bluuebunny/crossref_metadata_2025 huggingface dataset:
Surfactant‐free synthesis of amphiphilic diblock copolymer in aqueous phase by a self‐stability process
Authors: Ji Jing , Yan Lifeng , Xie Dinghai
Published: March 2008

Amphiphilic polymeric particles with hydrophobic cores and hydrophilic shells were prepared via living radical emulsion polymerization of styrene using a water‐soluble poly(acrylamide)‐based macro‐RAFT agent in aqueous solution in the absence of any surfactants. Firstly, the homopolymerization of acrylamide (AM) was carried out in aqueous phase by reversible addition‐fragmentation chain transfer radical polymerization (RAFT) using a trithiocarbonate as a chain transfer agent. Then the PAM‐based macro‐RAFT agent has been used as a water‐soluble macromolecular chain transfer agent in the batch emulsion polymerization of Styrene (St) free of surfactants. The RAFT controlled growth of hydrophobic block led to the formation of well‐defined poly(acrylamide)‐copolystyrene amphiphilic copolymer, which was able to work as a polymeric stabilizer (self‐stability). Finally, very stable latex was prepared, having no visible phase separation for several months. FTIR and 1H‐NMR measurements showed that the product was the block copolymer PAM‐co‐PS in the form of stable latex. Atomic force microscope (AFM), transmission electron microscope (TEM), and dynamic light scattering (DLS) studies indicated that the nanoparticles have a narrow particle size distribution and the average particle hydrodynamic radius was kept in the diameter of 58 nm. Core‐shell structure of the copolymer was also recorded by TEM. The mechanism of the self‐stability of polymer particles during the polymerization in the absence of surfactants was studied. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3098–3107, 2008
The outcome of infants younger than 6 months requiring ventilation for pneumonia caused by Mycobacterium tuberculosis
Authors: Goussard P. , Gie R.P. , Kling S. , Schaaf H.S. , Kritzinger F. , Andronikou S. , Beyers N. , Rossouw G.J.
Published: March 2008

Introduction

The outcome of young infants (<6 months) being ventilated for respiratory failure caused by Mycobacterium tuberculosis (MTB) has not been recorded.

Patients and Methods

A descriptive study of children <6 months admitted to the PICU from 1 February 1999 to 31 December 2005 with MTB causing respiratory failure.

Results

Seventeen infants were ventilated for respiratory failure caused by MTB: ten had ventilatory respiratory failure and seven had hypoxic failure. An index case was found in 47%. All chest radiographs (CXRs) were highly suggestive of tuberculosis. MTB was cultured in 15 cases. In the other two cases MTB was confirmed by histopathology. The median duration of ventilation was 6 days (range: 1–35 days) with a median PaO2/FiO2 of 85 and ventilatory index of 58. Transthoracic glandular enucleation was required to facilitate extubation in six babies. All the infants survived. At 6‐month follow‐up 35% had a normal CXR and all were asymptomatic. One child had CXR changes suggestive of bronchiectasis but was asymptomatic.

Conclusion

The outcome of infants <6 months ventilated for respiratory failure caused by MTB is very good if TB is recognized timeously and appropriate management started. The diagnosis of TB in these infants can be made with a high index of suspicion and careful evaluation of the CXR. Pediatr Pulmonol. 2008; 43:505–510. © 2008 Wiley‐Liss, Inc.
RAD001 (Everolimus) inhibits growth of prostate cancer in the bone and the inhibitory effects are increased by combination with docetaxel and zoledronic acid
Authors: Morgan Todd M. , Pitts Tiffany E.M. , Gross Ted S. , Poliachik Sandra L. , Vessella Robert L. , Corey Eva
Published: March 2008

Introduction

mTOR activity is increased in advanced prostate cancer (CaP) as a result of a high rate of PTEN mutations. RAD001 (Everolimus) is a new orally available mTOR inhibitor. The objective of our study was to evaluate the effects of RAD001 on the growth of CaP in the bone, both alone and in combination with docetaxel and zoledronic acid.

Methods

C4‐2 CaP cells were injected into tibiae of mice and the animals were treated with RAD001, docetaxel, and zoledronic acid alone or in combination. Histomorphometrical analysis, serum PSA measurements, bone mineral density (BMD), and µCT were used to determine the effects of treatment on tumor and bone.

Results

All three agents alone decreased tumor volume, and RAD001 and docetaxel also decreased levels of serum PSA by 68% and 65%, respectively (both P < 0.01). Combinations of the agents were more effective in decreasing tumor volume than single agents. Three‐drug treatment showed the greatest effect: 64% inhibition versus control (P < 0.01). Treatment with RAD001 interfered with the weight loss associated with growth of this tumor in the bone (non‐RAD001 groups: 4.0% decrease in body weight, P = 0.0014; RAD001 groups: increase of 3.6% in body weight, P = 0.0037).

