Overlap and activity glass transitions in plaquette spin models with hierarchical dynamics

We consider thermodynamic and dynamic phase transitions in plaquette spin models of glasses. The thermodynamic transitions involve coupled (annealed) replicas of the model. We map these coupled-replica systems to a single replica in a magnetic field, which allows us to analyse the resulting phase transitions in detail. For the triangular plaquette model (TPM), we find for the coupled-replica system a phase transition between high- and low-overlap phases, occuring at a coupling eps*(T), which vanishes in the low-temperature limit. Using computational path sampling techniques, we show that a single TPM also displays space-time transitions between active and inactive dynamical phases. These first-order dynamical transitions occur at a critical counting field s_c(T)>=0 that appears to vanish at zero temperature, in a manner reminiscent of the thermodynamic overlap transition. In order to extend the ideas to three dimensions we introduce the square pyramid model which also displays both overlap and activity transitions. We discuss a possible common origin of these various phase transitions, based on long-lived (metastable) glassy states.Comment: 12 pages, 9 fig

Fluctuating observation time ensembles in the thermodynamics of trajectories

The dynamics of stochastic systems, both classical and quantum, can be studied by analysing the statistical properties of dynamical trajectories. The properties of ensembles of such trajectories for long, but fixed, times are described by large-deviation (LD) rate functions. These LD functions play the role of dynamical free-energies: they are cumulant generating functions for time-integrated observables, and their analytic structure encodes dynamical phase behaviour. This "thermodynamics of trajectories" approach is to trajectories and dynamics what the equilibrium ensemble method of statistical mechanics is to configurations and statics. Here we show that, just like in the static case, there is a variety of alternative ensembles of trajectories, each defined by their global constraints, with that of trajectories of fixed total time being just one of these. We show that an ensemble of trajectories where some time-extensive quantity is constant (and large) but where total observation time fluctuates, is equivalent to the fixed-time ensemble, and the LD functions that describe one ensemble can be obtained from those that describe the other. We discuss how the equivalence between generalised ensembles can be exploited in path sampling schemes for generating rare dynamical trajectories.Comment: 12 pages, 5 figure

3D Library Displays: Bridging the Gap Between Physical and Online Patrons and Resources

In this session we will take participants through the process of planning and implementing a multidimensional book display using physical media and a variety of online tools, including library catalogs, social media, and websites. We may even integrate good old fashioned buttons! Along the way we’ll share information about what we’ve learned through research and practical experience and encourage attendees to brainstorm ways to implement these multidimensional displays in their own libraries

Microscale Fluid Behavior during Cryo-EM Sample Blotting

Blotting has been the standard technique for preparing aqueous samples for single-particle electron cryo-microscopy for over three decades. This technique removes the excess solution from a transmission electron microscope grid by pressing absorbent filter paper against the specimen before vitrification. However, this standard technique produces vitreous ice with inconsistent thickness from specimen to specimen and from region to region within the same specimen, the reasons for which are not understood. Here, high-speed interference contrast microscopy is used to demonstrate that the irregular pattern of fibers in the filter paper imposes tortuous, highly variable boundaries during the removal of excess liquid from a flat, hydrophilic surface. As a result, aqueous films of nonuniform thickness are formed while the filter paper is pressed against the substrate. This pattern of nonuniform liquid thickness changes again after the filter paper is pulled away, but the thickness still does not become completely uniform. We suggest that similar topographical features of the liquid film are produced during the standard technique used to blot EM grids and that these manifest in nonuniform ice after vitrification. These observations suggest that alternative thinning techniques, which do not rely on direct contact between the filter paper and the grid, may result in more repeatable and uniform sample thicknesses

Book Reviews

Book Review

Energy in Agriculture: The Use of Ethanol as an Unmixed Fuel for lnternal Combustion Engines

The use of ethanol (ethyl alcohol) as a fuel for spark ignited (Sl) internal combustion engines has been evaluated and considered satisfactory since the early1 900s. Today due to the increasing cost of petroleum and the current world oil uncertainty, which may greatly affect the future availability of petroleum, some alternative fuels for internal combustion engines are needed. Ethanol is one of the fuels that has shown promise as a petroleum substitute. Today the country of Brazil has chosen a path of less dependence on petroleum by developing an ethanol fuel technology. In the spring of 1980, cars designed to run exclusively on ethanol were offered for sale to the Brazilian public. Brazil has also encouraged its citizens to use ethanol by making it available to the consumer at half the cost of gasoline. This paper reviews the use of ethanol as an unmixed fuel for internal combustion engines. Anhydrous ethanol (no water present) is required when fuel mixtures are made with gasoline or diesel fuel. Presence of greater than 1.5% water in ethanol will cause separation of the ethanol from the petroleum fuel. On-farm production of ethanol will yield ethanol fuel with at least 5% water present or up to 50% water present. Thus, on-farm ethanol fuel product ion would necessitate adapting internal combustion engines for use of unmixed ethanol fuel

Component selection for livestock farms using linear programming

Also available online.Digitized 2007 AES MoU