Search results for "31"

Zvaigžņotā Debess: 2011, Vasara (212)

2011

Contents: “ZVAIGŽŅOTĀ DEBESS” FORTY YEARS AGO: A.Balklavs. Extremely Distant New Objects of Metagalaxy (abridged) ; Newspaper „Literaturnaja Rossija” 9 April 1971. Astronautics: Yesterday, Today, Tomorrow (abridged) ; CONFERENCE “The VIEW from SPACE. FIRST MANNED SPACE FLIGHT – 50”: M.Gills. Conference on the Eve of Human Space Flight Anniversary ; J.Ekmanis, S.Negrejeva. Mstislav Keldysh and Golden Age of Soviet Science ; T.Millers. Contribution of Scientists of the Institute of Inorganic Chemistry to the Development of Space Technologies and Materials ; G.Vilka. Remembrance of Friedrich Zander in Rīga ; O.Plepis. My Contribution to the Development of Space Medicine ; J.Stradiņš. Latvia’s …

Lower semicontinuity of weak supersolutions to the porous medium equation

2013

Weak supersolutions to the porous medium equation are defined by means of smooth test functions under an integral sign. We show that nonnegative weak supersolutions become lower semicontinuous after redefinition on a set of measure zero. This shows that weak supersolutions belong to a class of supersolutions defined by a comparison principle.

Ruthenium Metallodendrimers Based on Nitrile‐Functionalized Poly(alkylidene imine)s

2005

The preparation of the first- and second-generation of nitrile-functionalized poly(alkylidene imine) dendrimers with the organometallic ruthenium complex [Ru(η5-C5H5)(PPh3)2Cl] peripherally attached is described. The reaction of N,N′-bis(cyanomethyl)piperazine (1), N,N′-bis[N′′,N′′′-bis(cyanoethyl)aminoethyl]piperazine (2), or N,N,N′,N′-tetrakis(cyanoethyl)ethylenediamine (3) with [Ru(η5-C5H5)(PPh3)2Cl] (4) in the presence of TlPF6 gives the new air-stable ruthenium metallodendrimers 5, 6, and 7, respectively. These stable metallodendrimers are easily prepared and represent a novel quantitative method to solidify and chromatographically purify the otherwise semi-liquid nitrile-functionalize…

Evolution of a Non-Hermitian Quantum Single-Molecule Junction at Constant Temperature

2021

This work concerns the theoretical description of the quantum dynamics of molecular junctions with thermal fluctuations and probability losses. To this end, we propose a theory for describing non-Hermitian quantum systems embedded in constant-temperature environments. Along the lines discussed in [A. Sergi et al., Symmetry 10 518 (2018)], we adopt the operator-valued Wigner formulation of quantum mechanics (wherein the density matrix depends on the points of the Wigner phase space associated to the system) and derive a non-linear equation of motion. Moreover, we introduce a model for a non-Hermitian quantum single-molecule junction (nHQSMJ). In this model the leads are mapped to a tunneling…

Statistical analysis techniques for Partial Discharges measurement under DC voltage

2022

Partial discharges (PD) phenomenon for HVAC (High-Voltage-Alternating-Current) systems has already been widely studied in literature and from this it has been possible to produce a regulatory document that provides indications for description and identification of the different types of discharges. However, the growing diffusion of HVDC (High-Voltage-Direct-Current) systems makes necessary the development of analysis techniques also for DC case. In this paper data obtained from PD measurement under DC voltage were analyzed through the time-frequency map combined with a density-based clustering algorithm. The results show that, with this approach, it's possible to perform a noise rejection a…

Rehabilitation of the severely atrophied dentoalveolar ridge in the aesthetic region with corticocancellous grafts from the iliac crest and dental im…

2016

Background The aim of this study was to assess changes in bone volume after block bone augmentation and placement of dental implants and further evaluate the aesthetic outcome of the treatment. Material and Methods 9 Patients with atrophied anterior maxilla were included in this study. They received total of 21 implants. Dimensions of the alveolar ridge were measured from cone-beam computed tomography x-rays. The bone level at the implant sites was analysed from intraoral x-rays and the aesthetic outcome was assessed from clinical photographs using a pink aesthetic score (PES) scaling. Results The mean gained horizontal bone width at the marginal crest and 5 mm apically was accordingly 2.7m…

1H, 13C and 17O NMR spectral study of chlorinated 3,4-dihydroxybenzaldehydes (protocatechualdehydes)

1995

Abstract Chlorinated 3,4-dihydroxybenzaldehydes have been studied by means of 1 H, 13 C and 17 O NMR spectroscopy. The 1 H and 13 C NMR spectral assignments are based on 2-dimensional 13 C- 1 H chemical shift correlation spectroscopy (COSY). The 17 O NMR measurements at natural isotope content in organic solvents are problematic owing to the poor solubility of the compounds and/or broadness of the resonance lines. In aqueous alkaline solutions, however, all protocatechualdehydes exhibit “easy-to-detect” 17 O NMR spectral characteristics. The 17 O NMR chemical shifts in the range of 140–480 p.p.m. are interpreted as arising from the different canonical structures of formyl substituted phenol…

13C and15N NMR study of substituted 1,2,4-triazines

1995

13C and 15N NMR spectra of eight substituted 1,2,4-triazines were measured and assigned. The assignments of the 13C NMR spectra were based on the substituent chemical shifts and nJ(C,H) coupling constants. 15N NMR chemical shifts generally showing well separated ranges were assigned by the proton coupled 15N NMR spectra. 15N NMR chemical shifts of N-4 in 3- and 5-methoxy or -thiomethyl-substituted 1,2,4-triazines were found to be related significantly (confidence level >99%) with the π-charge at N-4 calculated by a semi-empirical molecular orbital (AM1) procedure. For the 15N NMR chemical shifts of N-1 and N-2, no reliable correlations with the molecular electronic properties such as AM1 π-…

?-Phenylsulfonyl-N-arylacetamides (?-phenylsulfonylacetanilides):1H,13C and15N NMR spectral characterization

2000

Mode of Delivery and the Effectiveness of Foreign Aid: The Example of Missionary Work

2010

Conventional development aid, typically a service from government to government, has been a relatively poor determinant of economic growth or human development in developing countries. In this paper we test whether a distinctly grass-roots delivery mode, as is the case with missionary work, leads to a more effective dispersion of foreign aid. In addition to its mode of delivery, missionary work is also of interest as there is a known positive correlation between the growth rate of Christianity and economic development. We estimate the economic growth impacts of development aid versus missionary work variables by using empirical data from 119 countries and discuss several explanations for ou…