Etudes Theoriques des Composes a Transition de Spin mono- et bi-nucleaires

Thèses Doctorat Lyon 1/Sciences 05-174.This work presents theoretical studies of spin crossover iron (II) compounds. The correlation between molecular structure and magnetic properties of mononuclear compounds is done using DFT calculations of the energy gap between spin states. These studies allowed to formulate qualitative conclusions concerning the role of the order-disorder phenomena. Thermodynamic parameters were evaluated through the calculations of vibrational properties.The study of binuclear complexes, showing intramolecular magnetic coupling, allowed the interpretation of different magnetic behaviours of these systems, in particular one or two step(s) spin transition. The magnetic coupling constants, which are not easily accessible through traditional magnetochemical measurements, were calculated applying the DFT/broken symmetry approach.Ce travail présente l'étude théorique des propriétés magnétiques de composés à transition de spin du fer(II) en fonction de la nucléarité des complexes et de la nature des ligands environnants.La corrélation entre la position des noyaux et les propriétés magnétiques des composés mononucléaires a été faite sur la base des calculs DFT du gap énergétique entre les différents états de spin. Ces études ont permis de tirer des nouvelles conclusions qualitatives quant au rôle du phénomène d'ordre-désordre dans les composés à transition de spin. Certaines paramètres thermodynamiques ont pu être évalué à travers les calculs des fréquences vibrationnelles.L'étude de systèmes binucléaires présentant un couplage magnétique intramoléculaire a permis l'interprétation des différents comportements magnétiques de ces systèmes (pas de transition, transition en une seule étape ou deux étapes). L'application de l'approche DFT/broken symmetry a permit la quantification des constantes d'échange, difficile d'accès aux mesures magnétochimiques traditionnelles

Evaluation of the Differences between Normal and Cancerous Prostate Tissue Response to Simple and Vibro-Neural Stimulation

Background: Early detection of prostate cancer has significant benefits for its treatment and can increase the survival chance in patients. In recent years, new methods such as shear wave elastography and vibro-elastography, as well as artificial tactile sensing, have been used to detect a mass in the prostate tissue in-vivo and ex-vivo. This paper aims to investigate the difference between normal and malignant prostate tissue reaction to simple and vibro-neural stimulation for prostate tissue mass detection in order to determine neural stimulation intensity, velocity, and frequency to obtain the best result in detecting the type and location of the tumor.Methods: This study has utilized neural stimulation devices in normal and cancerous tissues. The stimulation velocity, probe location, and the frequency of neural stimulation considered as the independent variables.Results: The results show that for superficial masses, although dependent on the probe, the accuracy of detection at the low speed of 5mm/s is 50% higher than other conditions. On the other hand, in deep masses, with increasing mass depth, the accuracy of detection at the medium speed of 8mm/s is 30% higher than the low speed. Finally, the results showed that with increased stimulation frequency, the possibility of tumor detection, and its accuracy increases by 35%.Conclusion: By improving the accuracy of the neural stimulation device, it can apply to detect hard materials such as tumors and malignant tissues

Comparison of the Effectiveness of Two Types of Single Port Minimal Invasive Neurosurgical Robots to Ablation and Resection of Brain Tumor

Background: Using minimally invasive neurosurgical robots is one of the most desirable ablation methods and resection of brain tumors. In this study, forward kinematics and Jacobian matrix calculated for two single-port robots for comparing the effectiveness of two types of single port minimal invasive surgical robots to ablation and resection of brain tumorMethods: The motion analysis of robots type 1 and 2 has compared to each other. Ablation manipulator in robot type 1 has five degrees of freedom, but in robot type 2, three revolute degrees of freedom of this manipulator has replaced with a revolute joint perpendicular to the previous three revolute joints.Results: Results showed that for resection surgery, in the same conditions, robot type 2 damaged 58.9 mm3 more of cerebral cortex tissue than robot type 1 to resect the brain tumors. To establish a static balance, robot type 2 needs to tolerate at least 41% more internal loading than robot type 1. The maximum velocity for robot type 1 in the contact location between the end-effector and the tumor is 1.7 times more than robot type 2. The maximum end-effector force of robot type 1 to apply the tumor for ablation surgery is more than 1.8 times in robot type 2, but the maximum moment and power for ablation surgery and resection of these two robots were the same less than 1% difference.Conclusion: Despite the more straightforward mechanism, a minimum number of joints, and better kinematics range of robot type 2, robot types 1 has the possibility for transformation, establishes the static balancing, and does a better ablation surgery with less damage to the brain

