bluuebunny/crossref_metadata_2025 huggingface dataset:
Migration, Identity and Belonging
Authors: Gilmartin Mary
Published: October 2008

The study of migration within geography takes a variety of forms. While geographers traditionally studied push and pull factors in migration, this approach was challenged for its reliance on quantitative methods and its emphasis on economic factors. New approaches to the study of migration in geography have thus incorporated qualitative techniques and focused on migrant identities and migrant subjectivities. They have also provided new theorizations of the relationship between mobility and belonging, particularly through the concepts of transnationalism and translocalism, and through scales of belonging that range from citizenship to the home. Despite claims of the demise of the nation‐state under globalization, the role of the nation‐state in regulating migration and migrants, and in managing and policing borders, highlights its ongoing importance. Similarly, the potential centrality of place to the ongoing study of migration is highlighted by recent research on cities and regions. This foregrounds the negotiated and mutable nature of place in the context of transformations at a variety of interconnected scales.
Regulation and Localization of Isoforms of the Aerobic Oxidative Cyclase in Chlamydomonas reinhardtii †
Authors: Allen Michael D. , Kropat Janette , Merchant Sabeeha S.
Published: October 2008

Tetrapyrrole synthesis is complex and is regulated at several points. The aerobic oxidative cyclase catalyzes the oxidative closure of the fifth ring characteristic of all chlorophylls. Chlamydomonas reinhardtii encodes two paralogous protein components of the cyclase, which are differentially accumulated based on copper nutrition and oxygen supply. CRD1 is accumulated in copper‐deficient conditions, whereas CTH1 is present in copper replete conditions. Here, we show that CRD1 expression is regulated through a copper‐responsive element located upstream of the transcription start site. The differential production of CRD1 transcript accounts for the differential accumulation of the corresponding polypeptide. The CTH1 locus produces two transcripts: a 2.1 kb one under copper‐replete conditions and a 3.1 kb one under copper‐deficient conditions. We show that the 2.1 kb transcript can be translated into protein in vitro whereas the 3.1 kb transcript cannot. Differential accumulation of the 2.1 vs the 3.1 kb transcript therefore accounts for the copper‐responsive accumulation of CTH1. Biochemical fractionation reveals that both CRD1 and CTH1 are localized to chloroplast envelope as well as thylakoid membranes.
Cybersex and the E‐teen: What Marriage and Family Therapists Should Know
Authors: Delmonico David L. , Griffin Elizabeth J.
Published: October 2008

Adolescents who use the Internet regularly (the “e‐teen”) present a new set of challenges for marriage and family therapists. This article introduces marriage and family therapists to (a) the basic technological concepts and unique psychological characteristics of the Internet important in understanding and addressing adolescent online sexual behavior, (b) the appropriate developmental expectations for teens online, including risk‐taking behaviors and critical decision‐making skills, and (c) suggested strategies for assessment, prevention, and intervention when dealing with problematic online sexual behavior in adolescents. Marriage and family therapists cannot ignore the role the Internet plays in adolescent sexual development and its implication for the family. This article will serve as a primer for the marriage and family therapist when presented with adolescents who engage in online sexual behaviors.
Emotional and Sexual Infidelity Offline and in Cyberspace
Authors: Whitty Monica T. , Quigley Laura‐Lee
Published: October 2008

This study investigated how men and women perceive online and offline sexual and emotional infidelity. Undergraduates from a large university in Northern Ireland participated in the study. It was found that men, when forced to decide, were more upset by sexual infidelity and women by emotional infidelity. It was also found that men were more likely to believe that women have sex when in love and that women believe that men have sex even when they are not in love. It was not, however, found that either men or women believed that having cybersex implied the other was also in love or that being in love online implied they were having cybersex. These results are explained through a social‐cognitive lens.
Nineteen novel microsatellite markers for the Olympia oyster, Ostrea conchaphila/lurida
Authors: STICK DAVID A. , LANGDON CHRIS J. , BANKS MICHAEL A. , CAMARA MARK D.
Published: October 2008

Accurate evaluation of remnant Ostrea conchaphila/lurida population structure is critical for developing appropriate restoration efforts. Here we report 19 polymorphic microsatellites suitable for analyses of population differentiation, pedigree reconstruction and linkage map construction. We screened clones from four enriched genomic libraries, identified 73 microsatellite‐containing sequences and designed polymerase chain reaction primers for 44 of these loci. We successfully optimized polymerase chain reaction conditions for 20 loci, including one monomorphic locus. In a Willapa Bay reference sample, mean observed and expected heterozygosities were 0.6729 and 0.8377. Nine loci deviated from Hardy‐Weinberg equilibrium. These markers have proven useful for genetic studies of the Olympia oyster.
Epileptiform activities in slices of hippocampus from mice after intra‐hippocampal injection of kainic acid
Authors: Le Duigou Caroline , Bouilleret Viviane , Miles Richard
Published: October 2008

