Operation at 1 MHz of 1.7-cycle multiple plate compression at 35-W average output power.

We generate 1.7-cycle and 35-µJ pulses at a 1-MHz repetition rate by using two-stage multiple plate continuum compression of Yb-laser pulses with 80-W average input power. By adjusting the plate positions with careful consideration of the thermal lensing effect due to the high average power, we compress the output pulse with a 184-fs initial duration to 5.7 fs by using only group-delay-dispersion compensation. This pulse achieves a sufficient beam quality (M2 < 1.5) reaching a focused intensity over 1014 W/cm2 and a high spatial-spectral homogeneity (98%). Our study holds promise for a MHz-isolated-attosecond-pulse source for advanced attosecond spectroscopic and imaging technologies with unprecedentedly high signal-to-noise ratios.

Enhance high harmonic generation (HHG) efficiency via compact multi-plate continuum post-compression for time-resolved angle-resolved photoemission spectroscopy.

Time-resolved angle-resolved photoemission spectroscopy (Tr-APRES) gives direct insight into electron dynamics by providing temporal-, energy-, and momentum-resolved information in one experiment. A major obstacle to using high harmonic generation (HHG) probe pulses for photoemission spectroscopy is the low conversion efficiency, that is, the low flux of probe photons. We use a Yb-KGW based duo-laser source with an oscillator to pump two separate amplifiers and generate two synchronized pulsed laser sources with average energies of 7.5 and 6 W. By using the multiplate continuum method and chirped mirrors, the resulting flux of HHG photons at 33-70 eV can be increased 50-fold (up to 1011 photons/s) by using post-compressed 30 fs pulses compared with the photon flux generated by the fundamental 190 fs pulses. Moreover, pulses from the 6 W amplifier are used to pump an optical parametric amplifier that can vary the wavelengths for photoexcitation. The system performance is demonstrated by applying Tr-ARPES to single-crystal graphite. The front tilt broadening is significantly suppressed by the off-plane mounted conical grating, leading to a 184 fs temporal resolution that is mainly limited by the pump pulse. The energy resolution is 176 meV.

Four New Polyhydroxy Cyclohexanes from the Stems of Fissistigma tientangense.

Four undescribed polyhydroxy cyclohexanes, fissoxhydrylenes A-D (1-4), together with two known biogenetically related polyhydroxy cyclohexanes (5 and 6) were isolated from the stems of Fissistigma tientangense Tsiang et P. T. Li. Their structures were elucidated by detailed analysis of NMR, HR-ESI-MS, IR, UV and Optical rotations data. The absolute configuration of 1 was confirmed by X-ray crystallographic. The absolute configurations of 2-4 were confirmed by chemical reaction and optical rotations. Compound 4 represent the first example of a no substituent polyhydroxy cyclohexanes from natural products. All isolated compounds were evaluated for their anti-inflammatory activities against the lipopolysaccharide-induced nitric oxide (NO) production in mouse macrophage RAW 264.7 cells in vitro. Compounds 3 and 4 showed inhibitory activities with the IC50 values of 16.63±0.06 µM and 14.38±0.08 µM, respectively.

Urban-rural differences in outcomes and management of vertebral fractures: A real-world observational study.

BACKGROUND: A fracture liaison services (FLSs) and its modified services reduce refractures and mortality and can be cost-effective. Limited studies have addressed whether urban-rural differences exist in vertebral fracture outcomes and management. Therefore, the aims of the study were to investigate any urban-rural differences in refracture, mortality, prescription pattern, and associated factors of vertebral fractures after receiving assistance from an FLSs. METHODS: Baseline characteristics and osteoporosis medication prescription patterns of participants were collected. After 1-year follow-up, mortality, refracture rate, and osteoporosis medication switching and adherence were evaluated. Multivariate logistic regressions were performed to identify baseline correlates on one-year mortality. RESULTS: There was higher mortality rate in the rural group but no urban-rural difference in the 1-year refracture rate after implementation of FLSs and medication management services (MMSs). The types of osteoporosis medications prescribed for both groups were similar, but participants in the rural group were less likely to change their osteoporosis medications during the 1-year follow-up timeframe and with lower adherence rate. The likelihood of being older and having chronic kidney disease, osteoarthritis, and neurological disease was higher in the rural group. CONCLUSION: Our multicomponent services have similar effectiveness in osteoporosis treatment between urban and rural areas. The overall adherence rate was lower in the rural group with higher mortality but no difference in the refracture rate in one year.

