Simulation of laser-induced ionization in wide bandgap solid dielectrics with a particle-in-cell code.

Modeling the laser-plasma interaction within solids is crucial in controlling ultrafast laser processing of dielectrics, where the pulse propagation and plasma formation dynamics are highly intricate. This is especially important when dealing with nano-scale plasmas where specific phenomena of plasma physics, such as resonance absorption, can significantly impact the energy deposition process. In this article, we report on adapting of a Particle-In-Cell code, EPOCH, to model the laser-plasma interaction within solids. This is performed by implementing a background permittivity and by developing and validating adapted field ionization and impact ionization modules. They are based on the Keldysh ionization theory and enable the modeling of ionization processes within solids. The implementation of these modules was validated through comparisons with a hydrodynamic code and existing literature. We investigate the necessary number of super-particles per cell to model realistic ionization dynamics. Finally, we apply the code to explore the dynamics of plasma formation in the regime of of quantized structuring of transparent films. Our study elucidates how a stack of nano-plasma layers can be formed by the interference of a pulse with its reflection on the exit surface of a high refractive index material.

Mathematical modeling of exercise fatigability in the severe domain: A unifying integrative framework in isokinetic condition.

Muscle fatigue is the decay in the ability of muscles to generate force, and results from neural and metabolic perturbations. This article presents an integrative mathematical model that describes the decrease in maximal force capacity (i.e. fatigue) over exercises performed at intensities above the critical force Fc (i.e. severe domain). The model unifies the previous Critical Power Model and All-Out Model and can be applied to any exercise described by a changing force F over time. The assumptions of the model are (i) isokinetic conditions, an intensity domain of Fc

Multidisciplinary analysis of cancer-related fatigue at the time of diagnosis: preliminary results of the BIOCARE FActory cohort.

PURPOSE: Cancer-related fatigue (CRF) is a common side effect of cancer and cancer treatment that significantly impairs the quality of life and can persist for years after treatment completion. Although fatigue is often associated with cancer treatment, it is also a result of the disease itself, even before intervention. CRF at the time of diagnosis may affect treatment timing or completion and is a consistent predictor of post-treatment fatigue at any time. The mechanisms underlying CRF are multidimensional and not well understood, particularly at the time of diagnosis. METHODS: Sixty-five breast cancer patients at the time of diagnosis were included. The participants completed self-assessment questionnaires about CRF, sleep disturbances, and emotional symptoms and wore an accelerometer to assess levels of spontaneous physical activity and sleep quality. During the experimental session, the participants underwent cognitive, neuromuscular, and exercise metabolism evaluations. RESULTS: Using augmented backward elimination regression, this study found that emotional symptoms and perceived sleep disturbances were the strongest predictors of CRF (adjusted r2 = 0.51). Neuromuscular fatigability and sleep disturbance were also associated with physical dimensions, whereas cognitive performance was associated with cognitive dimensions. CONCLUSION: At the time of diagnosis, emotional and cognitive dimensions are over-represented compared to the general population, and specific subdimensions have specific predictors that support the idea of distinct mechanisms. Evaluating CRF subdimensions and their potential mechanisms at the time of diagnosis would be particularly relevant for identifying high-risk patients and offering them appropriate interventions. TRIAL REGISTRATION: This study was registered at ClinicalTrials.gov (NCT04391543) in May, 2020.

Comparison of neuromuscular fatigability amplitude and etiologies between fatigued and non-fatigued cancer patients.

PURPOSE: Cancer-related fatigue (CRF) is the most reported side effect of cancer and its treatments. Mechanisms of CRF are multidimensional, including neuromuscular alterations leading to decreased muscle strength and endurance (i.e., fatigability). Recently, exercise fatigability and CRF have been related, while fatigability mechanisms remain unclear. Traditionally, fatigability is assessed from maximal voluntary contractions (MVC) decrease, but some authors hypothesized that the rate of force development (RFD) determined during a rapid contraction could also be an interesting indicator of functional alterations. However, to our knowledge, no study investigated RFD in cancer patients. The purpose of this study was to determine whether RFD, fatigability amplitude, and etiology are different between fatigued and non-fatigued cancer patients. METHODS: Eighteen participants with cancer, divided in fatigued or non-fatigued groups according their CRF level, completed a 5-min all-out exercise in ankle plantar flexor muscles composed of 62 isometric MVC of 4 s with 1 s rest, to assess fatigability amplitude as the force-time relationship asymptote (FA). Before and after exercise, fatigability etiologies (i.e., voluntary activation (VA) and evoked forces by electrical stimulation (Db100)) were assessed as well as RFD in 50 and 100 ms (RFD50 and RFD100, respectively) during rapid contractions. RESULTS: FA is significantly lower in fatigued group. Significant differences were found between pre- and post-exercise VA, Db100, RFD50, and RFD100 for both groups, with no statistical difference between groups. CONCLUSION: During treatments, fatigability is higher in fatigued patients; however, the mechanisms of fatigability and RFD alterations are similar in both groups. TRIAL REGISTRATION: ClinicalTrials.gov, NCT04391543, May 2020.

