Thermal Dissociation Temperature Research Articles

Quarkonia dissociation at finite magnetic field in the presence of momentum anisotropy

In this study, we investigate the potential of heavy quarkonia within a magnetized hot QGP medium having finite momentum anisotropy. The phenomenon of inverse magnetic catalysis is introduced into the system, influencing the magnetic field-modified Debye mass and thereby altering the effective quark masses. Concurrently, the impact of momentum anisotropy in the medium is considered that influence the particle distribution in the medium. The thermal decay width and dissociation temperature of quarkonium states, specifically the 1S and 2S states of charmonium and bottomonium, are computed. Our results reveal that both momentum anisotropy and the inverse magnetic catalysis effects play a significant role in modifying the thermal decay width and dissociation temperature of these heavy quarkonia states.

Evaluating the influence of Ar/N2 flow rate and pressure on the conversion efficiency of a solar-assisted Fe2O3 – FeO WS cycle for hydrogen production: A thermodynamic approach

A thermodynamic analysis is carried out to evaluate the effects of oxygen partial pressure (PO2) and molar flow rate of reduction agents (m˙N2/Ar) on the performance of Fe2O3−FeO solar thermochemical cycle (STC|Fe2O3−FeO). The chemical equilibrium and efficiency analysis parameters such as enthalpy, Gibbs free energy and entropy are calculated as a function of thermal dissociation temperature (TH). The chemical equilibrium analysis suggests that the thermal dissociation step is feasible above 1250 K while the re-oxidation step is practicable at 550 K. The efficiency analysis revealed that the highest value of conversion efficiency (ηsolar−to−fuel) reached up to 44.42% for N2 based cycle and 45.46% for Ar based cycle without using the recuperation technique. However, the conversion efficiency (ηsolar−to−fuel) attained the highest value of 57.84% for N2 based cycle and 59.14% for Ar based cycle with 50% heat recuperation.

Investigating cyclopentane hydrate nucleation and growth using microfluidics

The success of geological storage of carbon dioxide (CO2) in depleted oil and gas reservoirs relies among other aspects on the efficiency of CO2 injection, especially in the near-wellbore area where flow rates are high. CO2 hydrates pressure/temperature equilibrium conditions may be reached in this zone due to cooling associated with the Joule–Thomson effect; such CO2 hydrate formation may lead to strong injectivity loss and impair drastically the onsite well operations. In this study, cyclopentane hydrates (CPH) were employed as CO2 hydrate proxy (i.e. formation at atmospheric pressure) to mimic CO2 hydrate formation at higher pressure. In this study, the nucleation and growth processes were determined using a droplet-based in-house-microfluidic device. The generation of water droplets in cyclopentane liquid using the co-flow method was achieved. Trains of identical water droplets were stored in a serpentine channel. Each isolated droplet in this channel serves as a separate reactor. The temperature was controlled using a Peltier module to initiate hydrate nucleation at low temperatures. The isolated droplets provided the opportunity to statistically analyze the kinetic behaviors by varying key parameters, such as thermal history and water salinity. Detection of the onset of crystallization in water droplets over time and temperature allowed us to plot conversion curves based on imposed parameters. The effect of thermal history and dissociation temperature was first compared using pure water. This study marks the initial investigation into how NaCl influences CPH formation in microfluidic devices, focusing on isolated water droplets within serpentine tubes. The progression of ice nucleation, ice melting, the onset of CPH crystallization, CPH growth, and CPH dissociation are illustrated in water droplets exposed to changing temperatures. The addition of NaCl in the water during the procedure exhibited a noteworthy impact on CPH formations. With the same temperature profile, salt concentration delays nucleation (thermodynamic effect) and slows down growth. Our findings suggest that higher subcooling accelerates nucleation and growth rates. Initial lateral growth rates ranged from 4.22 μm/s to 2.14 μm/s, with a subcooling of 4.2 °C observed between 2 and 7 min for a pure water droplet.

Mechanism and inhibition of abnormal chromatographic behavior of serotype type a inactivated foot and mouth disease virus in high-performance size-exclusion chromatography

