Temperature-dependent Formation Research Articles

Temperature dynamics and its effects on gas influx handling during managed pressure drilling operations

With Managed Pressure Drilling (MPD) becoming increasingly important to oil and gas well construction, there has been a growing demand for comprehensive models that can accurately describe the well hydraulic dynamics, especially for complex well geometries, High-Pressure High-Temperature (HPHT) conditions, during well control events, etc. To meet this demand, new multi-phase hydraulic models have been developed. However, despite their improvement over the traditional lumped parameter models, these models typically do not consider detailed temperature effects, which markedly influence well hydraulics and need to be explicitly considered for accurate MPD control.The development of a new integrated multi-phase thermal and hydraulic modeling framework is presented in this paper. This integrated model can estimate the mud temperature in the drillstring and the annulus, as well as the temperature variations of the formation during complex well control situations. The model uses a semi-implicit finite volume approach and solves the mixture energy equation for the wellbore fluids, assuming that all the phases are in thermal equilibrium. Heat transfer between the drillstring and wellbore fluids, and between the wellbore fluids and the formation is calculated using thermal resistance networks.The steady-state and transient temperature behaviors during mud circulation are compared to the steady-state analytical model by Hasan and Kabir and commercial software. These comparisons show good agreement for both steady-state and transient cases. To demonstrate the importance of accurate temperature estimation of the drillstring and annulus fluids in HPHT conditions, offshore kick scenarios for non-aqueous drilling fluids and dynamic kick control methods are simulated. Simulation results indicate that the model enables real-time estimation of crucial parameters during well control, such as the wellbore pressure and temperature profiles, increased outflow and pit gain during kicks, gas thermodynamic behavior including solubility and unloading behavior at low pressure conditions, gas rising velocity, and temperature-dependent formation strength.

Temperature-Dependent Formation of N-Nitrosodimethylamine during the Storage of Ranitidine Reagent Powders and Tablets.

The purpose of this study was to elucidate the effect of high-temperature storage on the stability of ranitidine, specifically with respect to the potential formation of N-nitrosodimethylamine (NDMA), which is classified as a probable human carcinogen. Commercially available ranitidine reagent powders and formulations were stored under various conditions, and subjected to LC-MS/MS analysis. When ranitidine tablets from two different brands (designated as tablet A and tablet B) were stored under accelerated condition (40 °C with 75% relative humidity), following the drug stability guidelines issued by the International Conference on Harmonisation (ICH-Q1A), for up to 8 weeks, the amount of NDMA in them substantially increased from 0.19 to 116 ppm and from 2.89 to 18 ppm, respectively. The formation of NDMA that exceeded the acceptable daily intake limit (0.32 ppm) at the temperature used under accelerated storage conditions clearly highlights the risk of NDMA formation in ranitidine formulations when extrapolated to storage under ambient conditions. A forced-degradation study under the stress condition (60 °C for 1 week) strongly suggested that environmental factors such as moisture and oxygen are involved in the formation of NDMA in ranitidine formulations. Storage of ranitidine tablets and reagent powders at the high temperatures also increased the amount of nitrite, which is considered one of the factors influencing NDMA formation. These data indicate the necessity of controlling/monitoring stability-related factors, in addition to controlling impurities during the manufacturing process, in order to mitigate nitrosamine-related health risks of certain pharmaceuticals.

Temperature-Dependent Formation of Acetophenone Oligomers Accompanied by Keto–Enol Tautomerism: Real Space Distribution

We present a mechanistic study addressing formation, adsorption configuration, and stability of acetophenone oligomers on a catalytically active Pt(111) surface by a combination of scanning tunneli...

Temperature Window for Encapsulation of an Enzyme into Thermally Shrunk, CaCO3 Templated Polyelectrolyte Multilayer Capsules.

Encapsulation of enzymes allows to preserve their biological activities in various environmental conditions, such as exposure to elevated temperature or to proteases. This is particularly relevant for in vivo applications, where proteases represent a severe obstacle to maintaining the activity of enzymes. Polyelectrolyte multilayer capsules are suitable for enzyme encapsulation, where CaCO3 particles and temperature-dependent capsule formation are the best templates and the most adequate method, respectively. In this work, these two areas are combined and, ALP (alkaline phosphatase), which is a robust and therapeutically relevant enzyme, is encapsulated into thermally shrunk polyelectrolyte multilayer (PDADMAC/PSS)4 capsules templated on calcium carbonate particles (original average diameter: ≈3.5 µm). The activity of the encapsulated enzyme and the optimal temperature range for encapsulation are investigated. The enzymatic activity is almost four times higher upon encapsulation when the temperature range for encapsulation is situated just above the glass transition temperature (40 °C), while its optimal conditions are dictated, on the one hand, by the enzyme activity (better at lower temperatures) and, on the other hand, by the size and mechanical properties of capsules (better at higher temperatures).

