Chemical Events Research Articles

Management and health risk assessment of chemical contamination events in water distribution systems using PSO.

An accidental or intentional contamination event can raise health and sociopolitical concerns, erode public trust, and affect the operation of water distribution systems. In this regard, emergency management plans are required to describe the necessary measures in order to deal with a threat. This study was carried out to investigate the best ways to manage intrusion in a water distribution network. In this research, the optimal management approach to deal with chemical contamination in a water distribution network was examined under three scenarios using the particle swarm optimization method. In each scenario, three management solutions were used to manage the contamination, including closing the pipe, opening the fire hydrant, and using a combination of pipe closure and fire hydrant opening. Contamination risk impact on consumers' health was assessed in the network's emergency status and after implementation of the best pollution management scenarios. The results showed that in the benchmark network, pipe closure was slightly more successful than opening of the fire hydrant valve. In pollution management of a real network, pipe closure was less effective than the hydrant opening in all scenarios. Generally, all applied scenarios were successful in reducing the contamination risk among the exposed people, so that carcinogenic and non-carcinogenic risks reduced by 100% in all scenarios compared to the non-management state.

Factors Influencing Impulse Buying Behavior

Impulse buying is a classic example of undefinable strong emotional desire that motivates one to purchase a product. Interesting subject to study the reasons of breaking the rules where the extrinsic factors investigated in this study can be linked to the fight between the “New Brain(neocortex)vs. Old Brain(reptilian brain)” where reptilian brain always wins as it responds to six stimuli namely1) self-centered,2) contrast,3) tangible,4) beginning and end,5) visual,6) emotion that creates chemical events in the brain leading to take the decision in unconscious level or a transient state between conscious and unconscious level. Various factors quantified in this study bear the manifestation of these intrinsic factors. Data has been collected from the general population through online mode, and the SPSS tool has been used to substantiate the study

Decoding the reaction mechanism of the cyclocondensation of ethyl acetate2-oxo-2-(4-oxo-4H-pyrido [1.2-a] pyrimidin-3-yl) polyazaheterocycle and ethylenediamine using bond evolution theory.

We investigated the flow of electron density along the cyclocondensation reaction between ethyl acetate 2-oxo-2-(4-oxo-4H-pyrido[1.2-a]pyrimidin-3-yl) polyazaheterocycle (1) and ethylenediamine (2) at the ωB97XD/6-311++G(d,p)computational method within of bond evolution theory (BET). The exploration of potential energy surface shows that this reaction has three channels (1-3) with the formation of product 3 via channel-2 (the most favorable one) as the main product and this is in good agreement with experimental observations. The BET analysis allows identifying unambiguously the main chemical events happening along channel-2. The mechanism along first step (TS2-a) is described by a series of four structural stability domains (SSDs), while five SSDs for the last two steps (TS2-b and TS2-c). The first and third steps can be summarized as follows, the formation of N1-C6 bond (SSD-II), then, the restoration of the nitrogen N1 lone pair (SSD-III), and finally, the formation of the last O1-H1 bond (SSD-IV). For the second step, the formation of hydroxide ion is noted, as a result of the disappearance of V(C6,O7) basin and the transformation of C6-N1 single bond into double one (SSD-IV). Finally, the appearance of V(O7,H2) basin lead to the elimination of water molecule within the last domain is observed.

Allosteric Binding-Induced Intramolecular Mechanical-Strain Engineering.

Recently, polymer mechanochemistry has attracted much scientific interest due to its potential to develop degradable polymers. When the two ends of a polymer chain experience a linear pulling stress, molecular strain builds up, at sufficiently strong force, a bond scission of the weakest covalent bond results. In contrast, bond-breaking events triggered by conformational stress are much less explored. Here, we discovered that a Zn salen complex would undergo conformational switching upon allosteric complexation with alkanediammonium guests. By controlling the guest chain length, the torsional strain experienced by Zn complex can be modulated to induce bond cleavage with chemical stimulus, and reactivity trend is predicted by conformational analysis derived by DFT calculation. Such strain-release reactivity by a Zn(salen) complex initiated by guest binding is reminiscent of conformation-induced reactivity of enzymes to enable chemical events that are otherwise inhibited.

