bluuebunny/crossref_metadata_2025 huggingface dataset:
Synaptic process in the rat (Rattus norvegicus): Influence of methodology on results
Authors: Martínez‐Flores I. , Cabero LL. , Egozcue J. , Garcia M.
Published: February 2003

Synaptonemal complex (SC) analysis is a widely used method for assessing the effects of genotoxic agents in germ cells. Although the evolution of the SCs and their related annexed structures, such as nucleoli, has been well established, sometimes it is difficult to assess whether the abnormal features observed correspond to genotoxic effects or to an artefact related to the method used to obtain the SC preparations. In this article, we describe a new method of obtaining SC preparations for electron microscopy, as well as the results of a study of the first meiotic prophase in oocytes and spermatocytes of the rat (Rattus norvegicus Sprague Dawley) in which we analysed how the methodology used can influence the results. Besides important sex‐specific differences, mainly during desynapsis (diplotene), a relationship between several bivalents and nucleolar structures, that in some cases could disturb the synaptic process, was observed in oocytes. At the same time, the characteristic SC fragmentation in oocytes was verified, but this fragmentation, in addition to a sex‐specific component, was influenced by the method itself. By reducing to a minimum the artefacts produced by the method, it is possible to optimise the analysis of SCs as a method of testing genotoxic effects in the germ line. Microsc. Res. Tech. 60:450–457, 2003. © 2003 Wiley‐Liss, Inc.
Molecular structure of the adelite group of minerals—a Raman spectroscopic study
Authors: Martens Wayde , Frost Ray L. , Williams Peter A.
Published: February 2003

The application of Raman microscopy to the study of closely related mineral phases of the adelite group has allowed their molecular characterization. The adelite group of minerals are orthorhombic arsenates and vanadates of general formula AB2+(XO4)(OH), where X may be As5+or V5+, cation A may be Ca or Pb and cation B may be Co or Cu and others. Raman spectroscopy has proven most powerful for the identification of these minerals. In particular, the position of the hydroxyl stretching vibrations and most of the arsenate bands have been identified. The two minerals tangeite and calciovolborthite have previously been identified as the same mineral. Raman spectroscopy has proven that the minerals are not identical and have different structures. The application of Raman spectroscopy to the study of these minerals shows that increased distortion of the arsenate anion occurs as the cationic substitution from conichalcite to austinite to duftite occurs. Copyright © 2003 John Wiley & Sons, Ltd.
Spectral investigations on 2‐methyl‐3‐chloromethyl‐1,4‐naphthoquinone and 2,3‐bis(chloromethyl)‐1,4‐naphthoquinone under laser excitation
Authors: Umadevi M. , Vanelle P. , Terme T. , Ramakrishnan V.
Published: February 2003

Solvent effects on 2‐methyl‐3‐chloromethyl‐1,4‐naphthoquinone and 2,3‐bis(chloromethyl)‐1,4‐naphtho‐ quinone were investigated using optical absorption and fluorescence emission techniques and the orientation of 2‐methyl‐3‐chloromethyl‐1,4‐naphthoquinone on a silver surface was studied by surface‐enhanced Raman scattering (SERS). The observed spectral shift and the bandwidth of the optical absorption spectrum reveal the changes in dipole moment and the solvent reorganization energy in the excited state. The observed fluorescence quantum yield influences the weak intermolecular hydrogen bond and the dipole–dipole interaction in the excited state. Fluorescence polarization measurements provide the faster rotational relaxation of 2‐methyl‐3‐chloromethyl‐1,4‐naphthoquinone and 2,3‐bis(chloromethyl)‐1,4‐naphthoquinone in the excited state. SERS studies suggest that the orientation of 2‐methyl‐3‐chloromethyl‐1,4‐naphthoquinone on a silver surface is stand‐on. Copyright © 2003 John Wiley & Sons, Ltd.
Validation of a quantitative assay using GC/MS for trace determination of free and conjugated estrogens in environmental water samples
Authors: Mouatassim‐Souali Asmaa , Tamisier‐Karolak Sara L. , Perdiz Daniel , Cargouet Maëlle , Levi Yves
Published: February 2003

