Compact Chain Research Articles

Chain conformation and rheological properties of an acid-extracted polysaccharide from peanut sediment of aqueous extraction process

A polysaccharide (PPS) in peanut sediment of aqueous extraction process was obtained at pH4.0, purified via anion-exchange chromatography. The composition, chain conformation and rheological properties were investigated. PPS mainly consisted of arabinose, galacturonic acid, xylose, and rhamnose. The intrinsic viscosity [η] was 0.71 dL/g in 0.1 M NaNO3 solution. The weight-average molar mass Mw and polydispersity index were 3.77 × 105 g/mol and 1.25, suggesting high homogeneity. The average radius of gyration (Rg), hydrodynamic radius (Rh), Rg/Rh ratio and conformation parameter v were 25.5, 18.2, 1.40 and 0.21, respectively, indicating compact coil chain conformation with branched structure. Molecular morphology revealed that PPS displayed chain shape comprised of spheres with a diameter range of 15–50 nm and apparent length of chains mainly ranged from 100 to 300 nm. The aggregation caused by molecular self-association enhanced with concentration increasing. Additionally, Newtonian behavior was observed at various concentrations. Increase in temperature effectively broke this behavior. 10.0 wt.% PPS possessed activation energy of 21.7 KJ/mol, was structured liquid and almost fitted Cox-Merz rule. These closely related with its conformation and molecular self-association behavior.

Demonstration of a cavity-based pulse compression system for pulse shape correction

A compact X-band correction cavity chain (CC) has been successfully designed, fabricated and high power tested for the Compact Linear Collider (CLIC) project. The CC consists of eight spherical cavities and four polarizers, and each spherical cavity has a ${Q}_{0}$ of 45 000 and a diameter of 7 cm. The compact CC can correct a decaying pulse shape generated by a storage cavity without need of low efficiency pulse modulation or a solution based on long delay lines. A flattop output with small ripples can be obtained if the CC and the storage cavity are matched. Experiments of the CC with a barrel open cavity (BOC) were conducted on the XBOX2 test facility at CERN, and the high power results match the theoretical calculations. The appliance of the CC only reduces the pulse compression efficiency by 6% relatively if the transmission attenuation is ignored.

Towards a Stable and High-Performance Hindered Phenol/Polymer-Based Damping Material Through Structure Optimization and Damping Mechanism Revelation.

Although hindered phenol/polymer-based hybrid damping materials, with excellent damping performance, attract more and more attention, the poor stability of hindered phenol limits the application of such promising materials. To solve this problem, a linear hindered phenol with amorphous state and low polarity was synthesized and related polyurethane-based hybrid materials were prepared in this study. The structure and state of the hindered phenol were confirmed by nuclear magnetic resonance spectrum, Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The existence of intermolecular hydrogen bonds (HBs) between hindered phenol and polyurethane was confirmed by FT-IR, and the amorphous state of the hybrids was confirmed by XRD. Moreover, by a combination of molecular dynamics simulation and dynamic mechanical analysis, the relationship between the structure optimization of the hindered phenol and the high damping performance of the hybrids was quantitatively revealed. By constructing the synthetic hindered phenol, the intramolecular HBs between hindered phenols were restricted, while the strength and concentration of the intermolecular HBs increased by increasing the amount of hindered phenol. Thus, intermolecular interactions were enhanced, which lead to the compact chain packing of polyurethane, extended chain packing of hindered phenol, and good dispersion of hindered phenol in polyurethane. Therefore, the stability of the hindered phenol and the damping properties of the hybrids were both improved. The experiment results are expected to provide some useful information for the design and fabrication of high-performance polymeric damping materials.

