Vibrational and cohesive properties in 4d and 5d transition metals: systematics and interrelations.

Motivated by the striking regularities between experimental quantities related to the vibrational properties of the 4d and 5d series early noted by Fernández Guillermet and Grimvall [Phys. Rev. B, 1989, 40(3), 1521], a systematic theoretical study has been made of the vibrational density of states (VDOS) of Ag, Au, Pd, Pt, Rh, Ir, Ru, Os, Tc, Re, Mo, W, Nb, Ta, Zr and Hf. The frequency moments ωD(j), expressed as Debye temperatures θD(j) for 0 ≤ j ≤ 100 were evaluated. Various remarkable correlations between these quantities are reported, which have their roots in the relations of homology between the VDOS. From the θD(j), several k(j) quantities with dimensions of force constants are calculated. For the elements 4d and 5d transition series, these quantities are shown to be strongly correlated, with independence of the value of j. It is suggested that the various interrelations between the θD(j) and k(j) parameters arrived at in the current work have their roots in the homologous variations of the cohesion forces across the 4d and 5d transition series, as revealed by thermophysical properties such as the bulk modulus and the cohesive energy.

Systematics of vibrational properties of Au nanoparticles: a molecular dynamics approach.

This paper reports the results of a Molecular Dynamics (MD) study of the vibrational properties of spherical Au nanoparticles with a number of atoms (N) varying in the range 1985 ≤ N ≤ 53 117. The LAMMPS code is adopted to calculate the vibrational density of states (VDOS), represented by D(ω) versus ω function. Two interatomic potentials, an EAM and a MEAM are used. The first part of the work is devoted to the D(ω) versus ω relation of macroscopic Au, which is obtained by MD simulations as well as by a density-functional-theory calculation using the Vienna Ab Initio Simulation Package and the PHONOPY code. Additional experimental and theoretical results on the VDOS of Au are used to compare with the present results. Next, the effect of changing N and the interatomic potential upon the VDOS of the nanoparticles is established. In particular, the effect of the surface vibrational modes upon the results is discussed. Various moment frequency parameters ωD(j) expressing averages of the D(ω) versus ω function are evaluated, and expressed as Debye temperatures θD(j), using standard relations. Attending to the relevance of these quantities in the description of the thermodynamic properties of macroscopic solids, values of θD(j) corresponding to j = -3, 0, 1, 2 and 4 are reported. On this basis, a picture of the systematic effects of changing N upon the θD(j) values is established both for the EAM and the MEAM potential. In addition, various interrelations between the θD(j) values for nanoparticles are presented. In particular, remarkably simple correlations are reported between the average quantities θD(0), θD(1), θD(2) and θD(4) and θD(-3) i.e., the Debye temperature which accounts for the low-frequency part of the spectrum. Finally, a discussion is reported of the relation between θD(-3) and other properties that are usually adopted as a measure of cohesion in macroscopic solids. To this aim, new correlations involving the nanoscopic counterpart of the temperature of fusion of macroscopic elements as well as the cohesive energy for Au nanoparticles are presented.

Phenomenology of the heating, melting and diffusion processes in Au nanoparticles.

The paper reports the results of a molecular dynamics study of the heating and melting process of nanoparticles with 1985 to 84 703 atoms. Building on a previous study by the present authors [Bertoldi, et al., J. Phys. Chem. Solids, 2017, 111, 286-293] involving the energy versus temperature, the Lindemann index and the radial distribution function, the current work relies on the mean-square displacement, the Lindemann ratio and the simulated snapshots to characterize four regions in the process of heating-to-melting. A general pattern of the atomic configuration evolution upon heating and a systematics of the transition temperatures between the various identified steps, is proposed. In addition, the most significant, so-called "melting step" in this process is analyzed in terms of the quasi-chemical approach proposed by Bertoldi et al., which treats this step by invoking a dynamic equilibrium of the type Au (LEA-SPL) ⇌ Au (HEA-LPL) involving low-energy atoms (LEA) and high-energy atoms (HEA) forming the solid phase-like (SPL) and the liquid phase-like (LPL) states of the system, respectively. The "melting step" is characterized by evaluating the equal-Gibbs energy temperature, i.e., the "T0 temperature", previously introduced by the current authors, which is the thermodynamic counterpart of the temperature of fusion of macroscopic elemental solids. The diffusion coefficients at T0 are determined, and their spatial and temperature dependence is discussed. In particular, the activation energy for the atom movements in the HEA-LPL/LEA-SPL mixture at T0 is reported. The consistency between the current phenomenological picture and microscopic interpretation of the thermodynamic, kinetic and atomic configuration information obtained is highlighted.

[Reevaluating the shelf life of sterilized packaged items via a risk-analysis study]. / Réévaluation de la durée de péremption des dispositifs médicaux restérilisables via une analyse de risques.

