bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of chronic administration of a highly potent LHRH agonist on prostate size and secretory function in geriatric dogs
Authors: Vickery B. H. , McRae G. I. , Bonasch H.
Published: February 2007

Four geriatric male dogs of mixed breed were selected for study on the basis of palpable prostatic hyperplasia. Testosterone levels were determined by radioimmu‐noassay on plasma samples collected three times weekly. Prostate size was determined from lateral pneumocystograms taken at weekly intervals. Prostatic secretion was followed by ejaculating the dogs at weekly intervals. Two dogs were implanted with 125 ug/kg of pelleted D‐Trp6‐LHRH ethylamide (LHRH analog) and two were sham implanted. The pellets were removed 71 days later. Three months after the removal, one previously treated dog was sham implanted and one previously sham implanted dog was implanted with 170 ug/kg of pelleted analog. In each case, following analog implantation, plasma testosterone levels were elevated for up to 7 days, then declined precipitously, and were then maintained at less than 0.02 ng/ml for a prolonged period. Plasma testosterone levels returned to the pretreatment range 44 and 58 days after implantation, respectively, in two dogs, but remained low through the 60 days studied in the third. The radiographs in one treated animal were of insufficient quality for analysis. In the remaining two treated animals, prostate size progressively declined following implantation, after about a 2 wk lag time. In one animal the prostate dimensions reached a nadir of 40% of pretreatment values at five wk after implantation. In the other treated animal the prostate regressed to a position within the pelvic brim, a state resembling that seen in young dogs, and so the dimensions could not be accurately determined. After plasma testosterone levels reverted to pretreatment values, prostate dimensions slowly but progressively increased. A decline in ejaculate volume paralleled the decline in plasma testosterone and prostate size until the fifth week after implantation from when no ejaculate could be obtained. The data suggests that LHRH agonists may have utility in the therapy of hormone‐responsive prostatic pathologies.
Retinoic acid binding protein in normal and neoplastic rat prostate
Authors: Gesell Mark S. , Brandes Martin J. , Arnold Eugene A. , Isaacs J. T. , Ueda Hisako , Millan Juan C. , Brandes David
Published: February 2007

Sucrose density gradient analysis of cytosol from normal and neoplastic rat prostatic tissues exhibited a peak of (3H) retinoic acid binding in the 2S region, corresponding to the cytoplasmic retinoic acid binding protein (cRABP). In the Fisher‐Copenhagen FI rat, cRABP was present in the lateral lobe, but could not be detected in the ventral nor in the dorsal prostatic lobes. Four sublines of the R‐3327 rat prostatic tumor contained similar levels of this binding protein. The absence of cRABP in the normal tissue of origin of the R‐3327 tumor, the rat dorsal prostate, and reappearance in the neoplastic tissues follows a pattern described in other human and animal tumors. The occurrence of cRABP in the well‐differentiated as well as in the anaplastic R‐3327 tumors in which markers which reflect a state of differentiation and hormonal regulation, such as androgen receptor, 5a reductase, and secretory acid phosphatase are either markedly reduced or absent, points to cRABP as a marker of malignant transformation.
The pharmacokinetics of antibiotic diffusion in chronic bacterial prostatitis
Authors: Sharer William C. , Fair William R.
Published: February 2007

Historically chronic bacterial prostatitis in the male human has been relatively resistant to antimicrobial chemotherapy. The pharmacokinetic theory of drug diffusion into the prostate is reviewed. A brief description of the various canine models utilized to quantitate antimicrobial drug diffusion is presented. Specific data concerning the diffusion of various antimicrobial agents are abstracted followed by a brief discussion of mechanistic explanations for the success or failure of drug therapy.
Human prostatic adenocarcinoma: Comparative experimental treatment of the tumor line pc 82 in nude mice
Authors: Hoehn W. , Walther R. , Hermanek P.
Published: February 2007

A human prostatic adenocarcinoma, growing as a transplantable line in nude mice, was subjected comparatively to the usual endocrine treatment schedules including orchiectomy, estrogens, estramustine phosphate, and a study with flutamide (SCH 13521) and cyproterone acetate. The regression under treatment in tumor volume and in the histological pattern is demonstrated, and the possibilities and limitations of the nude mouse model are discussed.
Effects of estrogen administration on serum testosterone in copenhagen rats
Authors: Grossman H. Barton , Kleinert Edward L. , Herr Harry W. , Whitmore Willet F.
Published: February 2007

In order to develop a standard experimental method of exogenous estrogen therapy in the Copenhagen rat, several treatment regimens were evaluated to determine their effect on the serum testosterone. Diethylstilbestrol diphosphate (DES‐P) was administered either continuously in the drinking water or as a single intraperitoneal injection. Oral low‐dose estrogen (0.4‐1.6 μg/ml) yielded reliable suppression of serum testosterone to castrate levels. A single intraperitoneal injection of 0.5 mg DES‐P caused prompt suppression of serum testosterone with return to normal levels two weeks later.
Nuclei of stroma: Site of highest estrogen concentration in human benign prostatic hyperplasia
Authors: Kozák Ivan , Bartsch Wilfried , Krieg Michael , Voigt Klaus‐Dieter
Published: February 2007