Improved thermal stability of luminescence by anion modification in Na2Y(MoO4)(PO4):Tb3+,Eu3+ red-emitting phosphors

Abstract Polyhedral anions have been used as supporting host structure to improve the luminescent properties of phosphors. However, the underlying mechanism for improving the thermal stability of luminescence by anion modification is rarely studied. In this paper, it was reported for the first time that thermal quenching and luminescent properties of red-emitting phosphors, Na2-nY(MoO4)1+n(PO4)1-n:Tb3+,Eu3+, can be adjusted by the ratio of acid radicals. Rietveld refinements and Debye temperature calculations show that the subtle replacement of [MoO4]2– by [PO4]3– results in the shrinkage of the crystal lattice and an improvement in lattice rigidity of the host, but does not change the crystal type. A detailed explanation of the mechanism for adjustable thermal stability of luminescence is provided via temperature-dependent X-ray diffraction, Raman, formation energy, and work function. The strategy of anion modification reveals an effective method for improving the thermal stability and tuning the luminescent spectra of phosphors, it also sheds light on the development of new phosphors. Furthermore, Na1.4Tb0.5(MoO4)1.6(PO4)0.4:0.5Eu3+ red-emitting phosphor with an internal quantum efficiency of 66.67% can be efficiently excited with blue light (465 nm) and the integrated intensity at 425 K is 86.4% of that at 300 K. The controllable local structure-dependent luminescence makes this novel red-emitting phosphor attractive for both blue and near-UV chips based WLEDs.

Determination of critical micelle temperature of Pluronic® in Pluronic/gel phase liposome mixtures using steady-state anisotropy

Abstract Stealth strategies have improved some properties of drug nanocarriers, including circulation time in vivo and kinetic stability, which led to the novel-generation of stealth liposomes. Among these, Pluronic®/lipid mixtures provide one of the simplest and lowest-cost stealth liposomes, although the formation of Pluronic micelles above its critical micelle temperature (CMT) concurrently lead to undesirable effects in a drug-carrier approach. Recently, we proposed a fluorometric method to determine the CMT of Pluronics in Pluronic/fluid phase liposome mixtures, but the method fails in the presence of gel phase liposomes (Calori et al., 2019). The present study aimed to develop a simple and highly sensitive fluorometric method based on steady-state anisotropy (r) of 1,6-diphenyl-1,3,5-hexatriene (DPH) to determine CMT of Pluronics in Pluronic/gel phase liposome mixtures. From our results it was showed that rDPH is >0.2 in gel phase liposomes, but lower than that in Pluronic micelles. As a consequence, a drastic drop in rDPH values occurs with temperature-dependent micelle formation in Pluronic/lipid mixtures, due to the partitioning of DPH, previously loaded in liposomes, in formed micelles. The 1/rDPH values led to a clear and elegant deflection point assumed to be CMT, as confirmed by dynamic light scattering. By combining this novel method with response surface methodology, partial phase diagrams of the boundary between liposome and liposome plus Pluronic micelle can be obtained with few assays. This method may be also useful for the optimization of other stealth liposomes for application as drug delivery systems of prolonged circulation time in vivo.

Synthesis of 3-S- and 3-Se-glycals by using R-S-S-R and R-Se-Se-R as the nucleophile precursors promoted by Hf(OTf)4 and the temperature-dependent formation of the above-mentioned 3-S- and 3-Se products

By using Hf(OTf)4 as the catalyst, under certain conditions, reaction of tri-O-acetyl-d-glucal and ((2R ,3S)-3-acetoxy-2,3-dihydrofuran-2-yl)methyl acetate with alkyl(aryl) bisulfide/alkyl(aryl) biselenide as nucleophile precursor leads to temperature-dependent formation of C-1-S/Se and C-3-S/Se product. A temperature-dependent profile of the yield of these two products is given.

Crystallisation of iPB-1 based on preserved helix conformation

The intriguing problem during polymer crystallisation is to understand the crystal formation and transition, in particular the initiation in a liquid melt close to solid crystals and one solid crystal close to another. Polymorphic isotactic polybutene-1 (iPB-1) usually crystallises into kinetically favoured metastable form II from melt and then spontaneously transits to thermodynamically stable form I. Keeping in mind that polymer crystallisation is controlled by temperature-dependent prior chain conformation formation, we first successfully conserved form-I-favoured 3/1 helix conformation at low temperatures and determined its decomposition temperature as Td,3/1 = 132 °C. The detailed temperature-dependent helix conformation evolution of iPB-1 during the cooling/heating processes was outlined and the subsequent easy direct form I crystallisation via necessary diffusion and alignment of the preserved 3/1 helix conformation was deduced. The results would be helpful to understand the helix conformation roles in polymer crystallisation, polymorph selection and crystal transition.

