CiteULike: Author Gavrilova

Updating the topology of the dynamic Voronoi diagram for spheres in Euclidean d-dimensional space

ML Gavrilova — 2008-07-23T08:24:33-00:00

Computer Aided Geometric Design, Vol. 20, No. 4. (July 2003), pp. 231-242.

The problem of dynamic maintenance of a Voronoi diagram for a set of spheres moving independently in d-dimensional space is addressed in this paper. The maintenance of this Voronoi diagram for spheres moving along given trajectories, requires the calculation of topological events, that occur when d+2 spheres become tangent to a common sphere. The criterion for determination of the topological event in the Euclidean metric is derived as a solution of a system of non-linear algebraic equations. The criterion is given in the form of polynomial algebraic equations dependent on the coordinates and trajectories of the moving spheres. These equations are solved using numerical methods. Application of the method to study the structure of a system of polydisperse spheres in a three-dimensional Euclidean space is briefly discussed.

Baeocytes in the cyanobacterium Pleurocapsa sp.: Characterization of the differentiated cells produced by multiple fission

A Pinevich — 2008-05-09T14:35:35-00:00

Microbiology, Vol. 77, No. 1. (20 February 2008), pp. 62-68.

Abstract Electron microscopy of cyanobacterium Pleurocapsa sp. CALU 1126 revealed that multiple fission proceeds by successive binary fissions. The cultivation conditions were determined when the number of baeocytes (products of multiple fission) was comparable with that of macrocytes (products of binary fission), and cell sorting was achieved for the first time. Juvenile baeocytes were shown to differ from macrocytes in: (1) the absence of sheath; (2) the linear-peripheral configuration of their lamellar system; (3) lower content of phycobiliproteins and higher content of carotenoids; (4) the set of PSII polypeptides. Baeocytes can therefore be considered differentiated cells characterized by the uncoupling between energy and biosynthetic metabolism.

Towards User Modeling Meta-ontology

Michael Yudelson — 2008-02-13T08:40:16-00:00

User Modeling 2005 (2005), pp. 448-452.

The paper proposes meta-ontology of the user modeling field. Ontology is meant to structure the state-of-the-art in the field and serve as a central reference point and as a tool to index systems, papers and learning media. Such ontology is beneficial for both the user modeling research community and the students as it creates a shared conceptualization of the known approaches to building user models and their implementations.

Evaluation of dissociation constants of antigen-antibody complexes by ELISA.

BB Kim — 2006-06-12T14:17:26-00:00

J Immunol Methods, Vol. 131, No. 2. (7 August 1990), pp. 213-222.

In this communication some of the advantages and constraints in the use of ELISA (enzyme-linked immunosorbent assay) procedures to evaluate antigen-antibody dissociation constants (Kd) are discussed and experimental conditions under which the effective Kd is close to the true value are proposed. Interactions between horseradish peroxidase (POD), human myoglobin and insulin with mono- and polyclonal antibodies (McAb and PcAb) were used to demonstrate that ELISA can be used to determine the average Kd, characterizing the interaction between antigens and PcAb. The Kd values obtained by ELISA were similar to those determined by luminescent immuno-cofactor analysis (LICA).

p53 regulates mitochondrial respiration.

S Matoba — 2007-08-31T16:16:42-00:00

Science, Vol. 312, No. 5780. (16 June 2006), pp. 1650-1653.

The energy that sustains cancer cells is derived preferentially from glycolysis. This metabolic change, the Warburg effect, was one of the first alterations in cancer cells recognized as conferring a survival advantage. Here, we show that p53, one of the most frequently mutated genes in cancers, modulates the balance between the utilization of respiratory and glycolytic pathways. We identify Synthesis of Cytochrome c Oxidase 2 (SCO2) as the downstream mediator of this effect in mice and human cancer cell lines. SCO2 is critical for regulating the cytochrome c oxidase (COX) complex, the major site of oxygen utilization in the eukaryotic cell. Disruption of the SCO2 gene in human cancer cells with wild-type p53 recapitulated the metabolic switch toward glycolysis that is exhibited by p53-deficient cells. That SCO2 couples p53 to mitochondrial respiration provides a possible explanation for the Warburg effect and offers new clues as to how p53 might affect aging and metabolism.

