Evidence for unconventional superconductivity in single crystals of the antiferromagnetic heavy-electron compound URu2Si2

Specific heat C(T) and upper critical field Hc2(T) measurements have been performed on two single crystal specimens (denoted A and B) of the antiferromagnetic heavy-electron superconductor URu2Si2. Specific heat measurements on both single crystals reveal two distinct jumps, indicative of two superconducting phases. This is reminiscent of the antiferromagnetic heavy-electron compound UPt3 in which multiple superconducting transitions have been observed and attributed to coupled antiferromagnetic and multicomponent superconducting order parameters, although two superconducting phases associated with two different states of the crystal cannot be ruled out. The relative magnitudes of the two specific heat jumps observed in crystal B suggest that the two superconducting phases occupy nearly equal volume fractions of the crystal. At temperatures below the lower jump, the specific heat of both crystals can be described by C3(T) = γs(0)T+AT3 with γ3(0) ≈ 0.5γn(0), where γn(0) is the value of the normal-state electronic specific heat coefficient γn(T), extrapolated to T = 0. The two critical temperatures inferred from the specific heat jumps in crystal B, measured in magnetic fields H between 0 and 15kOe applied parallel to the c-axis, have a similar dependence on H. Resistive measurements of Hc2(T) on specimens from crystal A between 0 and 60 kOe reveal a kink near 2 kOe for H⌈c and strong positive curvature in Hc2(T) below ∼3 kOe for H⌈a. © 1991

The effect of steepness of temporal resource gradients on spatial root allocation

Plants are able to discriminately allocate greater biomass to organs that grow under higher resource levels. Recent evidence demonstrates that split-root plants also discriminately allocate more resources to roots that grow under dynamically improving nutrient levels, even when their other roots grow in richer patches. Here, we further tested whether, besides their responsiveness to the direction of resource gradients, plants are also sensitive to the steepness of environmental trajectories. Split-root Pisum sativum plants were grown so that one of their roots developed under constantly-high nutrient levels and the other root was subjected to dynamically improving nutrient levels of variable steepness. As expected, plants usually allocated a greater proportion of their biomass to roots that developed under constantly high resource availability; however, when given a choice, they allocated greater biomass to roots that initially experienced relatively low but steeply improving nutrient availabilities than to roots that developed under continuously-high nutrient availability. Such discrimination was not observed when the roots in the poor patch experienced only gentler improvements in nutrient availability. The results are compatible with the notion that responsiveness to the direction and steepness of environmental gradients could assist annual plants to increase their performance by anticipating resource availabilities foreseeable before the end of the growing season. The results exemplify the ability of plants to integrate and utilize environmental information and execute adaptive behaviors which, until recently, were attributed only to animals with central nervous systems

Width of margins in phyllodes tumors of the breast: the controversy drags on?—a systematic review and meta-analysis

Phyllodes tumors (PT) of the breast are rare fibroepithelial neoplasms. Information is controversial in the literature regarding to the optimal surgical management. Most studies suggested margins of at least 10 mm while some recent studies suggested narrower margins without an increased risk of local recurrences (LR) and distant metastases (DM). The objective of this systematic review was to identify and compare studies that assessed these different practices. A systematic review was performed through five databases up to April 2019. Studies exploring the association between the width of margins, subtypes of PT, and the LR and DM rates were considered for inclusion. A statistical model for analyzing sparse data and rare events was used. Thirteen studies met eligibility criteria and were selected. Considering a threshold of 10 mm (margins < 10 vs margins ≥ 10 mm), the 5-year incidence rate of LR was estimated to be 5.22 vs. 3.63 (diff. -1.59) per 100 person-years for benign PT, 9.60 vs. 7.33 (diff. -2.27) for borderline PT, and 28.58 vs. 21.84 (diff. -6.74) for malignant PT. For DM, it was estimated to be 0.88 vs. 0.86 (diff. -0.02) for benign PT, 1.61 vs. 1.74 (diff. 0.13) for borderline PT, and 4.80 vs 5.18 (diff. 0.38) for malignant PT. The data for a threshold of 1 mm were not sufficient to draw any conclusions. Irrespective of tumor grade, we found that DM was a rarer event than LR. Malignant PT had the highest incidence rate of LR and DM. This meta-analysis found a clear association between width of margins and LR rates. Whatever the tumor grade, surgical margins ≥ 10 mm guaranteed a lower risk of LR than margins < 10 mm. On the other hand, the width of margin did not influence the apparition of DM