Set-Theoretic Types for Polymorphic Variants

Polymorphic variants are a useful feature of the OCaml language whose current definition and implementation rely on kinding constraints to simulate a subtyping relation via unification. This yields an awkward formalization and results in a type system whose behaviour is in some cases unintuitive and/or unduly restrictive. In this work, we present an alternative formalization of poly-morphic variants, based on set-theoretic types and subtyping, that yields a cleaner and more streamlined system. Our formalization is more expressive than the current one (it types more programs while preserving type safety), it can internalize some meta-theoretic properties, and it removes some pathological cases of the current implementation resulting in a more intuitive and, thus, predictable type system. More generally, this work shows how to add full-fledged union types to functional languages of the ML family that usually rely on the Hindley-Milner type system. As an aside, our system also improves the theory of semantic subtyping, notably by proving completeness for the type reconstruction algorithm.Comment: ACM SIGPLAN International Conference on Functional Programming, Sep 2016, Nara, Japan. ICFP 16, 21st ACM SIGPLAN International Conference on Functional Programming, 201

Activity profile of top-class association football referees in relation to fitness test performance and match standard

The aim of this study was to examine the kinematic activity profiles, cardiovascular responses and physical fitness of top-class football referees (n=11) during the FIFA Confederations Cup 2005. Computerised match-analyses (n=9) were performed with a two-dimensional photogrammetric video system, and the cardiovascular demand imposed on the referees (n=12) was measured using heart rate recordings. Total distance covered was 10,218, s=643 m of which 3531, s=510 m was covered at high intensities (>3.6 m.s(-1)). Both total distance covered (r2=0.59; P=0.02) and high-intensity activities (r2=0.44; P=0.05) were related to the distance covered by the ball in the same match. The referees ran at high speed 37% further (P=0.01) in the actual tournament than during under-17 top-level officiating. After the 5-min interval during which high-speed running peaked, in the following 5 min the performance was reduced by 19% (P=0.01) in relation to the mean of the game. Mean heart rate was 161, s=9 b.min(-1) (86, s=3% of maximal heart rate (HRmax)). Mean heart rate (expressed as percentage of HRmax) was related in part (r2=0.36; P5 m.s(-1)) best describes the physical performance of referees; (3) heart rate recording can be a useful tool to determine the most intense periods of a match and (4) the new fitness tests adopted by FIFA were poor predictors of match activities

Capillary breakup and electrospinning of PA6 solutions containing FeCl3: experimental findings and correlations

In several applications, ranging from electronic to chemical sensing, great interest has grown for the exploitation of conducting polymer nanofibers, whose processing is, however, not straightforward, due to polymer low solubility and presence of rigid backbones. An interesting method to overcome this issue consists in the electrospinning of a spinnable polymer to obtain a template for the successive in situ polymerization of the conducting polymer monomers. Considering PANI nanofibers, a suitable template can be electrospun from PA6 solutions in formic acid containing FeCl3. In this system, the ionic salt may perturb or prevent H-bonds formation between amide groups of PA6 backbones: this could modify solution viscoelasticity, and thus affect fibres morphology. The aim of the present work is to identify the effect of FeCl3 on the solution rheological behaviour and to correlate it to electrospun fibres morphology. To this aim, solutions at several salt content underwent electrospinning and were characterized both in shear, by rotational rheometry, and extension, by capillary breakup rheometry, while fibres morphology and crystallinity were evaluated through SEM and DSC. The rheological analysis enlightens that a critical FeCl3 content exists above which the viscous component of the viscoelastic response becomes predominant. At the same concentration, the SEM observations of the electrospun fibres show the formation of severely inhomogeneous structures. A correlation between these results is proposed through the adimensional analysis of competing viscoelastic stabilization and surface tension-driven instability phenomena. Besides the aforementioned effects, the FeCl3 content affects also fibre crystallinity, as above a critical concentration fibres turn out to be completely amorphous. Interestingly, this concentration coincides with the one at which a transition is observed in the rheological behaviour

Ground-Penetrating Radar Theory and Application of Thin-Bed Offset-Dependent Reflectivity

