Electrons dynamics control by shaping femtosecond laser pulses in micro/nanofabrication: modeling, method, measurement and application

During femtosecond laser fabrication, photons are mainly absorbed by electrons, and the subsequent energy transfer from electrons to ions is of picosecond order. Hence, lattice motion is negligible within the femtosecond pulse duration, whereas femtosecond photon-electron interactions dominate the entire fabrication process. Therefore, femtosecond laser fabrication must be improved by controlling localized transient electron dynamics, which poses a challenge for measuring and controlling at the electron level during fabrication processes. Pump-probe spectroscopy presents a viable solution, which can be used to observe electron dynamics during a chemical reaction. In fact, femtosecond pulse durations are shorter than many physical/chemical characteristic times, which permits manipulating, adjusting, or interfering with electron dynamics. Hence, we proposed to control localized transient electron dynamics by temporally or spatially shaping femtosecond pulses, and further to modify localized transient materials properties, and then to adjust material phase change, and eventually to implement a novel fabrication method. This review covers our progresses over the past decade regarding electrons dynamics control (EDC) by shaping femtosecond laser pulses in micro/nanomanufacturing: (1) Theoretical models were developed to prove EDC feasibility and reveal its mechanisms; (2) on the basis of the theoretical predictions, many experiments are conducted to validate our EDC-based femtosecond laser fabrication method. Seven examples are reported, which proves that the proposed method can significantly improve fabrication precision, quality, throughput and repeatability and effectively control micro/nanoscale structures; (3) a multiscale measurement system was proposed and developed to study the fundamentals of EDC from the femtosecond scale to the nanosecond scale and to the millisecond scale; and (4) As an example of practical applications, our method was employed to fabricate some key structures in one of the 16 Chinese National S&T Major Projects, for which electron dynamics were measured using our multiscale measurement system

Influence of environmental variability on phylogenetic diversity and trait diversity within Calligonum communities

Since phylogenetic data provide the evolutionary history of the species and traits are the result of adaptation to the environmental conditions, joint analysis of these two aspects and ecological data may illuminate that how ecological processes affect the evolution of species and assembly of communities. In this study, we compared the community structure of sibling communities in order to illuminate the influence of environmental variability. We chose different Calligonum communities as research subjects which grow in active sand dunes and stabilized sand fields. Our results show that species which co-occurred in C. rubicundum community have greater phylogenetic evenness compared to species in other communities where co-occurring plants had similar traits. Soil variability might legitimately explain this result. Based on the similarity between the pattern of trait diversity and the pattern of phylogenetic diversity, we inferred that the evolution of traits is conservative and species of all but C. rubicundum communities are under more intense selection pressure

Simultaneous Formation of CH₃NH₃PbI₃ and electron transport layers using antisolvent method for efficient perovskite solar cells

A new antisolvent method was developed to prepare CH₃NH₃PbI₃ and electron transport layers for making efficient hybrid perovskite solar cells. By directly using [6,6]-phenyl-C61-butyric acid methyl ester in chlorobenzene solution as antisolvent, CH₃NH₃PbI₃ and electron transport layers were simultaneously formed in the films. This method not only simplifies the fabrication process of devices, but also produces uniform perovskite films and improves the interfacial structures between CH₃NH₃PbI₃ and electron transport layers. Large perovskite grains were observed in these films, with the average grain size of >1 μm. The so-formed CH₃NH₃PbI₃/electron transport layers demonstrated good optical and charge transport properties. And perovskite solar cells fabricated using these simultaneously-formed layers achieved a higher power conversion efficiency of 16.58% compared to conventional antisolvent method (14.92%). This method reduces nearly 80% usage of chlorobenzene during the fabrication, offering a more facile and environment-friendly approach to fabricate efficient perovskite solar cells than the conventional antisolvent method

Searching for dark-matter induced neutrino signals in dwarf spheroidal galaxies using 10 years of IceCube public data

This study searches for neutrino signals from 18 dwarf spheroidal galaxies (dSphs) using 10 years of publicly available muon-track data of the IceCube neutrino observatory. We apply an unbinned likelihood analysis on each of these dSphs to derive the significance the putative neutrino emission. To further enhance our sensitivity, we also stack all dSphs together to perform a joint analysis. However, no significant neutrino emission signal was detected in either the single-source or stacking analysis. Based on these null results, we derive constraints on the annihilation cross section of dark matter particles. Compared to the existing literature, our constraints via the channel $\chi\chi\rightarrow\mu^+\mu^-$ are comparable to the ones from the VERITAS observations of dSphs

4-(4-Nitro­benz­yl)morpholine

In the title compound, C11H14N2O3, an inter­molecular inter­action between a nitro group O atom and a neighboring benzene ring helps to stabilize the crystal structure [N⋯centroid = 3.933 (2) Å]. No classical hydrogen bonds are observed in the crystal packing

