Time series of the observational estimate of the Atlantic meridional overturning circulation (AMOC) have recently become available, but so far, no contemporaneous relation has been documented between ...them. Here, we analyze the variability of the 26°N Rapid Climate Change programme (RAPID) and the 41°N Argo‐based AMOC estimates on seasonal timescales, and we compare them to a simulation from a high‐resolution National Centers for Environmental Prediction (NCEP)‐forced ocean model. In our analysis of the observed time series, we find that the seasonal cycles of the non‐Ekman component of the AMOC between 26°N and 41°N are 180‐degrees out‐of‐phase. Removing the mean seasonal cycle from each time series, the residuals have a non‐stationary covariability. Our results demonstrate that the AMOC is meridionally covariable between 26°N and 41°N at seasonal timescales. We find the same covariability in the model, although the phasing differs from the observed phasing. This may offer the possibility of inferring AMOC variations and associated climate anomalies throughout the North Atlantic from discontinuous observations.
Key Points
First joint analysis of observed and modeled Atlantic overturning timeseries
Find meridional coherence at seasonal timescales
Find non‐stationary covariability after removing the mean seasonal cycle
To understand the origin of superconductivity, it is crucial to ascertain the nature and origin of the primary carriers available to participate in pairing. Recent quantum oscillation experiments on ...high-transition-temperature (high-Tc) copper oxide superconductors have revealed the existence of a Fermi surface akin to that in normal metals, comprising fermionic carriers that undergo orbital quantization. The unexpectedly small size of the observed carrier pocket, however, leaves open a variety of possibilities for the existence or form of any underlying magnetic order, and its relation to d-wave superconductivity. Here we report experiments on quantum oscillations in the magnetization (the de Haas-van Alphen effect) in superconducting YBa2Cu3O6.51 that reveal more than one carrier pocket. In particular, we find evidence for the existence of a much larger pocket of heavier mass carriers playing a thermodynamically dominant role in this hole-doped superconductor. Importantly, characteristics of the multiple pockets within this more complete Fermi surface impose constraints on the wavevector of any underlying order and the location of the carriers in momentum space. These constraints enable us to construct a possible density-wave model with spiral or related modulated magnetic order, consistent with experimental observations.
Recently, the niobium (Nb) doped topological insulator Bi2Se3, in which the finite magnetic moments of the Nb atoms are intercalated in the van der Waals gap between the Bi2Se3 layers, has been shown ...to exhibit both superconductivity with Tc ≃ 3 K and topological surface states. Here we report on muon spin rotation experiments probing the temperature and field dependence of effective magnetic penetration depth λeff (T) in the layered topological superconductor candidate Nb0.25Bi2Se3. The exponential temperature dependence of λ−2eff(T) at low temperatures suggests a fully gapped superconducting state in the bulk with the superconducting transition temperature Tc = 2.9 K and the gap to Tc ratio 2Δ/kBTc = 3.95 (19). We also reveal that the ratio Tc/λ−2eff is comparable to those of unconventional superconductors, which hints at an unconventional pairing mechanism. Furthermore, time-reversal symmetry breaking was excluded in the superconducting state with sensitive zero-field μSR experiments. We hope the present results will stimulate theoretical investigations to obtain a microscopic understanding of the relation between superconductivity and the topologically nontrivial electronic structure of Nb0.25Bi2Se3.