Testing the predictive capacity of a muscle fatigue model on electrically stimulated adductor pollicis.

PURPOSE: Based on the critical power (Pc or critical force; Fc) concept, a recent mathematical model formalised the proportional link between the decrease in maximal capacities during fatiguing exercises and the amount of impulse accumulated above Fc. This study aimed to provide experimental support to this mathematical model of muscle fatigability in the severe domain through testing (i) the model identifiability using non-exhausting tests and (ii) the model ability to predict time to exhaustion (tlim) and maximal force (Fmax) decrease. METHODS: The model was tested on eight participants using electrically stimulated adductor pollicis muscle force. The Fmax was recorded every 15 s for all tests, including five constant tests to estimate the initial maximal force (Fi), Fc, and a time constant (τ). The model's parameters were used to compare the predicted and observed tlim values of the incremental ramp test and Fmax(t) of the sine test. RESULTS: The results showed that the model accurately estimated Fi, Fc, and τ (CI95% = 2.7%Fi and 9.1 s for Fc and τ, respectively; median adjusted r2 = 0.96) and predicted tlim and Fmax with low systematic and random errors (11 ± 20% and - 1.8 ± 7.7%Fi, respectively). CONCLUSION: This study revealed the potential applications of a novel mathematical formalisation that encompasses previous research on the critical power concept. The results indicated that the model's parameters can be determined from non-exhaustive tests, as long as maximal capacities are regularly assessed. With these parameters, the evolution of maximal capacities (i.e. fatigability) at any point during a known exercise and the time to exhaustion can be accurately predicted.

Building a biopsychosocial model of cancer-related fatigue: the BIOCARE FActory cohort study protocol.

BACKGROUND: Cancer-related fatigue (CRF) is the most common side effect of cancer and cancer treatment. CRF prevalence is up to 50% in breast cancer patients and can continue several years after cancer remission. This persistent subjective sense of exhaustion is multifactorial. Numerous parameters have been evidenced to be related to CRF across biological, physical, psychological, social and/or behavioral dimensions. Although CRF has been studied for many years, the majority of previous studies focused on only one dimension, i.e., physical function. Moreover, few studies investigated CRF longitudinally with repeated measures. These are the two main obstacles that limit the understanding of CRF mechanisms. The purpose of this study is to create a biopsychosocial model of CRF with simultaneous and longitudinal anthropometric, clinical, biological, physical, psychological and sociological parameters. METHODS: BIOCARE FActory is a multicentric prospective study that will consist of an 18-month follow-up of 200 women diagnosed with breast cancer. Four visits will be scheduled at diagnosis, after treatments, and 12 and 18 months after diagnosis. The same procedure will be followed for each visit. Each session will be composed of anthropometric data collection, a semi-structured interview, cognitive tests, postural control tests, neuromuscular fatigability tests and a cardiorespiratory fitness test. Clinical and biological data will be collected during medical follow-ups. Participants will also complete questionnaires to assess psychological aspects and quality of life and wear an actigraphy device. Using a structural equation modeling analysis (SEM), collected data will build a biopsychosocial model of CRF, including the physiological, biological, psychological, behavioral and social dimensions of CRF. DISCUSSION: This study aims to highlight the dynamics of CRF and its correlates from diagnosis to post treatment. SEM analysis could examine some relations between potential mechanisms and CRF. Thus, the biopsychosocial model will contribute to a better understanding of CRF and its underlying mechanisms from diagnosis to the aftermaths of cancer and its treatments. TRIAL REGISTRATION: This study is registered at ClinicalTrials.gov ( NCT04391543 ), May 2020.

