Search

SummaryHomeostatic synaptic plasticity is important for maintaining stability of neuronal function, but heterogeneous expression mechanisms suggest that distinct facets of neuronal activity may shape the manner in which compensatory synaptic changes are implemented. Here, we demonstrate that local presynaptic activity gates a retrograde form of homeostatic plasticity induced by blockade of AMPA receptors (AMPARs) in cultured hippocampal neurons. We show that AMPAR blockade produces rapid (

The paper outlines a modelling technique that predicts how woven fabric constructions will change shape when subjected to the application of hydrostatic pressure. The initial specification required for the technique is in terms of a triangulated pattern for each fabric piece in the construction and an initial 3D location for each node. Fabric types are characterised by look-up tables describing the warp and weft tensile and shear behaviours. The modelling proceeds by seeking to find the minimum energy state of the construction where material strain energy is balanced by the energy required to inflate the construction by the application of hydrostatic energy. Examples are provided to illustrate the operation of the technique.

With traditional two-dimensional based interfaces, many CAD surface models are difficult to design and edit due to their 3D nature. This paper discusses a technique for the deformation of CAD surface models with haptic interaction based on shape control functions. With the technique, designers can use a haptic interface to directly touch a native B-rep CAD model, and deform it in real-time by pushing, pulling and dragging its surfaces in a natural 3D environment. The deformation is governed by shape control functions. By using the shape functions, designers can specify the area of deformation, and also have greater controls on the shape of deformation. This technique is numerically efficient, and can deform complex surface models involving several thousand control points in real-time. The haptic-based deforming approach gives designers greater flexibility for the manipulation of complex CAD surfaces.

In many applications it is necessary to define good-fitting 2D flattened patterns for user-defined regions of a larger 3D surface. This paper describes the major stages involved in pattern flattening and illustrates the process with examples. In generating 2D patterns, some distortion is inevitably involved if the target 3D surface is not developable. For situations where distortion is required, it can be quantified in terms of the energy that must be imparted to the 2D flattening in localised areas so that it takes-up the original 3D region of the surface. An orthotropic strain model is adopted to convert the strain values to energy values. Starting with a bi-parametric definition of a large 3D surface, an arbitrary defined region is specified by the user in terms of a contiguous series of cubic curves lying on the bi-parametric plane. To extract the 3D region, a polygon list is generated to represent the surface. The triangulation process is based on a 'marching front' algorithm. A process is described which then flattens this polygon list and performs an energy minimisation analysis every time the process attempts to flatten an over-constrained triangle. Further consideration is made of seam insertion in the 3D surface definition and of adaptively modifying the triangulation process so that more triangles are used in areas of high-energy concentration. Examples are also presented to illustrate the sensitivity of the strain profiles to the fabric grain direction when the pattern is applied to the 3D surface.

In this paper, a model for predicting the stresses within a strained anisotropic fabric is presented. The fabric is characterised by tensile test data in the warp and weft directions as well as shear behaviour. The data is in the form of look-up tables that are capable of representing the non-linear form of each response. The model operates simultaneously on a triangular representation for both the 2D pattern defined on an undistorted fabric and an equivalent triangulation of a 3D representation of the fabric. An energy relaxation technique is applied to the situation in order to predict how the 3D representation should react in order to reach a minimum energy state. Arbitrary constraining configurations can be applied by setting a flag for each node to indicate those fixed in 3D. The resultant forces on fixed nodes can be determined. The model has been successfully applied to two examples. In the second of these, validation took the form of measuring the physical force effects of the fabric on an experimental rig and comparing them with those predicted by the model. It was then demonstrated that the model could predict other forces that could not be easily measured.

