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排序方式: 共有121条查询结果,搜索用时 15 毫秒
1.
Maria A. Tikhonova Nadezhda G. Tikhonova Michael V. Tenditnik Marina V. Ovsyukova Anna A. Akopyan Nina I. Dubrovina Tamara G. Amstislavskaya Elena K. Khlestkina 《Molecules (Basel, Switzerland)》2020,25(22)
Functional nutrition is a valuable supplementation to dietary therapy. Functional foods are enriched with biologically active substances. Plant polyphenols attract particular attention due to multiple beneficial properties attributed to their high antioxidant and other biological activities. We assessed the effect of grape polyphenols on the life span of C57BL/6 mice and on behavioral and neuroinflammatory alterations in a transgenic mouse model of Parkinson disease (PD) with overexpression of the A53T-mutant human α-synuclein. C57BL/6 mice were given a dietary supplement containing grape polyphenol concentrate (GPC—1.5 mL/kg/day) with drinking water from the age of 6–8 weeks for life. Transgenic PD mice received GPC beginning at the age of 10 weeks for four months. GPC significantly influenced the cumulative proportion of surviving and substantially augmented the average life span in mice. In the transgenic PD model, the grape polyphenol (GP) diet enhanced memory reconsolidation and diminished memory extinction in a passive avoidance test. Behavioral effects of GP treatment were accompanied by a decrease in α-synuclein accumulation in the frontal cortex and a reduction in the expression of neuroinflammatory markers (IBA1 and CD54) in the frontal cortex and hippocampus. Thus, a GP-rich diet is recommended as promising functional nutrition for aging people and patients with neurodegenerative disorders. 相似文献
2.
Functional load (FL) quantifies the contributions by phonological contrasts to distinctions made across the lexicon. Previous research has linked particularly low values of FL to sound change. Here, we broaden the scope of enquiry into FL to its evolution at higher values also. We apply phylogenetic methods to examine the diachronic evolution of FL across 90 languages of the Pama–Nyungan (PN) family of Australia. We find a high degree of phylogenetic signal in FL, indicating that FL values covary closely with genealogical structure across the family. Though phylogenetic signals have been reported for phonological structures, such as phonotactics, their detection in measures of phonological function is novel. We also find a significant, negative correlation between the FL of vowel length and of the following consonant—that is, a time-depth historical trade-off dynamic, which we relate to known allophony in modern PN languages and compensatory sound changes in their past. The findings reveal a historical dynamic, similar to transphonologization, which we characterize as a flow of contrastiveness between subsystems of the phonology. Recurring across a language family that spans a whole continent and many millennia of time depth, our findings provide one of the most compelling examples yet of Sapir’s ‘drift’ hypothesis of non-accidental parallel development in historically related languages. 相似文献
3.
We study pattern avoidance in the context of partial words. The problem of classifying the avoidable binary patterns has been solved, so we move on to ternary and more general patterns. Our results, which are based on morphisms (iterated or not), determine all the ternary patternsʼ avoidability indices or at least give bounds for them. 相似文献
4.
R.M. Green 《Journal of Algebraic Combinatorics》2002,15(3):241-252
We introduce the notion of 321-avoiding permutations in the affine Weyl group W of type A
n – 1 by considering the group as a George group (in the sense of Eriksson and Eriksson). This enables us to generalize a result of Billey, Jockusch and Stanley to show that the 321-avoiding permutations in W coincide with the set of fully commutative elements; in other words, any two reduced expressions for a 321-avoiding element of W (considered as a Coxeter group) may be obtained from each other by repeated applications of short braid relations.Using Shi's characterization of the Kazhdan–Lusztig cells in the group W, we use our main result to show that the fully commutative elements of W form a union of Kazhdan–Lusztig cells. This phenomenon has been studied by the author and J. Losonczy for finite Coxeter groups, and is interesting partly because it allows certain structure constants for the Kazhdan–Lusztig basis of the associated Hecke algebra to be computed combinatorially.We also show how some of our results can be generalized to a larger group of permutations, the extended affine Weyl group associated to GL
n
() 相似文献
5.
Joel Brewster Lewis 《Journal of Combinatorial Theory, Series A》2011,118(4):1436-1450
We define a class Ln,k of permutations that generalizes alternating (up-down) permutations and give bijective proofs of certain pattern-avoidance results for this class. As a special case of our results, we give bijections between the set A2n(1234) of alternating permutations of length 2n with no four-term increasing subsequence and standard Young tableaux of shape 〈n3〉, and between the set A2n+1(1234) and standard Young tableaux of shape 〈3n−1,2,1〉. This represents the first enumeration of alternating permutations avoiding a pattern of length four. We also extend previous work on doubly-alternating permutations (alternating permutations whose inverses are alternating) to our more general context.The set Ln,k may be viewed as the set of reading words of the standard Young tableaux of a certain skew shape. In the last section of the paper, we expand our study to consider pattern avoidance in the reading words of standard Young tableaux of any skew shape. We show bijectively that the number of standard Young tableaux of shape λ/μ whose reading words avoid 213 is a natural μ-analogue of the Catalan numbers (and in particular does not depend on λ, up to a simple technical condition), and that there are similar results for the patterns 132, 231 and 312. 相似文献
6.
