169,872 research outputs found
The first centrohexaindane bearing twelve functional groups at its outer molecular periphery and related lower veratrole-derived centropolyindanes
No full textHarig M, Kuck D. The first centrohexaindane bearing twelve functional groups at its outer molecular periphery and related lower veratrole-derived centropolyindanes. EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. 2006;(7):1647-1655.The first T-d-symmetrical derivative of centrohexaindane bearing twelve functional groups has been synthesized. Six pairs of methoxy groups, each of which belong to six veratrole units fused to the topologically nonplanar (K-5) core, point outwards from the molecular center into the six directions of the Cartesian space. The synthesis of this first dodeca-substituted centrohexaindane was achieved along the "propellane route" established previously for the parent centrohexaindane, but the electron-rich character of some of the intermediates was found to require considerably modified methodology. Two hexamethoxy-substituted centrotriindanes, representing lower congeners of the title compound and bearing three veratrole units, were also synthesized. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006
Mass spectrometric fragmentation of di-, tri-, and hexaquinane-fused dimethyl muconates induced by single and double electron ionization
No full textHarig M, Kuck D. Mass spectrometric fragmentation of di-, tri-, and hexaquinane-fused dimethyl muconates induced by single and double electron ionization. ARKIVOC. 2020:9-19.The electron ionization mass spectra of nine muconic acid dimethyl esters that bear up to three muconate groups fused with a centropolycyclic di-, tri- and hexaquinane framework exhibit dominating fragmentation by loss of a methoxycarbonyl radical, (COOMe)-C-center dot, from the molecular radical cations, M center dot+. Pyrylio-annelated structures for the [M - COOMe](+) ions are postulated in analogy to literature reports on simple muconic acids esters. The congeners bearing two or three dimethyl muconate groups lose also two (COOMe)-C-center dot radicals after twofold ionization. The doubly charged fragment ions [M - 2 COOMe](2+) are proposed to contain two isolated pyrylium rings fused to the original tri- or hexaquinane core, thus representing polyaromatic distonic dications. [GRAPHICS]
2,3,6,7,10,11-hexamethoxytribenzotriquinacene: Synthesis, solid-state structure, and functionalization of a rigid analogue of cyclotriveratrylene
No full textHarig M, Neumann B, Stammler H-G, Kuck D. 2,3,6,7,10,11-hexamethoxytribenzotriquinacene: Synthesis, solid-state structure, and functionalization of a rigid analogue of cyclotriveratrylene. EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. 2004;2004(11):2381-2397.The syntheses of several tribenzotriquinacenes bearing six methoxy groups at the outer peripheral positions of the aromatic rings are reported. The centro-methyl derivative is accessible in surprisingly good yield through two-fold cyclodehydration in the final step of a synthesis route which requires special care in the preparation of some electron-rich key intermediates, such as 5,6-dimethoxy-2-methylindane-1,3-dione and bis(3,4-dimethoxyphenyl)methanol. X-ray single-crystal structure analysis of the centro-methyl derivative confirms its C-3v-symmetrical molecular structure but, at variance from the parent centro-methyltribenzotriquinacene and the similarly shaped cyclotriveratrylene, the hexamethoxytribenzotriquinacene analog does not form columnar stacks in the solid state. Functionalization of the three benzhydrylic bridgehead positions leads to the tetramethyl analog and the bridgehead triol in good yields. In contrast, attempts to functionalize the ortho positions by nitration or bromination mainly give rise to ring cleavage through electrophilic ipso attack, which parallels the behavior of cyclotribenzylenes and cyclotriveratrylenes. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004
An Elusive Nonaromatic Goal behind the Centropolyindanes: Aufbau of Veratrolo-Annelated Centropolyquinanes and Ozonolytic Abbau
