Perfusion and diffusion sensitive C stimulated-echo MRSI for metabolic imaging of cancer

Metabolic imaging with hyperpolarized [1-¹³C]-pyruvate can rapidly probe tissue metabolic profiles in vivo and has been shown to provide cancer imaging biomarkers for tumor detection, progression, and response to therapy. This technique uses a bolus injection followed by imaging within 1–2 minutes. The observed metabolites include vascular components and their generation is also influenced by cellular transport. These factors complicate image interpretation, especially since [1-¹³C]lactate, a metabolic product that is a biomarker of cancer, is also produced by red blood cells. It would be valuable to understand the distribution of metabolites between the vasculature, interstitial space, and intracellular compartments. The purpose of this study was to better understand this compartmentalization by using a perfusion and diffusion-sensitive stimulated-echo acquisition mode (STEAM) MRSI acquisition method tailored to hyperpolarized substrates. Our results in mouse models showed that among metabolites, the injected substrate ¹³C-pyruvate had the largest vascular fraction overall while ¹³C-alanine had the smallest vascular fraction. We observed a larger vascular fraction of pyruvate and lactate in the kidneys and liver when compared to back muscle and prostate tumor tissue. Our data suggests that ¹³C-lactate in prostate tumor tissue voxels was the most abundant labeled metabolite intracellularly. This was shown in STEAM images that highlighted abnormal cancer cell metabolism and suppressed vascular ¹³C metabolite signals.     

An elementary algorithm for reporting intersections of red/blue curve segments

Let E_r and E_b be two sets of x-monotone and non-intersecting curve segments, E=E_rE_b and |E|=n. We give a new sweep-line algorithm that reports the k intersecting pairs of segments of E. Our algorithm uses only three simple predicates that allow to decide if two segments intersect, if a point is left or right to another point, and if a point is above, below or on a segment. These three predicates seem to be the simplest predicates that lead to subquadratic algorithms. Our algorithm is almost optimal in this restricted model of computation. Its time complexity is O(nlogn+kloglogn) and it requires O(n) space.     

Grafting and polymer formation on silicon from unsaturated Grignards: II. Aliphatic precursors

Anodic decomposition of a vinylmagnesium halide or an ethynylmagnesium halide at a surface-hydrogenated silicon electrode leads to the formation of polymeric layers covalently anchored to the silicon surface. These layers have been characterized using spectroellipsometry and photoluminescence, infrared, and X-ray photoelectron spectroscopy. In the case of vinyl precursors, it appears that the multiple bonds are largely broken in the process. In the case of ethynyl, the layer formation rate is much higher for the chloride than for the bromide. The obtained polymer appears as a saturated skeleton bearing halide and unsaturated ethynyl groups. Furthermore, it appears that the solvent may be attacked by the ethynyl radicals leading to contamination of the polymer by solvent fragments, an effect that can largely be avoided by using appropriate solvents. The reaction pathways are discussed.     

A New Pooling Approach Based on Zeckendorf’s Theorem for Texture Transfer Information

The pooling layer is at the heart of every convolutional neural network (CNN) contributing to the invariance of data variation. This paper proposes a pooling method based on Zeckendorf’s number series. The maximum pooling layers are replaced with Z pooling layer, which capture texels from input images, convolution layers, etc. It is shown that Z pooling properties are better adapted to segmentation tasks than other pooling functions. The method was evaluated on a traditional image segmentation task and on a dense labeling task carried out with a series of deep learning architectures in which the usual maximum pooling layers were altered to use the proposed pooling mechanism. Not only does it arbitrarily increase the receptive field in a parameterless fashion but it can better tolerate rotations since the pooling layers are independent of the geometric arrangement or sizes of the image regions. Different combinations of pooling operations produce images capable of emphasizing low/high frequencies, extract ultrametric contours, etc.     

Manganese(III)-containing Wells-Dawson sandwich-type polyoxometalates: comparison with their manganese(II) counterparts

