Accretion disks in Algols: progenitors and evolution

There are only a few Algols with measured accretion disk parameters. These measurements provide additional constraints for tracing the origin of individual systems, narrowing down the initial parameter space. We investigate the origin and evolution of 6 Algol systems with accretion disks to find the initial parameters and evolutionary constraints for them. With a modified binary evolution code, series of close binary evolution are calculated to obtain the best match for observed individual systems. Initial parameters for 6 Algol systems with accretion disks were determined matching both the present system parameters and the observed disk characteristics. When RLOF starts during core hydrogen burning of the donor, the disk lifetime was found to be short. The disk luminosity is comparable to the luminosity of the gainer during a large fraction of the disk lifetime.Comment: 8 pages, 6 figures , accepted by A&

Polarization-sensitive resonance CSRS of deoxy-and oxyhaemoglobin

Polarization-sensitive coherent Stokes Raman scattering (CSRS) measurements of oxy- and deoxyhaemoglobin in aqueous solutions are reported. The excitation wavelengths used were chosen in the region of the Q absorption bands to achieve twofold electronic resonance. The dispersion profiles of all independent susceptibility (3) components and purely anisotropic and anti-symmetric scattering contributions were resolved within the frequency non-degenerate CSRS scheme. Eight bands of oxyhaemoglobin and five bands of deoxyhaemoglobin were observed in the range 1500-1680 cm-1. Simultaneously fitting sets of polarization spectra provided vibrational parameters (positions, bandwidths, amplitudes, phases and CSRS depolarization ratios) for each compound. Major bands were assigned to the non-totally symmetric v10, v11 and v19 modes of the porphyrin macrocycle. The phases calculated exhibited a correlation with the symmetry of the vibrations. On the basis of the spectral fits, the three additional peaks arising in the oxyhaemoglobin spectra could be ascribed to the bands of intermediate deoxyhaemoglobin. The occurrence is due to the partial photolysis of oxyhaemoglobin. Vibrational parameters of these bands were found to be essentially similar to the parameters of the bands observed in the spectra of the stable deoxyhaemoglobin. Despite the asymmetric character predicted, the major bands were all contributed to by a considerable isotropic component. A decrease in the depolarization ratio PR1212 of the anomalously polarized v19 mode from 7.7 in oxyhaemoglobin to 4.3 in deoxyhaemoglobin was observed. Such a decrease in anti-symmetric character of the vibration on release of the ligand supports the occurrence of deformation of the haem ring system

Advanced detectors and signal processing

Continued progress is reported toward development of a silicon on garnet technology which would allow fabrication of advanced detection and signal processing circuits on bubble memories. The first integrated detectors and propagation patterns have been designed and incorporated on a new mask set. In addition, annealing studies on spacer layers are performed. Based on those studies, a new double layer spacer is proposed which should reduce contamination of the silicon originating in the substrate. Finally, the magnetic sensitivity of uncontaminated detectors from the last lot of wafers is measured. The measured sensitivity is lower than anticipated but still higher than present magnetoresistive detectors

Spin-up and hot spots can drive mass out of a binary

The observed distribution of periods and mass ratios of Algols with a B type primary at birth was updated. Conservative evolution fails to produce the large fraction with a high mass ratio: i.e. q in [0.4-0.6]. Interacting binaries thus have to lose mass before or during Algolism. During RLOF mass is transferred continuously from donor to gainer. The gainer spins up; sometimes up to critical velocity. Equatorial material on the gainer is therefore less bound to the system. The material coming from the donor through the first Langrangian point impinges violently on the surface of the gainer or the edge of the accretion disc, creating a hot spot in the area of impact. The sum of rotational energy (fast rotation) and radiative energy (hot spot) depends on the mass-loss rate. The sum of both energies on a test mass located in the impact area equals exactly its binding energy at some critical value. As long as the mass transfer rate is smaller than this value the gainer accepts all the mass coming from the donor: RLOF happens conservatively. But as soon as the critical rate is exceeded the gainer will acquire no more than the critical value and RLOF runs into its liberal era. Low mass binaries never achieve mass-loss rates larger than the critical value. Intermediate mass binaries evolve mainly conservatively but mass will be blown away from the system during the short era of rapid mass transfer soon after RLOF-ignition. Binaries with 9+5.4 solar masses (P in [2-4] d) evolve almost always conservatively. Only during some 20,000 years the gainer is not capable of grasping all the material that comes from the donor. During this short lapse of time a significant fraction of the mass of the system is blown into interstellar space. The mass ratio bin [0.4-0.6] is now much better represented.Comment: 12 pages, 7 figures, accepted for publication in A&A; accepted versio

Description and performance of a highly sensitive confocal Raman microspectrometer

