Hasil untuk "Chemical industries"

J. Hartnett, T. Irvine, Young I Cho et al.

A. Ghaly, D. Dave, S. Budge et al.

Problem statement: Spoilage of food products is due to chemical, enzy matic or microbial activities One-fourth of the world's food supply an d 30% of landed fish are lost through microbial activity alone. With the ever growing world populat ion and the need to store and transport the food from one place to another where it is needed, food preservation becomes necessary in order to increase its shelf life and maintain its nutritional value, texture and flavor. The freshness and quality of fi sh have always gained the attention by Food Regulatory Agencies and Food Processing Industry. Proper handling, pretreatment and preservation techniques can improve the quality fish and fish products and increase their shelf life. Methodology: Historically salting, drying, smoking, fermentation and canning were the methods to prevent fish spoilage and exten d its shelf life. In response to consumer demand fo r texture, appearance and taste, new methods were developed including: Cooling, freezing and chemical preservation. A comprehensive review of the literat ure on the subject of fish spoilage and modern preservation techniques was carried out. Conclusion: Fish spoilage results from three basic mechanisms: Enzymatic autolysis, oxidation, microbial growth. Low temperature storage and chemical techniques for controlling water activity, enzymati c, oxidative and microbial spoilage are the most common in the industry today. A process involving t he addition of an EDTA (1 mM)-TBHQ (0.02%) combination and ascorbic acid and storage at refrig erated temperatures (5°C) in darkness can be the most positive for controlling the spoilage of fish and fish product. The suggested process would address antimicrobial activity as well as destructi ve oxidation of the desired lipids and fats. Howeve r, more efforts are required to understand the role of proximate composition of fish, post harvest histor y, environmental conditions, initial microbial load, t ype and nature of bacteria and their interaction in order to optimize the shelf-life of fish.

Mingliang Du, B. Guo, D. Jia

Poulomi Sannigrahi, A. Ragauskas, G. Tuskan

Pilar Jerez-Gómez, J. Céspedes-Lorente, Ramón Valle-Cabrera

M. Beyzavi, Rachel C. Klet, Samat Tussupbayev et al.

Yifei Zhang, J. Ge, Zheng Liu

Huanchen Zhai, Chenghan Li, Xing Zhang et al.

The main source of reduced nitrogen for living things comes from nitrogenase, which converts N2 to NH3 at the FeMo-cofactor (FeMo-co). Because of its role in supporting life, the uncertainty surrounding the catalytic cycle, and its compositional richness with eight transition metal ions, FeMo-co has fascinated scientists for decades. After much effort, the complete atomic structure was resolved. However, its electronic structure, central to reactivity, remains under intense debate. FeMo-co's complexity, arising from many unpaired electrons, has led to suggestions that it lies beyond the reach of classical computing. Consequently, there has been much interest in the potential of quantum algorithms to compute its electronic structure. Estimating the cost to compute the ground-state to chemical accuracy (~1 kcal/mol) within one or more FeMo-co models is a common benchmark of quantum algorithms in quantum chemistry, with numerous resource estimates in the literature. Here we address how to perform the same task using classical computation. We use a 76 orbital/152 qubit resting state model, the subject of most quantum resource estimates. Based on insight into the multiple configuration nature of the states, we devise classical protocols that yield rigorous or empirical upper bounds to the ground-state energy. Extrapolating these we predict the ground-state energy with an estimated uncertainty on the order of chemical accuracy. Having performed this long-discussed computational task, we next consider implications beyond the model. We distill a simpler computational procedure which we apply to reveal the electronic landscape in realistic representations of the cofactor. We thus illustrate a path to a precise computational understanding of FeMo-co electronic structure.

J. Phelan, S. Lang, Jaehoon Sim et al.

DNA-encoded library (DEL) technology is a powerful tool commonly used by the pharmaceutical industry for the identification of compounds with affinity to biomolecular targets. Success in this endeavor lies in sampling diverse chemical libraries. However, current DELs tend to be deficient in C(sp3) carbon counts. We report unique solutions to the challenge of increasing both the chemical diversity of these libraries and their C(sp3) carbon counts by merging Ni/photoredox dual catalytic C(sp2)-C(sp3) cross-coupling as well as photoredox-catalyzed radical/polar crossover alkylation protocols with DELs. The successful integration of multiple classes of radical sources enables the rapid incorporation of a diverse set of alkyl fragments.