Wavelength selective light-induced magnetic effects in the binuclear spin crossover compound {[Fe(bt)(NCS)2]2(bpym)}

International audienceUsing Fourier transform infrared spectroscopy, x-ray diffraction, and magnetic susceptibility measurements under light irradiation, the selective light-induced excited spin state trapping (LIESST) and the reversible-LIESST effect have been evidenced and studied in depth in the binuclear spin crossover compound {[Fe(bt)(NCS)2]2bpym}. In this system, each magnetic site can switch from low spin (LS) to high spin (HS), so that three states exist, namely, the LS-LS, HS-LS, and HS-HS. All these techniques shine a new light on the high phototunability of this system. In addition to the direct photoswitching from the LS-LS to the HS-LS or to the HS-HS state, here we show that photoinduced switching between the excited photoinduced states can be triggered in a reversible way: from HS-LS to HS-HS (irradiation around 800 nm), or reverse from HS-HS to HS-LS (irradiation around 1300 nm). The nature of the intermediate HS-LS state during the thermal and light-induced spin state changes is also discussed by comparing the spectroscopic measurements and the structural analysis. The loss of inversion symmetry in the HS-LS molecular state, where the two magnetic Fe sites are no more equivalent, is not accompanied by any long-range ordering of the noncentrosymmetric molecules in the crystal. Therefore the continuous double-step spin conversion corresponds to a double crossover

Transpapillary drainage has no added benefit on treatment outcomes in patients undergoing EUS-guided transmural drainage of pancreatic pseudocysts: a large multicenter study

Background and Aims The need for transpapillary drainage (TPD) in patients undergoing transmural drainage (TMD) of pancreatic fluid collections (PFCs) remains unclear. The aims of this study were to compare treatment outcomes between patients with pancreatic pseudocysts undergoing TMD versus combined (TMD and TPD) drainage (CD) and to identify predictors of symptomatic and radiologic resolution. Methods This is a retrospective review of 375 consecutive patients with PFCs who underwent EUS-guided TMD from 2008 to 2014 at 15 academic centers in the United States. Main outcome measures included TMD and CD technical success, treatment outcomes (symptomatic and radiologic resolution) at follow-up, and predictors of treatment outcomes on logistic regression. Results A total of 375 patients underwent EUS-guided TMD of PFCs, of which 174 were pseudocysts. TMD alone was performed in 95 (55%) and CD in 79 (45%) pseudocysts. Technical success was as follows: TMD, 92 (97%) versus CD, 35 (44%) (P = .0001). There was no difference in adverse events between the TMD (15%) and CD (14%) cohorts (P = .23). Median long-term (LT) follow-up after transmural stent removal was 324 days (interquartile range, 72-493 days) for TMD and 201 days (interquartile range, 150-493 days) (P = .37). There was no difference in LT symptomatic resolution (TMD, 69% vs CD, 62%; P = .61) or LT radiologic resolution (TMD, 71% vs CD, 67%; P = .79). TPD attempt was negatively associated with LT radiologic resolution of pseudocyst (odds ratio, 0.11; 95% confidence interval, 0.02-0.8; P = .03). Conclusions TPD has no benefit on treatment outcomes in patients undergoing EUS-guided TMD of pancreatic pseudocysts and negatively affects LT resolution of PFCs

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Energetics of Binuclear Spin Transition Complexes

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Études théoriques des composés à transition de spin mono- et bi- nucléaires

Ce travail présente l'étude théorique des propriétés magnétiques de composés à transition de spin du fer(II) en fonction de la nucléarité des complexes et de la nature des ligands environnants. La corrélation entre la position des noyaux et les propriétés magnétiques des composés mononucléaires a été faite sur la base des calculs DFT du gap énergétique entre les différents états de spin. Ces études ont permis de tirer des nouvelles conclusions qualitatives quant au rôle du phénomène d'ordre-désordre dans les composés à transition de spin. Certaines paramètres thermodynamiques ont pu être évalué à travers les calculs des fréquences vibrationnelles. L'étude de systèmes binucléaires présentant un couplage magnétique intramoléculaire a permis l'interprétation des différents comportements magnétiques de ces systèmes (pas de transition, transition en une seule étape ou deux étapes). L'application de l'approche DFT/broken symmetry a permit la quantification des constantes d'échange, difficile d'accès aux mesures magnétochimiques traditionnellesLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Quantum-chemical studies of the spin transition complex [Fe(DAPP)(abpt)](ClO4)2

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