Intra‐hippocampal kainate injection induces the emergence of recurrent seizures after a delay of 3–4 weeks. We examined the cellular and synaptic basis of this activityin vitrousing extracellular and intracellular records from longitudinal hippocampal slices. These slices permitted recordings from the dentate gyrus, the CA3 and CA1 regions and the subiculum of both the injected and the contralateral non‐injected hippocampus. A sclerotic zone was evident in dorsal regions of slices from the injected hippocampus, while ventral regions and tissue from the contralateral hippocampus were not sclerotic. Interictal field potentials of duration 50–200 ms were generated spontaneously in both ipsilateral and contralateral hippocampal slices, but not in the sclerotic region, at 3–12 months after injection. They were initiated in the CA1 and CA3 regions and the subiculum. They were blocked by antagonists at glutamatergic receptors and were transformed into prolonged epileptiform events by GABAergic receptor antagonists. The membrane potential and the reversal potential of GABAergic synaptic events were more depolarized in CA1 pyramidal cells from kainate‐treated animals than in control animals. Ictal‐like events of duration 8–80 s were induced by tetanic stimulation (50 Hz, 0.2–1 s) preferentially in dorsal contralateral and ventral ipsilateral slices. Similar events were initiated by focal application of a combination of high K+and GABA. These data show that both interictal and ictal‐like activities can be induced in slices of both ipsilateral and contralateral hippocampus from kainate‐treated animals and suggest that changes in cellular excitability and inhibitory synaptic signalling may contribute to their generation.
Disproportional effects of Igf2 knockout on placental morphology and diffusional exchange characteristics in the mouse
Authors: Coan P. M. , Fowden A. L. , Constancia M. , Ferguson‐Smith A. C. , Burton G. J. , Sibley C. P.
Published: October 2008

Both complete knockout of the Igf2 gene (Igf2null+/−) and knockout of its placental specific transcript alone (Igf2P0+/−) lead to fetal growth restriction in mice. However, in the Igf2null+/− this growth restriction occurs concurrently in gestation with placental growth restriction, whereas, placental growth restriction precedes fetal growth restriction in the Igf2P0+/− mouse. Previous studies have shown that the Igf2P0+/− placenta has proportionate reductions in its cellular compartments and its diffusional exchange characteristics. Yet, nothing is known about the structural development or diffusional exchange characteristics of the Igf2null+/− mouse. Hence, this study compares the structural properties (using stereology) and diffusional exchange characteristics (using measurement of permeability–surface area product, P.S, of three inert hydrophilic tracers) of the Igf2null+/− and the Igf2P0+/− placenta to identify the role of Igf2 in the development of the labyrinthine exchange membrane and its functional consequences. Our data show disproportionate effects of complete Igf2 ablation on the compartments of the placenta, not seen when the placental‐specific transcript alone is deleted. Furthermore, although the theoretical diffusing capacity (calculated from the stereological data) of the Igf2null+/− placenta was reduced relative to control, there was no effect of the complete knockout on permeability surface area available for small hydrophilic tracers. This is in contrast to the Igf2P0+/− placenta, where theoretical diffusion capacity and P.S values were reduced similarly. Total ablation of the Igf2 gene from the fetoplacental unit in the mouse therefore results in a disproportionate growth of placental compartments whereas, deleting the placental specific transcript of Igf2 alone results in proportional placental growth restriction. Thus, placental phenotype depends on the degree of Igf2 gene ablation and the interplay between placental and fetal Igf2 in the mouse.
Attenuation of changes in capillary fine structure and leukocyte adhesion improves muscle performance following chronic ischaemia in rats
Authors: Hudlická O. , Garnham A. , Shiner R. , Egginton S.
Published: October 2008

Acute ischaemia–reperfusion disrupts capillary fine structure and increases leukocyte adhesion in postcapillary venules. We determined whether chronic muscle ischaemia has similar consequences, and whether it is possible to ameliorate its effect on muscle performance. Following ischaemia (unilateral ligation, common iliac artery) rat hindlimb muscles were examined without other intervention or following treatment with an xanthine oxidase inhibitor (allopurinol), a Na+/H+ exchange blocker (amiloride), or an oxygen free radical scavenger (vitamin E). No significant leukocyte adhesion or rolling, nor changes in capillary fine structure were observed 3 days postsurgery, when limb use was limited. However, leukocyte rolling and adhesion almost trebled by 7 days (P < 0.001), when normal gait was largely restored. Capillary fine structure was disturbed over a similar time course, e.g. relative endothelial volume (control 46%, 7 days 61%; P < 0.05), that resolved by 5 weeks. Where activity was increased by mild electrical stimulation 3 days after ligation muscles showed enhanced capillary swelling (endothelial volume 66%versus 50%, P < 0.005), but improved fatigue index (52%versus 16%, P < 0.001) as a result of greater blood flow. Muscle fatigue after ligation was related to the extent of contraction‐induced hyperaemia (R2= 0.725), but not capillary swelling. Amiloride, and to a lesser extent allopurinol but not vitamin E, significantly decreased leukocyte rolling and adhesion, as well as capillary endothelial swelling. We conclude that increased activity of ischaemic muscles on recovery is likely to accentuate acidosis accompanying changes in microcirculation and contribute to enhanced muscle fatigue, whereas formation of oxygen free radicals may be attenuated by endogenous protective mechanisms.
Climbing fibre‐dependent changes in Golgi cell responses to peripheral stimulation
Authors: Xu W. , Edgley S. A.
Published: October 2008

