Complexity of confined water vitrification and its glass transition temperature.

The ability of vitrification when crossing the glass transition temperature (Tg) of confined and bulk water is crucial for myriad phenomena in diverse fields, ranging from the cryopreservation of organs and food to the development of cryoenzymatic reactions, frost damage to buildings, and atmospheric water. However, determining water's Tg remains a major challenge. Here, we elucidate the glass transition of water by analyzing the calorimetric behavior of nano-confined water across various pore topologies (diameters: 0.3 to 2.5 nm). Our approach involves subjecting confined water to annealing protocols to identify the temperature and time evolution of nonequilibrium glass kinetics. Furthermore, we complement this calorimetric approach with the dynamics of confined water, as seen by broadband dielectric spectroscopy and linear calorimetric measurements, including the fast scanning technique. This study demonstrated that confined water undergoes a glass transition in the temperature range of 170 to 200 K, depending on the confinement size and the interaction with the confinement walls. Moreover, we also show that the thermal event observed at ~136 K must be interpreted as an annealing prepeak, also referred to as the "shadow glass transition." Calorimetric measurements also allow the detection of a specific heat step above 200 K, which is insensitive to annealing and, thereby, interpreted as a true thermodynamic transition. Finally, by connecting our results to bulk water behavior, we offer a comprehensive understanding of confined water vitrification with potential implications for numerous applications.

An Exceptionally Salt Tolerant Copoly(Maleimide Sulfobetaine) - Structural Requirements for Ultra-Salt Tolerance.

Zwitterionic polymers are an important class of polymers with far-ranging applications. In the widely studied poly(meth)acrylate and poly(meth) acrylamide-based zwitterions, properties can be tuned by changing the nature of substituents attached to ammonium ions. However, these changes influenced salt tolerance of zwitterionic polymers only to a limited extent. Upon adding salt these polymers expanded in solution initially. Further increase in salt concentration caused the polymer chains to shrink similar to the common water soluble, uncharged polymers thereby deteriorating the viscosity of aqueous solutions. In contrast to the conventional poly(meth)acrylate and poly(meth)acrylamide-based zwitterions, zwitterionic copolymaleimides showed substituent dependent salt-tolerant nature. In the absence of any substituent on the polymer backbone such as zwitterionic poly(ethylene-alt-maleimide) (ZI-PEMA) the viscosity of salt solutions increased both with the increasing salt concentration as well as the concentration of polymer. This is likely due to the continuous expansion of polymer coil in salt solutions with increasing salt concentration caused primarily by the rigidity of the polymer backbone. ZI-PEMA also enhanced the saturation limit of mono- and divalent salts like sodium chloride and hydrated calcium bromide in water. This property is useful for various applications like fish curing, for making high-density fluids, refrigeration, etc. across various industrial sectors.

The effect of cobalt alloying on the phase transformation kinetics of Ni-Ti alloys.

This study investigates the influence of cobalt (Co) alloying addition and heat treatment temperature on the phase transformation behaviour controlling the superelasticity and shape memory effect (SME) of Nickel-Titanium (Ni-Ti) alloys, commonly known as nitinol. The microstructural evolution upon heat treatment conducted at a temperature ranging from 440 to 560 °C was thoroughly analyzed via Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), and Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS). Increase in heat treatment temperatures from 470 °C up to 530 °C led to the dissolution of particles present in as-received (cold-worked) condition. It was determined that Co addition into the Ni-Ti alloy system resulted in a change in the nucleation and growth kinetics of Ti-rich precipitates, leading to the formation of larger and fewer particles during processing. Both binary and ternary alloys showed a decrease in austenite finish temperature (Af) with increasing heat treatment temperatures, however, the rate of decrease was found to be higher for Co containing ternary alloys. This is linked with faster structural relaxation when Co is present and evidenced by lattice size variation during heat treatment. It is highlighted that heat treatment methodology needs to be tailored to the specific alloy composition for controlling superelasticity and SME via alloy design.

Structure and Characterization of Catanionic Complexes and Biocompatible Vesicles of N-Acyltaurine and Sarcosine Alkyl Ester: Encapsulation and Release Studies with 5-Fluorouracil.

Hydrated dispersions containing equimolar mixtures of cationic and anionic amphiphiles, referred to as catanionic systems, exhibit synergistic physicochemical properties, and mixing single-chain cationic and anionic lipids can lead to the spontaneous formation of vesicles as well as other phase structures. In the present work, we have characterized two catanionic systems prepared by mixing N-acyltaurines (NATs) and sarcosine alkyl esters (SAEs) bearing 11 and 12 C atoms in the acyl/alkyl chains. Turbidimetric and isothermal titration calorimetric studies revealed that both NATs form equimolar complexes with SAEs having matching acyl/alkyl chains. The three-dimensional structure of the sarcosine lauryl ester (lauryl sarcosinate, LS)-N-lauroyltaurine (NLT) equimolar complex has been determined by single-crystal X-ray diffraction. The LS-NLT equimolar complex is stabilized by electrostatic attraction and multiple hydrogen bonds, including classical, strong N-H···O hydrogen bonds as well as several C-H···O hydrogen bonds between the two amphiphiles. DSC studies showed that both equimolar complexes show single sharp phase transitions. Transmission electron microscopy and dynamic light scattering studies have demonstrated that the LS-NLT catanionic complex assemblies yield stable medium-sized vesicles (diameter 280-350 nm). These liposomes were disrupted at high pH, suggesting that the designed catanionic complexes can be used to develop base-labile drug delivery systems. In vitro studies with these catanionic liposomes showed efficient entrapment (73% loading) and release of the anticancer drug 5-fluorouracil in the physiologically relevant pH range of 6.0-8.0. The release rate was highest at pH 8.0, reaching about 78%, 90%, and 100% drug release at 2, 6, and 12 h, respectively. These observations indicate that LS-NLT catanionic vesicles will be useful for designing drug delivery systems, particularly for targeting organs such as the colon, which are inherently at basic pH.