In an earlier publication we found significantly more estrogen receptor‐positive cases in the stroma if compared with the epithelium of human benign prostatic hyperplasia (BPH). We were therefore interested to find out whether this preferential assay of estrogen receptor in stroma is reflected by a higher estrogen content in this tissue fraction. Estradiol (E2) and estrone (E1) were measured by RIA in whole BPH tissue, stroma, and epithelium as well as in the nuclear fraction of stroma and epithelium. For comparison, E2 and E1 were measured in blood also. The main results are as follows: 1) In all BPH samples the E2 (26.0 ± 3.5(SEM) pg/g (n = 20)) and E2 (53.5 ± 7.4 (14)) content was significantly higher than in the corresponding plasma (E2: 17.5 ± 2.3 pg/ml (11); E1: 26.5 ± 4.4 (7)), the mean ratio of E2/E1, was 0.52 and 0.69 for BPH and plasma, respectively; 2) in stroma significantly more E2 (53.6 ± 7.8 fmol/mg DNA (18)) and E1, (55.9 ± 8.4 (12)) were measured than in epithelium (E2: 15.7 ± 1.9(16); 1: 20.7 ± 3.2(13)); 3) in nuclei of stroma significantly higher E2 (38.0 ± 5.3 fmol/mg DNA (20)) and E1 (19.2 ± 4.8 (14)) concentrations were present than in epithelium (E2: 6.8 ± 3.1 (19); E1: 2.5 ± 0.5 (13)), the mean ratio of E2/ E1 for thenuclear fractions of stroma (2.3) and epithelium (2.7) increased dramatically if compared with the respective ratio in whole BPH tissue. In conclusion, there is a distinct accumulation of estrogens in the nuclei of stroma, E2 concentration being significantly higher than E1. These data support the hypothesis that E2 could play a preferential role in stimulating the growth of the BPH stroma.
Steroid receptors and hormone responsiveness of human prostatic carcinoma
Authors: Concolino G. , Marocchi A. , Margiotta G. , Conti C. , Di Silverio F. , Tenaglia R. , Ferraro F. , Bracci U.
Published: February 2007

Androgen (AR), estrogen (ER), and progesterone (PR) receptors have been found in human prostatic hyperplasia (BPH) and prostatic carcinoma (PC) (AR mainly in the epithelial compartment and ER in the stromal compartment). These steroid receptors have been studied in the cytosol of 59 prostatic cancers in order to select patients to be treated with endocrine therapy (orchiectomy, administration of antiandrogens). Tissues were collected through transvesical resection and needle biopsy. Tritiated metribolone (R1881), 17b‐estradiol and promegestone (R5020) with the use of exchange assay and a dextran‐coated charcoal method have been usually employed. In some specimens receptor content was also analyzed in the nuclear fraction. AR was found in the cytosol of 47 of 59 (79.66%), ER in 14 of 26 (53.85%), and PR in 13 of 15 (86.67%) tumors examined. AR was detected in the nuclear fraction of 11 of 26, ER in nine of 13, and PR in two of four tumors examined. AR was found to correlate with the histological grade of the cancers, whereas no correlation could be demonstrated between the histological grade and cytoplasmic or nuclear ER. On the basis of receptor studies, hormonal treatment was started with orchiectomy followed by the administration of cyproterone acetate (CPA) 50 mg twice a day in 26 eligible out of 38 patients available for follow‐up with tumors examined for cytoplasmic AR. The response to hormonal therapy depended strictly on the presence of AR. The endocrine treatment used seems, in our opinion, to be the most advisable form of therapy, and is capable of blocking the uptake of androgens of extratesticular origin by prostatic cells. Although the clinical advantages of progestational therapy for human PC are not yet established, the presence of PR in prostatic carcinoma leads us to believe that progestational compounds as well as the progestational activity of CPA may be effective on tumor growth of tissues that are positive for PR.
Squamous metastases from prostatic adenocarcinoma
Authors: Accetta Peter A. , Gardner William A.
Published: February 2007

Two patients with prostatic adenocarcinoma are reported whose metastases harbored large foci of squamous cell carcinoma. The prostatic origin of such areas was proven by immunoperoxidase staining for prostatic acid phosphatase (PAP) as well as the identification of transition zones between adenocarcinoma and squamous cell carcinoma. The possible role of estrogen therapy in inducing the squamous change is discussed.
Local hyperthermia for treatment of carcinoma of the prostate: A preliminary report
Authors: Yerushalmi A. , Servadio C. , Leib Z. , Fishelovitz Y. , Rokowsky E. , Stein J. A.
Published: February 2007

Following extensive experiments on animals, we have concluded a study on the treatment of 15 patients with prostatic carcinoma using localized deep microwave hyperthermia (LDMWH; 2.45 GHz), either alone or in combination with radiotherapy or hormonal therapy. The results of this pilot trial were encouraging and are herewith presented. A total of 146 LDMWH treatments were given. All patients tolerated the treatments well, and there were no complications; the condition of the rectal mucosa was checked routinely by rectoscopy. A pronounced and rapid subjective and objective response was recorded in all cases, as noted by reduction in tumor size, regression of ureteral or urethral obstruction, disappearance of pelvic pain and improvement in well being. LDMWH was effective by itself and appeared to potentiate the effects of radiotherapy or hormonal therapy.

