bluuebunny/crossref_metadata_2025 huggingface dataset:
Women Disarmed: The Militarization of Politics in Ireland 1913-23
Authors: Benton Sarah
Published: March 2012

The movement for ‘military preparedness’ in America and Britain gained tremendous momentum at the turn of the century. It assimilated the cult of manliness — the key public virtue, which allowed a person to claim possession of himself and a nation to reclaim possession of itself. An army was the means of marshalling a mass of people for regeneration. The symbol of a nation's preparedness to take control of its own soul was the readiness to bear arms.

Although this movement originated in the middle-class, Protestant cultures of the USA and England, its core ideas were adopted by many political movements. Affected by these ideas, as well as the formation of the Protestant Ulster Volunteers in 1913, a movement to reclaim Irish independence through the mass bearing of arms began in South and West Ireland in autumn 1914. Women were excluded from these Volunteer companies, but set up their own organization, Cumann na mBan, as an auxiliary to the men's. The Easter Rising in 1916 owed as much to older ideas of the coup d'état as new ideas of mass mobilization, but subsequent history recreated that Rising as the ‘founding’ moment of the Irish republic.

It was not until mass conscription was threatened two years later that the mass of people were absorbed into the idea of an armed campaign against British rule. From 1919 to 1923, the reality of guerrilla-style war pressed people into a frame demanding discipline, secrecy, loyalty and a readiness to act as the prime nationalist virtues. The ideal form of relationship in war is the brotherhood, both as actuality and potent myth. The mythology of brotherhood creates its own myths of women (as not being there, and men not needing them) as well as creating the fear and the myth that rape is the inevitable expression of brotherhoods in action. Despite explicit anxiety at the time about the rape of Irish women by British soldiers, no evidence was found of mass rape, and that fear has disappeared into oblivion, throwing up important questions as to when rape is a weapon of war.

The decade of war worsened the relationship of women to the political realm. Despite active involvement as ‘auxiliaries’ women's political status was permanently damaged by their exclusion as warriors and brothers, so much so that they disappear into the status of wives and mothers in the 1937 Irish Constitution.
Feminism and Institutionalized Racism: Inclusion and Exclusion at an Australian Feminist Refuge
Authors: Jan Wilson Tikka
Published: March 2012

This article is a microlevel discussion of indigenous/white relations at an Australian feminist refuge. It argues that the organization and practices of the refuge, including those which were specifically ‘feminist’ and those purporting to be anti-racist, reproduced a pattern of institutional racism which privileged and naturalized ‘whiteness’, white feminism and white women, and perpetuated the racial disadvantage of Aboriginal women, including continuing accountability to white colonizing women, loss of employment and economic security and contingent rather than guaranteed access to appropriate domestic violence crisis services. The article focuses on three interrelated concepts which were fundamental to the white women's construction and legitimation of their positions in the events: ‘sisterhood’, ‘multiculturalism’ and ‘the good feminist worker’.
Looking Good: The Lesbian Gaze and Fashion Imagery
Authors: Lewis Reina
Published: March 2012

This paper is concerned with the different forms of pleasure and identification activated in the consumption of dominant and subcultural print media. It centres on an analysis of the lesbian visual pleasures generated through the reading of fashion editorial in the new lesbian and gay lifestyle magazines. This consideration of the lesbian gaze is contrasted to the lesbian visual pleasures obtained from an against the grain reading of mainstream women's fashion magazines. The development of the lesbian and gay lifestyle magazines, in the context of the pink pound, produces a situation in which an eroticized lesbian visual pleasure is the overt remit of the magazine, rather than a clandestine pleasure obtained through a transgressive reading of dominant cultural imagery. In contrast to the polysemic free-play of fashion fantasy by which readers produce lesbian pleasure in the consumption of mainstream magazines, responses to the fashion content in the lesbian magazine Diva suggest that in a subcultural context readers deploy a realist mode of reading that demands a monosemic positive images iconography. The article uses the concept of subcultural competency to consider the different ways lesbians read mainstream and subcultural print media and suggests that the conflict over Diva‘s fashion spreads may be linked to changing patterns of identification and the use of dress for recognizability.
Gender, ‘Race’, Ethnicity in Art Practice in Post-Apartheid South Africa: Annie E. Coombes and Penny Siopis in Conversation
Authors: Coombes Annie E.
Published: March 2012

Siopis has always engaged in a critical and controversial way with the concepts of ‘race’ and ‘ethnicity’ in South Africa. For politically sensitive artists whose work has involved confronting the injustices of apartheid, the current post-apartheid situation has forced a reassessment of their practice and the terms on which they might engage with the fundamental changes which are now affecting all of South African society. Where mythologies of race and ethnicity have been strategically foregrounded in the art of any engaged artist, to the exclusion of many other concerns, the demise of apartheid offers the possibility of exploring other dimensions of lived experience in South Africa. For feminists, this is potentially a very positive moment when questions of gender – so long subordinated to the structural issue of ‘race’ under apartheid – can now be explored. Penny Siopis’ work has long been concerned with the lived and historical relations between black and white women in South Africa. The discussion focuses on the ambivalent and dependent relationships formed between white middle-class women and black domestic labour during apartheid. Siopis’ work engages with how the appropriation of black women's time, lives, labour and bodies has shaped her ‘own’ history.
Gram scale synthesis of high magnetic moment Fe100−xCox alloy nanoparticles: Reaction mechanism, structural and magnetic properties and its application on nanocomposite
Authors: Chinnasamy Chins , Herr Jonathan , Pai Riyanka , Cui Baozhi , Li Wanfeng , Liu Jinfang F.
Published: March 2012

