Interference-induced generation of a chirp-free short isolated attosecond pulse in the water window region with multicolor laser fields.

Compensating for the intrinsic attosecond chirp (atto-chirp) of wideband high-order harmonics in the water window region is a significant challenge, in order to obtain isolated attosecond pulses (IAPs) with a width of tens of attoseconds (as). Here, we propose to realize the generation of IAP with duration as short as 20 as, central energy of 365 eV, and bandwidth exceeding 150 eV from chirp-free high harmonics generated by a four-color driving laser, without the necessity for atto-chirp compensation with natural materials. Unlike any other gating methods that an IAP arises from only one electron ionization event, we take advantage of the interference between harmonic radiation produced by multiple ionizing events. We further demonstrate that such chirp-free short IAP survives after taking account of macroscopic propagation effects. Given that the synthesized multicolor laser field can also effectively increase the harmonic flux, this work provides a practical way for experiments to generate the broad bandwidth chirp-free IAPs in the water window region.

Unveiling Coherent Control of Halomethane Dissociation Induced by a Single Strong Ultraviolet Pulse.

We present a theoretical investigation into the coherent control of photodissociation reactions in halomethanes, specifically focusing on CH2BrCl by manipulating the spectral phase of a single femtosecond laser pulse. We examine the photodissociation of CH2BrCl under an ultrashort pulse with a quadratic spectral phase and reveal the sensitivity of both the total dissociation probability and the resulting radical products (Br+CH2Cl and Cl+CH2Br) to chirp rates. To gain insights into the underlying mechanism, we calculate the population distributions of excited vibrational states in the ground electronic state, demonstrating the occurrence of resonance Raman scattering (RRS) in the strong-field limit regime. By utilizing chirped pulses, we show that this RRS phenomenon can be suppressed and even eliminated through quantum destructive interference. This highlights the high sensitivity of photodissociation into Cl+CH2Br to the spectral phase, showcasing a phenomenon that goes beyond the traditional one-photon photodissociation of isolated molecules in the weak-field limit regime. These findings emphasize the importance of coherent control in the exploration and utilization of photodissociation in polyatomic molecules, paving the way for new advancements in chemical physics and femtochemistry.

Orbital-resolved photoelectron momentum distributions of F- ions in a counter-rotating bicircular field.

We present a theoretical study of the orbital-resolved photoelectron momentum distributions (PMDs) of F- ions by a two-color counter-rotating circularly polarized field. We show that the PMDs of F- ions can be modulated from an isotropic symmetric distribution into a three-lobe one by adding a weak fundamental counter-rotating field to the intense second harmonic circularly polarized field, and this modulation strongly depends on the initial atomic orbital. The PMDs simulated by the strong-field approximation method show good agreement with those obtained by solving the time-dependent Schrödinger equation. Based on the strong-field approximation method, we find that the radial momentum shift of PMDs for different orbitals is the fingerprint of orbital-dependent initial momentum at the tunnel exit. More importantly, we demonstrate that the lobes in PMDs appear in sequential order, highlighting that the scheme can be viewed as controllable rotating temporal Young's two-slit interferometer.

Controllable waveform terahertz generation using rippled plasma driven by an inhomogeneous electrostatic field.

We theoretically present the waveform controls of terahertz (THz) radiations generated from homogeneous and rippled plasma within inhomogeneous external electrostatic field. The Particle-in-cell (PIC) simulations is implemented to demonstrate generation and controllability of three types of THz pulses: single frequency THz pulse in homogeneous plasma, broadband THz pulse and dual frequency THz pulse in rippled plasma. The single frequency THz pulse can be tuned via shifting the knob of electron density of homogeneous plasma. Waveform of broadband THz pulse can be regulated into an envelope-like shape by varying amplitude of electron density of rippled plasma. The two center frequencies' interval of dual frequency THz pulse can be controlled by wave numbers of density distribution of rippled plasma. This work provides a potential means to generate the dual frequency THz pulses with two harmonic frequencies (ω+Ωω, Ω=2) or incommensurate frequencies (ω+Ωω, Ω=1.7,1.8, 2.2…).

