Complexity of computing topological degree of Lipschitz functions in n dimensions

Journal ArticleWe find lower and upper bounds on the complexity, comp(deg), of computing t h e topological degree of functions defined on the n-dimensional unit cube Cn, f : ?Cn Rn,n ? 2, which satisfy a Lipschitz condition with constant K and whose infinity norm at each point on t h e boundary of Cn is at least d, d > 0, and such that K8d ? 1. A lower bound, complow ~ 2n (K8d)n-1(c+n) is obtained for comp(deg), assuming that each function evaluation costs c and elementary arithmetic operations and comparisons cost unity. We prove t h a t the topological degree can be computed using A = ( [ K2d + 1 ] + l ) n ?( [| K2n + 1 ] - l ) n function evaluations. It can be done by an algorithm ?* d due to Kearfott, with cost given by comp(?*) ? A(c + n2-2(n ? 1)!). Thus for small n, say n ? 5, and small say K2d ? 9, the degree can be computed in time at most 105 (c + 300). For large n and / or large K2d the problem is intractable

Separable Image Warping with Spatial Lookup Tables

Image warping refers to the 2-D resampling of a source image onto a target image. In the general case, this requires costly 2-D filtering operations. Simplifications are possible when the warp can be expressed as a cascade of orthogonall-D transformations. In these cases, separable transformations have been introduced to realize large performance gains. The central ideas in this area were formulated in the 2-pass algorithm by Catmull and Smith. Although that method applies over an important class of transformations, there are intrinsic problems which limit its usefulness. The goal of this work is to extend the 2-pass approach to handle arbitrary spatial mapping functions. We address the difficulties intrinsic to 2-pass scanline algorithms: bottlenecking, foldovers, and the lack of closed-form inverse solutions. These problems are shown to be resolved in a general, efficient, separable technique, with graceful degradation for transformations of increasing complexity

VideoPlus: A Method for Capturing the Structure and Appearance of Immersive Environments

This paper presents a simple approach to capturing the appearance and structure of immersive scenes based on the imagery acquired with an omnidirectional video camera. The scheme proceeds by combining techniques from structure-from-motion with ideas from image-based rendering. An interactive photogrammetric modeling scheme is used to recover the locations of a set of salient features in the scene (points and lines) from image measurements in a small set of keyframe images. The estimates obtained from this process are then used as a basis for estimating the position and orientation of the camera at every frame in the video clip. By augmenting the video sequence with pose information, we provide the end-user with the ability to index the video sequence spatially as opposed to temporally. This allows the user to explore the immersive scene by interactively selecting the desired viewpoint and viewing direction

Development of an automated measure of iliac artery tortuosity that successfully predicts early graft-related complications associated with endovascular aneurysm repair

Abstract not availableN. Dowson, M. Boult, P. Cowled, T. De Loryn, R. Fitridg

Preclinical transgenic and patient-derived xenograft models recapitulate the radiological features of human adamantinomatous craniopharyngioma

To assess the clinical relevance of transgenic and patient-derived xenograft models of adamantinomatous craniopharyngioma (ACP) using serial magnetic resonance imaging (MRI) and high resolution post-mortem microcomputed tomography (μ-CT), with correlation with histology and human ACP imaging. The growth patterns and radiological features of tumors arising in Hesx1(Cre/+) ;Ctnnb1(lox(ex3)/+) transgenic mice, and of patient-derived ACP xenografts implanted in the cerebral cortex, were monitored longitudinally in vivo with anatomical and functional MRI, and by ex vivo μ-CT at study end. Pathological correlates with hematoxylin and eosin stained sections were investigated. Early enlargement and heterogeneity of Hesx1(Cre/+) ;Ctnnb1(lox(ex3)/+) mouse pituitaries was evident at initial imaging at 8 weeks, which was followed by enlargement of a solid tumor, and development of cysts and hemorrhage. Tumors demonstrated MRI features that recapitulated those of human ACP, specifically, T1 -weighted signal enhancement in the solid tumor component following Gd-DTPA administration, and in some animals, hyperintense cysts on FLAIR and T1 -weighted images. Ex vivo μ-CT correlated with MRI findings and identified smaller cysts, which were confirmed by histology. Characteristic histological features, including wet keratin and calcification, were visible on μ-CT and verified by histological sections of patient-derived ACP xenografts. The Hesx1(Cre/+) ;Ctnnb1(lox(ex3)/+) transgenic mouse model and cerebral patient-derived ACP xenografts recapitulate a number of the key radiological features of the human disease and provide promising foundations for in vivo trials of novel therapeutics for the treatment of these tumors

