bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of particle shape on dielectric enhancement in metal-insulator composites
Authors: Doyle W. T. , Jacobs I. S. 
Published: July 2002

Disordered suspensions of conducting particles exhibit substantial permittivity enhancements beyond the predictions of the Clausius–Mossotti equation and other purely dipolar approximations. The magnitude of the enhancement depends upon the shape of the particles. A recently developed effective cluster model for spherical particles [Phys. Rev. B 42, 9319 (1990)] that treats a disordered suspension as a mixture, or mesosuspension, of isolated spheres and close-packed spherical clusters of arbitrary size is in excellent agreement with experiments on well-stirred suspensions of spheres over the entire accessible range of volume loading. In this paper, the effective cluster model is extended to be applicable to disordered suspensions of arbitrarily shaped conducting particles. Two physical parameters are used to characterize a general suspension: the angular average polarizability of an isolated particle, and the volume loading at closest packing of the suspension. Multipole interactions within the clusters are treated exactly. External particle-shape-dependent interactions between clusters and isolated particles are treated in the dipole approximation in two ways: explicitly, using the Clausius–Mossotti equation, and implicitly, using the Wiener equation. Both versions of the model are used to find the permittivity of a monodisperse suspension of conducting spheroids, for which the model parameters can be determined independently. The two versions are in good agreement when the axial ratio of the particles is not extreme.
The Clausius–Mossotti version of the model yields a mesoscopic analogue of the dielectric virial expansion. It is limited to small volume loadings when the particles have an extremely nonspherical shape. The Wiener equation version of the model holds at all volume loadings for particles of arbitrary shape. Comparison of the two versions of the model leads to a simple physical interpretation of Wiener’s equation. The models are compared with experiments of Kelly, Stenoien, and Isbell [J. Appl. Phys. 24, 258 (1953)] on aluminum and zinc particles in paraffin, with Nasuhoglu’s experiments on iron particles in oil [Commun. Fac. Sci. Univ. Ankara 4, 108 (1952)], and with new X-band and Kα-band permittivity measurements on Ni-Cr alloy particles in a polyurethane binder.
Phase properties of microwave magnetic envelope dark solitons in yttrium iron garnet thin films (abstract)
Authors: Nash J. M. , Kabos P. , Patton C. E. , Staudinger R. 
Published: July 2002

Although microwave magnetic envelope (MME) solitons in thin yttrium iron garnet (YIG) films have been studied extensively, only recently have dark MME solitons been observed. For a single dark soliton, one has a carrier phase change of 180°. Reference 1 indicated such a change. However, the overall phase change for a given dark pulse experiment should be 0°. The objective of this work was to examine phase profiles in detail for the dark soliton experiment. The results show that both of the above expectations are, in fact, satisfied. The 5 GHz measurements were done with a magnetostatic wave delay line structure with a long and narrow 7.2 μm thick single crystal YIG film oriented in the surface wave configuration. A GaAs microwave switch produced 300 ns long bright pulses separated by a dark pulse with a width in the 15 ns range. The input power was 0.002–1.0 W. The output signal showed two main dark pulse features, independent of power level. At low powers, the changes in phase across both features were small. With increasing power, the phase change across the first feature showed a rapid increase while the phase change for the second feature remained small. The phase change for the first feature saturated at a large value, on the order of 200°, relative to the phase change at low power.
The phase change over the entire profile was always 0°. These results show: (1) There are significant phase changes at both low and high powers in the dark pulse experiment. (2) The phase change for a dark soliton must take into account the background phase change at lower powers. (3) Only the main dark pulse feature in the output profile exhibits single dark soliton characteristics through a clearly resolved phase saturation at 180°. (4) These thresholds are on the order of 10 mW for typical strip line transducer structures, compared to 100 mW or so for bright solitons.
Effects of magnetostatic interaction between two single-domain cobalt bars on crystal anisotropy and switching field (abstract)
Authors: Chou Stephen Y. , Kong Linshu 
Published: July 2002

