Evidence for Coexistence of Bulk Superconductivity and Itinerant Antiferromagnetism in the Heavy Fermion System CeCo(In1−x_{1-x}Cdx_x)5_5

In the generic phase diagram of heavy fermion systems, tuning an external parameter such as hydrostatic or chemical pressure modifies the superconducting transition temperature. The superconducting phase forms a dome in the temperature-tuning parameter phase diagram, which is associated with a maximum of the superconducting pairing interaction. Proximity to antiferromagnetism suggests a relation between the disappearance of antiferromagnetic order and superconductivity. We combine muon spin rotation, neutron scattering, and x-ray absorption spectroscopy techniques to gain access to the magnetic and electronic structure of CeCo(In$_{1-x}$Cd$_x$)$_5$ at different time scales. Different magnetic structures are obtained that indicate a magnetic order of itinerant character, coexisting with bulk superconductivity. The suppression of the antiferromagnetic order appears to be driven by a modification of the bandwidth/carrier concentration, implying that the electronic structure and consequently the interplay of superconductivity and magnetism is strongly affected by hydrostatic and chemical pressure.Comment: Article + Supplementary information 33 pages, 13 figure

Frequency comb offset dynamics of SESAM modelocked thin disk lasers

We present a detailed study of the carrier-envelope offset (CEO) frequency dynamics of SESAM modelocked thin disk lasers (TDLs) pumped by kW-class highly transverse multimode pump diodes with a typical M2 value of 200-300, and give guidelines for future frequency stabilization of multi-100-W oscillators. We demonstrate CEO frequency detection with > 30 dB signal-to-noise ratio with a resolution bandwidth of 100 kHz from a SESAM modelocked Yb:YAG TDL delivering 140 W average output power with 748-fs pulses at 7-MHz pulse repetition rate. We compare with a low-power CEO frequency stabilized Yb:CALGO TDL delivering 2.1 W with 77-fs pulses at 65 MHz. For both lasers, we perform a complete noise characterization, measure the relevant transfer functions (TFs) and compare them to theoretical models. The measured TFs are used to determine the propagation of the pump noise step-by-step through the system components. From the noise propagation analysis, we identify the relative intensity noise (RIN) of the pump diode as the main contribution to the CEO frequency noise. The resulting noise levels are not excessive and do not prevent CEO frequency stabilization. More importantly, the laser cavity dynamics are shown to play an essential role in the CEO frequency dynamics. The cavity TFs of the two lasers are very different which explains why at this point a tight CEO frequency lock can be obtained with the Yb:CALGO TDL but not with the Yb:YAG TDL. For CEO stabilization laser cavities should exhibit high damping of the relaxation oscillations by nonlinear intra-cavity elements, for example by operating a SESAM in the roll-over regime. Therefore the optimum SESAM operation point is a tradeoff between enough damping and avoiding multiple pulsing instabilities. Additional cavity components could be considered for supplementary damping independent of the SESAM operation point

A Warm Heart and a Clear Head

Prior studies on the association between weather and psychological changes have produced mixed results. In part, this inconsistency may be because weather's psychological effects are moderated by two important factors: the season and time spent outside. In two correlational studies and an experiment manipulating participants' time outdoors (total N = 605), pleasant weather (higher temperature or barometric pressure) was related to higher mood, better memory, and “broadened” cognitive style during the spring as time spent outside increased. The same relationships between mood and weather were not observed during other times of year, and indeed hotter weather was associated with lower mood in the summer. These results are consistent with findings on seasonal affective disorder, and suggest that pleasant weather improves mood and broadens cognition in the spring because people have been deprived of such weather during the winter.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73377/1/j.1467-9280.2005.01602.x.pd

Effects of pruning on workload and yields of native cacao under agroforests in Bolivia

Cacao Nacional Boliviano (CNB) is the denomination for cacao derived from wild populations found in the Bolivian Amazon, traditionally collected by local communities. But cultivation surfaces are increasing as CNB beans are recognised internationally for their organoleptic qualities. So far, little selection has been done on the semi-wild populations cultivated and agricultural practices might have to be adapted to better support farmers’ livelihoods. We studied three different agricultural systems: CNB in agroforestry with bananas, fruit and timber trees with a management focusing on weeding and cacao pruning (AF); CNB planted in the cleared understory of a largely unmanaged secondary forest with (SFwP) or without (SFnP) cacao tree pruning. We monitored the yearly dry bean yield, labour time required for field activities, and resulting efficiencies of these three systems on plots established in 2012. Cacao was planted using CNB progenies from locally selected trees. In all systems, the first cocoa pods matured 4 years after planting; production increased significantly in the 6th year and again between the 9th and 11th year. Cumulative dry yields in this third phase (2020-2022) were highest in SFnP (911.2 kg/ha), followed by AF (591.2 kg/ha) and SFwP (277.8 kg/ha). Heavy pruning was labour-intensive (up to 56% of total labour time) and limited yields but increased harvesting efficiency in the following years without pruning. In 2020-2022, harvesting in SFnP was 5 times more laborious as in SFwP and 2.7 times more as in AF, while its yield was only 3.3 and 1.5 times higher, respectively. Harvesting efficiency was thus higher in both pruned systems (AF: 7.3 kg/Workday, SFwP: 6.7 kg/WD), compared to the unpruned system (4.4 kg/WD). Our results underline the delicate balance between the practice of pruning, aiming at facilitating and concentrating the harvest at a limited height, and its effect on cacao physiology. Yet, association in AF shows that in completely managed systems, CNB is able to reach fair yield levels despite pruning. All in all, our results call for further domestication of CNB progenies aiming at earlier start of production, and adaptation of management practices (timing and intensity of pruning) for CNB

Distribution of resonances for open quantum maps

We analyze simple models of classical chaotic open systems and of their quantizations (open quantum maps on the torus). Our models are similar to models recently studied in atomic and mesoscopic physics. They provide a numerical confirmation of the fractal Weyl law for the density of quantum resonances of such systems. The exponent in that law is related to the dimension of the classical repeller (or trapped set) of the system. In a simplified model, a rigorous argument gives the full resonance spectrum, which satisfies the fractal Weyl law. For this model, we can also compute a quantity characterizing the fluctuations of conductance through the system, namely the shot noise power: the value we obtain is close to the prediction of random matrix theory.Comment: 60 pages, no figures (numerical results are shown in other references

Second-Kind integral solvers for TE and TM problems of diffraction by open-arcs

We present a novel approach for the numerical solution of problems of diffraction by open arcs in two dimensional space. Our methodology relies on composition of {\em weighted versions} of the classical integral operators associated with the Dirichlet and Neumann problems (TE and TM polarizations, respectively) together with a generalization to the open-arc case of the well known closed-surface Calder\'on formulae. When used in conjunction with spectrally accurate discretization rules and Krylov-subspace linear algebra solvers such as GMRES, the new second-kind TE and TM formulations for open arcs produce results of high accuracy in small numbers of iterations and short computing times---for low and high frequencies alike.Comment: 20 page