Classical electrodynamics as a nonlinear dynamical system

We report on preliminary investigations, of numerical and analytical character, on the dynamical properties of the classical Hamiltonian model for the interaction of electromagnetic radiation with a nonrelativistic charged point particle. We investigate the distribution of energy among the field normal modes when the energy is initially given to the particle, and we find that the high frequency modes have a tendency to be frozen, a fact that is in agreement with the qualitative trend expected from Nekhoroshev's theorem for systems of weakly coupled harmonic oscillators. Moreover we point out that, as a consequence of the dynamical interaction with the radiation field, the charged particle appears to have a highly fluctuating motion

Classical Electrodynamics as a nonlinear dynamical system

We report on preliminary investigations, of numerical and analytical character, on the dynamical properties of the classical Hamiltonian model for the interaction of electromagnetic radiation with a nonrelativistic charged point particle. We investigate the distribution of energy among the field normal modes when the energy is initially given to the particle, and we find that the high frequency modes have a tendency to be frozen, a fact that is in agreement with the qualitative trend expected from Nekhoroshev's theorem for systems of weakly coupled harmonic oscillators. Moreover we point out that, as a consequence of the dynamical interaction with the radiation field, the charged particle appears to have a highly fluctuating motion

The molecular landscape of propionic acidemia and methylmalonic aciduria in Latin America

Abstract In this work, we review the clinical and genetic data in 14 Latin American propionic acidemia (PA) and 15 methylmalonic aciduria (MMAuria) patients. In the PA patients, we have identified four different changes in the PCCA gene, including one novel one (c.414+5G>A) affecting the splicing process. The PCCB mutational spectrum included two prevalent changes accounting for close to 60% of the mutant alleles studied and one novel change (c.494G>C) which by functional analysis is clearly pathogenic. We have also identified the deep intronic change c.654+462A>G, and the results of the antisense treatment in the patient's cell line confirmed the functional recovery of PCC activity. All PA patients bearing out-offrame mutations presented the disease earlier while patients bearing in hemizygous fashion p.E168K and p.R165W presented the disease later. Regarding the MMAuria patients, we have found three novel mutations in the MUT gene (c.1068G>A, c.1587_1594del8 and c.593delA) and one in the MMAB gene (c.349-1 G>C). Two patients with MMAuria with homocystinuria cblC type are carriers of the frequent c.271dupA mutation. All mut 0 , cblB and cblC patients presented the symptoms early and in general had more neurological complications, while cblA and mut -patients exhibited a late-onset presentation, and in general the long-term outcome was better. The results presented in this work emphasize the importance of the genetic analysis of the patients not only for diagnostic purposes but also to research into novel therapies based on the genotype

Nursing evaluation during treatment with helmet continuous positive airway pressure in patients with respiratory failure due to COVID-19 pneumonia: A case series

Background: During COVID-19 outbreak, with the increasing number of patients presenting with acute respiratory failure, a large use of non invasive positive pressure ventilation was done in the emergency departments and medical wards despite the lack of recommendations. Objectives: This study describes the clinical characteristics of patients presenting to the hospital with acute respiratory failure due to COVID-19 related pneumonia undergoing treatment with helmet continuous positive airway pressure (CPAP) with a strict nursing evaluation and monitoring. Methods: A case series study enrolling adult patients admitted to an emergency department of an Italian hospital with acute respiratory failure due to COVID-19 pneumonia from March 18th to April 18th, 2020, was conducted. Only patients who strictly followed a local CPAP protocol were enrolled. Results: A total of 52 patients were included in this study. Thirty-eight patients (73%) were judged eligible for endotracheal intubation (ETI). Eighteen (34.6%) were intubated. Sixteen (30.8%) patients died: seven (38.9%) and nine (26.5%) in the eligible-for-ETI and non eligible-for-ETI group, respectively. The median hospital length of stay was different in the ETI and non-ETI group: 26 days (interquartile range [IQR]: 16–37) vs 15 days [IQR 9–17] (p = 0.005). The median invasive mechanical ventilation time was 11 days [IQR 7–21] with an ICU length of stay of 14.5 days [IQR 10–28]. During the CPAP trial, among patients eligible for ETI variations over time for positive end-expiratory pressure (p = 0.003) and respiratory rate (p = 0.059) were found between intubated and non-intubated patients. Conclusions: A short closed monitored CPAP trial could be considered for acute respiratory failure due to COVID-19 pneumonia before considering ETI. A progressive positive end-expiratory pressure titration should target reduction in a patient's respiratory rate. More studies are needed to evaluate the efficacy and predictors of failure of CPAP and non-invasive positive pressure ventilation in patients with acute respiratory failure due to COVID-19 pneumonia

Predictive accuracy of triage nurses evaluation in risk stratification of syncope in the emergency department

