Synthesis, Molecular Structures and Electrochemical Investigations of [FeFe]-Hydrogenase Biomimics [Fe₂(CO)_{6-n}(EPh₃)_{n}(mu-edt)] (E = P, As, Sb; n = 1, 2)

A series of ethane‐dithiolate (edt = S(CH_{2})_{2}S) complexes [Fe_{2}(CO)_{5}(EPh_{3})(µ‐edt)] and [Fe_{2}(CO)4(EPh_{3})_{2}(µ‐edt)] (E = P, As, Sb), biomimics of the core of [FeFe]‐hydrogenases, have been prepared and structurally characterised. The introduced ligand(s) occupies apical sites lying trans to the iron‐iron bond. NMR studies reveal that while in the mono‐substituted complexes the Fe(CO)_{3} moiety undergoes facile trigonal rotation, the Fe(CO)2(PPh3) centres do not rotate on the NMR timescale. The reductive chemistry has been examined by cyclic voltammetry both in the presence and absence of CO and the observed behavior is found to be dependent upon the nature of the substituents. With L = CO or SbPh_{3} potential inversion is seen leading to a two‐electron reduction, while for others (L = PPh_{3}, AsPh_{3}) a quasi‐reversible one‐electron reduction is observed. Protonation studies reveal that [Fe_{2}(CO)_{5}(PPh_{3})(µ‐edt)] is only partially protonated by excess HBF_{4}·Et_{2}O, thus ruling complexes [Fe_{2}(CO)_{5}(EPh3)(µ‐edt)(µ‐H)]^{+} out as a catalytic intermediates, but [Fe_{2}(CO)_{4}(PPh_{3})_{2}(µ‐edt)] reacts readily with HBF_{4}·Et_{2}O to produce [Fe_{2}(CO)_{4}(PPh3)_{2}(µ‐edt)(µ‐H)]^{+}. While all new complexes are catalysts for the reduction of protons in MeCN, their poor stability and relatively high reduction potentials does not make them attractive in this respect

Beating noise with abstention in state estimation

We address the problem of estimating pure qubit states with non-ideal (noisy) measurements in the multiple-copy scenario, where the data consists of a number N of identically prepared qubits. We show that the average fidelity of the estimates can increase significantly if the estimation protocol allows for inconclusive answers, or abstentions. We present the optimal such protocol and compute its fidelity for a given probability of abstention. The improvement over standard estimation, without abstention, can be viewed as an effective noise reduction. These and other results are exemplified for small values of N. For asymptotically large N, we derive analytical expressions of the fidelity and the probability of abstention, and show that for a fixed fidelity gain the latter decreases with N at an exponential rate given by a Kulback-Leibler (relative) entropy. As a byproduct, we obtain an asymptotic expression in terms of this very entropy of the probability that a system of N qubits, all prepared in the same state, has a given total angular momentum. We also discuss an extreme situation where noise increases with N and where estimation with abstention provides a most significant improvement as compared to the standard approach

Diversity, competition, extinction: the ecophysics of language change

As early indicated by Charles Darwin, languages behave and change very much like living species. They display high diversity, differentiate in space and time, emerge and disappear. A large body of literature has explored the role of information exchanges and communicative constraints in groups of agents under selective scenarios. These models have been very helpful in providing a rationale on how complex forms of communication emerge under evolutionary pressures. However, other patterns of large-scale organization can be described using mathematical methods ignoring communicative traits. These approaches consider shorter time scales and have been developed by exploiting both theoretical ecology and statistical physics methods. The models are reviewed here and include extinction, invasion, origination, spatial organization, coexistence and diversity as key concepts and are very simple in their defining rules. Such simplicity is used in order to catch the most fundamental laws of organization and those universal ingredients responsible for qualitative traits. The similarities between observed and predicted patterns indicate that an ecological theory of language is emerging, supporting (on a quantitative basis) its ecological nature, although key differences are also present. Here we critically review some recent advances lying and outline their implications and limitations as well as open problems for future research.Comment: 17 Pages. A review on current models from statistical Physics and Theoretical Ecology applied to study language dynamic

Addressing Personal Barriers to Advance Care Planning: Qualitative Investigation of a Mindfulness-Based Intervention for Adults with Cancer and Their Family Caregivers

