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

We have measured the narrowest half‐width at half‐maximum photoluminescence linewidth of 2.8 meV, in 40‐period lattice‐matched In0.53Ga0.47As/In0.52Al0.48As multiple quantum wells, grown by molecular‐beam epitaxy with growth interruption. A simple analysis of the linewidth suggests that the structure has near perfect interfaces. Temperature‐dependent photoluminescence linewidth data indicate impurity incorporation due to the growth interruption. However, the high quality of the multiple quantum well is not impaired as is seen in the room‐temperature absorption data, where excitonic features up to n=3 sublevel are clearly seen. Carrier lifetime in this multiple‐quantum‐well system has been measured, we believe for the first time, using the picosecond photoluminescence correlation technique. A lifetime of 860 ps is obtained, which is similar to the value obtained for high‐quality GaAs/AlGaAs and In0.53Ga0.47As/InP quantum wells. This further confirms the high quality obtained in this ternary material system...

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Optical properties of high‐quality InGaAs/InAlAs multiple quantum wells

Lasers that provide an energy encompassed in a focal volume of a few cubic wavelengths (λ3) can create relativistic intensity with maximal gradients using minimal energy. With particle-in-cell simulations we found that single 200-as pulses could be produced efficiently in a λ3 laser pulse reflection by means of deflection and phase compression caused by the coherent motion of the plasma electrons that emit these pulses. This novel technique is efficient (∼10%) and can produce single attosecond pulses from the millijoule to the joule level.

Isolated attosecond pulses generated by relativistic effects in a wavelength-cubed focal volume

We report experimental measurements of the voltage response of current-biased superconducting thin films excited by 30-ps-FWHM (full width at half-maximum) pulsed laser radiation. Experiments performed with Pb and Sn films irradiated by a full train of laser pulses provide direct evidence for the existence of a nonstationary intermediate state. The state was observed during the superconducting-to-normal transition, as well as during the recovery of the film from the nonequilibrium normal state into the superconducting state. Single-pulse laser experiments enabled us to study the superconducting-to-normal transition in detail. Depending on the optical power, both triangular and quadruangular voltage pulses were observed. The triangular pulses had amplitudes dependent on the laser power and reflected the transition to the intermediate state, where superconducting and normal domains coexisted. The quadrangular pulses were associated with the full transition into the normal state. Very short triangular voltage pulses with full widths of the order of hundreds of picoseconds and rise times as short as about 100 ps were observed for thin Pb films illuminated by a low, near-threshold, laser power. The pulse rise time was almost constant and it only depended weakly on the film thickness, while the pulse width and the fall time were verymore » sensitive to the optical input power as well as other experimental conditions (e.g., film thickness, Pb-substrate interface). The pulse decay was determined to be linear. The linear decay reflects a geometric relaxation of the intermediate state. An experiment performed with a stretched laser pulse (about 470 ps FWHM) demonstrated an initial thresholding effect and indicated that the subsequent voltage is proportional to the time integral of the laser pulse (optical energy).« less

Dynamics of the intermediate state in nonequilibrium superconductors

We propose an ultrafast shutter, based on the saturable properties of polymethine cyanide dyes, with a variable shutter speed of 10–40 psec and more. With this, one can measure the pulse duration of the mode‐locked ruby laser pulse. We can also deduce the fluorescence decay time of these solutions employed.

Gerard Mourou

Papers

Optical properties of high‐quality InGaAs/InAlAs multiple quantum wells

Isolated attosecond pulses generated by relativistic effects in a wavelength-cubed focal volume

Dynamics of the intermediate state in nonequilibrium superconductors

Variable Ultrafast Photographic Shutter

Molecular orientational relaxation times in liquids