Improved liquid-level sensor for cryogenics

Liquid-level indicator, consisting of a diode heated by a resistor, allows simultaneous use of two or three of the liquids nitrogen, hydrogen, and helium. Operation depends on strong temperature-dependence of the forward resistance of a germanium diode and the difference between liquid and vapor in heat-transfer properties

Advances in travel geometry and urban modelling

Urban travel geometry is a generalization of patterns of movement in cities and regions where route configuration and prevailing traffic speeds constrain or direct movement in distinctive and repeatable patterns. In this paper we use these properties to construct time surfaces on which distance equates to the time of travel in the urban plane. Such surfaces can be two- or three-dimensional and are useful in the study of urban structure, locational analysis, transport planning and traffic management. A particular niche addressed in this paper is non-conformal time surface transformations in which speed or the cost of travel is constrained according to co-ordinate directions. It is argued that such models may be more suited to gridded and orbital-radial cities than previously used conformal transformations. After explaining the rationale behind the approach, a mathematical basis is developed and several calibrated examples are provided based on regions in the UK. The paper concludes with some examples of potential applications, and an annex provides a detailed mathematical framework

Toll optimisation on river crossings serving large cities

There is renewed interest in the private sector financing and operation of major transportation projects, in which a significant financial contribution comes from toll revenues. Tolling is ideally suited to river crossings, where the tolls are relatively easy to administer and collect. Because of their span, bridges over river estuaries are particularly expensive to build and maintain and so need to be put on a firm financial footing. Toll revenue is therefore a key consideration if such projects are to be financially viable and risk is to be minimised. There may be other issues to do with who benefits from the bridge and whether differential tolls should apply to local residents and non-resident bridge users. In addition, such bridges may be linked to wider economic objectives, such as local development and regeneration. This paper describes a model for estimating optimum bridge tolls, from both a financial and a welfare perspective and provides a case study that illustrates a range of scenarios that are of general interest

Market area analysis under orbital-radial routing with applications to the study of airport location

The study of market areas provides one indication of the economic and strategic value of a facility or attraction and is a commonly used tool in geographical and economic analysis. In this paper, we study a class of models for use in stereotypical urban regions with an associated orbital–radial network. The aim of the paper is to provide the theoretical and analytical tools needed to understand the shapes, size and markets of an attraction as a function of both its location and the speeds of radial and orbital access to competing attractions. As a result, we need to identify several hitherto unrecognised constructs such as eclipsing in which, due to proximity to a fast orbital road, one attraction can eliminate the market of another. We outline a facility location methodology in a case study, based on London, concerning access to airports serving the metropolis. Among other things, we identify inner and outer eclipsing envelopes for a new airports, which substantially narrows the area of search for an optimum location

Optimizing the benefits of urban road user charging

Traffic congestion is a feature of most modern cities but attempts to control it or limit its effects have met with only modest success. There is significant and continuing interest in the concept of charging city vehicle users, although apart from the use of parking charges actual operational schemes are few and far between. In this paper we compare three alternative charging policies using a simplified model of travel demand and supply, which we combine with cost benefit techniques. The charging policies are area-based charging in which users pay to locate in or enter an area, terminal-charging based on supplementary parking fees in residential and non-residential locations and distance-based charging which is a charge related to how far users travel. The model allows for behavioural effects resulting from trip diversion and demand suppression, as well as capacity restraint (speed-flow feedback effects based on limited route capacity). In the case study we parameterize the model using data and geographical dimensions based on London. We show that area based charging delivers the least benefits whilst a hybrid policy based on terminal and distance based charges delivers the most. Because it is of topical interest we compare our results and predictions with the Mayor’s strategy for London, which is an area-based scheme. We conclude that the revenue generated using a hybrid policy would be as great as for an area based scheme whilst at the same time delivering substantially greater benefits to road users in terms of travel time and other savings

Flashbulb Memories? The Effects of When the Initial Memory Report was Obtained

Why have some researchers found reports of flashbulb memories to be stable, while others have observed inconsistencies? Paradoxically, it appears that relatively long delays between event and initial documentation have produced greater consistency of participants\u27 reports. To investigate this directly, we collected the initial documentation of hearing about O.J. Simpson\u27s acquittal either five hours or one week after the acquittal was read. Observed consistency of memories varied as a function of documentation time; following an eight-week retention, the delayed reports were more consistent. The delayed group also reported fewer propositions in their initial documentation. We proposed a consolidation model to explain these results: during the days immediately following a newsworthy event, the narrative structure of these memories changes in that some details are forgotten. After this consolidation period, the memories may solidify. Thus, it may have been easier for the delayed group to provide consistent memories at the two intervals

Comparison between disordered quantum spin 1/2 chains

We study the magnetic properties of two types of one dimensional XX spin 1/2 chains. The first type has only nearest neighbor interactions which can be either antiferromagnetic or ferromagnetic and the second type which has both nearest neighbor and next nearest neighbor interactions, but only antiferromagnetic in character. We study these systems in the presence of low transverse magnetic fields both analytically and numerically. Comparison of results show a close relation between the two systems, which is in agreement with results previously found in Heisenberg chains by means of a numerical real space renormalization group procedure.Comment: 7 page

Low-Frequency Radio Transients in the Galactic Center

We report the detection of a new radio transient source, GCRT J1746-2757, located only 1.1 degrees north of the Galactic center. Consistent with other radio transients toward the Galactic center, this source brightened and faded on a time scale of a few months. No X-ray counterpart was detected. We also report new 0.33 GHz measurements of the radio counterpart to the X-ray transient source, XTE J1748-288, previously detected and monitored at higher radio frequencies. We show that the spectrum of XTE J1748-288 steepened considerably during a period of a few months after its peak. We also discuss the need for a more efficient means of finding additional radio transients

On the muon neutrino mass

During the runs of the PS 179 experiment at LEAR of CERN, we photographed an event of antiproton-Ne absorption, with a complete pi+ -> mu+ ->e+ chain. From the vertex of the reaction a very slow energy pi+ was emitted. The pi+ decays into a mu+ and subsequently the mu+ decays into a positron. At the first decay vertex a muon neutrino was emitted and at the second decay vertex an electron neutrino and a muon antineutrino. Measuring the pion and muon tracks and applying the momentum and energy conservation and using a classical statistical interval estimator, we obtained an experimental upper limit for the muon neutrino mass: m_nu < 2.2 MeV at a 90% confidence level. A statistical analysis has been performed of the factors contributing to the square value of the neutrino mass limit.Comment: 18 pages, 5 eps figure

Phase Diagram for Splay Glass Superconductivity

Localization of flux lines to splayed columnar pins is studied. A sine-Gordon type renormalization group study reveals the existence of a Splay glass phase and yields an analytic form for the transition temperature into the glass phase. As an independent test, the $I-V$ characteristics are determined via a Molecular Dynamics code. The glass transition temperature supports the RG results convincingly. The full phase diagram of the model is constructed.Comment: 14 pages, uuencoded compressed tar file with 3 postscript figure