High-performance size-exclusion chromatography (HPSEC) has been developed for the rapid and quantitative analysis of inactivated foot and mouth disease virus (FMDV) and adopted by regulatory agencies and vaccine manufacturers. However, strong non-specific adsorption of type A/AKT III FMDV was found on some batches of TSK G4000 SWXL column, which significantly affected the analysis accuracy. The adsorption mechanism was studied by investigating the charge and hydrophobicity of A/AKT III FMDV and another serotype O/Mya 98, as well as several model proteins, by zeta potential and hydrophobic interaction chromatography analysis. Adsorption was related to both the FMDV strain and column lots. Some specific amino acids residues on the A/AKT III FMDV surface may strongly interact with the column if the silica-based stationary phase was not completely diol-modified. Several amino acids and chaotropic salts were screened as additives in the mobile phase to suppress the non-specific adsorption of AKT III FMDV in HPSEC analysis. Results showed that adding 0.4 M of arginine (Arg), lysine (Lys), NaClO4, or NaSCN achieved 100% FMDV recovery and normal retention time. Suppression of interaction between FMDV and the backbone of the silica matrix through competitive binding with residues of FMDV or the matrix is considered as the main mechanism by which these four additives act as suppressors. The addition of Arg, NaClO4, or NaSCN led to an apparent decrease in the thermal dissociation temperature Tm of FMDV, whereas Lys slightly increased viral stability. Finally, the mobile phase comprising 0.4 M Lys was screened as optimum that allowed accurate quantification of both two serotypes of FMDV according to method validation; particularly, a relative standard deviation (RSD) < 5% was achieved for AKT III FMDV using three different lots of columns.

Spliceosomal SL1 RNA binding to U1-70K: the role of the extended RRM.

The RNA recognition motif (RRM) occurs widely in RNA-binding proteins, but does not always by itself support full binding. For example, it is known that binding of SL1 RNA to the protein U1-70K in the U1 spliceosomal particle is reduced when a region flanking the RRM is truncated. How the RRM flanking regions that together with the RRM make up an ‘extended RRM’ (eRRM) contribute to complex stability and structural organization is unknown. We study the U1-70K eRRM bound to SL1 RNA by thermal dissociation and laser temperature jump kinetics; long-time molecular dynamics simulations interpret the experiments with atomistic resolution. Truncation of the helix flanking the RRM on its N-terminal side, ‘N-helix,’ strongly reduces overall binding, which is further weakened under higher salt and temperature conditions. Truncating the disordered region flanking the RRM on the C-terminal side, ‘C-IDR’, affects the local binding site. Surprisingly, all-atom simulations show that protein truncation enhances base stacking interactions in the binding site and leaves the overall number of hydrogen bonds intact. Instead, the flanking regions of the eRRM act in a distributed fashion via collective interactions with the RNA when external stresses such as temperature or high salt mimicking osmotic imbalance are applied.

Temperature-dependent kinetic analysis of cryogenic-specific reddish coloration synthesized with cryoplasma

We recently reported on the reddish coloration of a CH3OH/H2O ice irradiated by cryoplasma, which is similar in appearance to the reddish surfaces seen on some icy bodies in the outer Solar System, and is sustained only at cryogenic temperatures. In this study, we analyzed the time evolution of absorption spectra during irradiation of this ice at temperatures of 70–90 K, and found that the nominal production rates of the reddish materials decreased with increasing temperature. We conducted kinetic analysis, which revealed that although the formation of the materials that absorb at 500 nm showed no temperature dependence, their disappearance under cryoplasma irradiation showed a positive temperature dependence. This finding indicates that the interactions of excited plasma species with the reddish materials, coupled with thermally-driven processes, can increase the rates of disappearance of the reddish materials and result in their destruction even at temperatures below their thermal dissociation temperatures, which was found to be 120–150 K in our previous study. These results suggest that the effects of radiation-driven chemistry and thermally-driven chemistry in concert can influence the formation and stability of reddish materials such as those synthesized in this study.

Facile synthesis and characterization of hydroxyapatite particles for high value nanocomposites and biomaterials

Lately Hydroxyapatite has gained a lot of research interest and intense focus due to its structural as well as compositional similarity to the components of human bone mineral. The conversion of calcium-rich precursors to hydroxyapatite could lead to the development of a new sustainable alternative with a valuable environmental and socio-economically impact. Still, current approaches faces lots of challenges in terms of synthesis parameters compatible to a reproducible route for calcium phosphates (hydroxyapatite included) synthesis. The optimization of Rathje synthesis route and characterization of biogenic derived calcium phosphates from dolomitic marble and Mytilus galloprovincialis seashells, constitutes the main goals of this study. The synthesized materials were characterized using FTIR, SEM coupled with EDS, and X-ray diffraction at all synthesis stages. Precursors were also subjected to thermal analysis and differential scanning calorimetry for thermal transformations investigations and dissociation temperature setting. This study suggests that acid quantity and magnetic stirring are the key-factors for Ca/P molar ratio adjustment, hence for the amount of naturally-derived hydroxyapatite. This research also contributes to the development of new strategies for further optimization of the conversion procedure and removal of residual components.

