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2021 ◽  
Author(s):  
Yeong Zen Chua ◽  
Hoang Tam Do ◽  
Aarti Kumar ◽  
Moritz Hallermann ◽  
Dzmitry Zaitsau ◽  
...  

Abstract Saccharides are still commonly isolated from biological feedstock by crystallization from aqueous solutions. Precise thermodynamic data on solubility are essential to optimize the downstream crystallization process. Solubility modeling, in turn, requires knowledge of melting properties. In the first part of this work, following our previous work on amino acids and peptides, D-α-glucose, D-β-fructose, D-sucrose, D-α-galactose, and D-α-xylose were investigated with Fast Scanning Calorimetry (FSC) in a wide scanning rate range (2000 K·s−1 to 10000 K·s−1). Using the experimental melting properties of saccharides from FSC allowed successfully modeling aqueous solubility for D-sucrose and D-α-galactose with the equation of state PC-SAFT. This provides cross-validation of the measurement methods to determine accurate experimental melting properties with FSC. Unexpectedly, the experimental FSC melting temperatures, extrapolated to zero scanning rates for thermal lag correction, were higher than results determined with DSC and available literature data. To clarify this inconsistency, FSC measurements towards low scanning rates from 10000 K·s−1 to 1 K·s−1 (D-α-glucose, D-β-fructose, D-sucrose) overlapping with the scanning rates of DSC and literature data were combined. At scanning rates below 1000 K·s−1, the melting properties followed a consistent non-linear trend, observed in both the FSC and the literature data. In order to understand the non-linear decrease of apparent melting temperatures with decreasing heating rate, the endothermic peaks were investigated in terms of isoconversional kinetics. The activation energies in the non-linear dependency region are in the range of $$300<{E}_{A}< 600 {\text{kJ}}\bullet {\text{mo}}{\text{l}}^{-1}$$ 300 < E A < 600 kJ ∙ mol - 1 . These values are higher than the enthalpy of sublimation for D-α-glucose, indicating that the non-linear behavior does not have a physical nature but attributes to chemical processes corresponding to the decomposition of molecular compounds within the crystal lattice before melting. The melting properties reported in the literature, commonly determined with conventional methods such as DSC, lead to inaccurate results due to the decomposition of these biomolecules at low heating rates. In addition, the FSC results at lower scanning rates coincide with results from DSC and literature in the overlapping scanning rate range, further validating the accuracy of FSC measurements to determine reliable melting properties of thermally labile biomolecules. The experimental FSC melting properties determined at higher scanning rates are considered as the correct equilibrium melting properties, which are not influenced by any chemical processes. The combination of FSC and PC-SAFT opens the door to model solubility of solid compounds that commonly decompose before melting.


eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Tingting Zhao ◽  
Irina O Vvedenskaya ◽  
William KM Lai ◽  
Shrabani Basu ◽  
B Franklin Pugh ◽  
...  

In Saccharomyces cerevisiae, RNA Polymerase II (Pol II) selects transcription start sites (TSS) by a unidirectional scanning process. During scanning, a preinitiation complex (PIC) assembled at an upstream core promoter initiates at select positions within a window ~40-120 basepairs downstream. Several lines of evidence indicate that Ssl2, the yeast homolog of XPB and an essential and conserved subunit of the general transcription factor (GTF) TFIIH, drives scanning through its DNA-dependent ATPase activity, therefore potentially controlling both scanning rate and scanning extent (processivity). To address questions of how Ssl2 functions in promoter scanning and interacts with other initiation activities, we leveraged distinct initiation-sensitive reporters to identify novel ssl2 alleles. These ssl2 alleles, many of which alter residues conserved from yeast to human, confer either upstream or downstream TSS shifts at the model promoter ADH1 and genome-wide. Specifically, tested ssl2 alleles alter TSS selection by increasing or narrowing the distribution of TSSs used at individual promoters. Genetic interactions of ssl2 alleles with other initiation factors are consistent with ssl2 allele classes functioning through increasing or decreasing scanning processivity but not necessarily scanning rate. These alleles underpin a residue interaction network that likely modulates Ssl2 activity and TFIIH function in promoter scanning. We propose that the outcome of promoter scanning is determined by two functional networks, the first being Pol II activity and factors that modulate it to determine initiation efficiency within a scanning window, and the second being Ssl2/TFIIH and factors that modulate scanning processivity to determine the width of the scanning widow.


2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Kieu T. Tran ◽  
Tuyen T. T. Truong ◽  
Hoang V. Nguyen ◽  
Quan D. Nguyen ◽  
Quan Phung ◽  
...  

