Microscopic laser-driven high-energy colliders

The concept of a laser-guided $e^+e^-$ collider in the high-energy regime is presented and its feasibility discussed. Ultra-intense laser pulses and strong static magnetic fields are employed to unite in one stage the electron and positron acceleration and their head-on-head collision. We show that the resulting coherent collisions in the GeV regime yield an enormous enhancement of the luminosity with regard to conventional incoherent colliders

Satellite power system: Concept development and evaluation program. Volume 3: Power transmission and reception. Technical summary and assessment

Efforts in the DOE/NASA concept development and evaluation program are discussed for the solar power satellite power transmission and reception system. A technical summary is provided together with a summary of system assessment activities. System options and system definition drivers are described. Major system assessment activities were in support of the reference system definition, solid state system studies, critical technology supporting investigations, and various system and subsystem tradeoffs. These activities are described together with reference system updates and alternative concepts for each of the subsystem areas. Conclusions reached as a result of the numerous analytical and experimental evaluations are presented. Remaining issues for a possible follow-on program are identified

Characterization of a CCD array for Bragg spectroscopy

The average pixel distance as well as the relative orientation of an array of 6 CCD detectors have been measured with accuracies of about 0.5 nm and 50 $\mu$rad, respectively. Such a precision satisfies the needs of modern crystal spectroscopy experiments in the field of exotic atoms and highly charged ions. Two different measurements have been performed by illuminating masks in front of the detector array by remote sources of radiation. In one case, an aluminum mask was irradiated with X-rays and in a second attempt, a nanometric quartz wafer was illuminated by a light bulb. Both methods gave consistent results with a smaller error for the optical method. In addition, the thermal expansion of the CCD detectors was characterized between -105 C and -40 C.Comment: Submitted to Review of Scientific Instrument

Cardiolipin, α-d-glucopyranosyl, and l-lysylcardiolipin from Gram-positive bacteria: FAB MS, monofilm and X-ray powder diffraction studies

AbstractCardiolipin preparations from Streptococcus B, Listeria welshimeri, Staphylococcus aureus, and a glucosyl and lysyl derivative of cardiolipin were analysed for fatty acid composition and fatty acid combinations. Three different fatty acid patterns are described and up to 17 molecular species were identified in Streptococcus B lipids by high resolution FAB MS. The physicochemical properties of these lipids were characterised in the sodium salt form by monofilm experiments and X-ray powder diffraction. All lipids formed stable monofilms. The minimal space requirement of unsubstituted cardiolipin was dictated by the fatty acid pattern. Substitution with l-lysine led to a decrease of the molecular area, substitution with d-glucopyranosyl to an increase. On self assembly at 100% relative humidity, all preparations adopted lamellar structures. They showed a high degree of order, in spite of the heterogeneous fatty acid compositions and numerous fatty acid combinations. The repeat distances in lamellar fluid phase varied between 4.99 and 5.52 nm, the bilayer thickness between 3.70 and 4.46 nm. Surprising were the low values of sorbed water per molecule of the glucosyl and lysyl derivatives which were 58 and 60%, compared with those of the respective cardiolipin. When Na+ was replaced as counterion by Ba2+, the bilayer structure was retained, but the lipids were in the lamellar gel phase and the fatty acids were tilted between 32 and 53° away from the bilayer normal. Wide angle X-ray diffraction studies and electron density profiles are also reported. Particular properties of glucosyl cardiolipin are discussed

