bluuebunny/crossref_metadata_2025 huggingface dataset:
Treating Human Autoimmunity: Current Practice and Future Prospects
Authors: Rosenblum Michael D. , Gratz Iris K. , Paw Jonathan S. , Abbas Abul K.
Published: March 2012

Recent advances in understanding immune regulation set the stage for new targeted therapies for autoimmune disease.
Structure-Guided Design of a High-Affinity Platelet Integrin α
IIb
β
3
Receptor Antagonist That Disrupts Mg
2+
Binding to the MIDAS
Authors: Zhu Jieqing , Choi Won-Seok , McCoy Joshua G. , Negri Ana , Zhu Jianghai , Naini Sarasija , Li Jihong , Shen Min , Huang Wenwei , Bougie Daniel , Rasmussen Mark , Aster Richard , Thomas Craig J. , Filizola Marta , Springer Timothy A. , Coller Barry S.
Published: March 2012

A new drug blocks platelet aggregation by interacting with the integrin receptor differently from current drugs that cause adverse side effects.
What’s Up with BAT?
Authors: Nakamura Takahisa
Published: March 2012

Oxidative metabolism in brown adipose tissue speeds up when humans are exposed to cold.
Initial experience with distal guide catheter placement in the treatment of cerebrovascular disease: clinical safety and efficacy
Authors: Turk Aquilla , Manzoor Muhammad Usman , Nyberg Eric MacKenzie , Turner Raymond D , Chaudry Imran
Published: March 2012

Background

Advancements in technology have created a current generation of guide catheters that not only provide stable access but also allow navigation of tortuous portions of the carotid siphon facilitating more distal access. Clinical experience since the release of the current generation of guide catheters was reviewed to determine their safety and efficacy.

Methods

Between October 2007 and November 2011, all neurointerventional procedures requiring access to the intracranial arterial circulation performed at our institution were reviewed. Clinical performance and complication rates of current generation guide catheters were compared with conventional guide catheters.

Results

1188 neurointerventional procedures were performed, of which 659 were eligible for this study. When navigating the anterior circulation, intracranial purchase was achieved significantly more often with current generation 0.070 inch and 0.053 inch guide catheters compared with conventional guide catheters. Similarly, current generation 0.070 inch and 0.053 inch catheters navigated at least one sharp 90° turn significantly more often than conventional guide catheters. Guide catheter related complications were encountered in 1.4% of cases with both catheter generations and differences were not significant although more complications were found when guide catheter tip position was cervical rather than intracranial.

Conclusion

Current generation guide catheters allow distal access with a high rate of success while maintaining a low rate of complications. When intracranial location of the guide catheter was obtained, fewer complications occurred.
Missed opportunities—low levels of chlamydia retesting at Australian general practices, 2008–2009
Authors: Bowring Anna L , Gouillou Maelenn , Guy Rebecca , Kong Fabian Y S , Hocking Jane , Pirotta Marie , Heal Clare , Brett Tom , Donovan Basil , Hellard Margaret
Published: March 2012

Objective

Chlamydia reinfection is common and increases the risk of reproductive complications. Guidelines for Australian general practitioners recommend retesting 3–12 months after a positive result but not before 6 weeks. The authors describe retesting rates among 16–29-year-old patients diagnosed as having chlamydia at 25 general practice clinics participating in the Australian Collaboration for Chlamydia Enhanced Sentinel Surveillance system.

Methods

The authors calculated annual testing and positivity rates for 16–29-year-olds attending in 2008–2009, re-attendance and retesting rates within <6 weeks, 1.5–4 months and 1.5–12 months of a positive test in 2008–2009 and positivity at retest (where results were available).

Results

There were 50 408 individuals (60.4% women) who attended in 2008–2009. Annually, 7.4% and 7.3% were tested for chlamydia, of whom 9.1% and 8.0% tested positive, respectively. Within 1.5–4 months of a positive test, 24.6% re-attended and were retested (19% tested positive), 31.6% re-attended and were not retested and 43.9% did not re-attend. Within 1.5–12 months, 40% re-attended and were retested (16% tested positive), 40% re-attended and were not retested and 20% did not re-attend. Of individuals re-attending in 1.5–12 months but not retested, 50% had re-attended three or more times in the period. Within 6 weeks of a positive test, 25% were retested.

Discussion

A high proportion of 16–29-year-olds re-attended general practices in the recommended retest periods, but retesting rates were low and multiple missed opportunities were common. The findings highlight the need for strategies such as electronic clinician prompts, patient recall systems and promotion of retesting guidelines.
Where do sexually active female London students go to access healthcare? Evidence from the POPI (Prevention of Pelvic Infection) chlamydia screening trial
Authors: Green Ruth , Kerry Sarah R , Reid Fiona , Hay Phillip E , Kerry Sally M , Aghaizu Adamma , Oakeshott Pippa
Published: March 2012

Background

Little is known about where sexually active female students access healthcare.

Objectives

Using data from the Prevention of Pelvic Infection (POPI) cohort, the authors aimed to:

Describe where sexually active female students aged ≤27 years reported accessing healthcare.

Investigate the association between numbers of sexual partners during 12 months of follow-up and healthcare usage, health-related quality of life (EQ-5D) and demographic and behavioural characteristics.

Methods

Participants provided vaginal swabs and completed questionnaires on sexual health and quality of life at baseline and at a 12-month follow-up. The follow-up questionnaire also asked about healthcare attendances during the previous 12 months. Mann–Whitney tests were used to relate healthcare seeking behaviour and other characteristics to reported numbers of partners during follow-up.