Allosteric Binding‐Induced Intramolecular Mechanical‐Strain Engineering

AbstractRecently, polymer mechanochemistry has attracted much scientific interest due to its potential to develop degradable polymers. When the two ends of a polymer chain experience a linear pulling stress, molecular strain builds up, at sufficiently strong force, a bond scission of the weakest covalent bond results. In contrast, bond‐breaking events triggered by conformational stress are much less explored. Here, we discovered that a Zn salen complex would undergo conformational switching upon allosteric complexation with alkanediammonium guests. By controlling the guest chain length, the torsional strain experienced by Zn complex can be modulated to induce bond cleavage with chemical stimulus, and reactivity trend is predicted by conformational analysis derived by DFT calculation. Such strain‐release reactivity by a Zn(salen) complex initiated by guest binding is reminiscent of conformation‐induced reactivity of enzymes to enable chemical events that are otherwise inhibited.

Evaluation of the implementation of personal protective equipment for French military firefighters in a CBRN context.

Military firefighters are the first responders in the event of a chemical, biological, radiation, and nuclear (CBRN) event in the Marseille area. They receive initial training to intervene safely in a CBRN context. We wanted to evaluate the use of CBRN personal protective equipment (PPE) at a distance from this training. A prospective observational bicentric descriptive study on 20 operational firefighters operating on rescue and emergency vehicles. Two PPE dressing sessions, separated by 3 months, were evaluated and timed. A reminder of the correct procedure was given by the investigator after the first dressing. On average, 60.5 percent of the steps were correctly performed during the first dressing and 83 percent during the second dressing. Between the two dressings, there was a significant improvement (p < 0.01) in the team verification of the dressing and the chronological order of the dressing as well as the actions to be taken before dressing (remembering to make oneself comfortable, to urinate, to drink). The second dressing is on average 21 seconds faster than the first. Professional training and exercise experience of the firefighters in CBRN improve the success and speed of dressing in the absence of a prior reminder. Shorter and more frequent training and exercises, which simulate real-life situations for firefighters, lead to safer, more competent and faster donning of PPE.

Analysis of Soil Biological Conditions in Organic and Inorganic Agriculture Areas in Tanah Datar Regency

Enzyme activity due to soil microbial activity is an important event in knowing the status of microbial biomass and as an indicator of the occurrence of nutrient cycling. This activity is not just a chemical event, but rather a complex biological process related to the interaction of life interests between organism. The activities of each soil microbial group further emphasize its diversity status, and have an impact on various bioprocess events that allow the degradation and synthesis of soil organic matter. Respiration events are a description of the acceleration of bioprocesses carried out by soil microbial biomass. The implementation of an enzymatic process can reflect an integrated chemical process, physics and mineralization that occurs in the soil as a result of microbial activity, in maintaining and realizing the resilience of its ecosystem. This research is a survey method and soil sampling (purposive sampling) followed by soil testing in the laboratory with the following stages: (a) analysis of experimental soil samples at the Soil Biology Laboratory, Soil Research Institute, Bogor, (b) interview. Analysis of organic and organic soil nitrogenase activity in Jorong Carano Batirai and Jorong Aie Angek, Tanah Datar Regency obtained a total of 4 samples. Indicates the presence of nitrogenase activity, namely NOI, NAI, NOII and NAII. The highest nitrogenase activity based on ARA was in the NOII sample and the lowest was in the NAI sample. Land management affects urease activity, urease is an enzyme that is sensitive to various levels of land management. Higher urease activity with organic use, because the level of land management is less intensive and receives little inorganic fertilizer or pesticide.&#x0D; Keywords : soil enzyme activity, soil biological fertility

Facile Access to Saccharin‐Fused 1,4‐Dihydropyridines through [3+3] Annulation Reactions

AbstractAn efficient approach to saccharin‐fused 1,4‐DHPs has been established by using a [3+3] annulation process. The chemical event was enabled by a Et3N‐catalyzed tandem Michael/aza‐Pinner reaction of alkyl cyclic N‐sulfonyl ketimines as nucleophiles with α,α‐dicyanoolefins. Under mild conditions, the desired products were readily prepared in good to excellent yields and with broad functional group tolerance (up to 95 % yield, 29 examples). Notably, this practical methodology features the synthesis of pentacyclic spirooxindoles bearing a quaternary spiro‐stereocenter.

Surface Protolysis and Its Kinetics Impact the Electrical Double Layer.

Surface conductivity in the electrical double layer (EDL) is known to be affected by proton hopping and diffusion at solid-liquid interfaces. Yet, the role of surface protolysis and its kinetics on the thermodynamic and transport properties of the EDL are usually ignored as physical models consider static surfaces. Here, using a novel molecular dynamics method mimicking surface protolysis, we unveil the impact of such chemical events on the system's response. Protolysis is found to strongly affect the EDL and electrokinetic aspects with major changes in ζ potential and electro-osmotic flow.