Detection of mecA gene and drug-resistance analysis

Objective To determine whether coagulase-negative non-epidermal staphylococcus is methicillin-resistant coagulase-negative staphylococcus by mecA gene test, when the minimal inhibitory concentration(MIC)of oxacillin is between 0.5-2.0 mg/L. Methods The mecA gene was detected and analyzed by the cefoxitin disk diffusion, E-test, VITEK-2 Compact and polymerase chain reaction(PCR)purification. Results A total of 300 strains of coagulase-negative staphylococci were screened from 4032 patients(7.4%), of which 45 strains of Staphylococcus saprophyticus and 80 strains of Staphylococcus hemolyticus were identified by Compact VITEK-2.There was a statistically significant difference in the positive rate of mecA gene detection between Staphylococcus saprophyticus and Staphylococcus hemolyticus(P<0.05). The results of detection of cefoxitin disk diffusion(inhibitory zone diameter ≥25 mm), E-test(MIC of oxacillin between 0.5-2.0 mg/L)and Compact VITEK-2(MIC of oxacillin between 0.5-2.0 mg/L)showed that there were 81 strains of coagulase-negative non-Staphylococci, of which 10 strains with positive mecA gene were confirmed by PCR. Conclusions When the minimal inhibitory concentration(MIC)of oxacillin against coagulase-negative non-Staphylococci stains is between 0.5-2.0 mg/L, the guidelines of the American clinical laboratory standardization institute(CLSI)should be strictly implemented in clinical microbiology laboratory and the mecA gene must be tested.Based on the wide dissemination of the mecA gene in Staphylococcus aureus population, if the mecA gene test is negative, it is reported as methicillin-susceptible coagulase-negative Staphylococcus(MSCNS), and the reverse result is reported as methicillin-resistant coagulase-negative staphylococcus(MRCNS). Key words: Coagulase; Methicillin resistant; Staphylococcus; mecA gene

Highly compact GaN-based all-digital transmitter chain including SPDT T/Rx switch for massive MIMO applications

AbstractThis paper presents a fully digital transmitter chain from baseband to antenna, including a modulator, two truly digital (i.e. fully switched) microwave power amplifiers and a transmit/receive switch. Both, amplifier and switch monolithic microwave integrated circuits were implemented in a GaN HEMT process. The novel amplifier design provides greatly reduced complexity, needing only three voltage sources. Measurements were conducted using 5, 20, and 100 MHz wide baseband signals. Carrier frequencies cover the 900 and 2000 MHz bands. For the 5 MHz BB signal an ACLR of over 52 dB is reached, fulfilling the 3GPP specs for base station use while still maintaining a final-stage drain efficiency of 46% at 6.5 dB peak to average power ratio. Full-scale output power at 30 V supply voltage was measured to exceed 3 W at 80% drain efficiency. Further features of this digital amplifier approach include small form factor and frequency agility, making it an ideal candidate for software defined radio.

Screening and Molecular Characterization of Cellulase Producing Actinobacteria from Litchi Orchard

Background:Cellulolysis is of considerable economic importance in laundry detergents, textile and pulp and paper industries and in fermentation of biomass into biofuels.Objective:The aim was to screen cellulase producing actinobacteria from the fruit orchard because of its requirement in several chemical reactions.Methods:Strains of actinobacteria were isolated on Sabouraud’s agar medium. Similarities in cultural and biochemical characterization by growing the strains on ISP medium and dissimilarities among them perpetuated to recognise nine groups of actinobacteria. Cellulase activity was measured by the diameter of clear zone around colonies on CMC agar and the amount of reducing sugar liberated from carboxymethyl cellulose in the supernatant of the CMC broth. Further, 16S rRNA gene sequencing and molecular characterization were placed before NCBI for obtaining recognition with accession numbers.Results:Prominent clear zones on spraying Congo Red were found around the cultures of strains of three groups SK703, SK706, SK708 on CMC agar plates. The enzyme assay for carboxymethylcellulase displayed extra cellulase activity in broth: 0.14, 0.82 and 0.66 &amp;#181;mol mL-1 min-1, respectively at optimum conditions of 35°C, pH 7.3 and 96 h of incubation. However, the specific cellulase activities per 1 mg of protein did not differ that way. It was 1.55, 1.71 and 1.83 μmol mL-1 min-1. The growing mycelia possessed short compact chains of 10-20 conidia on aerial branches. These morphological and biochemical characteristics, followed by their verification by Bergey’s Manual, categorically allowed the strains to be placed under actinobacteria. Further, 16S rRNA gene sequencing, molecular characterization and their evolutionary relationship through phylogenetics also confirmed the putative cellulase producing isolates of SK706 and SK708 subgroups to be the strains of Streptomyces. These strains on getting NCBI recognition were christened as Streptomyces glaucescens strain SK91L (KF527284) and Streptomyces rochei strain SK78L (KF515951), respectively.Conclusion:Conclusive evidence on the basis of different parameters established the presence of cellulase producing actinobacteria in the litchi orchard which can convert cellulose into fermentable sugar.

