Green's functions on finite lattices and their connection to the infinite lattice limit

It is shown that the Green's function on a finite lattice in arbitrary space dimension can be obtained from that of an infinite lattice by means of translation operator. Explicit examples are given for one- and two-dimensional lattices

Modification of the Bloch law in ferromagnetic nanostructures

The temperature dependence of magnetization in ferromagnetic nanostructures (e.g., nanoparticles or nanoclusters) is usually analyzed by means of an empirical extension of the Bloch law sufficiently flexible for a good fitting to the observed data and indicates a strong softening of magnetic coupling compared to the bulk material. We analytically derive a microscopic generalization of the Bloch law for the Heisenberg spin model which takes into account the effects of size, shape and various surface boundary conditions. The result establishes explicit connection to the microscopic parameters and differs significantly from the existing description. In particular, we show with a specific example that the latter may be misleading and grossly overestimates magnetic softening in nanoparticles. It becomes clear why the usual $T^{3/2}$ dependence appears to be valid in some nanostructures, while large deviations are a general rule. We demonstrate that combination of geometrical characteristics and coupling to environment can be used to efficiently control magnetization and, in particular, to reach a magnetization higher than in the bulk material.Comment: 7 pages, 4 figure

Revisiting the luminosity function of single halo white dwarfs

White dwarfs are the fossils left by the evolution of low-and intermediate-mass stars, and have very long evolutionary timescales. This allows us to use them to explore the properties of old populations, like the Galactic halo. We present a population synthesis study of the luminosity function of halo white dwarfs, aimed at investigating which information can be derived from the currently available observed data. We employ an up-to-date population synthesis code based on Monte Carlo techniques, that incorporates the most recent and reliable cooling sequences for metal poor progenitors as well as an accurate modeling of the observational biases. We find that because the observed sample of halo white dwarfs is restricted to the brightest stars only the hot branch of the white dwarf luminosity function can be used for such purposes, and that its shape function is almost insensitive to the most relevant inputs, like the adopted cooling sequences, the initial mass function, the density profile of the stellar spheroid, or the adopted fraction of unresolved binaries. Moreover, since the cut-off of the observed luminosity has not been yet determined only lower limits to the age of the halo population can be placed. We conclude that the current observed sample of the halo white dwarf population is still too small to obtain definite conclusions about the properties of the stellar halo, and the recently computed white dwarf cooling sequences which incorporate residual hydrogen burning should be assessed using metal-poor globular clusters.Comment: 9 pages, 9 figures, accepted for publication in A&

Anomalous bond stretching phonons as a probe of charge fluctuations in perovskites

Important information on momentum resolved low energy charge response can be extracted from anomalous properties of bond stretching in plane phonons observed in inelastic neutron and X-ray scattering in cuprates and some other perovskites. We discuss a semiphenomenological model based on coupling of phonons to a single charge mode. The phonon dispersion and linewidth allow to locate the energy of the charge excitation in the mid infrared part of the spectrum and to determine some of its characteristics. New experiments on oxygen isotope substitution could allow to achieve a more detailed description. Corresponding relations following from the model can be used for the interpretation of experiments and as test of the model.Comment: presented at the M2S-HTSC-VIII conference in Dresde

The role of multimodal neuromonitoring during anesthesia for ablation of giant endocranial tumors

Catedra de anesteziologie și reanimatologie nr.2, Catedra de anesteziologie și reanimatologie nr.1 „Valeriu Ghereg”, Catedra de neurochirurgie, USMF „Nicolae Testemițanu”, Chișinău, Republica Moldova, Conferința stiințifică „Nicolae Anestiadi – nume etern al chirurgiei basarabene” consacrată centenarului de la nașterea profesorului Nicolae Anestiadi 26 august 2016Material şi metode. În studiu au fost incluse 2 loturi de pacienţi: I lot– 6 pacienţi cărora li s-a administrat anestezie combinată (i/v + pivot inhalator cu sevofluran); lotul II– 5 pacienţi cărora li s-a administrat anestezie totală intravenoasă (propofol+fentanil). Monitoring: TAs, TAd, TAm (invaziv), PVC, echilibru acidobazic, gazos (arteră şi venă periferică, bulbul jugular), electrolitic, acidul lactic, diurezei orară, PESS. Discuţii. În lotul pacienţilor cu anestezie inhalatorie s-a determinat o incidenţă înaltă a depresiei hemodinamice profunde (Tam - 74,3 mmHg, p= 0,02). Tot aici s-a determinat: utilizarea dozelor mai mici de analgetice şi miorelaxante (sol. atracurium bromid 0,35-0,4mg/kg) , trezire mai rapidă, incidenţă mai scăzută a greții şi tremorului postoperator. S-a reuşit efectuarea mai veridică a neuromonitorigului, datorită cantităţii mai mici de miorelaxante utilizate. La pacienţii cu anestezie intravenoasă s-a determinat o stabilitate hemodinamică (Tam - 82,7 mmHg, p ≤ 0,05), hemoragie intraoperatorie nesemnificativă. În lotul dat s-a reuşit efectuarea neuromonitorigului, cu doze obişnuite de miorelaxante (sol. atracurium bromid 0,5 mg/kg). Concluzii. Tehnicile descrise pot fi utilizate pentru neuromonitorizare multimodală în ablaţia de tumori endocraniene. Tehnica de anestezie inhalatorie, respectând farmacocinetica preparatelor, ar putea fi de preferat, din cauza evitării riscurilor de supra - sau sub dozare de medicamente anestezice, oferind o trezire mai rapidă, cu o evaluarea neurologică imediată, care este extrem de importantă.Materials and methods. The study included two groups of patients: I-st group - 6 patients receiving combined anesthesia (i / v + inhaled sevoflurane); II-nd group - 5 patients who received intravenous anesthesia (propofol + fentanyl).Monitoring: sBP, dBP, mBP (invasive), CVP, acid-base, gas (peripheral artery and vein, jugular bulb) and electrolytic balances, lactic acid, hourly diuresis, neurology evoked potentials. Discussion. In the group of patients with inhalation anesthesia was determined a higher incidence of hemodynamic depression (Tam - 74,3 mmHg, p= 0,02). Also it was determined: use of lower doses of analgetics and muscle relaxants (sol. atracurium bromid 0,35-0,4mg/kg), faster awakening, lower incidence of postoperative nausea and tremors. We managed a more accurate recording of evoked potentials due to the small amount of muscle relaxant used. In patients with intravenous anesthesia was determined a more stable BP (mBP - 82,7 mmHg, p ≤ 0,05), less intraoperative bleeding. In the group given was carrying neuromonitorigului managed with dose of muscle relaxant common (ground. atracurium aromide 0.5 mg / kg). Conclusions. The techniques described can be used for multimodal neuromonitoring in ablation of tumor endocranial. Inhalational anesthesia technique, respecting the pharmacokinetics preparations could be preferable because avoid the risks of over - or under dosage of anesthetic agents, providing an awakening faster with immediate neurological evaluation, which is extremely important

