the initial data u0(x) has a compact support, and we also show that the solution u(x, t) has the property of effective localization if the initial data u0(x) satisfies radially symmetric decay. Moreover, when 1 < q < l + m(p - 2), we obtain that the solution of the Cauchy problem blows up at any point of RNto arbitrary initial data with compact support.
ON THE HARDY–POINCARÉ INEQUALITY WITH BOUNDARY SINGULARITIES
Authors: FALL MOUHAMED MOUSTAPHA
Published: March 2012

Let Ω be a smooth bounded domain in ℝNwith N ≥ 1. In this paper we study the Hardy–Poincaré inequality with weight function singular at the boundary of Ω. In particular we provide sufficient and necessary conditions on the existence of minimizers.
NONNEGATIVE SOLUTIONS FOR INDEFINITE SUBLINEAR ELLIPTIC PROBLEMS
Authors: DE PAIVA FRANCISCO ODAIR
Published: March 2012

This paper is devoted to the study of existence, nonexistence and multiplicity of positive solutions for the semilinear elliptic problem [Formula: see text] where Ω is a bounded domain of ℝN, λ ∈ ℝ and g(x, u) is a Carathéodory function. The obtained results apply to the following classes of nonlinearities: a(x)uq+ b(x)upand c(x)(1 + u)p(0 ≤ q < 1 < p). The proofs rely on the sub-super solution method and the mountain pass theorem.
THE MECHANICAL CHARACTERIZATION AND IN VIVO EVALUATION OF POROUS TiNi AS GRAFT MATERIAL
Authors: ARPAK BERTAN , ARAZ KENAN , NAKAŞ İPEK , BOR ŞAKIR , NERGİZ İBRAHIM
Published: March 2012

To obtain TiNi foams with interconnected pores that have surface quality necessary for bone growth in addition to required mechanical performance, sintering with the space holder technique was employed in this study, which aimed to evaluate the bone healing process of TiNi graft materials. For this purpose, processed TiNi foams with three different porosities were placed into the created defects in the femur of rats. Moreover, the mechanical properties of the processed TiNi foams were conducted via monotonic compression tests in order to evaluate mechanical biocompatibility.
PRAPARATION AND CHARACTERISATION OF TiO2 NANOTUBULAR ARRAYS FOR ELECTRO-OXIDATION OF ORGANIC COMPOUNDS: EFFECT OF IMMOBILIZATION OF THE NOBLE METAL PARTICLES
Authors: HOSSEINI MIRGHASEM , MOMENI MOHAMAD MOHSEN
Published: March 2012

The morphology, composition and the electrochemical behavior of the anodic nanoporous layer, prepared by the galvanostatic anodisation of titanium, followed by galvanostatic deposition of noble metal particles have been investigated. The morphology and surface characteristics of result electrodes were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. The results indicated that noble metal particles were homogeneously deposited on the surface of TiO 2 nanotubes. The nanotubular TiO 2 layers consist of individual tubes of about 40-80 nm diameters. The electrocatalytic behavior of result electrodes for electro-oxidation of organic compounds (glucose, dopamine, ascorbic acid and hydrazine) was studied by cyclic voltammetry. The results showed that the result electrodes possess catalytic activity toward the oxidation organic compounds.
EFFECT OF REACTOR PRESSURE ON PRODUCTION OF ALUMINUM NANO-POWDER
Authors: EHSANI NASER , HOSSEINI SEYED HOJJATTOLLAH , SHEIBANI S. , VALEFI ZIA
Published: March 2012

In this paper aluminum nano-powder was produced by evaporation and condensation in a low pressure argon gas atmosphere. The process was modified according to the argon pressure to decrease the aluminum nano-particle size. Therefore, the argon gas pressure was changed from 0.1 to 1 mbar by change of injection flow rate, while other parameters were maintained constant. To evaluate the morphology of produced nano-powders at each argon pressure, the nano-powders were analyzed by Brunauer- Emmett- Teller (BET) method and transmission electron microscopy (TEM). It was found that the final particle diameter decreased with argon pressure. This decrease of particle size reaches a minimum of 85 nm, which corresponds to the pressure of 1 mbar. This powder had a specific surface area of 26.22 m2g-1.
Microwave assisted hydrothermal synthesize ofZnOnanorods and their characterization
Authors: SHOJAEE NADI , EBADZADEH TOURADJ , AGHAEI ALIREZA
Published: March 2012