Offset-dependent reflectivity or amplitude-variationwith- offset (AVO) analysis of ground-penetrating radar (GPR) data may improve the resolution of subsurface dielectric permittivity estimates. A horizontally stratified medium has a limiting layer thickness below which thin-bed AVO analysis is necessary. For a typical GPR signal, this limit is approximately 0.75 of the characteristic wavelength of the signal. Our approach to modeling the GPR thin-bed response is a broadband, frequency-dependent computation that utilizes an analytical solution to the three-interface reflectivity and is easy to implement for either transverse electric (TE) or transverse magnetic (TM) polarizations. The AVO curves for TE and TM modes differ significantly. In some cases, constraining the interpretation using both TE and TM data is critical. In two field examples taken from contaminated-site characterization data, we find quantitative thin-bed modeling agrees with the GPR field data and available characterization data

Chemical induction of spawning by serotonin in the ocean quahog Arctica islandica (Linne)

Serotonin injected into the anterior adductor muscle induced spawning in the ocean quahog Arcrica islandica (Linne) when using either individual or mass spawning techniques. This represents the fir st successful attempt to induce the release of gametes in this species which historically has been unresponsive to conventional spawning stimuli. The gametes released were competent and fertilization occurred without treating the encapsulated eggs with ammonium hydroxide or other chemicals. Larvae were reared through metamorphosis to early juvenile stage

Resolving Non-Determinism in Choreographies

Resolving non-deterministic choices of choreographies is a crucial task. We introduce a novel notion of realisability for choreographies –called whole-spectrum implementation– that rules out deterministic implementations of roles that, no matter which context they are placed in, will never follow one of the branches of a non-deterministic choice. We show that, under some conditions, it is decidable whether an implementation is whole-spectrum. As a case study, we analyse the POP protocol under the lens of whole-spectrum implementation

The effect of match standard and referee experience on the objective and subjective match workload of English Premier League referees

The aim of the present study was to examine the effect of match standard and referee experience upon the objective and subjective workload of referees during Premier and Football league soccer matches. We also examined the relationship between heart rate (HR) and ratings of perceived exertion (RPE) for assessing match intensity in soccer referees. Heart rate responses were recorded using short-range telemetry and RPE scores were collected using a 10-point scale. Analysis revealed a significant relationship between mean match HR and match RPE scores (r = 0.485, p < 0.05, n =18). There were significant differences in match HR (Premier league 83.6 2.6 %HRmax vs. Football league 81.5 2.2 %HRmax, p < 0.05) and match RPE scores (Premier league 7.8 0.8 vs. Football league 6.9 0.8, p < 0.05) between standards of competition. Referee experience had no effect upon match heart rate and RPE responses to Premier and Football league matches. The results of the present study demonstrate the validity of using HR and RPE as a measure of global match intensity in soccer referees. Referee experience had no effect upon the referees’ objective and subjective match workload assessments, whereas match intensity was correlated to competition standard. These findings have implications for fitness preparation and evaluation in soccer referees. When progressing to a higher level of competition, referees should ensure that appropriate levels of fitness are developed in order to enable them to cope with an increase in physical match demands

Photosynthetic responses to salinity in two obligate halophytes: Sesuvium portulacastrum and Tecticornia indica

Abstract Seedlings of the obligate halophytes Sesuvium portulacastrum L. and Tecticornia indica (Willd.) subsp. indica were grown with 0, 200, or 400 mM NaCl for 13 weeks to investigate whether salt tolerance was related to maintenance of adequate photosynthetic activity and pigment equipment. Both species showed growth optimum at 200 mM NaCl and better tissue hydration under salinity but different photosynthetic response to salinity. CO2 assimilation rate and stomatal conductance of S. portulacastrum were highest at 200 mM NaCl, while in T. indica they decreased with salinity. Pigment content increased under salinity in both species. The de-epoxidation state in S. portulacastrum suggests the need for energy dissipation at 400 mM NaCl, while its salt-induced decline in T. indica, despite the reduced photochemistry, suggests the involvement of adaptive mechanisms other than the xanthophyll cycle