Reliable preparation and regeneration of well-defined single-atom tips through laser annealing.

Single-atom tips (SATs) have crucial scientific and technological applications, such as in scanning probe microscopy and charged particle beam technology. We reported a reliable method of preparing and regenerating noble metal-covered W(111) SATs through laser annealing at approximately 1000 K under ultrahigh vacuum. The field emission patterns obtained during laser heating revealed the self-assembly process of a pyramidal tip. The SATs can be regenerated through laser annealing tens of times with little change in sharpness, indicating a long lifetime. Various pyramidal SATs can be generated and regenerated using visible-light, near-infrared, mode-locked, and continuous-wave lasers at different polarizations relative to the tip axis. The generation of well-defined pyramidal SATs through laser annealing can facilitate various applications of SATs.

Nonlinear compression toward high-energy single-cycle pulses by cascaded focus and compression.

The advancement of contemporary ultrafast science requires reliable sources to provide high-energy few-cycle light pulses. Through experiments and simulations, we demonstrate an arrangement of pulse postcompression, referred to as cascaded focus and compression (CASCADE), for generating millijoule-level, single-cycle pulses in a compact fashion. CASCADE is realized by a series of foci in matter, whereas pulse compression is provided immediately after each focus to maintain a high efficiency of spectral broadening. By implementing four stages of CASCADE in argon cells, we achieve 50-fold compression of millijoule-level pulses at 1030 nanometers from 157 to 3.1 femtoseconds, with an output pulse energy of 0.98 millijoules and a transmission efficiency of 73%. When driving high harmonic generation, these single-cycle pulses enable the creation of a carrier-envelope phase-dependent extreme ultraviolet continuum with energies extending up to 180 electron volts, providing isolated attosecond pulses at the output.

Spatially resolved spectral phase interferometry with an isolated attosecond pulse.

We demonstrate spatially resolved supercontinuum spectral phase interferometry with an isolated attosecond pulse (IAP). The measured spatial-spectral interferogram over the broadband region indicates a high degree of IAP coherence in both spatial and spectral domains. In addition, the spectral-delay interferogram shows periodic temporal oscillations over the full IAP continuous spectrum, which indicates high temporal coherence. The supercontinuum spectral phase interferometry with broadband IAP will contribute to exploring spatiotemporal dispersive electronic dynamics through phase-based spectroscopy in the future.

Greater than 50 times compression of 1030 nm Yb:KGW laser pulses to single-cycle duration.

Generation of octave-spanning spectrum that spans from 570 nm to 1300 nm utilizing 1030 nm 170 fs pulses from a Yb:KGW laser and a two-stage multiple-plate arrangement is demonstrated. 3.21 fs sub-single-cycle pulses are obtained after dispersion compensation. The high compression ratio of more than 50 times is achieved for two scenarios with widely different parameters including high input peak power at 1 kHz repetition rate and modest peak power at a high repetition rate of 100 kHz. The output pulses have good spatial mode quality and exhibit long-term stability. The achieved compression ratio and flexibility are unprecedented in ultrafast pulse compression to single-cycle regime. The experiments demonstrate that the technique of multiple-plate pulse compression is versatile and applicable for a wide range of laser pulse parameters.

Extension of water-window harmonic cutoff by laser defocusing-assisted phase matching.

