Radioisotope production using lasers:From basic science to applications

The discovery of chirped pulse amplification has led to great improvements in laser technology,enabling energetic laser beams to be compressed to pulse durations of tens of femtoseconds and focused to a few micrometers.Protons with energies of tens of MeV can be accelerated using,for instance,target normal sheath acceleration and focused on secondary targets.Under such conditions,nuclear reactions can occur,with the production of radioisotopes suitable for medical application.The use of high-repetition lasers to produce such isotopes is competitive with conventional methods mostly based on accelerators.In this paper,we study the production of^(67)Cu,^(63)Zn,^(18)F,and^(11)C,which are currently used in positron emission tomography and other applications.At the same time,we study the reactions^(10)B(p,α)^(7)Be and^(70)Zn(p,4n)^(67)Ga to put further constraints on the proton distributions at different angles,as well as the reaction^(11)B(p,α)^(8)Be relevant for energy production.The experiment was performed at the 1 PW laser facility at VegaⅢin Salamanca,Spain.Angular distributions of radioisotopes in the forward(with respect to the laser direction)and backward directions were measured using a high purity germanium detector.Our results are in reasonable agreement with numerical estimates obtained following the approach of Kimura and Bonasera[Nucl.Instrum.Methods Phys.Res.,Sect.A 637,164–170(2011)].

The relationship between the radio core-dominance parameter and spectral index in different classes of extragalactic radio sources(Ⅱ)

Active galactic nuclei(AGNs) can be divided into two major classes, namely radio-loud and radio-quiet AGNs. A small subset of the radio-loud AGNs is called blazars, which are believed to be unified with Fanaroff-Riley type Ⅰ/Ⅱ(FRI/Ⅱ) radio galaxies. Following our previous work(Fan et al.), we present a sample of 2400 sources with measured radio flux densities of the core and extended components. The sample contains 250 BL Lacs, 520 quasars, 175 Seyferts, 1178 galaxies, 153 FRI or FRⅡ galaxies and 104 unidentified sources. We then calculate the radio core-dominance parameters and spectral indices, and study their relationship. Our analysis shows that the core-dominance parameters and spectral indices are quite different for different types of sources. We also confirm that the correlation between core-dominance parameter and spectral index exists for a large sample presented in this work.

The relationship between the radio core-dominance parameter and spectral index in different classes of extragalactic radio sources(Ⅲ)

Active galactic nuclei(AGNs) can be divided into two major classes,namely radio-loud and radio-quiet AGNs.A small subset of the radio-loud AGNs is called blazars,which are believed to be unified with Fanaroff-Riley type Ⅰ and type Ⅱ(FRI&Ⅱ) radio galaxies.Following our previous work,we present a latest sample of 966 sources with measured radio flux densities of the core and extended components.The sample includes 83 BL Lacs,473 flat spectrum radio quasars,101 Seyferts,245 galaxies,52 FRIs&Ⅱs and12 unidentified sources.We then calculate the radio core-dominance parameters and spectral indices and study their relationship.Our analysis shows that the core-dominance parameters and spectral indices are quite different for different types of sources.We also confirm that the correlation between core-dominance parameter and radio spectral index extends over all the sources in a large sample presented.

On the role of the uncertainty principle in superconductivity and superfluidity

We discuss the general interplay between the uncertainty principle and the onset of dissipationless transport phenomena such as superconductivity and superfluidity. We argue that these phenomena are possible because of the robustness of many-body quantum states with respect to the external environment, which is directly related to the uncertainty principle as applied to coordinates and momenta of the carriers. In the case of superconductors, this implies relationships between macroscopic quantities such as critical temperature and critical magnetic field, and microscopic quantities such as the amount of spatial squeezing of a Cooper pair and its correlation time. In the case of ultracold atomic Fermi gases, this should be paralleled by a connection between the critical temperature for the onset of superfluidity and the corresponding critical velocity. Tests of this conjecture are finally sketched with particular regard to the understanding of the behaviour of superconductors under external pressures or mesoscopic superconductors, and the possibility to mimic these effects in ultracold atomic Fermi gases using Feshbach resonances and atomic squeezed states.