Objective Advance care planning (ACP) increases quality of life and satisfaction with care for those with cancer and their families, yet these important conversations often do not occur. Barriers include patients’ and families’ emotional responses to cancer, such as anxiety and sadness, which can lead to avoidance of discussing illness-related topics such as ACP. Interventions that address psychological barriers to ACP are needed. The purpose of this study was to explore the effects of a mindfulness intervention designed to cultivate patient and caregiver emotional and relational capacity to respond to the challenges of cancer with greater ease, potentially decreasing psychological barriers to ACP and enhancing ACP engagement. Method The Mindfully Optimizing Delivery of End-of-Life (MODEL) Care intervention provided 12 hours of experiential training to two cohorts of six to seven adults with advanced-stage cancer and their family caregivers (n = 13 dyads). Training included mindfulness practices, mindful communication skills development, and information about ACP. Patient and caregiver experiences of the MODEL Care program were assessed using semistructured interviews administered immediately postintervention and open-ended survey questions delivered immediately and at 4 weeks postintervention. Responses were analyzed using qualitative methods. Result Four salient themes were identified. Patients and caregivers reported the intervention (1) enhanced adaptive coping practices, (2) lowered emotional reactivity, (3) strengthened relationships, and (4) improved communication, including communication about their disease. Significance of results The MODEL Care intervention enhanced patient and caregiver capacity to respond to the emotional challenges that often accompany advanced cancer and decreased patient and caregiver psychological barriers to ACP

Mechanisms of glucosa hypersensitivity in ß-cells from normoglycemic, partially pancreatectomized mice

Increased beta-cell sensitivity to glucose precedes the loss of glucose-induced insulin secretion in diabetic animals. Changes at the level of beta-cell glucose sensor have been described in these situations, but it is not clear whether they fully account for the increased insulin secretion. Using a euglycemic-normolipidemic 60% pancreatectomized (60%-Px) mouse model, we have studied the ionic mechanisms responsible for increased beta-cell glucose sensitivity. Two weeks after Px (Px14 group), Px mice maintained normoglycemia with a reduced beta-cell mass (0.88 +/- 0.18 mg) compared with control mice (1.41 +/- 0.21 mg). At this stage, the dose-response curve for glucose-induced insulin release showed a significant displacement to the left (P < 0.001). Islets from the Px14 group showed oscillatory electrical activity and cytosolic Ca2+ ([Ca2+]i) oscillations in response to glucose concentrations of 5.6 mmol/l compared with islets from the control group at 11.1 mmol/l. All the above changes were fully reversible both in vitro (after 48-h culture of islets from the Px14 group) and in vivo (after regeneration of beta-cell mass in islets studied 60 days after Px). No significant differences in the input resistance and ATP inhibition of ATP-sensitive K+ (K(ATP)) channels were found between beta-cells from the Px14 and control groups. The dose-response curve for glucose-induced MTT (C,N-diphenyl-N''-4,5-dimethyl thiazol 2 yl tetrazolium bromide) reduction showed a significant displacement to the left in islets from the Px14 group (P < 0.001). These results indicate that increased glucose sensitivity in terms of insulin secretion and Ca2+ signaling was not due to intrinsic modifications of K(ATP) channel properties, and suggest that the changes are most likely to be found in the glucose metabolism

Topological reversibility and causality in feed-forward networks

Systems whose organization displays causal asymmetry constraints, from evolutionary trees to river basins or transport networks, can be often described in terms of directed paths (causal flows) on a discrete state space. Such a set of paths defines a feed-forward, acyclic network. A key problem associated with these systems involves characterizing their intrinsic degree of path reversibility: given an end node in the graph, what is the uncertainty of recovering the process backwards until the origin? Here we propose a novel concept, \textit{topological reversibility}, which rigorously weigths such uncertainty in path dependency quantified as the minimum amount of information required to successfully revert a causal path. Within the proposed framework we also analytically characterize limit cases for both topologically reversible and maximally entropic structures. The relevance of these measures within the context of evolutionary dynamics is highlighted.Comment: 9 pages, 3 figure

Nonlinear Jaynes-Cummings model of atom-field interaction

Interaction of a two-level atom with a single mode of electromagnetic field including Kerr nonlinearity for the field and intensity-dependent atom-field coupling is discussed. The Hamiltonian for the atom-field system is written in terms of the elements of a closed algebra, which has SU(1,1) and Heisenberg-Weyl algebras as limiting cases. Eigenstates and eigenvalues of the Hamiltonian are constructed. With the field being in a coherent state initially, the dynamical behaviour of atomic-inversion, field-statistics and uncertainties in the field quadratures are studied. The appearance of nonclassical features during the evolution of the field is shown. Further, we explore the overlap of initial and time-evolved field states.Comment: 14 pages, 6 figures is PS forma

Expansion history and f(R) modified gravity

We attempt to fit cosmological data using $f(R)$ modified Lagrangians containing inverse powers of the Ricci scalar varied with respect to the metric. While we can fit the supernova data well, we confirm the $a\propto t^{1/2}$ behaviour at medium to high redshifts reported elsewhere and argue that the easiest way to show that this class of models are inconsistent with the data is by considering the thickness of the last scattering surface. For the best fit parameters to the supernova data, the simplest 1/R model gives rise to a last scattering surface of thickness $\Delta z\sim 530$, inconsistent with observations.Comment: accepted in JCAP, presentation clarified, results and conclusions unchange