Yasin Yohana Kifwe, Godlisten Namwel Shao, Christina Fabian Pius

Abstract Background There is a challenge with employing dumpsites as waste disposal methods due to the formation of leachates. These leachates may include dangerous chemicals that may harm human health and the ecosystem. Despite the drawbacks of leachates, it contains precious minerals that can be retrieved and used to restore soil fertility for agricultural activities to contribute to the circular economy. Results The chemical composition of leachates from the Pugu dumpsite was assessed to explore their potential in agricultural application. Leachates were alkaline with a pH of 8.88 ± 0.98. The concentrations of NH4-N and PO4-P were 960.80 ± 610.44 and 431.60 ± 209.65 mg/L, respectively. The concentrations of minerals determined were Mg (33.73 ± 9.73), Na (485.70 ± 51.47), Ca (254.66 ± 6.04), and K (113.67 ± 8.53). The concentrations of heavy metals determined were Cd (0.03 ± 0.01), Cu (0.33 ± 0.09), Zn (0.32 ± 0.04), Cr (0.03 ± 0.01), Fe (2.63 ± 0.64), Ni (0.13 ± 0.03), and Pb (0.94 ± 0.06) mg/L. The concentrations of Cd, Cu, Zn, Cr, Fe, and Ni in the leachates under study, with the exception of Pb, were within the Tanzania Bureau of Standards (TBS)-established allowable limits for wastewater from cities and industries. Conclusions The study evaluated the chemical composition of leachate from the Pugu dumpsite to explore its potential in agricultural applications. The results showed that the leachates were alkaline with a pH of 8.88 ± 0.88, with concentrations of NH4-N and PO4-P exceeding the allowable limit for municipal and industrial wastewater effluents. Concentrations of minerals such as Mg, Na, Ca, and K were within limits set by the Tanzania Bureau of Standards (TBS) for city and industrial wastewater. However, the concentrations of PO4-P and NH4-N exceeded the permissible limit of TBS, which could have adverse effects on the ecosystem. The study proposes a subtle method to recover plant nutrients from leachate, thus contributing to the circular economy.

Alper Saricioglu, Mujde Erol Genevois, Michele Cedolin

The Bullwhip Effect, describing the amplification of demand variability up the supply chain, poses significant challenges in Supply Chain Management. This study examines how the COVID-19 pandemic intensified the Bullwhip Effect across U.S. industries, using extensive industry-level data. By focusing on the manufacturing, retailer, and wholesaler sectors, the research explores how external shocks exacerbate this phenomenon. Employing both traditional and advanced empirical techniques, the analysis reveals that COVID-19 significantly amplified the Bullwhip Effect, with industries displaying varied responses to the same external shock. These differences suggest that supply chain structures play a critical role in either mitigating or intensifying the effect. By analyzing the dynamics during the pandemic, this study provides valuable insights into managing supply chains under global disruptions and highlights the importance of tailoring strategies to industry-specific characteristics.

Benjamin Sorkin, Ned S. Wingreen

Phase separation of biomolecular condensates promotes membrane-free compartmentalization in cells. The dynamics of these biocondensates is routinely regulated by energy-consuming processes. Here, we devise a theory pinpointing how active chemical reactions, interconverting molecules between phase-separating and inert forms, can drive faster condensate coarsening. We find that mass conservation limits droplet volume growth to being linear in time regardless of activity, resembling the passive Lifshitz-Slyozov law. However, if reactions are restricted to occur only outside droplets, the rate of Ostwald ripening can be increased by an arbitrarily large factor. Our theory is quantitatively supported by recent experiments on ripening in the presence of fueled interconversion reactions, under precisely the predicted conditions. We posit that the ability to induce rapid biocondensate coarsening can be advantageous in synthetic-biological contexts, e.g., as a regulator of metabolic channeling.

Alea Miako Tokita, Timothée Devergne, A. Marco Saitta et al.

