Impact of high ionizing dose on high-power white LEDs

National audienceVisible cameras operating at 1 MGy of g radiation require radiation tolerant illumination system. Here, commercially available high-power white LEDs have been tested under X and g radiations. The light power of white commercial LED was shown to slightly decrease (less than 10 %) in post irradiation measurements. A closer analysis, based on the ABC model for efficiency droop, reveals that irradiation essentially increases the amount of trap assisted recombination, impacting the LED quantum efficiency mostly at low supply voltage. This suggests that favoring the LED operation at higher supply voltage could be a good strategy to enhance the radiation hardness of LED-based illumination systems

Impact of high ionizing dose on high-power white LEDs

National audienceVisible cameras operating at 1 MGy of g radiation require radiation tolerant illumination system. Here, commercially available high-power white LEDs have been tested under X and g radiations. The light power of white commercial LED was shown to slightly decrease (less than 10 %) in post irradiation measurements. A closer analysis, based on the ABC model for efficiency droop, reveals that irradiation essentially increases the amount of trap assisted recombination, impacting the LED quantum efficiency mostly at low supply voltage. This suggests that favoring the LED operation at higher supply voltage could be a good strategy to enhance the radiation hardness of LED-based illumination systems

Impact of high ionizing dose on high-power white LEDs

National audienceVisible cameras operating at 1 MGy of g radiation require radiation tolerant illumination system. Here, commercially available high-power white LEDs have been tested under X and g radiations. The light power of white commercial LED was shown to slightly decrease (less than 10 %) in post irradiation measurements. A closer analysis, based on the ABC model for efficiency droop, reveals that irradiation essentially increases the amount of trap assisted recombination, impacting the LED quantum efficiency mostly at low supply voltage. This suggests that favoring the LED operation at higher supply voltage could be a good strategy to enhance the radiation hardness of LED-based illumination systems

Investigations of the MGy dose level radiation effects on the photometric budget of a radiation-hardened CMOS-based camera

International audienceWe studied the impact of ionizing radiation at high dose levels (megagray, MGy) on the photometric budget of a radiation-resistant complementary metal oxide semi-conductor (CMOS)-based camera. This is achieved by measuring the radiation-induced degradation of each subpart, namely its illumination system, its optical system, and its CMOS image sensor. The acquired experimental results allow performing a rather realistic simulation of the radiation effects at the system level. Thanks to appropriate mitigation techniques, limited image darkening and color change are obtained at MGy dose levels. The presented results confirm the feasibility of a CMOS-based camera able to resist to MGy dose level of ionizing radiations with an acceptable degradation of the image quality, opening the way to its implementation in the most challenging harsh environments

Discovery, production and modification of 5 novel lantibiotics using the promiscuous nisin modification machinery

To find the right conditions to isolate natively expressed antimicrobial peptides from a wide range of different microorganisms can be a challenge. Here, we exploited a heterologous expression system to produce and characterize several novel lantibiotics. We identified 55 novel putative class I and class II lantibiotics after inspecting all publicly available prokaryotic genomes using the in-house developed mining tool BAGEL3. The genes encoding these new lantibiotics fused to the nisin leader peptide gene sequence were synthesized and the constructs were plugged into the nisin expression and modification system. Using this approach 30 peptides could be expressed, 27 of which were dehydrated by NisBC on at least 1 predicted position. Good antimicrobial activity against several pathogenic bacteria could be demonstrated for 5 novel heterologously modified lantibiotics. Lantibiotics from Corynebacterium lipophiloflavum DSM 44291 and Streptococcus agalactiae ATCC 13813, named flavucin and agalacticin, respectively, were fully modified and displayed high antimicrobial activity. The efficiency of functional expression was significantly enhanced when we made use of the native nisin leader cleavage site, instead of an artificial factor Xa site. Thus, we describe an efficient way for heterologous production of active lantipeptides, facilitating a rapid identification of promising molecules

High glycemic variability: An underestimated determinant of stroke functional outcome following large vessel occlusion

Abstract Background and purpose Early glycemic variability (GV) in diabetic patients is a poor prognosis factor following cardiovascular events. However, its influence on the course of acute ischemic stroke (AIS) with large vessel occlusion remains unclear. We investigated the relationship between high GV during acute stroke and three-month functional outcome among patients treated with combined intravenous thrombolysis and endovascular therapy for large vessel occlusion. Methods A single-center retrospective analysis of AIS patients with proximal intracranial occlusion who underwent thrombolysis and mechanical thrombectomy between January 2015 and May 2017. Early GV was assessed using standard deviation (SD) of blood glucose levels for the first 24 hours. The main outcome was functional status at three months as defined by the modified Rankin scale (mRS). Secondary outcomes were change in NIHSS score from baseline to 24 hours and occurrence of severe hemorrhagic transformation. Multivariate logistic regression analyses including GV, admission glycemia and mean glycemia were performed. Results Among the 93 patients evaluated, 26 had early high GV (≥ 20.9 mg/dl). High GV was associated with poor functional outcome (OR = 8.00; 95%CI [1.34–47.89]; P = 0.02) unlike admission glycemia and mean glycemia (OR = 2.92; 95%CI [0.51–16.60]; P = 0.23 and OR = 0.36; 95%CI [0.05-2.6]; p = 0.31, respectively). High GV was not associated with NIHSS at 24 hours or hemorrhagic transformation. Conclusion Acute high GV contributes to poorer functional outcome following AIS related to large vessel occlusion and should be considered as a new target in acute stroke management

Radiation vulnerability of standard and radiation-hardened optical glasses at MGy dose: Towards the design of tolerant optical systems

International audienceFacing the need of cameras able to withstand high levels (MGy) of ionizing radiation and the limited set of radiation-hardened optical glasses available to manufacture the lenses of their optical systems (OS), we performed an evaluation of standard and radiation hardened glasses. One of our objectives was to understand if selecting only radiation hardened glasses is always the best choice to reduce OS radio-darkening that is the main radiation-induced macroscopic degradation. For this, we performed X-ray in situ measurements of the radiation-induced attenuation (RIA) up to 100 kGy(SiO2) for several Ce-doped glasses from SCHOTT. Their responses are compared to their Ce-free counterparts. Due to the strong intrinsic attenuation of radiation hardened glasses caused by the Ce-codoping at shorter wavelengths, we found nearly no advantage to use radiation-hardened glasses at doses below 1 kGy(SiO2). We also performed post-irradiation RIA measurements on 31 standard glasses irradiated up to 1 MGy (γ-rays). The outcome is that several standard glasses especially the ones with a low Abbe number and a high refractive index are sufficiently radiation tolerant in terms of RIA and can serve as promising alternative to rad-hard ones. The use of these glasses less affect the color rendering of OS and strongly reduce their costs

Radiation Hardness Comparison of CMOS Image Sensor Technologies at High Total Ionizing Dose Levels

International audienceThrough the comparison of several CMOS image sensor technologies (including partially pinned photodidiode), the influence of the manufacturing process on the radiation induced degradation is stated up to total ionizing doses of 1 MGy(SiO2)