Results

Of 1865 women included in the analysis, 79% paid at least one visit to their general practice during follow-up, 23% attended an accident and emergency/walk-in clinic, 21% a family planning clinic and 14% a genitourinary medicine clinic. As the number of sexual partners increased (0–1, 2–3, 4+), women were more likely to have visited a genitourinary medicine clinic (10%, 16%, 30%, p<0.001) or accident and emergency/walk-in clinic (21%, 26%, 29%, p<0.002). Women with more sexual partners were also more likely to smoke, use condoms, be aged <16 years at sexual debut, have bacterial vaginosis, chlamydia or gonorrhoea at baseline and to have lower EQ5-D scores.

Conclusion

This is the first UK study of healthcare attendance in multiethnic female students recruited outside healthcare settings. The high attendance in general practice may represent a valuable opportunity for screening for sexually transmitted infections.
APPLICATION OF ICA–EEMD TO SECURE COMMUNICATIONS IN CHAOTIC SYSTEMS
Authors: LIN SHIH-LIN , TUNG PI-CHENG , HUANG NORDEN E.
Published: March 2012

We propose the application of ICA–EEMD to secure communication systems. ICA–EEMD is employed to retrieve the message data encrypted by a mixture of Gaussian white noise and chaotic noise. The results showed that ICA–EEMD can effectively extract the two original message data.
SYNCHRONIZABILITY OF COMPLEX NETWORKS WITH COMMUNITY STRUCTURE
Authors: JALILI MAHDI
Published: March 2012

Many real-world networks show community structure characterized by dense intra-community connections and sparse inter-community links. In this paper we investigated the synchronization properties of such networks. In this work we constructed such networks in a way that they consist of a number of communities with scale-free or small-world structure. Furthermore, with a probability, the intra-community connections are rewired to inter-community links. Two synchronizability measures were considered as the eigenratio of the Laplacian matrix and the phase order parameter obtained for coupled nonidentical Kuramoto oscillators. We found a power-law relation between the eigenratio and the inter-community rewiring probability in which as the rewiring probability increased, the eigenratio decreased, and hence, the synchronizability enhanced. The phase order parameter also increased by increasing the rewiring probability. Also, small-world networks with community structure showed better synchronization properties as compared to scale-free networks with community structure.
A Systematic Review of the Effectiveness of Qigong Exercise in Cardiac Rehabilitation
Authors: Chan Cecilia Lai-Wan , Wang Chong-Wen , Ho Rainbow Tin-Hung , Ho Andy Hau-Yan , Ziea Eric Tat-Chi , Taam Wong Vivian Chi-Woon , Ng Siu-Man
Published: March 2012

The objective of this study was to assess evidence for the efficacy and effectiveness of Chinese qigong exercise in rehabilitative programs among cardiac patients. Thirteen databases were searched through to November 2010, and all controlled clinical trials on Chinese qigong exercise among patients with chronic heart diseases were included. For each included study, data was extracted and validity was assessed. Study quality was evaluated and summarized using both the Jadad Scale and the criteria for levels of evidence. Seven randomized controlled trials (RCTs) and one non-randomized controlled clinical trial (CCT) published between 1988 and 2007 met the inclusion criteria. In total, these studies covered 540 patients with various chronic heart diseases including atrial fibrillation, coronary artery disease, myocardial infarct, valve replacement, and ischemic heart disease. Outcome measures emerged in these studies included subjective outcomes such as symptoms and quality of life; and objective outcomes such as blood pressure, ECG findings, and exercise capacity, physical activity, balance, co-ordination, heart rate, and oxygen uptake. Overall, these studies suggest that Chinese qigong exercise seems to be an optimal option for patients with chronic heart diseases who were unable to engage in other forms of physical activity; however, its efficacy and effectiveness in cardiac rehabilitation programs should be further tested.
PRICING DECISIONS FOR A CLOSED-LOOP SUPPLY CHAIN IN A FUZZY ENVIRONMENT
Authors: WEI JIE , ZHAO JING , LI YONGJIAN
Published: March 2012

This paper studies pricing problem for a closed-loop supply chain consisting of a manufacturer and a retailer in a fuzzy environment. The purpose of this paper is to explore how the manufacturer makes his decisions about wholesale price and transfer price and how the retailer makes her decisions about retail price and collecting price in the expected value standard. Each firm's optimal pricing strategies are established by using game theory under the centralized and decentralized decision cases, respectively. Managerial insights into the economic behavior of firms are also investigated, which can serve as the basis for empirical study in the future. Moreover, we analyze numerically the results and give some insights on the influence of some parameters.
OPTIMAL PROCUREMENT STRATEGY UNDER SUPPLY RISK
Authors: GURNANI HARESH , GÜMÜŞ MEHMET , RAY SAIBAL , RAY TRIDIP
Published: March 2012

With the rapid expansion of global business, newer suppliers with cheaper but possibly unreliable technologies have entered the marketplace to win orders from buyer firms by beating the price of their perfectly reliable (but expensive) competitors. We model the procurement problem as a Nash game where the buyer has to allocate its purchases between an expensive but reliable supplier, and a cheaper but unreliable supplier. The suppliers specify prices for different proportions of the order awarded to them. Our analysis shows that, when perfect information is available about the reliability level of the unreliable supplier, the Nash equilibrium is a sole-sourcing allocation and that the supplier selection decision depends on the reliability and cost differentials between the two suppliers. In addition, we model the case when the buyer and the reliable supplier have limited information about the reliability of the unreliable supplier. Even in such an asymmetric scenario, the buyer's equilibrium allocation is a sole-sourcing outcome, but depending on system conditions either a separating or a pooling equilibrium is possible. An interesting insight into the effect of information asymmetry is that it can result in higher or lower profits/costs for the channel partners (compared to the perfect information case). As such, the buyer may even benefit from information asymmetry regarding unreliable supplier due to its impact on the degree of competition between the two suppliers.
POSTPONED HOLDBACK PRICING, PROFIT AND CONSUMER SURPLUS
Authors: GERCHAK YIGAL
Published: March 2012

