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

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Erratum: “Proton acceleration by single-cycle laser pulses offers a novel monoenergetic and stable operating regime” [Phys. Plasmas 23, 043112 (2016)]

The invention concerns a Free Electron Laser - FEL - EUV or soft X-ray light source comprising: a fibre-based laser (1), comprising a plurality of amplifying fibres wherein an initial seed laser pulse is distributed and amplified, and means for grouping together the elementary pulses amplified in the said fibre in order to form a single amplified global laser pulse (3); a laser plasma accelerator - LPA - (6) based on Laser Wake-Field Acceleration (LWFA) in the bubble regime wherein the said global laser pulse (3) generates relativistic electron beams (10), a beam focusing system (12) transporting electron beams (10) from the laser plasma accelerator (6), an undulator (13) wherein relativistic electron beams (10) generate an electromagnetic beam, and a beam separator system, wherein the said electron beam and the said electromagnetic beam are separated.

Free-Electron Laser driven by fibre based laser feeding a Laser Plasma Accelerator

A new concept - chirped-pulse cascade-compression - is proposed and demonstrated. Initial experiments agree with numerical simulations, including compression of 35fs, 1.2mJ-pulses to 20fs, with negligible wavefront distortion. Scaling to higher energies will be possible.

Chirped-Pulse Cascaded Quadratic Compression of 1-mJ, 35-fs Pulses with Low Wavefront Distortions

High speed circuit testing using ultrafast optical techniques

The phenomena of optical breakdown (damage) of normally transparent optical materials such as fused silica involve ionization of valence band electrons by the intense incident laser field. Subsequent electron heating, acceleration, and impact ionization of secondary electrons in the laser field result in an exponential multiplication of free electrons, which causes the material breakdown. Laser-induced breakdown has been studied for three decades, and two major theories, the avalanche model and the photoionization model, exist for the breakdown process.1,2 In an avalanche- dominated process, a few initial electrons are generated through photoionization or thermal excitation from defects. These free electrons are accelerated by the intense laser field and create secondary electrons via collisions with atoms. The process repeats itself and eventually results in breakdown. In the photoionization theory, on the other hand, free electrons are created by multiphoton ionization or tunneling ionization only, and electron avalanche is negligible. In both models, the breakdown threshold is dependent on the laser pulse width.

Gerard Mourou

Papers

Erratum: “Proton acceleration by single-cycle laser pulses offers a novel monoenergetic and stable operating regime” [Phys. Plasmas 23, 043112 (2016)]

Free-Electron Laser driven by fibre based laser feeding a Laser Plasma Accelerator

Chirped-Pulse Cascaded Quadratic Compression of 1-mJ, 35-fs Pulses with Low Wavefront Distortions

High speed circuit testing using ultrafast optical techniques

Optical breakdown with femtosecond laser pulses