bluuebunny/crossref_metadata_2025 huggingface dataset:
Dielectric function of antiferroelectric thin films
Authors: Wesselinowa J. M.
Published: May 2005

A Green's function technique is developed to study the real and imaginary parts of the dielectric function ε(k, E) for antiferroelectric thin films below and above Tc. We calculate the two‐particle Green's function 〈〈Sz(k‖)Sz(–k‖)〉〉 beyond the random phase approximation taking into account the coupling between the transverse and the longitudinal relaxing mode. The dependence on temperature and film thickness is discussed and compared with the experimental data. Due to stronger damping effects in thin films the peak of the dielectric function becomes broader with decreasing film thickness. The temperature, where the dielectric function offers a maximum, can decrease or increase in dependence on the strength of the exchange interaction parameter. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Picosecond ultrasonic measurement of the velocity of phonons in water
Authors: Shelton L. J. , Yang F. , Ford W. K. , Maris H. J.
Published: May 2005

We report measurements of the sound velocity as a function of temperature in water using the picosecond acoustic interferometry technique. We show that this method can be used to make velocity measurements on very small sample volumes. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Avoiding Degeneracy in Multidimensional Unfolding by Penalizing on the Coefficient of Variation
Authors: Busing Frank M. T. A. , Groenen Patrick J. K. , Heiser Willem J.
Published: May 2005

Multidimensional unfolding methods suffer from the degeneracy problem in almost all circumstances. Most degeneracies are easily recognized: the solutions are perfect but trivial, characterized by approximately equal distances between points from different sets. A definition of an absolutely degenerate solution is proposed, which makes clear that these solutions only occur when an intercept is present in the transformation function. Many solutions for the degeneracy problem have been proposed and tested, but with little success so far. In this paper, we offer a substantial modification of an approach initiated bythat introduced a normalization factor based on thevariance in the usual least squares loss function. Heiser unpublishedthesis, (1981) and showed that the normalization factor proposed by Kruskal and Carroll was not strong enough to avoid degeneracies. The factor proposed in the present paper, based on the coefficient of variation, discourages or penalizes nonmetric transformations of the proximities with small variation, so that the procedure steers away from solutions with small variation in the interpoint distances. An algorithm is described for minimizing the re-adjusted loss function, based on iterative majorization. The results of a simulation study are discussed, in which the optimal range of the penalty parameters is determined. Two empirical data sets are analyzed by our method, clearly showing the benefits of the proposed loss function.
Likelihood Inference on the Underlying Structure of IRT Models
Authors: Bartolucci Francesco , Forcina Antonio
Published: May 2005

The assumptions underlying item response theory (IRT) models may be expressed as a set of equality and inequality constraints on the parameters of a latent class model. It is well known that the same assumptions imply that the parameters of the manifest distribution have to satisfy a more complicated set of inequality constraints which, however, are necessary but not sufficient. In this paper, we describe how the theory for likelihood-based inference under equality and inequality constraints may be used to test the underlying assumptions of IRT models. It turns out that the analysis based directly on the latent structure is simpler and more flexible. In particular, we indicate how several interesting extensions of the Rasch model may be obtained by partial relaxation of the basic constraints. An application to a data set provided by Educational Testing Service is used to illustrate the approach.
A Note on ROC Analysis and Non-Parametric Estimate of Sensitivity
Authors: Zhang Jun , Mueller Shane T.
Published: May 2005

In the signal detection paradigm, the non-parametric index of sensitivity A′, as first introduced by Pollack and Norman (1964), is a popular alternative to the more traditional d′ measure of sensitivity. Smith (1995) clarified a confusion about the interpretation of A′ in relation to the area beneath proper receiver operating characteristic (ROC) curves, and provided a formula (which he called A′′) for this commonly held interpretation. However, he made an error in his calculations. Here, we rectify this error by providing the correct formula (which we call A) and compare the discrepancy that would have resulted. The corresponding measure for bias b is also provided. Since all such calculations apply to “proper” ROC curves with non-decreasing slopes, we also prove, as a separate result, the slope-monotonicity of ROC curves generated by likelihood-ratio criterion.
Infection by the respiratory syncytial virus in infants and young children at high risk
Authors: Bonnet Damien , Schmaltz Achim A. , Feltes Timothy F.
Published: May 2005

The respiratory syncytial virus is the most common cause of infection of the lower respiratory tract in infants and young children, and is the leading cause of hospitalisation and death due to viral illness during the first year of life. In otherwise healthy infants, the virus usually causes only mild respiratory illness, but premature babies and infants with chronic lung disease, those with congenitally malformed hearts, or those who are immunodeficient, are at increased risk of serious illness, hospitalisation, and death. Recent infection with the virus is also associated with increased postoperative complications after corrective surgery for congenitally malformed hearts. No effective vaccine is currently available, and treatment is limited to supportive therapy. Prevention in groups deemed to be at high-risk, therefore, is essential. In addition to measures for control of infection, prophylactic immunotherapy is indicated in selected patients. Palivizumab (Synagis®) is a monoclonal antibody indicated for the prevention of serious viral disease of the lower respiratory tract in premature infants, those with chronic lung disease, and those with haemodynamically significant congenital cardiac lesions. Palivizumab is given intramuscularly, usually as a monthly injection during the so-called “season”. In a recent international, randomised, double-blind, placebo-controlled trial in 1,287 children less than or equal to 2 years old with haemodynamically significant congenital cardiac malformations, prophylaxis achieved a relative reduction of 45 per cent in the incidence of antigen-confirmed viral-related hospitalisation, and reduced the duration of hospital stay by 56 per cent. National and international guidelines, therefore, now recommend routine prophylaxis in the first year of life in children with haemodynamically significant congenital cardiac disease.
Data from the StEP TWO programme showing the effect on blood pressure and different parameters for obesity in overweight and obese primary school children
Authors: Graf Christine , Rost Sylvia V. , Koch Benjamin , Heinen Sandy , Falkowski Gisa , Dordel Sigrid , Bjarnason-Wehrens Birna , Sreeram Narayanswami , Brockmeier Konrad , Christ Hildegard , Predel Hans-Georg
Published: May 2005