Although LDMWH seems to be a promising and safe new method of treatment of prostatic cancer, either alone or in combination with other accepted forms of therapy, more controlled studies, which are at present underway, are needed to draw more definite conclusions.
Ultrastructural and analytical studies on the prostate of castrated rats
Authors: Timms B. G. , Chandler J. A.
Published: February 2007

Rat lateral and ventral prostate tissue was studied using ultrastructural and analytical techniques in adult animals castrated for periods of 3 to 20 days. As in previous reports involution of the prostatic epithelium following testosterone deprivation resulted in alterations of the amount, distribution, and conformation of the endoplasmic reticulum, Golgi, and lysosomes in addition to some nuclear changes. Although the fundamental changes were similar in both lobes there were specific effects on the individual lobes.

Reductions in the subcellular levels of zinc were more pronounced in the lateral prostate, particularly with respect to the secretory and stromal concentrations of the metal. Despite low concentrations of circulating testosterone, secretory activity was still evident after a 20‐ day castration period and would appear to reflect a different sensitivity in the lateral lobe to the lowered testosterone level or stimulation by other hormones when compared to the ventral lobe. The significance of the subcellular distribution pattern of zinc during the experimental periods is discussed in relation to the possible functional significance of the metal in prostatic tissue.
The glycosaminoglycans of normal and hyperplastic prostate
Authors: De Klerk Daniel P.
Published: February 2007

A study has been made of the glycosaminoglycans (GAG) of the fetus, normal adult, and benign hyperplastic prostate. In the adult normal prostate dermatan sulphate (DS) is the predominant GAG. The central zone has a slightly higher chondroitin sulphate (Ch AC) content than the peripheral Lone. Fctal prostates (22–27 weeks gestation) contain no heparan sulphatc (HS). Benign prostatic hyperplasia (BPH) has an increased content of Ch AC. On separation of BPH stroma and epithelium, the epithelial fraction contains only Ch AC and DS. HS and hyaluronic acid (HA) are confined to the prostatic stroma.
Locating the active sites of enzymes using mechanical properties
Authors: Sacquin‐Mora Sophie , Laforet Émilie , Lavery Richard
Published: February 2007

We have applied the calculation of mechanical properties to a dataset of almost 100 enzymes to determine the extent to which catalytic residues have distinct properties. Specifically, we have calculated force constants describing the ease of moving any given amino acid residue with respect to the other residues in the protein. The results show that catalytic residues are invariably associated with high force constants. Choosing an appropriate cutoff enables the detection of roughly 80% of catalytic residues with only 25% of false positives. It is shown that neither multidomain structures, nor the presence or absence of bound ligands hinder successful detections. It is however noted that active sites near the protein surface are more difficult to detect and that non‐catalytic, but structurally key residues may also exhibit high force constants. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Electronic structure of negative oxygen ion in ZrO2 crystal
Authors: Abarenkov I. V. , Matyukevich I. D.
Published: February 2007

With a rapid downscaling of the complementary metal‐oxide‐semiconductor (CMOS) devices, the ZrO2 becomes a promising candidate for application in microelectronic and therefore the information about the electronic structure of the perfect and defect ZrO2 crystal becomes important. In the present study, the local orbital Hartree–Fock approximation was applied to the ZrO2 crystal electronic structure calculations. The noncanonical orbitals localized on ions were employed, which are the solutions of the Hartree–Fock equations for ions in the confining potential simulating the crystal environment. The confining potential was calculated selfconsistently to bring the minimum to the crystal energy. The cluster expansion for the crystal energy was employed. The general idea of the method is similar to that of the study (1978, 20, 565), devoted to the electronic structure calculations of MgO crystal. In the present study, the more complicated system is considered. First, ZrO2 crystal has lower symmetry, and second the d‐orbitals are present among ions occupied orbitals. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Coronary heart disease: How do the benefits of ω‐3 fatty acids compare with those of aspirin, alcohol/red wine, and statin drugs?
Authors: Basu Hemendra , Pernecky Steven , Sengupta Aditi , Liepa George U.
Published: February 2007

At the present time the primary cause of death of most Americans is cardiovascular disease. Approximately 20 million Americans are currently being treated with some form of statin drugs as a means to lower their blood cholesterol levels, and many of these same people also consume some combination of omega‐3 FA, aspirin, and alcohol/red wine because of clinical data indicating that each of these, taken alone, seems to improve mortality. Recent studies with omega‐3 FA have demonstrated a positive impact on mortality from coronary heart disease as well as from “all causes,” and this article compares their metabolic benefits with those of aspirin, alcohol/red wine, and statin drugs. The article suggests that these four compounds may have synergistic qualities and that clinical trials to study this possibility are warranted.
Synthesis of hyperbranched P poly(glycerol‐diacid) oligomers
Authors: Wyatt Victor T. , Nuñez Alberto , Foglia Thomas A. , Marmer William N.
Published: February 2007

