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61.
Pattern formations in chaotic spatio-temporal systems modelled by coupled chaotic oscillators are investigated. We focus on
various symmetry breakings and different kinds of chaos synchronization-desynchronization transitions, which lead to certain
types of spontaneous spatial orderings and the emergence of some typical ordered patterns, such as rotating wave patterns
with splay phase ordering (orientational symmetry breaking) and partially synchronous standing wave patterns with in-phase
ordering (translational symmetry breaking). General pictures of the global behaviors of pattern formations and transitions
in coupled chaotic oscillators are provided. 相似文献
62.
The present paper deals with the interactions of bromine with poly-acrylonitrile (PAN). Kinetics and equilibria of the sorption of Br2 on PAN were studied at a concentration range of 0.01–0.1 mol/L and a temperature range of 25–40°C. Two kinds of sorption were found: a “reversible” sorption removable by water and an “irreversible” sorption removable by aqueous ammonia solutions. The irreversibly sorbed bromine is presumably linked by charge transfer to the nitrile groups of the PAN, as evidenced by UV spectra. The irreversible sorption follows the reversible sorption and is slower. Partition coefficients obtained from the linear Freundlich isotherms increased with temperature and, at 40°C, the values obtained were 97, 65, and 32 L/kg for the total, irreversible, and reversible sorptions, respectively. At 25°C the chemical potential, enthalpy, and change in entropy for the irreversible sorption were ?2.0 kcal/mol, 9.4 kcal/mol, and 38 cal·mol?1·K?1. Effects of a 6-day Br2 treatment and ammonia rinse were: decrease in dry T g from 74.5 to 61°C and in water from 38 to 35°C; no significant decrease in M W ; decrease in tensile strength measured after the bromine stage, and improvement after ammonia stage; increased swollen dimensions from 57% in water to 75%; and stabilization of swollen dimensions upon drying. The results support the existence of two phases in the less ordered regions of PAN. 相似文献
63.
Mahmood Haj‐Yahya Pushparathinam Gopinath Kolla Rajasekhar Hilda Mirbaha Marc I. Diamond Hilal A. Lashuel 《Angewandte Chemie (International ed. in English)》2020,59(10):4059-4067
The consistent observation of phosphorylated tau in the pathology of Alzheimer's disease has contributed to the emergence of a model where hyperphosphorylation triggers both tau disassociation from microtubules and its subsequent aggregation. Herein, we applied a total chemical synthetic approach to site‐specifically phosphorylate the microtubule binding repeat domain of tau (K18) at single (pS356) or multiple (pS356/pS262 and pS356/pS262/pS258) residues. We show that hyperphosphorylation of K18 inhibits 1) its aggregation in vitro, 2) its seeding activity in cells, 3) its binding to microtubules, and 4) its ability to promote microtubule polymerization. The inhibition increased with increasing the number of phosphorylated sites, with phosphorylation at S262 having the strongest effect. Our results argue against the hyperphosphorylation hypothesis and underscore the importance of revisiting the role of site‐specific hyperphosphorylation in regulating tau functions in health and disease. 相似文献
64.
Animal locomotion employs different periodic patterns known as animal gaits. In 1993, Collins and Stewart recognized that
gaits possessed certain symmetries and characterized the gaits of quadrupeds and bipeds using permutation symmetry groups,
which impose constraints on the locomotion center called the central pattern generator (CPG) in the animal brain. They modeled
the CPG by coupling four nonlinear oscillators and found that it was possible to reproduce all symmetries of the gaits by
changing the coupling strength. Here we propose to extend this idea using coupled chaotic oscillators synchronized using the
Pyragas method in order to characterize the CPG symmetries. We also evaluate the time series behavior when the foot is in
contact with the ground: this has potential robotic applications. 相似文献
65.