Synthesis and properties of blocked Di- and polyisocyanates

Tricresol-blocked di- and polyisocyanates (BDPs) of variable structure are synthesized, and their main physicochemical and technological properties are defined. They have lower melting points and thermal dissociation (deblocking) temperatures than do the known BDPs based on e-caprolactam, oximes, and secondary amines.. The new blocked isocyanates are tested as latent curing agents for polyurethane varnish compositions of electroinsulating assignment.

Monitoring DNA Hybridization and Thermal Dissociation at the Silica/Water Interface Using Resonantly Enhanced Second Harmonic Generation Spectroscopy

The immobilization of oligonucleotide sequences onto glass supports is central to the field of biodiagnostics and molecular biology with the widespread use of DNA microarrays. However, the influence of confinement on the behavior of DNA immobilized on silica is not well understood owing to the difficulties associated with monitoring this buried interface. Second harmonic generation (SHG) is an inherently surface specific technique making it well suited to observe processes at insulator interfaces like silica. Using a universal 3-nitropyrolle nucleotide as an SHG-active label, we monitored the hybridization rate and thermal dissociation of a 15-mer of DNA immobilized at the silica/aqueous interface. The immobilized DNA exhibits hybridization rates on the minute time scale, which is much slower than hybridization kinetics in solution but on par with hybridization behavior observed at electrochemical interfaces. In contrast, the thermal dissociation temperature of the DNA immobilized on silica is on average 12 °C lower than the analogous duplex in solution, which is more significant than that observed on other surfaces like gold. We attribute the destabilizing affect of silica to its negatively charged surface at neutral pH that repels the hybridizing complementary DNA.

말단 수산화기를 가진 폴리락타이드와 이미다졸로 블록된 이소시아네이트를 이용한 폴리우레탄 바이오접착제의 합성 및 물성 평가

A series of novel imidazole-blocked diisocyanate bioadhesives (IBAs) were synthesized from reaction of toluene 2, 4-diisocyanate (TDI), isophorone diisocyanate (IPDI), hydroxyl-terminated polylactide (HO-PLA-OH), 1,1,1-trimethylolpropane (TMP), and imidazole. Synthesis of IBAs was confirmed by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) revealed that the TDI-based IBA had lower thermal dissociation temperature and a faster deblocking rate than IBA based on IPDI. Hydroxyl-terminated polyurethane (HPU) was introduced to study the adhesive effect of the synthesized IBAs. Improvement on elastic modulus, tensile strength and water resistance of IBA-modified HPU in comparison with neat HPU suggested the good adhesive effect of IBA due to the strong chemical reaction between released NCO groups from IBA and hydroxyl groups from HPU.

Synthesis and properties of biodegradable polyurethane crosslinkers from methyl ethyl ketoxime-blocked diisocyanate

A series of novel biodegradable blocked polyurethane crosslinkers (BPUCs) were synthesized from the reaction of toluene 2,4-diisocyanate (TDI), isophorone diisocyanate (IPDI), polycaprolactone (PCL), 1,1,1-trimethylolpropane (TMP), and methyl ethyl ketoxime (MEKO). Synthesis of the accurate kind of BPUCs was confirmed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), and gel permeation chromatography (GPC). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to determine the deblocking temperatures of the BPUCs. The thermal analysis revealed that both TDI- and IPDI-based BPUC had the proper initial deblocking temperature (<160 °C) and the maximum deblocking temperature (<200 °C) for practical applications. Compared to IPDI-based BPUC, the TDI-based BPUC had a lower thermal dissociation temperature and a faster deblocking rate. Hydroxyl polyurethane (HPU) was introduced to study the crosslinking effect of prepared BPUCs. The reaction proceeded at various deblocking temperatures in different curing times. It was noticed that the elastic modulus and tensile strength of the HPU sample increased whereas elongation at break decreased with the addition of BPUC in comparison with pure HPU, which suggested better interfacial adhesion due to the strong chemical reaction between the released NCO groups from BPUC and hydroxyl groups from HPU. In addition, improvement on water resistance of the BPUC modified HPU samples compared to pure HPU samples also demonstrated the good crosslinking effect of prepared BPUCs. Open image in new window

Molecular analysis of botanical evidence by DNA thermal dissociation temperature

This work was based upon earlier studies which exploited indels located in the mitochondrial genome to discriminate between different varieties of grass. The nad7 and nad5 indels were amplified from the DNA of nine different varieties of amenity grass species typical of lawn and recreational use. Discrimination was achieved by differences in T m values as shown by dissociation curve and supported by gel electrophoresis. Experiments were also implemented to determine the applicability of a genetic test using samples that were exposed to different environmental conditions. These were designed to include simulated conditions experienced by real forensic samples and consisted of grass leaves, stored dry inside paper envelopes at room temperature, desiccated grass leaves contaminated with fungal growth, and also stains made from grass leaves on cotton cloth to simulate grass marks that might be found on clothing. These stains were stored in a variety of conditions including, contact with soil, water logged, dry and exposed to sunlight and also stored dry in the dark and at 4 °C for comparison. All samples except the soil and the fungus contaminated samples gave amplification products that could be distinguished by means of both gel electrophoresis and by T m determined by a dissociation curve.

