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Papers by wr rwr

New Astronomy Reviews, 2001

The VIIth catalogue of galactic PopulationI Wolf–Rayet stars provides improved coordinates, spect... more The VIIth catalogue of galactic PopulationI Wolf–Rayet stars provides improved coordinates, spectral types and bv photometry of known WR stars and adds 71 new WR stars to the previous WR catalogue. This census of galactic WR stars reaches 227 stars, comprising ...

Proceedings of The International Astronomical Union, 2003

The recent VIIth Catalogue of Galactic Wolf-Rayet Stars (van der Hucht 2001), lists 227 Populatio... more The recent VIIth Catalogue of Galactic Wolf-Rayet Stars (van der Hucht 2001), lists 227 Population I WR stars, comprising 127 WN, 87 WC, 10 WN/WC and 3 WO stars. Additional discoveries since then bring the census to >≈ 253 WR stars, including >≈ 27 WNL and 13 WCL stars within 50 pc of the Galactic Center. A re-determination of the optical photometric distances and the galactic distribution of WR stars shows in the solar neighbourhood (d < 3 kpc) a projected surface density of 2.7 WR stars per kpc2, a NWC/NWN number ratio of 1.3, and a WR binary frequency of 40 %. Compared with other Local Group galaxies, the NWC/NWN number ratio in the solar neighborhood is a factor ˜ 2 above the observed metallicity-dependent trend. This could imply that some 30 galactic WN stars in the d < 3 kpc volume are still hiding. Preliminary results of infrared photometric distance determinations are shown. The galactocentric distance (RWR) distribution per subtype shows RWN} and RWC} decreasing with later WN and WC subtypes. The observed trend is more indicative of WNE --> WCE and WNL --> WCL subtype evolution than of WNL --> WNE and WCL --> WCE subtype evolution.

1 While writing the revised version of this paper, we heard of the recent work of A. Elgart, G.M.... more 1 While writing the revised version of this paper, we heard of the recent work of A. Elgart, G.M. Graf, J. Schenker [EGS] concerning the equality of the bulk and edge conductances in a mobility gap, namely in a region where one has localized states.

New Astronomy Reviews, 2001

The VIIth catalogue of galactic Population I Wolf-Rayet stars provides improved coordinates, spec... more The VIIth catalogue of galactic Population I Wolf-Rayet stars provides improved coordinates, spectral types and bv photometry of known WR stars and adds 71 new WR stars to the previous WR catalogue. This census of galactic WR stars reaches 227 stars, comprising 127 WN stars, 87 WC stars, 10 WN/WC stars and 3 WO stars. This includes 15 WNL and 11 WCL stars within 30 pc of the Galactic Center. We compile and discuss WR spectral classification, variability, periodicity, binarity, terminal wind velocities, correlation with open clusters and OB associations, and correlation with H I bubbles, H II regions and ring nebulae. Intrinsic colours and absolute visual magnitudes per subtype are re-assessed for a re-determination of optical photometric distances and galactic distribution of WR stars. In the solar neighbourhood we find projected on the galactic plane a surface density of 3.3 WR stars per kpc 2, with a WC/WN number ratio of 1.5, and a WR binary frequency (including probable binaries) of 39%. The galactocentric distance ( RWR) distribution per subtype shows overlineR WR increasing with decreasing WR subtype, both for the WN and WC subtypes. This overlineR WR distribution allows for the possibility of WNE→WCE and WNL→WCL subtype evolution.

Neurophysiology, 1995

Studying the rostral wiping reflex, RWR, in intact grass frogs allowed us to identify two of its ... more Studying the rostral wiping reflex, RWR, in intact grass frogs allowed us to identify two of its forms: flexor and extensor reflexes (FWR and EWR, respectively). Reflex fields of FWR and EWR considerably overlap; when the common zones are stimulated, both reflex forms can be observed. “Mixed” forms of the reflex are also possible. The probability of initiation of a certain RWR form depends on the stimulus position. Both FWR and EWR are preserved after spinalization, but their receptive fields are somewhat displaced. The hindlimb movement was divided into three phases: positioning (P), lowering, or orientation (L), and brushing aside (BA). In the intact frog, each phase is of approximately similar duration. The reflex phases and their temporal relations are preserved after spinalization. Total movement duration became longer in spinal animals, as compared with that in intact ones; in addition, this duration began to depend on the stimulus position. In the intact frogs, the position of a “working” limb shows the linear dependence on the stimulus localization; this dependence is preserved after spinalization. Our results allow us to conclude that the central generator of wiping reflex includes several subsystems determining the reflex form in a probabilistic manner.

