nlstimedist: An R package for the biologically meaningful quantification of unimodal phenology distributions

Phenological investigation can provide valuable insights into the ecological effects of climate change. Appropriate modelling of the time distribution of phenological events is key to determining the nature of any changes, as well as the driving mechanisms behind those changes. Here we present the nlstimedist R package, a distribution function and modelling framework that describes the temporal dynamics of unimodal phenological events. The distribution function is derived from first principles and generates three biologically interpretable parameters. Using seed germination at different temperatures as an example, we show how the influence of environmental factors on a phenological process can be determined from the quantitative model parameters. The value of this model is its ability to represent various unimodal temporal processes statistically. The three intuitively meaningful parameters of the model can make useful comparisons between different time periods, geographical locations or species’ populations, in turn allowing exploration of possible causes

Ectodermal Influx and Cell Hypertrophy Provide Early Growth for All Murine Mammary Rudiments, and Are Differentially Regulated among Them by Gli3

Mammary gland development starts in utero with one or several pairs of mammary rudiments (MRs) budding from the surface ectodermal component of the mammalian embryonic skin. Mice develop five pairs, numbered MR1 to MR5 from pectoral to inguinal position. We have previously shown that Gli3Xt-J/Xt-J mutant embryos, which lack the transcription factor Gli3, do not form MR3 and MR5. We show here that two days after the MRs emerge, Gli3Xt-J/Xt-J MR1 is 20% smaller, and Gli3Xt-J/Xt-J MR2 and MR4 are 50% smaller than their wild type (wt) counterparts. Moreover, while wt MRs sink into the underlying dermis, Gli3Xt-J/Xt-J MR4 and MR2 protrude outwardly, to different extents. To understand why each of these five pairs of functionally identical organs has its own, distinct response to the absence of Gli3, we determined which cellular mechanisms regulate growth of the individual MRs, and whether and how Gli3 regulates these mechanisms. We found a 5.5 to 10.7-fold lower cell proliferation rate in wt MRs compared to their adjacent surface ectoderm, indicating that MRs do not emerge or grow via locally enhanced cell proliferation. Cell-tracing experiments showed that surface ectodermal cells are recruited toward the positions where MRs emerge, and contribute to MR growth during at least two days. During the second day of MR development, peripheral cells within the MRs undergo hypertrophy, which also contributes to MR growth. Limited apoptotic cell death counterbalances MR growth. The relative contribution of each of these processes varies among the five MRs. Furthermore, each of these processes is impaired in the absence of Gli3, but to different extents in each MR. This differential involvement of Gli3 explains the variation in phenotype among Gli3Xt-J/Xt-J MRs, and may help to understand the variation in numbers and positions of mammary glands among mammals

Navigational Support for Robotic Wheelchair Platforms: An Approach that Combines Vision and Range Sensors

An approach towards providing advanced navigational support to robotic wheelchair platforms is presented in this paper. Contemporary methods that are employed in robotic wheelchairs are based on the information provided by range sensors and its appropriate exploitation by means of obstacle avoidance techniques. However, since range sensors cannot support a detailed environment representation, these methods fail to provide advanced navigational assistance, unless the environment is appropriately regulated (e.g. with the introduction of beacons). In order to avoid any modifications to the environment, we propose an alternative approach that employs computer vision techniques which facilitate space perception and navigation. Computer vision has not been introduced todate in rehabilitation robotics, since the former is not mature enough to meet the needs of this sensitive application. However, in the proposed approach, stable techniques are exploited that facilitate reliable, automatic nav..

Automated Generation of Parametric BIMs based on Hybrid Video and Laser Scanning Data

Only very few constructed facilities today have a complete record of as-built information. Despite the growing use of Building Information Modelling and the improvement in as-built records, several more years will be required before guidelines that require as-built data modelling will be implemented for the majority of constructed facilities, and this will still not address the stock of existing buildings. A technical solution for scanning buildings and compiling Building Information Models is needed. However, this is a multidisciplinary problem, requiring expertise in scanning, computer vision and videogrammetry, machine learning, and parametric object modelling. This paper outlines the technical approach proposed by a consortium of researchers that has gathered to tackle the ambitious goal of automating as-built modelling as far as possible. The top level framework of the proposed solution is presented, and each process, input and output is explained, along with the steps needed to validate them. Preliminary experiments on the earlier stages (i.e. processes) of the framework proposed are conducted and results are shown; the work toward implementation of the remainder is ongoing

Independent 3D Motion Detection Through Robust Regression in Depth Layers

This paper presents a novel method for the detection of objects that move independently of the observer in a 3D dynamic environment. Independent3Dmotiondetection is formulated as a problem of robust regression applied to visual input acquired by a binocular, rigidly moving observer. The qualitative analysis of images acquired by a parallel stereo configuration yields a segmentation of a scene into depth layers. A depth layer consists of points of the 3D space for which depth variations are small compared to the distance from the observer. Robust regression is applied to each depth layer in order to segmentthe latter into coherently moving regions. Finally,acombination stage is applied across all layers in order to come up with an integrated view of independent motion in the whole 3D scene. In contrast to other existing approaches for independent motion detection which are based on the ill-posed problem of optical flow computation, the proposed method relies on normal flow fields for both stereo and motion processing. Experimental results show the effectiveness and robustness of the proposed scheme, which is capable of discriminating independent 3D motion in scenes with large depth variations.

Global Trifocal Adjustment

In this paper we introduce a fast and robust structure-less alternative to full bundle adjustment. The method is based on optimizing algebraic errors for trilinear constraints from triplets of views. It is shown that the error generated by a triplet of views can be described by a fixed triangular matrix regardless of the number of feature correspondences between the views. The method has been evaluated on various real and synthetic datasets and shows good convergence properties with a large convergence basin and solutions that are close to the optimal solution. The method has been compared to Global Epipolar Adjustment, GEA, which is based on the bilinear constraint. It will be shown that the method can handle the degenerate configurations of GEA