Energy doubling of 42 GeV electrons in a metre-scale plasma wakefield accelerator.

The energy frontier of particle physics is several trillion electron volts, but colliders capable of reaching this regime (such as the Large Hadron Collider and the International Linear Collider) are costly and time-consuming to build; it is therefore important to explore new methods of accelerating particles to high energies. Plasma-based accelerators are particularly attractive because they are capable of producing accelerating fields that are orders of magnitude larger than those used in conventional colliders. In these accelerators, a drive beam (either laser or particle) produces a plasma wave (wakefield) that accelerates charged particles. The ultimate utility of plasma accelerators will depend on sustaining ultrahigh accelerating fields over a substantial length to achieve a significant energy gain. Here we show that an energy gain of more than 42 GeV is achieved in a plasma wakefield accelerator of 85 cm length, driven by a 42 GeV electron beam at the Stanford Linear Accelerator Center (SLAC). The results are in excellent agreement with the predictions of three-dimensional particle-in-cell simulations. Most of the beam electrons lose energy to the plasma wave, but some electrons in the back of the same beam pulse are accelerated with a field of approximately 52 GV m(-1). This effectively doubles their energy, producing the energy gain of the 3-km-long SLAC accelerator in less than a metre for a small fraction of the electrons in the injected bunch. This is an important step towards demonstrating the viability of plasma accelerators for high-energy physics applications.

Dynamics of seismogenic volcanic extrusion at Mount St Helens in 2004-05.

The 2004-05 eruption of Mount St Helens exhibited sustained, near-equilibrium behaviour characterized by relatively steady extrusion of a solid dacite plug and nearly periodic shallow earthquakes. Here we present a diverse data set to support our hypothesis that these earthquakes resulted from stick-slip motion along the margins of the plug as it was forced incrementally upwards by ascending, solidifying, gas-poor magma. We formalize this hypothesis with a dynamical model that reveals a strong analogy between behaviour of the magma-plug system and that of a variably damped oscillator. Modelled stick-slip oscillations have properties that help constrain the balance of forces governing the earthquakes and eruption, and they imply that magma pressure never deviated much from the steady equilibrium pressure. We infer that the volcano was probably poised in a near-eruptive equilibrium state long before the onset of the 2004-05 eruption.

Illicit bath salts: not for bathing.

BACKGROUND: There has been an increase in the popularity of designer drugs known as "Bath Salts" in the United States. These products commonly contain mephedrone, mephylone, methylenedioxypyrovalerone (MDPV), or other cathinone derivatives with psychoactive properties similar to amphetamine and cocaine. Although recently outlawed, abuse of these products continues to occur in Mississippi. METHODS: We report a 19-year-old male who presented with paranoia and auditory as well as visual hallucinations. Auditory effects included voices that prompted him to kill people. The patient displayed anxiety, paranoia, and exhibited repeated bouts of inappropriate laughter. Urine toxicology analysis via GC/ MS detected MDPV, a compound structurally similar to methylenedioxymethamphetamine (MDMA). CONCLUSIONS: Clinicians should be aware that these designer drugs are not detected with common immunoassay drug screens. Symptoms most commonly associated with these substances include tachycardia, delusions, hallucinations, and paranoia. Psychosis, self harm, and death have been associated with some cases.