Astronomische Nachrichten, 2011

Photometric and spectroscopic characteristics of the WN5+O6 binary system, V444 Cyg, were studied... more Photometric and spectroscopic characteristics of the WN5+O6 binary system, V444 Cyg, were studied. The Wilson-Devinney (WD) analysis, using new BV observations carried out at the Ankara University Observatory, revealed the masses, radii, and temperatures of the components of the system as MWR=10.64 M⊙, MO=24.68 M⊙, RWR=7.19 R⊙, RO=6.85 R⊙, TWR=31 000 K, and TO=40 000 K , respectively. It was found that both components had a full spherical geometry, whereas the circumstellar envelope of the WR component had an asymmetric structure. The O-C analysis of the system revealed a period lengthening of 0.139±0.018 s yr-1, implying a mass loss rate of (6.76 ± 0.39) × 10-6 M⊙ yr-1 for the WR component. Moreover, 106 IUE-NEWSIPS spectra were obtained from NASA's IUE archive for line identification and determination of line profile variability with phase, wind velocities and variability in continuum fluxes. The integrated continuum flux level (between 1200-2000 \rA) showed a mild and regular increase from orbital phase 0.00 up to 0.50 and then a decrease in the same way back to phase 0.00. This is evaluated as the O component making a constant and regular contribution to the system's UV light as the dominant source. The C IV line, originating in the circumstellar envelope, had the highest velocity while N IV line, originating in deeper layers of the envelope, had the lowest velocity. The average radial velocity calculated by using the C IV line (wind velocity) was found as 2326 km s-1. Tables 2 and 3 and Figs. 4 and 8 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr or via http:://cdsweb.u-strasbg.fr/AN/332/616

Virus Research, 2006

Recombinants based on vaccinia virus vectors, especially on the highly attenuated modified vaccin... more Recombinants based on vaccinia virus vectors, especially on the highly attenuated modified vaccinia virus Ankara (MVA) strain, are now being tested in clinical trials for safety and immunogenicity, using prime/boost heterologous regimes of vaccination. Due to the limited replication capacity of MVA, it is necessary to develop procedures that can enhance the specific cellular immune responses to the recombinant antigen delivered by the MVA vector. In this investigation, we have characterized the systemic immune responses in BALB/c mice using interferon-gamma (IFN-␥) or interleukin-12 (IL-12) in an adjuvant-like manner elicited by MVA recombinants or naked DNA vectors expressing one of those cytokines in combination with the human immunodeficiency virus type 1 (HIV-1) envelope (Env) as antigen. In infected mice, virus gene expression in splenocytes and levels of cytokines IFN-␥ and IL-12 in serum were maximal by 6 h post-infection (hpi) with MVA recombinants expressing IFN-␥ (MVAIFN-␥) or IL-12 (MVAIL-12). In the infected animals, co-expression of HIV-1 env (MVAENV) and either IFN-␥ or IL-12 from MVA recombinants produced a two and three-fold increase of anti-env CD8+ T cell response, respectively. When priming was carried out with DNA vectors expressing HIV-1 env and either IFN-␥ or IL-12, the magnitude of the specific anti-env CD8+ T cell stimulation after MVAENV booster was further enhanced. Our findings revealed that IFN-␥ or IL-12 can be used to potentiate the cellular immune response to HIV-1 env, when delivered either from a single MVA recombinant or from a DNA vector. The increment of the CD8+ T cell response was higher in a DNA/MVA prime/boost protocol. Thus, the immune response of MVA vectors can be improved with the co-delivery of the cytokines IFN-␥ or IL-12.

Journal of Virology, 2000

In this paper, we present preliminary results of a study of colliding winds and atmospheric eclip... more In this paper, we present preliminary results of a study of colliding winds and atmospheric eclipses in three Magellanic Cloud WR+O binaries: Sand 1, Brey 22 and Brey 32. This study, based on time-series of spectra obtained with the Far Ultraviolet Spectroscopic Explorer, will allow us to estimate parameters describing the shock-cone resulting from the collision of the two winds as well as binary and stellar parameters. The most detailed analysis up to now is for Sand 1. Adopting an inclination of i = 40°, we find a total cone-opening angle of 80° and a streaming velocity along the shock of ~ 3000 km/s. We also find a luminosity ratio of LO/LWR = 3.5 ± 0.5 and stellar radii of RWR/R⊙ = 3.5 ± 0.3 and RO/R⊙ = 12 ± 5.