We present the synthesis and structural characterization, assessed by various techniques (FTIR, TGA, UV-vis, elemental analysis, single-crystal X-ray diffraction for three compounds, magnetic susceptibility, and electrochemistry) of five manganese-containing Wells-Dawson sandwich-type (WDST) complexes. The dimanganese(II)-containing complex, [Na(2)(H(2)O)(2)Mn(II)(2)(As(2)W(15)O(56))(2)](18-) (1), was obtained by reaction of MnCl(2) with 1 equiv of [As(2)W(15)O(56)](12-) in acetate medium (pH 4.7). Oxidation of 1 by Na(2)S(2)O(8) in aqueous solution led to the dimanganese(III) complex [Na(2)(H(2)O)(2)Mn(III)(2)(As(2)W(15)O(56))(2)](16-) (2), while its trimanganese(II) homologue, [Na(H(2)O)(2)Mn(II)(H(2)O)Mn(II)(2)(As(2)W(15)O(56))(2)](17-) (3), was obtained by addition of ca. 1 equiv of MnCl(2) to a solution of 1 in 1 M NaCl. The trimanganese(III) and tetramanganese(III) counterparts, [Mn(III)(H(2)O)Mn(III)(2)(As(2)W(15)O(56))(2)](15-) (4) and [Mn(III)(2)(H(2)O)(2)Mn(III)(2)(As(2)W(15)O(56))(2)](12-) (6), are, respectively, obtained by oxidation of aqueous solutions of 3 and [Mn(II)(2)(H(2)O)(2)Mn(II)(2)(As(2)W(15)O(56))(2)](16-) (5) by Na(2)S(2)O(8). Single-crystal X-ray analyses were carried out on 2, 3, and 4. BVS calculations and XPS confirmed that the oxidation state of Mn centers is +II for complexes 1, 3, and 5 and +III for 2, 4, and 6. A complete comparative electrochemical study was carried out on the six compounds cited above, and it was possible to observe the distinct redox steps Mn(IV/III) and Mn(III/II). Magnetization measurements, as a function of temperature, confirm the presence of antiferromagnetic interactions between the Mn ions in these compounds in all cases with the exception of compound 2.     

Grafting and polymer formation on silicon from unsaturated Grignards: I-aromatic precursors

Anodic decomposition of a phenylmagnesium halide at a surface-hydrogenated silicon electrode leads to formation of polymeric layers covalently anchored to the silicon surface. These layers have been characterized using spectroellipsometry, photoluminescence, infrared, and X-ray photoelectron spectroscopies. The phenyl ring appears preserved in the process, and the polymer formed is a polyphenylene. Contamination by aliphatic groups from the solvent may be minimized by using a solvent resistant to hydrogen abstraction by the phenyl radicals. Regioselectivity of the branching may be oriented to the para form by using 4-chlorophenylmagnesium bromide as the precursor.     

Spectroscopic imaging of the brain with phased-array coils at 3.0 T

The goal of this study was to develop and evaluate high-resolution magnetic resonance spectroscopic imaging (MRSI) utilizing the gains in signal-to-noise ratio (SNR) provided by combining higher magnetic field with high-sensitivity phased-array (PA) coils. We investigated the maximum improvement in spatial resolution as small as 0.09 cm(3) for brain MRSI while maintaining adequate SNR and acquisition time. The use of low peak power, dual-band spectral-spatial pulses was also investigated for application to 3 T MRSI of the brain using the body coil for radiofrequency excitation and PA coils for signal reception.     

Inscribing an axially symmetric polygon and other approximation algorithms for planar convex sets

Given a planar convex set C, we give sublinear approximation algorithms to determine approximations of the largest axially symmetric convex set S contained in C, and the smallest such set S^′ that contains C. More precisely, for any >0, we find an axially symmetric convex polygon QC with area |Q|>(1−)|S| and we find an axially symmetric convex polygon Q^′ containing C with area |Q^′|<(1+)|S^′|. We assume that C is given in a data structure that allows to answer the following two types of query in time T_C: given a direction u, find an extreme point of C in direction u, and given a line ℓ, find C∩ℓ. For instance, if C is a convex n-gon and its vertices are given in a sorted array, then T_C=O(logn). Then we can find Q and Q^′ in time O(^−1/2T_C+^−3/2). Using these techniques, we can also find approximations to the perimeter, area, diameter, width, smallest enclosing rectangle and smallest enclosing circle of C in time O(^−1/2T_C).     

Photonic nanoarchitectures in butterflies and beetles: valuable sources for bioinspiration

Nature began developing photonic nanoarchitectures millions of years before humankind. Often, in the living world, color is a communication channel that may influence the chance of the individual surviving as well as the chance to reproduce. Therefore, natural color‐generating structures are highly optimized by many millennia of evolution. In this review, a survey is presented of the development of natural photonic crystal‐type nanoarchitectures occurring in butterflies and beetles from the standpoint of physics and materials science, covering the past ten years. One‐, two‐, and three‐dimensional structures are reviewed, emphasizing the role that disorder, or irregularity, may play in natural nanoarchitectures to achieve certain visual effects. The characterization, modeling methods, and rapidly growing number of bioinspired or biomimetic applications are discussed.