No full textHarig M, Neumann B, Stammler H-G, Kuck D. An Elusive Nonaromatic Goal behind the Centropolyindanes: Aufbau of Veratrolo-Annelated Centropolyquinanes and Ozonolytic Abbau. CHEMPLUSCHEM. 2017;82(7):1078-1095.This study presents a potential experimental approach to the still elusive topologically nonplanar (K-5) parent hydrocarbon, centrohexaquinane (1), by a construction-dismantling (aufbau-abbau) strategy via electron-rich aromatic centropolyindanes. A series of veratrole-based centropolyindanes are synthesized and subjected to ozonolytic degradation. These include the 2,2'-spirobiindanes 30-32, fuso-diindane 33, triptindanes 3436, tribenzotriquinacene 37, and tetramethoxycentrohexaindane 9. Spirane 30 and propellane 36 are characterized by Xray structure analysis. Ozonolysis of 32 and 33 gives a keto ester (59) and a dimethyl muconate (60), respectively. Dime-thoxytriptindane 34 gives a [3.3.3] propellane-cis, cis-muconate (61) in good yield, the stereochemistry of which is determined by X-ray structure analysis. Tetramethoxytriptindane 35 gives the [3.3.3] propellane-bis-muconate 62 along with a [3.3.3] propellane-dialdehyde-muconate (63). Hexamethoxytriptindane 36 furnishes three products of mainly intra-dimethoxy cleavage, with the [3.3.3] propellane-tris-muconate 64 as the major component. X-ray structure analysis of 64 reveals molecular C-3 symmetry and all-cis, cis stereochemistry of the three muconate groups. Hexamethoxytribenzotriquinacene 37 gives the triquinacene-tris-muconate 68, albeit in very low yield. Ozonolysis of tetramethoxycentrohexaindane 9 affords the bis-muconate 10 in moderate yield, along with two further centrohexacyclic products of single-wing degradation
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
Spectroscopic characterisation of centropolyindanes
No full textParker SF, Zhong L, Harig M, Kuck D. Spectroscopic characterisation of centropolyindanes. PHYSICAL CHEMISTRY CHEMICAL PHYSICS. 2019;21(8):4568-4577.A highly promising class of three-dimensional polyaromatic hydrocarbons comprises the centropolyindanes. The characteristic feature of these compounds is the mutual fusion of several molecules of indane along the saturated C-C bonds of their cyclopentane rings. Among the polycyclic aromatic hydrocarbons, the centropolyindanes are special because of the saturated core of sp(3)-hybridised carbon atoms embedded in a three-dimensional environment of aromatic building blocks. While the centropolyindanes and their numerous derivatives have been studied in detail by NMR spectroscopy, mass spectrometry and X-ray diffraction, investigation of their vibrational features, and especially those of the neopentane core present in most cases, have not been performed so far. In the present paper, we report the first systematic study of a set of centropolyindanes by vibrational spectroscopy, using inelastic neutron scattering (INS), infrared and Raman spectroscopies
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
Real-Time polymerase chain reaction of immunoglobulin rearrangements for quantitative evaluation of minimal residual disease in multiple myeloma
No full textThe majority of patients with multiple myeloma (MM) have persistence of minimal residual disease (MRD), as determined by polymerase chain reaction (PCR) detection of clonal immunoglobulin H (IgH) gene rearrangements. As a result, PCR analysis has not provided clinically useful prognostic information in myeloma patients. Instead, quantitative PCR approaches are required to predict patient outcomes and assess response to novel treatment strategies. We adapted real-time PCR technology to quantify myeloma cells using the IgH rearrangement and then assessed the utility of this approach in 29 patients with myeloma who had undergone autologous stem cell transplantation. Because of the high cost of producing a specific reporting probe for each patient, H-chain V-region family-specific consensus probes were used in association with allele-specific oligonucleotides for PCR amplification. Because of the high frequency with which somatic hypermutation at the immunoglobulin locus occurs in MM, a number of mismatches occurred between the patient sequences and the consensus probe. However, construction of a limited number of probes allowed real-time PCR with a sensitivity of 10(-4) to 10(-5). To validate this method, we extensively evaluated assay accuracy and reproducibility. Results indicate that real-time PCR using consensus probes provides a feasible, accurate, and reproducible method for evaluating MRD in M M and possibly in other differentiated B-cell malignancies, and one that is less expensive than the use of patient-specific probes. This technique is being used to assess tumor depletion after immunologic purging and changes in tumor burden in patients undergoing stem cell transplantation and novel treatment approaches
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
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