Conclusions

RAD001 inhibited growth of C4‐2 cells in bone, an effect augmented by addition of docetaxel and zoledronic acid. Moreover RAD001 had a significant impact on maintenance of body weight. RAD001 may hold promise for its effects on both metastatic CaP and the important syndrome of tumor cachexia. Prostate 68:861–871, 2008. © 2008 Wiley‐Liss, Inc.
Cell‐Surface labeling and internalization by a fluorescent inhibitor of prostate‐specific membrane antigen
Authors: Liu Tiancheng , Wu Lisa Y. , Kazak Marat , Berkman Clifford E.
Published: March 2008

BACKROUND

Prostate‐specific membrane antigen (PSMA) remains an attractive target for imaging and therapeutic applications for prostate cancer. Recent efforts have been made to conjugate inhibitors of PSMA with imaging agents. Compared to antibodies, small‐molecule inhibitors of PSMA possess apparent advantages for in vivo applications. To date, there are no reports on the cellular fate of such constructs once bound the extracellular domain of PSMA. The present study was focused on precisely defining the binding specificity, time‐dependent internalization, cellular localization, and retention of inhibitor conjugates targeted to PSMA on LNCaP cells. A novel fluorescent inhibitor was prepared as a model to examine these processes.

METHODS

Fluorescence microscopy of LNCaP and PC‐3 cell lines was used to monitor the specificity, time‐dependent internalization, cellular localization, and retention of a fluorescent PSMA inhibitor.

RESULTS

Fluorescent inhibitor 2 was found to be a potent inhibitor (IC50 = 0.35 nM) of purified PSMA. Its high affinity for PSMA on living cells was confirmed by antibody blocking and competitive binding experiments. Specificity for LNCaP cells was demonstrated as no labeling by 2 was observed for negative control PC‐3 cells. Internalization of 2 by viable LNCaP cells was detected after 30 min incubation at 37°C, followed by accumulation in the perinuclear endosomes. It was noted that internalized fluorescent inhibitor can be retained within endosomes for up to 150 min without loss of signal.

CONCLUSIONS

Our results suggest that potent, small‐molecule inhibitors of PSMA can be utilized as carriers for targeted delivery for prostate cancer for future imaging and therapeutic applications. Prostate 68:955–964, 2008. © 2008 Wiley‐Liss, Inc.
Cytokine profiling of prostatic fluid from cancerous prostate glands identifies cytokines associated with extent of tumor and inflammation
Authors: Fujita Kazutoshi , Ewing Charles M. , Sokoll Lori J. , Elliott Debra J. , Cunningham Mark , De Marzo Angelo M. , Isaacs William B. , Pavlovich Christian P.
Published: March 2008

Background

Cytokines are key mediators of inflammation that may relate to prostate cancer initiation and progression, and that may be useful markers of prostatic neoplasia and related inflammation. In order to better understand the relationship between cytokines and prostate cancer, we profiled cytokines in prostatic fluids obtained from cancerous prostate glands and correlated them to both cancer status and inflammatory grade.

Methods

Prostatic fluid was collected from fresh radical prostatectomy specimens and analyzed by cytokine antibody microarray. For comparison, cases were selected from patients with either minimal or extensive cancer volume on final pathology. Among the cytokines with the greatest difference between the tumor volume groups, eight had their levels quantitated by ELISA. In addition, the grade of prostatic inflammation by neutrophils, macrophages and lymphocytes was scored for each case and examined for correlations with cytokine levels.

Results

Among 174 cytokines analyzed, HGF was the most increased (6.57‐fold), and along with IL18Bpa was significantly elevated in patients with extensive disease compared to those with minimal disease. IL17, GITR, and ICAM‐1 were elevated in specimens with significant neutrophilic inflammation into gland lumina, and IL18Bpa, IL17, GITR, and ICAM‐1 were elevated in specimens with significant lymphocytic inflammation in prostatic stroma.

Conclusions

Prostatic fluid cytokines were identified that may be useful for early cancer detection and prognostication efforts and for assessment of prostatic inflammation, particularly if they can be found not only in prostatic fluids obtained ex vivo, but in expressed prostatic secretions or urine samples from men with prostates still in situ. Prostate 68:872–882, 2008. © 2008 Wiley‐Liss, Inc.
Endothelial cells support the growth of prostate tissue in vivo
Authors: Bates Michael , Kovalenko Bruce , Wilson E. Lynette , Moscatelli David
Published: March 2008

INTRODUCTION

The contribution of vascular endothelial cells to prostate growth has not been investigated. We examined whether endothelial cells support growth of prostate tissue when co‐inoculated with prostate epithelial cells under the renal capsule.

METHODS

Vascular endothelial cells were isolated from mice and co‐inoculated under the renal capsule with a prostate luminal or basal epithelial cell line. After 60 days, kidneys were examined for growth of prostate tissue. Prostatic tissues were examined by immunohistochemistry for expression of cytokeratins 5 and 8, and vascular density was determined. To determine if increased expression of VEGF‐A would increase prostatic growth, transfected endothelial cells overexpressing VEGF‐A were co‐inoculated with the prostate luminal or basal epithelial lines.

RESULTS

Co‐inoculation of endothelial cells and prostate luminal or basal epithelial cells resulted in significant growth of prostatic tissue, whereas inoculation of any of the cell lines alone resulted in little growth. The growths from co‐inoculation of endothelial cells and luminal epithelial cells contained duct‐like structures that stained with antibodies to cytokeratin 8, whereas those from co‐inoculation of endothelial cells and basal epithelial cells contained cords of cells that stained with antibodies to cytokeratin 5. Overexpression of VEGF‐A had no effect on growth of the prostatic tissues.