Understanding the magnetostatic field effects of a single-domain particle on its neighbors during thin film deposition and magnetic recording is essential to the development of magnetic recording media. Here, we present a unique study of such effects using nanofabrication technology and magnetic force microscopy (MFM). We fabricated pairs of single-domain cobalt bars. Each bar is 35 nm thick, 50 nm wide, and 1 μm long. The twin bars were oriented side-by-side on a silicon substrate with a spacing that varied from 50 to 1000 nm. In fabrication, a resist template was first created on a silicon substrate, followed by e-beam evaporation of cobalt into the bar-shaped openings of the template as well as on the top of the template. Then, the resist was dissolved making the cobalt on top of the template lift off. MFM showed that as-fabricated bars are single magnetic domain. We polarized the magnetic moment of the twin single-domain bars in the same direction and measured the magnetic field needed for the following three cases: (a) switching the magnetization direction of only one of the twin bars, Ha; (b) switching both bars, Hb; and (c) switching one bar after the other bar was physically removed by a nanotechnique, Hc.
Two important facts can be seen. First, for a given bar spacing, Ha&lt;Hc&lt;Hb. The difference is due to the demagnetization field of the neighbor which is on the order of 150 Oe depending upon the bar spacing. Second, all three switching fields decrease significantly as the bar spacing becomes larger. For example, Hc is 2050 Oe for a 300 nm bar spacing and 1700 Oe for 1000 nm spacing. The spacing dependence of Hc clearly indicates that the intrinsic switching field of a bar has been significantly affected, during the cobalt deposition, by the demagnetization field of its neighbors. One explanation is that as soon as the first few atomic layers of cobalt were deposited into a nanoscale bar shaped opening in the resist template, a single domain is formed immediately creating a magnetostatic field. This field forces the c axis of the cobalt that was later deposited into the neighboring bar to align with the field, therefore enhancing the crystal anisotropy and intrinsic coercivity of the neighboring bar. This study implies that a small topology variation on a magnetic disk substrate may cause a large local coercivity variation due to the enhancement of crystal anisotropy and coercivity induced during the deposition by the demagnetization field of neighboring single-domain particles.
A Fourier transform-infrared reflection absorption spectroscopy study of the formation and decomposition of chemisorbed formate on clean and potassium-modified Ru(001)
Authors: Weisel M. D. , Chen J. G. , Hoffmann F. M. , Sun Y.-K. , Weinberg W. H. 
Published: July 2002

The formation and decomposition of formate species on the clean and on potassium-modified Ru(001) surfaces have been investigated with time-resolved vibrational spectroscopy and thermal desorption mass spectrometry (TDMS). Utilizing Fourier transform-infrared reflection absorption spectroscopy (FT-IRAS) we have characterized chemisorbed formate produced by the decomposition of formic acid on clean Ru(001), Ru(001)–(√3×√3)R30° K and on a K-multilayer adsorbed on Ru(001). The vibrational spectra show that formate is adsorbed on both clean Ru(001) and Ru(001)–(√3×√3)R30° K with C2v symmetry indicative of a bridged or bidentate species. There are, however, characteristic differences in the vibrational spectra, which indicate that for the Ru(001)–(√3×√3)R30° K surface the formate is directly bound to potassium. The vibrational spectrum of the latter species is found to be in good agreement with that of bulk potassium formate adsorbed on Ru(001).
Based on the agreement with literature data for bulk formate, we propose a bonding model for the potassium formate monolayer, which also accounts for the observed contraction of the potassium monolayer resulting from the compound formation. The thermal decomposition of the various formate overlayers has been monitored by simultaneous thermal desorption mass spectrometry and time-resolved FT-IRAS. This combination allows us to correlate the desorbing gas-phase products with the appearance and disappearance of surface intermediates. In the case of formate adsorbed on the clean Ru(001), the C–H and C–O bond cleavage reactions occur simultaneously, leading to the production of equal amounts of CO and CO2. The simultaneous observation of desorbing CO2 (TDMS) and of adsorbed CO (IR) confirms earlier work, which postulated a mechanism involving a coupling of the C–H and C–O bond cleavage reaction channels of two neighboring formates. The presence of potassium changes dramatically the reaction pathway of the formate as it suppresses the C–H bond cleavage channel, leaving CO and OH as the main decomposition products. Compound formation with potassium also leads to thermal stabilization of the formate in comparison to formate adsorbed on the clean surface. However, formate adsorbed on the potassium-modified ruthenium substrate is found to be thermally less stable than formate adsorbed on clean Ru(001).
Steady currents in composite conductors, eigenfunction expansions, and exactly solvable linear integral equations
Authors: Inayat-Hussain A. A. 
Published: July 2002

