The glassy behaviour of poorly crystalline Fe2O3 nanorods obtained by thermal decomposition of ferrous oxalate.

Nanorod ferrous oxalate dihydrate (FeC2O4 × 2H2O) which had been synthesized by the microemulsion method, was used as a precursor in the thermal decomposition process performed in air atmosphere. The formation of nanocrystalline hematite as the final product was preceded by the appearence of an intermediate product. Comprehensive study comprising several complementary techniques (x-ray diffraction, transmission electron microscopy, selected area electron diffraction, thermogravimetric/differential thermal analyses and SQUID magnetometry) confirmed that the intermediate product corresponds to the poorly crystalline Fe2O3. Due to the specific nanorod shape and poorly crystalline structure, the investigated Fe2O3 showed high coercive field value of ~0.5 T at 5 K. Special attention in this study was devoted to the peculiar magnetic properties of poorly crystalline Fe2O3, which were thoroughly investigated by employing sophisticated experimental procedures such as relaxation of thermoremanent magnetization for different cooling fields, zero field and field cooled memory effects as well as aging experiments for different waiting times. At low temperatures and weak applied magnetic fields, the investigated system behaves similarly to spin glasses, manifesting slow, collective relaxation dynamics of magnetic moments through memory, rejuvenation and aging effects.

Ferromagnetic properties of the Zn-Mn-O system.

Polycrystalline Zn-Mn-O samples with nominal manganese concentration x = 0.01 and 0.10 were synthesized by a solid state reaction route using (ZnC(2)O(4)·2H(2)O)(1-x) and (MnC(2)O(4)·2H(2)O)(x). Thermal treatment of the samples was carried out in air at temperatures of 673, 773 and 1173 K. The samples were investigated by x-ray diffraction, thermogravimetry, differential thermal analysis, transmission electron microscopy, magnetization measurements and electron paramagnetic resonance. Room temperature ferromagnetism is observed in Zn-Mn-O samples with x = 0.01 thermally treated at low temperatures (673, 773 K). It seems that the ferromagnetic phase could originate from interactions between Mn(2+) ions and acceptor defects incorporated in the ZnO crystal lattice during the thermal treatment of the samples.

[Psychotraumatic reactions in participants and non-participants in warfare--members of a special unit]. / Psihotraumatske reakcije kod ucesnika i neucesnika rata--pripadnika jedne specijalne jedinice.

The investigation was performed on a sample of members of a special parachute unit, aged 25-30 years. During combat activities in the territory of former Yugoslavia, in the period of 1991-92, they were exposed to intensive stress and psychotraumatic events which could have detrimental influence on personality and psychological functions, most frequently causing posttraumatic stress disorder. The results of investigation showed that in spite of numerous traumatic experiences, psychological stability and professional efficiency could be maintained in specially selected individuals with appropriate personality structure, who were particularly motivated and included in so-called elite units, which show high degree of group cohesion and mutual support. This investigation used for the first time the methodology, most frequently recommended in literature as standard for follow up and early diagnosis of psychological disorders caused by traumatic stress in war or everyday life. Practical value of the used methodology, which included the list of stress-inducing events, the scale of influence of stress-events and the interview for posttraumatic stress disorder, was confirmed.

Study on toxicity of Bordetella pertussis cultures and antigens.

The toxicity of 201 Bordetella pertussis strains isolated in Belgrade has been studied. The strains were grown on a modification of Cohen and Wheeler's medium. LD50 of examined strains ranging between 1.06 and 1.95 billion bacteria in 35 (17.41%), between 2.04 and 4.83 billion bacteria in 92 (45.77%) and between 5.31 and 7.79 billion bacteria in 46 (22.88%) were found. Low toxic cultures of B. pertussis strains with LD50 ranging between 9.0 and 14.1 billion bacteria in 28 (13.43%) were obtained. The culture of the strains with low toxicity was 7 to 14 times more toxic than those prepared from the strains with low toxicity. In the cultures of 51 B. pertussis strains, toxicity for mice was not correlated with the number of viable cells. The toxic substances which influenced the loss of mouse weight were found in the culture filtrate of B. pertussis. A considerable detoxifying effect of heating at 56 degrees C for 30 min on liquid cultures prepared from highly toxic strains of B. pertussis was observed. The susceptibility of two different strains of mice for pertussis vaccine has been examined. The Albany strain of mice was less susceptible to toxicity control of the vaccine by mouse-weight-gain test than the Torlak strain.