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Chemical Engineering Simulation

Liang Zhu
Despite more than 80 years of animal experiments and clinical practice, efficacy of hypothermia in improving treatment outcomes in patients suffering from cell and tissue damage caused by ischemia is still ongoing. This review will first describe the history of utilizing cooling in medical treatment, followed by chemical and biochemical mechanisms of cooling that can lead to neuroprotection often observed in animal studies and some clinical studies. The next sections will be focused on current cooling approaches/devices, as well as cooling parameters recommended by researchers and clinicians...
2018: Advances in Experimental Medicine and Biology
Dongzheng Yang, Xixi Hu, Daiqian Xie
The rate constants for H2 -HF energy transfer processes, especially for those in vibrationally excited states, are very demanding in astrophysics and chemical laser engineering, especially for those in vibrationally excited states. Based on our recent potential energy surface, we used the coupled-states approximation including the nearest neighboring Coriolis couplings with energy-based local basis set to perform dynamics calculation for the H2 -HF energy transfer system. Rate constants for vibrational transitions (1; 3) → (0; 4), (1; 3) → (2; 2), and (0; 3) → (1; 2) were obtained...
October 11, 2018: Journal of Computational Chemistry
Yuan Li, Marek B Majewski, Saiful M Islam, Shiqiang Hao, Akshay A Murthy, Jennifer G DiStefano, Eve D Hanson, Yaobin Xu, C Wolverton, Mercouri G Kanatzidis, Michael R Wasielewski, Xinqi Chen, Vinayak P Dravid
Molybdenum disulfide (MoS2) has been recognized as a promising cost-effective catalyst for water-splitting hydrogen production. However, the desired performance of MoS2 is often limited by insufficient edge-terminated active sites, poor electrical conductivity, and inefficient contact to the supporting substrate. To address these limitations, we developed a unique nanoarchitecture, namely winged Au@MoS2 heterostructures enabled by our discovery of the "seeding effect" of Au nanoparticles for the chemical vapor deposition synthesis of vertically-aligned few-layer MoS2 wings...
October 8, 2018: Nano Letters
Rafael S Costa, Susana Vinga
Over the last years, several genome-scale metabolic models (GEMs) and kinetic models of Escherichia coli were published. Their predictive performance varies according to the evaluation metric considered, the computational simulation methods used, and the type/quality of experimental data available. However, the GEM approach is often not compared with the kinetic modeling framework. Also, the different genome-scale reconstruction versions and simulation methods of mutant phenotypes are usually not validated to predict intracellular fluxes using large experimental datasets...
October 7, 2018: Biotechnology Progress
Dhivyaa Anandan, S Mary Stella, N Arunai Nambiraj, U Vijayalakshmi, Amit Kumar Jaiswal
Cancellous bone region of the human native bone has the potential to bear significant mechanical loads. However, due to the following parameters such as low trabecular volume, more porosity, less thickness and more interconnectivity, cancellous bone is accessible to damage in accidents or when aging. This research led to the effective fabrication and engineering of cancellous region of the bone for its application in reconstruction or filling of bone voids after resection of large tumor mass. Scaffolds containing hydroxyapatite (HAp), polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) (5% polymer and HAp concentrations) at different HAp: polymer composite ratios (50:50, 70:30 and 80:20), were fabricated by freeze-drying method using only water as solvent and ribose as crosslinker for the scaffolds...
October 5, 2018: Journal of Biomedical Materials Research. Part A
Enming Song, Rui Li, Xin Jin, Haina Du, Yuming Huang, Jize Zhang, Yu Xia, Hui Fang, Yoon Kyeung Lee, Ki Jun Yu, Jan-Kai Chang, Yongfeng Mei, Muhammad A Alam, Yonggang Huang, John A Rogers
Biomedical implants that incorporate active electronics and offer the ability to operate in a safe, stable fashion for long periods of time must incorporate defect-free layers as barriers to biofluid penetration. This paper reports an engineered material approach to this challenge that combines ultrathin, physically transferred films of silicon dioxide (t-SiO2 ) thermally grown on silicon wafers, with layers of hafnium oxide (HfO2 ) formed by atomic layer deposition and coatings of parylene (Parylene C) created by chemical vapor deposition, as a dual-sided encapsulation structure for flexible bioelectronic systems...