Unveiling the multifaceted interactions of antitumor drug mitoxantrone with ct-DNA through biophysical and in silico studies.

Mitoxantrone, an anthraquinone derivative, is a widely used anticancer drug with its well-known ability to engage in complex interactions with DNA. Although known for its intercalating ability, the enigma surrounding its binding modes with DNA persists. The existing corpus of literature primarily focuses on mitoxantrone-DNA interactions with short DNA sequences, thereby yielding insights into its interactive nature is limited to this specific sequence. This study aims to elucidate the diverse modes with which mitoxantrone interacts with calf thymus DNA using a combination of spectroscopy, calorimetry and in silico studies. The findings from spectroscopic, calorimetric and molecular dynamic results in correlation with existing literature, unveil a fascinating narrative: mitoxantrone intercalates at lower concentrations but promotes condensation at higher concentrations. Although intercalation with side chains positioned in the minor/major groove is the major binding mode in GC-rich sequences, molecular modelling studies hint at an alternative binding mode in AT-rich sequences where it exclusively displays pure electrostatic interaction. These findings underscore the pivotal role of both drug structure and base sequence in dictating binding mode and affinity. Such insights not only deepen the understanding of structure-activity relationships but also hold promise for guiding future drug design strategies.

Thermodynamic Study of 1,4-Bis(3-methylimidazolium-1-yl)butane Bis(trifluoromethylsulfonyl)imide ([C4(MIm)2][NTf2]2) from 6 to 350 K.

The molar heat capacity of 1,4-bis(3-methylimidazolium-1-yl)butane bis(trifluoromethylsulfonyl)imide dicationic ionic compound ([C4(MIm)2][NTf2]2) has been studied over the temperature range from 6 to 350 K by adiabatic calorimetry. In the above temperature interval, this compound has been found to form crystal, liquid, and supercooled liquid. For [C4(MIm)2][NTf2]2, the temperature of fusion T°fus = (337.88 ± 0.01) K has been determined by the fractional melting experiments, the enthalpy of fusion ΔfusH° = (52.79 ± 0.28) kJ mol-1 has been measured using the calorimetric method of continuous energy input, and the entropy of fusion ΔfusS° = (156.2 ± 1.7) J K-1 mol-1 has also been evaluated. The standard thermodynamic functions of the studied dicationic ionic compound, namely, the heat capacity Cp°(T), the enthalpy [H°(T) - H°(0)], the entropy S°(T) and the Gibbs free energy [G°(T) - H°(0)] have been calculated on the basis of the experimental data for the temperature range up to 350 K. The results have been discussed and compared with those available in the literature and in the NIST Ionic Liquids Database (ILThermo) for monocationic ionic compounds.

Comparative Studies for Cryopreservation of Agave Shoot Tips by Droplet-Vitrification.

The objective of this work was to assess the suitability of the Droplet-vitrification protocol previously developed with Agave peacockii shoot tips for the cryopreservation of six Agave species. Shoot tips were precultured for 1 day on a medium with 0.3 M sucrose in the dark, loaded in a solution with 1.6 M glycerol and 0.4 M sucrose for 20 min, and dehydrated by exposure to Plant Vitrification Solution 2 (PVS2) at 0 °C for 20 min. Complementary studies using histological analysis, Differential scanning calorimetry (DSC), and evaluation of morphological characteristics in cryo-derived plants were performed. Survival rates ranged from 84% to 100% and from 76% to 97% before and after cryopreservation regardless of the Agave species belonging to two taxonomic subgenera. Thermal analysis of shoot tips subjected to the successive steps of the Droplet-vitrification protocol identified ice crystal formation after loading treatment and glass transition after osmotic dehydration with PVS2. The average glass transition temperature (Tg) was -55.44 °C based on the results of four Agave species. The histological studies showed the anatomical differences that could be found in the meristematic structures depending on the loss of apical dominance. This is the most advanced research on cryopreservation of Agave shoot tips.

Sum of Skinfold-Corrected Girths Correlates with Resting Energy Expenditure: Development of the NRGCO Equation.

