From Corollary 3.5 in [Berkani, M; Sarih, M.; Studia Math. 148 (2001), 251– 257] we know that if S, T are commuting B-Fredholm operators acting on a Banach space X, then ST is a B-Fredholm operator. In this note we show that in general we do not have ind(ST) = ind(S) + ind(T), contrarily to what has been announced in Theorem 3.2 in [Berkani, M; Proc. Amer. Math. Soc. 130 (2002), 1717–1723]. However, if there exist U, V ∈ L(X) such that S, T, U, V are commuting and US + V T = I, then ind(ST) = ind(S) + ind(T), where ind stands for the index of a B-Fredholm operator.
The very young LMC clusters SL666, NGC2098 and NGC2100 were found to exhibit a variation of spectral types with distance from the cluster centre. From spectral dassification of their bright members it is found that the early type stars are accumulated in the inner region of the cluster whereas the late type ones are found in the outer areas. Star counts on photographic plates with different exposure times have shown that the bright stars are segregated in the central regions of the clusters. Both observational results from spectral classlfication and star counts give evidence that the most massive early type stars are located in the inner parts of the clusters. This allow us to suggest that the observed mass segregation is not due
to the relaxation mechanism of the clusters.
Freshwater pulmonate snails from three locations in Lake Furesø north of Copenhagen were screened for infection with furcocercariae (by shedding in the laboratory) and recovered parasite larvae were diagnosed by molecular methods (by performing PCR of rDNA and sequencing the internal transcribed spacer [ITS] region). Overall prevalence of infection in snails was 2%. Recovered cercariae from Lymnaea stagnalis (Linnaeus) were diagnosed as Diplostomum pseudospathaceum Niewiadomska, 1984 (prevalence 4%) and cercariae from Radix balthica (Linnaeus) as D. mergi (Dubois, 1932) (prevalence 2%). Pathogen-free rainbow trout were then exposed to isolated cercariae and infection success and site location of metacercariae in these fish were determined. Infection experiments confirmed that both species could infect rainbow trout with the eye lens as infection site for the metacercarial stage although infection success differed. Combination of molecular and biological assays may contribute to improvement of our knowledge on diagnosis, distribution and biology of diplostomids in fish.
Despite theoretical predictions on the existence of solar gravity oscillations (g modes), their detection is still marginal. The main reasons are their frequencies, ν<0.2 mHz, and amplitudes of
less than 10 cm/s. However, because these modes are extremely sensitive to the physical conditions in the very deep sun, they can give us detailed Information on the physics of the core. Using a resontant scattering spectrophotometer we measured the radial velocity of the Sun at the KI 769.9 nm. line with very high resolution and temporal stability. The observatíons carried out at Izaňa (Tenerife) continuously for the last three years, háve been used to search for solar g modes. Analysis of the whole lot of data as one single time series provides a spectral resolution of 12 nHz, and signal with amplitude above noise level, 1 cm/s. Several techniques are used in order to find.the signature of g modes and calculate the parameters Po and vr. Individua! peaks, well above noise level, are identified and their frequencies are likely to correspond with
g modes.