The effectiveness of case management for comorbid diabetes type 2 patients; the CasCo study. Design of a randomized controlled trial

BACKGROUND: More than half of the patients with type 2 diabetes (T2DM) patients are diagnosed with one or more comorbid disorders. They can participate in several single-disease oriented disease management programs, which may lead to fragmented care because these programs are not well prepared for coordinating care between programs. Comorbid patients are therefore at risk for suboptimal treatment, unsafe care, inefficient use of health care services and unnecessary costs. Case management is a possible model to counteract fragmented care for comorbid patients. It includes evidence-based optimal care, but is tailored to the individual patients' preferences.The objective of this study is to examine the effectiveness of a case management program, in addition to a diabetes management program, on the quality of care for comorbid T2DM patients. METHODS/DESIGN: The study is a randomized controlled trial among patients with T2DM and at least one comorbid chronic disease (N=230), who already participate in a diabetes management program. Randomization will take place at the level of the patients in general practices. Trained practice nurses (case managers) will apply a case management program in addition to the diabetes management program. The case management intervention is based on the Guided Care model and includes six elements; assessing health care needs, planning care, create access to other care providers and community resources, monitoring, coordinating care and recording of all relevant information. Patients in the control group will continue their participation in the diabetes management program and receive care-as-usual from their general practitioner and other care providers. DISCUSSION: We expect that the case management program, which includes better structured care based on scientific evidence and adjusted to the patients' needs and priorities, will improve the quality of care coordination from both the patients' and caregivers' perspective and will result in less consumption of health care services. TRIAL REGISTRATION: Netherlands Trial Register (NTR): NTR1847. (aut. ref.

Increase of mild disability in Japanese elders: A seven year follow-up cohort study

BACKGROUND: Japan has the highest life expectancy in the world. In a 2002 census government report, 18.5% of Japanese were 65 years old and over and 7.9% were over 75 years old. In this ageing population, the increase in the number of dependent older persons, especially those with mild levels of disability, has had a significant impact on the insurance budget. This study examines the increase of mild disability and its related factors. METHODS: All community-dwelling residents aged 65 and over and without functional decline (n = 1560), of Omishima town, Japan, were assessed in 1996 using a simple illustrative measure, "the Typology of the Aged with Illustrations" to establish a baseline level of function and were followed annually until 2002. The prevalence and incidence of low to severe disability, and their association with chronic conditions present at the commencement of the study, was analyzed. A polychotomous logistic regression model was constructed to estimate the association of each chronic condition with two levels of disability. RESULTS: An increase in mild functional decline was more prevalent than severe functional decline. The accumulation of mild disability was more prominent in women. The major chronic conditions associated with mild disability were chronic arthritis and diabetes in women, and cerebrovascular accident and malignancy in men. CONCLUSION: This study showed a tendency for mild disability prevalence to increase in Japanese elders, and some risk factors were identified. As mild disability increasingly prevalent, these findings will help determine priorities for its prevention in Japanese elders

Assessment of the direct effects of DDAH I on tumour angiogenesis in vivo

Nitric oxide (NO) has been strongly implicated in glioma progression and angiogenesis. The endogenous inhibitors of NO synthesis, asymmetric dimethylarginine (ADMA) and N-monomethyl-l-arginine (l-NMMA), are metabolized by dimethylarginine dimethylaminohydrolase (DDAH), and hence, DDAH is an intracellular factor that regulates NO. However, DDAH may also have an NO-independent action. We aimed to investigate whether DDAH I has any direct role in tumour vascular development and growth independent of its NO-mediated effects, in order to establish the future potential of DDAH inhibition as an anti-angiogenic treatment strategy. A clone of rat C6 glioma cells deficient in NO production expressing a pTet Off regulatable element was identified and engineered to overexpress DDAH I in the absence of doxycycline. Xenografts derived from these cells were propagated in the presence or absence of doxycycline and susceptibility magnetic resonance imaging used to assess functional vasculature in vivo. Pathological correlates of tumour vascular density, maturation and function were also sought. In the absence of doxycycline, tumours exhibited high DDAH I expression and activity, which was suppressed in its presence. However, overexpression of DDAH I had no measurable effect on tumour growth, vessel density, function or maturation. These data suggest that in C6 gliomas DDAH has no NO-independent effects on tumour growth and angiogenesis, and that the therapeutic potential of targeting DDAH in gliomas should only be considered in the context of NO regulation