bluuebunny/crossref_metadata_2025 huggingface dataset:
Ground‐penetrating radar and microwave tomography to evaluate the crack and joint geometry in historical buildings: some examples from Chania, Crete, Greece
Authors: Bavusi M. , Soldovieri F. , Piscitelli S. , Loperte A. , Vallianatos F. , Soupios P.
Published: September 2010

Diagnostics of historical buildings is crucial for the definition of a reliable restoration project or in the study of the seismic behaviour of a building. This was one of the objectives of the international project ‘Advanced techniques for Seismic RISK Reduction in Mediterranean Archipelago Regions’ (SE RISK). In particular, in the framework of the project, the present work is concerned with the exploitation of GPR for the inspection of two historical buildings of Crete Island, Greece, the Prefecture of Chania and Venizelo’s House. In particular, the surveys aim at gaining information about the structure of the floors fracture areas and structural joint zones via high‐resolution measurements thanks to the use of a 1500 MHz nominal centre frequency antenna. With regard to the Prefecture of Chania, the specific aim of the survey was to detect and localize fracture areas and joint zones thanks to a scanning line acquired orthogonally to the ‘defects visible’ at the surface of the floors. In Venizelo’s House, the aim was to detect and localize fracture areas in the stone masonry.

Besides the classical time data processing, a microwave tomography based approach was applied to the data. The comparison between the two approaches has shown that the results of both the procedures are in good agreement suggesting both the reliability of the standard processing routine and the new microwave approach. In addition, the microwave tomographic approach provides more detailed and higher resolution images allowing an easier data interpretation. The microwave tomographic approach also offers the advantage of performing an automatic procedure, thus mitigating the risk of introducing subjective elements as in the case of the classical approach.
Yield and quality of oat in response to varying rates of swine slurry
Authors: Buckley K. E. , Mohr R. M. , Therrien M. C.
Published: September 2010

An experiment was conducted at two locations in southern Manitoba in 2001 and 2002 to assess the effect of multiple rates of spring-applied swine slurry on seed yield, kernel quality, dry matter accumulation, protein concentration and lodging response of three adapted oat (Avena sativa L.) cultivars: AC Medallion, AC Ronald and AC Assiniboia. Treatments included three rates of swine slurry, an unfertilized check and an inorganic fertilizer treatment at the recommended N rate. In spite of the nutrient variability in swine slurry, oat grain and dry matter yield remained largely unresponsive to increases in slurry rate except when residual soil nutrients were very low. Thousand kernel weight and percentage of plump kernels appeared to be affected more by environment and cultivar than by slurry rate. High rates of swine slurry did not result in high crude protein concentrations in grain or dry matter and may, under some environmental conditions, decrease protein concentrations. The data suggest that few differences exist between oat cultivars in response to the use of swine slurry as a fertilizer. The inconsistent response to slurry application indicates that oat may not be the ideal crop to use in the year of slurry application but may respond well to residual nutrients from nutrients applied in the prior year.Key words: Oat, swine slurry, grain yield, biomass yield, crop quality
Influence of growth regulators on skin colour and scab diseases of red-skinned potatoes
Authors: Waterer D.
Published: September 2010

A uniform dark red skin colour is desirable in table potatoes; however, the colour of the popular red-skinned cultivar Norland is variable and tends to fade during storage. This study evaluated the potential to enhance skin colour of red potatoes by foliar application of the auxin-type herbicide 2,4-D or long-lasting analogs of the naturally occuring hormone abscisic acid (ABA). In field trials conducted from 2007 to 2009, the plant growth regulators (PGR) were applied to the foliage of Norland and AC Peregrine Red (a new dark red variety) potato plants when the crop was at the tuber set stage. Although the 2,4-D treatments altered the appearance of the foliage they had no consistent impact on yields or tuber shape, but did reduce the average tuber size. Objective and subjective assessments indicated that the 2,4-D treatments altered the skin colour of the tubers both immediately after harvest and after extended cold storage. The degree and nature of the colour change was somewhat dependent on the year, the rate of 2,4-D applied and the cultivar. The change in tuber appearance arising from the 2,4-D treatments was not always considered desirable by consumer panellists. The 2,4-D treatments also reduced tuber damage by common scab (Streptomyces scabies), but tended to increase grade out to powdery scab (Spongospora subterranea). The ABA analogs had no consistent impact on yields, skin colour or disease reaction. Key words: 2,4-dichlorophenoxyacetic acid, abscisic acid, common scab, powdery scab, Streptomyces scabies, Spongospora subterranea
Iwahori-Hecke Algebras of SL2over 2-Dimensional Local Fields
Authors: Lee Kyu-Hwan
Published: September 2010

In this paper we construct an analogue of Iwahori–Hecke algebras of SL2over 2-dimensional local fields. After considering coset decompositions of double cosets of a Iwahori subgroup, we define a convolution product on the space of certain functions on SL2, and prove that the product is well-defined, obtaining a Hecke algebra. Then we investigate the structure of the Hecke algebra. We determine the center of the Hecke algebra and consider Iwahori–Matsumoto type relations.
Carcinogenicity of occupational nickel exposures: An evaluation of the epidemiological evidence
Authors: Grandjean Philippe , Andersen Ole , Nielsen Gitte D.
Published: September 2010

