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PubMed2000

Theory for matrix elements of one-body transition operators in the quantum chaotic domain of interacting particle systems

Demonstrating the equivalence between the recent theory of Flambaum and collaborators which is based on smoothed strength functions, with the much earlier formulation due to French and collaborators which is based on embedded random matrix ensembles and smoothed transition strength densities, we derive a theory for matrix elements of one-body transition operators in the quantum chaotic domain of isolated finite interacting particle systems with a mean-field and a chaos generating two-body interaction (V). The role of the bivariate correlation coefficient (zeta) arising out of the noncommutability of V and the transition operator (in the theory of Flambaum et al., zeta=0) is tested in numerical embedded ensemble calculations with a one- plus two-body Hamiltonian generating order-chaos transitions.

Journal Article↗
PubMed2000

Carcinosarcoma of the liver.

An autopsy case of carcinosarcoma of the liver in an 84-year-old man is described. The 14 x 6-cm solid tumor was located in the hilus to the left lobe and was grayish-white with some translucent areas. Histologically, the tumor consisted of an intimate mixture of adenocarcinomatous and chondrosarcomatous elements with transitional areas in between. Immunohistochemically, cells of the adenocarcinomatous elements were positive for cytokeratin but negative for S100 protein, whereas cells of the chondrosarcomatous elements showed the reverse staining pattern. Cells of transitional areas were positive for both cytokeratin and S100 protein. Most previously reported cases of carcinosarcoma of the liver have involved elderly men and have had a poor prognosis. The findings of the present case support the view that carcinosarcomas represent carcinomas that develop a sarcomatous element via metaplasia of the epithelial element.

Adenocarcinoma↗
PubMed2006

Basis set limit electronic excitation energies, ionization potentials, and electron affinities for the 3d transition metal atoms: Coupled cluster and multireference methods.

Recently developed correlation consistent basis sets for the first row transition metal elements Sc-Zn have been utilized to determine complete basis set (CBS) scalar relativistic electron affinities, ionization potentials, and 4s(2)3d(n-2)-4s(1)d(n-1) electronic excitation energies with single reference coupled cluster methods [CCSD(T), CCSDT, and CCSDTQ] and multireference configuration interaction with three reference spaces: 3d4s, 3d4s4p, and 3d4s4p3d'. The theoretical values calculated with the highest order coupled cluster techniques at the CBS limit, including extrapolations to full configuration interaction, are well within 1 kcal/mol of the corresponding experimental data. For the early transition metal elements (Sc-Mn) the internally contracted multireference averaged coupled pair functional method yielded excellent agreement with experiment; however, the atomic properties for the late transition metals (Mn-Zn) proved to be much more difficult to describe with this level of theory, even with the largest reference function of the present work.

Journal Article↗
PubMed1992

Scanning X-ray microanalysis of microcarrier cultured endothelial cells: elemental changes during the transition to confluency and the effect of ionophore A23187.

Porcine endothelial cells were grown on microcarrier beads and examined by scanning electron microscopy (SEM) at various times after initiation of culture. Total cell coverage on the bead surface varied from mean values of approximately 7% (3h) to 80% (96h). Beam penetration into the subcellular matrix presents a major problem with SEM X-ray microanalysis of microcarrier cultured cells and necessitates the use of an accelerating voltage not exceeding 10kV. At this voltage and below, X-ray contribution from elements present in the microcarrier bead has minimal effect on the determination of cell elemental levels. Washing the cells with 0.15M sucrose was the least perturbing of the rinsing techniques investigated, removing surface culture medium but not internal diffusible ions. X-ray microanalysis revealed detectable levels of Na, P, S, Cl, K and Ca in the cells, with well-marked changes from initial attachment to confluency. The level of K decreased from approximately 1.0% at 3h to 0.4% at 24h, with a corresponding decrease in the K/Na ratio. This unexpectedly low level of K was invariably observed after 24h, and is a genuine feature of established microcarrier culture. The effect of ionophore A23187 was determined at the 3h culture stage, and resulted in significant increases in the concentration of divalent cations (Mg2+, Ca2+), monovalent ions (Na+, Cl-) and a decrease in the level of K+.

Animals↗
PubMed1990

[Analysis of histopathological prognostic factors in patients who underwent radical cystectomy in cancer of the bladder].