Elastic strain-hardening and shear-thickening exhibited by thermoreversible physical hydrogels based on poly(alkylene oxide)-grafted hyaluronic acid or carboxymethylcellulose.

The formation of strongly elastic physical gels based on poly(alkylene oxide)-grafted hyaluronan or carboxymethylcellulose, exhibiting both shear-thickening and strain-hardening have been studied using rheometry and explained using a slightly different interpretation of the transient network theory. The graft copolymers were prepared by a quantitative coupling reaction. Their aqueous solutions displayed a thermoreversible continuous transition from Newtonian fluid to viscoelastic solid which could be controlled by the reaction conditions. The evolution of all material properties of the gel could be categorized into two distinct temperature regimes with a fast evolution at low temperatures followed by a slow evolution at high temperatures. The activation energy of the zero shear viscosity and the relaxation time of the graft inside the interconnecting microdomains were almost identical to each other in both temperature regimes. This suggests that the number of microdomains remained approximately constant whereas the aggregation number inside the microdomains increased according to the binodal curve of the thermosensitive graft.

Controlled growth of large-scale uniform 1T' MoTe2 crystals with tunable thickness and their photodetector applications.

The monoclinic-phase 1T' MoTe2 crystal exhibits inversion symmetry as an anisotropic semi-metal, dictating its interesting quantum transport phenomenon and other novel physical properties. However, large-scale controllable growth of uniform MoTe2 crystals still remains a great challenge, hindering its further fundamental research and applications for novel devices. Herein, we report a modified growth method for synthesizing few-layer 1T' MoTe2 crystals with large-scale uniformity with the assistance of molecular sieves. The theoretical simulations demonstrated that due to the temperature-dependent formation energies of different edges, the edge of (010) orientation shows a higher thermodynamic stability than that of (100) orientation, and results in the anisotropic growth behavior of 1T' MoTe2 crystals while the temperature changes. The photoresponse of tri-layer 1T' MoTe2-based devices shows a broad-spectrum response from 532 nm to 1550 nm. The photo-response time of 1T' MoTe2 crystals demonstrates that it supposes to be the synergistic mechanism of photo-conductive and photo-radiation effects. Our findings not only provide a method for the controllable growth of anisotropic two-dimensional materials at a wafer scale, but also explore a broad-spectrum photodetector with the MoTe2-based device.

Temperature Activates Contact Aging in Silica Nanocontacts

Temperature-dependent atomic bond formation plays a dominant role in the generation of friction between nanoscale silica structures and an adjacent wafer, according to new experiments and simulations.

Temperature-dependent formation of redox sites in molybdenum trioxide studied by electron paramagnetic resonance spectroscopy

The formation and qualification of redox sites in transition metal oxides are always the active fields related to electronics, catalysis, sensors, and energy-storage units. In the present study, the temperature dependence of thermal reduction of MoO3 was surveyed at the range of 350 °C to 750 °C. Upon reduction, the formed redox species characterized by EPR spectroscopy are the MoV ion and superoxide anion radical (O2−) when the reduction was induced at the optimal temperature of 300−350 °C. When heating-up from 350 °C, the EPR signals started to decline in amplitude. The signals in the range of 400−450 °C decreased to half of that at 350 °C, and then to zero at ∼600 °C. Further treatment at even higher temperature or prolonged heating time at 500 °C caused more reduction and more free electrons were released to the MoO3 bulk, which results in a delocalized means similar to the anti-ferromagnetic coupling. These data herein are helpful to prepare and study the metal-oxide catalysts.

Structure and energetics of carbon defects in SiC (0001)/SiO2 systems at realistic temperatures: Defects in SiC, SiO2, and at their interface

We report systematic first-principles calculations that reveal the atomic configurations, stability, and energy levels of carbon defects in SiC (0001)/SiO2 systems. We clarify the stable position (i.e., in SiC, SiO2, or at SiC/SiO2 interfaces) of defects depending on the oxidation environment (an oxygen-rich or -poor condition). At finite temperatures, the chemical potential of atomic species was corrected referring to thermochemical tables in order to obtain the temperature-dependent defect formation energies. Under an oxygen-rich condition, we found that the dicarbon antisite [(C2)Si] in SiC is one of the favorable defects at a typical oxidation temperature of 1600 K and it creates a localized level near the conduction band edge of SiC, being a critical defect for n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs). A variety of carbon-dimer defects at a SiC/SiO2 interface, such as Si—CO—CO2, Si—CO—CO—Si, and Si—(CO)—CO2, are stable under the oxygen-rich condition at 1600 K, and they create localized levels relatively close to the valence band edge of SiC, thus being critical defects for p-channel MOSFETs. In the viewpoint of static energetics, our results suggest that the oxidation of SiC under a high-temperature oxygen-poor condition is effective in suppressing the generation of carbon defects.