Gram scale Fe100−xCox alloy nanoparticles with an average particle size of about 30 nm were synthesized in an inert atmosphere using a modified polyol process. The x-ray diffraction pattern clearly shows the formation of Fe100−xCox alloy nanoparticles. Electron microscopy studies depict the cubic morphology for the Fe57Co43 nanoparticles and nearly hexagonal shape for the Co66Fe34 alloy nanoparticles. The magnetic moment of Fe57Co43 nanoparticles that were synthesized in gram scale, were in the range of 21–21.5 kG (±0.5 kG) at room temperature and the Co66Fe34 nanoparticles were in the range 17.5–18 kG (±0.5 kG). Both samples had the intrinsic coercivity in the range of 150–165 Oe. The as-synthesized nanoparticles were used to fabricate the nanocomposite magnet by the hot press method. The composite demonstrated an exchange-coupled effect with a 15% enhancement of magnetic moment and remanence with a 2% addition of Fe57Co43 nanoparticles.
Ultrahard magnetic nanostructures
Authors: Sahota P. K. , Liu Y. , Skomski R. , Manchanda P. , Zhang R. , Franchin M. , Fangohr H. , Hadjipanayis G. C. , Kashyap A. , Sellmyer D. J.
Published: March 2012

The performance of hard-magnetic nanostructures is investigated by analyzing the size and geometry dependence of thin-film hysteresis loops. Compared to bulk magnets, weight and volume are much less important, but we find that the energy product remains the main figure of merit down to very small features sizes. However, hysteresis loops are much easier to control on small length scales, as epitomized by Fe-Co-Pt thin films with magnetizations of up to 1.78 T and coercivities of up to 2.52 T. Our numerical and analytical calculations show that the feature size and geometry have a big effect on the hysteresis loop. Layered soft regions, especially if they have a free surface, are more harmful to coercivity and energy product than spherical inclusions. In hard-soft nanocomposites, an additional complication is provided by the physical properties of the hard phases. For a given soft phase, the performance of a hard-soft composite is determined by the parameter (Ms - Mh)/Kh.
Simplified multi-track detection schemes using a priori information for bit patterned media recording
Authors: Kong Gyuyeol , Choi Sooyong
Published: March 2012

Simplified multi-track detection schemes using a priori information for bit patterned magnetic recording (BPMR) are proposed in this paper. The proposed detection schemes adopt the simplified trellis diagram, use a priori information, and detect the main-track data in the along- and cross-track directions. The simplified trellis diagram, which has 4 states and 8 branches, can be obtained by setting the corner entries of the generalized partial response (GPR) target to zero and replacing the four parallel branches with a single branch. However, these simplified techniques seriously suffer from performance degradation in high density BPMR channels. To overcome the performance degradation, a priori information is used to give higher reliability to the branch metric. In addition, to fully use the characteristics of channel detection with a two-dimensional (2D) GPR target, the proposed schemes estimate a priori information and detect the main-track data in the along- and cross-track directions by using a 2D equalizer with a 2D GPR target. The bit error rate performances of the proposed schemes are compared with the previous detection schemes when areal density is 3 Tb/in2. Simulation results show that the proposed schemes with simpler structures have more than 2 dB gains compared with the other detection schemes.
Unequal error correction strategy for magnetic recording systems with multi-track processing
Authors: Myint L. M. M. , Supnithi P.
Published: March 2012

In multi-track detection, the simultaneous recovery of user data of all tracks is obtained from multi-head or single-head reader with buffer. Due to incomplete inter-track interference (ITI) information of the outer tracks, unequal error rates exist among tracks. For a system with three-track processing, the center track exhibits a better performance than the others. In this work, we propose the unequal error protection (UEP) schemes to improve the overall system performance of a 2-D interference bit-patterned recording system with multi-track detection. The performances of the proposed schemes are investigated for the BPM channels with and without the media noise. Based on the simulation results, the proposed schemes offer the gain of about 0.2–0.3 dB over the equal error protection (EEP) scheme at a bit error rate of 10−4.
Effect of interlayer coupling on the reversal process of differential dual spin valves
Authors: Chandra Sekhar M. , Wang C. C. , Han G. C. , Lew W. S.
Published: March 2012

Differential dual spin valve (DDSV) is a potential read sensor for ultrahigh density magnetic recording. Recently, it has been found that self-biased DDSVs in which the two free layers (FLs) align in flux closure configuration could potentially remove permanent hard bias. In the present work, we have carried out a systematic study of the effect of the interlayer coupling through gap layer on the reversal process of a self-biased DDSV. From the uniform field response of the DDSV, it was found that the competition among magnetostatic coupling, interlayer coupling and the shape anisotropy of the FLs gives rise to distinctive reversal behaviors, and the magnetostatic coupling could not be perfectly compensated by the interlayer exchange coupling. The down track response of the DDSV reveals that interlayer coupling could play a dominant role on the performance of the DDSV.
Planar Hall effect sensors with shape-induced effective single domain behavior
Authors: Mor V. , Schultz M. , Sinwani O. , Grosz A. , Paperno E. , Klein L.
Published: March 2012

