bluuebunny/crossref_metadata_2025 huggingface dataset:
Mobile applications aimed at preparation for surgical procedures: a technological prospecting / Aplicativos móveis voltados ao preparo para procedimentos cirúrgicos: uma prospecção tecnológica
Authors: Caetano Jaqueline , Solange Vieira Tourinho Francis , Favero Alves Thais , Misiak Caldas Marciele
Published: March 2023

Objetivo: analisar as principais características dos aplicativos móveis, disponíveis em lojas virtuais, que tratam sobre a temática da realização de procedimentos cirúrgicos. Método: Prospecção tecnológica, de abordagem qualitativa do tipo exploratória, realizada por busca de aplicativos nas lojas virtuais Apple Store® e Google Play®, utilizando as palavras-chave: Centro Cirúrgico, Cirurgia, Simulador de cirurgia e Jogos de cirurgia, em português, inglês e espanhol. Realizou-se análise temática categorial dos achados. Resultados: 67 ocorrências foram classificadas em quatro categorias: ‘Aplicativos destinados à orientação para procedimento cirúrgico’, ‘Aplicativos sobre o trabalho em centro cirúrgico’, ‘Aplicativos voltados à equipe de saúde’, e ‘Aplicativos relacionados a jogos de entretenimento’. Considerações finais: os aplicativos voltam-se tanto para indivíduos que buscam orientações sobre procedimentos, quanto a profissionais da área da saúde. No entanto, há uma lacuna referente à orientações pré-operatórias específicas para pediatria, onde nenhuma ocorrência foi registrada.
A novel Drosophila serpin that inhibits serine proteases
Authors: Han Jin-Hua , Zhang Hong-Yan , Min Gi-Sik , Kemler Doris , Hashimoto Carl
Published: July 2002

Serpins define a large protein family in which most members function as serine protease inhibitors. Here we report the results of a search for serpins in Drosophila melanogaster that are potentially required for oogenesis or embryogenesis. We cloned and sequenced ovarian cDNAs that encode six distinct proteins having extensive sequence similarity to mammalian serpins, including residues important in the serpin inhibition mechanism. One of these new serpins in recombinant form inactivates, and complexes with, trypsin‐like proteases in vitro. To our knowledge, these results represent the first evidence for a serpin in Drosophila that functions as a serine protease inhibitor.
Proposed lipocalin fold for apolipoprotein M based on bioinformatics and site‐directed mutagenesis
Authors: Duan Jianxin , Dahlbäck Björn , Villoutreix Bruno O.
Published: July 2002

Apolipoprotein M (apoM) is a novel apolipoprotein that is predominantly present in high‐density lipoprotein. Sensitive sequence searches, threading and comparative model building experiments revealed apoM to be structurally related to the lipocalin protein family. In a 3D model, characterized by an eight‐stranded anti‐parallel β‐barrel, a segment including Asn135 could adopt a closed or open conformation. Using site‐directed mutagenesis, we demonstrated Asn135 in wild‐type apoM to be glycosylated, suggesting that the segment is solvent exposed. ApoM displays two strong acidic patches of potential functional importance, one around the N‐terminus and the other next to the opening of the β‐barrel.
Enhancing Xanthan Fermentations by Different Modes of Glucose Feeding
Authors: Amanullah A. , Satti S. , Nienow A. W.
Published: July 2002

This paper is the fourth in a series aimed at improving the understanding and operation of conventional agitated fermenters for the production of the commercially important gum, Xanthan. In the first, reproducible fermentations were established and this protocol was used in studies of different agitator types and of bulk mixing and dissolved oxygen concentration in the next two. Here, building on the previous work, the influence of different glucose feeding strategies on Xanthan production in a 20‐L agitated fermenter under equivalent conditions of agitation and dissolved oxygen is reported. The biological performances in three types of fed‐batch cultures (a two‐step glucose addition, multiple glucose‐pulse feeding and continuous feeding of glucose) are compared to two batch fermentations with different initial glucose concentrations. The work confirmed that improved performance cannot be achieved by increasing the initial glucose concentration above 50 g/L nor by a single 10 g/L pulse addition (initial glucose concentration of 40 g/L) while significant nitrogen is still present. On the other hand, the simple pulse and continuous feeding strategies, after nitrogen has been essentially exhausted and under conditions of nonlimiting dissolved oxygen and similar bulk mixing, can result in a greatly enhanced performance compared to batch fermentations. Using the final Xanthan gum concentration, the yield on glucose and the overall productivity as performance indices, values of 62 g/L, 0.82 g of Xanthan/g of glucose, and 0.72 g/(L·h), respectively, were obtained compared to literature values for conventional stirred bioreactors of 15–30 g/L, 0.27–0.86 g of Xanthan/g of glucose, and 0.12–0.43 g/(L·h) .
Asymmetric Reduction of Acetophenone with Calcium‐Alginate‐Entrapped Baker's Yeast in Organic Solvents
Authors: Griffin Daniel R. , Yang Fangxiao , Carta Giorgio , Gainer John L.
Published: July 2002

