bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid, theoretically artifact‐free calculation of static magnetic field induced by voxelated susceptibility distribution in an arbitrary volume of interest
Authors: Lee Seung‐Kyun , Hwang Seon‐Ha , Barg Ji‐Seong , Yeo Seok‐Jin
Published: March 2018

Purpose

To demonstrate a computationally efficient and theoretically artifact‐free method to calculate static field (B0) inhomogeneity in a volume of interest induced by an arbitrary voxelated susceptibility distribution.

Methods

Our method computes B0 by circular convolution between a zero‐filled susceptibility matrix and a shifted, voxel‐integrated dipolar field kernel on a grid of size NS+NT – 1 in each dimension, where NS and NT are the sizes of the susceptibility source and B0 target grids, respectively. The computational resource requirement is independent of source‐target separation. The method, called generalized susceptibility voxel convolution, is demonstrated on three susceptibility models: an ellipsoid, MR‐compatible screws, and a dynamic human heartbeat model.

Results

B0 in an ellipsoid calculated by generalized susceptibility voxel convolution matched an analytical solution nearly exactly. The method also calculated screw‐induced B0 in agreement with experimental data. Dynamic simulation demonstrated its computational efficiency for repeated B0 calculations on time‐varying susceptibility. On the contrary, conventional and alias‐subtracted k‐space‐discretized Fourier convolution methods showed nonnegligible aliasing and Gibbs ringing artifacts in the tested models.

Conclusion

Generalized susceptibility voxel convolution can be a fast and reliable way to compute susceptibility‐induced B0 when the susceptibility source is not colocated with the B0 target volume of interest, as in modeling B0 variations from motion and foreign objects.
Toward a noninvasive estimate of interstitial fluid pressure by dynamic contrast‐enhanced MRI in a rat model of cerebral tumor
Authors: Elmghirbi Rasha , Nagaraja Tavarekere N. , Brown Stephen L. , Keenan Kelly A. , Panda Swayamprava , Cabral Glauber , Bagher‐Ebadian Hassan , Divine George W. , Lee Ian Y. , Ewing James R.
Published: March 2018

Purpose

This study demonstrates a DCE‐MRI estimate of tumor interstitial fluid pressure (TIFP) and hydraulic conductivity in a rat model of glioblastoma, with validation against an invasive wick‐in‐needle (WIN) technique. An elevated TIFP is considered a mark of aggressiveness, and a decreased TIFP a predictor of response to therapy.

Methods

The DCE‐MRI studies were conducted in 36 athymic rats (controls and posttreatment animals) with implanted U251 cerebral tumors, and with TIFP measured using a WIN method. Using a model selection paradigm and a novel application of Patlak and Logan plots to DCE‐MRI data, the MRI parameters required for estimating TIFP noninvasively were estimated. Two models, a fluid‐mechanical model and a multivariate empirical model, were used for estimating TIFP, as verified against WIN‐TIFP.

Results

Using DCE‐MRI, the mean estimated hydraulic conductivity (MRI‐K) in U251 tumors was (2.3 ± 3.1) × 10−5 (mm2/mmHg‐s) in control studies. Significant positive correlations were found between WIN‐TIFP and MRI‐TIFP in both mechanical and empirical models. For instance, in the control group of the fluid‐mechanical model, MRI‐TIFP was a strong predictor of WIN‐TIFP (R2 = 0.76, p < .0001). A similar result was found in the bevacizumab‐treated group of the empirical model (R2 = 0.93, p = .014).

Conclusion

This research suggests that MRI dynamic studies contain enough information to noninvasively estimate TIFP in this, and possibly other, tumor models, and thus might be used to assess tumor aggressiveness and response to therapy.
A 2D spiral turbo‐spin‐echo technique
Authors: Li Zhiqiang , Karis John P. , Pipe James G.
Published: March 2018

Purpose

2D turbo‐spin‐echo (TSE) is widely used in the clinic for neuroimaging. However, the long refocusing radiofrequency pulse train leads to high specific absorption rate (SAR) and alters the contrast compared to conventional spin‐echo. The purpose of this work is to develop a robust 2D spiral TSE technique for fast T2‐weighted imaging with low SAR and improved contrast.

Methods

A spiral‐in/out readout is incorporated into 2D TSE to fully take advantage of the acquisition efficiency of spiral sampling while avoiding potential off‐resonance‐related artifacts compared to a typical spiral‐out readout. A double encoding strategy and a signal demodulation method are proposed to mitigate the artifacts because of the T2‐decay‐induced signal variation. An adapted prescan phase correction as well as a concomitant phase compensation technique are implemented to minimize the phase errors.

Results

Phantom data demonstrate the efficacy of the proposed double encoding/signal demodulation, as well as the prescan phase correction and concomitant phase compensation. Volunteer data show that the proposed 2D spiral TSE achieves fast scan speed with high SNR, low SAR, and improved contrast compared to conventional Cartesian TSE.

