scholarly journals The impact of metastable intermolrecular nanocomposite particles on kinetic decomposition of heterocyclic nitramines using advanced solid-phase decomposition models

2021 ◽  
Author(s):  
Sherif Elbasuney ◽  
Abdelaziz Hamed ◽  
M. Yehia ◽  
Hesham Ramzy ◽  
Ahmed Abdelgawad ◽  
...  
Keyword(s):  
Ferric Oxide ◽  
Active Sites ◽  
Solid Phase ◽  
Isoconversional Method ◽  
Mean Value ◽  
Oh Radicals ◽  
Uniform Dispersion ◽  
Kinetic Decomposition ◽  
Oxide Particles ◽  
The Impact

Abstract Oxygen atoms on the surface of oxide catalysts have low coordination number; they are negatively charged. Surface oxygen can act active sites for decomposition of energetic nitramines (i.e. HMX); additionally hydrous surface can release active ȮH radicals. Colloidal oxide particles can fulfil these requirements. Furthermore oxide particles can induce thermite reaction with aluminium particles. This study reports on the facile fabrication of colloidal ferric oxide particles of 5 nm; Colloidal Fe2O3/Al binary mixture was integrated into HMX matrix via co-precipitation technique; uniform dispersion of nanothermite particles was verified using SEM. Naonothermite particles experienced dramatic change in HMX thermal behaviour with an increase in total heat release by 63 %. The impact of themrite particles on HMX kinetic decomposition was evaluated using an integral isoconversional method of KAS, and Kissinger models. The mean value of apparent activation was reduced by 23.5 % and 24.3 % using Kissinger and KAS models respectively. This dramatic change in HMX decomposition can be ascribed to the ferric oxide reactivity and the facile integration of colloidal thermite particles.

Influence of Thermo-Mechanical Processing on the Microstructure of Beryllia Dispersed Nickel Alloys

1973 ◽  
Vol 31 ◽  
pp. 184-185
Author(s):  
M.S. Grewal ◽  
S.A. Sastri ◽  
N.J. Grant
Keyword(s):  
High Temperature ◽  
Nickel Alloys ◽  
Thermomechanical Processing ◽  
Cold Work ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Mechanical Processing ◽  
Uniform Dispersion ◽  
Oxide Particles ◽  
Nickel Base

Currently there is a great interest in developing nickel base alloys with fine and uniform dispersion of stable oxide particles, for high temperature applications. It is well known that the high temperature strength and stability of an oxide dispersed alloy can be greatly improved by appropriate thermomechanical processing, but the mechanism of this strengthening effect is not well understood. This investigation was undertaken to study the dislocation substructures formed in beryllia dispersed nickel alloys as a function of cold work both with and without intermediate anneals. Two alloys, one Ni-lv/oBeo and other Ni-4.5Mo-30Co-2v/oBeo were investigated. The influence of the substructures produced by Thermo-Mechanical Processing (TMP) on the high temperature creep properties of these alloys was also evaluated.

Development of Strategies for Glycopeptide Synthesis: An Overview on the Glycosidic Linkage

2020 ◽  
Vol 24 (21) ◽  
pp. 2475-2497
Author(s):  
Andrea Verónica Rodríguez-Mayor ◽  
German Jesid Peralta-Camacho ◽  
Karen Johanna Cárdenas-Martínez ◽  
Javier Eduardo García-Castañeda
Keyword(s):  
Chemical Synthesis ◽  
Solid Phase ◽  
Building Blocks ◽  
Heterogeneous Environments ◽  
Phase Synthesis ◽  
Low Concentrations ◽  
Biological Sources ◽  
Synthetic Routes ◽  
The Impact ◽  
Potential Use