Haptic devices (force feedback interfaces) show great promise for use in the design of CAD models. However, current haptic systems are used primarily to verify rather than to interact with CAD systems to design a model. The paper discusses a haptic-based CAD system—Virtual DesignWorks. It is the world's first haptic application for the design of CAD models based on component technology (COM+). With haptic devices, the system allows engineers, in virtual space, to directly touch a native B-Rep CAD model, and deform it by pushing, pulling and dragging its surfaces in a natural three-dimensional environment. Virtual DesignWorks adopts the novel COM-based haptic model, which demonstrates significant advantages compared to the traditional haptic models. Force feedback gives designers the greatest flexibility for the design of complex surfaces, and haptics has the potential to become a critical interface for design applications.

Several techniques of laparoscopic hysterectomies have been described, but loss of carbon dioxide (CO(2)) pneumoperitoneum is still a problem when the vagina is incised and the specimen has been removed. Our technique allows maintenance of CO(2) pneumoperitoneum by inserting a silicone tube into the vagina. The McCartney tube is open at its vaginal (proximal) end and a cap covers the outer distal end. The total hysterectomy specimen, adnexa, and, if necessary, lymph nodes can be easily removed through the tube.

An adaptive control algorithm (ACA) has been developed as an alternative to fixed temperature setpoint controls within buildings. This paper describes both the theory behind the ACA and the findings from an EU-funded research project, smart controls and thermal comfort (SCATs), from which the form of the ACA was developed. The ACA was also tested in two air-conditioned buildings as part of the SCATs project and the results are presented. The results show that use of the ACA has potential for energy savings in the climate-control services of a building with no reduction in the perceived thermal comfort levels of that building’s occupants. Further refinement and testing of the ACA is required before it can be marketed.

To compare total laparoscopic hysterectomy (TLH) with open hysterectomy in the management of endometrial carcinoma.Retrospective chart review (Canadian Task Force classification II-3).Gynecologic cancer center.All women with endometrial carcinoma managed between January 1, 1993, and June 30, 1999.Of 403 patients reviewed, in 161 (40%) the surgical intention was laparoscopic management, in 230 (57%) the intention was open management, and in 12 (3%) it was vaginal hysterectomy. Total laparoscopic hysterectomy was successfully completed in 153 (95%) of the laparoscopic group.Mean weight of women in the laparoscopic group (80.1 kg) was greater than that in the open group (73.3 kg, p = 0.002), and included 27 patients weighing over 100 kg (maximum individual weight 170 kg). Mean operating times were 138 minutes for laparoscopy and 121 minutes for the open procedure (p = 0.002). Complications differed, with significantly more occurring in the open group (43%, 100) than in the laparoscopic group (17%, 27, p0.00001). Mean postoperative hospital stay was significantly shorter for the laparoscopic group (4.3 days) than for the open group (8.5 days, p = 0.0001). Conclusion. TLH combined with laparoscopic surgical staging has many advantages over the open approach, especially in obese women.

Objectives. The aim of this study was to assess the technique of en bloc resection of ovarian cancer with concomitant rectosigmoid colectomy, in relation to perioperative complication rates, and its impact on survival following the procedure. Methods. A retrospective review was performed of the case notes of 129 consecutive procedures performed between 1989 and 2000 in a regional cancer center. Results. Overall, 48.8% of patients suffered a major or minor complication. Complications relating to bowel anastomosis occurred in 2.4%. Perioperative mortality was 3.1%. Median survival for the group as a whole was 30.6 months. Patients who were optimally debulked had a significantly longer median survival time. Conclusion. En bloc resection of ovarian cancer with concomitant rectosigmoid colectomy allows a high rate of optimal debulking with acceptable morbidity, mortality, and survival.