Revealing the Chemical Reaction Properties of a SiHCl3 Pyrolysis System by the ReaxFF Molecular Dynamics Method.

The pyrolysis kinetics of SiHCl3 and its reaction mechanism are essential for the chemical vapor deposition process in polysilicon industries. However, due to the high temperature and lack of in situ experimental detection technology, it is difficult to carry out experimental research on the pyrolysis kinetics of SiHCl3. In this work, reactive force field molecular dynamics simulations of SiHCl3 pyrolysis were performed to investigate the effect of temperature on the pyrolysis kinetics of SiHCl3 at the atomistic scale in a wide temperature range (1000–2000 K). The lumped Si clusters containing more than five Si atoms tended to appear at the later period of the reaction under a temperature lower than 1300 K, some of which even possessed polycyclic structures; nevertheless, small ones with less than two Si atoms such as SiHCl2 and HCl tended to emerge under a high temperature. The changes of partial energy terms with time evolution under various temperatures were proved to be rooted in the distribution of intermediates based on the momentary simulation period. In general, the reaction network at a low temperature was more complicated than that at a high temperature, resulting from the fact that more chemical events and intermediates came into existence, and the maximum number of Si atoms in one single molecule/radical was observed under a low temperature than that under a high temperature. As to the variation of SiHCl3 with the progress of the reaction, the linear fitting tendency disappeared under the temperature above 1300 K, which changed in fluctuation with the further elevation of temperature, elucidating the fact that SiHCl3 can act as a product and not just as a reactant to participate in elementary chemical events frequently.

A Closer Look at the Isomerization of 5-Androstene-3,17-Dione to 4-Androstene-3,17-Dione in Ketosteroid Isomerase

We report a comprehensive investigation of the 5-androstene-3,17-dione to 4-androstene-3,17-dione isomerization in Ketosteroid Isomerase, gas phase and aqueous solution, applying as tools the Unified Reaction Valley Approach (URVA) and the Local Vibrational Mode Analysis. Conformational changes of the steroid rings are monitored via Cremer-Pople puckering coordinates. URVA identifies simultaneous breakage of the C[Formula: see text]–H bond and O–H bond formation with the catalytic acid, leading to an intermediate with the acid positioned over ring [Formula: see text] as the major chemical events of the first reaction step. Via a barrier-less shift, a second intermediate is formed with the acid being positioned over ring [Formula: see text]. Then, according to URVA, breakage of the intermediate O–H bond, the formation of the new C[Formula: see text]–H bond accompanied by a double bond shift in rings [Formula: see text] and [Formula: see text] forms the major chemical events of the second reaction step, which is facilitated by favorable ring puckering. Reactions in protein and gas phase have comparable activation enthalpies, whereas the barrier in aqueous solution is higher, confirming that the major task of the enzyme pocket is to shield the migrating hydrogen atom and the catalyzing acid from interactions with solvent molecules diluting the catalytic power. We do not find exceptional H-bonding with Asp99 and Tyr14, excluding their catalytic activity. There is no strong hydrogen bonding in the TS, which could account for lowering the activation barrier. Our study provides a clear picture of the isomerization process, which will also inspire similar investigations of other important enzymatic reactions.

Detection of human serum albumin by room temperature nematic liquid crystals based on polarising microscopy, molecular docking and Raman spectroscopy

ABSTRACT Liquid crystal-based biosensors serve an essential role to detect biomolecules and chemical events as an effective, and simple detection tool. A biosensor that works on the principle of orientational reordering of liquid crystal molecules in presence of protein is reported. We employ a liquid crystal 4´-pentyl-4-biphenylcarbonitrile to detect the protein human serum albumin using multiple techniques. The composite of liquid crystal and protein forms nematic droplets. The transitions in the radial to bipolar configuration of the droplets are investigated via polarising optical microscopy. The detection limit is determined to be 100 µM. The interaction between protein and liquid crystal is performed through molecular docking . The binding sites, active residues, and binding energies are also calculated from the analysis. The binding energy required to bind 5CB with HSA at this site is −8.10 Kcal/mol. Raman spectroscopy is performed to determine the vibrational changes in the active residues, conformations of the disulphide bonds of the protein, which developed during the interaction with the liquid crystal. Raman spectroscopic studies confirm the interactions between the active residues of HSA and 5CB. The Raman parameters are studied at different HSA concentrations. This report demonstrates the applications of liquid crystals as transducing element in biosensing field.