Glycoproteins and glycopeptides are an interesting focus of research, because of their potential use as therapeutic agents, since they are related to carbohydrate-carbohydrate, carbohydrate-protein, and carbohydrate-lipid interactions, which are commonly involved in biological processes. It has been established that natural glycoconjugates could be an important source of templates for the design and development of molecules with therapeutic applications. However, isolating large quantities of glycoconjugates from biological sources with the required purity is extremely complex, because these molecules are found in heterogeneous environments and in very low concentrations. As an alternative to solving this problem, the chemical synthesis of glycoconjugates has been developed. In this context, several methods for the synthesis of glycopeptides in solution and/or solid-phase have been reported. In most of these methods, glycosylated amino acid derivatives are used as building blocks for both solution and solid-phase synthesis. The synthetic viability of glycoconjugates is a critical parameter for allowing their use as drugs to mitigate the impact of microbial resistance and/or cancer. However, the chemical synthesis of glycoconjugates is a challenge, because these molecules possess multiple reaction sites and have a very specific stereochemistry. Therefore, it is necessary to design and implement synthetic routes, which may involve various protection schemes but can be stereoselective, environmentally friendly, and high-yielding. This review focuses on glycopeptide synthesis by recapitulating the progress made over the last 15 years.

Introduction to geomicrobiology

2018 ◽  
Author(s):  
David L. Kirchman
Keyword(s):  
Fossil Fuels ◽  
Solid Phase ◽  
Direct Reduction ◽  
Iron Oxidation ◽  
Mineral Dissolution ◽  
Precipitation Process ◽  
Soluble Ions ◽  
Chemolithoautotrophic Bacteria ◽  
The Impact

Geomicrobiology, the marriage of geology and microbiology, is about the impact of microbes on Earth materials in terrestrial systems and sediments. Many geomicrobiological processes occur over long timescales. Even the slow growth and low activity of microbes, however, have big effects when added up over millennia. After reviewing the basics of bacteria–surface interactions, the chapter moves on to discussing biomineralization, which is the microbially mediated formation of solid minerals from soluble ions. The role of microbes can vary from merely providing passive surfaces for mineral formation, to active control of the entire precipitation process. The formation of carbonate-containing minerals by coccolithophorids and other marine organisms is especially important because of the role of these minerals in the carbon cycle. Iron minerals can be formed by chemolithoautotrophic bacteria, which gain a small amount of energy from iron oxidation. Similarly, manganese-rich minerals are formed during manganese oxidation, although how this reaction benefits microbes is unclear. These minerals and others give geologists and geomicrobiologists clues about early life on Earth. In addition to forming minerals, microbes help to dissolve them, a process called weathering. Microbes contribute to weathering and mineral dissolution through several mechanisms: production of protons (acidity) or hydroxides that dissolve minerals; production of ligands that chelate metals in minerals thereby breaking up the solid phase; and direct reduction of mineral-bound metals to more soluble forms. The chapter ends with some comments about the role of microbes in degrading oil and other fossil fuels.

A solid-phase extraction method that eliminates matrix effects of complex pulp mill effluents for the analysis of lipophilic wood extractives

2020 ◽  
Vol 35 (4) ◽  
pp. 577-588
Author(s):  
Sebastian España Orozco ◽  
Philipp Zeitlinger ◽  
Karin Fackler ◽  
Robert H. Bischof ◽  
Antje Potthast
Keyword(s):  
Solid Phase Extraction ◽  
Matrix Effects ◽  
Solid Phase ◽  
Internal Standard ◽  
Pulp Mill ◽  
Phase Extraction ◽  
Wood Extractives ◽  
Wood Extractive ◽  
Pulp Mill Effluents ◽  
The Impact

AbstractThe extraction of lipophilic wood extractives from pulp and paper process waters proves to be a challenging task, due to harsh and alternating process and sample conditions. This study has determined the potential use of polymeric sorbents for solid-phase extraction (SPE) and compared to classical silica-based reversed-phase packed columns, with polymeric hydrophilic-lipophilic balanced (HLB) cartridges being the sorbent with the most potential. Recovery functions were obtained with an internal standard mixture representative for the main lipophilic wood extractive groups, which are fatty acids and alcohols, sterols, sterol esters and triglycerides. The impact of pH, sample volume and sample matrix, expressed as TOC and cations, on the retention behavior of lipophilic extractives during SPE of industrial samples were determined with polymeric HLB sorbent. High variations in the composition of pulp mill matrices led to different optimal extraction conditions. Thus, a new SPE protocol was developed, which bypasses matrix interferences and omits the loss of analytes due to sample preparation. The method is applicable to different pulp mill effluents with large discrepancies in pH and sample matrices, resulting in recoveries >90 % with RSD <5 % for all lipophilic wood extractives.

