Kardioloogia

Eesti Arst 2012; 91(9):507–50

History as Communication in the works of Tartu-Moscow Schoool

[Abstract] The aim of this presentation will be to try and find a common ground between the cultural semiotics of the Tartu-Moscow school and the Western semiotic tradition which has greatly been influenced by Charles Peirce. I will concentrate on the works of Yuri Lotman and Boriss Uspensky, and try to bring out both the similarities and differences in their approaches. Lotman finds that human culture can be treated both as the sum of messages circulated by various addressers and as one message transmitted by the collective “I” if the humanity itself; from this point of view, culture can be viewed as a vast example of autocommunication, where information transferred in time from an earlier “I” to a later one leads to a restructuring of the “I” itself. For Uspensky, semiotic approach to history presupposes appealing to the point of view of the participants in the historical process: only those things are meaningful that are meaningful from their point of view. This approach, in turn, presupposes reconstructing the conceptual system that determines both the perception of certain events and the reaction to these events. This applies both to individuals and larger social groups, such as cultures. From the semiotic perspective, then, the historical process can be viewed as a process of communication where new information that is constantly created causes a certain reaction on the side of the receiver (the social group). Historical experience, in turn, influences the future turn of events: based on similar concepts and experiences, the society as a collective personality creates a program for the future and plans its future behavior. Every step in the movement of history changes both the present and the past, and with this also the future turn of event

Effect of tangential swirl air inlet angle on the combustion efficiency of a hybrid powder-solid ramjet

A new ramjet configuration using powder and solid fuel as propellant is investigated, namely, hybrid powder-solid ramjet (HPSR). Boron particles were used as the powder in this study. In order to improve combustion efficiency of boron and simplify the engine structure, a tangential swirl air inlet is adopted on the HPSR. Ignition model based on the multi-layer oxide structure and Global reaction combustion model of boron particles, the Lagrangian particle trajectory model and the realizable k-ε turbulence model were implemented to calculate three-dimensional two-phase flow and combustion in the HPSR with the different tangential air inlet angles (0°,5°, 10°, 15°, 20°, 25°). The effects of tangential air inlet angles on the ignition and combustion of boron were analyzed. The results show that when the tangential swirl air inlet angle is 10°, the combustion efficiency of boron particles and the total combustion efficiency of engine are the highest; the temperature distribution in the second combustion chamber is uniform, and the ignition distance of particles is small, for the HPSR configuration tested

Absorption Cross Sections of NH_3, NH_2D, NHD_2, and ND_3 in the Spectral Range 140-220 nm and Implications for Planetary Isotopic Fractionation

Cross sections for photoabsorption of NH_3, NH_2D, NHD_2, and ND_3 in the spectral region 140-220 nm were determined at ~298 K using synchrotron radiation. Absorption spectra of NH_2D and NHD_2 were deduced from spectra of mixtures of NH_3 and ND_3, of which the equilibrium concentrations for all four isotopologues obey statistical distributions. Cross sections of NH_2D, NHD_2, and ND_3 are new. Oscillator strengths, an integration of absorption cross sections over the spectral lines, for both A ← X and B ← X systems of NH_3 agree satisfactorily with previous reports; values for NH_2D, NHD_2, and ND_3 agree with quantum chemical predictions. The photolysis of NH_3 provides a major source of reactive hydrogen in the lower stratosphere and upper troposphere of giant planets such as Jupiter. Incorporating the measured photoabsorption cross sections of NH_3 and NH_2D into the Caltech/JPL photochemical diffusive model for the atmosphere of Jupiter, we find that the photolysis efficiency of NH_2D is lower than that of NH_3 by as much as 30%. The D/H ratio in NH_2D/NH_3 for tracing the microphysics in the troposphere of Jupiter is also discussed

