200 research outputs found
Development of a Bimetallic Pd-Ni/HZSM‑5 Catalyst for the Tandem Limonene Dehydrogenation and Fatty Acid Deoxygenation to Alkanes and Arenes for Use as Biojet Fuel
A tandem
process involving the dehydroaromatization of the terpene
limonene and the hydrodeoxygenation of stearic acid has been found
to be efficiently catalyzed by Pd-Ni/HZSM-5. The process involves
the generation of <i>p</i>-cymene from terpene with concomitant
formation of H<sub>2</sub>, which leads to the one-pot hydrodeoxygenation
of stearic acid to C<sub>17</sub> and C<sub>18</sub> alkanes; these
products can be used as kerosene additives for aviation fuel. Screening
a wide range of catalysts, the bimetallic Pd-Ni/HZSM-5 catalyst is
the most efficient, leading to quantitative conversion of stearic
acid to alkanes in limonene at 280 °C at a H<sub>2</sub> pressure
of 2 bar after 120 min. It has been found that single Ni or Pd catalysts
lead to a poor conversion of stearic acid in limonene at a H<sub>2</sub> pressure of 2 bar. The combination of physically mixed Pd- and Ni-sites
onto different supports (Pd/HZSM-5 or Pd/C, and Ni/HZSM-5, Ni/HY,
or Ni/HBEA) leads to catalysts which show satisfactory conversion
to <i>p</i>-cymene but generally have very low stearic acid
conversion rates. Directly incorporating Pd and Ni onto the HZSM-5
scaffold forms the Pd-Ni/HZSM-5 bimetallic catalyst, which demonstrates
a remarkable improvement in stearic acid conversion to C<sub>17</sub> and C<sub>18</sub> alkane products. In this catalyst system, Pd
is shown to be the active site for limonene dehydroaromatization,
while Ni catalyzes the separate stearic acid hydrodeoxygenation. The
acidity of HZSM-5 (modified by the Si/Al ratios) influences the performance
of the Pd-Ni bimetallic catalyst, and the proper pore size of HZSM-5
prevents side-reactions from limonene condensation. In addition, the
alloyed Pd-Ni nanoparticles (optimized with higher Pd/Ni ratios) on
the external surface of HZSM-5 enhance internal H<sup>•</sup> transfer between the two metals, thereby increasing the rate of
stearic acid hydrodeoxygenation. The catalytic compatibility of the
Pd and Ni sites, coupled with the proper pore sizes and optimized
level of Brönsted acid sites in HZSM-5, result in the design
of a multifunctional catalyst that is efficient for both steps of
the cascade reaction. Hence, a bimetallic 5%Pd-10%Ni/HZSM-5 catalyst
has been developed that allows for a simple approach for producing
aromatics and hydrocarbon components present in biojet fuel derived
from two biomass resources
Electronic Effects of Ring Fusion and Alkyne Substitution on Acene Properties and Reactivity
This
paper describes the synthesis and systematic study of substituted
acenes that have differences in conjugation both along their long
axes (by the number of fused benzene or thiophene rings) and along
their short axes (by the number of arylethynyl substituents). These
acenes include what we believe to be the first reported examples of
five new subclasses of substituted acenes. Systematic analyses of
data obtained using absorbance and fluorescence spectroscopies, cyclic
voltammetry, and DFT calculations reveal clear correlations between
these common structural perturbations to acene structure and the key
parameters, such as HOMO–LUMO gap, frontier molecular orbital
energies, and reactivity with singlet oxygen
Synthesis and Properties of Dithiocarbamate-Linked Acenes
A small
set of unsymmetrically substituted acene derivatives containing
either aniline or dithiocarbamate moieties was synthesized. A stepwise,
one-pot procedure was used to transform appropriate acenequinones
to aniline-linked acenes in one step with moderate yields. A heretofore-unreported
carbon disulfide activation process involving the formation of a trialkylammonium
dithiocarbamate intermediate was found to be essential to convert
these acene anilines to acene dithiocarbamates. The effects of the
aniline and dithiocarbamate moieties on the photophysical properties
of selected acene chromophores were assessed by UV/vis absorption
and fluorescence spectroscopies
DataSheet1_Non-coding ribonucleic acid-mediated CAMSAP1 upregulation leads to poor prognosis with suppressed immune infiltration in liver hepatocellular carcinoma.ZIP
Liver hepatocellular carcinoma (LIHC) is well-known for its unfavorable prognosis due to the lack of reliable diagnostic and prognostic biomarkers. Calmodulin-regulated spectrin-associated protein 1 (CAMSAP1) is a non-centrosomal microtubule minus-end binding protein that regulates microtubule dynamics. This study aims to investigate the specific role and mechanisms of CAMSAP1 in LIHC. We performed systematical analyses of CAMSAP1 and demonstrated that differential expression of CAMSAP1 is associated with genetic alteration and DNA methylation, and serves as a potential diagnostic and prognostic biomarker in some cancers, especially LIHC. Further evidence suggested that CAMSAP1 overexpression leads to adverse clinical outcomes in advanced LIHC. Moreover, the AC145207.5/LINC01748-miR-101–3p axis is specifically responsible for CAMSAP1 overexpression in LIHC. In addition to the previously reported functions in the cell cycle and regulation of actin