77 research outputs found
Energy efficiency analysis and optimization of heat exchange network under the goal of “double carbon”: a case for production process of isopropyl acetate
In order to response to the “double carbon” strategy for reducing emissions, chemical production processes were optimized to lower the amount of utility work and equipment investment expenses with increasing the system’s capacity for heat recovery. A sensitivity analysis and the energy efficiency analysis with pinch technique were performed on the distillation and purification of the 30 kt/a isopropyl acetate (IPAC) production process by using process simulation software of Aspen Plus. The IPAC refining tower optimization results show that the purity of the refined IPAC could be reached 99.9% at circumstances of 44 theoretical plates, 19 feed plates, and 0.755 reflux ratio. According to the optimized energy consumption data from Aspen Energy Analyzer (AEA), the cold and heat logistics matching was performed. It can be seen that the heat exchange network was tuned to maximize energy recovery by reducing the amount of utility work. The optimized cold and heat utility usage were 734.69 and 727.81 kW, which meaning that compared with original process, the cold and heat utility usage energy can be save with 10.0%, respectively. The optimized results provide a certain theoretical basis and solution for improving energy saving and reducing investment costs.</p
Automated One-Drop Assembly for Facile 2D Film Deposition
The
effective application of 2D materials is strongly dependent
on the mass production of high-quality large-area 2D thin films. Here,
we demonstrate a strategy for the automated manufacturing of high-quality
2D thin films using a modified drop-casting approach. Our approach
is simple; by using an automated pipette, a dilute aqueous suspension
is dropped onto a substrate heated on a hotplate, and controlled convection
by Marangoni flow and liquid removal causes the nanosheets to come
together to form a tile-like monolayer film in 1–2 min. Ti0.87O2 nanosheets are utilized as a model system
for investigating the control parameters such as concentrations, suction
speeds, and substrate temperatures. We perform the automated one-drop
assembly of a range of 2D nanosheets (metal oxides, graphene oxide,
and hexagonal boron nitride) and successfully fabricate various functional
thin films in multilayered, heterostructured, and sub-micrometer-thick
forms. Our deposition method enables on-demand large-size (>2 inchϕ)
manufacturing of high-quality 2D thin films while reducing the time
and sample consumption
Automated One-Drop Assembly for Facile 2D Film Deposition
The
effective application of 2D materials is strongly dependent
on the mass production of high-quality large-area 2D thin films. Here,
we demonstrate a strategy for the automated manufacturing of high-quality
2D thin films using a modified drop-casting approach. Our approach
is simple; by using an automated pipette, a dilute aqueous suspension
is dropped onto a substrate heated on a hotplate, and controlled convection
by Marangoni flow and liquid removal causes the nanosheets to come
together to form a tile-like monolayer film in 1–2 min. Ti0.87O2 nanosheets are utilized as a model system
for investigating the control parameters such as concentrations, suction
speeds, and substrate temperatures. We perform the automated one-drop
assembly of a range of 2D nanosheets (metal oxides, graphene oxide,
and hexagonal boron nitride) and successfully fabricate various functional
thin films in multilayered, heterostructured, and sub-micrometer-thick
forms. Our deposition method enables on-demand large-size (>2 inchϕ)
manufacturing of high-quality 2D thin films while reducing the time
and sample consumption
Automated One-Drop Assembly for Facile 2D Film Deposition
The
effective application of 2D materials is strongly dependent
on the mass production of high-quality large-area 2D thin films. Here,
we demonstrate a strategy for the automated manufacturing of high-quality
2D thin films using a modified drop-casting approach. Our approach
is simple; by using an automated pipette, a dilute aqueous suspension
is dropped onto a substrate heated on a hotplate, and controlled convection
by Marangoni flow and liquid removal causes the nanosheets to come
together to form a tile-like monolayer film in 1–2 min. Ti0.87O2 nanosheets are utilized as a model system
for investigating the control parameters such as concentrations, suction
speeds, and substrate temperatures. We perform the automated one-drop
assembly of a range of 2D nanosheets (metal oxides, graphene oxide,
and hexagonal boron nitride) and successfully fabricate various functional
thin films in multilayered, heterostructured, and sub-micrometer-thick
forms. Our deposition method enables on-demand large-size (>2 inchϕ)
manufacturing of high-quality 2D thin films while reducing the time
and sample consumption
Automated One-Drop Assembly for Facile 2D Film Deposition
The
effective application of 2D materials is strongly dependent
on the mass production of high-quality large-area 2D thin films. Here,
we demonstrate a strategy for the automated manufacturing of high-quality
2D thin films using a modified drop-casting approach. Our approach
is simple; by using an automated pipette, a dilute aqueous suspension
is dropped onto a substrate heated on a hotplate, and controlled convection
by Marangoni flow and liquid removal causes the nanosheets to come
together to form a tile-like monolayer film in 1–2 min. Ti0.87O2 nanosheets are utilized as a model system
for investigating the control parameters such as concentrations, suction
speeds, and substrate temperatures. We perform the automated one-drop
assembly of a range of 2D nanosheets (metal oxides, graphene oxide,
and hexagonal boron nitride) and successfully fabricate various functional
thin films in multilayered, heterostructured, and sub-micrometer-thick
forms. Our deposition method enables on-demand large-size (>2 inchϕ)
manufacturing of high-quality 2D thin films while reducing the time
and sample consumption
Automated One-Drop Assembly for Facile 2D Film Deposition
The
effective application of 2D materials is strongly dependent
on the mass production of high-quality large-area 2D thin films. Here,
we demonstrate a strategy for the automated manufacturing of high-quality
2D thin films using a modified drop-casting approach. Our approach
is simple; by using an automated pipette, a dilute aqueous suspension
is dropped onto a substrate heated on a hotplate, and controlled convection
by Marangoni flow and liquid removal causes the nanosheets to come
together to form a tile-like monolayer film in 1–2 min. Ti0.87O2 nanosheets are utilized as a model system
for investigating the control parameters such as concentrations, suction
speeds, and substrate temperatures. We perform the automated one-drop
assembly of a range of 2D nanosheets (metal oxides, graphene oxide,
and hexagonal boron nitride) and successfully fabricate various functional
thin films in multilayered, heterostructured, and sub-micrometer-thick
forms. Our deposition method enables on-demand large-size (>2 inchϕ)
manufacturing of high-quality 2D thin films while reducing the time
and sample consumption
RNA 3D Structure Prediction by Using a Coarse-Grained Model and Experimental Data
RNAs form complex secondary and three-dimensional
structures, and
their biological functions highly rely on their structures and dynamics.
