Tuning the Chiral Growth of Plasmonic Bipyramids via the Wavelength and Polarization of Light.

Circularly polarized light (CPL) is a versatile tool to prepare chiral nanostructures, but the mechanism for inducing enantioselectivity is not well understood. This work shows that the energy and polarization of visible photons can initiate photodeposition at different sites on plasmonic nanocrystals. Here, CPL on achiral gold bipyramids (AuBPs) creates hot holes that oxidatively deposit PbO2 asymmetrically. We show for the first time that the location of PbO2 photodeposition and hence optical dissymmetry depends on the CPL wavelength. Specifically, 488 and 532 nm CPL induce PbO2 growth in the middle of AuBPs, whereas 660 nm CPL induces PbO2 growth at the tips. Our observations show that wavelength-dependent plasmonic field distributions are more important than surface lightning rod effects in localizing plasmon-mediated photochemistry. The largest optical dissymmetry occurs at excitation wavelengths between the transverse and longitudinal resonances of the AuBPs because higher-order modes are required to induce chiral electric fields.

Transcriptomic landscape reveals germline potential of porcine skin-derived multipotent dermal fibroblast progenitors.

According to estimations, approximately about 15% of couples worldwide suffer from infertility, in which individuals with azoospermia or oocyte abnormalities cannot be treated with assisted reproductive technology. The skin-derived stem cells (SDSCs) differentiation into primordial germ cell-like cells (PGCLCs) is one of the major breakthroughs in the field of stem cells intervention for infertility treatment in recent years. However, the cellular origin of SDSCs and their dynamic changes in transcription profile during differentiation into PGCLCs in vitro remain largely undissected. Here, the results of single-cell RNA sequencing indicated that porcine SDSCs are mainly derived from multipotent dermal fibroblast progenitors (MDFPs), which are regulated by growth factors (EGF/bFGF). Importantly, porcine SDSCs exhibit pluripotency for differentiating into three germ layers and can effectively differentiate into PGCLCs through complex transcriptional regulation involving histone modification. Moreover, this study also highlights that porcine SDSC-derived PGCLCs specification exhibit conservation with the human primordial germ cells lineage and that its proliferation is mediated by the MAPK signaling pathway. Our findings provide substantial novel insights into the field of regenerative medicine in which stem cells differentiate into germ cells in vitro, as well as potential therapeutic effects in individuals with azoospermia and/or defective oocytes.

A review of global wilderness area identification since the 21st century.

Wilderness areas are natural landscape elements that are relatively undisrupted by human activity and play a critical role in maintaining ecological equilibrium, preserving naturalness, and ensuring ecosystem resilience. Since 2000, monitoring of global wilderness areas has increased owing to the availability of spatial map data and remote sensing imagery related to human activity and/or human footprint. Progress has been made in the remote sensing of wilderness areas by relying on available historical literature (e.g., published papers, books, and reports). However, to our knowledge, a synthesis of wilderness area research from a remote sensing perspective has not yet been performed. In this preliminary review, we discuss the concept of wilderness in different historical eras and systematically summarize dynamic wilderness monitoring at local, national, and global scales, available remotely sensed indicators, disparities and commonalities in identification methods, and mapping uncertainties. Finally, since this field remains in its initial stage owing to a lack of unified standards and vertical/horizontal comparisons, we present insights into future research directions, particularly with regard to remote sensing. The findings of this review may help to improve the overall understanding of current wilderness patterns (i.e., increases/decreases) and the mechanisms by which they change, as well as provide guidance for global nature conservation programs.

Evaluating annual soil carbon emissions under biochar-added farmland subjecting from freeze-thaw cycle.