Baker's yeast cells entrapped in alginate beads are shown to catalyze reactions in organic solvents when a cofactor regeneration scheme is implemented. This study focused on the reduction of acetophenone to 1‐phenylethanol, using baker's yeast as well as a cosubstrate to regenerate the cofactor. The product is a chiral alcohol, and it was desired to maintain a high enantiomeric excess. The effects of parameters such as the addition of a cosubstrate, water content, fermentation time, buffer pH, and bead diameter have been investigated. Such a general process may be quite useful when single enantiomers are needed, as well as for the production of other chemicals.
From peptide libraries to optimized nonpeptide ligands in the search for S‐farnesyltransferase inhibitors
Authors: Henlin J.M. , Kucharczyk N. , Desmet‐Beaufort C. , Loynel A. , Genton A. , Tucker G.C. , Atassi G. , Fauchère J.L. , Boutin J.A. , Bertrand M.
Published: July 2002

Abstract:A complete 331 776‐member library of tetrapeptides made of 24 amino acid building blocks was synthesized robotically on solid phase and subjected to a deconvolution based on the inhibitory potency of the sublibraries in a HPLC assay of the S‐farnesyltransferase activityin vitro. One of the non‐natural peptide and noncysteine‐containing leads Nip‐Trp‐Phe‐His (Nip = p‐nitrophenyl‐l‐alanine) was optimized chemically to give a proteolytically stable pseudopeptide with a 200‐fold potency compared with the original lead. The final compound was converted to the C‐terminal ethyl ester:p‐F‐C6H4‐CO(CH2)2‐CO‐Bta‐d‐Pheψ[CH2NH]His‐OEt(Bta = benzothienyl‐l‐alanine) and shown to behave as a prodrug which was hydrolyzed back to the C‐terminal acid following cell penetration. The method confirmed that several structurally original leads can be discovered in large libraries when deconvolution relies upon a highly specific assay and that these leads can be optimized by chemical modification to impart the final compound the desired pharmacological and pharmacokinetic properties.
Non‐adherence in pediatric transplantation: A review of the existing literature
Authors: Griffin Karla J. , Elkin T. David
Published: July 2002

Abstract: The degree of medical adherence in pediatric solid‐organ transplant recipients frequently correlates with the degree of psychological distress, family functioning, and the physiological side‐effects of immunosuppressant medications. This article examines the current literature regarding each of these factors and proposes recommendations for increasing the medical compliance among childhood transplant recipients.
Successful treatment of restless legs syndrome with an implanted pump for intrathecal drug delivery
Authors: Jakobsson B. , Ruuth K.
Published: July 2002

Two patients with incapacitating symptoms from restless legs syndrome, not adequately responding to conventional treatment with dopaminergic drugs, were implanted with a pump device (Isomed®) for intrathecal delivery of morphine and bupivacaine. The treatment resulted in total resolution of all symptoms with few side effects.
Immunohistochemical and ultrastructural observations of desmoplastic trichoepithelioma with a special reference to a morphological comparison with normal apocrine acrosyringeum
Authors: Yamamoto Osamu , Hamada Tetsuo , Doi Yoshiaki , Sasaguri Yasuyuki , Hashimoto Hiroshi
Published: July 2002

Background: Desmoplastic trichoepithelioma is a benign neoplasm considered to have follicular differentiation. Its sweat gland‐ or sebaceous‐lines of differentiation have been also reported. There have been, however, only a few reports regarding extensive immunohistochemical and ultrastructural investigations of this neoplasm.

Methods: Histopathological and immunohistochemical studies were performed on three cases of desmoplastic trichoepithelioma, comparing it with normal skin. One of these cases was ultrastructurally investigated.

Results: The cord‐like basaloid nests were reacted with the anti‐cytokeratin (CK)1/5/10/14, ‐CK5/8, ‐CK14 and ‐CK15 antibodies, but not with the anti‐CK6 antibody. Similar findings were observed in the outer layers of the normal follicular outer root sheath. Basaloid cell nests in one case, which showed ductal structures in the nests, also expressed CK7, CK8/18 and CK19. These keratins were also detected in the normal sweat glands. In addition, CK8/18 and CK19 were expressed in the basal cells of the outer root sheath. Keratinous cysts had inner reactions with the anti‐CK10/11 and ‐CK6 antibodies, and outer reactions with anti‐CK5/8 and ‐CK14 antibodies. Ultrastructurally, the cells in the cord‐like nests were basically immature and basaloid in appearance. A few cells contained Odland bodies, which were also observed in the normal apocrine acrosyringeum. The ductal structure was lined by the cells which bore numerous microvilli in the luminal surface.

Conclusion: The cells in desmoplastic trichoepithelioma are suggested to be in close association with the basal cells in the outer root sheath, which can differentiate into various parts of the folliculosebaceous apocrine unit.
Selective ex vivo expansion of cytomegalovirus‐specific CD4+ and CD8+ T lymphocytes using dendritic cells pulsed with a human leucocyte antigen A*0201‐restricted peptide
Authors: Vannucchi Alessandro M. , Glinz Stephanie , Bosi Alberto , Caporale Roberto , Rossi‐Ferrini Pierluigi
Published: July 2002

Adoptive transfer of ex vivo‐generated cytomegalovirus (CMV)‐specific T lymphocytes may be effective in preventing CMV disease in allogeneic haematopoietic stem cell transplantation (HSCT) recipients. We developed a procedure for expansion of CMV‐specific T lymphocytes based on the antigen‐presenting function of donor dendritic cells (DCs), pulsed with a human leucocyte antigen A*0201‐restricted pp65 nonamer peptide. CMV‐specific T lymphocytes were identified following induction of interferon γ (IFN‐γ) secretion prompted by peptide exposure. Both CD8+ and CD4+ CMV‐specific T lymphocytes were selectively produced in these cultures and showed CMV‐restricted cytotoxicity. The simultaneous and selective expansion of CD4+ and CD8+ CMV‐specific lymphocytes might be instrumental for more efficient in vivo function of infused CMV‐specific lymphocytes.
Contrasting roles for RANTES and macrophage inflammatory protein-1α (MIP-1α) in a murine model of allergic peritonitis
Authors: Das A M , Ajuebor M N , Flower R J , Perretti M , Mccoll S R
Published: July 2002