Handgrip fatiguing exercise can provide objective assessment of cancer-related fatigue: a pilot study.

PURPOSE: As a subjective symptom, cancer-related fatigue is assessed via patient-reported outcomes. Due to the inherent bias of such evaluation, screening and treatment for cancer-related fatigue remains suboptimal. The purpose is to evaluate whether objective cancer patients' hand muscle mechanical parameters (maximal force, critical force, force variability) extracted from a fatiguing handgrip exercise may be correlated to the different dimensions (physical, emotional, and cognitive) of cancer-related fatigue. METHODS: Fourteen women with advanced breast cancer, still under or having previously received chemotherapy within the preceding 3 months, and 11 healthy women participated to the present study. Cancer-related fatigue was first assessed through the EORTC QLQ-30 and its fatigue module. Fatigability was then measured during 60 maximal repeated handgrip contractions. The maximum force, critical force (asymptote of the force-time evolution), and force variability (root mean square of the successive differences) were extracted. Multiple regression models were performed to investigate the influence of the force parameters on cancer-related fatigue's dimensions. RESULTS: The multiple linear regression analysis evidenced that physical fatigue was best explained by maximum force and critical force (r = 0.81; p = 0.029). The emotional fatigue was best explained by maximum force, critical force, and force variability (r = 0.83; p = 0.008). The cognitive fatigue was best explained by critical force and force variability (r = 0.62; p = 0.035). CONCLUSION: The handgrip maximal force, critical force, and force variability may offer objective measures of the different dimensions of cancer-related fatigue and could provide a complementary approach to the patient reported outcomes.

Clinical and haemodynamic risk factors associated with discrepancies in lower limb length with capillary malformations: data from the national paediatric French cohort CONAPE.

BACKGROUND: Genetics discoveries have allowed for a better understanding of capillary malformations (CMs) associated with overgrowth syndrome. However, molecular analyses are still not easy to perform or interpret. Other analytical methods are needed. OBJECTIVES: To identify clinical and haemodynamic factors associated with leg length discrepancy (LLD) in children with CMs of the lower limbs. METHODS: Data were obtained from the multicentre French national cohort CONAPE (COhorte Nationale d'enfants atteints d'Angiome Plan de membrE inférieur), from children aged 2-12 years old with CMs of the lower limbs. Clinical characteristics were prospectively collected. Haemodynamic factors were measured by an sonographer who calculated the arterial blood flow (ABF) in both lower limbs. An ABF difference ≥ 50% between the two lower limbs was considered relevant. LLD ≥ 2% was determined by the same radiologist on centralized radiographs. RESULTS: We analysed data at baseline for 96 children. The mean ± SD age was 5·6 ± 3·1 years; 49 (51%) were male; and 14 (15%) showed LLD. In total, 32 patients (33%) had venous anomalies, 13 (14%) lymphatic anomalies and in one child a diagnosis of Parkes Weber syndrome was made. Only an increased circumference above the knee was more frequent with than without LLD (43% vs. 13%, P = 0·02). In all, 10/79 patients (13%) showed a difference in ABF ≥ 50%: four had LLD. The frequency of differences in ABF ≥ 50% was greater with than without LLD [33% (n = 4/12) vs. 9% (n = 6/67), P = 0·04]. CONCLUSIONS: ABF measured by Duplex ultrasonography is a simple, low-cost and noninvasive complementary examination for help in detecting LLD, with a difference of ≥ 50% possibly associated.

In-utero aspiration vs expectant management of anechoic fetal ovarian cysts: open randomized controlled trial.

