Retrieval of Aerosol Optical Properties over the Beijing Area Using POLDER/PARASOL Satellite Polarization Measurements

Aerosol optical properties over Beijing and Xianghe under several typical weather conditions （clear sky, light haze, heavy pollution and dust storm） are derived from POLDER （POLarization and Directionality of the Earth＇s Reflectances）/PARASOL （Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar） multi-directional, multi-spectral polarized signals using a more reliable retrieval algorithm as proposed in this paper. The results are compared with those of the operational retrieval algorithm of POLDER/PARASOL group and the ground-based AERONET （AErosol RObotic NETwork）/PHOTONS （PHOtometrie pour le Traitement Operational de Normalisation Satellitaire） measurements. It is shown that the aerosol optical parameters derived from the improved algorithm agree well with AERONET/PHOTONS measurement. The retrieval accuracies of aerosol optical thickness （AOT） and effective radius are 0.06 and 0.05 μm respectively, which are close to or better than the required accuracies （0.04 for AOT and 0.1 μm for effective radius） for estimating aerosol direct forcing.

Terahertz Radiation from a Longitudinal Electric Field Biased Femtosecond Filament in Air

The terahertz(THz)temporal waveform and spectrum from a longitudinal electrically biased femtosecond filament is studied experimentally.The initial direction of the electron motion inside the unbiased filament plasma is deduced from the transformation of the THz temporal waveform with applied fields of opposite polarities.Furthermore,a spectrum shift to lower frequency of the THz spectrum is observed in the presence of a biased field.It agrees well with theoretical predictions.

Characterization and performance of the Apollon short-focal-area facility following its commissioning at 1 PW level

We present the results of the first commissioning phase of the short-focal-length area of the Apollon laser facility(located in Saclay,France),which was performed with the first available laser beam(F2),scaled to a nominal power of 1 PW.Under the conditions that were tested,this beam delivered on-target pulses of 10 J average energy and 24 fs duration.Several diagnostics were fielded to assess the performance of the facility.The on-target focal spot and its spatial stability,the temporal intensity profile prior to the main pulse,and the resulting density gradient formed at the irradiated side of solid targets have been thoroughly characterized,with the goal of helping users design future experiments.Emissions of energetic electrons,ions,and electromagnetic radiation were recorded,showing good laser-to-target coupling efficiency and an overall performance comparable to that of similar international facilities.This will be followed in 2022 by a further commissioning stage at the multipetawatt level.

Capability of Visible-Near Infrared Spectroscopy in Estimating Soils Carbon, Potassium and Phosphorus

The spectroscopy technique has many advantages over conventional analytical methods since it is fast and easy to implement and with no use of chemical extractants. The objective of this study is to quantify soil total Carbon (C), available Phosphorus (P) and exchangeable potassium (K) using VIS-NIR reflectance spectroscopy. A total of 877 soils samples were collected in various agricultural fields in Mali. Multivariate analysis was applied to the recorded soils spectra to estimate the soil chemical properties. Results reveal the over performance of the Principal Component Regression (PCR) compared to the Partial Least Square Regression (PLSR). For coefficient of determination (R2), PLSR accounts for 0.29, 0.42 and 0.57;while the PCR gave 0.17, 0.34 and 0.50, respectively for C, P and K. Nevertheless, this study demonstrates the potential of the VIS-NIR reflectance spectroscopy in analyzing the soils chemical properties.

Classification of African Mosaic Virus Infected Cassava Leaves by the Use of Multi-Spectral Imaging

In this work, we have used multispectral imaging technology to classify cassava leaves infected by African mosaic virus by the use of their unique spectral finger print. The spectra are extracted from transmission, reflection and diffusion of their multispectral images;they have been then analyzed with statistical multivariate analysis techniques. Principal component analysis (PCA) has been used followed by K-means and Ascending Hierarchical Classification (AHC) to endorse the classification. The contribution of this work is the use of multispectral imagery which binds both spatial and spectral information to differentiate and sort infected leaves. The results show that the multimodal and imaging spectroscopy may allow blind identification and characterization of infected leaves.

The catalytic properties of DNA G‐quadruplexes rely on their structural integrity

The influence of the G‐quartet structural integrity on the catalytic activity of the G‐quadruplex(G4)was investigated by comparing the G4‐DNAzyme performances of a series of G4s with a G‐vacancy site and a G‐triplex(G‐tri).The results presented herein not only confirm that the structural integrity of the 3'‐end G‐quartet is necessary for G4s to be catalytically competent but also show how to remediate G‐vacancy‐mediated catalytic activity losses via the addition of guanine surrogates in an approach referred to as G‐vacancy complementation strategy that is applicable to parallel G4s only.Furthermore,this study demonstrates that the terminal G‐quartet could act as a proximal coordinating group and cooperate with the flanking nucleotide to activate the hemin cofactor.

Commissioning and first results from the new 2×100 TW laser at the WIS

At the Weizmann Institute of Science,a new high-power-laser laboratory has been established that is dedicated to the fundamental aspects of laser–matter interaction in the relativistic regime and aimed at developing compact laser-plasma accelerators for delivering high-brightness beams of electrons,ions,and x rays.The HIGGINS laser system delivers two independent 100 TW beams and an additional probe beam,and this paper describes its commissioning and presents the very first results for particle and radiation beam delivery.