The relationship between histopathological characteristics and their long-term prognosis was studied on a total of 110 patients with bladder cancer who underwent total cystectomy from 1978 to 1985 at Keio University Hospital in the period after computer tomography (CT) was initiated for the evaluation of tumor stagings. The actuarial five-year survival rate in the 110 patients estimated by Kaplan-Meier method was 54.3%. Disclosed as histological poor prognostic factors (p less than 0.05) were the presence of non-transitional cell elements (actuarial five-year survival rate: 26.3%), IFN gamma for growth patterns (26.3%), grade-3 for histological grades (39.1%), lymph-duct involvement ly(+) (28.2%), venous involvement v(+) (25.2%), muscle-invaded tumor and extravesical lymphnode involvement. As for the comparative relation among these histological factors, grade-3 tumors tended to have a high incidence of lymph-duct involvement (73.2%), venous involvement (26.8%) and positive lymph-nodes (35.7%) when compared to grade-2 tumors. The analysis of the degree of influence of those histological prognostic factors using the non-proportional hazard model revealed that the major priorities were positive lymphnodes (p = 0.0006), histological types (p = 0.0036) and lymph-duct involvement (p = 0.0839). These results suggest that intensive adjuvant treatment should be indicated for improving the prognosis of patients with bladder cancer who have undergone total cystectomy when non-transitional cell elements and/or vascular involvement are evidenced.

Aged↗
PubMed2005

Fast collapse but slow formation of secondary structure elements in the refolding transition of E. coli adenylate kinase.

The various models proposed for protein folding transition differ in their order of appearance of the basic steps during this process. In this study, steady state and time-resolved dynamic non-radiative excitation energy transfer (FRET and trFRET) combined with site specific labeling experiments were applied in order to characterize the initial transient ensemble of Escherichia coli adenylate kinase (AK) molecules upon shifting conditions from those favoring denaturation to refolding and from folding to denaturing. Three sets of labeled AK mutants were prepared, which were designed to probe the equilibrium and transient distributions of intramolecular segmental end-to-end distances. A 176 residue section (residues 28-203), which spans most of the 214 residue molecule, and two short secondary structure chain segments including an alpha-helix (residues 169-188) and a predominantly beta-strand region (residues 188-203), were labeled. Upon fast change of conditions from denaturing to folding, the end-to-end distance of the 176 residue chain section showed an immediate collapse to a mean value of 26 A. Under the same conditions, the two short secondary structure elements did not respond to this shift within the first ten milliseconds, and retained the characteristics of a fully unfolded state. Within the first 10 ms after changes of the solvent from folding to denaturing, only minor changes were observed at the local environments of residues 203 and 169. The response of these same local environments to the shift of conditions from denaturing to folding occurred within the dead time of the mixing device. Thus, the response of the CORE domain of AK to fast transfer from folding to unfolding conditions is slow at all three conformational levels that were probed, and for at least a few milliseconds the ensemble of folded molecules is maintained under unfolding conditions. A different order of the changes was observed upon initiation of refolding. The AK molecules undergo fast collapse to an ensemble of compact structures where the local environment of surface probes seems to be native-like but the two labeled secondary structure elements remain unfolded.

Adenylate Kinase↗
PubMed2002

Analysis of biogenic carbonates by inductively coupled plasma-mass spectrometry (ICP-MS). Flow injection on-line solid-phase preconcentration for trace element determination in fish otoliths.

The aragonite deposits within the ear bones (otoliths) of teleost fish retain a chemical signal reflecting the life history of fish (similar to rings of trees) and the nature of fish habitats. Otoliths dissolved in acid solutions contain high concentrations of calcium and a variety of proteins. Elimination of matrix salts and organic interferences during preconcentration is essential for accurate determination of trace elements in otolith solutions by inductively coupled plasma-quadrupole mass spectrometry. An iminodiacetate-based chelating resin (Toyopearl AF-Chelate 650 M) has been used for on-line preconcentration and matrix separation for the determination of 31 transition and rare elements. Successful preconcentration of the elements was achieved at pH 5 by on-line buffering, except Mn which required pH 8.8. Sample solutions were loaded on to the column for 1 min at 3.2 mL min(-1), and then eluted directly into the mass spectrometer with 4% v/v nitric acid. This procedure enabled up to 25-fold preconcentration with successful removal of the calcium matrix. The effect of heat-assisted oxidation with concentrated nitric acid was investigated to eliminate the organic matrix. It was found that heating to dryness after dissolution and further mineralization with the acid significantly improved the retention of the transition elements. The method was validated by analysis of a certified reference material produced from saggittal otoliths of emperor snapper ( Lutjanus sebae), and then applied to the determination of trace metal concentrations in juvenile bluefin tuna ( Thunnus thynnus) from the Western Pacific Ocean.

