Early macrophage response to obesity encompasses Interferon Regulatory Factor 5 regulated mitochondrial architecture remodelling

Adipose tissue macrophages (ATM) adapt to changes in their energetic microenvironment. Caloric excess, in a range from transient to diet-induced obesity, could result in the transition of ATMs from highly oxidative and protective to highly inflammatory and metabolically deleterious. Here, we demonstrate that Interferon Regulatory Factor 5 (IRF5) is a key regulator of macrophage oxidative capacity in response to caloric excess. ATMs from mice with genetic-deficiency of Irf5 are characterised by increased oxidative respiration and mitochondrial membrane potential. Transient inhibition of IRF5 activity leads to a similar respiratory phenotype as genomic deletion, and is reversible by reconstitution of IRF5 expression. We find that the highly oxidative nature of Irf5-deficient macrophages results from transcriptional de-repression of the mitochondrial matrix component Growth Hormone Inducible Transmembrane Protein (GHITM) gene. The Irf5-deficiency-associated high oxygen consumption could be alleviated by experimental suppression of Ghitm expression. ATMs and monocytes from patients with obesity or with type-2 diabetes retain the reciprocal regulatory relationship between Irf5 and Ghitm. Thus, our study provides insights into the mechanism of how the inflammatory transcription factor IRF5 controls physiological adaptation to diet-induced obesity via regulating mitochondrial architecture in macrophages.

Interferon Regulatory Factor 5 levels have been shown to increase in adipose tissue macrophages in diet-induced obesity. Here authors show that IRF5 transcriptionally represses the Growth Hormone Inducible Transmembrane Protein gene encoding a mitochondrial protein important for oxidative respiration in macrophages, thus driving the detrimental metabolic changes observed in obesity.

Femtosecond Resolution of the Nonballistic Electron Energy Transport in Warm Dense Copper

The ultrafast electron energy transport is investigated in laser-heated warm dense copper in a high flux regime (2.5±0.7×10^{13}  W/cm^{2} absorbed). The dynamics of the electron temperature is retrieved from femtosecond time-resolved x-ray absorption near-edge spectroscopy near the Cu L3 edge. A characteristic time of ∼1  ps is observed for the increase in the average temperature in a 100 nm thick sample. Data are well reproduced by two-temperature hydrodynamic simulations, which support energy transport dominated by thermal conduction rather than ballistic electrons.

Cardiac troponin I and BNP for predicting zero Agatston score in patients with diabetes mellitus

Funding Acknowledgements

Type of funding sources: None.

BACKGROUND

Coronary artery calcifications (CAC) scoring assessed by the Agatston score has shown an excellent prognostic value in large studies, particularly in diabetic patients, with a very low rate of cardiovascular events in patients with a zero Agatston score. Moreover, recent studies have suggested that high-sensitive cardiac troponin I (hs-cTnI) and brain natriuretic peptide (BNP) may be useful for detecting subclinical atherosclerosis, especially in diabetic patients. However, the link between hs-cTnI/BNP and the Agatston score has not been investigated in this population.

PURPOSE

The aim of this study was to investigate if hs-cTnI and BNP can bring additional value to predict zero Agatston score in patients with diabetes mellitus in addition to usual risk factors.

METHODS

Between 2015 and 2019, CAC score was prospectively performed in consecutive patients with diabetes mellitus with high cardiovascular risk. Patients with symptoms or known coronary artery disease were excluded. Within 24h from CT exam, peripheral blood samples were taken to measure hs-cTnI and BNP. The relationship between serum hs-cTnI/BNP concentrations and zero Agatston score was evaluated using univariate and multivariate binomial models. 77 variables have been used to build the model. The implication of hs-cTnI and BNP in this multivariate model was evaluated using nested models associated with Chi-squared test of independence.

