bluuebunny/crossref_metadata_2025 huggingface dataset:
Peripheral airway function in childhood asthma, assessed by single‐breath He and SF6 washout
Authors: Ljungberg Henrik K. , Gustafsson Per M.
Published: August 2003

To assess whether the peripheral airways are involved in pediatric asthma, 10 asthmatic children (aged 8–15 years), hyperresponsive to dry‐air hyperventilation challenge (DACh), performed spirometry and a vital capacity He/SF6 single‐breath washout test at rest, after DACh, and after beta2‐therapy. The normalized phase III slopes (SnIII) of the expired He and SF6 concentrations served as measures of overall ventilation inhomogeneity, and the (SF6 − He) SnIII difference served to indicate where along the peripheral airways obstruction occurs. While a greater increase in the He vs. SF6 slope indicates that obstruction has occurred in the vicinity of the acinar entrance, the reverse suggests obstruction deeper in the intraacinar airways. The mean (SD) fall in FEV1 after DACh was 35 (14)%. Both He and SF6 SnIII increased significantly (P < 0.05) after the challenge, and were restituted after beta2‐therapy (P < 0.05). After DACh, SnIII increased more for He than for SF6, resulting in a negative (SF6 − He) SnIII difference (P < 0.01), which was restituted after beta2‐therapy (P < 0.05). Even though there was no correlation between baseline FEV1 and the magnitude of the subsequent fall in this parameter after DACh (r2 = 0.04; n.s.), a strong correlation was found between the (SF6 − He) SnIII difference at rest and its change after DACh (r2 = 0.81; P < 0.001). We conclude that airways close to the acinar entrance participate in the airway response to DACh in asthmatic children. The magnitude of this peripheral airway response is related to the severity of resting peripheral airway dysfunction. Pediatr Pulmonol. 2003; 36:339–347. © 2003 Wiley‐Liss, Inc.
Severity of acid gastroesophageal reflux assessed by pH metry: Is it associated with respiratory disease?
Authors: Gorenstein Arkadi , Levine Arie , Boaz Mona , Mandelberg Avigdor , Serour Francis
Published: August 2003

About 50% of children with chronic respiratory diseases (RD) have “silent” gastroesophageal reflux (GER). Our purpose was to evaluate the possibility that RD in patients with GER reflects the presence of more severe acid reflux. We compared the severity of parameters from pH studies in children with chronic RD and “silent” GER, to children with signs of symptomatic gastrointestinal (GI) GER with and without RD. This study included 236 children (aged 1 month to 15 years) with abnormal 24‐hr pH monitoring among 718 patients studied for suspected diagnosis of GER. Patients were divided into three groups. Group 1 consisted of children with chronic RD but without any GI symptoms of GER. Group 2 was comprised of children with symptomatic GI presentation of GER such as regurgitation, vomiting, heartburn, and failure to thrive, but without any signs or symptoms of RD. Group 3 included children with prevalent RD and concomitant signs of symptomatic GER. Patients with predominant GI manifestations (group 2) had a significantly higher fraction of time with pH <4 (P < 0.01), total time value of pH <4 (P < 0.05), and longest episode with pH <4 (P < 0.05). Esophageal clearance was significantly longer in group 1 patients than in the other two groups (P < 0.05). Patients with mixed disease (group 3) were similar to patients in group 2. Patients with GI symptoms had significantly worse scores for all parameters evaluated except esophageal clearance score, compared to patients without GI symptoms. Longer esophageal clearance was the only parameter associated with respiratory signs in patients with respiratory symptoms compared to those without. In conclusion, the presence of RD in pediatric patients with silent GER is related to longer esophageal clearance, but is not related to severity of reflux. Pediatr Pulmonol. 2003; 36:330–334. © 2003 Wiley‐Liss, Inc.
Risk factors for recurrent wheezing following acute bronchiolitis: A 12‐month follow‐Up
Authors: Cifuentes Lorena , Caussade Solange , Villagrán Claudia , Darrigrande Paula , Bedregal Paula , Valdivia Gonzalo , Sánchez Ignacio
Published: August 2003

