The model of a simple perceptron using phaseencoded inputs and complex-valued weights is proposed. The aggregation function, activation function, and learning rule for the proposed neuron are derived and applied to Boolean logic functions. The complex-valued neuron (CVN) is shown to be superior to traditional perceptrons. Optical and analog circuit implementations are discussed and the CVN is s...

Choroidal neovascularisation developed in 62/66 (94%) eyes followed up for a mean period of 11.2 years after treatment with xenon arc feeder vessel coagulation for proliferative sickle retinopathy (PSR). In 27 eyes the neovascularisation was chorioretinal alone and in 35 eyes choriovitreal. Chorioretinal neovascularisation (CRN) was a benign complication but may convert to choriovitreal neovasc...

We report the results of a synthetic spectral analysis of Hubble STIS spectra of the AM CVn-type cataclysmic variable CP Eri obtained when the system was in quiescence. The FUV spectrum is best fitted by a helium-dominated, hybrid composition (DBAZ) white dwarf with Teff ∼ 17, 000K ± 1000K, log g∼ 8, He abundance ∼ 1000× solar, H abundance ∼ 0.1× solar, metallicity Z ∼ 0.05× solar, V sin i ∼ 40...

We present the latest results from a spectroscopic survey designed to uncover the hidden population of AM Canum Venaticorum (AM CVn) binaries in the photometric data base of the Sloan Digital Sky Survey (SDSS). We selected ∼2000 candidates based on their photometric colours, a relatively small sample which is expected to contain the majority of all AM CVn binaries in the SDSS (expected to be ∼5...

The AM Canum Venaticorum (AM CVn) binaries are a rare group of ultra-short period, masstransferring white dwarf binaries, some of which may be Type Ia supernova progenitors. More than a third of the total known population of AM CVn binaries have been discovered via the Sloan Digital Sky Survey (SDSS). Here, we discuss our search for new AM CVns in the SDSS spectroscopic data base, and present t...

Background Human immunodeficiency virus (HIV) is infecting over 34.0 million people worldwide, being responsible for one of the major current pandemics [1]. The most severely affected region is the Sub-Saharan Africa where nearly 1 in 20 adults is infected with HIV, accounting for 69% of infections worldwide [1]. Several strategies to halt HIV spread are currently being pursued, including the u...

We describe a spectroscopic survey designed to uncover an estimated ∼40 AM Canum Venaticorum (AM CVn) stars hiding in the photometric data base of the Sloan Digital Sky Survey. We have constructed a relatively small sample of about 1500 candidates based on a colour selection, which should contain the majority of all AM CVn binaries while remaining small enough that spectroscopic identification ...

We study two models for AM CVn stars: white dwarfs accreting (i) from a helium white dwarf companion and (ii) from a helium-star donor. We show that in the first model possibly no accretion disk forms at the onset of mass transfer. The stability and the rate of mass transfer then depend on the tidal coupling between the accretor and the orbital motion. In the second model the formation of AM CV...

XMM-Newton has been performing comprehensive studies of X-ray luminous RS CVn binary systems in its calibration and guaranteed time programs. We present results from ongoing investigations in the context of a systematic study of coronal emission from RS CVns. We concentrate here on coronal abundances and investigate the abundance pattern in RS CVn binaries as a function of activity and average ...

We say a subset Σ ⊆ FN of the free group of rank N is spectrally rigid if whenever T1, T2 ∈ cvN are R-trees in (unprojectivized) outer space for which ‖σ‖T1 = ‖σ‖T2 for every σ ∈ Σ, then T1 = T2 in cvN . The general theory of (non-abelian) actions of groups on R-trees establishes that T ∈ cvN is uniquely determined by its translation length function ‖ · ‖T : FN → R, and consequently that FN its...