Objective To investigate the phenotype and age-related penetrance of primary open-angle glaucoma (POAG) in Australian families with the most common Myocilin mutation (Gln368STOP). Design Cross-sectional genetic study. Participants Eight pedigrees carrying the Gln368STOP mutation were ascertained from 1730 consecutive cases of POAG in the Glaucoma Inheritance Study in Tasmania. Methods Index cases and available family members were examined for signs of glaucoma, and the presence of the GLC1A Gln368STOP mutation was ascertained by single-strand conformation polymorphism analysis and subsequent direct sequencing. Results From the eight pedigrees, 29 Gln368STOP mutation-carrying individuals with either ocular hypertension (OHT) or POAG were found, with a mean age at diagnosis of 52.4 ± 12.9 years and a mean peak intraocular pressure (IOP) of 28.4 ± 4.7 mmHg. A further 11 mutation carriers older than 40 years have been studied, who as yet show no signs of OHT or POAG. Within the 8 pedigrees, a further 31 individuals with OHT or POAG were identified who did not carry the Gln368STOP mutation. For these individuals the mean age at diagnosis was higher (62.3 ± 13.7 years, P P = 0.01). For Gln368STOP carriers, age-related penetrance for OHT or POAG was 72% at age 40 years and 82% at age 65 years. A positive family history of POAG was present in all index cases. Five of the eight pedigrees had a positive family history on both maternal and paternal sides. Seven of the eight pedigrees had one or more individuals with POAG who did not carry the mutation. Eight of the 29 Gln368STOP carriers with OHT or POAG had undergone trabeculectomy. Conclusions The GLC1A Gln368STOP mutation is associated with POAG, which in the pedigrees studied is of a younger age of onset and higher peak IOP than non-mutation glaucoma cases. In addition, Gln368STOP mutation glaucoma cases were more likely to have undergone glaucoma drainage surgery. We have not observed simple autosomal dominant inheritance patterns for POAG in these pedigrees. Other factors, as yet uncharacterized, are involved in expression of the POAG phenotype in Gln368STOP pedigrees.

We describe an assay scheme for glucose based on fluorescence resonance energy transfer (FRET) between concanavalin A (con A), labeled with the near-infrared fluorescent protein allophycocyanin (APC) as donor, and dextran labeled with malachite green (MG) as acceptor. Glucose competitively displaces dextran-MG and leads to reduction in FRET, assessed by time-domain fluorescence lifetime measurements using time-correlated single-photon counting. The assay is operative in the glucose concentration range 2.5–30 mM, and therefore suitable for use in monitoring diabetes control. Albumin and serum inhibit FRET but the interference can be prevented by removal of high molecular weight substances by membrane filters. APC shows promise for incorporation in an implanted glucose sensor which can be interrogated from outside the body.

A field study of the thermal comfort of workers in natural ventilated office buildings in Oxford and Aberdeen, UK, was carried out which included information about use of building controls. The data were analysed to explore that what effect the outdoor temperature has on the indoor temperature and how this is affected by occupants’ use of environmental controls during the peak summer (June–August). The proportion of subjects using a control was related to indoor and outdoor temperatures to demonstrate the size of the effect. The results suggest that the use of controls is also related to thermal sensation and their appropriate use is a significant part of adaptive behaviour to modify the indoor thermal conditions. The results make it possible to predict the effect of temperature on the ventilation rate in naturally ventilated buildings.

While considerable progress has been made in fabric modelling techniques, which could be used in garment computer aided design (CAD) systems, less attention has been paid to the way in which garments might be specified in a CAD system. The final shape taken by a garment is often achieved through the incorporation of darts, seams, edges, stiffening pads and local stretch of the fabric. In order to gain credibility, CAD systems should have to functionally handle the level of complexity normally found in garment assemblies combined with a simple interface to specify the constructional detail. Different conceptual approaches are possible. Given an accurate drape algorithm, garment block patterns in a chosen fabric could simply be anchored or attached around the mannequin in order to achieve a visualisation of a garment. If changes were necessary, the user would alter the 2D patterns and re-run the visualisation. An alternative and possibly more productive approach would be to specify in 3D, with advanced drawing tools, the 3D shape required. Processing of the 3D garment piece using expert rules would indicate the 2D shape and constructional detail required to achieve the final form. This paper describes a CAD system that is under development and which aims to facilitate both the approaches.