Golgi cells are important elements of the cerebellar cortex, controlling the flow of mossy fibre information to other cells via granule cells. Several anatomical reports suggest that climbing fibre afferents contact Golgi cells, and electrophysiological studies suggest that they depress Golgi cell firing. We reinvestigated this issue and, given that climbing fibres mediate synaptic plasticity in the cerebellar cortex, we have examined the effects of conjunctive stimulation of peripheral afferents and climbing fibres on Golgi cell responses. The results confirm that climbing fibre stimulation depresses Golgi cell firing at short latency. Golgi cells responded to stimulation of peripheral afferents with longer latency depressions of firing and after conjunctive stimulation with climbing fibres these were significantly reduced. The reductions developed progressively over 20 min of conjunctive stimulation and were persistent (up to 84 min). Temporal conjunction of the inputs was important because non‐synchronous stimulation of climbing fibres and peripheral afferents failed to alter the peripheral afferent‐evoked response in Golgi cells. In control experiments using either the same climbing fibre stimulation alone, or peripheral afferent stimulation paired with brainstem stimulation that did not activate climbing fibres, responses were not depressed. The results thus show that conjunctive stimulation of climbing fibres with other inputs to Golgi cells can induce long‐term changes in Golgi cell responses in vivo. This raises the possibility that changes in Golgi cell peripheral responses mediated by climbing fibres can potentially contribute to cerebellar motor learning.
Internalized Kv1.5 traffics via Rab‐dependent pathways
Authors: Zadeh Alireza Dehghani , Xu Hongjian , Loewen Matthew E. , Noble Geoffrey P. , Steele David F. , Fedida David
Published: October 2008

Little is known about the postinternalization trafficking of surface‐expressed voltage‐gated potassium channels. Here, for the first time, we investigate into which of four major trafficking pathways a voltage‐gated potassium channel is targeted after internalization. In both a cardiac myoblast cell line and in HEK293 cells, channels were found to internalize and to recycle quickly. Upon internalization, Kv1.5 rapidly associated with Rab5‐and Rab4‐positive endosomes, suggesting that the channel is internalized via a Rab5‐dependent pathway and rapidly targeted for recycling to the plasma membrane. Nevertheless, as indicated by colocalization with Rab7, a fraction of the channels are targeted for degradation. Recycling through perinuclear endosomes is limited; colocalization with Rab11 was evident only after 24 h postsurface labelling. Expression of dominant negative (DN) Rab constructs significantly increased Kv1.5 functional expression. In the myoblast line, Rab5DN increased Kv1.5 current densities to 1305 ± 213 pA pF−1 from control 675 ± 81.6 pA pF−1. Rab4DN similarly increased Kv1.5 currents to 1382 ± 155 pA pF−1 from the control 522 ± 82.7 pA pF−1 at +80 mV. Expression of the Rab7DN increased Kv1.5 currents 2.5‐fold in HEK293 cells but had no significant effect in H9c2 myoblasts, and, unlike the other Rab GTPases tested, over‐expression of wild‐type Rab7 decreased Kv1.5 currents in the myoblast line. Densities fell to 573 ± 96.3 pA pF−1 from the control 869 ± 135.5 pA pF−1. The Rab11DN was slow to affect Kv1.5 currents but had comparable effects to other dominant negative constructs after 48 h. With the exception of Rab11DN and nocodazole, the effects of interference with microtubule‐dependent trafficking by nocodazole or p50 overexpression were not additive with the Rab dominant negatives. The Rab GTPases thus constitute dynamic targets by which cells may modulate Kv1.5 functional expression.
Modeling the Effects of Initial Tube-Tubesheet Clearance, Wall Reduction and Material Strain Hardening on Rolled Joint Strength
Authors: Al-Aboodi A. , Merah N. , Shuaib A. R. , Al-Nassar Y. , Al-Anizi S. S.
Published: October 2008

The tube-to-tubesheet joint strength is measured in terms of residual contact pressure between the tube’s outer surface and tubesheet hole surfaces. The joint integrity is affected by several design parameters, including the type of tube and tubesheet materials, the level of expansion, and the initial radial clearance between the tube and tubesheet. In the present work, an axisymmetric finite element model based on the sleeve diameter and rigid roller concepts is developed. The model has been used to evaluate the combined effects of clearance, wall reduction level, and strain hardening of tube and tubesheet materials on the interfacial pressure between tube and tubesheet. The finite element results show that the initial clearance effect is dependent on the strain hardening capability of the tube material. For low strain hardening tube materials, the interfacial pressure remains almost constant well above the Tubular Exchanger Manufacturing Association maximum radial over tolerance of 0.0254mm(0.001in.). These results are validated by the experimental data developed during the research program. As expected, a drastic reduction in joint strength is observed at high values of radial clearances. The cutoff clearance (clearance at which the interfacial pressure starts to drop) is found to vary linearly with tube material hardening level. The residual pressure is found to increase slightly for moderate strain hardening tube materials but shows lower cutoff clearances. Wall reductions ranging from 1% to 12% were utilized in calculating the contact pressure as a function of radial clearance. The results show that for low strain hardening materials the optimum value of residual contact stress is obtained for the industry recommended value of 5%. Finally, because of the absence of plastic deformation in the ligament, the level of tubesheet material strain hardening does not have any noticeable effect on the joint strength.
J

-Resistance Properties of Narrow Gap GTAW Welds for Ferritic Primary Loop Piping
Authors: Yoo One , Yoon Ki-Seok , Choi Tack-Sang , Lee Bong-Sang , Kim Min-Chul
Published: October 2008