It has been shown that sewage effluent can discharge human hormones and pharmaceuticals, particularly estrogens and synthetic chemicals, which are able to disrupt animal and human endocrine systems into surface waters. Since many surface waters receive sewage effluent and are subsequently used to produce drinking water, it is of principal interest to assess their contamination level and thereby their possible public health and environmental impact. To date, no data concerning the occurrence of estrogens present in the French aquatic environment are available. We therefore developed and validated an analytical procedure, which allows simultaneous quantitative determination of three natural estrogens, 17β‐estradiol, estriol, and estrone and one of the synthetic estrogens most widely used in contraception, ethinylestradiol, in water. Water samples are extracted using solid‐phase extraction (SPE) and then separated by gas‐chromatography coupled with mass spectrometric detection. Under our conditions, detection limits of estrogens reached the pg range of injected sample, i. e. less than 0.1 ng L–1. Conjugated estrogens were also investigated using the same procedure as described above but with a enzymatic hydrolysis preliminary step before extraction. The analysis of samples collected from four wastewater treatment plants and from surface water showed significant concentrations of estrogens ranging from 2 to 18 ng L–1 and from 0.5 to 3 ng L–1, respectively. Furthermore, no estrogen conjugated forms were detected in the water samples.
Thermal modulator array for analyte modulation and comprehensive two‐dimensional gas chromatography
Authors: Burger Ben V. , Snyman Tertia , Burger Wina J. G. , van Rooyen Willie F.
Published: February 2003

Segmented thermal modulators were fabricated for the modulation of column effluent in one‐dimensional gas chromatography, comprehensive two‐dimensional gas chromatography, and as sample introduction devices in other analytical techniques. Thermal desorption of analytes from the modulator was achieved by computer‐controlled application of large DC currents at low voltages sequentially to consecutive segments or stages of the modulator heaters for periods between 100 and 400 ms per segment. This procedure produced sharply focussed analyte peaks. Unsegmented heaters and heaters having 2, 4, 6, 8, and 10 segments or stages were compared with respect to their focusing efficiency. The 10‐stage heater was found to give sharper focusing than heaters with a smaller number of segments. Analyte pulses with peak widths at half‐height of ca. 150 ms were generated by the 10‐stage heater. The application of a 10‐stage modulator in a comprehensive two‐dimensional analysis of a light petroleum condensate gave results of acceptable quality.
Impedance measurements on oxide films on aluminium obtained by pulsed tensions
Authors: Belmokre K. , Azzouz N. , Hannani A. , Pagetti J.
Published: February 2003

We have performed this study on oxide films sealed or not in boiling water. The films are first obtained on type 1050 A aluminium substrat by pulsed tensions anodizing technique, in a sulfuric acid solution.

Afterwards the, Electrochemical Impedance Spectroscopy (EIS) is employed to appreciate the films behaviour in a neutral solution of 3.5% K2SO4, in which the interface processes interest only the ageing phenomenon of the oxide films and not their corrosion. We have also attempted a correlation between pulse parameters of anodization and the electrical parameters characterizing these films. The sealing influence on ageing has been studied as well.

For all films, ageing is appreciated using impedance diagrams evolution versus time.

The results show:

– the existence of two capacitive loops confirming the presence of two oxide layers characteristic of oxide films obtained in a sulfuric acid medium. The first loop, at high frequencies, is related to the external porous layer and the second one, at lower freqencies, is related to the internal barrier layer.

– the thickness of the barrier layer varies between 25 and 40 nm in relation with the electrical pulse parameters.