RESULTS

A total of 844 patients with diabetes were enrolled (61 ± 7 years, 57% men, mean diabetes duration 18 years). In this population, 294 (35%) had a zero Agatston score, 253 (30%) an Agatston score from 1 to 100, 161 (19%) from 101 to 400, and 136 (16%) higher than 400. In univariate analysis, hs-cTnI and BNP concentrations were associated with a zero Agatston score (respectively OR, 2.63 [95% CI, 1.51-5.01]; p < 0.001 and OR, 1.09 [95% CI, 1.01-1.22]; p = 0.03). In multivariate analysis, hs-cTnI and BNP concentrations were associated with a zero Agatston score (respectively OR, 2.38 [95% CI, 1.51-4.76]; p = 0.009 and OR, 1.18 [95% CI, 1.07-1.32]; p = 0.001). Among the 77 variables, the multivariate model including age, gender, smoking, dyslipidaemia, duration of the diabetes, arterial hypertension, presence of diabetic neuropathy, hs-cTnI and BNP concentrations, significantly discriminated the zero Agatston score (AUC = 0.81; p < 0.001). The most discriminant threshold was ≤ 3ng/l for hs-cTnI and <17ng/l for BNP. In nested models, both hs-cTnI and BNP brought information to this multivariate model to predict a zero Agatston score (respectively p = 0.003 and p < 0.001 to the Chi-squared test). Moreover, removing hs-cTnI and BNP from the model results in a significant reduction in model performance (AUC = 0.79; p = 0.004).

CONCLUSIONS

Cardiac biomarkers hs-cTnI and BNP are associated with a zero Agatston score, which is correlated with a very low risk of cardiovascular events in asymptomatic patients with diabetes mellitus.

Abstract Figure. ROC curve to predict zero Agatston score

Hypercalcemia as a Biomarker of Poor Prognosis in Frail Elderly Patients with COVID-19

The objective of this cohort study was to determine whether hypercalcemia in early COVID-19 was associated with 3-month mortality in frail elderly patients. Circulating calcium and albumin concentrations at hospital admission and 3-month mortality were assessed in geriatric patients hospitalized for COVID-19 with normal-to-high calcium concentrations. Hypercalcemia was defined as corrected calcium >2.5mmol/L. Covariables were age, sex, functional abilities, malignancies, hypertension, cardiomyopathy, number of acute health issues, use antibiotics and respiratory treatments. In total, 94 participants (mean±SD 88.0±5.5years; 47.9% women; 22.3% hypercalcemia; 0% hypocalcemia) were included. Sixty-five participants who survived at 3months exhibited less often hypercalcemia at baseline than the others (13.9% versus 41.4%, P=0.003). Hypercalcemia was associated with 3-month mortality (fully-adjusted HR=3.03, P=0.009) with specificity=0.86 and sensitivity=0.41. Those with hypercalcemia had shorter survival time than those with normocalcemia (log-rank P=0.002). In conclusion, hypercalcemia was associated with poorer survival in hospitalized frail elderly COVID-19 patients.

Intubation decision criteria in adult epiglottitis

OBJECTIVES

To identify contributive criteria in decision-making for intubation in acute epiglottitis, based on clinical and endoscopic data in adult patients, and to study clinical and biological characteristics and management.

MATERIALS AND METHODS

Diagnosis was established by flexible endoscopy showing epiglottic edema in association with general signs of sepsis in 28 patients consulting into two French hospitals between 2005 and 2016. Retrospective univariate and multivariate analysis between patients managed by intubation (Group I) or surveillance (Group S) was performed on clinical and endoscopic data.

RESULTS

Ten patients were intubated (36%). On univariate analysis, 4 variables were suggestively associated with intubation. On multivariate analysis, associations remained suggestive for dyspnea (OR=50.6; 95% CI=[2.7; 940.1]) and supraglottic edema extension (OR=42.2; 95% CI=[2.2; 799.5]). The area under the curve identifying intubated patients on these 2 criteria was 90.8%, testifying to high discrimination.

CONCLUSION

Intubation must always be considered in epiglottitis. Dyspnea and supraglottic extension of the edema seem to be the two main criteria to be considered in airway control decision-making.

