Femtosecond Spectroscopy with Vacuum Ultraviolet Pulse Pairs

We combine different wavelengths from an intense high-order harmonics source with variable delay at the focus of a split-mirror interferometer to conduct pump-probe experiments on gas-phase molecules. We report measurements of the time resolution (<44 fs) and spatial profiles (4 {\mu}m x 12 {\mu}m) at the focus of the apparatus. We demonstrate the utility of this two-color, high-order-harmonic technique by time resolving molecular hydrogen elimination from C2H4 excited into its absorption band at 161 nm

Ultrafast Internal Conversion in Ethylene. II. Mechanisms and Pathways for Quenching and Hydrogen Elimination

Through a combined experimental and theoretical approach, we study the nonadiabatic dynamics of the prototypical ethylene (C$_2$H$_4$) molecule upon $\pi \rightarrow \pi^*$ excitation with 161 nm light. Using a novel experimental apparatus, we combine femtosecond pulses of vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) radiation with variable delay to perform time resolved photo-ion fragment spectroscopy. In this second part of a two part series, the extreme ultraviolet (17 eV$< h \nu < 23$ eV) probe pulses are sufficiently energetic to break the C-C bond in photoionization, or photoionize the dissociation products of the vibrationally hot ground state. The experimental data is directly compared to ab initio molecular dynamics simulations accounting for both the pump and probe steps. Enhancements of the CH$_2^+$ and CH$_3^+$ photoion fragment yields, corresponding to molecules photoionized in ethylene (CH$_2$CH$_2$) and ethylidene (CH$_3$CH) like geometries are observed within 100 fs after $\pi \rightarrow \pi^*$ excitation. Quantitative agreement between theory and experiment on the relative CH$_2^+$ and CH$_3^+$ yields provides experimental confirmation of the theoretical prediction of two distinct transition states and their branching ratio (Tao, et al. J. Phys. Chem. A. 113, 13656 (2009)). Fast, non-statistical, elimination of H$_2$ molecules and H atoms is observed in the time resolved H$_2^+$ and H$^+$ signals

Laser beam coupling with capillary discharge plasma for laser wakefield acceleration applications

One of the most robust methods, demonstrated up to date, of accelerating electron beams by laser-plasma sources is the utilization of plasma channels generated by the capillary discharges. These channels, i.e., plasma columns with a minimum density along the laser pulse propagation axis, may optically guide short laser pulses, thereby increasing the acceleration length, leading to a more efficient electron acceleration. Although the spatial structure of the installation is simple in principle, there may be some important effects caused by the open ends of the capillary, by the supplying channels etc., which require a detailed 3D modeling of the processes taking place in order to get a detailed understanding and improve the operation. However, the discharge plasma, being one of the most crucial components of the laser-plasma accelerator, is not simulated with the accuracy and resolution required to advance this promising technology. In the present work, such simulations are performed using the code MARPLE. First, the process of the capillary filling with a cold hydrogen before the discharge is fired, through the side supply channels is simulated. The main goal of this simulation is to get a spatial distribution of the filling gas in the region near the open ends of the capillary. A realistic geometry is used for this and the next stage simulations, including the insulators, the supplying channels as well as the electrodes. Second, the simulation of the capillary discharge is performed with the goal to obtain a time-dependent spatial distribution of the electron density near the open ends of the capillary as well as inside the capillary. Finally, to evaluate effectiveness of the beam coupling with the channeling plasma wave guide and electron acceleration, modeling of laser-plasma interaction was performed with the code INF&RNOComment: 11 pages, 9 figure

On production and asymmetric focusing of flat electron beams using rectangular capillary discharge plasmas

A method for the asymmetric focusing of electron bunches, based on the active plasma lensing technique is proposed. This method takes advantage of the strong inhomogeneous magnetic field generated inside the capillary discharge plasma to focus the ultrarelativistic electrons. The plasma and magnetic field parameters inside the capillary discharge are described theoretically and modeled with dissipative magnetohydrodynamic computer simulations enabling analysis of the capillaries of rectangle cross-sections. Large aspect ratio rectangular capillaries might be used to transport electron beams with high emittance asymmetries, as well as assist in forming spatially flat electron bunches for final focusing before the interaction point.Comment: 16 pages, 7 figures, 1 tabl

Ultrafast Diagnostics for Electron Beams from Laser Plasma Accelerators

We present an overview of diagnostic techniques for measuring key parameters of electron bunches from Laser Plasma Accelerators (LPAs). The diagnostics presented here were chosen because they highlight the unique advantages (e.g., diverse forms of electromagnetic emission) and difficulties (e.g., shot-to-shot variability) associated with LPAs. Non destructiveness and high resolution (in space and time and energy) are key attributes that enable the formation of a comprehensive suite of simultaneous diagnostics which are necessary for the full characterization of the ultrashort, but highly-variable electron bunches from LPAs

Predicting the cumulative chance of live birth over multiple complete cycles of in vitro fertilization : an external validation study

We would like to thank the women who participated in the OPTIMIST study and the staff of the participating hospitals for their contributions to the OPTIMIST study.Peer reviewedPostprin