Acute kidney injury in patients with tetralogy of Fallot who have undergone surgical correction

Catedra de anesteziologie și reanimatologie nr.2, USMF „Nicolae Testemițanu”, Departamentul Reanimare și Terapie Intensivă, Spitalul Clinic Republican, Chișinău, Republica Moldova, Conferința stiințifică „Nicolae Anestiadi – nume etern al chirurgiei basarabene” consacrată centenarului de la nașterea profesorului Nicolae Anestiadi 26 august 2016Introducere. Leziunea renală acută (LRA) este una dintre cele mai frecvente și severe complicații în chirurgia cardiacă. Aplicarea criteriilor de clasificare RIFLE (risc, injurie, insuficiență și stadiul final al bolii renale) au fost validate la populațiile pediatrice. Scop. De a determina, retrospectiv apariția LRA în grupul de pacienți până la 18 ani, utilizând criteriile RIFLE modificate, validate la copii (pRIFLE), relația dintre LRA cu alte complicații după corecția chirurgicală a tetralogiei Fallot. Materiale și metode. Din baza de date a IMSP Spitalul Clinic Republican, au fost selectați 45 de copii, supuși corecției chirurgicale a tetralogiei Fallot între iunie 2010 și decembrie 2015. Leziunea renală acută a fost definită ca o scădere a cantității clearance-ului estimat al creatininei pe baza criteriilor pediatrice modificate pentru RIFLE (pRIFLE). Rezultate. Douăzeci și două de pacienți (48,9%) au avut LRA în funcție de categoriile pRIFLE. Dintre cei 45 pacienți, 15 (33,3%) au corespuns criteriilor pRIFLE de risc; 6 (13,3%) au atins criteriile de injurie și 1 (2,2%) au întrunit criteriile de insuficiență. Trei pacienți (6,7%) au decedat. Apariția MODS s-a întâlnit la 19 (42,2%) pacienți, sepsis s-a întîlnit la 3 (6,7%) pacienți. Durata de ventilație mecanică (p <0,001) și durata de ședere în unitatea de terapie intensivă ( p <0,001) au fost semnificativ mai mare în comparație cu grupul de pacienți care nu au dezvoltat semne de leziune renală acută. Concluzii. Disfuncția renală acută a fost asociată în mod independent, cu o apariție crescută a complicațiilor postoperatorii, dar cu o mortalitate redusă după corecția chirurgicală a tetralogiei Fallot.Introduction. Acute kidney injury (AKI) is one of the most common and severe complications in cardiac surgery. Application of the classification RIFLE (risk, injury, failure and end stage renal disease) have been validated in pediatric populations. Purpose. To determine AKI appearance in the patients up to 18 years, using modified RIFLE criteria, validated in children (pRIFLE), the relationship between AKI with other complications after surgical correction of Fallot's tetralogy. Materials and methods. From the database of the Republican Clinical Hospital, were selected 45 children undergoing surgical correction of Fallot's tetralogy between June 2010 and December 2015. acute kidney injury was defined as a decrease in estimated creatinine clearance based on criteria pediatric modified RIFLE (pRIFLE). Results. Twenty-two patients (48,9%) had AKI by pRIFLE category. Of the 45 patients, 15 (33.3%) met the criteria pRIFLE risk; 6 (13.3%) corresponded to the criteria of injury and one (2.2%) met criteria for failure. Three patients (6.7%) died. The occurrence of MODS was encountered in 19 (42.2%) patients, sepsis was met in 3 (6.7%) patients. Duration of mechanical ventilation (p <0.001) and length of stay in the intensive care unit p <0.001) were significantly higher compared with the group of patients who did not develop signs of acute kidney injury. Conclusions. Acute kidney dysfunction was independently associated with an increased occurrence of postoperative complications, but with reduced mortality after surgical correction of Fallot's tetralogy

Nickel catalyst faceting in plasma-enhanced direct current chemical vapor deposition of carbon nanofibers

8 pagesInternational audienceVertically aligned multi-walled carbon nanofibers (CNFs) were grown by plasma-enhanced chemical vapor deposition with Ni catalysts on the top of nanofibers. Transmission electron microscopy was used to study the morphology and crystallography of Ni catalysts, which are essential for the nucleation and growth of CNFs. A model for the faceted shape of Ni catalytic particles is proposed. It is shown that the exposed polyhedral surfaces of Ni catalytic particles for vertically aligned CNFs are composed of {111}, {110}, and {100}, a faceting that appears to be characteristic of the growth atmosphere