Nonlinear ionization dynamics of hot dense plasma observed in a laser-plasma amplifier

Understanding the behaviour of matter under conditions of extreme temperature, pressure, density and electromagnetic fields has profound effects on our understanding of cosmologic objects and the formation of the universe. Lacking direct access to such objects, our interpretation of observed data mainly relies on theoretical models. However, such models, which need to encompass nuclear physics, atomic physics and plasma physics over a huge dynamic range in the dimensions of energy and time, can only provide reliable information if we can benchmark them to experiments under well-defined laboratory conditions. Due to the plethora of effects occurring in this kind of highly excited matter, characterizing isolated dynamics or obtaining direct insight remains challenging. High-density plasmas are turbulent and opaque for radiation below the plasma frequency and allow only near-surface insight into ionization processes with visible wavelengths. Here, the output of a high-harmonic seeded laser-plasma amplifier using eight-fold ionized krypton as the gain medium operating at a 32.8 nm wavelength is ptychographically imaged. A complex-valued wavefront is observed in the extreme ultraviolet (XUV) beam with high resolution. Ab initio spatio-temporal Maxwell-Bloch simulations show excellent agreement with the experimental observations, revealing overionization of krypton in the plasma channel due to nonlinear laser-plasma interactions, successfully validating this four-dimensional multiscale model. This constitutes the first experimental observation of the laser ion abundance reshaping a laser-plasma amplifier. The presented approach shows the possibility of directly modelling light-plasma interactions in extreme conditions, such as those present during the early times of the universe, with direct experimental verification.

Two-Color Soft X-Ray Lasing in a High-Density Nickel-like Krypton Plasma

We report evidence of strong lasing on the 4p-4s transition at 62.7 nm in nickel-like krypton occurring simultaneously with the usual 4d-4p lasing at 32.8 nm. The gain dynamics of both transitions were experimentally and numerically investigated and found comparable. The two-color amplifier was seeded by the same harmonic pulse, therefore producing a short-duration coherent two-color soft x-ray laser pulse. Both transitions offer similar prospects of pulse energy and duration and could lead to the delivery of intense and ultrashort two-color coherent soft x-ray pulses with a controllable delay.

Tunable High Spatio-Spectral Purity Undulator Radiation from a Transported Laser Plasma Accelerated Electron Beam

Undulator based synchrotron light sources and Free Electron Lasers (FELs) are valuable modern probes of matter with high temporal and spatial resolution. Laser Plasma Accelerators (LPAs), delivering GeV electron beams in few centimeters, are good candidates for future compact light sources. However the barriers set by the large energy spread, divergence and shot-to-shot fluctuations require a specific transport line, to shape the electron beam phase space for achieving ultrashort undulator synchrotron radiation suitable for users and even for achieving FEL amplification. Proof-of-principle LPA based undulator emission, with strong electron focusing or transport, does not yet exhibit the full specific radiation properties. We report on the generation of undulator radiation with an LPA beam based manipulation in a dedicated transport line with versatile properties. After evidencing the specific spatio-spectral signature, we tune the resonant wavelength within 200-300 nm by modification of the electron beam energy and the undulator field. We achieve a wavelength stability of 2.6%. We demonstrate that we can control the spatio-spectral purity and spectral brightness by reducing the energy range inside the chicane. We have also observed the second harmonic emission of the undulator.

P2489What are the main determinants of an increase in bnp level in asymptomatic diabetic patients without known cardiac disease?

Background

Diabetes mellitus is associated with a high risk of heart failure. The predictors of futures heart failure events in diabetic patients are not clearly understood. BNP measurement can be used as a surrogate endpoint for the diagnosis of heart failure. We investigated the determinants of an increase in BNP level in a large cohort of asymptomatic diabetic patients without known cardiac disease

Methods

This prospective study included consecutive stable diabetic (type 1 or 2) patients coming for yearly check-up between March 2015 and July 2018 in the university center for the study of diabetes and its complications. Patients with an history of cardiac disease (coronary artery disease, atrial fibrillation, cardiomyopathy, previous heart failure ...) were excluded. All patients had a complete clinical exam, blood pressure measurement (3 consecutive times – mean of 2 lasts measurements), ECG, and blood sample including HbA1C, risk factors assessment, renal function (CKD-EPI) and BNP measurement. Data are presented as mean±SD or median - Spearman's rank and multivariate regression were used for analysis.