Obesity in childhood, which is associated with cardiovascular risk factors such as hypertension, is on the increase. Countermeasures are necessary. In this paper, we present the baseline and final data from the StEP TWO programme, a prospective study to prevent overweight and obesity in primary schools. Methods: We recorded and calculated, from 1689 children, anthropometric data, including analyses of bioelectric impedance, waist and hip circumferences, body mass index and its standard deviation, and the ratio of waist to hip. Blood pressure was measured after 5 minutes at rest. From the three schools involved in a programme of intervention, 121 children were invited to take part, and 40 (33.1 per cent) completed the programme. The effect was compared with 155 overweight and obese children identified at the 4 control schools. Results: 830 (49.5 per cent) boys and 848 girls (50.5 per cent) took part. Their mean age was 8.2 plus or minus 1.3 years, their height was 1.31 plus or minus 0.09 metres, they weighed 30.0 plus or minus 8.2 kilograms, and their mean index of body mass was 17.1 plus or minus 2.9 kilograms per metre squared. Of the children, 7.3 per cent were obese, 10.4 per cent were overweight, 75.7 per cent had normal weights, and 6.6 per cent were underweight. Resting hypertension was observed in 2.3 per cent of the children. Increased blood pressure was associated with a higher body weight, body mass index, standard deviation score for body mass index, and waist and hip circumferences (each p < 0.001), but not with the ratio of waist to hip. Hypertension at rest was also found in 11.0 per cent of obese children, 4.4 per cent of those who were overweight, 1.2 per cent of those with normal weight, and 1.0 per cent of underweight children (p < 0.001). After the intervention, the increase of the body mass index tended to be lower in those in whom we had intervened (p = 0.069), and in these the decrease of the standard deviation score for body mass index was significantly higher (p = 0.028). Systolic blood pressure was reduced by about 10 millimetres of mercury in those in whom we had intervened (p = 0.002), while there were no changes in the control group. Diastolic blood pressure was lowered by 3 millimetres of mercury, but this was not significant. Conclusion: Obese children had the highest values for systolic and diastolic blood pressure. Increased levels of blood pressure are associated with other parameters of obesity, such as the circumference of the waist and hip. Early preventive measurements in childhood are necessary, and appropriate intervention appears to be effective.
Congenital right atrial diverticulum, atrial septal defect within the oval fossa, and complex pulmonary valvar obstruction in an infant with chromosome 8(p23.1) deletion
Authors: Gengsakul Aungkana , Sett Suvro S. , Hosking Martin C. K.
Published: May 2005

We describe an unusual right atrial aneurysm, occurring with progressive obstruction of the right ventricular outflow tract and increasing cyanosis, in a nine-month-old boy with chromosome 8(p23.1) deletion. Surgical resection of the diverticulum, and relief of the right ventricular obstruction, was successful, although impairment of right ventricular compliance persists after 19 months follow-up.
Idiopathic aneurysm of the inferior caval vein
Authors: Tansel Turkan , Harmandar Bugra , Onursal Ertan
Published: May 2005

Idiopathic aneurysms of the inferior caval vein are uncommon in children and adults. We describe a 14 year old boy with a saccular aneurysm of the inferior caval vein, in whom no surgical intervention was required to repair the aneurysm. The patient is being followed-up periodically for the evaluation of any increase in the diameter of the inferior caval vein.
Suizidalität, Parasuizidalität und selbstverletzende Verhaltensweisen von Patientinnen mit Symptomen einer Borderline-Störung
Authors: Fleischhaker Christian , Böhme Renate , Sixt Barbara , Schulz Eberhard
Published: May 2005

Zusammenfassung. In Deutschland ist Tod durch Suizid die zweithäufigste, in den USA die dritthäufigste Todesursache im Jugendalter. Als Risikofaktoren für vollendete Suizide werden impulsive Handlungsmuster, Selbstverletzungen, Depressionen, Sozialstörungen sowie frühkindlicher Missbrauch benannt. Für Patienten mit einer Borderline-Störung liegt die Suizidrate bei fünf bis zehn Prozent. Die Dialektisch-Behaviorale Therapie (DBT) wurde von Marsha Linehan zur Behandlung von Frauen mit Borderline-Persönlichkeitsstörungen (Diagnosestellung nach DSM-Kriterien) entwickelt, die entweder chronisch suizidal sind und/oder sich selber verletzen. Gegenüber der Standard-DBT wurde für die Arbeit mit Jugendlichen eine Reihe von Modifikationen vorgenommen, um die Behandlung der jugendlichen Zielgruppe anzupassen. Durch unsere Arbeitsgruppe wurde die Dialektisch-Behaviorale Therapie für Adoleszente (DBT-A) für den deutschen Sprachraum überarbeitet und angepasst. In der vorliegenden Arbeit werden die ersten Ergebnisse der DBT-A-Pilotstudie mit zwölf Jugendlichen vorgestellt. Die Ergebnisse sind sehr vielversprechend.
Chronische Krankheiten
Authors: Tröster Heinrich
Published: May 2005

