scholarly journals OBTAINING NEW FLOCCULANTS BASED ON HIGH-SUBSTITUTED CATIONIC STARCHES

2017 ◽  
Vol 61 (1) ◽  
pp. 89 ◽  
Author(s):  
Sergei M. Butrim ◽  
Tatiana D. Bil´dyukevich ◽  
Nataliya S. Butrim ◽  
Tatiana L. Yurkshtovich ◽  
Fedor N. Kaputskiy
Keyword(s):  
Supramolecular Structure ◽  
Cold Water ◽  
Potato Starch ◽  
Model Systems ◽  
Degree Of Crystallinity ◽  
Alkaline Condition ◽  
Polymeric Chain ◽  
Alkaline Catalyst ◽  
Long Time ◽  
A Charge

In this work synthesis of the high-substituted cationic starches by reaction of starches of different botanical origin with 3-chloro-2-hydroxypropyltrimetylammonium chloride in the presence of the alkaline catalyst was carried out by semi-dry way. The assessment of their flocculating properties on the model systems of kaolinic dispersions was carried out. It was established that the efficiency of a starch cationization substantially depends on its nature. This is due to various initial supermlecular structure and morphology of starch granules. The largest rate and degree of a cationization was characteristic for potato starch, and the least – for corn. The offered heterogeneous method of synthesis allows to receive the high-substituted cationic starches with preservation their granular and minimum changes in supramolecular structure. At achievement of particular extent of high-substituted (DScat> 0.1) cationic starches form the transparent colloid dispersions in cold water. Cationization of starches to higher DScat. demands increase in a consumption of cationic reagent and the catalyst. Formation of cationic bonds in starch was confirmed with results of element and IR-spectroscopical analyses. When carrying out a cationization of starch in an alkaline condition there can be changes of the supramolecular structure of a polysaccharide depending on a temperature and type of starch. Unessential decrease in a degree of crystallinity of all types of starches after their cationization at ambient temperature was demonstrated by the diffractograms received in work. Despite slight amorphicity of starch after their cationization it should be noted that all cationic starches having DScat> 0.1, easily disperse in cold water with formation of the homogeneous transparent pastes. The kinetics and efficiency of a flocculation of model kaolinic suspensions with synthesized cationic starches was investigated. Kaolinic suspensions for lack of flocculant are rather stable for a long time. Introduction to the system of cationic starch leads to fast destabilization of kaolinic dispersions. At the same time for all cationic starches with increase in a dose in the range of 0.5 – 7.5 mg/g(kaolin) the flocculation rate of particles of kaolin dispersions increases. The most efficiently a flocculation of dispersions of kaolin happens to the largest rate in the presence of cationic potato starch. It was established that the efficiency of a flocculation of mineral kaolinic systems is defined not only by a molecular mass of polymer, but also the sizes of non-draining chains which in the strong degree depend on a charge of microions and a rigidity of a polymeric chain. It was shown that the synthesized flocculants are not inferior in efficiency to the polyacrylamide derivants which are applied now.Forcitation:Butrim S.M., Bildyukevich T.D., Butrim N.S., Yurkshtovich T.L., Kaputskiy F.N. Obtaining new flocculants based on high-substituted cationic starches. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 1. P. 89-95

scholarly journals Unveiling the Dynamics of KRAS4b on Lipid Model Membranes

2021 ◽  
Author(s):  
Cesar A. López ◽  
Animesh Agarwal ◽  
Que N. Van ◽  
Andrew G. Stephen ◽  
S. Gnanakaran
Keyword(s):  
Molecular Mechanisms ◽  
Hypervariable Region ◽  
Small Gtpase ◽  
Model Systems ◽  
Coarse Grained ◽  
Regulatory Function ◽  
Limited Information ◽  
Long Time ◽  
Cell Growth And Differentiation ◽  
State Models

AbstractSmall GTPase proteins are ubiquitous and responsible for regulating several processes related to cell growth and differentiation. Mutations that stabilize their active state can lead to uncontrolled cell proliferation and cancer. Although these proteins are well characterized at the cellular scale, the molecular mechanisms governing their functions are still poorly understood. In addition, there is limited information about the regulatory function of the cell membrane which supports their activity. Thus, we have studied the dynamics and conformations of the farnesylated KRAS4b in various membrane model systems, ranging from binary fluid mixtures to heterogeneous raft mimics. Our approach combines long time-scale coarse-grained (CG) simulations and Markov state models to dissect the membrane-supported dynamics of KRAS4b. Our simulations reveal that protein dynamics is mainly modulated by the presence of anionic lipids and to some extent by the nucleotide state (activation) of the protein. In addition, our results suggest that both the farnesyl and the polybasic hypervariable region (HVR) are responsible for its preferential partitioning within the liquid-disordered (Ld) domains in membranes, potentially enhancing the formation of membrane-driven signaling platforms. Graphic Abstract

scholarly journals The role of spin in the degradation of organic photovoltaics

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ivan Ramirez ◽  
Alberto Privitera ◽  
Safakath Karuthedath ◽  
Anna Jungbluth ◽  
Johannes Benduhn ◽  
...  
Keyword(s):  
Transient Absorption ◽  
Bulk Heterojunction ◽  
Critical Factor ◽  
Model Systems ◽  
Transient Absorption Spectroscopy ◽  
Triplet States ◽  
Paramagnetic Resonance ◽  
Time Resolved ◽  
A Charge