CONCLUSION

Endothelial cells contribute to the growth of prostatic epithelial cells. Prostate 68:893–901, 2008. © 2008 Wiley‐Liss, Inc.
Comparison of composer and ORCHESTRAR
Authors: Dolan Michael A. , Keil Matthias , Baker David S.
Published: March 2008

Although the number of known protein structures is increasing, the number of protein sequences without determined structures is still much larger. Three‐dimensional (3D) protein structure information helps in the understanding of functional mechanisms, but solving structures by X‐ray crystallography or NMR is often a lengthy and difficult process. A relatively fast way of determining a protein's 3D structure is to construct a computer model using homologous sequence and structure information. Much work has gone into algorithms that comprise the ORCHESTRAR homology modeling program in the SYBYL software package. This novel homology modeling tool combines algorithms for modeling conserved cores, variable regions, and side chains. The paradigm of using existing knowledge from multiple templates and the underlying protein environment knowledgebase is used in all of these algorithms, and will become even more powerful as the number of experimentally derived protein structures increases. To determine how ORCHESTRAR compares to Composer (a broadly used, but an older tool), homology models of 18 proteins were constructed using each program so that a detailed comparison of each step in the modeling process could be carried out. Proteins modeled include kinases, dihydrofolate reductase, HIV protease, and factor Xa. In almost all cases ORCHESTRAR produces models with lower root‐mean‐squared deviation (RMSD) values when compared with structures determined by X‐ray crystallography or NMR. Moreover, ORCHESTRAR produced a homology model for three target sequences where Composer failed to produce any. Data for RMSD comparisons between structurally conserved cores, structurally variable regions, side‐chain conformations are presented, as well as analyses of active site and protein–protein interface configurations. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Power factor correction circuit application using AlGaN/GaN HFETs
Authors: Yoshida Seikoh , Masuda Mitsuru , Niiyama Yuki , Kambayashi Hiroshi , Nomura Takehiko , Ikeda Nariaki
Published: March 2008

We demonstrated the application of a power factor correction (PFC) circuit using AlGaN/GaN HFETs for the first time. The AlGaN/GaN HFET with a large current and a high breakdown voltage operation was fabricated. That is, the maximum drain current was over 50 A, and the minimum on‐resistance was less than 70 mohm. The breakdown voltage was over 600 V. Using these HFETs, an AC‐DC converter with a power factor correction (PFC) circuit was fabricated. Irregular input waves of AC current and voltage were converted to very smooth input sign waves of AC voltage and current. The power factor was over 99%. Using this circuit, AC 100 V was successfully converted to DC 200 V. the output conversion efficiency from AC input to DC output was 93%. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of AlGaAs cladding layer on GaInNAs/GaAs MQW p‐i‐n photodetector
Authors: Chen Y. F. , Chen W. C. , Chuang R. W. , Su Y. K. , Tsai H. L.
Published: March 2008

The electronic properties of GaInNAs/GaAs multiple‐quantum‐well (MQW) p‐i‐n photodetector with AlGaAs cladding layer have been studied. By applying a higher band gap Al0.3Ga0.7As to the photodetector, a substantial reduction in dark current was observed owing to an inherent difficulty for holes to surmount the high potential barrier between MQW and the cladding layer heterojunction under a reverse bias. The dark current obtained was as low as 4.1 pA at ‐3.5 V for a device with Al0.3Ga0.7As cladding layer as compared to 22 μA also at ‐3.5 V for a similar device without the Al0.3Ga0.7As cladding layer. The photo/dark current contrast ratios obtained were 4.2×104 and 11, respectively, for devices with and without an Al0.3Ga0.7As cladding layer at ‐3.5 V. In addition, peak responsivity of 1 mA/W was measured at around 1150 nm. Two orders of magnitude increase in the rejection ratio were realized between 1150 and 1250 nm at ‐2.0 V. The GaInNAs/GaAs MQW p‐i‐n photodetector was demonstrated with the AlGaAs cladding layer potentially providing a higher photo/dark current contrast ratio and higher responsivity rejection ratio. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Voltage‐dependence of the human dopamine D2 receptor
Authors: Sahlholm Kristoffer , Nilsson Johanna , Marcellino Daniel , Fuxe Kjell , Århem Peter
Published: March 2008

The dopamine D2 receptor plays a critical role in activity‐dependent synaptic plasticity in the striatum, and regulates the transitions between different states of electrical activity. The D2 receptor is the main target for antipsychotics, and its affinity towards dopamine has been shown to be increased in psychotic patients. Recently, voltage‐sensitivity has been reported for the ligand binding and G protein‐coupling properties of some neurotransmitter receptors, raising the question whether the D2 receptor is also regulated by voltage. Our present electrophysiology data from Xenopus oocytes indicate that the D2 receptor is indeed voltage‐sensitive. Comparing concentration–response relationships for the activation of G protein‐coupled inward rectifier potassium (GIRK) channels via D2 receptor stimulation by quinpirole or dopamine at −80 and at +40 mV revealed rightward shifts upon depolarisation of nearly tenfold, for both agonists. Our results are likely to bear relevance to the function of the D2 receptor in gating synaptic input and in regulating plasticity. Synapse 62:476–480, 2008. © 2008 Wiley‐Liss, Inc.
Teaching the Operating Room
Authors: Ferrari M.L.
Published: March 2008

TEACHING THE OPERATING ROOM Margaret A. Burns, R. N., Helen M. Lundahl, R.N., Virginia T. Rockwell, R.N., and Janet M. Redgate, R.N., 337 pages, Association of Operating Room Nurses, Inc., New York, N. Y., 1967. $11.00.
Back to Nursing
Authors: Gaffrey E.A.
Published: March 2008