New Method for Injectable Quinine Quality Assurance Control Using a Multi-Spectral Microscope

Africa is the world region that is most affected by malaria. Among the therapies used, injectable quinine is considered to be one of the effective antimalarial drug, however non-quality assured antimalarials clearly have a strong market penetration across Africa. To overcome this problem, it becomes more and more necessary to set up quantitative and qualitative analysis system for antimalarial quality control. The objective of the present investigation is an attempt to use customized multispectral microscope equipped with UV-Visible lasers for injectable quinine quality assurance control routinely. For that, we have established the calibration curve of quinine solution concentration as a function of area under light intensity histogram crossing the solution. From this calibration curve, we can check the conformity of any injectable quinine according to the pharmacopoeia involved. The proposed technique is a promising alternative for drug quality control routinely.

Design and current progress of the Apollon 10 PW project

The objective of the Apollon project is the generation of 10 PW peak power pulses of 15 fs at 1 shot/minute. In this paper the Apollon facility design, the technological challenges and the current progress of the project will be presented.

Stable femtosecond X-rays with tunable polarization from a laser-driven accelerator

Technology based on high-peak-power lasers has the potential to provide compact and intense radiation sources for a wide range of innovative applications.In particular,electrons that are accelerated in the wakefield of an intense laser pulse oscillate around the propagation axis and emit X-rays.This betatron source,which essentially reproduces the principle of a synchrotron at the millimeter scale,provides bright radiation with femtosecond duration and high spatial coherence.However,despite its unique features,the usability of the betatron source has been constrained by its poor control and stability.In this article,we demonstrate the reliable production of X-ray beams with tunable polarization.Using ionization-induced injection in a gas mixture,the orbits of the relativistic electrons emitting the radiation are reproducible and controlled.We observe that both the signal and beam profile fluctuations are significantly reduced and that the beam pointing varies by less than a tenth of the beam divergence.The polarization ratio reaches 80%,and the polarization axis can easily be rotated.We anticipate a broad impact of the source,as its unprecedented performance opens the way for new applications.

Exploring Sequence Space to Design Controllable G-Quadruplex Topology Switches

As nonclassical nucleic acid structures,G-quadruplexes(G4s)not only play important roles in gene regulation and stability maintenance,but are also widely used in nanotechnology.Structural diversity is one of the main factors explaining the popularity of G4s,but a comprehensive and integrated study of different factors determining G4 structural versatility is currently lacking.

High-Harmonic Generation and Correlated Electron Emission from Relativistic Plasma Mirrors at 1 kHz Repetition Rate

We report evidence for the first generation of XUV spectra from relativistic surface high-harmonic generation(SHHG)on plasma mirrors at a kilohertz repetition rate,emitted simultaneously with energetic electrons.SHHG spectra and electron angular distributions are measured as a function of the experimentally controlled plasma density gradient scale length Lg for three increasingly short and intense driving pulses:24 fs and a0=1:1,8 fs and a0=1:6,and finally 4 fs and a0≈2:1,where a0 is the peak vector potential normalized by mec/e with the elementary charge e,the electron rest mass me,and the vacuum light velocity c.For all driver pulses,we observe correlated relativistic SHHG and electron emission in the range Lg∈½λ/20,λ/4,with an optimum gradient scale length of Lg≈λ/10.This universal optimal Lg-range is rationalized by deriving a direct intensity-independent link between the scale length Lg and an effective similarity parameter for relativistic laser-plasma interactions.

Nonlinear ionization dynamics of hot dense plasma observed in a laser-plasma amplifier

Understanding the behaviour of matter under conditions of extreme temperature,pressure,density and electromagnetic fields has profound effects on our understanding of cosmologic objects and the formation of the universe.Lacking direct access to such objects,our interpretation of observed data mainly relies on theoretical models.However,such models,which need to encompass nuclear physics,atomic physics and plasma physics over a huge dynamic range in the dimensions of energy and time,can only provide reliable information if we can benchmark them to experiments under well-defined laboratory conditions.Due to the plethora of effects occurring in this kind of highly excited matter,characterizing isolated dynamics or obtaining direct insight remains challenging.High-density plasmas are turbulent and opaque for radiation below the plasma frequency and allow only near-surface insight into ionization processes with visible wavelengths.Here,the output of a high-harmonic seeded laser-plasma amplifier using eightfold ionized krypton as the gain medium operating at a 32.8 nm wavelength is ptychographically imaged.A complexvalued wavefront is observed in the extreme ultraviolet(XUV)beam with high resolution.Ab initio spatio-temporal Maxwell–Bloch simulations show excellent agreement with the experimental observations,revealing overionization of krypton in the plasma channel due to nonlinear laser-plasma interactions,successfully validating this four-dimensional multiscale model.This constitutes the first experimental observation of the laser ion abundance reshaping a laserplasma amplifier.The presented approach shows the possibility of directly modelling light-plasma interactions in extreme conditions,such as those present during the early times of the universe,with direct experimental verification.

Relativistic-intensity near-single-cycle light waveforms at kHz repetition rate

The development of ultra-intense and ultra-short light sources is currently a subject of intense research driven by the discovery of novel phenomena in the realm of relativistic optics,such as the production of ultrafast energetic particle and radiation beams for applications.It has been a long-standing challenge to unite two hitherto distinct classes of light sources:those achieving relativistic intensity and those with pulse durations approaching a single light cycle.While the former class traditionally involves large-scale amplification chains,the latter class places high demand on the spatiotemporal control of the electromagnetic laser field.Here,we present a light source producing waveformcontrolled 1.5-cycle pulses with a 719 nm central wavelength that can be focused to relativistic intensity at a 1 kHz repetition rate based on nonlinear post-compression in a long hollow-core fiber.The unique capabilities of this source allow us to observe the first experimental indications of light waveform effects in laser wakefield acceleration of relativistic energy electrons.