The health effects documented in recent epidemiological studies of nickel‐exposed workers relate to past exposures, mostly of unknown magnitude and unknown nickel speciation. Major studies have been carried out at nickel smelters and refineries. Although each study suffers from some deficiencies, as is common in such retrospective studies, the findings in concert strongly indicate that nickel emitted from the calcining and sintering operations is a potent carcinogen resulting in nasal and pulmonary cancers. Some risk appears to be present in other refinery operations, such as Orford furnace, copper and nickel sulfate, and crushing departments, and one study has suggested a risk associated with soluble nickel compounds in the electrolysis department, although this finding has not been confirmed. Only one study demonstrated an exposure‐response relationship, which, however, was not statistically significant. Other studies showed a relationship between increased exposure time and augmented cancer risk. In nickel‐using industries, no excess cancer related to nickel exposures has been demonstrated beyond doubt; concurrent exposures to other potential carcinogens constitute a confounding variable that makes interpretation difficult. However, the studies have not excluded that a cancer hazard may be present outside the nickel‐producing facilities. Further, case‐referent studies of respiratory cancers suggest that a nickel‐related etiology may well exist in the nickel‐using industries. As the exact identity of the carcinogenic form or forms of nickel remains unknown, exposure to all nickel compounds should be kept as low as reasonably achievable.
1,1,1‐trichloroethane (methyl chloroform) in urine as biological index of exposure
Authors: Imbriani M. , Ghittori S. , Pezzagno G. , Huang J. , Capodaglio E.
Published: September 2010

Fifteen human volunteers were exposed to 1,1,1‐trichloroethane (methyl chloroform) vapor at 72–495 mg/m3 for a period of 2 to 4 hours at rest (ten cases) and during light physical exercise (five cases). Subsequently 60 workers occupationally exposed to 1,1,1‐trichloroethane in a refrigerator manufacturing plant were studied (median value: 178 mg/m3; geometrical standard deviation: 2.19 mg/m3). As expected, the relative uptake (R) of 1,1,1‐trichloroethane decreased in the course of exposure at rest (R = 0.44 after 20 minutes of exposure; R = 0.26 after 240 minutes of exposure). Both in the experimentally exposed subjects and in the occupationally exposed workers, the urinary concentration of 1,1,1‐trichloroethane showed a linear relationship to the corresponding environmental time‐weighted average concentration. The correlation coefficients (r) were 0.95 in occupationally exposed subjects and more than 0.90 in experimentally exposed groups.

A linear equation also existed between urinary concentration and amount of 1,1,1‐trichloroethane absorbed (r = 0.88). The findings indicate that the urinary concentration of 1,1,1‐trichloroethane can be used as an appropriate biological exposure indicator. In occupationally exposed subjects performing moderate work, the urinary 1,1,1‐trichloroethane concentration corresponding to the time‐weighted average of the threshold limit value was found to be 860 μg/L and its 95% lower confidence limit (biological threshold) 805 μg/L.
Screening for occupational disease among workers in a high‐risk trade: Examination of cost, yield, and potential for increased efficiency
Authors: Schwartz David A. , Rosenstock Linda , Barnhart Scott , Inui Thomas S.
Published: September 2010

We evaluated the cost and yield of a general health surveillance program emphasizing the identification of occupationally related diseases among workers in a high‐risk trade. Of approximately 4,000 eligible members of two local plumbers and pipefitters unions, 639 were screened in this program. Screening tests indicated either by specific occupational exposures (eg, chest X‐ray, spirometry, and audiometry) or general clinical risk factors (urine analysis for those with a positive urine dipstick, and stool heme occult testing for those over 45 years of age) proved to be far less costly for each positive finding than those procedures (physical examination, complete blood count, and blood chemistry panel) that were not specifically indicated. A discriminant analysis revealed predictor variables (age, years in the trade, and presence of respiratory symptoms) that, in subsequent screening efforts, could be used in the unscreened population either to identify individuals who are more likely to have any positive test result or to “tailor” the content of the initial screening program for a single individual. Increasing the yield and decreasing the direct costs of screening activities may make programs like these more affordable. In addition, this program assisted workers in filing for compensation and thus served to promote the appropriate transfer of cost for the identification and management of occupational diseases from traditional forms of payment to workers' compensation insurance programs.
Determinants of pattern of breathing during respirator use
Authors: Harber Philip , Shimozaki Steven , Barrett Thomas , Fine Gil
Published: September 2010

The relationship between the pattern of breathing in response to respirator‐type loads and an individual's psychophysiologic sensitivity to loads (load scaling sensitivity, LSS) was investigated in the study of 11 normal volunteers. LSS was measured by having the subjects numerically rate a series of resistors; Stevens's Psychophysical Law was used to evaluate sensitivity as the slope relating log (sensation) to log (stimulus). Peak pressure and actual added resistance were the stimuli. Inspiratory time, peak pressure, duty cycle, and tidal volume were inversely related to independently measured LSS during exercise and with a respirator‐type dead space and inspiratory resistance load. Because the need for changes in respiratory timing is a major adaptation in respirator use, it suggests that workers who are very sensitive to loads may have limited ability to adapt to respirator use.
An update of respiratory cancer and occupational exposure to arsenicals
Authors: Sobel Wendy , Bond Gregory G. , Baldwin Charles L. , Ducommun Dale J.
Published: September 2010