Straw biochar is a commonly recognized agricultural amendment that can improve soil quality and reduce carbon emissions while sequestering soil carbon. However, the mechanisms underlying biochar's effects on annual soil carbon emissions in seasonally frozen soil areas and intrinsic drivers have not been clarified. Here, a 2-y field experiment was conducted to investigate the effects of different biochar dosages (0, 15, and 30, t ha-1; B0 (CK), B15, and B30, respectively) on carbon emissions (CO2 and CH4) microbial colony count, and soil-environment factors. The study period was the full annual cycle, including the freeze-thaw period (FTP) and the crop growth period (CP). Structural equation modeling (SEM) was developed to reveal the key drivers and potential mechanisms of biochar on carbon emissions. Biochar application reduced soil carbon emissions, with the reduction rate positively related to the biochar application rate (B30 best). During FTP, the reduction rate was 11.5% for CO2 and 48.2% for CH4. During CP, the reduction rate was 17.9% for CO2 and 34.5% for CH4. Overall, compared with CK, B30 treatment had a significant effect on reducing total soil carbon emissions (P < 0.05), with an average decrease of 16.7% during the two-year test period. The study also showed that for soils with continuous annual cycles (FTP and CP), carbon emissions were best observed from 10:00-13:00. After two years of freeze-thaw cycling, biochar continued to improve soil physical and chemical properties, thereby increasing soil microbial colony count. Compared with B0, the B30 treatment significantly increased the total colony count by 74.3% and 263.8% during FTP and CP (P < 0.05). Structural equation modeling (SEM) indicated that, with or without biochar application, the soil physicochemical properties directly or indirectly affected soil CO2 and CH4 emission fluxes through microbial colony count. The total effects of biochar application on CO2 emission fluxes were 0.50 (P < 0.05) and 0.64 (P < 0.01), respectively, but there was no significant effect on CH4 emission fluxes (P > 0.05). Among them, soil water content (SWC), soil temperature (ST) and soil organic carbon (SOC) were the main environmental determinants of CO2 emission fluxes during the FTP and CP. The total effects were 0.57, 0.65, and 0.53, respectively. For CH4, SWC, soil salinity (SS) and actinomycete colony count were the main environmental factors affecting its emission. The total effects were 0.50, 0.45, 0.44, respectively. For freeze-thaw alternating soils, the application of biochar is a feasible option for addressing climate change through soil carbon sequestration and greenhouse gas emissions mitigation. Soil water-heat-salt-fertilization and microbial communities are important for soil carbon emissions as the reaction matrix and main participants of soil carbon and nitrogen biochemical transformation.

Efficient and Selective Photogeneration of Stable N-Centered Radicals via Controllable Charge Carrier Imbalance in Cesium Lead Halide Nanocrystals.

Despite the versatility of semiconductor nanocrystals (NCs) in photoinduced chemical processes, the generation of stable radicals has been more challenging due to reverse charge transfer or charge recombination even in the presence of sacrificial charge acceptors. Here, we show that cesium lead halide (CsPbX3) NCs can selectively photogenerate either aminium or aminyl radicals from amines, taking advantage of the controllable imbalance of the electron and hole populations achieved by varying the solvent composition. Using dihalomethane as the solvent, irreversible removal of the electrons from CsPbX3 NCs enabled by the photoinduced halide exchange between the NCs and the dihalomethane resulted in efficient oxidative generation of the aminium radical. In the absence of dihalomethane in solvent, the availability of both electrons and holes resulted in the production of an aminyl radical via sequential hole transfer and reductive N-H bond dissociation. The negative charge of the halide ions on the NC's lattice surface appears to facilitate the aminyl radical production, competing favorably with the reversible charge transfer reverting to the reactant.

Cognitive Impairment Is Associated with New-Onset Stroke: Evidence from a Nationwide Prospective Cohort Study.

INTRODUCTION: Stroke is closely related to cognitive function, and many patients experience cognitive impairment after stroke; however, whether cognitive impairment is associated with an increased risk of stroke remains inconclusive. This study aims to investigate whether cognitive impairment is associated with new-onset stroke (first ever nonfatal stroke) using a national prospective study. METHODS: Data from the China Health and Retirement Longitudinal Study (CHARLS) from 2011 to 2018 were used. A total of 11,961 Chinese participants aged ≥45 years without a history of stroke were included in the present study and divided into a cognitive impairment group and a normal group according to the baseline cognitive score. Logistic regression analysis was used to analyse the association between baseline cognitive function and new-onset stroke. RESULTS: During the 6.96-year follow-up period, 875 participants experienced new-onset stroke. Compared with the cognitively normal group, the odds ratio (95% confidence intervals) for new-onset stroke in the cognitively impaired group was 1.21 (1.04, 1.40) when not adjusted for confounders and 1.22 (1.01, 1.48) after adjusting for established confounding factors, including demographic data, medical history, physical examination, and laboratory indicators. CONCLUSION: Cognitive impairment was associated with new-onset stroke among middle-aged and elderly Chinese individuals. Further studies should be carried out to confirm the causal relationship between cognitive impairment and stroke.

