Proučavanje strukturnih svojstava nekih jednostavnih tekućih metala u različitim referentbim sustavima

In the present paper three reference systems: Percus-Yevick hard sphere (PYHS), one component plasma (OCP) and charged hard sphere (CHS) are employed to investigate the temperature-dependent structural properties of some simple liquid metals. The structure factor S(q), pair-distribution function g (r) and interatomic distance r1 of nearest neighbour atoms for Mg, Zn, Al, In, Tl and Pb are reported. Our own model potential is employed along with the local field correction due to Sarkar et al. (SS) to describe electron-ion interaction. It is seen that the CHS method alongwith the present form of model potential can explain more accurately the structural behaviour than PYHS and OCP methods.Za istraživanje temperaturno-ovisnih svojstava strukture nekih jednostavnih tekućih metala, primijenili smo tri referentna sustava: Percus–Yevickov tvrde kugle, jednokomponentne plazme i nabijenih kuglica. Izvješćujemo o strukturnom faktoru S(q), funkciji raspodjele parova g(r) i o međuatomskim razmacima r1 najbližih atoma u Mg, Zn, Al, In, Tl i Pb. Rabimo naš vlastiti modelski potencijal i popravku lokalnog polja prema Sarkaru i sur. za opis međudjelovanja elektron-ion. Nalazimo da metoda nabijene tvrde kuglice s primijenjenim modelskim potencijalom točnije opisuje strukturna svojstva nego druge dvije metode

Enhanced thermoelectric properties in Sb/Ge core/shell nanowires through vacancy modulation

In the present work, we have modified the physical and electronic structure of Sb/Ge core/shell nanowires via vacancy creation and doping with foreign atoms with the aim to improve their thermoelectric energy conversion efficiency. Sb/Ge-NWs having a diameter of 1.5 Å show metallicity with 2Go quantum conductance. The stability of the nanowires is assessed through the calculation of their formation energy. The formation of one vacancy at either the Sb- and Ge-site modifies substantially the electronic properties. From the comparison of the thermoelectric properties of the nanowires with and without the vacancy, we have found that the figure of merit for the Sb/Ge NW with one Sb vacancy increases of 0.18 compared to the pristine NW. The NW doping with different transition metals: Fe, Co, Ni and Cu have been found to also enhance the conversion efficiency. Thus, our calculations show that the thermoelectric performance of metal–semiconductor core–shell NWs can be in principle improved as much as 80% by vacancy formation and doping

Salvageability of renal function following renal revascularisation in children with Takayasu’s arteritis-induced renal artery stenosis

Background. Renal artery revascularisation procedures are usually carried out on children with renal artery stenosis from varied causes, including Takayasu’s   arteritis. Reports on the outcome of such procedures in children usually refer to the improvement in blood pressure, with only minimal mention of effects on renal  function.Objective. Salvageability renal function in children who underw ent renal  revascularisation for Takayasu’s arteritis-induced renal artery stenosis (TARAS) was the focus of this study.Methods. We undertook a retrospective analysis of children aged ≤16 years with angiographically confirmed TARAS who underwent renal artery revascularisation procedures between 1990 and 2010. Outcomes of renal function were studied over a period of 2 years and were defined as: (i) improvement: >20% increase in estimated glomerular filtration rate (e-GFR) from presurgery value; (ii) stabilisation: e-GFR within 20% of presurgery value; and (iii) failure: >20% deterioration in e-GFR from presurgery value. The GFR was estimated using the Schwartz formula.Results. Twenty children (9 males and 11 females, age range 2 - 14 years) had 27 renal artery revascularisation procedures. Thirteen of the patients (65.0%) had bilateral renal artery stenosis. The baseline mean e-GFR was 88.6 (standard deviation (SD) 25.4) mL/min/1.73 m2 and the mean duration of follow-up was 28.80 (SD 25.62) months. All the patients had stable or improved renal function until the 2-year follow-up, when the proportion decreased to 92.3% (12/13), as failure was recorded in one child. Bilateral revascularisation was found to be significantly associated with improvement in renal function in the early postoperative period  (p=0.04).Conclusion. Renal artery revascularisation procedures are successful in salvaging renal function in children with TARA

Jednadžbe stanja, energije vezanja, volumni moduli i Gruneisenove konstante 3d, 4d i 5d prijelaznih metala

A model pseudopotential, depending on an effective core radius but otherwise parameter-free, is proposed to study the equation of state by incorporating the s-d hybridization effects. A new criterion for the selection of the exchange and correlation effects is also put forward. The equations of state for Cu, Ta, Mo, W and Pt have been studied up to the pressure of 1000 GPa. The binding energy, pressure, bulk modulus and frequency-independent Grüneisen constant as functions of volume for transition metals are calculated. The theoretical results are compared with available experimental results. The successful application to 27 metals has confirmed our formalism.Uvodimo model potencijala koji ovisi o polumjeru efektivne sredice a ne o drugim parametrima radi proučavanja jednadžbe stanja s uključenim s-d efektima hibridizacije. Postavljamo također nov kriterij za odabir efekata izmjena i korelacija. Proučavamo jednadžbu stanja Cu, Ta, Mo, W i Pt za tlakove do 1000 GPa. Izračunavamo energije vezanja, tlak, volumne module i frekventno-neovisne Gruneisenove konstante. Ishodi računa uspoređuju se s eksperimentalnima za sve poznate podatke. Uspješna primjena našeg formalizma za 27 metala ga potvrđuje

Electrical Transport properties of Ni-Cr binary alloys

Electrical transport properties viz. electrical resistivity and thermal conductivity of Ni-Cr binary alloys are determine by our recognized single parametric model potential in wide range of Cr concentration. In this work, screening functions (Ichimaru and Utsumi, Farid et al. and Sarkar et al.) are employed along with the Hartree and Taylor functions to study the relative influence of the exchange and correlation effect. Given liquid alloys are studied as a function of their composition at three different temperatures according to Faber-Ziman model. Computed values of electrical transport properties are in good agreement with the experimental data available in literature