In situ probing of switchable nanomechanical properties of responsive high-density polymer brushes on poly(dimethylsiloxane): An AFM nanoindentation approach

Nanomechanical characteristics of end grafted polymer brushes were studied by AFM based, colloidal probe nanoindentation measurements. A high-density polymer brush of poly(2-hydroxyethyl methacrylate) (PHEMA) was precisely prepared on the surface of a flexible poly(dimethylsiloxane) (PDMS) substrate oxidized in ultraviolet/ozone (UVO). Exposure times less than 10min resulted in laterally homogeneous oxidized surfaces, characterized by a SiOx thickness ∼35nm and an increased modulus up to 9MPa, as shown by AFM nanoindentation measurements. We have demonstrated that a high surface density of up to ∼0.63chains/nm2 of the well-defined PHEMA brushes can be grown from the surface of oxidized PDMS by surface-initiated atom transfer radical polymerization (SI-ATRP) from trimethoxysilane derivatives mixed-SAM. The reversible nanomechanical changes of PHEMA layer between extended (hydrated state) and collapsed (dehydrated state) chain upon immersing in selective and non-selective solvents were investigated by in situ AFM nanoindentation analysis in liquid environments. The elastic modulus derived from force-indentation curves obtained for swollen PHEMA grafted chains in water was estimated to be equal 2.7±0.2MPa, which is almost two orders of magnitude smaller than the modulus of dry PHEMA brush. Additionally, under cyclohexane immersion, the modulus of the PHEMA layer decreased by one order of magnitude, indicating a more compact chain packing at the PDMS surface.

Theoretical Saxs Signatures of Conformational Heterogeneity and Homogeneity of Disordered Protein Ensembles

The biological function of an intrinsically disordered protein (IDP) is based upon its conformational ensemble which is in turn governed by the IDP's amino acid sequence. In view of the different functions served by different IDPs, this ensemble-function view reinforces the physical expectation that the disordered chains of non-homopolymeric amino acid sequences---IDPs and unfolded chains of globular proteins---are heterogeneous, i.e., their ensemble distributions of conformations are different from those of homopolymers that habor a uniform intrachain interaction. Indeed, recent analyses indicate that conformational heterogeneity is key to reconciling the apparent inconsistency between IDP dimensions determined by SAXS and FRET. This development notwithstanding, it was stated recently that SAXS data on disordered proteins can be adequately accounted for by homopolymer chain models. It is important, therefore, to address the information content of SAXS data, to assess to what extent SAXS data can discriminate between heterogeneous and homogeneous conformational ensembles. We have conducted extensive simulations of subensembles of chain conformations with narrow ranges of radius of gyration Rg and end-to-end distance REE, and compared the molecular form factors (MFFs) and dimensionless Kratky plots of these highly heterogeneous (sub)ensembles with those computed for homogeneous ensembles. We find that the MFFs of heterogeneous and homogeneous ensembles are quite similar when the chain conformations are relatively open, suggesting that SAXS may not be capable of clearly distinguishing heterogeneous from homogeneous conformational ensembles of well-solvated or slightly compact chains. In contrast, MFFs for more compact ensembles are more sensitive to conformational heterogeneity. We have also developed an analytical theory for sequence-dependent MFFs. The theory provides insight into how different conformational ensembles that share the same average REE can have different average Rg's. Ramifications of our findings for the interpretation of experimental data are discussed.

