scholarly journals Photodissociation Mechanisms of Major Mercury(II) Species in the Atmospheric Chemical Cycle of Mercury

2020 ◽  
Vol 132 (19) ◽  
pp. 7675-7680
Author(s):  
Antonio Francés‐Monerris ◽  
Javier Carmona‐García ◽  
A. Ulises Acuña ◽  
Juan Z. Dávalos ◽  
Carlos A. Cuevas ◽  
...  
Keyword(s):  
Chemical Cycle

scholarly journals Investigation of Arctic ozone depletion sampled over midlatitudes during the Egrett Campaign of spring/summer 2000

2004 ◽  
Vol 4 (1) ◽  
pp. 141-168 ◽  
Author(s):  
D. E. M. Ross ◽  
J. A. Pyle ◽  
N. R. P. Harris ◽  
J. D. McIntyre ◽  
G. A. Millard ◽  
...  
Keyword(s):  
Ozone Depletion ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Chemical Transport Model ◽  
Middle Latitudes ◽  
Halogen Chemistry ◽  
Show Evidence ◽  
Research Aircraft ◽  
Chemical Cycle ◽  
The Uk

Abstract. A unique halocarbon dataset has been obtained using the Australian high altitude research aircraft, the Grob G520T Egrett, during May–June 2000 with GC instrument (DIRAC), which has been previously deployed on balloon platforms. The halocarbon data generally shows a good anticorrelation with ozone data obtained simultaneously from commercial sensors. On 5 June 2000, at 380 K, the Egrett entered a high latitude tongue of air over the UK CFC-11 and O3 data obtained on the flight show evidence of this feature. The dataset has been used, in conjunction with a 3D chemical transport model, to infer ozone depletion encountered in the midlatitude lower stratosphere during the flight. We calculate that ozone is depleted by 20% relative to its winter value in the higher latitude airmass. A suite of ozone loss tracers in the model have been used to track ozone depletion according to location relative to the vortex and chemical cycle responsible. The model, initialised on 9 December, indicates that 50% of the total chemical ozone destruction encountered in June in the middle latitudes occurred between the 90–70° N equivalent latitude band and that 70% was due to halogen chemistry.

scholarly journals The Kremlin Chemical Cartwheels (From the History of Negotiations on the Prohibition of Chemical Weapons)

2019 ◽  
pp. 174-193
Keyword(s):  
Great Britain ◽  
Early Years ◽  
Toxic Chemicals ◽  
Chemical Weapons ◽  
Chemical Weapon ◽  
Vital Interest ◽  
History Of ◽  
Chemical Cycle ◽  
Peaceful Development ◽  
Heads Of State

The article deals with the Russian use of toxic chemicals in the territory of Great Britain, which became an irrefutable fact of violation of the Convention on the Prohibition of Chemical Weapons. An article refers to the history of agreeing on the Convention and its provisions that was carried out in several stages, particularly in the bilateral Soviet- American negotiations, that Ukrainian diplomats joined as well. The author analyzed the long-term and difficult drafting process of the Convention on the Prohibition of Chemical Weapons; investigated the early years of its operation as a significant element of the international security system. He emphasizes that the first years the Convention was functioning clearly indicate that only the political will of the heads of state can choose the direct path of the strict fulfillment of the commitments they have undertaken. Furthermore, the author stresses that Ukraine has never had chemical weapons or related objects, but as an industrialized country it has chemical cycle production, using the dangerous and highly toxic chemicals. Ukraine has a vital interest in the functioning of such a stable international mechanism, that would make the use of these chemicals for the purposes of chemical warfare impossible and would comprehensively promote the peaceful development of the chemical industry. Therefore, in November 2018, during the Fourth Review Conference of Countries that are parties to the Convention on the Prohibition of Chemical Weapons, the Ukrainian delegation condemned Russia’s aggressive actions on the uses of chemical weapons in Great Britain and on the cover those who used this weapon in Syria. The delegation also supported the Conference’s resolutions on the improvement of the mechanism of the identification of the perpetrators of chemical attacks. Keywords: chemical weapon, Committee on Disarmament, history of Ukrainian diplomacy.

scholarly journals Conformational changes of a Swi2/Snf2 ATPase during its mechano-chemical cycle

2008 ◽  
Vol 36 (6) ◽  
pp. 1881-1890 ◽  
Author(s):  
Robert Lewis ◽  
Harald Dürr ◽  
Karl-Peter Hopfner ◽  
Jens Michaelis
Keyword(s):  
Conformational Changes ◽  
Chemical Cycle

scholarly journals Preparation of Physical and Chemical and Thermodynamic Properties of Aluminum Alloys-Cerium

2012 ◽  
Vol 9 (1) ◽  
pp. 01-07 ◽  
Author(s):  
M. Razazi ◽  
R. N. Amini ◽  
B. B. Eshov ◽  
A. B. Badalov
Keyword(s):  
Intermetallic Compounds ◽  
Melting Temperature ◽  
Enthalpy Of Formation ◽  
Empirical Method ◽  
Enthalpy Of Dissolution ◽  
Chemical Compositions ◽  
Chemical Cycle ◽  
Semi Empirical ◽  
Physical And Chemical ◽  
Maximal Stability

