Passively mode-locked 2-μm Tm:YAP laser with a double-wall carbon nanotube absorber

We report on a diode-pumped passively continuous wave （cw） mode-locked Tm：YAP laser with a double-wall carbon nanotube （DWCNT） absorber operating at a wavelength of 2023 nm for the first time, to the best our knowledge. The DWCNT absorber is fabricated on a hydrophilic quartz substrate by using the vertical evaporation technique. The output power is as high as 375 mW. A stable pulse train with a repetition rate of 72.26 MHz is generated with a highest single pulse energy of 5.2 μJ.

Distribution Pattern of Vascular Plant Species of Mountains in Nepal and their Fate Against Global Warming

This study aims to find the altitudinal distribution pattern of vascular plant species reported from high mountain of Nepal(Manang) along the whole Himalayan elevation gradient, and evaluate their fate against climate change. Data was gathered from multiple sources, field investigations, literatures, and herbarium specimens. Altogether, 303 vascular plant species were reported from Manang. We used a published data to calculate distribution range of each species by interpolating between its upper and lower elevation limits. The relationship between elevation and species richness is elucidated by generalized linear model. The consequence of global warming upon Manang's vascular plant species was estimated based on projected temperature change for next century and adiabatic lapse rate along the elevation gradient of the Himalayas. The vascular plant species richness has a unimodel relationship with elevation along the whole elevation gradient of Nepal as well as in three biogeographical regions of Nepal. Vascular plants of Manang are found distributed from low land Terai to high alpine regions of Nepal and their elevation distribution range varies from 200 to 4700 m. Out of 303 vascular plants of Manang, only seven species might be affected if temperature increase by 1.5°C, whereas at least 70 species will be affected with 5°C temperature increased. However, the majority of species(233 species) have wider distribution range(> 1000 m) and more than 5°C temperature tolerance range, thus they are likely to be less affected from global warming by the end of 21 st century.

Importance of the Role of Gibberellic Acid and Potassium Nitrate in Seed Germination Habanero

The habanero chili （Capsicum chinense Jacq.） is a species of great demand in the domestic and international markets. One problem in the cultivation is low percentage of seed germination. There is little information on the use of promoters and imbibition time to increase this parameter, without compromising the quality of seedlings. In this context, authors assessed the independent effect of GAs （gibberellic acid） and KNOs at concentrations of 0, 100, 200, 300, 400 and 500 mg·L1. Seeds without preconditioning were the witness. The experimental unit was a Petri dish with 50 seeds on filter paper placed equidistant. There were three replicates per treatment and the experimental design was randomized complete block. Imbibition time was 24 h. The experimental units were kept in an incubator at 22 ± 2 ℃. From the time of planting and for periods of 24 h for 14 d, experimental units were reviewed to determine the time at the beginning of germination and the total cumulative percentage. The authors also determined the number of normal and abnormal seedlings, the length of hypocotyl and radicle, weight of fresh and dry matter of seedlings. On the fifth day after sowing in vitro, concentrations of 500 mg·L^-1 of GAs, 300 and 400 mg·L^-1 KNO3, increased 208% the percentage of seed germination of habanero chile. On day 14 after sowing in vitro concentrations of 500 mg·L^-1 GA3, 300 and 400 mg·L^-1 KNO3, increased 23% normal seedlings and 40% dry matter thereof, with respect to seeds obtained without preconditioning. Unconditioned seeds before sowing produced 125% more seedlings.

Twenty-Hour Sleep Deprivation Does Not Affect Perceived Vection Strength

We examined the effect of sleep deprivation on self-motion perception (vection). We measured the strength of vection, its latency, and its duration in two conditions: Sleep-Deprivation and Normal-Sleep (by using the between-subject design). For the Sleep-Deprivation condition, participants did not sleep for about 20 hours. We also recorded subjective sleepiness with a subjective rating scale that was filled out by the participants. Results showed that vection strength did not differ between the two conditions. Sleep deprivation did not have any clear effect on vection. As expected, subjective sleepiness significantly increased following sleep deprivation. Further, subjective sleepiness significantly correlated with vection latency and duration only in the Normal-Sleep condition. Vection was immune to sleep deprivation. We conclude that when people are not deprived of sleep, sleepiness can enhance the perceived strength of vection.

Effective N-methyl-2-pyrrolidone wet cleaning for fabricating highperformance monolayer MoS2 transistors

Two-dimensional semiconductors,such as MoS2 are known to be highly susceptible to diverse molecular adsorbates on the surface during fabrication,which could adversely affect device performance.To ensure high device yield,uniformity and performance,the semiconductor industry has long employed wet chemical cleaning strategies to remove undesirable surface contaminations,adsorbates,and native oxides from the surface of Si wafers.A similarly effective surface cleaning technique for two-dimensional materials has not yet been fully developed.In this study,we propose a wet chemical cleaning strategy for MoS2 by using N-methyl-2-pyrrolidone.The cleaning process not only preserves the intrinsic properties of monolayer MoS2,but also significantly improves the performance of monolayer MoS2 field-effect-transistors.Superior device on current of 12 μA·μm-1 for a channel length of 400 nm,contact resistance of 15 kΩ·μm,field-effect mobility of 15.5 cm^2·V^-1·s^-1,and the average on-off current ratio of 10^8 were successfully demonstrated.

