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

Based on fundamentally new approaches, ELI’s (Extreme Light Infrastructure) scientific program is ambitious, far‐reaching, compelling, with the goal to time‐resolve the structure of matter from solid to vacuum. We give an overview of the guiding principles underpinning ELI, like the concept of the power‐pulse‐duration conjecture, relativistic laser‐matter interaction and the new ultrarelativistic regime: gateways to the generation of synchronized bursts of high energy particles and radiations in the attosecond and zeptosecond range.

A Qualitative Introduction to Extreme Light Infrastructure

We used Fresnel diffraction from knife-edges to demonstrate spatial coherence of tabletop and ultrafast X-ray sources produced by laser-plasma interaction, and show that source size is limited by the spatial spread of absorbed laser energy.

Demonstration of spatial coherence with a compact and ultrafast X-ray source

Purpose: The interacting phenomena that happen between femtosecond lasers in edematous or pathological corneas are still not clearly known. Their characterization is fundamental to develop femtosecond laser use for penetrating and lamellar keratoplasty. The plasma threshold corresponds to the minimal energy that must be focalised into the cornea in order to induce ionization of matter. The possibility of making one corneal cut depends on plasma creation. We determined incident energy thresholds to obtain plasma in function of different corneal depths and hydrations. Methods: We use a Nd:Glass femtosecond laser, with a CPA system, and 1065 nm wavelength. The repetition rate is adjustable from 1 to 10 KHz, with maximum pulse energy of 60 µJ. The pulse delivery is done through an objective adapted on an optic table. The samples are fixed to an anterior chamber system and moved 3–dimensionally by micrometric precision motors. Human corneas are obtained from the French Eye Bank. Three corneal groups with 10 corneas each are organized depending on corneal pachymetry: Group 1: 100 µm +/– 75 µm, Group 2: 700 µm +/– 45 µm, Group 3: 500 µm +/– 25 µm. The control group is composed of silicon dioxide samples. The samples are analyzed in confocal microscopy of the experimental set up. Results: The incident energy threshold is similar in the control group and in the group 3; it ranges from 5 J/cm² on surface to 10 J/cm² at 500 µm depth. In cornea Groups 2 and 1, the incident energy threshold increases, respectively, of 5 J/cm² and of 10 J/cm² for each 100 µm of corneal depth that the laser beam travels through. Conclusions:In each given group, the incident energy threshold increases proportionally to the corneal thickness the laser beam traveled through. To the same corneal thickness, the threshold is higher in the most edematous corneas. The knowledge of these results is fundamental in order to determinate cut parameters and side effects in corneas with hydration above the normal.

Femtosecond laser: incident energy thresholds and corneal hydration

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.

Gerard Mourou

Papers

A Qualitative Introduction to Extreme Light Infrastructure

Demonstration of spatial coherence with a compact and ultrafast X-ray source

Femtosecond laser: incident energy thresholds and corneal hydration

Electro-Optic Sampling: Device Embodiments And Possibilities

Switching-time measurements of a resonant-tunneling diode.