211 research outputs found

    Albert Camus and the Anticolonials: Why Camus Would Not Play the Zero Sum Game

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    In 1994, I returned from Paris to Hyde Park just in time to catch a lecture about Albert Camus that an esteemed colleague, the late Tony Judt, was giving at the University of Chicago. I was much younger then, eager to engage in debate, and I had just spent most of the past two years turning over the recently opened pages of Camus’ private papers in Paris and trolling through the private papers of other prominent French intellectuals, as well as newly declassified state archives for what was to become my first book, Uncivil War.2 I had also done dozens of interviews with Camus’ friends and fellow travelers (Jean Daniel, Germaine Tillion, Jean Pélégri, etc.), as well as old adversaries (including Françis Jeanson). To the person, out of the many dozens of interviews I conducted, when asked about Albert Camus everyone agreed that he had died well before his time, that he was a deeply admirable and humane writer, and that he had paid much too heavy of a price for efforts to achieve a peaceful solution to the bloody drama in Algeria. Moreover, when I conducted these interviews throughout the 1990s, every single interviewee I spoke with, including Claude Levi-Strauss, Pierre Bourdieu, and Jacques Vergės, also admitted that they had all modified their stances on Algerian nationalism and were far more critical of their unchecked anticolonialism having seen its failures in Algeria.3 Finally, they all agreed that Camus could not be understood without foregrounding Algeria and decolonization in any reading of him. Yet, what they said about Camus contrasted remarkably with Judt’s statements. I cannot remember what set me off, but I knew that I did not understand or agree with what Judt was saying about Albert Camus. Part of my objection to Judt’s broader work on French intellectuals was the contrast between his emphasis on the Second World War and the Cold War and my own emphasis on decolonization. To be sure, decolonization was then a new and emerging field, but, there was enough known to suggest that decolonization had transformed France and therefore Camus in fundamental and indisputable ways. Hence, decolonization’s role was not as minor as Judt had maintained. Legitimate and scholarly objections aside, I quite simply made a royal ass out of myself by criticizing him so publically (something I later deeply regretted). This essay is a kind of posthumous apology to my colleague, Tony Judt. My visceral over-reaction to Judt’s talk 20 years ago reflects a continuing Camus debate. Why do Albert Camus and decolonization, a distant historical figure on the one hand and an intricate historical process on the other, continue to ignite such spirited disagreement among friends and colleagues

    Phase controlled superconducting proximity effect probed by tunneling spectroscopy

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    Using a dual-mode STM-AFM microscope operating below 50mK we measured the Local Density of States (LDoS) along small normal wires connected at both ends to superconductors with different phases. We observe that a uniform minigap can develop in the whole normal wire and in the superconductors near the interfaces. The minigap depends periodically on the phase difference. The quasiclassical theory of superconductivity applied to a simplified 1D model geometry accounts well for the data.Comment: Accepted for publication in Physical Review Letter

    Tuning Energy Relaxation along Quantum Hall Channels

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    The chiral edge channels in the quantum Hall regime are considered ideal ballistic quantum channels, and have quantum information processing potentialities. Here, we demonstrate experimentally, at filling factor 2, the efficient tuning of the energy relaxation that limits quantum coherence and permits the return toward equilibrium. Energy relaxation along an edge channel is controllably enhanced by increasing its transmission toward a floating ohmic contact, in quantitative agreement with predictions. Moreover, by forming a closed inner edge channel loop, we freeze energy exchanges in the outer channel. This result also elucidates the inelastic mechanisms at work at filling factor 2, informing us in particular that those within the outer edge channel are negligible.Comment: 8 pages including supplementary materia

    Strong back-action of a linear circuit on a single electronic quantum channel

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    What are the quantum laws of electricity in mesoscopic circuits? This very fundamental question has also direct implications for the quantum engineering of nanoelectronic devices. Indeed, when a quantum coherent conductor is inserted into a circuit, its transport properties are modified. In particular, its conductance is reduced because of the circuit back-action. This phenomenon, called environmental Coulomb blockade, results from the granularity of charge transfers across the coherent conductor. Although extensively studied for a tunnel junction in a linear circuit, it is only fully understood for arbitrary short coherent conductors in the limit of small circuit impedances and small conductance reduction. Here, we investigate experimentally the strong back-action regime, with a conductance reduction of up to 90%. This is achieved by embedding a single quantum channel of tunable transmission in an adjustable on-chip circuit of impedance comparable to the resistance quantum RK=h/e2R_K=h/e^2 at microwave frequencies. The experiment reveals important deviations from calculations performed in the weak back-action framework, and matches with recent theoretical results. From these measurements, we propose a generalized expression for the conductance of an arbitrary quantum channel embedded in a linear circuit.Comment: 11 pages including supplementary information, to be published in Nature Physic

    Energy Relaxation in the Integer Quantum Hall Regime

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    We investigate the energy exchanges along an electronic quantum channel realized in the integer quantum Hall regime at filling factor νL=2\nu_L=2. One of the two edge channels is driven out-of-equilibrium and the resulting electronic energy distribution is measured in the outer channel, after several propagation lengths 0.8 μ0.8~\mum≤L≤30 μ\leq L\leq30~\mum. Whereas there are no discernable energy transfers toward thermalized states, we find efficient energy redistribution between the two channels without particle exchanges. At long distances L≥10 μL\geq10~\mum, the measured energy distribution is a hot Fermi function whose temperature is lower than expected for two interacting channels, which suggests the contribution of extra degrees of freedom. The observed short energy relaxation length challenges the usual description of quantum Hall excitations as quasiparticles localized in one edge channel.Comment: To be published in PRL, 10 pages including supplementary materia