AbstractStability is now a critical factor in the commercialization of organic photovoltaic (OPV) devices. Both extrinsic stability to oxygen and water and intrinsic stability to light and heat in inert conditions must be achieved. Triplet states are known to be problematic in both cases, leading to singlet oxygen production or fullerene dimerization. The latter is thought to proceed from unquenched singlet excitons that have undergone intersystem crossing (ISC). Instead, we show that in bulk heterojunction (BHJ) solar cells the photo-degradation of C60 via photo-oligomerization occurs primarily via back-hole transfer (BHT) from a charge-transfer state to a C60 excited triplet state. We demonstrate this to be the principal pathway from a combination of steady-state optoelectronic measurements, time-resolved electron paramagnetic resonance, and temperature-dependent transient absorption spectroscopy on model systems. BHT is a much more serious concern than ISC because it cannot be mitigated by improved exciton quenching, obtained for example by a finer BHJ morphology. As BHT is not specific to fullerenes, our results suggest that the role of electron and hole back transfer in the degradation of BHJs should also be carefully considered when designing stable OPV devices.

Deep Donor and Acceptor Levels Induced by High Temperature and long time Annealing in LEC Gallium Arsenide

1991 ◽  
Vol 240 ◽  
Author(s):  
G. Marrakchi ◽  
A. Kalboussi ◽  
G. Guillot ◽  
M. Ben Salem ◽  
H. Maaref ◽  
...  
Keyword(s):  
High Temperature ◽  
Cold Water ◽  
Deep Level ◽  
Electron Trap ◽  
Single Donor ◽  
Long Duration ◽  
Donor And Acceptor ◽  
Deep Donor ◽  
Long Time ◽  
Lec Gaas

ABSTRACTThe effects of high temperature isothermal annealing on the electrical properties of donor and acceptor defects in n-type LEC GaAs are investigated. The annealing experiments are performed under As-rich atmosphere at 1000°C for 1–4 and 16 hours followed by a very quick quenching into cold water of the quartz ampoules containing the samples. The donor and acceptor levels are detected respectively by standard (DLTS) and optical (ODLTS) deep level spectroscopy. DLTS results show the presence of one single donor level present in unannealed and annealed samples at Ec - 0.79eV which is identified as the well known electron trap EL2 Only the sample annealed for 16 hs exhibits the presence of a new electron trap named TAI at Ec - 0.32eV. The appearance of TAI is correlated in one hand with the evolution of EL2 concentration and in the other hand to the effect of long duration (16 hs) of the treatment. For acceptor levels, two hole traps HT1 and HT2 are detected respectively at EV + 0.18 eV and EV+ 0.28 eV. HT1 is detected only in samples annealed for 4 and 16 hs and HT2 is detected in all studied samples. Photoluminescence (PL) measurements show the presence of the 1.44 eV band corresponding to gallium antisite GaAs defect. This band observed in unannealed and annealed samples shows that GaAs remains stable even after thermal annealing at lOOO°C for 16 hs and it is correlated with the presence of HT2.

On the transferability of electron density in binary vanadium borides VB, V3B4 and VB2

2015 ◽  
Vol 71 (6) ◽  
pp. 777-787 ◽  
Author(s):  
Bürgehan Terlan ◽  
Lev Akselrud ◽  
Alexey I. Baranov ◽  
Horst Borrmann ◽  
Yuri Grin
Keyword(s):  
Quantum Theory ◽  
Crystal Structures ◽  
Electron Density ◽  
Critical Points ◽  
Atoms In Molecules ◽  
Model Systems ◽  
Suitable Model ◽  
Interatomic Distances ◽  
Systematic Analysis ◽  
A Charge