Operational decisions of a monopolist firm affect expected social welfare, a fact typically ignored by OM models. Specifically, the price selected directly affects the consumer surplus, which has to be added to firm's profit to find the social welfare. We assume an uncertain, price-sensitive, demand. Production capacity is selected at the outset, but the price is chosen after demand uncertainty realized itself. This model was proposed by Van Mieghem and Dada (1999), but we extend it to other demand functions. We then compute the resulting consumer surplus. Finally, we consider such issues in a decentralized supply chain with revenue sharing.
STUDY OF $p\bar{\Lambda}$ AND $p\bar{\Sigma}$ SYSTEMS IN CONSTITUENT QUARK MODELS
Authors: HUANG HONGXIA , PING JIALUN , WANG FAN
Published: March 2012

The [Formula: see text] systems with J = 0 and J = 1 are dynamically investigated within the framework of two constituent quark models: the chiral quark model and the quark delocalization color screening model. The model parameters are taken from our previous work, which gave a good description of the proton–antiproton S-wave elastic scattering cross-section experimental data. The [Formula: see text] elastic scattering processes with coupling to [Formula: see text] state are studied. The results show that, there is no s-wave bound state as indicated by an enhancement near the threshold of [Formula: see text] in J/ψ decay. However, a [Formula: see text] resonance state is given in the quark delocalization color screening model.
CHANNEL CONDUCTANCE OF ABA STACKING TRILAYER GRAPHENE NANORIBBON FIELD-EFFECT TRANSISTOR
Authors: SADEGHI HATEF , AHMADI M. T. , MOUSAVI S. M. , ISMAIL RAZALI , GHADIRY MAHDIAR H.
Published: March 2012

In this paper, our focus is on ABA trilayer graphene nanoribbon (TGN), in which the middle layer is horizontally shifted from the top and bottom layers. The conductance model of TGN as a FET channel is presented based on Landauer formula. Besides the good reported agreement with experimental study lending support to our model, the presented model demonstrates that minimum conductivity increases dramatically by temperature. It also draws parallels between TGN and bilayer graphene nanoribbon, in which similar thermal behavior is observed. Maxwell–Boltzmann approximation is employed to form the conductance of TGN near the neutrality point. Analytical model in degenerate regime in comparison with reported data proves that TGN-based transistor will operate in degenerate regime like what we expect in conventional semiconductors. Moreover, our model confirms that in similar condition, the conductivity of TGN is less than bilayer graphene nanoribbon as reported in some experiments.
SPECIFIC HEAT AND THERMODYNAMIC CRITICAL FIELD FOR CALCIUM UNDER THE PRESSURE AT 120 GPa
Authors: SZCZȨSNIAK RADOSŁAW , DURAJSKI ARTUR P. , JAROSIK MARCIN W.
Published: March 2012

In the paper, the thermodynamic parameters of the superconducting state for Calcium under the pressure at 120 GPa have been determined. The numerical analysis has been made in the framework of the Eliashberg approach. In particular, the free energy difference between the superconducting and normal state has been calculated. On the basis of the obtained results, the specific heat for the superconducting (CS) and normal (CN) state, as well as the thermodynamic critical field (HC) have been determined. It has been shown that the characteristic values of the considered thermodynamic functions do not obey the BCS universal laws: ΔC(TC)/CN(TC) = 2.48 and [Formula: see text].
THERMODYNAMICAL PROPERTIES OF A TRAPPED INTERACTING BOSE GAS
Authors: YANG SHI-JIE , LIU YUECHAN , FENG SHIPING
Published: March 2012

The thermodynamical properties of interacting Bose atoms in a harmonic potential are studied within the mean-field approximation. For weak interactions, the quantum statistics is equivalent to an ideal gas in an effective mean-field potential. The eigenvalue of the Gross–Pitaevskii equation is identified as the chemical potential of the ideal gas. The condensation temperature and density profile of atoms are calculated. It is found that the critical temperature Tc decreases as the interactions increase. Below the critical point, the condensation fraction exhibits a universal relation of N0/N = 1-(T/Tc)γ, with the index γ ≈ 2.3 independent of the interaction strength, the chemical potential, as well as the frequency of the confining potential.
INTELLIGENT UNDERSTANDING OF USER INTERACTION IN IMAGE SEGMENTATION
Authors: SPINA THIAGO V. , DE MIRANDA PAULO A. V. , FALCÃO ALEXANDRE X.
Published: March 2012

We have developed interactive tools for graph-based segmentation of natural images, in which the user guides object delineation by drawing strokes (markers) inside and outside the object. A suitable arc-weight estimation is paramount to minimize user time and maximize segmentation accuracy in these tools. However, it depends on discriminative image properties for object and background. These properties can be obtained from some marker pixels, but their identification is a hard problem during delineation. Careless arc-weight re-estimation reduces user control and drops performance, while interactive arc-weight estimation in a step before interactive object extraction is the best option so far, albeit it is not intuitive for nonexpert users. We present an effective solution using the unified framework of the image foresting transform (IFT) with three operators: clustering for interpreting user interaction and determining when and where arc weights need to be re-estimated; fuzzy classification for arc-weight estimation; and marker competition based on optimum connectivity for object extraction. For validation, we compared the proposed approach with another interactive IFT-based method, which computes arc weights before extraction. Evaluation involved multiple users (experts and nonexperts), a dataset with several natural images, and measurements to quantify accuracy, precision, efficiency (user time and computation time), and user control, being some of them novel measurements, proposed in this work.
EXPERIENCES ON AN INTERNET LINK CHARACTERIZATION AND NETWORKED CONTROL OF A SMART WHEEL
Authors: TEJADO INÉS , VINAGRE BLAS M. , ROMERO MIGUEL , DE MADRID ÁNGEL P. , CHEN YANGQUAN
Published: March 2012

