Hasil untuk "Physical and theoretical chemistry"

Karaaslan Melek, Gokdere Nuran, Ozturk Batuhan et al.

Apple is one of the four most produced fruits in the world. The remaining pulp from production accounts for over 25 % of the processed fruit. Apple pulp and peel contain phenolic compounds such as flavonoids and flavonoid glycosides, making them a potential candidate for green nanoparticle synthesis. Green synthesis refers to the production of nanoparticles through a process that utilizes a natural molecule and metal salts as reducing agents. In this study, metal nanoparticles were synthesized using an extract prepared from apple pomace waste via green synthesis. The synthesized nanoparticles were characterized using UV–visible spectroscopy, Raman, optical microscopy, energy-dispersive X-ray, atomic force microscopy, and scanning electron microscope. The antibacterial, antibiofilm, antiquorum sensing, and anticancer activities of the synthesized nanoparticles were then investigated. According to the antibacterial activity results, the best activity was seen with silver nanoparticles against Staphylococcus epidermidis ATCC 12228 with 15.625 μg/mL. Similarly, the best antibiofilm activity was seen with silver nanoparticles. However, significant biofilm inhibition was seen with zinc nanoparticles, tin nanoparticles, and cobalt nanoparticles at higher concentrations. Anticancer activity was studied in six different cell lines: HCT-116 and SW480 colon cancer cell lines, A549 and H1975 lung cancer cell lines, and A2780 and OVCAR3 ovarian cancer cell lines. The best activity was shown with nickel nanoparticles.

Shantanu Mishra, Valentina Malave, Rasmus Svensson et al.

Skeletal editing of cyclic molecules has garnered considerable attention in the context of drug discovery and green chemistry, with notable examples in solution-phase synthesis. Here, we extend the scope of skeletal editing to the single-molecule scale. We demonstrate tip-induced oxygen deletion and ring contraction of an oxygen-containing seven-membered ring on bilayer NaCl films to generate molecules containing the perylene skeleton. The products were identified and characterized by atomic force and scanning tunneling microscopies, which provided access to bond-resolved molecular structures and orbital densities. Insights into the reaction mechanisms were obtained by density functional theory calculations. Our work expands the toolbox of tip-induced chemistry for single-molecule synthesis.

Sunil Pipliya, Sitesh Kumar, Prem Prakash Srivastav

The primary concern regarding the pineapple juice processing industry is its insufficient stability. The goal of this investigation is to evaluate the storage stability and shelf life of cold plasma (CP) and thermally treated pineapple juice samples (S1, untreated; S2, optimized plasma-treated; S3, extreme plasma-treated; S4, thermally-treated) packed in glass (GL) and polyethylene terephthalate (PET) bottles at 5, 15, and 25°C. The color parameters increased with time and storage temperature. However, the bioactive substances decreased during storage for all the samples. Moreover, all the samples at elevated temperatures showed a higher degradation rate for bioactive compounds and color parameters. The changes in color parameter values across all samples showed zero-order kinetics, while the bioactive compounds followed a 1st-order kinetics. The application of various packing materials and storage temperatures had a significant impact (p < 0.05) on the microbiological, enzyme inactivation, and biochemical characteristics of the samples. However, there was an insignificant effect (p > 0.05) on the pH, acidity, and soluble solids. CP and thermally-treated samples reduced natural microbiota below the detection limit (<1-log CFU/mL). The sensory quality of S2, S3, and S4 samples remained above the acceptable limit (OA>5) for 120 d at 5 ℃. The shelf-life of the optimized CP-treated juice sample packed in GL bottles was 90, 50, and 25 days at 5, 15, and 25°C, respectively, based on AA≥20 mg/100 mL, OA≥5, ΔE*≤12, and microbial count≤6-log CFU/mL. In conclusion, CP is an effective non-thermal method that may extend the shelf life of pineapple juice packed in GL bottles by up to 90 days in refrigerated conditions (5 °C).

A.M. Guseva, A.I. Sinkevich, S.D. Smetannikova et al.