Mortality was updated through 1982 for 611 arsenic‐exposed employees originally studied through 1973. In the earlier report, total mortality was observed to have been below the comparable U.S. population; however, mortality was significantly elevated for respiratory cancer. The focus of the update was on respiratory cancer and of special interest was whether the risk of respiratory cancer remained in excess for individuals alive as of the end of the last study. In the update, 9 additional respiratory cancers were observed subsequent to 1973, the end of the follow‐up in the original study, versus 7.8 expected. The risk ratio for the time‐interval 1974–1982 (standardized mortality ratio SMR = 116) was diminished compared to that reported in the original study (SMR = 330). When the entire study period was analyzed, the risk of respiratory cancer did not appear to decline with interval since exposure cessation. Analyses by duration of arsenic exposure and interval since first exposure did not reveal any obvious dose‐response relationships.
Use of hospital discharge data in the surveillance of occupational disease
Authors: Rosenman Kenneth D.
Published: September 2010

Computerized hospital discharge diagnoses are useful for occupational disease surveillance. One thousand one hundred twenty‐six individuals with asbestosis and 268 individuals with silicosis were identified in New Jersey for the four‐year period 1979–1982. Computer‐generated maps help to dramatize the localization of these conditions to certain geographic areas.

The attributes and limitations of using hospital discharge diagnoses for occupational disease surveillance are discussed: initial follow‐up data are presented for individuals with silicosis.
Surveillance of occupational skin disease using the supplementary data system
Authors: O'Malley Michael , Thun Michael , Morrison Jack , Mathias C. G. Toby , Halperin W. E.
Published: September 2010

The utility of the Supplementary Data System (SDS) compiled by the Bureau of Labor Statistics (BLS) in conducting surveillance of occupational skin disease was evaluated by examining 14,703 workers' compensation cases reported to the SDS for the year 1981. Combined with state employment denominators obtained from the BLS Employment and Earnings Program, rates of illness (cases of dermatitis/10,000 employed) calculated for eight major industrial divisions varied significantly according to the criteria used for reporting cases. Despite quantitative variations in the rate of skin disease that depended on specific reporting criteria, the relative ranking of the major industrial divisions remained unchanged, with highest rates of skin disease consistently found in three major industry divisions: agriculture, manufacturing, and construction. This ranking of major industry divisions by rate of dermatitis corresponded extremely well with rankings generated from the 1981 Annual Survey (Spearman rank correlation = .98, p < .01). At the two‐digit level of the Standard Industrial Classification, the rankings based on the SDS had a 77% rank correlation with those from the Annual Survey. Two‐digit SIC codes identified from the top 10 in both sets of rankings included crop and livestock production from the agricultural division and leather products, food products, rubber and plastic products from the manufacturing division.
Malignant melanoma in the printing industry
Authors: Mclaughlin Joseph K. , Malker Hans S. R. , Blot William J. , Ericsson Jan L. E. , Gemne Gosta , Fraumeni Joseph F.
Published: September 2010

To evaluate a recent report of malignant melanoma among printers, we used the Cancer‐Environment Registry of Sweden, which links national cancer incidence and employment data. Employees in the newspaper printing industry had almost twice the incidence of melanoma than expected (p < 0.01). Elevated risks were found not only among typographers and machine repairers, but also among journalists, editors, and business executives in the printing industry. Further studies are needed to clarify this relationship and identify specific exposures that may be responsible.
Erythropoietin plus insulin‐like growth factor‐I protects against neuronal damage in a murine model of human immunodeficiency virus‐associated neurocognitive disorders
Authors: Kang Yeon‐Joo , Digicaylioglu Murat , Russo Rossella , Kaul Marcus , Achim Cristian L. , Fletcher Lauren , Masliah Eliezer , Lipton Stuart A.
Published: September 2010

Objective

Prolonged human immunodeficiency virus‐1 (HIV‐1) infection leads to neurological debilitation, including motor dysfunction and frank dementia. Although pharmacological control of HIV infection is now possible, HIV‐associated neurocognitive disorders (HAND) remain intractable. Here, we report that chronic treatment with erythropoietin (EPO) and insulin‐like growth factor‐I (IGF‐I) protects against HIV/gp120‐mediated neuronal damage in culture and in vivo.

Methods

Initially, we tested the neuroprotective effects of various concentrations of EPO, IGF‐I, or EPO+IGF‐I from gp120‐induced damage in vitro. To assess the chronic effects of EPO+IGF‐I administration in vivo, we treated HIV/gp120‐transgenic or wild‐type mice transnasally once a week for 4 months and subsequently conducted immunohistochemical analyses.

Results

Low concentrations of EPO+IGF‐I provided neuroprotection from gp120 in vitro in a synergistic fashion. In vivo, EPO+IGF‐I treatment prevented gp120‐mediated neuronal loss, but did not alter microgliosis or astrocytosis. Strikingly, in the brains of both humans with HAND and gp120‐transgenic mice, we found evidence for hyperphosphorylated tau protein (paired helical filament‐I tau), which has been associated with neuronal damage and loss. In the mouse brain following transnasal treatment with EPO+IGF‐I, in addition to neuroprotection we observed increased phosphorylation/activation of Akt (protein kinase B) and increased phosphorylation/inhibition of glycogen synthase kinase (GSK)‐3β, dramatically decreasing downstream hyperphosphorylation of tau. These results indicate that the peptides affected their cognate signaling pathways within the brain parenchyma.

