There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Recent years have witnessed many breakthroughs in research on graphene (the first two-dimensional atomic crystal) as well as a significant advance in the mass production of this material. This one-atom-thick fabric of carbon uniquely combines extreme mechanical strength, exceptionally high electronic and thermal conductivities, impermeability to gases, as well as many other supreme properties, all of which make it highly attractive for numerous applications. Here we review recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.

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A roadmap for graphene

QUANTUM gravitational effects are usually ignored in calculations of the formation and evolution of black holes. The justification for this is that the radius of curvature of space-time outside the event horizon is very large compared to the Planck length (Għ/c3)1/2 ≈ 10−33 cm, the length scale on which quantum fluctuations of the metric are expected to be of order unity. This means that the energy density of particles created by the gravitational field is small compared to the space-time curvature. Even though quantum effects may be small locally, they may still, however, add up to produce a significant effect over the lifetime of the Universe ≈ 1017 s which is very long compared to the Planck time ≈ 10−43 s. The purpose of this letter is to show that this indeed may be the case: it seems that any black hole will create and emit particles such as neutrinos or photons at just the rate that one would expect if the black hole was a body with a temperature of (κ/2π) (ħ/2k) ≈ 10−6 (M/M)K where κ is the surface gravity of the black hole1. As a black hole emits this thermal radiation one would expect it to lose mass. This in turn would increase the surface gravity and so increase the rate of emission. The black hole would therefore have a finite life of the order of 1071 (M/M)−3 s. For a black hole of solar mass this is much longer than the age of the Universe. There might, however, be much smaller black holes which were formed by fluctuations in the early Universe2. Any such black hole of mass less than 1015 g would have evaporated by now. Near the end of its life the rate of emission would be very high and about 1030 erg would be released in the last 0.1 s. This is a fairly small explosion by astronomical standards but it is equivalent to about 1 million 1 Mton hydrogen bombs. It is often said that nothing can escape from a black hole. But in 1974, Stephen Hawking realized that, owing to quantum effects, black holes should emit particles with a thermal distribution of energies — as if the black hole had a temperature inversely proportional to its mass. In addition to putting black-hole thermodynamics on a firmer footing, this discovery led Hawking to postulate 'black hole explosions', as primordial black holes end their lives in an accelerating release of energy.

Black Hole Explosions

Terahertz spectroscopy systems use far-infrared radiation to extract molecular spectral information in an otherwise inaccessible portion of the electromagnetic spectrum. Materials research is an essential component of modern terahertz systems: novel, higher-power terahertz sources rely heavily on new materials such as quantum cascade structures. At the same time, terahertz spectroscopy and imaging provide a powerful tool for the characterization of a broad range of materials, including semiconductors and biomolecules.

Materials for terahertz science and technology

Single-shot laser induced breakdown, in wide band gap materials such as SiO2 and MgF2, has been studied over almost 5 orders of magnitude in duration from 150 fs to 7 ns. A Ti:sapphire chirped pulse amplification system was used in this experiement, so the pulse duration could be continuously adjusted without changing any other parameters. The damage threshold was detected by looking at the plasma formation and the change of material transmission coefficient. The avalanche mechanism was found to dominate over the entire pulse-width range even for 150 fs pulses where we would expect multi-photon processes to take over. A strong departure from the conventional fluence threshold scaling law is observed for pulses shorter than 10 ps, where beyond this point the fluence threshold increases. Also, it is observed for the first time that for short pulses the damage threshold becomes very accurate and less statistical than that for longer pulses.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Laser-induced breakdown as a function of pulse duration: from 7 ns to 150 fs

Relativistic electron beam slicing by wakefield in plasmas

Summary form only given. We present what is, to our best knowledge, the first self-starting mode-locked Yb/sup 3+/:KY(WO/sub 4/)/sub 2/ (Yb:KYW) laser based on Kerr-lensing effect. The 10-at.% Yb/sup 3+/-doped KY(WO/sub 4/)/sub 2/ crystal is 4-mm long with Brewster angle for the E//b signal beam and is cooled to 18/spl deg/C. The gain material is CW end-pumped by two 100 /spl mu/m stripe laser diodes operating at 940 nm with a spectral bandwidth of /spl sim/3 nm FWHM. One of these diodes is slightly damaged and its light is focused to a beam diameter of 120 /spl mu/m/spl times/30 /spl mu/m (1/e/sup 2/ intensity) with 1.25 W reaching the crystal. The light of the other diode is focused to a beam diameter of 110 /spl mu/m/spl times/30 /spl mu/m (1/e/sup 2/ intensity) with 1.35 W reaching the crystal. Over 90% pump light is absorbed and we obtain 580 mW CW output power with a 2% output coupler without prisms in the cavity.

Diode-pumped Kerr-lens mode-locked Yb:KYW laser

We investigate the energy conversion efficiency from the laser to the accelerated ion beams in the interaction of different duration laser pulses with a simple plane foil, while the laser energy is kept constant. By employing multi-dimensional particle-in-cell simulations, we demonstrate that an intense few-cycle pulse is more beneficial for the energy transferring from the laser to the generated ions. Owing to the short acceleration time window of few-cycle pulses, the overwhelming majority of laser energy could be transferred to ions through a high-efficiency radiation pressure acceleration mechanism before the rupture of the target caused by transverse instabilities and finite spot effects. More importantly, it is found that a laser pulse with a too short duration also fails to reach the highest energy conversion efficiency for a given laser energy. The optimal pulse duration is related to laser energy and ion species. Our three-dimensional particle-in-cell simulations show that the highest energy conversion efficiency is obtained with a laser pulse with a duration of two cycles, which, unlike a single-cycle pulse, is the optimal duration for the given laser energy (49 J). Furthermore, when the laser energy is reduced to 12 J, four-cycle becomes the optimal duration.

Efficiency enhancement of ion acceleration from thin target irradiated by multi-PW few-cycle laser pulses

We show that ultrafast optical techniques have made possible the direct investigation of basic nonstationary transport, ie velocity overshoot and resonant tunneling, which governs the operation of modern high-speed devices

Gerard Mourou

Papers

Laser-induced breakdown as a function of pulse duration: from 7 ns to 150 fs

Relativistic electron beam slicing by wakefield in plasmas

Diode-pumped Kerr-lens mode-locked Yb:KYW laser

Efficiency enhancement of ion acceleration from thin target irradiated by multi-PW few-cycle laser pulses

Ultrafast Optics Applied to Modern Device Research