Abstract: A hologram reticle and method of patterning a target. A layout pattern for an image to be transferred to a target is converted into a holographic representation of the image. A hologram reticle is manufactured that includes the holographic representation. The hologram reticle is then used to pattern the target. Three-dimensional patterns may be formed in a photoresist layer of the target in a single patterning step. These three-dimensional patterns may be filled to form three-dimensional structures. The holographic representation of the image may also be transferred to a top photoresist layer of a top surface imaging (TSI) semiconductor device, either directly or using the hologram reticle. The top photoresist layer may then be used to pattern an underlying photoresist layer with the image. The lower photoresist layer is used to pattern a material layer of the device.

Abstract: It is an object of the present invention to provide a manufacturing method of a photomask and a manufacturing method of a semiconductor apparatus using the photomask that optimize a sub resolution assist feature on the photomask so as to ensure the depth of focusing for a formed image of a pattern for circuit formation on the photomask, preferably to the miniaturization of a pattern of the semiconductor apparatus.

Abstract: The invention relates to a filter device for an illumination system, especially for the correction of the illumination of the illuminating pupil, including a light source, with the illumination system being passed through by a bundle of illuminating rays from the light source to an object plane, with the bundle of illuminating rays impinging upon the filter device, including at least one filter element which can be introduced into the beam path of the bundle of illuminating rays, with the filter element including an actuating device, so that the filter element can be brought with the help of the actuating device into the bundle of illuminating rays.

Abstract: Discharging stability and resolution power for the pitch between a specified pixel and a pixel of an identical color adjacent with the specified pixel forming a stripe pattern of an optical device constituting by arranging plural elongate pixels on a substrate by using an ink jet printing apparatus are intended to be improved, wherein an optical device is manufactured by determining plural discharging positions to the inside of each of the pixels of an optical device, determining the plural discharging positions to the positions different from each other in the longitudinal direction of the pixel, specifying each of the plural nozzles with a natural number n counted sequentially from the end of the pixel, defining a surplus as b when dividing the natural number n with a repetitive number a (b is an integer satisfying: 0?b?a?1), corresponding the surplus b to each of the plural nozzles, and printing the pixel by repeating the unit step of conducting discharge from the nozzles corresponding to the surplus b.

Abstract: Siloxane epoxy materials employed as redistribution layers in electronic packaging and coatings for imprinting lithography, and methods of fabrication are disclosed.

Abstract: An electrostatic image forming method is described. The method includes forming latent images corresponding to yellow, magenta and cyan images on a photoreceptor, developing corresponding latent images by developers containing yellow, magenta and cyan toner to form yellow, magenta and cyan images and transferring the yellow, magenta and cyan images on a recording material, and the yellow toner and the magenta have specific reflectance characteristics described in the specification.

Abstract: The present invention provides an image forming apparatus that has high-durability and can prevent image degradation that could be caused by an increase in residual potential on a photoconductor, occurrence of image blur and incidental images and can stably form a high-quality image even when repetitively used for long hours, and includes at least an electrophotographic photoconductor, a non-contact type corona discharge charging unit, an exposing unit, a developing unit, a transfer unit and a charge eliminating unit configured to eliminate a residual charge on the photoconductor by irradiating the electrophotographic photoconductor with light, wherein the outermost surface layer of the electrophotographic photoconductor contains at least a filler and an is amine compound having a specific structure, and the exposure dose of the charge eliminating unit is controlled at at least two stages during a time from the start of image forming operation to the end of the image forming operation.

Abstract: An electrophotographic photoreceptor, comprising: an electroconductive substrate; and a photosensitive layer located overlying the electroconductive substrate, wherein the photosensitive layer is a single-layered layer comprising a charge generation material and an electron transport material having the following specific formula (1): wherein the charge generation materials is a titanylphthalocyanine having a specific CuK? 1.542 ? X-ray diffraction spectrum.

Abstract: To provide an image-receiving sheet for electrophotography that suppresses blocking, allows toner images to fix satisfactorily, has excellent glossiness and reduced brittleness and can form high-quality images and to provide a process for image formation using the image-receiving sheet for electrophotography, an image-receiving sheet for electrophotography includes a substrate containing a base and a resin layer arranged on at least one side of the base; and at least one toner-image-receiving layer arranged on the resin layer of the substrate. The resin layer arranged between the toner-image-receiving layer and the base includes a polyethylene resin having a mass-average density of 0.935 g/cm3 or less and/or a melt flow rate MFR of 11 g/10 min. or less. In addition, an image-receiving sheet for electrophotography including a support and at least one toner-image-receiving layer over the support, the toner-image-receiving layer including a polyolefin resin.