Conclusion

A robust 2D spiral TSE technique is feasible and provides a potential alternative to conventional 2D Cartesian TSE for T2‐weighted neuroimaging.
Spinal excitability changes do not influence the mechanisms of split‐hand syndrome in amyotrophic lateral sclerosis
Authors: Cengiz Bülent , Mercan Metin , Kuruoğlu Reha
Published: March 2018

Introduction: We studied spinal excitability and its relation to motor unit action potential (MUAP) changes in the thenar and hypothenar muscles in patients with amyotrophic lateral sclerosis (ALS). Methods: Quantitative MUAP and peak ratio interference analyses were performed, and cutaneous silent period (CutSP) was measured in the abductor digiti minimi (ADM) and first dorsal interosseous (FDI) muscles of patients with ALS and controls. Results: Patients with ALS revealed more prominently increased duration (P = 0.002), number of phases (P = 0.02), size index (P = 0.02), and thickness (P = 0.02) in ADM than in FDI. The number of small segments was significantly decreased in ADM (P = 0.036) compared with controls. CutSP latency was prolonged in both ADM and FDI in ALS (P < 0.05). Discussion: Although the reinnervation capacity was notably higher in the ADM of patients with ALS, the lack of a significant difference in CutSP measurements between ADM and FDI argues against spinal excitability changes in the development of split‐hand syndrome. Muscle Nerve 58: 503–508, 2018
Effects of oxidized/treated non‐metallic fillers obtained from waste printed circuit boards on mechanical properties and shrinkage of unsaturated polyester‐based composites
Authors: Kovačević Tihomir , Rusmirović Jelena , Tomić Nataša , Mladenović Goran , Milošević Miloš , Mitrović Nenad , Marinković Aleksandar
Published: March 2018

The investigation of the influence of acid/base treatment and addition level of non‐metallic fractions (NMFs), obtained by processing of printed circuit boards, on the mechanical properties and shrinkage of unsaturated polyester resin (UPR)‐based composites was main topic presented in this paper. NMF particles were treated using four different oxidative/etching agents: H2SO4/KMnO4 (NMF1), H2SO4/HNO3 (NMF2), HNO3 (NMF3), and NaOH (NMF4). Treated NMF(1–4) particles were characterized using fourier transform infrared, Boehm titration, optical microscopy and SEM analysis. Tensile strength and micro Vickers hardness of UPR/NMF(1–4) composites were the most improved with addition of 0.5wt% of filler, for 5.9–24.7%, in comparison to composite filled with non‐treated NMF particles. Cross‐linking density (ν), storage, and loss modulus (G' and G''), damping factor (tanδ) and glass transition temperature (Tg) of the composites were determined from the dynamic–mechanical analysis (DMA) testing. Shrinkage measurements, performed using Aramis 6.2.0, showed significant improvement in shrinkage reducing, for 17.8–30.6%, by introduction the oxidized NMF particles. Qualitative/quantitative evaluation of NMF(1–4) surface functionalities helped in understanding their influences on mechanical, DMA and shrinkage properties change of studied composites. POLYM. COMPOS., 40:1170–1186, 2019. © 2018 Society of Plastics Engineers
Effect of amine functionalized MWCNT‐epoxy interfacial interaction on MWCNT dispersion and mechanical properties of epoxy‐amine composites
Authors: Zhang Qingjie , Bai Gang , Xiao Wei , Sui Gang , Yang Xiaoping
Published: March 2018

The incorporation of functionalized nano‐fillers into epoxy‐based composites shows a potential to improve material performances, which based on the modification mechanism is well understood. In this study, amine functionalized multiwall carbon nanotube (MWCNT‐NH2) as an example was prepared and selected as a type of functionalized nano‐fillers to modify two kinds of tri‐functionality epoxy resins, i.e. diglycidyl‐4, 5‐epoxycyclohexane‐1, 2‐dicarboxylate (DGEAC) and n, n‐diglycidyl‐4‐glycidy‐loxyaniline (TGPAP). The interfacial interaction of MWCNT‐NH2 with DGEAC or TGPAP was investigated by using molecular dynamics (MDs) simulations. Further investigation on how the interfacial interactions affected the dispersion of MWCNT‐NH2 in each epoxy resin was conducted and their effects on the mechanical properties of the resulting nanocomposites were characterized. The MD simulation results indicated that a higher interfacial strength between MWCNT‐NH2 and TGPAP molecule was formed, no matter with non‐covalent or covalent interaction, due to the presence of benzene ring and nitrogen atom in the backbone of TGPAP molecule. Moreover, the experimental results showed that the stronger binding strength of MWCNT‐NH2 with TGPAP can bring more positive effect on the dispersion of MWCNT‐NH2 in the TGPAP‐based resin matrix, and then resulting in the considerable improved tensile toughness compared with the neat sample and MWCNT‐NH2 reinforced DGEAC‐based ones. POLYM. COMPOS., 39:E2552–E2561, 2018. © 2018 Society of Plastics Engineers
Redesign of LAOBP to bind novel l‐amino acid ligands
Authors: Banda‐Vázquez Jesús , Shanmugaratnam Sooruban , Rodríguez‐Sotres Rogelio , Torres‐Larios Alfredo , Höcker Birte , Sosa‐Peinado Alejandro
Published: March 2018

Computational protein design is still a challenge for advancing structure‐function relationships. While recent advances in this field are promising, more information for genuine predictions is needed. Here, we discuss different approaches applied to install novel glutamine (Gln) binding into the Lysine/Arginine/Ornithine binding protein (LAOBP) from Salmonella typhimurium. We studied the ligand binding behavior of two mutants: a binding pocket grafting design based on a structural superposition of LAOBP to the Gln binding protein QBP from Escherichia coli and a design based on statistical coupled positions. The latter showed the ability to bind Gln even though the protein was not very stable. Comparison of both approaches highlighted a nonconservative shared point mutation between LAOBP_graft and LAOBP_sca. This context dependent L117K mutation in LAOBP turned out to be sufficient for introducing Gln binding, as confirmed by different experimental techniques. Moreover, the crystal structure of LAOBP_L117K in complex with its ligand is reported.
p53 promotes its own polyubiquitination by enhancing the HDM2 and HDMX interaction
Authors: Medina‐Medina Ixaura , Martínez‐Sánchez Mayra , Hernández‐Monge Jesús , Fahraeus Robin , Muller Petr , Olivares‐Illana Vanesa
Published: March 2018

