Psi-calculi: a framework for mobile processes with nominal data and logic

The framework of psi-calculi extends the pi-calculus with nominal datatypes for data structures and for logical assertions and conditions. These can be transmitted between processes and their names can be statically scoped as in the standard pi-calculus. Psi-calculi can capture the same phenomena as other proposed extensions of the pi-calculus such as the applied pi-calculus, the spi-calculus, the fusion calculus, the concurrent constraint pi-calculus, and calculi with polyadic communication channels or pattern matching. Psi-calculi can be even more general, for example by allowing structured channels, higher-order formalisms such as the lambda calculus for data structures, and predicate logic for assertions. We provide ample comparisons to related calculi and discuss a few significant applications. Our labelled operational semantics and definition of bisimulation is straightforward, without a structural congruence. We establish minimal requirements on the nominal data and logic in order to prove general algebraic properties of psi-calculi, all of which have been checked in the interactive theorem prover Isabelle. Expressiveness of psi-calculi significantly exceeds that of other formalisms, while the purity of the semantics is on par with the original pi-calculus.Comment: 44 page

Non-Deterministic Kleene Coalgebras

In this paper, we present a systematic way of deriving (1) languages of (generalised) regular expressions, and (2) sound and complete axiomatizations thereof, for a wide variety of systems. This generalizes both the results of Kleene (on regular languages and deterministic finite automata) and Milner (on regular behaviours and finite labelled transition systems), and includes many other systems such as Mealy and Moore machines

Urgent care centers in the U.S.: Findings from a national survey

<p>Abstract</p> <p>Background</p> <p>Due to long waits for primary care appointments and extended emergency department wait times, newer sites for episodic primary care services, such as urgent care centers, have developed. However, little is known about these centers. The purpose of this study is to provide information about the organization and functioning of urgent care centers based on a nationally representative U.S. sample.</p> <p>Methods</p> <p>We conducted a mail survey with telephone follow-up of urgent care centers identified via health insurers' websites, internet searches, and a trade association mailing list. Descriptive statistics are presented.</p> <p>Results</p> <p>Urgent care centers are open beyond typical office hours, and their scope of services is broader than that of many primary care offices. While these characteristics are similar to hospital emergency departments, such centers employ significant numbers of family physicians. The payer distribution is similar to that of primary care, and physicians' average salaries are comparable to those for family physicians overall. Urgent care centers report early adoption of electronic health records, though our findings are qualified by a lack of strictly comparable data.</p> <p>Conclusion</p> <p>While their hours and scope of services reflect some characteristics of emergency departments, urgent care centers are in many ways similar to family medicine practices. As the health care system evolves to cope with expanding demands in the face of limited resources, it is unclear how patients with episodic care needs will be treated, and what role urgent care centers will play in their care.</p

The Decreasing Significance of Stigma in the Lives of Bisexual Men: Keynote Address, Bisexual Research Convention, London

This article is constructed around a keynote address given at the Bisexual Research Convention, held in London 2010. The keynote was delivered by sociologist Eric Anderson, on behalf of himself and the other authors of this article. The keynote reflected upon a body of ongoing research, funded by the American Institute of Bisexuality and collected by this team of researchers, into the changing relationship between men and homophobia. It first contextualizes 20th-century attitudes toward homo/bisexuality before showing a declining significance of biphobia and homophobia in men's lives today. In accordance with the keynote, this article draws from preliminary findings of multiple ongoing studies of bisexual men in the United States and the United Kingdom

alpha-, r-, and s-process element trends in the Galactic thin and thick disks

From a detailed elemental abundance analysis of 102 F and G dwarf stars we present abundance trends in the Galactic thin and thick disks for 14 elements (O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, Ba, and Eu). Stellar parameters and elemental abundances (except for Y, Ba and Eu) for 66 of the 102 stars were presented in our previous studies (Bensby et al. 2003, 2004a). The 36 stars that are new in this study extend and confirm our previous results and allow us to draw further conclusions regarding abundance trends. The s-process elements Y and Ba, and the r-element Eu have also been considered here for the whole sample for the first time. With this new larger sample we now have the following results: 1) Smooth and distinct trends that for the thin and thick disks are clearly separated; 2) The alpha-element trends for the thick disk show typical signatures from the enrichment of SNIa; 3) The thick disk stellar sample is in the mean older than the thin disk stellar sample; 4) The thick disk abundance trends are invariant with galactocentric radii (R_m); 5) The thick disk abundance trends appear to be invariant with vertical distance (Z_max) from the Galactic plane. Adding further evidence from the literaure we argue that a merger/interacting scenario with a companion galaxy to produce a kinematical heating of the stars (that make up today's thick disk) in a pre-existing old thin disk is the most likely formation scenario for the Galactic thick disk.Comment: Accepted for publication in A&A, 20 page