Abstract: In a manufacturing method of a developing agent, by mixing a coloring agent fine particle with at least a surfactant, an aqueous solvent and an organic solvent, thereby dispersing the coloring agent fine particle in a solvent containing the surfactant, the aqueous solvent and the organic solvent, it becomes possible to obtain favorable coloring agent dispersibility and to improve the OHP transparency in the resulting developing agent.

Abstract: A polyester resin for toner, which has superior fixing property, storage stability, and image density in an electrophotographic image forming process or an electrostatic printing process, and a toner including the same are disclosed. The polyester resin for toner is produced by carrying out esterification reaction and polycondensation reaction of reactant comprising aromatic dibasic acid of 80 to 100 mol % with respect to the total dibasic acid, trivalent or higher acid of 0.5 to 30 mol % with respect to the total dibasic acid, aromatic diol of equal to or less than 90 mol % with respect to the total dibasic acid, and aliphatic diol of 10 to 80 mol % with respect to the total dibasic acid, in the presence of a polycondensation catalyst selected from the group consisting of TiO2/SiO2 coprecipitates, TiO2/ZrO2 coprecipitates and the mixture thereof.

Abstract: A method of preparing toner includes preparing a pigment dispersion solution by dispersing a pigment in a mixed surfactant solution composed of an anionic reactive surfactant and a nonionic reactive surfactant, mixing the pigment dispersion solution with a polymer latex prepared by polymerizing a toner composition comprising an amphiphilic macromonomer having at least one reactive functional group at an end thereof and at least one polymerizable monomer, and adding an inorganic salt to a mixed solution of the polymer latex and the pigment dispersion solution to be agglomerated, wherein a shape of toner particles can be controlled to have circularity of 0.5-1.0 by adjusting an amount of the nonionic reactive surfactant to be 20-100 parts by weight based on 100 parts by weight of the anionic reactive surfactant. In addition, a method of forming an image uses the toner, and an image forming apparatus to form an image employs the toner.

Abstract: A polyester toner includes particles of a resin, a colorant, an optional wax, and a polyion coagulant, where the toner is prepared by an emulsion aggregation process.

Abstract: A transfer substrate includes a transfer material layer on a support substrate via a light absorbing layer. Antireflection patterns for preventing light reflection on an interface of the support substrate and the light absorbing layer are provided between the support substrate and the light absorbing layer. Thickness of this antireflection patterns is set to a value with which an absorptance of light having a predetermined wavelength absorbed in the light absorbing layer is maximized.

Abstract: The invention describes a process and a device for producing at least one three-dimensional object, a photo-polymerizable material is solidified by means of simultaneous or almost simultaneous exposure of a build area or partial build area in a building plane via electromagnetic radiation, wherein a distance between a support plate, at which the object to be generated is built, and the building plane is changed during at least one exposure phase. It is possible according to the invention to solidify the three-dimensional object in a main direction during a radiation phase exceeding a current prescribed hardening depth, without interrupting supply of electromagnetic energy during the irradiation phase. Further, it is possible to control a current hardening depth of the photopolymerizable material during a building phase. Embodiments of suitable devices are also described.

Abstract: A radiation-sensitive composition containing 1 to 80% by weight of a solid component and 20 to 99% by weight of a solvent. The solid component contains a compound B which has (a) a structure derived from a polyphenol compound A by introducing an acid-dissociating group to at least one phenolic hydroxyl group of the polyphenol compound A which is synthesized by a condensation between a di- to tetrafunctional aromatic ketone or aromatic aldehyde each having 5 to 36 carbon atoms with a compound having 1 to 3 phenolic hydroxyl groups and 6 to 15 carbon atoms, and (b) a molecular weight of 400 to 2000. The composition containing the compound B is useful as an acid-amplified, non-polymeric resist material, because it is highly sensitive to radiation such as KrF excimer lasers, extreme ultraviolet rays, electron beams, and X-rays, and provides resist patterns with a high resolution, high heat resistance, and high etching resistance.