A novel connection is uncovered between the simple physics of steady current flow in a composite conductor and the theory of integral equations. With a judicious choice of eigenfunction expansions, exploitation of the physical continuity of current flow across a chosen interface in a composite conductor is shown to yield an infinite class of integral equations with exact closed-form solutions. The mathematical derivation of this class is based on the elementary (but also new) notion of formally equating two different eigenfunction expansions of a given arbitrary function. The new class contains as special cases the celebrated Abel integral equation of classical mechanics and the Kramers–Kronig relations of electromagnetic scattering. But it also contains new integral equations (with exact solutions), some with the Cauchy-singularity 1/(x−y) in their kernels, and a new summation equation. These new equations are in themselves intriguing and their exact solutions do not appear to be derivable by the known methods for solving integral equations. An application of the new class of integral equations is given in the context of a particular composite conductor, which consists of a semi-infinite strip imbedded in an otherwise homogeneous whole space conductor (containing a uniform current flow parallel to the strip).
The coefficient in the eigenfunction expansion of the potential in the strip satisfies a one-dimensional singular integral equation with a Cauchy-singularity. This singularity is regularized by the application of an integral equation and its exact solution from the new class, resulting in an integral equation with a smooth kernel. This equation together with the eigenfunction expansion provides an elegant representation for the potential in the strip. (The only known exact solutions are for the cases of elliptic-cylinder and ellipsoid geometries in two and three dimensions, respectively.) The new class of integral equations yields the first examples of singular kernels which possess a bilinear expansion in terms of two different complete sets of eigenfunctions, with only the diagonal terms (i.e., those terms in which the summation indices or integration variables are equal) in the expansion being nonzero. Such an expansion for square-integrable kernels (as opposed to singular kernels) is well known in the Hilbert–Schmidt theory of Hermitian operators and in Schmidt’s extension to the non-Hermitian case, and it forms the basis for a method of solving Fredholm integral equations. None of these theories, however, yields the bilinear expansions for the singular kernels of our new class.
Linear and electronic transport in strongly coupled binary ionic mixtures. Applications to the hydrogen–helium system
Authors: Léger D. , Deutsch C. 
Published: July 2002

This paper is devoted to a systematic investigation of linear transport properties in strongly coupled binary ionic mixtures of pointlike ions interacting solely through Coulomb interactions. The basic formalism rests upon suitable extensions of the Boltzmann–Ziman equation. Validity conditions for the Lorentzian approximation are thoroughly discussed. High temperature and inelastic contributions to electron transport are emphasized. The formalism is, hereafter, specialized to a thorough investigation of electric, thermal, and mechanical transport coefficients. Basic transport quantities are expressed under a reduced form that allows an easy analytical treatment of temperature and inelastic corrections, parametrized with α=T/TF and ■=βℏω, respectively. The former are derived from exact solutions of transport equation through various jellium dielectric functions. Calculation of inelastic contributions is performed through the variational method. Electron transport at T=0 is then thoroughly investigated, including electric and thermal conductivities as well as thermopower and shear viscosity. These results are furthermore extended to an exact calculation of the electric conductivity up to order α2 including properly inelastic contributions, derived in terms of successive moments of the ion–ion structure factors.
Results are presented under an analytic and compact form, convenient for a numerical implementation to strongly coupled H+–He2+ mixtures of astrophysical interest. Calculations are performed within binary ionic mixture (BIM) and polarized BIM (PBIM) frameworks, respectively. Ion–ion structure factors are computed through the hypernetted-chain (HNC) scheme, by neglecting bridge diagrams. Most of these results pertain to homogeneous phases. First, the focus is on BIM and a systematic investigation of the Γ-rs and c2 dependence of the transport quantities is performed. Also, attention is paid to the influence of the jellium dielectric function. The T=0 elastic limit is considered first. Next, inelastic and finite temperature corrections are addressed, and BIM to PBIM results are compared. Finally, the electric resistivity behavior is investigated in the vicinity of critical demixing. Discrepancy between BIM and PBIM are thus stressed.
Review Article: Cystic Degeneration/Spongiosis Hepatis in Rats
Authors: Karbe Eberhard , Kerlin Roy L. 
Published: July 2002