– the sealing acts favorably against anodic oxide films ageing.
Flow‐accelerated corrosion behavior of SA106 Gr. C weldment
Authors: Kim J. H. , Kim I. S. , Zheng Y. G.
Published: February 2003

Chemical and geometrical effects of weld on flow‐accelerated corrosion (FAC) of SA106 Gr.C low alloy steel pipe was investigated using rotating cylinder electrode in 3.5‐wt% sodium chloride solution and simulated feedwater of nuclear power plants. Polarization tests and weight loss tests were conducted at rotating speed of 2000 rpm (3.14 m/s) with variation of chemical and geometric parameters. The results showed that the chemical effects were relatively larger than the geometrical effects, and the welded parts became local anode and preferentially corroded, which was explained by the differences between microstructural and compositional parameters. On the other hand, under active corrosion conditions, the heat affected zone was severely corroded and microstructural effects were dominant.
Dielectric Response of Aramid Fiber‐Reinforced PEEK
Authors: Korbakov Nina , Harel Hannah , Feldman Yuri , Marom Gad
Published: February 2003

Dielectric spectroscopy was applied for the first time to aramid fiber‐reinforced PEEK, wherein the effect of the fiber on the dielectric response was examined for both amorphous and crystalline poly(ether ether ketone) (PEEK) over wide temperature and frequency ranges. Whereas the temperature behavior of the dielectric losses of the materials exhibited the typical α and β processes of PEEK, the specific effect of the fibers in the crystalline PEEK was revealed in shifting the α process to a higher temperature. The unique effect of the fibers was expressed by a significantly higher activation energy and lower dielectric strength for the α relaxation, reflecting a higher constraint level that is imposed by the fiber. It is proposed that this additional constraint is associated with fiber generated transcrystallinity.

Scanning electron micrograph of transverse fracture surface of crystallized unidirectional aramid fiber‐reinforced PEEK.

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Scanning electron micrograph of transverse fracture surface of crystallized unidirectional aramid fiber‐reinforced PEEK.
Dynamic Light Scattering of Semi‐Dilute Hydrophobically Modified Alkali‐Soluble Emulsion Solutions with Varying Length of Hydrophobic Alkyl Chains
Authors: Dai S. , Tam K. C. , Jenkins R. D.
Published: February 2003

Dynamic light scattering as well as rheological technique was used to study the semi‐dilute hydrophobically modified alkali‐soluble emulsion (HASE) solutions. The solution viscosity increases dramatically, when the overlap concentrationC*is exceeded. Two diffusional modes are evident from the decay time distributions of light scattering and they are related to the hydrodynamic correlation length and the apparent hydrodynamic radius of the HASE clusters. The hydrodynamic correlation lengths, as determined from the fast diffusion mode decrease in proportion to the polymer concentrations but increase with increasing the hydrophobicity of the hydrophobes of the macromonomers. The apparent hydrodynamic radii of the clusters, as determined from the slow diffusion mode, increase with increasing polymer concentrations. When the carbon number of the hydrophobes is increased from C1to C8, both the viscosities and diffusion coefficients of the slow mode remain almost unchanged. However, they are strongly dependent on the carbon chain length when the carbon number exceeds C12, especially for the polymer with C20alkyl chains. The solution viscosities decrease and diffusion coefficients of the slow mode increase with increasing temperatures, however, the parameters ofDη/Tremain constant.

Comparison of microstructures of semi‐dilute HASE solutions with (a) short hydrophobic alkyl groups and (b) long hydrophobic alkyl groups was made. For (a) with small hydrophobes, the aggregation number per association junction is smaller and there are more aggregation junctions in the network cluster. The hydrodynamic correlation length,ξh, which is the averaged distance between two aggregation junctions, is shorter. As for (b) with larger hydrophobes, the aggregation number is larger with fewer aggregation junctions in the network cluster. The hydrodynamic correlation length is longer.