Correction to: Photo- and temperature-dependent formation of tryptophan/silver nanoparticles

In the original publication of the article, the co-author’s name was incorrectly published as “O. N. Kachalova”.

Numerical investigation of the WC re-precipitation impact on the residual stress state in WC20 wt.-%Co hardmetal

In WC-Co hardmetals severe micro stresses form between the carbide and binder phases during the cooling stage of the liquid phase sintering process. The main cause of these micro residual stresses is the difference in the coefficients of thermal expansion in each of the constituent phases. There have also been discussions as to whether or not the solution and re-precipitation of elemental tungsten may be an additional driver for the temperature-dependent formation of residual stresses [1, 2]. To further investigate the influence of the re-precipitation effect on the residual stress state in hardmetals, a numerical approach combining the diffusion modelling capabilities of thermocalc/DICTRA [3] is applied in conjunction with temperature-dependent nonlinear mechanical analysis utilizing the finite element method. This combination allows for a qualitative estimate of the re-precipitation effect on the final residual stress state in hardmetals. Additionally, the temperature dependence of the residual stress state in hardmetals is investigated, with and without consideration of the solution and re-precipitation of W and C in the binder.A detailed 2.5D representative volume element based on EBSD images of a WC20wt.-%Co hardmetal has been derived for use in mechanical FE simulation. In the mechanical analysis, the cobalt binder is modelled as temperature-dependent elastic-viscoplastic isotropic material with isotropic hardening. Carbides are modelled as purely orthotropic elastic materials with temperature-dependent description of the elastic constants. The DICTRA results are applied as additional internal loads to the mechanical model via two equivalent coefficients of thermal expansion. A comparison of model results obtained with and without re-precipitation effect permits the impact of the re-precipitation effect on the residual stress state to be examined qualitatively.Finally, the model results are compared to experimental measurements of the residual stress state in WC20wt.-%Co hardmetal specimens, obtained via neutron diffraction.

Dual-Responsive Photocatalytic Polymer Nanogels.

Selective activation of photocatalysts under constant light conditions has recently been targeted to produce multi-responsive systems. However, controlled activation, with easy recovery of the photocatalysts, induced by external stimuli remains a major challenge. Mimicking the responsiveness of biological systems to multiple triggers can offer a promising solution. Herein, we report dual-responsive polymer photocatalysts in the form of nanogels consisting of a cross-linked poly-N-isopropylacrylamide nanogel, copolymerised with a photocatalytically active monomer. The dual-responsive polymer nanogels undergo a stark decrease in diameter with increasing temperature, which shields the photocatalytic sites, decreasing the activity. Temperature-dependent photocatalytic formation of NAD+ in water demonstrates the ability to switch photocatalysis on and off. Moreover, the photocatalysed syntheses of several fine chemicals were carried out to demonstrate the utility of the designed material.

Self-Assembly of the Bio-Surfactant Aescin in Solution: A Small-Angle X-ray Scattering and Fluorescence Study

This work investigates the temperature-dependent micelle formation as well as the micellar structure of the saponin aescin. The critical micelle concentration ( c m c ) of aescin is determined from the concentration-dependent autofluorescence (AF) of aescin. Values between c m c aescin , AF (10 ∘ C) = 0.38 ± 0.09 mM and c m c aescin , AF (50 ∘ C) = 0.32 ± 0.13 mM were obtained. The significance of this method is verified by tensiometry measurements. The value determined from this method is within the experimental error identical with values obtained from autofluorescence ( c m c aescin , T ( WP ) (23 ∘ C) = 0.33 ± 0.02 mM). The structure of the aescin micelles was investigated by small-angle X-ray scattering (SAXS) at 10 and 40 ∘ C. At low temperature, the aescin micelles are rod-like, whereas at high temperature the structure is ellipsoidal. The radii of gyration were determined to ≈31 Å (rods) and ≈21 Å (ellipsoid). The rod-like shape of the aescin micelles at low temperature was confirmed by transmission electron microscopy (TEM). All investigations were performed at a constant pH of 7.4, because the acidic aescin has the ability to lower the pH value in aqueous solution.