We show that shape anisotropy induces effective single domain behavior in elliptical structures of thin permalloy films with long axis ranging between several microns to several millimeters, provided that the ratio of the film long and short axes is large enough. We also show that the thin film elliptical structures exhibit a wide range of effective anisotropy fields, from less than 10 Oe up to more than 100 Oe. We discuss the advantage of shape anisotropy in the fabrication of planar Hall effect sensors with high field resolution.
Head field evaluation by anomalous Hall effect of recording layer with soft underlayer
Authors: Yamakawa Kiyoshi , Ohsawa Yuichi , Kiya Takanori , Ise Kazuyuki , Muraoka Hiroaki
Published: March 2012

In order to evaluate head field of planar heads under the presence of both a recording layer and a soft underlayer without head-medium interface problem, an integrated system of a planar head with an anomalous Hall effect (AHE) element was proposed. Head field is detected by an AHE sensor formed in a recording medium of which layer structure is quite similar to that of regular recording media. Fabrication of the integrated planar head and its measurement result are described.
Effects of oxide additives on inter-grain interaction of CoPtCr-oxide
Authors: Hou Hao-Cheng , Liao Jung-Wei , Wang Liang-Wei , Chen Rong-Zhi , Chiu Chun-Hao , Lin Hong-Ji , Chang Fan-Hsiu , Lai Chih-Huang
Published: March 2012

By using first order reversal curves (FORCs), we reveal distinct magnetization reversal behavior in the CoPtCr films with different oxide additives, including Ta2O5, SiO2 and their mixtures. Increasing the ratio of Ta2O5-to-SiO2 alters the inter-grain interaction from an exchange coupling (parallel) to a dipolar-field coupling (anti-parallel). During the sputtering process, the Ta2O5 additives release extra oxygen to induce the formation of CrOx, observed from X-ray absorption spectroscopy. The reduced grain-to-grain exchange coupling strength by increasing Ta2O5 additives could be attributed to the increased volume concentration of oxides and/or the presence of the CrOx.
Development and validation of a 10 kHz–1 MHz magnetic susceptometer with constant excitation field
Authors: Tafur Javier , Herrera Adriana P. , Rinaldi Carlos , Juan Eduardo J.
Published: March 2012

The design and validation of a mutual inductance AC susceptometer with constant excitation field of up to 4.25 Oe, operating at frequencies from 10 kHz to 1 MHz, is presented. Considerations such as parasitic capacitances between wire turns and sensing bridge electronics were taken into account in order to extend the operating frequency range. An 18AWG wire with considerable insulator thickness was used for coil construction to keep parasitic capacitive reactance negligible relative to coil inductive reactance, and to obtain controlled field operation. A high speed instrumentation amplifier (slew rate over 33 V/μs) was designed and constructed using voltage feedback LM7171 operational amplifiers. The system was calibrated with Dy2O3 to account for mismatches in signal amplitude and phase shifts due to the electronics, coil coupling and imperfections, and external disturbances. AC susceptometer operation in the 10 kHz–1 MHz frequency range was validated by measuring the complex susceptibility of cobalt ferrite nanoparticles suspended in solvents of different viscosities. Good agreement was found between the experimental Brownian relaxation times and those predicted theoretically from the viscosity of the suspending media and the hydrodynamic diameter of the nanoparticles.
Impact of Fe doping on radiofrequency magnetotransport in La0.7Sr0.3Mn1−xFexO3
Authors: Barik S. K. , Mahendiran R.
Published: March 2012

We report four probe ac electrical impedance (Z) in La0.7Sr0.3Mn1−xFexO3 (x ≤ 0.15) as a function of temperature (T) and magnetic field (H) in response to radio frequency (f = 0.1−5 MHz) ac current flowing directly through the sample. It is found that Z(T,H = 0) shows an abrupt increase around Curie temperature with increasing f and this excess resistance is suppressed under an external magnetic field. A large magnetoimpedance of ΔZ/Z = −21% at f = 1 MHz for x = 0.05 and −8.5% at f = 5 MHz for x = 0.15 are observed for H = 500 Oe. We suggest that the magnetoimpedance results from suppression of the high frequency transverse permeability by an external magnetic field. Optimization of composition and frequency of ac current will enable us to obtain much larger low-field magnetoimpedance value suitable for practical applications at room temperature.
Effect of hydriding degree on the microstructure and magnetic properties of sintered NdFeB magnets
Authors: Guo Shuai , Liu Youhao , Chen Bicheng , Yan Changjiang , Chen Renjie , Lee Don , Yan Aru
Published: March 2012

The effects of hydriding degree on the microstructure and magnetic properties of sintered NdFeB magnets have been studied. The degree of crushing depends on the absorption content of hydrogen and affects the magnetic properties of final magnet. Insertion of hydrogen atoms leads to a significant increase of the unit cell volume. And the crush mechanism depends on the internal stress resulting from differences in the expansion rates of the two phases. The remanence of final magnets increases monotonously while the coercivity decreases sharply with the increasing of hydriding degree, attributed to the strip fracture features and the morphology of particles.
A permanent magnet tubular linear generator for wave energy conversion
Authors: Yu Haitao , Liu Chunyuan , Yuan Bang , Hu Minqiang , Huang Lei , Zhou Shigui
Published: March 2012