In present study ZnO nanorods were synthesized in an aqueous solution using a domestic microwave oven for irradiation. The nanorods have been grown on substrates immersed in an aqueous solution which contains zinc nitrate and hexamethylenetetramine as precursors. Eventually, effect of some parameters such as precursor's concentration and heating time on growth mechanism was characterized. The product phase was detected using X-ray diffraction (XRD). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) exhibited the resultant structure is uniform and single crystalline. Finally Uv-Vis spectroscopy was used to measure the nanorod's band gap.
The Comparison between Boron Carbide (B4C) with other Common Inhibitors on Physical and Mechanical Properties of WC/Co
Authors: Tamizifar H. , Hadian A.M. , Tamizifar M.
Published: March 2012

The hardness, toughness and sum of cracks measurement of fine-grained WC - Co hard metals were studied. Thirty commercial and experimental hard metal grades with different additives such as boron carbide ( B 4 C ), vanadium carbide ( VC ), chromium carbide ( Cr 3 C 2) and silicon carbide ( SiC ) were prepared in a commercial sinter HIP furnace. Physical, mechanical and microstructure properties were investigated to build up a representative hardness/sum of cracks measurement band. This band was then used to estimate the most effective sintering temperature and the amount of each additives. Afterwards, influence of grain growth inhibitors in optimum condition were compared. The results showed that the grades, doped with B 4 C and VC as growth inhibitor exhibits more hardness than other comparable doped alloys. However, Cr 3 C 2 is favorable in toughness improvement.
A SIMPLE METHOD FOR PREPARATION OF FLUORESCENT NANOSTRUCTURE SILICA WITH HEXAGONAL ARRAY
Authors: BADIEI ALIREZA , GOLDOOZ HASSAN
Published: March 2012

A nanostructure modified silica with good fluorescence properties was prepared by grafting Al 3+ ions on the surface of nanoporous silica and then binding of 8-hydroxyquinoline (8- HQ ) to the grafted Al 3+ ions. The prepared material, denoted as NS - AlQ 2, was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), nitrogen adsorption–desorption measurements, FT-IR and fluorescence spectra. This compound shows emission spectra approximately in the emission range of AlQ 3 complex. This procedure provides a simple method for grafting fluorescent molecules in the channels of nanoporous silica materials.
SYNTHESIS AND DIELECTRIC PROPERTIES OF NANOCRYSTALLINE BASRTIO3
Authors: Golmohammad M. , Nemati A. , Faghihi Sani M. A.
Published: March 2012

Ba 0.7 Sr 0.3 TiO 3 was prepared via simple sol-gel method by using titanium tetrabutoxide, barium and strontium carbonates, citric acid and ethylene glycol as starting materials. Simultaneous Thermal Analysis (STA) was used to examine thermal behavior of xerogel. The crystallite size of BST was about 21nm calculated by X-Ray diffraction (XRD) and confirmed by transition electron microscopy (TEM). Using these nanocrystalline powders, BST pellets were prepared and sintered in various temperatures. The grain size effect on electrical properties was studied and found that as the grain size decreased, the dielectric constant decreased too.
CHARACTERIZATION OF NICKEL OXIDE NANOPARTICLES SYNTHESIZED VIA RAPID MICROWAVE-ASSISTED ROUTE
Authors: MOHAMMADYANI D. , HOSSEINI S.A. , SADRNEZHAAD S.K.
Published: March 2012

Nickel oxide ( NiO ) nano-particles were produced via a rapid microwave-assisted method. Ni ( OH )2precursor was obtained by slow drop-wise addition of 0.1M sodium hydroxide to 0.1M nickel nitrate. The mixture was vigorously stirred until the pH reached 7.2. The mixture was then irradiated with microwave to deposit Ni ( OH )2at an intensified precipitation rate. Drying of the precipitate at 320°C resulted in formation of NiO nano-powder. Mean dimension of this powder was ~30nm according to the images analyzed by transmission electron microscope (TEM) and scanning electron microscope (SEM). X-ray diffraction (XRD) patterns revealed well-crystallized/high-purity nanostructures of the synthesized powder. Microwave utilization increased homogeneity and decreased the mean particle size of the produced NiO powder.
MEASUREMENT OF NONLINEAR RESPONSES AND OPTICAL LIMITING BEHAVIOR OF TIO2/PS NANO-COMPOSITE BY SINGLE BEAM TECHNIQUE WITH DIFFERENT INCIDENT INTENSITIES
Authors: MAJLES ARA M. H. , DEHGHANI Z.
Published: March 2012