Abstract: Disclosed is a process of preparing a printing plate comprising imagewise exposing a light sensitive printing plate material comprising a hydrophilic support and provided thereon, an image formation layer and an oxygen shielding layer in that order, and developing the exposed material with an aqueous solution having a pH of from 3 to 9, wherein the image formation layer contains a photopolymerization initiator (A), a water-soluble polymeric binder (B), a polymerizable ethylenically unsaturated compound (C) and a sensitizing dye (D) represented by formula (1) or (2), and the aqueous solution contains at least one selected from compound A, compound A?, compound B, compound B? and a compound represented by formula (3),

Abstract: The invention provides a planographic printing plate precursor that is writable by laser exposure and is composed of a support, a photosensitive recording layer formed on the support, and a backcoat layer containing an epoxy resin, the backcoat layer being formed on the side of the support opposite to the photosensitive recording layer side; and a stack of the planographic printing plate precursors. According to the invention, scratches on the photosensitive recording side of the planographic printing plate precursor can be prevented when brought into contact with another planographic printing plate precursor in the stack without interleaving slip sheets, and productivity in a plate making process can be improved.

Abstract: There are provided a photosensitive composition used in one-shot exposure of exposing it via a photomask to light from a UV lamp or in direct writing with light from a UV lamp or laser light to form a patterned latent image to be developed with an alkaline aqueous solution, wherein a difference between maximum absorbance and minimum absorbance, in a wavelength range of 355 to 405 nm, of a dry coating thereof before light exposure is within 0.3 per 25 ?m film thickness of the dry coating, and a dry film obtained by applying the photosensitive composition onto a carrier film and then drying it.

Abstract: A defoamer solution is introduced into a pre-rinsing solution, developer, or post-rinsing solution in a lithographic processing apparatus in relation to the surface area of processed imageable element. Surfactants can then be used in the developer if desired, and the recirculation rates of various solutions can be reduced.

Abstract: A laser sensitive lithographic printing plate comprises an electrochemically grained, anodized, hydrophilically treated aluminum substrate with a reflection optical density of 0.30 or higher; a free radical polymerizable photosensitive layer; and a water soluble or dispersible overcoat. The photosensitive layer comprises a polymeric binder, a free radical polymerizable monomer, a free radical initiator, and a sensitizing dye. Such dark aluminum substrate in combination with the hydrophilic treatment allows both clean background and good printing durability. Such plate can be exposed with a suitable laser at lower dosage to cause hardening in the exposed areas. The exposed plate can be developed with a regular liquid developer or with ink and/or fountain solution.

Abstract: A coating composition for forming etch mask patterns may include a polymer and an organic solvent. The polymer may have an aromatic ring substituted by a vinyl ether functional group. The polymer may be, for example, a Novolak resin partially substituted by a vinyl ether functional group or poly(hydroxystyrene) partially substituted by a vinyl ether functional group.

Abstract: Provided herein is a method of manufacturing a gas sensor. The method includes forming electrodes on a surface of a substrate, manufacturing a paste having a complex of CNTs and a metal-ligand complex comprising a metal that has gas adsorption selectivity for specific gases, coating the paste on the substrate to cover the electrodes, patterning the paste by a photolithography process, and reducing the metal-ligand complex included in the patterned paste.

Abstract: The present invention aims to provide a pattern forming process which allows efficiently, highly precisely forming of a permanent pattern such as interconnection patterns and also allows achieving both tent property and resolution at high level. The pattern forming process includes laminating a photosensitive layer on a substrate to be processed in a pattern forming material which comprises at least the photosensitive layer, and exposing two or more arbitrarily selected regions in the photosensitive layer with light of a different amount of energy, wherein a laser beam emitted from a light irradiating unit having ‘n’ imaging portions receiving light from a light irradiating unit and outputting the light is modulated before the photosensitive layer is exposed with the laser beam through a microlens array in which microlenses each having a non-spherical surface capable of compensating the aberration due to distortion of output surfaces of the imaging portions are arrayed.

