53 research outputs found

    Co-design of an in-line holographic microscope with enhanced axial resolution: selective filtering digital holography

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    International audienceCommon-path digital in-line holography is considered as a valuable 3D diagnostic techniques for a wide range of applications. This configuration is cost effective and relatively immune to variation in the experimental environment. Nevertheless, due to its common-path geometry, the signal to noise-ratio of the acquired hologram is weak as most of the detector (i.e. CCD/CMOS sensor) dynamics is occupied by the reference field signal, whose energy is orders of magnitude higher than the field scattered by the imaged object. As it is intrinsically impossible to modify the ratio of energy of reference to the object field, we propose a co-design approach (Optics/Data Processing) to tackle this issue. The reference to object field ratio is adjusted by adding a 4-f device to a conventional in-line holographic setup , making it possible to reduce the weight of the reference field while keeping the object field almost constant. Theoretical analysis of the Cràmer-Rao lower bounds of the corresponding imaging model illustrate the advantages of this approach. These lower bounds can be asymptotically reached using a parametric inverse problems reconstruction. This implementation results in a 60 % gain in axial localization accuracy (for of 100 ”m diameter spherical objects) compared to a classical in-line holography setup

    Making subaltern shikaris: histories of the hunted in colonial central India

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    Academic histories of hunting or shikar in India have almost entirely focused on the sports hunting of British colonists and Indian royalty. This article attempts to balance this elite bias by focusing on the meaning of shikar in the construction of the Gond ‘tribal’ identity in late nineteenth and early twentieth-century colonial central India. Coining the term ‘subaltern shikaris’ to refer to the class of poor, rural hunters, typically ignored in this historiography, the article explores how the British managed to use hunting as a means of state penetration into central India’s forest interior, where they came to regard their Gond forest-dwelling subjects as essentially and eternally primitive hunting tribes. Subaltern shikaris were employed by elite sportsmen and were also paid to hunt in the colonial regime’s vermin eradication programme, which targeted tigers, wolves, bears and other species identified by the state as ‘dangerous beasts’. When offered economic incentives, forest dwellers usually willingly participated in new modes of hunting, even as impact on wildlife rapidly accelerated and became unsustainable. Yet as non-indigenous approaches to nature became normative, there was sometimes also resistance from Gond communities. As overkill accelerated, this led to exclusion of local peoples from natural resources, to their increasing incorporation into dominant political and economic systems, and to the eventual collapse of hunting as a livelihood. All of this raises the question: To what extent were subaltern subjects, like wildlife, ‘the hunted’ in colonial India

    Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

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    IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

    Auto-Ă©talonnage en microscopie sans lentille couleur.

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    International audienceLensless color microscopy (also called in-line digital color holography) is a recent quantitative 3D imaging method used in several areas including biomedical imaging and microfluidics. By targetting cost effective and compact designs, the wavelength of the low-end sources used is only imprecisely known, in particular because of their temperature and power supply voltage dependence. This imprecision is the source of biases during the reconstruction step. An additional source of error is the crosstalk phenomenon, i.e., the mixture in color sensors of signals originating from different color channels. We propose to use a parametric inverse problem approach to achieve the self-calibration of a digital color holographic setup. This process provides an estimation of the central wavelengths and of the crosstalk. We show that taking the crosstalk phenomenon into account in the reconstruction step improves its accuracy.La microscopie sans lentille couleur (Ă©galement appelĂ©e holographie numĂ©rique couleur en ligne) est une mĂ©thode d'imagerie 3D quantitative rĂ©cente utilisĂ©e dans plusieurs domaines, dont l'imagerie biomĂ©dicale et la microfluidique. Lorsqu'on s'intĂ©resse Ă  des conceptions bas coĂ»t et compactes, les longueurs d'ondes des sources utilisĂ©es ne sont pas connues prĂ©cisemment, notamment en raison de leur dĂ©pendance Ă  la tempĂ©rature et Ă  la tension d'alimentation. Cette imprĂ©cision est la source de biais lors de l'Ă©tape de reconstruction. Une source d'erreur supplĂ©mentaire qui peut ĂȘtre prĂ©sente dans ce type de montage, est le phĂ©nomĂšne de "cross talk", c'est-Ă -dire le mĂ©lange des signaux des diffĂ©rentes longueurs d'ondes sur les canaux RGB de la matrice de Bayer du capteur. Nous proposons d'utiliser une approche de type problĂšmes inverses paramĂ©trique pour rĂ©aliser un auto-Ă©talonnage de ce type de configuration holographique couleur bas coĂ»t. Cette approche fournit une estimation des longueurs d'ondes centrales des sources et du "cross-talk". Nous montrons que la prise en compte du phĂ©nomĂšne de "cross-talk" dans la phase de reconstruction amĂ©liore sa prĂ©cision
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