Theoretical and experimental studies on the atmospheric degradation of 2-bromo-3,3,3-trifluoropropene

2015 ◽  
Vol 17 (32) ◽  
pp. 20543-20550 ◽  
Author(s):  
Weiwang Chen ◽  
Xiaomeng Zhou ◽  
Yajun Han
Keyword(s):  
Degradation Products ◽  
Experimental Studies ◽  
Atmospheric Degradation ◽  
Halon Replacement

2-Bromo-3,3,3-trifluoropropene (2-BTP) is applied in confined places as a potential Halon replacement. This work reports the atmospheric degradation products and the mechanism of 2-BTP, and results show BTP to be an environmentally acceptable compound.

Karl D. Nolph State of the Art Lecture: Feasible and Future Options for Salvation of the Peritoneal Membrane

2009 ◽  
Vol 29 (2_suppl) ◽  
pp. 195-197 ◽  
Author(s):  
Raymond T. Krediet ◽  
Annemieke M. Coester ◽  
Inna Kolesnyk ◽  
Marijke de Graaff ◽  
Machteld M. Zweers ◽  
...  
Keyword(s):  
Degradation Products ◽  
Experimental Studies ◽  
Renin Angiotensin System ◽  
Polyol Pathway ◽  
Dietary Sodium ◽  
High Dose ◽  
Peritoneal Membrane ◽  
Angiotensin System ◽  
Advanced Glycosylation End Products ◽  
Osmotic Agents

A review is given of the various available strategies that can be used to protect the peritoneal membrane. A discussion of experimental studies on approaches that are still experimental, but that might be applied in patients in the future, follows. The currently available approaches include dietary sodium restriction, use of high-dose loop diuretics and of inhibitors of the renin–angiotensin system. All should preferably be combined with a dialysis prescription aimed at reducing the patient's exposure to glucose and its degradation products. The experimental studies indicate favorable effects of combining osmotic agents, together with drugs that interfere with the polyol pathway and the formation of advanced glycosylation end-products.

scholarly journals Evaluation of the daytime tropospheric loss of 2-methylbutanal

2021 ◽  
Author(s):  
María Asensio ◽  
María Antiñolo ◽  
Sergio Blázquez ◽  
José Albaladejo ◽  
Elena Jiménez
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Degradation Products ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
Phase Reaction ◽  
Gaseous Products ◽  
Flight Mass Spectrometry ◽  
Atmospheric Degradation ◽  
The Impact

Abstract. Saturated aldehydes, e.g. 2-methylbutanal (2MB, CH3CH2CH(CH3)C(O)H), are emitted into the atmosphere by several biogenic sources. The first step in the daytime atmospheric degradation of 2MB involves gas-phase reactions initiated by hydroxyl (OH) radicals, chlorine (Cl) atoms and/or sunlight. In this work, we report the rate coefficients for the gas-phase reaction of 2MB with OH (kOH) and Cl (kCl) together with the photolysis rate coefficient (J) in the ultraviolet solar actinic region in Valencia (Spain) at different times of the day. The temperature dependence of kOH was described in the 263–353 K range by the following Arrhenius expression: kOH(T)=(8.88±0.41)×10-12 exp[(331±14)/T] cm3 molecule-1 s-1. At 298 K, the reported kOH and kCl are (2.68±0.07)×10-11 cm3 molecule-1 s-1 and (2.16±0.16)×10-11 cm3 molecule-1 s-1. Identification and quantification of the gaseous products of the Cl-reaction and those from the photodissociation of 2MB were carried out in a smog chamber by different techniques (Fourier transform infrared spectroscopy, proton transfer time-of-flight mass spectrometry, and gas chromatography coupled to mass spectrometry). The formation and size distribution of secondary organic aerosols formed in the Cl-reaction was monitored by a fast mobility particle sizer spectrometer. A discussion on the relative importance of the first step in the daytime atmospheric degradation of 2MB is presented together with the impact of the degradation products in marine atmospheres.

scholarly journals THE INFLUENCE OF A POLYPEPTIDE PREPARATION ON A STRUCTURAL-FUNCTIONAL STATE PERIODONT IN ADJURANT PERIODONITIS (EXPERIMENTAL RESEARCH)

2020 ◽  
pp. 29-34
Author(s):  
G.M. Silenko ◽  
O.B. Belikov ◽  
N.I. Belikova ◽  
M.V. Khrebor ◽  
Y.I. Silenko
Keyword(s):  
Lipid Peroxidation ◽  
Humoral Immunity ◽  
Blood Clotting ◽  
Alveolar Bone ◽  
Degradation Products ◽  
Experimental Studies ◽  
Nonspecific Resistance ◽  
Experimental Animals ◽  
Periodontal Tissues ◽  
Periodontal Inflammation

