Introducing Quantified Cuts in Logic with Equality

Cut-introduction is a technique for structuring and compressing formal proofs. In this paper we generalize our cut-introduction method for the introduction of quantified lemmas of the form $\forall x.A$ (for quantifier-free $A$) to a method generating lemmas of the form $\forall x_1\ldots\forall x_n.A$. Moreover, we extend the original method to predicate logic with equality. The new method was implemented and applied to the TSTP proof database. It is shown that the extension of the method to handle equality and quantifier-blocks leads to a substantial improvement of the old algorithm

Robustness of topologically protected edge states in quantum walk experiments with neutral atoms

Discrete-time quantum walks allow Floquet topological insulator materials to be explored using controllable systems such as ultracold atoms in optical lattices. By numerical simulations, we study the robustness of topologically protected edge states in the presence of decoherence in one- and two-dimensional discrete-time quantum walks. We also develop a simple analytical model quantifying the robustness of these edge states against either spin or spatial dephasing, predicting an exponential decay of the population of topologically protected edge states. Moreover, we present an experimental proposal based on neutral atoms in spin-dependent optical lattices to realize spatial boundaries between distinct topological phases. Our proposal relies on a new scheme to implement spin-dependent discrete shift operations in a two-dimensional optical lattice. We analyze under realistic decoherence conditions the experimental feasibility of observing unidirectional, dissipationless transport of matter waves along boundaries separating distinct topological domains.Comment: 16 pages, 10 figure

A Review On Alpha Case Formation And Modeling Of Mass Transfer During Investment Casting Of Titanium Alloys

Titanium alloys have excellent corrosion resistance, high temperature strength, low density, and biocompatibility. Therefore, they are increasingly used for aerospace, biomedical, and chemical applications. Investment casting is a well-established process for manufacturing near-net-shape intricate parts for such applications. However, mass transfer arising from metal-mold reactions is still a major problem that drastically impairs the surface and properties of the castings. Although there have been astounding developments over the past 20 years, they remain scattered in various research papers and conference proceedings. This review summarizes the current status of the field, gaps in the scientific understanding, and the research needs for the expansion of efficient casting of titanium alloys. The uniqueness of this paper includes a comprehensive analysis of the interfacial reactions and mass transfer problems. Additionally, momentum and heat transfer are presented where applicable, to offer a holistic understanding of the transport phenomena involved in investment casting. Solutions based on modeling and experimental validation are discussed, highlighting ceramic oxide refractories like zirconia, yttria, calcia, alumina, and novel refractories namely, calcium zirconate and barium zirconate. It was found that while mold material selection is vital, alloy composition should also be carefully considered in mitigating metal-mold reactions and mass transfer

High-Temperature Interactions Between Titanium Alloys And Strontium Zirconate Refractories

We investigated interactions between Ti6Al4V alloys and strontium zirconate (SrZrO3) ceramic to assess its potential as a refractory mold material in investment casting. We developed a robust yet simple procedure to examine both the liquid–solid and solid–solid interactions using pellets in drop casting and diffusion couple methods. Reaction layers were characterized using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray diffraction (XRD). The results were compared to alumina (Al2O3) which is still a common refractory ceramic for molds in investment casting. Our findings indicate that Ti6Al4V surfaces in contact with SrZrO3 had no apparent changes in surface chemistry nor microstructure. On the other hand, Ti6Al4V surfaces in contact with Al2O3 developed γ-TiAl and α 2-Ti3Al intermetallics with thicknesses of ~ 100 μm in diffusion couples and ~ 10 μm in drop-casting experiments. Nanoindentation results showed that the surface of Ti6Al4V in contact with Al2O3 was significantly harder compared to SrZrO3, confirming our conclusion. Given the time and costs associated with mechanical and chemical removal of reaction layers on Ti6Al4V castings, SrZrO3 can be a better choice for a mold material in the investment casting of titanium alloys

When should a diagnosis of influenza be considered in adults requiring intensive care unit admission? Results of population-based active surveillance in Toronto

INTRODUCTION: There is a paucity of data about the clinical characteristics that help identify patients at high risk of influenza infection upon ICU admission. We aimed to identify predictors of influenza infection in patients admitted to ICUs during the 2007/2008 and 2008/2009 influenza seasons and the second wave of the 2009 H1N1 influenza pandemic as well as to identify populations with increased likelihood of seasonal and pandemic 2009 influenza (pH1N1) infection. METHODS: Six Toronto acute care hospitals participated in active surveillance for laboratory-confirmed influenza requiring ICU admission during periods of influenza activity from 2007 to 2009. Nasopharyngeal swabs were obtained from patients who presented to our hospitals with acute respiratory or cardiac illness or febrile illness without a clear nonrespiratory aetiology. Predictors of influenza were assessed by multivariable logistic regression analysis and the likelihood of influenza in different populations was calculated. RESULTS: In 5,482 patients, 126 (2.3%) were found to have influenza. Admission temperature ≥38°C (odds ratio (OR) 4.7 for pH1N1, 2.3 for seasonal influenza) and admission diagnosis of pneumonia or respiratory infection (OR 7.3 for pH1N1, 4.2 for seasonal influenza) were independent predictors for influenza. During the peak weeks of influenza seasons, 17% of afebrile patients and 27% of febrile patients with pneumonia or respiratory infection had influenza. During the second wave of the 2009 pandemic, 26% of afebrile patients and 70% of febrile patients with pneumonia or respiratory infection had influenza. CONCLUSIONS: The findings of our study may assist clinicians in decision making regarding optimal management of adult patients admitted to ICUs during future influenza seasons. Influenza testing, empiric antiviral therapy and empiric infection control precautions should be considered in those patients who are admitted during influenza season with a diagnosis of pneumonia or respiratory infection and are either febrile or admitted during weeks of peak influenza activity