October 5, 2018: ACS Nano
William R Smith, Weikai Qi
The molecular simulation of chemical reaction equilibrium (CRE) is a challenging and important problem of broad applicability in chemistry and chemical engineering. The primary molecular-based approach for solving this problem has been the reaction ensemble Monte Carlo (REMC) algorithm [Turner et al. Molec. Simulation2008, 34, (2), 119-146], based on classical force-field methodology. In spite of the vast improvements in computer hardware and software since its original development almost 25 years ago, its more widespread application is impeded by its computational inefficiency...
September 26, 2018: ACS Central Science
Helena Massana-Cid, Joan Codina, Ignacio Pagonabarraga, Pietro Tierno
Collections of interacting active particles, self-propelling or not, have shown remarkable phenomena including the emergence of dynamic patterns across different length scales, from animal groups to vibrated grains, microtubules, bacteria, and chemical- or field-driven colloids. Burgeoning experimental and simulation activities are now exploring the possibility of realizing solid and stable structures from passive elements that are assembled by a few active dopants. Here we show that such an elusive task may be accomplished by using a small amount of apolar dopants, namely synthetic active but not self-propelling units...
October 1, 2018: Proceedings of the National Academy of Sciences of the United States of America
Ronja Driller, Sophie Janke, Monika Fuchs, Evelyn Warner, Anil R Mhashal, Dan Thomas Major, Mathias Christmann, Thomas Brück, Bernhard Loll
Terpenes constitute the largest and structurally most diverse natural product family. Most terpenoids exhibit a stereochemically complex macrocyclic core, which is generated by C-C bond forming of aliphatic oligo-prenyl precursors. This reaction is catalysed by terpene synthases (TPSs), which are capable of chaperoning highly reactive carbocation intermediates through an enzyme-specific reaction. Due to the instability of carbocation intermediates, the proteins' structural dynamics and enzyme:substrate interactions during TPS catalysis remain elusive...
September 28, 2018: Nature Communications
Yongjian Yang, Yun Kyung Shin, Shichun Li, Thomas D Bennett, Adri C T van Duin, John C Mauro
Classical force fields have been broadly used in studies of metal-organic framework crystals. However, processes involving bond breaking or forming are prohibited due to the nonreactive nature of the potentials. With emerging trends in the study of zeolitic imidazolate frameworks (ZIFs) that include glass formation, defect engineering, and chemical stability, enhanced computational methods are needed for efficient computational screening of ZIF materials. Here, we present simulations of three ZIF compounds using a ReaxFF reactive force field...
October 18, 2018: Journal of Physical Chemistry. B
Fatma Larbi, Araceli García, Luis J Del Valle, Ahmed Hamou, Jordi Puiggalí, Naceur Belgacem, Julien Bras
Process simulation is a useful tool that has been widely used to analyze, design and optimize energy balances in chemical technologies including those related to biomass processing, biorefinery processes and chemical engineering. The presented data set serves as basis for the simulation of chitin purification, nanofibers and nanocrystals production processes, considering laboratory experimental procedures described in previous experimental articles.
October 2018: Data in Brief
Clara Abaurrea Velasco, Masoud Abkenar, Gerhard Gompper, Thorsten Auth
Active agents-like phoretic particles, bacteria, sperm, and cytoskeletal filaments in motility assays-show a large variety of motility-induced collective behaviors, such as aggregation, clustering, and phase separation. The behavior of dense suspensions of engineered phoretic particles and of bacteria during biofilm formation is determined by two qualitatively different physical mechanisms: (i) volume exclusion (short-range steric repulsion) and (ii) quorum sensing (longer-range reduced propulsion due to alteration of the local chemical environment)...
August 2018: Physical Review. E
Larah Kriselle B Paragas, Mark Daniel G de Luna, Ruey-An Doong
An environment-friendly iodine and potassium co-doped g-C3 N4 (IKC3 N4 ) photocatalyst was synthesized via the co-pyrolysis of urea and potassium iodate. Various characterization techniques were employed to evaluate the physical, thermal and chemical characteristics of the as-synthesized photocatalyst. Sulfamethoxazole (SMX) was used as a representative antibiotic pollutant. SMX removal by IK-C3 N4 photocatalysts exceeded 99% (∼23 times higher than that of pure g-C3 N4 ) within 45 min of visible light irradiation...
November 2018: Chemosphere
Ulf W Liebal, Lars M Blank, Birgitta E Ebert
Microbial carbon dioxide assimilation and conversion to chemical platform molecules has the potential to be developed as economic, sustainable processes. The carbon dioxide assimilation can proceed by a variety of natural pathways and recently even synthetic CO2 fixation routes have been designed. Early assessment of the performance of the different carbon fixation alternatives within biotechnological processes is desirable to evaluate their potential. Here we applied stoichiometric metabolic modeling based on physiological and process data to evaluate different process variants for the conversion of C1 carbon compounds to the industrial relevant platform chemical succinic acid...