Machine learning potentials (MLPs) have become a popular tool in chemistry and materials science as they combine the accuracy of electronic structure calculations with the high computational efficiency of analytic potentials. MLPs are particularly useful for computationally demanding simulations such as the determination of free energy profiles governing chemical reactions in solution, but to date such applications are still rare. In this work we show how umbrella sampling simulations can be combined with active learning of high-dimensional neural network potentials (HDNNPs) to construct free energy profiles in a systematic way. For the example of the first step of Strecker synthesis of glycine in aqueous solution we provide a detailed analysis of the improving quality of HDNNPs for datasets of increasing size. We find that next to the typical quantification of energy and force errors with respect to the underlying density functional theory data also the long-term stability of the simulations and the convergence of physical properties should be rigorously monitored to obtain reliable and converged free energy profiles of chemical reactions in solution.

Jorma Vitkala

The presentation will focus on the quality monitoring of the different stages of the safety glass processing.  Defects in processed glass are extremely expensive, causing unnecessary work, energy costs and increasing CO2 emissions. Quality monitoring can be carried out at many different stages of production. This presentation will mainly focus on the problems of the tempering process and how to avoid different quality problems. I will also explain what causes defects and how and by what changes in settings defects can be avoided. Defects will focus on tempering process problems such as roller wave, edge kink, anisotropy, white haze, scratches, flaws, coating defects and how to indicate them. Measuring glass output temperature from bottom surface is one key indicator to good quality especially on coated glass. The latest quality control systems and their new possibilities will be examined from different perspectives. I will do some practical test runs and show how changes in the different settings affect the final quality. It has been estimated that the various degrees of error at different stages of glass production are up to more than 15%. Removing faulty glass from production at an early stage will save large amounts of money.

Thomas P. Fay, Nicolas Ferré, Miquel Huix-Rotllant

Electronic polarization and dispersion are decisive actors in determining interaction energies between molecules. These interactions have a particularly profound effect on excitation energies of molecules in complex environments, especially when the excitation involves a significant degree of charge reorganisation. The direct reaction field (DRF) approach, which has seen a recent revival of interest, provides a powerful framework for describing these interactions in quantum mechanics/molecular mechanics (QM/MM) models of systems, where a small subsystem of interest is described using quantum chemical methods and the remainder is treated with a simple MM force field. In this paper we show how the DRF approach can be combined with the electrostatic potential fitted (ESPF) multipole operator description of the QM region charge density, which significantly improves the efficiency of the method, particularly for large MM systems, and for typical calculations effectively eliminates the dependence on MM system size. We also show how the DRF approach can be combined with fluctuating charge descriptions of the polarizable environment, as well as previously used atom-centred dipole-polarizability based models. We further show that the ESPF-DRF method provides an accurate description of molecular interactions in both ground and excited electronic states of the QM system and apply it to predict the gas to aqueous solution solvatochromic shifts in the UV/visible absorption spectrum of acrolein.

Xiaolan Luo, X. Ge, Shaoqing Cui et al.

Himadri Ghatak

The study presents a TGA-FT-IR analysis of low-temperature thermochemical transformations of Rice straw hydrolysis residue (RSHR). Isothermal decomposition of RSHR was carried out for 3 h, at decomposition temperatures of 200, 250, 300, and 350 oC. At 200 oC, the rate of mass loss never exceeds %1/min and except for the first five minutes, it is less than %0.5/min. The initial rate of mass loss at 250 oC is %1.6/min which quickly drops to %0.6/min in the first 10 minutes and goes on further decreasing thereafter. At 300 oC, there is a rapid initial mass loss with the initial rate peaking at %8.8/min. At 350 oC, there is an initial burst of volatiles accounting for most of the mass loss with the initial rate of mass loss being %50/min. The residual mass obtained after these runs was 81.5, 38, 24, and 15%, respectively. FT-IR spectra of evolved gases suggest that volatile oxygenated organics along with non-condensable components like CO2, and CO are evolved during low-temperature thermal decomposition of RSHR. Carbonyls – acids, esters, aldehydes, and ketones – are the main functional groups in the volatiles. Strong absorption bands ranging 3400 – 3900 cm-1 indicated the presence of alcohols and phenols as other functional groups. Decomposition residues, the biochar, were demethoxylated and dehydrogenated compared to RSHR but retained their basic lignocellulosic nature.