The objective of this study was to identify wheezing recurrences and related risk factors in two groups of infants with bronchiolitis: respiratory syncytial virus (RSV) (+) and RSV (−) as determined by RSV enzyme immunoassay. A 1‐year prospective cohort study was conducted with infants younger than 2 years old. Follow‐up was made monthly, by a clinical visit and/or by telephone, checking the number of wheezing episodes per month and possible related risk factors. There were 96 subjects enrolled, of whom 77 reached complete follow‐up: 36 were RSV (+) (46.8%), and 41 were RSV (−) (53.2%). In the RSV (+) group, there were 17 males (47%), vs. RSV (−) with 30 males (73%) (P < 0.05); 22 RSV (+) (61%) were admitted to hospital, vs.14 RSV (−) (34%) (P < 0.05). Mean age was not significantly different in both groups. The mean number of recurrences was 3.36 episodes/infant/year in the RSV (+) and 2.34 in the RSV (−) group (P = 0.06). Crude relative risk (RR) for a new recurrence of an obstructive episode was 1.33 (95% CI, 0.99–1.79). After adjustment for several potential confounders, the RR was 1.41 (95% CI, 1.03–1.93). Hospitalization stay was longer in the RSV (+) than the RSV (−) group (P < 0.05). In the RSV (+) group, patients who had been hospitalized showed more recurrences (4.18) than those with outpatient treatment (2.07) (P < 0.05); this difference did not exist in the RSV (−) group. The related risk factors for recurrent wheeze in the RSV (−) group were male gender, number of siblings, and daycare attendance (P < 0.05). In the RSV (+) group, the risk of recurrent wheeze was only increased by admission to hospital during the acute bronchiolitis episode (P < 0.05). We speculate that there may be a higher rate of increased airway reactivity and/or preexisting diminished lung function in RSV (+) infants requiring hospitalization for their initial illness. In conclusion, RSV‐proven bronchiolitis, particularly in those infants who are hospitalized, is associated with a higher recurrence of wheezing episodes in the subsequent 12 months. Other factors appear to account for recurrent wheeze in the RSV (−) group. Pediatr Pulmonol. 2003; 36:316–321. © 2003 Wiley‐Liss, Inc.
Severe acute respiratory syndrome in children
Authors: Wong Gary W.K. , Li Albert M. , Ng P.C. , Fok Tai F.
Published: August 2003

Severe acute respiratory syndrome (SARS) is a newly described and highly contagious respiratory infection. Many adult patients will develop progressive hypoxia, and a large proportion will develop respiratory distress syndrome (RDS), possibly related to massive and uncontrolled activation of the immune system. The mortality has been reported to be quite high, especially in the elderly with comorbid conditions. The causative agent has been identified as a novel coronavirus, and children appear to acquire the infection by close‐contact household exposure to an infected adult. However, the severity is much milder and the clinical progression much less aggressive in young children. The exact pathophysiology of SARS is still unclear, and the medical treatment of SARS remains controversial. The main treatment regime used in Hong Kong is a combination of ribavirin and steroid. To date, there have been no reported case fatalities in children with this disease. The success of reducing the burden of this infection in children will depend on proper isolation of infected adults early in the course of illness. Strict public health policy and quarantine measures are the key in controlling the infection in the community. Pediatr Pulmonol. 2003; 36:261–266. © 2003 Wiley‐Liss, Inc.
Perfluorocarbons attenuate oxidative lung damage
Authors: Dani C. , Costantino M.L. , Martelli E. , Corno C. , Fiore G.B. , Buonocore G. , Longini M. , Di Filippo A. , Tozzini S. , Rubaltelli F.F.
Published: August 2003

The aim of this study was to investigate the effect of tidal liquid ventilation (TLV) compared to conventional mechanical ventilation (CMV) on oxidative lung damage in the setting of acute respiratory distress syndrome (ARDS). After repeated lung lavages, 10 minipigs were treated with CMV or TLV for 4 hr before the animals were sacrificed. Samples for blood gas analysis and bronchial aspirate samples were withdrawn before the induction of lung injury, and at 10 min, 2 hr, and 4 hr after the beginning of ventilatory support. To assess lung oxidative damage, total hydroperoxide (TH) and advanced oxidation protein product (AOPP) concentrations were measured in bronchial aspirate samples. After 2 and 4 hr of ventilatory support, partial oxygen tension (PaO2) and base excess (BE) were significantly higher in the TLV group than in the CMV group, while PaCO2 was slightly higher, but with no statistical significance. In the CMV group, the AOPP level was significantly higher at 4 hr than at baseline. TH and AOPP bronchial aspirate concentrations were higher in the CMV group than in the TLV group at 2 and 4 hr of ventilation. We conclude that animals treated with TLV showed lower oxidative lung damage compared to animals treated with CMV. Pediatr Pulmonol. 2003; 36:322–329. © 2003 Wiley‐Liss, Inc.
Synthesis, Structure, Molecular Orbital and Valence Bond Calculations for Tetrazole Azide, CHN7
Authors: Hammerl Anton , Klapötke Thomas M. , Nöth Heinrich , Warchhold Markus , Holl Gerhard
Published: August 2003

The synthesis, NMR spectroscopic characterization and structure determination of highly explosive tetrazole azide, a very nitrogen‐rich material (88.3% N) is reported. Tetrazole azide was prepared in high yield from the diazotation reaction of aminotetrazole, followed by treatment of the formed diazonium salt with sodium azide. Synthesis in diethylether/methanol and recrystallization from diethylether afforded colorless cubes: CHN7 (1): monoclinic, P1 21/n1, a=1346.6(5), b=499.6(2), c=1360.9(5) pm, β=105.14(1)0, V=0.884(2) nm3, Z=8, ϱ=1.670 g cm−3. The observed structural parameters (X‐ray) are in good accordance with the results from molecular orbital (MO) calculations. The computed electrostatic potential (B3LYP) suggests a pronounced shock and friction sensitivity which was confirmed experimentally. Quantitative valence bond (VB) calculations were performed for the most important 21 VB structures in order to obtain the structural weights and to obtain an assessment for the importance of the various individual VB structures considered.
Energetic, Low‐Melting Salts of Simple Heterocycles
Authors: Drake Gregory , Hawkins Tommy , Brand Adam , Hall Leslie , Mckay Milton , Vij Ashwani , Ismail Ismail
Published: August 2003

