Peculiar Behavior of Si Cluster Ions in Solid Al

A peculiar ion behavior is found in a Si cluster, moving with a speed of ~0.22c (c: speed of light) in a solid Al plasma: the Si ion, moving behind the forward moving Si ion closely in a several angstrom distance in the cluster, feels the wake field generated by the forward Si. The interaction potential on the rear Si may balance the deceleration backward force by itself with the acceleration forward force by the forward Si in the longitudinal moving direction. The forward Si would be decelerated normally. However, the deceleration of the rear Si, moving behind closely, would be reduced significantly, and the rear Si may catch up and overtake the forward moving Si in the cluster during the Si cluster interaction with the high-density Al plasma

A systolic architecture for the correlation and accumulation of digital sequences

A fully systolic architecture for the implementation of digital sequence correlator/accumulators is described. These devices consist of a two-dimensional array of processing elements that are conceived for efficient fabrication in Very Large Scale Integrated (VLSI) circuits. A custom VLSI chip that was implemented using these concepts is described. The chip, which contains a four-lag three-level sequence correlator and four bits of accumulation with overflow detection, was designed using the Integrated UNIX-Based Computer Aided Design (CAD) System. Applications of such devices include the synchronization of coded telemetry data, alignment of both real time and non-real time Very Large Baseline Interferometry (VLBI) signals, and the implementation of digital filters and processes of many types

Continuous wave detector has wide frequency range

Portable battery-operated detector indicates the presence of steady state signals exceeding a predetermined value over a wide frequency range by the closure of output relay contacts. It was designed to monitor electronic equipment used in the Saturn 2 program

Structure of strongly coupled, multi-component plasmas

We investigate the short-range structure in strongly coupled fluidlike plasmas using the hypernetted chain approach generalized to multicomponent systems. Good agreement with numerical simulations validates this method for the parameters considered. We found a strong mutual impact on the spatial arrangement for systems with multiple ion species which is most clearly pronounced in the static structure factor. Quantum pseudopotentials were used to mimic diffraction and exchange effects in dense electron-ion systems. We demonstrate that the different kinds of pseudopotentials proposed lead to large differences in both the pair distributions and structure factors. Large discrepancies were also found in the predicted ion feature of the x-ray scattering signal, illustrating the need for comparison with full quantum calculations or experimental verification

Sideband cooling while preserving coherences in the nuclear spin state in group-II-like atoms

We propose a method for laser cooling group-II-like atoms without changing the quantum state of their nuclear spins, thus preserving coherences that are usually destroyed by optical pumping. As group-II-like atoms have a $^1S_0$ closed-shell ground state, nuclear spin and electronic degrees of freedom are decoupled, allowing for independent manipulation. The hyperfine interaction that couples these degrees of freedom in excited states can be suppressed through the application of external magnetic fields. Our protocol employs resolved-sideband cooling on the forbidden clock transition, $^1S_0 \to {}^3P_0$, with quenching via coupling to the rapidly decaying $^1P_1$ state, deep in the Paschen-Back regime. This makes it possible to laser cool neutral atomic qubits without destroying the quantum information stored in their nuclear spins, as shown in two examples, $^{171}$Yb and $^{87}$Sr.Comment: 4 pages, 3 figures v4: minor changes in text, changes in the references, published versio

Building multiparticle states with teleportation

We describe a protocol which can be used to generate any N-partite pure quantum state using Einstein-Podolsky-Rosen (EPR) pairs. This protocol employs only local operations and classical communication between the N parties (N-LOCC). In particular, we rely on quantum data compression and teleportation to create the desired state. This protocol can be used to obtain upper bounds for the bipartite entanglement of formation of an arbitrary N-partite pure state, in the asymptotic limit of many copies. We apply it to a few multipartite states of interest, showing that in some cases it is not optimal. Generalizations of the protocol are developed which are optimal for some of the examples we consider, but which may still be inefficient for arbitrary states.Comment: 11 pages, 1 figure. Version 2 contains an example for which protocol P3 is better than protocol P2. Correction to references in version

Why one-size-fits-all vaso-modulatory interventions fail to control glioma invasion: in silico insights