The number of control systems connected by local or global communication networks is increasing. In this type of system, the effects of time-varying network-induced delays and data losses are major drawbacks, and in order to achieve an efficient closed-loop system performance, a simple and feasible strategy compensates for these undesirable effects based on the characterization of the experimental network by using real traffic measurements. This paper aims to control a platform called Smart Wheel through Internet by applying this compensation strategy to three different controllers, of fractional and integer orders, based on the previous analysis of the Internet link. Experimental and simulation results are given to show the effectiveness of the proposed control strategies and the advantages of the Internet link modeling.
ON THE DNA OF ELEVEN MAMMALS
Authors: MACHADO J. TENREIRO , COSTA ANTÓNIO C. , QUELHAS MARIA DULCE
Published: March 2012

This paper studies the DNA code of eleven mammals from the perspective of fractional dynamics. The application of Fourier transform and power law trendlines leads to a categorical representation of species and chromosomes. The DNA information reveals long range memory characteristics.
HOW TO APPROXIMATE THE FRACTIONAL DERIVATIVE OF ORDER 1 < α ≤ 2
Authors: SOUSA ERCILIA
Published: March 2012

The fractional derivative of order α, with 1 < α ≤ 2 appears in several diffusion problems used in physical and engineering applications. Therefore to obtain highly accurate approximations for this derivative is of great importance. Here, we describe and compare different numerical approximations for the fractional derivative of order 1 < α ≤ 2. These approximations arise mainly from the Grünwald–Letnikov definition and the Caputo definition and they are consistent of order one and two. In the end some numerical examples are given, to compare their performance.
EXISTENCE AND CONTINUATION THEOREMS OF RIEMANN–LIOUVILLE TYPE FRACTIONAL DIFFERENTIAL EQUATIONS
Authors: KOU CHUNHAI , ZHOU HUACHENG , LI CHANGPIN
Published: March 2012

In this paper we study the existence and continuation of solution to the general fractional differential equation (FDE) with Riemann–Liouville derivative. If no confusion appears, we call FDE for brevity. We firstly establish a new local existence theorem. Then, we derive the continuation theorems for the general FDE, which can be regarded as a generalization of the continuation theorems of the ordinary differential equation (ODE). Such continuation theorems for FDE which are first obtained are different from those for the classical ODE. With the help of continuation theorems derived in this paper, several global existence results for FDE are constructed. Some illustrative examples are also given to verify the theoretical results.
THE INCREMENTAL RATIO BASED CAUSAL FRACTIONAL CALCULUS
Authors: ORTIGUEIRA MANUEL D. , RIVERO MARGARITA , TRUJILLO JUAN J.
Published: March 2012

The generalized incremental ratio fractional derivative is revised and its main properties deduced. It is shown that in the case of analytic functions, it enjoys some interesting properties like: linearity and causality and has a semi-group structure. Some simple examples are presented. The enlargement of the set of functions for which the group properties of the fractional derivative are valid is done. With this, it is shown that some well-known results are valid in a more general set-up. Some examples are presented.
CHAOS IN DIFFUSIONLESS LORENZ SYSTEM WITH A FRACTIONAL ORDER AND ITS CONTROL
Authors: XU YONG , GU RENCAI , ZHANG HUIQING , LI DONGXI
Published: March 2012

This paper aims to investigate the phenomenon of Diffusionless Lorenz system with fractional-order. We discuss the stability of equilibrium points of the fractional-order system theoretically, and analyze the chaotic behaviors and typical bifurcations numerically. We find rich dynamics in fractional-order Diffusionless Lorenz system with appropriate fractional order and system parameters. Besides, the control problem of fractional-order Diffusionless Lorenz system is examined using feedback control technique, and simulation results show the effectiveness of the method.
CHAOS OF THE PROPAGATING PULSE WAVE IN A RING OF SIX-COUPLED BISTABLE OSCILLATORS
Authors: KAMIYAMA KYOHEI , ENDO TETSURO
Published: March 2012

In this paper, some properties of the chaotic propagating pulse wave in a ring of six-coupled bistable oscillators are investigated. When coupling factor α becomes large beyond a certain critical value, the standing pulse wave converts to a propagating pulse wave. Further, as α is increased, the propagating pulse wave behaves chaotically. We find some interesting properties of the chaotic propagating pulse wave such as random change of propagating direction and stepwise change of pulse position with respect to time. In particular, we notice that the shape of probability density of one-direction propagation time and distance is similar to that of Logistic map.
DYNAMICS OF A PREY-DEPENDENT DIGESTIVE MODEL WITH STATE-DEPENDENT IMPULSIVE CONTROL
Authors: QIAN LINNING , LU QISHAO , BAI JIARU , FENG ZHAOSHENG
Published: March 2012

In this paper, we study the dynamical behavior of a prey-dependent digestive model with a state-dependent impulsive effect. Using the Poincaré map and the Lambert W-function, we find the analytical expression of discrete mapping. Sufficient conditions are established for transcritical bifurcation and period-doubling bifurcation through an analytical method. Exact locations of these bifurcations are explored. Numerical simulations of an example are illustrated which agree well with our theoretical results.
SCALE-FREE LUBY TRANSFORM CODES
Authors: ZHAO YULI , LAU FRANCIS C. M. , ZHU ZHILIANG , YU HAI
Published: March 2012