cytoskeleton, CAMSAP1-related genes are enriched in cancer- and immune-associated pathways. As expected, CAMSAP1-associated LIHC is infiltrated in the suppressed immune microenvironment. Specifically, except for immune cell infiltration, it is significantly positively correlated with immune checkpoint genes, especially CD274 (PD-L1), and cancer-associated fibroblasts. Prediction of immune checkpoint blockade therapy suggests that these patients may benefit from therapy. Our study is the first to demonstrate that besides genetic alteration and DNA methylation, AC145207.5/LINC01748-miR-101-3p-mediated CAMSAP1 upregulation in advanced LIHC leads to poor prognosis with suppressed immune infiltration, representing a potential diagnostic and prognostic biomarker as well as a promising immunotherapy target for LIHC.</p
Governance strategies to achieve zero-energy buildings in China
<p>In response to climate change, governments are developing policies to move toward ultra-low-energy or ‘zero-energy’ buildings (ZEBs). Policies, codes, and governance structures vary among regions, and there is no universally accepted definition of a ZEB. These variables make it difficult, for countries such as China that wish to set similar goals, to determine an optimum approach. This paper reviews ZEBs policies, programmes, and governance approaches in two jurisdictions that are leading ZEBs development: Denmark and the state of California in the United States. Different modes of governance (hierarchy: principal–agent relations, market: self organizing and network: independent actors) are examined specifically in relation to policy instruments (prescriptive, performance or outcome-based). The analysis highlights differences in institutional conditions and examines available data on energy performance resulting from a building policy framework. The purpose is to identify ZEBs governance and implementation deficits in China and analyse alternative governance approaches that could be employed in China, which is currently developing ZEBs targets and policies. Conclusions suggest that the ZEBs governance structure in China could benefit from widened participation by all societal actors involved in achieving ZEBs targets. China's ZEBs policies would benefit from employing a more balanced hybrid governance approach.</p
Upper Airway Changes after Orthodontic Extraction Treatment in Adults: A Preliminary Study using Cone Beam Computed Tomography
<div><p>Objective</p><p>Whether the orthodontic treatment with premolar extraction and maximum anchorage in adults will lead to a narrowed upper airway remains under debated. The study aims to investigate the airway changes after orthodontic extraction treatment in adult patients with Class II and hyperdivergent skeletal malocclusion.</p><p>Materials and Methods</p><p>This retrospective study enrolled 18 adults with Class II and hyperdivergent skeletal malocclusion (5 males and 13 females, 24.1 ± 3.8 years of age, BMI 20.33 ± 1.77 kg/m<sup>2</sup>). And 18 untreated controls were matched 1:1 with the treated patients for age, sex, BMI, and skeletal pattern. CBCT images before and after treatment were obtained. DOLPHIN 11.7 software was used to reconstruct and measure the airway size, hyoid position, and craniofacial structures. Changes in the airway and craniofacial parameters from pre to post treatment were assessed by Wilcoxon signed rank test. Mann-Whitney U test was used in comparisons of the airway parameters between the treated patients and the untreated controls. Significant level was set at 0.05.</p><p>Results</p><p>The upper and lower incisors retracted 7.87 mm and 6.10 mm based on the measurement of U1-VRL and L1-VRL (P < 0.01), while the positions of the upper and lower molars (U6-VRL, and L6-VRL) remained stable. Volume, height, and cross-sectional area of the airway were not significantly changed after treatment, while the sagittal dimensions of SPP-SPPW, U-MPW, PAS, and V-LPW were significantly decreased (P < 0.05), and the morphology of the cross sections passing through SPP-SPPW, U-MPW, PAS, and V-LPW became anteroposteriorly compressed (P <0.001). No significant differences in the airway volume, height, and cross-sectional area were found between the treated patients and untreated controls.</p><p>Conclusions</p><p>The airway changes after orthodontic treatment with premolar extraction and maximum anchorage in adults are mainly morphological changes with anteroposterior dimension compressed in airway cross sections, rather than a decrease in size.</p></div
Thermodynamic Insight into Thermal Cracking of <i>n</i>‑Hexane in the H‑FAU Zeolite
To
understand catalytic cracking processes of alkanes in the petrochemical
industry, the monomolecular cracking mechanism of n-hexane in the H-FAU zeolite has been examined using ab initio molecular
dynamics simulations combined with enhanced sampling techniques. It
has been found that the adsorption energies of short n-alkanes are linearly correlated with the chain length and contact
areas with the zeolite framework, while no such correlation can be
applied to the short n-alkenes. High-dimensional
free energy landscapes characterizing four cracking modes of n-hexane at three different temperatures have been drawn.