A novel three-phase permanent magnet tubular linear generator (PMTLG) with Halbach array is proposed for the sea wave energy conversion. Non-linear axi-symmetrical finite element method (FEM) is implemented to calculate the magnetic fields along air-gap for different Halbach arrays of PMTLGs. The PMTLG characteristics are analyzed and the simulation results are validated by the experiment. An assistant tooth is implemented to greatly minimize the end and cogging effects which cause the oscillatory detent force.
Spectral properties of electromotive force induced by periodic magnetization reversal of arrays of coupled magnetic glass-covered microwires
Authors: Rodionova V. , Ilyn M. , Ipatov M. , Zhukova V. , Perov N. , Zhukov A.
Published: March 2012

In this paper we present the calculated spectra of signals originating from the magnetization reversal of a system of two identical bistable magnetic moments. We show that in contrast to the spectrum characteristic of magnetization reversal in any common ferromagnetic material, the amplitude of the harmonics in the calculated spectra can change periodically. Also, we present experimental spectra of signals induced by the magnetization reversal of two magnetically coupled glass-covered. Periodic variation of the harmonics amplitude predicted by the calculations was observed in the experimental spectra.
Monitoring iron oxide nanoparticle surface temperature in an alternating magnetic field using thermoresponsive fluorescent polymers
Authors: Polo-Corrales Liliana , Rinaldi Carlos
Published: March 2012

We report indirect measurements of the surface temperature of iron oxide nanoparticles in an alternating magnetic field (AMF) through the temperature induced change in fluorescence of a thermoresponsive/fluorescent polymer consisting of poly(N-isopropylacrylamide) (pNIPAM) copolymerized with a fluorescent modified acrylamide (FMA) monomer with fluorescent intensity that increases as its surroundings change from hydrophilic to hydrophobic. When the particles are suspended in water and subjected to external heating, the fluorescence is observed to remain constant up to about 35 °C, above which temperature it increases. When the particles dissipate heat internally in an AMF, the fluorescence intensity increases immediately upon application of the AMF, even though the temperature (as measured by an immersed fiber-optic probe) is below 35 °C. The observed increase in fluorescence intensity indicates a change in the microenvironment of the FMA due to the transition of the pNIPAM from hydrophilic to hydrophobic. This in turn suggests that the nanoparticle surface temperature is above 35 °C and therefore higher than the temperature of the surrounding medium.
High frequency study of core-shell and uncoated Fe3O4 nanoparticles
Authors: Kuanr Bijoy K. , Veerakumar V. , Kuanr Alka V. , Lingam Kiran , Mishra S. R. , Camley R. E. , Celinski Z.
Published: March 2012

Nanoparticles of Fe3O4 (core) were synthesized and some were covered with a thin layer of Au (shell) to create a core-shell structure. The dynamic magnetic properties were studied using a vector network analyzer. It was found that, at a given applied magnetic field, the core-shell nanoparticles resonate at lower frequency compared to the uncoated Fe3O4 nanoparticles and the resonance frequency increased with increasing applied field for both the core-shell and the uncoated nanoparticles. Also, the core-shell nanoparticles exhibited additional resonances. Further, the core-shell nanoparticles exhibited a larger linewidth compared to the uncoated counterparts for all the particle sizes. The experimental absorption data have been compared with the results obtained from an effective medium theory.
A comparison between magnetic and reflection loss characteristics of substituted strontium ferrite and nanocomposites of ferrite/carbon nanotubes
Authors: Ghasemi Ali , Shirsath Sagar E. , Liu Xiaoxi , Morisako Akimitsu
Published: March 2012

Large-scale carbon nanotubes (CNTs)/substituted strontium ferrite nanocomposites have been fabricated by hetero-coagulation. The structure and morphology of nanoparticles and nanocomposites were evaluated by high-resolution transmission electron microscopy (HRTEM). HRTEM confirmed that strontium ferrite was successfully attached to carbon nanotubes. The vibrating sample magnetometer (VSM) confirmed the relatively strong dependence of saturation magnetization with the volume percentage of multi-walled carbon nanotubes (MWCNTs). Reflection loss of nanocomposites at 12–18 GHz was evidently enhanced, as compared to that of strontium ferrite nanoparticles. The maximum reflection loss increased significantly with an increase in volume percentage of MWCNTs. It was proved that the microwave absorbing bandwidth was modulated simply by manipulating the thickness of nanocomposites. Reflection loss evaluations indicate that the nanocomposites display a great potential application as wide-band electromagnetic wave absorbers.
Microstructure study of pinning sites of highly (0001) textured Sm(Co,Cu)5 thin films grown on Ru underlayer
Authors: Zhao Haibao , Wang Hao , Liu Xiaoqi , Wang Jian-Ping
Published: March 2012

In this paper, microstructure study of pinning sites of highly (0001) textured Sm(Co,Cu)5 thin films was presented. Various types of pinning sites were identified, such as voids, grain/matrix boundaries (or crystalline/amorphous boundaries), grain boundaries between crystalline grains, and composition inhomogeneity in grains. One key finding of TEM elemental mapping was that Cu atoms were rich in the inner part of Sm(Co,Cu)5 grains (defined by Sm and Co concentrations), instead of the outer part of grains, such as grain boundaries. Cu served as an alloying element in Sm(Co,Cu)5 grains, not as a doping element to form Cu-rich grain boundaries. A model of Sm(Co,Cu)5 films with lateral graded anisotropy due to composition/crystallization variation can explain the huge difference between the HC and HK.
Spin stability and magnetic screening of a magnetic impurity in four-terminal Landauer setup with Rashba spin-orbit coupling
Authors: Su Yu-Hsin , Chen Chien-Liang , Chen Kuo-Wei , Chang Ching-Ray
Published: March 2012