Results

3743 patients (mean age 57±14 y.o. – 57% male – 78% / 18% / 4% of type 2, type 1 or other type of diabetes respectively – Mean duration of diabetes 17 [1–63] y. – 44% treated with insulin) were studied. Mean±SD / median [min-max] BNP level was 25±39 / 12 [4–737] ng/L. BNP was <20 / 21–35 / 36–50 / 51–100 / 101–400 / >400 ng/L in 69 / 15 / 6 / 7 / 3 / 0.1% of the population respectively. The parameters most correlated with BNP level in type 1 and type 2 diabetes were age, duration of diabetes, renal function, HbA1C, and pulsed pressure. For multivariate analysis, renal function was removed of the model as it was highly correlated with age (r=−0.68). Multivariate analysis demonstrated that in type 1 diabetes, high BNP level was linked to age (p<0.001), pulsed pressure (p<0.001), duration of diabetes (p=0.003) and HbA1C (p=0.02). In type 2 diabetes, high BNP level was linked to age (p<0.0001), pulsed pressure (p<0.0001), duration of diabetes (p=0.005) but not HbA1C (p=0.09). Interestingly the type of treatment (mainly insulin treatment) was not independently related to an increase in BNP level.

Conclusion

Age, pulsed pressure and duration of diabetes are the main determinants of an increased level of BNP in asymptomatic diabetic patients without any history of cardiac disease. This result could help to select a population who could benefit to a more extensive follow up concerning heart failure.

The European Society of Paediatric Oncology Ependymoma-II program Core-Plus model: Development and initial implementation of a cognitive test protocol for an international brain tumour trial

It is increasingly accepted that survival alone is an inadequate measure of the success of childhood brain tumour treatments. Consequently, there is growing emphasis on capturing quality of survival. Ependymomas are the third most frequently occurring brain tumours in childhood and present significant clinical challenges. European Society of Paediatric Oncology Ependymoma II is a comprehensive international program aiming to evaluate outcomes under different treatment regimens and improve diagnostic accuracy. Importantly, there has been agreement to lower the age at which children with posterior fossa ependymoma undergo focal irradiation from three years to either eighteen months or one year of age. Hitherto radiotherapy in Europe had been reserved for children over three years due to concerns over adverse cognitive outcomes following irradiation of the developing brain. There is therefore a duty of care to include longitudinal cognitive follow-up and this has been agreed as an essential trial outcome. Discussions between representatives of 18 participating European countries over 10 years have yielded European consensus for an internationally accepted test battery for follow-up of childhood ependymoma survivors. The 'Core-Plus' model incorporates a two-tier approach to assessment by specifying core tests to establish a minimum dataset where resources are limited, whilst maintaining scope for comprehensive assessment where feasible. The challenges leading to the development of the Core-Plus model are presented alongside learning from the initial stages of the trial. We propose that this model could provide a solution for future international trials addressing both childhood brain tumours and other conditions associated with cognitive morbidity.

High-flux source of coherent XUV pulses for user applications

We present experimental results obtained at a user-oriented XUV beamline implemented at the ELI Beamlines facility. The coherent XUV radiation is produced via high harmonic generation in gases in a loose focusing geometry. The beamline is designed to be driven by 1 kHz, 100 mJ, 20 fs pulses centered at a wavelength of 830 nm. Results such as XUV spectra, beam wavefront and pulse energy obtained during the beamline commissioning with a commercial 1 kHz, 5 mJ, 40 fs laser system are presented. A unique XUV spectrometer for source characterization designed to reach a very high sensitivity is described in detail, and we demonstrate a novel technique for single-shot and every-shot XUV pulse energy measurement.

L'utilisation par la viticulture française d'un exercice de prospective pour l'élaboration d'une stratégie d'adaptation au changement climatique

Foresight studies are regularly conducted at sectoral or geographical scales, in order to help policy makers and economic actors to define their strategy of adaptation to climate change (CC).

