Flexible Block Research Articles

Exploring biphenyl-2,4,4′-tricarboxylic acid as a flexible building block for the hydrothermal self-assembly of diverse metal–organic and supramolecular networks

This contribution reports the hydrothermal self-assembly synthesis, characterization, thermal stability, structural and topological features, and luminescence or magnetic properties of a new series of nine coordination compounds.

Prototyping design of a flexible DSP block with pipeline structure for FPGA

Prototyping design of a flexible DSP block with pipeline structure for FPGA

Highly crystalline covalent organic frameworks from flexible building blocks.

Two novel 2D covalent organic frameworks (TPT-COF-1 and TPT-COF-2) were synthesized from the flexible 2,4,6-triaryloxy-1,3,5-triazine building blocks on a gram scale, which show high crystallinity and large surface area. The controllable formation of highly ordered frameworks is mainly attributed to the self-assembly Piedfort unit of 2,4,6-triaryloxy-1,3,5-triazine.

Convergence Analysis of Alternating Direction Method of Multipliers for a Family of Nonconvex Problems

The alternating direction method of multipliers (ADMM) is widely used to solve large-scale linearly constrained optimization problems, convex or nonconvex, in many engineering fields. However there is a general lack of theoretical understanding of the algorithm when the objective function is nonconvex. In this paper we analyze the convergence of the ADMM for solving certain nonconvex consensus and sharing problems, and show that the classical ADMM converges to the set of stationary solutions, provided that the penalty parameter in the augmented Lagrangian is chosen to be sufficiently large. For the sharing problems, we show that the ADMM is convergent regardless of the number of variable blocks. Our analysis does not impose any assumptions on the iterates generated by the algorithm, and is broadly applicable to many ADMM variants involving proximal update rules and various flexible block selection rules.

Sentinel-1A: Analysis of FDBAQ Performance on Real Data

This paper concerns the performance of the flexible dynamic block adaptive quantizer (FDBAQ), which is the onboard data compression scheme used by Sentinel-1 (S-1), i.e., the C-band synthetic aperture radar (SAR) constellation whose first satellite (Sentinel-1A) has been launched on April 3, 2014. The data rate that results from the fine resolution and the wide swath of S-1 would exceed, without data compression, the S-1 hardware limitations. The FDBAQ has been proposed as an efficient method to reduce the instrument data rate and limit the onboard storage requirement. The capabilities of such a compression scheme have not been tested on real data before. Preflight simulation and analysis were based on a simplified processing scheme and radar backscattering information taken from past missions. The purpose of this paper is to present the first results of the analysis of real acquisitions, comprising thousands of products, in every S-1 acquisition mode, acquired during and after the commissioning phase. Advantages and limits are presented in detail, comparing FDBAQ and the traditional block adaptive quantizer (BAQ) compression scheme, in terms of quantization noise level, signal-to-noise ratio, and average bit and data rates.

Intra Predictive Depth Map Coding Using Flexible Block Partitioning.

A complete encoding solution for efficient intra-based depth map compression is proposed in this paper. The algorithm, denominated predictive depth coding (PDC), was specifically developed to efficiently represent the characteristics of depth maps, mostly composed by smooth areas delimited by sharp edges. At its core, PDC involves a directional intra prediction framework and a straightforward residue coding method, combined with an optimized flexible block partitioning scheme. In order to improve the algorithm in the presence of depth edges that cannot be efficiently predicted by the directional modes, a constrained depth modeling mode, based on explicit edge representation, was developed. For residue coding, a simple and low complexity approach was investigated, using constant and linear residue modeling, depending on the prediction mode. The performance of the proposed intra depth map coding approach was evaluated based on the quality of the synthesized views using the encoded depth maps and original texture views. The experimental tests based on all intra configuration demonstrated the superior rate-distortion performance of PDC, with average bitrate savings of 6%, when compared with the current state-of-the-art intra depth map coding solution present in the 3D extension of a high-efficiency video coding (3D-HEVC) standard. By using view synthesis optimization in both PDC and 3D-HEVC encoders, the average bitrate savings increase to 14.3%. This suggests that the proposed method, without using transform-based residue coding, is an efficient alternative to the current 3D-HEVC algorithm for intra depth map coding.

Segmental HOG: new descriptor for glomerulus detection in kidney microscopy image.