Novel oligomeric prepolymers were synthesized by acid‐catalyzed condensation of glycerol with iminodiacetic, azelaic, or succinic acid. The prepolymers were obtained, on average, in 62% yield and were characterized by 13C NMR, 1H NMR, matrix‐assisted laser desorption ionization‐time of flight‐mass spectrometry, and gel permeation chromatography. The synthesized oligomers had an average M.W. of 1543 Daltons (average polydispersity (PD)=1.34, average degree of polymerization (DOP)=5.5). Hyperbranching was evident in the oligomers produced when using azelaic acid and succinic acid as co‐monomers with glycerol, whereas the reaction between iminodiacetic acid and glycerol resulted in linear products bearing cyclic urethane structures.
Microstructures formed by spray freezing of food fats
Authors: Gwie C. G. , Griffiths R. J. , Cooney D. T. , Johns M. L. , Wilson D. I.
Published: February 2007

The spray‐freezing of two food fats, tripalmitin (PPP) and cocoa butter (CB) and mixtures thereof, has been modeled experimentally using a novel single droplet freezing apparatus configured so that temperature profiles or samples for microstructure analysis can be obtained. For 2 mm diameter droplets suspended in a cold air flow at temperatures around 2–15°C, initial cooling rates were on the order of 10 K s−1 and the temperature profiles could be correlated directly to DSC data collected at 20 K min−1, indicating that minimal supercooling of the materials occurred in the droplet form. Microstructure analysis confirmed that PPP crystallized preferentially in mixtures, and that the surface structure was very sensitive to storage conditions. The bulk structure was much less sensitive, and the internal microstructure of the PPP droplets revealed distinct nucleation sites, which were absent from the CB: These persisted in the mixtures up to 50 wt%. X‐ray analysis indicated that the fats crystallized in their more stable forms, namely, β for PPP and Form V/V1 in CB.
The lichenicolous Phoma species (coelomycetes) on Cladonia
Authors: DIEDERICH Paul , KOCOURKOVÁ Jana , ETAYO Javier , ZHURBENKO Mikhail
Published: February 2007

The lichenicolous Phoma species on Cladonia are revised. A statistical analysis of the conidial size suggests that three species are involved: P. cladoniicola sp. nov. a common and widespread species in the Northern Hemisphere occurring on a wide range of Cladonia species; P. foliaceiphila sp. nov. known from C. foliacea and C. fimbriata in Europe; and P. grumantiana sp. nov. known from C. symphycarpia and C. mateocyatha in Svalbard and the USA.
Photobiont selectivity in the epiphytic lichens Hypogymnia physodes and Lecanora conizaeoides
Authors: HAUCK Markus , HELMS Gert , FRIEDL Thomas
Published: February 2007

In two lichen species, Hypogymnia physodes and Lecanora conizaeoides, often used as model organisms for pollution-sensitive and pollution-tolerant epiphytic lichens, respectively, the hypothesis was tested that the toxitolerance of the Trebouxia photobiont limits the tolerance of the entire lichen symbiosis. Being lecanoralean-trebouxioid associations, H. physodes and L. conizaeoides represent the most common type of lichens. Photobionts of both lichen species deriving from microhabitats with varying supply of S and heavy metals were identified using nuclear ITS nrDNA sequencing. The photobiont of L. conizaeoides was identified as T. simplex, whereas the photobiont of H. physodes belongs to an undescribed Trebouxia species, related to T. jamesii subsp. angustilobata and provisionally named as T. hypogymniae Hauck & Friedl ined. Since T. hypogymniae ined. is also known from Lecidea silacea, which is characteristic of rock and slag with high heavy metal content, a high sensitivity of this alga to pollutants is unlikely to be a key factor for the relatively low toxitolerance of H. physodes. Furthermore, the photobiont cannot be crucial for the extremely high toxitolerance of L. conizaeoides, as T. simplex is also known from pollution-sensitive lichens of the fruticose genus Pseudevernia. These findings suggest that the photobiont is not generally a key factor determining pollution sensitivity in the most common type of lichen symbiosis. The high specificity for T. simplex in L. conizaeoides in existing populations of L. conizaeoides suggest that already established thalli could be a source of photobiont cells for re-lichenization.
On the ensemble average capacity of multiple‐input multiple‐output channels in outdoor line‐of‐sight multipath urban environments
Authors: Lim H. M. , Constantinou C. C. , Arvanitis T. N.
Published: February 2007

Many statistical multiple‐input multiple‐output (MIMO) channel models have been extensively developed over the past few years. However, to better understand and exploit such MIMO channels, there is a need for a MIMO channel model that has a basis in the physical propagation mechanisms. In this paper, a wideband semideterministic MIMO model is derived to quantify the mean capacity in an urban line‐of‐sight (LOS) microcell. Specifically, the model considers scattering from large‐scale discontinuities on building faces randomly distributed along a street canyon. Using geometrical optics and the uniform theory of diffraction, the spatial correlations between any two receiving signals are evaluated and are used to compute the upper bound of the average MIMO capacity.
Predicting cyclone tracks in the north Indian Ocean: An artificial neural network approach
Authors: Ali M. M. , Kishtawal C. M. , Jain Sarika
Published: February 2007