Binary vanadium borides are suitable model systems for a systematic analysis of the transferability concept in intermetallic compounds due to chemical intergrowth in their crystal structures. In order to underline this structural relationship, topological properties of the electron density in VB, V3B4 and VB2 reconstructed from high-resolution single-crystal X-ray diffraction data as well as derived from quantum chemical calculations, are analysed in terms of Bader's Quantum Theory of Atoms in Molecules [Bader (1990). Atoms in Molecules: A Quantum Theory, 1st ed. Oxford: Clarendon Press]. The compounds VB, V3B4 and VB2 are characterized by a charge transfer from the metal to boron together with two predominant atomic interactions, the shared covalent B—B interactions and the polar covalent B—M interactions. The resembling features of the crystal structures are well reflected by the respective B—B interatomic distances as well as by ρ(r) values at the B—B bond critical points. The latter decrease with an increase in the corresponding interatomic distances. The B—B bonds show transferable electron density properties at bond critical points depending on the respective bond distances.

scholarly journals Hydrophobic Starch-Based Films Using Potato Washing Slurries and Spent Frying Oil

Foods ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 2897
Author(s):  
Sílvia Petronilho ◽  
André Oliveira ◽  
M. Rosário Domingues ◽  
Fernando M. Nunes ◽  
Manuel A. Coimbra ◽  
...  
Keyword(s):  
Potato Starch ◽  
Contact Angles ◽  
Single Step ◽  
Frying Oil ◽  
Biodegradable Films ◽  
Water Contact ◽  
Alkaline Catalyst ◽  
Application Range ◽  
Structural Differences

Starch is a promising candidate for preparing biodegradable films with useful gas barriers and thermoplastic capabilities. However, these materials are hydrophilic and brittle, thus limiting their application range. To overcome these drawbacks, it has been hypothesized that starch can be hydrophobized and plasticized during the starch-based film production using a single-step approach and following transesterification principles. In this work, KOH powder and spent frying oil (SFO) were used as an alkaline catalyst and a source for triacylglycerides, respectively, to promote the modification of starch. Different ratios of SFO (w/w related to the dried starch weight) were tested. When compared to the neat films (without a catalyst and SFO), the incorporation of at least 15% SFO/KOH gave rise to transparent, hydrophobic (water contact angles of ca. 90°), stretchable (ca. 20×), elastic (ca. 5×), and water tolerant starch-based films, contrary to the films produced without the catalyst. ATR-FTIR and 1H NMR revealed structural differences among the produced films, suggesting that starch was modified with the SFO-derived fatty acids. Therefore, adding KOH during the potato starch/spent frying oil-based film’s production was determined to be a promising in situ strategy to develop starch-based materials with improved hydrophobicity and flexibility, while valorizing the potato chip industry’s byproducts.

scholarly journals Viscoelastic and Textural Characteristics of Gels Obtained from Potato Starch Roasted under Several Temperature-Time Conditions

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
María D. Torres ◽  
Francisco Chenlo ◽  
Ramón Moreira
Keyword(s):  
Soluble Fraction ◽  
Profile Analysis ◽  
Amylose Content ◽  
Potato Starch ◽  
Degree Of Crystallinity ◽  
Texture Profile ◽  
Gel Texture ◽  
Apparent Amylose Content ◽  
Textural Parameters ◽  
Roasting Temperature

The influence of roasting conditions on the potato starch (PS) composition, solubility, crystallinity, gel-forming thermal profiles, and texture of the corresponding gels was studied. Thermorheological testing of roasted starches with (RPS) and without (RPSI) the soluble fraction was conducted on a stress-controlled rheometer. Texture profile analysis (TPA) was used to determine the RPS final gel texture. Solubility tests showed equivalent effects of starch roasting for samples treated at 190°C for 8 h (RPS190-8), 210°C for 6 h (RPS210-6), and 230°C for 4 h (RPS230-4). The apparent amylose content of RPS linearly increased with the decreasing degree of crystallinity. Elastic (G′) and viscous (G″) properties of RPS depended markedly on apparent amylose content and crystallinity. G′gel values of roasted starches linearly increased with the amylose content suggesting a promotion of the amylose breakdown with roasting temperature. Gels prepared with RPS roasted between 120 and 170°C exhibited intermediate strength and fully thermal reversible features. Roasting between 190 and 210°C favoured strong and fully thermal reversible gels. Although RPS230-4 gels exhibited similar strength to RPS190-8 and RPS210-4, no fully thermal reversible gels were obtained. The soluble fraction removal led to a drop the RPSI gels strength with increasing roasting temperature. No water syneresis was identified for RPS gels during one-week ageing, except for RPS230 gels. Relationships between textural parameters from TPA and viscoelastic gel properties determined by rheology were established.

scholarly journals Bottom Temperatures in Drake Passage

2017 ◽  
Vol 47 (1) ◽  
pp. 101-122 ◽  
Author(s):  
Karen L. Tracey ◽  
Kathleen A. Donohue ◽  
D. Randolph Watts
Keyword(s):  
Cold Water ◽  
Extreme Event ◽  
Spatial Scales ◽  
Drake Passage ◽  
High Variability ◽  
Measured Temperature ◽  
Bottom Temperature ◽  
Long Time ◽  
Bottom Waters ◽  
Circumpolar Current