BackgroundThe detection of the glomeruli is a key step in the histopathological evaluation of microscopic images of the kidneys. However, the task of automatic detection of the glomeruli poses challenges owing to the differences in their sizes and shapes in renal sections as well as the extensive variations in their intensities due to heterogeneity in immunohistochemistry staining.Although the rectangular histogram of oriented gradients (Rectangular HOG) is a widely recognized powerful descriptor for general object detection, it shows many false positives owing to the aforementioned difficulties in the context of glomeruli detection.ResultsA new descriptor referred to as Segmental HOG was developed to perform a comprehensive detection of hundreds of glomeruli in images of whole kidney sections. The new descriptor possesses flexible blocks that can be adaptively fitted to input images in order to acquire robustness for the detection of the glomeruli. Moreover, the novel segmentation technique employed herewith generates high-quality segmentation outputs, and the algorithm is assured to converge to an optimal solution. Consequently, experiments using real-world image data revealed that Segmental HOG achieved significant improvements in detection performance compared to Rectangular HOG.ConclusionThe proposed descriptor for glomeruli detection presents promising results, and it is expected to be useful in pathological evaluation.

Solvent controlled ion association in structured copolymers: Molecular dynamics simulations in dilute solutions.

Tailoring the nature of individual segments within ion containing block co-polymers is one critical design tool to achieve desired properties. The local structure including the size and distribution of the ionic blocks, as well as the long range correlations, are crucial for their transport ability. Here, we present molecular dynamics simulations on the effects of varying the concentrations of the ionizable groups on the conformations of pentablock ionomer that consist of a center block of ionic sulfonated styrene tethered to polyethylene and terminated by a bulky substituted styrene in dilute solutions. Sulfonation fractions f (0 ≤ f ≤ 0.55), spanning the range from ionomer to polyelectrolytes, were studied. Results for the equilibrium conformation of the chains in water and a 1:1 mixture of cyclohexane and heptane are compared to that in implicit poor solvents with dielectric constants ε = 1.0 and 77.73. In water, the pentablock collapses with the sulfonated groups on the outer surface. As f increases, the ionic, center block increasingly segregates from the hydrophobic regions. In the 1:1 mixture of cyclohexane and heptane, the flexible blocks swell, while the center ionic block collapses for f > 0. For f = 0, all blocks swell. In both implicit poor solvents, the pentablock collapses into a nearly spherical shape for all f. The sodium counterions disperse widely throughout the simulation cell for both water and ε = 77.73, whereas for ε = 1.0 and mixture of cyclohexane and heptane, the counterions largely condense onto the collapsed pentablock.

Fast HEVC Coding Unit Decision Based On BP-Neural Network

High Efficiency Video Coding (HEVC) employs a highly flexible quad-tree coding block partitioning structure characterized by a coding unit (CU), prediction unit (PU) and transform unit (TU). Taking the computational complexity of CU splitting in HEVC into consideration, a novel fast CU selection algorithm based on a back-propagation neural network (BPNN) is proposed in this paper. To find the best prediction mode at the current CU, the BPNN classifier is designed for two kinds of outputs representing “split” and “unsplit”. Thus, whether to split the current CU or not is directly judged by the outputs of the BPNN classifier. With this new scheme, the unnecessary CU splitting process can be skipped in advance. Experiments and results show that the proposed algorithm could greatly reduce the high computational complexity and the average time savings reaches 47.75% in Random Access Main configuration and 41.94% in Low Delay B Main configuration with a BD-bit rate increase of 1.89%.

Role of PEG Segment in Stereocomplex Crystallization for PLLA/PDLA-b-PEG-b-PDLA Blends

The isothermal crystallization behavior and morphology of neat poly(l-lactic acid) (PLLA) and its blends with poly(d-lactic acid) (PDLA) and PDLA-b-poly(ethylene glycol) (PEG)-b-PDLA have been investigated. The glass transition temperature of the PLLA/PDLA blend, and especially the PLLA/PDLA-b-PEG-b-PDLA blend, is much lower than that of neat PLLA, indicating the plasticization effect of both low molecular weight PDLA and flexible PEG block. Both the PLLA/PDLA and PLLA/PDLA-b-PEG-b-PDLA blends can form stereocomplex (SC) crystals. However, the PDLA in the PLLA/PDLA blend postponed the crystallization rate of the blend, whereas the PEG chains in PLLA/PDLA-b-PEG-b-PDLA not only promoted the formation of SC crystals but also facilitated the crystallization of the PLLA matrix. The evolution of the crystal structure and morphologies of PLLA and its blends during the isothermal crystallization process have revealed the significant role of flexible PEG chains in the stereocomplex crystallization.

