Mechanisms and time-scales in breakup of 6,7Li

The current and near future of nuclear physics is being directed by the availability of radioactive ion beams and exotic nuclei near the neutron drip line. Reactions with the weakly-bound but stable {u2076}Li and {u2077}Li nuclei were thus studied as a testbed for relating nuclear structure of weakly-bound and unstable nuclei to nuclear reaction outcomes within a coherent framework, an important goal in nuclear reaction theory. Coincidence measurements of charged fragments produced from the reactions of {u2076},{u2077}Li with high-Z targets were carried out, at sub-barrier energies, using a large-area position sensitive detector array at back-angles. The wide and continuous angular coverage of the detector, and the choice of sub-barrier energies, were crucial in obtaining clear conclusions. For the reactions with {u2076}Li, the observed {u03B1} + d and {u03B1} + p coincidences show direct cluster breakup ({u2076}Li {u21E2}{u03B1} + d), but also large yields of breakup triggered by n-transfer ({u2076}Li {u21E2}{u2075}Li {u21E2}{u03B1} + p). Coincidences between {u03B1} + {u03B1} were also observed indicating breakup triggered by d-transfer ({u2076}Li {u21E2}{u2078}Be {u21E2}{u03B1} + {u03B1}). For the {u2077}Li-induced reactions, direct cluster breakup ({u2077}Li {u21E2}{u03B1} + t) was observed, but more probable was p-pickup by the projectile resulting in {u03B1} + {u03B1} coincidences ({u2077}Li {u21E2}{u2078}Be {u21E2}{u03B1} + {u03B1}). The measured relative energy gives an indication of the time-scales for each breakup mode, allowing a comparison with the time-scales for direct nuclear reactions and fusion. These measurements demonstrate that the reaction dynamics and outcomes are determined not only by the properties of the two colliding nuclei, but also by the ground-state and excited state properties of their neighbours. This is a key insight for understanding and predicting reactions of weakly-bound nuclei near the limits of nuclear existence. Furthermore, the results suggest that in sub-barrier collisions of {u2076}Li and {u2077}Li with all but the lightest nuclei, the most likely nuclear reactions will lead to breakup of the projectile-like nucleus, forming elements lighter than Li. This needs to be tested experimentally for collisions with much lighter nuclei, and possible implications for lithium abundances in cosmological processes investigated

Removal of Power Line Interference from Electrocardiograph (ECG) using Proposed Adaptive Filter Algorithm

ECG signals in measurements are contaminated by noises including power line interference. In recent years, adaptive filters with different approaches have been investigated to remove power line interference in ECG.In this paper, an adaptive filter is proposed to cancel power line interference in ECG signals. The proposed algorithm is experimented with MIT-BIH ECG signals data base. The algorithm2019;s results are compared with the results of other adaptive filter algorithms using Least Mean Square (LMS), Normalized Least Mean Square (NLMS) by Signal to Noise (SNR). Theses works are performed by LabVIEW software

On asymptotic periodic solutions of fractional differential equations and applications

In this paper we study the asymptotic behavior of solutions of fractional differential equations of the form $D^{\alpha}_Cu(t)=Au(t)+f(t), u(0)=x, 0<\alpha\le1, ( *)$ where $D^{\alpha}_Cu(t)$ is the derivative of the function $u$ in the Caputo's sense, $A$ is a linear operator in a Banach space \X that may be unbounded and $f$ satisfies the property that $\lim_{t\to \infty} (f(t+1)-f(t))=0$ which we will call asymptotic $1$-periodicity. By using the spectral theory of functions on the half line we derive analogs of Katznelson-Tzafriri and Massera Theorems. Namely, we give sufficient conditions in terms of spectral properties of the operator $A$ for all asymptotic mild solutions of Eq. (*) to be asymptotic $1$-periodic, or there exists an asymptotic mild solution that is asymptotic $1$-periodic.Comment: 13 pages. arXiv admin note: text overlap with arXiv:1910.0860

Asymptotic periodic solutions of differential equations with infinite delay

In this paper, by using the spectral theory of functions and properties of evolution semigroups, we establish conditions on the existence, and uniqueness of asymptotic 1-periodic solutions to a class of abstract differential equations with infinite delay of the form \begin{equation*} \frac{d u(t)}{d t}=A u(t)+L(u_t)+f(t) \end{equation*} where $A$ is the generator of a strongly continuous semigroup of linear operators, $L$ is a bounded linear operator from a phase space $\mathscr{B}$ to a Banach space $X$, $u_t$ is an element of $\mathscr{B}$ which is defined as $u_t(\theta)=u(t+\theta)$ for $\theta \leq 0$ and $f$ is asymptotic 1-periodic in the sense that $\lim\limits_{t \rightarrow \infty}(f(t+1)-$ $f(t))=0$. A Lotka-Volterra model with diffusion and infinite delay is considered to illustrate our results.Comment: 13 page

The COVID-19 global pandemic : a review of the Vietnamese Government response

The profound effect of COVID-19 pandemic has not eluded Vietnam, a lower-middle-income country that borders China, the country where the outbreak originated. Currently facing a second wave, Vietnam experienced several months of insignificant community-transmission, when the epidemic was effectively under control. This paper provides an account of the policies developed by the national COVID-19 response team during the first wave, from January to July 2020. Three key components were identified, including (i) the timely and decisive responses from the national and local authorities in the early phase of the pandemic, (ii) a society-wide approach, supported by an effective risk communication strategy which managed to gain the public trust, and (iii) an effective preventive medicine and infectious disease control system, residing in early case identification, strict isolation, effective contact tracing and compulsory quarantine of close contacts. While several other important components of the health system, such as financing and human resources remain largely under-explored, the results of this study show that a mixture of measures may lead to an effective epidemic management

Classical dynamical modelling of near-barrier breakup

The complete fusion of light, weakly-bound nuclides is known to be significantly suppressed with respect to comparable well-bound projectiles or with respect to single barrier penetration model calculations. Strong α-clustering in these light systems mean that they very easily disintegrate into clusters, either via direct excitation of their intrinsic cluster continuum, or via transfer reactions which connect to unbound states in neighbouring nuclides. This breakup is thought to reduce the probability for complete fusion. Here we discuss which processes cause breakup, whether or not breakup happens fast enough, and the interpretation of measurements made at the Australian National University of breakup using classical dynamical models. Understanding the intimate details of breakup, and the resonances through which it proceeds, will be crucial in determining its likely influence on fusion.This work was supported by Australian Research Council Grant Nos. FT120100760 and DP170102423

Resonances in transfer-triggered Breakup of ⁷Li in near-barrier collisions

Above-barrier complete fusion cross sections of weakly-bound 6,7Li and 9Be are known to be suppressed with respect to single-barrier penetration model calculations. Breakup of the projectile - either via direct excitation of continuum states, or by transfer of nucleons - is thought to be the cause, preventing complete capture of the projectile charge. Using the example of 7Li→8Be→ α + α we show how the contributions to breakup from different resonances in 8Be can be identified, and discuss their likely influence on fusionSupport from Australian Research Council grants FL110100098, DP130101569, DE140100784 and DP14101337 is acknowledged. Support for accelerator operations through the NCRIS program is acknowledged