AbstractLong time series of bottom temperatures in the Southern Ocean are rare. The cDrake array with over 40 current- and pressure-recording inverted echo sounders, moored across Drake Passage to monitor the Antarctic Circumpolar Current (ACC) variability and transport, measured temperature at 1 and 50 m above the seafloor at depths ≥ 3500 m and at the southern continental margin. The 4-yr dataset provided an opportunity to examine the temporal and spatial scales of bottom temperature variability. High variability was observed; ranges were 0.5°–0.9°C in the northern passage and 0.3°–0.6°C in the southern passage. Standard deviations in the two regions were 0.1°–0.15°C and <0.05°C, respectively. Meandering of the ACC with its deep-reaching thermocline accounted for up to 50% of the observed bottom temperature variance. Northern passage temperatures, spaced less than 40 km apart, were correlated with each other, while those in the southern portion, separated by 60–70 km, were not. A gap in the West Scotia Ridge provided a deep passageway for cold water to reach the northern passage from the southern basin; an extreme event during February 2008 brought bottom waters with in situ temperatures below 0.38°C as far north as 57°S. Strong vertical temperature gradients between 1 and 50 m above the bottom occurred intermittently due to intrusions associated with deep eddy circulations arising beneath the meandering jet and to flow over steep topography, permitting the generation of internal waves. High variability in temperature on interannual time scales requires record lengths of 13–17 yr to estimate long-term trends reliably.

scholarly journals Moisture Effect on Characteristics of Slowly Digestible Potato Starch Prepared under Electron Beam Irradiation

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Vinh Tien Nguyen ◽  
Loc Nguyen Thi ◽  
Khanh Son Trinh
Keyword(s):  
Electron Beam ◽  
Amylose Content ◽  
Potato Starch ◽  
Average Molecular Weight ◽  
Degree Of Crystallinity ◽  
In Vitro Digestibility ◽  
Moisture Contents ◽  
Physicochemical Changes

This study evaluates the effect of initial moisture contents (11.74–29.84%) on physicochemical changes, in vitro and in vivo digestibilities of potato starch irradiated with electron beam (EB). After a constant dose of EB irradiation, intrinsic viscosity and average molecular weight of potato starch decreased for all investigated moisture contents. When the moisture of starch was lower than 18%, the depolymerization predominated, hence increasing the amylose content. At higher moisture, water can strongly absorb EB and produce highly active species that induced the crosslinking of amylose molecules and the disruption of large crystals into smaller defective crystals. As a result, we found a maximum in amylose content at 14.84% moisture and a minimum in the degree of crystallinity at 17.5% moisture. Thermal stabilities between the irradiated samples were not significantly different. In vitro digestibility results showed that higher moistures during EB treatment induced structural changes that led to the conversion of resistant starch (RS) fraction into slowly digestible starch (SDS). Moreover, an in vivo digestive model in mice showed that EB-treated starch was able to maintain blood glucose at a stable level for a long time. This study showed a potential for SDS production from potato starch using EB irradiation technology, even in large scale.

scholarly journals Electronic properties of the topological insulators Bi₂Se₃ and Bi₂Te₃

2021 ◽  
Author(s):  
◽  
Robin Gühne
Keyword(s):  
Electronic Properties ◽  
Single Crystals ◽  
Topological Insulators ◽  
Three Dimensional ◽  
Surface States ◽  
Quantitative Agreement ◽  
Model Systems ◽  
Electronic Spin ◽  
Band Inversion ◽  
A Charge

<p>The three-dimensional topological insulators Bi₂Se₃ and Bi₂Te₃ are model systems of a new class of materials with an insulating bulk and gapless surface states. Their small band gaps and the heavy elements are essential for the topologically non-trivial band structure, but these features are similarly responsible for other remarkable properties, such as their high thermoelectric performance.  This thesis investigates the electronic properties of the topological insulators Bi₂Se₃ and Bi₂Te₃ with a broad range of experimental methods. Ferromagnetism in Mn doped Bi₂Te₃ is shown to disappear under sample sintering. A surprisingly large magnetoresistance and a charge carrier independent change in the sign of the thermopower with increasing Mn content are discussed.¹²⁵Te nuclear magnetic resonance (NMR) of Bi₂Te₃ single crystals suggest an unusual electronic spin susceptibility and complex NMR shifts. The quadrupole interaction of ²⁰⁹Bi nuclei in Bi₂Se₃ single crystals is shown to be a signature of the band inversion in quantitative agreement with first-principle calculations. Furthermore, it is proposed that the strong spin-orbit coupling of conduction electrons causes a non-trivial orientation dependent quadrupole splitting of the ²⁰⁹Bi resonance.</p>

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