The mean-field-assisted Landauer-Keldysh formalism is employed to study the orientation of a magnetic impurity embedded in two-dimensional electron gas with Rashba spin-orbit coupling. Interesting physics arises about the stability of the impurity spin. The spin of Rashba electrons interacting with magnetic impurity spin has two steady states, while the stable or unstable state depends on the local charge current and the exchange coupling strength between the local impurity spin and itinerant electrons. Furthermore, the stable steady state of impurity spin gives rise to an interesting phenomenon, magnetic screening effect in a 2DEG system.
Effect of dust non-linear charge and size-distribution on dust-acoustic double-layers in dusty plasmas
Authors: Ishak-Boushaki M. , Annou R. , Bharuthram R.
Published: March 2012

The investigation of the existence of arbitrarily large amplitude electrostatic dust-acoustic double layers is conducted in a four-component plasma consisting of electrons, two distinct positive ion species of different temperatures, and massive negatively-charged dust particles that are assumed spheres of different radii distributed according to a power-law. The dependence of the dust grain charge on its size is considered to be nonlinear. The number densities of electrons and ions are assumed to follow a Boltzmann distribution, whereas the dynamics of charged dust grains is described by fluid equations. Comparison is conducted between plasmas containing size-distributed dust grains and those containing monosize dust grains, while examining the criteria for the existence of dust-acoustic double layers along with the dependence of their amplitudes and Mach numbers on plasma parameters.
Dielectric spectra broadening as the signature of dipole-matrix interaction. I. Water in nonionic solutions
Authors: Levy Evgeniya , Puzenko Alexander , Kaatze Udo , Ishai Paul Ben , Feldman Yuri
Published: March 2012

Whenever water interacts with another dipolar entity, a broadening of its dielectric relaxation occurs. Often this broadening can be described by the Cole-Cole (CC) spectral function. A new phenomenological approach has been recently presented [A. Puzenko, P. Ben Ishai, and Y. Feldman, Phys. Rev. Lett. 105, 037601 (2010)]10.1103/PhysRevLett.105.037601 that illustrates a physical mechanism of the dipole-matrix interaction underlying the CC behavior in complex systems. By considering the relaxation amplitude Δɛ, the relaxation time τ, and the broadening parameter α, one can construct a set of 3D trajectories, representing the dynamic behavior of different systems under diverse conditions. Our hypothesis is that these trajectories will contribute to a deeper understanding of the dielectric properties of complex systems. The paper demonstrates how the model describes the state of water in aqueous solutions of non-ionic solutes. For this purpose complex dielectric spectra for aqueous solutions of D-glucose and D-fructose are analyzed.
Single lens photometric machine vision with 3D imaging for fiber-to-chip coupling
Authors: Liu Xu , Hu Hongmei , Sun Xiaohan
Published: March 2012

A single lens photometric machine vision (SLPMV) optical microbench is presented and built for fiber-to-chip coupling. By a rotation mechanics in SLPMV, the multi-view-camera can scan the various surface status of the chips coupled. To realize 3D imaging more explicitly, the modified photometric stereo algorithm is proposed through acquiring the images of weak saturation, matching the scanning illuminative angles, and rectifying rectangularly the original images. The reconstructed images have had similar qualities as those obtained by scanning electron microscopy and have unveiled the detailed information obscured in the 2D images. For the InP-based optical waveguide chip coupled with wedge-shaped fiber, the insertion loss tested on the SLPMV is 3 dB less than one on the conventional testing station. The SLPMV could serve as a more cost-effective and compact scientific observation instrumentation in imaging informatics than commercial ones.
Invited Article: A materials investigation of a phase-change micro-valve for greenhouse gas collection and other potential applications
Authors: Manginell Ronald P. , Moorman Matthew W. , Rejent Jerome A. , Vianco Paul T. , Grazier Mark J. , Wroblewski Brian D. , Mowry Curtis D. , Achyuthan Komandoor E.
Published: March 2012

The deleterious consequences of climate change are well documented. Future climate treaties might mandate greenhouse gas (GHG) emissions measurement from signatories in order to verify compliance. The acquisition of atmospheric chemistry would benefit from low cost, small size/weight/power of microsystems. In this paper, we investigated several key materials science aspects of a phase-change microvalve (PCμV) technology with low power/size/weight/cost for ubiquitous GHG sampling. The novel design, based on phase-change material low-melting-point eutectic metal alloys (indium-bismuth, InBi and tin-lead, SnPb), could be actuated at temperatures as low as 72 °C. Valve manufacturing was based on standard thick and thin-film processes and solder technologies that are commonly used in industry, enabling low-cost, high-volume fabrication. Aging studies showed that it was feasible to batch fabricate the PCμVs and store them for future use, especially in the case of SnPb alloys. Hermetic sealing of the valve prototypes was demonstrated through helium leak testing, and Mil spec leak rates less than 1 × 10−9 atm cm3/s were achieved. This confirms that the sample capture and analysis interval can be greatly expanded, easing the logistical burdens of ubiquitous GHG monitoring. Highly conservative and hypothetical CO2 bias due to valve actuation at altitude in 1 cm3 microsamplers would be significantly below 1.0 and 2.2 ppmv for heat-treated InBi and SnPb solders, respectively. The CO2 bias from the PCμV scales well, as a doubling of sampler volume halved the bias. We estimated the shelf life of the SnPb PCμVs to be at least 2.8 years. These efforts will enable the development of low cost, low dead volume, small size/weight microsystems for monitoring GHGs and volatile organic compounds.
Modeling and simulation of high voltage and radio-frequency transformer
Authors: Salazar Andrés O. , Barbosa Giancarlos C. , Vieira Madson A. A. , Quintaes Filipe de O. , da Silva Jacimário R.
Published: March 2012