Applications such as garment manufacture and composite structure fabrication require a two dimensional (2D) woven material to assume a three dimensional (3D) shape. The specification of the process is usually initiated by defining the 3D surface. Hence, the problem arises of determining the best 2D pattern. The problem is made more complex by the anistropic nature of woven fabrics which are often used as raw material. Such materials display a variation in mechanical properties with respect to the woven structure. This paper presents a model for determining the optimum 2D pattern for a specified 3D surface where optimality is determined in terms of minimising the energy distribution required to force the 2D pattern to assume the 3D shape. The 3D surface specification is assumed to consist of a polygonal mesh. The model allows affine transformations to be applied to the weave structure which can be unique for each polygon in the mesh. Important considerations in the modelling process include the following: 1. The degree to which the specified 3D surface departs from a developable surface. 2. The energy components used to model the woven structure and their sensitivity to weave direction. Essentially, these stem from tensile strain in each direction of the weave and shear strain. 3. The prediction of weave geometry as it reacts to the energy distribution being applied. The model is demonstrated by applying it to a relatively simple pyramidal 3D shape. Energy values are optimised to produce a pattern that requires the minimum overall energy to be applied to the 2D pattern in order for it to assume the 3D shape. This 2D pattern is sensitive to the orientation of the woven structure with predictions being made of how the woven structure will behave in 3D.

We describe a method of determining the distribution function associated with acceptors partaking in Forster resonance energy transfer (FRET) from excited donors. Unlike previous approaches to this problem the method described makes no a priori assumption about the nature of the distribution. The use of an acceptor distribution function in analyte sensing is demonstrated for the first time. In the case of glucose sensing via FRET from Concanavalin A labelled with allophycocyanin to malachite green labelled dextran, the change in the acceptor distribution is shown to be a more sensitive sensing parameter than either the mean fluorescence lifetime or Forster γ value.

The near-infrared fluorescence resonance energy transfer kinetics of the phycobiliprotein allophycocyanin (APC) to malachite green (MG) have been investigated. A model is proposed to account for the fluorescence decay whereby MG binds to APC with a donor–acceptor site distribution which can be best described by 2D quenching kinetics. The results highlight a potential fallacy when interpreting the dimensionality of complex systems or the location of binding sites from Forster decay kinetics. The use of APC in trans-dermal measurements is proposed.

The problem of deriving patterns from 3D surfaces is described. An algorithm is presented for the flattening of 3D surfaces described in terms of a list of triangles. The algorithm incorporates an energy model in terms of the strain energy required to deform the edges of the triangular mesh. Also considered is the problem of arbitrarily siting darts or gussets to assist in the fitting process. The operation of the algorithm is demonstrated by fitting patterns to a classical geometric shape. The sensitivity of the final pattern to the algorithm's parameters is examined. Results are presented which quantify the strain energy reductions as a result of inserting darts or gussets in the pattern.

The aim of this study was to determine the major nutritive components present in fresh eggs of the freshwater turtle, Emydura macquarii , and to investigate the utilisation of these components during embryonic development. Comparison of the compositions of the initial egg contents (yolk plus albumen), the hatchling and the residual yolk indicated that embryonic development was accompanied by the loss of approximately 15% of the initial dry matter, 25% of the energy content, 8.8% of the protein and 41% of the lipid. Thus, in addition to oxidation of fatty acids, some of the energy consumed during development (17.6%) was derived from catabolism of protein. A feature of the yolk lipids was the presence of high proportions of α -linolenic acid (18:3n-3), particularly in the triacylglycerol and a high concentration of α -tocopherol, similar to than in the yolk of birds. The yolk phospholipid contained a high concentration of arachidonic acid (20:4n-6) and eicosapentaenoic acid (20:5n-3) but a relatively low amount of docosahexaenoic acid (DHA) (22:6n-3). By contrast, the phospholipid of the hatchling was enriched in DHA but contained only a small concentration of eicosapentaenoic acid, suggesting the possible conversion of eicosapentaenoic acid to DHA by the embryo. The amount of calcium recovered in the hatchling was almost twice that of the initial egg contents suggesting mobilisation of calcium from the shell.