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

State of the climate in 2018

In 2018, the dominant greenhouse gases released into Earth’s atmosphere—carbon dioxide, methane, and nitrous oxide—continued their increase. The annual global average carbon dioxide concentration at Earth’s surface was 407.4 ± 0.1 ppm, the highest in the modern instrumental record and in ice core records dating back 800 000 years. Combined, greenhouse gases and several halogenated gases contribute just over 3 W m−2 to radiative forcing and represent a nearly 43% increase since 1990. Carbon dioxide is responsible for about 65% of this radiative forcing. With a weak La Niña in early 2018 transitioning to a weak El Niño by the year’s end, the global surface (land and ocean) temperature was the fourth highest on record, with only 2015 through 2017 being warmer. Several European countries reported record high annual temperatures. There were also more high, and fewer low, temperature extremes than in nearly all of the 68-year extremes record. Madagascar recorded a record daily temperature of 40.5°C in Morondava in March, while South Korea set its record high of 41.0°C in August in Hongcheon. Nawabshah, Pakistan, recorded its highest temperature of 50.2°C, which may be a new daily world record for April. Globally, the annual lower troposphere temperature was third to seventh highest, depending on the dataset analyzed. The lower stratospheric temperature was approximately fifth lowest. The 2018 Arctic land surface temperature was 1.2°C above the 1981–2010 average, tying for third highest in the 118-year record, following 2016 and 2017. June’s Arctic snow cover extent was almost half of what it was 35 years ago. Across Greenland, however, regional summer temperatures were generally below or near average. Additionally, a satellite survey of 47 glaciers in Greenland indicated a net increase in area for the first time since records began in 1999. Increasing permafrost temperatures were reported at most observation sites in the Arctic, with the overall increase of 0.1°–0.2°C between 2017 and 2018 being comparable to the highest rate of warming ever observed in the region. On 17 March, Arctic sea ice extent marked the second smallest annual maximum in the 38-year record, larger than only 2017. The minimum extent in 2018 was reached on 19 September and again on 23 September, tying 2008 and 2010 for the sixth lowest extent on record. The 23 September date tied 1997 as the latest sea ice minimum date on record. First-year ice now dominates the ice cover, comprising 77% of the March 2018 ice pack compared to 55% during the 1980s. Because thinner, younger ice is more vulnerable to melting out in summer, this shift in sea ice age has contributed to the decreasing trend in minimum ice extent. Regionally, Bering Sea ice extent was at record lows for almost the entire 2017/18 ice season. For the Antarctic continent as a whole, 2018 was warmer than average. On the highest points of the Antarctic Plateau, the automatic weather station Relay (74°S) broke or tied six monthly temperature records throughout the year, with August breaking its record by nearly 8°C. However, cool conditions in the western Bellingshausen Sea and Amundsen Sea sector contributed to a low melt season overall for 2017/18. High SSTs contributed to low summer sea ice extent in the Ross and Weddell Seas in 2018, underpinning the second lowest Antarctic summer minimum sea ice extent on record. Despite conducive conditions for its formation, the ozone hole at its maximum extent in September was near the 2000–18 mean, likely due to an ongoing slow decline in stratospheric chlorine monoxide concentration. Across the oceans, globally averaged SST decreased slightly since the record El Niño year of 2016 but was still far above the climatological mean. On average, SST is increasing at a rate of 0.10° ± 0.01°C decade−1 since 1950. The warming appeared largest in the tropical Indian Ocean and smallest in the North Pacific. The deeper ocean continues to warm year after year. For the seventh consecutive year, global annual mean sea level became the highest in the 26-year record, rising to 81 mm above the 1993 average. As anticipated in a warming climate, the hydrological cycle over the ocean is accelerating: dry regions are becoming drier and wet regions rainier. Closer to the equator, 95 named tropical storms were observed during 2018, well above the 1981–2010 average of 82. Eleven tropical cyclones reached Saffir–Simpson scale Category 5 intensity. North Atlantic Major Hurricane Michael’s landfall intensity of 140 kt was the fourth strongest for any continental U.S. hurricane landfall in the 168-year record. Michael caused more than 30 fatalities and $25 billion (U.S. dollars) in damages. In the western North Pacific, Super Typhoon Mangkhut led to 160 fatalities and$6 billion (U.S. dollars) in damages across the Philippines, Hong Kong, Macau, mainland China, Guam, and the Northern Mariana Islands. Tropical Storm Son-Tinh was responsible for 170 fatalities in Vietnam and Laos. Nearly all the islands of Micronesia experienced at least moderate impacts from various tropical cyclones. Across land, many areas around the globe received copious precipitation, notable at different time scales. Rodrigues and Réunion Island near southern Africa each reported their third wettest year on record. In Hawaii, 1262 mm precipitation at Waipā Gardens (Kauai) on 14–15 April set a new U.S. record for 24-h precipitation. In Brazil, the city of Belo Horizonte received nearly 75 mm of rain in just 20 minutes, nearly half its monthly average. Globally, fire activity during 2018 was the lowest since the start of the record in 1997, with a combined burned area of about 500 million hectares. This reinforced the long-term downward trend in fire emissions driven by changes in land use in frequently burning savannas. However, wildfires burned 3.5 million hectares across the United States, well above the 2000–10 average of 2.7 million hectares. Combined, U.S. wildfire damages for the 2017 and 2018 wildfire seasons exceeded $40 billion (U.S. dollars)

Between Commerce and Empire: David Hume, Colonial Slavery, and Commercial Incivility

Eighteenth-century Enlightenment thought has recently been reclaimed as a robust, albeit short-lived, cosmopolitan critique of European imperialism. This essay complicates this interpretation through a study of David Hume’s reflections on commerce, empire and slavery. I argue that while Hume condemned the colonial system of monopoly, war and conquest, his strictures against empire did not extend to colonial slavery in the Atlantic. This was because colonial slavery represented a manifestly uncivil institution when judged by enlightened metropolitan sensibilities, yet also a decisively commercial institution pivotal to the eighteenth-century global economy. Confronted by the paradoxical ‘commercial incivility’ of modern slavery, Hume opted for disavowing the link between slavery and commerce, and confined his criticism of slavery to its ancient, feudal and Asiatic incarnations. I contend that Hume’s disavowal of the commercial barbarism of the Atlantic economy is part of a broader ideological effort to separate the idea of commerce from its imperial origins and posit it as the liberal antithesis of empire. The implications of analysis, I conclude, go beyond the eighteenth-century debates over commerce and empire, and more generally pertain to the contradictory entwinement of liberalism and capitalism