We investigate high spectral efficiency wireless multiple-input multiple-output (MIMO) systems in... more We investigate high spectral efficiency wireless multiple-input multiple-output (MIMO) systems in fading environments. We assume frequency flat fading, channel state information at both the transmitter and receiver sides, and linear preceding based on singular value decomposition (SVD). For this MIMO SVD scenario, the optimal solution in terms of achievable rate requires water-filling to optimally allocate the power to the different channel eigenmodes. Alternatively, reduced complexity power allocation methods can be employed, where the allocation is based on statistical expectations of functions related to the singular values of the channel gain matrix. In this paper we study these power allocation methods, by using the exact distribution of an arbitrary (ordered) eigenvalue of Wishart matrices, with the probability density function of the ¿th largest eigenvalue given as a sum of terms xße-x¿. We derive expressions for the achievable rate for both zero-outage and non-zero-outage strategies. We show that, often, the low-complexity methods have performance very similar to water-filling methods.

Astronomy & Astrophysics, 2002

A newly developed 3-D Monte Carlo model is used, in conjunction with a multi-line non-LTE radiati... more A newly developed 3-D Monte Carlo model is used, in conjunction with a multi-line non-LTE radiative transfer model, to determine the mass-loss rate of the Wolf-Rayet (W-R) star in the massive binary V444 Cyg (WN5+O6). This independent estimate of mass-loss rate is attained by fitting the observed He I (5876 Å) and He II (5412 Å) line profiles, and the continuum light curves of three Stokes parameters (I, Q,U) in the (V) band simultaneously. The high accuracy of our determination arises from the use of many observational constraints, and the sensitivity of the continuum polarization to the mass-loss rate. Our best fit model suggests that the mass-loss rate of the system is (M⊙WR=0.6( ± 0.2) × 10-5 Msolar yr-1), and is independent of the assumed distance to V444 Cyg. The fits did not allow a unique value for the radius of the W-R star to be derived. The range of the volume filling factor for the W-R star atmosphere is estimated to be in the range of 0.050 (for RWR=5.0 Rsun) to 0.075 (for RWR=2.5 Rsun). We also found that the blue-side of He I (5876 Å) and He II (5412 Å) lines at phase 0.8 is relatively unaffected by the emission from the wind-wind interaction zone and the absorption by the O-star atmosphere; hence, the profiles at this phase are suitable for spectral line fittings using a spherical radiative transfer model.

New Astronomy Reviews, 2001

The VIIth catalogue of galactic PopulationI Wolf–Rayet stars provides improved coordinates, spect... more The VIIth catalogue of galactic PopulationI Wolf–Rayet stars provides improved coordinates, spectral types and bv photometry of known WR stars and adds 71 new WR stars to the previous WR catalogue. This census of galactic WR stars reaches 227 stars, comprising ...

Proceedings of The International Astronomical Union, 2003

The recent VIIth Catalogue of Galactic Wolf-Rayet Stars (van der Hucht 2001), lists 227 Populatio... more The recent VIIth Catalogue of Galactic Wolf-Rayet Stars (van der Hucht 2001), lists 227 Population I WR stars, comprising 127 WN, 87 WC, 10 WN/WC and 3 WO stars. Additional discoveries since then bring the census to >≈ 253 WR stars, including >≈ 27 WNL and 13 WCL stars within 50 pc of the Galactic Center. A re-determination of the optical photometric distances and the galactic distribution of WR stars shows in the solar neighbourhood (d < 3 kpc) a projected surface density of 2.7 WR stars per kpc2, a NWC/NWN number ratio of 1.3, and a WR binary frequency of 40 %. Compared with other Local Group galaxies, the NWC/NWN number ratio in the solar neighborhood is a factor ˜ 2 above the observed metallicity-dependent trend. This could imply that some 30 galactic WN stars in the d < 3 kpc volume are still hiding. Preliminary results of infrared photometric distance determinations are shown. The galactocentric distance (RWR) distribution per subtype shows RWN} and RWC} decreasing with later WN and WC subtypes. The observed trend is more indicative of WNE --> WCE and WNL --> WCL subtype evolution than of WNL --> WNE and WCL --> WCE subtype evolution.

1 While writing the revised version of this paper, we heard of the recent work of A. Elgart, G.M.... more 1 While writing the revised version of this paper, we heard of the recent work of A. Elgart, G.M. Graf, J. Schenker [EGS] concerning the equality of the bulk and edge conductances in a mobility gap, namely in a region where one has localized states.