HDM2 and HDMX are two homologs essential for controlling p53 tumor suppressor activity under normal conditions. Both proteins bind different sites on the p53 N‐terminus, and while HDM2 has E3 ubiquitin ligase activity towards p53, HDMX does not. Nevertheless, HDMX is required for p53 polyubiquitination and degradation, but the underlying molecular mechanism remains unclear. Alone, HDMX and HDM2 interact via their respective C‐terminal RING domains but here we show that the presence of p53 induces an N‐terminal interface under normal cellular conditions. This results in an increase in HDM2‐mediated p53 polyubiquitination and degradation. The HDM2 inhibitor Nutlin‐3 binds the N‐terminal p53 binding pocket and is sufficient to induce the HDM2‐HDMX interaction, suggesting that the mechanism depends on allosteric changes that control the multiprotein complex formation. These results demonstrate an allosteric interchange between three different proteins (HDMX‐HDM2‐p53) and help to explain the molecular mechanisms of HDM2‐inhibitory drugs.
A probabilistic network model for structural transitions in biomolecules
Authors: Habeck Michael , Nguyen Thach
Published: March 2018

Biological macromolecules often undergo large conformational rearrangements during a functional cycle. To simulate these structural transitions with full atomic detail typically demands extensive computational resources. Moreover, it is unclear how to incorporate, in a principled way, additional experimental information that could guide the structural transition. This article develops a probabilistic model for conformational transitions in biomolecules. The model can be viewed as a network of anharmonic springs that break, if the experimental data support the rupture of bonds. Hamiltonian Monte Carlo in internal coordinates is used to infer structural transitions from experimental data, thereby sampling large conformational transitions without distorting the structure. The model is benchmarked on a large set of conformational transitions. Moreover, we demonstrate the use of the probabilistic network model for integrative modeling of macromolecular complexes based on data from crosslinking followed by mass spectrometry.
Structures of jacalin‐related lectin PPL3 regulating pearl shell biomineralization
Authors: Nakae Setsu , Shionyu Masafumi , Ogawa Tomohisa , Shirai Tsuyoshi
Published: March 2018

The nacreous layer of pearl oysters is one of the major biominerals of commercial and industrial interest. Jacalin‐related lectins, including PPL3 isoforms, are known to regulate biomineralization of the Pteria penguin pearl shell, although the molecular mechanisms are largely unknown. The PPL3 crystal structures were determined partly by utilizing microgravity environments for 3 isoforms, namely, PPL3A, PPL3B, and PPL3C. The structures revealed a tail‐to‐tail dimer structure established by forming a unique inter‐subunit disulfide bond at C‐termini. The N‐terminal residues were found in pyroglutamate form, and this was partly explained by the post‐translational modification of PPL3 isoforms implied from the discrepancy between amino acid and gene sequences. The complex structures with trehalose and isomaltose indicated that the novel specificity originated from the unique α‐helix of PPL3 isoforms. Docking simulations of PPL3B to various calcite crystal faces suggested the edge of a β‐sheet and the carbohydrate‐binding site rich in charged residues were the interface to the biomineral, and implied that the isoforms differed in calcite interactions.
Improved protein model quality assessments by changing the target function
Authors: Uziela Karolis , Menéndez Hurtado David , Shu Nanjiang , Wallner Björn , Elofsson Arne
Published: March 2018

Protein modeling quality is an important part of protein structure prediction. We have for more than a decade developed a set of methods for this problem. We have used various types of description of the protein and different machine learning methodologies. However, common to all these methods has been the target function used for training. The target function in ProQ describes the local quality of a residue in a protein model. In all versions of ProQ the target function has been the S‐score. However, other quality estimation functions also exist, which can be divided into superposition‐ and contact‐based methods. The superposition‐based methods, such as S‐score, are based on a rigid body superposition of a protein model and the native structure, while the contact‐based methods compare the local environment of each residue. Here, we examine the effects of retraining our latest predictor, ProQ3D, using identical inputs but different target functions. We find that the contact‐based methods are easier to predict and that predictors trained on these measures provide some advantages when it comes to identifying the best model. One possible reason for this is that contact based methods are better at estimating the quality of multi‐domain targets. However, training on the S‐score gives the best correlation with the GDT_TS score, which is commonly used in CASP to score the global model quality. To take the advantage of both of these features we provide an updated version of ProQ3D that predicts local and global model quality estimates based on different quality estimates.
The modules of trans‐acyltransferase assembly lines redefined with a central acyl carrier protein
Authors: Vander Wood Drew A. , Keatinge‐Clay Adrian T.
Published: March 2018