Multi-block copolymers based on poly(p-phenylene)s with excellent durability and fuel cell performance

We present a promising candidate for a hydrocarbon-based electrolyte membrane material, which shows higher fuel cell performance and durability than Nafion 212. Sulfonated poly(p-phenylene) (sPP)-based multi-block copolymers with optimized flexible hydrophobic blocks were synthesized using a Ni(0)-catalyzed cross-coupling polymerization. The resulting copolymers showed well-developed nanophase separation between the hydrophilic and hydrophobic domains and highly connected hydrophilic nanochannels, which gave rise to enhanced proton conduction and low dimensional variation. Moreover, the sPP-b-PAES(6.5K)-3.0 membranes with poly(arylene ether sulfone) (PAES) oligomer as a hydrophobic block material exhibited a significantly higher fuel cell performance than Nafion 212 under fully and partially hydrated conditions. Furthermore, this material exhibited superior long-term stability compared with Nafion 212. To the best of our knowledge, this material is the first reported hydrocarbon-based ionomer that has both a fuel cell performance and durability that are superior to those of Nafion.

An EHD-mixed lubrication analysis of main bearings for diesel engine based on coupling between flexible whole engine block and crankshaft

Purpose – The purpose of this paper is to develop a good calculation model to accurately predict the lubrication characteristic of main bearings of diesel engine and improve the service life. Design/methodology/approach – Based on the coupling of the whole flexible engine block and the flexible crankshaft reduced by the Component Mode Synthesis (CMS) method, considering mass-conserving boundary conditions, the average flow model equation and Greenwood/Tripp asperity contact theory, an elastohydrodynamic (EHD)-mixed lubrication model of the main bearings for the diesel engine is developed and researched with the finite volume method and the finite element method. Findings – Obviously, the mixed lubrication of bearings is normal, while full hydrodynamic lubrication is transient. The results show that under the whole flexible block model, maximum oil film pressure, maximum asperity contact pressure and radial shell deformation decrease, while minimum oil film thickness increases. Oil flow over edge decreases, and so does friction loss. Therefore, coordination deformation ability of whole engine block is favorable to mean load. In the whole block model, friction contact happens on both upper shell and lower shell positions. In addition, average oil film fill ratio at the key position becomes smaller in the whole engine block model, and consequently increases the chances of cavitations erosion more. So, wearing resistance of both upper and lower shells and anti-cavitations erosion ability must be enhanced simultaneously. Originality/value – Based on the coupling of the whole flexible engine block and the flexible crankshaft reduced by the CMS method, considering mass-conserving boundary conditions, the average flow model equation and Greenwood/Tripp asperity contact theory, an EHD-mixed lubrication model of the main bearings for the diesel engine is built, which can predict the lubrication of journal bearings more accurately.

Statistical and spatiotemporal correlation based low-complexity video coding for high-efficiency video coding

High-efficiency video coding (HEVC) is a new coding standard that adopts the quadtree splitting structure based on coding tree units instead of macroblocks, and can support more coding modes and more partitions. Although it can improve compression efficiency, the flexible quadtree block partition and mode selection result in high computational complexity in real-time applications. We propose a low-complexity video coding algorithm for HEVC by utilizing statistical correlation and spatiotemporal correlation, which consists of an early determination of SKIP mode (EDSM) method and an early termination of reference frame selection (ETRFS) method. Since there is a strong correlation for the rate distortion (RD) cost for the SKIP mode between adjacent frames, EDSM detects the SKIP mode according to the threshold derived from the former training frame. Meanwhile, ETRFS terminates the process of reference frame selection using the motion vector and reference frame information from neighboring blocks to skip unnecessary candidate frames. Experimental results demonstrate that the proposed method can achieve about 45.01% complexity reduction on average with a 1.11% BD-rate increase and 0.04 BD-PSNR decrease for random access. The complexity reduction, BD-rate increase, and BD-PSNR decrease for low delay are 46.16%, 0.99%, and 0.03, respectively.

A flexible and adaptive simpler block GMRES with deflated restarting for linear systems with multiple right-hand sides

Block GMRES is one of the most popular algorithms for solving large non-Hermitian linear systems with multiple right-hand sides. The simpler block GMRES algorithm is a variation of block GMRES, which avoids the factorization of a block upper Hessenberg matrix; and it is much simpler to program and requires less work than block GMRES. However, theoretical results given in this paper indicate that it is less stable due to the ill-conditioning of the basis used. In order to overcome this difficulty, we propose an adaptive simpler block GMRES algorithm for large linear systems with multiple right-hand sides. Theoretical analysis is made to show the reason why the new algorithm is superior to its original counterpart. Moreover, we consider how to restart and precondition the adaptive simpler block GMRES algorithm, and propose a flexible and adaptive simpler block GMRES algorithm with deflated restarting. Numerical experiments show the numerical behavior of our new algorithm.

A variety of metal–organic and supramolecular networks constructed from a new flexible multifunctional building block bearing picolinate and terephthalate functionalities: hydrothermal self-assembly, structural features, magnetic and luminescent properties

A novel multifunctional building block was designed and applied for the synthesis of diverse coordination compounds.