OBJECTIVE: To assess the efficacy and safety of in-utero aspiration (IUA) of anechoic fetal ovarian cysts. METHODS: This multicenter, prospective, randomized open trial in two parallel groups included women from nine outpatient fetal medicine departments with singleton pregnancy ≥ 28 weeks of gestation and a female fetus with an ultrasound-diagnosed simple ovarian cyst, defined as a single fully anechoic cystic structure measuring ≥ 30 mm. They were allocated randomly to IUA under ultrasound guidance or expectant management. All procedures were performed by trained senior obstetricians. Primary outcome was need for neonatal intervention, by laparoscopy, laparotomy or transabdominal aspiration. Secondary outcomes were in-utero involution of the cyst and oophorectomy at birth. Analyses were conducted according to the intention-to-treat principle. RESULTS: Of 61 participants, 34 were allocated to IUA and 27 to expectant management. Three IUA procedures (9%) could not be performed (one due to fetal position and two due to aspirations being dry). The remaining 31 IUA procedures were uneventful. The incidence of neonatal intervention did not differ significantly between the IUA and the expectant management groups (20.6% vs 37.0%; relative risk (RR), 0.55; 95% CI, 0.24-1.27). Nonetheless, IUA was associated with increased incidence of in-utero involution of the cyst (47.1% vs 18.5%; RR, 2.54; 95% CI, 1.07-6.05) and reduced rate of oophorectomy (3.0% vs 22.0%; RR, 0.13; 95% CI, 0.02-1.03) compared with expectant management. CONCLUSION: IUA of anechoic fetal ovarian cysts, compared with expectant management, was not associated with a reduction in overall neonatal interventions but was associated with a reduced oophorectomy rate. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

The neuromuscular fatigue induced by repeated scrums generates instability that can be limited by appropriate recovery.

The aim of this study was to evaluate the influence of the fatigue on the machine scrum pushing sagittal forces during repeated scrums and to determine the origin of the knee extensor fatigue. Twelve elite U23 rugby union front row players performed six 6-s scrums every 30 s against a dynamic scrum machine with passive or active recovery. The peak, average, and the standard deviation of the force were measured. A neuromuscular testing procedure of the knee extensors was carried out before and immediately after the repeated scrum protocol including maximal voluntary force, evoked force, and voluntary activation. The average and peak forces did not decrease after six scrums with passive recovery. The standard deviation of the force increased by 70.2 ± 42.7% (P < 0.001). Maximal voluntary/evoked force and voluntary activation decreased (respectively 25.1 ± 7.0%, 14.6 ± 5.5%, and 24 ± 9.9%; P < 0.001). The standard deviation of the force did not increase with active recovery and was associated with lower decrease of maximal voluntary/evoked force and voluntary activation (respectively 12.8 ± 7.9%, 4.9 ± 6.5%, and 7.6 ± 4.1%; all P < 0.01). As a conclusion repeated scrummaging induced an increased machine scrum pushing instability associated with central and peripheral fatigue of the knee extensors. Active recovery seems to limit all these manifestations of fatigue.

High pressure balloon dilatation of the ureterovesical junction in primary obstructive megaureter: Infectious morbidity.

INTRODUCTION: The objective of this study is to investigate the infectious morbidity associated with high-pressure balloon dilatation (HPBD) and an indwelling double J stent, in primary obstructive megaureter. METHODS: We reviewed the cases of 12 patients undergoing endoscopic treatment for primary obstructive megaureter from January 2012 to January 2015. The characteristics of the infection and data concerning the patient and the intervention were analyzed. RESULTS: The frequency of preoperative urinary tract infection (UTI) was 58%. The procedure was feasible in 100% of cases. Two patients required a second dilatation. One patient underwent Cohen's ureteral reimplantation after failure of the second dilatation. The frequency of postoperative UTI was 25%. All these infections occurred in patients with a double J stent. None of the patients had UTI after stent removal. None of the patients developed postoperative vesicoureteral reflux (VUR) after HPBD. CONCLUSION: Endoscopic balloon dilatation has been shown to have good short- mid- and long-term outcomes. In our experience, the morbidity of this procedure mostly results from infections, exclusively related to the use of a double J stent. The placement of a double J stent has a significant medical and economic impact. A definitive decision about the utility of double J stents will require studies of further dilatation without the placement of a double J stent. LEVEL OF EVIDENCE: 4.

Neonatal brain MRI: how reliable is the radiologist's eye?

INTRODUCTION: White matter (WM) analysis in neonatal brain magnetic resonance imaging (MRI) is challenging, as demonstrated by the issue of diffuse excessive high signal intensity (DEHSI). We evaluated the reliability of the radiologist's eye in this context. METHODS: Three experienced observers graded the WM signal intensity on axial T2-weighted 1.5T images from 60 different premature newborns on 2 occasions 4 weeks apart with a semi-quantitative classification under identical viewing conditions. RESULTS: The intra- and inter-observer correlation coefficients were fair to moderate (Fleiss' kappa between 0.21 and 0.60). CONCLUSION: This is a serious limitation of which we need to be aware, as it can lead to contradictory conclusions in the challenging context of term-equivalent age brain MRI in premature infants. These results highlight the need for a semiautomatic tool to help in objectively analyzing MRI signal intensity in the neonatal brain.