The aim of this article is to study the indices of cellular, humoral immunity and nonspecific resistance, indices of free radical lipid oxidation and thrombocytoactive properties of periodontal tissues in animals with adjuvant periodontitis. In our study, adjuvant periodontitis was reproduced by the method of A.M. Kaminsky, immunizing rats with a homologous periodontal tissue in admixture with a Freund's adjuvant in a 1: 1 ratio. The course consisted of four single injections of 0.2 ml per animal intramuscularly at weekly intervals. Immunization did not lead to changes in the development and behavior of rats. One month after immunization, experimental animals experienced symptoms characteristic of generalized periodontitis in humans. They were manifested in the form of gums, resorption of alveolar bone, mobility and tooth loss. The induction of adjuvant periodontitis in experimental animals led to a significant increase in lipid peroxidation processes in periodontal tissues and a decrease in SOD and catalase activity. In animals with adjuvant periodontitis, which have been injected with periodontal polypeptides, there is a decrease in the reactions of GF compared with patients. In particular, there was a 40.9% decrease in the level of TBK-active products, although the level of MDA accumulation in the incubation process had not decreased significantly. It is noteworthy that in this group of animals increased activity of AO enzymes, which in patients was sharply reduced. Significant changes in the BPO lipid state were also observed in the blood of animals. The peroxidation reactions were significantly reduced, but not as significantly as in periodontal tissues. In particular, spontaneous erythrocyte hemolysis was lower by 14.2%, the level of TBK-active products by 39.4%, and MDA by 34.9%. An increase in the activity of SOD and catalase was observed, as well as a 40.4% decrease in the concentration of ceruloplasmin, which testifies to the elimination of the inflammatory response upon introduction of polypeptides. The treatment of animals with periodontylline was accompanied by an increase in the anti-aggregation properties of periodontal tissues. This is confirmed by the following indicators of the aggregate: the angle of aggregation is reduced by 31.8%, the optical density by 29%, the aggregation time is increased by 42.9% compared with the group of animals with adjuvant periodontitis. The introduction of parodontilin had a pronounced effect on the condition of blood clotting and fibrinolysis. We observed a significant increase in recalcification time, thrombin, prothrombin time. If the disease has a significant increase in the time of euglobulin fibrinolysis, then in the treatment of this indicator becomes less by 69.4%, the products of para-coagulation disappear from the bloodstream and the concentration of fibrin degradation products decreases. The treatment of animals was accompanied by an increase in immunity, which was manifested by an increase in T and B lymphocytes and Ig G. titer. Studies have shown that the treatment of diseased animals with a polypeptide drug leads to an improvement in the cellular, humoral immunity and nonspecific resistance of the organism, as well as the presence of a pronounced immunomodulatory effect of periodontin. The previously established relationship between blood clotting systems, sex, immunity, nonspecific resistance of the organism is confirmed in these experimental studies. If the induction of periodontitis is primarily associated with autoimmune processes, leading to impaired homeostasis, then the introduction of periodontin has a modulating effect on both immunity and indicators of lipid peroxidation and microcirculatory and coagulative hemostasis . In animals, regression of dental symptoms was noted, signs of periodontal inflammation, bleeding, swelling disappeared, and tooth mobility decreased. These data indicate the high therapeutic efficacy of thymic drugs in the treatment of generalized periodontitis. Research in this area remains relevant.

scholarly journals A Systematic Experimental and Computational Analysis of Commercially Available Aliphatic Polyesters

2019 ◽  
Vol 9 (16) ◽  
pp. 3397
Author(s):  
Tommaso Casalini ◽  
Monica Bassas-Galia ◽  
Hervé Girard ◽  
Andrea Castrovinci ◽  
Alessandro De Carolis ◽  
...  
Keyword(s):  
Computational Analysis ◽  
Degradation Products ◽  
Degradation Kinetics ◽  
Experimental Studies ◽  
Polyglycolic Acid ◽  
Local Drug Delivery ◽  
Aliphatic Polyesters ◽  
Wide Range ◽  
Material Choice ◽  
Optimal Material

Aliphatic polyesters, such as polylactic acid (PLA), polyglycolic acid (PGA), and their copolymer polylactic-co-glycolic acid (PLGA) have become an established choice in the biomedical field in a wide range of applications, from nanoparticles for local drug delivery to bone fixation screws, and, hence, in a huge spectrum of uses in different medical devices currently available on the market worldwide. The reason for their popularity lies in their combination of interesting peculiarities: in situ degradation, intrinsic biocompatibility (degradation products are recognized and metabolized), processability with standard industrial technologies, and tailorable properties. The knowledge of the degradation rate is an essential requirement for optimal device design when, e.g., fast adsorption time is required, or mechanical properties must be assured over a given time span. In this regard, experimental studies can be time- and money-consuming, due to the time scales (weeks–months) involved in the hydrolysis process. This work aims at providing to both industry and academia robust guidelines for optimal material choice through a systematic experimental and computational analysis of most commonly used PLGA formulations (selected from commercially available products), evaluating the degradation kinetics and its impact on polymer properties.

scholarly journals New peritoneal dialysates, for which benefits ?