Ruth Perin Stryker, R. N., 312 pages, W. B. Saunders Company, Philadelphia, Pa., 1967. $5.75.
The Art of Clear Thinking
Authors: Horwitz Rita
Published: March 2008

THE ART OF CLEAR THINKING, by Rudolf Flesch, Ph.D., Harper & Row, Inc., New York, 1951, 212 pages. Price $5.95.
Logic of Operating Room Nursing
Authors: Jenks Elaine
Published: March 2008

LOGIC OF OPERATING ROOM NURSING, by Jacqueline Willingham, R.N., Springer Publishing Company, Inc., New York, 1967, 111 pages. Price $2.50.
Molecular mechanisms of liquid slip
Authors: MARTINI A. , ROXIN A. , SNURR R. Q. , WANG Q. , LICHTER S.
Published: March 2008

It is now well-established that the liquid adjacent to a solid need not be stationary – it can slip. How this slip occurs is unclear. We present molecular-dynamics (MD) simulation data and results from an analytical model which support two mechanisms of slip. At low levels of forcing, the potential field generated by the solid creates a ground state which the liquid atoms preferentially occupy. Liquid atoms hop through this energy landscape from one equilibrium site to another according to Arrhenius dynamics. Visual evidence of the trajectories of individual atoms on the solid surface supports the view of localized hopping, independent of the dynamics outside a local neighbourhood. We call this defect slip. At higher levels of forcing, the entire layer slips together, obviating the need for localized defects and resulting in the instantaneous motion of all atoms adjacent to the solid. The appearance of global slip leads to an increase in the number of slipping atoms and consequently an increase in the slip length. Both types of slip observed in the MD simulations are described by a dynamical model in which each liquid atom experiences a force from its neighbouring liquid atoms and the solid atoms of the boundary, is sheared by the overlying liquid, and damped by the solid. In agreement with the MD observations, this model predicts that above a critical value of forcing, localized slipping occurs in which atoms are driven from low-energy sites, but only if there is a downstream site which has been vacated. Also as observed, above a second critical value, all the liquid atoms adjacent to the wall slip. Finally, the dynamical equation predicts that at extremely large values of forcing, the slip length approaches a constant value, in agreement with the MD simulation results.
How should we construct psychiatric family history scores? A comparison of alternative approaches from the Dunedin Family Health History Study
Authors: Milne B. J. , Moffitt T. E. , Crump R. , Poulton R. , Rutter M. , Sears M. R. , Taylor A. , Caspi A.
Published: March 2008

Background

There is increased interest in assessing the family history of psychiatric disorders for both genetic research and public health screening. It is unclear how best to combine family history reports into an overall score. We compare the predictive validity of different family history scores.

Method

Probands from the Dunedin Study (n=981, 51% male) had their family history assessed for nine different conditions. We computed four family history scores for each disorder: (1) a simple dichotomous categorization of whether or not probands had any disordered first-degree relatives; (2) the observed number of disordered first-degree relatives; (3) the proportion of first-degree relatives who are disordered; and (4) Reed's score, which expressed the observed number of disordered first-degree relatives in terms of the number expected given the age and sex of each relative. We compared the strength of association between each family history score and probands' disorder outcome.

Results

Each score produced significant family history associations for all disorders. The scores that took account of the number of disordered relatives within families (i.e. the observed, proportion, and Reed's scores) produced significantly stronger associations than the dichotomous score for conduct disorder, alcohol dependence and smoking. Taking account of family size (i.e. using the proportion or Reed's score) produced stronger family history associations depending on the prevalence of the disorder among family members.

Conclusions

Dichotomous family history scores can be improved upon by considering the number of disordered relatives in a family and the population prevalence of the disorder.
The ‘good-enough’ music teacher
Authors: Swanwick Keith
Published: March 2008

Teaching and learning are complex processes and evaluating the work of music teachers is neither obvious nor simple. The outcomes of educational transactions may not be completely or immediately apparent. Furthermore, the contexts in which musical skills and understanding are acquired are multiple, going well beyond the formal categories of ‘general’ class music teacher or the ‘private’ instrumental and vocal teacher. In many of these alternative settings, standardised student assessment or teacher evaluation processes may be inappropriate. In this paper, an approach to evaluating teaching and learning draws on Swanwick's three principles for music educators. To these three principles is added the need to understand the educational and social context in which a teacher works. These criteria help to identify the ‘good-enough’ teacher's contribution to students' musical development. The concept of the ‘good-enough’ teacher is exemplified, not in the context of conventional formal teaching settings but in a third, much less defined role, that of music leader. The extent to which music leaders contribute to their musical environment is evaluated in a study of their continuing professional development. This evaluation was initiated by Youth Music, a UK organisation working alongside the formal and community-based sectors to support music-making and training.
A method for the detection of the severe rain‐on‐snow event on Banks Island, October 2003, using passive microwave remote sensing
Authors: Grenfell T. C. , Putkonen J.
Published: March 2008