Zusammenfassung. Zur Übersicht über Anforderungen und Belastungen in Familien mit chronisch kranken Kindern und Jugendlichen wird ein allgemeines Rahmenkonzept vorgestellt, das der Familienstresstheorie entlehnt ist. Es beschreibt den Zusammenhang zwischen den potenziellen Stressoren, mit denen Familien mit chronisch kranken Kindern und Jugendlichen konfrontiert sind, den moderierenden und vermittelnden Prozessen, die verantwortlich dafür sind, wie sich die Stressoren auswirken und der psychosozialen Anpassung, die Aufschluss darüber gibt, wie gut es der Familie und den betroffenen Kindern und Jugendlichen gelingt, die Anforderungen und Belastungen zu bewältigen.
Entwicklung eines Fragebogens zur familienbezogenen Lebensqualität (FLQ) für Mütter mit chronisch kranken Kindern
Authors: Tröster Heinrich
Published: May 2005

Zusammenfassung. Zur Entwicklung eines Fragebogens zur familienbezogenen Lebensqualität von Müttern mit chronisch kranken Kindern wurden Aussagen zusammengestellt, die bedeutsame Aspekte des persönlichen Wohlbefindens von Müttern, die durch die Betreuung und Versorgung ihres Kindes in die Familie eingebunden sind, beinhalten. Die Überprüfung der Faktorenstruktur des Fragebogens zur familienbezogenen Lebensqualität (FLQ) an zwei Stichproben von Müttern mit epilepsiekranken Kindern ergab drei gut interpretierbare Faktoren, auf deren Grundlage drei Subskalen gebildet wurden (Entlastung und Selbstverwirklichung, Energie und Aktivität, Sozialer Rückhalt in der Familie). Zur Überprüfung der Validität des FLQ wurden Zusammenhänge mit familiären Stressoren (kritische Lebensereignisse, krankheitsbedingte Anforderungen, Funktionsbeeinträchtigungen und Verhaltensauffälligkeiten des Kindes), der mütterlichen Belastung (psychovegetative Stresssymptome, PSI), dem mütterlichen Coping und der Funktionsfähigkeit der Familie ermittelt. Der FLQ war weitgehend unabhängig von den objektiven Anforderungen, die sich für die Mütter aus den familiären Stressoren ergeben. Substanzielle Zusammenhänge ergaben sich mit der mütterlichen Belastung, der familiären Funktionsfähigkeit und der Adaptivität des mütterlichen Copings.
Belastungserleben, Krankheitsbewältigung und gesundheitsbezogene Lebensqualität der Eltern von Kindern mit atopischer Dermatitis
Authors: Terpitz Corinna , Tröster Heinrich , Rothert Carsten , Schöne Dietmar , Disch Rainer , Noeker Meinolf
Published: May 2005

Zusammenfassung. Theoretischer Hintergrund: Eltern von Kindern mit atopischer Dermatitis (AD) fühlen sich häufig durch die Erkrankung belastet und in ihrer Lebensqualität eingeschränkt. Neurodermitisschulungen für die Eltern zielen nicht nur darauf ab, den Hautzustand der Kinder, sondern auch die gesundheitsbezogene Lebensqualität der Eltern zu verbessern. Fragestellung: In dieser Studie sollten die Schulung der Eltern von Kindern mit AD im Rahmen der stationären Rehabilitation evaluiert und Determinanten des Rehabilitationserfolgs identifiziert werden. Methode: In einer Längsschnittuntersuchung wurden 68 Eltern von Kindern mit AD (Alter 0;6 - 7;10 Jahre) zu ihrem Belastungserleben, ihrem Coping und ihrer gesundheitsbezogenen Lebensqualität vor und nach der Schulung befragt. Ergebnisse: Nach der Rehabilitation sind der Hautzustand der Kinder, das Coping und die gesundheitsbezogene Lebensqualität der Eltern verbessert. Eltern mit einer niedrigen Lebensqualität und ungünstigem Coping profitieren am meisten von der Rehabilitation. Die Abnahme dysfunktionaler Kognitionen durch die Schulung ist ein Prädiktor für Verbesserungen der Lebensqualität nach drei Monaten. Schlussfolgerungen: Aus den Ergebnissen lässt sich schließen, dass die Vermittlung von Bewältigungsstrategien im Rahmen einer stationären Rehabilitation einen wichtigen Beitrag zur Verbesserung der Lebensqualität der Eltern leistet.
On the seasonal asymmetry of the diurnal and semidiurnal geomagnetic variations
Authors: Chulliat A. , Blanter E. , Le Mouël J.‐L. , Shnirman M.
Published: May 2005

The diurnal and semidiurnal variations of the geomagnetic field are investigated at 18 observatories using long series of hourly values (up to 97 years at Sitka). The seasonal variations of amplitude of the 12‐hour and 24‐hour lines are obtained for the H and Z components using a 28‐day sliding window. The Fourier analysis is performed using either all days within the window or only the five quietest days. At midlatitudes a strong lack of symmetry about the summer solstice is observed for both lines and both components. This effect is enhanced when selecting quiet days. When averaged over the entire series, the sign of this seasonal asymmetry is the same at 9 out of 10 midlatitude observatories for both lines and for a given component; it is opposite for the H and Z components. Such a coherent seasonal asymmetry is not found at low and high latitudes. At high latitudes a strong annual variation is found inside the polar caps, while a strong semiannual variation is found in the auroral zones. When selecting quiet days, these two effects are weaker, and the seasonal asymmetry becomes comparable to that at midlatitudes. At all latitudes the year‐to‐year variations of the seasonal asymmetry are uncorrelated with solar activity. It is suggested that lower thermospheric winds may have a similar seasonal asymmetry between spring and autumn equinoxes. Such an asymmetry is present in the published literature but has been overlooked. Possible causes for this wind asymmetry are reviewed.
Analysis of waves in Saturn's dayside magnetosphere: Voyager 1 observations
Authors: Lepping R. P. , Sittler E. C. , Mish W. H. , Curtis S. A. , Tsurutani B. T.
Published: May 2005