Predicting cyclone tracks in the Indian Ocean has been a challenging problem. In this paper, we used past 12 hours of observations (2 positions, at 6 hourly intervals and the present position) to predict the position of a cyclone 24 hours in advance in terms of latitude and longitude. For this purpose we adopted an artificial neural network approach using 32 years (1971–2002) of tropical cyclone best track analysis over the Indian Ocean. The mean absolute error between the estimated and actual latitude (longitude) is 0.75 (0.87) degrees with correlation coefficient of 0.98 (0.99) for the prediction data set that was not used for developing the model. The mean error of estimation of the distance between the best track and the predicted positions is 137.5 km. Forecasts for 12, 36, 48, 60 and 72 hours were also attempted.
On the transformation of Pacific Water into Indonesian Throughflow Water by internal tidal mixing
Authors: Koch‐Larrouy Ariane , Madec Gurvan , Bouruet‐Aubertot Pascale , Gerkema Theo , Bessières Laurent , Molcard Robert
Published: February 2007

The Indonesian archipelago is characterized by strong internal tides, which are trapped in the different semi‐enclosed seas of the archipelago. Using tidal model results a parameterization of the associated 3d tidal mixing is developed. The resulting average vertical diffusivity is 1.5 cm2/s, which independently agrees with the estimates inferred from observations. Introduced in a regional OGCM, the parameterization improves the water mass characteristics in the different Indonesian seas, suggesting that the horizontal and vertical distributions of the mixing are adequately prescribed. In particular, the salinity maximum of the inflow water is reduced along the main route, mainly in the Dewakang sill area. But also it is erased in the Halmahera and Seram seas, the entrance of the eastern route, so that salty waters doesn't penetrate the Banda Sea. As a result the simulated Indonesian Throughflow Water are in good agreement with observations.
Regional carbon fluxes from an observationally constrained dynamic ecosystem model: Impacts of disturbance, CO2 fertilization, and heterogeneous land cover
Authors: Desai Ankur R. , Moorcroft Paul R. , Bolstad Paul V. , Davis Kenneth J.
Published: February 2007

The Ecosystem Demography (ED) model was parameterized with ecological, forest inventory, and historical land use observations in an intensively managed, wetland‐rich forested landscape in the upper midwest United States. Model results were evaluated against a regional network of eddy covariance flux towers and analyzed about the roles of disturbance, forest management, and CO2 fertilization. The model captured modern regional vegetation structure with worst comparison in wetlands. Model net ecosystem exchange of CO2 (NEE) was highly correlated on monthly (r2 = 0.65) and annual (r2 = 0.53) timescales to 7 years of NEE observed at a 396‐m‐tall eddy covariance (EC) tower and to 2 years of growing season NEE from 13 regional stand‐scale EC sites of varying cover and age (r2 = 0.64). Model summer NEE had higher than observed net uptake for the tall tower and mature hardwood sites, and correlation to growing season ecosystem respiration at these sites was poor (r2 = 0.09). Exclusion of forestry led to overestimation of aboveground living plant biomass accumulation by 109% between two forest inventory cycles (1996–2004). On the long‐term (200 years), forestry significantly altered ecosystem cover and age, and increased NEE by 32%. CO2 fertilization over that time period increased NEE by 93% owing to a doubling of plant density. While the model showed that harvest and afforestation had smaller impacts on NEE than CO2 increase, the former were still significant and require consideration when making future NEE predictions or scaling plot‐level data to regional and global flux estimates.
Development of objective‐oriented groundwater models: 1. Robust parameter identification
Authors: Sun Ne‐Zheng , Yeh William W.‐G.
Published: February 2007

When the structure of an aquifer is complex and unknown, determining the complexity of model structure and identifying its spatially distributed parameters become very difficult. This two‐paper series describes an approach for objective‐oriented model construction that can identify a model with simplified structure and assure its reliability for predetermined model applications. The theoretical basis of the methodology includes the definition of structure error, the conditions of structure reducibility, the calculation of the worst‐case parameter (WCP), and the solution of a generalized inverse problem. In the first paper of the series we extend the basic theory established in our previous works from zonation parameterization to any kind of parameterization. The extension makes the methodology more general and complete. We present an effective direct search algorithm that can form a nonnested structure series with an optimized pattern for solving the generalized inverse problem. We use numerical examples to show how the WCP depends on the structure complexity, prior information, boundary conditions, and the objectives of model application. Generally speaking, with more prior information, simpler boundary conditions, fewer objectives, and lower accuracy requirement, the WCP will have a simpler shape. As a result, a reliable model can be identified with less observation data. In part 2 of this series we will give the conditions of structure reducibility and the method for robust experimental design. A robust experimental design is independent of the true parameter and can provide sufficient information for identifying an objective‐oriented model.
Optimization of a high-pressure pore water extraction device
Authors: Cyr Martin , Daidié Alain
Published: February 2007

High-pressure squeezing is a technique used for the extraction of the pore water of porous materials such as sediments, soils, rocks, and concrete. The efficiency of extraction depends on the maximum pressures on the materials. This article presents the design of a high-pressure device reaching an axial pressure of 1000MPa which has been developed to improve the efficiency of extraction. The increase in squeezing pressure implies high stresses inside the chamber, so specialized expertise was required to design a safe, functional device that could withstand pressures significantly higher than common laboratory equipment. The design includes finite element calculations, selection of appropriate materials, and descriptive construction details for the apparatus. It also includes an experimental study of the performance of the apparatus in terms of extraction efficiency.
Si–Ge interdiffusion in strained Si/strained SiGe heterostructures and implications for enhanced mobility metal-oxide-semiconductor field-effect transistors
Authors: Xia Guangrui (Maggie) , Hoyt Judy L. , Canonico Michael
Published: February 2007

