Abstract: An information flow control means for location between a first and second computer network where the first network has a higher security classification than the second network. The information flow control means comprises an information switch having an information input, a first output connected to the first network, a second output connected to the second network, a controller having at least two states, a first state controlling the information switch to connect the input to the first output and a second state controlling the information switch to connect the input to the second output, and an information diode having an input for receiving information from the second network and an output for transferring information received from the second network to the first network through a connection from the information diode output to the first network and which prevents information flowing from the output to the input.

Abstract: A diffractive device has a surface relief structure which when illuminated by a light source, generates one or more diffraction effects which are observable from a range of viewing angles around the device. At least part of the surface relief structure is arranged in a series of tracks, each track being less than 0.25 mm in width. The device, which may be embossed onto a metallised foil, is suitable for use as an anti-forgery authentication element on valuable documents.

Abstract: A gravity gradiometer including first and second proof masses and a device for providing simultaneous free flight of the proof masses under the influence of the gravitional force in which the gradient is to be measured and a capacitance device for monitoring the movement of the centers of mass with respect to each other during free flight by monitoring capacitance between portions of the two proof masses.

Abstract: An object detection system including passive sensors for receiving electromagnetic radiation from a moving object and generating intensity signals representative of the received radiation, and a processing system for subtracting the intensity signals to obtain a differential signature representative of the position of the moving object. An image acquisition system including at least one camera for acquiring an image of at least part of a moving object, in response to a trigger signal, and an analysis system for processing the image to locate a region in the image including markings identifying the object and processing the region to extract the markings for optical recognition.

Abstract: A method of modifying at least part of the surface of a polymer or polymer matrix composite material including: (i) oxidising at least part of the surface of the polymer or polymer matrix material and (ii) subsequently treating the oxidised surface with an organofunctional coupling agent and/or chelating agent, simultaneously with a static and/or a high frequency alternating physical field.

Abstract: An ophthalmic lens suited for extended-wear for periods of at least one day on the eye without a clinically significant amount of corneal swelling and without substantial wearer discomfort. The lens has a balance of oxygen permeability and ion or water permeability, with the ion or water permeability being sufficient to provide good on-eye movement, such that a good tear exchange occurs between the lens and the eye. A preferred lens is a copolymerization product of a oxyperm macromer and an ionoperm monomer. The invention encompasses extended wear contact lenses, which include a core having oxygen transmission and ion transmission pathways extending from the inner surface to the outer surface.

Abstract: The present invention provides an E3 esterase from an organophosphate resistant strain of L. cuprina. The invention further provides DNA sequences encoding such E3 esterases and cells transformed with the DNA sequences. In addition, the invention relates to the use of the enzyme and transformed cells as bioremediation agents.

Abstract: The present invention provides a method for the silencing of specific genes by DNA methylation. The method involves introducing into a cell a single stranded oligonucleotide containing 5-methyl deoxycytosine. The single stranded oligonucleotide has a sequence complementary to a portion of the DNA sequence of the gene to be silenced.

Abstract: The disclosure of the current invention describes a method of handling a message or a document to be released external of a secure computer environment. The message or the document is first directed to a trusted sealing device which displays the message or the document to a human user for visual checking. If the message or document is acceptable to the human user, the method associates the message or the document with a seal produced by the trusted sealing device. The message or the document is then directed along with the associated seal to a gateway which deletes portions of the header and checks the validity of the associated seal. If, as a result of this verification, it is determined that the associated seal is validly associated with the message or the document, the method attaches predetermined header portions to the message or document and communicates the message or the document from the secure computer environment.

Abstract: Corneal onlays for use in surgical implantation into or onto the cornea of a mammal are described. The corneal onlays according to the invention have an optical axis region with optical characteristics which provide visual acuity therethrough and are comprised of a non-biodegradable non-hydrogel ocularly biocompatible material, characterized in that the onlay has a porosity sufficient to allow passage therethrough of tissue fluid components having a molecular fluid weight greater than 10,000 daltons so as to provide for a flux of tissue fluid between cells anterior of the implanted onlay and cells posterior thereof. The porosity of the optical axis region is such that it allows the flux of tissue fluid components whilst excluding ingrowth of ocular tissue. The onlay is further characterized by being adapted for epithelial recolonization.

Abstract: A method and means to control the degree to which the presence of covert information may be reduced, eliminated or corrupted in documents created on a computer device (particularly complex documents) before the document is transmitted outside a secure environment in which the document is created. The process of handling a document in a secure environment comprises the preferred step of displaying the document or a predetermined portion thereof in a manner which conforms to the rule that no pixel of the display is written to more than once for the current portion of the document being displayed.