Animals↗
PubMed2005

Human parahippocampal activity: non-REM and REM elements in wake-sleep transition.

The covert-rapid-eye-movement (REM) sleep hypothesis of dreaming suggests that elements of REM sleep emerge during sleep onset, leading to vivid hypnagogic imagery. Based on parahippocampal electrocorticography of epileptic patients we found an increase in REM-like 1.5-3.0 Hz parahippocampal activity during wake-sleep transition, which peaks after on average 30s of sleep onset, and reaches 82% of REM sleep value. The increase in 1.5-3.0 Hz parahippocampal activity followed alpha dropout, but did not relate to short-term fluctuations in alpha waves or sleep spindles. Non-REM sleep-specific slow (<1.25 Hz) activity showed a continuous increase during wake-sleep transition in both temporal scalp and parahippocampal recordings. It is suggested that REM-like parahippocampal rhythmic slow activity is an after-effect of hypothalamic wake-promoting centers' switch-off at sleep onset, leading to an inhibited hippocampal functioning and hypnagogic hallucinations.

Cortical Synchronization↗
PubMed2002

Bcc and Fcc transition metals and alloys: a central role for the Jahn-Teller effect in explaining their ideal and distorted structures.

Transition metal elements, alloys, and intermetallic compounds often adopt the body centered cubic (bcc) and face centered cubic (fcc) structures. By comparing quantitative density functional with qualitative tight-binding calculations, we analyze the electronic factors which make the bcc and fcc structures energetically favorable. To do so, we develop a tight-binding function, DeltaE(star), a function that measures the energetic effects of transferring electrons within wave vector stars. This function allows one to connect distortions in solids to the Jahn-Teller effect in molecules and to provide an orbital perspective on structure determining deformations in alloys. We illustrate its use by considering first a two-dimensional square net. We then turn to three-dimensional fcc and bcc structures, and distortions of these. Using DeltaE(star), we rationalize the differences in energy of these structures. We are able to deduce which orbitals are responsible for instabilities in seven to nine valence electron per atom (e(-)/a) bcc systems and five and six e(-)/a fcc structures. Finally we demonstrate that these results account for the bcc and fcc type structures found in both the elements and binary intermetallic compounds of group 4 through 9 transition metal atoms. The outline of a theory of metal structure deformations based on loss of point group operation rather than translational symmetry is presented.

Journal Article↗
PubMed1993

Perceptual strategies in prelingual speech segmentation.

Previous work has suggested that infants may segment continuous speech by a BRACKETING STRATEGY that segregates portions of the speech stream based on prosodic cues to their endpoints. The two present studies were designed to assess whether infants also can deploy a CLUSTERING STRATEGY that exploits asymmetries in transitional probabilities between successive elements, aggregating elements with high transitional probabilities and identifying points of low transitional probabilities as boundaries between units. These studies examined effects of the structure and redundancy of speech context on infants' discrimination of two target syllables using an operant head-turning procedure. After discrimination training on the target syllables in isolation, discrimination maintenance was tested when the target syllables were embedded in one of three contexts. Invariant Order contexts were structured to promote clustering, whereas the Redundant and Variable Order contexts were not. Thirty-six seven-month-olds were tested in Experiment I, in which stimuli were produced with varying intonation contours; 36 eight-month-olds were tested in Experiment 2, in which stimuli were produced with comparable flat pitch contours. In both experiments, performance of the three groups was equivalent in an initial 20-trial test. However, in a second 20-trial test, significant improvements in performance were shown by infants in the Invariant Order condition. No such gains were shown by infants in the other two conditions. These studies suggest that clustering may complement bracketing in infants' discovery of units of language.