This work presents a methodology for designing a 50 kW RF transformer operating at a frequency of 400 kHz with a view to operation with minimal magnetic losses used in the project experimental treatment of industrial wastes and effluents of petrochemical thermal plasma. This innovator model of a RF transformer offers many advantages over traditional transformers, the main ones being their small size for this power level, high power density, low electromagnetic radiation level, and easy and economic manufacturing. The equivalent circuit was obtained practically and theoretically at the university lab. From the project, simulations are made to evaluate the performance of different parameters as a function of magnetic induction, current density, and temperature.
Characterization of domain wall–based traps for magnetic beads separation
Authors: Donolato M. , Lofink F. , Hankemeier S. , Porro J. M. , Oepen H. P. , Vavassori P.
Published: March 2012

We characterize the magnetic behavior of an array of magnetic bead traps based on domain walls (DWs) formed in zig-zag permalloy wires patterned on a Si substrate. Using magnetic force and magneto-optical Kerr effect microscopy, we study the nucleation and annihilation of DWs for two different wire widths. Through scanning electron microscopy with polarization analysis, we analyze in detail the magnetization configuration of the DWs in the presence of a magnetic bead previously trapped by the DW stray field. Finally, we patterned the magnetic nanostructures directly on a polydimethylsiloxane (PDMS) substrate, and we show that the functionality of the device is completely maintained. These results pave the way to the integration of DW-based devices in a PDMS lab-on-a-chip system for magnetic bead separation.
Explicit all-atom modeling of realistically sized ligand-capped nanocrystals
Authors: Kaushik Ananth P. , Clancy Paulette
Published: March 2012

We present a study of an explicit all-atom representation of nanocrystals of experimentally relevant sizes (up to 6 nm), “capped” with alkyl chain ligands, in vacuum. We employ all-atom molecular dynamics simulation methods in concert with a well-tested intermolecular potential model, MM3 (molecular mechanics 3), for the studies presented here. These studies include determining the preferred conformation of an isolated single nanocrystal (NC), pairs of isolated NCs, and (presaging studies of superlattice arrays) unit cells of NC superlattices. We observe that very small NCs (3 nm) behave differently in a superlattice as compared to larger NCs (6 nm and above) due to the conformations adopted by the capping ligands on the NC surface. Short ligands adopt a uniform distribution of orientational preferences, including some that lie against the face of the nanocrystal. In contrast, longer ligands prefer to interdigitate. We also study the effect of changing ligand length and ligand coverage on the NCs on the preferred ligand configurations. Since explicit all-atom modeling constrains the maximum system size that can be studied, we discuss issues related to coarse-graining the representation of the ligands, including a comparison of two commonly used coarse-grained models. We find that care has to be exercised in the choice of coarse-grained model. The data provided by these realistically sized ligand-capped NCs, determined using explicit all-atom models, should serve as a reference standard for future models of coarse-graining ligands using united atom models, especially for self-assembly processes.
Rapid multi sample DNA amplification using rotary-linear polymerase chain reaction device (PCRDisc)
Authors: Sugumar D. , Kong L. X. , Ismail Asma , Ravichandran M. , Su Yin Lee
Published: March 2012

Multiple sample DNA amplification was done by using a novel rotary-linear motion polymerase chain reaction (PCR) device. A simple compact disc was used to create the stationary sample chambers which are individually temperature controlled. The PCR was performed by shuttling the samples to different temperature zones by using a combined rotary-linear movement of the disc. The device was successfully used to amplify up to 12 samples in less than 30 min with a sample volume of 5 μl. A simple spring loaded heater mechanism was introduced to enable good thermal contact between the samples and the heaters. Each of the heater temperatures are controlled by using a simple proportional–integral–derivative pulse width modulation control system. The results show a good improvement in the amplification rate and duration of the samples. The reagent volume used was reduced to nearly 25% of that used in conventional method.
Enhanced microwave absorption property of bowl-like Fe3O4 hollow spheres/reduced graphene oxide composites
Authors: Xu Huai-Liang , Bi Hong , Yang Ruey-Bin
Published: March 2012