Hakvoort G. Hol C. M. van Ekeren P. J. 《Journal of Thermal Analysis and Calorimetry》2001,64(1):367-375
A number of compounds is investigated for DSC calibration during cooling. Adamantane and Zn show fast reversible transitions
and can be applied both for temperature and for heat calibrations. A third compound, namely 4,4’-azoxyanisole, has a liquid
crystal to isotropic liquid transition at 409K. This compound can be used for temperature calibration. Heat calibration with
this compound is more problematic because of the small heat effect and the construction of the baseline. Other compounds like
NaNO3, In, Hg and Pb, show a slight supercooling. Nevertheless they can be used for heat calibration. The use of large samples
of NaNO3 and In gives the possibility to construct the equilibrium onset temperatures of the cooling peaks, so these two compounds
are also appropriate for temperature calibration on cooling.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
8.
The best strategy for collision avoidance under emergency conditions is to maximize wrt the controls the timewise minimum
distance between the host ship and the intruder ship. In a restricted waterway area, two main constraints must be satisfied:
the lateral deviation of the host ship from the original course is to be contained within certain limits; the longitudinal
distance covered by the host ship is to be subject to a prescribed bound. At the maximin point of the encounter, the time
derivative of the relative distance vanishes; this yields an inner boundary condition (orthogonality between the relative
position vector and the relative velocity vector) separating the main phases of the maneuver: the avoidance and recovery phases.
In this way, the optimal trajectory problem (a Chebyshev problem) can be converted into a Bolza problem with an inner boundary
condition. Numerical solutions are obtained via the multiple-subarc sequential gradient-restoration algorithm (SGRA).
Because the optimal trajectory is not suitable for real-time implementation, a guidance scheme approximating the optimal trajectory
in real time is to be developed. For ship collision avoidance, the optimal trajectory results show that the rudder angle time
history has a bang-bang form characterized by the alternation of saturated control subarcs of opposite signs joined by rapid
transitions. Just as the optimal trajectory can be partitioned into three phases (avoidance phase, recovery phase, steady
phase), a guidance trajectory can be constructed in the same way. For the avoidance and recovery phases, use of decomposition
techniques leads to an algorithm computing the time lengths of these phases in real time. For the steady phase, a feedback
control scheme is used to maneuver the ship steadily. Numerical results are presented.
Portions of this paper were presented by the senior author at the 13th International Workshop on Dynamics and Control, Wiesensteig,
Germany, 22-26 May 2005, in honor of George Leitmann.
This research was supported by NSF Grant CMS-02-18878. 相似文献
9.
Ram M. Narayanan Brett R. J. Snuttjer 《International Journal of Infrared and Millimeter Waves》1997,18(11):2077-2109
Millimeter-wave short range radar systems have unique advantages in surface navigation applications, such as military vehicle
mobility, aircraft landing assistance, and automotive collision avoidance. In collision avoidance applications, characterization
of clutter due to terrain and roadside objects is necessary in order to maximize the signal-to-clutter ratio (SCR) and to
minimize false alarms. The results of two types of radar cross section (RCS) measurements at 95 GHz are reported in this paper.
The first set of measurements presents data on the normalized RCS (NRCS) as well as clutter distributions of various terrain
types at low grazing angles of 5° and 7.5°. The second set of measurements presents RCS data and statistics on various types
of roadside objects, such as metallic and wooden sign posts. These results are expected to be useful for designers of short-range
millimeter-wave collision avoidance radar systems.
Brett Snuttjer is presently an Air Force Lieutenant at Rome Laboratory, Rome, NY 13441 相似文献
10.
Bo Li Haichao Zhang Yuxiao Niu Dechao Ran Bing Xiao 《Mathematical Methods in the Applied Sciences》2023,46(1):1096-1110
This paper investigates the problem of trajectory tracking control for quadrotor unmanned aerial vehicle (UAV) in the presence of dynamic obstacles and external disturbance forces/torques. More specifically, two new sliding mode disturbance observers are firstly designed to estimate the external disturbances, in which the observation errors can converge to zero in finite time. Furthermore, utilizing the observation information, a new sliding mode surface-like variable-based position tracking control scheme and a novel nonsingular terminal sliding mode-based attitude synchronization control scheme are developed to drive the UAV tracking the reference trajectory with obstacle avoiding. Moreover, the tracking errors of the close-loop control system can converge to zero within finite time by the analyses of Lyapunov methodology. Finally, the numerical simulation results are presented to illustrate the effectiveness of the proposed control schemes. 相似文献