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In the 2015 review paper ‘Petawatt Class Lasers Worldwide’ a comprehensive overview of the current status of high-power facilities of
was presented. This was largely based on facility specifications, with some description of their uses, for instance in fundamental ultra-high-intensity interactions, secondary source generation, and inertial confinement fusion (ICF). With the 2018 Nobel Prize in Physics being awarded to Professors Donna Strickland and Gerard Mourou for the development of the technique of chirped pulse amplification (CPA), which made these lasers possible, we celebrate by providing a comprehensive update of the current status of ultra-high-power lasers and demonstrate how the technology has developed. We are now in the era of multi-petawatt facilities coming online, with 100 PW lasers being proposed and even under construction. In addition to this there is a pull towards development of industrial and multi-disciplinary applications, which demands much higher repetition rates, delivering high-average powers with higher efficiencies and the use of alternative wavelengths: mid-IR facilities. So apart from a comprehensive update of the current global status, we want to look at what technologies are to be deployed to get to these new regimes, and some of the critical issues facing their development.
As part of further investigations into three linked haemorrhagic fever with renal syndrome (HFRS) cases in Wales and England, 21 rats from a breeding colony in Cherwell, and three rats from a household in Cheltenham were screened for hantavirus. Hantavirus RNA was detected in either the lungs and/or kidney of 17/21 (81%) of the Cherwell rats tested, higher than previously detected by blood testing alone (7/21, 33%), and in the kidneys of all three Cheltenham rats. The partial L gene sequences obtained from 10 of the Cherwell rats and the three Cheltenham rats were identical to each other and the previously reported UK Cherwell strain. Seoul hantavirus (SEOV) RNA was detected in the heart, kidney, lung, salivary gland and spleen (but not in the liver) of an individual rat from the Cherwell colony suspected of being the source of SEOV. Serum from 20/20 of the Cherwell rats and two associated HFRS cases had high levels of SEOV-specific antibodies (by virus neutralisation). The high prevalence of SEOV in both sites and the moderately severe disease in the pet rat owners suggest that SEOV in pet rats poses a greater public health risk than previously considered.
A. N. Lewis’s scheme of Tasmania’s Pleistocene glacial history in terms of three full glaciations —Malanna (ice cap), Yolande (valley glacier) and Margaret (cirque glacier)—is criticized on a number of specific and general grounds. The area reliably known to be glaciated is thought to be much smaller than Lewis claimed. Future work on Tasmanian glaciations should not be grafted on to Lewis’s scheme and should aim especially to provide more reliable evidence for distinguishing and evaluating the glacial phases.
Parasite burden varies widely between individuals within a population, and can covary with multiple aspects of individual phenotype. Here we investigate the sources of variation in faecal strongyle eggs counts, and its association with body weight and a suite of haematological measures, in a cohort of indigenous zebu calves in Western Kenya, using relatedness matrices reconstructed from single nucleotide polymorphism (SNP) genotypes. Strongyle egg count was heritable (h2 = 23·9%, s.e. = 11·8%) and we also found heritability of white blood cell counts (WBC) (h2 = 27·6%, s.e. = 10·6%). All the traits investigated showed negative phenotypic covariances with strongyle egg count throughout the first year: high worm counts were associated with low values of WBC, red blood cell count, total serum protein and absolute eosinophil count. Furthermore, calf body weight at 1 week old was a significant predictor of strongyle EPG at 16–51 weeks, with smaller calves having a higher strongyle egg count later in life. Our results indicate a genetic basis to strongyle EPG in this population, and also reveal consistently strong negative associations between strongyle infection and other important aspects of the multivariate phenotype.
Undoped, 4µm thick GaN layers grown by Metal Organic Chemical Vapor Deposition were used for fabrication of high stand off voltage (356 V) Schottky diode rectifiers. The figure of merit VRB2/RON, where VRB is the reverse breakdown voltage and RON is the on-resistance, was ~ 4.53 MW-cm−2 at 25°C. The reverse breakdown voltage displayed a negative temperature coefficient, due to an increase in carrier concentration with increasing temperature. Secondary Ion Mass Spectrometry measurements showed that Si and O were the most predominant electrically active impurities present in the GaN.
Regioregular polythiophenes baring 3-(p-methoxyethoxyethoxy)-phenyl substituents (PEOPT) show high photoluminescence efficiencies. Exposing thin films of this polymer to vapors of chloroform or annealing them by heat treatment results in a red shift of the absorption maximum due to solvent or heat induced ordering which gives rise to more planar conformations. The fact, that annealed thin films of PEOPT exhibit absorption edges at relatively low energies and thus have an enhanced spectral range makes them suitable for use in photodiodes / solar cells. The photoinduced charge generation efficiency in PEOPT is significantly enhanced by the addition of a strong electron acceptor like fullerene, as observed by quenching of the luminescence and by photoinduced absorption measurements in the infrared and UV-Vis regime. The efficiency of the photoinduced charge transfer from PEOPT to a methanofullerene is found to depend on the ordering of PEOPT in thin films.
The photo-induced charge transfer between tetracyano-anthraquino-dimethane (TCAQ) derivatives and poly(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene vinylene) MDMO-PPV was studied by means of photoinduced absorption (PIA) spectroscopy in the VIS and IR spectral region and lightinduced electron spin resonance (LESR) spectroscopy. Three different TCAQ derivatives with alkyl-side chains for increased solubility compared to TCAQ and one of them attached to a C60 molecule serve as strong electron acceptors. The photoinduced absorption in the VIS near-IR range shows a broad plateau around 1.8 eV followed by two peaks at 1.35 and 1.24eV for all three acceptors. All PIA features have a power law excitation intensity dependence with an exponent close to 0.5 as expected for bimolecular kinetics. The modulation frequency dependent excited state absorption decreases with a power law. LESR studies of all donor-acceptor combinations show one radical line at a g = 2.0028 with.H = 3.5 Gauss, originating from TCAQ anion and the polymer cation.