J -resistance properties of automatic narrow gap gas tungsten arc welds (NGGTAWs) for ferritic primary loop piping were investigated. The piping diameter is 1066mm, and its thickness is 76mm. The tensile, microhardness, and J-R tests were performed, and microstructures of the welds were examined. Tensile and J-R tests were conducted at 316°C and 177°C for temperature effect, and at 1mm∕min and 1000mm∕min for strain rate effect. The results were compared with other welds, which are fabricated by the conventional shielded metal arc weld (SMAW) process. The NGGTAW welds investigated in this paper have lower J-R curves than the SMAW welds. Fracture surfaces of the NGGTAW welds showed deep ditches and holes due to inclusions and pores. It is believed that the high density of the inclusions and the pores, which exist in the NGGTAW welds, is responsible for this lower toughness and the fracture surface appearances. Therefore, to improve the NGGTAW weld toughness, it is recommended that sulfur content should be limited to a considerably low level, and the pores should be eliminated by modifying the welding procedure specification.
Determination of J-Integral Using the Load-COD Record for Circumferential Through-Wall Cracked Pipes
Authors: Huh Nam-Su , Kim Yun-Jae
Published: October 2008

The present paper provides experimental J estimation equation based on the load-crack opening displacement (COD) record for testing the circumferential through-wall cracked pipe under combined tension and bending. Based on the limit analysis and the kinematically admissible rigid-body rotation field, the plastic η-factor for the load-COD record is derived and is compared with that for the load-load line displacement record. Comparison with the J results from detailed elastic-plastic finite element analysis shows that the proposed method based on the load-COD record provides reliable J estimates even for shallow cracks (small crack angle), whereas the conventional approach based on the load-load line displacement record gives erroneous results for shallow cracks. Thus, the proposed J estimation method could be recommended for testing the circumferential through-wall cracked pipe, particularly with shallow cracks.
Computational and Experimental Studies of High Temperature Crack Initiation in the Presence of Residual Stress
Authors: O’Dowd Noel P. , Nikbin Kamran M. , Wimpory Robert C. , Biglari Farid R. , O’Donnell Manus P.
Published: October 2008

Residual stresses have been introduced into a notched compact tension specimen of a 347 weld material by mechanical compression. The required level of compressive load has previously been determined from finite-element studies. The residual stress in the vicinity of the notch root has been measured using neutron diffraction and the results compared with those obtained from finite-element analysis. The effect of stress redistribution due to creep has been examined and it is found that a significant reduction in stress is measured after 1000h at 650°C. The implications of these results with regard to the development of damage in the specimen due to creep relaxation are examined.
Discrete Models for Seismic Analysis of Liquid Storage Tanks of Arbitrary Shape and Fill Height
Authors: Drosos G. C. , Dimas A. A. , Karabalis D. L.
Published: October 2008

A finite element method (FEM)-based formulation is developed for an effective computation of the eigenmode frequencies, the decomposition of total liquid mass into impulsive and convective parts, and the distribution of wall pressures due to sloshing in liquid storage tanks of arbitrary shape and fill height. The fluid motion is considered to be inviscid (slip wall condition) and linear (small free-surface steepness). The natural modal frequencies and shapes of the sloshing modes are computed, as a function of the tank fill height, on the basis of a conventional FEM modeling. These results form the basis for a convective-impulsive decomposition of the total liquid mass, at any fill height, for the first few (two or three at most) sloshing modes, which are by far the most important ones in comparison to all other higher modes. This results into a simple yet accurate and robust model of discrete masses and springs for the sloshing behavior. The methodology is validated through comparison studies involving vertical cylindrical tanks. Additionally, the application of the proposed methodology to conical tanks and to the seismic analysis of spherical tanks on a rigid or flexible supporting system is demonstrated and the results are compared to those obtained by rigorous FEM analyses.
Study of 193nm photoresist degradation during short time fluorocarbon plasma exposure. I. Studies of modified layer formation
Authors: Sumiya M. , Bruce R. , Engelmann S. , Weilnboeck F. , Oehrlein G. S.
Published: October 2008

The mechanism of modified layer formation for 193nm photoresist (PR) during a short time (up to ∼10s) fluorocarbon plasma exposure was investigated. We employed a shutter approach to achieve rapidly steady-state plasma condition when processing PR surfaces. The time evolution of the optical constants and the thickness of the modified layer on the PR surface were obtained using two layer optical modeling of ellipsometric data for the processed PR material. This enabled us to determine the time-resolved etching rate of the PR and the kinetics of modified layer formation. The change in the surface chemical composition of the PR materials was determined by x-ray photoelectron spectroscopy (XPS). A graphitic layer with a higher refractive index as compared to the bulk PR material was formed on the PR surface within a few (∼3s) seconds of plasma exposure. The XPS data revealed that before a fluorinated surface developed, cleavage at ester groups of the side chain in the polymer and dangling bond formation took place, leading to cross-linking. To investigate the influence of the oxygen content of the polymer on surface roughness formation, we compared the surface evolution of oxygen-rich 193 and 248nm PRs, which have a smaller oxygen content. Remarkable differences in the etching behavior during the initial plasma interaction period were observed for the two materials. Whereas for 193nm PR, etching was observed immediately and the material exhibited higher surface roughness, for the 248nm PR material fluorocarbon film deposition took place initially. Once a fluorinated surface had developed, steady-state etching took place, but the 248nm PR exhibited lower surface roughness than the 193nm material. XPS measurements showed that when comparing the fluorine content of the surface layer to the oxygen content, the fluorine content was relatively more important for the 248nm PR than for the 193nm PR. For the latter, oxygen in the side groups of the bulk PR enhanced the PR etching rate initially and led to a rapid surface roughness formation. This coincides with the development of a fluorinated surface.
Nonvolatile memory and antifuse behavior in Pt∕a-TiO2∕Ag structures
Authors: Busani T. , Devine R. A. B.
Published: October 2008

