169,748 research outputs found
Aplanktonic zones in the Red Sea
No full textWe use micropalaeontological and stable isotope results for a series of cores from north to south through the Red Sea, to assess temporal and spatial patterns of change in planktonic foraminiferal faunas leading up to the remarkable full-glacial Red Sea aplanktonic zones. Aplanktonic zones reflect salinities in the Red Sea in excess of the lethal 49 p.s.u. limit, caused by reduced exchange transport through the Strait of Bab el Mandab due to glacial sea-level lowering. Concerning the last glacial cycle, aplanktonic conditions began at 39 ka BP in the north, where salinities eventually reached 55–57 p.s.u. Paradoxically, planktonic faunas are reported to have survived the last glacial maximum in the northern Gulf of Aqaba, suggesting a poorly understood freshwater dilution at that time. Aplanktonic conditions (S?49 p.s.u.) reached the south-central Red Sea by 22 ka BP, while planktonic foraminiferal faunas continued, albeit in very low abundances and limited diversity (S?45 p.s.u.), in the southernmost Red Sea. During marine isotope stage (MIS) 6, the 49 p.s.u. isohaline appears to have resided in the central Red Sea, between cores KL11 and MD921017. We observe a systematic sequence of species disappearances before all glacial maxima of the last 500 kyr. Absence of a logical relationship with sea levels suggests that the disappearance sequences are not related to a general salinity increase. Instead, we argue that the sequences were driven by complex reorganisations in hydrography (stratification), productivity (food availability) and subsurface oxygenation (reproduction-habitats). The onset is marked by dramatic basin-wide expansion of conditions that today are restricted to only the southern Red Sea, suggesting an expansion of the dominance of NE monsoonal circulation over the entire Red Sea. This expansion occurred 15 or more kyr before the aplanktonic zones of MIS-12, 6 and 2, and also before MIS-10 and 8, which never reach the aplanktonic stage. Regarding the last glacial cycle, this event occurred as early as 75 ka BP (MIS-4/5 boundary). After this major climatic reorganisation, we reconstruct progressive intensification of the new conditions, especially marked by northward expansion and intensification of the subsurface oxygen minimum zone (OMZ). During the last glacial cycle, a shallow and very distinct OMZ affected the central Red Sea as early as 68 ka BP, and the north as late as 55 ka BP. The OMZ expansion/intensification appears to have been interrupted by episodes of increased ventilation
BILIPROTEINS FROM THE BUTTERFLY Pieris brassicae STUDIED BY TIME-RESOLVED FLUORESCENCE AND COHERENT ANTI-STOKES RAMAN SPECTROSCOPY
No full textThe fluorescence decay time of the biliverdin IX7 chromophore present in biliproteins isolated from Pieris brassicae is determined to be 44 ± 3 ps. This value suggests a cyclic helical chromophore structure. The vibrational frequencies determined by CARS-spectroscopy are compared with those of model compounds. The data confirm that the chromophore in the protein-bound state adopts a cyclic-helical, flexible conformation
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
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
Picosecond time-resolved fluorescence of phycobiliproteins
No full textThe α- and β-subunits of C-phycocyanin from Mastigocladus laminosus were prepared according to revised procedures. Both subunits are isolated as dimers, which can be dissociated into monomers with detergent mixtures. The fluorescence decay kinetics are similar for the respective monomers and dimers. In no case could they be fitted by only one (α-subunit) or two exponentials (β-subunit) which are predicted by theory for samples with a unique chromophore—protein arrangement containing one and two chromophores, respectively. It is suggested that there exists a heterogeneity among the chromophores of the subunits, which may persist in the highly aggregated complexes present in cyanobacterial antennas
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
Characterization of solid dispersions of carbamazepine and PEG6000/vinylcaprolactam/vinylacetate copolymer
No full textPurpose.
to investigate the solid-state properties and dissolution performances of solid dispersions of carbamazepine and a new
marketed copolymer proposed for hot melt extrusion.
Methods.