Magnetic field fluctuations were observed in the data of Voyager 1 on its inbound leg in Saturn's magnetosphere from about 19 to 8.4 Saturn radii, during the interval 7–17 hours before closest approach. These low‐amplitude oscillations had the appearance of irregular micropulsations. The wave periods in the spacecraft frame varied between ≈1 and 20 min with a tendency to be inversely correlated with the field strength. An eigenfunction analysis yielding wave propagation direction as a function of frequency showed that at and near peak frequency two distinct types of waves were present, one propagating along field lines (within 30°) usually at the higher frequencies considered, (4–14) × l0−3 Hz, and the other propagating along (the azimuthal direction in a standard spherical coordinate system) at lower frequencies, (0.8–4) × l0−3 Hz. The power spectral density (in (nT)2/Hz) at the peaks tended to be inversely related to frequency over the full set of frequencies. An interpretation of these results is that Alfven waves are propagating along field lines at the higher frequencies with wavelengths between 1/4 and 1/2 RS. These occur in both the mantle and plasma sheet. The waves traveling along , which are observed to occur in the low‐latitude plasma mantle, are apparently manifestations of rapidly corotating MHD waves with large compressional components and are probably due to the operation of the centrifugal flute instability at the plasma sheet‐mantle boundary. For both types, wave absorption occurs with a high‐frequency cutoff at or near the gyrofrequency of O+ (and/or N+). Our results establish the framework for MHD waves within Saturn's outer magnetosphere, and it is expected that the Cassini mission, for which orbit insertion occurred on 1 July 2004, will add considerably to that presented here.
Numerical modeling of an estuary: A comprehensive skill assessment
Authors: Warner John C. , Geyer W. Rockwell , Lerczak James A.
Published: May 2005

Numerical simulations of the Hudson River estuary using a terrain‐following, three‐dimensional model (Regional Ocean Modeling System (ROMS)) are compared with an extensive set of time series and spatially resolved measurements over a 43 day period with large variations in tidal forcing and river discharge. The model is particularly effective at reproducing the observed temporal variations in both the salinity and current structure, including tidal, spring neap, and river discharge–induced variability. Large observed variations in stratification between neap and spring tides are captured qualitatively and quantitatively by the model. The observed structure and variations of the longitudinal salinity gradient are also well reproduced. The most notable discrepancy between the model and the data is in the vertical salinity structure. While the surface‐to‐bottom salinity difference is well reproduced, the stratification in the model tends to extend all the way to the water surface, whereas the observations indicate a distinct pycnocline and a surface mixed layer. Because the southern boundary condition is located near the mouth the estuary, the salinity within the domain is particularly sensitive to the specification of salinity at the boundary. A boundary condition for the horizontal salinity gradient, based on the local value of salinity, is developed to incorporate physical processes beyond the open boundary not resolved by the model. Model results are sensitive to the specification of the bottom roughness length and vertical stability functions, insofar as they influence the intensity of vertical mixing. The results only varied slightly between different turbulence closure methods of k‐ɛ, k‐ω, and k‐kl.
Correlation between ferromagnetism and hole localization in very thin (Ga,Mn)As epilayers
Authors: Hamaya K. , Kitamoto Y. , Yamazaki Y. , Taniyama T. , Moriya R. , Munekata H.
Published: May 2005

The magnetic and magnetotransport properties of very thin as-grown (Ga,Mn)As epilayers are reported. A 10-nm-thick epilayer shows a marked decrease in the Curie temperature and conductivity. The magnetoresistance (MR) increases with decreasing temperature in the temperature range below 20 K and the MR hysteresis curves show a characteristic feature which is different from that of thicker epilayers. We attribute the characteristic feature to the localization of hole carriers at the surface region of the epilayer.
Magnetoresistance behavior of a magnetic tunnel junction with perpendicularly magnetized Co∕Pd multilayers
Authors: Lim Dongwon , Kim Sungdong , Lee Seong-Rae
Published: May 2005

We investigated perpendicularly magnetized magnetic tunnel junctions (pMTJs) using Co∕Pd multilayers and the effects of multilayer structure on the magnetoresistance. We obtained a tunneling magneto-resistance (TMR) ratio of 12.6% in a pseudo-pMTJ with a 9-nm-thick Pd underlayer. The number of bilayers of Pd∕Co affected the magnetic anisotropy and the junction resistance. The TMR increased with the Pd underlayer because the interface uniformity and interface structure of the tunnel barrier (AlOx) layer were improved. An exchange-biased pMTJ with IrMn had a small TMR because the antiferromagnetic layer increased the resistance of the pMTJ and reduced the spin polarization.
Inverse magnetoresistance in magnetic tunnel junction with a plasma-oxidized Fe electrode and the effect of annealing on its transport properties
Authors: Park Chando , Zhu Jian-Gang , Peng Yingguo , Laughlin David E. , White Robert M.
Published: May 2005

