Simulation Study of an LWFA-based Electron Injector for AWAKE Run 2

The AWAKE experiment aims to demonstrate preservation of injected electron beam quality during acceleration in proton-driven plasma waves. The short bunch duration required to correctly load the wakefield is challenging to meet with the current electron injector system, given the space available to the beamline. An LWFA readily provides short-duration electron beams with sufficient charge from a compact design, and provides a scalable option for future electron acceleration experiments at AWAKE. Simulations of a shock-front injected LWFA demonstrate a 43 TW laser system would be sufficient to produce the required charge over a range of energies beyond 100 MeV. LWFA beams typically have high peak current and large divergence on exiting their native plasmas, and optimisation of bunch parameters before injection into the proton-driven wakefields is required. Compact beam transport solutions are discussed.Comment: Paper submitted to NIMA proceedings for the 3rd European Advanced Accelerator Concepts Workshop. 4 pages, 3 figures, 1 table Changes after revision: Figure 2: figures 2 and 3 of the previous version collated with plots of longitudinal electric field Line 45: E_0 = 96 GV/m Lines 147- 159: evaluation of beam loading made more accurate Lines 107 - 124: discussion of simulation geometry move

Organically Modified Silica Nanoparticles Are Biocompatible and Can Be Targeted to Neurons In Vivo

The application of nanotechnology in biological research is beginning to have a major impact leading to the development of new types of tools for human health. One focus of nanobiotechnology is the development of nanoparticle-based formulations for use in drug or gene delivery systems. However most of the nano probes currently in use have varying levels of toxicity in cells or whole organisms and therefore are not suitable for in vivo application or long-term use. Here we test the potential of a novel silica based nanoparticle (organically modified silica, ORMOSIL) in living neurons within a whole organism. We show that feeding ORMOSIL nanoparticles to Drosophila has no effect on viability. ORMOSIL nanoparticles penetrate into living brains, neuronal cell bodies and axonal projections. In the neuronal cell body, nanoparticles are present in the cytoplasm, but not in the nucleus. Strikingly, incorporation of ORMOSIL nanoparticles into the brain did not induce aberrant neuronal death or interfered with normal neuronal processes. Our results in Drosophila indicate that these novel silica based nanoparticles are biocompatible and not toxic to whole organisms, and has potential for the development of long-term applications

Physiochemical properties of ORMOSIL nanoparticles.

<p>(<b>A</b>) The absorption and emission spectra for rhodamine-ORMOSIL (^RORM) particles. The typical emission band of rhodamine is λ_max 600 nm. (<b>B</b>) The ORMOSIL nanoparticle size distribution profile as measured by the dynamic light scattering (DLS) method indicates that the diameter of ORMOSIL nanoparticles are on average 20 nm. (C) A transmission electron microscope (TEM) image of ORMOSIL nanoparticles. Bar = 100 nm.</p

ORMOSIL incorporates into cell bodies and neuritis in primary neuronal cultures.

<p>(A) Unconjugated ORMOSIL is observed in 4 day old primary neuronal cultures. 4 day old primary neuronal cultures generated from larval brains were incubated with ^RORM. Cultures were imaged using the 568 nm filter. ^RORM is observed within the cytoplasm of the cell body in a discrete pattern and within neuritis (arrows). Images were taken using the 100× objective. Bar = 5 µm. (B) Unconjugated ORMOSIL is also observed 3 days after ORMOSIL treatment. To determine how ORMOSIL affected the growth of cultures, ORMOSIL treated cultures were allowed to grow and again imaged after 3 days of ORMOSIL treatment. These cultures were now 7 days old. These treated cultures showed growth with very long neuronal projections compared to day 4. ^RORM was still observed within the cell bodies (insert) and the neuritis (arrows,). Note that the fluorescence intensity at day 7 was similar to the intensity observed at day 4. Images were taken using the 100× objective. Bar = 5 µm. (C) Receptor-conjugated ORMOSIL is observed in 4 day old primary neuronal cultures. 4 day old primary neuronal cultures generated from larval brains were incubated with transferrin receptor conjugated ORMOSIL (TfR-^RORM). TfR-^RORM can be observed within the cell body and within the neuritis. Images were taken using the 100× objective. No significant different in the distribution of ORMOSIL was seen between ^RORM and TfR-^RORM treated cultures. Bar = 5 µm. (D) Peptide -conjugated ORMOSIL is observed in 4 day old primary neuronal cultures. 4 day old primary neuronal cultures generated from larval brains were incubated with peptide-conjugated ORMOSIL (Peptide-^RORM). Peptide-^RORM can be observed within the cell body and within the neuritis. Images were taken using the 100× objective. No significant different in the distribution of ORMOSIL was seen between ^RORM and peptide-^RORM treated cultures. Bar = 5 µm. (E) Untreated control cultures. Control 4 day old cultures treated with buffer do not show fluorescence using the 568 nm filter. Images were taken using the 100× objective. Bar = 5 µm. (F, G, H) ORMOSIL is absent from the cell body nucleus. 4 day old primary neuronal cultures were incubated with ^RORM (F, red). Incubated cultures were fixed and stained with DAPI to localize the nuclei (G, blue). A representative merged image (H) indicates that ORMOSIL is absent from the cell body nucleus. Note that ORMOSIL is present in a discrete pattern within the cell body cytoplasm. Images were taken using the 100× objective. Bar = 5 µm. (I) Quantification of cell body growth after ORMOSIL treatment. Graphs depict cell body growth for 120 hours (5 days) after ORMOSIL treatment. For untreated cultures, cultures expressing synaptotagmin-EGFP (SYNT-EGFP) was used. The effect of treatment was evaluated for unconjugated ORMOSIL (ORMOSIL) and for peptide-conjugated ORMOSIL (pep-ORMOSIL). For each time point 8–12 cells from three different experiments were analyzed. The average diameter and standard error was calculated and the average cell body diameter in microns was plotted against time in hours. No statistically significant difference was seen between ORMOSIL treated (unconjugated or peptide-conjugated) and cultures expressing SYNT-EGFP. (J) Quantification of neurite growth after ORMOSIL treatment. Graphs depict neurite growth for 120 hours (5 days) after ORMOSIL treatment. For each time point 8–12 cell from three different experiments were analyzed. The average projection length in micron was plotted against time in hours. The standard error was calculated and plotted. No statistically significant difference was seen in neurite growth between ORMOSIL treated (unconjugated or peptide-conjugated) and cultures expressing SYNT-EGFP.</p

