HRTEM studies of amorphous ZrNiTiCu nanocrystalline composites.

Ball milling of easy glass forming Ti(25)Zr(17)Ni(29)Cu(29) alloys lead to the formation of an amorphous structure accompanied by a substantial increase of powder microhardness. The powders show clear glass transition effect and a few stage crystallization starting above 500 degrees C. High-resolution transmission electron microscope technique allowed identifying nanocrystalline inclusions as Cu(12)NiTi(7) within the amorphous powder. The amorphous powders mixed with nanocrystalline iron or silver powders were hot pressed to form composites. A narrow 200 nm broad intermediate single-phase layer at the amorphous-phase/iron interface containing all elements present in the composite was identified using transmission electron microscope and high-angle annular dark field detector techniques. scanning transmission electron microscopy energy dispersive spectroscopy line profile showed gradual change of composition within the intermediate zone. Amorphous phase contains small nanocrystals of size close to 10 nm identified using High-resolution transmission electron microscope as Cu(12)NiTi(7.) Compression tests have shown better plasticity of composites than in the case of pure hot-pressed amorphous powder; furthermore, high elastic limit of composites and the ultimate compression stress of about 1800 MPa for composites containing 20% Fe and near 700 MPa for those with 20% Ag.

Structure investigations of ferromagnetic Co-Ni-Al alloys obtained by powder metallurgy.

Elemental powders of Co, Ni and Al in the proper amounts to obtain Co(35)Ni(40)Al(25) and Co(40)Ni(35)Al(25) nominal compositions were ball milled in a high-energy mill for 80 h. After 40 h of milling, the formation of a Co (Ni, Al) solid solution with f.c.c. structure was verified by a change of the original lattice parameter and crystallite size. Analytical transmission electron microscopy observations and X-ray diffraction measurements of the final Co (Ni, Al) solid solution showed that the crystallite size scattered from 4 to 8 nm and lattice parameter a = 0.36086 nm. The chemical EDS point analysis of the milled powder particles allowed the calculation of the e/a ratio and revealed a high degree of chemical homogeneity of the powders. Hot pressing in vacuum of the milled powders resulted in obtaining compacts with a density of about 70% of the theoretical one. An additional heat treatment increased the density and induced the martensitic transformation in a parent phase. Selected area diffraction patterns and dark field images obtained from the heat-treated sample revealed small grains around 300 nm in diameter consisting mainly of the ordered gamma phase (gamma'), often appearing as twins, and a small amount of the L1(0) ordered martensite.

TEM and HRTEM studies of ball milled 6061 aluminium alloy powder with Zr addition.

The effect of mechanical alloying on the microstructure of atomized 6061 aluminium alloy powder and 6061 powder with a zirconium addition was studied in the work. The atomized 6061 aluminium alloy powder and 6061 powder with addition of 2 wt.% Zr were milled in a planetary ball mill and investigated using X-ray diffraction measurements, conventional and high-resolution electron microscopy (TEM/HRTEM) and high-angle annular dark field scanning transmission electron microscopy combined with energy dispersive X-ray microanalysis. An increase of stresses was observed in milled powders after the refinement of crystallites beyond 100 nm. In the powder with zirconium addition, some part of the Zr atoms diffused in aluminium forming a solid solution containing up to 0.5 wt.% Zr. The remaining was found to form Zr-rich particles containing up to 88 wt.% Zr and were identified as face centred cubic (fcc) phase with lattice constant a= 0.48 nm. That fcc phase partially transformed into the L1(2) ordered phase. Eighty-hour milling brought an increase of microhardness (measured with Vickers method) from about 50 HV (168 MPa) for the initial 6061 powder to about 170 HV (552 MPa). The addition of zirconium had no influence on the microhardness.

Microstructure and properties of hot compacted powders of aluminium alloys.

Atomized 6061 aluminium alloy powders with and without the addition of 2 wt% Zr were milled for 80 h in a planetary ball mill and hot pressed in vacuum. The milled powders showed microhardness of about 170 HV, which increased after hot pressing up to 260 HV and up to 280 HV for powders without and with the Zr additions, respectively. Compression tests showed the high yield stress of 300 MPa obtained for the hot-pressed sample produced from the initial powders compared with ultimate compression strength of above 800 MPa for that of the milled sample and slightly higher for that with Zr additions. The effect of hot pressing on the structure of powders was investigated using a conventional analytical and high-resolution electron microscopy and high angle annular dark-field scanning transmission electron microscopy combined with energy dispersive X-ray microanalysis. The samples of initial powders hot pressed in vacuum showed a cell structure with particles of the Mg(2)Si and AlFeSi phases in intercell areas. In the milled and hot-pressed sample, the homogeneous structure of small grains of size below 200 nm was observed. The AlFeSi and Mg(2)Si particles with size 20-100 nm were uniformly distributed as well as the Zr rich particles in the Zr containing alloy. The Zr-rich particles containing up to 80 at% Zr were identified as a metastable fcc cubic phase with lattice parameter a= 0.48 nm.