Contraction velocity influence the magnitude and etiology of neuromuscular fatigue during repeated maximal contractions.

This study aimed to compare the magnitude and etiology of neuromuscular fatigue during maximal repeated contractions performed in two contraction modes (concentric vs isometric) and at two contraction velocities (30/s vs 240°/s). Eleven lower limb-trained males performed 20 sets of maximal contractions at three different angular velocities: 0°/s (KE0), 30/s (KE30), and 240°/s (KE240). Cumulated work, number of contraction, duty cycle, and contraction time were controlled. Torque, superimposed and resting twitches, as well as gas exchange, were analyzed. Increasing contraction velocity was associated with greater maximal voluntary torque loss (KE0: -9.8 ± 3.9%; KE30: -16.4 ± 8.5%; KE240: -32.6 ± 6.3%; P < 0.05). Interestingly, the torque decrease was similar for a given cumulated work. Compared with KE0, KE240 generated a greater evoked torque loss (Db100: -24.3 ± 5.3% vs -5.9 ± 6.9%; P < 0.001), a higher O2 consumption (23.7 ± 6.4 mL/min/kg vs 15.7 ± 3.8 mL/min/kg; P < 0.001), but a lower voluntary activation (VA) loss (-4.3 ± 1.6% vs -11.2 ± 4.9%; P < 0.001). The neuromuscular perturbations were intermediate for KE30 (Db100: -10.0 ± 6.8%; VA: -7.2 ± 2.8%). Although the amount of mechanical work cumulated strongly determined the magnitude of torque decrease, the contraction velocity and mode influenced the origin of the neuromuscular fatigue. The metabolic stress and peripheral fatigue increased but reduction of VA is attenuated when the contraction velocity increased from 0°/s to 240°/s.

A solver based on pseudo-spectral analytical time-domain method for the two-fluid plasma model.

A number of physical processes in laser-plasma interaction can be described with the two-fluid plasma model. We report on a solver for the three-dimensional two-fluid plasma model equations. This solver is particularly suited for simulating the interaction between short laser pulses with plasmas. The fluid solver relies on two-step Lax-Wendroff split with a fourth-order Runge-Kutta scheme, and we use the Pseudo-Spectral Analytical Time-Domain (PSATD) method to solve Maxwell's curl equations. Overall, this method is only based on finite difference schemes and fast Fourier transforms and does not require any grid staggering. The Pseudo-Spectral Analytical Time-Domain method removes the numerical dispersion for transverse electromagnetic wave propagation in the absence of current that is conventionally observed for other Maxwell solvers. The full algorithm is validated by conservation of energy and momentum when an electromagnetic pulse is launched onto a plasma ramp and by quantitative agreement with wave conversion of p-polarized electromagnetic wave onto a plasma ramp.

The learning process of the hydrolocalization technique performed during ultrasound-guided regional anesthesia.

BACKGROUND: Because poor echogenicity of the needle remains a safety issue, we decided to analyze the learning process of the hydrolocalization technique (Hloc) performed to continuously identify needle-tip anatomical position during many ultrasound-guided regional anesthesia procedures. METHODS: Ten senior anesthesiologists naïve to the Hloc agreed to participate in the study. They were requested to perform 40 out-of-plane (OOP) approach ultrasound-guided axillary blocks (AB) each using the Hloc. The Hloc, which is a needle-tip localization principle, was performed by means of repetitive injections of a small amount of a local anesthetic solution (0.5-1 ml) under an ultrasound beam. Details of the learning process and skill acquisition of the Hloc were derived from the following parameters: the duration of block placement, a measure of the perceived difficulty of needle-tip visualization, a measure of block placement difficulty, and the amount of local anesthetics solution required for the technique. RESULTS: Four hundred ABs were performed. The success rate of an ultrasound-guided AB was 98%. The Hloc was successful in all patients. Skill acquisition over time of the Hloc was associated with a significant reduction of both the duration and the perceived difficulty of ABs placement. Apprenticeship data revealed that 20 blocks were required to successfully place AB within 5 min in most cases using the Hloc. CONCLUSION: The Hloc performed during the OOP approach of ultrasound-guided regional anesthesia is a simple technique with a relatively short learning process feasible for efficient placement of ABs.