ISDSR+: Improving the Security and Availability of Secure Routing Protocol

In ad hoc networks that allow devices to dynamically configure networks via wireless communication, a secure routing protocol is a technology that guarantees the validity of routing with the use of cryptographic authentication. The secure DSR with ID-based sequential aggregate signatures (ISDSR) is a recently introduced secure routing protocol with “cryptographically compact chain,” where each device signs both the routing information and signatures generated by the previous device without increasing the size of signatures and the ID information propagated via packets can be utilized as a public key. However, ISDSR requires communication with a centralized key generation center (KGC), and thus a new device may experience difficulties in joining the protocol. Moreover, the implementation results of ISDSR have not been presented. In this work, we present ISDSR+, a new secure routing protocol without a centralized KGC that uses distributed key generation and the conventional features of ISDSR. ISDSR+ relies on a novel signature scheme where any node can receive a secret key as long as the number of available KGCs is more than a certain threshold. In other words, even if several KGCs are unavailable, the remaining available KGCs can still provide secret keys. We furthermore show promising results of ISDSR+ via a prototype implementation on Raspberry Pis. The results show the computational time of 0.1 s for both the secret key generation and the round trip time (RTT) of routing information under reasonable settings. The RTT of ISDSR+ is better than that of a naive secure routing protocol with RSA signatures.

Monte Carlo simulation of coil-to-globule transition of compact polymer chains: Role of monomer interacting

Coil-to-globule transitions are fundamental problems existing in polymer science for several decades; however, some features are still unclear, such as the effect of chain monomer interaction. Herein, we use Monte Carlo simulation to study the coil-to-globule transition of simple compact polymer chains. We first consider the finite-size effects for a given monomer interaction, where the short chain exhibits a one-step collapse while long chains demonstrate a two-step collapse, indicated by the specific heat. More interestingly, with the decrease of chain monomer interaction, the critical temperatures marked by the peaks of heat capacity shift to low values. A closer examination from the energy, mean-squared radius of gyration and shape factor also suggests the lower temperature of coil-to-globule transition.

Support points

This paper introduces a new way to compact a continuous probability distribution $F$ into a set of representative points called support points. These points are obtained by minimizing the energy distance, a statistical potential measure initially proposed by Székely and Rizzo [InterStat 5 (2004) 1–6] for testing goodness-of-fit. The energy distance has two appealing features. First, its distance-based structure allows us to exploit the duality between powers of the Euclidean distance and its Fourier transform for theoretical analysis. Using this duality, we show that support points converge in distribution to $F$, and enjoy an improved error rate to Monte Carlo for integrating a large class of functions. Second, the minimization of the energy distance can be formulated as a difference-of-convex program, which we manipulate using two algorithms to efficiently generate representative point sets. In simulation studies, support points provide improved integration performance to both Monte Carlo and a specific quasi-Monte Carlo method. Two important applications of support points are then highlighted: (a) as a way to quantify the propagation of uncertainty in expensive simulations and (b) as a method to optimally compact Markov chain Monte Carlo (MCMC) samples in Bayesian computation.

Origin of Internal Friction in Disordered Proteins Depends on Solvent Quality.

Protein dynamics often exhibit internal friction; i.e., contributions to friction that cannot solely be attributed to the viscosity of the solvent. Remarkably, even unfolded and intrinsically disordered proteins (IDPs) exhibit this behavior, despite typically being solvent-exposed. Several competing molecular mechanisms have been suggested to underlie this phenomenon, in particular dihedral relaxation and intrachain interactions. It has also recently been shown that single-molecule data reflecting internal friction in the disordered protein ACTR cannot be explained using polymer models unless this friction is dependent on protein collapse. However, the connection between the collapse of the chain and the underlying mechanism of internal friction has been unclear. To address this issue, we combine molecular simulation and single-molecule experimental data to investigate how chain compaction affects protein dynamics in the context of ACTR. Chain reconfiguration times and internal friction estimated from all-atom simulations are in semiquantitative agreement with experimental data. We dissect the underlying molecular mechanism with all-atom and coarse-grained simulations and clearly identify both intrachain interactions and dihedral angle transitions as contributions to internal friction. However, their relative contribution is strongly dependent on the compactness of the IDP; while dihedral relaxation dominates internal friction in expanded configurations, intrachain interactions dominate for more compact chains. Our results thus imply a continuous transition between mechanisms and provide a link between internal friction in IDPs and that in more compact and folded states of proteins.