Two new species of Craterellus (Cantharellales, Hydnaceae) with veined hymenophore from north-eastern China

In this contribution to the genus Craterellus in northern China, two new species are introduced: Craterellus connatus and C. striatus. These species and C. atrobrunneolus, initially described in south-western China, are highly similar and closely related. The species delimitation is molecularly supported by multigene phylogenetic analysis of the nr LSU and tef-1α region. Craterellus connatus is characterised by its medium-sized basidiomata, greyish-brown and smooth pileus with an off-white margin, the hymenophore with a strongly anastomosing vein, turning khaki upon drying, connate stipe, broad ellipsoid to ellipsoid basidiospores (6.1–7.8 × 4.8–5.9 μm), slender basidia with (2)4–6 sterigmata and the absence of clamp connection. Craterellus striatus is characterised by its small-sized basidiomata, fibrillose, greyish-brown to yellowish-brown, fully perforated pileus with a brown fringe, the hymenophore with a forking vein, the stipe inflated at the base, broad ellipsoid to ellipsoid basidiospores (6.8–8.0 × 5.1–6.0 μm), 2–6 spored basidia, encrusted hyphae and the absence of clamp connection. Detailed macroscopic and microscopic descriptions, accompanied by illustrations and a taxonomic discussion, are presented. A key to the Chinese Craterellus species is also provided

1,3-Dithian-2-one azine

In an asymmetric unit of the title compound, C8H12N2S4, there are two crystallographically independent half mol­ecules lying on inversion centers. One of the mol­ecules is disordered over two positions with relative occupancies of 82.0 (2) and 18.0 (2) for the major and minor components. In the crystal structure, mol­ecules are linked into a three-dimensional framework via inter­molecular C—H⋯N hydrogen-bonding inter­actions

Characterization of a cryptic plasmid pSM429 and its application for heterologous expression in psychrophilic Pseudoalteromonas

<p>Abstract</p> <p>Background</p> <p><it>Pseudoalteromonas </it>is an important genus widespread in marine environment, and a lot of psychrophilic <it>Pseudoalteromonas </it>strains thrive in deep sea and polar sea. By now, there are only a few genetic systems for <it>Pseudoalteromonas </it>reported and no commercial <it>Pseudoalteromonas </it>genetic system is available, which impedes the study of <it>Pseudoalteromonas</it>, especially for psychrophilic strains. The aim of this study is to develop a heterologous expression system for psychrophilic <it>Pseudoalteromonas</it>.</p> <p>Results</p> <p>A cryptic plasmid pSM429 isolated from psychrophilic <it>Pseudoalteromonas </it>sp. BSi20429 from the Arctic sea ice, was sequenced and characterized. The plasmid pSM429 is 3874 bp in length, with a G+C content of 28%. Four putative open reading frames (ORFs) were identified on pSM429. Based on homology, the ORF4 was predicted to encode a replication initiation (Rep) protein. A shuttle vector (<it>Escherichia coli, Pseudoalteromonas</it>), pWD, was constructed by ligating pSM429 and pUC19 and inserting a chloramphenicol acetyl transferase (CAT) cassette conferring chloramphenicol resistance. To determine the minimal replicon of pSM429 and to check the functionality of identified ORFs, various pWD derivatives were constructed. All derivatives except the two smallest ones were shown to allow replication in <it>Pseudoalteromonas </it>sp. SM20429, a plasmid-cured strain of <it>Pseudoalteromonas </it>sp. BSi20429, suggesting that the <it>orf4 </it>and its flanking intergenic regions are essential for plasmid replication. Although not essential, the sequence including some repeats between <it>orf1 </it>and <it>orf2 </it>plays important roles in segregational stability of the plasmid. With the aid of pWD-derived plasmid pWD2, the erythromycin resistance gene and the <it>cd </it>gene encoding the catalytic domain of a cold-adapted cellulase were successfully expressed in <it>Pseudoalteromonas </it>sp. SM20429.</p> <p>Conclusions</p> <p>Plasmid pSM429 was isolated and characterized, and the regions essential for plasmid replication and stability were determined, helping the development of pSM429-based shuttle vectors. The shuttle vectors pWD and its derivatives could be used as cloning vectors for <it>Pseudoalteromonas</it>, offering new perspectives in the genetic manipulation of <it>Pseudoalteromonas </it>strains. With the aid of pWD-derived vector and its host, the erythromycin resistance gene and the <it>cd </it>gene of a cold-adapted protein were successfully expressed, indicating that the potential use of this system for recombinant protein production, especially for cold-adapted proteins.</p