CsPbBr3 perovskite quantum-dot paper exhibiting a highest 3 dB bandwidth and realizing a flexible white-light system for visible-light communication

We propose a flexible white-light system for high-speed visible-light communication(VLC)applications,which consists of a semipolar blue InGaN/GaN single-quantum-well micro-light-emitting diode(LED)on a flexible substrate pumping green CsPbBr3 perovskite quantum-dot(PQD)paper in nanostructure form and red CdSe QD paper.The highest bandwidth for CsPbBr3 PQD paper,229 MHz,is achieved with a blue micro-LED pumping source and a high data transmission rate of 400 Mbps;this is very promising for VLC application.An 817 MHz maximum bandwidth and a 1.5 Gbps transmission speed are attained by the proposed semipolar blue micro-LEDs.The proposed flexible white light system and the high-bandwidth PQD paper could pave the way for VLC wearable devices.

Flexoelectricity Driven Fano Resonance in Slotted Carbon Nanotubes for Decoupled Multifunctional Sensing

Multifunctionality,interference-free signal readout,and quantum effect are important considerations for flexible sensors equipped within a single unit towards further miniaturization.To address these criteria,we present the slotted carbon nanotube(CNT)junction features tunable Fano resonance driven by flexoelectricity,which could serve as an ideal multimodal sensory receptor.Based on extensive ab initio calculations,we find that the effective Fano factor can be used as a temperature-insensitive extrinsic variable for sensing the bending strain,and the Seebeck coefficient can be used as a strain-insensitive intrinsic variable for detecting temperature.Thus,this dual-parameter permits simultaneous sensing of temperature and strain without signal interference.We further demonstrate the applicability of this slotted junction to ultrasensitive chemical sensing which enables precise determination of donor-type,acceptor-type,and inert molecules.This is due to the enhancement or counterbalance between flexoelectric and chemical gating.Flexoelectric gating would preserve the electron–hole symmetry of the slotted junction whereas chemical gating would break it.As a proof-of-concept demonstration,the slotted CNT junction provides an excellent quantum platform for the development of multistimuli sensation in artificial intelligence at the molecular scale.

Manipulation of spectral amplitude and phase with plasmonic nano-structures for information storage

Optical storage devices, such as compact disk （CD） and digital versatile disc （DVD）, provide us a platform for cheap and compact information storage media. Nowadays, information we obtain every day keeps increasing, and therefore how to increase the storage capacity becomes an important issue. In this paper, we reported a method for the increase of the capacity of optical storage devices using metallic nano-structures. Metallic nano-structures exhibit strong variations in their reflectance and/or transmittance spectra accompanied with dramatic optical phase modulation due to localized surface plasmon polariton resonances. Two samples were fabricated for the demonstration of storage capacity enhancement through amplitude modulation and phase modulation, respectively. This work is promising for high-density optical storage.

Gas Kinetic Scheme for Anisotropic Savage-Hutter Model

The gas-kinetic scheme is applied to a depth-integrated continuum model for avalanche flows,namely the Savage-Hutter model.In this method,the continuum fluxes are calculated based on the pseudo particle motions which are relaxed from nonequilibrium to equilibrium states.The processes are described by the Bhatnagar-GrossKrook(BGK)equation.The benefit of this scheme is its capability to resolve shock discontinuities sharply and to handle the vacuum state without special treatments.Because the Savage-Hutter equation bears an anisotropic stress on the tangential space of the topography,the equilibrium distribution function of the microscopic particles are shown to be bi-Maxwellian.These anisotropic stresses are the key to preserve the coordinate objectivity in the Savage-Hutter model.The effect of the anisotropic stress is illustrated by two examples:an axisymmetric dam break and a finite mass sliding on an inclined plane chute.It is found that the propagation of the flow fronts significantly depends on the orientation of the principal axes of the tangential stresses.

Flexoelectricity Driven Fano Resonance in Slotted Carbon Nanotubes for Decoupled Multifunctional Sensing

Mulifunctionality,interference fre signal readout,and quantum eft are important considerations for flexible sensors equipped within a single unit towards further miniaturization.To address these criteria,we present the slotted carbon nanotube(CNT)junction features lunable Fano resonance driven by flexoelectricity,which could serve as an ideal multimodal sensory receptor.Based on extensive ab initio calculations,we find that the efective Fano factor can be used as a temperature insensitive extrinsic variable for sensing the bending strain,and the Seebeck cefficient can be used as a strain-insensitive intrinsic variable for detecting temperalure.Thus,this dual parameter permits simultaneous sensing of temperature and strain without signal interference.We further demonstrale the applcability of this slotted junction to ultrasensitive chemical sensing which enables precise determination of donor type.acceptor type.and inert molecules.This is due to the enhancement or counterbalance between flexoelectric and chemical gating.Flexoelectric gating would preserve the electron-hole symmetry of the slotted junction whereas chemical gating would break it.As a proof-of-concept demonstration,the slotted CNT junction provides an excellent quantum platform for the development of mulistimuli sensation in artificial itelligence at the molecular scale.