To understand the transport properties of Fe3O4 based magnetic tunnel junctions (MTJ), MTJs with a Fe3O4 electrode prepared by in situ plasma oxidation of a thin Fe film have been fabricated on oxidized silicon wafers with standard photolithography. High resolution transmission electron microscopy (HRTEM) was used to investigate the interface of the MTJs, and the magnetic and electrical transport properties of the MTJs were measured at different temperatures. TEM cross-section micrographs showed that the plasma oxidized Fe layer was directly in contact with the tunnel barrier (AlOx), giving the predicted inverse magnetoresistance (MR). As the temperature was lowered, asymmetry in the MR and magnetic hysteresis (MH) curves appeared. A thin FeO phase at the interface seemed to produce this asymmetry. The effects of annealing on the transport properties are also discussed.
Fabrication of ferromagnetic single-electron tunneling devices by utilizing metallic nanowire as hard mask stencil
Authors: Niizeki T. , Kubota H. , Ando Y. , Miyazaki T.
Published: May 2005

The stacked magnetic tunnel junctions (MTJs) are microfabricated into ferromagnetic single-electron tunneling devices (F-SETs) by using electron-beam lithography. The F-SETs have a couple of small MTJs (30×500nm2–0.1×100μm2), which are connected via a metallic nanowire. The large tunnel magnetoresistance ratio as much as 40% (at RT) and small junction area dependence of the RA (resistance×area) are obtained. The electrostatic energy of F-SETs estimated from the minimum junction area corresponds to the temperature of 1K, which is high enough to observe Coulomb blockade phenomena in a dilution refrigerator.
Current-induced switching in a single exchange-biased ferromagnetic layer
Authors: Chen T. Y. , Ji Y. , Chien C. L. , Stiles M. D.
Published: May 2005

We demonstrate current-induced switching effects in a single exchanged-biased ferromagnetic layer. A nanodomain can be switched within the ferromagnetic layer by a spin-polarized current injected through a point contact. The high resistance of the hysteretic switching is due to the formation of a domain wall between the nanodomain and the rest of the layer. The switching behavior observed in a single layer is a type of spin-transfer torque effect which is the inverse effect of domain-wall magnetoresistance. At room temperature, nonhysteretic switching behavior with a broad switching current density range is observed.
Thermal stability parameters in synthetic antiferromagnetic free layers in magnetic tunnel junctions
Authors: Saito Y. , Sugiyama H. , Inomata K.
Published: May 2005

We conducted a detailed comparative study of thermal stability properties of magnetic tunnel junctions (MTJs) with Ni81Fe19, Co90Fe10, and synthetic antiferromagnetic (Syn-AF) free layers. The properties were investigated using the junction magnetoresistance of current-perpendicular MTJ devices with a word line as probes. The observed sweep-rate-dependent coercivities were analyzed using the Sharrock formula. The results confirmed that the properties of KuV∕kBT values in the MTJs with the Ni81Fe19 free layer is mainly determined by the shape anisotropy, which is not true in the MTJs with the Co90Fe10 and Syn-AF free layers. The study also confirmed that the effective volume of the Syn-AF free layer increased due to the interlayer coupling and that the shape anisotropy in the Syn-AF free layer was less than that in the mono-free layer.
Characterization of CoFeB electrodes for tunnel junctions
Authors: Cardoso S. , Cavaco C. , Ferreira R. , Pereira L. , Rickart M. , Freitas P. P. , Franco N. , Gouveia J. , Barradas N. P.
Published: May 2005

This paper compares structural and magnetic properties of CoFeB thin films and tunnel junction electrodes, with a boron content of 10 at % (CFB10) and 20 at % (CFB20). X-ray diffraction of 20–60 Å thick CoFeB films indicates amorphous structure in the as-deposited state, independent of the B content. The CFB10 films develop a strong (111) texture after annealing at 280 °C, while CFB20 films require annealing at 320 °C. However, films with either composition can remain amorphous upon anneal, if thinner than 40 Å. The crystallization temperature was corroborated by analysis of exchange bias and coercive fields. Tunnel junctions based on CFB10 and CFB20 were fabricated by ion beam and magnetron sputtering, respectively, and patterned down to 1×2μm2. From magnetic measurements, bottom-pinned MnIr∕CFB10 or MnIr∕CFB20 junctions have similar exchange fields upon anneal. For top-pinned structures, week exchange is obtained using CFB20∕MnIr. Synthetic antiferromagnets (CFB∕Ru∕CFB) were also studied. Antiferromagnetic coupling (AF) can be produced with 6–8 Å thick Ru spacers in glass∕CFB10∕Ru∕CFB10 multilayers, while CFB20∕Ru∕CFB20 amorphous structures are only weekly AF coupled. CFB10-based junctions can sustain annealing up to 360 °C without degradation of the magnetic properties of the CFB electrodes and ferromagnetic coupling fields (Hf), while maintaining TMR values of 30%.
Giant magnetoresistive structures based on CrO2 with epitaxial RuO2 as the spacer layer
Authors: Miao G. X. , Gupta A. , Sims H. , Butler W. H. , Ghosh S. , Xiao Gang
Published: May 2005

Epitaxial ruthenium dioxide (RuO2)∕chromiumdioxide(CrO2) thin film heterostructures have been grown on (100)-TiO2 substrates by chemical vapor deposition. Both current-in-plane (CIP) and current-perpendicular-to-plane (CPP) giant magnetoresistive stacks were fabricated with either Co or another epitaxial CrO2 layer as the top electrode. The Cr2O3 barrier, which forms naturally on CrO2 surfaces, is no longer present after the RuO2 deposition, resulting in a highly conductive interface that has a resistance at least four orders of magnitude lower. However, only very limited magnetoresistance (MR) was observed. Such low MR is due to the appearance of a chemically and magnetically disordered layer at the CrO2 and RuO2 interfaces when Cr2O3 is transformed into rutile structures during its intermixing with RuO2.
Segregation in aqueous methanol enhanced by cooling and compression
Authors: Dougan L. , Hargreaves R. , Bates S. P. , Finney J. L. , Réat V. , Soper A. K. , Crain J.
Published: May 2005