Propofol anesthesia improves stroke outcomes over isoflurane anesthesia—a longitudinal multiparametric MRI study in a rodent model of transient middle cerebral artery occlusion

General anesthesia is routinely used in endovascular thrombectomy procedures, for which volatile gas and/or intravenous propofol are recommended. Emerging evidence suggests propofol may have superior effects on disability and/or mortality rates, but a mode-of-action underlying these class-specific effects remains unknown. Here, a moderate isoflurane or propofol dosage on experimental stroke outcomes was retrospectively compared using serial multiparametric MRI and behavioral testing. Adult male rats (N = 26) were subjected to 90-min filament-induced transient middle cerebral artery occlusion. Diffusion-, T2- and perfusion-weighted MRI was performed during occlusion, 0.5 h after recanalization, and four days into the subacute phase. Sequels of ischemic damage—blood–brain barrier integrity, cerebrovascular reactivity and sensorimotor functioning—were assessed after four days. While size and severity of ischemia was comparable between groups during occlusion, isoflurane anesthesia was associated with larger lesion sizes and worsened sensorimotor functioning at follow-up. MRI markers indicated that cytotoxic edema persisted locally in the isoflurane group early after recanalization, coinciding with burgeoning vasogenic edema. At follow-up, sequels of ischemia were further aggravated in the post-ischemic lesion, manifesting as increased blood–brain barrier leakage, cerebrovascular paralysis and cerebral hyperperfusion. These findings shed new light on how isoflurane, and possibly similar volatile agents, associate with persisting injurious processes after recanalization that contribute to suboptimal treatment outcome

Motor-Skill Learning in Alzheimer’s Disease: A Review with an Eye to the Clinical Practice

Since elderly people suffering from dementia want to go on living independently for as long as possible, they need to be able to maintain familiar and learn new practical skills. Although explicit or declarative learning methods are mostly used to train new skills, it is hypothesized that implicit or procedural techniques may be more effective in this population. The present review discusses 23 experimental studies on implicit motor-skill learning in patients with Alzheimer’s disease (AD). All studies found intact implicit motor-learning capacities. Subsequently, it is elaborated how these intact learning abilities can be exploited in the patients’ rehabilitation with respect to the variables ‘practice’ and ‘feedback.’ Recommendations for future research are provided, and it is concluded that if training programs are adjusted to specific needs and abilities, older people with AD are well able to (re)learn practical motor skills, which may enhance their autonomy

Undulator-Based Laser Wakefield Accelerator Electron Beam Energy Spread and Emittance Diagnostic

The design and current status of experiments to couple the Tapered Hybrid Undulator (THUNDER) to the Lawrence Berkeley National Laboratory (LBNL) laser plasma accelerator (LPA) to measure electron beam energy spread and emittance are presented

BRCA1 mutation carriers have a lower number of mature oocytes after ovarian stimulation for IVF/PGD

Purpose The aim of this study was to determine whether BRCA1/2 mutation carriers produce fewer mature oocytes after ovarian stimulation for in vitro fertilization (IVF) with preimplantation genetic diagnosis (PGD), in comparison to a PGD control group. Methods A retrospective, international, multicenter cohort study was performed on data of first PGD cycles performed between January 2006 and September 2015. Data were extracted from medical files. The study was performed in one PGD center and three affiliated IVF centers in the Netherlands and one PGD center in Belgium. Exposed couples underwent PGD because of a pathogenic BRCA1/2 mutation, controls for other monogenic conditions. Only couples treated in a long gonadotropin-releasing hormone (GnRH) agonist-suppressive protocol, stimulated with at least 150 IU follicle stimulating hormone (FSH), were included. Women suspected to have a diminished ovarian reserve status due to chemotherapy, auto-immune disorders, or genetic conditions (other than BRCA1/2 mutations) were excluded. A total of 106 BRCA1/2 mutation carriers underwent PGD in this period, of which 43 (20 BRCA1 and 23 BRCA2 mutation carriers) met the inclusion criteria. They were compared to 174 controls selected by frequency matching. Results Thirty-eight BRCA1/2 mutation carriers (18 BRCA1 and 20 BRCA2 mutation carriers) and 154 controls proceeded to oocyte pickup. The median number of mature oocytes was 7.0 (interquartile range (IQR) 4.0-9.0) in the BRCA group as a whole, 6.5 (IQR 4.0-8.0) in BRCA1 mutation carriers, 7.5 (IQR 5.5-9.0) in BRCA2 mutation carriers, and 8.0 (IQR 6.0-11.0) in controls. Multiple linear regression analysis with the number of mature oocytes as a dependent variable and adjustment for treatment center, female age, female body mass index (BMI), type of gonadotropin used, and the total dose of gonadotropins administered revealed a significantly lower yield of mature oocytes in the BRCA group as compared to controls (p = 0.04). This finding could be fully accounted for by the BRCA1 subgroup (BRCA1 mutation carriers versus controls p = 0.02, BRCA2 mutation carriers versus controls p = 0.50). Conclusions Ovarian response to stimulation, expressed as the number of mature oocytes, was reduced in BRCA1 but not in BRCA2 mutation carriers. Although oocyte yield was in correspondence to a normal response in all subgroups, this finding points to a possible negative influence of the BRCA1 gene on ovarian reserv