Beschermde gebieden Noordzee: noodzaak en mogelijkheden

This study on protected areas in the North Sea has been carried out for the Directorate of Nature, Environment and Fauna Management of the Ministry of Agriculture, Nature Management and Fisheries. It is part of a project (project number 22) of the Nature Policy Plan of this Ministry. The objective of the study, as defined by the Directorate of Nature, Environment and Fauna Management, is to review the necessity and feasibility of the designation of protected areas in the Dutch sector of the North Sea as a contribution to the conservation and, where possible, rehabilitation of a natural diversity of ecologically valuable areas with their specific communities and characteristic species. The objectives for the designation of marine protected areas are given in chapter 2 of the report: To preserve, rehabilitate and develop natural values in the Dutch sector of the North Sea by limiting the effects of those human activities that cause detectable changes in the North Sea ecosystem . To protect groups of animals which are an integral part of the natural values of the Dutch sector of the North Sea and whose existence or 'normal' functioning is currently threatened within this part of the North Sea. The study only addresses those human activities which can be controlled within the boundaries of the Dutch sector of the North Sea itself: fisheries, off-shore mining, sand and gravel extraction, military activities, shipping, pipelines and telecommunication cables. Pollution from land-based sources, atmospheric deposition, dumping and calamities have therefore not been considered in this report. Chapter 3 contains a description of the North Sea ecosystem (plankton, benthos, fish, seabirds and marine mammals). An effort was made to develop an ecological zoning for each of these groups of animals (see map on back cover). In many cases it has been possible to present relevant (a)biotic parameters. These parameters have played an important role in the final choice of protected areas. The distribution of plankton is to a large extent related to the position of water-bodies in the Dutch sector of the North Sea. The following areas can be identified: coastal water, southern North Sea, central North Sea and the Frisian Front area. The distribution of micro-, meio- and macrobenthos is largely determined by sediment types (sand, mud, gravel, stones). By and large, the following clusters can be identified with respect to infauna (macrobenthos living in the sediments) and epifauna (macrobenthos living on the seafloor): the Southern Bight including the coastal zone, Oystergrounds, Dogger Bank, the area north of the Dogger Bank, the Frisian Front area and the Klaverbank. The distribution of fish is not only determined by such factors as temperature, food, sediment type and water depth, but also by the presence of spawning and nursery areas and the location of migratory routes. With respect to seabirds, four different areas can be identified: the coastal zone, the Southern Bight, the Frisian Front area and the northern part of the Dutch sector of the North Sea. The distribution of seabirds is determined by such factors as the presence of breeding areas, migratory and wintering movements, feeding methods and availability of food. The distribution of marine mammals depends on the species. Porpoises are found both in the northern part of the Dutch sector of the North Sea and in the coastal zone north of the Frisian Islands. Dolphins are rarely seen in coastal waters. The effects of human activities in the Dutch sector of the North Sea are discussed in chapter 4 and can be summarized as follows. Fishery is a frequent large-scale activity which throughout the Dutch sector of the North Sea has resulted in considerable changes within the ecosystem. There is hardly any place where benthic communities can develop undisturbed. At least 10 benthic species have disappeared or their numbers have decreased substantially. The spawning stocks and stability of many fish stocks have decreased substantially as well. Some bird species, however, have increased in numbers. In addition, intensive fisheries have possibly contributed to the decline of sea mammal populations. Offshore mining can, as a result of discharges of cuttings contaminated with oil-based muds (OBM), result in long-term local effects on the benthic system. Effects of water-based muds (WBM) cannot be ruled out, but will be found in smaller areas over a shorter period of time than the effects of OBM. Effects of discharges of production water have not been observed but could occur locally with effects on plankton, fish and birds. It seems unlikely that acoustic disturbance by offshore mining (including seismic surveys) should affect sea mammals which are more that 100 m away from the installation producing the disturbance. Some disturbance may occur as a result of ship and helicopter movements associated with offshore mining. Sand and gravel extraction and the laying of pipelines and telecommunication cables will result in local effects on the benthic system. The destruction of shellfish beds in the coastal zone by sand or gravel extraction might have long-term effects on scoters. It is not possible to quantify the effects of substances introduced into the marine environment by shipping and military activities. Noise produced by such activities may affect communication between sea mammals and behaviour of seabirds. There may be a recovery of those populations which are affected by fisheries. discharges from mining installations, sand and gravel extraction and the laying of pipelines and telecommunication cables after termination of these activities in certain parts of the Dutch sector of the North Sea. This would contribute to the recovery and conservation of these populations in the North Sea in general (see chapter 5). In general, recovery of communities may take 1 to 20 years (benthos and fish), 5 to 50 years (for seabirds) and 20 to more then 50 years (for sea mammals). Recovery will be impossible if gravel extraction has resulted in the removal of the entire layer of gravel on the seafloor. Chapters 6 and 7 give the objectives and related criteria which are used for the designation and the selection of areas which qualify for a protected status. The first criterion addresses the extent to which specific activities have developed into a threat to the existence or normal functioning of groups of animals or species in the Dutch sector of the North Sea. Fishery activities result in large-scale effects on a large number of ecological groups (benthos, fish, seabirds, marine mammals) in the Dutch sector of the North Sea. Discharges of cuttings contaminated with OBM result in long-term local benthic effects. Other discharges by offshore mining installations and sand and