Here, the term “module” is redefined for trans‐acyltransferase (trans‐AT) assembly lines to agree with how its domains cooperate and evolutionarily co‐migrate. The key domain in both the polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) modules of assembly lines is the acyl carrier protein (ACP). ACPs not only relay growing acyl chains through the assembly line but also collaborate with enzymes in modules, both in cis and in trans, to add a specific chemical moiety. A ketosynthase (KS) downstream of ACP often plays the role of gatekeeper, ensuring that only a single intermediate generated by the enzymes of a module is passed downstream. Bioinformatic analysis of 526 ACPs from 33 characterized trans‐AT assembly lines reveals ACPs from the same module type generally clade together, reflective of the co‐evolution of these domains with their cognate enzymes. While KSs downstream of ACPs from the same module type generally also clade together, KSs upstream of ACPs do not—in disagreement with the traditional definition of a module. Beyond nomenclature, the presented analysis impacts our understanding of module function, the evolution of assembly lines, pathway prediction, and assembly line engineering.
Quantum information‐theoretic measures for the static screened Coulomb potential
Authors: Isonguyo Cecilia N. , Oyewumi Kayode J. , Oyun Opeyemi S.
Published: March 2018

In this research work, the quantum information‐theoretic analysis of the static screened Coulomb potential has been carried out by studying both analytically and numerically the entropic measures, Fisher information as well as the Onicescu information energy of its wave function. Explicit expressions of these information‐theoretic measures were obtained. Using the Srivastava–Daoust linearization formula in terms of the multivariate Lauricella hypergeometric function, the Rényi entropy, Tsallis entropy, Onicescu information energy were analytically obtained. From the results obtained, it is observed that some of the Shannon entropies are negative, indicating that, negative entropies exists for the probability densities that are highly localized. The trends in the variation of the information‐theoretic measures with the potential screening parameter a for this atomic model are discussed. The Bialynicki‐Birula, Mycielski inequality (BBM), and the Fisher information based uncertainty relation are also verified.
Organolithium complex as a gas sensing material for oxides from ab initio calculations and molecular dynamics simulations
Authors: Ingale Nilesh , Konda Ravinder , Chaudhari Ajay
Published: March 2018

Gas sensing study of C2H4Li complex toward oxides viz. CO, CO2, NO, NO2, SO, and SO2 gas molecules has been carried out using ab initio method. Different possible configurations of gas molecule adsorption on C2H4Li complex are considered. The structural parameters of most stable configuration of gas molecule adsorbed complexes are thoroughly analysed. Electronic properties are studied using total density of states (DOS) plot. Charge transferred between the gas molecule and the substrate is studied using NBO charge analysis. Gas sensing of all the six gas molecules is possible at ambient conditions. Atom centred density matrix propagation (ADMP) molecular dynamics simulations confirmed that all the gas molecules remain adsorbed on C2H4Li complex at room temperature during the simulation. This study suggests that the C2H4Li complex acts as a novel gas sensing material for CO, CO2, NO, NO2, SO, and SO2 gas molecules at ambient conditions, below room temperature as well as at high pressure.
Mechanisms of phosphine‐catalyzed [4 + 3] annulation of allenoates with C, N‐cyclic azomethine imines: A DFT investigation
Authors: Xu Hao , Zhu Yanyan , Guo Peng , Liu Chunmei , Shan Jiankai , Tang Mingsheng
Published: March 2018

In this article, mechanisms of phosphine‐catalyzed [4 + 3] annulation of allenoates with C, N‐cyclic azomethine imines have been investigated using density functional theory. The catalytic cycle for the title reaction consists of five steps. Namely, the first step is the nucleophilic addition of phosphine catalyst, the second one is the CC bond formation, the third one is the proton transfer process, and the next one is the ring‐closure process, the last one is dissociation of the catalyst and the product generation. The calculated results indicate that the nucleophilic addition of phosphine catalyst is rate‐determining. With the use of Cat as the chiral catalyst, optically active products were obtained in good yields with excellent enantioselectivities while the CC bond formation is stereoselectivity‐determining. Furthermore, the theoretically predicted the main product is SS configuration, which is in good agreement with the experimental results. The special role of the catalysts and origin of stereoselectivity was also identified by NBO, GRI, and FMO analyses. This work might be helpful for understanding the significant roles of phosphine catalyst and thus provide valuable insights on the rational design of potential catalysts for this kind of reactions.
Small‐scale distribution of copper in a Technosol horizon studied by nano‐scale secondary ion mass spectrometry
Authors: Rennert Thilo , Höschen Carmen , Rogge Derek , Steffens Markus
Published: March 2018

Rationale

In contaminated soil, copper (Cu) is commonly distributed among various very small particles. To enlighten the qualitative distribution of Cu in a contaminated Technosol (a soil developed from deposited technogenic material) on the sub‐micron scale, we used nano‐scale secondary ion mass spectrometry (NanoSIMS).

Methods

We studied seven areas (up to 40 μm × 40 μm) on a thin section of a soil horizon by NanoSIMS, measuring 12C−, 18O−, 32S−, 63Cu− and 56Fe16O−. We evaluated the NanoSIMS measurements with a novel digital image processing tool to enlighten the composition of measured areas and thus the distribution of Cu at the sub‐micron scale. Image processing comprised spatial and spectral smoothing, normalization, endmember extraction and supervised classification.

Results

Copper was present in all areas studied on the thin section in hotspots. 63Cu− was never the ion with the highest number of mean‐normalized counts (MNCs). In classes indicating Cu accumulation, Fe or S had the highest MNCs with mostly small values for O, pointing to the presence of Cu in sulfides. Copper adsorbed on Fe oxides was also indicated. Direct interaction of Cu with organic matter was less important. Copper‐containing minerals were rather adjacent to or surrounded by an organic matrix.