Devices consisting of hexa-alkoxythriphenylene derivatives as hole transport materials and 8-hydroxyquinoline aluminium (Alq3) as emitting layer with ITO as anode and magnesium as cathode are presented. Moreover X-ray diffraction studies of evaporated triphenylene films were performed leading to a better understanding of crystal structure, morphology and the alignment of the triphenylene molecules on the surface of the substrate.
The continuing shrinkage of feature size and environmental concerns regarding the use of lead containing solder are major driving forces in the search for alternative technologies for metal interconnects in electronic packaging. Electrically conductive adhesives are considered a potential substitute for the lead-tin solder. This study concentrated on interfacial properties of eutectic solder and silver-filled epoxy adhesives. A freeze fracture technique was employed in order to preserve interfacial information. The chemical composition of the fractured faces varied; the adhesive side was rich in tin, whereas the eutectic solder side showed lead-rich characteristics.
A new oxydative-resistant, fusible and processible ethylene/acetylene copolymer has been synthesized. The content of rigid (acetylene) and flexible (ethylene) fragments has been widely varied. The structure of the nascent powders and the films compressed at room temperature have been investigated by SEM and WAXS. DSC has been used for studying the thermal properties. DC conductivity of the iodine doped samples has been measured as a function of temperature. It is shown that the doping leads to arising conductivity in the samples even at 10 Mol % acetylene fragments in copolymer. The conductivity up to 10−3 S/cm is reached for the samples with acetylene fragment concentration about 20 Mol %. It is found that a charge carrier transport in investigated copolymers is caused by doped polyacetylene fragments and described by the hopping Mechanism.
Bipolaron-like dications have been produced in both diphenyl and bis-thienyl polyenes by oxidative doping in solution. However, until now spectroscopie studies of the charge state generation beyond the hexaene have been precluded due to lack of solubility and processibility. We have now been able to extend these studies to the decaene by incorporating solubilizing substituents on the thienyl end caps. For the neutral species, degenerate four wave Mixing (DFWM) studies indicate that χ(3) is still increasing as a function of conjugation length. Introduction of mesomerically interactive RS groups on the thiophene rings further increases both solubility and optical nonlinearity.
Conjugated polymers can be use to provide charge transport and emissive layers in a range of thin-film electroluminescent devices. Electroluminescence results from radiative decay of excitons which are formed by electron-hole capture. Device efficiency is particularly sensitive to the balancing of electron and hole currents injected from opposite electrodes, and this is best achieved at the heterojunction between two polymer layers with different electronegativities. We report here the properties of a conjugated polymer with high electron affinity, a cyano derivative of poly (p-phenylene vinylene), PPV. This polymer shows an electron affinity considerably higher than than that of PPV, and is therefore suitable for use as the electron transporting layer in heterostructure LEDs. It shows efficient photoluminescence due to radiative decay of singlet excitons, and photoinduced absorption in the IR, similar to that in PPV, which we attribute to excitations of photogenerated triplet excitons. EL devices formed with a heterojunction between PPV and this cyano derivative of PPV, with indium/tin oxide as positive electrode, PPV, cyano-PPV layers and an aluminium negative electrode, show internal quantum efficiencies as high as 4%.
Collective excitations, such as plasmons, rotons, electron-hole liquid, and excitonic Molecules, have been extensively studied in condensed Matter.1 Wannier excitons in inorganic semiconductors are bound by the exchange interactions between two electrons of the exciton, and the bound state of More than two excitons is not possible. We demonstrate here a new type of collective excitations,2 bound states of Multiple charge-transfer (CT) excitons. Coulomb interactions in one dimension are shown to bind a train of several (More than two) CT excitons. Experimental evidence for these new type of elementary excitations is reported in a quasi-one-dimensional CT crystal of anthracene PMDA. High density excitation by femtosecond light pulses generates Multi-exciton chains, which we refer to as excitonic n-strings with n = 1, 2, 3, etc., along the stack axis of the crystal. Both the n = 2 excitonic string (biexciton) and the n = 3 string (tri-exciton) are observed. This report provides evidence for an n > 2 exciton chain in this system.2 The stability of the n-string exciton is supported by our theoretical calculations based on the extended Hubbard Hamiltonian in one dimension.
A large class of new layered semiconductors — lead iodide compounds — is of great interest because of possible optoelectronic applications due to pronounced excitonic effects. These compounds may be regarded as naturally grown semiconductor/insulator superlat-tices, with perovskite lead iodide (semiconductor) layers sandwiched by alkylammonium (insulator) layers. Exciton binding energies and oscillator strength in these structures are enhanced due to the so-called “dielectric confinement” caused by large difference between dielectric constants of adjoining layers. The binding energies, wave functions,& diamagnetic coefficient of excitons in these naturally grown superlattices are calculated with allowance for the image potential and the superlattice structure of the compounds. The localization of excitons in lead iodide layers causes also a strong dependence of a polariton spike in reflection spectra on the polarization of electromagnetic wave. The results obtained are in agreement with the experimental data.
The photorefractive properties of photoconducting polymers doped with nonlinear azo dyes are investigated by means of polarization and field-dependent four-wave Mixing experiments. The nonlocal response of the photorefractive effect is shown by two-beam coupling experiments. High diffraction efficiencies (> 5%) and net coupling gain (6 cm-l) are demonstrated at low power with a semiconductor laser diode in 105 μm films. Under some conditions, gratings due to photoisomerization of the azo dye molecules are also present and their properties are discussed.