The massive neutron star or low-mass black hole in 2S 0921-630

We report on the optical spectroscopy of the eclipsing halo low-mass X-ray binary 2S 0921-630, which reveals the absorption-line radial velocity curve of the K0 III secondary star with a semiamplitude K-2=92.89+/-3.84 km s(-1), a systemic velocity gamma=34.9+/-3.3 km s(-1), and an orbital period P-orb of 9.0035+/-0.0029 days (1 sigma). Given the quality of the data, we find no evidence for the effects of X-ray irradiation. Using the previously determined rotational broadening of the mass donor and applying conservative limits on the orbital inclination, we constrain the compact object mass to be 2.0-4.3 M-circle dot (1 sigma), ruling out a canonical neutron star at the 99% level. Since the nature of the compact object is unclear, this mass range implies that the compact object is either a low-mass black hole with a mass slightly higher than the maximum possible neutron star mass (2.9 M-circle dot) or a massive neutron star. If the compact object is a black hole, it confirms the prediction of the existence of low-mass black holes, while if the object is a massive neutron star, its high mass severely constrains the equation of state of nuclear matter.

Mapping stone surface temperature fluctuations: Implications for lichen distribution and biomodification on historic stone surfaces

The exposure of historic stone to processes of lichen-induced surface biomodification is determined, first and foremost, by the bioreceptivity of those surfaces to lichen colonization. As an important component of surface bioreceptivity, spatiotemporal variation in stone surface temperature plays a critical role in the spatial distribution of saxicolous lichen on historic stone structures, especially within seasonally hot environments. The ornate limestone and tufa stairwell of the Monastery of Cartuja (1516), Granada, Spain, exhibits significant aspect-related differences in lichen distribution. Lichen coverage and
diurnal fluctuations in stone surface temperature on the stairwell were monitored and mapped, under anticyclonic conditions in summer and winter, using an infrared thermometer and Geographical Information Systems approach. This research suggests that it is not extreme high surface temperatures that
determine the presence or absence of lichen coverage on stonework. Instead, average stone surface temperatures
over the course of the year seem to play a critical role in determining whether or not surfaces are receptive to lichen colonization and subsequent biomodification. It is inferred that lichen, capable of surviving extreme surface temperatures during the Mediterranean summer in an ametabolic state, require a respite period of lower temperatures within which they can metabolize, grow and reproduce.
The higher the average annual temperature a surface experiences, the shorter the respite period for any lichen potentially inhabiting that surface. A critical average temperature threshold of approximately 21 ?C has been identified on the stairwell, with average stone surface temperatures greater than this
generally inhibiting lichen colonization. A brief visual condition assessment between lichen-covered and lichen-free surfaces on the limestone sections of the stairwell suggests relative bioprotection induced by lichen coverage, with stonework quality and sharpness remaining more defined beneath lichen-covered surfaces. The methodology employed in this paper may have further applications in the monitoring and mapping of thermal stress fatigue on historic building materials.

Antiplatelet therapy versus observation in low-risk essential thrombocythemia with CALR mutation

The role of antiplatelet therapy as primary prophylaxis of thrombosis in low-risk essential thrombocythemia has not been studied in randomized clinical trials. We assessed the benefit/risk of low-dose aspirin in 433 low-risk essential thrombocythemia patients (CALR-mutated n=271, JAK2V617F-mutated n=162) who were on antiplatelet therapy or observation only. After a 2215 person-years follow-up free from cytoreduction, 25 thrombotic and 17 bleeding episodes were recorded. In CALR-mutated patients, antiplatelet therapy did not affect the risk of thrombosis but was associated with a higher incidence of bleeding (12.9 vs. 1.8 x1000 patient-years, p=0.03). In JAK2V617F-mutated patients, low-dose aspirin was associated with a reduced incidence of venous thrombosis with no effect on the risk of bleeding. Coexistence of JAK2V617F-mutation and cardiovascular risk factors increased the risk of thrombosis, even after adjusting for treatment with low-dose aspirin (incidence rate ratio: 9.8; 95% confidence interval: 2.3-42.3; p=0.02). Time free from cytoreduction was significantly shorter in CALR-mutated than in JAK2V617F-mutated essential thrombocythemia (median time 5 years and 9.8 years, respectively; p=0.0002) usually to control extreme thrombocytosis. In conclusion, in patients with low-risk, CALR-mutated essential thrombocythemia, low-dose aspirin does not reduce the risk of thrombosis and may increase the risk of bleeding.