Conclusions

The combination of NanoSIMS analyses with digital image processing gave us new insights into the distribution of Cu in contaminated soil. We suggest this combination as a new powerful tool for the identification of ionic contaminants in soil and other solid phases in the environment.
Role of search for domain knowledge and architectural knowledge in alliance partner selection
Authors: Yayavaram Sai , Srivastava Manish K. , Sarkar MB
Published: March 2018

Research Summary: The literature on technological alliances emphasizes that search for knowledge drives alliance formation. However, in conceptualizing technological knowledge, prior work on alliances has not made a distinction between domain knowledge—knowledge that firms possess in distinct technological domains—and architectural knowledge—knowledge that firms possess about how to combine elements from different technological domains. We argue that firms seek partners that are similar in domain knowledge to deepen their knowledge, and partners that are dissimilar in architectural knowledge to broaden their knowledge. Our results indicate that the likelihood of alliance formation increases when two firms are similar in domain knowledge and dissimilar in architectural knowledge. Further, our results show that these effects are positively moderated by the degree of decomposability of a firm's knowledge base.

Managerial Summary: In dynamic environments, companies need to continually deepen and broaden their technological knowledge, and they often look for alliance partners who can provide them that knowledge. For knowledge deepening, companies are more likely to form alliances with those companies that have expertise in similar technological fields. For knowledge broadening, they are more likely to form alliances with those companies that have expertise in the same technological fields, but have different recipes for combining knowledge from those fields. Furthermore, a company with a modular knowledge base is more likely to seek a partner that has expertise in similar technological fields or whose recipes for combining knowledge from different technological fields are different from the recipes it has.
Effect of Broken Rice Flour Addition on Cassava Starch‐Based Foams
Authors: Machado Caroline M. , Longhi Elâine M. , Spada Jordana C. , Tessaro Isabel C.
Published: March 2018

Large amounts of waste generated by the disposal of non‐biodegradable packaging is a major concern that has stimulated the search for new materials for the development of environmentally friendly packaging. This study aims to produce cassava starch‐based foams incorporated with broken rice, a co‐product of rice milling. Foams were obtained by a thermopressing process, and the influence of broken rice concentration on the formulations is investigated. Broken rice addition is tested for 0 (control sample), 10, 15, 20, and 30% (w/w). Foams containing broken rice show lower thickness and higher density. With respect to water absorption capacity, the control foam and those with 10 and 15% (w/w) of broken rice addition do not present significant statistical differences for any of the tested times. Mechanical properties (tensile strain and maximum flexural stress) are positively influenced by the addition of 10% (w/w) broken rice. Foams made from formulations containing 10% (w/w) broken rice demonstrate higher tensile strain and maximum flexural stress values compared to control foams. Additionally, these foams exhibit a good appearance without superficial cracks.
Using Modified Starch/Maltodextrin Microparticles for Enhancing the Shelf Life of Ascorbic Acid by the Spray‐Drying Method
Authors: Palma‐Rodríguez Heidi M. , Alvarez‐Ramírez Jose , Vargas‐Torres Apolonio
Published: March 2018

Chayotextle (Sechiumedule Sw.) starch is modified by acid hydrolysis for 3 h (MChS‐3h) or 6 h (MChS‐6h) and blended with 50 or 25% gum Arabic (GA). MChS‐3h, MChS‐6h, MChs‐3h‐GA, MChS‐6h‐GA, and GA formulations are used for microencapsulation of ascorbic acid (AA) by the spray‐drying method. The particle size, surface AA%, AA% retention, AA stability, X‐ray diffraction, and morphology of the microcapsules are considered to characterize the different microcapsule formulations. The amylose content decreases with hydrolysis time. Microcapsules made with MChS‐6h and MChS‐6h‐GA (75:25) show reduced values of median diameter (D [v, 0.5]) compared with microcapsules made with MChS‐3h and MChS‐3h‐GA (75:25). The concentration of GA has a positive effect on the particle size of microcapsules, a characteristic that is also observed in microscopy images. The percentage of retained AA is slightly greater for microcapsules made with MChS‐6h and MChS‐6h‐GA. The surface AA% shows similar values for all of the microcapsule formulations. However, the stability of AA over 12 weeks of storage exhibits some differences among the examined microcapsule formulations. Microcapsules made with MChS‐3h and MChS‐3h‐GA show a lower percentage of AA loss than microcapsules made with MChS‐6h and MChS‐6h‐GA. X‐Ray diffraction (XRD) analysis shows that AA is dispersed at the molecular level in the MChS and GA matrices of microcapsules. These results indicate that hydrolysis time plays a central role in the retention percentage and stability of AA.
Structures and properties of waste silicone cross‐linked polyethylene de‐cross‐linked selectively by solid‐state shear mechanochemical technology
Authors: Sun Fasen , Bai Shibing , Wang Qi
Published: March 2018