The synthesis of three new families of heterocyclic‐based salts was undertaken and accomplished. Three triazole systems, 1H‐1,2,4‐triazole, 4‐amino‐1,2,4‐triazole, and 1H‐1,2,3‐triazole, were used as proton bases with nitric (HNO3), perchloric (HClO4), and dinitramidic (HN(NO2)2) acid systems. In all cases, stable salts were recovered and fully characterized by vibrational spectra (IR, Raman), multinuclear NMR spectroscopy, material balance, density measurements, and elemental analyses, as well as DSC, TGA and initial safety testing (impact). Many of these salts have melting points well below 100 °C, yet high decomposition onsets, defining them as new, highly energetic members of the well known class of materials identified as ionic liquids. Additionally, the single crystal X‐ray diffraction study of 1,2,4‐triazolium perchlorate was investigated, revealing the expected structure.
Synthesis, Characterization and Thermal Behaviour of Guanidinium‐5‐aminotetrazolate (GA) – A New Nitrogen‐Rich Compound
Authors: Neutz Jochen , Grosshardt Otto , Schäufele Stephan , Schuppler Heike , Schweikert Wenka
Published: August 2003

This work describes the synthesis and the thermoanalytical characterization of guanidinium‐5‐aminotetrazolate (GA). GA is a new nitrogen‐rich energetic material. It is not mentioned in the chemical literature so far. The molecular structure of the compound has been determined by IR, 1H‐, 13C‐ and 15N‐NMR spectroscopy. The thermal properties, the decomposition pathways and its volatile products were investigated by thermal analysis and are discussed.
Thermal Decomposition of Pentaerythritol Tetranitrate
Authors: Tarver Craig M. , Tran Tri D. , Whipple Richard E.
Published: August 2003

A chemical kinetic model for the thermal decomposition of the solid high explosive pentaerythritol tetranitrate (PETN) is developed for prediction of times to thermal explosion using the Chemical TOPAZ heat transfer computer code. The model is based on times to thermal explosion measured in a new One Dimensional Time to Explosion (ODTX) apparatus. ODTX experiments are reported for pure PETN and for Semtex 1A. The pure PETN results are accurately modeled using a four reaction decomposition process in which an autocatalytic process produces intermediate reaction product gases, which subsequently react in a second order gas phase process to produce the final reaction products. Semtex 1A exhibits longer times to explosion than PETN at low temperatures, indicating that its endothermic binder decomposition absorbs heat produced by PETN decomposition. This binder reaction is modeled as a first order endothermic process. Three experiments on 5.08 cm diameter unconfined cylinders of PETN ramp heated to explosion at different rates are reported. The PETN model accurately predicts the thermocouple records and explosion times for these unconfined experiments in which only intermediate gaseous products can form.
Voids and Density Distributions in 2,4,6,8,10,12‐Hexanitro‐2,4,6,8,10,12‐Hexaazaisowurtzitane (CL‐20) Prepared Under Various Conditions
Authors: Hoffman D. Mark
Published: August 2003

The density distributions of six samples of CL‐20 were measured using the density gradient technique. This technique was used to determine which preparation procedure produced the highest average CL‐20 density. Assuming crystals with fewer flaws result in reduced sensitivity to shock initiation, higher average crystal density (closest to the theoretical maximum density) would imply the least number of voids or inclusions. Based on hot‐spot theory, better crystals, i.e., smaller number of flaws will reduce the shock sensitivity and perhaps other impact initiation mechanisms as well. Six samples from different synthesis and crystallization procedures gave average densities from 2.042 to 2.0230 g/cm3 as measured by density gradient. Assuming the voids have no density, the crystals were between 99.90 to 98.98% of the theoretical maximum density (TMD for ε‐CL‐20 is 2.044 g/cm3). An attempt was made to account for the density difference by identifying voids in the crystals using polarized light microscopy. This method also gave some insight into the different morphologies produced by different crystallization techniques. In 3 cases voids on the order of several micrometers could be resolved in large CL‐20 crystals.
Properties of Gas‐Generating Mixtures Related to Different Fuel and Oxidizer Compositions
Authors: Engelen Karen , Lefebvre Michel H.
Published: August 2003

This work focuses on solid energetic materials designed to produce high‐pressure gas for pressurizing or inflating devices. In small gas generators sodium azide is often used. Unfortunately, this chemical exhibits drawbacks concerning toxicity and yield of gas. Other classical gas‐generating agents are double base propellants. However, they deliver toxic and reactive gases and their combustion temperatures are high. In previous work a series of alternative gas‐generating compositions have been proposed, fuelled with double base propellants, azodicarbonamide, nitroguanidine or guanidine nitrate and oxidized with potassium nitrate or potassium perchlorate. They were theoretically and experimentally evaluated on a series of combustion properties, such as ignition delay, burning rate, vivacity, specific energy, etc. The purpose of this paper is to experimentally examine the gas production of the previously proposed compositions. The yield of gas is determined through static pressure measurements after a closed vessel test, while the composition of the combustion gases is investigated through gas analysis. The addition of an oxidizer causes a significant drop in the yield of gas, but avoids the formation of hazardous gases, such as H2 and CO, in most of the studied cases. The only exception is the mixture of a double base propellant with potassium nitrate: potassium nitrate does not fully react with the double base propellant and therefore the formation of CO and H2 is not prevented.
Polymer Nanocomposites from Energetic Thermoplastic Elastomers and Alex®
Authors: Diaz Emmanuela , Brousseau Patrick , Ampleman Guy , Prud'homme Robert Emery
Published: August 2003

