Sökresultat

We discuss three implementations of the CCFM evolution equations in event generator programs. We find that some of them are able to describe observables such as forward jet rates in DIS at HERA, but only if the so-called consistency constraint is removed. We also find that these results are sensitive to the treatment of non-singular terms in the gluon splitting function.

In multicellular organisms cells grow, divide and adopt different fates, resulting in tissues and organs with specific functions. In recent years, a number of studies have brought quantitative knowledge about how these processes are orchestrated, shedding new light on cells as active and central players in morphogenesis. We explore recent advances in understanding plant morphogenesis from a quanti

In plants the dorsoventral boundary of leaves defines an axis of symmetry through thecentre of the organ separating the top (dorsal) and bottom (ventral) tissues. Although thepositioning of this boundary is critical for leaf morphogenesis, how the boundary is established andhow it influences development remains unclear. Using live-imaging and perturbation experimentswe show that leaf orientation,

Multicellular development produces patterns of specialized cell types. Yet, it is often unclear how individual cells within a field of identical cells initiate the patterning process. Using live imaging, quantitative image analyses and modeling, we show that during Arabidopsis thaliana sepal development, fluctuations in the concentration of the transcription factor ATML1 pattern a field of identic

Various applications of the mean field theory (MFT) technique for obtaining solutions close to optimal minima in feedback networks are reviewed. Using this method in the context of the Boltzmann machine gives rise to a fast deterministic learning algorithm with a performance comparable with that of the backpropagation algorithm (BP) in feature recognition applications. Since MFT learning is bidire

We present a general method, the δ-test, which establishes functional dependencies given a sequence of measurements. The approach is based on calculating conditional probabilities from vector component distances. Imposing the requirement of continuity of the underlying function, the obtained values of the conditional probabilities carry information on the embedding dimension and variable dependenc

In a few recent papers we introduced the chirality-flow formalism, which was shown to make calculations of tree-level Feynman diagrams simple and transparent. Chirality flow, which is based on the spinor-helicity formalism, allows to often immediately analytically write down a tree-level Feynman diagram in terms of spinor inner products. In this paper, we argue that there is also a significant sim

This thesis is composed of six papers, which all concern different methods and tools used for the analysis of barcodes in nanochannel-based Optical DNA Mapping (ODM). The first four papers consider densely-labeled barcodes while the last two consider sparsely-labeled barcodes.Paper I presents a combinatorial auction algorithm for contig assembly ussing ODM barcodes as scaffolds.Paper II concerns m

This invention provides a method for protein structure alignment. More particularly, the present invention provides a method for identification, classification and prediction of protein structures. The present invention involves two key ingredients. First, an energy or cost function formulation of the problem simultaneously in terms of binary (Potts) assignment variables and real-valued atomic coo

Many cell functions rely on the ability of microtubules to self-organize as complex networks. In plants, cortical microtubules are essential to determine cell shape as they guide the deposition of cellulose microfibrils, and thus control mechanical anisotropy in the cell wall. Here we analyze how, in turn, cell shape may influence microtubule behavior. Using a computational model of microtubules e

The plant shoot apical meristem holds a stem cell niche from which all aerial organs originate. Using a computational approach we show that a mixture of monomers and heterodimers of the transcription factors WUSCHEL and HAIRY MERISTEM is sufficient to pattern the stem cell niche, and predict that immobile heterodimers form a regulatory ‘pocket’ surrounding the stem cells. The model achieves to rep

The modelling of biological systems often consists into differential equation models that need to be fitted to experimental data. During this complex process, the practical experience of the biologist and the theoretical abstraction of the modeller require back-and-forth refinements of the model, design of new experiments and inclusion of more data-points into the fitting procedure. Available opti

A variety of pathogenic bacteria can infect humans and the increase in bacteria resistant to common antibiotics is a large threat to human health worldwide. This work presents a method, based on optical DNA mapping (ODM) in nanofluidic channels, that can detect the type of bacterial present in a sample by matching the obtained maps of large DNA molecules to a database of fully assembled bacterial

Crossover is the process of recombining the genetic features of two parents. For many applications where crossover is applied to permutations, relevant genetic features are pairs of adjacent elements, also called edges in the permutation order. Recombination of edges without errors is thought to be an NP-hard problem, typically approximated by heuristics that either introduce new edges or are only

In this study, inspired by the work of Nakazato and Kitahara (1980 Prog. Theor. Phys. 64 2261), we consider the theoretical problem of tracer particle diffusion in an environment of diffusing hardcore interacting crowder particles. The tracer particle has a different diffusion constant from the crowder particles. Based on a transformation of the generating function, we provide an exact formal expa