There is an ongoing debate on the therapeutic potential of vaso-modulatory interventions against glioma invasion. Prominent vasculature-targeting therapies involve functional tumour-associated blood vessel deterioration and normalisation. The former aims at tumour infarction and nutrient deprivation medi- ated by vascular targeting agents that induce occlusion/collapse of tumour blood vessels. In contrast, the therapeutic intention of normalising the abnormal structure and function of tumour vascular net- works, e.g. via alleviating stress-induced vaso-occlusion, is to improve chemo-, immuno- and radiation therapy efficacy. Although both strategies have shown therapeutic potential, it remains unclear why they often fail to control glioma invasion into the surrounding healthy brain tissue. To shed light on this issue, we propose a mathematical model of glioma invasion focusing on the interplay between the mi- gration/proliferation dichotomy (Go-or-Grow) of glioma cells and modulations of the functional tumour vasculature. Vaso-modulatory interventions are modelled by varying the degree of vaso-occlusion. We discovered the existence of a critical cell proliferation/diffusion ratio that separates glioma invasion re- sponses to vaso-modulatory interventions into two distinct regimes. While for tumours, belonging to one regime, vascular modulations reduce the tumour front speed and increase the infiltration width, for those in the other regime the invasion speed increases and infiltration width decreases. We show how these in silico findings can be used to guide individualised approaches of vaso-modulatory treatment strategies and thereby improve success rates

Fiber-Cavity-Based Optomechanical Device

We describe an optomechanical device consisting of a fiber-based optical cavity containing a silicon nitiride membrane. In comparison with typical free-space cavities, the fiber-cavity's small mode size (10 {\mu}m waist, 80 {\mu}m length) allows the use of smaller, lighter membranes and increases the cavity-membrane linear coupling to 3 GHz/nm and quadratic coupling to 20 GHz/nm^2. This device is also intrinsically fiber-coupled and uses glass ferrules for passive alignment. These improvements will greatly simplify the use of optomechanical systems, particularly in cryogenic settings. At room temperature, we expect these devices to be able to detect the shot noise of radiation pressure.Comment: 4 pages, 3 figures; the following article has been submitted to Applied Physics Letter

