Core-sheath structured electrospun nanofibrous membranes for oil-water separation

In recent years, both the increasing frequency of oil spill accidents and the urgency to deal seriously with industrial oil-polluted water, encouraged material scientists to design highly efficient, cost effective oil-water separation technologies. We report on electrospun nanofibrous membranes which are composed of core-sheath structured cellulose-acetate (CA)-polyimide (PI) nanofibers. On the surface of the CA-PI fibers a fluorinated polybenzoxazine (F-PBZ) functional layer, in which silica nanoparticles (SNPs) were incorporated, has been applied. Compared with F-PBZ/SNP modified CA fibers reported before for the separation of oil from water, the PI-core of the core-shell F-PBZ/SNP/CA-PI fibers makes the membranes much stronger, being a significant asset in their use. Nanofibrous membranes with a tensile strength higher than 200 MPa, a high water contact angle of 160 degrees and an extremely low oil contact angle of 0 degrees were obtained. F-PBZ/SNP/CA-PI membranes seemed very suitable for gravity-driven oil-water separation as fast and efficient separation (>99%) of oil from water was achieved for various oil-water mixtures. The designed core-sheath structured electrospun nanofibrous membranes may become interesting materials for the treatment of industrial oil-polluted water

Von Neumann Regular Cellular Automata

For any group $G$ and any set $A$, a cellular automaton (CA) is a transformation of the configuration space $A^G$ defined via a finite memory set and a local function. Let $\text{CA}(G;A)$ be the monoid of all CA over $A^G$. In this paper, we investigate a generalisation of the inverse of a CA from the semigroup-theoretic perspective. An element $\tau \in \text{CA}(G;A)$ is von Neumann regular (or simply regular) if there exists $\sigma \in \text{CA}(G;A)$ such that $\tau \circ \sigma \circ \tau = \tau$ and $\sigma \circ \tau \circ \sigma = \sigma$, where $\circ$ is the composition of functions. Such an element $\sigma$ is called a generalised inverse of $\tau$. The monoid $\text{CA}(G;A)$ itself is regular if all its elements are regular. We establish that $\text{CA}(G;A)$ is regular if and only if $\vert G \vert = 1$ or $\vert A \vert = 1$, and we characterise all regular elements in $\text{CA}(G;A)$ when $G$ and $A$ are both finite. Furthermore, we study regular linear CA when $A= V$ is a vector space over a field $\mathbb{F}$; in particular, we show that every regular linear CA is invertible when $G$ is torsion-free elementary amenable (e.g. when $G=\mathbb{Z}^d, \ d \in \mathbb{N}$) and $V=\mathbb{F}$, and that every linear CA is regular when $V$ is finite-dimensional and $G$ is locally finite with $\text{Char}(\mathbb{F}) \nmid o(g)$ for all $g \in G$.Comment: 10 pages. Theorem 5 corrected from previous versions, in A. Dennunzio, E. Formenti, L. Manzoni, A.E. Porreca (Eds.): Cellular Automata and Discrete Complex Systems, AUTOMATA 2017, LNCS 10248, pp. 44-55, Springer, 201

Coordinated oscillations in cortical actin and Ca2+ correlate with cycles of vesicle secretion.

The actin cortex both facilitates and hinders the exocytosis of secretory granules. How cells consolidate these two opposing roles was not well understood. Here we show that antigen activation of mast cells induces oscillations in Ca(2+) and PtdIns(4,5)P(2) lipid levels that in turn drive cyclic recruitment of N-WASP and cortical actin level oscillations. Experimental and computational analysis argues that vesicle fusion correlates with the observed actin and Ca(2+) level oscillations. A vesicle secretion cycle starts with the capture of vesicles by actin when cortical F-actin levels are high, followed by vesicle passage through the cortex when F-actin levels are low, and vesicle fusion with the plasma membrane when Ca(2+) levels subsequently increase. Thus, cells employ oscillating levels of Ca(2+), PtdIns(4,5)P(2) and cortical F-actin to increase secretion efficiency, explaining how the actin cortex can function as a carrier as well as barrier for vesicle secretion

Arithmetic and Geometric Progressions in Productsets over Finite Fields

Given two sets \cA, \cB \subseteq \F_q of elements of the finite field \F_q of $q$ elements, we show that the productset \cA\cB = \{ab | a \in \cA, b \in\cB\} contains an arithmetic progression of length $k \ge 3$ provided that $k<p$, where $p$ is the characteristic of \F_q, and # \cA # \cB \ge 3q^{2d-2/k}. We also consider geometric progressions in a shifted productset \cA\cB +h, for f \in \F_q, and obtain a similar result

Stellar Populations and Ages of M82 Super Star Clusters

We present high signal-to-noise optical spectra of two luminous super star clusters in the starburst galaxy M82. The data for cluster F and the nearby, highly reddened cluster L were obtained with the William Herschel Telescope (WHT) at a resolution of 1.6A. The blue spectrum (3250-5540A) of cluster F shows features typical of mid-B stars. The red spectra (5730-8790A) of clusters F and L show the Ca II triplet and numerous F and G-type absorption features. Strong Ca II and Na I interstellar absorption lines arising in M82 are also detected, and the 6283A diffuse interstellar band appears to be present. The quality of the WHT spectra allows us to considerably improve previous age estimates for cluster F. By comparing the blue spectrum with theoretical model cluster spectra using the PEGASE spectral synthesis code (Fioc & Rocca-Volmerange 1997), we derive an age of 60+/-20 Myr. The strength of the Ca II triplet is also in accord with this age. Cluster L appears to have a similar age, although this is much less certain. The measured radial velocities for the two clusters differ substantially, indicating that they are located in different regions of the M82 disk. Cluster F appears to be deep in M82, slightly beyond the main starburst region while the highly obscured cluster L lies near the outer edges of the disk. We derive an absolute V magnitude of -16.5 for F indicating that it is an extremely massive cluster. The presence of such a luminous super star cluster suggests that the M82 starburst experienced an episode of intense star formation approximately 60 Myr ago.Comment: 10 pages and 5 figures for publication in MNRA