Abstract: A process for the production of lower molecular weight polymers by free radical polymerization, characterized in that there is added to the polymerization system a compound of the general formula I ##STR1## wherein R.sup.1 is hydrogen, chlorine, an alkyl group, or a group capable of activating the vinylic carbon towards free radical addition;R.sup.2 is hydrogen or an optionally substituted alkyl, alkenyl, aryl, cycloalkenyl or cycloalkyl group or the group --COZ, where Z is R.sup.3 or OR.sup.3, where R.sup.3 is hydrogen or an optionally substituted alkyl, alkenyl or aryl group.X is a hydrogen atom, an alkyl or aryl group, or a halogen, and the two X groups may be the same or different.The invention also includes polymers or oligomers made by the process and novel compounds of the general formula I as defined above.

Abstract: A visual indicator assembly for use with an underwater mine system comprises a surface position marker (11) having a buoyancy device (23), the marker (11) being adapted to provide visual and/or audible indications on the surface that a mine has been "fired". The assembly further comprises a support device (13) for supporting the marker (11) underwater and a severable coupling (37) which, when severed, releases the marker (11) to float to the surface. The assembly further comprises a release means selectively operable to sever the coupling (37) and to release the marker (11) to float to the surface.

Abstract: This invention relates to a diode pumped slab laser in the form of a slab where two opposite faces are adapted to receive pumping radiation with the faces being cut at the Brewsters angle at one end to provide entrance/exit faces for the lasing radiation. The laser radiation beam follows a zig-zag path in the slab and is contained within the slab by total internal reflection. The laser slab is contained within an optical cavity which results in the laser beam completing a double zig-zag beam path. The design results in good pump/mode matching, mitigates thermally induced birefringence problems, overcomes amplified spontaneous emission problems, requires no coatings or curved surfaces, and is easy and relatively inexpensive to make. The slab can be used within both Quasi-CW and CW modes.

Abstract: A heat transfer device (20) which comprises a collapsible envelope (2) including a liquid transfer (7) which, in use, is in an expanded form and includes a liquid (8) that evaporates from one wall (6) of the envelope and condenses on another wall (5), the condensed liquid being returned via the liquid transfer means (7) to the wall (6) at which evaporation took place.

Abstract: The invention relates to a method of modifying the surface of a fabric which comprises the successive steps of: i) exposing the fabric surface to UV radiation; and ii) oxidative treatment of the fabric.

Abstract: A method and apparatus for establishing and maintaining synchronization of a demultiplexer for use with a digital transmissions system. The invention utilizes a repetitive synchronization pattern which may be interleaved within a frame or inserted as a block at a particular point within a frame. Frames of words including at least one synchronization bit and at least one data bit are received. The received synchronization bit or bits of a frame or frame or frames is cross correlated with the expected value of the respective bit or bits. A synchronization signal is formed by summing the cross correlation values. It is then compared with a threshold signal to indicate the state of synchronization.

Abstract: A method of obtaining oceanographic and meteorological data from high frequency radar spectral information including the steps of transmitting a plurality of signals to a remote geographic location, recording signals backscattered from the said location, generating a family of Doppler clutter spectra from the recorded backscattered signal and analyzing the Doppler clutter spectra in terms of a model or models to generate oceanographic and meteorological data estimates. The Doppler spectra are categorized according to Suitability for Deatiled Analysis (SDA). The SDA takes account of the clutter-to-noise ratio in the spectrum, the amplitudes of the Bragg-lines, multimode propagation, spectral broadening and other spectral parameters. Spectra with a low SDA are inappropriate for extracting directional wave spectrum estimates of reasonable accuracy but are useful for obtaining wind direction estimates.

Abstract: A frequency surveillance method for monitoring background atmospheric noise evels in unoccupied channels in an operating frequency band of a high frequency communication system. In the method, the unoccupied channels are scanned a number of times to obtain analogue signals. The obtained signals are transformed to a digital form and averaged. The averaged digital signals are filtered to remove substantially all radio frequency interference. Absolute signals are then produced by scaling or comparing the filtered signals with a known noise level. The background noise levels are obtained by further averaging the absolute signals. A visual display unit is used to display the background noise levels as a function of frequencies. A frequency surveillance apparatus is also disclosed.

Abstract: An infrared intrusion sensor includes an array of infrared detectors, infrared collection optics, a focal plane scanning device having a dither adapted to repetitively scan the infrared radiation across the detector array, signal process devices, and local or remote displays. The sensor incorporates heterodyne detection techniques with a local oscillator signal derived from the scanning frequency of the focal plane scanning device. The sensor has a low false alarm rate and enhanced detection range. A method of processing the signals includes analog to digital conversion, integration of the digital signals to produce a background signal, phase sensitive detection of the digital signal producing a target signal, and comparison of the background and target signals producing a difference signal. The difference signal is integrated to produce a background noise signal and processed to become a threshold signal which is finally compared to the difference signal to produce an alarm signal.