The results of an experimental study of the magnetic domain structure on the basal plane of RFe11Ti single crystals (R=Y, Gd, Ho, Er) by magnetic force microscopy are presented. At room temperature, the compounds are characterized by magnetocrystalline anisotropy of the «easy axis» type. Based on the magnetic force microscopy data, the sizes of domains on the basal plane of the samples were determined. Using the Bodenberger-Hubert method, the surface energy density of domain walls γ was determined for all compounds based on the magnetic force microscopy data: YFe11Ti – 4,05 mJ/m2, GdFe11Ti – 5,93 mJ/m2, HoFe11Ti – 4,97 mJ/m2, ErFe11Ti – 2,98 mJ/m2. The cube counting method was used to calculate the fractal dimension DL of the stray fields of the domain structure at different heights from the surface (0,1 – 9 μm). DL on the surface of the z(0) sections has values of 2,62 for compounds with R = Y, Gd, Ho and 2,72 for R=Er. For all samples, DL has a maximum near the surface.

Adam D. Rains, Thomas Nordlander, Stephanie Monty et al.

Detailed chemical studies of F/G/K -- or Solar-type -- stars have long been routine in stellar astrophysics, enabling studies in both Galactic chemodynamics, and exoplanet demographics. However, similar understanding of the chemistry of M and late-K dwarfs -- the most common stars in the Galaxy -- has been greatly hampered both observationally and theoretically by the complex molecular chemistry of their atmospheres. Here we present a new implementation of the data-driven \textit{Cannon} model, modelling $T_{\rm eff}$, $\log g$, [Fe/H], and [Ti/Fe] trained on low-medium resolution optical spectra ($4\,000-7\,000\,$\SI{}{\angstrom}) from 103 cool dwarf benchmarks. Alongside this, we also investigate the sensitivity of optical wavelengths to various atomic and molecular species using both data-driven and theoretical means via a custom grid of MARCS synthetic spectra, and make recommendations for where MARCS struggles to reproduce cool dwarf fluxes. Under leave-one-out cross-validation, our \textit{Cannon} model is capable of recovering $T_{\rm eff}$, $\log g$, [Fe/H], and [Ti/Fe] with precisions of 1.4\%, $\pm0.04\,$dex, $\pm0.10\,$dex, and $\pm0.06\,$dex respectively, with the recovery of [Ti/Fe] pointing to the as-yet mostly untapped potential of exploiting the abundant -- but complex -- chemical information within optical spectra of cool stars.

Kourosh Darvish, Marta Skreta, Yuchi Zhao et al.

Chemistry experiments can be resource- and labor-intensive, often requiring manual tasks like polishing electrodes in electrochemistry. Traditional lab automation infrastructure faces challenges adapting to new experiments. To address this, we introduce ORGANA, an assistive robotic system that automates diverse chemistry experiments using decision-making and perception tools. It makes decisions with chemists in the loop to control robots and lab devices. ORGANA interacts with chemists using Large Language Models (LLMs) to derive experiment goals, handle disambiguation, and provide experiment logs. ORGANA plans and executes complex tasks with visual feedback, while supporting scheduling and parallel task execution. We demonstrate ORGANA's capabilities in solubility, pH measurement, recrystallization, and electrochemistry experiments. In electrochemistry, it executes a 19-step plan in parallel to characterize quinone derivatives for flow batteries. Our user study shows ORGANA reduces frustration and physical demand by over 50%, with users saving an average of 80.3% of their time when using it.

Balázs Bradák, Mayuko Nishikawa, Christopher Gomez

The study introduces a theory about a giant impact on the surface of Dione. Our study suspects a relatively low-velocity (≤5 km/s) collision between a c.a. 50–80 km diameter object and Dione, which might have resulted in the resurfacing of its intermediate cratered terrain. The source of the impactor might have been a unique satellite-centric debris, a unique impactor population, suspected in the Saturnian system. Other possible candidates are asteroid(s) appearing during the outer Solar System heavy bombardment period, or a collision, which might have happened during the “giant impact phase” in the early Saturnian system (coinciding with the Late Heavy Bombardment, or not).

Maxwell X. Cai, Kin Long Kelvin Lee

In physics, density $ρ(\cdot)$ is a fundamentally important scalar function to model, since it describes a scalar field or a probability density function that governs a physical process. Modeling $ρ(\cdot)$ typically scales poorly with parameter space, however, and quickly becomes prohibitively difficult and computationally expensive. One promising avenue to bypass this is to leverage the capabilities of denoising diffusion models often used in high-fidelity image generation to parameterize $ρ(\cdot)$ from existing scientific data, from which new samples can be trivially sampled from. In this paper, we propose $ρ$-Diffusion, an implementation of denoising diffusion probabilistic models for multidimensional density estimation in physics, which is currently in active development and, from our results, performs well on physically motivated 2D and 3D density functions. Moreover, we propose a novel hashing technique that allows $ρ$-Diffusion to be conditioned by arbitrary amounts of physical parameters of interest.

