On the spiral structure of M33

The spiral structure of M33 has been examined on the basis of 197 associations. The parameters of the orientation of the plane are derived. It is supposed to be a system consisting of seven logarithmic spirals. Two principal arms have been interpreted through the use of the density-wave theory. The remaining multiple arm features of M33 may be explained with the stochastic self-propagating model. The distribution of surface brightness segments speaks for the existence of different mechanisms of star formation in M33.     

Assessment aspect of contamination of the Arctic estuary ecosystems

Estuarine ecosystem may be considered as ‘pulse-targets’ where information about contamination of all-river basin and about scale and forms of contaminants input to the seas is concentrated. The nucleus of the estuarine processes of contaminants transformation and sedimentation is the critical salinity zone. In the real natural conditions of the Arctic the salinity dependent processes are masked by hydrodynamic effect. The tasks of effective chemical and biological monitoring of Russian Arctic estuarine ecosystems are formulated.     

Macrobenthic communities of the Pechora Sea: the past and the present on the threshhold of the prirazlomnoye oil-field exploitation

On data of bottom sampling, carried out by means of grab, trawl and underwater photography in August–September of 1993 in the area of the Pechora Sea, quantitative regularities of macrobenthos distribution are described for the ecological monitoring purposes. Maps of -biodiversity and biomass indices, bottom communities and trophic zones, singled out by dominant method, are presented. Assessment of structure changes of the investigated area bottom communities during the last 60–70 years is fulfilled. It is shown that the described communities on the whole are of natural undisturbed character and that the revealed changes are within the natural fluctuations in the abundance of benthic populations or may be interpreted in terms of methodical differences in the data analysis and generalization by different authors.     

Interannual variability in water masses in the Greenland Sea and adjacent areas

Oceanographic data covering the period 1950–1998 are used to determine interannual variations in the convection intensity and water mass structure in the Greenland Sea and adjacent areas. Extremely cold winters throughout 1965–1970 assisted intensification of the water vertical exchange in the Greenland and Norwegian seas. As a result, cold and fresh Greenland Sea Deep Water (GSDW) production was extremely high in the central Greenland Sea while in the southern Norwegian Sea warm and salty water spread downwards. The recent rapid warming in the Greenland Sea Gyre interior from 1980 originates, we argue, from an increase in the Atlantic Water (AW) temperature due to the advection of warm waters into the region with the Return Atlantic Current. The negative water temperature and salinity trends in the upper 300 m layer of the Atlantic Water in the Norwegian Sea prevailed during 1950–1990, whereas during 1980–1990 the water temperature trends are indicative of warming of that layer. Observation series obtained onboard the Ocean Weather Ship Mike confirmed the existence of layers with advectiondriven high oxygen concentrations in intermediate and deep layers. The depth of oxygen maxima and the values of oceanographic parameters at this horizon can be regarded as indicators of the convection intensity in the Arctic domain. A simultaneous rise in NAO index and GSDW temperature points to a link between atmospheric and thermohaline circulation. Weakening in water exchange with the North Atlantic could be the reason for the Polar Water recirculation increase within the Nordic seas.     

The brightest blue stars in M33 galaxy as unresolved star groups

The brightest blue stars in the M33 galaxy have peculiar images. A method to resolve them into components was applied. The brightest members stars atV15–16 mag were recognized as multiple ones. Some stars up toV=17 mag have multiple structures, too. The image of the brightest blue stars consist of two or more components and probably some of them, in fact, resemble dense stellar groups such of R 136 in 30 Dor.     

A new 75-day cepheid in M31

The light curve of the variable with a period of 75^d and amplitude of the lightA _B0 ^m .5 were obtained. It was assumed that the variable was a cepheid. Having in mind the absence of cepheids withP>50^d in M31 it is possible that the new variable is a cepheid-like variable similar to V810 Cen.     

The structure of the spiral arm S4 in andromeda galaxy

TheUBV photometry of 690 stars in the spiral arm S4 and the U magnitudes of 120 stars in the spiral arm S6 with the help of the 2 m RCC telescope of the Rozhen Observatory at the Bulgarian Academy of Sciences, has been used to obtain the colour-magnitude and colour-colour diagrams across the arms. Our age estimations are compared with van den Bergh's (1964). The age gradient across the S4 arm has been found. The colour excessE _B-V is highest at the inner edge of the arm S4. From the age we have evaluated the velocity of star formation propagation across the arm S4 60 km s^–1 , pattern frequency _p 14 km s^–1 kpc^–1 and corotation radiusR _c20 kpc. The structure of S4 along the arm is complicated. In the OB 82 region an age gradient is absent. The young associationOB 79b is located near the outer edge of S4 and it has a large absorptionA _v2^m.5 contrary to the density wave prediction. This association bears no relation to the spiral density wave and it is probably, supernova events that stimulated the star formation in it. The colour excessE _R-V is randomly distributed and the youngest stars are concentrated in the middle of the S6 arm. A value of pattern frequency _p = 12km s^–1 kpc^–1 andR _c=12 kpc of our Galaxy has been obtained from the age distribution of the open clusters and cepheids across the Carina-Sagittarius arm. The spiral structure of M31 is compared with that of the galaxy. There is a similarity between S4 in M31 and Carina-Sagittarius in the Galaxy, and also between the S6 and Perseus arms. The Orion arm in the Galaxy bears no relation to the wave density.     

Preliminary results of measurements of atmospheric turbulence over the sea

We perform the experimental verification of the applicability of the theory of similarity to the wave boundary layer and the assessment of wave-induced perturbations of the air flow depending on various conditions of stratification of the atmosphere and the state of the sea. The measurements were carried out from a stationary platform located in the coastal part of the Black Sea. The experimental procedure is based on the simultaneous measurements of the profile and fluctuations of the wind speed at 5–6 levels in the 1.3–21-m layer, the elevations of the sea surface, the directions of waves and winds, and the mean gradients of temperature and humidity of air. The structure of the boundary layer in the region of measurements depends on the direction of the wind. For weak and moderate onshore winds (< 9 m/sec), the approximate balance is preserved between the production and dissipation of turbulent energy in the cases of unstable and neutral stratification. On the average, the estimates of friction velocity according to the profiles are higher than the dissipative estimates by 10% mainly due to the deficiency of dissipation near the surface. For the offshore wind, the structure of the boundary layer abruptly changes and is determined not by the local parameters but by strong turbulent eddies formed over the dry land. The intensity of low-frequency turbulent fluctuations and the gradient of wind velocity near the surface in the coastal zone are 1.5–2 times higher than for the open sea. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 3, pp. 42–61, May–June, 2007.     

Effect of the shape of an underwater coastal slope on the hydrodynamic instability parameters of a long-shore wave current in a surf zone

This paper reports the results of a numerical study on the hydrodynamic instability parameters of a long-shore wave current in a surf zone with convex and concave bottom profiles. The limits of the change of the relative length of a long-shore meander have been derived in the form of 2/66, and structural and dynamic peculiarities of perturbations in a surf zone with various bottom profiles have been demonstrated.Translated by Vladimir A. Puchkin.