scholarly journals Eustachian Tube Dysfunction in Children With Adenoid Hypertrophy: The Role of Adenoidectomy for Improving Ear Ventilation

2021 ◽  
pp. 014556132198945
Author(s):  
Alessandra Manno ◽  
Giannicola Iannella ◽  
Vincenzo Savastano ◽  
Tommaso Vittori ◽  
Serena Bertin ◽  
...  
Keyword(s):  
Eustachian Tube ◽  
Otitis Media With Effusion ◽  
Preoperative Evaluation ◽  
Mean Value ◽  
Eustachian Tube Dysfunction ◽  
Adenoid Hypertrophy ◽  
Before And After ◽  
Middle Ear Ventilation ◽  
Tube Dysfunction ◽  
The Impact

Introduction: To our knowledge, few papers have addressed preoperative evaluation of the impact of adenoid hypertrophy (AH) on the pathogenesis of eustachian tube dysfunction (ETD) in children with otitis media with effusion (OME). Aim: The aim of this study was 2-fold: first, to evaluate ETD using tubomanometry and Eustachian Tube Score 7 (ETS-7), in a group of children having AH; second, to assess the clinical impact of adenoidectomy on the ETD of these patients. Methods: Fifty patients, aged 4 to 15 years, underwent adenoidectomy based on various parameters: size of the adenoids causing canal obstruction (grades 1-4), the presence of OME, and recurrent episodes of rhinosinusitis. The function of the eustachian tube was evaluated using ETS-7 before and after surgical treatment. The patients were followed up for 6 months. Results: Forty children presented ETD. Of these, 36 had a grade 4 AH. The preoperative mean value for ETS-7 was 6.62. The mean postoperative ETS-7 score showed a value of 9.60 with a statistical difference compared to the preoperative value ( P = .0015). Conclusions: Adenoid hypertrophy has a high impact on the frequency of ETD. In the patients observed in the present study, the ETS-7 score appeared to be a valid tool for assessing ETD both preoperatively and postoperatively. Adenoidectomy seemed to be effective in improving ETD as well as middle ear ventilation.

scholarly journals Solid-Phase Extraction Embedded Dialysis (SPEED), an Innovative Procedure for the Investigation of Microbial Specialized Metabolites

Marine Drugs ◽  
2021 ◽  
Vol 19 (7) ◽  
pp. 371
Author(s):  
Phuong-Y Mai ◽  
Géraldine Le Goff ◽  
Erwan Poupon ◽  
Philippe Lopes ◽  
Xavier Moppert ◽  
...  
Keyword(s):  
Solid Phase Extraction ◽  
Solid Phase ◽  
Chemical Space ◽  
Molecular Profile ◽  
Phase Extraction ◽  
Specialized Metabolites ◽  
Streptomyces Albidoflavus ◽  
Cultivation Process ◽  
The Impact

Solid-phase extraction embedded dialysis (SPEED technology) is an innovative procedure developed to physically separate in-situ, during the cultivation, the mycelium of filament forming microorganisms, such as actinomycetes and fungi, and the XAD-16 resin used to trap the secreted specialized metabolites. SPEED consists of an external nylon cloth and an internal dialysis tube containing the XAD resin. The dialysis barrier selects the molecular weight of the trapped compounds, and prevents the aggregation of biomass or macromolecules on the XAD beads. The external nylon promotes the formation of a microbial biofilm, making SPEED a biofilm supported cultivation process. SPEED technology was applied to the marine Streptomyces albidoflavus 19-S21, isolated from a core of a submerged Kopara sampled at 20 m from the border of a saltwater pond. The chemical space of this strain was investigated effectively using a dereplication strategy based on molecular networking and in-depth chemical analysis. The results highlight the impact of culture support on the molecular profile of Streptomyces albidoflavus 19-S21 secondary metabolites.