Enhancement of deuterated ethane on Jupiter

We report laboratory measurements of cross sections of CH_3D and C_2H_5D in the extreme ultraviolet. The results are incorporated in a photochemical model for the deuterated hydrocarbons up to C_2 in the upper atmosphere of Jupiter, taking into account the fast reactions for exchanging H and D atoms between H_2 and CH_4, H + HD ↔ D + H_2, CH_3 + D ↔ CH_2D + H. Since there is no reliable kinetics measurement for the reaction, CH_2D + H → CH_3 + D, we use Yung et al.'s estimate for its rate constant. The strong temperature dependence for this reaction leads to large isotopic fractionation for CH_3D and C_2H_5D in the upper atmosphere of Jupiter, where their production rates depend on the abundance of deuterated methyl radical. The model predicts that the D/H ratio in deuterated ethane is about 15 times that of the bulk atmosphere. A confirmation of this result would provide a sensitive test of the photochemistry of hydrocarbons in the atmosphere of Jupiter

Isotopic Fractionation of Nitrogen in Ammonia in the Troposphere of Jupiter

Laboratory measurements of the photoabsorption cross section of ^(15)NH_3 at wavelengths between 140 and 220 nm are presented for the first time. Incorporating the measured photoabsorption cross sections of ^(15)NH_3 and ^(14)NH_3 into a one-dimensional photochemical diffusive model, we find that at 400 mbar, the photolytic efficiency of ^(15)NH_3 is about 38% greater than that of ^(14)NH_3. In addition, it is known that ammonia can condense in the region between 200 and 700 mbar, and the condensation tends to deplete the abundance ratio of ^(15)NH_3 and ^(14)NH_3. By matching the observed ratio of ^(15)NH_3 and ^(14)NH_3 at 400 mbar, the combined effect of photolysis and microphysics produces the ratio of (2.42 ± 0.34) × 10^(-3) in the deep atmosphere, in excellent agreement with the Galileo spacecraft measurements. The usefulness of the isotopic composition of ammonia as a tracer of chemical and dynamical processes in the troposphere of Jupiter is discussed

Absorption cross sections of HCl and DCl at 135-232 nanometers: implications for photodissociation on Venus

Cross sections for photoabsorption of HCl and DCl are determined in the spectral region of 135-232 nm using radiation from a synchrotron light source. At wavelengths near the onset of absorption (λ > 200 nm), cross sections of HCl are approximately 5-10 times larger than those of DCl. These data are used to calculate rates of photodissociation of HCl and DCl in the Venusian atmosphere. For the entire wavelength region measured, the rate of photodissociation of DCl is only 16% that of HCl. The difference in rates of photodissociation contributes to the exceptionally large [D]/[H] ratio of the Venusian atmosphere

Formation Reaction Mechanism And Infrared Spectra Of Criegee Intermediate Anti-trans-methacrolein Oxide [ch2c(ch3)choo] And Its Associated Precursor And Adduct Radicals

Methacrolein oxide (MACRO, CH$_{2}$C(CH$_{3}$)CHOO) is an important Criegee intermediate produced in ozonolysis of isoprene, the most abundantly-emitted non-methane hydrocarbon in the atmosphere. We employed a step-scan Fourier-transform infrared spectrometer to investigate the source reaction of MACRO in laboratories. Upon UV irradiation of precursor 1,3-diiodo-2-methyl-prop-1-ene CH$_{2}$IC(CH$_{3}$)CHI {\bf (1)}, the 3-iodo-2-methyl-prop-1-en-3-yl CH$_{2}$C(CH$_{3}$)CHI radical {\bf (2)} was detected, confirming the fission of the allylic C-I bond rather than the vinylic C-I bond. Upon UV irradiation of {\bf (1)} and O$_{2}$ near 21 Torr, {\it anti-trans}-MACRO {\bf (3a)} was observed to have an intense OO-stretching band near 917 \wn, much greater than those of {\it syn}-CH$_{3}$CHOO and (CH$_{3}$)$_{2}$COO, supporting a stronger O-O bond in MACRO because of resonance stabilization. At increased pressure (86-346 Torr), both reaction adducts CH$_{2}$C(CH$_{3}$)CHIOO {\bf (4)} and (CHI)C(CH$_{3}$)CH$_{2}$OO {\bf (5)} radicals were observed, indicating that O$_{2}$ can add to either carbon of the delocalized propenyl radical moiety of {\bf (2)}. We also employed a quantum-cascade laser and an UV laser to investigate the yield and kinetics of MACRO. The yield of MACRO is only ~5 \% from the source reaction, significantly smaller than other carbonyl oxides. The rate coefficients of the formation reaction and the self-reaction of MACRO will also be discussed