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The presented study is devoted to the structural and biological properties of four derivatives of fluorenylspirohydantoin based on experimental data. The crystal structure of one of those, (9ʹ-fluorene)-spiro-5-(2-thiohydantoin), is described. The compound crystallizes in monoclinic crystal system and P21/c space group. We have pursued isolation of single crystals and biological activity tests of (9ʹ-fluorene)-spiro-5-hydantoin, (9ʹ-fluorene)-spiro-5-(2,4-dithiohydantoin), (9ʹ-fluorene)-spiro-5-(2-thiohydantoin), and (4ʹ,5ʹ-diaza-9ʹ-fluorene)-spiro-5-hydantoin. The compounds have been tested in both adherent and suspension tumor cell lines. The cell proliferation has been assessed by the WST-assay (Roche Applied Science). The antimicrobial activity against both Gram-positive, Gram-negative bacteria, and the yeast Candida albicans has been studied. [ABSTRACT FROM AUTHOR]

The structure of 2-(4-hydroxyphenyl)-substituted indan-1,3-dione and phenalene-1,3-dione is investigated using a combination of solid-state NMR, single crystal X-ray analyses and quantum chemical calculations. It is shown that 2-(4-hydroxyphenyl)-1,3-indandione exists as a diketo tautomer while 2-(4-hydroxyphenyl)-1,3-phenalenedione exists in the enol form. [ABSTRACT FROM AUTHOR]

A new method for growth of diamond seed crystals at metastable conditions is described. The process is realized isothermally (at temperatures in the range of 1000 K to 1400 K) in the closed volume of a quartz ampoule, via appropriate chemical transport reactions or in a CVD-apparatus. Vitreous carbon materials and other non-equilibrium forms of carbon, representing state of frozen-in disorder, increased thermodynamic potential and chemical affinity, are used as a constant driving force of isothermal crystallization. The experiments are based on the detailed analysis of the thermodynamic properties of carbon modifications and on the influence of dispersity and the degree of disorder on their thermodynamic potential. Additional kinetic factors, influencing the diamond growth, like introduction of active substrates and mechanism of incorporation of carbon atoms in growing diamond face are also analyzed discussed in their possible technical application. [ABSTRACT FROM AUTHOR]

During a 20-year period (1964-1983), the authors managed 60 children with intracranial ependymomas. In 37 patients the tumors were located in the posterior cranial fossa, and in the remaining 23 they were supratentorial. The histological examination in 26 children revealed ependymoblastomas. The average duration of the clinical evolution was 4 months and 5 days in the supratentorial neoplasms and 3 months and 6 days in the subtentorial. Besides the intracranial hypertension, present in about 80% of the patients, specific localizing signs were seen in 70% of the children with subtentorial and in 40% of those with supratentorial tumors. Because of the growth pattern in posterior fossa ependymomas and despite the prevalence of histologically benign neoplasms, radical resection was accomplished in only 21.6% of the cases, as compared with 30.4% in supratentorial tumors. The postoperative mortality remains high: 29.7% in subtentorial tumors and 17.4% in supratentorial. The 1-year survival rate in subtentorial neoplasms was 70.3%, the 3-year survival 29.7%, and the 5-year survival 16.2%. The corresponding figures for supratentorial ependymomas were more favorable: 82.6%, 43.5%, and 26.1%, respectively. The most important factors for improving the outcome at the present time appear to be as radical a resection as possible, supplemented with postoperative radiotherapy and chemotherapy. [ABSTRACT FROM AUTHOR]