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Comparison of microstructures of semi‐dilute HASE solutions with (a) short hydrophobic alkyl groups and (b) long hydrophobic alkyl groups was made. For (a) with small hydrophobes, the aggregation number per association junction is smaller and there are more aggregation junctions in the network cluster. The hydrodynamic correlation length,ξh, which is the averaged distance between two aggregation junctions, is shorter. As for (b) with larger hydrophobes, the aggregation number is larger with fewer aggregation junctions in the network cluster. The hydrodynamic correlation length is longer.
Synthesis of Well‐Defined Poly(methyl methacrylate) by a Normal Atom‐Transfer Radical Polymerization Procedure with a New Catalyst, Cuprous N,N‐Diethyldithiocarbamate
Authors: Li Peng , Qiu Kun‐Yuan
Published: February 2003

Cuprous N,N‐Diethyldithiocarbamate, Cu(S2CNEt2), was successfully used as a catalyst in p‐toluenesulfonyl chloride initiating atom‐transfer radical polymerization of methyl methacrylate in both bulk and solution in a heterogeneous system with 2,2′‐bipyridine as the ligand. The polymerization was controlled under various concentration ratios of the monomer to initiator, the molecular weight matched the predetermined value, and the molecular weight distribution of resulting polymers was quite low (Mw/Mn < 1.10). Solvents with different polarity had no significant effect on the living nature of this process. Well‐defined poly(methyl methacrylate) with α‐p‐toluenesulfonyl and ω‐diethylthiocarbamoylthiyl group was obtained. That the polymer chain was capped with an ultraviolet light sensitive group was confirmed by chain extension reactions.

Dependence of Mn and Mw/Mn on the monomer conversion of bulk polymerization of MMA at 80 °C with p‐TsCl/Cu(S2CNEt2)/bpy initiation system. Conditions the same as in Figure 5.

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Dependence of Mn and Mw/Mn on the monomer conversion of bulk polymerization of MMA at 80 °C with p‐TsCl/Cu(S2CNEt2)/bpy initiation system. Conditions the same as in Figure 5.
Hydrogen Bonding Interaction and Miscibilization of Ternary Blends of Poly(2‐vinylpyridine), Poly(N‐vinyl‐2‐pyrrolidone), and 4,4′‐(1,4‐Phenylenediisopropylidene)bisphenol
Authors: Li Xue‐Dong , Goh Suat H.
Published: February 2003

The interaction energy densities of poly(2‐vinylpyridine) (P2VPy)/4,4′‐(1,4‐phenylenediisopropylidene)bisphenol (PDIPBP) blend and poly(N‐vinyl‐2‐pyrrolidone) (PVP)/PDIPBP blend were determined using melting point depression method. The interaction between PVP and PDIPBP is stronger than that between P2VPy and PDIPBP. Wide‐angle X‐ray diffraction study revealed that PDIPBP crystallizes out from the polymer/PDIPBP blends at high PDIPBP contents. The phase equilibrium calculation supports that the single‐Tg behavior is a result of miscibilization rather than an overlap of two close Tg's of two separated phases. The critical miscibilization content of PDIPBP obtained from spinodal phase boundary calculation is lower than the saturation content, and therefore, there is enough PDIPBP in the amorphous phase to miscibilize P2VPy and PVP. Scanning electron microscopy showed a drastic reduction in domain size in single‐Tg blends.

Ternary phase diagram of P2VPy/PVP/PDIPBP blends. (○) miscible blends; (•) immiscible blends; (— × —) calculated phase boundary (Coordinate in volume fraction).

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Ternary phase diagram of P2VPy/PVP/PDIPBP blends. (○) miscible blends; (•) immiscible blends; (— × —) calculated phase boundary (Coordinate in volume fraction).
Novel Fluorinated Hybrid Polymer by Radical Polyaddition of Bis(α‐trifluoromethyl‐β,β‐difluorovinyl) Terephthalate onto Dialkoxydialkylsilanes
Authors: Fujiwara Hirotada , Narita Tadashi , Hamana Hiroshi , Horie Naohiro
Published: February 2003