Cell accumulation and CC chemokine production were assessed in the peritoneal cavity of ovalbumin (OVA)-sensitized mice following antigen challenge. Intraperitoneal challenge with OVA induced a significant eosinophil influx from 6 h post-challenge with increased numbers persisting at 24 h. At 6 h there was also a marked presence of neutrophils. Messenger RNA expression and protein levels for the chemokines RANTES and MIP-1α were measured in the cell pellets and supernatants, respectively, from peritoneal washes following OVA challenge. RANTES mRNA was detected from 2 h to 4 h following OVA injection, whereas mRNA for MIP-1α was only detectable at 4 h. RANTES protein was first detected from 4 h after OVA injection and by 24 h the protein levels had increased further. Basal levels of MIP-1α were detected in peritoneal washes. These levels peaked at 2 h after OVA challenge and rapidly declined to basal levels by 6 h. A functional role for the chemokines was assessed using neutralizing polyclonal antibodies. Co-injection of OVA with anti-RANTES antibodies resulted in a significant inhibition of eosinophil infiltration into the cavity at 6 h and 24 h (63% and 52% inhibition, respectively) without significantly influencing the number of neutrophils present. In contrast, injection of anti-MIP-1α antibodies only inhibited neutrophil migration at the 6 h time point by 44% without significantly affecting the accumulation of eosinophils. These results demonstrate an important role for RANTES in mediating eosinophil influx in allergic inflammation and a contrasting role for MIP-1α in mediating neutrophil recruitment.
Maternal and birth colony effects on survival of Weddell seal offspring from McMurdo Sound, Antarctica
Authors: Hastings Kelly K. , Testa J. Ward
Published: July 2002

1. Maternal and birth colony effects on offspring survival to weaning and to reproductive age were examined for Weddell seals using mark–recapture models and over 25 years of mark–resight data from McMurdo Sound, Antarctica.

2. Pre‐weaning mortality (proportion of the total pups found dead on the ice surface) varied significantly with maternal age and was significantly higher for primiparous mothers than for multiparous mothers.

3. Offspring survival to reproductive age also increased significantly with maternal age and experience. Survival of offspring from birth to 6 years of age increased significantly with maternal body length only for male offspring.

4. Increased survivorship of offspring with maternal age was only evident for offspring of multiparous (rather than primiparous) mothers. This suggests that the age when mothers have their first pup may not affect survival of offspring, although lack of effect of age on offspring survival for primiparous mothers may be due to insufficient variation in age of first reproduction in our sample for us to detect a trend.

5. Pre‐weaning survival of offspring also varied significantly among pupping colonies. In 1983, a year of low reproduction and low first‐year survival for the McMurdo population (Testa 1987b; Hastings 1996), first‐year survival was lower for offspring born in Outer Erebus Bay (west of 166·7°E) than for offspring born in Inner Erebus Bay (east of 166·7°E).

6. Maternal effects on offspring survival may be related to quality of breeding site. Maternal age and experience varied significantly among pupping colonies. That pup population size was stable at all colonies over the study period suggests non‐random age‐distribution of mothers may not be an artefact of population growth, but instead result from intraspecific competition for space in good pupping colonies.

7. Offspring survival, pup population size, and mean maternal age at colonies were significantly positively correlated. This suggests that favourable environmental conditions and high maternal or paternal quality may interact to enhance survival of offspring at larger colonies.
The molecular and cellular biology of the chemokines
Authors: Balkwill F.
Published: July 2002

Chemokines are the largest mammalian cytokine family so far identified. They have distinct molecular structures and are unique among the cytokines in their chemotactic properties and ability to inhibit bone marrow progenitor‐cell growth. A wealth of in vitro and in vivo data show that chemokines act as directional forces in immune and inflammatory responses, working with integrins to target subsets of effector cells to specific tissue sites. The selective action of individual chemokines on leucocyte subsets makes them ideal molecules to sort, as well as direct, leucocyte traffic. In addition to their in vitro and in vivo actions on haemopoietic precursors, chemokines can also modulate angiogenesis and some may activate leucocytes. There is still much to learn about the chemokines and their intracellular pathways, and more ligands and receptors will undoubtedly be discovered. However, chemokines are aleady known to be central to the co‐ordination of leucocyte responses and represent important therapeutic targets in a number of diseases.
A prospective study of antibiotic use and associated infections in young children
Authors: Bergus  , Levy  , Kirchner  , Warren  , Levy
Published: July 2002