L'hydrologie urbaine: nouvelles problématiques, nouvelles approches de solutions

La pratique de l'hydrologie, appliquée au milieu urbain, a beaucoup évolué depuis les années 1960. De nouveaux outils scientifiques, méthodologiques et technologiques ont été mis au point. En ce qui concerne les eaux pluviales urbaines, un changement de philosophie complet s'est produit. Aujourd'hui, des développements rapides continuent à se produire pour faire face de la meilleure manière possible aux graves problèmes qui se posent en zone urbaine : inondation et pollution du milieu naturel. Deux approches récentes illustrent ces développements : la gestion des risques et l'approche globale sur le bassin versant. Une évaluation de plus en plus précise de l'aléa et de la vulnérabilité s'avère nécessaire ainsi qu'une planification hydrologique bassin versant par bassin versant. Celle-ci devrait conduire à définir et à hiérarchiser les principaux objectifs que l'on se fixe dans les domaines du contrôle des inondations, du contrôle de l'érosion, de l'amélioration du milieu naturel et de la protection de l'environnement. Les actions à mener doivent utiliser les outils de modélisation des phénomènes hydrologiques sur les bassins versants. L'efficacité de ces approches est illustrée par un exemple pris sur le bassin versant de la rivière Beauport au Québec.Urban hydrology practice has evolved a great deal, keeping up with the evolution of urban problems. Thus, professional engineers have had to keep up with this evolution, in order to understand the effects of urbanization on the hydrological behavior of the systems for which they have to recommend best solutions. Engineers have also had to evolve from the traditional approach of a limited vision of the problem, of its extent and of its impacts on the system. A global vision of the entire system, grouping every watershed element, such as forestry, agriculture or urbanization, is necessary if one is to circumscribe the problem, to analyze it and to reach to the best long-lasting solution. This article represents a synthesis of the hydrological disturbance phenomenon caused by uncontrolled urbanization, not properly planned, which is often characterized by numerous short-term solutions, often ineffective in the context of a long-lasting approach.Examples of natural disasters caused by meteorological events are more and more frequent. Take the case of Vaison-la-Romaine, in September 1992, where the Groseau devastated the Vaison community. More recently, the 1996 summer floods in the Saguenay region, in Québec, demonstrate once more that water always tends to return to its original bed, now occupied by artificial structures. When these types of events are analyzed in detail, we notice that meteorological phenomena are not always the main cause of the disaster cause and that often part of the responsibility lies with the occurrence of human activity in the catchment. This observation shows the importance of using wisdom and humility towards these natural forces and of anticipating, during design, a "secure" passage for the inevitable flows that one day will exceed the structure capacity. Knowing all the interactions that exist in the heart of the stormwater management problems, it is risky to intervene in isolation without analyzing the impact of the action. The approach must then be global and coherent; the tool necessary for success is the stormwater master plan made on a watershed basis. The master plan allows us to properly describe the problematical elements, to identify the real causes and to optimize the location of the control solutions. It also allows us to manage the increase in stormwater due to urbanization, with the "flow set point" concept of each watercourse tributary.This article presents an application example where the global analysis approach is used and where the solution involves different interventions and developments, which, when combined, effectively treat backwater effects, flooding and erosion in the presented area. The master plan of the watershed containing this sector had already been conceived and the specific flows of each of its tributaries had been identified; the global approach method therefore allowed us to settle the local problems in the studied area while respecting the flow granted by the master plan. Finally, a floodable plain, containing marshes, completes the intervention plan by combining the restoration of certain watercourse ecological characteristics with the need for flood control. This example demonstrates the necessity and the advantages of approaching urban drainage problems at the watershed level. However, watershed management concepts lead planners and designers to deal with antagonisms: urbanization or renaturalization? Obviously, in urban areas, the return to natural conditions is impossible and the disturbances to watercourses generated by urbanization cannot all be compensated for. Rather, we must aspire to the establishment of a balanced environment by controlling inflows produced by the watershed and by supporting the system to receive them. The notion of feasibility must always occupy the thoughts of the master plan designers and planners. The credibility and the continuity of the master plan depend on all these considerations; any unrealistic flow order, on an implementation level, can compromise the balance of the management plan and its applicability, which in turn can lead to a confused plan, possibly having disastrous consequences. The ultimate consequence of the management plan is the protection of the watercourse, the development of which can be designed to meet different criteria, such as flood control, erosion control, ecological potential enhancement, etc. It is at this stage that management becomes most complex: flood control, for example, does not apply to the same type of events as erosion control. The former requires management of major hydrological events, whereas the second needs implies control of frequent flows, which are at the origin of bank undermining caused by differential volume excesses. The management scheme must then handle multiple events and multiple criteria; consequently, it becomes more complex but also grows in value and justifies itself more adequately. Furthermore, the whole question of watercourse quality, in the broad sense of the term, must be managed from a frequent-event point of view, as this yields the best physical, ecological and aesthetic image of the aquatic environment. To this effect, present efforts in the control of combined sewage network overflows can be seen as a predecessor of what will later be extended to the entire stormwater network. This whole aspect of management has not been treated in this paper, as many others are dedicated to doing so. The evolution of the situation is similar in France and in Québec; coherent watershed management must rest on clear political goals regarding environmental use, risk protection and urban development. The stormwater master plan must, permanently, become part of the water resource master plan for the whole watershed, with its objectives of flood control, erosion control and maintenance of acceptable physical-chemical and biochemical water quality, as well as assured resource use (drinking water--, hydroelectricity, agriculture, industrial waters, etc.). This water resource master plan will have to be integrated in the same way as the French Water Agencies do today, and as Québec is preparing to do so

VLSI architectures for computing multiplications and inverses in GF(2-m)

Finite field arithmetic logic is central in the implementation of Reed-Solomon coders and in some cryptographic algorithms. There is a need for good multiplication and inversion algorithms that are easily realized on VLSI chips. Massey and Omura recently developed a new multiplication algorithm for Galois fields based on a normal basis representation. A pipeline structure is developed to realize the Massey-Omura multiplier in the finite field GF(2m). With the simple squaring property of the normal-basis representation used together with this multiplier, a pipeline architecture is also developed for computing inverse elements in GF(2m). The designs developed for the Massey-Omura multiplier and the computation of inverse elements are regular, simple, expandable and, therefore, naturally suitable for VLSI implementation