Stable nonvolatile conductivity switching and antifuse behavior have been observed in amorphous-TiO2 films in 0.002cm2 Ag/amorphous-TiO2∕Pt structures. Resistivity switching from a high resistance state of ∼108Ω to a low resistance state of 1.5Ω occurs typically at a positive bias threshold of ∼0.74V. As expected for a metal-oxide-metal structure, Fowler–Nordheim conduction dominates the high resistance state while the low resistance state is assumed to be due to electric field induced conducting filaments of Ag. For a total charge of >100mC under positive bias, antifuse behavior is evidenced. Stability and reversibility of the resistive switching and antifuse behavior were studied.
Sub-50-nm track pitch mold using electron beam lithography for discrete track recording media
Authors: Sbiaa R. , Tan E. L. , Seoh R. M. , Aung K. O. , Wong S. K. , Piramanayagam S. N.
Published: October 2008

Using electron beam lithography and ZEP 520 resist, molds with a track pitch of 50nm were fabricated on thermal silicon oxide for discrete track recording applications. In this article, the detailed process for patterning a mold with 50nm track pitch and 10nm feature size is described. Although bilayer polymethylmethacrylate of 120nm thickness is able to pattern tracks of micrometer length and pitch down to 70nm, patterned tracks with pitches below 70nm exhibited waviness and edge roughness. In contrast, fine patterns with 50nm pitch were achieved with a single 60nm layer of ZEP 520 resist. Pattern transfer using ion milling followed by reactive ion etching produced 10nm features. High resolution scanning electron microscopy was used to evaluate the size and uniformity of the tracks during each step of the process.
Comparative study of Cl2, Cl2∕O2, and Cl2∕N2 inductively coupled plasma processes for etching of high-aspect-ratio photonic-crystal holes in InP
Authors: Carlström C. F. , van der Heijden R. , Andriesse M. S. P. , Karouta F. , van der Heijden R. W. , van der Drift E. , Salemink H. W. M.
Published: October 2008

An extensive investigation has been performed on inductively coupled plasma etching of InP. An important motivation for this work is the fabrication of high-aspect-ratio holes for photonic crystals. The essential chemistry is based on Cl2 with the addition of N2 or O2 for sidewall passivation. The influence of different process parameters such as gas flows, temperature, pressure, ion energy, and inductively coupled plasma power on the hole geometry is presented. It is concluded that photonic crystals can be etched with Cl2 only; however, temperature and pressure control is critical. Adding passivation gases largely broadens the window in the parameter space for hole etching. Most importantly, etching of narrow holes can be carried out at higher temperatures where the etching is mass limited and spontaneous etching of InP by Cl2 occurs.
Fabrication of concave gratings by curved surface UV-nanoimprint lithography
Authors: Chen Yung-Pin , Lee Yuet-Ping , Chang Jer-Haur , Wang Lon A.
Published: October 2008

The authors report a new method for fabricating submicron gratings on curved substrates by combining thermoforming and nanoimprint technologies. A preshaping film was used to provide uniform pressure distribution throughout the whole concave substrate with the diameter of 60mm and the radius of curvature of 92.5mm. The concave glass could be resin coated uniformly by a conventional spin coater through the support of a soft holder. Either the preshaping film or the soft holder could be a buffer layer to prevent the curved glass from crumbling, which may result from high gas pressure during the imprint process. As for demonstration, a Rowland circle type concave grating with a period of 1.2μm was made, and the measured first order reflectance was about 20% at various wavelengths.
Field-emission fluorescent lamp using carbon nanotubes on a wire-type cold cathode and a reflecting anode
Authors: Huang J. X. , Chen Jun , Deng S. Z. , She J. C. , Xu N. S.
Published: October 2008

Wire-type cold cathode was prepared by direct growth of carbon nanotube (CNT) on stainless-steel wire using thermal chemical vapor deposition. By varying the growth temperature, gas flow direction, and reactant gas mixture, improved field-emission uniformity and stability were achieved. The results show that the CNT cathodes grown by H2/C2H2 mixture exhibit better current stability than those grown by Ar/C2H2 mixture. Fully sealed fluorescent lamps have been fabricated using wire-type CNT cold cathode. Luminescent efficiencies of 37 and 21 lm/W were obtained for the fully sealed lamps with green and white phosphor screens.
Electron field emission from ZnOx nanoparticles decorated on vertically aligned carbon nanotubes prepared by vapor-phase transport
Authors: Wisitsoraat A. , Tuantranont A. , Patthanasettakul V. , Mongpraneet S.
Published: October 2008