To develop the radical polyaddition of bisperfluoroisopropenyl esters, the reactions of bis(α‐trifluoromethyl‐β,β‐difluorovinyl) terephthalate [CF2C(CF3)OCOC6H4COOC(CF3)CF2] (BFP) with dialkoxydialkylsilane were examined to prepare fluorinated hybrid polymers bearing dialkylsilyl groups in the main chain. Prior to polyaddition, the radical addition reaction of 2‐benzoyloxypentafluoropropene [CF2C(CF3)OCOC6H5] (BPFP) has been investigated to afford the results that diethoxydimethylsilane (DEOMS) or dimethoxydimethylsilane with BPFP initiated by oxo radical are the best combination for the preparation of polymers. The mechanism of the addition reaction was proposed. Radical polyaddition of BFP with DEOMS initiated by benzoyl peroxide or di‐tert‐butyl peroxide has yielded polymers of up to molecular weight 1 × 106 with rather broad molecular weight distribution. A mechanism for the polyaddition reaction is proposed based on the radical addition reaction between BPFP and DEOMS. The step‐growth polymerization is initiated by hydrogen abstraction of DEOMS to add a perfluoroisopropenyl group, followed by a 1,7‐shift of the radical in the intermediate. The relationship between addition reaction mechanism and polyaddition mechanism was also discussed.

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Two‐Photon Pattern Bleaching for Characterizing Structural Changes in Polymer Films
Authors: Van Keuren Edward , Schrof Wolfgang
Published: February 2003

Using two‐photon absorption, an array of spots in a dye‐doped polymer film can be bleached, creating a three‐dimensional structure that can be imaged with two‐photon or confocal microscopy. Microscopic deformations resulting from various treatments to the film can be characterized, for example, swelling or shrinking. This technique is demonstrated on dye‐doped poly(vinyl alcohol), in which the effect of swelling with the addition of water to the film is shown.

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An Infrared Approach toward Measuring the Thickness of Polyelectrolyte Films
Authors: Montrel Michael M. , Stroustrup Nicholas
Published: February 2003

IR spectroscopy is applied to study polyelectrolyte films of 0.1–5 μm thickness. This approach permits to obtain not only the usual chemical information about polymer conformation, chemical bonds, interacting groups, and molecular/ionic state, but also important structural parameters of the film, such as total thickness, average thickness of each layer, and sparseness of polymer packing. All these information can be obtained from one single sample.

IR cell for thickness measurements of a polyelectrolyte film. The pathlength d of the cell is measured twice: before and after film deposition. The film thickness, Δd = de − df, can be calculated using the interference maxima that determine values de and df.

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IR cell for thickness measurements of a polyelectrolyte film. The pathlength d of the cell is measured twice: before and after film deposition. The film thickness, Δd = de − df, can be calculated using the interference maxima that determine values de and df.
SANS from adsorbed polymer layers
Authors: King Stephen , Griffiths Peter , Hone John , Cosgrove Terence
Published: February 2003

One of the areas in which small‐angle neutron scattering (SANS) has had a profound impact over the last twenty years is the investigation of polymers and surfactants adsorbed at the solid/liquid and liquid/liquid interfaces. This is of course also an area of considerable commercial importance. Control of the structure of an adsorbed layer is thus a key priority of the colloid scientist. Equally important, however, is the ability to probe the arrangement of the adsorbed polymer molecules and to extract quantitative information from what might well be a complex, multicomponent system. SANS in combination with the principle of deuterium contrast variation is uniquely placed to provide this information.
A few remarks on classic problems of scattering by polymer solutions and mixtures
Authors: Benoît Henri , Jannink Gérard
Published: February 2003

The problem of scattering by multicomponent systems has been the object of many papers. Here it will be shown that the scattering can be split into two terms, one corresponding to the compressibility of the system and the other depending only on fluctuations of the number of molecules of different constituents. In neutron scattering on samples far from critical conditions, the compressibility term is negligible. In the second part, a simple demonstration of the random phase approximation theorem is proposed, which makes the theorem more understandable for nonspecialists.
Linear, branched and hyperbranched macromolecules in dilute solution
Authors: Ganazzoli Fabio
Published: February 2003