Interpretation

Our findings suggest that chronic combination therapy with EPO+IGF‐I provides neuroprotection in a mouse model of HAND, in part, through cooperative activation of phosphatidylinositol 3‐kinase/Akt/GSK‐3β signaling. This combination peptide therapy should therefore be tested in humans with HAND. ANN NEUROL 2010;68:342–352
Role of interleukin‐1β in postoperative cognitive dysfunction
Authors: Cibelli Mario , Fidalgo Antonio Rei , Terrando Niccolò , Ma Daqing , Monaco Claudia , Feldmann Marc , Takata Masao , Lever Isobel J. , Nanchahal Jagdeep , Fanselow Michael S. , Maze Mervyn
Published: September 2010

Objective:

Although postoperative cognitive dysfunction (POCD) often complicates recovery from major surgery, the pathogenic mechanisms remain unknown. We explored whether systemic inflammation, in response to surgical trauma, triggers hippocampal inflammation and subsequent memory impairment, in a mouse model of orthopedic surgery.

Methods:

C57BL/6J, knock out (lacking interleukin [IL]‐1 receptor, IL‐1R−/−) and wild type mice underwent surgery of the tibia under general anesthesia. Separate cohorts of animals were tested for memory function with fear conditioning tests, or euthanized at different times to assess levels of systemic and hippocampal cytokines and microglial activation; the effects of interventions, designed to interrupt inflammation (specifically and nonspecifically), were also assessed.

Results:

Surgery caused hippocampal‐dependent memory impairment that was associated with increased plasma cytokines, as well as reactive microgliosis and IL‐1β transcription and expression in the hippocampus. Nonspecific attenuation of innate immunity with minocycline prevented surgery‐induced changes. Functional inhibition of IL‐1β, both in mice pretreated with IL‐1 receptor antagonist and in IL‐1R−/− mice, mitigated the neuroinflammatory effects of surgery and memory dysfunction.

Interpretation:

A peripheral surgery‐induced innate immune response triggers an IL‐1β‐mediated inflammatory process in the hippocampus that underlies memory impairment. This may represent a viable target to interrupt the pathogenesis of postoperative cognitive dysfunction. ANN NEUROL 2010;68:360–368
Exercise and Alzheimer's disease biomarkers in cognitively normal older adults
Authors: Liang Kelvin Y. , Mintun Mark A. , Fagan Anne M. , Goate Alison M. , Bugg Julie M. , Holtzman David M. , Morris John C. , Head Denise
Published: September 2010

Objective

In addition to the increasingly recognized role of physical exercise in maintaining cognition, exercise may influence Alzheimer's disease (AD) pathology, as transgenic mouse studies show lowered levels of AD pathology in exercise groups. The objective of this study was to elucidate the association between exercise and AD pathology in humans using Pittsburgh compound‐B (PIB), amyloid‐β (Aβ)42, tau, and phosphorylated tau (ptau)181 biomarkers.

Methods

Sixty‐nine older adults (17 males, 52 females) aged 55 to 88 years, were recruited and confirmed to be cognitively normal. A questionnaire on physical exercise levels over the past decade was administered to all. Cerebrospinal fluid samples were collected from 56 participants, and amyloid imaging with PIB was performed on 54 participants.

Results

Participants were classified based on biomarker levels. Those with elevated PIB (p = 0.030), tau (p = 0.040), and ptau181 (p = 0.044) had significantly lower exercise, with a nonsignificant trend for lower Aβ42 (p = 0.135) to be associated with less exercise. Results were similar for PIB after controlling for covariates; tau (p = 0.115) and ptau181 (p = 0.123) differences were reduced to nonsignificant trends. Additional analyses also demonstrated that active individuals who met the exercise guidelines set by the American Heart Association had significantly lower PIB binding and higher Aβ42 levels with and without controlling for covariates (PIB: p = 0.006 and p = 0.001; Aβ42: p = 0.042 and p = 0.046). Last, the associations between exercise engagement and PIB levels were more prominent in APOE epsilon 4 noncarriers.

Interpretation

Collectively, these results are supportive of an association between exercise engagement and AD biomarkers in cognitively normal older adults. Ann Neurol 2010;68:311–318
Neurological disorders in complex humanitarian emergencies and natural disasters
Authors: Mateen Farrah J.
Published: September 2010

Complex humanitarian emergencies include the relatively acute, severe, and overwhelming health consequences of armed conflict, food scarcity, mass displacement, and political strife. Neurological manifestations of complex humanitarian emergencies are important and underappreciated consequences of emergencies in populations worldwide. This review critically assesses the existing knowledge of the range of neurological disorders that accompany complex humanitarian emergencies and natural disasters in both the acute phase of crisis and the “long shadow” that follows. Ann Neurol 2010;68:282–294
JC virus persistence following progressive multifocal leukoencephalopathy in multiple sclerosis patients treated with natalizumab
Authors: Ryschkewitsch Caroline F. , Jensen Peter N. , Monaco Maria Chiara , Major Eugene O.
Published: September 2010