Acoustic Stimulation↗
PubMed2006

Variability-induced transition in a net of neural elements: From oscillatory to excitable behavior.

Starting with an oscillatory net of neural elements, increasing variability induces a phase transition to excitability. This transition is explained by a systematic effect of the variability, which stabilizes the formerly unstable, spatially uniform, temporally constant solution of the net. Multiplicative noise may also influence the net in a systematic way and may thus induce a similar transition. Adding noise into the model, the interplay of noise and variability with respect to the reported transition is investigated. Finally, pattern formation in a diffusively coupled net is studied, because excitability implies the ability of pattern formation and information transmission.

Journal Article↗
PubMed2006

Solid-state (207)Pb NMR studies of lead-group 16 and mixed transition-metal/lead-group 16 element-containing materials.

(207)Pb solid-state NMR studies have been conducted on binary lead-group 16 and mixed transition-metal/lead group 16 materials, correlating the NMR chemical shifts of the materials with their structures. The experimental results show that the (207)Pb chemical shifts are strongly influenced by the local electronic structure. Data are reported for lead selenide, lead selenate, calcium plumbate, strontium plumbite, barium plumbite, lead borate, lead zirconate, lead tungstate, lead meta-tantalate, lead niobate, lead molybdate, lead meta-vanadate, lead sulfite, and lead sulfate.

Journal Article↗
PubMed2003

Colliding primary lung cancers of adenosquamous carcinoma and large cell neuroendocrine carcinoma.

We report an extremely rare case of primary lung cancer showing various histological elements diagnosed as the collision of an adenosquamous carcinoma and a large cell neuroendocrine carcinoma by loss of heterozygosity (LOH) analysis of the human androgen receptor (AR) and phosphoglycerate kinase (PGK-1) genes. The tumor exhibited a tiny ground-glass opaque shadow suggesting atypical adenomatous hyperplasia 18 months prior to surgery. However, the tumor grew rapidly, and the resected tumor consisted of two closely located nodules. The larger nodule was composed of well-differentiated adenocarcinomatous and moderately to poorly differentiated squamous cell carcinomatous elements, while the smaller nodule consisted of a large cell neuroendocrine carcinomatous element with partial squamoid differentiation having focal continuity with the adenocarcinomatous element. Both the adenocarcinomatous and squamous cell carcinomatous elements revealed transitional features and LOH of AR and PGK-1 genes, while the large cell neuroendocrine carcinomatous element showed a monoclonal pattern but possessed both alleles of AR and PGK-1 genes. From these clinical and pathological results, the parental cell of the large cell neuroendocrine carcinomatous element was considered to be different from that of the adenosquamous carcinomatous element.

Amino Acid Sequence↗
PubMed1996

Bladder cancer in various population groups in the greater Durban area of KwaZulu-Natal, South Africa.

OBJECTIVE: To study the incidence of different histological types of bladder cancer in various racial groups living within the same geographical region. PATIENTS AND METHODS: The study included 615 new patients with bladder cancer seen at three Provincial hospitals in Durban from January 1980 to January 1990. The patients were classified as Caucasian (white people of European descent). African (indigenous black people), Asian (people originating from the Indian subcontinent) or Coloured (people of mixed race). The bladder tumours were classified according to standard histopathological criteria as transitional cell carcinoma, adenocarcinoma or sarcoma. Mixed tumours consisted of both carcinomatous and sarcomatous or undifferentiated elements. RESULTS: Transitional cell carcinoma constituted 95% of the cancers in Caucasians, compared with only 30% in Africans, whereas squamous cell carcinoma occurred in 53% of the African patients, but in only 2% of the Caucasians. In Asian patients, 75% of the tumours were transitional cell and 18% were squamous cell carcinoma, whereas in Coloureds 82% were transitional cell and 9% squamous cell carcinoma. Undifferentiated carcinoma occurred in 8% of African and only 1% of Caucasian patients, whereas adenocarcinoma, mixed tumours and sarcoma occurred in 9% of African patients and only 2% of Caucasian patients. Ova of Schistosoma haematobium were seen in microscopic sections of the bladder tumour in 85% of the patients with squamous cell carcinoma, in 50% of those with undifferentiated tumours and adenocarcinoma, in 17% of those with mixed tumours or sarcoma, and in only 10% of the patients with transitional cell carcinoma. At presentation, African patients were a mean of > 20 years younger than Caucasians. In African patients with squamous cell carcinoma, 90% had stage T3 or T4 disease at presentation, whereas in Caucasian patients with transitional cell carcinoma 76% had stage T1 or T2 disease at presentation. From the study group, it appears that bladder cancer is about six times more common in Caucasians than in Africans. However, the value for Caucasian patients with bladder cancer probably underestimates the true value by about five times, so that bladder cancer in the greater Durban area may be as much as 30 times more common in Caucasians than in Africans. CONCLUSION: In African patients, endemic Schistosomiasis appears to be related to a high incidence of not only squamous cell carcinoma, but also undifferentiated tumours and adenocarcinoma of the bladder. The effective management of squamous cell carcinoma of the bladder in African patients will depend on the eradication of Schistosomiasis and the early detection of bladder cancer at a stage when it may still be cured by radical treatment.