New Astronomy Reviews, 2001

The VIIth catalogue of galactic Population I Wolf-Rayet stars provides improved coordinates, spec... more The VIIth catalogue of galactic Population I Wolf-Rayet stars provides improved coordinates, spectral types and bv photometry of known WR stars and adds 71 new WR stars to the previous WR catalogue. This census of galactic WR stars reaches 227 stars, comprising 127 WN stars, 87 WC stars, 10 WN/WC stars and 3 WO stars. This includes 15 WNL and 11 WCL stars within 30 pc of the Galactic Center. We compile and discuss WR spectral classification, variability, periodicity, binarity, terminal wind velocities, correlation with open clusters and OB associations, and correlation with H I bubbles, H II regions and ring nebulae. Intrinsic colours and absolute visual magnitudes per subtype are re-assessed for a re-determination of optical photometric distances and galactic distribution of WR stars. In the solar neighbourhood we find projected on the galactic plane a surface density of 3.3 WR stars per kpc 2, with a WC/WN number ratio of 1.5, and a WR binary frequency (including probable binaries) of 39%. The galactocentric distance ( RWR) distribution per subtype shows overlineR WR increasing with decreasing WR subtype, both for the WN and WC subtypes. This overlineR WR distribution allows for the possibility of WNE→WCE and WNL→WCL subtype evolution.

Neurophysiology, 1995

Studying the rostral wiping reflex, RWR, in intact grass frogs allowed us to identify two of its ... more Studying the rostral wiping reflex, RWR, in intact grass frogs allowed us to identify two of its forms: flexor and extensor reflexes (FWR and EWR, respectively). Reflex fields of FWR and EWR considerably overlap; when the common zones are stimulated, both reflex forms can be observed. “Mixed” forms of the reflex are also possible. The probability of initiation of a certain RWR form depends on the stimulus position. Both FWR and EWR are preserved after spinalization, but their receptive fields are somewhat displaced. The hindlimb movement was divided into three phases: positioning (P), lowering, or orientation (L), and brushing aside (BA). In the intact frog, each phase is of approximately similar duration. The reflex phases and their temporal relations are preserved after spinalization. Total movement duration became longer in spinal animals, as compared with that in intact ones; in addition, this duration began to depend on the stimulus position. In the intact frogs, the position of a “working” limb shows the linear dependence on the stimulus localization; this dependence is preserved after spinalization. Our results allow us to conclude that the central generator of wiping reflex includes several subsystems determining the reflex form in a probabilistic manner.

Astronomische Nachrichten, 2011

Photometric and spectroscopic characteristics of the WN5+O6 binary system, V444 Cyg, were studied... more Photometric and spectroscopic characteristics of the WN5+O6 binary system, V444 Cyg, were studied. The Wilson-Devinney (WD) analysis, using new BV observations carried out at the Ankara University Observatory, revealed the masses, radii, and temperatures of the components of the system as MWR=10.64 M⊙, MO=24.68 M⊙, RWR=7.19 R⊙, RO=6.85 R⊙, TWR=31 000 K, and TO=40 000 K , respectively. It was found that both components had a full spherical geometry, whereas the circumstellar envelope of the WR component had an asymmetric structure. The O-C analysis of the system revealed a period lengthening of 0.139±0.018 s yr-1, implying a mass loss rate of (6.76 ± 0.39) × 10-6 M⊙ yr-1 for the WR component. Moreover, 106 IUE-NEWSIPS spectra were obtained from NASA's IUE archive for line identification and determination of line profile variability with phase, wind velocities and variability in continuum fluxes. The integrated continuum flux level (between 1200-2000 \rA) showed a mild and regular increase from orbital phase 0.00 up to 0.50 and then a decrease in the same way back to phase 0.00. This is evaluated as the O component making a constant and regular contribution to the system's UV light as the dominant source. The C IV line, originating in the circumstellar envelope, had the highest velocity while N IV line, originating in deeper layers of the envelope, had the lowest velocity. The average radial velocity calculated by using the C IV line (wind velocity) was found as 2326 km s-1. Tables 2 and 3 and Figs. 4 and 8 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr or via http:://cdsweb.u-strasbg.fr/AN/332/616