JC virus (JCV) DNA in the cerebrospinal fluid (CSF) provides the laboratory confirmatory diagnosis of progressive multifocal leukoencephalopathy (PML) in patients whose clinical symptoms and magnetic resonance imaging findings are consistent with PML.The Laboratory of Molecular Medicine and Neuroscience (LMMN), National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), made the confirmatory laboratory diagnosis in 35 multiple sclerosis (MS) patients treated with natalizumab. Thirteen patients had 3 or more CSF samples taken from weeks to months following PML diagnosis. Seven of the 13 patients demonstrated persistence of JCV DNA in the CSF even though all patients experienced immune reconstitution inflammatory syndrome (IRIS), 11 patients had plasma exchange, and 2 had immunoabsorption. Specific anti‐JCV antibody was measured in plasma/sera samples from 25 of the 35 patients. Most of the samples showed moderate to high or rising antibody levels from the time of PML diagnosis. However, plasma from 1 patient at or near the time of PML diagnosis had a titer considered seronegative and 2 other plasma samples from patients had titers considered at baseline for seropositivity. In several PML cases, viral persistence and neurological deficits have continued for several years, indicating that once initiated, JCV infection may not entirely clear, even with IRIS. Ann Neurol 2010;68:384–391
Natalizumab dosage suspension: Are we helping or hurting?
Authors: West Timothy W. , Cree Bruce A.C.
Published: September 2010

The risk of developing progressive multifocal leukoencephalopathy increases with the duration of treatment with natalizumab. Planned dosage interruptions have been proposed as a means of decreasing cumulative risk. The clinical consequences of dosage interruption were evaluated in a single center cohort of natalizumab‐treated patients. Medical records were reviewed for 84 patients identified with multiple sclerosis who received 12 or more infusions of natalizumab at an academic multiple sclerosis center. Eighty‐one percent (68/84) underwent a dosage interruption, and 19% (16/84) had no interruption in natalizumab treatment. Of those with a treatment interruption, 27.9% (19/68) experienced a clinical relapse within 6 months of the suspension, whereas none of the patients with ongoing treatment experienced a flare during months 12 to 18 of treatment (p = 0.017, Fisher exact test). Survival analysis showed that Kaplan‐Meier curves comparing dosage interruption to ongoing treatment diverged (p = 0.025). Median time from treatment interruption to relapse onset was 3 months. No clinical predictors associated with an increased risk of developing flares during dosage interruption were identified. Among the 19 patients who had a flare, 7 had severe flares, with a mean number of 16 Gad+ lesions on brain magnetic resonance imaging (range, 6–40). Their median Expanded Disability Status Scale at natalizumab interruption was 3.0 and increased to 6.0 during the flare (p = 0.0008). Natalizumab dosage interruption is associated with clinical flares and return of radiographic inflammatory disease activity. Some of these flares can be clinically severe, with a high number of contrast‐enhanced lesions, suggesting a possible rebound of disease activity. Ann Neurol 2010;68:395–399
Broadband study of the scattering of ultrasound by polystyrene‐latex‐in‐water suspensions
Authors: Kaatze U. , Trachimow C. , Pottel R. , Brai M.
Published: September 2010

Ultrasonic absorption spectra have been measured between 0.1 and 2000 MHz of aqueous suspensions of polystyrene latex globules. Samples of different diameter (60 to 100 nm) and different concentration of the polystyrene latex particles (volume fraction between 0.05 and 0.38) have been studied. The broadband spectra exhibit a Debye‐type relaxation term in the frequency range around some MHz and a contribution with special characteristics at higher frequencies. The former term is assumed to be due to counterion effects in the surface layer of the globules. No special attention is payed to this effect. The latter contribution is attributed to scattering and mode conversion mechanisms. An approximate explicit and an exact formulation of the theoretical description of the sound wave attenuation by the scattering process are discussed. The explicit formulation enables valuable insights into the mode conversion mechanisms but does not allow for a complete representation of the measured spectra. Application of the exact version leads to the conclusion that in the frequency range under consideration monopole and quadrupole oscillations of the polystyrene latex globules are the dominant cause of ultrasonic wave attenuation. It is found that even at the elevated concentrations used effects of multiple scattering are of minor importance here.
Impurity spin dynamics and quantum coherence in mesoscopic rings
Authors: Schwab P. , Eckern U.
Published: September 2010

We investigate the effects of impurity spin dynamics on quantum coherence in mesoscopic metallic rings. Spin relaxation induces temporal current fluctuations which are closely related to persistent currents in such systems. The persistent current is suppressed in the presence of magnetic impurities. We discuss spin‐polarisation effects, spin‐glass ordering, and the Kondo effect which are shown to restore the current even in the presence of magnetic scattering.
On the Yang‐Mills effective action with instanton gauge field
Authors: Tinebra F.
Published: September 2010

The calculation of the determinant for the second order covariant derivative operator is analyzed in the space R4 and for Yang‐Mills instanton field configurations. The problems inherent to the ultraviolet ζ‐function renormalization method and infrared divergencies of this operator are reviewed. A method for estimating the asymptotic coefficients of its determinant has been discussed and the failure of the general conformal invariance induced by any regularization technique has also been considered. A particular solution valid for a Yang‐Mills multi instanton configuration, valuable in order to get the non conformally invariant piece of the general solution, is the main result obtained here. We give it as an integral equation, namely in a semi‐explicit form.
Combinatorial computation of Clebsch‐Gordan coefficients
Authors: Schertler Klaus , Thoma Markus H.
Published: September 2010