Pulsed Laser Annealed Ga Hyperdoped Poly-Si/SiO_(x)Passivating Contacts for High-Efficiency Monocrystalline Si Solar Cells

Polycrystalline Si(poly-Si)-based passivating contacts are promising candidates for high-efficiency crystalline Si solar cells.We show that nanosecond-scale pulsed laser melting(PLM)is an industrially viable technique to fabricate such contacts with precisely controlled dopant concentration profiles that exceed the solid solubility limit.We demonstrate that conventionally doped,hole-selective poly-Si/SiO_(x)contacts that provide poor surface passivation of c-Si can be replaced with Ga-or B-doped contacts based on non-equilibrium doping.We overcome the solid solubility limit for both dopants in poly-Si by rapid cooling and recrystallization over a timescale of∼25 ns.We show an active Ga dopant concentration of∼3×10^(20)cm^(−3)in poly-Si which is six times higher than its solubility limit in c-Si,and a B dopant concentration as high as∼10^(21) cm^(−3).We measure an implied open-circuit voltage of 735 mV for Ga-doped poly-Si/SiO_(x)contacts on Czochralski Si with a low contact resistivity of 35.5±2.4 mΩcm^(2).Scanning spreading resistance microscopy and Kelvin probe force microscopy show large diffusion and drift current in the p-n junction that contributes to the low contact resistivity.Our results suggest that PLM can be extended for hyperdoping of other semiconductors with low solubility atoms to enable high-efficiency devices.

三轴形变核^(131)Ba中的奇异集体激发模式

利用意大利Legnaro实验室串列静电加速器提供的65 MeV^(13)C束流与122Sn靶的熔合蒸发反应布居了^(131)Ba的高自旋态,并搭建了新的能级纲图.新的能级纲图由15条转动带组成,包括三对手征双重带,其中两对正宇称手征带为赝自旋-手征四重带.正负宇称手征带通过一系列增强的E1跃迁连接,表明它们之间存在八极关联.在低自旋区域搭建了一条新的转动带,通过一系列γ跃迁向νh1_(1/2)晕带退激.这种能级结构与摇摆带相似,但基于现有的实验证据还难以将它确认为摇摆带,不能排除其他集体激发机制,如γ振动的影响.

BL Lac的光学多普勒因子估算

蝎虎天体(BL Lacertae object,BL Lac)是一类特殊的活动星系核,表现出极端的观测特征,如高光度和偏振、快速光变、超光速运动、射电核主导、极高能辐射等,极端观测特性可能都与喷流效应有关,而表征喷流效应的物理量是多普勒因子(Doppler factor).多普勒因子有助于了解BL Lac的辐射物理和本征特性.基于BL Lac和Fanaroff-Riley typeⅠ/Fanaroff-Riley typeⅡ(G)的统一模型思路,提出BL Lac的本征视星等与红移(哈勃图)的分布应该与FRⅠ/FRⅡ(G)的观测视星等与红移的分布相似,并提出了估算BL Lac的光学多普勒因子的方法.该方法所估算的多普勒因子与前人的光学多普勒因子比较具有很好的相关性,说明该光学波段估算BL Lac多普勒因子的方法是可靠的.

Mean-field effects on matter and antimatter elliptic flow

We report our recent work on mean-field potential effects on the elliptic flows of matters and antimatters in heavy ion collisions leading to the production of a baryon-rich matter.Within the framework of a multiphase transport(AMPT) model that includes both initial partonic and final hadronic interactions,we have found that including mean-field potentials in the hadronic phase leads to a splitting of the elliptic flows of particles and their antiparticles,providing thus a plausible explanation of the different elliptic flows between p and anti-p,K+and K-,and π+ and π- observed by the STAR Collaboration in the Beam Energy Scan(BES) program at the Relativistic Heavy Ion Collider(RHIC).Using a partonic transport model based on the Nambu-Jona-Lasinio(NJL) model,we have also studied the effect of scalar and vector mean fields on the elliptic flows of quarks and antiquarks in these collisions.Converting quarks and antiquarks at hadronization to hadrons via the quark coalescence model,we have found that the elliptic flow differences between particles and antiparticles also depend on the strength of the quark vector coupling in baryon-rich quark-gluon plasma,providing thus the possibility of extracting information on the latter's properties from the BES program at RHIC.

Light emitting devices based on Si nanoclusters:the integration with a photonic crystal and electroluminescence properties

We present the properties and potentialities of light emitting devices based on amorphous Si nanoclusters. Amorphousnanostructures may constitute an interesting alternative to Si nanocrystals for the monolithic integration of optical andelectrical functions in Si technology. In fact, they exhibit an intense room temperature electroluminescence (EL). The ELproperties of these devices have been studied as a function of current and of temperature. Moreover, to improve theextraction efficiency of the light, we have integrated the emitting system with a 2D photonic crystal structure opportunelyfabricated by using conventional optical lithography to reduce the total internal reflection of the emitted light. The extractionefficiency in such devices increases by a factor of 4 at a resonance wavelength.