Low temperature-low pressure argon, nitrogen, and air plasmas generated with rf radiation have been used to treat cotton cellulose and other saccharides. The physical and chemical nature of each substrate was altered by the cold plasma. Although no gross topographical changes of the cotton surface were visible even under the electron microscope, plasma-treated cotton wetted more rapidly and more uniformly than its control, and other saccharides were more soluble in water and other chemical reagents (such as ammonium hydroxide) after plasma treatment. Free radicals were created within the cellulose matrix and structures of all other saccharides. ESR signals, which indicate presence of carbon radicals, degenerated asymmetrically, implying that other types of radicals also existed. ESCA spectra of cotton cellulose showed that some carbon atoms had been oxidized and some oxygen atoms reduced during plasma activation. Activated cottons displayed chemiluminescence and had redox powers that varied with their environments. When cotton and organic monomers were simultaneously present in cold plasma, reactive centers initiated polymerization ofthin films upon the cotton surface. Plasmaactivated cottons exhibited the same chemical reactions as a-hydroxyperoxides or their precursors from living organisms. 相似文献
66.
Hilda Geiringer 《Mathematische Zeitschrift》1955,63(1):514-524
Ohne Zusammenfassung
Issai Schur zum Gedächtnis 相似文献
67.
James?N?BaraniukEmail author Hilda?Maibach Gail?Whalen Daniel?J?Clauw 《BMC neuroscience》2004,5(1):58
Background
Define covariates of cerebrospinal corticotropin-releasing hormone (CRH) levels in normal humans. CRHCSF was measured in 9 normal subjects as part of an intensive study of physiological responses stressors in chronic pain and fatigue states. CRHCSF was first correlated with demographic, vital sign, HPA axis, validated questionnaire domains, baseline and maximal responses to pain, exercise and other stressors. Significant factors were used for linear regression modeling. 相似文献68.
69.
A method to quantify sub-ppm levels of formaldehyde in acetone has been developed and it is reported here. In this method, the different reactivities and stabilities of sulfite with formaldehyde and acetone are used to separate the two carbonyl compounds. Sulfite reacts with formaldehyde to form hydroxymethanesulfonate (HMS), the non-volatile and stable nature of which allows its separation from bulk acetone solvent. The resulting HMS is then converted back to formaldehyde under basic conditions, and formaldehyde is derivatized with 2,4-dinitrophenylhydrazine (DNPH) and quantified in its DNP hydrazone form using high-performance liquid chromatography-UV detection. The method detection limit at the 99% confidence level was 0.051 mg L−1. A batch of samples can be processed within 4 h. The method has been applied to quantify the amount of formaldehyde in an analytical-grade acetone and in a commercial nail polish remover and the level of formaldehyde was found to be 0.175 and 0.184 mg L−1, respectively. 相似文献
70.
Rex A. Palmer Hilda T. Palmer Christopher S. Frampton Brian S. Potter 《Journal of chemical crystallography》2007,37(1):1-14
The molecular framework of steroids was firmly established from the successful X-ray analysis of cholesteryl iodide crystals
over fifty years ago. At the time, this was a triumph for the rapidly developing technique of X-ray crystallography. We describe
here new analyses of cholesteryl iodide using crystals of forms I and II(A) which are at least 50 years old. Comparison of these two structures reveals subtle differences in the geometry of the steroid
skeleton, the attached side chain and the covalently bound iodine. The crystals of both forms occur in the same monoclinic
space group, P21, with similar but nevertheless different unit cells, particularly in the b-axis length. As a consequence, there are subtle
differences in the packing mechanisms of the two polymorphs. The two forms were originally classified by Bernal and Crowfoot,
on the basis of their studies of more than 60 crystals of sterols and sterol derivatives, as “normal, type A - the common
form” (corresponding to form II) and “reverse or type B” (corresponding to form I), respectively. Those crystals of form I
which have survived for almost 55 years are poor X-ray diffractors at room temperature and have been analysed at liquid N
temperature, diffracting well under these conditions. Form II crystals diffract well at room temperature and for this reason
the crystals were not cooled. The main differences in geometry occur in the side-chain which is disordered in the room temperature
form II crystals, whilst the individual ring conformations in the steroid skeleton are similar, ring A being a strained chair,
ring B a 7α/8β half-chair, ring C a symmetrical chair and D a 13β/14α half-chair.
(A) Originally denoted Forms B and A respectively. See Additional Note (A) for explanation.
相似文献
Rex A. PalmerEmail: |