Life Test Based on Progressively Group-Censored Samples From Exponential Distribution With Periodic Change in Failure Rate

A life test experiment based on progressively group censored sample with periodic change in the failure rate of an exponential distribution is considered. Estimates of the two failure rates under different conditions of usage of an item together with their asymptotic standard error are obtained by the method of maximum likelihood. A numerical example is given using the data available in the form of grouped observations under two conditions of usage during alternate time intervals of fixed lengths T/Sub1 and T/Sub2

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

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

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