December 2018: Metabolic Engineering Communications
Maria Jose Esplandiu, Kuan Zhang, Jordi Fraxedas, Borja Sepulveda, David Reguera
The development of effective autonomous micro- and nanomotors relies on controlling fluid motion at interfaces. One of the main challenges in the engineering of such artificial machines is the quest for efficient mechanisms to power them without using external driving forces. In the past decade, there has been an important increase of man-made micro- and nanomotors fueled by self-generated physicochemical gradients. Impressive proofs of concept of multitasking machines have been reported demonstrating their capabilities for a plethora of applications...
September 18, 2018: Accounts of Chemical Research
Varun Prasath Padmanabhan, Ravichandran Kulandaivelu, Sankara Narayanan T S Nellaiappan
Core-shell hydroxyapatite (HAP) - gum acacia (GA) nanocomposite, in which the HAP acts as a core while the GA serves as a shell, was synthesized by precipitation techniqueusing Ca(NO3 )2 .4H2 O and NH4 H2 PO4 as precursors for Ca and P, respectively. The crystallite size and morphology of the synthesized core-shell HAP-GA nanocomposite was evaluated by X-ray diffraction measurement and transmission electron microscopy. The crystallite size of GA-HAP nanocomposite is markedly decreased from 89 nm to 63 nm when the concentration of GA in the reaction mixture is increased from 0 to 10%...
November 1, 2018: Materials Science & Engineering. C, Materials for Biological Applications
Maria Myrto Folia, Magnus Rattray
Stochastic models are of fundamental importance in many scientific and engineering applications. For example, stochastic models provide valuable insights into the causes and consequences of intra-cellular fluctuations and inter-cellular heterogeneity in molecular biology. The chemical master equation can be used to model intra-cellular stochasticity in living cells, but analytical solutions are rare and numerical simulations are computationally expensive. Inference of system trajectories and estimation of model parameters from observed data are important tasks and are even more challenging...
2018: Statistics and Computing
Yunfeng Ding, Luis E Contreras-Llano, Eliza Morris, Michelle Mao, Cheemeng Tan
The functioning of synthetic gene circuits depends on their local chemical context defined by the types and concentrations of biomolecules in the surrounding milieu that influences gene transcription and translation. This chemical-context dependence of synthetic gene circuits arises from significant yet unknown cross talk between engineered components, host cells, and environmental factors and has been a persistent challenge for synthetic biology. Here, we show that the sensitivity of synthetic gene networks to their extracellular chemical contexts can be minimized, and their designed functions rendered robust using artificial cells, which are synthetic biomolecular compartments engineered from the bottom-up using liposomes that encapsulate the gene networks...
September 12, 2018: ACS Applied Materials & Interfaces
Jing Cun Fan, Feng Chao Wang, Jie Chen, Yin Bo Zhu, De Tang Lu, He Liu, Heng An Wu
Polymer flooding is a promising chemical enhanced oil recovery (EOR) method, which realizes more efficient extraction in porous formations characterized with nanoscale porosity and complicated interfaces. Understanding the molecular mechanism of viscoelastic polymer EOR in nanopores is of great significance for the advancement of oil exploitation. Using molecular dynamics simulations, we investigated the detailed process of a viscoelastic polymer displacing oil at the atomic scale. We found that the interactions between polymer chains and oil provide an additional pulling effect on extracting the residual oil trapped in dead-end nanopores, which plays a key role in increasing the oil displacement efficiency...
June 2018: Royal Society Open Science
Hernan Biava, Toni Schreiber, Sagie Katz, Jan-Stefan Völler, Michael Stolarski, Claudia Schulz, Norbert Michael, Nediljko Budisa, Jacek Kozuch, Tillmann Utesch, Peter Hildebrandt
Electrostatic interactions are essential for controlling the protein structure and function. Whereas so far experimental and theoretical efforts focused on the effect of local electrostatics, this work aims at elucidating the long-range modulation of electric fields in proteins upon binding to charged surfaces. The study is based on cytochrome c (Cytc) variants carrying nitrile reporters for the vibrational Stark effect that are incorporated into the protein via genetic engineering and chemical modification...
September 6, 2018: Journal of Physical Chemistry. B
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