Poly(vinyl alcohol) as a structuring agent for peroxotungstic acid

Poly(vinyl alcohol) (PVAL) is an interesting architecture-directing material and is useful for synthesizing transition metal oxides through the sol-gel method. In this work, the interaction between PVAL and peroxotungstic acid (PTA) in aqueous media was investigated by conductivity, zeta potential, small-angle X-ray scattering, isothermal titration calorimetry and fluorescence measurements. The strong exothermic effect and the change in organization in aqueous media, from extended chains to compact chains forming fractal structures, confirm the interaction between PTA and PVAL. Powders were obtained from these systems by removal of water and subsequent calcination. An increase in the crystal size and changes in morphology were observed with the increasing of PVAL concentration. The band gap values, obtained by diffuse reflectance spectroscopy, were between 2.50 and 2.60 eV and showed that the obtained oxides are able to absorb light in the visible part of the electromagnetic spectra.

Predicting The Orbit of TRAPPIST-1i

The TRAPPIST-1 system provides an exquisite laboratory for advancing our understanding exoplanetary atmospheres, compositions, dynamics and architectures. A remarkable aspect of TRAPPIST-1 is that it represents the longest known resonance chain, where all seven planets share near mean motion resonances with their neighbors. Prior to the measurement of 1h's period, Luger et al. (2017) showed that six possible and highly precise periods for 1h were expected, assuming it also participated in the resonant chain. We show here that combining this argument with a Titius-Bode law fit of the inner six worlds narrows the choices down to a single precise postdiction for 1h's period, which is ultimately the correct period. But a successful postdiction is never as convincing as a successful prediction, and so we take the next step and apply this argument to a hypothetical TRAPPIST-1i. We find two possible periods predicted by this argument, either 25.345 or 28.699 days. If successful, this may provide the basis for planet prediction in compact resonant chain systems. If falsified, this would indicate that the argument lacks true predictive power and may not be worthwhile pursuing further in our efforts to build predictive models for planetary systems.

Isolation and identification of Citrobacter freundii from chicken meat samples using cultural and molecular techniques

Because of Citrobacter freundii medical and economical importance and that there are only little local studies about it, this study aimed to isolate and identify this important bacterial species from others that have a similar biochemical and morphological characteristics. Twenty five chicken meat samples were collected randomly from local markets in Baghdad city during 2017; Citrobacter was isolated from the collected samples using selective and differential media and identified using biochemical tests, the identification was confirmed using Vitek 2 compact and polymerase chain reaction for 16S rRNA and the isolated bacteria identified as C. freundii.

Flares of the H2O Maser Emission in the Young Stellar Object GH2O 092.67+03.07 (IRAS 21078+5211)

The results of monitoring the H2O maser observed toward the region GH2O 092.67+03.07 (IRAS 21078+5211) located in the Giant Molecular Cloud Cygnus OB7 are presented. The observations were carried out with the 22-m radio telescope of the Pushchino Radio Astronomy Observatory in 2006–2017. Strong flares of the H2O maser emission with flux densities up to 19 800 Jy were detected. The flares exhibited both global (over the source) and local characters. All the flares were accompanied by strong variations in the H2O spectra within the corresponding radial-velocity ranges. Individual H2O components form both compact clusters and chains 1–2-AU long. Analysis of the variations of the fluxes, radial velocities, and line shapes of features during the flares showed that the medium may be strongly fragmented, with small-scale turbulent motions taking place in the H2Omaser region.

Influence of Constraints within a Cyclic Polymer on Solution Properties.

Cyclic polymers with internal constraints provide new insight into polymer properties in solution and bulk and can serve as a model system to explain the stability and mobility of cyclic biomacromolecules. The model system used in this work consisted of cyclic polystyrene structures, all with a nearly identical molecular weight, designed with 0-3 constraints located at strategic sites within the cyclic polymer, with either 4 or 6 branch points. The total number of branch points (or arms) within the cyclic ranged from 0 to 18. Molecular dynamic (MD) simulations showed that as the number of arms increased within the cyclic structure, the radius of gyration and the hydrodynamic radius generally decreased, suggesting the greater number of constraints resulted in a more compact polymer chain. The simulations further showed that the excluded volume was much greater for the cyclics compared to a linear polymer at the same molecular weight. The spirocyclic, a structure consisting of three rings joined in series, showed significant excluded volume effects in agreement with experimental data; the reason for which is unclear at this stage. Interestingly, under a size exclusion chromatography flow, the radius of hydration for all the cyclic structures increased compared with the DLS data, and could be explained from the greater swelling of the rings perpendicular to the flow found from previous simulations on rings. This data suggests that the greater compactness, greater excluded volume and structural rearrangements under flow of constrained cyclic polymers could be used to provide a physical basis for understanding greater stability and activity of cyclic biological macromolecules.