gravel extraction have local but possibly large-scale effects on benthos in specific relatively small areas such as the Frisian Front area or the Klaverbank. The second criterion addresses the question whether a prohibition or restriction of certain human activities in specific areas would reduce the threat to those groups of animals or species which were identified through the application of the first criterion. Alternatives for prohibitive or restrictive measures are also discussed. The designation of protected areas where certain activities are prohibited or restricted has the potential to contribute to the conservation or recovery of threatened species. In a number of cases there is no alternative other than the designation of protected areas. This is true of the threat to the benthos and fish which is caused by fisheries activities in the (Dutch sector of the) North Sea, and, in specific relatively small areas, it is also true of the threat to benthos caused by discharges from offshore mining installations and by sand and gravel extraction. The third criterion is used for identifying the areas most suitable for a protected Status on the basis of the ecology of groups of animals or species which need protection. Ecological criteria such as diversity, representativeness. integrity and vulnerability have been used. The application of ecological criteria results in the general conclusion that, within the Dutch sector of the North Sea, the following types of areas qualify for a protected status: a sandy area, a muddy area, an area with frontal characteristics and a gravel area. A protected area should contain coastal waters and an adequate depth gradient. An unbroken area which contains areas of all types would be the most effective option for protection. For the protection of benthos species with a limited migration, areas of circa one hundred square kilometers each should be sufficient; for fish species with an extensive migration pattern it would be necessary to protect a large part of the whole North Sea. It is concluded that for the protection of those species which are most characteristic of the Dutch sector of the North Sea it is necessary to protect an area with a total surface of some 31 ICES blocks (each some 60 x 60 square kilometers). The fourth criterion addresses the question whether there are adequate legal instruments to ensure effective protection of the selected areas. On the basis of existing legal instruments it is, in principle, possible to protect these areas. However; there are certain problems associated with measures which are required with respect to fisheries, gravel extraction and offshore mining. On the basis of the above criteria it is concluded that two areas within the Dutch sector of the North Sea qualify for a protected status: 1. An area directly northwest of the Frisian Islands (see Figs A and B). In this unbroken area of some 10,000 square kilometers it will be possible to protect a combination of different types of benthic communities (coastal waters, sandy bottoms, the Frisian Front area, muddy areas and restricted areas with gravel and stones). The area will also have an adequate depth gradient. The proposed area contains important spawning and nursery areas for fish (including squid) and habitats of many (non-commercial) fish species. Seasonal migratory routes to and from the Wadden Sea are concentrated in this area. Relatively large numbers of porpoises as well as dolphins and seabirds occur in this area. Protection of this area also strengthens the functioning of the Wadden Sea as a nursery area and supports the recolonisation of benthos in the Wadden Sea after, for instance, severe winters. There are two alternative options for the exact location of the area to be protected. The first alternative (Fig. A) has been chosen especially with an emphasis on conservation and recovery of the diversity of communities in the Dutch sector of the North Sea. The second alternative (Fig. B) more closely relates to existing measures regarding fisheries. The proportion of muddy areas is very low in this alternative. An expansion of the proposed area in an easterly direction could be considered only if it connected the area with similar protected areas in the German sector of the North Sea. An expansion of the proposed area in a southerly direction would more closely relate to the ecological interests of the Wadden Sea. The following protective measures are proposed for this area: The area will be closed for all types of fisheries throughout the year; Discharges from offshore mining installations which contain oil will be prevented (OBM) or minimized (production water); Additional area-specific protective measures with respect to offshore mining, shipping, military activities, sand extraction, dumping and the laying of pipelines can be considered whenever the situation in this area calls for such measures. Such measures should also be considered for areas to be used as reference areas for scientific research; The application of policies resulting from the implementation of international conventions with respect to conservation (the EC Bird Directive, the Conventions of Bonn, Berne and Ramsar, the proposed EC Habitat Directive). 2. Klaverbank (see Figs A and B). The Klaverbank, the only gravel area of importance in the Dutch sector of the North Sea, has a still relatively undisturbed benthic fauna which is specific to this type of area. The Klaverbank (approximately 800 square kilometers) should be given a protected status under which gravel extraction is prohibited. and discharges from offshore mining installations which contain oil will be prevented (OBM) or minimized (production water). Fisheries too should be prohibited but the limited size of this area rules out effective implementation and enforcement of such a measure. It is therefore advisable to develop proposals in cooperation with the United Kingdom for the designation of a protected area in the UK sector of the North Sea which should contain a large gravel area and possibly also the Klaverbank. If a decision is taken to protect these areas, it will be necessary to develop a management plan. Chapter 8 gives a possible outline for such a management plan, including certain relevant issues. Firstly, it will be necessary to define objectives for these specific areas in addition to the objectives already defined for the designation of protected areas in general. Secondly, it will be necessary to attune measures for the management of these areas to the objectives of their protection. A management plan will also have to address the organizational structure required for effective management of these areas. Arrangements for adequate enforcement and effective control of measures taken are also necessary. Programmes for scientific research will have to be developed

