bluuebunny/crossref_metadata_2025_split huggingface dataset:
“Sponge‐like” structures in polymer blends: visualization, physico‐mathematical analysis, and universality
Authors: Hashimoto Takeji , Jinnai Hiroshi , Nishikawa Yukihiro , Koga Tsuyoshi 
Published: February 2003

AbstractMesoscopic structures formed during an ordering process in thermodynamically unstable, isometric, binary molecular mixtures were explored by time‐resolved scattering (TRS) and laser scanning confocal microscopy (LSCM). Three‐dimensional (3D) bicontinuous structures, which were constructed for the first time by time‐resolved LSCM, were found to have a “sponge‐like” structure composed of two phases. The structure factor obtained by 3D Fourier transformation of the sponge was found to be identical to that obtained by TRS, confirming that the sponge truly reflects the structural entities evolving in the system. Furthermore, the sponge was shown for the first time to be theoretically predictable by using 3D computer simulations based on the time‐dependent Ginzburg‐Landau theory. The sponge was subjected to differential geometrical analysis: its Gaussian curvature K, mean curvature H, and their distributions were successfully determined for the first time. The result revealed that the sponge has hyperbolic interfaces with area‐averaged curvatures satisfying <K> < 0 and <H > ≅ 0 and that its interface has some deviations from a minimal surface. The sponge was found to be strikingly similar to that occurring in oil/water/surfactant systems at the hydrophile‐lipophile‐balance, though their characteristic length scales are diversely different (μ vs nm), implying universality of the sponge.
On the mixed finite element method with Lagrange multipliers
Authors: Babuška Ivo , Gatica Gabriel N. 
Published: February 2003

AbstractIn this note we analyze a modified mixed finite element method for second‐order elliptic equations in divergence form. As a model we consider the Poisson problem with mixed boundary conditions in a polygonal domain of R2. The Neumann (essential) condition is imposed here in a weak sense, which yields the introduction of a Lagrange multiplier given by the trace of the solution on the corresponding boundary. This approach allows to handle nonhomogeneous Neumann boundary conditions, theoretically and computationally, in an alternative and usually easier way. Then we utilize the classical Babuška‐Brezzi theory to show that the resulting mixed variational formulation is well posed. In addition, we use Raviart‐Thomas spaces to define the associated finite element method and, applying some elliptic regularity results, we prove the stability, unique solvability, and convergence of this discrete scheme, under appropriate assumptions on the mesh sizes. Finally, we provide numerical results illustrating the performance of the algorithm for smooth and singular problems. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 192–210, 2003
Viral respiratory infections in young children attending day care in urban Northeast Brazil
Authors: Souza Leda Solano de Freitas , Ramos Eduardo Antônio Gonçalves , Carvalho Fernando Martins , Guedes Virgínia Maria Castro Ribeiro , Souza Lídia Silva , Rocha Cristiane Machado , Soares Andréa Barreto , Velloso Luciana de Freitas , Macedo Izolete Santos , Moura Fernanda Edna Araujo , Siqueira Marilda , Fortes Silvana , Jesus Cibele Cruz de , Santiago Christiane Maria Gaspar , Carvalho Ana Maria da Silva , Arruda Eurico 
Published: February 2003

AbstractA cohort of children attending a day care center in Salvador (Bahia, Brazil) was studied prospectively to determine the incidence of viral respiratory infectious episodes and to identify the viruses associated with them. Two hundred seventy‐one nasopharyngeal samples were collected over a 1‐year period for examination, using indirect immunofluorescence with monoclonal antibodies against adenovirus, influenza A and B, parainfluenzae 1–3, and respiratory syncytial virus, and reverse transcriptase‐polymerase chain reaction for picornavirus.Examination yielded positive results in 116 samples (42.8%). Rhinovirus was identified alone in 56 samples (48.3%) and was observed along with other viruses in 11 additional samples. Incidence density of viral respiratory infectious episodes was 7.66 episodes/1,000 child‐days. Pediatr Pulmonol. 2003; 35:184–191. © 2003 Wiley‐Liss, Inc.
Chest physiotherapy in infants with cystic fibrosis: To tip or not? A five‐year study
Authors: Button Brenda M. , Heine Ralf G. , Catto‐Smith Anthony G. , Olinsky Anthony , Phelan Peter D. , Ditchfield Michael R. , Story Ian 
Published: February 2003