Polymer Nanocomposites (PNs) obtained from linear energetic copolyurethane thermoplastic elastomers (ETPEs) based on GAP and a commercially available nanometric aluminum (Alex) were characterized. Two methods were performed to prepare the PNs: in‐situ and by solvent evaporation. The thermal and mechanical properties of the pure ETPEs, of the composite ETPE/Al (micrometric) and of the nanocomposite ETPE/Alex were studied. The percentage of Alex was adjusted to obtain the optimum mechanical properties. The beneficial effects of the nanopowder on the material properties are highlighted. The introduction of nanoaluminum improves the elasticity and strength of the original ETPE and, consequently, makes it easier to use, to handle, and to process. It indicates that PNs can be considered for future applications in energetic material, such as in gun propellants, rocket propellants and insensitive melt‐cast explosive formulations.
Why Wild Values Occur in Pyrotechnic Sensitivity Analysis
Authors: Chao Min‐Te , Fuh Cheng‐Der
Published: August 2003

In sensitivity studies when estimating the location and scale parameters for the underlying latent distribution “wild values” are often encountered. This is typically caused by the non‐existence of the corresponding estimates. A simple condition is developed, which is both necessary and sufficient for the existence of the Maximum Likelihood Estimates (MLE) in all types of sensitivity studies we are aware of. This condition can thus be employed in an iteration procedure to ensure proper convergence.
Off‐shell supergravity in five dimensions and supersymmetric brane world scenarios
Authors: Zucker M.
Published: August 2003

We review the construction of${\cal N}=2$off‐shell Poincaré supergravity in five dimensions. We describe in detail the minimal multiplet, which is the basic building block, containing the propagating fields of supergravity. All matter multiplets containing (8 + 8) components, being the smallest matter multiplets in five dimensions, are constructed. Using these multiplets the complete tensor calculus for supergravity is developed. As expected it turns out, that there exist three distinct minimal (i.e. containing (48 + 48) field components) off‐shell supergravities. The lagrangians for these theories and their gauged variants are given explicitly. These results are used in the second part to develop a tensor calculus on the orbifold\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$S^1/\mathbb{Z}_2$\end{document}. Gauged supergravity on the orbifold\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$S^1/\mathbb{Z}_2$\end{document}with additional cosmological constants at the fixpoints, is constructed. This generalizes the work of Randall‐Sundrum to local supersymmetry. The developed tensor calculus is used to extend this model to include matter located at the fixpoints. Chiral and super Yang‐Mills multiplets at the fixpoints are considered.
Decreased gene expression of steroid 5 alpha‐reductase 2 in human prostate cancer: Implications for finasteride therapy of prostate carcinoma
Authors: Luo Jun , Dunn Thomas A. , Ewing Charles M. , Walsh Patrick C. , Isaacs William B.
Published: August 2003

BACKGROUND

Steroid 5α‐reductase 2 (SRD5A2) catalyzes the conversion of testosterone to the more potent androgen, DHT, in the prostate. The therapeutic influence of SRD5A2 inhibitor finasteride on prostate cancer is currently unknown. The direction and extent of changes in SRD5A2 expression in disease tissues is a relevant issue in this regard.

METHODS

The expression differences of SRD5A2 in tissues representative of normal, benign, and malignant growth in the human prostate were examined in parallel by comparative analysis of relevant microarray gene expression data. Semiquantitative RT‐PCR was used to further verify the gene expression differences of SRD5A2.

RESULTS

Consistently decreased expression of SRD5A2 was observed in 25 prostate cancer samples when compared to 25 matched normal samples and nine BPH samples. Expression differences among these samples for six other genes were presented in parallel as indicators of the direction and extent of expression changes. These additional genes include SRD5A1, Hepsin (overexpressed in prostate cancer), AMACR (overexpressed in prostate cancer), Keratin 8 (epithelial marker), smooth muscle actin (stromal marker), Nell2 (overexpressed in BPH). Semiquantitative RT‐PCR verified the expression differences for SRD5A2 in six normal, six BPH, and six prostate cancer samples.

CONCLUSIONS

Results from this study, combined with those from previous studies, indicate an association of prostate cancer with reduced 5α‐reductase enzymatic activity as a result of remarkably decreased expression of the SRD5A2 gene. The implications of this study for finasteride therapy of prostate cancer are discussed. Prostate 57: 134–139, 2003. © 2003 Wiley‐Liss, Inc.
Inhibition of prostate cancer cell growth by activated eosinophils
Authors: Furbert‐Harris Paulette , Parish‐Gause Debra , Laniyan Ibrahim , Hunter Keith A. , Okomo‐Awich Josephine , Vaughn Theresa R. , Forrest Kesha C. , Howland Christina , Abdelnaby Abier , Oredipe Oladipo A.
Published: August 2003

BACKGROUND

Host Immune response to prostate cancer primarily involves the CTL and NK effector cells. Recent immunotherapeutic strategies incorporating cytokine genes into the tumor cell and/or dendritic cells have had encouraging results. In this study, we describe the inhibitory activity of a third potential effector cell, the eosinophil, against DU 145 and PC‐3 prostate tumor cells growth in vitro.