This study examines antibiotic usage and associated infections in infants and young children in Iowa. Longitudinal data were collected using a cohort recruited at birth from eight hospitals in eastern Iowa. Parents of recruited children were mailed questionnaires at 6 weeks, and 3, 6, 9, 12, 16, and 20 months of age. The cumulative incidence of antibiotic use and associated infections was determined using Kaplan–Meier survival analysis. There were data on 1368 children. Antibiotic use was common in our cohort and increased with age. Beginning at age 3 months, approximately 50% of the cohort was exposed to an antibiotic during each reporting period. Otitis media was the most common indication and was responsible for 67.3% of antibiotic use. Children were most frequently treated with amoxicillin, followed by the cephalosporins and sulphonamides. By 12 and 20 months of age 79.0% and 92.5% of the children, respectively, had been treated with at least one course of antibiotics. Children received antibiotics for a median of 43 days by 20 months of age. Males were more likely to experience any antibiotic exposure than females (hazard ratio = 1.18) and showed a trend for more days of use (P = 0.052). There was a small but significant variation in antibiotic usage in the different recruitment communities (P = 0.02).
Complication of a venous wallstent
Authors: Dowling Richard , Mitchell Peter , Cox Geoffrey S , Thomson Ken R
Published: July 2002

A case is reported here of effort‐related thrombosis of the axillary and subclavian veins (Paget–Schrotter syndrome) treated primarily with a combination of thrombolysis, percutaneous balloon angioplasty (PTA) and stent insertion, but without immediate rib resection. The subsequent course was complicated by fracture of the stent, managed by first rib resection.
Trisomy 22: prenatal diagnosis – a case report
Authors: Harding K. , Freeman J. , Weston W. , Smith J. R.
Published: July 2002

Multiple abnormalities of a fetus were detected on a routine antenatal anomaly scan at 19 weeks' gestation. Amniocentesis and karyotype analysis showed trisomy 22. The ultrasound and postmortem features are presented. Copyright © 1995 International Society of Ultrasound in Obstetrics and Gynecology
Secondary Structure of the ITS1 Transcript and its Application in a Reconstruction of the Phylogeny of Boraginales
Authors: Gottschling M. , Hilger H. H. , Wolf M. , Diane N.
Published: July 2002

Abstract: In this study, we present the possibilities for calculating systematic relationships on higher taxonomical levels based exclusively on ITS1. This is demonstrated for Boraginales (Boraginaceae s.str., Cordiaceae, Ehretiaceae, Heliotropiaceae, Hydrophyllaceae and Lennoaceae). Secondary structure of the ITS1 region is more conserved than the primary structure (i.e., sequence itself) and is therefore a tool for optimizing alignments. It increases the number of structural characters. Information inferred from the secondary structure enables us to construct well‐resolved phylogenetic trees at higher taxonomic levels. A general secondary structure of ITS1 for Boraginales, with four major helices, is proposed here. In each subtaxon, derivations from this structure are found. The paraphyly of Boraginaceae s.l. is evident from both a comparison of secondary structures and from bootstrap analysis. Boraginaceae s.str. are the sister group of a clade formed by Hydrophyllaceae, Cordiaceae, Ehretiaceae, Heliotropiaceae and Lennoaceae. The last four taxa constitute a monophyletic group which is the sister group of Hydrophyllaceae. Lennoaceae are closely related to Ehretiaceae, and these two taxa in turn are the sister group of Cordiaceae.
Surface diffusion of AlAs on GaAs in metalorganic vapor phase epitaxy studied by high-vacuum scanning tunneling microscopy
Authors: Kasu Makoto , Kobayashi Naoki
Published: July 2002

After depositing a 1/6 monolayer of AlAs on a very flat GaAs (001) surface by metalorganic vapor-phase epitaxy, we have studied AlAs two-dimensional (2D) nuclei by high-vacuum scanning tunneling microscopy. AlAs 2D nuclei elongate in the [110] direction, like GaAs. The density of AlAs 2D nuclei in the saturation region was 5×1010 cm−2 at 580 °C. The saturated AlAs 2D nucleus density decreased as the temperature increased. From the saturated AlAs 2D nucleus densities the surface diffusion coefficient of AlAs on GaAs was calculated to be 1.5×10−7 cm2/s at 530 °C. This is one order of magnitude smaller than that of GaAs on GaAs.
Nanoporous carbon produced by ball milling
Authors: Chen Ying , Fitz Gerald John , Chadderton Lewis T. , Chaffron Laurent
Published: July 2002

A nanoporous structure was produced in the samples of graphite after ball milling at ambient temperature. The specific internal surface area of the micropores, as determined using the t-plot method, is higher than the external surface area of particles and mesopores. Phase transformations from hexagonal to turbostratic, and to amorphous structures were investigated using x-ray diffraction analysis and transmission electron microscopy. Formation of the nanoporous structure is associated with that of the disordered carbon. The disordered and nanoporous structure is probably fullerene-like in nature.
Resolving the hydrogen bond dynamics conundrum
Authors: Luzar Alenka
Published: July 2002

This paper analyzes dynamic properties of hydrogen bonds in liquid water. We use molecular dynamics simulation to calculate different probability densities that govern the time evolution of the formation and rupture of hydrogen bonds. We provide analytical connections between these functions. Excellent agreement with our simulation results is observed. We prove transition state theory rate constant to be identical to the inverse of the associated mean first passage time (hydrogen bond lifetime). Hence, the analysis establishes its Arrhenius temperature dependence. We give the explicit relation between reactive flux correlation function for the relaxation dynamics of hydrogen bonds, and their first passage time probability densities. All the different observations in the existing literature, associated with various estimates of hydrogen bonding times in liquid water that are affected (or not affected) by particular bond criteria, as well as by different definitions of hydrogen bond lifetimes applied in simulation, can be easily reconciled within the framework of reactive flux correlation function approach.
Production and characterization of highly intense and collimated cluster beams by inertial focusing in supersonic expansions
Authors: Piseri P. , Podestà A. , Barborini E. , Milani P.
Published: July 2002