AbstractThere is controversy about the need for postural drainage physiotherapy in asymptomatic infants with cystic fibrosis (CF). We aimed to compare the effectiveness of standard postural drainage chest physiotherapy (SPT) with a modified physiotherapy regimen without head‐down tilt (MPT) in young infants with CF. Twenty newly diagnosed infants with CF (mean age, 2.1 months; range, 1–4) were randomized to SPT or MPT. Parents kept a detailed symptom and treatment diary for the following 12 months. Serial chest radiographs, taken at diagnosis, 12 months, 2½ years, and 5 years after diagnosis, were assessed using the Brasfield score. Pulmonary function tests were compared between groups after 5 years. Of the 20 infants, 16 (80%) completed the review at 12 months, and 14 (70%) at 2½ and 5 years. Patients receiving SPT had more days with upper respiratory tract symptoms than those on MPT (70 ± 32.8 vs. 37 ± 24.9 days; P = 0.04) and required longer courses of antibiotics (23 ± 28.5 vs. 14 ± 11.2 days; P = 0.05). Chest x‐ray scores were similar at diagnosis but were worse at 2½ years for those receiving SPT (P = 0.03). Forced vital capacity and forced expired volume in 1 sec (FEV1) at 5–6 years was lower for SPT than for MPT (P < 0.05). In conclusion, MPT was associated with fewer respiratory complications than SPT in infants with CF. Pediatr Pulmonol. 2003; 35:208–213. © 2003 Wiley‐Liss, Inc.
Chronic interstitial lung disease with lung fibrosis in a girl: Uncommon sequelae of Epstein‐Barr virus infection
Authors: Ankermann Tobias , Claviez Alexander , Wagner Hans‐Joachim , Krams Matthias , Riedel Frank 
Published: February 2003

AbstractA 12‐month‐old immunocompetent girl presented with tachypnea, inspiratory crackles, mild hypoxemia, and failure to thrive after an acute Epstein‐Barr virus (EBV) infection. The course of acute EBV infection was demonstrated by viral load measurement in plasma and peripheral blood mononuclear cells (PBMC) by using real‐time polymerase chain reaction (PCR). EBV DNA was further detected by PCR in bronchoalveolar lavage (BAL) fluid and from a lung‐tissue specimen obtained by open‐lung biopsy, which indicates the pulmonary involvement of active EBV infection. Histology revealed an uncharacteristic interstitial infiltration and fibrosis. Following topic and systemic treatment with corticosteroids, the child became asymptomatic and showed normal weight gain as well as mental and physical development. Pulmonary parenchymal involvement during the course of primary EBV infection may result in interstitial lung disease and fibrosis not only in immunodeficient, but in immunocompetent children as well. Treatment with combined inhaled and oral steroids seems to be a treatment option in these patients. Pediatr Pulmonol. 2003; 35:234–238. © 2003 Wiley‐Liss, Inc.
Forced expiratory parameters in healthy preschool children (3–6 years of age)
Authors: Zapletal A. , Chalupová J. 
Published: February 2003

AbstractIn a group of 173 healthy preschool children 3–6 years of age (body height, 90–130 cm; 102 boys and 71 girls) out of total 279 children examined, maximum expiratory flow‐volume (MEFV) curves were recorded in cross‐sectional measurements. The majority (62%) of preschool children were able to generate an MEFV curve as correctly as older children. From the curves, maximum expiratory flows at 25%, 50%, and 75 % of vital capacity (MEF25, MEF50, and MEF75), peak expiratory flow (PEF), forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC), and area delineated by MEFV curve (Aex) were obtained. The purpose of the study was to establish reference values of forced expiratory parameters in preschool children suitable for assessment of lung function abnormalities in respiratory preschool children. The values of the studied parameters increased nonlinearly and correlated significantly with body height (P < 0.0001); the correlation was much lower with age. A simple power regression equation was calculated for the relationship between each parameter and body height. A best‐fit regression equation relating functional parameters and body height was a power function. Based on the obtained regression equations with upper and lower limits, we prepared tables listing reference values of forced expiratory parameters in healthy Caucasian preschool children, against which patients can be compared. No statistically significant gender differences were observed for MEF25, MEF50, MEF75, PEF, FEV1, FVC, and Aex by extrapolation. The reference values were close to those obtained in our older children. A decline of the ratios PEF/FVC, FEV1/FVC and MEF/FVC with increasing body height suggested more patent airways in younger and smaller preschool children. Pediatr Pulmonol. 2003; 35:200–207. © 2003 Wiley‐Liss, Inc.
High pressure study of the electrical transport phenomena in AlGaN/GaN heterostructures
Authors: Consejo Ch. , Konczewicz L. , Contreras S. , Jouault B. , Łepkowsky S. , Zielinski M. , Robert J. L. , Lorenzini Ph. , Cordier Y. 
Published: February 2003