scholarly journals The potentially hazardous NEA 2001 BB16

2019 ◽  
Vol 28 (1) ◽  
pp. 180-190
Author(s):  
Ireneusz Wlodarczyk
Keyword(s):  
Mean Value ◽  
Optical Observations ◽  
Uniform Sampling ◽  
The Earth ◽  
22Nd Century ◽  
Lyapunov Time ◽  
Gravitational Model ◽  
Calculated Probability ◽  
Potential Impact ◽  
The Impact

AbstractWe computed the impact solutions of the potentially dangerous Near Earth Asteroid (NEA) 2001 BB16 based on 47 optical observations from January 20.08316 UTC, 2001, through February 09.15740 UTC, 2016, and one radar observation from January 19.90347 UTC, 2016. We used two methods to sample the starting Line of Variation (LOV). First method, called thereafter LOV1, with the uniform sampling of the LOV parameter, out to LOV = 5 computing 3000 virtual asteroids (VAs) on both sides of the LOV, which gives 6001 VAs and propagated their orbits to JD2525000.5 TDT=February 12, 2201. We computed the non-gravitational parameterA2=(34.55±7.38)·10–14 au/d2 for nominal orbit of 2001 BB16 and possible impacts with the Earth until 2201. For potential impact in 2195 we find A2=20.0·10−14 au/d2. With a positive value of A2, 2001 BB16 can be prograde rotator. Moreover, we computed Lyapunov Time (LT) for 2001 BB16, which for all VAs, has a mean value of about 25 y. We showed that impact solutions, including the calculated probability of a possible collision of a 2001 BB16 asteroid with the Earth depends on how to calculate and take into account the appropriate gravitational model, including the number of perturbing massive asteroids. In some complicated cases, it may depend also on the number of clones calculated for a given sigma LOV1. The second method of computing the impact solutions, called thereafter LOV2, is based on a non-uniformly sampling of the LOV. We showed that different methods of sampling the LOV can give different impact solutions, but all computed dates of possible impacts of the asteroid 2001 BB16 with the Earth occur in accordance at the end of the 22nd century.

scholarly journals A Study of the Impact of Graphite on the Kinetics of SPS in Nano- and Submicron WC-10%Co Powder Compositions

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 331-363
Author(s):  
Eugeniy Lantcev ◽  
Aleksey Nokhrin ◽  
Nataliya Malekhonova ◽  
Maksim Boldin ◽  
Vladimir Chuvil'deev ◽  
...  
Keyword(s):  
Activation Energy ◽  
Solid Phase ◽  
Continuous Heating ◽  
Diffusion Creep ◽  
Hard Alloys ◽  
Fine Grained ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
The Impact ◽  
Kinetics Of

This study investigates the impact of carbon on the kinetics of the spark plasma sintering (SPS) of nano- and submicron powders WC-10wt.%Co. Carbon, in the form of graphite, was introduced into powders by mixing. The activation energy of solid-phase sintering was determined for the conditions of isothermal and continuous heating. It has been demonstrated that increasing the carbon content leads to a decrease in the fraction of η-phase particles and a shift of the shrinkage curve towards lower heating temperatures. It has been established that increasing the graphite content in nano- and submicron powders has no significant effect on the SPS activation energy for “mid-range” heating temperatures, QS(I). The value of QS(I) is close to the activation energy of grain-boundary diffusion in cobalt. It has been demonstrated that increasing the content of graphite leads to a significant decrease in the SPS activation energy, QS(II), for “higher-range” heating temperatures due to lower concentration of tungsten atoms in cobalt-based γ-phase. It has been established that the sintering kinetics of fine-grained WC-Co hard alloys is limited by the intensity of diffusion creep of cobalt (Coble creep).

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