Waste silicone cross‐linked polyethylene (Si‐XLPE) recycling effectively by using solid‐state shear mechanochemical (S3M) technology was investigated to make the better performance thermoplastic polyethylene. To make this thermoplastic material, the cross‐linked structures of waste Si‐XLPE that was consisted of the siloxane bonds must be de‐cross‐linked selectively instead of the destruction of the material main chains. The properties of recycled Si‐XLPE materials were investigated by gel fraction measurements, gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter, torque rheological measurements, scanning electron microscope (SEM) and thermogravimetric analyzer (TG). From the results, it could be seen that the cross‐linking bonds of the Si‐XLPE were destroyed selectively by S3M technology and the mechanochemical milling also played a significant role in improving the materials process‐ability and mechanical properties. Gel fraction measurements, GPC and FTIR showed that S3M technology could interrupt the cross‐linked structures of Si‐XLPE rather than the backbone chains by initiating the de‐cross‐linking reaction obviously; Torque rheological results further confirmed that the recycled Si‐XLPE materials gained better plastic characteristics and process‐ability after mechanochemical milling. Compared with the untreated Si‐XLPE, the tensile strength and elongation at break of Si‐XLPE samples after 10 cycles milling increased by 118.4% and 330.4%, respectively. J. VINYL ADDIT. TECHNOL., 25:149–158, 2019. © 2018 Society of Plastics Engineers
Total, global and surface solar radiation: the case for Ockham's razor
Authors: Stanhill Gerald
Published: March 2018

This brief note examines the different names and symbols that have been, and still are, used by scientists for the solar radiation reaching the Earth's surface and uses Ockham's razor to make the case for limiting their use to the internationally agreed term Global radiation.
Development and evaluation of a bait station for selectively dispensing bait to invasive wild pigs
Authors: Lavelle Michael J. , Snow Nathan P. , Halseth Joe M. , Kinsey John C. , Foster Justin A. , VerCauteren Kurt C.
Published: March 2018

Populations of invasive wild pigs (Sus scrofa; hereafter, wild pigs) are expanding, requiring cost‐effective tools for control, and disease prevention, such as toxic or vaccine baits. Specifically, development of a novel and humane toxicant is underway for control of wild pigs in the United States and Australia. A species‐specific bait station for delivering the toxic bait must be used to protect nontarget animals. Further, a bait station must be designed to maximize feeding by wild pigs by accommodating their group‐feeding behaviors. We sought to develop a bait station that delivered bait to the maximum proportion of wild pigs and excluded the most ubiquitous nontarget species, specifically white‐tailed deer (Odocoileus virginianus) and raccoons (Procyon lotor). We used direct observations and cameras during 2015 to evaluate wild pig feeding behavior and nontarget access for various sizes, arrangements, and construction materials of prototype bait stations in pen and field settings in Texas, USA. We found that a bait station constructed of 2 back‐to‐back troughs, 1.1 m in length, without a divider was sufficient for feeding the largest proportion of wild pigs in pens. Using this design of bait station at 30 field sites, we found that wild pigs fed more frequently from plastic than metal bait stations, although both bait stations reduced feeding by wild pigs compared with control sites. From near‐video imagery at 3 field sites, we identified that 80% of wild pigs (33 of 41), 0% of white‐tailed deer (0 of 7), and 17% of raccoons (1 of 6) accessed the bait stations on the final night of testing following a 2‐week acclimation and training period. Future steps toward development of a wild pig‐specific bait station include adding resistance to the lids of bait stations to completely exclude raccoons and identify baiting strategies that most efficiently acclimate wild pigs to using bait stations. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.
Constraining scalar resonances with top-quark pair production at the LHC
Authors: Franzosi Diogo Buarque , Fabbri Federica , Schumann Steffen
Published: March 2018

Abstract

Constraints on models which predict resonant top-quark pair production at the LHC are provided via a reinterpretation of the Standard Model (SM) particle level measurement of the top-anti-top invariant mass distribution,

$$ m\left(t\overline{t}\right) $$

m

t

t
¯

. We make use of state-of-the-art Monte Carlo event simulation to perform a direct comparison with measurements of

$$ m\left(t\overline{t}\right) $$

m

t

t
¯

in the semi-leptonic channels, considering both the boosted and the resolved regime of the hadronic top decays. A simplified model to describe various scalar resonances decaying into top-quarks is considered, including CP-even and CP-odd, color-singlet and color-octet states, and the excluded regions in the respective parameter spaces are provided.
Linear growth of the entanglement entropy and the Kolmogorov-Sinai rate
Authors: Bianchi Eugenio , Hackl Lucas , Yokomizo Nelson
Published: March 2018

Abstract

The rate of entropy production in a classical dynamical system is characterized by the Kolmogorov-Sinai entropy rate h
KS given by the sum of all positive Lyapunov exponents of the system. We prove a quantum version of this result valid for bosonic systems with unstable quadratic Hamiltonian. The derivation takes into account the case of time-dependent Hamiltonians with Floquet instabilities. We show that the entanglement entropy S

A
of a Gaussian state grows linearly for large times in unstable systems, with a rate Λ
A
≤ h

KS
determined by the Lyapunov exponents and the choice of the subsystem A. We apply our results to the analysis of entanglement production in unstable quadratic potentials and due to periodic quantum quenches in many-body quantum systems. Our results are relevant for quantum field theory, for which we present three applications: a scalar field in a symmetry-breaking potential, parametric resonance during post-inflationary reheating and cosmological perturbations during inflation. Finally, we conjecture that the same rate Λ
A
appears in the entanglement growth of chaotic quantum systems prepared in a semiclassical state.
Double-trace flows and the swampland
Authors: Giombi Simone , Perlmutter Eric
Published: March 2018