This paper reports the characteristics and performance of a new type of Luby Transform codes, namely scale-free Luby Transform (SF-LT) codes. In the SF-LT codes, the degree of the encoded symbol follows a modified power-law distribution. Moreover, the complexity and decoding performance of SF-LT codes are compared with LT codes based on robust soliton degree distribution and LT codes based on suboptimal degree distribution. The results show that SF-LT codes outperform other LT codes in terms of the probability of successful decoding over an ideal channel and a binary erasure channel. Moreover, the encoding/decoding complexity for the SF-LT codes is superior.
A SPECTRAL RADIUS ESTIMATE AND ENTROPY OF HYPERCUBES
Authors: GELLER WILLIAM , KITCHENS BRUCE , MISIUREWICZ MICHAŁ , RAMS MICHAŁ
Published: March 2012

We consider a problem in Mathematical Biology that leads to a question in Graph Theory, which can be solved using an old but not widely known upper estimate of the spectral radius of a non-negative matrix. We provide a new proof of this estimate.
TWIN GROUPS OF VIRTUAL 2-BRIDGE KNOTS AND ALMOST CLASSICAL KNOTS
Authors: NAKAMURA TAKUJI , NAKANISHI YASUTAKA , SATOH SHIN , TOMIYAMA YUMI
Published: March 2012

Every virtual knot has a pair of groups called the upper and lower groups of the knot. In this paper we treat two topics on those groups: We first give a sufficient condition for a pair of groups which are realized by a certain virtual knot as the upper and lower groups. Secondly we give a necessary condition for a virtual knot to be almost classical in terms of the first elementary ideals of the groups.
STUDY ON SYNTHESIS AND EVOLUTION OF NANOCRYSTALLINE Mg4Ta2O9 BY AQUEOUS SOL–GEL PROCESS
Authors: WU H. T. , YANG C. H. , WU W. B. , YUE Y. L.
Published: March 2012

Nanosized and highly reactive Mg4Ta2O9 were successfully synthesized by aqueous sol–gel method compared with conventional solid-state method. Ta-Mg-citric acid solution was first formed and then evaporated resulting in a dry gel for calcination in the temperature ranging from 600°C to 800°C for crystallization in oxygen atmosphere. The crystallization process from the gel to crystalline Mg4Ta2O9 was identified by thermal analysis and phase evolution of powders was studied using X-ray diffraction (XRD) technique during calcinations. Particle size and morphology were examined by transmission electron microscopy (TEM) and high resolution scanning electron microscopy (HR-SEM). The results revealed that sol–gel process showed great advantages over conventional solid-state method and Mg4Ta2O9 nanopowders with the size of 20–30 nm were obtained at 800°C.
RESTRICTIONS ON THE GEOMETRY OF THE PERIODIC VORTICITY EQUATION
Authors: ESCHER JOACHIM , WUNSCH MARCUS
Published: March 2012

We prove that several evolution equations arising as mathematical models for fluid motion cannot be realized as metric Euler equations on the Lie group DIFF∞(𝕊1) of all smooth and orientation-preserving diffeomorphisms on the circle. These include the quasi-geostrophic model equation, cf. [A. Córdoba, D. Córdoba and M. A. Fontelos, Formation of singularities for a transport equation with nonlocal velocity, Ann. of Math. 162 (2005) 1377–1389], the axisymmetric Euler flow in ℝd(see [H. Okamoto and J. Zhu, Some similarity solutions of the Navier–Stokes equations and related topics, Taiwanese J. Math. 4 (2000) 65–103]), and De Gregorio's vorticity model equation as introduced in [S. De Gregorio, On a one-dimensional model for the three-dimensional vorticity equation, J. Stat. Phys. 59 (1990) 1251–1263].
CHARACTERIZATION OF NANO-STRUCTURED BAINITIC STEEL
Authors: BELADI HOSSEIN , TIMOKHINA ILANA B. , HODGSON PETER D. , ADACHI YOSHITAKA
Published: March 2012

A 0.79 C -1.5 Si -1.98 Mn -0.98 Cr -0.24 Mo -1.06 Al -1.58 Co ( wt %) steel was isothermally heat treated at 200°C for 10 days to produce a nano-structured bainitic steel. The microstructure consisted of nanobainitic ferrite laths with a high dislocation density and retained austenite films having extensive twins. The crystallographic analysis using TEM and EBSD revealed that the bainitic ferrite laths are close to the Nishiyama-Wassermann orientation relationship with their parent austenite. There was only one type of packet identified in a given transformed austenite grain. Each packet consisted of two different blocks having variants with the same habit plane, but different crystallographic orientations. Atom Probe Tomography (APT) revealed that the carbon content of nanobainitic ferrite laths was much higher than expected from the para-equilibrium level. This was explained due to the long heat treatment time, which led to the formation of fine Fe - C clusters on areas with high dislocation densities in bainitic ferrite laths.
Purification of Attrition Milled Nano-size Boron Carbide Powder
Authors: Sokhansanj A. , Hadian A.M.
Published: March 2012