Background: Syncope is a common clinical problem that accounts for 1-3% of all emergency department (ED) visits. Its prognosis is extremely variable with a 1-year mortality that may reach 30%. There are no available data about the accuracy of nursing triage in identifying high-risk syncope. The aim of our study was to evaluate the predictive accuracy of nursing triage in identifying high-risk syncope. Methods: We conducted a retrospective study on 678 consecutive patients who presented with syncope at four EDs. For each patient, nursing triage, comorbidities, clinical features and adverse events that occurred both in the ED and at 10-day follow-up were assessed. Adverse events included death, readmission to ED, need for major therapeutic procedures, cardiopulmonary resuscitation, intensive care unit admittance, acute antiarrhythmic therapy and major causes of syncope identi fied during the ED evaluation. Predictive accuracy of nursing triage was evaluated. Results: We observed a total of 55 (8.1%) adverse events. Eight of them (9.4%) occurred among the 85 patients who were identified as high priority by nursing triage. Sensitivity (Sn) and specificity (Sp) of urgent nursing triage in identifying adverse outcomes in the ED (19 patients) were 21% (95% CI 3% to 39%) and 88% (95% CI 85% to 90%), while the positive likelihood ratio (LR+) and negative likelihood ratio (LR-) were 1.7 and 0.9, respectively. Sn and Sp for 10-day adverse events were 15% (95% CI 5% to 24%) and 88% (95% CI 85% to 90%), respectively, with a LR+ of 1.18 and a LR- of 0.98. Conclusions: Nursing triage was characterised by a low predictive accuracy in identifying high-risk individuals

New bis-, tris- and tetrakis(pyrazolyl)borate ligands with 3-pyridyl and 4-pyridyl substituents: synthesis and coordination chemistry

The new ligands dihydrobis[3-(4-pyridyl)pyrazol-1-yl]borate [Bp(4py)](-), hydrotris[3-(4-pyridyl)pyrazol-1-yl]borate [Tp(4py)](-), tetrakis[3-(4-pyridyl)pyrazol-1-yl]borate [Tkp(3py)](-), dihydrobis[3-(3-pyridyl)pyrazol-1-yl]borate [Bp(3py)](-), hydrotris[3-(3-pyridyl)pyrazol-1-yl]borate [Tp(3py)](-) and tetrakis[3-(3-pyridyl)pyrazol-1-yl]borate [Tkp(4py)](-) are derivatives of the well known bis-, tris- and tetrakis-(pyrazolyl)borate cores, bearing 4-pyridyl or 3-pyridyl substituents attached to the pyrazolyl C-3 positions. These pyridyl groups cannot chelate to the metal ions in the poly(pyrazolyl) cavity but are externally directed. Structural studies on a range of metal complexes show how, in many cases, coordination of these pendant pyridyl groups to the M(pyrazolyl), core of an adjacent metal complex fragment results in formation of coordination oligomers or polymeric networks. [Tl(B-3py)], [TlBp4y] and [Tl(Tp(4py))] form one-dimensional polymeric chains via coordination of one of their pendant pyridyl units to the Tl(I) centre of an adjacent complex fragment; in contrast, in [Tl(Tp(3py))] coordination of all three pendant pyridyl units to separate Tl(I) neighbours results in formation of a two-dimensional polymeric sheet. In [Tl(Tkp(3py))] and [Tl(Tkp(4py))] the Tl(I) is coordinated by two or three of the four pyrazolyl arms, respectively; bridging interactions of pendant 4-pyridyl groups with adjacent Tl(I) centres result in a two-dimensional sheet forming in each case. In Ag(Tkp(4py)) each Ag(I) ion is coordinated by two pyrazolyl rings, and two bridging pyridyl ligands from other complex units, resulting in a one-dimensional chain consisting of pairs of cross-linked zigzag chains. In contrast to these polymeric coordination networks, the structures of [Cu(Tp(4py))] and [(Tp(3py))Cd(CH3CO2)] are dimers, with a pendant pyridyl residue from the first metal centre attaching to a vacant coordination site on the second, and vice versa; these dimers are stabilised by pi-stacking interactions between sections of the two ligands. [Ni(Tp(3py)),] is monomeric, with an octahedral coordination geometry arising from two tris(pyrazolyl)borate chelates; the array of pendant 3-pyridyl groups is involved only in intramolecular hydrogen-bonding. [(Tp(4pY))Re(CO)(3)] is also monomeric, with a facial arrangement of three pyrazolyl ligands and three carbonyls, with the pendant 4-pyridyl groups not further coordinated. [(Tp(2py))Re(CO)(3)], based on the related ligand hydrotris[3-(2-pyridyl)pyrazol-1-yl]borate, has a similar fac-(CO)(3)(pyrazolyl)(2) coordination geometry