Toughening mechanisms in novel nano-silica epoxy polymers

A crosslinked epoxy polymer has been modified by the addition of nano-silica particles. The particles were introduced via a sol-gel technique which gave a very well dispersed phase of nanosilica particles which were about 20 nm in diameter. The glass transition temperature was unchanged by the addition of the nano-particles, but both the modulus and toughness were increased. The fracture energy increased from 100 J/m2 for the unmodified epoxy to 460 J/m2 for the epoxy with 13 vol% of nano-silica. The microscopy studies showed evidence of debonding of the nano-particles and subsequent plastic void growth of the epoxy polymer. A theoretical model of plastic void growth was used to confirm this mechanism

Behavioral types in programming languages

A recent trend in programming language research is to use behav- ioral type theory to ensure various correctness properties of large- scale, communication-intensive systems. Behavioral types encompass concepts such as interfaces, communication protocols, contracts, and choreography. The successful application of behavioral types requires a solid understanding of several practical aspects, from their represen- tation in a concrete programming language, to their integration with other programming constructs such as methods and functions, to de- sign and monitoring methodologies that take behaviors into account. This survey provides an overview of the state of the art of these aspects, which we summarize as the pragmatics of behavioral types

Carbonate fuel cell endurance: Hardware corrosion and electrolyte management status

Endurance tests of carbonate fuel cell stacks (up to 10,000 hours) have shown that hardware corrosion and electrolyte losses can be reasonably controlled by proper material selection and cell design. Corrosion of stainless steel current collector hardware, nickel clad bipolar plate and aluminized wet seal show rates within acceptable limits. Electrolyte loss rate to current collector surface has been minimized by reducing exposed current collector surface area. Electrolyte evaporation loss appears tolerable. Electrolyte redistribution has been restrained by proper design of manifold seals

On the nature of symbolic execution

In this paper, we provide a formal definition of symbolic execution in terms of a symbolic transition system and prove its correctness with respect to an operational semantics which models the execution on concrete values. We first introduce such a formal model for a basic programming language with a statically fixed number of programming variables. This model is extended to a programming language with recursive procedures which are called by a call-by-value parameter mechanism. Finally, we show how to extend this latter model of symbolic execution to arrays and object-oriented languages which feature dynamically allocated variables

Quasienergy Spectroscopy of Excitons

We theoretically study nonlinear optics of excitons under intense THz irradiation. In particular, the linear near infrared absorption and resonantly enhanced nonlinear sideband generation are described. We predict a rich structure in the spectra which can be interpreted in terms of the quasienergy spectrum of the exciton, via a remarkably transparent expression for the susceptibility, and show that the effects of strongly avoided quasienergy crossings manifest themselves directly, both in the absorption and transmitted sidebands.Comment: 4 pages RevTex, 3 eps figs included, as publishe

Dental Educators’ Perceptions of Educational Learning Domains

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153618/1/jddjde019010.pd

Pristup procjeni zdravstvenoga rizika za ljude prilikom izgradnje gradskoga parka

A Human Health Risk Assessment (HHRA) was undertaken for a proposed park development “River Landing”, to be constructed along the north bank of the South Saskatchewan River in the City of Saskatoon, Saskatchewan, Canada. The purpose of the HHRA was to determine whether chemical constituents identified at the site, including polycyclic aromatic hydrocarbons (PAHs), petroleum hydrocarbons (PHCs), and toxic and heavy metals, would adversely affect the health of construction workers and potential park users. Although more traditional remediation options were considered, the risk assessment approach was chosen since it represented the best available technology. The HHRA was undertaken using protocols and methodologies proposed and readily accepted by the Canadian Council of Ministers of the Environment (CCME), Health Canada, and the United States Environmental Protection Agency (US EPA). Results of the risk assessment revealed that the magnitude and distribution of the chemicals at the site were such that extensive remediation was not required, and that the site could be developed without any significant restrictions on the proposed use. The assessment revealed that potential exposure to soil constituents would not result in adverse health risk to construction workers involved in park development or future park users.Napravljena je procjena zdravstvenoga rizika za ljude (izv. human health risk assessment, HHRA) za projekt gradskoga parka “River Landing” koji bi se trebao izgraditi duž sjeverne obale rijeke South Saskatchewan u Saskatoonu, saveznoj državi Saskatchewan u Kanadi. Svrha je procjene bila utvrditi mogu li kemijski spojevi zatečeni na gradilištu, uključujući policikličke aromatske ugljikovodike, naftne ugljikovodike te toksične i teške metale, štetno utjecati na zdravlje građevinskih radnika i korisnika parka. Premda je razmotrena i uporaba tradicionalnijih metoda sanacije, izabran je ovaj pristup procjeni rizika zbog toga što rabi najbolju dostupnu tehnologiju. Procjena rizika provedena je prema protokolima i metodama koje je odmah usvojio Kanadski savjet ministara za zaštitu okoliša (izv. Canadian Council of Ministers of the Environment, CCME), savezni ured za zdravlje Health Canada te Agencija za zaštitu okoliša Sjedinjenih Država (izv. United States Environmental Protection Agency, US EPA). Procjena rizika pokazala je da količina i rasprostranjenost kemikalija na gradilištu nisu takvi da zahtijevaju opsežniju sanaciju, te da se lokacija može izgraditi bez značajnih ograničenja u namjeni. Procjenom je također utvrđeno da eventualno izlaganje sastavnicama tla neće dovesti do štetnih posljedica za zdravlje građevinskih radnika koji rade na parku, a niti za buduće korisnike parka

Mapping quantum Hall edge states in graphene by scanning tunneling microscopy

Quantum Hall edge states are the paradigmatic example of the bulk-boundary correspondence. They are prone to intricate reconstructions calling for their detailed investigation at high spatial resolution. Here, we map quantum Hall edge states of monolayer graphene at a magnetic field of 7 T with scanning tunneling microscopy. The graphene sample features a gate-tunable lateral interface between areas of different filling factor. We compare the results with detailed tight-binding calculations quantitatively accounting for the perturbation by the tip-induced quantum dot. We find that the edge state pattern is mapped with little perturbation by adequate choice of gate voltage. We observe extended compressible regions, the antinodal structure of edge states and their meandering along the lateral interface.Comment: 23 pages, 23 figure

Gold Coast diagnostic criteria increase sensitivity in amyotrophic lateral sclerosis

Objective: This study evaluates diagnostic accuracy of the proposed ‘Gold Coast’ (GC) diagnostic criteria for amyotrophic lateral sclerosis (ALS). Methods: Five European centres retrospectively sampled consecutive patients referred for electromyography on suspicion of ALS. Patients were classified according to the GC criteria, the revised El Escorial (rEE) criteria and the Awaji (AW) criteria without and with the ‘Possible’ category (+ Poss). Reference standard was ALS confirmed by disease progression at follow-up. Results: Of 404 eligible patients 272 were diagnosed as ALS, 94 had mimicking disorders, 35 were lost for follow-up, and three had insufficient data. Sensitivity for the GC criteria was 88.2% (95% CI: 83.8-91.8%), which was higher than for previous criteria, of which the AW + Poss criteria reached the highest sensitivity of 77.6% (95% CI: 72.2–82.4%) (p < 0.001). Specificity was high for all criteria. The increase in sensitivity for the GC criteria was mainly due to the inclusion of 28 patients with progressive muscular atrophy (PMA). Conclusions: The simpler GC criteria increase the sensitivity, primarily due to considering PMA as a form of ALS with high specificity preserved. Significance: This validation study supports that GC criteria should be used in clinical practice and may be used for inclusion in trials