Controlling the atomic-orbital-resolved photoionization for neon atoms by counter-rotating circularly polarized attosecond pulses.

We theoretically investigate the atomic-orbital-resolved vortex-shaped photoelectron momentum distributions (PMDs) and ionization probabilities by solving the two-dimensional time-dependent Schrödinger equation (2D-TDSE) of neon in a pair of delayed counter-rotating circularly polarized attosecond pulses. We found that the number of spiral arms in vortex patterns is twice the number of absorbed photons when the initial state is the ψm=±1 state, which satisfy a change from c2n+2 to c2n (n is the number of absorbed photons) rotational symmetry of the vortices if the 2p state is replaced by 2p+ or 2p- states. For two- and three-photon ionization, the magnetic quantum number dependence of ionization probabilities is quite weak. Interestingly, single-photon ionization is preferred when the electron and laser field corotate and ionization probabilities of 2p- is much larger than that of 2p+ if the proper time delay and wavelength are used. The relative ratio of ionization probabilities between 2p- and 2p+ is insensitive to laser peak intensity, which can be controlled by changing the wavelength, time delay, relative phase and amplitude ratio of two attosecond pulses.

Characterization of the metabolites of irisflorentin by using ultra-high performance liquid chromatography combined with quadrupole/orbitrap tandem mass spectrometry.

Irisflorentin is one of the bioactive constituents from the root of Belamcanda chinensis (L.) DC, which displayed anti-inflammatory and anti-tumor activities. In this work, the in vitro metabolism of irisflorentin was investigated using liver microsomes and hepatocytes. The metabolites were identified by ultra-high performance liquid chromatography combined with quadrupole/orbitrap tandem mass spectrometry. Under the current conditions, a total of 11 metabolites were detected and structurally identified according to accurate masses, fragment ions and retention times. Metabolite M10, identified as 6,7-dihydroxy-5,3',4',5'-tetramethoxy isoflavone, was biosynthesized and unambiguously characterized by nuclear magnetic resonance spectroscopy. The metabolic pathways of irisflorentin included oxidation, demethylation and glucuronidation. M10 was the most abundant metabolite in all tested species. Further phenotyping studies revealed that α-naphthoflavone and ketoconazole displayed significant inhibitory effect on the formation of M10. Cytochrome P450 (CYP) 1A2 and 3A4 were the major enzymes responsible for the formation of M10 by using individual recombinant human CYP450 enzymes. For the first time the current study provides an overview of the in vitro metabolic fates of irisflorentin, which is helpful for us to predict the human metabolism and the potential drug-drug interactions caused by irisflorentin.

Comparison of high-resolution synchrotron-radiation-based phase-contrast imaging and absorption-contrast imaging for evaluating microstructure of vascular networks in rat brain: from 2D to 3D views.

Conventional imaging methods such as magnetic resonance imaging, computed tomography and digital subtraction angiography have limited temporospatial resolutions and shortcomings like invasive angiography, potential allergy to contrast agents, and image deformation, that restrict their application in high-resolution visualization of the structure of microvessels. In this study, through comparing synchrotron radiation (SR) absorption-contrast imaging to absorption phase-contrast imaging, it was found that SR-based phase-contrast imaging could provide more detailed ultra-high-pixel images of microvascular networks than absorption phase-contrast imaging. Simultaneously, SR-based phase-contrast imaging was used to perform high-quality, multi-dimensional and multi-scale imaging of rat brain angioarchitecture. With the aid of image post-processing, high-pixel-size two-dimensional virtual slices can be obtained without sectioning. The distribution of blood supply is in accordance with the results of traditional tissue staining. Three-dimensional anatomical maps of cerebral angioarchitecture can also be acquired. Functional partitions of regions of interest are reproduced in the reconstructed rat cerebral vascular networks. Imaging analysis of the same sample can also be displayed simultaneously in two- and three-dimensional views, which provides abundant anatomical information together with parenchyma and vessels. In conclusion, SR-based phase-contrast imaging holds great promise for visualizing microstructure of microvascular networks in two- and three-dimensional perspectives during the development of neurovascular diseases.