Intense and collimated supersonic cluster beams have been produced by exploiting inertial focusing effects. To this goal we have developed and tested a novel focusing nozzle (focuser). Using this device with a pulsed microplasma cluster source we have obtained cluster beams with a divergence of 10 mrad and average densities of 3×1010 atoms/cm3 (2×1012 atoms/cm3 pulsed) corresponding to deposition rates of 2 nm/s at 300 mm distance from the source nozzle. With a focusing nozzle cluster thermal relaxation and mass distribution in a supersonic expansion can be controlled. We have measured the cluster transverse velocities, with extremely high precision, by characterizing the cluster beam deposition on a substrate by an atomic force microscope. Besides the relevance for the understanding of relaxation processes in expanding jets, the inertial focusing of clusters has several important consequences for the synthesis of nanostructured films with controlled structure and for all the experimental techniques requiring intense and collimated cluster beams. Due to its simplicity the focusing nozzle presented here can be used with a wide variety of cluster sources.
Detection of nickel atom by laser induced fluorescence during carbon nanotube formation in a laser produced plume
Authors: De Boer G. , Arepalli S. , Holmes W. , Nikolaev P. , Range C. , Scott C.
Published: July 2002

In situ monitoring of catalyst nickel atoms by laser induced fluorescence during carbon nanotube formation in a laser-produced plume was performed at the Johnson Space Center nanotube production laboratory. The results indicate that ablation of nickel and plume dynamics are strongly related to the oven temperature. Nickel atoms have a long lifetime of several milliseconds and have an electronic temperature of at least 1500 K during carbon nanotube formation.
Large eddy simulation of turbulent channel flows by the variational multiscale method
Authors: Hughes Thomas J. R. , Oberai Assad A. , Mazzei Luca
Published: July 2002

The variational multiscale formulation of LES is applied to two-dimensional equilibrium and three-dimensional nonequilibrium channel flows. Simple, constant-coefficient Smagorinsky-type eddy viscosities, without wall damping functions, are used to model the decay of small scales, an approach which is not viable for wall-bounded flows within the traditional LES framework. Nevertheless, very good results are obtained.
Dielectric relaxation in dielectric mixtures: Application of the finite element method and its comparison with dielectric mixture formulas
Authors: Tuncer Enis , Gubański Stanisław M. , Nettelblad B.
Published: July 2002

In this article, the frequency dependent dielectric properties, ε(ω), of an “ideal” binary composite structure were investigated by using the finite element method in the frequency domain. The material properties of the phases, i.e., dielectric permittivity, ε, and direct-current conductivity, σ, were assumed to be frequency independent. Moreover, the inclusion phase was more conductive than the matrix phase. The inclusions were infinitely long unidirectional cylinders which could be assumed to be hard disks in two dimensions in the direction perpendicular to the cylinder direction. Three different inclusion concentration levels were considered, e.g., low, intermediate, and high. The calculated dielectric relaxations were compared with those of the dielectric mixture formulas in the literature and it was found that there were no significant differences between the formulas and the numerical solutions at low inclusion concentration. Furthermore, the obtained responses were curve fitted by the addition of the Cole–Cole empirical expression and the ohmic losses by using a complex nonlinear least squares algorithm in order to explain the plausible physical origin of the Cole–Cole type dielectric relaxation. The dielectric relaxations were Debye-like when the concentration of the inclusions were low. For intermediate and high concentrations, the responses obtained from the numerical simulations deviated from that of the Debye one, whose curve fittings with the Cole–Cole empirical expression were inadequate.
Linear stability analyses of natural convection flows in a differentially heated square cavity with conducting horizontal walls
Authors: Xin Shihe , Le Quéré Patrick
Published: July 2002

The stability of two-dimensional (2D) natural convection flows with respect to both two- and three-dimensional perturbations is investigated numerically. Several methods (Arnoldi’s method, preconditioned Newton’s iteration and preconditioned continuation method) are put together for this purpose and applied to natural convection in a differentially heated square cavity with conducting horizontal walls for a large range of Prandtl numbers. These methods are first validated by comparison with results reported in the literature for several Prandtl numbers for both two-dimensional and three-dimensional perturbations. They are then used to extend the stability of the 2D base flows to two-dimensional perturbations for other Prandtl numbers, and to investigate in detail the stability of these two-dimensional base solutions with respect to three-dimensional perturbations for a large range of Prandtl number. For Prandtl number equal to 1 the base solutions are more unstable to three-dimensional perturbations and the most unstable three-dimensional mode, which is oscillatory, is connected to the third most unstable two-dimensional mode; for larger Prandtl numbers (3, 7, and 20), the 2D base flows are found more stable to three-dimensional perturbations than to the 2D ones and the most unstable modes are thus two dimensional; for smaller Prandtl numbers (0.71, 0.1, and 0.015) the base solutions are again more unstable to three-dimensional perturbations. These three-dimensional modes are however no longer connected to the most unstable two-dimensional oscillatory modes and correspond to stationary perturbations. Furthermore for Pr=0.015 and 0.1 the critical Rayleigh number is approximately 40 times smaller than that found for two-dimensional perturbations, indicating a dramatic change in the nature of the instability which seems to be linked to Taylor–Görtler-type instability.
Atomically accurate Si grating with 5.73 nm period
Authors: Kirakosian A. , Bennewitz R. , Crain J. N. , Fauster Th. , Lin J.-L. , Petrovykh D. Y. , Himpsel F. J.
Published: July 2002