Molecular segregation in methanol-water mixtures is studied across a wide concentration range as a function of temperature and pressure. Cluster distributions obtained from both neutron diffraction and molecular dynamics simulations point to significantly enhanced segregation as the mixtures are cooled or compressed. This evolution toward greater molecular heterogenity in the mixture accounts for the observed changes in the water-water radial distribution function and there are indications also of a change in the topology of the water clusters. The observed behavior is consistent with an approach to an upper critical solution point. Such a point would appear to be “hidden” below the freezing line, thereby precluding observation of the two-fluid region.
Low-loss Ca5−xSrxA2TiO12[A=Nb,Ta] ceramics: Microwave dielectric properties and vibrational spectroscopic analysis
Authors: Bijumon Pazhoor Varghese , Sebastian Mailadil Thomas , Dias Anderson , Moreira Roberto Luiz , Mohanan Pezholil
Published: May 2005

Complex perovskite-type Ca5−xSrxA2TiO12[A=Nb,Ta] (0⩽x⩽5) ceramics were prepared by conventional solid-state ceramic route. The crystal structure, microwave dielectric properties, and vibrational spectroscopic characteristics of these materials are reported. The structure and microstructure were investigated by x-ray diffraction and scanning electron microscopy techniques. The microwave dielectric properties were measured in the 3–5-GHz frequency range by the resonance method. Structural evolutions from orthorhombic to an averaged pseudocubic phase, with associated changes in dielectric properties, were observed as a function of composition. The structure-property relationships in these ceramics were established using Raman and Fourier transform infrared spectroscopic techniques. Raman analysis showed characteristic bands of ordered perovskite materials, with variation in both intensity and frequency as a function of composition.
Cathodoluminescence of small silicon nanoparticles under electron-beam excitation
Authors: Abuhassan L. H. , Khanlary M. R. , Townsend P. , Nayfeh M. H.
Published: May 2005

The temperature (300–25K) behavior of visible luminescence from silicon nanoparticles in thin films under electron-beam bombardment [cathodoluminescence (CL)] is reported. Emission signals occur near 420, 450, 630, and 750nm. Unlike cathodoluminescence of fused silica or heavily oxidized porous layers, which is known to fade with cooling, the nanoparticle films are found to exhibit luminescence that variously fade away or grow with cooling. The CL bands of the film are also observed in the photoluminescence spectra under 365- and 254-nm excitations. There is an approximate coincidence of the peak energy observed for the photoluminescence and CL spectra. The temperature behavior of the cathodoluminescence points to a strong contribution from spatial quantum confinement at nanostructures.
A comparative study of optical properties of poly(9,9-dioctylfluorene) and poly(p-phenylenevinylene) oligomers
Authors: Ng M.-F. , Sun S. L. , Zhang R. Q.
Published: May 2005

A systematic study comparing the optical properties of poly(9,9-dioctylfluorene) oligomer (PFO) of different sizes with those of the well-studied poly(p-phenylenevinylene) oligomer (PPV) was carried out using a time-dependent localized density-matrix approach based on intermediate neglect of differential overlap/spectroscopy Hamiltonian. The derived theoretical optical gap for PFO of infinite size is about 2.9 eV, while that of PPV is about 2.7 eV, agreeing well with the experimental data (2.95 and 2.2–2.5 eV, respectively). The actual physical sizes of the lowest excited-state exciton (Wannier exciton) were obtained to be ∼2.5nm (about four repeating units) of PFO while ∼2.7nm for PPV (about five repeating units). The result indicates that the optical properties of PFO would saturate to its bulk behavior at a smaller size than that of PPV. Furthermore, the intensity of band-edge absorption of PFO is similar to that of PPV, suggesting that the PFO oligomer can perform as efficiently as PPV in optoelectronic application.
Artificial control of ZnO nanodots by ion-beam nanopatterning
Authors: Kim Sang-Woo , Ueda Masaya , Funato Mitsuru , Fujita Shigeo , Fujita Shizuo
Published: May 2005

The use of focused ion-beam (FIB) nanopatterning for manipulating self-assembled ZnO nanodots is described. Highly aligned ZnO-nanodot arrays with various periodicities (e.g., 750, 190, and 100 nm) on FIB-nanopatterned SiO2∕Si substrates were prepared by metal-organic chemical-vapor deposition (MOCVD). The artificially assembled ZnO nanodots had an amorphous structure. Ga atoms incorporated into the surface areas of FIB-patterned nanoholes during FIB engraving were found to play an important role in the artificial control of ZnO, resulting in the production of ZnO nanodots on the FIB-nanopatterned areas. The nanodots evolved into single-crystalline dot clusters and rods with increasing MOCVD-growth time. In addition, microphotoluminescence measurements showed that the ZnO-nanodot arrays have low-dimensional quantum characteristics.
Optical properties and electronic structure of polycrystalline Ag1−xCuxInSe2 alloys
Authors: Albornoz J. G. , Serna R. , León M.
Published: May 2005