Abstract: Techniques, methods, and structures disclosed in relation to extreme ultraviolet (EUV) lithography in semiconductor processing. In one exemplary implementation, a method may comprise using ion beam deposition to deposit a first multilayer stack of thin films on a substrate to planarize and smooth surface defects on the substrate. The method includes using atomic layer deposition to deposit a second multilayer stack of thin films on the first multilayer stack of thin films. The second multilayer stack of thin films may comprise an extreme ultraviolet reflective multilayer stack. The second multilayer stack of thin films may comprise fewer surface defects than the first multilayer stack of thin films. The method may further comprise processing an extreme ultraviolet mask blank to form an extreme ultraviolet reflective mask.

Abstract: The photomask of this invention includes, on a transparent substrate, a semi-shielding portion having a transmitting property against exposing light, a transparent portion having a transmitting property against the exposing light and surrounded with the semi-shielding portion, and an auxiliary pattern surrounded with the semi-shielding portion and provided around the transparent portion. The semi-shielding portion and the transparent portion transmit the exposing light in an identical phase with respect to each other. The auxiliary pattern transmits the exposing light in an opposite phase with respect to the semi-shielding portion and the transparent portion and is not transferred through exposure.

Abstract: A silver halide color photographic light-sensitive material, having at least one each of blue-, green-, and red-sensitive emulsion layers containing yellow, magenta, and cyan couplers, respectively, on a support; wherein said blue-sensitive emulsion layer contains at least one coupler of formula (I); and wherein the light-sensitive material satisfies expression a-1) and/or b-1): wherein, Q forms a 5- to 7-membered ring with the —N?C—N(R1)-; R1 and R2 each are a substituent; m is 0 to 5; and X is a hydrogen atom, or a coupling split-off group; 0.5?Dmax(UV)/Dmin(UV)?1.1??a-1) wherein Dmax(UV)/Dmin(UV) is the smallest of the value in a wavelength range of 340 to 450 nm; 1300?(B?C)/A?20000??b-1) wherein B is yellow Dmax, C is yellow Dmin; and A is an amount mol/m2 of the coupler of formula (I).

Abstract: In domestic installations of any type of furnace or equivalent, proof of lean combustion is necessary to satisfy requirements of certification agencies. Exhibiting proof of lean combustion during the operation of an integrated fuel reformer and fuel cell system can be problematic because the point of combustion and its nature may shift during operation. In addition, the preferred ratio of fuel to air in these fuel-reforming systems is often near a stoichiometry of one. In the present invention, the combination of a flame-detecting device, a temperature sensing device and an oxygen or hydrocarbon sensor is used to verify the occurrence of combustion, and show proof of lean combustion.

Abstract: Disclosed is a combustion apparatus using an air fuel ratio sensor, which detects the operation of the air fuel sensor based on pressure of gas and air introduced into a combustion chamber and adjusts the amount of gas and air introduced into the combustion chamber using a controller based on data detected by the air fuel sensor.

Abstract: The invention comprises a sectional candle apparatus. The candle is made in a plurality of sectional candle wax portions. A plurality of thin non combustable wafers separate each of the candle portions or sections from one another with openings centrally of each wafers or spacers so that one continues wick may extend through the candle portions and through the spacer. The candle can be turned by the wick down to one of the spacers and then the remaining unburned portion of one uppermost candle sectional portion broken off evenly across the spacer to provide an even top surface to the candle.

Abstract: To provide a burner structure that is capable of efficiently cooling a nozzle main body with a small amount of air, and takes an efficient countermeasure against a falling clinker or radiation heat. The burner structure includes: a pulverized coal-air mixture path provided in a burner central portion and supplying a mixture of a fuel and a primary air; a secondary air path provided around the pulverized coal-air mixture path and supplying a secondary air; a cooling air path provided around or above and below the secondary air path and supplying a cooling air; a nozzle main body attached to furnace-side end portions of the pulverized coal-air mixture path and the secondary air path in a tiltable form and provided with a flame holder at its tip end; and a cooling air nozzle attached to a furnace-side end portion of the cooling air path in a tiltable form.

Abstract: An orthodontic appliance for attachment to a tooth with adhesive is provided that resists debonding due to impact. The appliance is provided with a compliant interface between the adhesive and the point of impact. An appliance may be provided with an orthodontic bracket suspended from a mechanical bonding base that is to be secured with adhesive to a tooth. The suspension provides compliant movement between the appliance and the mechanical bond. The movement is preferably resilient or elastic movement, but may be plastic. The movement resists fracture of the adhesive by more slowly decelerating an impacting mass, reducing forces on the adhesive. A pad attached at its outer periphery to a mesh which leaves the inner central portion of the pad free may provide the compliance, so the pad exhibits flex, suspending the bracket to move with impacting masses, absorbing energy and reducing forces transmitted to the adhesive.