Boron carbide is one of the advanced ceramic materials which is used in a wide range of applications. However, this material needs a high sintering temperature (~2200°C). Using nano-size powders for producing ceramic parts results in lowering sintering temperature and also enhances toughness and hardness of the material. One of the methods for producing ceramic nano powders is attrition milling. However, as the milling balls and wall are made of steel, some impurities specially iron will be introduced to the powder during milling. Chemical analysis of the milled powder shows that more than 33wt% of the powder consists of iron. These uncontrolled impurities affect the mechanical and physical properties of sintered ceramic parts that are made of such a powder. Therefore, these impurities must be removed from the powder. Hydro metallurgical beneficiation technique with two different solvents has been used for purification of the powder. The result of chemical analysis after purification showed that the weight percentage of iron in powder dropped to 9% and 0.8% (depending on the solvents). Moreover, the sintering behavior of hot-pressed boron carbide powder with different percentages of iron as sintering aid has been studied. The results showed excellent densification and hardness of the sintered parts.
EFFECT OF AMMONIA SOLUTION ON COMPOSITION, STRUCTURE AND MAGNETIC PROPERTIES OF CHEMICALLY PREPARED Co-B NANO-PARTICLES
Authors: SABAROU HOOMAN , ATAIE ABOLGHASEM
Published: March 2012

In this study, the effect of ammonia solution addition as a pH adjusting component on the thermal behavior, phase composition, morphology, and magnetic properties of reduced Co - B nano-particles fabricated by chemical reduction route have been studied using DSC, XRD, SEM, and VSM techniques, respectively. Chemical composition of the samples was measured by ICP.

The ICP results showed that basic pH of reagent solution, derived from utilizing ammonia solution, caused the boron content to decrease. XRD results indicated an amorphous structure for both samples synthesized with and without ammonia solution. Analysis of the DSC results showed that crystallization behavior has dramatically altered, owing to utilize ammonia solution. While the sample synthesized without ammonia solution showed three distinctive exothermic peaks at 216,470, and 540°C, the sample synthesized in the presence of ammonia solution exhibited only two exothermic peaks at 235 and 470°C and one endothermic peak at 370°C. SEM images reveal that the samples have a net- like morphology and the net is formed by many interconnected spherical fine particles with sizes less than 100 nm. Saturation magnetization of the sample synthesized in the presence of ammonia solution has improved significantly, probably due to the less amount of boron.
SYNTHESIS OF MO-CO ALLOY NANOPOWDER BY CO-PRECIPITATION METHOD FOLLOWED BY H2 REDUCTION
Authors: SABERYAN KAMAL , FIROOZI SADEGH , MORADMAND AMIN , REYHANI ALI
Published: March 2012

Cobalt-Molybdenum alloy nanopowder has magnetic properties and is used as catalyst for production of carbon nanotubes. Properties of this nanopowder depend on, for example, its size, morphology and internal residual stress. Synthesis of nanopowder of Molybdenum-Cobalt alloy by co-precipitation in an aqueous media using NH 4 OH as precipitating agent followed by calcination and reduction was investigated. The synthesis was started by dissolving salts of Cobalt and Molybdenum in water. A suspension of alumina or silica powders was used as a bed for precipitation. The effect of bed materials on size and morphology of the precipitate was investigated. The particles observed with scanning electron microscope possess a spherical shape and a needle shape for the samples participated on alumina and silica beds, respectively. XRD analysis of the calcined precipitate showed the formation of mixed oxide of CoMoO 4 as well as single oxides of Co 3 O 4 and MoO 3. Particle size of the precipitate observed with transmission electron microscope was about 100 nm. Finally, the powders were reduced by hydrogen gas in a tubular furnace to prepare metallic nanopowder with composition of Co 3 Mo .
EFFECT OFZnADDITION ON LUMINESCENCE OFY2O3:EuNANOPOWDERS USING SOLUTION COMBUSTION METHOD
Authors: TOHIDLOU ESMAEIL , GANJKHANLOU YADOLAH , KAZEMZAD MAHMOOD , AFARANI MAHDI SHAFIEE
Published: March 2012

In this study, the effect of Zn doping on photoluminescence, Chromaticity and structural properties of Y2O3: Eu compound were studied. For this purpose, various Y2O3: Eu samples containing different Zn2+concentration and distribution were prepared by combustion method. The resultant samples were characterized by X-ray diffractometry (XRD), Photoluminescence spectroscopy (PL) and scanning electron microscopy (SEM). The XRD patterns of samples were also examined by Rietveld refinement method and results showed that the samples had nano-sized crystallites. It has been also shown that doping of Zn2+ion in structure of Y2O3: Eu compound can effectively enhance the PL intensity and chromaticity of Y2O3: Eu compound, while doping of Zn at surface of Y2O3: Eu powder reduces PL intensity, crystallinity and chromaticity of this compound.
SYNTHESIS AND MANIPULATION OF WO3 NANO PARTICLES FOR GAS SENSING APPLICATIONS
Authors: Heidari Elham kamali , Mahmoodi Seyed Reza , Marzbanrad Ehsan , Raisi Babak , Zmani Cyrus
Published: March 2012

Ultra fine WO 3 nanoparticles were synthesized by nanocasting route, using mesoporous SiO 2 as a template. BET measurements showed a specific surface area of 700m2/gr for synthesized SiO 2 while after impregnation and template removal, this area was reduced to 43m2/gr for WO 3 nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5nm possessing a monoclinic structure which is the favorite crystal structure for gas sensing applications. Alternative electric field was applied to align synthesized WO 3 nanoparticles between electrodes. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO 2 at 250°C.
ULTRA FINE-GRAINED AZ31 MAGNESIUM ALLOY OBTAINED BY A COMBINATION OF GRAIN REFINEMENT AND EQUAL CHANNEL ANGULAR PRESSING
Authors: TORBATI-SARRAF S.A. , MAHMUDI R.
Published: March 2012