METHODS

Subconfluent monolayer cultures of DU 145 and PC‐3 cells were incubated with peripheral blood eosinophils from allergic or asthmatic individuals and also with eosinophil cultured supernatants. Newly established eosinophil cell lines were also studied. After harvesting, the plates were washed and stained with Hematoxylin/eosin (H/E) then photographed. The combination of monolayer cell growth inhibition and colony formation inhibition assays were used to evaluate eosinophil inhibitory activity. In the colony formation inhibition assay one hundred cells per well in 6‐well plates were incubated overnight, after which peripheral blood eosinophils, conditioned media and cytokines, IL‐4 and TNF‐α were added. The plates were harvested after 10 days incubation period. Colonies were stained and counted.

RESULTS

Hypo‐ and hyperdense peripheral blood eosinophils from allergic and asthmatic individuals as well as eosinophil cell lines established from these subpopulations inhibited both DU 145 and PC‐3 cell growth at 58–78% and 10–38%, respectively. IL‐5 up‐regulated eosinophil cell line activity by 21–24%. The conditioned media which contained the released mediators of activated eosinophils were potent in their actions on both DU 145 and PC‐3, inhibiting colony formation by as much as 90–100%.

CONCLUSION

These results clearly demonstrate the inhibitory potential of activated eosinophils and their released “soup” of mediators and therefore support the hypothesis that eosinophils may participate in host response to prostate cancer together with CTLs and NK cells. Furthermore, this study offers insights into possible strategies for enhancing eosinophilic activity in prostate cancer. Prostate 57: 165–175, 2003. © 2003 Wiley‐Liss, Inc.
Presence of neuroendocrine cells during postnatal development in rat prostate: Immunohistochemical, molecular, and quantitative study
Authors: Rodríguez Rosario , Pozuelo José M. , Martín Rocío , Henriques‐Gil Nuno , Haro María , Arriazu Riánsares , Santamaría Luis
Published: August 2003

BACKGROUND

This work was undertaken to study the prostate neuroendocrine cells (PNEC) during the post‐natal development of rats.

METHODS

Forty male Wistar rats (pre‐pubertals, pubertals, young, and aged adults) were used for immunohistochemistry of chromogranin A (cgA), serotonin (SER), and protein gene product 9.5 (PGP9.5). They were also evaluated for numerical cell density (NV SER) and PNEC number per prostate (N SER). Five additional young adult rats were used for a RT‐PCR study (mRNA cgA detection).

RESULTS

Weak immunoreactivity to cgA was observed in pubertal rats. No PNEC immunostained to PGP 9.5 was observed. Cells expressing SER were detected in all the groups exclusively located in periurethral ducts. The NV SER increased significantly in pubertal animals. In aged animals, it decreased to levels observed in pre‐pubertal rats. The N SER increased significantly from pre‐pubertal to young adults, decreasing in aged adults. There was weak production of cgA mRNA, with more expression in the dorsal prostate.

CONCLUSIONS

PNEC differ in rats when compared to humans: they are weakly immunopositive to cgA, do not express PGP 9.5, only show immunoreactivity to SER, and do not appear in acini. The changes in the amount of rat PNEC during the post‐natal development suggest an androgenic influx. PNEC might regulate the contractility of periurethral ducts. Prostate 57: 176–185, 2003. © 2003 Wiley‐Liss, Inc.
1‐D random walk in presence of a totally reflecting barrier
Authors: Orlowski Marius
Published: August 2003

A rigorous analysis of counting paths for 1‐D random walk in the presence of a reflecting barrier is presented. This paper defines and distinguishes between partially and totally reflecting barriers. So far, in the literature only a special case of partially reflecting barrier has been dealt with. An exact combinatorial formula is proven which describes the probability distribution of a diffusing particle at a totally reflecting barrier, allowing computation of any random walk redistribution of a diffusing species near or at the totally reflecting barrier. The analysis shows that for a particle starting its random walk at the barrier, the probability of finding it at the interface is diminishing with the number of diffusion steps N as 1/(N/2 + 1) and that the peak of the probability distribution is moving away from the barrier with the increasing number of steps as . This analysis has implications on the treatment of diffusion of impurities and point defects in thin films and in subsurface layers.
Modeling ferroelectric properties of dipole planes
Authors: Farag Nayel , Kliem Herbert
Published: August 2003