Abstract: The self-ligating bracket for use in orthodontics comprises a base; an occlusal wall and a gingival wall extending from the base and having at least one ligature wing; a slot separating the occlusal wall and the gingival wall; a slide retained in a guide provided in the occlusal and/or gingival wall and arranged for being displaced between a closed position, in which the slide bridges the slot, and an open position in which the slot is open in the labial direction; means capable of retaining the slide in both its closed and open position; at least one recess in which a spring is seated and which is arranged in the gingival or occlusal wall of the bracket and is provided with an opening that faces the slide and from which a spring projects; a first stop on the slide which abuts against the at least one spring in the open position of the slide; a projection is which provided on the slide and which is so arranged that during displacement of the slide to its closed position it will abut against the spring before

Abstract: A device is disclosed to unilaterally or bilaterally illuminate the oral cavity that is useful for commercial cheek retractors. The present invention also discloses a bite block designed to implement the device for lateral illumination of the oral cavity.

Abstract: The present invention relates to dental trays including a light source, a heat element or a combined light source and heating element that serves to enhance the treatment capacity of the composition. The dental tray is self-contained meaning that no external attachments that project from the mouth during use are required.

Abstract: A heat pack 30 is provided which contains the reactants for an exothermic chemical reaction. The heat pack 30 having physical contact with or close physical proximity to a package 10 during the ensuing exothermic reaction causes package 10 and material contained within package 10 to be heated.

Abstract: The invention provides an elastic dental wedge for use in securing a matrix band or a cavity filling material mold against an object tooth. The dental wedge of the instant invention can be easily inserted and removed during dental treatment procedures. Also described herein are the methods of using this dental wedge in tooth restorations, orthodontic operations, etc.

Abstract: Dental implant (10) for supporting a dental prosthesis on a jaw bone, is equipped with a main body (12), which comprises a securing portion (14) intended to be anchored in the bone tissue and, lying opposite it, a head portion (16). The head portion (16) protrudes radially beyond the securing portion (14) with respect to the longitudinal axis of the main body (12) to form a support face (26), in such a way that, in the state of insertion in the jaw bone, the pressure of the dental implant (10) on the jaw bone is reduced, and a sinking movement of the dental implant (10) into the jaw bone is effectively avoided, even over quite long periods of time.

Abstract: A computer-implemented system and method of intra-oral analysis for measuring plaque removal is disclosed. The system includes hardware for real-time image acquisition and software to store the acquired images on a patient-by-patient basis. The system implements algorithms to segment teeth of interest from surrounding gum, and uses a real-time image-based morphing procedure to automatically overlay a grid onto each segmented tooth. Pattern recognition methods are used to classify plaque from surrounding gum and enamel, while ignoring glare effects due to the reflection of camera light and ambient light from enamel regions. The system integrates these components into a single software suite with an easy-to-use graphical user interface (GUI) that allows users to do an end-to-end run of a patient record, including tooth segmentation of all teeth, grid morphing of each segmented tooth, and plaque classification of each tooth image.

Abstract: A substantially transparent display sheet for mounting of fabric and trim samples is provided which allows one to easily view the samples directly against various furniture and fabrics to determine color coordination. The samples are mounted on the display sheet so as to provide sufficient free space adjacent each of the samples to permit the fabric/furniture to be easily viewed through the sheet. A sample book is also provided which includes a front and back cover, and plurality of stacked display sheets bound therebetween.

Abstract: An apparatus for testing aspects of how a child learns includes a toy-like base having upstanding pegs. The child is encouraged to place donut shaped hand pieces onto the pegs. The hand pieces test the ability of the child to discriminate between different colors, and separately between different textures and different shapes and also tests the child's abilities in perception and creativity. The base also is able to test the child's ability to discern and copy tones and rhythms. Information of the child's performance is automatically collected within the apparatus and then compared with a normative baseline. Remediation focuses on activities related to the learning channels where the child is least astute and periodic retesting measures the ability of the child to improve in those channels to enable improvement of remediation approaches.

