A Nonparametric Test for Ordered Alternatives in Two-Way Layouts with Censored Data

A nonparametric test is presented to test for ordered alternatives of the treatment effects when the data follow a two-way layout. The observations are subject to arbitrary right censorship. The test is similar to the one developed by Hettmansperger and Norton (1987) for uncensored observations.     

资源与资源利用者的脉冲收获控制

研究一类资源以Cui-Lawson增长为基础的具有状态依赖脉冲收获的生态系统.首先对无脉冲作用的系统进行定性分析,得到正平衡点存在和稳定的充分条件.其次对具有状态依赖的脉冲系统,利用微分方程几何理论中后续函数法得到系统的阶一周期解存在的充分条件,证明该周期解是轨道渐近稳定的,同时利用数值模拟讨论了系统生态意义.     

Relaxin-like gonad-stimulating peptide is highly conserved in starfish Asterina pectinifera

Relaxin-like gonad-stimulating peptide (RGP) in starfish is the only known invertebrate peptide hormone responsible for final gamete maturation, rendering it functionally analogous to gonadotropins in vertebrates. Recently, RGP was purified from the radial nerves of starfish Asterina pectinifera, which belongs to the Order Valvatida in the Class Asteroidea. A. pectinifera is an endemic Japanese species, inhabiting rocky shores from northern to southern Japanese waters. This study examined whether genetic variation or polymorphism is found in RGP. Comparing cDNA sequences of RGP in A. pectinifera from 10 local populations in Japanese waters, we found that the coding DNA sequences (CDSs) were exactly the same. This result indicated that RGP is a highly conserved peptide in A. pectinifera. Furthermore, the CDS of RGP identified in Certonardoa semiregularis, which also belongs to Order Valvatida, was completely consistent with that of A. pectinifera. Thus, this also suggested that the chemical structure of A. pectinifera RGP is conserved among starfish of the Order Valvatida beyond species.     

Dynamics of prey-flock escaping behavior in response to predator's attack

The dynamic behavior of prey-flock in response to predator's attack was investigated by using molecular dynamics (MD) simulations in a two-dimensional (2D) continuum model. By locally applying interactive forces between prey individuals (e.g. attraction, repulsion, and alignment), a coherently moving state in the same direction was obtained among individuals in prey-flock. When a single predator was introduced to the prey population, the prey-flock was correspondingly deformed by the predator's continuous attacks towards the prey-flock's center. In response to the predator's attack, three regimes in the flock size (compression (Regime I), expansion (Regime II), compression (Regime III)) were revealed if the predator's attack speed (kappa) was comparatively low to the escape speed of prey-flock. If noise was added to the predator's attacking course, a higher degree of variation was observed in the patterns of compression and expansion in the prey-flock size. However, the scaling behavior in the changes in prey-flock size was present in different levels of noise with the increase in predation risk (R) when kappa takes an appropriately low value. During the procedure of escaping, order breaking in alignment (phi) of prey population was observed, while the degree of alignment was dependent upon the changes in parameters of kappa and R.     

Dynamics of amyloid β fibrils revealed by solid-state NMR

We have investigated the site-specific backbone dynamics of mature amyloid β (Aβ) fibrils using solid-state NMR spectroscopy. Overall, the known β-sheet segments and the turn linking these two β-strands exhibit high order parameters between 0.8 and 0.95, suggesting low conformational flexibility. The first approximately eight N-terminal and the last C-terminal residues exhibit lower order parameters between ～0.4 and 0.8. Interestingly, the order parameters increase again for the first two residues, Asp(1) and Ala(2), suggesting that the N terminus could carry some structural importance.     

Redox-controlled backbone dynamics of human cytochrome c revealed by N NMR relaxation measurements

Redox-controlled backbone dynamics in cytochrome c (Cyt c) were revealed by 2D ¹⁵N NMR relaxation experiments. ¹⁵N T₁ and T₂ values and ¹H-¹⁵N NOEs of uniformly ¹⁵N-labeled reduced and oxidized Cyt c were measured, and the generalized order parameters (S²), the effective correlation time for internal motion (τ_e), the ¹⁵N exchange broadening contributions (R_ex) for each residue, and the overall correlation time (τ_m) were estimated by model-free dynamics formalism. These dynamic parameters clearly showed that the backbone dynamics of Cyt c are highly restricted due to the covalently bound heme that functions as the stable hydrophobic core. Upon oxidation of the heme iron in Cyt c, the average S² value was increased from 0.88 ± 0.01 to 0.92 ± 0.01, demonstrating that the mobility of the backbone is further restricted in the oxidized form. Such increases in the S² values were more prominent in the loop regions, including amino acid residues near the thioether bonds to the heme moiety and positively charged region around Lys87. Both of the regions are supposed to form the interaction site for cytochrome c oxidase (CcO) and the electron pathway from Cyt c to CcO. The redox-dependent mobility of the backbone in the interaction site for the electron transfer to CcO suggests an electron transfer mechanism regulated by the backbone dynamics in the Cyt c-CcO system.