Different amounts of Al -5 Ti -1 B master alloy ( TiBAl ) were added to the AZ 31 magnesium alloy ( Mg -3 Al -1 Zn -0.2 Mn ) as grain refiner and the resulting microstructure and grain size distributions were studied after extrusion and equal channel angular pressing (ECAP). Results showed that the addition of 0.6% TiBAl had the strongest grain refinement effect, reducing the grain sizes by 54.5 and 48.5% in the extruded and ECAPed conditions, respectively. The observed grain refinement was partly due to the presence of the thermally-stable micron- and submicron-sized particles in the melt which act as nucleation sites during solidification. During the high-temperature extrusion and ECAP processes, dynamic recrystallization (DRX) and grain growth are likely to occur. However, the mentioned particles will help in reducing the grain size by the particle stimulated nucleation (PSN) mechanism. Furthermore, the pinning effect of these particles can oppose grain growth by reducing the grain boundary migration. These two phenomena together with the partitioning of the grains imposed by the severe plastic deformation in the ECAP process have all contributed to the achieved ultrafine-grained structure in the AZ 31 alloy.
Microstructure and Mechanical Properties of the Twist Extruded Pure Copper after Rolling
Authors: Bahadori Sh. Ranjbar , Akbari Mousavi S. A. A. , Shahab A. R.
Published: March 2012

Recently, severe plastic deformation processes have been the essence of metal forming researches to produce ultrafine-grained materials. Twist Extrusion is one of the most unprecedented methods developed in recent years, but has some deficiencies. The main one is the microstructure and mechanical heterogeneity, occurring after twist extrusion. Performing rolling as a conventional forming technique was suggested as a solution in this paper. It not only decreased the grain size, but also reduced the mechanical heterogeneity, and improved the grain size distribution. Employing the twist extrusion process on pure copper samples was carried out using a twisted die with 60° die angle, and the samples were processed through rolling subsequently. The results demonstrated that employing the rolling process enhanced grain size homogeneity and bulk strength.
FABRICATION OF TI/SIC SURFACE NANO-COMPOSITE LAYER BY FRICTION STIR PROCESSING
Authors: SHAMSIPUR ALI , KASHANI-BOZORG SEYED FARSHID , ZAREIE-HANZAKI ABBAS
Published: March 2012

In the present investigation, novel Ti / SiC surface nano-composite layer was successfully fabricated by dispersing nano-sized SiC particles into commercially pure titanium plates employing friction stir processing technique. The process parameters such as tool rotation and advancing speeds were adjusted to produce defect-free surface composite layer, however, uniform distribution of the nano-size SiC particles in a matrix of titanium was achieved after the second pass. The micro hardness value of the Ti / SiC nano-composite surface layer was found to be ~534 HV; this is 3.3 times higher than that of the commercially pure titanium substrate. No reaction was detected between SiC powders and the titanium matrix after friction stir processing.
STRUCTURAL AND MORPHOLOGICAL EVALUATION OF NANO-SIZED MoSi2 POWDER PRODUCED BY MECHANICAL MILLING
Authors: SAMEEZADEH MAHMOOD , FARHANGI HASSAN , EMAMY MASOUD
Published: March 2012

Nano-sized intermetallic powders have received great attention owing to their property advantages over conventional micro-sized counterparts. In the present study nano-sized MoSi 2 powder has been produced successfully from commercially available MoSi 2 (3 μm) by a mechanical milling process carried out for a period of 100 hours. The effects of milling time on size and morphology of the powders were studied by SEM and TEM and image analyzing system. The results indicate that the as-received micrometric powder with a wide size distribution of irregular shaped morphology changes to a narrow size distribution of nearly equiaxed particles with the progress of attrition milling up to 100 h, reaching an average particle size of 71 nm. Structural evolution of milled samples was characterized by XRD to determine the crystallite size and lattice microstrain using Williamson-Hall method. According to the results, the crystallite size of the powders decreases continuously down to 23 nm with increasing milling time up to 100 h and this size refinement is more rapid at the early stages of the milling process. On the other hand, the lattice strain increases considerably with milling up to 65 h and further milling causes no significant changes of lattice strain.
FABRICATION AND CHARACTERIZATION OF AL-AL4C3 NANOCOMPOSITE BY MECHANICAL ALLOYING
Authors: MOHAMMAD SHARIFI E. , ENAYATI M. H. , KARIMZADEH F.
Published: March 2012

Aluminum carbide ( Al 4 C 3) seems to be an ideal reinforcement for producing aluminum matrix composites. Al 4 C 3 has high hardness and shear strength as well as a high melting point. The dispersion of Al 4 C 3 particles in the matrix produces a pinning effect that reduces aluminum grain growth, which improves the mechanical properties. In this study, aluminum powders were mixed with 4.5 wt.% graphite and mechanically alloyed using a high-energy ball mill in order to produce Al - Al 4 C 3 nanocomposite. The structural evaluation of powder particles after different milling times was studied by X-ray diffractometry, scanning electron microscopy and microhardness measurements. The aluminum crystallite size estimated with broadening of XRD peaks by Williamson–Hall formula. XRD results suggested that the grain size of aluminum decreased to nanometer range (30 nm) during ball milling. No Al 4 C 3 formed during the mechanical alloying process. Milled powders were then annealed at 300-600 °C for 1 h under argon atmosphere. Annealing at temperatures higher than 300 °C led to formation of Al 4 C 3 phase which increased as annealing temperature increased. Aluminum grain size remained in nanometer range after annealing process. The microhardness of powder particles increased after annealing. Both effects are due to the formation of nanosized Al 4 C 3 particles.
ELASTIC MODULUS MEASUREMENT OF NANOCOMPOSITE MATERIALS BY ATOMIC FORCE MICROSCOPY
Authors: Safanama Dorsa Sadat , Marashi Pirooz , Zolfaghari Hesari Alireza , Firoozi Sadegh , Aboutalebi Seyed Hamed , Jalilzadeh Somayeh
Published: March 2012

