170,678 research outputs found
Comments on Lahiri & Reetz
No full textGibbon D. Comments on Lahiri & Reetz. In: Gussenhoven C, Warner N, eds. Laboratory Phonology 7. Berlin, Boston: DE GRUYTER; 2002: 677-685
Bärbel Reetz, Das Paradies war für uns. Emmy Ball-Hennings und Hugo Ball. Berlin, Insel Verlag, 2015
No full textKurzreferat zu Bärbel Reetz' "Das Paradies war für uns" (Suhrkamp 2016)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Hydrogen and Pd-clusters
No full textIsotherms of Pd-H clusters with different sizes differ from bulk isotherms: they show a largely enhanced solubility in the low-concentration regime. The isotherms resemble those of bulk above the critical point, they show no flat plateau region, but a slope. However, the existence of a hysteresis gives evidence for a phase transition even in small Pd-H clusters. Structural studies of 6.0 nm clusters show a transition between two cubic phases. 3.8 nm Pd-H clusters always show an icosahedral structure in the low and high concentration regime. For an intermediate size of 5.0 nm Pd-H clusters, the lattice structure changes during H-absorption, from cubic to, most probably, icosahedral. The slope in the cluster isotherm's two-phase region is here attributed to stress emerging between the surfactant shell and the cluster during hydrogen-loading. (C) 2003 Elsevier B.V. All rights reserved
Phase transition and lattice expansion during hydrogen loading of nanometer sized palladium clusters
No full textIn situ X-ray diffraction (XRD) measurements for Pd-clusters (3.8 and 6.0 nm) are performed during hydrogen loading and unloading. The lattice parameter increases as a function of the hydrogen partial pressure. The expansion is smaller than that of bulk palladium and is shown to be cluster-size dependent. An (alpha-alpha') phase transition was observed for the large clusters but small clusters do not show this transition. XRD analysis of the as-prepared clusters show that the 3.8-nm sized clusters predominantly have an icosahedral structure, while the 6.0-nm sized clusters have a cubic structure. The effect of size and structure of the cluster on the lattice expansion and on the phase transition will be discussed. (C) 2002 Elsevier B.V. All rights reserved
A search for shorter, more convergent routes to enantiopure naphthopyrans related to the aphid insect pigments
No full textThe naphtho[2,3-c]pyran ring system is generally found amongst natural products as the 5,10- or 6,9-quinones. These compounds display a wide range of biological activities, and as such, have been synthesised by various research groups. The synthetic work described in this thesis is directed towards finding shorter, more convergent routes to enantiopure quinone A 10, quinone A' 11 and quinone-pm 13, three derivatives of the aphid insect pigments protoaphin-fb 6, protoaphin-sl 7 and protoaphin-pm 9, respectively.
The first chapter describes the previous syntheses of some naphtho[2,3-c]pyrans including those relating to the aphid insect pigment derivatives. Also detailed is the ability of these naphthopyranquinones to act as potential bioreductive alkylating and dialkylating agents. The latter part of the chapter records some of the previously achieved assemblies of quinones A 10 and A' 11 in both racemic and enantiopure form, as well as the only synthesis of enantiopure quinone-pm 13.
Chapter 2 involves the preparation of regioselectively halogenated aryldioxolanes starting with the allylation of brominated and chlorinated phenols. The isomerisation of these dioxolanes into the corresponding halogenated 2-benzopyrans is then investigated.
Chapter 3 examines the regioselectivity of the Diels-Alder reaction between protected benzopyranquinones and the substituted diene 1-methoxy-1,3-bis(trimethylsilyloxy)-buta-1,3-diene 80. Such protection involves preparing the acetates and methoxymethyl ethers of the benzopyranquinones. The latter part of the chapter describes the direct bromination of benzopyranquinones.
Chapter 4 reports on the stereoselective reaction between metal phenolates and the chiral aldehyde 108 to subsequently afford naphthyldioxolanes 264, 291, 292 and 295. The rearrangement reaction of the derived naphthyldioxolane 295 is then investigated
3D High-temperature laser profilometry during sintering
No full textMost crucial for components of complex shape or heterogeneous micro structure, precise control of sintering has decisive influence on dimensional accuracy, mechanical integrity and reliability of sintered components. In these cases, only in situ 3D high-temperature shape screening during shrinkage would allow revealing temporary sinter warpage and hereby caused potential defects. Against this background, nokra Optische Prüftechnik und Automation GmbH, HTM Reetz GmbH and BAM developed a testing device for in situ 3D shape screening for ceramic and glass-ceramic tapes up to 1000°C by means of high-temperature laser profilometry. The local repeatability of the sample-sensor distance (sample height profile) is 10 µm at 1000°C. Current work is focused on dropping these restrictions in sample shape and temperature. In a second testing device, currently being in development, samples up to 5 cm x 5 cm x 5 cm can be measured at temperatures up to 1500°C.The presentation illustrates the current state of this work and possible applications of the method
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
ASSESSING 14 C BLANKS IN THE SMALL-SCALE ANALYSIS OF N -ALKANE COMPOUND-SPECIFIC-RADIOCARBON-ANALYSIS
No full textABSTRACT
Compound-specific radiocarbon analysis (CSRA) provides the possibility to date sample material at a molecular level.
N
-alkanes are considered as specific compounds with high potential to CSRA. As these compounds originate from plant waxes, their radiocarbon (
14
C) analysis can provide valuable information about the age and origin of organic materials. This helps to reconstruct and understand environmental conditions and changes in vegetation in the past. However, CSRA has two main challenges: The small sample size of CSRA samples, making them extremely sensitive to blank effects, and the input of unknown amounts of extraneous carbon during the analytical procedure. According to the previous study from Sun and co-workers, we used different-sized aliquots of leaves
Fagus sylvatica
(
n
C27,
n
C29) and
Festuca rubra agg
(
n
C31,
n
C33) as modern standards and two commercial standards (
n
C26,
n
C28) as fossil standards for blank determination. A third commercial standard (
n
C27) with predetermined radiocarbon content of F
14
C = 0.71 (
14
C age of 2700 BP) serves to evaluate the blank correction. We found that the blank assessment of Sun and co-workers is also applicable to
n
-alkanes, with a minimum sample size of 15 µg C for dependable CSRA dates. We determined that the blank introduced during the analytical procedure has a mass of (4.1 ± 0.7) µg carrying a radiocarbon content of F
14
C = 0.25 ± 0.05. Applying the blank correction to a sediment sample from Lake Holzmaar (Germany) shows that all four isolated
n
-alkanes have similar
14
C ages. However, the bulk material of the sediment and branches found in the sediment core are younger than the CSRA dates. We conclude that the disparity between the actual age of analysed organic material and the age inferred from radiocarbon results, which can occur in sediment traps due to delayed deposition, is the reason for the CSRA age
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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