Shape-preserving machining produces gradient nanolaminate medium entropy alloys with high strain hardening capability

A high density of grain boundaries can potentially increase structural materials' strength, but at the expense of losing the materials' strain hardening ability at high flow stress levels. However, endowing materials with grain size gradients and a high density of internal interfaces can simultaneously increase the strength and strain hardening ability. This applies particularly for through-thickness gradients of nanoscale interface structures. Here we apply a machining method that produces metals with nanoscale interface gradients. Conventional bulk plastic deformation such as rolling, a process applied annually to about 2 billion tons of material, aims to reduce the metal thickness. We have modified this process by introducing severe strain path changes, realized by leading the sheet through a U-turn while preserving its shape, an approach known as ‘hard turning’. We applied this process at both room temperature and 77 K to a NiCrCo medium entropy alloy. Micropillar compression was conducted to evaluate the mechanical response. After hard turning at room temperature, the surface microstructure obtained a ∼50% increase in yield stress (0.9 GPa) over the original state with homogeneous grain size (0.4 GPa), but the initial strain hardening rate did not show significant improvement. However, after hard turning at 77 k, the gradient nanolaminate structure tripled in yield stress and more than doubled its initial strain hardening rate. The improvements were achieved by introducing a specific microstructure that consists of gradient nanolaminates in the form of nanospaced twins and martensite in the face center cubic (fcc) phase. This microstructure was formed only at cryogenic temperature. It was found after turning at room temperature that only nanospaced twins were present in the fcc phase inside nanolaminates that had formed at the surface. The origin of the enhanced strain hardening mechanism was studied. Joint density functional theory (DFT) and axial next nearest neighbor Ising (ANNNI) models were used to explain the temperature-dependent phase formation of the NiCrCo nanolaminate at the surface of the hard-turned material.

19F Dark-State Exchange Saturation Transfer NMR Reveals Reversible Formation of Protein-Specific Large Clusters in High-Concentration Protein Mixtures.

Proteins frequently exist as high-concentration mixtures, both in biological environments and increasingly in biopharmaceutical co-formulations. Such crowded conditions promote protein–protein interactions, potentially leading to formation of protein clusters, aggregation, and phase separation. Characterizing these interactions and processes in situ in high-concentration mixtures is challenging due to the complexity and heterogeneity of such systems. Here we demonstrate the application of the dark-state exchange saturation transfer (DEST) NMR technique to a mixture of two differentially 19F-labeled 145 kDa monoclonal antibodies (mAbs) to assess reversible temperature-dependent formation of small and large protein-specific clusters at concentrations up to 400 mg/mL. 19F DEST allowed quantitative protein-specific characterization of the cluster populations and sizes for both mAbs in the mixture under a range of conditions. Additives such as arginine glutamate and NaCl also had protein-specific effects on the dark-state populations and cluster characteristics. Notably, both mAbs appear to largely exist as separate self-associated clusters, which mechanistically respond differently to changes in solution conditions. We show that for mixtures of differentially 19F-labeled proteins DEST NMR can characterize clustering in a protein-specific manner, offering unique tracking of clustering pathways and a means to understand and control them.

MADS-Box Genes are Involved in Cultivar- and Temperature-Dependent Formation of Multi-pistil and Polycarpy in Prunus avium L.

The frequent occurrence of polycarpy is the most serious problem directly compromising sweet cherry productivity in warm regions of the world. MADS-box genes play an important role in regulating the pistil development; however, limited evidence is available for understanding the regulatory mechanisms of MADS-box genes underlying multi-pistil formation in sweet cherry. In our study, we found that the multi-pistil occurred more frequently in the warm region of Shanghai than the cool region of Dalian. Particularly, the multi-pistil rate of ‘Tieton’ reaches 80–90%, which is much higher than that of ‘Lapins’ with 20–30% in Shanghai. PaAG, PaTM6, and PaMADS3/4/5/12 were found to be sensitive to different natural temperatures related to the formation of multiple pistils according to the quantitative real-time PCR assay. Moreover, the heat shock element in the promoter of PaMADS12 was identified. Using the GUS histochemical assay, we found that the expression level of the β-glucuronidase in the transgenic N. benthamiana leaves containing the GUS reporter gene driven by the PaMADS12 promoter was much higher at 35 °C than that at 25 °C. This suggested that PaMADS12 is a heat-induced transcription factor functioning in multi-pistil formation. Together, these results indicated that heat induced the expression of PaMADS12, and PaAG, PaTM6, and PaMADS3/4/5/12 were important components of the regulatory network controlling multi-pistil formation in sweet cherry.