Searching for Multiple Populations in Star Clusters Using the China Space Station Telescope

Multiple stellar populations(MPs) in most star clusters older than 2 Gyr, as seen by lots of spectroscopic and photometric studies, have led to a significant challenge to the traditional view of star formation. In this field, spacebased instruments, in particular the Hubble Space Telescope(HST), have made a breakthrough as they significantly improved the efficiency of detecting MPs in crowded stellar fields by images. The China Space Station Telescope(CSST) and the HST are sensitive to a similar wavelength interval, but the CSST covers a field of view which is about 5–8 times wider than that of HST. One of its instruments, the Multi-Channel Imager(MCI),will have multiple filters covering a wide wavelength range from NUV to NIR, making the CSST a potentially powerful tool for studying MPs in clusters. In this work, we evaluate the efficiency of the designed filters for the MCI/CSST in revealing MPs in different color–magnitude diagrams(CMDs). We find that CMDs made with MCI/CSST photometry in appropriate UV filters are powerful tools to disentangle stellar populations with different abundances of He, C, N, O and Mg. On the contrary, the traditional CMDs are blind to multiple populations in globular clusters(GCs). We show that CSST has the potential of being the spearhead instrument for investigating MPs in GCs in the next decades.

A triplet of the only pulsation mode detected in the DAV star G132–12

Hydrogen atmosphere pulsating white dwarfs,also known as DAV stars,are the most abundant type of pulsating white dwarfs.High-temperature DAV stars in general exhibit a small number of pulsation modes and stable frequencies.G132-12 is one of the pulsating hydrogen atmosphere white dwarf stars which lies close to the blue edge of the instability strip.Previous researches reported that G132-12 might have only one pulsation mode with the period of 212.69 s.To study the pulsation properties of G132-12 in detail,we carried out a bi-site observation campaign in October 2019.Time series photometric data were collected during around 154 h in total.A Fourier analysis reveals three frequencies which are identified as the triplet of an l=1 g-mode pulsation with the period of 212.499 s.The rotational period is derived as Prot=35.0±6.7 h and the inclination of the rotational axis to the line of sight is 70°.G132-12 could be an ideal target for measuring the cooling scale of this white dwarf star with only one excited pulsation mode detected.

Comparative case study of two methods to assess the eruptive potential of selected active regions

Solar eruptive events,like flares and coronal mass ejections,are characterized by the rapid release of energy that can give rise to emission of radiation across the entire electromagnetic spectrum and to an abrupt significant increase in the kinetic energy of particles.These energetic phenomena can have important effects on the space weather conditions and therefore it is necessary to understand their origin,in particular,what is the eruptive potential of an active region(AR).In these case studies,we compare two distinct methods that were used in previous works to investigate the variations of some characteristic physical parameters during the pre-flare states of flaring ARs.These methods consider:i)the magnetic flux evolution and magnetic helicity accumulation,and ii)the fractal and multi-fractal properties of flux concentrations in ARs.Our comparative analysis is based on time series of photospheric data obtained by the Solar Dynamics Observatory between March 2011 and June 2013.We selected two distinct samples of ARs:one is distinguished by the occurrence of more energetic M-and X-class flare events,that may have a rapid effect on not just the near-Earth space,but also on the terrestrial environment;the second is characterized by no-flares or having just a few C-and B-class flares.We found that the two tested methods complement each other in their ability to assess the eruptive potentials of ARs and could be employed to identify ARs prone to flaring activity.Based on the presented case study,we suggest that using a combination of different methods may aid to identify more reliably the eruptive potentials of ARs and help to better understand the pre-flare states.

Possible Location of the Next Major Earthquakes in the Northern Apennines: Present Key Role of the Romagna-Marche-Umbria Wedge

It is argued that in some zones of the Northern Apennines, in particular the Rimini-Ancona thrust system, the Romagna Apennines and the Alta Valtiberina trough, the probability of major earthquakes is now higher than in other Apennine zones. This hypothesis is suggested by the comparison of the present short-term kinematics of the Romagna-Marche-Umbria wedge in the Northern Apennines, deduced by the distribution of major shocks in the last tens of years, with the previous repeated behavior of the same wedge, evidenced by the distribution of major earthquakes in the last seven centuries. The seismotectonics of the Apennine region here considered is closely connected with the larger context that involves the progressive migration (from south to north) of seismicity along the peri-Adriatic zones. The information provided by this study can be used to better manage the resources for prevention in Italy.