A vicinal surface of silicon is found that exhibits an atomically accurate step pattern with a period of 5.73 nm, corresponding to 17 atomic rows per (111) terrace. It can be viewed as reconstructed Si(557) surface, where a triple step is combined with a single Si(111)7×7 unit. The driving forces for establishing regular step patterns are discussed.
Sub-attonewton force detection at millikelvin temperatures
Authors: Mamin H. J. , Rugar D.
Published: July 2002

A 290-nm-thick single-crystal silicon cantilever has been cooled in vacuum to a temperature of 110 mK in order reduce its thermal motion and thereby improve the achievable force resolution. Since the thermal conductivity of the silicon cantilever is extremely low at millikelvin temperatures, an improved optical fiber interferometer was developed to measure the subangstrom thermal motion with optical powers as low as 2 nW. At the lowest temperature, the cantilever exhibited a quality factor of 150 000 and achieved a noise temperature of 220 mK, with a corresponding force noise of 820 zN in a 1 Hz bandwidth.
Maxwell–Wagner polarization in ceramic composites BaTiO3–(Ni0.3Zn0.7)Fe2.1O4
Authors: Yu Zhi , Ang Chen
Published: July 2002

Dense ceramic composites consisting of two phases, ferroelectric BaTiO3 and ferrite (Ni0.3Zn0.7)Fe2.1O4, were synthesized via the solid state reaction route. The results indicate that insulating BaTiO3 can be well compatible to the conductive phase (Ni0.3Zn0.7)Fe2.1O4. The electrical conduction and dielectric behavior of the materials vary with the ratio of the two phases. The dielectric behavior is greatly influenced by the conductive phase. At x=0.3, a very high apparent dielectric constant peak with frequency dispersion was observed, and attributed to Maxwell–Wagner polarization. The application of the Maxwell–Wagner polarization model in dielectric materials is briefly discussed.
Magnetic and transport characteristics on high Curie temperature ferromagnet of Mn-doped GaN
Authors: Sasaki Takahiko , Sonoda Saki , Yamamoto Yoshiyuki , Suga Ken-ichi , Shimizu Saburo , Kindo Kouichi , Hori Hidenobu
Published: July 2002

Mn-doped GaN films on sapphire (0001) substrates were grown by molecular beam epitaxy system using ammonia as nitrogen source. The result of magnetization measurement gives Curie temperature as high as 940 K. The field and temperature dependencies of the magnetization show coexistence of ferromagnetic and paramagnetic phases. In addition, the temperature dependencies of electrical resistance and carrier concentration were measured to investigate the relation between the ferromagnetism and transport property. Below about 10 K, a similar anomalous increase of magnetization and resistance is observed.
Use of ion implantation to facilitate the discovery and characterization of ferromagnetic semiconductors
Authors: Theodoropoulou N. , Hebard A. F. , Chu S. N. G. , Overberg M. E. , Abernathy C. R. , Pearton S. J. , Wilson R. G. , Zavada J. M.
Published: July 2002

The discovery of epitaxially grown ferromagnetic, type III–V semiconductors (Ga,Mn)As (Tc=110 K) and (In,Mn)As (Tc=35 K) holds promise for developing semiconductor electronics that utilize the electron’s spin degree of freedom in addition to its charge. It has been theoretically predicted that some semiconducting systems could be ferromagnetic above room temperature, when optimally doped (p-GaN with 5% Mn). We report here on the use of ion implantation to incorporate magnetic ions into a variety of semiconducting substrates, thereby facilitating investigation of the nature of ferromagnetism in semiconducting systems that are difficult to grow with other methods. The magnetic ions, Mn, Fe, and Ni, were implanted into each of the epitaxially grown semiconductors GaN, GaP, and SiC to achieve volume concentrations between 1 and 5 at. %. The implanted samples were subsequently annealed at 700–1000 °C to recrystallize the samples and remove implant damage. The implanted samples were examined with both x-ray diffraction and transmission electron microscopy to characterize their microstructure and with superconducting quantum interference device (SQUID) to determine magnetic properties. In most cases, no secondary phases were found. The magnetic measurements [hysteresis, coercive fields, and differences between field-cooled (FC) and zero field-cooled (ZFC) magnetizations] indicate ferromagnetism up to room temperature for some samples that could not be attributed to superparamagnetism or any other magnetic phase. Particularly, p-GaP:C with high hole concentration, when doped by implantation with 3 at. % Mn, showed ferromagnetic behavior very close (Tc=250 K) to room temperature. In summary, we found that ferromagnetic behavior is very dependent on the concentration of the magnetic impurities for all samples and it is even more dramatically affected by the type and the concentration of the majority carriers, in qualitative agreement with the theory.
Electric field detection in laser-plasma interaction experiments via the proton imaging technique
Authors: Borghesi M. , Campbell D. H. , Schiavi A. , Haines M. G. , Willi O. , MacKinnon A. J. , Patel P. , Gizzi L. A. , Galimberti M. , Clarke R. J. , Pegoraro F. , Ruhl H. , Bulanov S.
Published: July 2002