Cystic degeneration/spongiosis hepatis in rats has been proposed to be a preneoplastic and/or neoplastic lesion by some authors, because of its proliferative properties and persistent increased cell turnover rate in stop experiments using hepatocarcinogens , and the assumption that it can develop into a sarcoma. The neoplastic potential of cystic degeneration is questioned in this review article. Cystic degeneration, which appears to derive from altered Ito cells, does not have neoplastic histomorphologi c characteristics, although it may be composed of cells with an increased mitotic index. In this regard, persistent proliferation is also seen with other nonneoplastic lesions. Arguments are presented to show that the induced, probably extremely rare sarcoma that was associated with cystic degeneration most likely derives from the very rare induced spherical Ito-cell aggregate with an unusually high cellular turnover rate in rats treated with hepatocarcinogens , and not from cystic degeneration. Also, in none of 12 referenced standard oncogenicity studies with chemically induced cystic degeneration was the lesion associated with mesenchymal (Ito-cell) tumors. Consequently, evidence is lacking that cystic degeneration in rats should be classifi ed as a preneoplastic or neoplastic lesion. The 12 oncogenicity studies in rats with induced cystic degeneration showed a marked sex predilection, with males more likely to develop either spontaneous or chemically induced lesions. In these 12 studies, cystic degeneration was more often associated with hepatocellular hypertrophy or hepatotoxicity, rather than hepatocarcinogenicity. Thus, it is concluded that hepatocarcinogens induce cystic degeneration, not because they are carcinogenic, but because they have other effects on the liver, and that cystic degeneration may be a secondary/reparative change. Cystic degeneration in fi sh parallels the situation in rats in many respects, yet the existence of the lesion in other species, including man, is not as well supported. Based on the data presented in this review, spontaneous and induced cystic degeneration in rats and fi sh is not a preneoplastic or neoplastic lesion and risk assessment for man can be based on no-effect levels and safety margins, as for other nonneoplasti c adverse effects that have no counterpart in man.
A Randomized Comparison of two Short Intensive Chemotherapy Regimens in Children and Young Adults With Osteosarcoma: Results in Patients With Metastases: A Study of the European Osteosarcoma Intergroup
Authors: Bramwell Vivien H. C. , Burgers Marion V. , Souhami Robert L. , Taminiau Antonie H. M. , Van Der Eijken Jan W. , Craft Alan W. , Malcolm Archie J. , Uscinska Barbara , Kirkpatrick Anna L. , Machin David , Van Glabbeke Martine M. 
Published: July 2002

Purpose. To report the outcome of 37 patients with metastatic osteosarcoma entered into a large randomized trial (EOI
80831/MRC B002) comparing two different regimens of chemotherapy in patients with osteosarcoma.Methods. Patients with biopsy‐proven osteosarcoma localized and metastatic, age 40 years or younger, were randomized
to receive either two‐drug treatment with doxorubicin/cisplatin (DOX 25 mg m−2
day−1 × 3 + DDP 100 mg m−2 on
day 1 q 3 weeks × 6 courses) or three‐drug treatment comprising high‐dose methotrexate (HDMTX 8 mg m−2
administered every weeks × 4 courses) given 10 days before DOX/DDP.Results. Twenty‐four patients with metastatic disease received the two‐drug arm treatment and 13 received three‐drug
treatment. Despite chance imbalance in numbers, there were no major differences in age, sex, primary site or performance
status. Baseline alkaline phosphatase (AP) was elevated more frequently (96 vs 42%) in the two‐drug arm. Twenty‐one
of 24 patients in the two‐drug arm and 11/13 patients in the three‐drug arm had evaluable primary tumors concurrent with
metastases. Respective clinical response rates for the two‐ and three‐drug arms were 48% and 40% for primary tumors,
and 33% and 55% for metastases. Respective survivals at 2 and 4 years were 36% and 9% for the two‐drug arm, and 69%
and 52% for the three‐drug arm, and survival was better for patients with normal AP at presentation. When adjusted for
AP, survival was not significantly different between the two treatments (hazard ratio 0.52, 95% confidence interval
0.22–1.23, p = 0.14). There were three long‐term survivors among the metastatic patients, all of whom received the
three‐drug therapy.Discussion. It is likely that random bias in the population (small numbers, imbalance in size of groups, uneven distribution
of AP) accounts for the difference in outcome favoring the three‐drug treatment in patients with metastatic disease. More
reliance can be placed on the finding that disease‐free and overall survival in the adjuvant component of this study
(Bramwell et al., J Clin Oncol 1992; 10: 1579–91) were better after two‐drug treatment.
Enhanced MDM2 Oncoprotein Expression in Soft Tissue Sarcoma: Several Possible Regulatory Mechanisms
Authors: Pollock Raphael E. , Lang Aiquing , El-Naggar Adel K. , Radinsky Robert , Hung Mien Chie 
Published: July 2002