Severe wintertime rain‐on‐snow (ROS) events create a strong ice layer (or layers) in the snow on arctic tundra that act as a barrier to ungulate grazing. They are linked with large‐scale ungulate (reindeer, caribou, elk, and musk‐ox) herd declines via starvation and reduced calf production rate when the animals are unable to penetrate the resulting subsnowpack ice layer. ROS events also produce considerable perturbation in the mean wintertime soil temperature under the snowpack. ROS is a sporadic but well‐known and significant phenomenon that is currently very poorly documented. Characterization of the distribution and occurrence of severe ROS events is based only on anecdotal evidence, indirect observations of carcasses found adjacent to iced snowpacks, and irregular detection by a sparse observational weather network. We have analyzed in detail a particular ROS event that took place on Banks Island in early October 2003 that resulted in the death of 20,000 musk oxen. We make use of multifrequency passive microwave imagery from the Special Sensor Microwave Imager satellite sensor suite in conjunction with a strong‐fluctuation‐theory (SFT) emissivity model. We show that a combination of time series analysis and cluster analysis based on microwave spectral gradients and polarization ratios provides a means to detect the stages of the ROS event resulting from the modification of the vertical structure of the snowpack, specifically wetting the snow, the accumulation of liquid water at the base of the snow during the rain event, and the subsequent modification of the snowpack after refreezing. SFT model analysis provides quantitative confirmation of our interpretation of the evolution of the microwave properties of the snowpack as a result of the ROS event. In addition to the grain coarsening owing to destructive metamorphism, we detect the presence of the internal water and ice layers, directly identifying the physical properties producing the hazardous conditions. This analysis offers the potential to characterize both the frequency and global distribution of ROS using multifrequency satellite passive microwave imagery.
Anisotropy and Magnetostriction in Magnetic Oxides
Authors: Slonczewski J. C.
Published: March 2008

Recent theories of the anisotropy and magnetostriction due to the presence of Co2+ in spinel ferrites are reviewed and new work on the effects of Fe2+ is presented. The effects of these ions are great because the orbital angular momentum is not fully quenched by the crystal field. In the case of Co2+, the orbital moment of the ground state is coupled strongly to the trigonal axis of the crystal field. The very large anisotropy and magnetostriction arise from spin-orbit coupling in first order. The theory is found to account for many of the effects of cobalt-iron ferrite and cobalt-manganese ferrite at higher temperatures. The contribution of Fe2+ to these effects is less extreme but still striking. Here the orbital moment is more nearly quenched but the spin is still coupled strongly to the trigonal axis. The coupling gives rise to cubic anisotropy in second order approximation. This term appears to account for the large compositional dependence of anisotropy in manganese-rich manganese-iron ferrite. A crystal-field calculation of the orthorhomic distortion of the low-temperature form of magnetite is found to be consistent with observations at about 80°K, assuming a high degree of Verwey ordering. However, the anisotropy calculated on the same assumption is found to be inconsistent with experiment. It is concluded that the one-ion crystal-fieldtheory is largely applicable to the effects of Co2+ and Fe2+ in ferrites. However, it does not work when the concentration of Fe2+ is high.
Paramagnetism of Polycrystalline Gadolinium, Terbium, and Dysprosium Metals
Authors: Arajs Sigurds , Colvin R. V.
Published: March 2008

The paramagnetic susceptibilities of polycrystalline gadolinium, terbium, and dysprosium metals have been studied between 300–1500°K. The measurements are in good agreement with predictions which use the localized f-electron model of interacting rare-earth ions and the Van Vleck theory of paramagnetism. Departures from the Van Vleck theory are attributed to paramagnetism of conduction electrons. An approximate value of this contribution has been calculated for dysprosium.
Recording and Reproduction of NRZI Signals
Authors: Schools R. S.
Published: March 2008

A systematic theoretical study of a saturation type of recording and reproduction in digital magnetic tape systems was undertaken so that the details of these processes could be more clearly understood. The dependence of tape magnetization and of output signal pulse width and amplitude on the major system parameters has been investigated and determined. These parameters are the magnetic field distribution of the recording head, write current waveform, tape thickness and hysteresis characteristics, head-to-tape spacing, reading gap length, and bit density. A portion of this study is presented here, concerning the extension of the sinusoidal theory to include the reproduction of signals resulting from saturation recording. This is done by a Fourier analysis of the tape magnetization and a term-by-term summation of harmonic responses to obtain the resultant signal. The results show why high writing field gradients, high tape B-H “squareness,”and thin tapes are needed for high-density recording. They indicate possible reasons for emf pulse peak position asymmetries during readback. Two examples of output calculations are included. One shows the signal amplitude and pulse width vs bit density, compared with experimental measurements. The other presents the field distribution above the magnetized tape, indicating the influence of the presence of the read head.
Distribution of Cations in Spinels
Authors: Miller Arthur
Published: March 2008

The concept of octahedral site preference energy in spinels has been extended to include Madelung and short-ranged as well as crystal field terms. A set of site preference energies is formulated which can be used to predict the ionic distribution of spinels involving the nontransition as well as the transition ions. The agreement between predicted and experimentally determined ionic distributions is surprisingly good, and a number of heretofore puzzling distributions are explained.
Evidence for Triangular Moment Arrangements in MO · Mn2O3
Authors: Jacobs I. S.
Published: March 2008