Junjie Cheng, Jie Hu, Jiawei Wang et al.

As oil and chemical spills pose a significant threat to the water environment, the need to develop efficient sorbent materials to remove oil and organic pollutants from water has arisen. This study aimed to develop a simple modification scheme to impart oil and water selective absorption capacity to a common three-dimensional porous material. Commercially available polyurethane sponges were used as the base material, and vinyl silica aerogel particles were loaded onto the sponges using polydimethylsiloxane as an adhesion agent. As a result, the water contact angle of the modified sponge increased from 118° to 149.2°, and the water absorption decreased from 106.5 g/g to 0.2 g/g; it could absorb oil in oil-water mixtures without absorbing water and maintain an excellent level of selective absorption ability after 20 cycles. This modification scheme is easy to operate and robust and is a scheme of practical application.

G. Velmurugan, V. Siva Shankar, L. Natrayan et al.

In the current scenario, natural fiber-based biodegradable composites have increased because natural composite fibers are very cheap, biodegradable, lightweight, fireproof, and nontoxic. The present research work was carried out to optimize the mechanical properties of hybrid composites reinforced by Calotropis gigantea and hemp. To achieve these objectives, the following process parameters were determined, and RSM carried out optimization with the Box-Behnken experimental setup at three different levels: compression molding temperature (°C), pressure (bar), and time (min). The fibers were pretreated for 4 hours with a 5% NaOH solution to prevent moisture absorption. Regression equations were constructed to evaluate the mechanical properties, and the best process parameters were established. The results reveal that a pressure of 35 bar, a time duration of 7 minutes, and a temperature of 176°C are the best conditions for compression molding. The second aim was to compare CGF and hemp fiber-derived activated carbon adsorbents by determining physical adsorption properties, chemical compositions, and scanning electron microscope. Natural fibers were shown to be ideal candidates for manufacturing mesoporous activated carbon adsorbents with high surface area (1389–1433 m2/g), high mesopore percentage (63–68%), and high carbon content (80–87%). Even though hemp activated carbon had a greater mesoporous structure (69%) than CGF-derived activated carbons, the CGF-derived activated carbons had larger surface areas and higher C content.

Hassien M. Alnashiri

The Red Sea forms an important marine ecosystem with its rich species diversity and the different ecosystems, including the coral reefs. The region has received relatively less heavy metal pollution owing to comparatively lesser industrial pollution. This study attempts to review the records of heavy metal bioaccumulation reported in the last two decades. This review is an endeavour to audit the heavy metal bioaccumulation, revealed over the past twenty years, such as As, Cr, Cu, Fe, Cd, Hg, Mn, Zn Ni, Co, Se, and Pb, as reported from various regions of the Red Sea in organisms such as plankton, molluscs, crustaceans, and fish. Though the results of various studies reviewed here are not comparable to each other due to differences in organisms, types of tissues studied, and different methods of analysis as well as nature of their inhabiting sites, this review will be a baseline data of the heavy metal bioaccumulation, which can help in future evaluation in the context of the rapid developmental activity prevalent in the coasts of the Red Sea. The findings compiled emphasize the need for a comprehensive biomonitoring program that can conserve the unique biodiversity of the Red Sea.

G. Sanzone, Jinlong Yin, Hai-lin Sun

Many research works have demonstrated that the combination of atomically precise cluster deposition and theoretical calculations is able to address fundamental aspects of size-effects, cluster-support interactions, and reaction mechanisms of cluster materials. Although the wet chemistry method has been widely used to synthesize nanoparticles, the gas-phase synthesis and size-selected strategy was the only method to prepare supported metal clusters with precise numbers of atoms for a long time. However, the low throughput of the physical synthesis method has severely constrained its wider adoption for catalysis applications. In this review, we introduce the latest progress on three types of cluster source which have the most promising potential for scale-up, including sputtering gas aggregation source, pulsed microplasma cluster source, and matrix assembly cluster source. While the sputtering gas aggregation source is leading ahead with a production rate of ∼20 mg·h−1, the pulsed microplasma source has the smallest physical dimensions which makes it possible to compact multiple such devices into a small volume for multiplied production rate. The matrix assembly source has the shortest development history, but already show an impressive deposition rate of ~10 mg·h−1. At the end of the review, the possible routes for further throughput scale-up are envisaged.