In this work, the authors studied electron field emission from well-ordered ZnOx nanoparticles decorated on vertically aligned carbon nanotubes (CNTs). The vertically aligned CNTs are grown by thermal chemical vapor deposition with gravity effect and water-assisted etching at 700°C. ZnOx nanoparticles are then decorated on CNTs by exposing CNTs to evaporated ZnOx vapor under H2∕Ar ambient at different pressures. The effect of process pressure on structural, chemical, and electron field-emission properties of ZnOx decorated on vertically aligned CNTs is characterized. ZnOx nanoparticles are observed to be deposited on top of CNTs. Low pressure (5–20torr) results in fine ZnOx nanoparticles 5–15nm in diameter uniformly distributed on the cap of CNTs, whereas high pressure (>100Torr) results in large ZnOx particles and agglomeration on CNTs. In addition, electron field emission from vertically aligned CNTs is found to be further improved by ZnOx nanoparticle decoration at low pressure, and a low turn-on electric field of ∼1.5V∕μm is observed. On the other hand, large ZnOx particles decorated at high pressure result in electron field-emission degradation. The effects of ZnOx nanoparticles on electron field emission from CNTs have been explained based on the Fowler–Nordheim analysis and plausible hypotheses have been proposed.
Fabrication and properties of Cu–Ni mixed-metal periodical array for midinfrared filtering and hydrophobic application
Authors: Huang Wen-Hsien , Yang Yu-Lin , Wu Shich-Chuan
Published: October 2008

Cu was grown successfully on Ni film as a conductive layer that demonstrated a stronger Cu (111) preferred crystallographic orientation. Furthermore, we studied the scale effect of various periods of patterned Ni lines separated by variable widths of SiO2. When Cu was electroplated onto this patterned Ni, it preferentially deposited on the Ni edges adjacent to the SiO2 stripes, resulting in a Cu–Ni–Cu–SiO2, Cu–SiO2–Cu, or Cu–Cu structure, depending on the dimensions of the starting Ni pattern and the deposition time. There are two reflective dips at 2.2 and 8μm wavelengths using Fourier transform infrared spectroscopy, which revealed a trend of narrower bandwidth in reflective spectra and a redshift effect with increasing deposition time. Interestingly, a hydrophobic surface was also observed due to its particular surface-roughness structures that could be controlled by the deposition time and altered the contact angle from 72° to 110° without coating any extra low free-energy materials.
Specific spectral features in electron emission from nanocrystalline silicon quasi-ballistic cold cathode detected by an angle-resolved high resolution analyzer
Authors: Sakai Daisuke , Oshima Chunhei , Ohta Toshiyuki , Koshida Nobuyoshi
Published: October 2008

A display-type analyzer with ±20° acceptance angle and high-energy resolution has been applied to analysis of the operation mechanism in a nanocrystalline polysilicon quasiballistic emitter. Angle-resolved emission patterns and the corresponding energy distributions are measured as a function of the applied device voltage in the range from 10to20V. The experimental data suggest that there are two kinds of emission band in the energy spectra. The one emission peak at lower energies exhibits definitely directional features, whereas a significantly large angular dispersion is observed in another emission peak at higher energies. The intensity of the latter emission band becomes dominant in the range of the applied device voltage higher than 15V. These results can be explained from the correlation between the silicon nanostructure in the device and the major carrier transport mode there. The analysis presented here supports the previously proposed model that the quasiballistic emission is based on the field-induced generation of energetic electrons in nanocrystalline silicon diode.
Deposition of NiOx thin films with radio frequency magnetron sputtering and their characteristics as a source/drain electrode for the pentacene thin film transistor
Authors: Yun Dong-Jin , Rhee Shi-Woo
Published: October 2008

Ni O x films were deposited with radio frequency (rf) magnetron sputtering at various sputtering powers (25–300W) and deposition temperatures (room temperature to 200°C) using NiO target and pure O2 as a sputtering gas. Crystallinity, bonding state (Ni+3 and Ni+2), work function, and the resistivity of the film were measured and the performance of the pentacene thin film transistor (TFT) with the NiOx film as a source/drain (S/D) electrode was evaluated. The film properties such as roughness, work function, crystallinity, and bonding state of Ni and O were similar at each sputtering power, and the NiOx film was deposited at around 150W and room temperature showed lower resistivity of 1.34×104μΩcm, lower surface roughness of 0.206nm, and higher work function of 5.2eV. With the increase in the deposition temperature, the ratio of Ni2+ ions to Ni3+ ions in the NiOx film was increased, the work function was decreased and the resistivity was increased. A pentacene TFT with NiOx film deposited at 150W and room temperature showed a device performance better than that with gold film, with mobility of 0.178cm2∕Vs, threshold voltage of 0.34V, and on/off ratio of 5.0×105.
Use of ion beam assisted deposition and low temperature annealing for the fabrication of low loss, vertically stacked alumina waveguide structures
Authors: Nightingale J. R. , Goswami R. , Duperre J. , Dawson J. M. , Hornak L. A. , Korakakis D.
Published: October 2008