Ferrimagnetic spinel-type compounds frequently have lower spontaneous magnetizations than predicted by the simple Néel model, with tetrahedral A-site moments antiparallel to octahedral B-site moments. Yafet and Kittel suggested triangular moment arrangements, in which the moments of one kind subdivide into two groups making angles with each other. A linear increase in net magnetization with field at high field and low temperature is expected for the triangular arrangement but not for the antiparallel ferrimagnetic one. Measurements are reported of magnetization curves at 4.2°K in pulsed fields up to 140-kilo oersteds on compounds of the form MO · Mn2O3 where M is Mn, Co, Zn, and Mg, and mixtures thereof. A high field susceptibility is observed in these, and is absent in Fe3O4, thus supporting a triangular model and directly measuring the strength of the B-B interaction. The observed composition dependence of the spontaneous moment and the high field susceptibility are in approximate agreement with a simple molecular field model. The spontaneous moment of Mn3O4 is 1.56±0.04 Bohr magneton/molecule, with the B-site moments subdivided into groups at angles. From a comparison with high-temperature susceptibility data, it is suggested that the net A-site moment is dominant.
Flux-flow behaviors on a Bi2Sr2CaCu2O8+δ (Bi-2212) stack
Authors: Kim Sang-Jae , Hatano Takeshi , Blamire Mark
Published: March 2008

We investigated long intrinsic Josephson junctions (IJJs) as an oscillator on a Bi2Sr2CaCu2O8+d (Bi-2212) whisker. The oscillator utilizes the effect of flux-flow motion in long IJJs. In-plane areas with the same junction geometry, 15×1.7μm2 were fabricated by using a three-dimensional focused-ion-beam (FIB) etching method. Those oscillator junctions exhibited uniform multibranch structures and clearly upturned curves under He. The flux-flow velocities (Vff) reached 8.7×105m∕s at 6.2T and 10K. We describe the characteristic flux-flow behaviors on long IJJs for high-frequency device applications.
Effect of solvent on absorption spectra of all-trans-β-carotene under high pressure
Authors: Liu W. L. , Zheng Z. R. , Dai Z. F. , Liu Z. G. , Zhu R. B. , Wu W. Z. , Li A. H. , Yang Y. Q. , Su W. H.
Published: March 2008

The absorption spectra of all-trans-β-carotene in n-hexane and carbon disulfide (CS2) solutions are measured under high pressure at ambient temperature. The common redshift and broadening in the spectra are observed. Simulation of the absorption spectra was performed by using the time-domain formula of the stochastic model. The pressure dependence of the 0-0 band wavenumber is in agreement with the Bayliss theory at pressure higher than 0.2GPa. The deviation of the linearity at lower pressure is ascribed to the reorientation of the solvent molecules. Both the redshift and broadening are stronger in CS2 than that in n-hexane because of the more sensitive pressure dependence of dispersive interactions in CS2 solution. The effect of pressure on the transition moment is explained with the aid of a simple model involving the relative dimension, location, and orientation of the solute and solvent molecules. The implication of these results for light-harvesting functions of carotenoids in photosynthesis is also discussed.
Solving the Schrödinger and Dirac equations of hydrogen molecular ion accurately by the free iterative complement interaction method
Authors: Ishikawa Atsushi , Nakashima Hiroyuki , Nakatsuji Hiroshi
Published: March 2008

The nonrelativistic Schrödinger equation and the relativistic four-component Dirac equation of H2+ were solved accurately in an analytical expansion form by the free iterative complement interaction (ICI) method combined with the variational principle. In the nonrelativistic case, we compared the free ICI wave function with the so-called “exact” wave function as two different expansions converging to the unique exact wave function and found that the free ICI method is much more efficient than the exact method. In the relativistic case, we first used the inverse Hamiltonian to guarantee Ritz-type variational principle and obtained accurate result. We also showed that the ordinary variational calculation also gives a nice convergence when the g function is appropriately chosen, since then the free ICI calculation guarantees a correct relationship between the large and small components of each adjacent order, which we call ICI balance. This is the first application of the relativistic free ICI method to molecule. We calculated both ground and excited states in good convergence, and not only the upper bound but also the lower bound of the ground-state energy. The error bound analysis has assured that the present result is highly accurate.
Electrochemical charge transfer at a metallic electrode: A simulation study
Authors: Reed Stewart K. , Madden Paul A. , Papadopoulos Aristides
Published: March 2008

The calculation of the Marcus free energy curves for electron transfer events between a redox species and a metallic electrode in an atomistic simulation designed to model the electrochemical interface with an ionic liquid is described. The calculation is performed on a system comprising a molten salt mixture confined between model metallic electrodes [Reed et al., J. Chem. Phys. 126, 084704 (2007)] which are maintained at a constant electrical potential. The calculation therefore includes a self-consistent description of the screening of the electrode potential by the liquid and the polarization of the electrode by the ions (image charge effects). The purpose of the study was to examine how the Marcus curves depend on the applied potential and on the distance of the redox species from an electrode. The pronounced oscillations in the mean electrical potential seen in molten salt systems in the “double-layer” region are not reflected in the reaction free energy for the electron transfer event. The reorganization energy depends markedly on the distance of the redox ion from the electrode surface because of image charge effects.
Computational coarse graining of a randomly forced one-dimensional Burgers equation
Authors: Ahuja Sunil , Yakhot Victor , Kevrekidis Ioannis G.
Published: March 2008