AbstractThe effect of pressure on electrical transport phenomena has been studied in AlGaN/GaN heterostructures grown on Si substrates. The two‐dimensional character of the conducting carriers has been verified with high magnetic field measurements (up to 13 T) at low temperature (T = 1.5 K). The two‐dimensional electron gas (2DEG) concentration and mobility were measured as a function of hydrostatic pressure up to 1100 MPa and at different temperatures. The observed pressure changes of the free carrier concentration have been compared with theoretical predictions, taking into account the polarization change in the nitrides and using a fully self‐consistent resolution of Schrödinger and Poisson equations.
Tight binding modelling of band offsets in GaN and ZnSe based heterostructures
Authors: Ünlü H. 
Published: February 2003

AbstractWe present a new nonorthogonal sp3 tight binding model to study the band offsets of widegap heterostructures as a function of interface strain due to external pressure and lattice mismatch and thermal expansion gradient. As examples we discuss the GaN and ZnSe based heterostructures, because their properties are important for optoelectronic applications. Good agreement is found between theory and experiment for valence band offsets of various heterostructures at T = 300 K.
Calculated high pressure crystal structure transformations for phosphorus
Authors: Ahuja Rajeev 
Published: February 2003

AbstractIn this paper we have studied the structural stability of the sp bonded element, P, by means of the first principles calculations. The theoretical calculations made use of a full potential linear muffin‐tin orbital (FPLMTO) method adopting the local density approximation to the density functional theory. We reproduce the observed crystallographic phase stability of P as a function of compression. Our results confirm the recent experimental finding of Akahama et al. We have also proposed a new structure for an experimentally reported unidentified intermediate phase in between simple cubic and simple hexagonal phase. This new structure is similar to what has been observed for Si. We have explained the stability of different phases under pressure using our calculated density of states (DOS).
William Paul: a scientist, a teacher, and a friend
Authors: Cardona Manuel 
Published: February 2003

AbstractThe author belongs to the first generation of graduate students Bill Paul supervised at Harvard. He learned from Bill the physics of semiconductors, especially under high pressure, and also how to manage a research group. Last, but not least, he also learned from him the rules of ethics of the scientific endeavor which seem to be often forgotten in recent times. The “Bill Paul Experience” left a permanent imprint on the speaker's future career. After a short biographical sketch, the article discusses the scientific lineage of Bill Paul and presents a bibliometric analysis of his publications. This is followed by a discussion of what the speaker and the Institute of Scientific Information (ISI) believe are Bill's most important contributions to Semiconductor Science, in particular the application of high pressure to the investigation of the band structure of semiconductors and the wide field of amorphous materials.
Variation of the optical absorption edge in AgGaS2 single crystals at high pressure
Authors: Power Ch. , Gilliland S. , Segura A. , Gonzalez J. 
Published: February 2003

AbstractIn this paper the optical absorption edge of AgGaS2 is measured as a function of pressure up to 26 GPa in order to verify the effect of the three phases transitions occurring in that pressure domain. The direct energy gap increases linearly with pressure at the rate of about 4.0 × 10–2 eV GPa–1 up to 10.2 GPa. The absence of any discontinuity in the energy gap in the pressure range of 4.10.2 GPa confirms that the volume change, in the chalcopirite to monoclinic second‐order transition, if it exists, is very small. When the pressure is raised above 10.2 GPa, the energy gap drops suddenly by about 1.1 eV and the spectral form of the absorption coefficient is typical of semiconductors with indirect‐gap transitions. This is consistent with the transition to the orthorhombic‐type structure and the pressure coefficient of the band gap is –7.5 × 10–2 eV GPa–1. In the pressure range 226 GPa (NaCl‐type phase) the pressure coefficient is about –1.7 × 10–2 eV GPa–1. When we released the pressure to atmospheric values, we observe a red shift in the recovered sample of about 1 eV and after annealing to 24 hours at 500 K the band gap does not revert to its original value.
Ammonium halides NH4Cl, NH4F, and NH4Br
Authors: Tikhomirova G. V. , Babushkin A. N. 
Published: February 2003