Excitation of Small Quantum Systems by High-Frequency Fields

The excitation by a high frequency field of multi--level quantum systems with a slowly varying density of states is investigated. A general approach to study such systems is presented. The Floquet eigenstates are characterized on several energy scales. On a small scale, sharp universal quasi--resonances are found, whose shape is independent of the field parameters and the details of the system. On a larger scale an effective tight--binding equation is constructed for the amplitudes of these quasi--resonances. This equation is non--universal; two classes of examples are discussed in detail.Comment: 4 pages, revtex, no figure

Coherent states for the hydrogen atom

We construct wave packets for the hydrogen atom labelled by the classical action-angle variables with the following properties. i) The time evolution is exactly given by classical evolution of the angle variables. (The angle variable corresponding to the position on the orbit is now non-compact and we do not get exactly the same state after one period. However the gross features do not change. In particular the wave packet remains peaked around the labels.) ii) Resolution of identity using this overcomplete set involves exactly the classical phase space measure. iii) Semi-classical limit is related to Bohr-Sommerfield quantization. iv) They are almost minimum uncertainty wave packets in position and momentum.Comment: 9 pages, 2 figures, minor change in language and journal reference adde

Interpolation in variable exponent spaces

In this paper we study both real and complex interpolation in the recently introduced scales of variable exponent Besov and Triebel–Lizorkin spaces. We also take advantage of some interpolation results to study a trace property and some pseudodifferential operators acting in the variable index Besov scale

Geometric and Statistical Properties of the Mean-Field HP Model, the LS Model and Real Protein Sequences

Lattice models, for their coarse-grained nature, are best suited for the study of the ``designability problem'', the phenomenon in which most of the about 16,000 proteins of known structure have their native conformations concentrated in a relatively small number of about 500 topological classes of conformations. Here it is shown that on a lattice the most highly designable simulated protein structures are those that have the largest number of surface-core switchbacks. A combination of physical, mathematical and biological reasons that causes the phenomenon is given. By comparing the most foldable model peptides with protein sequences in the Protein Data Bank, it is shown that whereas different models may yield similar designabilities, predicted foldable peptides will simulate natural proteins only when the model incorporates the correct physics and biology, in this case if the main folding force arises from the differing hydrophobicity of the residues, but does not originate, say, from the steric hindrance effect caused by the differing sizes of the residues.Comment: 12 pages, 10 figure