HRTEM studies of NiNbZr + Ag amorphous-nanocrystalline composites.

Amorphous powder of composition corresponding to Ni60Ti20Zr20 (in at%) was obtained by ball milling in a high-energy mills starting from pure elements. Formation of the amorphous structure was observed already after 20 h of milling, although complete amorphization occurred after 40 h. The microhardness of powders increased from about 30 HV for pure elements to above 400 HV (1290 MPa) after 40 h of milling. Transmission electron microscopy (TEM) allowed to identify nanocrystalline inclusions of intermetallic phases of size 2-10 nm. Uniaxial hot pressing was performed in vacuum at temperature below the crystallization T(x) it is 510 degrees C and pressure of 600 MPa, Mixed amorphous powders and nanocrystalline silver powders were used to form a composite, in which microhardness was near 970 MPa HV and 400 HV for the amorphous phase and nanocrystalline silver, respectively. The compression strength of the composite containing 20 wt% of nanocrystalline Ag powder was equal to 600 MPa and plastic strain was 2%. Microstructure studies showed low porosity of composites of less than 1%, uniform distribution of the silver phase and a transition zone between both components, about 150 nm thick, where diffusion of nickel, niobium and zirconium into silver was observed. High-resolution TEM allowed identifying the structure of nanocrystalline inclusions in the amorphous matrix after hot pressing as either Ni(3)Zr or Ni(17)Nb(3). The identification was performed basing on measurements of angles and interatomic distances using inverse Fourier transformed images with enhanced contrast using Digital Micrograph computer program.

[Stroke in the course of cerebral arteritis]. / Udar niedokrwienny mózgu w przebiegu zapalenia naczyn tetniczych.

In this paper we wanted to present cases of stroke occurring in the course of cerebral vasculitis. Cerebral vasculitis occurs most often in patients with infections, tumours and connective tissue diseases. Idiopathic vasculitis is observed very rarely and making the diagnosis meets great difficulties. Three patients (2 women and 1 man) with idiopathic cerebral arteritis aged 28-41 who underwent treatment in our department are prevented. There were no known stroke risk factors in anamnesis and diagnostic investigations. All patients had headaches before the occurrence of stroke. Electrocardiography, echocardiography were normal. Two patients had arteriography--small arterial occlusions and changes in arteries' walls were seen. Ischaemic changes in both cerebral hemispheres were shown in CT and MRI scans. One patient had high serum level of antinuclear antibodies one year later the diagnosis of lupus erythematosus was made. In patients with cerebral vasculitis extensive laboratory investigations should be carried out and combined with a detailed follow-up study. Neurological changes could be the first symptom of connective tissue disease.

[Primary and secondary intraventricular hemorrhage--clinical analysis]. / Krwawienia dokomorowe pierwotne i wtórne--analiza kliniczna.

In the recent decades an evident increase in the number of diagnosed intraventricular haemorrhages has been noted. The trial was undertaken of assessing of the incidence of primary and secondary intraventricular haemorrhages, the role of aetiological factors in various types of haemorrhages, the risk factors and the results of imaging procedures, as well as the clinical symptoms and treatment methods. The analysed group comprised 90 patients in hospital with the diagnosis of intraventricular haemorrhage in the years 1989-1996. The diagnosis was based on the results of computerized tomography /CT/ and on autopsy in one case. The clinical course of the cases varied considerably: very serious mainly in secondary intraventricular haemorrhages with high mortality. No signs pathognomic for intraventricular haemorrhage were found. The prognosis in primary intraventricular haemorrhage was better. Hypertension as risk factor was present in 71 cases. Pathological changes of blood vessels were found in 23 cases.

[Measurement of acetylcholine receptor antibodies in serum of patients with myasthenia gravis]. / Badanie poziomu przeciwcial przeciw receptorom acetylocholiny w surowicy chorych z miastenia.

The aim of this study is the evaluation of the level of antiacetylcholine receptor antibodies in patients with different types of myasthenia (according to Osserman's classification) and establishing of correlation between the level of such antibodies and the clinical state of the patients. 63 patients with diagnosed myasthenia and 30 healthy controls without immunological diseases were evaluated. In all of them standard neurological examination was performed and the levels of antiacetylcholine receptor antibodies were measured. In 45 patients electrophysiological investigations were carried out. In 43 cases elevated levels of antiacetylcholine receptor antibodies were noted. In 20 patients the levels were within normal range. The level of antibodies showed correlation with the clinical type of myasthenia according to Osserman (the more severe was myasthenia, the higher was the level of antibodies). But the clinical state of the patient at the moment of examination did not show any clear correlation with the level of antibodies. Acetylcholine receptor antibodies measurement has significant diagnostic value in myasthenia. Nevertheless it should be interpreted with other diagnostic techniques.