The dielectric function ε(ω) of polycrystalline bulk samples of the quaternary chalcopyrite semiconductors Ag1−xCuxInSe2 with x=0.0,0.2,0.4,0.6,0.8,1.0 has been determined by spectroscopic ellipsometry in the energy range from 0.5to4.7eV at room temperature. Accurate values of refractive indices n and extinction coefficients k representative of bulk materials are obtained from the data. The value of the main energy gap is very sensitive to the composition and varies from 1.225to1.009eV as x increases (Cu content). The structures observed in ε(ω) have been analyzed by fitting the numerically differentiated experimental spectrum (second derivative) to analytical line shapes. As a result, the energies corresponding to different electronic transitions have been determined as a function of the composition, and they have been identified within the electronic band structure of chalcopyrites.
Quantum integrability of quadratic Killing tensors
Authors: Duval C. , Valent G.
Published: May 2005

Quantum integrability of classical integrable systems given by quadratic Killing tensors on curved configuration spaces is investigated. It is proven that, using a “minimal” quantization scheme, quantum integrability is ensured for a large class of classic examples.
Variational principles for locally variational forms
Authors: Brajerčík J. , Krupka D.
Published: May 2005

We present the theory of higher order local variational principles in fibered manifolds, in which the fundamental global concept is a locally variational dynamical form. Any two Lepage forms, defining a local variational principle for this form, differ on intersection of their domains, by a variationally trivial form. In this sense, but in a different geometric setting, the local variational principles satisfy analogous properties as the variational functionals of the Chern–Simons type. The resulting theory of extremals and symmetries extends the first order theories of the Lagrange–Souriau form, presented by Grigore and Popp, and closed equivalents of the first order Euler–Lagrange forms of Haková and Krupková. Conceptually, our approach differs from Prieto, who uses the Poincaré–Cartan forms, which do not have higher order global analogues.
The effect of growth rates on the microstructures of EuBa2Cu3O7−x films on SrTiO3 substrates
Authors: Lin Y. , Wang H. , Hawley M. E. , Foltyn S. R. , Jia Q. X.
Published: May 2005

We report our detailed studies of the microstructures of EuBa2Cu3O7−x (Eu123) films by using high-resolution x-ray diffraction. Reciprocal space maps show that the growth rate plays an important role in nucleation of a-axis Eu123 films on SrTiO3 (STO) substrates at a given deposition temperature. It is further revealed that a pseudotetragonal distortion often occurs in Eu123 films. This distortion, however, can be eliminated by decreasing the deposition rate. The low mobility of Eu atoms on the STO substrate is suggested to be the main reason for these phenomena.
Geographic Mobility and Residential Instability in Impoverished Rural Illinois Places
Authors: Foulkes Matt , Newbold K Bruce
Published: May 2005

Impoverished rural places are often depicted as immobile communities populated by less skilled, less educated nonmovers who have been left behind by selective out-migrants. Yet certain poor rural localities exhibit high rates of in-migration and residential mobility, an underresearched phenomenon not easily explained by conventional migration theory. The authors explore factors associated with high rates of geographic mobility in impoverished rural localities in Illinois. With the aid of place data from the 2000 Census, the authors test a hypothesized model of geographic mobility within rural impoverished Illinois places. In addition to factors commonly found in the residential mobility literature, such as age distribution, employment security, and life stage, the model also tests the effects of various indicators of housing costs and housing supply on geographic mobility rates in poor and nonpoor places. The results indicate that, after controlling for age structure and household type, accessible housing in the form of rental housing is strongly associated with high mobility rates, though the overall fit of the models is better for nonpoor places. These findings raise questions regarding whether geographic mobility in impoverished places behaves according to long-standing theory, and have implications for policies for tackling rural development, housing, and poverty issues.
Technology in Context: Mediating Factors in the Utilization of Planning Technologies
Authors: Goelman Ari
Published: May 2005

My research explores the question: how can theorists better understand the ways in which planning technologies are used by municipal planners? In the case-study municipality, a recently introduced web-GIS technology had little demonstrable success in attaining two of its stated goals: enabling increased public access to municipal geographic information and encouraging planners to produce their own maps. My research links these outcomes not only to the technologies themselves, but to organizational structure and human agency. Planners and planning theorists can gain additional insight into the impact of planning technologies through closer attention to the process through which planners come to use information technologies and the way this process both alters and is constrained by existing organizational constraints, including previously adopted technologies.
Holliday junction-binding peptides inhibit distinct junction-processing enzymes
Authors: Kepple Kevin V. , Boldt Jeffrey L. , Segall Anca M.
Published: May 2005

Holliday junctions (HJ) are the central intermediates in both homologous recombination and site-specific recombination performed by tyrosine recombinases such as the bacteriophage λ Integrase (Int) protein. Previously, our lab identified peptide inhibitors of Int-mediated recombination that prevent the resolution of HJ intermediates. We now show that two of these inhibitors bind HJ DNA in the square-planar conformation even in the absence of Int protein. The peptides prevent unwinding of branched DNA substrates by the RecG helicase of
Escherichia coli
and interfere with the resolution of HJ substrates by the RuvABC complex. Our results suggest that these peptides target all proteins that process HJ in the square-planar conformation. These inhibitors should be extremely useful for dissecting homologous recombination and recombination-dependent repair
in vitro
and
in vivo
.
Insulin stimulates the halting, tethering, and fusion of mobile GLUT4 vesicles in rat adipose cells
Authors: Lizunov Vladimir A. , Matsumoto Hideko , Zimmerberg Joshua , Cushman Samuel W. , Frolov Vadim A.
Published: May 2005