A confocal Raman microspectrometer was developed for the study of small biological objects such as single living cells and metaphase and polytene chromosomes. It employs a confocal detection scheme, well known from confocal fluorescence microscopes, in order to avoid signal contributions from the environment of the samples. The resolution is 0.45 ± 0.05 m in the lateral direction and 1.3 ± 0.1 m in the axial direction. The laser excitation wavelength is 660 nm. At this wavelength biological samples do not degrade in the laser radiation as was the case when laser radiation of 514.5 nm was used. The signal throughput from the sample position to the detector was optimized to the extent that in the spectral region around a 1000 cm-1 Raman shift 15% of the Raman scattered light collected by the microscope objective is detected. For signal detection a liquid nitrogen-cooled slow-scan CCD camera is used. Laser powers of 5-10 mW suffice to obtain high-quality Raman spectra, with signal integration times of the order of minutes. As an example, spectra obtained from the nucleus and the cytoplasm of an intact human lymphocyte are shown

Discrimination of human cytotoxic lymphocytes from regulatory and B-lymphocytes by orthogonal light scattering

Light scattering properties of human lymphocyte subpopulations selected by immunofluorescence were studied with a flow cytometer. Regulatory and B-lymphocytes showed a low orthogonal light scatter signal, whereas cytotoxic lymphocytes identified with leu-7, leu-11 and leu-15 revealed a large orthogonal light scatter signal. Two populations in light scatter histograms could be observed with monoclonal antibodies directed against determinants present on both regulatory and cytotoxic lymphocytes. By analysis of the lymphocytes of 16 individuals we found a linear relation between the number of cells with a large orthogonal light scattering and the number of cytotoxic lymphocytes identified with leu-7, leu-11 and leu-15. These observations demonstrate physical differences between cytotoxic lymphocytes and regulatory and B lymphocytes. Moreover, the results suggest a method to estimate the amount of cytotoxic lymphocytes without using monoclonal antibodies

Mass loss out of close binaries. II

Liberal evolution of interacting binaries has been proposed previously by several authors in order to meet various observed binary characteristics better than conservative evolution does. Since Algols are eclipsing binaries the distribution of their orbital periods is precisely known. The distribution of their mass ratios contains however more uncertainties. We try to reproduce these two distributions theoretically using a liberal scenario in which the gainer star can lose mass into interstellar space as a consequence of its rapid rotation and the energy of a hot spot. In a recent paper (Van Rensbergen et al. 2010, A&A) we calculated the liberal evolution of binaries with a B-type primary at birth where mass transfer starts during core hydrogen burning of the donor. In this paper we include the cases where mass transfer starts during hydrogen shell burning and it is our aim to reproduce the observed distributions of the system parameters of Algol-type semi-detached systems. Our calculations reveal the amount of time that an Algol binary lives with a well defined value of mass ratio and orbital period. We use these data to simulate the distribution of mass ratios and orbital periods of Algols. Binaries with a late B-type initial primary hardly lose any mass whereas those with an early B primary evolve in a non-conservative way. Conservative binary evolution predicts only ~ 12 % of Algols with a mass ratio q above 0.4. This value is raised up to ~ 17 % using our scenario of liberal evolution, which is still far below the ~ 45 % that is observed. Observed orbital periods of Algol binaries larger than one day are faithfully reproduced by our liberal scenario. Mass ratios are reproduced better than with conservative evolution, but the resemblance is still poor.Comment: 11 pages, 6 figures, accepted for publication in A&A; accepted versio

Optimization of macromolecular prodrugs of the antitumor antibiotic adriamycin

In our earlier work [10] on aminoribosyl-bound prodrugs of adriamycin (ADR) using poly(α-l-glutamic acid) (PGA) grafted in high yield (90–100 mol.%) with various peptide spacers as a plasma-soluble macromolecular carrier we observed rather low cytotoxic activities in L1210 leukemia and B16 melanoma in vitro assays. These results may be tentatively explained by a decreased susceptibility of the spacer-bound adriamycin moiety to hydrolysis by lysosomal enzymes due to the high spacer load. This hypothesis was tested by the study of two conjugates prepared by a different route. Peptide conjugates of adriamycin (Gly-Gly-Leu—ADR and Gly-Gly-Gly-Leu—ADR) were synthesized using the trityl N-protecting group and were coupled to PGA in 4.5 mol.% load according to the method described earlier [11]. However, these conjugates were almost totally devoid of cell growth-inhibiting activity in L1210 and B16 in vitro tests. The data suggest that either the uptake of the polymeric prodrugs into the cell by pinocytosis is highly dependent on spacer load or molecular weight, or that lysosomal digestion is too slow for efficient release of ADR. Possibly, enzymatic degradation of PGA which is known to occur only between pH 4 and 6 is rate-limiting for release of the drug. Current studies include the enzymatic degradation of PGA—peptide spacer—drug systems using p-nitroaniline as a model drug and papain as the enzyme. By variation of the length and load of spacer it can be estimated under which conditions the release of drug (using UV spectrometry) is faster than degradation of the polymer (as determined by viscometry). In addition, the uptake of PGA and derivatives with a fluorescent label into tumor cells is studied using laser flow cytometry and laser microscopy