Abstract

We explore the idea that large N, non-supersymmetric conformal field theories with a parametrically large gap to higher spin single-trace operators may be obtained as infrared fixed points of relevant double-trace deformations of superconformal field theories. After recalling the AdS interpretation and some potential pathologies of such flows, we introduce a concrete example that appears to avoid them: the ABJM theory at finite k, deformed by

$$ {\displaystyle \int {\mathcal{O}}^2} $$

∫

O
2

, where

$$ \mathcal{O} $$

O

is the superconformal primary in the stress-tensor multiplet. We address its relation to recent conjectures based on weak gravity bounds, and discuss the prospects for a wider class of similarly viable flows. Next, we proceed to analyze the spectrum and correlation functions of the putative IR CFT, to leading non-trivial order in 1/N. This includes analytic computations of the change under double-trace flow of connected four-point functions of ABJM superconformal primaries; and of the IR anomalous dimensions of infinite classes of double-trace composite operators. These would be the first analytic results for anomalous dimensions of finite-spin composite operators in any large N CFT3 with an Einstein gravity dual.
Bootstrapping the (A1, A2) Argyres-Douglas theory
Authors: Cornagliotto Martina , Lemos Madalena , Liendo Pedro
Published: March 2018

Abstract

We apply bootstrap techniques in order to constrain the CFT data of the (A
1
, A
2) Argyres-Douglas theory, which is arguably the simplest of the Argyres-Douglas models. We study the four-point function of its single Coulomb branch chiral ring generator and put numerical bounds on the low-lying spectrum of the theory. Of particular interest is an infinite family of semi-short multiplets labeled by the spin ℓ. Although the conformal dimensions of these multiplets are protected, their three-point functions are not. Using the numerical bootstrap we impose rigorous upper and lower bounds on their values for spins up to ℓ = 20. Through a recently obtained inversion formula, we also estimate them for sufficiently large ℓ, and the comparison of both approaches shows consistent results. We also give a rigorous numerical range for the OPE coefficient of the next operator in the chiral ring, and estimates for the dimension of the first R-symmetry neutral non-protected multiplet for small spin.
Structure of stable degeneration of K3 surfaces into pairs of rational elliptic surfaces
Authors: Kimura Yusuke
Published: March 2018

Abstract

F-theory/heterotic duality is formulated in the stable degeneration limit of a K3 fibration on the F-theory side. In this note, we analyze the structure of the stable degeneration limit. We discuss whether stable degeneration exists for pairs of rational elliptic surfaces. We demonstrate that, when two rational elliptic surfaces have an identical complex structure, stable degeneration always exists. We provide an equation that systematically describes the stable degeneration of a K3 surface into a pair of isomorphic rational elliptic surfaces. When two rational elliptic surfaces have different complex structures, whether their sum glued along a smooth fiber admits deformation to a K3 surface can be determined by studying the structure of the K3 lattice. We investigate the lattice theoretic condition to determine whether a deformation to a K3 surface exists for pairs of extremal rational elliptic surfaces. In addition, we discuss the configurations of singular fibers under stable degeneration.

The sum of two isomorphic rational elliptic surfaces glued together admits a deformation to a K3 surface, the singular fibers of which are twice that of the rational elliptic surface. For special situations, singular fibers of the resulting K3 surface collide and they are enhanced to a fiber of another type. Some K3 surfaces become attractive in these situations. We determine the complex structures and the Weierstrass forms of these attractive K3 surfaces. We also deduce the gauge groups in F-theory compactifications on these attractive K3 surfaces times a K3. E
6, E
7, E
8, SU(5), and SO(10) gauge groups arise in these compactifications.
Universality for shape dependence of Casimir effects from Weyl anomaly
Authors: Miao Rong-Xin , Chu Chong-Sun
Published: March 2018

Abstract

We reveal elegant relations between the shape dependence of the Casimir effects and Weyl anomaly in boundary conformal field theories (BCFT). We show that for any BCFT which has a description in terms of an effective action, the near boundary divergent behavior of the renormalized stress tensor is completely determined by the central charges of the theory. These relations are verified by free BCFTs. We also test them with holographic models of BCFT and find exact agreement. We propose that these relations between Casimir coefficients and central charges hold for any BCFT. With the holographic models, we reproduce not only the precise form of the near boundary divergent behavior of the stress tensor, but also the surface counter term that is needed to make the total energy finite. As they are proportional to the central charges, the near boundary divergence of the stress tensor must be physical and cannot be dropped by further artificial renormalization. Our results thus provide affirmative support on the physical nature of the divergent energy density near the boundary, whose reality has been a long-standing controversy in the literature.
Exact finite volume expectation values of $$ \overline{\varPsi}\varPsi $$ in the massive Thirring model from light-cone lattice correlators
Authors: Hegedűs Árpád
Published: March 2018

Abstract

In this paper, using the light-cone lattice regularization, we compute the finite volume expectation values of the composite operator

$$ \overline{\varPsi}\varPsi $$

Ψ
¯

Ψ

between pure fermion states in the Massive Thirring Model. In the light-cone regularized picture, this expectation value is related to 2-point functions of lattice spin operators being located at neighboring sites of the lattice. The operator

$$ \overline{\varPsi}\varPsi $$

Ψ
¯

Ψ

is proportional to the trace of the stress-energy tensor. This is why the continuum finite volume expectation values can be computed also from the set of non-linear integral equations (NLIE) governing the finite volume spectrum of the theory. Our results for the expectation values coming from the computation of lattice correlators agree with those of the NLIE computations. Previous conjectures for the LeClair-Mussardo-type series representation of the expectation values are also checked.
New nonperturbative scales and glueballs in confining supersymmetric gauge theories
Authors: Anber Mohamed M. , Poppitz Erich
Published: March 2018