We report some theoretical results obtained for star polymers and dendrimers under different solvent conditions using the Gaussian self‐consistent approach. The focus is mainly on the model assumptions and approximations, and on the results. We discuss the Θ state in terms of both the Θ temperature and the molecular size, and then we consider the good‐solvent conditions also through the intramolecular dynamics.
The crystallization and melting of linear polyethylene studied by temperature‐modulated SAXS and WAXD
Authors: Goderis Bart , Reynaers Harry , Koch Michel H.J.
Published: February 2003

Temperature‐reversible and ‐irreversible morphological events could be separated in the case of linear polyethylene during quasi‐isothermal crystallization by using simultaneous temperature‐modulated synchrotron SAXS and WAXD. Crystallization and subsequent annealing was followed at 126 °C for 90 min while applying a temperature modulation with an amplitude of 1 °C and a period of 2 min. The crystal growth rate associated with the irreversible part of the crystallization decreases with increasing temperature in a cycle. The crystalline lamellae irreversibly thicken with time. The actual crystallite thickness, however, exhibits a superimposed modulation out of phase with that of the temperature modulation. Melting was studied during heating at 1 °C/min after cooling at 10 °C/min. A temperature modulation was superimposed with an amplitude of 2 °C and a period of 3 min. Once again temperature‐reversible crystal thickness changes and irreversible crystal thickening could be observed.
“Sponge‐like” structures in polymer blends: visualization, physico‐mathematical analysis, and universality
Authors: Hashimoto Takeji , Jinnai Hiroshi , Nishikawa Yukihiro , Koga Tsuyoshi
Published: February 2003

Mesoscopic 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  < 0 and  ≅ 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

In 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

A 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

There 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

A 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

In 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

The 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

We 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

In 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

The 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

In 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

The 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

The 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

The 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

The 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

The 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

From 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

Raman 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

This 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

InGaAsP 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.
Protein‐metal ion interactions, stoichiometries and relative affinities determined by on‐line size exclusion gel filtration mass spectrometry
Authors: Benson Linda M. , Kumar Rajiv , Cavanagh John , Naylor Stephen
Published: February 2003

The modulation of metal ions on protein function is well recognized and of paramount importance in protein biochemistry. To date, very few methods allow direct determination of protein‐metal ion interactions, as well as exact stoichiometric binding ratios. In this work we demonstrate the usefulness of two on‐line size exclusion gel filtration mass spectrometry approaches to directly detect protein‐metal ion adducts, as well as determine exact protein‐metal ion stoichiometries. We show that on‐line size exclusion column chromatography (SEC) and rapid in‐line desalting (RILED) coupled to microelectrospray mass spectrometry (μESI‐MS) can be used for such analyses. The SEC approach can be effectively used to both separate proteins in a complex mixture and exchange buffers prior to the electrospray process. While RILED does not allow for protein separation, it provides a much faster high‐throughput desalting procedure than the conventional SEC technique. Specifically, we show that SEC/μESI‐MS and RILED/MS can be used to determine calcium ion binding stoichiometries to a high‐affinity, metal ion binding protein, calbindin D28K. Furthermore, the same approaches can also be used to determine metal ion binding stoichiometries of low‐affinity metal‐binding proteins such as Spo0F. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of unknown compounds in azithromycin bulk samples with liquid chromatography coupled to ion trap mass spectrometry
Authors: Debremaeker D. , Visky D. , Chepkwony H. K. , Van Schepdael A. , Roets E. , Hoogmartens J.
Published: February 2003

A selective reversed‐phase liquid chromatography/mass spectrometry (LC/MSn) method is described for the identification of azithromycin impurities and related substances in commercial azithromycin samples. Mass spectral data are acquired on an LCQ ion trap mass spectrometer equipped with an atmospheric pressure chemical ionization interface operated in positive ion mode. The LCQ provides on‐line LC/MSn capability, making it ideally suited for identification purposes. In comparison with UV detection, this hyphenated technique provides as its main advantage efficient identification of novel substances without time‐consuming isolation and purification procedures. Using this technique, six novel related substances detected in commercial azithromycin samples have been studied. Copyright © 2003 John Wiley & Sons, Ltd.