On the topological Helly theorem

The main result of this paper is the following theorem, related to the missing link in the proof of the topological version of the classical result of Helly: Let be any family of simply connected compact subsets of R² such that for every i,j∈{0,1,2} the intersections Xi∩Xj are path connected and is nonempty. Then for every two points in the intersection there exists a cell-like compactum connecting these two points, in particular the intersection is a connected set.     

Strain sensors based on carbon nanotubes-cuprous oxide composite

This paper presents the design, fabrication and experimental results of carbon nanotubes-cuprous oxide (CNTs-Cu₂O) composite based strain sensors. The press-tablets were fabricated from the blend of CNTs (25 wt%) and Cu₂O (75 wt%) at a pressure of 353 MPa. The diameter of multiwalled carbon nanotubes (MWCNTs) varied between 10 and 30 nm. The sizes of Cu₂O micro-particles were in the range of 3-4 μm. The thickness of the press-tablets was 1 mm. The samples were installed on the polymer elastic beam by glue. The electric contacts to the samples were made by silver paste. The inter-electrodes distance (length) and diameter of the surface-type samples were in the range of 6-8 mm and 10 mm, respectively. The DC resistance of the strain sensors increases under tension and decreases under compression, while the average strain sensitivities are in the range of 44-46 and 24-28 for tension and compression, respectively. The simulation is in good agreement with the experimental results.     

Modeling two-dimensional opto-acoustic studies of excited media

The use of the opto-acoustic effect in tomographic studies of excited media under strong absorption of the initiating laser radiation is discussed. We present the results of two-dimensional model experiments showing the possibility of good reconstruction of a secondary acoustic source even in the case of significant absorption of the initiating radiation. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 1, pp. 83–86, January, 1999.     

Berberis alkaloids XXXV. The structure of nummularine

The new N-benzyltetrahydroisoquinoline alkaloid nummularine has been isolated from the leaves ofBerberis nummularia. On the basis of a study of its spectral characteristics (PMR, IR, and mass spectra), the structure of nummularine has been established as 6-hydroxy-N-(3-hydroxy-4-methoxybenzyl)-7-methoxy-1-methyltetrahydroisoquinoline.Translated from Khimiya Prirodnykh Soedinenii, Vol. 33, No. 1, pp. 91–93, January–February, 1997.     

Berberis alkaloids XXXIX. New alkaloids fromB. densiflora

The alkaloid composition of the leaves ofBerberis densiflora has been studied. Berberine, -allocryptopine. oxyacanthine, glaucine, thalicmidine, isocorydine, O-methylcorypalline and the new bases densinine and densiberine have been isolated. The structures of the new alkaloids have been established by a study of spectral characteristics and chemical transformations. This is the first time that any of the known alkaloids, apart from berberine, have been isolated from a plant of this pecies and it is the first time that -allocryptopine and O-methylcorypalline have been isolated from theBerberis genus.     

Berberis alkaloids. The new alkaloid oblongamine

Summary 1. The alkaloid compositions of young shoots ofBerberis integerrima andB. oblonga have been studied. Berbamunine, hydroxyacanthine, magnoflorine, berberine, and palmatine have been isolated.2. The new monoquaternary bisbenzylisoquinoline alkaloid oblongamine has been isolated from the roots ofB. oblonga.3. The most probable structure of oblongamine has been suggested on the basis of chemical reactions and spectral characteristics.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. M. I. Kalinin Andizhan State Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 80–83, January–February, 1977.     

Berberis alkaloids

This review systematizes literature information on alkaloids of plants of the genusBerberis. The main chemical and spectral methods of establishing their structures, and also their pharmacological properties, are considered. The review includes literature sources up to 1992.     

Berberis alkaloids. XXII. Interbrinine and intebrimine — New alkaloids from Berberis integerrima

The known alkaloids reticuline, isoboldine, isocorydine, glaucine, armepavine, oxyacanthine, and heliamine and the new alkaloids intebrinine and intebrimine have been isolated from the total alkaloids of the leaves ofBerberis integerrima, and structures have been proposed for the latter two on the basis of spectral characteristics and independent synthesis.Andizhan State Medical Institute. Institute of the Chemistry of Plant Substances, Uzbekistan Republic Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedeninii, No. 1, pp. 70–73, January–February, 1993.