Photoemission of the Upconverted Hot Electrons in Mn-Doped CsPbBr3 Nanocrystals.

Hot electrons play a crucial role in enhancing the efficiency of photon-to-current conversion or photocatalytic reactions. In semiconductor nanocrystals, energetic hot electrons capable of photoemission can be generated via the upconversion process involving the dopant-originated intermediate state, currently known only in Mn-doped cadmium chalcogenide quantum dots. Here, we report that Mn-doped CsPbBr3 nanocrystals are an excellent platform for generating hot electrons via upconversion that can benefit from various desirable exciton properties and the structural diversity of metal halide perovskites (MHPs). Two-dimensional Mn-doped CsPbBr3 nanoplatelets are particularly advantageous for hot electron upconversion due to the strong exciton-dopant interaction mediating the upconversion process. Furthermore, nanoplatelets reveal evidence for the hot electron upconversion via long-lived dark excitons in addition to bright excitons that may enhance the upconversion efficiency. This study establishes the feasibility of hot electron upconversion in MHP hosts and demonstrates the potential merits of two-dimensional MHP nanocrystals in the upconversion process.

Synthesis and Properties of Strongly Quantum-Confined Cesium Lead Halide Perovskite Nanocrystals.

ConspectusSemiconducting metal halide perovskite (MHP) nanocrystals have emerged as an important new class of materials as the source of photons and charges for various applications that can outperform many other semiconductor nanocrystals utilized for the same purposes. However, the majority of the studies of MHP nanocrystals focused on weakly or nonconfined systems, where the quantum confinement giving rise to various size-dependent and confinement-enhanced photophysical properties cannot be explored readily. This was partially due to the challenge in producing strongly quantum-confined MHP nanocrystals, since the traditional kinetic control approach was less effective for the size control. Recent synthetic progress in MHP nanocrystals utilizing the equilibrium-based size control achieved the precise control of quantum confinement with high ensemble uniformity, enabling the exploration of the unique properties of MHP nanocrystals under strong quantum confinement. In this Account, we review the recent progress made in the synthesis of strongly quantum-confined cesium lead halide nanocrystals and investigation of the properties of exciton modified by strong quantum confinement. The main body of this Account discusses the key results of the research in this field in two separate sections. Section 2 describes the thermodynamic equilibrium-based synthesis method to control the size of cesium lead halide perovskite quantum dots in strongly confined regime. Size control in anisotropic nanocrystals with one- and two-dimensional quantum confinement is also discussed. Section 3 covers the following three topics that highlight the effects of quantum confinement on various spectroscopic properties of excitons in cesium lead halide perovskite nanocrystals: (1) Size-dependent absorption cross section of cesium lead halide quantum dots; (2) confinement effect on exciton fine structure and access to the dark exciton exhibiting intense and long-lived photoluminescence; (3) activation of forbidden exciton transition via dynamic lattice distortion by the photoexcited charge carriers enhanced by quantum confinement. The impact of strong quantum confinement goes beyond the properties of excitons covered in this Account and is expected to expand the functionality of MHP nanocrystals as the source of photons and charges. For instance, realization of the possible enhancement of photon down- and upconversion and hot carrier generation via quantum confinement will further increase the usefulness of strongly confined MHP nanocrystals in their applications.

High-speed wavelength-swept femtosecond source from 1055 to 1300†nm using a GHz femtosecond fiber laser.

In this Letter, we demonstrate a high-speed broadband wavelength-swept femtosecond source (WFS) that leverages the soliton self-frequency shift (SSFS) and intensity-wavelength encoding technologies. The optical wavelength of the high-speed WFS can be continuously swept from 1055 nm to nearly 1300 nm at a sweeping rate of 100 kHz. This WFS is especially seeded by a femtosecond mode-locked all-fiber laser at 1055 nm that has a fundamental repetition rate of ∼1.0 GHz, a maximum output power of 7 W, and a compressed pulse width of 220 fs. It is anticipated that this high-speed broadband WFS can be a promising source for applications that require fast wavelength scanning and high-speed data processing.

890-nm-excited SHG and fluorescence imaging enabled by an all-fiber mode-locked laser.