AbstractThe resistance of ammonium chloride (NH4Cl), fluoride (NH4F) and bromide (NH4Br) is investigated at pressures from 20 to 50 GPa in the temperature range 7400 K. The transition from high‐resistance to low‐resistance state was found at pressures of about 15 GPa for NH4Br, 27 GPa for NH4Cl, and 42 GPa for NH4F, respectively. The characteristic temperature and pressure of the transition are shown to depend on the duration of the pressure treatment. All the ammonium halides show metal‐like behaviour under high pressures similar to that of alkali halides. The non‐monotonic temperature dependence of the resistivity, which disappears after sufficiently long pressure treatment, indicates the existence of intermediate states.
Pressure evolution of the phonon modes and force constants of Tb3Al5O12 and Lu3Al5O12
Authors: Papagelis K. , Arvanitidis J. , Ves S. , Kourouklis G. A. 
Published: February 2003

AbstractThe pressure evolution of the Raman modes of Tb3Al5O12 and Lu3Al5O12 has been measured at room temperature and analyzed theoretically with the rigid ion model. Satisfactory agreement between experiment and theory has been found. The extracted pressure variation of the bond bending and bond stretching force constants shows that the compressibility of the various polyhedra types increases with increasing cation coordination, indicating that the dodecahedra play an important role in the compressibility of the garnet structure. Finally, an estimation of the pressure coefficients for the transverse optical infrared active mode frequencies is given.
Pressure behavior of Te isoelectronic centers in S‐rich ZnS1–xTex alloy
Authors: Li G. H. , Fang Z. L. , Su F. H. , Ma B. S. , Ding K. , Han H. X. , Sou I. K. , Ge W. K. 
Published: February 2003

AbstractThe photoluminescence from ZnS1–xTex alloy with 0 < x < 0.3 was investigated under hydrostatic pressure up to 7 GPa. Two peaks were observed in the alloys with x < 0.01, which are related to excitons bound to isolated Te isoelectronic impurities (Te1 centers) and Te pairs (Te2 centers), respectively. Only the Te2 related emissions were observed in the alloys with 0.01 < x < 0.03. The emissions in the alloys with 0.03 < x < 0.3 are attributed to the excitons bound to the Ten (n ≥ 3) cluster centers. The pressure coefficient of the Te1 related peak is 89(4) meV/GPa, about 40% larger than that of the band gap of ZnS. On the other hand, the pressure coefficient of the Te2 related emissions is only 52(4) meV/GPa, about 15% smaller than that of the ZnS band gap. A simple Koster–Slater model has been used to explain the different pressure behavior of the Te1 and Te2 centers. The pressure coefficient of the Te3 centers is 62(2) meV/GPa. Then the pressure coefficients of the Ten centers decrease rapidly with further increasing Te composition.
On the elastic properties of InAs under hydrostatic pressure
Authors: Ellaway S.W. , Faux D.A. 
Published: February 2003

AbstractThe effective elastic stiffnesses C11 and C12 of InAs are determined as a function of hydrostatic pressure by atomistic simulation. Both C11 and C12 are found to increase linearly with pressure. Other quantities such as the Young's modulus, C44, the axial strain and the anisotropy coefficient are nearly independent of pressure. Frogley et al. proposed that non‐linear elasticity is required to explain anomalous band‐gap pressure coefficients through an approximately linear increase in the two‐dimensional Poisson's ratio [Phys. Rev. B 62, 13612 (2000)]. Our calculations confirm the increase in the two‐dimensional Poisson's ratio. Results are in good agreement if the experimental value of C′11, the pressure derivative of the elastic stiffness, is used. It is suggested that experimental data for band‐gap pressure coefficients might be used to improve the quality of atomistic interatomic potentials for the III–V semiconductors.
LiH under high pressure and high temperature: A first‐principles study
Authors: Wang Y. , Ahuja R. , Johansson B. 
Published: February 2003