In the hospital, all the reprocessed reusable medical devices (RMD) are conditioned with a sterile barrier system and a protection package and they expire after three months. The objective of this study is to reevaluate this shelf life via a risk-analysis study focusing on the steps whose malfunction can fail RMD sterility. The first step is analysing current conditions of packaging, transportation and storage of RMD. The risk-analysis study has been built on French National Authority for Health template. Risks are prioritized in three categories: non critical risks, risks that need to be kept track of and risks to manage as a priority. Storage conditions have been evaluated in 52 wards in ten different structures. All of the wards respect the paper side of the pouches. They were stored in a dedicated storage unit in 85 % of the units. They were closed at the moment of the observation in 58 % of the cases. RMD were stacked in 81 % of the units and 36 % of them had at leat one expired RMD in their storage unit. The risk-analysis study identified two risks to manage as a priority. Some RMD were damaged during transportation to a subcontractor hospital. This step is barely manageable due to the human factor but the transport rules have been reminded in order to lower the risks on the materials. The operating rooms common storage include shelves that alter pouches and wraps, but a replacement of equipments is under discussion. Thanks to a better understanding of RMD circuit current conditions, allowing a better control of sensitive steps, their shelf life is reevaluated up to 6 months for containers and 4 months for other pouches.

[Prospective evaluation of the direct costs of prostate enucleation by the HoLEP® laser during the learning curve period]. / Évaluation prospective des coûts directs de l'énucléation prostatique par le laser HoLEP® pendant la courbe d'apprentissage.

OBJECTIVE: Holmium laser enucleation of the prostate (HoLEP) has been shown to be effective in treating large prostates compared to prostate transurethral resection (TURP). There are no published data evaluating specifically the impact of the learning curve on the direct costs of HoLEP. The objective of this study was to evaluate the direct costs generated by the use of HoLEP laser during the learning curve period. METHOD: The costs of all medical devices (DM) and drugs used, pre- and post-operative parameters during surgery have been prospectively collected between March and October 2016. RESULTS: A total of 32 patients were included in the study with a mean age of 70.8 years and a mean prostate volume of 68.6 cm3. The mean cost of anesthesia was 39.0 € and that of drugs and DM used for surgery was 257.95 € but could reach 470.76 € in case of conversion to bipolar resection. The mean duration of enucleation and morcellation was 150minutes with a mean weight of enucleated specimens of 40.4g. The total mean duration of patient care was 197minutes at an estimated hourly cost of € 636. CONCLUSIONS: Despite some limitations, this study makes it possible to analyze the direct costs of the management of benign prostatic hypertrophy using HoLEP, an innovative surgical technique, and to specify that these costs are more related to bipolar conversion and voluminous adenomas especially during the learning curve. LEVEL OF EVIDENCE: 5.

[Severe toxicity following capecitabine administration because of dihydropyrimidine deshydrogenase (DPD) deficiency]. / Toxicité sévère à la capécitabine liée à un déficit enzymatique en dihydropyrimidine déshydrogénase (DPD).

Capecitabine is an anticancer agent, prodrug of 5 fluorouracil (5-FU) administered orally and with a narrow therapeutic index. In gastrointestinal cancer, capecitabine is indicated for the treatment of colorectal cancer and metastatic unresectable gastric cancer. The 5-FU is active by incorporation in the biosynthesis of nucleic acids. Inhibition of endogenous synthesis of thymidine is the main way of toxicity of 5-FU. 5-FU is metabolised by the dihydopyrimydine dehydrogenase (DPD). Patients with a DPD deficiency can experience severe toxicity of 5-FU. We report the case of a patient who presented signs of major toxicity justifying hospitalization in intensive care unit 11 days after capecitabine initiation. Investigations showed that he had a DPD deficiency. This case leads to explain the different biological ways to identify patients at risk of developing severe toxicity following capecitabine administration because of DPD deficiency. Is it possible to make a systematic screening before initiation of treatment with 5-FU or prodrug of 5-FU?

[Interindividual pharmacokinetic variability in long-term antibiotherapy]. / Variabilité pharmacocinétique intra-individuelle et traitement antibiotique prolongé.

OBJECTIVE: The authors wanted to assess intraindividual pharmacokinetic variability, with a case of long-term amikacin therapy. DESIGN: A 92-year-old female patient, weighing 44kg, with renal failure, was treated by amikacin for 52 days. Her individual pharmacokinetic parameters were assessed 12 times in the course of therapy. The intraindividual variability of key parameters was quantified and compared with published interindividual variability. RESULTS: Intraindividual volume and clearance variability was measured at about one fourth to one third of the value observed for interindividual variability. Half-life intraindividual variability was almost equivalent to the interindividual variability: 24.5% versus 32%. CONCLUSIONS: The high pharmacokinetic variability observed has important potential clinical consequences. This case illustrates the need to ensure the effectiveness of treatment, to re-evaluate periodically the patient's status in order to take into account the intraindividual variability of pharmacokinetics parameters.