We demonstrate second-harmonic generation (SHG) microscopy excited by the ∼890-nm light frequency-doubled from a 137-fs, 19.4-MHz, and 300-mW all-fiber mode-locked laser centered at 1780 nm. The mode-locking at the 1.7-µm window is realized by controlling the emission peak of the gain fiber, and uses the dispersion management technique to broaden the optical spectrum up to 30 nm. The spectrum is maintained during the amplification and the pulse is compressed by single-mode fibers. The SHG imaging performance is showcased on a mouse skull, leg, and tail. Two-photon fluorescence imaging is also demonstrated on C. elegans labeled with green and red fluorescent proteins. The frequency-doubled all-fiber laser system provides a compact and efficient tool for SHG and fluorescence microscopy.

Homocysteine Associated With Low Cognitive Function Independent of Asymptomatic Intracranial and Carotid Arteries Stenoses in Chinese Elderly Patients: An Outpatient-Based Cross-Sectional Study.

INTRODUCTION: A high homocysteine (Hcy) concentration is correlated with cognitive impairment; however, the exact underlying mechanism is still not fully elucidated. The present study aimed to investigate whether asymptomatic intracranial and carotid arteries stenoses are involved in Hcy-related low cognitive function. METHODS: This was a cross-sectional study in outpatient clinics. Residents aged ≥60 years, who came to the Stroke and Rehabilitation Clinic of Shandong Provincial Third Hospital in Jinan, Shandong Province from December 2019 to May 2020 to seek consultation due to abnormal transcranial Doppler reports (eg., increased cerebral blood flow velocity) were eligible. Information including demographics, medical history, lifestyle habits were collected. Fasting blood was used to detect total serum homocysteine level (tHcy). Cerebrovascular magnetic resonance angiography and neck vascular ultrasound examination were used to confirm the diagnosis of intracranial and carotid artery stenoses. The Mini-Mental State Examination was used to assess the cognitive function of each participant. Logistic regression was used to evaluate the relationship between tHcy levels and cognitive function. RESULTS: This study included 236 participants (mean age: 64.0 (SD, 7.5) years, female: 58.1%). Multivariable analyses adjusted for several potential confounders, including creatinine and cardiovascular risk factors, showed that tHcy was associated with carotid artery stenosis (CAS). After adjusting for CAS, ICAS and several potential confounders, the association between tHcy level and low cognitive function remained significant (odds ratio: 1.09, 95% confidence interval: (1.03, 1.16), P = 0.032) . CONCLUSION: Increased serum tHcy level was associated with low cognitive function independent of asymptomatic intracranial and carotid arteries stenoses.

Cryopreservation of porcine skin-derived stem cells using melatonin or trehalose maintains their ability to self-renew and differentiate.

Porcine skin-derived stem cells (pSDSCs) are a type of adult stem cells (ASCs) that retain the ability to self-renew and differentiate. Currently, pSDSCs research has entered an intense period of development; however there has been no research regarding methods of cryopreservation. In this paper, we explored an efficient cryopreservation method for pSDSCs. Our results demonstrated that cryopreserving 50 µm diameter pSDSCs aggregates resulted in a lower apoptosis rate and a greater ability to proliferate to form larger spherical cell aggregates than during single-cell cryopreservation. To further optimize the cryopreservation method, we added different concentrations of melatonin (N-acetyl-5-methoxytryptamine, MLT) and trehalose (d-trehalose anhydrous, TRE) to act as cryoprotectants (CPAs) for the pSDSCs. After comparative experiments, we found that the cryopreservation efficiency of 50 mM TRE was superior. Further experiments demonstrated that the reason why 50 mM TRE improved cryopreservation efficiency was that it reduced the intracellular oxidative stress and mitochondrial damage caused by cryopreservation. Taken together, our results suggest that cryopreserving 50 µm diameter pSDSCs aggregates in F12 medium with 10% dimethyl sulfoxide (DMSO) and 50 mM TRE promotes the long-term storage of pSDSCs.

Magnetic Effect of Dopants on Bright and Dark Excitons in Strongly Confined Mn-Doped CsPbI3 Quantum Dots.