Summary of ORMOSIL feeding experiments in Drosophila.

<p>Summary of ORMOSIL feeding experiments in Drosophila.</p

ORMOSIL incorporation does not affect the movement of synaptotagmin vesicles.

<p>(A, B) <i>In vivo</i> imaging suggests that ORMOSIL incorporation does not affect the movement of GFP-tagged synaptotagmin vesicles within living dissected ORMOSIL treated larvae. Single frames from a representative movie containing both GFP-tagged synaptotagmin vesicles (SYNT-GFP, A) and ^RORM (B) simultaneously imaged show the movement of SYNT-GFP vesicles within a larval segmental nerve incubated with ORMOSIL. Note that the SYNT vesicle shows movement in each frame (arrow). (<b>B</b>) Note that ORMOSIL is also observed within the same larval segmental nerve (arrow). Note that ORMOSIL does not dramatically change in each frame (arrow). A 1 min movie is depicted. Movies were taken using the 100× objective. Bar = 10 µm. (C,D) Kymographs show that ORMOSIL treatment does not affect the movement of GFP-tagged synaptotagmin vesicles. Kymographs from the above movies show that the movement dynamics of SYNT-GFP vesicles are not affected in ^RORM treated larvae. The movement of a SYNT-GFP vesicle is seen moving from the left to the right (arrow, C), while a slight shift is seen for ORMOSIL (arrow, D).</p

The short-term survival of dissected living larvae is not affected by ORMOSIL nanoparticles.

<p>Dissected living larvae were treated with ^RORM (1 mg/ml and 0.2 mg/ml are shown) or buffer and larval survival was quantified by evaluating the twitching phenotype. We assigned “survival” values or survival points according to the extent of twitching observed when the larva was stimulated with a forceps. As described in the text, the more the larva twitched, the higher the “survival” value, indicating that the dissected larva was alive <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029424#pone.0029424-Gunawardena3" target="_blank">[43]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029424#pone.0029424-Gunawardena4" target="_blank">[44]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029424#pone.0029424-Hurd1" target="_blank">[45]</a>. The extent of twitching was recorded every 15 minutes for a total of 60 minutes. No significant difference was seen between the survival of ORMOSIL treated or buffer treated dissected living larvae.</p

Escalation of Drug Use in Early-Onset Cannabis Users vs Co-twin Controls

Context Previous studies have reported that early initiation of cannabis (marijuana) use is a significant risk factor for other drug use and drug-related problems. Objective To examine whether the association between early cannabis use and subsequent progression to use of other drugs and drug abuse/dependence persists after controlling for genetic and shared environmental influences. Design Cross-sectional survey conducted in 1996-2000 among an Australian national volunteer sample of 311 young adult (median age, 30 years) monozygotic and dizygotic same-sex twin pairs discordant for early cannabis use (before age 17 years). Main Outcome Measures Self-reported subsequent nonmedical use of prescription sedatives, hallucinogens, cocaine/other stimulants, and opioids; abuse or dependence on these drugs (including cannabis abuse/dependence); and alcohol dependence. Results Individuals who used cannabis by age 17 years had odds of other drug use, alcohol dependence, and drug abuse/dependence that were 2.1 to 5.2 times higher than those of their co-twin, who did not use cannabis before age 17 years. Controlling for known risk factors (early-onset alcohol or tobacco use, parental conflict/separation, childhood sexual abuse, conduct disorder, major depression, and social anxiety) had only negligible effects on these results. These associations did not differ significantly between monozygotic and dizygotic twins. Conclusions Associations between early cannabis use and later drug use and abuse/dependence cannot solely be explained by common predisposing genetic or shared environmental factors. The association may arise from the effects of the peer and social context within which cannabis is used and obtained. In particular, early access to and use of cannabis may reduce perceived barriers against the use of other illegal drugs and provide access to these drugs