    Quantum coherence engineering in the integer quantum Hall regime

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    We present an experiment where the quantum coherence in the edge states of the integer quantum Hall regime is tuned with a decoupling gate. The coherence length is determined by measuring the visibility of quantum interferences in a Mach-Zehnder interferometer as a function of temperature, in the quantum Hall regime at filling factor two. The temperature dependence of the coherence length can be varied by a factor of two. The strengthening of the phase coherence at finite temperature is shown to arise from a reduction of the coupling between co-propagating edge states. This opens the way for a strong improvement of the phase coherence of Quantum Hall systems. The decoupling gate also allows us to investigate how inter-edge state coupling influence the quantum interferences' dependence on the injection bias. We find that the finite bias visibility can be decomposed into two contributions: a Gaussian envelop which is surprisingly insensitive to the coupling, and a beating component which, on the contrary, is strongly affected by the coupling.Comment: 4 pages, 5 figure

    Antibunched photons emitted by a dc-biased Josephson junction

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    We show experimentally that a dc biased Josephson junction in series with a high-enough-impedance microwave resonator emits antibunched photons. Our resonator is made of a simple microfabricated spiral coil that resonates at 4.4 GHz and reaches a 1.97kΩ characteristic impedance. The second order correlation function of the power leaking out of the resonator drops down to 0.3 at zero delay, which demonstrates the antibunching of the photons emitted by the circuit at a rate of 6×10^7 photons per second. Results are found in quantitative agreement with our theoretical predictions. This simple scheme could offer an efficient and bright single-photon source in the microwave domain

    Impact of Memory Frequency Scaling on User-centric Smartphone Workloads

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    Improving battery life in mobile phones has become a top concern with the increase in memory and computing requirements of applications with tough quality-of-service needs. Many energy-efficient mobile solutions vary the CPU and GPU voltage/frequency to save power consumption. However, energy-aware control over the memory bus connecting the various on-chip subsystems has had much less interest. This measurement-based study first analyse the CPU, GPU and memory cost (i.e. product of utilisation and frequency) of user-centric smartphone workloads. The impact of memory frequency scaling on power consumption and quality-of-service is also measured. We also present a preliminary analysis into the frequency levels selected by the different default governors of the CPU/GPU/memory components.We show that an interdependency exists between the CPU and memory governors and that it may cause unnecessary increase in power consumption, due to interference with the CPU frequency governor. The observations made in this measurement-based study can also reveal some design insights to system designers

    Malaria control-two years' use of insecticide treated bednets compared with insecticide house spraying in KwaZulu-Natal

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    Objectives. The objective of this study was to produce data indicating whether insecticide-treated bednets should replaced insecticide house spraying as a malaria control method in South Africa. We report 2 years of preliminary data on malaria incidence comparing areas receiving insecticidetreated bednets and those subjected to house spraying in northern KwaZulu-Natal.Design, setting and subjects. In order to measure significant reductions in malaria incidence between the two interventions, a geographical information system (GIS) was used to identify and create seven pairs of geographical blocks (areas) in the malaria high-risk areas of Ndumu and Makanis in Ingwavuma magisterial district, KwaZulu-Natal. Individual blocks were then randomly allocated to either insecticide-treated bednets or house spraying with  deltamethrin. Malaria cases were either routinely recorded by surveillance agents at home or were reported to the nearest health facility.Results and conclusions. The results show that 2 years' use of insecticide-treated bednets by communities in Ndumu and Makanis, KwaZulu-Natal, significantly reduced the malaria incidence both in 1997 (rate ratio (RR) = 0.879, 95% confidence interval (CI) 0.80- 0.95, P = 0.04) and in 1998 (RR = 0.667, CI 0.61 - 0.72, P= 0.0001). Using a t-test, these significant reductions were further confirmed by an assessment of the rate of change between 1996 and 1998, showing a 16% reduction in malaria incidence in blocks using  treated bednets and an increase of 45% in sprayed areas (t =2.534, P = 0.026 (12 df)). In order to decide whether bednets should replace house spraying in South Africa, we need more data on the efficacy of treated bednets, their long-term acceptability and the cost of the two interventions

    Malaria control – two years' use of insecticide treated bednets compared with insecticide house spraying in Kwazulu-Natal

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    Objectives_ The objective of this study was to produce data indicating whether insecticide-treated bednets should replac insecticide house spraying as a malaria control method in South Africa_ We report 2 years of preliminary data on malaria incidence comparing areas receiving insecticidetreated bednets and those subjected to house spraying in northern KwaZulu-Natal.Design, setting and subjects. In order to measure significant reductions in malaria incidence between the two interventions, a geographical information system (GIS) was used to identify and create seven pairs of geographical blood ; (areas) in the malaria high-risk areas of Ndumu and Makani in Ingwavuma magisterial district, KwaZulu-Natal, Individual blocks were then randomly allocated to either insecticide-treated bednets or house spraying with deltamethrin. Malaria cases were either routinely recorded by surveillance agents at home or were reported to the nearest health facility_Results and conclusions. The results show that 2 years' use of insecticide-treated bednets by communities in Ndumu and Makanis, KwaZulu-Natal, significantly reduced the malaria incidence both in 1997 (rate ratio (RR) =0_879, 95% confidence interval (Cn 0.80 - 0.95, P =0.04) and in 1998 (RR = 0.667, Cl 0_61 - 0.72, P = 0.0001). Using a t-test, these significant reductions were further confirmed by an assessment of the rate of change between 1996 and 1998, showing a 16% reduction in malaria incidence in blocks using bednets and an increase of 45% in sprayed areas (t = 2.534, P = 0.026 (12 df». In order to decide whether bednets : should replace house spraying in South Africa, we need more : data on the efficacy of treated bednets, their long-term acceptability and the cost of the two interventions
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