This research work demonstrates a novel hybrid electrolyte based on a deep eutectic solvent (DES) combined with organic solvents for high-performance supercapacitors. DES was formed between ethylene glycol (EG) and lithium bis((trifluoromethyl)sulfonyl) imide (LiTFSI) and diluted by ethylene carbonate (EC) or acetonitrile (AN) with different amounts (10–50% wt.). Such a combination gives superior properties for hybrid electrolytes compared to pure DESs and reduces the volatility of mixed organic solvents. Regarding the electrochemical properties, DES-AN mixtures exhibited a better performance under high applied voltage and more reversible behavior than DES-EC ones, which suffered from the increasing distance in the electrical double layer. DES 1 : 4 + 20% wt. AN exhibited favorable electrolyte properties such as high ionic conductivity (3.1 mS·cm−1 at 30oC), relatively lower viscosity (14.28 mPa s at 30oC, approximately 2 times lower thanDES pure), and quite large electrochemical stability window up to 3.4 V (at 20–30% wt. AN) compared to the baseline electrolyte (LiTFSI/TBABF4 in AN). With these interesting properties, selected hybrid electrolyte (DES 1 : 4 + 20% wt. AN) tested in the symmetric capacitor using the activated carbon offered decent capacitance (15 F·g−1 at 3.4 V with a scanning rate of 1 A·g−1 and remains around 95% after 100 cycles) and good charge-discharge durability (>80% retention after 2000 cycles), especially the EDLC with DES 1 : 4 + 20% wt. AN shows good rate capacity (13.2 F·g−1 at 2 A·g−1, remaining 6 F·g−1 at 10 A·g−1).


2021 ◽  
Vol 24 (2) ◽  
pp. 73-77
Author(s):  
Jianzhi Sun ◽  
Yan Dong ◽  
Xinfang Wang ◽  
Chunyan Kong ◽  
Jinming Hong ◽  
...  

In this paper, MoO3 microrods was prepared using corn straw as biological template via roasting process.The components and crystal characterization of the material were investigated via X-ray diffraction(XRD),scanning electron microscopy( SEM), and the electrochemistry property and mechanism was studied.The results show that the MoO3 material synthesized by template method is Orthorhombic structures.And the MoO3 particles were submicron and micron rods with uniform distribution and a smooth surface. MoO3 microrods had an average diameter that ranged from 1 to 2 μm. The result indicated that the MoO3 as the new negative of aluminum battery delivers a higher discharge capacity of 190 mAh/g at a scanning rate of 1mv/s, which showing good capacity and cycling performance.


Frequenz ◽  
2020 ◽  
Vol 74 (11-12) ◽  
pp. 377-382
Author(s):  
Dhruv Chaudhary ◽  
Rahul Agrawal ◽  
Suresh C. Gupta

AbstractIn this paper, the scanning rate (SR) is enhanced for substrate integrated waveguide (SIW) based periodic leaky wave antenna (LWA) with continuous beam scanning. Delay line is inserted in the SIW based periodic LWA to modify the group delay profile which in turn increase the SR of the SIW based periodic LWA. Addition of the delay line enhances the SR of the SIW LWA to approximately three times from 15.6° to 47° per GHz. The prototype of the proposed LWA is fabricated and experimentally measured. The simulated and measured results show that the proposed LWA scans the angular range from −30° to +27° within a frequency span of only 1.2 GHz from 14.8 to 16 GHz (relative bandwidth of 7.7 %).


2020 ◽  
Vol 70 (5) ◽  
pp. 486-492
Author(s):  
Manoj Kumar Garg ◽  
Jasmine Saini

A dual-frequency and radiation pattern reconfigurable microstrip patch antenna for detecting a stationary as well as a non-stationary target is described. Six angular patches, that collectively form a circular shape, are used. All the six patches radiate one by one after a fixed interval of time and their feed controlling is done by six PIN diodes. The switching of PIN diodes is controlled by an embedded biasing network. This antenna provides radiation beam scanning characteristics. It gives the main lobe scanning at every 60o clockwise (or anticlockwise) continuously by applying a signal to patches one by one. The purpose of introducing the slot is to get the radiation pattern in the desired direction since by changing the length, width, and position of the slot, the direction of the radiation pattern can be controlled. The slotted antenna operates in a C band with two frequencies 4.21 GHz and 4.82 GHz and provides a radiation pattern, 90o apart from each other. The scanning rate of 0.6 deg/ms is obtained; however, the scanning rate can be changed with the help of ATMEGA 2560 microcontroller. This compact Microstrip patch antenna can be widely used for short-range applications i.e. ground surveillance radar, missile control, mobile battlefield surveillance for military and many other applications in a modern wireless communication system. The designed antenna along with the switching application will be able to track the stationary as well as a non-stationary target.


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