Histoire et évolution des appellations d'origine françaises

During the 20th century, wine appellations of origin have largely developed to represent a significant part of the wine production of some countries, especially in Europe. The globalization of the production, trade and consumption of wine is a major fact of the 21st century economy. The question of appellations of origin and more generally geographical indications must be asked: Is it a survival 100 years after the first law on appellations of origin was adopted in France? Historical knowledge makes it possible to understand how law, both national and international, has been marked by major developments in this area. Regulations on the origin of products have undergone significant changes over the last century, extending well beyond the wine and spirits sector to cover many other sectors. In addition, international institutions are very involved in the development of this concept, be it the FAO in order to protect and sustainably develop agricultural products from emerging countries or whether it is WIPO or WTO in order to implement protection of signs of origin in the context of intellectual property. Since its creation in 1924 the OIV has been largely attentive to the issue of appellations of origin, in their different forms, (AOP, AOC) and according to the country. It continues to play an important role in reflecting and thinking about the role of legal norms in the globalized wine economy and international trade. A symposium organized in Dijon in May 2019, has commemorated and evoked the centenary of the concept of the appellation of origin in France, bringing together speakers from several disciplines, including historians and jurists, on this theme of the appellation of 'origin. The proposed communication present the main orientations identified during this conference, and in particular the strengths and weaknesses of this concept vis-à-vis the theme of international protection.

Detection of in vivo hepatitis B virus surface antigen mutations-A comparison of four routine screening assays

An important requirement for a state-of-the-art hepatitis B surface antigen (HBsAg) screening assay is reliable detection of mutated HBsAg. Currently, there is a striking shortage of data regarding the detection rates of in vivo HBsAg mutations for these clinically important assays. Therefore, we compared the detection rates of four commercial HBsAg screening assays using a global cohort of 1553 patients from four continents with known HBV genotypes. These samples, which represent the broadest spectrum of known and novel HBsAg major hydrophilic region (MHR) mutations to date, were analyzed for the presence of HBsAg using the Roche Elecsys^® HBsAg II Qualitative, Siemens ADVIA Centaur XP HBsAg II, Abbott Architect HBsAg Qualitative II and DiaSorin Liaison^® HBsAg Qualitative assays, respectively. Of the 1553 samples, 1391 samples could be sequenced; of these, 1013 (72.8%) carried at least one of the 345 currently known amino acid substitutions (distinct HBsAg mutation) in the HBsAg MHR. All 1553 patient samples were positive for HBsAg using the Elecsys^® HBsAg II Qual assay, with a sensitivity (95% confidence interval) of 99.94% (99.64%-100%), followed by the Abbott Architect 99.81% (99.44%-99.96%), Siemens ADVIA 99.81% (99.44%-99.96%) and DiaSorin Liaison^® 99.36% (98.82%-99.69%) assays, respectively. Our results indicate that the Elecsys^® HBsAg II Qual assay exhibits the highest sensitivity among the commercial HBsAg screening assays, and demonstrate that its capacity to detect HBV infection is not compromised by HBsAg MHR mutants.

Ketosis-prone atypical diabetes in Cameroonian people with hyperglycaemic crisis: frequency, clinical and metabolic phenotypes

AIM

It is unclear whether ketosis-prone diabetes is a specific type or a subtype of Type 2 diabetes. We aimed to describe the clinical and metabolic features of ketosis-prone diabetes in a sub-Saharan population.

METHODS

We consecutively enrolled and characterized 173 people with non-autoimmune diabetes admitted for hyperglycaemic crisis at the Yaoundé Central Hospital, Cameroon. Blood samples were collected for fasting glucose, HbA_1c , lipid profile and C-peptide assays with insulin resistance and secretion estimation by homeostasis model assessment. People were classified as having Type 2 diabetes (n = 124) or ketosis-prone diabetes (n = 49). Ketosis-prone diabetes was sub-classified as new-onset ketotic phase (n = 34) or non-ketotic phase (n = 15).

