Single-shot observation of nonlinear pulse splitting in a Kerr medium.

We report single-shot, time-resolved observation of self-steepening and temporal splitting of near-infrared, 50 fs, micro-joule pulses propagating nonlinearly in flint (SF11) glass. A coherent, smooth-profiled, 60-nm-bandwidth probe pulse that propagated obliquely to the main pulse through the Kerr medium recorded a time sequence of longitudinal projections of the main pulse's induced refractive index profile in the form of a phase-shift "streak," in which frequency-domain interferometry recovered with ∼10 fs temporal resolution. A three-dimensional simulation based on a unidirectional pulse propagation equation reproduced observed pulse profiles.

Single-shot visualization of evolving laser wakefields using an all-optical streak camera.

We visualize ps-time-scale evolution of an electron density bubble--a wake structure created in atmospheric density plasma by an intense ultrashort laser pulse--from the phase "streak" that the bubble imprints onto a probe pulse that crosses its path obliquely. Phase streaks, recovered in one shot using frequency-domain interferometric techniques, reveal the formation, propagation, and coalescence of the bubble within a 3 mm long ionized helium gas target. 3D particle-in-cell simulations validate the observed density-dependent bubble evolution, and correlate it with the generation of a quasimonoenergetic ∼ 100 MeV electron beam. The results provide a basis for understanding optimized electron acceleration at a plasma density n(e) ≈ 2 × 10(19) cm(-3), inefficient acceleration at lower density, and dephasing limits at higher density.

Single-shot visualization of evolving, light-speed structures by multiobject-plane phase-contrast imaging.

We demonstrate a single-shot method of visualizing the evolution of light-speed, laser-generated structures as they propagate over hundreds of Rayleigh lengths (typically ≥10 cm) through a tenuous medium. An ultrashort probe pulse crosses the object's path at a small angle (θ<5°) and a specific time delay. Copies of the phase-modulated probe are then relay-imaged to separate detectors from selected object planes along the propagation path. A phase-contrast technique based on Kerr effect and nonlinear absorption converts phase to intensity modulation, improving sensitivity in tenuous media. A continuous record of the probe phase modulation along the propagation path is reconstructed.

The interaction between acute oligomer Abeta(1-40) and stress severely impaired spatial learning and memory.

In this study, we investigated whether stress can enhance the toxicity of oligomer Abeta(1-40) in the mouse brain. Stress was applied to the animals, consisting of a 2-day inescapable foot shock followed by 3-weekly situation reminders (SRs). We found that stress significantly affected not only the amygdala-dependent (anxiety) but also the hippocampal-dependent (spatial learning and memory) behaviors through the oxidative damage caused in these two regions. However, oligomer Abeta(1-40) treatment alone did not induce behavioral impairment. In addition, combined oligomer Abeta(1-40) and stress treatment increased the glucocorticoid receptor (GR)/mineralocorticoid receptor (MR) ratio and the expression of corticotrophin releasing factor 1 (CRF-1) receptor in the hippocampus. Changes in the components of the hypothalamic-pituitary-adrenal (HPA) axis, such as the GR/MR ratio and CRF-1 level, were observed, accompanied by increasing Abeta accumulation, oxidative stress, nuclear transcription factor (NF-kappaB) hypoactivity, and apoptotic signaling in the hippocampus, and decreasing calbindin D28K and NMDA receptor 2A/2B (NR2A/2B) in the hippocampus, along with alteration of the cholinergic neurons (ChAT) in the medium septum/diagnoid band (MS/DB), noradrenergic neurons (TH) in the locus coeruleus (LC), and serotonergic neurons (5-HT) in the Raphe nucleus. Therefore, apoptosis and synaptic dysfunction in the hippocampus severely induced the impairment of spatial learning and memory. These results suggest that stress may play an important role in the early stages of Alzheimer's disease (AD), and an antioxidant strategy might be a potential therapeutic approach for stress-mediated disorders.

Novel 3D Neuron Regeneration Scaffolds Based on Synthetic Polypeptide Containing Neuron Cue.

Neural tissue engineering has become a potential technology to restore the functionality of damaged neural tissue with the hope to cure the patients with neural disorder and to improve their quality of life. This paper reports the design and synthesis of polypeptides containing neuron stimulate, glutamic acid, for the fabrication of biomimetic 3D scaffold in neural tissue engineering application. The polypeptides are synthesized by efficient chemical reactions. Monomer γ-benzyl glutamate-N-carboxyanhydride undergoes ring-opening polymerization to form poly(γ-benzyl-l-glutamate), then hydrolyzes into poly(γ-benzyl-l-glutamate)-r-poly(glutamic acid) random copolymer. The glutamic acid amount is controlled by hydrolysis time. The obtained polymer molecular weight is in the range of 200 kDa for good quality of fibers. The fibrous 3D scaffolds of polypeptides are fabricated using electrospinning techniques. The scaffolds are biodegradable and biocompatible. The biocompatibility and length of neurite growth are improved with increasing amount of glutamic acid in scaffold. The 3D scaffold fabricated from aligned fibers can guide anisotropic growth of neurite along the fiber and into 3D domain. Furthermore, the length of neurite outgrowth is longer for scaffold made from aligned fibers as compared with that of isotropic fibers. This new polypeptide has potential for the application in the tissue engineering for neural regeneration.

Single-shot tomographic movies of evolving light-velocity objects.

Tomography--cross-sectional imaging based on measuring radiation transmitted through an object along different directions--enables non-invasive imaging of hidden stationary objects, such as internal bodily organs, from their sequentially measured projections. Here we adapt tomographic methods to visualize--in one laser shot--the instantaneous structure and evolution of a laser-induced object propagating through a transparent Kerr medium. We reconstruct 'movies' of a laser pulse's diffraction, self-focusing and filamentation from phase 'streaks' imprinted onto probe pulses that cross the main pulse's path simultaneously at different angles. Multiple probes are generated and detected compactly and simply, making the system robust, easy to align and adaptable to many problems. Our technique could potentially visualize, for example, plasma wakefield accelerators, optical rogue waves or fast ignitor pulses, light-velocity objects, whose detailed space-time dynamics are known only through intensive computer simulations.

Long-term social isolation exacerbates the impairment of spatial working memory in APP/PS1 transgenic mice.

The interaction between gene and environment is known to play a major role in the etiology of several neuropsychiatric disorders, including Alzheimer's disease (AD). The present study evaluated whether environmental manipulations such as social isolation may affect the genetic predisposition to accelerate the onset of AD-related symptoms in an adult APP/PS1 double mutant transgenic mouse model. Transgenic and wild-type male mice were housed either singly or in groups from the age of 3 months, and their behavior was compared at 7 months. Isolation had several effects on the APP/PS1 transgenic mice, including exacerbating the impairment of spatial working memory associated with increased Aß42/Aß40 ratio in the hippocampus; increased levels of MnSOD in the CA1-CA3 subregions of the hippocampus, basolateral part of the amygdala (BLA), and locus coeruleus (LC); and decreased numbers of cholinergic cells in the diagonal band of Broca (DB), noradrenergic neurons in LC, serotonergic neurons in the Raphe nucleus, and levels of NMDA 2B receptor (NR2B) in the hippocampus region. Our findings demonstrate the susceptibility of APP/PS1 transgenic adult male mice to environmental manipulation and show that social isolation has remarkable effects on the genetically determined AD-like symptoms.