Ferroelectric properties of a system of electric dipoles arranged in a plane are calculated with a Monte Carlo simulation, the importance‐sampling method. The plane is a substructure of the perovskite structure found in barium titanate. Two sorts of dipoles are simulated: 1) permanent dipoles with two possible antiparallel orientations, 2) induced point dipoles. The permanent dipoles represent the titanium ions, and the induced point dipoles represent the oxygen atoms of the dipole plane. The dipoles are located between two plane‐parallel electrodes of a capacitor. The effect of the electrodes to the local electric field is taken into account with the method of images. With the Monte Carlo simulation the polarization of the dipole plane in dependence on the applied field is calculated. For the case without applied field we find a spontaneous polarization if the values for the polarizabilities of the induced dipoles are chosen appropriate. The temperature dependence of the spontaneous polarization is computed. From the simulations with applied field we get hysteresis loops of the polarization. We calculate the temperature dependence of the coercive field and the remanent polarization. For the susceptibility a Curie–Weiss law is found.
Statistical fluctuation of universal mobility curves in sub‐100 nm MOSFETs due to random oxide interface
Authors: Kaya Savas
Published: August 2003

We explore the behavior of universal mobility in sub‐100 nm Si MOSFETs, using a novel 3D statistical simulation approach. Our approach is based on 3D Brownian dynamics in devices with realistic Si/SiO2interfaces reconstructed from a Gaussian or exponential correlation function. In this approach carrier trajectories in the bulk are treated via 3D Brownian dynamics, while the carrier‐interface roughness scattering is treated using a novel empirical model. Owing to the high efficiency of the transport kernel, effective mobility in 3D MOSFETs with realistic Si/SiO2can be simulated in a statistical manner. We first demonstrate a practical calibration procedure for the interface mobility and affirm the universal behaviour in the long channel limit, using single atomic steps and a correlation length of 6 nm. Next, effective mobility in ensembles of MOSFETs with gate length down to 10 nm is investigated. It is found that random‐discrete nature of the Si/SiO2interface leads to a distribution of carrier mobility below the interface, which can deviate considerably from universal mobility curves whenLgate< 6Λ, whereΛis the correlation length for the SiO2interface. Based on recent dataΛ= 2.8 nm, our simulations indicate that universal‐mobility curves should be reliable for MOSFET designs down to a gate length of 17 nm. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Green's function approach for transport calculation in a In0.53Ga0.47As/In0.52Al0.48As modulation‐doped heterostructure
Authors: Vasileska D. , Prasad C. , Wieder H. H. , Ferry D. K.
Published: August 2003

The gate voltage dependence of the low‐field electron mobility has been investigated in a In0.53Ga0.47As/In0.52Al0.48As modulation‐doped heterostructure using a real‐time Green's function formalism. All scattering mechanisms relevant for this material system have been incorporated in the theoretical model, including alloy disorder scattering, Coulomb scattering from the ionized impurities in the buffer layer, acoustic phonon and piezoelectric scattering. The simulation results for the subband structure suggest occupation of two subbands at VG = 0 V. Good agreement is observed between the simulated sheet electron densities and the experimentally extracted ones from Hall and Shubnikov‐De Haas oscillatory magnetoresistance measurements. The mobility results for the structure investigated suggest that alloy‐disorder scattering is the dominant mobility degradation mechanism. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Proceedings of the 4th Motorola Workshop on Computational Materials and Electronics
Authors: Demkov Alex , Fonseca Leonardo , Liu Chun‐Li
Published: August 2003

The 4th Motorola Workshop on Computational Materials and Electronics was held on 14–15 November 2002 in Tempe, Arizona, USA. Focus areas were computational materials and quantum transport, including molecular electronics, and nanodevices. The cover picture shows a prototype 1 nm silicon quantum dot formed by high‐temperature synthesis which luminesces in the ultraviolet at 400 nm, taken from [1]. The proceedings of the workshop series are published in this journal for the third time, following the 2nd and 3rd Motorola Workshops in phys. stat. sol. (b) 226, No. 1 (2001), and phys. stat. sol. (b) 233, No. 1 (2002), respectively.

This issue is completed by Original Papers including the Editor's Choice by M. Q. Weng and M. W. Wu, a many‐body study on spin dephasing in n‐type GaAs quantum wells in the presence of high magnetic fields [2].
A user‐assisted approach to component clustering
Authors: Sartipi Kamran , Kontogiannis Kostas
Published: August 2003

In this paper, we present a user‐assisted clustering technique for software architecture recovery based on a proximity measure that we call component association. The component association measure is computed on the shared properties among groups of highly related system entities. In this approach, the software system is modeled as an attributed relational graph with the software constructs (entities) represented as nodes and data/control dependencies represented as edges. The application of data mining techniques on the system graph allows us to generate a component graph where the edges are labeled by the association strength values among the components. An interactive partitioning technique is used to partition a system into cohesive components. Graph visualization tools and cluster quality evaluation metrics are applied by the user to assess and fine tune the partition result. Copyright © 2003 John Wiley & Sons, Ltd.
Theoretical framework and empirical evidence of students' cognitive processes in three dimensions of content, complexity, and time
Authors: von Aufschnaiter Claudia , von Aufschnaiter Stefan
Published: August 2003

In the literature, learners' cognitive development is mainly discussed with respect to changes in learners' content‐dependent knowledge (conceptual change or growth). Additional dimensions of time and complexity may also be taken into account to describe cognitive processes in at least three dimensions. We discuss these three dimensions of content, complexity, and time theoretically and show empirically what results can be found with such a framework. The primary database consists of 27 students who worked in groups of three on physics tasks during three sessions in an experimental setting. All activities were videotaped and analyzed in great detail. Results indicate that students' meanings always refer to a narrow area of content, are developed bottom‐up with respect to complexity, and show time‐dependent dynamics in which maxima of 30 seconds and 5 minutes are important time scales. Comparison with outcomes of additional experimental settings on the same topic with more and less advanced students indicate the results to have a greater validity. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 616–648, 2003
Development of chemistry attitudes and experiences questionnaire (CAEQ)
Authors: Dalgety Jacinta , Coll Richard K. , Jones Alister
Published: August 2003

