The total charge-changing cross sections and partial cross sections for the production of projectile fragments are measured in the interactions of 400 A MeV 20 Ne with aluminum,carbon and polyethylene targets sandwiched with CR-39 plastic nuclear track detectors.The measured total charge-changing cross sections are compared with the predictions using the Bradt-Peters semi-empirical formula,and the NUCFRAG2 and PHITS models.It is shown that the measured experimental results are in good agreement with the theoretical model prediction and other experimental results,and it can be clearly seen that the partial cross sections for fragment production show obvious odd-even effects.
High-spin states in 84 Rb have been studied by using the 70Zn(18O, p3n)84Rb reaction at beam energy of 75MeV. Three regular magnetic dipole bands including strong M1 and weak E2 transitions have been observed in this nucleus which shows the characteristic feature of magnetic rotation. These bands are interpreted in the projected shell model for the first time on the basis of the four-quasiparticle configuration of the type π(fp)π(g29/2)v(g9/2). It is shown that the calculated sequence lies roughly in the same energy range as the experimental one but the interval between neighboring levels is larger than the corresponding experimental value. We believe that a 4-quasiparticle band crossing with the 2-quasiparticle band will depress the energies of the states.
How ATP binding initiates the docking process of kinesin＇s neck linker is a key question in understanding kinesin mechanisms. By exploiting a molecular dynamics method, we investigate the initial conformation of kinesin＇s neck linker in its docking process. We find that, in the initial conformation, the neck linker has interactions with /30 and forms a ＇cover-neck bundle＇ structure with/30. From this initial structure, the formation of extra turns and the docking of the cover- neck bundle structure can be achieved. The motor head provides a forward force on the initial cover-neck bundle structure through ATP-induced rotation. This force, together with the hydrophobic interaction of ILE327 with the hydrophobic pocket on the motor head, drives the formation of the extra turn and initiates the neck linker docking process. Based on these findings, a pathway from ATP binding-induced motor head rotation to neck linker docking is proposed.
There have been many recent studies devoted to the consequences of stochasticity in protein circuitry. Stress conditions, including DNA damage, hypoxia, heat shock, nutrient deprivation, and oncogene activation, can result in the activation and accumulation of p53. Several experimental studies show that oscillations can be induced by DNA damage following nuclear irradiation. To explore the underlying dynamical features and the role of stochasticity, we discuss the oscillatory dynamics in the well-studied regulatory network motif. The fluctuations around the fixed point of a delayed system are Gaussian in the limit of sufficiently weak delayed feedback, and remain Gaussian along a limit cycle when viewed tangential to the trajectory. The experimental results are recapitulated in this study. We illustrate several features of the p53 activities, which are robust when the parameters change. Furthermore, the distribution in protein abundance can be characterized by its non-Gaussian nature.
With the aid of stochastic delayed-feedback differential equations, we derive an analytic expression for the power spectra of reacting molecules included in a generic biological network motif that is incorporated with a feedback mechanism and time delays in gene regulation. We systematically analyse the effects of time delays, the feedback mechanism, and biological stochasticity on the power spectra. It has been clarified that the time delays together with the feedback mechanism can induce stochastic oscillations at the molecular level and invalidate the noise addition rule for a modular description of the noise propagator. Delay-induced stochastic resonance can be expected, which is related to the stability loss of the reaction systems and Hopf bifurcation occurring for solutions of the corresponding deterministic reaction equations. Through the analysis of the power spectrum, a new approach is proposed to estimate the oscillation period.