Emergency evacuation and vulnerable people: a case study of a chemical exposure emergency scenario involving people with disabilities

Emergency evacuation of critical infrastructures, e.g., airports and high density crowd buildings, like shopping centres or entertainment venues, is considered a critical issue in terms of evacuees' safety; bottlenecks may lead to crowd jamming, causing evacuation delays and possibly putting in danger the evacuees. Vulnerable people, such as people with disabilities are more likely to be injured or killed in an emergency, triggered by a natural or man-made disaster; they are rarely consulted on provisions for their safety and most of them are not prepared for emergencies. This case-study involves the evacuation of people with disabilities at an airport terminal due to a chemical exposure event, under a broader emergency evacuation exercise, targeting at: a) proposing a 'Critical Indicators list' for the inclusion of people with disabilities in evacuation exercises of public buildings; b) providing the lessons learned; and c) reflecting on suggestions regarding preparedness, evacuation and triage in such events.

From Tokenization to Self-Supervision: Building a High-Performance Information Extraction System for Chemical Reactions in Patents.

Chemical reactions and experimental conditions are fundamental information for chemical research and pharmaceutical applications. However, the latest information of chemical reactions is usually embedded in the free text of patents. The rapidly accumulating chemical patents urge automatic tools based on natural language processing (NLP) techniques for efficient and accurate information extraction. This work describes the participation of the Melax Tech team in the CLEF 2020—ChEMU Task of Chemical Reaction Extraction from Patent. The task consisted of two subtasks: (1) named entity recognition to identify compounds and different semantic roles in the chemical reaction and (2) event extraction to identify event triggers of chemical reaction and their relations with the semantic roles recognized in subtask 1. To build an end-to-end system with high performance, multiple strategies tailored to chemical patents were applied and evaluated, ranging from optimizing the tokenization, pre-training patent language models based on self-supervision, to domain knowledge-based rules. Our hybrid approaches combining different strategies achieved state-of-the-art results in both subtasks, with the top-ranked F1 of 0.957 for entity recognition and the top-ranked F1 of 0.9536 for event extraction, indicating that the proposed approaches are promising.

A DNA Nanocomplex Containing Cascade DNAzymes and Promoter-Like Zn-Mn-Ferrite for Combined Gene/Chemo-dynamic Therapy.

Sequential control of exogenous chemical events inside cells is a promising way to regulate cell functions and fate. Herein we report a DNA nanocomplex containing cascade DNAzymes and promoter-like Zn-Mn-Ferrite (ZMF), achieving combined gene/chemo-dynamic therapy. The promoter-like ZMF decomposed in response to intratumoral glutathione to release a sufficient quantity of metal ions, thus promoting cascade DNA/RNA cleavage and free radical generation. Two kinds of DNAzymes were designed for sequential cascade enzymatic reaction, in which metal ions functioned as cofactors. The primary DNAzyme self-cleaved the DNA chain with Zn2+ as cofactor, and produced the secondary DNAzyme; the secondary DNAzyme afterwards cleaved the EGR-1 mRNA, and thus downregulated the expression of target EGR-1 protein, achieving DNAzyme-based gene therapy. Meanwhile, the released Zn2+ , Mn2+ and Fe2+ induced Fenton/Fenton-like reactions, during which free radicals were catalytically generated and efficient chemo-dynamic therapy was achieved. In a breast cancer mouse model, the administration of DNA nanocomplex led to a significant therapeutic efficacy of tumor growth suppression.

A DNA Nanocomplex Containing Cascade DNAzymes and Promoter‐Like Zn‐Mn‐Ferrite for Combined Gene/Chemo‐dynamic Therapy

AbstractSequential control of exogenous chemical events inside cells is a promising way to regulate cell functions and fate. Herein we report a DNA nanocomplex containing cascade DNAzymes and promoter‐like Zn‐Mn‐Ferrite (ZMF), achieving combined gene/chemo‐dynamic therapy. The promoter‐like ZMF decomposed in response to intratumoral glutathione to release a sufficient quantity of metal ions, thus promoting cascade DNA/RNA cleavage and free radical generation. Two kinds of DNAzymes were designed for sequential cascade enzymatic reaction, in which metal ions functioned as cofactors. The primary DNAzyme self‐cleaved the DNA chain with Zn2+ as cofactor, and produced the secondary DNAzyme; the secondary DNAzyme afterwards cleaved the EGR‐1 mRNA, and thus downregulated the expression of target EGR‐1 protein, achieving DNAzyme‐based gene therapy. Meanwhile, the released Zn2+, Mn2+ and Fe2+ induced Fenton/Fenton‐like reactions, during which free radicals were catalytically generated and efficient chemo‐dynamic therapy was achieved. In a breast cancer mouse model, the administration of DNA nanocomplex led to a significant therapeutic efficacy of tumor growth suppression.