Titanium dioxide (titania) is a cheap, nontoxic and highly efficient photocatalyst being extensively applied for the degradation of organic pollutants, air purification, water splitting, reduction of nitrogen to ammonia, and optical devices due to its optical behaviors. The third-order nonlinear optical properties of TiO 2/ PS nano-composite were studied by means of single beam transmission technique, using a continuous-wave (CW) He - Ne laser beam with a wavelength of 632.8 nm with three different incident intensities. The magnitude and sign of the third-order nonlinear refractive index ( n 2) and nonlinear absorption (β) of TiO 2/ PS nano-composite were determined by use of both the closed-aperture and opened-aperture z -scan techniques. Z -scan technique, developed by Sheik-Bahae et al., has been used widely in material characterization. A single-beam (also called z -scan method) for measuring the sign and magnitude of nonlinear refraction that has simplicity and very high sensitivity has been reported recently. Optical limiting property of TiO 2/ PS nano-composite is studied.

The positive sign obtained for nonlinear refractive index indicated that there is a self-focusing effect in the sample. The nonlinear refractive index was in order of 10-8 (cm2/W) and the nonlinear absorption coefficient was obtained in order of 10-2 (cm/W) with negative sign. The values of nonlinear refractive index and nonlinear absorption coefficient are enhanced by decreasing the intensity.
EFFECTS OF PROCESS CONTROL AGENT ADDITION IN PROCESSING OF NANO-CRYSTALLINE TiB2 VIA SHS METHOD
Authors: NOZARI AMIN , ATAIE ABOLGHASEM , HESHMATI-MANESH SAEED
Published: March 2012

Nano-crystalline titanium diboride ( TiB 2) was prepared by self-propagating high-temperature synthesis through putting a hot filament on top of the compact mixture of TiO 2, H 3 BO 3 and Mg with a stoichiometric ratio. Effects of the addition of various chloride salts e.g. NaClO 4 and NH 4 Cl as process control agents on phase evolution and chemical analysis and the morphology of the products were investigated by XRD and SEM techniques, respectively. Analysis of the X-ray diffraction patterns confirmed the formation of TiB 2 together with some intermediate phases such as Mg 3 B 2 O 6 and Mg 2 TiO 4 in as synthesized powder. MgO phase was detected as a major phase in the XRD patterns. Nano-crystalline TiB 2 became the major phase in some of the leached samples by HCl . The results also showed that the powder particle characteristics were influenced by the addition of the chloride salts.
DEVELOPMENT OF CRYSTALLOGRAPHIC TEXTURE AND GRAIN REFINEMENT IN THE ALUMINUM LAYER OF CU-AL-CU TRI-LAYER COMPOSITE DEFORMED BY EQUAL CHANNEL ANGULAR EXTRUSION
Authors: TOLAMINEJAD B. , TAHERI A.KARIMI , SHAHMIRI M. , ARABI H.
Published: March 2012

The present research is concerned with the aluminum layer of a loosely packed tri-layer copper-aluminum-copper composite deformed by ECAE process. Electron back scattered diffraction (EBSD), transmission electron microscope, and X-ray technique were employed to investigate the detailed changes occurring in the microtexture, microstructure (cell size and misorientation), and dislocation density evolution during consecutive passes of ECAE process performed on the composite based on route Bc. According to tensile test results, the yield stress of the aluminum layer was increased significantly after application of ECAE throughout the four repeated passes and then slightly decreased. An ultrafine grain size within the range of 500-600 nm was obtained in the Al layer by increasing the thickness of copper layers. It was observed that the reduction of grain size in the aluminum layer is nearly 57% more than that of an ECAE-ed single layer aluminum billet. Also, the grain refinement of the aluminum layer is accelerated throughout 8 passes. This observation was attributed to the higher rate of dislocation interaction, cell formation and texture development during the ECAE of the composite compared to those of the single billet.
PRODUCING NANOCOMPOSITE LAYER ON THE SURFACE OF AS-CAST AZ91 MAGNESIUM ALLOY BY FRICTION STIR PROCESSING
Authors: ASADI P. , BESHARATI GIVI M. K. , FARAJI G.
Published: March 2012

Friction stir processing (FSP) is an effective tool to produce a surface composite layer with enhanced mechanical properties and modified microstructure of as-cast and sheet metals. In the present work, the mechanical and microstructural properties of as-cast AZ 91 magnesium alloy were enhanced by FSP and an AZ 91/ SiC surface nanocomposite layer has been produced using 30 nm SiC particles. Effect of the FSP pass number on the microstructure, grain size, microhardness, and powder distributing pattern of the surface developed has been investigated. The developed surface nanocomposite layer presents a higher hardness, an ultra fine grain size and a better homogeneity. Results show that, increasing the number of FSP passes enhances distribution of nano-sized SiC particles in the AZ 91 matrix, decreases the grain size, and increases the hardness significantly. Also, changing of the tool rotating direction results much uniform distribution of the SiC particles, finer grains, and a little higher hardness.
TEMPERATURE DEPENDENCE STUDY OF NONCONTACT AFM IMAGES USING MOLECULAR DYNAMICS SIMULATIONS
Authors: NEJAT PISHKENARI HOSSEIN , MEGHDARI ALI
Published: March 2012