Physical mixtures [PM] were prepared by mixing in mortar and pestle for 10 min carbamazepine [CBZ, polymorphic form
III] and PEG6000/vinylcaprolactam/vinylacetate copolymer (Soluplus® BASF) in various drug/polymer ratios (1:9, 3:7, 1:1,
7:3 w/w). Co-melted formulations [CM] were prepared by heating the PM at 170°C on a hot plate for 15 min, allowing to cool at room temperature and grinding the resulting glasses in a mortar. PXRD study, DSC analysis and dissolution test
(paddle apparatus, 500mL of 0.0125% SLS solution, 37±0.5°C, 100 rpm, UV detection at 287 nm) were performed on all samples.
Results.
drug-polymer solid-state interaction, resulting in complete loss of CBZ crystallinity was found to occur in CM with
drug/polymer ratios 1:9 and 3:7 w/w. Accordingly, the glass transition recorded for these dispersions was lowered with
respect to that of the pure polymer. Non-interacted crystalline CBZ was detected in all PM as well as in 1:1 and 7:3 CM
formulations. Furthermore, non-interacted amorphous CBZ was thought to be present in the 7:3 CM formulation, resulting in
drug crystallization up on heating in the DSC experiment. As far as dissolution properties are concerned, PM presented
similar or only slightly higher dissolution rate with respect to the pure drug, whilst 1:9 and 3:7 CMF demonstrated a remarkable improvement of dissolution rate (the amount dissolved at t=10min doubled that of the pure CBZ). The 7:3 CM formulation was affected by a decreased dissolution rate probably caused by the formation of CBZ hydrate during the test.
Conclusion.
solid dispersion of CBZ with a new PEG6000/vinylcaprolactam/vinylacetate copolymer can be successfully prepared by comelting method, resulting in a high degree of drug-polymer interaction and consequently a remarkable improvement of drug
dissolution rate
FÖRSTER TRANSFER CALCULATIONS BASED ON CRYSTAL STRUCTURE DATA FROM Agmenellum quadruplicatum C-PHYCOCYANIN
No full textExcitation energy transfer in C-phycocyanin is modeled using the Forster inductive resonance mechanism. Detailed calculations are carried out using coordinates and orientations of the chromophores derived from X-ray crystallographic studies of C-phycocyanin from two different species (Schirmer et al, J. Mol. Biol. 184, 257–277 (1985) and ibid., 188, 651-677 (1986)). Spectral overlap integrals are estimated from absorption and fluorescence spectra of C-phycocyanin of Mastigocladus laminosus and its separated subunits. Calculations are carried out for the β-subunit, αβ-monomer, (αβ)3-trimer and (αβ)0-hexamer species with the following chromophore assignments: β155 = 's’(sensitizer), β84 =‘f (fluorescer) and α84 =‘m’(intermediate):]:. The calculations show that excitation transfer relaxation occurs to 3=98% within 200 ps in nearly every case; however, the rates increase as much as 10-fold for the higher aggregates. Comparison with experimental data on fluorescence decay and depolarization kinetics from the literature shows qualitative agreement with these calculations. We conclude that Forster transfer is sufficient to account for all of the observed fluorescence properties of C-phycocyanin in aggregation states up to the hexamer and in the absence of linker polypeptides
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
A 0.12mm<sup>2</sup> Wien-Bridge Temperature Sensor with 0.1°C (3σ) Inaccuracy from -40°C to 180°C
No full text Resistor-based temperature sensors can achieve much higher resolution and energy efficiency than conventional BJT-based sensors [1], but they typically occupy more area (> 0.25 mm 2 ) and have lower operating temperatures (le 125 {circ} {C}) [2]-[4]. This work describes a 0.12mm 2 resistor-based sensor that uses a Wien-bridge (WB) filter to achieve 0.1 {circ} {C} (3 sigma) inaccuracy from - 40 {circ} {C} to 180 {circ} {C}. Compared to a state-of-the-art WB sensor [4], it occupies 6 × less area and achieves comparable relative accuracy over a 76% wider operating range. Session 10.3 Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic InstrumentationMicroelectronic
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