Abstract: A motor driven globe disposed on a support surface. The globe includes a rotating globe shell and a rotation mechanism configured to rotate the shell about a vertical axis of rotation. The rotation mechanism includes a motor concealed inside the rotating shell and a support platform disposed on the support surface and substantially concealed inside a recess formed in an outside surface of the rotating shell. An output shaft aligned with the axis of rotation connects the motor inside the interior of the rotating shell to the support platform. The motor includes a motor body nonrotatably coupled to the interior of the rotating shell. Surface interaction forces between the support platform and support surface are greater than or equal to a rotational drive force generated by the motor and applied to the output shaft causing the motor body and the rotating shell coupled thereto to rotate about the output shaft.

Abstract: An interactive learning system has a book, electronic memory, and system electronics. The book has at least one selectable object with a tactile feature. The electronic memory has stored therein data associated with the tactile feature. The system electronics comprises a selection sensor configured to detect the selection of the at least one selectable object, an audio signal generator, and a processor operatively coupled to the electronic memory, the sensor and the audio signal generator. Selection of the tactile feature causes the audio signal generator to produce an audible signal based on the data associated with the tactile feature.

Abstract: A kit and method for teaching a child positive thinking skills, including awareness of self talk, recognizing self-defeating or irrational thinking, using positive and coping self talk, thought-stopping negative thoughts, replacing self-defeating and irrational thoughts with positive or coping thoughts, regularly using positive thinking skills and self thought check ups. The kit and method further are used to teach the child positive thinking skills associated with positive self esteem and feelings of efficacy, as well as increased emotional resilience and stress resistance. The kit includes one or more thought assessment and thought remedying devices for achieving those goals by carrying out the method. The kit may further include other supporting devices which may be used to enhance the efficiency of the method. The method includes one or more steps for using the kit.

Abstract: The Learning/Play Quilt or Denim/Learning Play Quilt is a compilation of components of children's clothing sewn together to facilitate development or practice of fine motor skills (dexterity) such as zipping, buttoning, lacing, tying, snapping, hooking, use of Velcro, and buckling. The quilt format provides an extensive selection of fine motor skills not found in other formats such as books, vests, dolls and mats, and, at the same time, provides utilitarian uses as a cover for the child in a car seat or stroller. It also features pockets for storage of small toys and treasures. The components of children's clothing also expose children to numbers, letters and words while the embroidery thereon creates a product that is attractive and, therefore, promotes the child's interest in learning. The recommended lap quilt size predisposes its use to places where supervision is more readily available then if used on a bed. This is not only a safety feature but one in which more peer and adult interaction can occur.

Abstract: [Problem] To provide a medical training simulation model having a display enabling training by a simulation model simulating the structure of an organism, and objective and visual recognition of the three-dimensional position of an inserted endoscope, a finger or the like in an organ or tissue.

Abstract: A method performed by a mobile terminal may include selecting a song, receiving information associated with the selected song and simultaneously outputting the selected song with received music information to a plurality of output devices. The method may also include displaying lyrics of the song while simultaneously playing the song.

Abstract: This invention is a system for interactive learning for language and other studies, providing an immersion experience with other students. Program material, which can be easily and inexpensively recorded by teachers, students and other users, is encoded to make it interactive when it is decoded upon playback, in such a way that the part that the student is to speak, sing or play is played back through the student's headphones, prompting the student to perform the part properly in response to on-screen action, while the rest of the program material's audio, such as other characters' dialogue, is played back through a loudspeaker. The student-performed part is then recorded, so that upon playback the student can see how his or her efforts sound, compare with the original and/or mesh with the rest of the program. This permits the user to write dialogues, skits, words, expressions, lyrics, etc., to record them, and use the recordings for effective interactive voice training.

Abstract: The claimed subject matter pertains to systems and methods that facilitate learning of algorithms through incremental discovery in an interactive environment. An algorithm can be decomposed into its base parts and a representation of the algorithm and its parts can be presented to the user in the form of puzzles and/or quizzes. The user can learn the algorithm by solving a sequence of puzzles and/or quizzes that lead the user to reinvent the logical and strategic thinking associated with the algorithm.

Abstract: A computer assisted learning system is provided. The system comprises a predetermined learning structure; a set of nodes based on the learning structure, each node having at most three sub-nodes associated therewith; and a group interaction environment for users or students to interact among themselves, or with a system administrator or an expert.