Can We Envision a Role for Imagination in Chemistry Learning?

The scale of chemical events at the particulate level is sufficiently small that anybody who contemplates the science at this level uses their imagination. Significant efforts have been made for decades to provide guardrails to chemistry novices about visualizing chemistry from the perspective of atoms and molecules. Is it time to consider the imaginative act in constructing meaning more closely as a component of learning chemistry?

Catalytic upgrading of the polymeric constituents in Covid-19 masks

A substantial volume of various types of Covid-19 masks has been disposed of since the start of the global pandemic. These facemasks are made of non-degradable polymeric materials. As such, they currently signify a major source of microplastic pollution in the environment. Through incineration or pyrolysis, thermal processing has emerged as a mainstream approach in the waste management of the ever-increasing loads of generated facemasks. Via a combined experimental-theoretical framework, we report herein salient features that govern thermal decomposition of the distinct plastic-based components in 3 M N95 (with a respirator) and surgical facemasks. Protective three-four layers in the considered masks are composed of polypropylene (PP) that degrades in a one-step across the temperature window 330 – 480 °C. Char residues from the decomposition of ear straps (consisting of polyester) attain 24% and 15% fractions of the initial mass in the case of surgical and N95 masks, respectively. Thermo kinetic parameters are derived for the different components of the facemask by using the Coats-Redfern approach from the thermogravimetric analysis data. Here we also report the potentiality of producing value-added products from the face mask using the GCMS by virtue of the catalytic oxidation of the material expending the Niobium doped CeO2 catalyst under controlled conditions. Constructed mechanisms through density functional theory (DFT) computations illustrated the nature of chemical reactions that mark the two-stage decomposition curve of polyurethane (the material used in the nose area in N95 masks). These chemical events characterize rupture of C-C(O) bonds, sequential departure of CO2/C2H4 molecules, and fission of the C-C linkages. Outcomes from this investigation provide important information (i.e., thermal stability regions of the deployed polymers and potential emission profiles) needed in the urgent pursuit to safely and economically recycle polymeric constituents in Covid-19 masks, and potentially other types of medical wastes.

Basic physicochemical processes governing self‐healable polymers†

AbstractThis short review outlines basic chemical and physical principles that can be utilized in the development of self‐healing polymers. Physical processes include the interdiffusion of polymer chains, the introduction of phase‐separated morphologies, shape memory effects or incorporating active nanoparticles into a polymer matrix. Dynamic covalent, free radical or supramolecular bonds are predominantly chemical processes. However, self‐healing will also involve a combination of physical and chemical events, such as taking advantage of enhanced van der Waals forces resulting in inter‐digitated copolymer morphologies or embedded reactive encapsulated fluids that burst open upon damage to fill up a wound. Sufficient molecular mobility for autonomous self‐healing under ambient conditions can also be achieved while maintaining high strength and stiffness in precisely designed commodity polymers. The efficient storage and recovery of conformational entropic energy stored during damage or excess of surface energy resulting from damage will drive the reduction of newly generated interfaces created upon damage by shallowing and widening wounds until healed. © 2021 Society of Industrial Chemistry.

Pseudoperoxidase activity, conformational stability, and aggregation propensity of the His98Tyr myoglobin variant: implications for the onset of myoglobinopathy.

The autosomal dominant striated muscle disease myoglobinopathy is due to the single point mutation His98Tyr in human myoglobin (MB), the heme protein responsible for binding, storage, and controlled release of O2 in striated muscle. In order to understand the molecular basis of this disease, a comprehensive biochemical and biophysical study on wt MB and the variant H98Y has been performed. Although only small differences exist between the active site architectures of the two proteins, the mutant (a) exhibits an increased reactivity toward hydrogen peroxide, (b) exhibits a higher tendency to form high‐molecular‐weight aggregates, and (c) is more prone to heme bleaching, possibly as a consequence of the observed H2O2‐induced formation of the Tyr98 radical close to the metal center. These effects add to the impaired oxygen binding capacity and faster heme dissociation of the H98Y variant compared with wt MB. As the above effects result from bond formation/cleavage events occurring at the distal and proximal heme sites, it appears that the molecular determinants of the disease are localized there. These findings set the basis for clarifying the onset of the cascade of chemical events that are responsible for the pathological symptoms of myoglobinopathy.