Adenocarcinoma↗
PubMed1991

Transitional cell carcinoma with sarcomatous elements in the urinary tract. Six cases examined by immunohistochemistry.

We report six cases of carcinoma showing sarcomatous change in the urinary tract examined by conventional histochemistry and immunohistochemistry. All of the cases were transitional cell carcinoma with or without focal squamous cell carcinoma. Sarcomatous components resembling spindle cell sarcoma with a marked myxoid stroma or chondrosarcomatous element were also observed in all cases. The sarcomatous elements were closely associated with the areas of squamous cell carcinoma in three cases. Various histochemical staining procedures demonstrated mesenchymal features in the stroma of sarcomatous areas. By immunohistochemical examination, the epithelial components showed positive reactions for keratin, epithelial membrane antigen and, focally, carcinoembryonic antigen. The sarcomatous components revealed a positive immunoreaction for keratin but lacked other epithelial markers in all cases. Chondrosarcomatous elements in two cases were positive for both keratin and S-100 protein. These findings indicate that sarcomatous elements in carcinoma may represent mesenchymal metaplasia with partial or complete loss of epithelial features. However, further study will be necessary in order to determine whether heterogeneous elements, such as chondrosarcomatous areas, are epithelial or truly mesenchymal in origin.

Aged↗
PubMed2003

Trace element differentiation in ferruginous accumulation soil patterns under tropical rainforest of southern Cameroon, the role of climatic change.

Regions under tropical rainforest cover, such as central Africa and Brazil are characterised by degradation and dismantling of old ferricrete structures. In southern Cameroon, these processes are relayed by present-day ferruginous accumulation soil facies, situated on the middle and the lower part of hill slopes. These facies become progressively harder towards the surface, containing from bottom to top, mainly kaolinite, kaolinite-goethite and Al-rich goethite-hematite, and are discontinuous to the relictic hematite-dominated ferricrete that exist in the upper part of the hill slope. These features were investigated in terms of geochemical differentiation of trace elements. It appears that, in contrast to the old ferricrete facies, the current ferruginous accumulations are enriched in transitional trace elements (V, Cr, Co, Y, Sc) and Pb, while alkali-earth elements are less differentiated. This recent chemical accumulation is controlled both by intense weathering of the granodiorite bedrock and by mobilisation of elements previously accumulated in the old ferricrete. The observed processes are clearly linked to the present-day humid climate with rising groundwater tables. They slowly replace the old ferricretes formed during Cretaceous time under more seasonal climatic conditions, representing an instructive case of continuos global change.

Journal Article↗
PubMed2000

EELS analysis of cation valence states and oxygen vacancies in magnetic oxides

Transition metal oxides are a class of materials that are vitally important for developing new materials with functionality and smartness. The unique properties of these materials are related to the presence of elements with mixed valences of transition elements. Electron energy-loss spectroscopy (EELS) in the transmission electron microscope is a powerful technique for measuring the valences of some transition metal elements of practical importance. This paper reports our current progress in applying EELS for quantitative determination of Mn and Co valences in magnetic oxides, including valence state transition, quantification of oxygen vacancies, refinement of crystal structures, and identification of the structure of nanoparticles.

Journal Article↗