101,270 research outputs found
Dynamics of the lignin glass transition
No full textVURAL, DERYA/0000-0002-0120-3024; Petridis, Loukas/0000-0001-8569-060XWOS: 000442270800017PubMed: 30046795The dynamics of lignin, a complex and heterogeneous major plant cell-wall macromolecule, is of both fundamental and practical importance. Lignin is typically heated to temperatures above its glass transition to facilitate its industrial processing. We performed molecular dynamics simulations to investigate the segmental () relaxation of lignin, the dynamical process that gives rise to the glass transition. It is found that lignin dynamics involves mainly internal motions below T-g, while segmental inter-molecular motions are activated above T-g. The segments whose mobility is enhanced above T-g consist of 3-5 lignin monomeric units. The temperature dependence of the lignin segmental relaxation time changes from Arrhenius below T-g to Vogel-Fulcher-Tamman above T-g. This change in temperature dependence is determined by the underlying energy landscape being restricted below T-g but exhibiting multiple minima above T-g. The Q-dependence of the relaxation time is found to obey a power-law up to Q(max), indicative of sub-diffusive motion of lignin above T-g. Temperature and hydration affect the segmental relaxation similarly. Increasing hydration or temperature leads to: (1) the process starting earlier, i.e. the beta process becomes shortened, (2) Q(max) decreasing, i.e. the lengthscale above which subdiffusion is observed increases, and (3) the number of monomers constituting a segment increasing, i.e. the motions that lead to the glass transition become more collective. The above findings provide molecular-level understanding of the technologically important segmental motions of lignin and demonstrate that, despite the heterogeneous and complex structure of lignin, its segmental dynamics can be described by concepts developed for chemically homogeneous polymers.Genomic Science Program, Office of Biological and Environmental Research, U.S. Department of Energy (DOE) [FWP ERKP752]; Office of Science of the U. S. Department of EnergyUnited States Department of Energy (DOE) [DE-AC02-05CH11231]; DOEUnited States Department of Energy (DOE) [DE-AC05-00OR22725]This research was supported by the Genomic Science Program, Office of Biological and Environmental Research, U.S. Department of Energy (DOE), under Contract FWP ERKP752. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U. S. Department of Energy under Contract No. DE-AC02-05CH11231. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for DOE under Contract DE-AC05-00OR22725
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
A new species of Teucrium sect. Stachyobotrys (Lamiaceae) from the south of Turkey
No full textA new species of Teucrium L., Teucrium aladagense Vural & H. Duman, is described from Aladag mountain, located in Adana, Kayseri, and Nigde provinces in Turkey. The species belongs to Teucrium L. sect. Stachyobotrys Benth. A description, distribution map, habitat, information on trichome morphology, and the threatened category of the species are provided. The differences between the new species and its allies T. lamiifolium d'Urv s.l. and T. hircanicum L. are discussed, and an identification key is provided for the identification of similar taxa
Determination of dynamical heterogeneity from dynamic neutron scattering of proteins
No full textsmith, jeremy c/0000-0002-2978-3227WOS: 000432700300017PubMed: 29580551Motional displacements of hydrogen (H) in proteins can be measured using incoherent neutron-scattering methods. These displacements can also be calculated numerically using data from molecular dynamics simulations. An enormous amount of data on the average mean-square motional displacement (MSD) of H as a function of protein temperature, hydration, and other conditions has been collected. H resides in a wide spectrum of sites in a protein. Some H are tightly bound to molecular chains, and the H motion is dictated by that of the chain. Other H are quite independent. As a result, there is a distribution of motions and MSDs of H within a protein that is denoted dynamical heterogeneity. The goal of this paper is to incorporate a distribution of MSDs into models of the H incoherent intermediate scattering function, I(Q,t), that is calculated and observed. The aim is to contribute information on the distribution as well as on the average MSD from comparison of the models with simulations and experiment. For example, we find that simulations of I(Q, t) in lysozyme are well reproduced if the distribution of MSDs is bimodal with two broad peaks rather than a single broad peak.Department of Energy, Office of Basic Energy SciencesUnited States Department of Energy (DOE) [ER46680]; Genomic Science Program, Office of Biological and Environmental Research, United States Department of Energy [FWP ERKP752]This work was supported by the Department of Energy, Office of Basic Energy Sciences under contract number ER46680 (D.V. and H.R.G.) and by the Genomic Science Program, Office of Biological and Environmental Research, United States Department of Energy under contract FWP ERKP752 (J.C.S.)
Usher syndrome associated with Fuchs’ heterochromic uveitis: a case report
No full textEce Turan-Vural, Banu Torun-Acar, Nejla Tükenmez, M Şahin Sevim, Bulent Buttanri, Suphi AcarOphthalmology Clinic, Haydarpasa Numune Education and Research Hospital, Istanbul, TurkeyAbstract: We report a case of Usher syndrome in association with unilateral Fuchs' heterochromic uveitis.Keywords: Fuchs’ heterochromic uveitis, Usher syndrome, deafness, blindnes
Handwritten biographical information on Paulina T. McClung Merritt
No full textA handwritten biography of Paulina T. McClung Merritt by an unknown author, 1892.
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
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
Pelevin’s Trinity in the novel “t”: author – protagonist – reader
No full textThe article attempts to interpret Pelevin's artistic strategy in the novel "T" by exploring its subject organization and addressing the key problems of the author, the protagonist, and the reader as they are seen by the researcher. The article analyzes the peculiarities of constructing the narrative reality in the novel "T", and goes on to discuss Pelevin's philosophic models of the development of the humankind, and the emergence of his new anthropology
A new species of Teucrium sect. Stachyobotrys (Lamiaceae) from the south of Turkey
No full textA new species of Teucrium L., Teucrium aladagense Vural \& H. Duman, is
described from Aladag mountain, located in Adana, Kayseri, and Nigde
provinces in Turkey. The species belongs to Teucrium L. sect.
Stachyobotrys Benth. A description, distribution map, habitat,
information on trichome morphology, and the threatened category of the
species are provided. The differences between the new species and its
allies T. lamiifolium d'Urv s.l. and T. hircanicum L. are discussed, and
an identification key is provided for the identification of similar
taxa
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