Striking the right balance of intermolecular coupling for high-efficiency singlet fission.

Singlet fission is a process that splits collective excitations, or excitons, into two with unity efficiency. This exciton splitting process, unique to molecular photophysics, has the potential to considerably improve the efficiency of optoelectronic devices through more efficient light harvesting. While the first step of singlet fission has been characterized in great detail, subsequent steps critical to achieving overall highly-efficient singlet-to-triplet conversion are only just beginning to become well understood. One of the most elementary suggestions, which has yet to be tested, is that an appropriately balanced coupling is necessary to ensure overall highly efficient singlet fission; that is, the coupling needs to be strong enough so that the first step is fast and efficient, yet weak enough to ensure the independent behavior of the resultant triplets. In this work, we show how high overall singlet-to-triplet conversion efficiencies can be achieved in singlet fission by ensuring that the triplets comprising the triplet pair behave as independently as possible. We show that side chain sterics govern local packing in amorphous pentacene derivative nanoparticles, and that this in turn controls both the rate at which triplet pairs form and the rate at which they decay. We show how compact side chains and stronger couplings promote a triplet pair that effectively couples to the ground state, whereas bulkier side chains promote a triplet pair that appears more like two independent and long-lived triplet excitations. Our results show that the triplet pair is not emissive, that its decay is best viewed as internal conversion rather than triplet-triplet annihilation, and perhaps most critically that, in contrast to a number of recent suggestions, the triplets comprising the initially formed triplet pair cannot be considered independently. This work represents a significant step toward better understanding intermediates in singlet fission, and how molecular packing and couplings govern overall triplet yields.

Retractable Compact Directed Complete Poset (Acts)

Taking domains in the one hand and actions of a semigroup (automaton) on the other, as two crucial notions in mathematics as well as in computer science, we consider the notion of compact directed complete poset (acts), and investigate the interesting notion of absolute retractness for such ordered structures. As monomorphisms and embeddings for domain acts are different notions, we study absolute retractness with respect to both the class of monomorphisms and that of embeddings for compact directed complete poset (acts). We characterize the absolutely retract compact dcpos as complete compact chains. Also, we give some examples of compact directed complete poset acts which are (ε-)absolutely retract (with respect to embeddings) and show that completeness is not a sufficient condition for (ε-)absolute retractness.

Breaking the chains: hot super-Earth systems from migration and disruption of compact resonant chains

"Hot super-Earths" (or "Mini-Neptunes") between 1 and 4 times Earth's size with period shorter than 100 days orbit 30-50\% of Sun-like type stars. Their orbital configuration -- measured as the period ratio distribution of adjacent planets in multi-planet systems -- is a strong constraint for formation models. Here we use N-body simulations with synthetic forces from an underlying evolving gaseous disk to model the formation and long-term dynamical evolution of super-Earth systems. While the gas disk is present, planetary embryos grow and migrate inward to form a resonant chain anchored at the inner edge of the disk. These resonant chains are far more compact than the observed super-Earth systems. Once the gas dissipates resonant chains may become dynamically unstable. They undergo a phase of giant impacts that spreads the systems out. Disk turbulence has no measurable effect on the outcome. Our simulations match observations if a small fraction of resonant chains remain stable, while most super-Earths undergo a late dynamical instability. Our statistical analysis restricts the contribution of stable systems to less than $25\%$. Our results also suggest that the large fraction of observed single planet systems does not necessarily imply any dichotomy in the architecture of planetary systems. Finally, we use the low abundance of resonances in Kepler data to argue that, in reality, the survival of resonant chains happens likely only in $\sim 5\%$ of the cases. This leads to a mystery: in our simulations only 50-60\% of resonant chains became unstable whereas at least 75\% (and probably 90-95\%) must be unstable to match observations.