24 research outputs found
Quasihomomorphisms from the integers into Hamming metrics
A function f : Z → Qn is a c-quasihomomorphism if the Hamming distance between
f(x + y) and f(x) + f(y) is at most c for all x, y ∈ Z. We show that any c-quasihomomorphism
has distance at most some constant C(c) to an actual group homomorphism; here C(c) depends
only on c and not on n or f. This gives a positive answer to a special case of a question posed
by Kazhdan and Ziegler
Design and Comparison of Calibration Algorithms of a Heterogeneous 3D Acquisition System Composed by Time-of-Flight and Colour Cameras
International audienceDespite the quality of the results obtained during the last two decades by different algorithms aiming to solve the problem of Structure From Motion-SFM, the use of color cameras all alone requires either an excessive number of devices (tens to several hundred), that cannot easily be available in practice, or may suffer from ambiguity in the 3D reconstruction of scenes. As an alternative, approaches based on multi-modal sensors, using different types of sensors, can provide compact system configurations requiring far fewer devices than mono-modal approaches, and without ambiguity in the 3D reconstruction. In this paper, we present a comprehensive study of a 3D acquisition system consisting of two pairs of Color and Time-of-Flight cameras. After briefly exploring the operating principles of Time-of-Flight cameras and the main practical problems of their implementations, we make a detailed study of different types of noise and errors in the measurements made by this type of cameras and correcting them when necessary. Subsequently, we make a comparison of different methods of calibrating color cameras that we apply to Time-of-Flight cameras and we end with the stereoscopic calibration of our entire acquisition system
Investigating cellular signaling reactions in single attoliter vesicles
10.1021/ja044605xJournal of the American Chemical Society12792908-2912JACS
Large scale transient 5-HT3 receptor production with the Semliki Forest Virus Expression System
The expression of recombinant proteins with the Semliki Forest Virus (SFV) system has been scaled up to bioreactor scale. As a model protein for this study the human 5-HT(3) receptor was chosen. The gene for the receptor was subcloned into the SFV expression plasmid pSFV1. Virus production by in vivo packaging and production of the recombinant protein was scaled up, the latter to a reactor volume of 11.5 l. A Vibromix(TM) agitation system was chosen to overcome aggregation problems of BHK cells in suspension. In the process, cells were first grown to a density of 10(6) cells/ml, the medium was then exchanged with fresh medium and the culture was infected with the recombinant virus at an estimated multiplicity of infection of 30. 24 h post infection we measured an expression level of 3 million functional 5-HT(3) receptors per cell. For harvesting, the cells were pelleted by centrifugation. The receptor protein was purified in a single step (Hovius et al., 1998) by exploiting the hexa-His tag at minimal protein loss (51% yield). Experiments to optimise expression resulted in yields up to 8 million receptors per cell, when the pH of a suspension culture was controlled at pH 7.3. Rapid virus generation and protein production, high protein yields as well as successful large scale application have made the SFV expression system attractive to produce large quantities of recombinant protein in a very short time. After optimisation of the expression conditions (in particular by setting the pH at 7.3), yields were increased twofold
Management of clinically node-negative early-stage oral cancer: network meta-analysis of randomized clinical trials
The best treatments for the clinically node-negative (cN0) neck in early-stage oral squamous cell carcinoma (OSCC) patients are a subject of ongoing debate and there is no consensus. A network meta-analysis (NMA) of randomized clinical trials (RCTs) was conducted to determine the most effective treatment and to rank treatments based on their effectiveness. A systematic search was performed in accordance with the PRISMA guidelines to retrieve RCTs that compared therapeutic neck dissection (TND), sentinel lymph node biopsy (SLNB), and elective neck dissection (END). The outcomes analysed were overall survival (OS), disease-specific survival (DSS), disease-free survival (DFS), and nodal recurrence. Hazard ratios and risk ratios were calculated by direct meta-analysis and NMA. Ten RCTs with a total of 1858 patients were eligible for inclusion. Direct meta-analysis showed END to be superior to TND and comparable to SLNB. The NMA revealed no statistically significant difference between END and SLNB (very low quality evidence) regarding OS, DSS, DFS, and nodal recurrence. However, END was found to significantly improve OS and DFS, and reduce nodal recurrence when compared to TND (moderate quality evidence). END ranked as probably the top treatment option for maximizing OS and DSS, and reducing nodal recurrence in early-stage OSCC, followed by SLNB and TND. There was very low quality evidence supporting SLNB as non-inferior to END for patients with early-stage OSCC. This NMA yielded favourable results for the use of END (with moderate quality evidence) in early-stage OSCC patients, although excellent results have also been obtained with SLNB. However, data in the literature for SLNB are scarce, as this technique has not yet been formalized in many countries. There is a need to further explore SLNB for early-stage OSCC patients, as well as its value in detecting occult lymph node metastases on the contralateral side. More studies comparing morbidity, quality of life, and costs between the different management strategies for the clinically negative neck in early-stage OSCC patients are needed