We extend a recently demonstrated scheme [Optica4, 976 (2017)OPTIC82334-253610.1364/OPTICA.4.000976] to overcome the limit of conventional harmonic cutoff for different pulse durations, laser wavelengths, and gas targets. By tuning the truncation of long wavelength lasers, we show that the defocusing-assisted phase matching (DAPM) can be achieved in a tightly focused beam and highly ionized short gas cell, and can be used to effectively extend the harmonic cutoff energy and optimize its yield. An analysis of phase matching reveals that at longer wavelengths, greater cutoff extension to the water window region is achieved because of the larger harmonic intrinsic phase (proportional to the cube of laser wavelength), and because DAPM works at relatively higher laser intensities using a Ne target. This scheme provides a promising method for efficiently generating intense attosecond light sources in the extreme ultraviolet to x-rays.

Near- and Extended-Edge X-Ray-Absorption Fine-Structure Spectroscopy Using Ultrafast Coherent High-Order Harmonic Supercontinua.

Recent advances in high-order harmonic generation have made it possible to use a tabletop-scale setup to produce spatially and temporally coherent beams of light with bandwidth spanning 12 octaves, from the ultraviolet up to x-ray photon energies >1.6 keV. Here we demonstrate the use of this light for x-ray-absorption spectroscopy at the K- and L-absorption edges of solids at photon energies near 1 keV. We also report x-ray-absorption spectroscopy in the water window spectral region (284-543 eV) using a high flux high-order harmonic generation x-ray supercontinuum with 10^{9} photons/s in 1% bandwidth, 3 orders of magnitude larger than has previously been possible using tabletop sources. Since this x-ray radiation emerges as a single attosecond-to-femtosecond pulse with peak brightness exceeding 10^{26} photons/s/mrad^{2}/mm^{2}/1% bandwidth, these novel coherent x-ray sources are ideal for probing the fastest molecular and materials processes on femtosecond-to-attosecond time scales and picometer length scales.

EUV scatterometer with a high-harmonic-generation EUV source.

We have developed an extreme ultraviolet (EUV) scatterometer based on the analysis of coherent EUV light diffracted from a periodic array with nano-scale features. We discuss the choice of appropriate orders of the high harmonics generated coaxially along with the intense Ti:sapphire laser pulses for high resolution spatial performance. We describe an inverse-problem methodology for determining the structural parameters, and present preliminary measurement results confirming the functionality of the scatterometer. A rigorous coupled-wave analysis measurement algorithm was developed to extract accurately and quickly the relevant constitutive parameters from a measured diffraction pattern using a library-matching process.

Non-invasive manipulation of Drosophila behavior by two-photon excited red-activatable channelrhodopsin.

Scattering and absorption limit light penetration through inhomogeneous tissue. To reduce scattering, biochemists have shifted the wavelengths of excitation light for optogenetic actuators and fluorescent proteins to the orange-red range, while physicists have developed multiphoton technologies for deep tissue stimulation. We have built a rapid multiphoton spectroscopic screening system of genetically encoded red-activatable channelrhodopsin (ReaChR), and considered specific behaviors in transgenic Drosophila melanogaster as readouts to optimize the laser parameters for two-photon optogenetic activation. A wavelength-tunable optical parametric amplifier was adopted as the major light source for widefield two-photon excitation (TPE) of ReaChR. Our assays suggest that the optimized TPE wavelength of ReaChR is 1250 nm. Exploiting its capacity for optogenetic manipulation to induce macroscopic behavioral change, we realized rapid spectroscopic screening of genetically encoded effectors or indicators in vivo, and used modulation of ReaChR in the fly as a successful demonstration of such a system.

Ultraviolet surprise: Efficient soft x-ray high-harmonic generation in multiply ionized plasmas.