The addition of angular momenta can be reduced to elementary coupling processes of spin‐‐particles. In this way, a method is developed which allows for a non‐recursive, simultaneous computation of all Clebsch‐Gordan coefficients concerning the addition of two angular momenta. The relevant equations can be interpreted easily, analogously to simple probabilistic considerations. They provide an improved understanding of the addition of angular momenta as well as a practicable evaluation of Clebsch‐Gordan coefficients in an easier way than within the well‐known methods.
Spin‐charge fluctuations in itinerant helical magnets
Authors: Brenig Wolfram
Published: September 2010

Using a generalized random phase approach quantum fluctuations beyond the helical mean‐field states of the Hubbard model off half filling are discussed. The collective mode spectrum is shown to exhibit spin‐charge mixing and is found to be strongly renormalized by coupling to low‐energy incoherent particle‐hole excitations. Results for the collective mode dispersion which displays a significant anisotropy are presented for selected helical phases. Moreover phase space regions of ‘missing’ modes are identified with a finite wave length instability of the helical states suggesting novel inhomogeneous phases of the doped Hubbard model.

P.A.C.S. : 71.27.+a, 75.30.Fv, 75.40.Gb
Properties of the t‐J model in the dynamical mean field theory: One‐particle properties in the antiferromagnetic phase
Authors: Obermeier Thomas , Pruschke Thomas , Keller Joachim
Published: September 2010

We study the one‐particle properties of the t‐J model within the framework of Vollhardt's dynamical mean field theory. By introducing an AB‐sublattice structure we explicitly allow for a broken symmetry for the spin degrees of freedom and are thus able to calculate the one‐particle spectral function in the antiferromagnetic phase. We observe surprisingly rich structures in the one‐particle density of states for T < T N at finite doping up to 15%. These structures can be related to the well known results for one single hole in the Néel background. We are thus able to establish the relevance of this at a first sight academic limit to physical properties of the t‐J model with a finite density of holes in the thermodynamical limit.
Ferromagnetism in the Hubbard model on the square lattice: Improved instability criterion for the Nagaoka state
Authors: Wurth P. , Uhrig G. , Müller‐Hartmann E.
Published: September 2010

The instability of the fully polarized ferromagnetic state (Nagaoka state) with respect to single spin flips is re‐examined for the Hubbard model on the square lattice with a large family of variational wave functions which include correlation effects of the majority spins in the vicinity of the flipped spin. We find a critical hole density of δcr = 0.251 for U = ∞ and a critical coupling of Ucr = 77.7t. Both values improve previous variational results considerably.
Spin waves and static susceptibility in the weakly doped t‐J model
Authors: Vojta Matthias , Becker Klaus W.
Published: September 2010

We investigate the spin dynamics in weakly doped high‐temperature superconductors. The system is described by the two‐dimensional t‐J model. Our focus is on the interaction between mobile holes and spin waves. The calculations are based on a recently introduced cumulant method for computing the ground state energy of correlated electronic systems. Contrary to previous works using dynamical quantities like correlation functions or spectral densities our approach contains a static view to the system. This new method treats spin and hole dynamics on the same basis and allows for the calculation of static and dynamical quantities. We present results for spin‐wave energies and transverse static susceptibilities for small hole concentrations and various values of t/J. We find a strong renor‐malization of the spin‐wave energies due to the spin‐hole interaction. In agreement with neutron scattering experiments the spin‐wave velocity vanishes at a critical hole density of a few percent which is equivalent to the instability of the antiferromagnetic order.
Coulomb interactions in Al doped FeSi at low temperatures
Authors: Friemelt K. , Ditusa J. F. , Bucher E. , Aeppli G.
Published: September 2010

A metal‐insulator transition is observed in Al doped FeSi. For samples in the metallic region, a T1/2 contribution to the low temperature conductivity is found. An analysis based on the Coulomb interaction model in disordered systems is presented to explain this behavior. It is shown that the sum of Coulomb interactions and localization theories yields the best description of the results.
High resolution neutron scattering study of low‐energy magnetic excitations in Nd2‐xCexCuO4
Authors: Loewenhaupt M. , Metz A. , Pyka N. M. , Paul D. McK. , Martin J. , Duijn V. H. M. , Franse J. J. M. , Mutka H. , Schmidt W.
Published: September 2010

The low‐energy magnetic excitations (ħω ≤ 2 meV) of polycrystalline samples of Nd2‐xCexCuO4 with x = 0, 0.1 and 0.15 have been measured with high resolution inelastic neutron scattering using time‐of‐flight technique at temperatures below 0.3 K. All observed scattering originates from transitions within the ground state doublet of Nd3+. For Nd2CuO4 the response is inelastic, and shows at least three different modes, of which one is almost dispersionless. For x = 0.1 the excitation spectrum shifts towards lower energies, but the main features of the undoped compound are still visible, whereas for x = 0.15 the response is mainly quasi‐elastic but remains localised in Q‐space around the first magnetic Bragg point (0.5 0.5 1). A comparison with data obtained on a triple‐axis‐spectrometer on single crystals with x = 0.0 and x = 0.15 reveals that the response of the doped sample in the [0 0 1] direction is still inelastic.
Disorder in ballistic systems: A numerical analysis
Authors: Altland Alexander , Loosen Roland
Published: September 2010

