L. Novakovic - Academia.edu (original) (raw)

Papers by L. Novakovic

Radiation Physics and Chemistry (1977), 1983

The addition of antioxidants to polymers increases their thermooxidative stability as indicated b... more The addition of antioxidants to polymers increases their thermooxidative stability as indicated by a delay and/or a retardation of degradation. The present paper considers the influence of the nature of the antioxidant (hindered phenols, aromatic amines, and organic compounds containing sulphur atoms) on the thermooxidative behaviour of a low density polyethylene at 200oc. The following characteristics have been measured in polymer samples with zero, 0.I; 0.5; and 1.0 wt% content of antioxidant: the induction time of the oxidation process, rate of autoxidation and rate of polymer degradation (up to about 20% weight loss). The difference in thermal stability in radiation crosslinked material and comparative retardation of the thermooxidative degradation is observed up to a absorbed dose of 200 kGy.

Radiation Physics and Chemistry (1977), 1985

In part one of this series the effects of a phenolic, an amine and a thioester antioxidant on the... more In part one of this series the effects of a phenolic, an amine and a thioester antioxidant on the thermo-oxidative stability of irradiated and unirradiated low-density polyethylene was reported. In this paper the effects of combined phenolic and thioester stabilizers are described. Isothermal thermogravimetric analysis was used to study the systems. Pronounced synergism was observed with the induction periods, the time when the initial weight loss begins and the 5% weight loss. At about 50% of each stabilizer increases greater than twofold were observed both with the unirradiated and irradiated polymers. The rate constants for oxygen uptake were decreased. However, the rates of degradation at 5% weight loss fell between the values of the two pure stabilizers with no pronounced synergism in either case. In the absence of oxygen little effect of either antioxidant or their mixtures was observed. The corresponding activation energies were somewhat higher, however, with the irradiated samples containing antioxidants. Dynamic thermogravimetry was used for this study. A kinetic analysis indicated that there were somewhat different modes of degradation at lower-and highertemperature ranges.

Materials Chemistry and Physics, 1994

ABSTRACT This paper presents a study of the temperature dependence of the dielectric permittivity... more ABSTRACT This paper presents a study of the temperature dependence of the dielectric permittivity, electric resistivity and magnetic susceptibility of the diphosphate M2P2O7, where M = Co(II) andNi(II). The study, which was carried out in the temperature range 290–1000 K, indicated that both compounds sustain three phase transitions each. The existing literature offers a description of one phase transition for both compounds (α → β).

Materials Chemistry and Physics, 1989

The paper presents the study of temperature dependence of the dielectric permitivity, resistivity... more The paper presents the study of temperature dependence of the dielectric permitivity, resistivity and magnetic susceptibility of that crystal phase of BaNi2(P04j2 which is stable at room temperature. The investigation indicated that, in the temperature range 290-1100 K, the examined compound sustains three phase transitions on heating, which is partly consistent with data found in literature. The optical diffuse reflectance spectrum at room temperature enabled us to establish the fact that, in this phase, the Ni2+ ion exists in an octahedral surrounding. temperature phase [ll. High-temperature phases of these compounds are obtained by heating to a temperature of around llOO°C and hardeningfast cooling of the sample with water. By the use of X-ray diffraction analysis on the powder it was established that high-temperature phases of the above mentioned compounds are isostructural, and that they crystallize in a trigonal (rhombohedral system, space group R? (C3 2i) with one stoichiometric unit per unit cell (Z=l) Ll,31. This crystal structure has a layered character. Along the space diagonal of rhombohedron, layers of 0254-0584/89/$3.50 0 Elsevier Sequoia/Printed in The Netherlands

Clinical and Experimental Dermatology

Morphoea is a localized inflammatory disorder of the dermis and subcutaneous fat and radiotherapy... more Morphoea is a localized inflammatory disorder of the dermis and subcutaneous fat and radiotherapy is a rarely reported cause (estimated incidence of 2 per 1000). Morphoea is commonly mistaken for an inflammatory recurrence of breast cancer, resulting in unnecessary investigations and treatment. We report the case of a 40-year-old woman who developed radiation-induced morphoea of the breast 7 months following adjuvant radiotherapy. She was treated with topical and systemic steroids as well as psoralen plus ultraviolet (UV)A before proceeding to UVA1 phototherapy. We also review the literature and discuss other management options.

Journal of Physics F: Metal Physics, 1984

Hall effect measurements have been performed in the ferromagnetic and paramagnetic regions of the... more Hall effect measurements have been performed in the ferromagnetic and paramagnetic regions of the alloy Mn1.11Al0.89. In the ferromagnetic region the Hall resistivity shows the existence of a ferromagnetic component arising from the magnetisation of the alloy. In the paramagnetic region just above the Curie temperature the Hall resistivity is a linear function of applied magnetic field and exhibits a

Abmraet--Two-cyck creep recovery penetration measurements at 15&C are used to determine the visco... more Abmraet--Two-cyck creep recovery penetration measurements at 15&C are used to determine the viscoelastic parameters for irradiated low density and linear low density polyethylenes, pure and with 0.5% antioxidant. The amplitudes and the time factors of each cycle are calculated using the mechanical model Uon.