Ali Kaan Kurbanzade, Ansaar M. Baig, Sanjay Mehrotra

Unmanned aerial vehicles, commonly known as drones, have emerged as a disruptive technology with the potential to revolutionize operations across various industries. Drones are the fast-growing internet-of-things technology and are estimated to have a $100 billion market value in the next decade. Exploring drone operations through research has the potential to yield innovative academic insights and create significant practical effects in diverse industries, offering a competitive edge. Drawing insights from both academic and industry literature, this article describes how technological advancements in UAVs may disrupt traditional operational practices in different industries (e.g., commercial last-mile delivery, commercial pickup and delivery, telecommunication, insurance, healthcare, humanitarian, environmental, urban planning, homeland security), identifies the value of this evolving disruptive technology from sustainability and operational innovation perspectives, argues the significance of this area for operations management by conceptualizing a research agenda. The current state of the art focuses on the computing aspect of analytical models to tackle a variety of synthetic drone-related problems, with mixed integer optimization being the primary tool. There is a very significant research gap that should focus on drone operations management with industry know-how by partnering with actual stakeholders and using a variety of tools (i.e., econometrics, field experiments, game theory, optimal control, utility functions). This article aims to promote research on UAVs from operations management and industry-specific point of view.

David T. Limmer, Andreas W. Götz, Timothy H. Bertram et al.

Atmospheric aerosols facilitate reactions between ambient gases and dissolved species. Here, we review our efforts to interrogate the uptake of these gases and the mechanisms of their reactions both theoretically and experimentally. We highlight the fascinating behavior of $\mathrm{N}_2\mathrm{O}_5$ in solutions ranging from pure water to complex mixtures, chosen because its aerosol-mediated reactions significantly impact global ozone, hydroxyl, and methane concentrations. As a hydrophobic, weakly soluble, and highly reactive species, $\mathrm{N}_2\mathrm{O}_5$ is a sensitive probe of the chemical and physical properties of aerosol interfaces. We employ contemporary theory to disentangle the fate of $\mathrm{N}_2\mathrm{O}_5$ as it approaches pure and salty water, starting with adsorption and ending with hydrolysis to HNO$_3$, chlorination to $\mathrm{ClNO}_2$, or evaporation. Flow reactor and gas-liquid scattering experiments probe even greater complexity as added ions, organic molecules, and surfactants alter interfacial composition and reaction rates. Together, we reveal a new perspective on multiphase chemistry in the atmosphere.

Rui Sun, Jie Kang, Xuemeng Wang et al.

The demand for renewable energy is increasing. <i>Klebsiella pneumoniae</i> is one of the most promising strains to produce 2,3-butanediol (2,3-BD). Compared with chemical methods, the biological production of 2,3-BD has the characteristics of substrate safety, low cost, and low energy consumption. However, excessive glucose concentrations can cause damage to cells. Therefore, this study investigated the effect of sRNA-SgrS as a sugar transport regulator on the fermentative production of 2,3-BD by <i>K. pneumoniae</i> in response to sugar stress. We designed multiple mutants of <i>K. pneumoniae</i> HD79 to redistribute its carbon flux to produce 2,3-BD. It was found that the 2,3-BD yield of <i>sgrS</i> overexpressed strain decreased by 44% compared with the original strain. The results showed that a high concentration of sRNA-SgrS could accelerate the degradation of <i>ptsG</i> mRNA (encoding the glucose transporter EIICB^Glc) and downregulate the expression levels of the <i>budA</i> gene (encoding the α-acetyllactate decarboxylase) and the <i>budB</i> gene (encoding the α-acetyllactate synthase) and <i>budC</i> gene (encoding the 2,3-BD dehydrogenase) but had no effect on the <i>ack</i> gene (encoding the acetate kinase) and the <i>ldh</i> gene (encoding the lactate dehydrogenase). It provides a theoretical basis and a technical reference for understanding the complex regulation mechanism of sRNA in microorganisms and the genetics and breeding in industrial fermentation engineering.