Synthesis and characterization of reactive blocked‐isocyanate coupling agents from methyl ethyl ketoxime, ethyl cellosolve/ε‐caprolactam blocked aromatic and aliphatic diisocyanates

AbstractA series of water‐dispersible blocked polyisocyanates were synthesized from toluene 2,4‐diisocyanate (TDI), isophorone diisocyanate (IPDI), dimethylol propionic acid, methyl ethyl ketoxime (MEKO), ethyl cellosolve (EC), and ϵ‐caprolactam (CL). The physical properties, such as the viscosity, pH, and storage stability, of the blocked‐polyisocyanate adducts were measured. All aqueous dispersions of the blocked polyisocyanates showed good storage stability. The prepared blocked polyisocyanates were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, and thermogravimetric analysis techniques. The FTIR confirmed that the NCO groups of the original TDI and IPDI molecules were completely blocked by the blocking agents. The thermal analysis measurements revealed that both the blocked TDI‐ and IPDI‐based polyisocyanates started to deblock at about 55–85°C. Compared to the CL‐blocked polyisocyanates, the MEKO‐ and EC‐blocked polyisocyanates had lower thermal dissociation temperatures and faster deblocking rates. We also found that the initial deblocking temperatures of the TDI‐based adducts were lower than those of the IPDI‐based adducts. The water resistance and tensile properties of the composite films from the blocked‐polyisocyanate crosslinkers and hydroxyl–polyurethane emulsion (HPUE) matrix were studied. The tensile strength increased and the elongation at break were lower in the composites compared to the pure HPUE film. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Thermal activation of the co‐chaperonins GroES and gp31 probed by mass spectrometry

Many biological active proteins are assembled in protein complexes. Understanding the (dis)assembly of such complexes is therefore of major interest. Here we use mass spectrometry to monitor the disassembly induced by thermal activation of the heptameric co-chaperonins GroES and gp31. We use native electrospray ionization mass spectrometry (ESI-MS) on a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer to monitor the stoichiometry of the chaperonins. A thermally controlled electrospray setup was employed to analyze conformational and stoichiometric changes of the chaperonins at varying temperature. The native ESI-MS data agreed well with data obtained from fluorescence spectroscopy as the measured thermal dissociation temperatures of the complexes were in good agreement. Furthermore, we observed that thermal denaturing of GroES and gp31 proceeds via intermediate steps of all oligomeric forms, with no evidence of a transiently stable unfolded heptamer. We also evaluated the thermal dissociation of the chaperonins in the gas phase using infrared multiphoton dissociation (IRMPD) for thermal activation. Using gas-phase activation the smaller (2-4) oligomers were not detected, only down to the pentamer, whereafter the complex seemed to dissociate completely. These results demonstrate clearly that conformational changes of GroES and gp31 due to heating in solution and in the gas phase are significantly different.

Thermal dissociation behavior of copolymers bearing hemiacetal ester moieties and their reactions with epoxides

AbstractCopolymers from 1‐propoxyethyl methacrylate and various vinyl monomers such as n‐butyl methacrylate and styrene were synthesized, and the thermal dissociation reaction of the copolymers containing the hemiacetal ester structure was examined. The copolymers, having the ability of thermal dissociation, could control the thermal dissociation temperature because of the bulkiness and flexibility of the vinyl comonomers, the copolymer compositions, and so on. Furthermore, the possibility of control of the initiation in thermally latent addition with epoxides in the case of copolymers was also studied. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3966–3977, 2006

Characteristics of Thin Film of Nano-Hybrid Synthesized from Acrylic Resin and Colloidal Silca-Silane Sol

Organic-inorganic hybrid blends were prepared in variation with the ratio of sol solution to urethaneacrylic resin. Such sol solutions were synthesized from colloidal silica (CS)/ methyltrimethoxysilane(MTMS)/vinyltrimethoxysilane(VTMS) by sol-gel reaction through two step reactions. Thin films of organic-inorganic hybrid blends were prepared using spin coater on the glass and aluminum sheets. In order to understand surface properties of thin films, contact angle and roughness were measured. Surface contact angle and roughness of thin films increased as the amount of sol solution increased. Thermal dissociation temperature of thin films was observed using TGA. Thin films were stable until 270 oC. Thermal dissociation temperature of thin films improved with increasing sol solution. In order to observe insulation property of thin films, electrical resistance measurements were performed. Surface and volume resistance of thin films increased as the amount of sol solution increased.

