Abstract: Improved photonic band-gap optical fibre. The present invention relates in particular to improved photonic band-gap optical fibres that can confine light to a core region of the fibre by the action of both a photonic band-gap cladding and an antiresonant core boundary, at the interface between the core and cladding.

Abstract: Novel preforms and methods of making novel preforms are described. The preforms are suitable for being drawn into photonic bandgap optical fibres. In one form, the preform comprises a stack of elongate members having, in transverse cross section, a triangular close-packed arrangement of circular cross section capillaries, which define interstitial regions containing solid rods. The stack is supported around a relatively large capillary, which defines an inner region of the stack. The stack may be adapted by varying the number of rods in any given interstitial region, in order to generate various different configurations of cladding structure, which can be made into optical fibres having surprising operational characteristics, such as a split gap.

Abstract: The invention relates to a method and apparatus for measuring and recording traffic at nodes in a data transmission network. In particular the invention provides a method of accurately counting individual activities of traffic at individual nodes. The invention is carried out in hardware by using a counter or number of counters which count individual activities of traffic on a preset activity condition being sensed at a node. The invention has the advantage that accurate measurement of traffic at a node is achieved. The invention is also easy to implement in hardware and overcomes the problems inherent in present software solutions.

Abstract: A method of manufacturing an optical fibre, comprises: (i) forming a preform (10) for drawing into the fibre, the preform (10) comprising a bundle of elongate elements, (20,50) arranged to form a first region that becomes a cladding region of the fibre and a second region that becomes a core region of the fibre; (ii) drawing the preform (10) into the fibre. The bundle of elongate elements (20,50) comprises a plurality of elongate elements (20) of a lower purity dielectric material and at least one elongate element (50) of a higher purity dielectric material. The first region comprises a plurality of the lower purity elements (20) and the second region comprises the higher purity element (50).

Abstract: An elongate waveguide for guiding light includes a core having an elongate region of relatively low refractive index; a microstructured region around the core having elongate regions of relatively low refractive index interspersed with elongate regions of relatively high refractive index; and a boundary at the interface between the core and the microstructured region, the boundary including in the transverse cross-section, a region of relatively high refractive index, which is connected to the microstructured region at a plurality of nodes, at least one relatively enlarged region around the boundary (and excluding a boundary having twelve nodes and six enlarged regions substantially at a mid-point between six pairs of relatively more-widely-spaced apart neighboring nodes).

Abstract: A method of manufacturing a microstructured fibre, comprises: providing a preform comprising a plurality of elongate holes; mating at least one, but not all, of the holes with a connector to connect the hole(s) to an external pressure-controller; drawing the preform into the fibre whilst controlling gas pressure in the hole(s) connected to the pressure-controller. The connector is also claimed.

Abstract: An optical fibre comprises: (i) a plurality of elongate, tubular, higher-refractive-index regions (20,50) of dielectric material, the regions being concentric about a longitudinal axis; (ii) a plurality of elongate, tubular lower-refractive-index regions, arranged between the higher-index regions (20,50), and comprising bridging regions (30), of a solid dielectric material, and a plurality of elongate holes (40); and (iii) a core region (10). The higher-index regions (20,50) and the lower-index regions (40) together define a cladding structure arranged to guide light in the core region (10). The elongate holes (40) are arcuate in cross-section.

Abstract: 1) Fungicidal compositions comprising: a) at least one pyridylmethylbenzamide derivative of formula (I): in which the various radicals are as defined in the description, and b) at least one compound (II), which is propamocarb. 2) Method of curatively or preventively combating phytopathogenic fungi in crops, characterized in that an effective, nonphytotoxic amount of one of these fungicidal compositions is applied to the aerial parts of the plants.

Abstract: Apparatus for transferring a vial of fluid material to or from a storage plate containing a number of vials is provided. The apparatus comprises a first plunger disposed on one side of a defined storage plate support position and movable axially into engagement with a vial held in use in a storage plate at the support position to move the vial out of the storage plate in the direction away from the support position on the other side of the support position; and a closed path conveyor having one or more slots to receive a vial, selectively alignable with the axis of the first plunger.

Abstract: The invention relates to a method and apparatus for measuring and recording traffic at nodes in a data transmission network. In particular the invention provides a method of accurately counting individual activities of traffic at individual nodes. The invention is carried out in hardware by using a counter or number of counters which count individual activities of traffic on a preset activity condition being sensed at a node. The invention has the advantage that accurate measurement of traffic at a node is achieved. The invention is also easy to implement in hardware and overcomes the problems inherent in present software solutions.

Abstract: An approach for multidimensional substring selectivity estimation utilizes set hashing to generate cross-counts as needed, instead of storing cross-counts for the most frequently co-occurring substrings. Set hashing is a Monte Carlo technique that is used to succinctly represent the set of tuples containing a given substring. Then, any combination of set hashes will yield a cross-count when intersected. Thus, the set hashing technique is useful in three-, four- and other multidimensional situations, since only an intersection function is required.

Abstract: A data network in which at least one switch is provided with the facility for estimating current network demands using a polygonal approximation to scaled cumulant generating function. The approximaton is iteratively refined in accordance with sampled data passing through the switch. The switch estimates the demand associated with a new data processing request as it is received by the switch and decides whether to accept the request based on available resources.

Abstract: A data network in which at least one switch is provided with the facility for estimating current network demands using a polygonal approximation to scaled cumulant generating function. The approximation is iteratively refined in accordance with sampled data passing through the switch. The switch estimates the demand associated with a new data processing request as it is received by the switch and decides whether to accept the request based on available resources.

Abstract: A method and system for compressing a data base that permits queries on the compressed representation of the data base. Another feature is that an approximation of the values of the data base are derivable directly from the compressed representation of the data base. Yet another feature is correction of poor approximations of the reconstructed data. Still another feature is the capability of performing aggregate queries of the compressed representation of the data base.

Abstract: A portable, remote controlled air sampler for measuring the solid, liquid, and gaseous emissions from sources such as a fossil fuel power plant, or ambient air. The sampler comprises a pump operated suction head movably mounted on a guide means for sucking a sample of air through a selected portion of an air filter strip, a motor operated translating means for translating the suction head along the guide means, and a radio operated, remote control system for selectively actuating the translating means and suction head. The preferred embodiment of the sampler is sufficiently lightweight to be suspended from a buoyant balloon six feet in diameter or less, or having a gas capacity of 115 cubic feet or less.