In the period 1976-1987, the number of intracranial arachnoid cysts treated at our institute was 60: sylvian, 29; midline supratentorial, 13; subtentorial, 18. The diagnosis was mainly made by means of the results of a combination of CT, dynamic cisternography, and ventriculography. Based on an analysis of the preoperative investigations and operative results, an attempt was made to determine the appropriate treatment more precisely in cysts at different locations. The direct microsurgical approach with membrane excision was mainly used in combination with a preliminary VA shunt to treat hydrocephalus. The direct approach was supplemented with secondary cavity shunting in 5 cases. In more than half of the patients we used membrane excision alone (mainly children with sylvian cysts). In suprasellar cysts we consider the subfrontal approach to be more appropriate than the transventricular one. We restricted the use of primary cyst shunting as an alternative treatment to only 3 infants, with huge cysts. The follow-up reveals that 82.7% of the cases were favorably affected to varying degrees. [ABSTRACT FROM AUTHOR]

Raman spectra of ferritungstite are interpreted on the basis of model calculations. The presence of two broad vibrational bands in the spectral range 600-1000 cm is explained through the combination of two factors. Mainly, two principle bands in the spectral ranges 600-750 and 850-1000 cm are characteristic of the pyrochlore-type structure attained by ferritungstite and correspond to symmetric and asymmetric stretching of the W-O bonds, respectively. Also, broadening of the Raman lines results from structural disorder caused by the presence of iron atoms. [ABSTRACT FROM AUTHOR]

Quantal penetration through a (stationary) one-dimensional potential barrier is considered as a time evolution of an initially prepared wave packet. The large-time asymptotics of the process is concerned. Locality of the potential imposes certain analytical properties of the interaction amplitudes in the energy representation. The results are presented in terms of development of the phase-space (Wigner's) quasi-distribution. The phase-space evolution kernel is constructed, and it is shown that in the presence of a positive potential no part of the distribution is transported faster than the free particle. For the case of a small initial momentum uncertainty, the deformation of the coordinate density is considered, including a possible advance of its maximum, which would not mean any noncausal signal transport. [ABSTRACT FROM AUTHOR]

Whiskers and thin platelets of pyrite have been found growing coherently on the face of small cubic pyrite crystals from the Strashimir and Gradishte hydrothermal lead-zinc deposits. The host crystals formed framboids and spheroids of macroscopic size inside large crystals of chalcopyrite from which they are separated by concentric gaps. The whiskers, one to several μm in width, are elongated along [001] and bounded by {100}, partly by {210} and {111} faces. Scanning electron microscopic (SEM) observation revealed longitudinal steps and grooves, flat rectangular pits, drop-like and elongated bulges on their side faces. High-voltage electron microscopic (HVEM) studies showed that the thin whiskers are perfect and dislocation-free, although some ribbon-like whiskers and platelets contain internal longitudinal channels and small isometric fluid inclusions. Based on these observations, the following growth mechanism is proposed. Whiskers grow in the restricted volume of the internal cavities in chalcopyrite from stagnant solutions under a diffusion regime. The growth proceeds in two stages: (1) Initially, pyramidal 'pedestals' are formed due to morphological instability of the host crystal surfaces and multiapex growth, (2) Whiskers grow rapidly by unidirectional supply of material and competition between neighbouring individual whiskers, the growth taking place at the tip by a two-dimensional nucleation mechanism. The whiskers and thin platelets are considered to be peculiar highly anisometric skeletal crystals. [ABSTRACT FROM AUTHOR]

A retrospective study was performed in 100 children, who were operated on between 1954 and 1984 for cerebellar astrocytoma. Twenty-nine patients died during the 1st month after the operation. Of the patients who survived, 24 lived up to 5 years, 17 up to 10 years, and 30 lived 20 or more years. In 22 cases, tumor recurrence was the reason for reoperation. Radiation therapy was used in 25 cases with histological malignancy and/or after partial removal of the tumor. The analysis in 6 cases with brainstem involvement allowed us to conclude that in such cases the prognosis is poor with regard to survival. Although total removal of cerebral astrocytomas appears to be the most effective form of treatment, we are of the opinion that even subtotal excision may be compatible with long-term survival. This suggests that many of these tumors may show benign biological behavior. [ABSTRACT FROM AUTHOR]