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.

/pdf/a-roadmap-for-graphene-1nstzmbk5x.pdf

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

Summary form only given. The development of laser chains based on the chirped pulse amplification leads now to peak powers higher than 100 TW. The focused intensity can reach 10/sup 21/ W/cm/sup 2/. To keep the laser matter interaction in the femtosecond regime, the pulse has to exhibit a high temporal contrast. The most important problem consists in the presence of an amplified spontaneous emission (ASE) background coming from the amplification process. At the output of the laser the ratio between the femtosecond pulse intensity and the ASE level is about 10/sup 6/ leading to an ASE intensity as high as 10/sup 15/ W/cm/sup 2/, far above the ionization threshold of most materials and susceptible to strongly modify the interaction process. We propose to rely on an unbalanced nonlinear Sagnac interferometer which is implemented after the first CPA system amplifies pulses to the millijoule level.

Nonlinear Sagnac interferometer for temporal pulse cleaning of high peak power femtosecond laser

http://link.springer.com/content/pdf/10.1007/978-3-642-85176-6_65.pdf

Chirped-Pulse Amplification of Ultrashort Pulses Using Neodymium- and Erbium-Doped Fiber Amplifiers

Summary form only given. A typical meter size linear Ti:sapphire regenerative amplifier has submillimeter mode size and output energy of 1-10 mJ limited by saturation fluence of Ti:sapphire (0.9j/cm/sup 2/) and intracavity losses. Subsequent amplification to joule scale energy requires a saturated gain of 100-1000 which is hard to reach with a single multipass amplifier so multiple stages of multipass amplifiers are used resulting in beam quality degradation and overall complexity of the laser system. A ring resonator with an intracavity lens was used in a high-energy/large-mode regenerative amplifier as such a cavity has a larger mode size compared with a linear one with the same footprint. However, for broadband 20-30 femtosecond lasers, only reflective optics can be used to avoid chromatic aberrations.

High-energy broadband regenerative amplifier for chirped-pulse amplification

We have measured the transient response of tin microstrips to short current pulses whose amplitude exceeded the dc critical current I c of the sample. The current pulses were generated by an electro-optic switching technique. The voltage across the microstrip was measured indirectly by integrating the sample into a transmission line and measuring the transmission characteristics. For a fixed pulse duration, no voltage was measured until a threshold I c1 (>I c ) was reached. Above I c1 , the voltage developed at a delay time of τ d . When current amplitude exceeded a second threshold I c2 , the voltage onset occurred with no observable delay. These results were partially explained by existing theories that employed TDGL calculations.

Transient response of tin microstrips to supercritical current pulses

Ultra-compact electron beam technology based on laser wakefield acceleration (LWFA) could have a significant impact on radiotherapy treatments. Recent developments in LWFA high-density regime (HD-LWFA) and low-intensity fiber optically transmitted laser beams could allow for cancer treatments with electron beams from a miniature electronic source. Moreover, an electron beam emitted from a tip of a fiber optic channel could lead to new endoscopy-based radiotherapy, which is not currently available. Low-energy (10 keV–1 MeV) LWFA electron beams can be produced by irradiating high-density nano-materials with a low-intensity laser in the range of ~1014 W/cm2. This energy range could be useful in radiotherapy and, specifically, brachytherapy for treating superficial, interstitial, intravascular, and intracavitary tumors. Furthermore, it could unveil the next generation of high-dose-rate brachytherapy systems that are not dependent on radioactive sources, do not require specially designed radiation-shielded rooms for treatment, could be portable, could provide a selection of treatment energies, and would significantly reduce operating costs to a radiation oncology clinic.

/pdf/fiber-optic-based-laser-wakefield-accelerated-electron-beams-6jv107u9.pdf

Gerard Mourou

Papers

Nonlinear Sagnac interferometer for temporal pulse cleaning of high peak power femtosecond laser

Chirped-Pulse Amplification of Ultrashort Pulses Using Neodymium- and Erbium-Doped Fiber Amplifiers

High-energy broadband regenerative amplifier for chirped-pulse amplification

Transient response of tin microstrips to supercritical current pulses

Fiber-Optic Based Laser Wakefield Accelerated Electron Beams and Potential Applications in Radiotherapy Cancer Treatments