Si–Ge interdiffusivity in epitaxial strained Si∕Si1−yGey/strained Si/relaxed Si1−x0Gex0 heterostructures is extracted for Ge fractions between 0 and 0.56 over the temperature range of 770–920°C. Boltzmann-Matano analysis is applied to determine interdiffusivity from diffused Ge profiles in strained Si/relaxed Si1−x0Gex0 heterostructures [L. Boltzmann, Wiedemanns Ann. Phys. 53, 959 (1894) and C. Matano, Jpn. J. Phys. 8, 109 (1933)]. A model for the interdiffusivity suitable for use in the process simulator TSUPREM-4 is constructed. Si–Ge interdiffusivity increases by 2.2 times for every 10% increase in Ge fraction for interdiffusion in strained Si/relaxed Si1−x0Gex0 samples. Significantly enhanced Si–Ge interdiffusion is observed for Si1−yGey layers under biaxial compressive strain. Si–Ge interdiffusivity is found to increase by 4.4 times for every 0.42% increase in the magnitude of biaxial compressive strain in the Si1−yGey, which is equivalent to a decrease in the Ge percentage in the substrate by 10at.%. These results are incorporated into an interdiffusion model that successfully predicts experimental interdiffusion in various SiGe heterostructures. The extracted activation energy and prefactor for the interdiffusivity are 4.66eV and 310cm2∕s, respectively, for the temperature and Ge fraction ranges of this study. Threading dislocation densities on the order of 107cm−2 are shown to have negligible effect on Si–Ge interdiffusion in Si∕Si0.69Ge0.31 structures. Substituting the strained Si layers surrounding the Si1−yGey peak layer with SiGe layers is shown to have little effect on the Si–Ge interdiffusivity. The implications of these findings for the design and process integration of enhanced mobility strained Si/strained SiGe metal-oxide-semiconductor field-effect transistors are discussed.
Discrete particle simulation of shock wave propagation in a binary Ni+Al powder mixture
Authors: Eakins D. , Thadhani N. N.
Published: February 2007

Numerical simulations of shock wave propagation through discretely represented powder mixtures were performed to investigate the characteristics of deformation and mixing in the Ni+Al system. The initial particle arrangements and morphologies were imported from experimentally obtained micrographs of powder mixtures pressed at densities in the range of 45%–80% of the theoretical maximum density (TMD). Simulations were performed using these imported micrographs for each density compact subjected to driver velocities (Up) of 0.5, 0.75, and 1km∕s, and the resulting shock velocity (Us) was used to construct the Us-Up equation of state. The simulated equation of state for the 60% TMD mixture was validated by matching results obtained from previous gas-gun experiments. The details of shock wave propagation through the Ni+Al powder mixtures were explored on several scales. It is shown that the shock compression of mixtures of powders of dissimilar densities and strength is associated with heterogeneous deformation processes leading to focused flow, particulation, and vortex formation, resulting in local fluctuations in pressure and temperature, which collectively are responsible for highly irregular “shock” fronts and unstable high-pressure states in granular media.
Current impulse response of thin InP p+-i-n+ diodes using full band structure Monte Carlo method
Authors: You A. H. , Cheang P. L.
Published: February 2007

A random response time model to compute the statistics of the avalanche buildup time of double-carrier multiplication in avalanche photodiodes (APDs) using full band structure Monte Carlo (FBMC) method is discussed. The effect of feedback impact ionization process and the dead-space effect on random response time are included in order to simulate the speed of APD. The time response of InP p+-i-n+ diodes with the multiplication region of 0.2μm is presented. Finally, the FBMC model is used to calculate the current impulse response of the thin InP p+-i-n+ diodes with multiplication lengths of 0.05 and 0.2μm using Ramo’s theorem [Proc. IRE 27, 584 (1939)]. The simulated current impulse response of the FBMC model is compared to the results simulated from a simple Monte Carlo model.
Nonlinearity of strain and strain hysteresis in morphotropic LaSr-doped lead zirconate titanate under unipolar cycling with high electric fields
Authors: Kungl Hans , Fett Theo , Wagner Susanne , Hoffmann Michael J.
Published: February 2007

The strain behavior of morphotropic, 1La2Sr-doped lead zirconate titanate was investigated. Particular attention was paid to the electric field induced strain (S-E characteristic) in the high field range for morphotropic materials having different Zr∕Ti ratios. Unipolar electrical cycles with maximum fields between 1 and 3kV∕mm were applied to the poled materials under load-free conditions. Strain curves were recorded and the data were evaluated with respect to field dependence of strain and strain hysteresis. Nonlinearity of strain was detected for all materials. Depending on the composition, marked differences were found with respect to the types of nonlinearity. The corresponding data on strain hysteresis indicate that the nonlinearity was due to a loss generating strain mechanism. Therefore the nonlinearity was attributed to domain switching. A phenomenological model is suggested, which is based on the assumptions of a distribution of domain switching over a field range. This field range is characterized by the activation field parameter Ea, which is specific for each composition. The model is capable of explaining the types of nonlinearity in strain that have been observed.
A micromechanical model for nonlinear acoustic properties of interfaces between solids
Authors: Kim Jin-Yeon , Lee Jun-Shin
Published: February 2007