We present a numerical analysis of the single particle energy spectra of ballistic condensed matter systems and compare with recent theoretical results. We show that the presence even of weak disorder induces full chaoticity on time scales larger than the elastic disorder scattering time. To disentangle the effect of boundary, respectively disorder scattering on the spectral statistics, different types of correlation functions are introduced and discussed.
Striped phase in the cuprates as a semiclassical phenomenon
Authors: Zaanen Jan , Oleś Andrzej M.
Published: September 2010

The striped phase, a novel type of electron solid, has been observed recently in a number of doped Mott‐Hubbard insulators (including cuprates). This solid consists of a parallel array of charged‐domain walls, bound states of carriers and Néel walls in the antiferromagnetic spin system. The existence of these states has been predicted well in advance of their experimental observation on the basis of semiclassical (‘Hartree‐Fock’) theory. Nevertheless, it is not at all clear whether semiclassics yields a correct explanation. In this paper we will focus especially on the variety of striped phases realized in the cuprates, characterized by a domain wall filling of half a hole per domain wall unit cell. We will unfold the reasons why semiclassics, as applied to simple Hubbard models, favours strongly a filling of one hole per domain wall unit cell, as is for instance the case in the nickelates. Nevertheless, the occurrence of half‐filled walls as semiclassical ground states cannot be excluded on general grounds. It might be that Hubbard models do not incorporate the microscopic situation correctly. Instead, we derive a qualitative criterion: in order to acquire a special stability on the semiclassical level, the half‐filled domain walls should be characterized by a quadrupling of the period along the walls, involving a modulation in the longitudinal spin‐ and/or charge channel.

64.60. ‐ i, 71.27. + a, 74.72. ‐ h, 75.10. ‐ b
Influence of boundary conditions on the ordering of elastic dipoles
Authors: Schotte Klaus‐Dieter , Topalis Panagiotis , Schotte Ursula
Published: September 2010

We consider elastic dipoles in several two‐dimensional geometries. Using Cauchy integral techniques and the image method, the state of elastic equilibrium under different boundary conditions can be determined. The results are used to find the ground state of systems of anisotropic dipoles via the simulated annealing method. Only in the case of fixed boundaries the ordering depends on the boundary condition.
Quasiclassical approach to impurity effect on magnetooscillations in 2D metals
Authors: Mirlin A. D. , Altshuler E. , Wölfle P.
Published: September 2010

We develop a quasiclassical method based on the path integral formalism, to study the influence of disorder on magnetooscillations of the density of states and conductivity. The treatment is appropriate for electron systems in the presence of a random potential with large correlation length or a random magnetic field, which are characteristic features of various 2D electronic systems presently studied in experiment. In particular, we study the system of composite fermions in the fractional quantum Hall effect device, which are coupled to the Chem‐Simons field and subject to a long‐range random potential.
Anomalous peak effect in heavy‐fermion, intermediate‐valence and A15 superconductors: Evidence for a Fulde‐Ferrell‐Larkin‐Ovchinnikov state?
Authors: Gegenwart P. , Deppe M. , Köppen M. , Kromer F. , Lang M. , Modler R. , Weiden M. , Geibel C. , Steglich F. , Fukase T. , Toyota N.
Published: September 2010

An experimental study based upon magnetic and dilatometric measurements is presented for the clean high‐κ superconductors UPd2Al3, CeRu2 and V3Si. All three compounds show an enhanced spin susceptibility. Their superconducting state is strongly Pauli limited, and an anomalous peak effect is observed at T<(0.8‐0.9)Tc, slightly below Hc2(T). This phenomenon appears to be qualitatively consistent with a first‐order transition between weak and collective pinning, caused by the formation of a staggered order parameter in a generalized Fulde‐Ferrell‐Larkin‐Ovchinnikov phase (M. Tachiki et al., Z. Phys. B, in press).
D‐wave superconductivity: New paradigm?
Authors: Maki Kazumi , Won Hyekyung
Published: September 2010

As the 10th anniversary of the discovery of high Tc cuprate superconductors by Bednorz and Müller is approaching, a simple picture of high Tc cuprates based on d‐wave superconductivity is emerging. Here we shall describe the effect of impurity scattering and compare with experiments on Zn‐substituted LSCO and YBCO. We shall discuss some characteristics of the vortex state in d‐wave superconductor. In a magnetic field parallel to the c axis a square vortex lattice tilted by 45° from the a axis is stable, which have been seen experimentally though elongated in the b direction in monocrystals of YBCO.
Electronic structure calculations and strong correlations: A model study
Authors: Runge Erich , Zwicknagl Gertrud
Published: September 2010

Metals with strong correlations are a major challenge for realistic electronic structure calculations. The complexity of the systems under consideration precludes a direct fully microscopic treatment by means of the theoretical and computational methods available at present. The present paper analyzes the applicability and restrictions of common approximation schemes by comparing their predictions for a model pertinent to heavy fermion metals to the exact solution. The criteria chosen for the assessment are the density distribution in the ground state as well as the energy scale for low‐lying excitations.
Towards an incremental expansion of strong correlation effects in solids
Authors: Stoll Hermann
Published: September 2010