Photoelectron momentum distributions of F- ions by a few-cycle laser pulse.

The two-dimensional photoelectron momentum distributions (PMD) of F- ions induced by a linearly polarized few-cycle laser pulse are analyzed with the saddle-point (SP) method. The validity of the SP method is confirmed by comparing the PMD with those obtained from direct numerical integration of the transition probability amplitude in the context of strong-field approximation (SFA). We analyze the intra- and inter-cycle interference patterns in the two-dimensional PMD and show that the two-dimensional PMD can be effectively monitored by changing the carrier-envelope phase of few-cycle laser pulse. In addition, by separately calculating the two-dimensional PMD formed in the different detachment steps, we find that the rich oscillatory patterns in the two-dimensional PMD can be mainly attributed to the interference effects of electronic wave packets in the classical propagation step after the ionization, and part of intra-cycle interference fringes' shape is affected by the sub-barrier phase.

Dynamic tracing for epidermal growth factor receptor mutations in urinary circulating DNA in gastric cancer patients.

The mutations of epidermal growth factor receptor are detected in gastric cancer, indicating its suitability as a target for receptor tyrosine kinase inhibitors, as well as a marker for clinical outcome of chemotherapeutic treatments. However, extraction of quality tumor tissue for molecular processes remains challenging. Here, we aimed to examine the clinical relevance of urinary cell-free DNA as an alternative tumor material source used specifically for monitoring epidermal growth factor receptor mutations. Therefore, 120 gastric cancer patients with epidermal growth factor receptor mutations and 100 healthy controls were recruited for the study. The gastric patients also received epidermal growth factor receptor inhibitor treatment for a serial monitoring study. Paired primary tumor specimens were obtained with blood and urine samples, which were taken at a 1-month interval for a duration of 12 months. We found that urinary cell-free DNA yielded a close agreement of 92% on epidermal growth factor receptor mutation status when compared to primary tissue at baseline, and of 99% epidermal growth factor receptor mutation status when compared to plasma samples at different time points. Thus, our data suggest that urinary cell-free DNA may be a reliable source for screening and monitoring epidermal growth factor receptor mutations in the primary gastric cancer.

Induction of microRNA-9 mediates cytotoxicity of curcumin against SKOV3 ovarian cancer cells.

BACKGROUND: Curcumin, a phenolic compound extracted from the rhizomes of Curcuma longa, has shown cytotoxic effects against a variety of cancers. The aim of this study was to identify potential microRNA (miRNA) mediators of the anticancer effects of curcumin in ovarian cancer cells. MATERIALS AND METHODS: SKOV3 ovarian cancer cells were treated with curcumin (10-60 µM) and miR-9 expression, cell proliferation, and apoptosis were assessed. The effects of miR-9 depletion on curcumin-mediated growth suppression were also examined. Phosphorylation of Akt and forkhead box protein O1 (FOXO1) was measured in cells with miR-9 overexpression or curcumin treatment. RESULTS: Curcumin caused a significant and dose-dependent increase of miR-9 expression in SKOV3 cells, while significantly impeding cell proliferation and stimulating apoptosis. Depletion of miR-9 significantly (p<0.05) attenuated the growth-suppressive effects of curcumin on SKOV3 cells, coupled with reduced percentages of apoptotic cells. In contrast, overexpression of miR-9 significantly enhanced the cleavage of caspase-3 and poly(ADP-ribose) polymerase and promoted apoptotic death in SKOV3 cells. Western blot analysis showed that both miR-9 overexpression and curcumin similarly caused a significant (p<0.05) decline in the phosphorylation of Akt and FOXO1, compared to untreated cells. CONCLUSIONS: The present study provided evidence that curcumin exerts its cytotoxic effects against SKOV3 ovarian cancer cells largely through upregulation of miR-9 and subsequent modulation of Akt/FOXO1 axis. Further studies are needed to identify direct targets of miR-9 that mediate the anticancer effects of curcumin in ovarian cancer cells.