Solid State Communications, 1990

Polymer Degradation and Stability, 2006

The effects of gamma irradiation in air and accelerated aging of low-density polyethylene (LDPE) ... more The effects of gamma irradiation in air and accelerated aging of low-density polyethylene (LDPE) were studied through dielectric loss (tan d) analysis in the temperature range from 25 to 325 K and using thermally stimulated discharge current (TSDC) measurements. The radiationinduced oxidation was observed using IR spectroscopy. The influence of radiation dose and accelerated aging on the intensities and the positions of the g and b dielectric relaxation maxima were correlated with maxima of TSDC measurements, and found to be strongly dependent upon the changes in the microstructure of the amorphous phase and on the surface of the crystallites induced by oxidation and crosslinking.

Journal of the European Academy of Dermatology and Venereology, 1997

Journal of Physics and Chemistry of Solids, 1971

Clinical and Experimental Dermatology, 2012

Whole-body ultraviolet (UV)A1 (340-400 nm) phototherapy was first introduced 30 years ago, but is... more Whole-body ultraviolet (UV)A1 (340-400 nm) phototherapy was first introduced 30 years ago, but is currently available in the UK in only three dermatology departments. A workshop to discuss UVA1 was held by the British Photodermatology Group in May 2009, the aim of which was to provide an overview of UVA1 phototherapy and its role in practice, and to identify areas in which further studies are required. The conclusions were that UVA1 phototherapy is an effective treatment in several inflammatory skin diseases, including localized scleroderma and atopic eczema (AE); however, deficiencies and limitations exist in the published evidence base. For most diseases, such as AE, other treatments also exist, which are generally more effective than UVA1. However, for some diseases, particularly morphoea, the evidence of efficacy is stronger for UVA1 than for other treatments. Acute adverse effects of UVA1 are minimal. The risk of long-term adverse effects, particularly skin cancer, is unknown. Medium to high doses of UVA1 are needed for efficacy in most situations, but the equipment to deliver such doses is large, expensive and difficult to install. UVA1 is currently underprovided, and the recommendation of the workshop is that more tertiary centres should have access to UVA1 phototherapy in the UK.

British Journal of Dermatology, 2009

Photodermatoses are a group of skin disorders induced by ultraviolet radiation (UVR) and, in some... more Photodermatoses are a group of skin disorders induced by ultraviolet radiation (UVR) and, in some cases, visible light. To establish a diagnosis it is important to carefully take a history, physical examination and perform phototesting as well as other testing when appropriate (patch and photopatch tests, antinuclear antibodies, porphyrin profile). This article focuses on the photodermatoses that affect the elderly, which with the ageing of population, particularly in the industrialized societies, are becoming an increasingly important group for the healthcare systems. The most common photodermatoses with onset in the elderly are chronic actinic dermatitis and drug induced photosensitivity.

$Research paper thumbnail of Effects of solar-simulated radiation dose fractionation on CD1a+ Langerhans cells and CD11b+ macrophages in human skin$

British Journal of Dermatology, 2001

There are few human studies investigating the immunosuppressive effects of exposure to solar-simu... more There are few human studies investigating the immunosuppressive effects of exposure to solar-simulated radiation (SSR) and its relationship with sunburn/erythema, and few comparative data on the importance of SSR exposure regimens. To evaluate whether SSR-induced erythema is a reliable end-point for assessing damage to antigen-presenting cells (APCs) in human skin. We compared the relationship between SSR-induced erythema and alterations in epidermal CD1a+ Langerhans cells (LCs) and CD11b+ macrophages in human volunteers after single exposures to 0, 0.5, 1, 2 or 3 minimal erythema doses (MED). We also investigated whether SSR exposure leads to an accumulation or accommodation of the same end-points by comparing the effects of a relatively low cumulative SSR dose (3 MED) given in varying daily dose fractions (4 x 0.75 MED, 2 x 1.5 MED and 1 x 3 MED). Single SSR exposures induced a dose-dependent increase in erythema. CD1a+ LCs remaining in the irradiated epidermis showed a dose-dependent increase in cell size and altered morphology. Significant depletion of CD1a+ LCs and presence of CD11b+ macrophages only occurred in sites irradiated with 2 MED and 3 MED. Dose fractionation had no effect on the final erythemal response but the 4 x 0.75 MED and 1 x 3 MED protocols were better tolerated than 2 x 1.5 MED for alterations in CD1a+ LC and CD11b+ cell numbers. In contrast, dose fractionation protected against alterations in CD1a+ LC morphology or cell size. We found that erythema is a poor indicator of alterations in epidermal APCs and that dose fractionation is an important parameter in the immunological effects of ultraviolet radiation.

Clinical and Experimental Dermatology, 2005

We report two patients in whom episodes of polymorphic light eruption were followed by recurrent ... more We report two patients in whom episodes of polymorphic light eruption were followed by recurrent erythema multiforme on exposed and nonexposed sites. Treating the polymorphic light eruption with prophylactic PUVA and/or oral prednisolone or cyclosporin prevented the development of erythema multiforme, suggesting that the two events are related. It is possible that erythema multiforme develops as a response to the same causative antigen as polymorphic light eruption.