Abstract

We show that new nonperturbative scales exist in four-dimensional$$ \mathcal{N} $$N= 1 super-Yang-Mills theory compactified on a circle, with an iterated-exponential dependence on the inverse gauge coupling. The lightest states with the quantum numbers of four-dimensional glueballs are nonrelativistic bound states of dual Cartan gluons and superpartners, with binding energy equal to$$ {e}^{-{e}^{1/{g}^2}} $$e−e1/g2in units of the confining mass gap. Focusing on SU(2) gauge group, we construct the nonrelativistic effective theory, show that the lightest glueball/glueballino states fill a chiral supermultiplet, and determine their “doubly-nonperturbative” binding energy. The iterated-exponential dependence on the gauge coupling is due to nonperturbative couplings in the long distance theory,$$ \uplambda \sim {e}^{-\frac{1}{g^2}} $$λ∼e−1g2, which are responsible for attractive interactions, in turn producing exponentially small,$$ \sim {e}^{-\frac{1}{\lambda }} $$∼e−1λ, effects.
On classical de Sitter and Minkowski solutions with intersecting branes
Authors: Andriot David
Published: March 2018

Abstract

Motivated by the connection of string theory to cosmology or particle physics, we study solutions of type II supergravities having a four-dimensional de Sitter or Minkowski space-time, with intersectingDp-branes and orientifoldOp-planes. Only few such solutions are known, and we aim at a better characterisation. Modulo a few restrictions, we prove that there exists no classical de Sitter solution for any combination ofD3/O3andD7/O7, while we derive interesting constraints for intersectingD5/O5orD6/O6, or combinations ofD4/O4andD8/O8. Concerning classical Minkowski solutions, we understand some typical features, and propose a solution ansatz. Overall, a central information appears to be the way intersectingDp/Opoverlap each other, a point we focus on.
A computer test of holographic flavour dynamics. Part II
Authors: Asano Yuhma , Filev Veselin G. , Kováčik Samuel , O’Connor Denjoe
Published: March 2018

Abstract

We study the second derivative of the free energy with respect to the fundamental mass (the mass susceptibility) for the Berkooz-Douglas model as a function of temperature and at zero mass. The model is believed to be holographically dual to a D0/D4 intersection. We perform a lattice simulation of the system at finite temperature and find excellent agreement with predictions from the gravity dual.
Diffusion for holographic lattices
Authors: Donos Aristomenis , Gauntlett Jerome P. , Ziogas Vaios
Published: March 2018

Abstract

We consider black hole spacetimes that are holographically dual to strongly coupled field theories in which spatial translations are broken explicitly. We discuss how the quasinormal modes associated with diffusion of heat and charge can be systematically constructed in a long wavelength perturbative expansion. We show that the dispersion relation for these modes is given in terms of the thermoelectric DC conductivity and static susceptibilities of the dual field theory and thus we derive a generalised Einstein relation from Einstein’s equations. A corollary of our results is that thermodynamic instabilities imply specific types of dynamical instabilities of the associated black hole solutions.
KLT-type relations for QCD and bicolor amplitudes from color-factor symmetry
Authors: Brown Robert W. , Naculich Stephen G.
Published: March 2018

Abstract

Color-factor symmetry is used to derive a KLT-type relation for tree-level QCD amplitudes containing gluons and an arbitrary number of massive or massless quark-antiquark pairs, generalizing the expression for Yang-Mills amplitudes originally postulated by Bern, De Freitas, and Wong. An explicit expression is given for all amplitudes with two or fewer quark-antiquark pairs in terms of the (modified) momentum kernel.

We also introduce the bicolor scalar theory, the “zeroth copy” of QCD, containing massless biadjoint scalars and massive bifundamental scalars, generalizing the biadjoint scalar theory of Cachazo, He, and Yuan. We derive KLT-type relations for tree-level amplitudes of biadjoint and bicolor theories using the color-factor symmetry possessed by these theories.
Production of pikromycin using branched chain amino acid catabolism in Streptomyces venezuelae ATCC 15439
Authors: Yi Jeong Sang , Kim Minsuk , Kim Eun-Jung , Kim Byung-Gee
Published: March 2018

Branched chain amino acids (BCAA) are catabolized into various acyl-CoA compounds, which are key precursors used in polyketide productions. Because of that, BCAA catabolism needs fine tuning of flux balances for enhancing the production of polyketide antibiotics. To enhance BCAA catabolism for pikromycin production in Streptomyces venezuelae ATCC 15439, three key enzymes of BCAA catabolism, 3-ketoacyl acyl carrier protein synthase III, acyl-CoA dehydrogenase, and branched chain α-keto acid dehydrogenase (BCDH) were manipulated. BCDH overexpression in the wild type strain resulted in 1.3 fold increase in pikromycin production compared to that of WT, resulting in total 25 mg/L of pikromycin. To further increase pikromycin production, methylmalonyl-CoA mutase linked to succinyl-CoA production was overexpressed along with BCDH. Overexpression of the two enzymes resulted in the highest titer of total macrolide production of 43 mg/L, which was about 2.2 fold increase compared to that of the WT. However, it accumulated and produced dehydroxylated forms of pikromycin and methymycin, including their derivatives as well. It indicated that activities of pikC, P450 monooxygenase, newly became a bottleneck in pikromycin synthesis.