A scheme based on local correlation‐energy increments, which has been applied successfully to the investigation of dynamical correlation effects in semiconductors and ionic crystals, is extended here to include non‐dynamical (static) electron correlation as well. It is shown how to use abinitio multi‐configuration self‐consistent‐field and multi‐reference configuration‐interaction calculations for this purpose, and test applications are reported for potential curves of molecules at the dissociation limit.
Two Anderson impurities in the framework of the non‐crossing approximation: Spectral functions and spin correlations
Authors: Schiller A. , Zevin V.
Published: September 2010

Using a novel slave boson mapping, which was recently proposed by us for two Anderson impurities embedded in a metal, we present here spectral functions for all pseudoparticles involved in the mapping. These were numerically calculated in the framework of the Non‐Crossing Approximation for different temperatures and inter‐impurity distances, both for the degenerate (Nf = 6) and nondegenerate (Nf = 2) models. For the nondegenerate case, temperature dependencies of the partial occupancies and the spin‐spin correlation function suggest that an antiferromagnetic (AFM)‐like ground state is formed at suitable inter‐impurity separation. By contrast, Kondo quenching of the impurity moments takes place for the isotropic Nf = 6 case even when a direct AFM interaction is introduced in order to amplify the indirect (inherent) one. Numerical calculations are in agreement with our previous prediction [Phys. Rev. B 47, 14,297 (1993)] that no AFM‐like ground state can appear for two isotropic degenerate impurities.
Microcanonical thermodynamics of first order phase transitions studied in the potts model
Authors: Gross D. H. E. , Ecker A. , Zhang X. Z.
Published: September 2010

Phase transitions of first and second order can easily be distinguished in small systems in the microcanonical ensemble. Configurations of phase coexistence, which are suppressed in the conventional canonical formulation, carry important information about the main characteristics of first order phase transitions like the transition temperature, the latent heat, and the interphase surface tension. The characteristic backbending of the microcanonical caloric equation of state T(E) (not to be confused with the well known Van der Waals loops in ordinary thermodynamics or mean field approximations) leading to a negative specific heat is intimately linked to the interphase surface entropy.
Single ion description of photoemission spectra of metallic cerium systems
Authors: Hüfner S.
Published: September 2010

The conflicting evidence presented for and against the single ion description of photoemission data of metallic cerium compounds is analysed. It can be shown that for low TK materials the single ion description of photoemission spectra (in the cluster or Anderson‐Hamiltonian approximation) of metallic cerium compounds is valid. However, some of the thermal effects seen in the photoemission spectra are caused either by the temperature dependence of the Fermi function or by coupling to phonons.
Heavy fermions and superconductivity in doped cuprates
Authors: Tornow Sabine , Zevin Vilen , Zwicknagl Gertrud
Published: September 2010

We present a Fermi liquid description for the low‐energy excitations in rare earth cuprates Nd2‐xCexCuO4. The strongly renormalized heavy quasiparticles which appear in the doped samples originate from the coherent decoupling of rare earth spins and correlated conduction electrons. The correlations among the conduction electrons are simulated by assuming a spin density wave ground state. We discuss results for the thermodynamic properties in the insulating, normal metallic and superconducting phases which are in fair agreement with experimental data. In addition, the model predicts interesting behaviour for the superconducting state of samples with low transition temperature Tc which may help to assess the validity of the underlying assumptions.
The Anderson transition in conjugated polymers
Authors: Markoš P. , Evangelou S. N.
Published: September 2010

We study the electronic transport properties of mutually connected wires with loops in a “spaghetti”—like morphology by transfer matrix scaling methods. We obtain the conductance of the system and show the existence of an Anderson metal‐insulator transition. Our results are discussed in connection with recent experiments in conjugated polymers.
Correlated hyperspherical harmonics: Application to systems of three bosons
Authors: Zickendraht W. , Levinger J. S.
Published: September 2010

We study the use of expansions in correlated hyperspherical harmonics to calculate the energy of the ground state of a system of three identical spinless bosons, for a model potential. In our model the potential is the sum of a harmonic oscillator and an inverse square repulsion of variable strength. We find excellent convergence.
Strategies for reproduction and ageing
Authors: Bernardes A. T.
Published: September 2010

The process of accumulation of deleterious mutations is the fundamental reason of ageing, according to the evolutionary theory. In this theory, the individuals better fitted to reproduce will suffer this accumulation in adulthood or old age. We present results obtained from Monte Carlo simulations of the Penna model dealing with the influence of environmental conditions in the reproductive regimes and its consequences on the population ageing: longevity and catastrophic senescence. Moreover, the role of antagonistic pleiotropy in the time evolution is discussed. A puzzling experimental result obtained in species with gender differentiation is the existence of different survival probabilities for males and females. This matter is discussed here in the context of antagonistic pleiotropy.
Decrease of soft vibrational modes with increasing density of two‐level states in the metallic glass Zr‐Rh
Authors: Junge B. , Gey W.
Published: September 2010

Experiments are reported on the specific heat below 1 K of 13 melt quenched ZrRh alloys in the superconducting state (Tc>4.2 K) where electronic degrees of freedom are frozen out. Large differences of the quasilinear (two‐level system, TLS) contributions given by λTLS occur with no correlation to the rhodium concentration. The coefficient α of the cubic, phonon‐type term is found to decrease with the density of TLS for this metallic glass. This is counter‐intuitive to the soft‐potential model and differs from the relation found for insulating glasses.