Spectra of dense pure hydrogen plasma in Balmer area

Y Vitel — 2007-04-27T20:20:53-00:00

Journal of Quantitative Spectroscopy and Radiative Transfer, Vol. 83, No. 3-4. (1 February 2004), pp. 387-405.

We study experimentally the pure dense hydrogen plasma spectra in Balmer area. Dense plasma with electron concentrations up to [approximate]1019 cm-3 has been created by pulse discharge in quartz capillary. Diagnostics of the plasma is made on the basis of optical measurements at [lambda]=632.8 nm. The temperature profile is defined from independent measurements of brightness and transparency at different distances from the centre of the capillary. Detailed study is performed for two discharge conditions: at electron density Ne=6.5x1018 cm-3 and temperature T=18000 K and Ne[approximate]1.5x1019 cm-3, T=23000 K. The self-consistent scheme to calculate the weakly nonideal plasma spectra based on the microfield model and unperturbed oscillator strengths distribution is also described. For the lower density regime we have obtained a satisfactory agreement of measured spectra with calculated ones. For higher electron density the lowering of experimental spectra was obtained near Balmer series limit in comparison with calculations. Further measurements at higher electron densities (Ne>1019 cm-3) are required to prove the obtained tendency for some "clearing up" of dense hydrogen plasma spectra at Balmer area.

L2DTL/CDT2 and PCNA Interact with p53 and Regulate p53 Polyubiquitination and Protein Stability through MDM2 and CUL4A/DDB1 Complexes.

Damon Banks — 2006-07-27T13:16:12-00:00

Cell Cycle, Vol. 5, No. 15. (1 August 2006)

The CUL4-ROC1 E3 ligase complex regulates genome stability, replication and cell cycle progression. A novel WD40 domain-containing protein, L2DTL/CDT2 and PCNA were identified as proteins associated with CUL4/DDB1 complexes. Inactivation of CUL4A, L2DTL, PCNA, DDB1 or ROC1 induced p53 stabilization and growth arrest. L2DTL, PCNA and DDB1/CUL4A complexes were found to physically interact with p53 tumor suppressor and its regulator MDM2/HDM2. The isolated CUL4A complexes display potent and robust polyubiquitination activity towards p53 and this activity is dependent on L2DTL, PCNA, DDB1, ROC1 and MDM2/HDM2. We also found that the interaction between p53 and CUL4 complex is regulated by DNA damage. Our data further showed that MDM2/HDM2 is rapidly proteolyzed in response to UV irradiation and this process is regulated by CUL4/DDB1 and PCNA. Our studies demonstrate that PCNA, L2DTL and the DDB1-CUL4A complex play critical and differential roles in regulating the protein stability of p53 and MDM2/HDM2 in unstressed and stressed cells.

The clinical uses of leptin.

P Gorden — 2006-01-25T10:26:25-00:00

Curr Opin Pharmacol, Vol. 3, No. 6. (December 2003), pp. 655-659.

Leptin is the first of a group of adipocyte-secreted hormones to be used clinically to treat hypoleptinemic states. In children with congenital leptin deficiency and extreme obesity, leptin induces satiety and a dramatic loss of weight. In hypoleptinemic patients with extreme insulin resistance and lipodystrophy, leptin ameliorates insulin resistance, hyperglycemia, hyperinsulinemia, dyslipidemia and hepatic steatosis. In both these leptin-deficient states, leptin therapy restores gonadotrophin secretion, as well as luteinizing hormone and thyroid-stimulating hormone pulsitility.