Glucose transport in adipose cells is regulated by changing the distribution of glucose transporter 4 (GLUT4) between the cell interior and the plasma membrane (PM). Insulin shifts this distribution by augmenting the rate of exocytosis of specialized GLUT4 vesicles. We applied time-lapse total internal reflection fluorescence microscopy to dissect intermediates of this GLUT4 translocation in rat adipose cells in primary culture. Without insulin, GLUT4 vesicles rapidly moved along a microtubule network covering the entire PM, periodically stopping, most often just briefly, by loosely tethering to the PM. Insulin halted this traffic by tightly tethering vesicles to the PM where they formed clusters and slowly fused to the PM. This slow release of GLUT4 determined the overall increase of the PM GLUT4. Thus, insulin initially recruits GLUT4 sequestered in mobile vesicles near the PM. It is likely that the primary mechanism of insulin action in GLUT4 translocation is to stimulate tethering and fusion of trafficking vesicles to specific fusion sites in the PM.
Coatomer-bound Cdc42 regulates dynein recruitment to COPI vesicles
Authors: Chen Ji-Long , Fucini Raymond V. , Lacomis Lynne , Erdjument-Bromage Hediye , Tempst Paul , Stamnes Mark
Published: May 2005

Cytoskeletal dynamics at the Golgi apparatus are regulated in part through a binding interaction between the Golgi-vesicle coat protein, coatomer, and the regulatory GTP-binding protein Cdc42 (Wu, W.J., J.W. Erickson, R. Lin, and R.A. Cerione. 2000. Nature. 405:800–804; Fucini, R.V., J.L. Chen, C. Sharma, M.M. Kessels, and M. Stamnes. 2002. Mol. Biol. Cell. 13:621–631). The precise role of this complex has not been determined. We have analyzed the protein composition of Golgi-derived coat protomer I (COPI)–coated vesicles after activating or inhibiting signaling through coatomer-bound Cdc42. We show that Cdc42 has profound effects on the recruitment of dynein to COPI vesicles. Cdc42, when bound to coatomer, inhibits dynein binding to COPI vesicles whereas preventing the coatomer–Cdc42 interaction stimulates dynein binding. Dynein recruitment was found to involve actin dynamics and dynactin. Reclustering of nocodazole-dispersed Golgi stacks and microtubule/dynein-dependent ER-to-Golgi transport are both sensitive to disrupting Cdc42 mediated signaling. By contrast, dynein-independent transport to the Golgi complex is insensitive to mutant Cdc42. We propose a model for how proper temporal regulation of motor-based vesicle translocation could be coupled to the completion of vesicle formation.
Capacitative calcium entry
Authors: Putney James W.
Published: May 2005

A long-standing mystery in the cell biology of calcium channel regulation is the nature of the signal linking intracellular calcium stores to plasma membrane capacitative calcium entry channels. An RNAi-based screen of selected Drosophila genes has revealed that a calcium-binding protein, stromal interaction molecule (STIM), plays an essential role in the activation of these channels and may be the long sought sensor of calcium store content.
Medroxyprogesterone Acetate Elevation of Nm23-H1 Metastasis Suppressor Expression in Hormone Receptor–Negative Breast Cancer
Authors: Palmieri Diane , Halverson Douglas O. , Ouatas Taoufik , Horak Christine E. , Salerno Massimiliano , Johnson Jennifer , Figg W. Douglas , Hollingshead Melinda , Hursting Stephen , Berrigan David , Steinberg Seth M. , Merino Maria J. , Steeg Patricia S.
Published: May 2005

Background: Reestablishment of metastasis suppressor gene expression may constitute a therapeutic strategy for high-risk breast cancer patients. We previously showed that medroxyprogesterone acetate (MPA), a progestin that has been tested as treatment for advanced breast cancer, elevates expression of the Nm23-H1 metastasis suppressor gene in hormone receptor–negative metastatic human breast carcinoma cell lines in vitro via a glucocorticoid receptor–based mechanism. Here, we tested whether MPA treatment inhibits metastatic colonization of a hormone receptor–negative breast cancer cell line in vivo. Methods: We tested the soft-agar colony-forming efficiency of untransfected MDA-MB-231T human breast carcinoma cells and MDA-MB-231T cells transfected with antisense Nm23-H1 in the presence and absence of MPA. Pharmacokinetic studies were used to establish dose and injection schedules that led to MPA serum levels in mice similar to those achievable in humans. For in vivo studies, nude mice were injected intravenously with MDA-MB-231T cells. After 4 weeks, mice were randomized to control or MPA arms. Endpoints included incidence, number, and size of gross pulmonary metastases; Nm23-H1 protein expression in gross metastases; and side effects. All statistical tests were two-sided. Results: MPA reduced colony formation of MDA-MB-231T cells by 40%–50% but had no effect on colony formation of Nm23-H1 antisense transfectants. Metastases developed in 100% (95% confidence interval [CI] = 78% to 100% and 77% to 100%, respectively) of control mice injected with MDA-MB-231T cells. In two independent experiments, only 73% (95% CI = 45% to 92%) and 64% (95% CI = 35% to 87%) of mice injected with 2 mg of MPA developed metastases. Mice injected with 2 mg of MPA showed reductions in the mean numbers, per mouse, of all metastases and of large (>3 mm) metastases ( P = .04 and .013, respectively). Nm23-H1 was expressed at high levels in 43% of pulmonary metastases in MPA-treated mice but only 13% of metastases in untreated mice. Mice receiving at least 1-mg doses of MPA gained more weight than control-treated mice but exhibited no bone density alterations or abnormal mammary fat pad histology. Conclusion: Our preclinical results show that MPA appears to elevate Nm23-H1 metastasis suppressor gene expression, thereby reducing metastatic colonization. The data suggest a new use for an old agent in a molecularly defined subset of breast cancer patients.