A novel kind of Fe3O4 hollow spheres/reduced graphene oxide (r-GO) composites has been synthesized by a facile solvothermal method. The scanning electron microscopy and transmission electron microscopy images show bowl-like Fe3O4 hollow spheres with an average outer diameter of 395 nm and a shell thickness of 100 nm decorating on the both sides of r-GO sheets. The co-existence of both D and G peaks in Raman spectra confirms the presence of r-GO state, and an increased D/G intensity ratio of the composites suggests a substantial increase in disorder degree in the r-GO sheets due to the Fe3O4 hollow spheres anchoring on the surface. Compared to pristine r-GO, pure Fe3O4 nanoparticles, and the reported solid nano-Fe3O4/r-GO, both a wider and stronger absorption have been achieved in the frequency range of 2–18 GHz. In particular, the sample containing 30 wt. % as-synthesized hollow Fe3O4/r-GO with a coating layer thickness of 2.0 mm exhibits a maximum absorption of 24 dB at 12.9 GHz as well as a bandwidth of 4.9 GHz (from frequency of 10.8–15.7 GHz) corresponding to reflection loss at −10 dB. The measured complex relative permittivity and permeability data reveal that the enhanced microwave properties are contributed by a major improved dielectric loss and a minor magnetic loss resulting from the incorporation of hollow Fe3O4 on r-GO.
Ethanol adsorption on the Si (111) surface: First principles study
Authors: Gavrilenko Alexander V. , Bonner Carl E. , Gavrilenko Vladimir I.
Published: March 2012

Equilibrium atomic configurations and electron energy structure of ethanol adsorbed on the Si (111) surface are studied by the first principles density functional theory. Geometry optimization is performed by the total energy minimization method. Equilibrium atomic geometries of ethanol, both undissociated and dissociated, on the Si (111) surface are found and analysed. Reaction pathways and predicted transition states are discussed in comparison with available experimental data in terms of the feasibility of the reactions occurring. Analysis of atom and orbital resolved projected density of states indicates substantial modifications of the Si surface valence and conduction electron bands due to the adsorption of ethanol affecting the electronic properties of the surface.
2D properties of core turbulence on DIII-D and comparison to gyrokinetic simulations
Authors: Shafer M. W. , Fonck R. J. , McKee G. R. , Holland C. , White A. E. , Schlossberg D. J.
Published: March 2012

Quantitative 2D characteristics of localized density fluctuations are presented over the range of 0.3<r/a<0.9 in L-mode plasmas on DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)]. Broadband density fluctuations increase in amplitude from ñ/n<0.5% in the deep core to ñ/n∼2.5% near the outer region. The observed Doppler-shift due to the E×B velocity matches well with the measured turbulence group and phase velocities (in toroidally rotating neutral beam heated plasmas). Turbulence decorrelation rates are found to be ∼200 kHz at the edge and to decrease toward the core (0.45<r/a<0.9) where they approach the E×B shearing rate (∼50 kHz). Radial and poloidal correlation lengths are found to scale with the ion gyroradius and exhibit an asymmetric poloidally elongated eddy structure. The ensemble-averaged turbulent eddy structure changes its tilt with respect to the radial-poloidal coordinates in the core, consistent with an E×B shear mechanism. The 2D spatial correlation and wavenumber spectra [S(kr,kθ)] are presented and compared to nonlinear flux-tube GYRO simulations at two radii, r/a=0.5 and r/a=0.75, showing reasonable overall agreement, but the GYRO spectrum exhibits a peak at finite kr for r/a=0.75 that is not observed experimentally; E×B shear may cause this discrepancy.
Long-distance directed transfer of microwaves in tubular sliding-mode plasma waveguides produced by KrF laser in atmospheric air
Authors: Zvorykin V. D. , Levchenko A. O. , Shutov A. V. , Solomina E. V. , Ustinovskii N. N. , Smetanin I. V.
Published: March 2012

A new regime of the sliding-mode propagation of microwave radiation in plasma waveguides in atmospheric air is studied both experimentally and theoretically. The mechanisms of air photoionization and relaxation under propagation of 25-ns pulses of KrF laser are investigated. It is shown that a tubular plasma waveguide of large radius (much larger than wavelength of the microwave signal) can be produced in the photoionization of air molecules by 248-nm radiation of KrF-laser. We experimentally demonstrate the laser-enhanced transfer of 38-GHz microwave signal to a distance of at least 60 m. The mechanism of the transfer is determined by total internal reflection of the signal on the optically less dense wall of the plasma waveguide. Analytical and numerical simulations performed for various waveguide radii and microwave radiation wavelengths show that the propagation length increases with decrease in the wavelength reaching a few kilometers for submillimeter waves. Medium-size KrF laser facility with about 400-J energy in a train of picosecond pulses is suggested for the directed transfer of microwave radiation to 1-km distance.
A DFT+U study of acetylene selective hydrogenation on oxygen defective anatase (101) and rutile (110) TiO2 supported Pd4 cluster
Authors: Yang Jie , Lv Cun-Qin , Guo Yong , Wang Gui-Chang
Published: March 2012

The reaction mechanisms for selective acetylene hydrogenation on three different supports, Pd4 cluster, oxygen defective anatase (101), and rutile (110) titania supported Pd4, cluster are studied using the density functional theory calculations with a Hubbard U correction (DFT+U). The present calculations show that the defect anatase support binds Pd4 cluster more strongly than that of rutile titania due to the existence of Ti3+ in anatase titania. Consequently, the binding energies of adsorbed species such as acetylene and ethylene on Pd4 cluster become weaker on anatase supported catalysts compared to the rutile supported Pd4 cluster. Anatase catalyst has higher selectivity of acetylene hydrogenation than rutile catalyst. On the one hand, the activation energies of ethylene formation are similar on the two catalysts, while they vary a lot on ethyl formation. The rutile supported Pd catalyst with lower activation energy is preferable for further hydrogenation. On the other hand, the relatively weak adsorption energy of ethylene is gained on anatase surface, which means it is easier for ethylene desorption, hence getting higher selectivity. For further understanding, the energy decomposition method and micro-kinetic analysis are also introduced.
Doping helium nanodroplets with high temperature metals: Formation of chromium clusters
Authors: Ratschek Martin , Koch Markus , Ernst Wolfgang E.
Published: March 2012