The effect of temperature on the noncontact atomic force microscopy (NC-AFM) surface imaging is investigated with the aid of molecular dynamics (MD) analysis based on the Sutton-Chen (SC) interatomic potential. Particular attention is devoted to the tip and sample flexibility at different temperatures. When a gold coated probe is brought close to the Au (001) surface at high temperatures, the tip and surface atoms are pulled together and their distance becomes smaller. The tip and sample atoms displacement varies in the different environment temperatures and this leads to the different interaction forces. Along this line, to study the effect of temperature on the resulting images, we have employed the well-known NC-AFM model and carried out realistic non-equilibrium MD 3D simulations of atomic scale imaging at different close approach positions to the surface.
SYNTHESIS OF NANO-CRYSTALLINE Cu-Cr ALLOY BY MECHANICAL ALLOYING
Authors: SHEIBANI S. , HESHMATI-MANESH S. , ATAIE A.
Published: March 2012

In this paper, the influence of toluene as the process control agent (PCA) and pre-milling on the extension of solid solubility of 7 wt.% Cr in Cu by mechanical alloying in a high energy ball mill was investigated. The structural evolution and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, respectively. The solid solution formation at different conditions was analyzed by copper lattice parameter change during the milling process. It was found that both the presence of PCA and pre-milling of Cr powder lead to faster dissolution of Cr . The mean crystallite size was also calculated and showed to be about 10 nm after 80 hours of milling.
Synthesis of carbon nanotube–Poly aniline nano composite and evaluation of electrochemical properties
Authors: Nikzad Leila , Vaezi M.R. , Yazdani B.
Published: March 2012

In this paper, carbon nanotube (CNT)- polyaniline (PANI) nanocomposites were developed from in situ polymerization of aniline. The CNT can be prepared by either acid treatment of CNTs suspension by grafting functional groups to CNTs surface. In this study, CNT and acid treatment CNT was used for preparation of nanocomposite. The PANI-CNT nanocomposite was characterized by FTIR, SEM. CNT can be prepared by either acid treatment of CNTs suspension to make them ionized or by grafting functional groups to CNTs surface. In addition, the electrochemical measurements such as cyclic voltametric (CV) curves showed that the conductivity of the obtained nanocomposite increased. Therefore, the supercapacitors behavior of polyaniline improves with adding CNT especially with acid treatment CNT.
EFFECT OF REVERSE MICELLE WATER POOL IN SYNTHESIS OF ZIRCONIA STABILIZED COPPER NANOCOMPOSITE
Authors: Abdizadeh H. , Vahidshad Y. , Baharvandi H. R. , Akbari Baseri M.
Published: March 2012

In the water-in-oil (W/O) microemulsions based on anionic (AOT) surfactants, the ω value (molar ratio of water to surfactant), precursor, and surfactant could remarkably affect the synthesis of CuO - ZrO 2 nanocomposite and the morphologies of the sol-gel products simultaneously. In this study, CuO - ZrO 2 nanoparticles are synthesized using microreactors made of surfactant/water/n-hexane microemulsions and discusses the effect of different microemulsion variables on the particle size and particle size distribution by water-to-surfactant molar ratio. The obtained powders are characterized by DTA, XRD, SEM, EDS, and TEM and their physical properties are compared. For AOT surfactant the particle size increased with increasing the water to surfactant molar ratio. The particles size of CuO - ZrO 2 nanocomposite in sample with anionic surfactant with molar ratio of 6 that calcined at 600°C is between 15-20 nm.
A COMPARISON OF 85%W-15%CU COMPOSITES SYNTHESIZED BY NANO AND MICRO POWDERS
Authors: DEHGHNIAN C. , TAKESTANI M.
Published: March 2012

Two kinds of tungsten-copper composites with the composition of 85% W -15% Cu were synthesized using mechanochemically produced nano size and conventional micro size powders. The densification, mechanical and electrical properties of these composites was examined. It was found that the samples sintered from nanopowders had more densities and better physical and mechanical properties than those produced from micro sized powders. The micro W - Cu powder mixtures were pressed to 60 percent of its theoretical density but the nano composite powders were difficult to press due to its high friction energy and only reached to 30 percent of its theoretical density. The highest densities were obtained from nano composite mixtures at 1200°C.
PHOTOCATALYTIC OXIDATION OF VOLATILE ORGANIC COMPOUNDS OVER ELECTROSPUN ACTIVATED TIO2/CARBON NANOFIBER COMPOSITE
Authors: Gholamvand Zahra , Aboutalebi Seyed Hamed , Keyanpour-Rad Mansoor
Published: March 2012

