Multilevel trellis coded modulations for the Rayleigh fadingchannel

The authors present coded 8-phase-shift-keyed (8-PSK) modulations for the Rayleigh fading channel. The schemes are based on multilevel trellis-coded-modulation constructions and utilize maximum free Hamming distance binary convolutional codes as building blocks. A suboptimal multistage decoder that utilizes interstage interleaving and iterative decoding is proposed and evaluated. Examples are constructed to show that the proposed schemes outperform the best modified codes of the Ungerboeck type due to significantly higher implicit time diversity, yielding seven branches of built-in time diversity, whereas the Ungerboeck code yields four branches of time diversity for a 64-state system. The transmission delay is higher, however. The new schemes can provide three levels of unequal error protection when 8-PSK or 8-differential-phase-shift-keying (8-DPSK) modulations are used. They provide 10-14-dB channel signal-to-noise ratio gain over uncoded 4-DPSK at a bit error rate of 10^-3 for a modest decoding complexity     

Synthesis and fastness properties of styryl and azo disperse dyes derived from 6-nitro substituted 3-aryl-2-methyl-4(3H)-quinazolinone

The synthesis of 6-nitro substituted 3-aryl-2-methyl-4(3 H )-quinazolinones from readily available starting materials, such as isatoic anhydride, is described. One of these, 3-phenyl-2-methyl-4(3 H )-quinazolinone, has been utilised to prepare a range of styryl disperse dyes for polyester. Novel azo disperse dyes based on 6-nitro-3-( m -diethylaminophenyl)-2-methyl-4(3 H )-quinazolinone as coupling component are reported. The application properties of the dyes on polyester and their fastness properties have been evaluated, with the latter being disappointing.     

Perturbative treatment of conservative and non-conservative oscillators

We treat certain nonlinear oscillator problems by means of a perturbative procedure starting from an initial approximation that is itself nonlinear, albeit solvable. Frequency corrections and the initial amplitudes of the oscillators are determined analytically. After elimination of the secular terms, the expressions for the (periodic) trajectories are presented as well     

Technology assessment methods for radiology systems

This article discusses the strengths and weaknesses of technology assessment methods for the evaluation of novel and complex radiology systems, including picture archiving and communication systems (PACS), computed radiography (CR), teleradiology, and other new models for the delivery of radiology services. Using examples from PACS and CR, we review early economic assessments of PACS from the radiology department. We then broaden our perspective to discuss the analytic criteria that can be used to evaluate economic analyses of PACS as the health care delivery system shifts toward managed care. We close with a proposal for optimizing the integration of information technology into the clinical environment through ongoing target data collection during the implementation of new radiology systems.     

A Study of the Addition of Alkylamines and Hydrazine to Fullerenes

A 1:1 monoadduct of 1-aminobutane with C₆₀, C₆₀(H)(n-C₄H₉NH), has been characterized by mass spectrometry, infrared spectroscopy and other techniques. Addition of 1,4-diaminobutane to C₆₀ gives rise to a 1:2 adduct of the diamine with C₆₀, while hydrazine hydrate gives multiple addition products. Under conditions of diimide reduction, C₆₀ gives products resulting from the addition of hydrazine units as well as reduction.     

Laparoscopic splenic cystectomy: a case report

Congenital epidermoid splenic cysts are very rare. They are known to become symptomatic as a consequence of enlargement, hemorrhage, rupture, or infection. Recent options in the treatment of splenic cysts have included percutaneous drainage, partial splenectomy, or open splenic cystectomy. The authors present the first report of a pediatric patient with a large epidermoid cyst of the spleen treated by laparoscopic partial cyst excision and omental packing. Follow-up at 1 year confirms no recurrence. Laparoscopy provides a minimal access method of obtaining pathological confirmation of diagnosis, reduction of cyst complications, and a short hospital stay, while preserving splenic function.     

Plane-wave scattering by a magnetoplasma cylinder

The scattering of H-polarised plane waves by an infinitely long axially magnetised cylinder of uniform plasma is investigated for the case in which the radius of the cylinder is small in comparison with the wavelength of the incident wave. The scattering amplitude is found to be a maximum at two frequencies, which are shown to be related to the familiar dipolar resonant frequency of an isotropic plasma column. Approximate expressions for the two resonant frequencies are derived.