Structure of Mega-Hemocyanin Reveals Protein Origami in Snails

Mega-hemocyanin is a 13.5 MDa oxygen transporter found in the hemolymph of some snails. Similar to typical gastropod hemocyanins, it is composed of 400kDa building blocks but has additional 550kDa subunits. Together, they form a large, completely filled cylinder. The structural basis for this highly complex protein packing is not known so far. Here, we report the electron cryomicroscopy (cryo-EM) structure of mega-hemocyanin complexes from two different snail species. The structures reveal that mega-hemocyanin is composed of flexible building blocks that differ in their conformation, but not in their primary structure. Like a protein origami, these flexible blocks are optimally packed, implementing different local symmetries and pseudosymmetries. A comparison between the two structures suggests a surprisingly simple evolutionary mechanism leading to these large oxygen transporters.

ChemInform Abstract: An Efficient Method for the Preparation of 3‐Hydroxyl‐5‐substituted 2‐Pyrrolidones and Application in the Divergent Synthesis of (‐)‐Preussin and Its Analogues.

AbstractThis describes the syntheses of (‐)‐preussin (XIb) and analogues (XI).

Fast intra mode decision algorithm for HEVC based on dominant edge assent distribution

As the latest video coding standard, high efficiency video coding (HEVC) is a successor to H.264/AVC. To improve the coding efficiency of intra coding, HEVC employs a flexible quad-tree coding block partitioning structure and 35 intra prediction modes. The optimal prediction mode is selected through rough mode decision (RMD) and rate distortion optimisation (RDO) process. Due to the huge search space of all of the possible depth levels (CU sizes) and intra prediction modes, intra coding of HEVC is a very time-consuming and complicated process, which limits the application of HEVC. In order to reduce the intra coding complexity, we propose a fast mode decision algorithm for HEVC intra prediction which is based on dominant edge assent (DEA) and its distribution. The four DEAs in the directions of degree 0, 45, 90 and 135 are computed first; then, the dominant edge is decided according to the minimum DEA. Next, a subset of prediction modes in accordance with the dominant edge is chosen for the RMD process. The rule is as follows: When the standard deviation of DEA is distinctly small, we skip the RMD process and take the direct current (DC) mode and planar modes as the candidate modes for the RDO process; when the minimum DEA is distinctly small, we select seven modes as the candidate modes for the RMD process; otherwise, we select 11 modes for the RMD process. Lastly, the prediction unit (PU) size-based number of RDO candidate modes (3 for PU size 4?×?4 and 8?×?8 and 1 for the other PU sizes) is modified according to experimental analysis. Compared with HM 9.1, Shen's proposal and da Silva's proposal, which are two state-of-the-art fast intra mode decision algorithms, the experimental results reveal that the proposed algorithm can save 36.26, 13.85 and 20.81 % coding time on average with a negligible loss of coding efficiency, respectively.

Lipid-Pro: a computational lipid identification solution for untargeted lipidomics on data-independent acquisition tandem mass spectrometry platforms.

A major challenge for mass spectrometric-based lipidomics, aiming at describing all lipid species in a biological sample, lies in the computational and bioinformatic processing of the large amount of data that arises after data acquisition. Lipid-Pro is a software tool that supports the identification of lipids by interpreting large datasets generated by liquid chromatography--tandem mass spectrometry (LC-MS/MS) using the advanced data-independent acquisition mode MS(E). In the MS(E) mode, the instrument fragments all molecular ions generated from a sample and records time-resolved molecular ion data as well as fragment ion data for every detectable molecular ion. Lipid-Pro matches the retention time-aligned mass-to-charge ratio data of molecular- and fragment ions with a lipid database and generates a report on all identified lipid species. For generation of the lipid database, Lipid-Pro provides a module for construction of lipid species and their fragments using a flexible building block approach. Hence, Lipid-Pro is an easy to use analysis tool to interpret complex MS(E) lipidomics data and also offers a module to generate a user-specific lipid database. Lipid-Pro is freely available at: http://www.neurogenetics.biozentrum.uni-wuerzburg.de/en/project/services/lipidpro/. Supplementary data are available at Bioinformatics online.

Bifunctional organic polymeric catalysts with a tunable acid-base distance and framework flexibility.

Acid-base bifunctional organic polymeric catalysts were synthesized with tunable structures. we demonstrated two synthesis approaches for structural fine-tune. In the first case, the framework flexibility was tuned by changing the ratio of rigid blocks to flexible blocks within the polymer framework. In the second case, we precisely adjusted the acid-base distance by distributing basic monomers to be adjacent to acidic monomers, and by changing the chain length of acidic monomers. In a standard test reaction for the aldol condensation of 4-nitrobenzaldehyde with acetone, the catalysts showed good reusability upon recycling and maintained relatively high conversion percentage.