On the Massless Vector Fields in a Rindler Space

We study the quantum theory of the mass-less vector fields on the Rindler space. We evaluate the Bogoliubov coefficients by means of a new technique based upon the use of light-front coordinates and Mellin transform. We briefly comment about the ensuing Unruh effect and its consequences.

From individual elements to macroscopic materials: in search of new superconductors via machine learning

An approach to supervised classification and regression of superconductive materials is proposed which builds on the DeepSet technology.This enables us to provide the chemical constituents of the examined compounds as an input to the algorithm,while avoiding artefacts that could originate from the chosen ordering in the list.The performance of the method are successfully challenged for both classification(tag a given material as superconducting)and regression(quantifying the associated critical temperature).We then searched through the International Mineralogical Association list with the trained neural network.Among the obtained superconducting candidates,three materials were selected to undergo a thorough experimental characterization.Superconductivity has been indeed confirmed for the synthetic analogue of michenerite,PdBiTe,and observed for the first time in monchetundraite,Pd2NiTe2,at critical temperatures in good agreement with the theory predictions.This latter is the first certified superconducting material to be identified by artificial intelligence methodologies.

Emergingγ-soft-like spectrum in^(196)Pt in the SU3-IBM(Ⅰ)

Recently,studies have argued that a spherical-like spectrum emerges in the SU3-IBM,thus creating new approaches to understanding y-softness in realistic nuclei.In a previous study,γ-softness with degeneracy of the ground and quasi-y bands was observed.In this paper,another special point connected to the middle degenerate point is discussed.It is found to be related to the properties of^(196)Pt.This emergentγ-softness is also shown to be important for understanding the prolate-oblate asymmetric shape phase transition.The low-lying spectra,B(E2)values,and quadrupole moments in^(196)Pt are discussed,and we show that the new model can account for several observed features.This is the first part of the discussion on theγ-soft-like spectrum of^(196)Pt.

Processing of molybdenum industrial waste into sustainable and efficient nanocatalysts for water electrolysis reactions

The increasing need for sustainable energy and the transition from a linear to a circular economy pose great challenges to the materials science community.In this view,the chance of producing efficient nanocatalysts for water splitting using industrial waste as starting material is attractive.Here,we report low-cost processes to convert Mo-based industrial waste powder into efficient catalysts for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER).pH controlled hydrothermal processing of Mo-based industrial waste powder leads to pure orthorhombic MoO_(3) nanobelts(50–200 nm wide,10µm long)with promising OER performances at 10 mA·cm^(−2) with an overpotential of 324 mV and Tafel slope of 45 mV·dec^(−1) in alkaline electrolyte.Indeed,MoS_(2)/MoO_(3) nanostructures were obtained after sulfurization during hydrothermal processes of the MoO_(3) nanobelts.HER tests in acidic environment show a promising overpotential of 208 mV at 10 mA·cm^(−2) and a Tafel slope of 94 mV·dec^(−1).OER and HER performances of nanocatalysts obtained from Mo industrial waste powder are comparable or better than Mo-based nanocatalysts obtained from pure commercial Mo reagent.This work shows the great potential of reusing industrial waste for energy applications,opening a promising road to join waste management and efficient and sustainable nanocatalysts for water splitting.

复杂网络：结构和动力学

耦合的生物化学系统、神经网络、相互作用的群居物种、互联网和万维网只是由大量高度相互连接的动态个体组成的系统的少数几个例子。获取这类系统的全局特征的首选方法是建立图模型——图中的点代表动态个体，边代表个体间的相互作用。一方面，科学家们需要处理结构问题如刻画一个复杂连线体系的拓扑结构、揭示建立在现实网络基础上的统一原理，以及完善模型从而模拟网络的增长和复制网络结构特性；另一方面，在研究复杂网络动力学时会产生许多相关问题，例如研究一个大的动态系统如何通过复杂连接的相互作用来表现集体行为的。我们回顾了近来在研究复杂网络的结构和动力学方面的主要概念以及取得的结果，总结了这些思想在许多不同学科包括从非线性科学到生物学、从统计力学到医药学以及工程学等领域的有关应用。

复杂网络:结构与动力学

(续本刊2006年第3期) 3 静态与动态鲁棒性 网络的鲁棒性是指当网络中的部分节点或边被破坏时,网络仍然能够继续维持其功能的能力.这是一个具有明显实际意义的论题,因为它直接影响着任何发生在网络上的过程的效率,而且它也是复杂网络文献中最早被探索的论题之一.……