In this article we describe the development of the Chemistry Attitudes and Experiences Questionnaire (CAEQ) that measures first‐year university chemistry students' attitude toward chemistry, chemistry self‐efficacy, and learning experiences. The instrument was developed as part of a larger study and sought to fulfill a need for an instrument to investigate factors that influence student enrollment choice. We set out to design the instrument in a manner that would maximize construct validity. The CAEQ was piloted with a cohort of science and technology students (n = 129) at the end of their first year. Based on statistical analysis the instrument was modified and subsequently administered on two occasions at two tertiary institutions (n = 669). Statistical data along with additional data gathered from interviews suggest that the CAEQ possesses good construct validity and will prove a useful tool for tertiary level educators who wish to gain an understanding of factors that influence student choice of chemistry enrolment. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 649–668, 2003
Portraying science in the classroom: The manifestation of scientists' beliefs in classroom practice
Authors: Southerland Sherry A. , Gess‐Newsome Julie , Johnston Adam
Published: August 2003

If the goals of science education reform are to be realized, science instruction must change across the academic spectrum, including at the collegiate level. This study examines the beliefs and teaching practices of three scientists as they designed and implemented an integrated science course for nonmajors that was designed to emphasize the nature of science. Our results indicated that, like public school teachers, scientists' beliefs about the nature of science are manifested in their enactment of curriculum—although this manifestation is clearly not a straightforward or simplistic one. Personal beliefs about the nature of science can differ from those of the course, thus resulting in an enactment that differs from original conceptions. Even when personal beliefs match those of the course, sophisticated understandings of the nature of science are not enough to ensure the straightforward translation of beliefs into practice. Mitigating factors included limited pedagogical content knowledge, difficulty in achieving integration of the scientific disciplines, and lack of opportunity and scaffolding to forge true consensus between the participating scientists. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 669–691, 2003
What “ideas‐about‐science” should be taught in school science? A Delphi study of the expert community
Authors: Osborne Jonathan , Collins Sue , Ratcliffe Mary , Millar Robin , Duschl Rick
Published: August 2003

Recent arguments in science education have proposed that school science should pay more attention to teaching the nature of science and its social practices. However, unlike the content of science, for which there is well‐established consensus, there would appear to be much less unanimity within the academic community about which “ideas‐about‐science” are essential elements that should be included in the contemporary school science curriculum. Hence, this study sought to determine empirically the extent of any consensus using a three stage Delphi questionnaire with 23 participants drawn from the communities of leading and acknowledged international experts of science educators; scientists; historians, philosophers, and sociologists of science; experts engaged in work to improve the public understanding of science; and expert science teachers. The outcome of the research was a set of nine themes encapsulating key ideas about the nature of science for which there was consensus and which were considered to be an essential component of school science curriculum. Together with extensive comments provided by the participants, these data give some measure of the existing level of agreement in the community engaged in science education and science communication about the salient features of a vulgarized account of the nature of science. Although some of the themes are already a feature of existing school science curricula, many others are not. The findings of this research, therefore, challenge (a) whether the picture of science represented in the school science curriculum is sufficiently comprehensive, and (b) whether there balance in the curriculum between teaching about the content of science and the nature of science is appropriate. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 692–720, 2003
Mapping nitrate in the global ocean using remotely sensed sea surface temperature
Authors: Switzer Anna C. , Kamykowski Daniel , Zentara Sara‐Joan
Published: August 2003

Nitrogen is the most broadly limiting factor for marine phytoplankton on ecological timescales. Nitrate, as the most oxidized inorganic species, plays a significant role in nitrogen availability based on nutrient flux to the euphotic zone from deeper waters, and is a major determinant of new production. Increased new production relates to higher trophic level abundance and to carbon dioxide drawdown from the atmosphere. The present work is the first stage in the development of a technique to generate a scaled index of nitrate availability in the surface waters of the global ocean using satellite‐derived temperature data. The technique currently involves a fixed matrix of nitrate depletion temperatures (NDT) and remotely‐sensed sea surface temperature (SST) from the monthly‐averaged AVHRR Pathfinder series. The magnitude of the difference between these two temperatures at a given location indicates the degree of nitrate presence or absence. Graded monthly nitrate presence/absence maps over a 10‐year period were created based on the size of the difference between these two temperatures. A 10‐year average of these differences exhibits major nitrate distribution features similar to those observed in maps based on National Oceanic Data Center archived measurements. In contrast, monthly nitrate maps provide a unique and dynamic representation of nitrate availability in the global ocean. This nutrient monitoring capability based on remotely sensed data can contribute to the estimation of new production in the global ocean, improving management of various world fisheries and improving estimation of the atmospheric draw down of carbon dioxide, a major greenhouse gas.
Evaluating the impacts of land management and climate variability on crop production and nitrate export across the Upper Mississippi Basin
Authors: Donner Simon D. , Kucharik Christopher J.
Published: August 2003