We investigated the magnetic effect of Mn2+ ions on an exciton of Mn-doped CsPbI3 quantum dots (QDs), where we looked for the signatures of an exciton magnetic polaron known to produce a large effective magnetic field in Mn-doped CdSe QDs. In contrast to Mn-doped CdSe QDs that can produce ∼100 T of magnetic field upon photoexcitation, manifested as a large change in the energy and relaxation dynamics of a bright exciton, Mn-doped CsPbI3 QDs exhibited little influence of a magnetic dopant on the behavior of a bright exciton. However, a µs-lived dark exciton in CsPbI3 QDs showed 40% faster decay in the presence of Mn2+, equivalent to the effect of ∼3 T of an external magnetic field. While further study is necessary to fully understand the origin of the large difference in the magneto-optic property of an exciton in two systems, we consider that the difference in antiferromagnetic coupling of the dopants is an important contributing factor.

High-power femtosecond all-fiber laser system at 1.5 µm with a fundamental repetition rate of 4.9 GHz.

In this Letter, we demonstrate a high-power femtosecond all-fiber laser system at 1.5 µm that operates at a fundamental repetition rate of up to 4.9 GHz. This high repetition rate laser system delivers an average power of 10 W and a pulsewidth of 63 fs in an all-fiber configuration-the best overall performance at 1.5 µm, so far, in terms of the all-fiber design, high average power, short pulsewidth, and high fundamental repetition rate. Integrated from 10 Hz to 10 MHz, this high-power femtosecond all-fiber laser system exhibits a relative intensity noise of only 0.4%. It is anticipated that this femtosecond laser system is promising for various applications, such as high-speed micromachining, wide-field multiphoton bioimaging, and nonlinear optics.

An enhanced fluorescence detection of a nitroaromatic compound using bacteria embedded in porous poly lactic-co-glycolic acid microbeads.

The detection of explosive nitroaromatic compounds has caused worldwide concern for human safety. In this study, we introduce a fluorescent biosensor based on porous biocompatible microspheres loaded with a bioreporter for the detection of nitroaromatic compounds. Poly(lactic-co-glycolic acid) microbeads were designed as biosensors embedded with the bacterial bioreporters. The genetically engineered bacterial bioreporter can express a green fluorescent protein in response to nitroaromatic compounds (e.g., trinitrotoluene and dinitrotoluene). The modified surface structure in microbeads provides a large surface area, as well as easy penetration, and increases the number of attached bioreporters for enhanced fluorescent signals of biosensors. Moreover, the addition of the M13 bacteriophage in open porous microbeads significantly amplified the fluorescence signal for detection by the π-π interaction between peptides in the M13 bacteriophage and nitroaromatic compounds. The modification of the surface morphology, as well as the genetically engineered M13 phage, significantly amplifies the fluorescence signal, which makes the detection of explosives easier, and has great potential for the stand-off remote sensing of TNT buried in the field.

The overall diet quality in childhood is prospectively associated with the timing of puberty.

PURPOSE: The influences of nutrition in childhood on puberty onset could have sustained consequences for health and wellbeing later in life. The aim of this study was to investigate the prospective association of diet quality prior to puberty with the timing of puberty onset. METHODS: We considered data from 3983 SCCNG (Southwest China Childhood Nutrition and Growth) study participants with dietary data, anthropometric measurement, and information on potential confounders at their baseline assessment (mean age: 7.1 years for girls and 7.3 years for boys; mean length of follow-up was 4.2 years). Cox proportional hazard regression estimating hazard ratios (HRs) and 95% confidence intervals (CIs) were used to examine the relationship between diet quality and puberty onset. Dietary intake at baseline was assessed using a validated food frequency questionnaire. Diet quality was determined using the Chinese Children Dietary Index (CCDI) which measures adherence to current dietary recommendations (theoretical range: 0-160 points). Age at Tanner stage 2 for breast/genital development (B2/G2), menarche or voice break (M/VB) were used as pubertal markers. RESULTS: The CCDI score ranged from 56.2 to 136.3 for girls and 46.1-131.5 for boys. Pubertal markers consistently indicate that girls and boys with higher diet quality were more likely to enter their puberty later than their counterparts with lower CCDI scores (higher vs. lower CCDI tertiles: adjusted HR for age at B2: 0.85 (95% CI, 0.81-0.94), p for trend = 0.02; G2: 0.86 (95% CI,0.80-0.96), p for trend = 0.02; M: 0.86 (95% CI,0.80-0.95), p for trend = 0.02; VB: 0.86 (95% CI,0.79-0.98), p for trend = 0.03), after adjustment for paternal education level, baseline energy intake, and pre-pubertal body fat. CONCLUSIONS: Our data suggested a later puberty onset and later timing of progressed puberty stages in children with a high diet quality, which were independent of pre-pubertal body fat.