Virus Research, 2006

Recombinants based on vaccinia virus vectors, especially on the highly attenuated modified vaccin... more Recombinants based on vaccinia virus vectors, especially on the highly attenuated modified vaccinia virus Ankara (MVA) strain, are now being tested in clinical trials for safety and immunogenicity, using prime/boost heterologous regimes of vaccination. Due to the limited replication capacity of MVA, it is necessary to develop procedures that can enhance the specific cellular immune responses to the recombinant antigen delivered by the MVA vector. In this investigation, we have characterized the systemic immune responses in BALB/c mice using interferon-gamma (IFN-␥) or interleukin-12 (IL-12) in an adjuvant-like manner elicited by MVA recombinants or naked DNA vectors expressing one of those cytokines in combination with the human immunodeficiency virus type 1 (HIV-1) envelope (Env) as antigen. In infected mice, virus gene expression in splenocytes and levels of cytokines IFN-␥ and IL-12 in serum were maximal by 6 h post-infection (hpi) with MVA recombinants expressing IFN-␥ (MVAIFN-␥) or IL-12 (MVAIL-12). In the infected animals, co-expression of HIV-1 env (MVAENV) and either IFN-␥ or IL-12 from MVA recombinants produced a two and three-fold increase of anti-env CD8+ T cell response, respectively. When priming was carried out with DNA vectors expressing HIV-1 env and either IFN-␥ or IL-12, the magnitude of the specific anti-env CD8+ T cell stimulation after MVAENV booster was further enhanced. Our findings revealed that IFN-␥ or IL-12 can be used to potentiate the cellular immune response to HIV-1 env, when delivered either from a single MVA recombinant or from a DNA vector. The increment of the CD8+ T cell response was higher in a DNA/MVA prime/boost protocol. Thus, the immune response of MVA vectors can be improved with the co-delivery of the cytokines IFN-␥ or IL-12.

Journal of Virology, 2000

In this paper, we present preliminary results of a study of colliding winds and atmospheric eclip... more In this paper, we present preliminary results of a study of colliding winds and atmospheric eclipses in three Magellanic Cloud WR+O binaries: Sand 1, Brey 22 and Brey 32. This study, based on time-series of spectra obtained with the Far Ultraviolet Spectroscopic Explorer, will allow us to estimate parameters describing the shock-cone resulting from the collision of the two winds as well as binary and stellar parameters. The most detailed analysis up to now is for Sand 1. Adopting an inclination of i = 40°, we find a total cone-opening angle of 80° and a streaming velocity along the shock of ~ 3000 km/s. We also find a luminosity ratio of LO/LWR = 3.5 ± 0.5 and stellar radii of RWR/R⊙ = 3.5 ± 0.3 and RO/R⊙ = 12 ± 5.

We investigate high spectral efficiency wireless multiple-input multiple-output (MIMO) systems in... more We investigate high spectral efficiency wireless multiple-input multiple-output (MIMO) systems in fading environments. We assume frequency flat fading, channel state information at both the transmitter and receiver sides, and linear preceding based on singular value decomposition (SVD). For this MIMO SVD scenario, the optimal solution in terms of achievable rate requires water-filling to optimally allocate the power to the different channel eigenmodes. Alternatively, reduced complexity power allocation methods can be employed, where the allocation is based on statistical expectations of functions related to the singular values of the channel gain matrix. In this paper we study these power allocation methods, by using the exact distribution of an arbitrary (ordered) eigenvalue of Wishart matrices, with the probability density function of the ¿th largest eigenvalue given as a sum of terms xße-x¿. We derive expressions for the achievable rate for both zero-outage and non-zero-outage strategies. We show that, often, the low-complexity methods have performance very similar to water-filling methods.

Astronomy & Astrophysics, 2002

A newly developed 3-D Monte Carlo model is used, in conjunction with a multi-line non-LTE radiati... more A newly developed 3-D Monte Carlo model is used, in conjunction with a multi-line non-LTE radiative transfer model, to determine the mass-loss rate of the Wolf-Rayet (W-R) star in the massive binary V444 Cyg (WN5+O6). This independent estimate of mass-loss rate is attained by fitting the observed He I (5876 Å) and He II (5412 Å) line profiles, and the continuum light curves of three Stokes parameters (I, Q,U) in the (V) band simultaneously. The high accuracy of our determination arises from the use of many observational constraints, and the sensitivity of the continuum polarization to the mass-loss rate. Our best fit model suggests that the mass-loss rate of the system is (M⊙WR=0.6( ± 0.2) × 10-5 Msolar yr-1), and is independent of the assumed distance to V444 Cyg. The fits did not allow a unique value for the radius of the W-R star to be derived. The range of the volume filling factor for the W-R star atmosphere is estimated to be in the range of 0.050 (for RWR=5.0 Rsun) to 0.075 (for RWR=2.5 Rsun). We also found that the blue-side of He I (5876 Å) and He II (5412 Å) lines at phase 0.8 is relatively unaffected by the emission from the wind-wind interaction zone and the absorption by the O-star atmosphere; hence, the profiles at this phase are suitable for spectral line fittings using a spherical radiative transfer model.