Ion beam assisted deposition (IBAD) and low temperature annealing in an air atmosphere are used to significantly lower optical losses and environmentally stabilize electron beam deposited, stacked waveguide structures consisting of amorphous aluminum oxide and silica. IBAD is used to add energy to the deposition process and promote film densification, consequently lowering optical propagation losses by reducing the number of light-scattering void regions. Postdeposition, low temperature (600°C and lower) annealing in an air atmosphere for short amounts of time (<5min) is used to further reduce losses by means of relaxing thin film stress and lowering scattering losses at the alumina/silica interface in stacked multilayer structures.
Deposition of WNxCy for diffusion barrier application using the imido guanidinato complex W(NiPr)Cl3[PriNC(NMe2)NiPr]
Authors: Ajmera Hiral M. , Heitsch Andrew T. , Anderson Timothy J. , Wilder Corey B. , Reitfort Laurel L. , McElwee-White Lisa , Norton David P.
Published: October 2008

A solution of the tungsten imido guanidinato complex W(NPri)Cl3[PriNC(NMe2)NPri] (1) in benzonitrile was used to deposit tungsten nitride carbide (WNxCy) thin films by chemical vapor deposition in the temperature range of 400–750°C. Films grown with 1 were composed of W, N, C, and O as determined by Auger electron spectroscopy. X-ray photoelectron spectroscopy results indicated that no Cl impurity was present in the film. The apparent activation energy in the reaction limited growth regime was 0.54eV. The films deposited below 500°C were amorphous, while films deposited at and above 500°C were nanocrystalline (grain size <50Å). The lowest resistivity of 0.98mΩcm was obtained for film deposited at 450°C. Films, 45–55nm thick, deposited at 450–500°C were able to prevent bulk Cu diffusion after vacuum annealing at 500°C for 30min. The properties of thin films deposited with 1 were compared to those from the isopropyl imido complex, Cl4(RCN)W(NPri) (2a, R=CH3, 2b, R=Ph), to provide insight into the effect of imido and guanidinato ligands on film properties.
Effect of ZnO catalyst on carbon nanotube growth by thermal chemical vapor deposition
Authors: Lee Shih-Fong , Chang Yung-Ping , Lee Li-Ying
Published: October 2008

In this study, carbon nanotubes (CNTs) were synthesized on a catalyst of ZnO nanorods using thermal chemical vapor deposition. ZnO nanorods were coated on silicon substrates by a hydrothermal process. The CNT growth temperature was maintained at 900°C at an ambient pressure. Methane and argon gases are used for the CNT synthesis. In this work, scanning electron microscopy (SEM) and transmission electron microscopy images were used to observe the surface morphology and sidewall structure, energy-dispersive spectrometry (EDS) was used to identify and analyze the chemical composition of the surface of the CNTs, and Raman spectroscopy was employed to investigate the CNT structures. The research reveals that the carbon nanotubes grown on ZNO nanorods show a multiwalled structure with defective graphite sheets on the walls. The SEM images show that the surface of CNTs grown on the ZnO nanorod catalyst were covered by the nanonode carbon nanoparticles. Raman spectra show that the appearance of the relatively strong D peaks in CNT films grown on ZnO catalyst can possibly result from the existence of nanonodes and the structural defects on the nanotube’s graphite sheets. EDS results reveal that the CNTs grown on ZnO nanorods do not need any purification process to optimize the field-emission characteristics of the CNTs. Field-emission tests indicate that the CNT grown on ZnO catalyst films have a low turn-on emission field and high emission current density. The Fowler-Nordheim plot showed a good linear fit, indicating that the emission current of CNTs follows Fowler-Nordheim behavior. The authors attributed the improvement of field-emission properties to the change in the electronic geometrical structure of the local emission region in CNTs.
Transferring optical proximity correction effects into a process model
Authors: Li Jianliang , Yan Qiliang , Melvin Lawrence S.
Published: October 2008

Because of the ever-decreasing feature size in modern photolithography, the complexity of semiconductor patterns continues to increase dramatically, resulting in prolonged tape-out times. The most time-consuming process in the tape-out flow is model-based optical proximity correction (OPC), which employs two components: a process model and a recipe. The process model predicts how the manufacturing process will behave at a given location on a wafer, whereas the recipe controls how the model information is used to modify the pattern. The recipe uses the model multiple times for each fraction of a polygon in a semiconductor device pattern, resulting in hundreds of billions of complex and time-consuming calculations. To analyze a design-team-drawn device pattern for semiconductor manufacturability, these tape-out calculations need to be performed. This study is designed to reduce the semiconductor pattern manufacturing analysis time by creating an OPC recipe simulation in the process model for use in rapid analysis and filtering of the drawn semiconductor design. In this study, the authors introduce a method of calculating the OPC effect by modifying the optical model, which is equivalent to transferring the OPC effect into the process model.
Single-pass forming for three-dimensional microstructures by high-speed shearing of multilayer thin films
Authors: Hamaguchi Tetsuya , Yonemoto Hiroki , Nagato Keisuke , Tsuchiya Kensuke , Nakao Masayuki
Published: October 2008

The authors propose a single-pass forming technique for three-dimensional microstructures by shearing multilayer thin films. At a high strain rate, when strain is applied to a material at a speed higher than that of plastic wave propagation, the material is generally fractured without plastic deformation. In their experiment, a punch freely falling onto the back of a microfabricated mold allowed a high strain rate to be applied to the substrate. Multilayer thin films of eight evaporated layers of 250-nm-thick Si and SiO were successfully deformed to the bottom layer when the strain rate was over 1000–1500 s−1.
Iterative imprint for multilayered nanostructures by feeding, vacuum forming, and bonding of sheets
Authors: Suzuki Hideaki , Nagato Keisuke , Sugimoto Shuntaro , Tsuchiya Kensuke , Hamaguchi Tetsuya , Nakao Masayuki
Published: October 2008