Bird populations most exposed to climate change are less sensitive to climatic variation

The phenology of many species shows strong sensitivity to climate change; however, with few large scale intra-specific studies it is unclear how such sensitivity varies over a species' range. We document large intra-specific variation in phenological sensitivity to temperature using laying date information from 67 populations of two co-familial European songbirds, the great tit (Parus major) and blue tit (Cyanistes caeruleus), covering a large part of their breeding range. Populations inhabiting deciduous habitats showed stronger phenological sensitivity than those in evergreen and mixed habitats. However, populations with higher sensitivity tended to have experienced less rapid change in climate over the past decades, such that populations with high phenological sensitivity will not necessarily exhibit the strongest phenological advancement. Our results show that to effectively assess the impact of climate change on phenology across a species' range it will be necessary to account for intra-specific variation in phenological sensitivity, climate change exposure, and the ecological characteristics of a population. Intra-specific variations may contribute to heterogeneous responses to climate change across a species' range. Here, the authors investigate the phenology of two bird species across their breeding ranges, and find that their sensitivity to temperature is uncoupled from exposure to climate change.Peer reviewe

Gαi2- and Gαi3-Specific Regulation of Voltage-Dependent L-Type Calcium Channels in Cardiomyocytes

BACKGROUND: Two pertussis toxin sensitive G(i) proteins, G(i2) and G(i3), are expressed in cardiomyocytes and upregulated in heart failure. It has been proposed that the highly homologous G(i) isoforms are functionally distinct. To test for isoform-specific functions of G(i) proteins, we examined their role in the regulation of cardiac L-type voltage-dependent calcium channels (L-VDCC). METHODS: Ventricular tissues and isolated myocytes were obtained from mice with targeted deletion of either Gα(i2) (Gα(i2) (-/-)) or Gα(i3) (Gα(i3) (-/-)). mRNA levels of Gα(i/o) isoforms and L-VDCC subunits were quantified by real-time PCR. Gα(i) and Ca(v)α(1) protein levels as well as protein kinase B/Akt and extracellular signal-regulated kinases 1/2 (ERK1/2) phosphorylation levels were assessed by immunoblot analysis. L-VDCC function was assessed by whole-cell and single-channel current recordings. RESULTS: In cardiac tissue from Gα(i2) (-/-) mice, Gα(i3) mRNA and protein expression was upregulated to 187 ± 21% and 567 ± 59%, respectively. In Gα(i3) (-/-) mouse hearts, Gα(i2) mRNA (127 ± 5%) and protein (131 ± 10%) levels were slightly enhanced. Interestingly, L-VDCC current density in cardiomyocytes from Gα(i2) (-/-) mice was lowered (-7.9 ± 0.6 pA/pF, n = 11, p<0.05) compared to wild-type cells (-10.7 ± 0.5 pA/pF, n = 22), whereas it was increased in myocytes from Gα(i3) (-/-) mice (-14.3 ± 0.8 pA/pF, n = 14, p<0.05). Steady-state inactivation was shifted to negative potentials, and recovery kinetics slowed in the absence of Gα(i2) (but not of Gα(i3)) and following treatment with pertussis toxin in Gα(i3) (-/-). The pore forming Ca(v)α(1) protein level was unchanged in all mouse models analyzed, similar to mRNA levels of Ca(v)α(1) and Ca(v)β(2) subunits. Interestingly, at the cellular signalling level, phosphorylation assays revealed abolished carbachol-triggered activation of ERK1/2 in mice lacking Gα(i2). CONCLUSION: Our data provide novel evidence for an isoform-specific modulation of L-VDCC by Gα(i) proteins. In particular, loss of Gα(i2) is reflected by alterations in channel kinetics and likely involves an impairment of the ERK1/2 signalling pathway

Single Particle Difraction at FLASH

Single-pulse coherent diffraction patterns have been collected from randomly injected single particles with a soft X-ray free-electron laser (FEL). The intense focused FEL pulse gives a high-resolution low-noise coherent diffraction pattern of the object before that object turns into a plasma and explodes. A diffraction pattern of a single particle will only be recorded when the particle arrival into the FEL interaction region coincides with FEL pulse arrival and detector integration. The properties of the experimental apparatus coinciding with these three events set the data acquisition rate. For our single particle FLASH diffraction imaging experiments: (1) an aerodynamic lens stack prepared a particle beam that consisted of particles moving at 150-200 m/s positioned randomly in space and time, (2) the 10 fs long FEL pulses were delivered at a fixed rate, and (3) the detector was set to integrate and readout once every two seconds. The effect of these experimental parameters on the rate of data acquisition using randomly injected particles will be discussed. Overall, the ultrashort FEL pulses do not set the limit of the data acquisition, more important is the effective interaction time of the particle crossing the FEL focus, the pulse sequence structure and the detector readout rate. Example diffraction patterns of randomly injected ellipsoidal iron oxide nanoparticles in different orientations are presented. This is the first single particle diffraction data set of identical particles in different orientations collected on a shot-to-shot basis. This data set will be used to test algorithms for recovering 3D structure from single particle diffraction