We explore a computational approach to coarse graining the evolution of the large-scale features of a randomly forced Burgers equation in one spatial dimension. The long term evolution of the solution energy spectrum appears self-similar in time. We demonstrate coarse projective integration and coarse dynamic renormalization as tools that accelerate the extraction of macroscopic information (integration in time, self-similar shapes, nontrivial dynamic exponents) from short bursts of appropriately initialized direct simulation. These procedures solve numerically an effective evolution equation for the energy spectrum without ever deriving this equation in closed form.
Blow up, global existence, and infinite propagation speed for the weakly dissipative Camassa–Holm equation
Authors: Guo Zhengguang
Published: March 2008

In this paper, we consider the weakly dissipative Camassa–Holm equation. First, we try to improve other authors’ results and get some new criterion on blow up, then discuss the global existence of the solution. Finally, we intend to establish sufficient conditions on the propagation speed for the weakly dissipative Camassa–Holm equation.
Pseudospin model of above-barrier states in a three-component multiple-sublattice crystal
Authors: Kovarskiĭ V. L. , Kuznetsov A. Yu.
Published: March 2008

A model of a structurally disordered crystal with three equivalent states per site is studied. An effective pseudospin model Hamiltonian which takes account of above-barrier motion is constructed. An expression is obtained for the nonequilibrium free energy for one- and four-sublattice ordering. The state of metastable disorder for a one-sublattice structure and an equilibrium phase transition for a four-sublattice model are studied. The results are used to interpret Mössbauer studies of the Jahn–Teller crystal Cu(H2O)6⋅SiF6. A theoretical explanation is given for the statics-dynamics transition, observed in the disordered phase of this crystal as the structural phase transition point is approached.
Unit cell parameters and thermal expansion of silane SiH4
Authors: Gal’tsov N. N. , Klimenko N. A. , Prokhvatilov A. I.
Published: March 2008

X-Ray investigations of the temperature dependences of the lattice parameters and volumes of the low- and high-temperature phases of the light silane SiH4 have been performed. The linear and volume thermal expansion coefficients have been determined. It has been established that the thermal expansion of the low-temperature phase is anisotropic and increases substantially as the orientational phase transition point is approached. Using as a basis the results obtained for and the published data on the specific heat CP and the compressibility, the specific heat CV of silane is analyzed and the contributions of the translational and rotational motions of the molecules are determined separately. It is shown that the contribution of the librational subsystem to the specific heat of silane becomes appreciable only at temperatures above 25K. The Grüneisen coefficients γ are calculated. It is shown that in the low-temperature phase γ depends appreciably on temperature, while in the high-temperature phase γ is virtually constant and close to the value characteristic for the crystals of inert elements.
Field-reversed configuration formation scheme utilizing a spheromak and solenoid induction
Authors: Gerhardt S. P. , Belova E. V. , Yamada M. , Ji H. , Ren Y. , McGeehan B. , Inomoto M.
Published: March 2008

A new field-reversed configuration (FRC) formation technique is described, where a spheromak transitions to a FRC with inductive current drive. The transition is accomplished only in argon and krypton plasmas, where low-n kink modes are suppressed; spheromaks with a lighter majority species, such as neon and helium, either display a terminal tilt-mode, or an n=2 kink instability, both resulting in discharge termination. The stability of argon and krypton plasmas through the transition is attributed to the rapid magnetic diffusion of the currents that drive the kink-instability. The decay of helicity during the transition is consistent with that expected from resistivity. This observation indicates a new scheme to form a FRC plasma, provided stability to low-n modes is maintained, as well as a unique situation where the FRC is a preferred state.
A novel design of dielectric perfect invisibility devices
Authors: Ochiai T. , Leonhardt U. , Nacher J. C.
Published: March 2008

The aim of an invisibility device is to guide light around any object put inside, being able to hide objects from sight. In this work, we propose a novel design of dielectric invisibility media based on negative refraction and optical conformal mapping that seems to create perfect invisibility. This design has some advantages and more relaxed constraints compared with already proposed schemes. In particular, it represents an example where the time delay in a dielectric invisibility device is zero. Furthermore, due to the impedance matching of negatively refracting materials, the reflection should be close to zero. These findings strongly indicate that perfect invisibility with optically isotropic materials is possible. Finally, the area of the invisible space is also discussed.
Formation of secondary electron cascades in single-crystalline plasma-deposited diamond upon exposure to femtosecond x-ray pulses
Authors: Gabrysch M. , Marklund E. , Hajdu J. , Twitchen D. J. , Rudati J. , Lindenberg A. M. , Caleman C. , Falcone R. W. , Tschentscher T. , Moffat K. , Bucksbaum P. H. , Als-Nielsen J. , Nelson A. J. , Siddons D. P. , Emma P. J. , Krejcik P. , Schlarb H. , Arthur J. , Brennan S. , Hastings J. , Isberg J.
Published: March 2008

Secondary electron cascades were measured in high purity single-crystalline chemical vapor deposition (CVD) diamond, following exposure to ultrashort hard x-ray pulses (140fs full width at half maximum, 8.9keV energy) from the Sub-Picosecond Pulse Source at the Stanford Linear Accelerator Center. We report measurements of the pair creation energy and of drift mobility of carriers in two CVD diamond crystals. This was done for the first time using femtosecond x-ray excitation. Values for the average pair creation energy were found to be 12.17±0.57 and 11.81±0.59eV for the two crystals, respectively. These values are in good agreement with recent theoretical predictions. The average drift mobility of carriers, obtained by the best fit to device simulations, was μh=2750cm2∕Vs for holes and was μe=2760cm2∕Vs for electrons. These mobility values represent lower bounds for charge mobilities due to possible polarization of the samples. The results demonstrate outstanding electric properties and the enormous potential of diamond in ultrafast x-ray detectors.
“Maximum” entropy production in self-organized plasma boundary layer: A thermodynamic discussion about turbulent heat transport
Authors: Yoshida Z. , Mahajan S. M.
Published: March 2008