High-harmonic generation is a universal response of matter to strong femtosecond laser fields, coherently upconverting light to much shorter wavelengths. Optimizing the conversion of laser light into soft x-rays typically demands a trade-off between two competing factors. Because of reduced quantum diffusion of the radiating electron wave function, the emission from each species is highest when a short-wavelength ultraviolet driving laser is used. However, phase matching--the constructive addition of x-ray waves from a large number of atoms--favors longer-wavelength mid-infrared lasers. We identified a regime of high-harmonic generation driven by 40-cycle ultraviolet lasers in waveguides that can generate bright beams in the soft x-ray region of the spectrum, up to photon energies of 280 electron volts. Surprisingly, the high ultraviolet refractive indices of both neutral atoms and ions enabled effective phase matching, even in a multiply ionized plasma. We observed harmonics with very narrow linewidths, while calculations show that the x-rays emerge as nearly time-bandwidth-limited pulse trains of ~100 attoseconds.

Decomposed fuzzy systems and their application in direct adaptive fuzzy control.

In this paper, a novel fuzzy structure termed as the decomposed fuzzy system (DFS) is proposed to act as the fuzzy approximator for adaptive fuzzy control systems. The proposed structure is to decompose each fuzzy variable into layers of fuzzy systems, and each layer is to characterize one traditional fuzzy set. Similar to forming fuzzy rules in traditional fuzzy systems, layers from different variables form the so-called component fuzzy systems. DFS is proposed to provide more adjustable parameters to facilitate possible adaptation in fuzzy rules, but without introducing a learning burden. It is because those component fuzzy systems are independent so that it can facilitate minimum distribution learning effects among component fuzzy systems. It can be seen from our experiments that even when the rule number increases, the learning time in terms of cycles is still almost constant. It can also be found that the function approximation capability and learning efficiency of the DFS are much better than that of the traditional fuzzy systems when employed in adaptive fuzzy control systems. Besides, in order to further reduce the computational burden, a simplified DFS is proposed in this paper to satisfy possible real time constraints required in many applications. From our simulation results, it can be seen that the simplified DFS can perform fairly with a more concise decomposition structure.

Generation of bright isolated attosecond soft X-ray pulses driven by multicycle midinfrared lasers.

High harmonic generation driven by femtosecond lasers makes it possible to capture the fastest dynamics in molecules and materials. However, to date the shortest subfemtosecond (attosecond, 10(-18) s) pulses have been produced only in the extreme UV region of the spectrum below 100 eV, which limits the range of materials and molecular systems that can be explored. Here we experimentally demonstrate a remarkable convergence of physics: when midinfrared lasers are used to drive high harmonic generation, the conditions for optimal bright, soft X-ray generation naturally coincide with the generation of isolated attosecond pulses. The temporal window over which phase matching occurs shrinks rapidly with increasing driving laser wavelength, to the extent that bright isolated attosecond pulses are the norm for 2-µm driving lasers. Harnessing this realization, we experimentally demonstrate the generation of isolated soft X-ray attosecond pulses at photon energies up to 180 eV for the first time, to our knowledge, with a transform limit of 35 attoseconds (as), and a predicted linear chirp of 300 as. Most surprisingly, advanced theory shows that in contrast with as pulse generation in the extreme UV, long-duration, 10-cycle, driving laser pulses are required to generate isolated soft X-ray bursts efficiently, to mitigate group velocity walk-off between the laser and the X-ray fields that otherwise limit the conversion efficiency. Our work demonstrates a clear and straightforward approach for robustly generating bright isolated attosecond pulses of electromagnetic radiation throughout the soft X-ray region of the spectrum.

Mobile robot self-localization system using single webcam distance measurement technology in indoor environments.

A single-webcam distance measurement technique for indoor robot localization is proposed in this paper. The proposed localization technique uses webcams that are available in an existing surveillance environment. The developed image-based distance measurement system (IBDMS) and parallel lines distance measurement system (PLDMS) have two merits. Firstly, only one webcam is required for estimating the distance. Secondly, the set-up of IBDMS and PLDMS is easy, which only one known-dimension rectangle pattern is needed, i.e., a ground tile. Some common and simple image processing techniques, i.e., background subtraction are used to capture the robot in real time. Thus, for the purposes of indoor robot localization, the proposed method does not need to use expensive high-resolution webcams and complicated pattern recognition methods but just few simple estimating formulas. From the experimental results, the proposed robot localization method is reliable and effective in an indoor environment.