Due to their particular properties, the beams of the multi-MeV protons generated during the interaction of ultraintense (I>1019 W/cm2) short pulses with thin solid targets are most suited for use as a particle probe in laser-plasma experiments. The recently developed proton imaging technique employs the beams in a point-projection imaging scheme as a diagnostic tool for the detection of electric fields in laser-plasma interaction experiments. In recent investigations carried out at the Rutherford Appleton Laboratory (RAL, UK), a wide range of laser-plasma interaction conditions of relevance for inertial confinement fusion (ICF)/fast ignition has been explored. Among the results obtained will be discussed: the electric field distribution in laser-produced long-scale plasmas of ICF interest; the measurement of highly transient electric fields related to the generation and dynamics of hot electron currents following ultra-intense laser irradiation of targets; the observation in underdense plasmas, after the propagation of ultra-intense laser pulses, of structures identified as the remnants of solitons produced in the wake of the pulse.
Global deperturbation analysis from energetic, magnetic, and radiative measurements: Application to Te2
Authors: Pazyuk E. A. , Stolyarov A. V. , Tamanis M. Ya. , Ferber R. S.
Published: July 2002

In the framework of a unified physical model, employed as a basis Hund’s case ‘‘c,’’ a quantitative description has been worked out for experimental data of term values, g factors, and lifetimes of excited B0+u and A1u states, as well as for relative intensities in B0+u–X0+g, A1u–X1g, and B0+u–X1g transitions. The model includes a minimum number of adjustable fitting parameters: deperturbed molecular constants for both states, intramolecular interaction matrix element (η), two electronic matrix elements of magnetic interactions (Gz,G±), as well as two parallel (Re∥B0u+–X0g+, Re∥A1u–X1g) and two perpendicular (Re⊥B0u+–X1g, Re⊥A1u–X0g+) electronic transition moments. The B0+u state g factors and the intensity distribution over P, R, Q branches in B0+u–X1g transition was found to be most sensitive to weak heterogeneous (ΔΩ=±1) perturbations, and a simple analytic connection between those characteristics has been proposed. The Ω-doubling constant for A1u state levels was evaluated. By transforming the responsible electronic matrix elements to Hund’s case ‘‘a’’ basis, the A1u state has been found to be basically a 3Σ1 component of the B 3Σ−u state, with a small admixture (<14%) of a 3Π1 component of the A 3Πu state, and a change in term notation from A1u to B1u is proposed.
Dissociative electron attachment to CCl4: Lifetime of the CCl4−* intermediate
Authors: Popple R. A. , Finch C. D. , Smith K. A. , Dunning F. B.
Published: July 2002

Dissociative electron attachment to CCl4 is studied by measuring the angular and velocity distribution of Cl− ions produced in collisions with velocity selected K(np) Rydberg atoms. Analysis of the data using a Monte Carlo collision code that models the detailed kinematics of the reaction indicates that the lifetime of the CCl4−* intermediate initially formed by Rydberg electron capture is 7.5±2.5 ps and that, upon dissociation, only a small fraction of the excess energy of reaction appears as translational energy of the Cl− and CCl3 fragments.
Surface tension of water droplets: A molecular dynamics study of model and size dependencies
Authors: Zakharov Viktor V. , Brodskaya Elena N. , Laaksonen Aatto
Published: July 2002

The applicability of two frequently used interaction potentials for water, the five-site ST2 model and the four-site TIP4P model, is investigated in computer simulations of water droplets of varying cluster size from N=64 to N=512. The orientation of the water molecules in the surface region is investigated for the both models. Surface properties, such as work of cluster formation, local density profiles, kinetic and total energy profiles, and pressure profiles as a function of the droplet size, obtained using the two models are compared. Moreover, the surface potential and the electric potential profiles are calculated. Surface tension is calculated and its dependence on the cluster size is investigated. It is found that surface properties are very sensitive to the used potential models. For example, the water molecules are found to lie differently in the inner region of the surface layer, the ST2 molecules being predominantly perpendicular to the surface, while the TIP4P molecules lie mainly parallel to the surface. In the outer surface region, the molecular planes are perpendicular to the surface for the both models. The TIP4P model allows a calculation of the surface tension, giving a value 54 mN/m which is somewhat lower than the experimental value for the plane surface, while for the ST2 model, larger clusters are needed than those treated in the present study.
How to mesh up Ewald sums. II. An accurate error estimate for the particle–particle–particle-mesh algorithm
Authors: Deserno Markus , Holm Christian
Published: July 2002

We construct an accurate estimate for the root mean square force error of the particle–particle–particle mesh (P3M) algorithm by extending a single particle pair error measure which has been given by Hockney and Eastwood. We also derive an easy to use analytic approximation to the error formula. This allows a straightforward and precise determination of the optimal splitting parameter (as a function of system specifications and P3M parameters) and hence knowledge of the force accuracy prior to the actual simulation. The high quality of the estimate is demonstrated in several examples.
S
2
(a
1
Δ)
production in the reaction of S 1D atoms with COS: Spectroscopy and dynamics
Authors: Richter R. C. , Rosendahl A. R. , Hynes A. J. , Lee E. P. F.
Published: July 2002