A micromechanical model for an interface between two solids in elastoplastic contact is presented to predict the acoustic linear and nonlinear interfacial stiffnesses during loading-unloading cycle. This interface is a representative model for apparently closed cracks and imperfect bonds that are interacting with ultrasonic waves sent for evaluating quality of their interfaces. For a better physical description of the elastoplastic contact behavior of the interface, the previous model [Kim et al., J. Mech. Phys. Solids 52, 1911 (2004)] is improved in two important aspects: the unloading model for unit contact element (asperity) and the geometrical and statistical parameters of the interface. The model is validated with experimental results. The interface parameters are obtained by fitting measured reflection coefficients during loading-unloading cycle with the theoretical model. Using so obtained parameters, the linear and second-order interfacial stiffnesses and the nonlinearity in transmitted longitudinal waves are calculated. The theoretical nonlinear transmission amplitude is in good comparison with the experimental result, demonstrating the capability of the present modeling framework in predicting both linear and nonlinear ultrasonic responses of imperfect interfaces. It is observed that the effect of adhesive force, which is not taken into account in the model, can be important in a certain stage of the unloading phase.
Elusive structure of HCl monohydrate
Authors: Buch V. , Mohamed F. , Parrinello M. , Devlin J. P.
Published: February 2007

The study addresses the structure of crystalline HCl monohydrate which is composed of H3O+ and Cl−. The published x-ray diffraction patterns indicate an element of disorder, the nature of which is debated in the literature and is addressed in the present study. The computational investigations include searches for alternative crystal structures employing an empirical potential, and on-the-fly simulations as implemented in the density functional code QUICKSTEP employing Gaussian basis sets. The experimental work focuses on Fourier-transform infrared (FTIR) spectra of crystal nanoparticles. Simulations of FTIR spectra and of the x-ray diffraction patterns are consistent with crystal monohydrate structure composed of ferroelectric domains, joined by “boundary tissue” of antiferroelectric structure.
On the nature of incompressible magnetohydrodynamic turbulence
Authors: Gogoberidze G.
Published: February 2007

A novel model of incompressible magnetohydrodynamic turbulence in the presence of a strong external magnetic field is proposed for the explanation of recent numerical results. According to the proposed model, in the presence of the strong external magnetic field, incompressible magnetohydrodynamic turbulence becomes nonlocal in the sense that low-frequency modes cause decorrelation of interacting high-frequency modes from the inertial interval. It is shown that the obtained nonlocal spectrum of the inertial range of incompressible magnetohydrodynamic turbulence represents an anisotropic analogue of Kraichnan’s nonlocal spectrum of hydrodynamic turbulence. Based on the analysis performed in the framework of the weak-coupling approximation, which represents one of the equivalent formulations of the direct interaction approximation, it is shown that incompressible magnetohydrodynamic turbulence could be both local and nonlocal, and therefore anisotropic analogues of both the Kolmogorov and Kraichnan spectra are realizable in incompressible magnetohydrodynamic turbulence.
Contactless ultrasonic device to measure surface acoustic wave velocities versus temperature
Authors: Hubert C. , Nadal M.-H. , Ravel-Chapuis G. , Oltra R.
Published: February 2007

A complete optical experimental setup for generating and detecting surface acoustic waves [Rayleigh waves (RWs)] in metals versus temperature up to the melting point is described. The RWs were excited by a pulsed Nd:YAG laser and detected by a high sensitivity subangstrom heterodyne interferometer. A special furnace was used to heat the sample using infrared radiation with a regulation of the sample temperature less than 0.1K. First measurements on an aluminum alloy sample are presented to validate the setup.
Reduction in potential barrier height of AlGaN∕GaN heterostructures by SiN passivation
Authors: Onojima N. , Higashiwaki M. , Suda J. , Kimoto T. , Mimura T. , Matsui T.
Published: February 2007

SiN passivation on AlGaN∕GaN heterostructures was carried out using catalytic or plasma-enhanced chemical vapor deposition (Cat-CVD or PECVD), which has been found to increase two-dimensional electron gas (2DEG) density. The 2DEG density can be closely related to AlGaN surface properties via polarization effects. AlGaN potential barrier heights of AlGaN∕GaN heterostructures with and without SiN passivation were systematically investigated using x-ray photoelectron spectroscopy (XPS) and capacitance-voltage (C-V) measurements. The results for the XPS and C-V measurements were consistent and demonstrated that a reduction in the AlGaN potential barrier height was actually induced by SiN passivation. Furthermore, Cat-CVD SiN passivation lowered the AlGaN potential barrier height more significantly than PECVD SiN passivation did, suggesting that the passivation method can influence the AlGaN potential barrier height.
Correlation between exchange bias dynamics and magnetization reversal asymmetry in [Pt∕Co]3∕Pt∕IrMn multilayers
Authors: Malinowski Gregory , van Dijken Sebastiaan , Czapkiewicz Maciej , Stobiecki Tomasz
Published: February 2007