Our study aimed to validate existing equations and develop the new NRGCO equation to estimate resting energy expenditure (REE) in the Colombian population with moderate-to-high physical activity levels. Upon satisfying the inclusion criteria, a total of 86 (43F, 43M) healthy adults (mean [SD]: 27.5 [7.7] years; 67.0 [13.8] kg) were evaluated for anthropometric variables and REE by indirect calorimetry using wearable gas analyzers (COSMED K4 and K5). Significant positive correlations with REE were found for body mass (r = 0.65), body mass-to-waist (r = 0.58), arm flexed and tensed girth (r = 0.66), corrected thigh girth (r = 0.56), corrected calf girth (r = 0.61), and sum of breadths (∑3D, r = 0.59). As a novelty, this is the first time a significant correlation between REE and the sum of corrected girths (∑3CG, r = 0.63) is reported. Although existing equations such as Harris-Benedict (r = 0.63), Mifflin-St. Jeor (r = 0.67), and WHO (r = 0.64) showed moderate-to-high correlations with REE, the Bland-Altman analysis revealed significant bias (p < 0.05), indicating that these equations may not be valid for the Colombian population. Thus, participants were randomly distributed into either the equation development group (EDG, n = 71) or the validation group (VG, n = 15). A new model was created using body mass, sum of skinfolds (∑8S), corrected thigh, corrected calf, and age as predictors (r = 0.755, R2 = 0.570, RMSE = 268.41 kcal). The new NRGCO equation to estimate REE (kcal) is: 386.256 + (24.309 × BM) - (2.402 × ∑8S) - (21.346 × Corrected Thigh) + (38.629 × Corrected Calf) - (7.417 × Age). Additionally, a simpler model was identified through Bayesian analysis, including only body mass and ∑8S (r = 0.724, R2 = 0.525, RMSE = 282.16 kcal). Although external validation is needed, our validation resulted in a moderate correlation and concordance (bias = 91.5 kcal) between measured and estimated REE values using the new NRGCO equation.

Whole-body volume of oxygen consumption while walking: Agreement between measured and estimated values.

Predictive equations are widely employed for estimating the volume of oxygen consumption (VO2) while walking, which is ultimately employed to determine energy expenditure and tailor exercise prescription. This study aimed to test the agreement between the measured VO2 and estimated VO2 during a walking protocol on a treadmill at 3.5, 4.5, 5.5, and 6.5 km/h. Thirty-eight young adults (50% women) participated in this cross-sectional study. The Omnical (Maastricht Instruments, Maastricht, The Netherlands) and K5 (Cosmed, Rome, Italy) metabolic systems were used to measure VO2. To determine the predictive equations, a comprehensive literature search was conducted using the MEDLINE database from May 2022 to July 2023. Seven predictive equations were found and included for estimating VO2 values. We calculated the mean bias (mean difference between measured VO2 and estimated VO2) obtained at each speed using one-sample t-tests. We compared the VO2 measured and estimated values using repeated measures analysis of variance and the Bland-Altman method. One-sample t-tests showed that all score errors were different from zero (ranging from 1.1 to 5.4 mL/kg/min). Thus, no predictive equation estimated similar VO2 values in comparison with the Omnical and K5 metabolic systems at all intensities. However, the Weyand equation showed the lowest bias across all intensities (score error of 1.1 mL/kg/min). This study showed a lack of agreement between the Omnical and K5 systems compared to diverse predictive equations specially designed to estimate VO2 during walking. Nevertheless, based on our results, the Weyand equation should be the preferred option.

Efficacy of providing energy expenditure information to guide weight loss interventions in people with obesity: A randomized controlled trial.

Resting energy expenditure (REE) and metabolic fuel utilization (carbohydrate or fat) proxied by respiratory quotient (RQ) from indirect calorimetry enables more precise measurement of energy needs and fat oxidation capacity. The study compared the effectiveness of providing energy expenditure information during diet and exercise weight intervention versus standard of care (SOC) on weight loss outcomes. Fifty-two participants with obesity were recruited from a specialist weight loss service, randomized 1:1 to intervention (INT) or SOC only. Participants in INT received four-weekly dietetic counselling, using biofeedback from energy expenditure data to recommend caloric restriction and physical activity goals, in addition to SOC. The primary outcome was the mean difference in weight loss between both groups after 24 weeks. Secondary outcomes include participant acceptability and tolerability using indirect calorimetry. Participants in the INT group demonstrated additional weight loss (-2.3 kg [95% CI: -3.1, -1.5]; p <.001), reduced waist circumference (-3.9 cm [95% CI: -5.48, -2.26]; p <.001), and decreased body fat percentage (-1.5% [95% CI:-2.31, -0.72], p <.001), compared to SOC, after adjusting for baseline body mass index, age, and sex. Forty-two percent (10/24) of participants in INT group achieved the minimum clinically significant threshold of 5% weight loss from baseline, compared to 8% (2/26) in the SOC group (p = .007). Participant acceptability and tolerability of indirect calorimetry were high, with mean scores of 4.5 ± 0.6 and 4.2 ± 0.7 (5-point Likert scale). The study establishes the safety and practical integration of biofeedback using indirect calorimetry promoting improved self-regulation and enhancing weight loss.