The reaction S(1D)+COS(X 1Σ+)→S2(a 1Δ)+CO(X 1Σ+) has been studied using pulsed photolytic production of S(1D) together with laser-induced fluorescence detection of S2(a 1Δ). S(1D) was produced by 212.8 nm (Nd:YAG fifth harmonic) photolysis of OCS. The nascent S2(a 1Δ) product has been observed under single collision conditions. Rotational and vibrational population distributions for excited S2(a 1Δ) have been obtained. The observed vibrational distribution was analyzed using surprisal analysis and was found to be much colder than predicted by purely statistical arguments, although it extends to at least v=6. A rotational population distribution was obtained for v=2 of the S2(a 1Δ) state. It shows a maximum around J=45, which is hotter than thermal but much colder than the statistical prediction. Resolved emission experiments were performed to verify calculated Franck–Condon factors for the S2 f 1Δ–a 1Δ transition. Ab initio calculations suggest several possible routes leading from reactants to products in the singlet reaction channel but predict significant reaction barriers for the triplet channel.
Influence of oxygen content and structural defects on low-temperature mechanical properties of high-temperature superconducting single crystals and ceramics
Authors: Lubenets S. V. , Natsik V. D. , Fomenko L. S. , Kaufmann H.-J. , Bobrov V. S. , Izotov A. N.
Published: July 2002

The data for the microhardness and fracture toughness of Y–Ba–Cu–O and Bi-based single crystals and ceramics in the temperature range 77–293 K are presented and analyzed. Our study reveals that the microhardness of high temperature superconductors is very sensitive to the oxygen stoichiometry, the phase composition, the temperature, and to the microstructural defects such as impurities, intergranular boundaries, and voids. Attention is drawn to the anisotropy of the micromechanical properties and to the features of the fracture in the vicinity of the indentation. The data available on the plasticity of Y–Ba–Cu–O and Bi–Sr–Ca–Cu–O from micro- and macrotests are compared.
Stochastic estimation as a statistical tool for approximating turbulent conditional averages
Authors: Brereton G. J.
Published: July 2002

In this paper, extensions to conventional stochastic estimation techniques are presented, whereby uncertainties in individual estimates may be deduced. Test applications to time series of velocity measurements in a turbulent boundary layer confirm the fidelity of the uncertainty estimation procedure and illustrate how the optimal choice of stochastic estimation model can be strongly dependent on the event upon which the average is conditioned. They also demonstrate how stochastic estimations may be refined to yield more accurate descriptions of particular coherent motions, and how they can reveal the existence of rare events, different in statistical character to their more frequent counterparts, which might otherwise be undetected by conventional stochastic estimation.
Singular solutions of the Zakharov equations for Langmuir turbulence
Authors: Papanicolaou G. C. , Sulem C. , Sulem P. L. , Wang X. P.
Published: July 2002

A dynamic rescaling method is used to simulate numerically the dynamics of a collapsing wave packet in three-dimensional Langmuir turbulence, governed by the vector Zakharov equations. Subsonic and supersonic regimes are considered. For a large class of initial conditions with a single maximum for the field intensity, the collapse is found to be nearly self-similar and weakly anisotropic, while in the subsonic or near subsonic limit the electric field may develop strong anisotropy at early times and break apart into two peaks.
Near-wake of a perturbed, horizontal cylinder at a free-surface
Authors: Lin J.-C. , Sheridan J. , Rockwell D.
Published: July 2002

A horizontal cylinder intersecting a free surface is subjected to controlled vertical perturbations, and the consequent vortex formation is characterized by high-image-density particle image velocimetry, which leads to instantaneous patterns of velocity, vorticity, and streamlines. For the limiting case of the stationary cylinder, the near wake does not exhibit rapid formation of organized vortical structures in a manner similar to Kármán vortices. Application of perturbations, however, generates phase-locked vortex formation over a wide range of excitation frequencies, even at relatively low amplitudes, indicating that the near wake in presence of a free surface is convectively, rather than absolutely, unstable. At a sufficiently high value of excitation frequency, the formation of the initial vortex undergoes an abrupt change in timing, which is analogous to that occurring for Kármán vortex formation from a completely submerged cylinder. All of these features of the near wake are interpreted in terms of foci, saddle points, and reattachment points of the streamwise topology.
Numerical study of hypersonic reacting boundary layer transition on cones
Authors: Johnson Heath B. , Seipp Trevor G. , Candler Graham V.
Published: July 2002

Hypersonic gas flow over cones is solved using computational fluid dynamics to obtain accurate boundary layer profiles. A linear stability analysis is performed on the profiles to determine the amplification rates of naturally occurring disturbances, and this information is used with the eN method to predict the boundary layer transition location. The effects of free-stream total enthalpy and chemical composition on transition location are studied to give a better understanding of recent experimental observations. Namely, there is an increase in transition Reynolds number with increasing free-stream total enthalpy, and this increase is greater for gases with lower dissociation energies. The results show that linear stability predicts the same trends that were observed in the experiments, but with N=10, it consistently overpredicts the transition Reynolds numbers by about a factor of 2. The results of numerical experiments are presented which show the effect of reaction endo- or exothermicity on disturbance amplification rates.
Growth and collapse of a vapor bubble in a narrow tube
Authors: Ory E. , Yuan H. , Prosperetti A. , Popinet S. , Zaleski S.
Published: July 2002

The fluid mechanical aspects of the axisymmetric growth and collapse of a bubble in a narrow tube filled with a viscous liquid are studied numerically. The tube is open at both ends and connects two liquid reservoirs at constant pressure. The bubble is initially a small sphere and growth is triggered by a large internal pressure applied for a short time. After this initial phase, the motion proceeds by inertia. This model simulates the effect of an intense, localized, brief heating of the liquid which leads to the nucleation and growth of a bubble. The dimensionless parameters governing the problem are discussed and their effects illustrated with several examples. It is also shown that, when the bubble is not located at the midpoint of the tube, a net flow develops capable of pumping fluid from one reservoir to the other. The motivation for this work is offered by the possibility to use vapor bubbles as actuators in fluid-handling microdevices.