Non-steroidal anti-inflammatory drugs (NSAIDs) specifically inhibit cyclooxygenase (COX) activity and are widely used as anti-arthritics, post-surgical analgesics, and for the relief of acute ...musculoskeletal pain. Recent studies suggest that non-specific NSAIDs, which inhibit both COX-1 and COX-2 isoforms, delay bone healing. The objectives of this study were 2-fold; first, to measure the relative changes in the normal expression of COX-1 and COX-2 mRNAs over a 42 day period of fracture healing and second, to compare the effects of a commonly used non-specific NSAID, ketorolac, with a COX-2 specific NSAID, Parecoxib (a pro-drug of valdecoxib), on this process. Simple, closed, transverse fractures were generated in femora of male Sprague–Dawley rats weighing approximately 450 g each. Total RNA was prepared from the calluses obtained prior to fracture and at 1, 3, 5, 7, 10, 14, 21, 35 and 42 days post-fracture and levels of COX-1 and COX-2 mRNA were measured using real time PCR. While the relative levels of COX-1 mRNA remained constant over a 21-day period, COX-2 mRNA levels showed peak expression during the first 14 days of healing and returned to basal levels by day 21. Mechanical properties of the calluses were then assessed at 21 and 35 days post-fracture in untreated animals and animals treated with either ketorolac or high or low dose parecoxib. At both 21 and 35 days after fracture, calluses in the group treated with the ketorolac showed a significant reduction in mechanical strength and stiffness when compared with controls (
p<0.05). At the 21-day time point, calluses of the parecoxib treated animals showed a lower mean mechanical strength than controls, but the inhibition was not statistically significant. Based on physical analysis of the bones, 3 of 12 (25%) of the ketorolac-treated and 1 of 12 (8%) of the high dose parecoxib-treated animals showed failure to unite their fractures by 21 days, while all fractures in both groups showed union by 35 days. Histological analysis at 21 days showed that the calluses in the ketorolac-treated group contained substantial amounts of residual cartilage while neither the control nor the parecoxib-treated animals showed comparable amounts of cartilage at this stage. These results demonstrate that ketorolac and parecoxib delay fracture healing in this model, but in this study daily administration of ketorolac, a non-selective COX inhibitor had a greater affect on this process. They further demonstrate that a COX-2 selective NSAID, such as parecoxib (valdecoxib), has only a small effect on delaying fracture healing even at doses that are known to fully inhibit prostaglandin production.
We measure magnetic quantum oscillations in the underdoped cuprates YBa2Cu3O6+x with x=0.61, 0.69, using fields of up to 85 T. The quantum-oscillation frequencies and effective masses obtained ...suggest that the Fermi energy in the cuprates has a maximum at hole doping p approximately 0.11-0.12. On either side, the effective mass may diverge, possibly due to phase transitions associated with the T=0 limit of the metal-insulator crossover (low-p side), and the postulated topological transition from small to large Fermi surface close to optimal doping (high p side).
We present magnetization and magnetostriction studies of LaCoO3 in magnetic fields approaching 100 T. In contrast with expectations from single-ion models, the data reveal two distinct first-order ...transitions and well-defined magnetization plateaus. The magnetization at the higher plateau is only about half the saturation value expected for spin-1 Co3+ ions. These findings strongly suggest collective behavior induced by interactions between different electronic configurations of Co3+ ions. We propose a model that predicts crystalline spin textures and a cascade of four magnetic phase transitions at high fields, of which the first two account for the experimental data.
The adenine nucleotide translocase (ANT) of the mitochondrial inner membrane exchanges ADP for ATP. Mitochondria were isolated from human vastus lateralis muscle (n = 9). Carboxyatractyloside ...titration of O2 consumption rate (Jo) at clamped ADP of 21 μM gave ANT abundance of 0.97 ± 0.14 nmol ANT/mg and a flux control coefficient of 82% ± 6%. Flux control fell to 1% ± 1% at saturating (2 mM) ADP. The KmADP for Jo was 32.4 ± 1.8 μM. In terms of the free (−3) ADP anion this KmADP was 12.0 ± 0.7 μM. A novel luciferase-based assay for ATP production gave KmADP of 13.1 ± 1.9 μM in the absence of ATP competition. The free anion KmADP in this case was 2.0 ± 0.3 μM. Targeted proteomic analyses showed significant acetylation of ANT Lysine23 and that ANT1 was the most abundant isoform. Acetylation of Lysine23 correlated positively with KmADP, r = 0.74, P = 0.022. The findings underscore the central role played by ANT in the control of oxidative phosphorylation, particularly at the energy phosphate levels associated with low ATP demand. As predicted by molecular dynamic modeling, ANT Lysine23 acetylation decreased the apparent affinity of ADP for ANT binding.
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