The INTELSAT VII/VIIA generation of global communications satellites

Developed primarily to provide continuation of services from the INTELSAT V satellites in the Pacific Ocean Region, this latest generation of satellites also has utility for operation in other roles. Several new technologies are combined to give cost-effective international satellite communications on a global, regional and domestic basis. This new higher power satellite will form a fundamental part of the INTELSAT global network, having been designed to match the projected traffic demands and future service requirements.     

The statistical distribution of switch-on delay in single-modesemiconductor lasers I: equilibrium off-condition

The theory of stochastic processes as applied to photon emission and absorption events is used to calculate the distribution of delay in switch-on from a sub-threshold condition in directly modulated semiconductor lasers down to a probability of 10^-10. This involves the derivation of the relative probability distribution of photon number in the laser late enough in the switch-on process such that deterministic relations can be applied thereafter. This distribution, assumed constant in some treatments, is found to change only a little from its initial form, which is a negative binomial, From this one deduces a delay distribution whose width is proportional to the period of the switch-on transient, relatively independently of the precise starting point, but which can be narrowed by injection of additional spontaneous emission. Experiment satisfactorily supports the theory     

QoS‐Guaranteed Multiuser Scheduling in MIMO Broadcast Channels

This paper proposes a new multiuser scheduling algorithm that can simultaneously support a variety of different quality‐of‐service (QoS) user groups while satisfying fairness among users in the same QoS group in MIMO broadcast channels. Toward this goal, the proposed algorithm consists of two parts: a QoS‐aware fair (QF) scheduling within a QoS group and an antenna trade‐off scheme between different QoS groups. The proposed QF scheduling algorithm finds a user set from a certain QoS group which can satisfy the fairness among users in terms of throughput or delay. The antenna trade‐off scheme can minimize the QoS violations of a higher priority user group by trading off the number of transmit antennas allocated to different QoS groups. Numerical results demonstrate that the proposed QF scheduling method satisfies different types of fairness among users and can adjust the degree of fairness among them. The antenna trade‐off scheme combined with QF scheduling can improve the probability of QoS‐guaranteed transmission when supporting different QoS groups.     

Monolithically integrated laser/rear-facet monitor arrays withV-groove for passive optical fiber alignment

An InGaAsP/InP laser monolithically integrated with a rear facet monitor and a fiber V-groove has been demonstrated for the first time. The integrated device incorporates an etched-facet laser fabricated using an in situ, multistep, reactive ion etch process. The integrated V-groove, which is etched directly into the InP substrate, is designed to enable passive alignment of an optical fiber to the active region of the laser. Passive coupling efficiencies of 18% and 8% have been obtained using cleaved multimode and single mode fibers, respectively. Responsivities of the rear facet monitor were as high as 0.49 A/W     

The development of a model to estimate the bistatic transmissionloss associated with intersystem interference

This paper presents a new method for evaluating transmission loss, which is a key factor used in determining the impact of interference between terrestrial radio relay systems and Earth-satellite systems operating at the same frequency. The current model used by the CCIR was developed in the early 1970's when system packing density was low and large earth station antennas allowed the consideration of narrow beam approximations, resulting in a small common volume of intersection of the two beams. The recent increase in microwave communications traffic and improvements in technology have meant that smaller earth station antennas, including very small aperture terminals (VSATs), can be employed and hence the model requires revision. Results from the new model proposed are compared with two experimental geometries and good agreement is found     

Impurity analysis of heavy metal fluoride glass fibres using selectively excited photoluminescence

A technique based on selectively excited fibre impurity luminescence (SEFIL) has been developed and successfully applied to the quantitative analysis of Pr3+, Nd3+ and Fe3+ in heavy metal fluoride glass optical fibres. With fibre standards, SEFIL provides accurate analysis at impurity levels well below the requirements for long-distance fibre applications.     

Phase-noise behaviour of frequency dividers implemented with GaAs heterojunction bipolar transistors

Near carrier phase-noise performance of GaAs microwave frequency dividers (4 GHz) is investigated. The divide-by-4 circuits are fabricated using heterojunction bipolar transistor (HBT) technology. The phase-noise behaviour of the HBT divider chips is correlated with transistor 1/f noise and is insensitive to bias current variations.     

Phospholipids ofRhizobium meliloti andAgrobacterium tumefaciens: Lack of effect of Ti plasmid

We have studied the phospholipid composition ofRhizobium meliloti strains which do or do not contain the large, tumor-inducing (Ti) plasmid ofAgrobacterium tumefaciens. The major phospholipids of stationary phase cells were phosphatidylethanolamine (PE) (22%), phosphatidyl-N-methylethanolamine (22%), phosphatidylcholine (PC) (27%), phosphatidylglycerol (11.4%), and cardiolipin (11%); as average percent of lipid phosphorus. Phosphatidyl-N,N-dimethylethanolamine (3.7%) was also present. The proportions of PE were higher, and PC lower, in logarithmic phase cells. No significant differences were seen in the proportions of phospholipids in strains with or without the Ti plasmid. Qualitative examination of the phospholipids ofA. tumefaciens with or without the Ti plasmid similarly revealed no differences.     

Response properties of single units in an association area of the kitten neocortex

Two percept-genetic methods, the Meta-Contrast Technique (MCT) and the Serial Afterimage Test (AI), were used to study adaptive aspects of perception in a group of 37 subjects suffering from manifest anxiety. The perceptual processes laid bare by these methods reflected not only anxiety but also defensive formations. MCT and AI correlated with each other in these respects and, when combined, correlated with rated symptoms. In accordance with the theory behind percept-genetic methods, anxiety signs appearing late in the test serials were more likely to correspond to manifest symptoms than signs which appeared early. The AI test scores seemed to reflect a difference between anxiety experienced as an inherent quality of life and anxiety as a foreign force struggling for dominance.     

Early unconjugated hyperbilirubinaemia after paracetamol overdosage

A rapid increase of predominantly unconjugated bilirubin in the blood -- which was not due to haemolysis -- was observed in 38 of 60 patients who had taken an overdose of paracetamol. Studies in the rat given an overdose of the drug showed that within 24 hours there was a striking reduction in the activity of bilirubin glucuronyl-transferase and the content of cytochrome P.450 in the liver. It is suggested that such early damage of the hepatic endoplasmic reticulum contributes to the hyperbilirubinaemia of paracetamol poisoning.