In this study, TiO 2/ PAN -based fibers were prepared by electrospinning a composite solution containing both the desirable contents of TiO 2 and a 10 wt. % PAN polymer solution dissolved in N , N -dimethylformamide. The TiO 2 loaded electrospun PAN nanofibers were then carbonized at 1000 °C in N 2 atmosphere furnace after stabilization at 230 °C in air. Then CNF / TiO 2 nanofibers were oxidized at 450 °C in air. The morphology and structure of the TiO 2-embeded carbon nanofibers were investigated by SEM and Raman spectroscopy. Specific surface area was determined using BET equation from N 2 adsorption analysis. Photocatalytic tests were conducted in a UV illuminated set-up specialized for the filters using ethanol vapor. The results have shown that ethanol vapor was efficiently degraded on TiO 2/ CNF composite nanofiber mat under UV illumination. The aim of this study was to further investigate the feasibility of TiO 2/ ACF for practical indoor air purification.
PREPARATION AND CHARACTERIZATION OF HYDROXYAPATITE-SILICA COMPOSITE NANOPOWDERS
Authors: LATIFI S.M. , FATHI M.H. , GOLOZAR M.A.
Published: March 2012

One of the most important objectives in the field of biomaterials science and engineering is development of new materials as bone substitutes. Silica ( SiO 2) has an important role in the biomineralization and biological responses. The aim of this research was to prepare and characterize hydroxyapatite-silica ( HA - SiO 2) composite nanopowder with different content of silica. Hydroxyapatite-silica composite nanopowders with 20 and 40 wt% silica were prepared using a sol–gel method at 600°C with phosphoric pentoxide and calcium nitrate tetrahydrate as a source of hydroxyapatite; also, tetraethylorthosilicate and methyltriethoxisilane as a source of silica. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) techniques were used for characterization and evaluation of the products. The results indicated the presence of nanocrystalline hydroxyapatite phase beside amorphous silica phase in prepared composite nanopowders. Moreover, by increasing the content of silica in composite nanopowders, the crystallinity will be decreased,and the ability of the product as a bone substitute material might be controlled by changing the content of the ingredients and subsequently its structure.
HARDNESS STUDY OF THE PULSE ELECTRODEPOSITED NANOSCALE MULTILAYERS OFCR-NI
Authors: ETMINANFAR M.R. , HEYDARZADEH SOHI M.
Published: March 2012

Nanoscale multilayers of Cr - Ni coatings were deposited on low carbon steel by pulse electroplating and agitation modulation in chromium (III)-nickel (II) bath. The coatings were characterized by using SEM, EDS, XRD and microhardness techniques. For hardness measurement, the total thickness of the coatings was fixed at 5 μm and the thickness of the monolayers in the coatings varied from 20 to 100 nm. Single chromium and single nickel coatings with similar thickness of 5 μm were also produced by using DC electroplating. Microhardness testing was carried out on the surface of the coatings by using a range of loads from 25 to 1000 gf. A composite hardness model was used to estimate and compare the hardness of the single and multilayer coatings. It was shown that multilayer deposition significantly increases the hardness of the coating and the hardness increases further as the thickness of the nano- monolayers is reduced.
HOT CORROSION RESISTANCE AND MECHANICAL BEHAVIOR OF ATMOSPHERIC PLASMA SPRAYED CONVENTIONAL AND NANOSTRUCTURED ZIRCONIA COATINGS
Authors: SAREMI MOHSEN , KEYVANI AHMAD , HEYDARZADEH SOHI MAHMOUD
Published: March 2012

Conventional and nanostructured zirconia coatings were deposited on In-738 Ni super alloy by atmospheric plasma spray technique. The hot corrosion resistance of the coatings was measured at 1050°C using an atmospheric electrical furnace and a fused mixture of vanadium pent oxide and sodium sulfate respectively. According to the experimental results nanostructured coatings showed a better hot corrosion resistance than conventional ones. The improved hot corrosion resistance could be explained by the change of structure to a dense and more packed structure in the nanocoating. The evaluation of mechanical properties by nano indentation method showed the hardness (H) and elastic modulus (E) of the YSZ coating increased substantially after hot corrosion.