[Anticardiolopin antibodies as a risk factor in stroke]. / Przeciwciala antykardiolipinowe jako czynnik ryzyka udaru niedokrwiennego mózgu.

The level of anticardiolipin antibodies (aCL) in sera of 53 patients with ischemic cerebrovascular disease aged 35-55 years with mean age 48.4 +/- 5.03, was studied using a solid phase enzyme immunosorbent assay (ELISA). The investigation was done half year after the ischemic stroke. The control group consisted of 21 healthy participants matched for age and sex. The presence of aCL was found in sera of 17 persons (32.1%), in 9 it was IgG class antibodies. It was indicated that the risk of repeated cerebral ischemic events was relatively higher in aCL positive patients than in aCL negative. Relapses were found in 6 aCL positive patients (35.3%) (in 5 cases from the group of 9 IgG positive) and in 2 persons (5.6%) aCL negative patients. The existence of aCL can be helpful to determine pathogenesis of the disease and its prognosis.

[Clinical and electroencephalographic signs of side effects in patients after myelography using "amipaque"]. / Kliniczne i elektroencefalograficzne objawy uboczne u chorych po mielografii wykonanej preparatem "amipaque".

The authors present the results of own investigations on the occurrence of side effects following myelography with the contrast medium Amipaque administered usually by the lumbar route. Sixty patients aged 21-65 years with various diseases of the spinal cord and cauda equina were studied. Clinical and myelographic investigations were performed before and after myelography. In 6 out of 60 cases (10%) transient neurological disturbances developed including epileptic seizures, speech disturbances of the type of aphasia and dysartria, visual disturbances and twitching of lower extremities. Other symptoms and signs included: headaches, vomiting, collapse. One patient with cardiorespiratory failure died hours after myelography with evidence of increased symptoms of cardiorespiratory failure. EEG changes appeared after myelography in 2/3 of cases and persisted for up to 12 days. The authors call attention to the high proportion of neurological complications and EEG changes which must be taken into account when indications to myelography are considered. Particular caution is necessary in cases with coexistent cardiorespiratory failure.

[Electroencephalographic and clinical correlates in patients with occlusion or stenosis of the carotid arteries and their intracranial branches]. / Korelacje elektroencefalograficno-kliniczne u chorych z niedroznoscia lub zwezeniem tetnic szyjnych i ich wewnatrzczaszkowych odgalezien.

Electroencephalographic-clinical investigations were carried out in 94 patients with ischaemic syndromes of the cerebral hemispheres divided into two groups: with occlusion or stenosis of arteries in the neck (37 patients) and with lesions of intracranial arteries (57 patients). In all cases EEG was done and the diagnosis was verified on the basis of cerebral arteriography. The types of signs in EEG and the correlations between them and the clinical manifestations and their intensity were analysed. These data were related to the results of angiography. No significant differences were observed between the patterns of EEG changes with regard to the location, extent and morphology between the group with lesions of neck arteries and the group with lesions of intracranial arteries.

[Attempt at the classification of chronic and recurrent headaches]. / Próba klasyfikacji przewleklych i nawracajacych bólów glowy.

The authors describe a proposal of classification of chronic and recurrent headaches based on criteria different from those used as yet. The initial criterion of headache classification was its extent and location: 1) diffuse, 2) partial, 3) posterior, b) anterior, 3)localized. Another element is: 1) unequivical or 2) non-unequivical clinical pattern. Definite clinical entities, probable aetiological factors, or possible pathological mechanisms are referred to definite extent and localization, and unequivocal or non-unequivocal clinical patterns.

[Benign childhood epilepsy with spike activity in the area of the precentral gyrus]. / Lagodna padaczka dziecieca z wyladowaniami iglic w okolicy zakretu przedsrodkowego.

The authors report 18 cases of benign childhood epilepsy with spike activity in the Rolandic area. These cases were isolated from a group of 103 children with partial epilepsy. In agreement with the observations of other authors the benign course of this form of epilepsy is stressed. The isolation of this type of epilepsy is necessary in view of its practical management, treatment and prognosis. Neuroradiological and neurological examinations failed to demonstrate any evidence of organic brain disease in this epilepsy. Focal EEG changes with spike activity in the frontal or temporal area regressed gradually until complete normalization of the record. The authors agree with the view of other authors that the diagnosis of this epilepsy in typical from does not require radioneurological contrast investigations.