AbstractThe behaviours of LiH under high pressure and high temperature are studied using first‐principles calculation. We have studied the pressure dependence of the electronic energy band gap as well as possible insulator‐metal phase transition. We have calculated temperature, heat capacity, and equation‐of‐state along the principal Hugoniot. The calculated results agree well with the experiments.
Hydrostatic pressure dependence of recombination mechanisms in GaInNAs, InGaAsP and AlGaInAs 1.3 μm quantum well lasers
Authors: Sweeney S. J. , Jin S. R. , Tomić S , Adams A. R. , Higashi T. , Riechert H. , Thijs P. J. A. 
Published: February 2003

AbstractFrom measurements of the threshold current and lasing energy as a function of pressure in InGaAsP/InP, AlGaInAs/InP and GaInNAs/GaAs based multiple quantum well lasers we determine the relative importance of the monomolecular, radiative and Auger recombination processes. For the InP based devices, we find that a simple combination of radiative and non‐radiative Auger recombination can fully explain the pressure dependence of the threshold current where the threshold carrier density is approximately constant as a function of pressure. For the GaInNAs/GaAs devices we observe a large increase in threshold current with pressure. This we show is due to the interaction of the nitrogen level with the conduction band which gives rise to an increased conduction band effective mass resulting in an increase in threshold carrier density of ∼12% over 10 kbar. This large increase in nth increases the monomolecular, radiative and unusually, the Auger recombination current with pressure explaining the large increase in threshold current with pressure.
Pressure effects on transition metal monoxide NiO
Authors: Ishida Y. , Mita Y. , Kobayashi M. , Endo S. 
Published: February 2003

AbstractRaman and absorption measurements under high pressure were performed in NiO single crystals at room temperature. A drastic increase of the absorption intensity was observed in the whole visible range. Furthermore, the intensity of a defect induced Raman peak located around 500 cm–1 becomes remarkably, especially at 25 GPa. Neither of the spectral changes recover even after removing the pressure. These results indicate that a permanent lattice disorder is introduced. The remarkable spectral changes are explained to be a result of defects (especially singly charged nickel vacancies) introduced by a deformation of the crystal due to the non‐hydrostatic compression.
Electronic structure and optical properties of CdTe rock‐salt high pressure phase
Authors: Güder H. S. , Gilliland S. , Sans J. A. , Segura A. , González J. , Mora I. , Muñoz V. , Muñoz A. 
Published: February 2003

AbstractThis paper reports on optical absorption and reflectance measurements in thin CdTe samples up to 15 GPa. All studied samples become virtually opaque at the pressure transition between the zinc‐blende and rock‐salt phases (3.9 GPa). As pressure increases up to 10 GPa, a relative transparency region is observed between 1.2 eV and 2.4 eV, whose high energy edge shifts to higher photon energies. Above 10 GPa the transparency region gradually shrinks and disappears at about 11 GPa. The low energy side of the absorption spectrum is attributed to free carrier absorption, as electronic structure calculations show that rock‐salt CdTe is a semimetal or a low gap semiconductor. Band filling effects lower the band‐to‐band absorption coefficient and give rise to a “transparency” range, whose upper energy side is assigned to the direct transition at the Γ point, on the basis of its pressure coefficient. The shrinking and disappearance of the transparency region, along with a large increase of the reflectance in the mid infrared, is interpreted as the occurrence of a phase transition to the Cmcm metallic phase.
Coupling of large optical loss with Auger recombination in 1.3 μm InGaAsP lasers investigated using hydrostatic pressure
Authors: Jin S. R. , Sweeney S. J. , Adams A. R. , Thijs P. J. A. 
Published: February 2003

AbstractInGaAsP lasers with different losses have been investigated under hydrostatic pressure at room temperature. It is shown that, for large loss devices, the threshold current decreases more rapidly with increasing pressure than the expected variation of the typical direct band‐to‐band Auger recombination currents. We also measured the spontaneous emission in a large loss device to determine the pressure dependence of the respective recombination current component at laser threshold. It is found that the Auger current reduces strongly and the radiative current also decreases with increasing pressure. This is attributed to a reduction of the total loss coupled with Auger recombination with pressure.