2018 ◽  
Vol 1 (3) ◽  
pp. 105-110
Author(s):  
François Vrtovsnik
Keyword(s):  
Degradation Products ◽  
Meta Analysis ◽  
Experimental Studies ◽  
Residual Renal Function ◽  
Diffusive Transport ◽  
Waste Products ◽  
Low Sodium ◽  
Dialysis Solution ◽  
High Prevalence ◽  
Adynamic Bone

The ideal peritoneal dialysis solution should allow efficient withdrawal of waste products of the metabolism and water and solutes equilibrium with minimal side effects for the patient and the peritoneal membrane. Glucose degradation products (GDP) resulting from the manufacturing process play a major toxic role and new biocompatible PD solutions with low GDP content and a more physiological bicarbonate or bicarbonate/lactate buffer have brought a clear benefit in experimental studies; however, in clinical cohorts and meta-analysis, the benefits of these solutions appear limited to better preservation of residual renal function and of diuresis. Glucose is the principal osmotic agent although hypertonic glucose solutions have a deleterious effect on PD, and their use should be restrained. Dialysate concentrations of sodium, calcium and magnesium are close to plasma; their diffusive transport is thus limited and their net peritoneal transport mainly depends on the ultrafiltration volume. A dialysate calcium concentration above 1.25 mmol/l generates a calcium load which may contribute to the high prevalence of adynamic bone disease in PD patients; this should be avoided. Low sodium dialysis solutions experimentally improve sodium diffusive transport and extraction in PD patients; the clinical benefit of this approach has to be confirmed.

scholarly journals A zero-dimensional view of atmospheric degradation of levoglucosan (LEVCHEM_v1) using numerical chamber simulations

2021 ◽  
Vol 14 (2) ◽  
pp. 907-921
Author(s):  
Loredana G. Suciu ◽  
Robert J. Griffin ◽  
Caroline A. Masiello
Keyword(s):  
Gas Phase ◽  
Degradation Products ◽  
Heterogeneous Reaction ◽  
Reaction Rate Constant ◽  
Chemical Degradation ◽  
Secondary Products ◽  
Modeling Framework ◽  
Mixing Ratios ◽  
Fire Plumes ◽  
Atmospheric Degradation

Abstract. Here, we developed a zero-dimensional (0-D) modeling framework (LEVCHEM_v1) to provide insights into the atmospheric degradation of a key tracer emitted during biomass burning – levoglucosan (LEV), while additionally exploring its effects on the dynamics of secondary organic aerosols (SOA) and other gases. For this, we updated existing chemical mechanisms (homogeneous gas-phase chemistry and heterogeneous chemistry) in the BOXMOXv1.7 model to include the chemical degradation of LEV and its intermediary degradation products in both phases (gas and aerosol). In addition, we added a gas-particle partitioning mechanism to the model to account for the effect of evaporation and condensation on the phase-specific concentrations of LEV and its degradation products. Comparison of simulation results with measurements from various chamber experiments (spanning summer and winter conditions) show that the degradation timescale of LEV varied by phase, with gas-phase degradation occurring over ∼1.5–5 d and aerosol-phase degradation occurring over ∼8–36 h. These relatively short timescales suggest that most of the initial LEV concentration can be lost chemically or deposited locally before being transported regionally. We varied the heterogeneous reaction rate constant in a sensitivity analysis (for summer conditions only) and found that longer degradation timescales of LEV are possible, particularly in the aerosol phase (7 d), implying that some LEV may be transported regionally. The multiphase chemical degradation of LEV has effects on SOA and other gases. Several first- or second-generation products resulted from its degradation; most of the products include one or two carbonyl groups, one product contains a nitrate group, and a few products show the cleavage of C−C bonds. The relative importance of the products varies depending on the phase and the timing of the maximum concentration achieved during the simulation. Our estimated secondary organic aerosol SOA yields (4 %–32 %) reveal that conversion of LEV to secondary products is significant and occurs rapidly in the studied scenarios. LEV degradation affected other gases by increasing the concentrations of radicals and decreasing those of reactive nitrogen species. Decreases of the mixing ratios of nitrogen oxides appear to drive a more rapid increase in ozone compared with changes in volatile organic compounds levels. An important next step to confirm longer degradation timescales will be to extend the evaluation of the modeled LEV degradation beyond 3–6 h by using more extensive data from chambers and, possibly, from fire plumes. The mechanism developed here can be used in chemical transport models applied to fire plumes to trace LEV and its degradation products from source to deposition, to assess their atmospheric implications and to answer questions relevant to fire tracing, carbon and nitrogen cycling, and climate.

