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Nihil humanum alienum estBaruch Spinoza Sorte de Bildungsroman sociologico-pugilistique qui retrace une expérience personnelle d’initiation à un métier du corps aussi reconnu pour sa symbolique héroïque – Mohammed Ali est sans nul doute, avant même Pelé, l’homme vivant le plus célèbre et célébré de la planète – qu’il est méconnu dans sa réalité prosaïque, ce livre est aussi une expérimentation scientifique. Il voudrait offrir une démonstration en actes de la fécondité d’une approche qui prend...
We present a quantitative, near-term experimental blueprint for the quantum simulation of topological insulators using lattice-trapped ultracold polar molecules. In particular, we focus on the so-called Hopf insulator, which represents a three-dimensional topological state of matter existing outside the conventional tenfold way and crystalline-symmetry-based classifications of topological insulators. Its topology is protected by a linking number invariant, which necessitates long-range spin-orbit-coupled hoppings for its realization. While these ingredients have so far precluded its realization in solid-state systems and other quantum simulation architectures, in an accompanying Letter [T. Schuster et al., Phys. Rev. Lett. 127, 015301 (2021)], we predict that Hopf insulators can arise naturally from the dipolar interaction. Here, we investigate a specific polar molecule architecture, where the effective “spin” is formed from sublattice degrees of freedom. We introduce two techniques that allow one to optimize dipolar Hopf insulators with large band gaps, and which should also be readily applicable to the simulation of other exotic band structures. First, we describe the use of Floquet engineering to control the range and functional form of dipolar hoppings and, second, we demonstrate that molecular AC polarizabilities (under circularly polarized light) can be used to precisely tune the resonance condition between different rotational states. To verify that this latter technique is amenable to current-generation experiments, we calculate, from first principles, the AC polarizability for σ+ light for 40K 87Rb. Finally, we show that experiments are capable of detecting the unconventional topology of the Hopf insulator by varying the termination of the lattice at its edges, which gives rise to three distinct classes of edge mode spectra.
To the degree that physician commitment is possible, systems should appeal to physicians' calculative motivations using extrinsic rewards rather than normative involvement in the organization.
Reforming the international monetary system is a game that any number can play. The second half of the 19 th century saw a series of international monetary conferences designed to place the leading European countries on a common monetary standard. The 1920s saw the Brussels and Genoa Conferences. 1944 saw Bretton Woods. 1967 saw the creation of Special Drawing Rights, which US Treasury Secretary Henry Fowler hailed as “the most ambitious and significant effort in the area of international monetary affairs since Bretton Woods.” 1968 saw the creation of the two-tier gold market, which President Johnson welcomed as “the most significant reforms of the international monetary system since Bretton Woods.” 1971 saw the Smithsonian Agreement, which President Nixon lauded as “the most significant monetary achievement in the history of the world.” The point being, of course, that none of these international agreements fundamentally changed the trajectory of the international system. The most striking feature of the international monetary system from an historical perspective is continuity rather than change. Over this period the international system evolved from a gold standard to a gold exchange standard, to a gold-dollar standard, and then to a dollar standard. It is evolving now into a multiple reserve currency system. International monetary conferences and official initiatives can influence the system at the margin, both for better or for worse, but the “actually existing system” (to invoke language derived from a very different context) reflects a powerful underlying market logic. It is the thesis of this paper that a multiple reserve currency system is coming. The system for which we need to prepare is one in which the dollar, the euro and the renminbi will all be consequential international and reserve currencies. The international monetary system is growing more multipolar because the world economy is growing more multipolar. After World War II, when the United States (US) accounted for the majority of the industrial production of the non-Soviet world, it made sense that the dollar was the principal unit in which exporters and importers invoiced and settled their trade, in which international loans were extended, and in which central banks held their reserves. But this situation makes less sense today when the US accounts for only some 20 per cent of the combined output of countries engaged in international transactions. Because habits die hard, the dollar continues to play a disproportionately important role. But simply because this is true today does not mean that it will be true tomorrow. Countries that trade with and borrow from the euro area will increasingly seek to hold euros as reserves. Countries that trade with and borrow from the PRC will similarly seek to hold renminbi, if not today then in the not-too-distant future.
Linear oligophenylene diynes containing 6, 9, and 12 phenylene rings were synthesized in high yields using the nucleophilic aromatic substitution (S(N)Ar) of perfluoroarenes by aryllithium reagents as the key carbon-carbon bond-forming reaction. This reaction was demonstrated to proceed readily at low temperatures with sterically hindered substrates and in the presence of base-sensitive silylalkynyl groups. Diynes synthesized by this methodology were readily zirconocene-coupled into large dimeric macrocycles using the zirconocene reagent Cp(2)Zr(py)(Me(3)SiC triple bond CSiMe(3)).
Abstract The crosslinking chemistry of a new elastomer based on brominated poly(isobutylene‐co‐4‐methylstyrene) has been investigated using model compounds. In order to mimic the conditions that prevail within the highly allphatic rubber, the study was carried out in mineral oil using catalysts that are compatible with such low polarity media. Electrophilic aromatic substitution reactions occur in a system consisting of p ‐isopropylbenzyl bromide and p ‐isopropyl toluene in the presence of zinc oxide and zinc stearate. The reaction proceeds after a significant induction period while no induction period is seen for a similar reaction with zinc bromide as the catalyst. The in situ formation of reactive species containing ZnBr bonds appears to be an important step in the overall process. The stoichiometric ratio of zinc salt to benzylic bromide is important. High ratios lead to the accumulation of benzylic stearate or benzylic alcohol in the system which retards the alkylation reaction. The model study emphasizes the importance of stoichiometry of reagents in this reaction and provides insight into the crosslinking mechanism. © 1993 John Wiley & Sons, Inc.
Copper is all bound up: The copper-catalyzed α-arylation of carbonyl compounds occurs through oxidative addition of iodoarenes to the C-bound CuI enolate species 1 to form an aryl–CuIII intermediate (see scheme). Computational results provide insight into the origins of the relative reactivity of various CuI enolate complexes in the reactions with iodoarenes. Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
Recent research indicates that multi-hop wireless networks can suffer from extreme imbalances in the throughput achieved by simultaneous competing flows. We address this problem by designing a practical distributed algorithm to compute a time-slot based schedule that provides end-to-end max-min fairness. Our system uses randomized priorities based on local weights to arbitrate access between nodes that directly compete with each other (we call this weighted slot allocation or WSA). The local weights are in turn computed by a higher layer called end-to-end fairness using local weights (EFLoW). EFLoW implements an additive-increase multiplicative-decrease (AIMD) algorithm that can automatically adapt to changes in traffic demands and network conditions. In each iteration, EFLoW only uses state obtained from within a given node's contention region. We have implemented WSA and EFLoW in both a simulator and a real system by using the overlay MAC layer (OML). Unlike previous work on end-to-end fairness, our approach does not use a centralized coordinator and works for traffic patterns with any number of sources and sinks. Also, since we compute both the fair allocation and a schedule to achieve it, we do not make any assumptions about the efficiency of carrier-sense (CS) based MACs - this is very important in the light of recent work which shows that current CS-based MACs can be very unfair even when all nodes are limited to sending at their fair rate. Our results show that WSA and EFLoW can prevent starvation of flows and improve fairness without sacrificing efficiency for a wide variety of traffic patterns.