Water molecular flow control with a (5,5) nanocoil switch.

Molecular dynamics simulation was employed to investigate the diffusion behaviors of water molecules within a (5,5) carbon nanocoil (CNC) at different tensile strains, the length and coil diameter of CNC are 22 and 6.83 Ǻ, respectively. Condensed-phase, optimized molecular potentials for atomistic simulation studies were employed to model the interaction between atoms. The results show that the diffusion in the axial direction can be enhanced by the tensile strain and the water molecule flow can be blocked at a higher strain once the deformed areas appear at the higher strain. Moreover, the deformed (5,5) CNC at strain of 2.8 can recover its original structure at strain of 0, indicating that the adjustment of diffusion coefficient is repeatable by applying different strains in the axial direction.

Noniterative data inversion of phase retrieval by omega oscillating filtering for optical arbitrary waveform measurement.

We propose a noniterative data inversion process for the phase retrieval by omega oscillating filtering method that could measure both isolated attosecond pulses and periodic optical arbitrary waveform (OAW). The built-in phase modulation depth recovery not only prevents the need of independent calibration (a critical advantage in the extreme ultraviolet regime) but provides a self-consistency check for the data integrity. Our experiments successfully retrieved OAW with ~100% duty cycle in the near infrared regime.

The complete mitochondrial genome of Leucoptera malifoliella Costa (Lepidoptera: Lyonetiidae).

The mitochondrial genome (mitogenome) of Leucoptera malifoliella (=L. scitella) (Lepidoptera: Lyonetiidae) was sequenced. The size was 15,646 bp with gene content and order the same as those of other lepidopterans. The nucleotide composition of L. malifoliella mitogenome is highly A+T biased (82.57%), ranked just below Coreana raphaelis (82.66%) (Lepidoptera: Lycaenidae). All protein-coding genes (PCGs) start with the typical ATN codon except for the cox1 gene, which uses CGA as the initiation codon. Nine PCGs have the common stop codon TAA, four PCGs have the common stop codon T as incomplete stop codons, and nad4l and nad6 have TAG as the stop codon. Cloverleaf secondary structures were inferred for 22 tRNA genes, but trnS1(AGN) was found to lack the DHU stem. The secondary structure of rrnL and rrnS is generally similar to other lepidopterans but with some minor differences. The A+T-rich region includes the motif ATAGA, but the poly (T) stretch is replaced by a stem-loop structure, which may have a similar function to the poly (T) stretch. Finally, there are three long repeat (154 bp) sequences followed by one short repeat (56 bp) with four (TA)(n) intervals, and a 10-bp poly-A is present upstream of trnM. Phylogenetic analysis shows that the position of Yponomeutoidea, as represented by L. malifoliella, is the same as traditional classifications. Yponomeutoidea is the sister to the other lepidopteran superfamilies covered in the present study.

Bright coherent ultrahigh harmonics in the keV x-ray regime from mid-infrared femtosecond lasers.

High-harmonic generation (HHG) traditionally combines ~100 near-infrared laser photons to generate bright, phase-matched, extreme ultraviolet beams when the emission from many atoms adds constructively. Here, we show that by guiding a mid-infrared femtosecond laser in a high-pressure gas, ultrahigh harmonics can be generated, up to orders greater than 5000, that emerge as a bright supercontinuum that spans the entire electromagnetic spectrum from the ultraviolet to more than 1.6 kilo-electron volts, allowing, in principle, the generation of pulses as short as 2.5 attoseconds. The multiatmosphere gas pressures required for bright, phase-matched emission also support laser beam self-confinement, further enhancing the x-ray yield. Finally, the x-ray beam exhibits high spatial coherence, even though at high gas density the recolliding electrons responsible for HHG encounter other atoms during the emission process.