Purpose. MDM2 is an oncogene whose protein product may promote tumorigenesis by blocking
wild‐type p53 tumor suppressor mediated G0/G1 cell cycle arrest, thereby inhibiting repair of damaged DNA prior to cell division. While
MDM2 DNA amplification is frequently observed in human sarcoma, the mechanisms linking this amplification to MDM2
oncoprotein over‐production as well as its functional significance have not been well characterized in patients with soft
tissue sarcoma.Methods. A tissue bank of resected soft tissue sarcomas and autologous normal tissues was assembled; all specimens were
snap frozen within 15 min of resection. DNA and RNA were extracted from tissues using isoamyl alcohol and phenol
chloroform extraction methods, respectively; cell lysates were prepared using PBSTDS lysis buffer. DNA and mRNA were
confirmed as being non‐degraded and were then examined for MDM2 DNA amplification (Southern blots) and mRNA
over‐expression (Northern blots) using actin (DNA) and glyceraldehyde‐3‐phosphate dehydrogenase (mRNA) as loading
controls. The MDM2 protein was examined on Western blots using the MDM2‐specific monoclonal antibody IF2
(Oncogene Science, Inc). The presence of p53 DNA and expression of p53 mRNA was examined by rehybridizing the
Southern and Northern filters using a p53‐specific cDNA probe.Results. Soft tissue sarcomas and autologous normal tissues were screened for MDM2 DNA amplification, which was
detected in 10 of 30 tumors screened. After screening, there was sufficient biomaterials from six specimens for subsequent
Northern and Western analysis to see whether MDM2 gene amplification correlated with over‐expression of MDM2
mRNA and MDM2 protein. In addition, we examined whether other mechanisms may lead to over‐expression of the
MDM2 oncoprotein. Several possible mechanisms of MDM2 oncoprotein over‐expression were identified. These most
commonly included MDM2 DNA amplification, MDM2 mRNA over‐expression and MDM2 oncoprotein over‐expression.
However, some soft tissue sarcoma patient specimens had no evidence of MDM2 mRNA over‐expression yet had
MDM2 oncoprotein over‐production in the tumor relative to autologous normal tissue, implying possible post‐transcriptional
regulation. Of functional relevance, MDM2 oncoprotein over‐production by tumors was associated with large
decreases in the percentage of cells in the G0/G1 cell cycle interface compared with autologous normal tissue cells.Discussion. It is likely that there are multiple mechanisms underlying human soft tissue sarcoma MDM2 oncoprotein
over‐production. Consequently, strategies that decrease MDM2 over‐production, such as transcriptional repression to
inhibit MDM2 promoter activity or RNA antisense approaches, may ultimately offer the best therapeutic efficacy.
Role of LIM Domains in Mediating Signaling Protein Interactions
Authors: Brown Susan , Coghill Imogen D. , McGrath Meagan J. , Robinson Paul A. 
Published: July 2002

AbstractLIM domains are double zinc‐finger motifs that mediate protein interactions between transcription factors, cytoskeletal and signaling proteins. This review outlines the protein interactions mediated by LIM domains with signaling proteins including tyrosine and serine/threonine kinases and phosphatases.