Acyclic edge colourings of graphs with the number of edges linearly bounded by the number of vertices

Let G be any finite graph. A mapping c:E(G)→{1,…,k} is called an acyclic edge k-colouring of G, if any two adjacent edges have different colours and there are no bichromatic cycles in G. In other words, for every pair of distinct colours i and j, the subgraph induced in G by all the edges that have colour i or j is acyclic. The smallest number k of colours such that G has an acyclic edge k-colouring is called the acyclic chromatic index of G and is denoted by .Determining the acyclic chromatic index of a graph is a hard problem, both from theoretical and algorithmical point of view. In 1991, Alon et al. proved that for any graph G of maximum degree Δ(G). This bound was later improved to 16Δ(G) by Molloy and Reed. In general, the problem of computing the acyclic chromatic index of a graph is NP-complete. Only a few algorithms for finding acyclic edge colourings have been known by now. Moreover, these algorithms work only for graphs from particular classes.In our paper, we prove that for every graph G which satisfies the condition that |E(G^′)|?t|V(G^′)|−1 for each subgraph G^′⊆G, where t?2 is a given integer, the constant p=2t³−3t+2. Based on that result, we obtain a polynomial algorithm which computes such a colouring. The class of graphs covered by our theorem is quite rich, for example, it contains all t-degenerate graphs.     

Molecular Distribution and Pasting Properties of UV-Irradiated Corn Starches

Suspension (30 %, w/w) of corn starch (25 % amylose) in water was irradiated by UV-light with wavelength greater than 250 nm at 25°C, under a stream of nitrogen or air, for time intervals ranging from 5 to 25 h. Effects of the irradiation on the transition enthalpy and temperature for melting, and the pasting viscosity profile of the irradiated starch were examined. Weight-average molecular weight (M_w) and radius of gyration (R_g) of the irradiated starch molecules were measured by high performance size exclusion chromatography coupled with multiangle laser light scattering and differential refractive index detectors (HPSEC-MALLS-RI). In the case of starch irradiated under nitrogen, the transition enthalpy (ΔH) decreased with increasing irradiation time whereas the melting temperature was not changed. Similarly, the peak paste viscosity (P_v) decreased from 97 to 56 RVU by 25 h irradiation. Average M_w and R_g of amylopectin and amylose fractions, which were 93 × 10⁶ and 144 nm, and 2.0 × 10⁶ and 104 nm, respectively, were decreased by irradiation to 32.2 × 10⁶ and 93.7 nm, and 0.7 × 10⁶ and 83.6 nm by the irradiation for 15 h under nitrogen, respectively. When the starch was irradiated with aeration, sharp drops of all measured parameters were observed in 5 h of irradiation (ΔH 11.4 J/g, P_v 53.2 RVU, amylopectin M_w 50 × 10⁶). After 15 h under air, however, all measured values increased (ΔH 16.8 J/g, P_v 65.5 RVU, amylopectin M_w 63.1 × 10⁶). Molecular size distribution profiles confirmed oxidative the photodegradation in the early stage (up to 5 h), and cross-linking reactions in the late stage (5—15 h) of irradiation under aeration.     

Manganese-Labeled Alginate Hydrogels for Image-Guided Cell Transplantation

Cell transplantation has been studied extensively as a therapeutic strategy for neurological disorders. However, to date, its effectiveness remains unsatisfactory due to low precision and efficacy of cell delivery; poor survival of transplanted cells; and inadequate monitoring of their fate in vivo. Fortunately, different bio-scaffolds have been proposed as cell carriers to improve the accuracy of cell delivery, survival, differentiation, and controlled release of embedded stem cells. The goal of our study was to establish hydrogel scaffolds suitable for stem cell delivery that also allow non-invasive magnetic resonance imaging (MRI). We focused on alginate-based hydrogels due to their natural origin, biocompatibility, resemblance to the extracellular matrix, and easy manipulation of gelation processes. We optimized the properties of alginate-based hydrogels, turning them into suitable carriers for transplanted cells. Human adipose-derived stem cells embedded in these hydrogels survived for at least 14 days in vitro. Alginate-based hydrogels were also modified successfully to allow their injectability via a needle. Finally, supplementing alginate hydrogels with Mn ions or Mn nanoparticles allowed for their visualization in vivo using manganese-enhanced MRI. We demonstrated that modified alginate-based hydrogels can support therapeutic cells as MRI-detectable matrices.     

The photodynamic effect of Victoria blue BO on peripheral blood mononuclear and leukemic cells

The photodynamic effect of Victoria blue BO (VB-BO) and photoirradiation on peripheral blood mononuclear cells was studied. The cells were preincubated with VB-BO followed by photoirradiation and overnight culture. The highest percentage of dead cells (propidium iodide assay in flow cytometry) was seen in the monocyte population. The lymphocytes showed a lower sensitivity to VB-BO photodynamic action than the monocytes (12% vs 80% of PI-positive cells). The effect of VB-BO and phototreatment on lymphocyte function was studied using a mitogen-induced proliferation assay. A decrease of mitogen response was observed. The VB-BO and photoirradiation were also used on leukemic cells. The leukemic cells from acute myeloid leukemia and B precursors leukemia were sensitive to VB-BO photodynamic action. The high VB-BO sensitivity of monocytes and leukemic cells (myeloid and lymphoid B derived) suggests possible application of VB-BO for selective depletion of monocytes or sensitive leukemic cells.     

Adhesion of Triple-Negative Breast Cancer Cells under Fluorescent and Soft X-ray Contact Microscopy

Understanding cancer cell adhesion could help to diminish tumor progression and metastasis. Adhesion mechanisms are currently the main therapeutic target of TNBC-resistant cells. This work shows the distribution and size of adhesive complexes determined with a common fluorescence microscopy technique and soft X-ray contact microscopy (SXCM). The results presented here demonstrate the potential of applying SXCM for imaging cell protrusions with high resolution when the cells are still alive in a physiological buffer. The possibility to observe the internal components of cells at a pristine and hydrated state with nanometer resolution distinguishes SXCM from the other more commonly used techniques for cell imaging. Thus, SXCM can be a promising technique for investigating the adhesion and organization of the actin cytoskeleton in cancer cells.     

"Review of Reading disabilities: The interaction of reading, language, and neuropsychological deficits": Comment on book review.

The book review by M. L. Simner and S. J. Lupker entitled Reading disabilities: The interaction of reading, language, and neuropsychological deficits (see record 2007-03865-001) by Donald G. Doehring, Ronald L. Trites, P. G. Patel, and Christina A. M. Fiedorowicz was generally characterized by a lack of appreciation of the complexities involved in reading disabilities research. The review reflected a poor understanding of the theoretical framework, and many comments were simply a reiteration of problematic areas the authors themselves discussed in the book. Further, the reviewers misinterpreted several issues. The main focus of the book was to present a review of the literature with respect to the development of the subgroup concept in reading disabilities, and specifically to present the data for three subtypes defined by Doehring and his colleagues. Another issue the reviewers address as a major concern is the validity of the subtypes. The last main issue of concern expressed by the reviewers involves the usefulness of subtyping as a means of understanding reading disabilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)