The electron transfer in the cracking process was analyzed by quantifying
the charge evolution for carbon atoms. The formation of carbonium
ions in each cracking mode is found to be the rate-limiting step.
At high temperature, free energy differences are nonpositive values,
suggesting that the cracking of n-hexane is spontaneous,
which is also coincident with the experimental observation. The cracking
of the central C–C bond of n-hexane is easier
than the cracking of terminal C–C bonds, which is due to the
lower free energy barrier. The present work sheds new insights into
the cracking process of n-alkanes in the industrially
used FAU zeolite catalysts
Supplementary document for Point-by-point visual enhancement with spatially and spectrally tunable laser illumination - 6142167.pdf
painting design and the detailed scene segmentation result
Mutations in hepatitis B virus polymerase are associated with the postoperative survival of hepatocellular carcinoma patients
<div><p>Proofreading deficiencies of hepatitis B virus polymerase result in frequent DNA mutations in the hepatitis B virus genome. Here, we performed sequencing analysis of the hepatitis B virus polymerase gene to assess its association with the postoperative survival in 92 patients with HBV-related hepatocellular carcinoma by using the Kaplan–Meier method. The 2525, 2733, 2738, 2768, 2946, 3063, 3066, 3109, 31, 529, 735, 939, 1078, 1137, 1383, 1461, 1485, 1544, and 1613 mutation sites were identified as being associated with HCC outcomes by the log-rank test. After adjusting for clinical characteristics by using the Cox hazard model, site 31 (relative risk, 8.929; 95% confidence interval, 3.433–23.22; <i>P</i> = 0.000) in the spacer domain and sites 529 (relative risk, 5.656; 95% confidence interval, 1.599–19.999; <i>P</i> = 0.007) and 1078 (relative risk, 3.442; 95% confidence interval, 1.070–11.068; <i>P</i> = 0.038) in the reverse transcriptase domain of hepatitis B virus polymerase were identified as independent predictors of postoperative survival in hepatitis B virus related hepatocellular carcinoma. The mutations at the 31 (Ser314Pro), 529 (Asp480Asn), and 1078 (Ser663Ala) sites all resulted in amino acid changes in hepatitis B virus polymerase and were associated with shortened life-span. The 31 and 529 sites were located in the overlapping region for the PreS and S genes but did not induce amino acid substitution in these two regions. Our finding of the correlation between hepatitis B virus DNA polymerase mutations and hepatocellular carcinoma survival will help identify the patients subgroup with poor prognosis, and help the clinicians to refine the therapeutic decision individualized.</p></div
Understanding the Hydrocracking of Polycyclic Aromatic Hydrocarbons within FAU Zeolites: Hydrogen Splitting Catalyzed by the Frustrated Lewis Pair
To understand the hydrocracking of aromatic rings in
the petrochemical
industry, the first step, hydrogen splitting on catalytic centers,
has been studied based on density functional theory. Using ab initio
thermodynamic analysis, the Lewis acid site (LAS) composed of a single
extraframework-Al3+ atom is predicted to be most stable
mononuclear extraframework aluminum species during high-temperature
calcination. Based on unbiased ab initio molecular dynamics (AIMD)
simulations, this LAS is found to be the best catalytic center for
hydrogen splitting, where hydrogen can be split spontaneously, resulting
in the stable tetrahydroanthracen-1-ylium cation. With the help of
AIMD and metadynamics, free energy landscapes characterizing hydrogen
splitting processes on five different catalytic centers, viz., single
extraframework-Al3+ atom, two molecular frustrated Lewis
pair (FLP) sites, and two ionic FLP sites, have been examined. Each
hydrogen splitting occurs via a single-step concerted mechanism. Two
molecular FLP sites exhibit higher splitting reactivity with lower
free energy barriers. Further charge analysis reveals that the reactivity
of FLP sites is strongly affected by the local electric field generated
by the hydride acceptor and proton acceptor within FLP sites
- …