Nanocomposite fiber materials, particularly those constructed with uniform reinforcements, have been sought for a long time in materials science. The hoped-for enhancement of the properties of polymer–nanofiber composites have remained elusive, owing in part to the difficulties in performing mechanical measurements. Harnessing the strength of atomic force spectroscopy therefore offers a new handle for the measurement of mechanical properties such as elastic modulus. The paper, here, addresses distance dependent measurements (DDM) performed on the multi-walled carbon nanofiber (CNF) reinforced composite fibers. To quantitatively measure the elastic modulus of nanocomposite materials, measurements were carried out on different points on the surface of the sample and Force-Distance curves were then plotted. The obtained results fairly agree to previously measured values. The great improvement in elastic modulus was achieved without sacrificing the mechanical strength and stiffness of the polymer, and with minimal weight penalty.
SYNTHESIS OF BARIUM HEXAFERRITE/IRON OXIDES MAGNETIC NANO-COMPOSITES VIA HIGH ENERGY BALL MILLING AND SUBSEQUENT HEAT TREATMENT
Authors: MOLAEI M.J. , ATAIE A. , RAYGAN S.
Published: March 2012

Barium hexaferrite ( BaFe 12 O 19) is a hard magnetic ceramic with superior magnetic properties and in powder form has potential for application in high density recording media. In this research a mechano-chemical approach was applied in order to achieve a nano-structured magnetic composite. Graphite was used to reduce barium hexaferrite in mechanical milling medium under argon atmosphere. Milling was carried out with a ball to powder mass ratio of 35 and rotation speed of 300 rpm. Effects of milling time on phase composition and morphology of the samples were evaluated by XRD and SEM techniques, respectively.

XRD results revealed that after 20 hours of milling, nano-composite of BaFe 12 O 19/ Fe 3 O 4/ Fe 2 O 3 was obtained. By extending the milling time to 40 hours, FeO was detected as the dominant crystalline phase with crystallite size of 22 nm. Composite of Fe / FeO / Fe 3 O 4 was synthesized by controlled heat treatment of the 40 hours milled sample. SEM results revealed that particle size in the aforementioned heat treated composite sample reached to about 89 nm and the morphology of the samples changed slightly.
STUDY OF MECHANICAL PROPERTIES AND FRACTURE MODE OF ALUMINA-SILICON CARBIDE NANOCOMPOSITES
Authors: RAHIMNEZHAD YAZDI A. , BAHARVANDI H.R. , ABDIZADEH H. , EHSANI N.
Published: March 2012

In this study Al 2 O 3- SiC nanocomposites have been fabricated by mixing of alumina and silicon carbide nano powders, followed by hot pressing at 1700°C. The mechanical properties and fracture mode of Al 2 O 3- SiC nanocomposites containing different volume fractions (5, 10 and 15%) of nano scale SiC particles were investigated and compared with those of alumina. Al 2 O 3- SiC powders were prepared by planetary milling in isopropanol. Fracture mode of specimens was investigated by means of scanning electron microscopy. Nanocomposites were tougher than alumina when they were hot pressed at the same temperature, and the values of nanocomposite's flexural strength and hardness were higher than those of alumina. Flexural strength, hardness and fracture toughness of the nanocomposites increase by increasing the volume percent of SiC up to 10% and then decrease slightly. The Scanning electron microscopy observations showed that fracture mode changes from intergranular for alumina to transgranular for nanocomposites. Finally X-ray diffraction analysis couldn't detect any chemical reactions between Al 2 O 3 and SiC particles.
FORMATION OF TiN/TiB2/TiAl NANO-COMPOSITE BY MECHANICAL ALLOYING OF A POWDER MIXTURE OF Ti-Al-BN
Authors: YAZDI ROUHOLLAH , KASHANI-BOZORG SEYED FAESHID
Published: March 2012

In this investigation, TiN / TiB 2/ TiAl nano-composite powder was produced by mechanical alloying technique and subsequent heat treatment. A powder mixture of Ti , BN , and Al with a molar ratio of 4:2:1 was milled for up to 70 h. Microstructures were studied and characterized using X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy. The results indicated that TiN and TiB 2-based phases were formed in an amorphous Ti ( Al ) matrix after 30 h of ball milling. With progression of the milling, the amorphous Ti ( Al ) solid solution is partially crystallized and the particle size reduced significantly. Subsequent annealing of the milled product at 600 °C for 0.5 h resulted in the transformation of the unstable amorphous Ti ( Al ) to TiAl crystal structure and formation of TiN / TiB 2/ TiAl nano-composite powder.
Production of Nanocrystalline Magnetite for Adsorption of Cr(VI) Ions
Authors: JAVADI N. , RAYGAN SH. , SEYYED EBRAHIMI S. A.
Published: March 2012

Higher environmental standards have made the removal of toxic metals such as hexavalent chromium from wastewater; an important problem for environmental protection. Iron oxide is a particularly interesting adsorbent to be considered for this application.

In this study, a new method combining adsorption and magnetic separation was developed to remove Cr ( VI ) from wastewater. The nanocrystalline magnetite as adsorbent was produced via thermo- mechanical reduction of hematite. Various parameters which affect the adsorption of Cr ( VI ) such as time, pH, temperature and initial concentration were investigated using thermo-gravimeters (TG), X-Ray diffraction (XRD), scanning electron microscopy (SEM) and atomic adsorption spectroscopy (AAS) techniques. The maximum adsorption was occurred at pH 2. The adsorption data were fitted well to Langmuir isotherm model. The adsorption of Cr ( VI ) increased significantly with increasing of temperature and time.