This study is based on the analysis of the data obtained through a yearlong thermal comfort survey in one of the even naturally ventilated buildings in Oxford. It is concerned with how much the use of available controls contributes to thermal comfort by modifying the indoor thermal environment. The results show that the availability of the controls and their appropriate use plays a significant role in modifying the indoor thermal conditions. Cross ventilation plays a significant role in lowering the indoor temperature.

Although substantial information is available regarding the fatty acid composition of lipids of the yolk and of the developing tissues of the chicken embryo, there is little knowledge on this topic for other avian species. The aim of the present study was to compare the yolk and embryonic tissue fatty acid profiles for a species selecting its food in the wild (the lesser black backed gull) with one fed on a standard commercial diet (the commercially reared pheasant). The fatty acid compositions of the yolk lipids were determined, and major differences were observed between the two species. In particular, the phospholipid of the gull yolk was enriched in 20:4n-6 and 22:6n-3 (18.8 and 7.1%, respectively, by weight of total fatty acids) in comparison with the pheasant (4.0 and 4.1%, respectively). The fatty acid compositions of the embryonic tissues were determined using eggs incubated in the laboratory. For the liver and heart, the fatty acid composition of the lipids in the two species reflected the initial yolk composition, with the gull tissue lipids generally containing higher proportions of 20:4n-6 and 22:6n-3 than those of the pheasant. In contrast, the fatty acid profiles of the brain phospholipid were essentially identical in the two species, with 20:4n-6 and 22:6n-3 comprising approximately 9 and 17%, respectively, of total fatty acids in both cases.

A comparative study has been made of the major lipid fractions and their fatty acid compositions in the yolk of eggs from ostriches under wild and farmed conditions. There were no differences in the lipid contents and proportions of the lipid fractions between the two groups of yolks. In both groups of yolks triacylglycerol and phospholipid were the major fractions. In the eggs from the wild ostriches, all the lipid fractions displayed substantial concentrations of C18 polyunsaturated fatty acids, triacylglycerol being particularly rich in linolenic acid and phospholipid rich in linoleic acid; phospholipid displayed substantial concentrations also of C20 and C22 polyunsaturates. There were considerable differences in the fatty acid compositions between the yolks. Those from the farmed birds displayed lower proportions of C18 polyunsaturates, particularly linolenic acid, throughout the lipid fractions. Compensatory increases were displayed most obviously in the concentrations of oleic acid and palmitoleic acid as well as other acids. The distinctive and extensive changes in fatty acid composition, particularly relating to the polyunsaturates, are discussed with respect to overall dietary requirements and specificities for embryo metabolism and possible effects on reproductive performance.

A technique for simulating the surfaces of leather is described. It is based upon the random distribution of points over a 2D domain and subsequent triangulation. When illuminated using a simple lighting model, the resultant lighting variations have been shown to closely match those of real leather. Fully rendered examples are presented which illustrate the approach.

Development patterns for simple surfaces are considered in terms of Gaussian curvature. Patterns are derived for elliptic- and hyperbolic-curvature regions. Similar methods are applied to garment pieces that have been defined as 3D mathematical models at a workstation. Approximations are applied to patterns to reduce the complexity to a level acceptable to the clothing industry.

Laparoscopic pelvic lymphadenectomy for gynecological malignancy involves mobilizing and exteriorizing the lymph nodes. We removed the nodes by passing a 4- to 5-cm-diameter tube through the vagina to the abdomen following the hysterectomy. The nodes were passed through the tube rather than pulled through the abdominal ports. The tube is easy to insert and is a valuable conduit for exteriorizing tissue during laparoscopic pelvic surgery for gynecological cancer.