RESULTS

Ketosis-prone diabetes was found in 28.3% of the hyperglycaemic crises. Age at diabetes diagnosis was comparable in Type 2 and ketosis-prone diabetes [48 ± 14 vs 47 ± 11 years; P = 0.13] with a similar sex distribution. Overall BMI was 27.7 ± 13.4 kg/m² and was ≥ 25 kg/m² in 55.8% of those taking part, however, 73.5% of those with ketosis-prone diabetes reported weight loss of > 5% at diagnosis. Blood pressure and lipid profile were comparable in both types. Ketosis-prone diabetes in the ketotic phase was characterized by lower insulin secretion and higher serum triglycerides compared with non-ketotic ketosis prone and Type 2 diabetes. Type 2 and ketosis prone diabetes in the non-ketotic phase were comparable in terms of lipid profile, blood pressure, waist-to-hip ratio, BMI and fat mass, insulin secretion and insulin resistance indices.

CONCLUSIONS

Ketosis-prone diabetes is likely to be a subtype of Type 2 diabetes with the potential to develop acute insulinopenic episodes.

Vitamin D and the Mechanisms, Circumstances and Consequences of Falls in Older Adults: A Case-Control Study

OBJECTIVES

To determine i) whether cases of elderly fallers had lower serum 25-hydroxyvitamin D (25OHD) concentration than controls without history of falls; and ii) whether serum 25OHD concentration was associated with specific mechanisms, circumstances and consequences of falls.

DESIGN

Case-control study with a 1:2 ratio.

SETTING

Geriatric ward of the University Hospital of Angers, France, between February 2012 and March 2014.

PARTICIPANTS

216 inpatients (72 cases and 144 age- and gender-matched controls).

MEASUREMENT

Falls were defined as involuntary events causing the person to the ground or other lower level. The main mechanisms, circumstances and consequences of falls were identified using standardized questionnaires. Vitamin D deficiency was defined as serum 25OHD concentration ≤25nmol/L. Age, gender, body mass index, polypharmacy, use antihypertensive drugs, use psychoactive drugs, disability, cognitive performance, serum concentrations of parathyroid hormone, creatinine and albumin, and season of evaluation were used as potential confounders.

RESULTS

216 participants (72 cases and 144 controls) were included in the study. There was no between-group difference in the prevalence of vitamin D deficiency (P=0.176). After adjusting for confounding factors, vitamin D deficiency was positively associated with falls (OR=4.03, P=0.014). Finally, the fallers with vitamin D deficiency exhibited more often orthostatic hypotension (68.8% against 33.3%, P=0.039) and a history of recurrent falls (85% against 50%, P=0.002) than those without vitamin D deficiency.

CONCLUSION

This case-control study reported that vitamin D deficiency was associated with falls in older inpatients. There was a greater prevalence of orthostatic hypotension and of the reccurrence of falls among fallers with vitamin D deficiency, suggesting that vitamin D may influence the conditions predisposing to falls rather than the fall by itself.

Triggering signaling pathways using F-actin self-organization

The spatiotemporal organization of proteins within cells is essential for cell fate behavior. Although it is known that the cytoskeleton is vital for numerous cellular functions, it remains unclear how cytoskeletal activity can shape and control signaling pathways in space and time throughout the cell cytoplasm. Here we show that F-actin self-organization can trigger signaling pathways by engineering two novel properties of the microfilament self-organization: (1) the confinement of signaling proteins and (2) their scaffolding along actin polymers. Using in vitro reconstitutions of cellular functions, we found that both the confinement of nanoparticle-based signaling platforms powered by F-actin contractility and the scaffolding of engineered signaling proteins along actin microfilaments can drive a signaling switch. Using Ran-dependent microtubule nucleation, we found that F-actin dynamics promotes the robust assembly of microtubules. Our in vitro assay is a first step towards the development of novel bottom-up strategies to decipher the interplay between cytoskeleton spatial organization and signaling pathway activity.