Spectral tomographic imaging with aplanatic metalens

Tomography is an informative imaging modality that is usually implemented by mechanical scanning,owing to the limited depth-of-field(DOF)in conventional systems.However,recent imaging systems are working towards more compact and stable architectures;therefore,developing nonmotion tomography is highly desirable.Here,we propose a metalens-based spectral imaging system with an aplanatic GaN metalens(NA=0.78),in which large chromatic dispersion is used to access spectral focus tuning and optical zooming in the visible spectrum.After the function of wavelength-switched tomography was confirmed on cascaded samples,this aplanatic metalens is utilized to image microscopic frog egg cells and shows excellent tomographic images with distinct DOF features of the cell membrane and nucleus.Our approach makes good use of the large diffractive dispersion of the metalens and develops a new imaging technique that advances recent informative optical devices.

Conductance switching of a phthalocyanine molecule on an insulating surface

We study the electron transport through the double-barrier junction consmte^l o~ tne pn^nalocyamn~ molecule adsorbed on a NaCl bilayer on a metal substrate and the STM tip from first principles. The hydrogen tautomerization reaction happened in the molecule changes the spatial extensions of the molecular 7c orbitals under the tip, leading to junction conductance switching. Shifting the molecule to locate on different ions also varies the conductance. Tile transport channels of the tautomers on different adsorbed sites are identified.

High-quality 2-μm Q-switched pulsed solid-state lasers using spin-coating-coreduction approach synthesized Bi_2Te_3 topological insulators

In this paper, the fabrication process and characterization of Bi_2Te_3 topological insulators(TIs) synthesized by the spin-coating-coreduction approach(SCCA) is reported. With this approach, high-uniformity nano-crystalline TI saturable absorbers(TISAs) with large-area uniformity and controllable thickness are prepared. By employing these prepared TIs with different thicknesses as SAs in 2-μm solid-state Q-switched lasers, thickness-dependent output powers and pulse durations of the laser pulses are obtained, and the result also exhibits stability and reliability. The shortest pulse duration is as short as 233 ns, and the corresponding clock amplitude jitter is around 2.1%, which is the shortest pulse duration in Tl SA-based Q-switched 2-μm lasers to the best of our knowledge.Moreover, in comparison with the TISA synthesized by the ultrasound-assisted liquid phase exfoliation(UALPE)method, the experimental results show that lasers with SCCA synthesized TISAs have higher output powers, shorter pulse durations, and higher pulse peak powers. Our work suggests that the SCCA synthesized TISAs could be used as potential SAs in pulsed lasers.

Enhanced laser action from smart fabrics made with rollable hyperbolic metamaterials

Rollable photonic devices that can adapt to freeform surfaces with reduced dimensions while maintaining their original functionalities are highly desirable.Among photonic devices,metamaterials with hyperbolic dispersion in momentum space,defined as hyperbolic metamaterial(HMM),possess a large photonic density of states that has been proven to boost light-matter interaction.However,these devices are mainly developed on rigid substrates,restricting their functionalities.Here,we present the attempt to integrate flexible and rollable HMMs consisting of polymer and metal multilayers on paper substrate.Quite interestingly,this design enables to exhibit high photonic density of states and scattering efficiency to enhance stimulated emission and induce pronounced laser action.The flexible and rollable HMM structure remains well its functionalities on freeform surfaces with curvature radius of 1 mm,and can withstand repeated bending without performance degradation.The intensity of laser action is enhanced by 3.5 times as compared to the flat surface.We anticipate that this flexible and rollable HMM structure can serve as a diverse platform for flexible photonic technologies,such as light-emitting devices,wearable optoelectronics,and optical communication.

Multi-Mesh-Scale Approximation of Thin Geophysical Mass Flows on Complex Topographies

This paper is devoted to a multi-mesh-scale approach for describing the dynamic behaviors of thin geophysical mass flows on complex topographies.Because the topographic surfaces are generally non-trivially curved,we introduce an appropriate local coordinate system for describing the flow behaviors in an efficient way.The complex surfaces are supposed to be composed of a finite number of triangle elements.Due to the unequal orientation of the triangular elements,the distinct flux directions add to the complexity of solving the Riemann problems at the boundaries of the triangular elements.Hence,a vertex-centered cell system is introduced for computing the evolution of the physical quantities,where the cell boundaries lie within the triangles and the conventional Riemann solvers can be applied.Consequently,there are two mesh scales:the element scale for the local topographic mapping and the vertex-centered cell scale for the evolution of the physical quantities.The final scheme is completed by employing the HLL-approach for computing the numerical flux at the interfaces.Three numerical examples and one application to a large-scale landslide are conducted to examine the performance of the proposed approach as well as to illustrate its capability in describing the shallow flows on complex topographies.