Fine-tuning of thermal dissociation temperature using copolymers with hemiacetal ester moieties in the side chain: effect of comonomer on dissociation temperature

Synthesis of polymers with hemiacetal ester moieties in the side chain by radical copolymerization of 1-alkoxyethyl methacrylate with various vinyl monomers and their thermal dissociation behavior are described. Radical copolymerization of 1-alkoxyethyl methacrylates with vinyl monomers was carried out in the presence of 2,2′-azoisobutyronitrile at 60°C to afford the corresponding copolymers with hemiacetal ester moieties in the side chain. The thermal dissociation behavior of the obtained copolymers was examined by means of TG–DTA measurements to observe that the dissociation temperatures of hemiacetal ester units depended on their comonomer components. The polarity of the comonomers and the ability to form hydrogen-bonding were key forces to control their thermal dissociation behavior.

Structure-initiator activity dependence of aminimides as thermally latent initiators in the polymerization of glycidyl phenyl ether

Novel aliphatic aminimides were synthesized from the corresponding carboxylic acid esters, 1,1-dimethylhydrazine, and epoxides in 54–95% yields. Bulk polymerization of glycidyl phenyl ether (GPE) with 3 mol % of the aminimides was evaluated by DSC as a model process for curing of epoxy resin. All the aminimides showed no exothermic DSC peak below 120 °C but showed sharp exothermic peaks above 137 °C, indicating good thermal latency. Good relationships were observed between the calculated bond length from the carbonyl carbon to the α-carbon of the aliphatic group (RC), DSC onset temperatures, and the thermal dissociation temperatures (Td 's) of the aminimides. The aminimide with a longer RC bond length showed lower Td and DSC onset temperature, that is, higher activity. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3428–3433, 2000

Double-Stranded Cyclic Oligonucleotides with Non-Nucleotide Bridges

A series of double-stranded, cyclic oligodeoxynucleotides with non-nucleotide bridges have been synthesized, and their physicochemical properties and susceptibility to enzymes have been investigated. These bridged duplexes are of potential interest for their binding properties to transcription factors and other DNA-binding proteins. Triethylene glycol has been employed as the bridge to alter the lipophilicity of the duplex and avoid the potential for enzymatic cleavage. The synthetic route involved the synthesis of a 3'-phosphorylated, nicked double-stranded precursor with the final internucleotide bond being formed chemically using a water soluble carbodiimide. These bridged duplexes have high thermal dissociation temperatures, and the Tm for a triethylene-bridged 20 base pair duplex was higher than that for the corresponding pentathymidylate-bridged duplex. EcoR I endonuclease cleaved a ligated, bridged duplex at a slower rate than the corresponding unmodified duplex, whereas the unligated, bridged duplex was cleaved more rapidly. Sufficient amounts of the bridged octamer and dodecamer were prepared for proton NMR spectroscopic studies, and 2D COSY and NOESY spectra were obtained. The results indicate that the ligated duplex has a B-form conformation.

Polyurethane elastomers based on molecular weight advanced poly(ethylene ether carbonate) polyols. IV. Effects of poly(propylene glycol) modified diols

AbstractA series of polyurethane elastomers with a (A{BC}m)n type of structure have been prepared and characterized based on poly(propylene glycol) modified poly(ethylene ether carbonate) polyols, where the poly(propylene glycol) content and block length were varied systematically. Strength and modulus properties showed a marked dependence on modifier level and exhibited synergistic property improvements at 25–50 wt % modifier, relative to both unmodified poly(ethylene ether carbonate) diol and poly(propylene glycol) controls. DMA results indicated an increased modulus for the modified plaques throughout the rubbery plateau region, with higher thermal dissociation temperatures. Excellent organic solvent resistance was maintained with 25–50 wt % poly(propylene glycol) modification in the soft segment. Chemical structure of the polyurethane elastomers was established by proton and 13C‐NMR spectroscopy. The morphology of these modified polyurethanes appears to be quite complex. Since the modified soft segments are block copolymers of blocks with a tendency toward immiscibility, some microphase separation within the soft segment domains of the polyurethane polymers might be expected. The soft segment Tg is highest where properties are maximized, suggesting changes in phase mixing. © 1992 John Wiley &amp; Sons, Inc.