Chemical compositions, microstructure and hardness of alloys and Al - Ce intermetallic compounds have been studied. The method of calorimetry solution determined the enthalpy of dissolution. Enthalpy of formation of intermetallic compounds In thermo chemical cycle has been calculated. It was revealed the regularity of their changes depending on the composition. Melting temperature of intermetallic compounds of the system has been specified by Semi empirical method. It has defined the specified set pattern in the changes on melting temperature and enthalpy of formation of IM on the concentration of Maximal stability in the composition of Al2Se.

scholarly journals The ATPase mechanism of myosin 15, the molecular motor mutated in DFNB3 human deafness

2020 ◽  
Author(s):  
Fangfang Jiang ◽  
Yasuharu Takagi ◽  
Arik Shams ◽  
Sarah M. Heissler ◽  
Thomas B. Friedman ◽  
...  
Keyword(s):  
Molecular Motor ◽  
Motor Domain ◽  
Actin Binding ◽  
Duty Ratio ◽  
Strain Sensing ◽  
Cochlear Hair Cells ◽  
Adp Release ◽  
Chemical Cycle ◽  
Thermodynamic Coupling ◽  
Rate Limit

AbstractCochlear hair cells possess an exquisite bundle of actin-based stereocilia that detect sound. Unconventional myosin 15 (MYO15A) traffics and delivers critical molecules required for stereocilia development and is essential for building the mechanosensory hair bundle. Mutations in the human MYO15A gene interfere with stereocilia trafficking and cause hereditary hearing loss, DFNB3. To understand the molecular mechanism of how MYO15A delivers proteins within stereocilia, we performed a kinetic study of the ATPase motor domain to characterize its mechano-chemical cycle. Using the baculovirus-Sf9 system, we purified a recombinant minimal motor domain (S1) by co-expressing the mouse MYO15 ATPase, essential and regulatory light chains that bind its IQ domains, and UNC45 and HSP90A chaperones required for correct folding of the ATPase. MYO15 purified with either UNC45A or UNC45B co-expression had similar ATPase activities (kcat = ~ 6 s−1 at 20°C). Using stopped-flow and quenched-flow transient kinetic analyses, we measured the major rate constants describing the ATPase cycle, including ATP, ADP and actin binding, hydrolysis and phosphate release. Actin-attached ADP release was the slowest measured transition (~ 12 s−1 at 20°C), although this did not rate-limit the ATPase cycle. The kinetic analysis shows the MYO15 motor domain has a moderate duty ratio (~ 0.5) and weak thermodynamic coupling between ADP and actin binding. This is consistent with MYO15 being adapted for strain sensing as a monomer, or processive motility if oligomerized into ensembles. Our kinetic characterization enables future studies into how deafness-causing mutations affect MYO15 and ultimately disrupt stereocilia trafficking necessary for normal hearing.

scholarly journals Kinetic Control over Droplet Ripening in Fuel-Driven Active Emulsions

2020 ◽  
Author(s):  
Marta Tena-Solsona ◽  
Jacqueline Janssen ◽  
Caren Wanzke ◽  
Fabian Schnitter ◽  
Hansol Park ◽  
...  
Keyword(s):  
Collective Behavior ◽  
Ostwald Ripening ◽  
Underlying Mechanism ◽  
Droplet Growth ◽  
Metabolic Reaction ◽  
Reaction Cycle ◽  
Experimental Systems ◽  
Theoretical Predictions ◽  
Chemical Cycle ◽  
Kinetics Of

Active droplets are made of phase-separated molecules that are activated and deactivated by a metabolic reaction cycle. Such droplets play a crucial role in biology as a class of membrane-less organelles. Moreover, theoretical studies show that active droplets can evolve to the same size or spontaneously self-divide when energy is abundant. All of these exciting properties, i.e., emergence, decay, collective behavior, and self-division, are pivotal to the functioning of life. However, these theoretical predictions lack experimental systems to test them quantitively. Here, we describe the synthesis of synthetic active droplets driven by a metabolic chemical cycle and we find a surprising new behavior, i.e., the dynamics of droplet-growth is regulated by the kinetics of the fuel-driven reaction cycle. Consequently, these droplets ripen orders of magnitude faster compared to Ostwald ripening. Combining experiments and theory, we elucidate the underlying mechanism, which could help better understand how cells regulate the growth of membrane-less organelles.<br>

scholarly journals Direct measurement of the mechanical work during translocation by the ribosome

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Tingting Liu ◽  
Ariel Kaplan ◽  
Lisa Alexander ◽  
Shannon Yan ◽  
Jin-Der Wen ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Direct Measurement ◽  
Applied Force ◽  
Mechanical Work ◽  
Regulatory Role ◽  
Characteristic Distance ◽  
Detailed Understanding ◽  
Chemical Cycle ◽  
The One ◽  
Stable Structures

A detailed understanding of tRNA/mRNA translocation requires measurement of the forces generated by the ribosome during this movement. Such measurements have so far remained elusive and, thus, little is known about the relation between force and translocation and how this reflects on its mechanism and regulation. Here, we address these questions using optical tweezers to follow translation by individual ribosomes along single mRNA molecules, against an applied force. We find that translocation rates depend exponentially on the force, with a characteristic distance close to the one-codon step, ruling out the existence of sub-steps and showing that the ribosome likely functions as a Brownian ratchet. We show that the ribosome generates ∼13 pN of force, barely sufficient to unwind the most stable structures in mRNAs, thus providing a basis for their regulatory role. Our assay opens the way to characterizing the ribosome's full mechano–chemical cycle.

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