The increased use of nitrogen (N) fertilizers in the Mississippi Basin since the 1950s is partially responsible for an increase in crop production, but also a massive increase in nitrate export by the Mississippi River. We used the IBIS terrestrial ecosystem model, including new maize and soybean submodels, and the HYDRA hydrological transport model to investigate the role of climate variability, land cover and N‐fertilizer application on crop yield, N cycling and nitrate export in the Upper Mississippi Basin from 1974–1994. Simulated annual mean maize and soybean yields were both within 20% of USDA historical estimates in over 80% of the crop‐growing counties. There was also strong agreement between simulated and USGS estimated annual nitrate export for the Mississippi River at Clinton, Iowa (r2 = 0.81), the outlet of the basin, and the Minnesota River at Jordan, Minnesota (r2 = 0.78). The model also indicated a 30% increase in N‐fertilizer application across the basin would have caused only a 4% increase in mean maize yield, but a 53% increase in mean dissolved inorganic nitrogen (DIN) leaching, while a 30% decrease in N‐fertilizer application would have caused a 10% decrease in maize yield, but a 37% decrease in DIN leaching. At higher levels of N‐fertilizer usage, nitrate export becomes increasingly sensitive to the hydrologic conditions, particularly when there is ample residual N in the soil. Therefore any effort to reduce nitrate export without significantly affecting crop yields would have to account for previous soil‐N conditions and climate variability.
Cenozoic deformation and tectonic style of the Andes, between 33° and 34° south latitude
Authors: Giambiagi Laura B. , Ramos Victor A. , Godoy Estanislao , Alvarez P. Pamela , Orts Sergio
Published: August 2003

The Andes of Argentina and Chile between latitudes 33° and 34°S are composed from west to east of an Oligocene to Miocene volcanic arcs and the Neogene east‐vergent Aconcagua fold and thrust belt of the Cordillera Principal, and the basement‐block faulted Cordillera Frontal. A regional cross section suggests that shortening across the Andes was achieved by thrusting along detachments at several levels in the crust. While thin‐skinned deformation along newly formed thrusts occurred in Mesozoic sequences of the eastern Cordillera Principal, reactivation of preexisting Jurassic and Oligocene normal faults has resulted in additional hybrid thick‐ and thin‐skinned structures in the western Cordillera Principal. Five major thrusting events are recognized in this part of the Andes: (1) Early to Middle Miocene tectonic inversion of the extensional faults in the western Cordillera Principal, (2) Middle to Late Miocene development of the Aconcagua fold and thrust belt, (3) Late Miocene uplift of Cordillera Frontal, (4) Late Miocene–Early Pliocene out‐of‐sequence thrusting in the Cordillera Principal, and (5) Pliocene to present deformation of the foreland.
Multicomponent ocean bottom cable data in gas hydrate investigation offshore of Norway
Authors: Andreassen Karin , Berteussen Karl A. , Sognnes Helge , Henneberg Kerstin , Langhammer Jan , Mienert Juergen
Published: August 2003

A multicomponent seismic ocean bottom cable (OBC) line from the northern flank of the Storegga Slide offshore of Norway is the first OBC line ever acquired over a gas hydrate‐related bottom simulating reflector (BSR). The seismic data are of very good quality, and display strongP‐Sconverted wave reflections for the whole sediment column. AllP‐Sreflections follow the sediment layers and are therefore interpreted to be caused by increased shear modulus and density due to sediment compaction. NoP‐Sreflections are associated with the BSR along this line, indicating that the gas hydrate‐bearing sediments at the base of the hydrate stability zone are not stiff enough to increase the shear modulus of the sediments to produceP‐Sconverted wave reflections. Seismic interpretation and seismic stratigraphic modeling suggest that the BSR in this area is a contrast in compressional wave velocity only, mainly caused by small amounts of free gas confined to dipping sediment layers beneath the BSR. Gas hydrate saturation above the BSR, tentatively estimated to be about 1–1.5% of the sediment pore space, is most likely too low to distinguish between different models for microscale gas hydrate distribution.
Information approach to optimal selection of spectral channels
Authors: Sofieva V. F. , Kyrölä E.
Published: August 2003

In this paper we examine methods for the selection of measurement subsets using information theory. These methods are applied to an overdetermined inverse problem typical to high‐resolution spectrometry. The optimal selection of spectral channels becomes especially important with the recent introduction of high spectral resolution satellite instruments for monitoring the atmosphere. The vast amount of data these instruments provide in a continuous fashion makes it necessary to carefully consider which channels are really needed in the retrieval of geophysical quantities. Two optimization problems in channel selection, both taking the information content of the measurements as a criterion, are defined and discussed. The concept of the information content of each individual measurement is introduced, and basic analytical relations are derived. A sequential deselecting procedure is developed, and a fast algorithm for channel selection is proposed. These provide approximations to solutions of the optimization problem. The efficiencies of these selection procedures and a sequential selection procedure [Rodgers, 1996] are compared by means of a Monte Carlo generation of the forward model in a low‐dimensional case. As a real application, the selection of the most informative spectral channels for GOMOS measurements is considered.