A thermodynamic model of a plasma boundary layer, characterized by enhanced temperature contrasts and “maximum entropy production,” is proposed. The system shows bifurcation if the heat flux entering through the inner boundary exceeds a critical value. The state with a larger temperature contrast (larger entropy production) sustains a self-organized flow. An inverse cascade of energy is proposed as the underlying physical mechanism for the realization of such a heat engine.
The electronic structure of surface chains in the layered semiconductor In4Se3(100)
Authors: Losovyj Ya. B. , Klinke Melanie , Cai En , Rodriguez Idaykis , Zhang Jiandi , Makinistian L. , Petukhov A. G. , Albanesi E. A. , Galiy P. , Fiyala Ya. , Liu Jing , Dowben P. A.
Published: March 2008

The ordered (100) surface of layered In4Se3 single crystals is characterized by semiconducting quasi-one-dimensional indium (In) chains. A band with significant dispersion in the plane of the surface is observed near the valence band maximum. The band exhibits an anisotropic dispersion with ∼1eV band width along the In chain direction. The dispersion of this band is largely due to the hybridization of In-s and Se-p orbitals, but the hybridization between In-s and Se-p and In-p and Se-p orbitals is also critical in establishing the band gap.
Grain refinement assisted strengthening of carbon nanotube reinforced copper matrix nanocomposites
Authors: Kim K. T. , Eckert J. , Menzel S. B. , Gemming T. , Hong S. H.
Published: March 2008

Carbon nanotube reinforced copper matrix (CNT/Cu) nanocomposites were fabricated by the modified molecular-level mixing process, which produces a homogeneous dispersion of CNTs in a fine grained metal matrix. These nanocomposites, consisting of 1.5μm Cu matrix grains and 5vol% of multiwall CNTs, show a high strengthening capability; enhancing the yield strength of unreinforced Cu by 2.3 times. The enhanced yield strength stems from the reinforcing effect of CNTs and additional hardening of the Cu matrix by grain refinement. The results reveal that the metallurgical treatment of the matrix is important for the development of high-strength CNT/metal nanocomposites.
Defect reduction in GaN/(0001)sapphire films grown by molecular beam epitaxy using nanocolumn intermediate layers
Authors: Cherns D. , Meshi L. , Griffiths I. , Khongphetsak S. , Novikov S. V. , Farley N. , Campion R. P. , Foxon C. T.
Published: March 2008

Transmission and scanning electron microscopies are used to examine the epitaxial lateral overgrowth of GaN on GaN nanocolumns grown on AlN/(0001)sapphire by molecular beam epitaxy. Initially, N-rich growth gave a bimodal morphology consisting of defect-free Ga-polar nanocolumns emanating from a compact, highly defective N-polar layer. Under subsequent Ga-rich conditions, the nanocolumns grew laterally to produce continuous Ga-polar overlayers. Threading dislocation (TD) densities in the overlayer were in the range of 108–109cm−2, up to two orders of magnitude less than in the N-polar underlayer. It is proposed that the change in polarity is a key factor controlling the reduction in TD density.
Ultraviolet emission from Sb-doped p-type ZnO based heterojunction light-emitting diodes
Authors: Mandalapu L. J. , Yang Z. , Chu S. , Liu J. L.
Published: March 2008

Heterojunction light emitting diodes (LEDs) were fabricated by making Au∕Ni top Ohmic contacts on Sb-doped p-type ZnO film with low specific contact resistivity and Al∕Ti back Ohmic contacts on n-type Si substrate. Near-band edge and deep-level emissions were observed from the LED devices at both low temperatures and room temperature, which is due to band-to-band and band-to-deep level radiative recombinations in ZnO, respectively. The electroluminescence emissions precisely match those of photoluminescence spectra from Sb-doped p-type ZnO, indicating that the ZnO layer acts as the active region for the radiative recombinations of electrons and holes in the diode operation.
Dissipation from microscale and nanoscale beam resonators into a surrounding fluid
Authors: Judge John A. , Vignola Joseph F. , Jarzynski Jacek
Published: March 2008

Simple models for estimating viscous damping, acoustic radiation loss, and loss due to collisions with individual molecules of rarefied gas are presented and examined to show how quality factor of microscale and nanoscale resonators varies with ambient fluid pressure p and resonator geometry. For sufficiently low length to thickness aspect ratios, acoustic radiation loss is the dominant loss mechanism at pressures great enough that the fluid acts as a continuum, and the acoustic loss transitions seamlessly at low pressure to loss due to direct transfer of momentum to individual fluid molecules (both models have loss proportional to fluid pressure). For beams with greater aspect ratio, viscous loss, with loss proportional to p, dominates over a certain range of pressures, and the width of this region depends on the acoustic radiation efficiency of the beam. The transition between rarefied gas behavior and viscous (continuum) behavior occurs when the mean free path lmfp, a function of pressure, becomes shorter than the viscous skin depth δ, which is related to beam size but also influenced by aspect ratio.