Here we developed a general coarse-grained framework for RNA 3D structure
prediction. A new, hybrid coarse-grained model that explicitly describes
the electrostatics and hydrogen-bond interactions has been constructed
based on experimental structural statistics. With the simulated annealing
simulation protocol, several RNAs of less than 30-nt were folded to
within 4.0 Ă… of the native structures. In addition, with limited
restraints on Watson–Crick basepairing based on the data from
NMR spectroscopy and small-angle X-ray scattering (SAXS) information,
the current model was able to characterize the complex tertiary structures
of large size RNAs, such as 5S ribosome and U2/U6 snRNA. We also demonstrated
that the pseudoknot structure was better captured when the coordinating
Mg<sup>2+</sup> cations and limited basepairing restraints were included.
The accuracy of our model has been compared favorably with other RNA
structure prediction methods presented in the previous study of <i>RNA-Puzzles</i>. Therefore the coarse-grained model presented
here offers a unique approach for accurate prediction and modeling
of RNA structures
Probing the Effect of Conformational Constraint on Phosphorylated Ligand Binding to an SH2 Domain Using Polarizable Force Field Simulations
Preorganizing a ligand in the conformation it adopts
upon binding
to a protein has long been considered to be an effective way to improve
affinity by making the binding entropy more favorable. However, recent
thermodynamic studies of a series of complexes of the Grb2 SH2 domain
with peptide analogues having constrained and flexible replacements
for a phosphotyrosine residue revealed that less favorable binding
entropies may result from constraining ligands in their biologically
active conformations. Toward probing the origin of this unexpected
finding, we examined the complexes of four phosphotyrosine-derived
analogues with the Grb2 SH2 domain using molecular dynamics simulations
with a polarizable force field. Significantly, the computed values
for the relative binding free energies, entropies, and enthalpies
of two pairs of constrained and unconstrained ligands reproduced the
trends that were determined experimentally, although the relative
differences were overestimated. These calculations also revealed that
a large fraction of the ligands lacking the constraining element exist
in solution as compact, macrocyclic-like structures that are stabilized
by interactions between the phosphate groups and the amide moieties
of the C-terminal pY+2 residues. In contrast, the three-membered ring
in the constrained ligands prevents the formation of such macrocyclic
structures, leading instead to globally extended, less ordered conformations.
Quasiharmonic analysis of these conformational ensembles suggests
that the unconstrained ligands possess significantly lower entropies
in solution, a finding that is consistent with the experimental observation
that the binding entropies for the unconstrained ligands are more
favorable than for their constrained counterparts. This study suggests
that introducing local constraints in flexible molecules may have
unexpected consequences, and a detailed understanding of the conformational
preferences of ligands in their unbound states is a critical prerequisite
to correlating changes in their chemical structure with protein binding
entropies and enthalpies
A Moonlighting Enzyme Links <i>Escherichia coli</i> Cell Size with Central Metabolism
<div><p>Growth rate and nutrient availability are the primary determinants of size in single-celled organisms: rapidly growing <i>Escherichia coli</i> cells are more than twice as large as their slow growing counterparts. Here we report the identification of the glucosyltransferase OpgH as a nutrient-dependent regulator of <i>E. coli</i> cell size. During growth under nutrient-rich conditions, OpgH localizes to the nascent septal site, where it antagonizes assembly of the tubulin-like cell division protein FtsZ, delaying division and increasing cell size. Biochemical analysis is consistent with OpgH sequestering FtsZ from growing polymers. OpgH is functionally analogous to UgtP, a <i>Bacillus subtilis</i> glucosyltransferase that inhibits cell division in a growth rate-dependent fashion. In a striking example of convergent evolution, OpgH and UgtP share no homology, have distinct enzymatic activities, and appear to inhibit FtsZ assembly through different mechanisms. Comparative analysis of <i>E. coli</i> and <i>B. subtilis</i> reveals conserved aspects of growth rate regulation and cell size control that are likely to be broadly applicable. These include the conservation of uridine diphosphate glucose as a proxy for nutrient status and the use of moonlighting enzymes to couple growth rate-dependent phenomena to central metabolism.</p></div
OpgH<sup>N</sup> appears to function as an FtsZ monomer sequestering protein.
<p>(A) Concentration-dependent inhibition of FtsZ's GTPase activity by OpgH<sup>N</sup>. The GTP hydrolysis rate of 5 µM FtsZ is shown at differing ratios of OpgH<sup>N</sup>. OpgH<sup>N</sup> alone is at 5 µM. Error bars equal standard deviation (n = 3). (B) FtsZ GTPase rates at increasing concentrations of OpgH<sup>N</sup>. The critical concentration for assembly of FtsZ was determined at OpgH<sup>N</sup> concentrations of 0 µM, 2.5 µM, 5 µM, or 10 µM. (See <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003663#pgen.1003663.s009" target="_blank">Figure S9C, S9D</a> for additional controls.)</p
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