The authors proposed an iterative imprint method for multilayered nanostructures. A thermoplastic sheet is fed onto a nanostructured mold and thermally imprinted by vacuum pumping between the mold and the sheet. Next, the imprinted sheet is thermally bonded onto a sheet that had been formed in the preprocess and that is held by an upper punch at the position opposite to the mold, and then the upper punch picks the sheet up from the mold. Repeating these processes realizes precision multilayered structures while maintaining horizontal positions of the upper punch and the vacuum-forming mold. This method will lead to the low-cost, high-accuracy fabrication of three-dimensional photonic devices. The authors formed 400×400×270 nm3 square hollows with an 800 nm pitch on the surface of a polymethyl methacrylate sheet of 1 μm thickness. The decrease in the light intensity diffracted by the mold surface as a result of the filling of the sheet was monitored in real time during the forming. The authors also successfully bonded another sheet and observed the hollows with 1 μm intervals in the thickness direction.
Self-aligned metal-contact and passivation technique for submicron ridge waveguide laser fabrication
Authors: Teng J. H. , Lim E. L. , Chua S. J. , Ang S. S. , Chong L. F. , Dong J. R. , Yin R.
Published: October 2008

One challenge in fabricating submicron ridge waveguide photonic devices is the formation of metal contacts and passivation. In this article, the authors report a self-aligned metal-contact and passivation technique suitable for submicron to nanoscale ridge waveguide device fabrication. The technique uses two different dielectric materials, e.g., SiO2 and Si3N4, with a different wet-etching selectivity. The first dielectric material (SiO2) acts as the etching mask and the second dielectric material (Si3N4) with a much lower etching rate acts as the passivation film. An undercut is formed in the semiconductor below the SiO2 mask by a wet-etching process. The semiconductor surface on top of the ridge waveguide will be fully exposed to metal contact by the lift-off process. A 0.7-μm-wide InGaAsP∕InP ridge waveguide laser was fabricated using the technique proposed. Mode simulation showed that the 0.7-μm-wide and 1.2-μm-deep ridge waveguide in the InGaAsP∕InP laser structure has good optical field confinement. Lasing is obtained on the 0.7-μm-wide ridge waveguide laser under current injection. An ∼240nm ridge waveguide is also demonstrated as an example of the technology for deep-submicron waveguide structure fabrication. The whole process is completely compatible with the existing compound semiconductor process and can be extended to fabricating other submicron to nanoscale devices.
The square cat
Authors: Putterman E. , Raz O.
Published: October 2008

We present a simple two-dimensional model of a “cat”—a body with zero angular momentum that can rotate itself with no external forces. The model is used to explain the nature of a gauge theory and to illustrate the importance of noncommutative operators. We compare the free-space cat in Newtonian mechanics and the same problem in Aristotelian mechanics at low Reynolds numbers (with the velocity proportional to the force rather than to the acceleration). This example shows the analogy between (angular) momentum in Newtonian mechanics and (torque) force in Aristotelian mechanics. We discuss a topological invariant common to the model in free space and at low Reynolds number.
Influence of a humidor on the aerodynamics of baseballs
Authors: Meyer Edmund R. , Bohn John L.
Published: October 2008

We investigate whether storing baseballs in a controlled humidity environment significantly affects their aerodynamic properties. We measure the change in diameter and weight of baseballs as a function of relative humidity in which the balls are stored. The trajectories of pitched and batted baseballs are modeled to assess the difference between those stored at 30% relative humidity versus 50% relative humidity. We find that a drier baseball will curve slightly more than a humidified one for a given pitch velocity and rotation rate. We also find that aerodynamics alone would add 2ft to the distance a wetter baseball ball is hit. This increased distance is compensated by a 6ft reduction in the batted distance due to the change in the coefficient of restitution of the ball. We discuss consequences of these results for baseball played at Coors Field in Denver, where baseballs have been stored in a humidor at 50% relative humidity since 2002.
The angular momentum of photons in a circularly polarized beam
Authors: Kiang D. , Young K.
Published: October 2008

We find the angular momentum of a photon in a circularly polarized beam by evaluating the energy and angular momentum imparted by a classical plane wave to a point charge for an arbitrary linear response. The only quantum ingredient used is the energy of a photon E=ℏω. Maxwell’s equations are not invoked beyond plane waves. Several previous results emerge as special cases of the derivation, which connects readily to experiments that measure the angular momentum of classical light.
The classical dynamics of Rydberg Stark atoms in momentum space
Authors: Murray-Krezan J.
Published: October 2008

The classical dynamics of a bound electron in a static electric field is discussed. The well-known Hamiltonian–Jacobi equations are examined and reexpressed in momentum coordinates, the preferred coordinates for the interpretation of many experimental measurements. It is shown that the combined Coulomb and static electric fields result in classically forbidden regions in momentum space. The equations of motion are discussed and the role of the electron’s angular momentum is described.
Energy and momentum in special relativity
Authors: Adkins Gregory S.
Published: October 2008

The special relativistic expressions for momentum and energy are obtained by requiring their conservation in a totally inelastic variant of the Lewis–Tolman symmetric collision. The resulting analysis is simpler and more straightforward than the usual textbook treatments of relativistic dynamics.