A new method for stable and continuous doping of superfluid helium nanodroplets (HeN) with high-melting elements such as refractory metals is presented. The method exploits the advantages of electron bombardment heating and avoids stray fields induced by high currents or high frequency fields. It is thus especially suitable for magnetic studies of atoms and clusters in HeN. The source is characterized by means of mass spectroscopic investigations of HeN doped with chromium atoms and clusters. Source temperatures of up to (1650 ± 50) °C were reached and Cr clusters up to Cr9 could be formed in HeN.
Fourier transform infrared isotopic study of ZnC3: Identification of the ν1(a′) mode
Authors: Bejjani Micheline , Kinzer R. E. , Rittby C. M. L. , Graham W. R. M.
Published: March 2012

An isomer of ZnC3 with bent structure in its 1A′ electronic state has been detected in the products from the dual laser ablation of carbon and zinc rods that were trapped in solid Ar at ∼12 K. Measurements of 13C isotopic shifts have enabled the identification of the ν1(a′) asymmetric carbon stretching fundamental at 1858.9 cm−1. The experimental results are in good agreement with the predictions of DFT-B3LYP/6-311G(d) calculations that indicate a singlet bent isomer ground state structure with triplet linear and singlet cyclic isomers lying slightly higher in energy. This is the first optical detection of any isomer of ZnC3.
1H NMR relaxation in glycerol solutions of nitroxide radicals: Effects of translational and rotational dynamics
Authors: Kruk D. , Korpala A. , Rössler E. , Earle K. A. , Medycki W. , Moscicki J.
Published: March 2012

1H spin-lattice relaxation rates in glycerol solutions of selected nitroxide radicals at temperatures between 200 K and 400 K were measured at 15 MHz and 25 MHz. The frequency and temperature conditions were chosen in such a way that the relaxation rates go through their maximum values and are affected by neither the electron spin relaxation nor the electron-nitrogen nucleus hyperfine coupling, so that the focus could be put on the mechanisms of motion. By comparison with 1H spin-lattice relaxation results for pure glycerol, it has been demonstrated that the inter-molecular electron spin–proton spin dipole-dipole interactions are affected not only by relative translational motion of the solvent and solute molecules, but also by their rotational dynamics as the interacting spins are displaced from the molecular centers; the eccentricity effects are usually not taken into account. The 1H relaxation data have been decomposed into translational and rotational contributions and their relative importance as a function of frequency and temperature discussed in detail. It has been demonstrated that neglecting the rotational effects on the inter-molecular interactions leads to non-realistic conclusions regarding the translational dynamics of the paramagnetic molecules.
Structural changes of Pd13 upon charging and oxidation/reduction
Authors: Reveles J. Ulises , Köster A. M. , Calaminici P. , Khanna S. N.
Published: March 2012

First-principle generalized gradient corrected density functional calculations have been performed to study the stability of cationic and anionic Pd13+/−, and neutral Pd13O2 clusters. It is found that while cationic Pd13+ favors a Cs geometry similar to the neutral Pd13, both anionic Pd13− and neutral Pd13O2 favor a compact ∼Ih structure. A detailed analysis of the electronic structure shows that the stabilization of the delocalized 1P and 2P cluster orbitals, and the hybridization of the 1D orbitals with the oxygen atomic p orbitals play an important role in the energetic ordering of Cs and ∼Ih isomers. A structural oscillation is predicted during an oxidation/reduction cycle of Pd13 in which small energy barriers between 0.3 and 0.4 eV are involved.
Mode coupling in two-dimensional plasma crystals: Role of the wake model
Authors: Röcker T. B. , Ivlev A. V. , Kompaneets R. , Morfill G. E.
Published: March 2012

The theory of mode-coupling instability in 2D plasma crystal is combined with a self-consistent model of plasma wakes. The wake model is based on the solution of a kinetic equation for ions, providing realistic representation of their kinetics for the sheath environment. Furthermore, the self-consistent approach allows us to express the interparticle interaction via experimentally measurable parameters. It is suggested that distinct features of dispersion relations predicted by different wake models can be identified experimentally.
Unusual rigidity and ideal strength of CrB4 and MnB4
Authors: Gou Huiyang , Li Zhiping , Niu Hui , Gao Faming , Zhang Jingwu , Ewing Rodney C. , Lian Jie
Published: March 2012

By means of first-principles calculations, we report superior rigidity, ideal tensile, and shear strength for orthorhombic CrB4 and MnB4. The analysis of microscopic deformation mechanism reveals that the unique rectangular boron units in CrB4 and MnB4 are responsible for the consolidation of the directionality of boron-boron covalent bonds and the exceptional rigidity and ideal strength. The unusual mechanical properties of the orthorhombic tetraborides highlight their potential applications as intrinsically superhard materials. The unique rectangular boron unit also implies a criterion for designing and synthesizing transition metal boride based-materials with ultimate hardness and strength.