Beyond protein intake: does dietary fat intake in the year preceding pregnancy and during pregnancy have an impact on gestational diabetes mellitus?

PURPOSE: Studies regarding the association between dietary fat intake and gestational diabetes mellitus (GDM) are limited and provide conflicting findings. Thus, the study aims to examine the association of dietary fat intake in the year preceding pregnancy and during pregnancy with the risk of GDM, taking the relevance of dietary protein intake on GDM into consideration. METHODS: A prospective study was conducted in 6299 singleton pregnancies, using the data from the Nutrition in Pregnancy and Growth in Southwest China (NPGSC). A validated food frequency questionnaire was used to assess dietary fat intake in the year preceding pregnancy and during the first and second trimesters of pregnancy. Logistic regression analysis was used to assess the prospective associations of dietary fat intake and the type and source of dietary fats in different time windows with GDM risk. RESULTS: Higher intake of total fat [OR (95% CI): 2.21 (1.19-4.20), P = 0.02] during 12-22 weeks of gestation was associated with higher GDM risk. However, adjustment for animal protein intake greatly attenuated this association [OR (95% CI): 1.81 (0.93, 3.64), P = 0.11]. Total fat intake neither in the year preceding pregnancy nor during the early pregnancy was associated with GDM risk. Moreover, insignificant associations were observed between intakes of vegetable fat, animal fat, cholesterol, saturated fatty acid, monounsaturated fatty acid and polyunsaturated fatty acid one year before pregnancy and during the first and second trimesters and GDM risk. CONCLUSION: Our study indicated that dietary fat intake one year before pregnancy and across the two pregnancy trimesters preceding the diagnosis of GDM has no relevance on GDM risk among Chinese women, particularly those with normal BMI, low, or normal calorie intake.

Claudin14 promotes colorectal cancer progression via the PI3K/AKT/mTOR pathway.

Colorectal cancer is the third leading cancer in the world in terms of incidence and mortality. The role of differentially expressed Claudin-14 (CLDN14) in CRC has not been reported. We observed that CLDN14 was associated with the progression of CRC. Our functional studies have shown that CLDN14 promoted the proliferation of CRC cells. In addition, CLDN14 also increased the migration and invasion of CRC cells. In vivo experiments also showed that CLDN14 promoted the growth of colorectal cancer via the PI3K/AKT/mTOR. In summary, our research suggests that CLDN14 promotes the progression of colorectal cancer. Our findings may provide new strategies for clinical management and patient prognosis of CRC.

Iron-Catalyzed Regiodivergent Alkyne Hydrosilylation.

Although tremendous effort has been devoted to the development of methods for iron catalysis, few of the catalysts reported to date exhibit clear superiority to other metal catalysts, and the mechanisms of most iron catalysis remain unclear. Herein, we report that iron complexes bearing 2,9-diaryl-1,10-phenanthroline ligands exhibit not only unprecedented catalytic activity but also unusual ligand-controlled divergent regioselectivity in hydrosilylation reactions of various alkynes. The hydrosilylation protocol described herein provides a highly efficient method for preparing useful di- and trisubstituted olefins on a relatively large scale under mild conditions, and its use markedly improved the synthetic efficiency of a number of bioactive compounds. Mechanistic studies based on control experiments and density functional theory calculations were performed to understand the catalytic pathway and the observed regioselectivity.

>100 W GHz femtosecond burst mode all-fiber laser system at 1.0 µm.

In this work, we report a >100 W femtosecond (fs) burst mode all-fiber laser system at 1.0 µm that operates at an intra-burst repetition rate of up to 1.2 GHz. This fiber laser system provides the highest output power that has been reported so far for GHz fs fiber lasers, to the best of our knowledge. In addition to the superior output power, this fiber laser system also shows a promising overall figure of merit, specifically in terms of pulse width (473 fs), long-term reliability (<0.67% power fluctuation) and system compactness (all-fiber configuration). We anticipate that this all-fiber laser system can be a promising ultrafast laser source for these applications requiring fs pulses with both high average power and high repetition rate, such as micromachining, bioimaging and frequency metrology.