A decade ago we introduced empirically derived formulas which allowed one to estimate the performance which can be achieved in the design of broad-band antireflection (AR) coatings based upon the indices of refraction ofthe materials to used, the bandwidth required, and the overall thickness of the coating. This has proved to be a useful tool to avoid attempting impossible designs and to guide ...

Occam filters are a class of filters for additive random noise, based on the idea that when a lossy data compression algorithm is applied to a noisy signal with the allowed loss set equal to the noise strength, the loss and the noise tend to cancel rather than add. In this paper, we apply non-linear Occam filters to broad-band signals. Using the chirp signal as a specific example, we find that ...

In this work we study the reflection of circularly polarised light from a nano-structured biological material found in the exocuticle of scarabus beetles. This material is made of a stack of ultra-thin (~5 nm) uniaxial layers arranged in a left-handed helicoidal stack, which resonantly reflects circularly polarized light. A chirp in the layer thickness combined with a finite absorption coeffici...

We present parametrized broad-band spectral models valid at frequencies between 30 and 300 MHz for six bright radio sources selected from the 3C survey, spread in right ascension from 0 to 24 h. For each source, data from the literature are compiled and tied to a common flux density scale. These data are then used to parametrize an analytic polynomial spectral calibration model. The optimal pol...

We present the results of a BeppoSAX observation of the nearby spiral galaxy NGC 4945 in the 0.1–200 keV energy band. The nuclear X-ray emission emerges above '7 keV, through an absorber with column density NH ∼ a few 1024 cm−2. Its remarkable variability (doubling/halving timescale ∼104 s) is not associated with any appreciable spectral changes, ruling out variations of the interposed absorber...

We study the broad band (3-100 keV) spectrum of Cygnus X–2 with INTEGRAL. We find that the spectrum is well fitted by a Comptonized component with a seed-photons temperature of ∼ 1 keV, an electron temperature of ∼ 3 keV and an optical depth τ ∼ 8. Assuming spherical geometry, the radius of the seed-photons emitting region is ∼ 17 km. The source shows no hard X-ray emission; it was detected onl...

With the emergence of broadband wireless networks and increasing demand of multimedia information on the Internet, wireless multimedia services are foreseen to become widely deployed in the next decade. Real-time video transmission typically has requirements on quality of service (QoS). However, wireless channels are unreliable and the channel bandwidth varies with time, which may cause severe ...

A plasmonic interference pattern can be formed when multiple surface plasmon waves overlap coherently. Utilizing a sharp edge coupling mechanism, we experimentally demonstrate plasmonic interference patterns that can be designed at will by shaping the edges in a metallic film. The patterns can also be dynamically tailored by adjusting the wavelength, the polarization, and the incident angle of ...

We present intermediate resolution 0.9–2.5μm IR spectra of 12 highly reddened stars, including some well known and some unfamiliar sources. A new technique for extracting calibration curves from standard star data is employed, and is found to be very successful. The reddening to each object is fully discussed and is calculated from both the continua (which was split into shortand long-wavelengt...

AbstractBridging and Transmission of VDSL2 broadband over power lines has received considerable attention recently to cater to broadband distribution within the premises of a residence. Power lines are fundamentally different from telephone lines both in topology and load impedance. Power lines have a thicker gauge and shorter straight lengths, apart from a large number of bridge taps (BT) with...