The dependence of exchange bias field on magnetic field sweep rate was investigated for [Pt∕Co]3∕t Pt∕IrMn multilayers. For structures with t=0nm and t=0.3nm, the bias field decreases above a field sweep rate of a few T/s. The observed reduction of exchange bias at high frequencies correlates with a magnetization reversal asymmetry at low field sweep rates. Multilayers with t=0.1nm exhibit symmetric reversal and constant bias. The correlation between exchange bias dynamics and magnetization reversal asymmetry is explained by the frequency dependence of the domain wall motion to domain nucleation ratio.
Wavelength-encoded optical psychrometer for relative humidity measurement
Authors: Montanini Roberto
Published: February 2007

In this article an optical psychrometer, in which temperature measurements are performed by means of two fiber Bragg grating sensors used as dry-bulb and wet-bulb thermometers, is introduced. The adopted design exploits both the high accuracy of psychrometric-based relative humidity measurements with acknowledged advantages of wavelength-encoded fiber optic sensing. Important metrological issues that have been addressed in the experimental work include calibration of the fiber Bragg grating temperature sensors, evaluation of response time, sensitivity, hysteresis, linearity, and accuracy. The calibration results give confidence that, with the current experimental setup, measurement of temperature can be done with an uncertainty of ±0.2°C and a resolution of 0.1°C. A detailed uncertainty analysis is also presented in the article to investigate the effects produced by different sources of error on the combined standard uncertainty uc(U) of the relative humidity measurement, which has been estimated to be roughly within ±2% in the range close to saturation.
Precise DNA placement and stretching in electrode gaps using electric fields in a microfluidic system
Authors: Dukkipati Venkat Ram , Pang Stella W.
Published: February 2007

Control over the placement of stretched deoxyribonucleic acid (DNA) molecules in a microfluidic system is a critical requirement for molecular nanotechnology. A technique is developed where a large number of DNA molecules can be immobilized specifically at one end to the electrode tip and stretched in a microchannel using high frequency ac fields. λ-DNA molecules are immobilized and stretched using 100kHz ac fields in a 100μm wide and 75μm deep Si microchannel. Using a floating electrode in between two biased electrodes, stretched T2 DNA molecules are immobilized across a 5μm wide electrode gap by electric field and hydrodynamic flow.
Spatial and Geographical Effects in Regional Multiplier Analysis
Authors: Hanink Dean M
Published: February 2007

In this paper I extend regional multiplier analysis by incorporating both spatial (neighbor) and geographical (place-contained) effects. Multipliers, taken as elasticities, are estimated by regression analyses of the associations between retail trade earnings by place of work and total income by place of residence (from earnings, property, and transfers) across New England's counties in 2002. The multiplier analyses are conducted in two basic forms, both estimated using a simultaneous autoregressive specification and both incorporating a spatial neighbor income variable. In one, geographical effects are treated as dummy variables alone, so their impact on a particular income multiplier coefficient is read only indirectly. In the other, geographical effects are allowed to interact with property and transfer income so that their multiplier coefficients in the region vary from county to county depending upon particular geographical characteristics. The spatial effect of neighboring county income is consistent across the two forms, and suggests a competitive effect in the region's retail sector. Further results indicate that the region's property income and transfer receipts tend to offset each other in geographical context in their impact on retail-trade income.
Social Influence on Travel Behavior: A Simulation Example of the Decision to Telecommute
Authors: Páez Antonio , Scott Darren M
Published: February 2007

This paper addresses interagent interactions, an issue that has received limited attention in travel behavior research. Drawing upon the theory of externalities and the sociological notion of social networks, we develop a discrete choice model that incorporates elements of social influence in addition to more conventional factors such as the attributes of alternatives and the characteristics of decisionmakers. Using simulation, we apply the model to the case of telecommuting—that is, the decision to telecommute or not—over two waves. The experiment suggests that some marginal adopters of telecommuting are influenced heavily in the second wave by the decisions of others in the first wave. Furthermore, the example illustrates the importance of social influence on new adopters of telecommuting in the second wave.
Urban Spatial Change and Excess Commuting
Authors: Ma Kang-Rae , Banister David
Published: February 2007

In this paper we revisit the excess-commuting technique and its links with urban form. The uncertainty in measurement is highlighted, as are the problems relating to changes in excess commuting over time. The measure of the theoretical maximum commute is proposed and added to the traditional excess-commuting measure so that the use of both the minimum and maximum levels can capture the concept of commuting potential. This measure is what we call the ‘extended excess-commuting measure’. These concepts are tested through the use of a simulation exercise. As well as arguing for the inclusion of socioeconomic variables in analysis, we demonstrate that decentralisation in urban spatial structure can lead to either an increase or a decrease in average commuting distance. Some of the inconsistencies in the use of excess commuting can be reduced through the use of actual commutes together with the commuting range, as these factors in combination lead to a clearer understanding of commuting efficiency.
Ethnic Segregation and Educational Performance at Secondary School in Bradford and Leicester
Authors: Johnston Ron , Wilson Deborah , Burgess Simon
Published: February 2007

Evidence suggests considerable variation among British ethnic groups in their performance at different stages of their educational careers. Many members of those groups are concentrated in particular parts of certain cities, and as a consequence many attend ethnically segregated schools. Using pupil-level and school-level data from the Pupil Level Annual School Census in England, we explore the relationship between performance and various student and school characteristics in Bradford (which has a large Pakistani population) and Leicester (with a large Indian population). We find evidence of a correlation between school ethnic composition and performance in Bradford but not in Leicester.