3D printing of gas jet nozzles for laser-plasma accelerators

Recent results on laser wakefield acceleration in tailored plasma channels have underlined the importance of controlling the density profile of the gas target. In particular, it was reported that the appropriate density tailoring can result in improved injection, acceleration, and collimation of laser-accelerated electron beams. To achieve such profiles, innovative target designs are required. For this purpose, we have reviewed the usage of additive layer manufacturing, commonly known as 3D printing, in order to produce gas jet nozzles. Notably we have compared the performance of two industry standard techniques, namely, selective laser sintering (SLS) and stereolithography (SLA). Furthermore we have used the common fused deposition modeling to reproduce basic gas jet designs and used SLA and SLS for more sophisticated nozzle designs. The nozzles are characterized interferometrically and used for electron acceleration experiments with the Salle Jaune terawatt laser at Laboratoire d'Optique Appliquée.

Which oral antidiabetic drug to combine with metformin to minimize the risk of hypoglycemia when initiating basal insulin?: A randomized controlled trial of a DPP4 inhibitor versus insulin secretagogues

We conducted a pilot study to evaluate two therapeutic strategies at the time of insulin initiation in type 2 diabetic patients insufficiently controlled with metformin+insulin-secretagogues (IS, sulfonylureas or glinides). Patients were randomized to remain under the same dual therapy or to receive metformin+DPP4 inhibitors while starting insulin. Similar glycemic control was achieved in both groups. However less hypoglycemia was observed with DPP4 inhibitors despite higher doses of insulin.

Shock assisted ionization injection in laser-plasma accelerators

Ionization injection is a simple and efficient method to trap an electron beam in a laser plasma accelerator. Yet, because of a long injection length, this injection technique leads generally to the production of large energy spread electron beams. Here, we propose to use a shock front transition to localize the injection. Experimental results show that the energy spread can be reduced down to 10 MeV and that the beam energy can be tuned by varying the position of the shock. This simple technique leads to very stable and reliable injection even for modest laser energy. It should therefore become a unique tool for the development of laser-plasma accelerators.

Demonstration of a Circularly Polarized Plasma-Based Soft-X-Ray Laser

We report the first experimental demonstration of a laser-driven circularly polarized soft-x-ray laser chain. It has been achieved by seeding a 32.8 nm Kr ix plasma amplifier with a high-order harmonic beam, which has been circularly polarized using a four-reflector polarizer. Our measurements testify that the amplified radiation maintains the initial polarization of the seed pulse in good agreement with our Maxwell-Bloch modeling. The resulting fully circular soft-x-ray laser beam exhibits a Gaussian profile and yields about 10^{10} photons per shot, fulfilling the requirements for laboratory-scale photon-demanding application experiments.

Spatial properties of odd and even low order harmonics generated in gas

High harmonic generation in gases is developing rapidly as a soft X-ray femtosecond light-source for applications. This requires control over all the harmonics characteristics and in particular, spatial properties have to be kept very good. In previous literature, measurements have always included several harmonics contrary to applications, especially spectroscopic applications, which usually require a single harmonic. To fill this gap, we present here for the first time a detailed study of completely isolated harmonics. The contribution of the surrounding harmonics has been totally suppressed using interferential filtering which is available for low harmonic orders. In addition, this allows to clearly identify behaviors of standard odd orders from even orders obtained by frequency-mixing of a fundamental laser and of its second harmonic. Comparisons of the spatial intensity profiles, of the spatial coherence and of the wavefront aberration level of 5ω at 160 nm and 6ω at 135 nm have then been performed. We have established that the fundamental laser beam aberrations can cause the appearance of a non-homogenous donut-shape in the 6ω spatial intensity distribution. This undesirable effect can be easily controlled. We finally conclude that the spatial quality of an even harmonic can be as excellent as in standard generation.