What Can We Do to Preserve the Peritoneum?

2003 ◽  
Vol 23 (2_suppl) ◽  
pp. 14-19 ◽  
Author(s):  
Raymond T. Krediet ◽  
Machteld M. Zweers ◽  
Roos Van Westrhenen ◽  
Marja M. Ho-dac-Pannekeet ◽  
Dirk G. Struijk
Keyword(s):  
Animal Models ◽  
Blood Vessels ◽  
Degradation Products ◽  
Experimental Studies ◽  
Mesothelial Cell ◽  
Exposure Model ◽  
Continuous Exposure ◽  
Glucose Degradation Products ◽  
Dialysis Solutions

Background Long-term peritoneal dialysis may lead to peritoneal membrane failure. Loss of ultrafiltration is the most important clinical abnormality. Loss of ultrafiltration is associated with an increased number of peritoneal blood vessels, with fibrotic alterations, and with loss of mesothelium. Continuous exposure to bioincompatible dialysis solutions is likely to be important in the pathogenesis of these alterations. Methods This article reviews the toxicity of various constituents of dialysate, current assessments of interventions, and the results of interventions aimed at preserving the peritoneum. Results Glucose, possibly in combination with lactate, and glucose degradation products (GDPs) are likely to be the most toxic constituents of dialysate. Diabetiform peritoneal neoangiogenesis is likely to be mediated by vascular endothelial growth factor (VEGF). Release of VEGF might be influenced by glucose-induced cellular pseudohypoxia, which is likely to be increased by exposure to lactate. Glucose and GDPs are both toxic to peritoneal cells. Glucose degradation products induce the formation of advanced glycosylation end-products at a much faster rate than does glucose itself, but the relative importance of GDPs and glucose in clinical PD has not been clarified. The effects of interventions should first be assessed in long-term animal models, followed by clinical studies on peritoneal transport and on effluent markers that may reflect the status of the peritoneum. Possible interventions aim at reducing peritoneal exposure to glucose, GDPs, and lactate. Techniques include peritoneal resting, replacing some glucose-based exchanges with amino acid–based and icodextrin-based dialysate, using bicarbonate as a buffer, and administering solutions that have a low GDP content. Exposure to various dialysis solutions with a reduced GDP content has resulted in an increase in the effluent concentration of the mesothelial cell marker CA125, irrespective of the buffer used. Experimental studies in a long-term peritoneal exposure model in rats showed that the combination of a reduction in the concentration of lactate and replacement of lactate with pyruvate resulted in a reduction of the number of peritoneal blood vessels. Results of drug therapy have been studied in various animal models. Their use in patients is still experimental. Conclusions Strategies to preserve the peritoneum aim at reducing membrane exposure to bioincompatible solutions. Currently available dialysis fluids that are more biocompatible are likely to have some beneficial effects. Further research on the development of dialysis solutions that use combinations of osmotic agents and alternative buffers is necessary.

Determination of atmospheric degradation products of toluene by tandem mass spectrometry

1984 ◽  
Vol 56 (8) ◽  
pp. 1329-1335 ◽  
Author(s):  
Robert J. O'Brien ◽  
Bruce E. Dumdei ◽  
Susan V. Hummel ◽  
Richard A. Yost
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Degradation Products ◽  
Tandem Mass ◽  
Atmospheric Degradation

CHF2CF2OCHF2: conformational analysis and direct dynamics study of its reaction with Cl atoms and atmospheric fate

2020 ◽  
Vol 44 (11) ◽  
pp. 4276-4284 ◽  
Author(s):  
Bidisha Baidya ◽  
Makroni Lily ◽  
Dimpal Patgiri ◽  
Shemphang Hynniewta ◽  
Asit K. Chandra
Keyword(s):  
Conformational Analysis ◽  
Degradation Products ◽  
Direct Dynamics ◽  
Atmospheric Fate ◽  
Atmospheric Degradation ◽  
Kinetics Of ◽  
Cl Atoms

Conformers of CHF2CF2OCHF2 are identified, and the kinetics of its reaction with Cl atoms and final atmospheric degradation products are studied to assess atmospheric impact.

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