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

Absorption and redistribution of ultrafast pulsed laser energy in silicon is examined with 800 nm radiation for pulse durations ranging from 80 fs to 7 ns. The results are successfully interpreted in terms of an avalanche ionization process. Thresholds for vaporization are measured and compared to a theoretical model that incorporates a two temperature electron-lattice heating process. Ionization layer thickness and time-resolved melting and vaporization events are described in terms of a thermodynamic process involving the absorption of ionized electron energy by the lattice and its subsequent phase transformation to the liquid and vapor state. An average solid density plasma heating layer of 78 nm is extracted from the model and used to fit threshold fluence data. More detailed experimental results are found to provide close agreement with, and continuation of, the avalanche ionization coefficient curve of silicon [1] for electric field strengths extending to 4 × 107 volts/cm.

Electron-Lattice Heating from Avalanche Ionization in Silicon with Near Infrared Ultrafast Laser Pulses

With the development of environmentally stable carrier and Kerr-type modelocked erbium fiber lasers[1,2], compact and reliable femtosecond pulse sources become more and more of a reality. Current research therefore increasingly centers on applications of these devices. Particularly interesting is the use of ultrafast fiber oscillators as seeds for high-power amplifiers. The high saturation energy of erbium amplifiers potentially allows the generation of pulses with an energy content in excess of 1 μJ[3]. However, as soon as the amplified pulse power exceeds the soliton power higher-order soliton formation greatly reduces the pulse quality and increases the pulse width.

Generation of high power ultrashort pulses in erbium oscillator power amplifier systems

Short optical pulses have been involved in a number of areas of science and technology. It is now possible to generate optical pulses of less than 10 fs duration corresponding to only a few optical cycles. One of the most important applications of these short optical pulses is in electronics, where, in conjunction with the electro-optic effect, electrical waveforms now can be characterized with a few hundred femtosecond resolution - corresponding to 1 THz in bandwidth. This technique makes possible the characterization in situ of high-speed optoelectronic and electronic devices as well as circuits operating in the picosecond time scale or 100 GHz frequency domain.

Impact Of Ultrafast Optics In High-Speed Electronics

Le verrou principal pour le developpement des systemes femtoseconde robustes et rentables est l'incertitude du seuil de dommages du cristal de Ti: Saphir. Nous avons d'abord caracterise le seuil dielectrique de dommages du Ti: Saphir.

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Caractérisation du seuil de dommage dans les cristaux de saphir dopé au titane avec des impulsions de durée nanoseconde, picoseconde et femtoseconde

Summary form only given. Using a KDP type II crystal with a predelay we were able to generate high contrast laser pulses with a duration as short as 75 fs at /spl lambda/=0.53 /spl mu/m. At the crystals output we have used a deformable mirror to correct for accumulated B-integral to focus laser pulses to the intensity of 2.10/sup 19/ W/cm/sup 2/. Second harmonic generation in this system was studied.

Gerard Mourou

Papers

Electron-Lattice Heating from Avalanche Ionization in Silicon with Near Infrared Ultrafast Laser Pulses

Generation of high power ultrashort pulses in erbium oscillator power amplifier systems

Impact Of Ultrafast Optics In High-Speed Electronics

Caractérisation du seuil de dommage dans les cristaux de saphir dopé au titane avec des impulsions de durée nanoseconde, picoseconde et femtoseconde

Efficient second-harmonic generation of sub-100 fs pulses from high power Nd:glass laser