Engineering spatial gradients of signaling proteins using magnetic nanoparticles

Intracellular biochemical reactions are often localized in space and time, inducing gradients of enzymatic activity that may play decisive roles in determining cell's fate and functions. However, the techniques available to examine such enzymatic gradients of activity remain limited. Here, we propose a new method to engineer a spatial gradient of signaling protein concentration within Xenopus egg extracts using superparamagnetic nanoparticles. We show that, upon the application of a magnetic field, a concentration gradient of nanoparticles with a tunable length extension is established within confined egg extracts. We then conjugate the nanoparticles to RanGTP, a small G-protein controlling microtubule assembly. We found that the generation of an artificial gradient of Ran-nanoparticles modifies the spatial positioning of microtubule assemblies. Furthermore, the spatial control of the level of Ran concentration allows us to correlate the local fold increase in Ran-nanoparticle concentration with the spatial positioning of the microtubule-asters. Our assay provides a bottom-up approach to examine the minimum ingredients generating polarization and symmetry breaking within cells. More generally, these results show how magnetic nanoparticles and magnetogenetic tools can be used to control the spatiotemporal dynamics of signaling pathways.

Design strategies of hybrid metallic nanoparticles for theragnostic applications

Metallic nanoparticles (MNPs) such as iron oxide and gold nanoparticles are interesting platforms to build theragnostic nanocarriers which combine both therapeutic and diagnostic functions within a single nanostructure. Nevertheless, their surface must be functionalized to be suitable for in vivo applications. Surface functionalization also provides binding sites for targeting ligands, and for drug loading. This review focuses on the materials and surface chemistry used to build hybrid nanocarriers that are inorganic cores functionalized with organic materials. The surface state of the MNPs largely depends on their synthesis routes, and dictates the strategies used for functionalization. Two main strategies can be found in the literature: the design of core-shell nanosystems, or embedding nanoparticles in organic materials. Emerging tendencies such as the use of clusters or alternative coating materials are also described. To present both hydrophilic and lipophilic nanosystems, we chose the doxorubicin anticancer agent as an example, as the molecule presents an affinity for both types of materials.

A low membrane lipid phase transition temperature is associated with a high cryotolerance of Lactobacillus delbrueckii subspecies bulgaricus CFL1

The mechanisms of cellular damage that lactic acid bacteria incur during freeze-thaw processes have not been elucidated to date. Fourier transform infrared spectroscopy was used to investigate in situ the lipid phase transition behavior of the membrane of Lactobacillus delbrueckii ssp. bulgaricus CFL1 cells during the freeze-thaw process. Our objective was to relate the lipid membrane behavior to membrane integrity losses during freezing and to cell-freezing resistance. Cells were produced by using 2 different culture media: de Man, Rogosa, and Sharpe (MRS) broth (complex medium) or mild whey-based medium (minimal medium commonly used in the dairy industry), to obtain different membrane lipid compositions corresponding to different recovery rates of cell viability and functionality after freezing. The lipid membrane behavior studied by Fourier transform infrared spectroscopy was found to be different according to the cell lipid composition and cryotolerance. Freeze-resistant cells, exhibiting a higher content of unsaturated and cyclic fatty acids, presented a lower lipid phase transition temperature (Ts) during freezing (Ts=-8°C), occurring within the same temperature range as the ice nucleation, than freeze-sensitive cells (Ts=+22°C). A subzero value of lipid phase transition allowed the maintenance of the cell membrane in a relatively fluid state during freezing, thus facilitating water flux from the cell and the concomitant volume reduction following ice formation in the extracellular medium. In addition, the lipid phase transition of freeze-resistant cells occurred within a short temperature range, which could be ascribed to a reduced number of fatty acids, representing more than 80% of the total. This short lipid phase transition could be associated with a limited phenomenon of lateral phase separation and membrane permeabilization. This work highlights that membrane phase transitions occurring during freeze-thawing play a fundamental role in the cryotolerance of Lb. delbrueckii ssp. bulgaricus CFL1 cells.

Impact of wave front and coherence optimization in coherent diffractive imaging

We present single shot nanoscale imaging using a table-top femtosecond soft X-ray laser harmonic source at a wavelength of 32 nm. We show that the phase retrieval process in coherent diffractive imaging critically depends on beam quality. Coherence and image fidelity are measured from single-shot coherent diffraction patterns of isolated nano-patterned slits. Impact of flux, wave front and coherence of the soft X-ray beam on the phase retrieval process and the image quality are discussed. After beam improvements, a final image reconstruction is presented with a spatial resolution of 78 nm (half period) in a single 20 fs laser harmonic shot.