Hydroxy derivatives of 4-methyl-2H-chromen-2-one were prepared from hydroquinone and resorcinol through their reaction with ethyl acetoacetate. These hydroxy coumarins were then converted into ...corresponding alkoxy derivatives by reaction with alkyl halides. The yields of 6- and 7-alkoxy-4-methylcoumarins 3a-i and 4a-i were 55−95%. Oxidation of these compounds by selenium dioxide under conventional and microwave-assisted heating conditions produced corresponding 4-formyl compounds 5b-h and 6b-h with yields of 40−67% and 90−93%, respectively. Several 6- and 7-alkoxy-4-methylcoumarins 3a-i, 4a-i and nearly all 6- and 7-alkoxy-4-formylcoumarins 5b-h, 6b-h are novel compounds.
Access to clean water is still limited in a number of regions, especially country sides, rural, and mountainous areas in Vietnam. Therefore, studies on clean water production by using sustainable and ...affordable processes for locals to access to clean water are of great importance. In this research, we produced laterite-based adsorbents by thermal treatment of natural laterite. The produced adsorbents were characterized in terms of morphology, crystallite, chemical composition, surface functional groups, surface charges, and surface area. The adsorption processes of Ni
2+
and Cu
2+
onto thermally treated laterite were studied. The treated laterite was also deployed to the removal of pollutants from real rain water. Finally, treated laterite was used in a combination system to purify rain water to produce drinking water for households in Hai Dong commune, Hai Hau district, Nam Dinh province. The results showed that the adsorption of Ni
2+
and Cu
2+
by thermally treated laterite reached equilibrium after 40 min and followed the Langmuir sorption isotherm, with the maximum uptake of 27.6 mg/g for Cu
2+
and 17.4 mg/g for Ni
2+
. The second-order-kinetic model described the best the adsorption of Cu
2+
and Ni
2+
from aqueous solution, implying chemisorption was predominant mechanism. The treated laterite was suitable for heavy metal removal but less effective for the removal of anions from water. The combination of solar heating system with treated laterite, sand, and activated carbon allowed to safely produce drinking water from rain water, which presented the water quality respecting the Vietnam national standard for drinking water (QCVN 01:09/BYT).
High-resolution Moho and lithosphere–asthenosphere boundary depth models for Vietnam and its surrounding areas are determined based on a recently released geoid model constructed from surface and ...satellite gravity data (GEOID_LSC_C model) and on 3ʹʹ resolution topography data (mixed SRTM model). A linear density gradient for the crust and a temperature-dependent density for the lithospheric mantle were used to determine the lithospheric structure under the assumption of local isostasy. In a first step, the impact of correcting elevation data from sedimentary basins to estimate Moho depth has been evaluated using CRUST1.0 model. Results obtained from a test area where seismic data are available, which demonstrated that the sedimentary effect should be considered before the inversion process. The geoid height and elevation-corrected sedimentary layer were filtered to remove signals originating below the lithosphere. The resulting Moho and lithosphere–asthenosphere boundary depth models computed at 1ʹ resolution were evaluated against seismic data as well as global and local lithospheric models available in the study region. These comparisons indicate a consistency of our Moho depth estimation with the seismic data within 1.5 km in standard deviation for the whole Vietnam. This new Moho depth model for the study region represents a significant improvement over the global models CRUST1.0 and GEMMA, which have standard deviations of 3.2 and 3.3 km, respectively, when compared to the seismic data. Even if a detailed geological interpretation of the results is out of scope of this paper, a joint analysis of the obtained models with the high-resolution Bouguer gravity anomaly is finally discussed in terms of the main geological patterns of the study region. The high resolution of our Moho and lithosphere–asthenosphere boundary depth models contribute to better constrain the lithospheric structure as well as tectonic and geodynamic processes of this region. The differences in Moho depth visible in the northeast and southwest sides of the Red River Fault Zone confirmed that the Red River Fault Zone may be considered the boundary between two continental blocks: South China and Indochina blocks. However, no remarkable differences in lithosphere–asthenosphere boundary depth were obtained from our results. This suggests that the Red River Fault Zone developed within the crust and remained a crustal fault.
Abstract
The paper focuses on the nonlinear vibration of functionally graded graphene nanoplatelet reinforced composite doubly curved shallow shells resting on elastic foundations. The graphene ...nanoplatelet reinforced composites are assumed to be distributed uniformly and functionally graded through the thickness. The material properties are assumed to be temperature-dependent and are estimated through the Halpin–Tsai micromechanical model, while the Poisson’s ratio, density mass, and thermal expansion are implemented by the rule of mixtures. The mathematical formulation is developed based on the classical shell theory and Von Karman-Donnell geometrical nonlinearity assumption. The dynamical responses of a simply supported functionally graded-graphene nanoplatelet reinforced composite doubly curved shallow shells are obtained by employing the Airy’s stress function and the Galerkin’s method. The responses of nonlinear vibration as time history, frequency-amplitude curve, phase plane graphs, and Poincare maps are carried out in this paper. In addition, the effects of the environment, graphene nanoplatelets weight fraction, graphene nanoplatelets distribution patterns, and thickness-to-length ratio are scrutinized. The obtained results are also compared and validated with those of other studies.
Background. HCV testing is an important first step for treatment and prevention, particularly for those who are highly vulnerable to HCV infection such as people who inject drugs (PWID). In settings ...where direct-acting antiretroviral medicines are becoming more available, limited information exists about who and where to target to increase the prevalence of HCV testing among PWID. This study is aimed at understanding the prevalence of HCV testing uptake and its determinants of medical services and risk behaviors. Methods. From February 2016 to April 2017, a sample of 509 PWID was interviewed using a structured questionnaire on their history of HCV testing, confirmation, services using in the previous year as well as HCV-related knowledge, and risk behaviors. Multiple logistic regression identified factors associated with ever being tested for HCV before enrollment in the program. Results. Approximately 33% reported ever testing for HCV. Most cited sources of testing are public hospitals and general clinics (68.9%) and outpatient clinics (18.9%). Having ever tested for HCV was positively associated with accessing health services within the prior 12 months (aOR=2.25; 95% CI 1.11-4.58), being currently enrolled in a methadone treatment program (aOR=2.35; 95% CI 1.34-4.08), and/or on ART treatment (aOR=2.30; 95% CI 1.30-4.08). Those who ever delayed in seeking healthcare services for any reason were less likely to get tested for HCV (aOR=0.54; 95% CI 0.35-0.84). Conclusion. HCV testing prevalence is low among PWID in Hanoi despite a very high prevalence of HCV infection. To improve the cascade of HCV testing, it is critical that intervention programs scale up linkages among methadone, outpatient clinics, and HCV services, take steps to reduce stigma and discrimination in both community and, especially, in health care settings, and increase awareness of HCV for PWID by integrating HCV into routine counseling at health care services.
The series of 2-amino-7-propargyloxy-4H-chromene-3-carbonitriles 5a-t were synthesized from corresponding 2-amino-7-phydroxy-4H-chromene-3-carbonitriles 4a-t and propargyl bromide. Two procedures ...were used in these syntheses: K2CO3/acetone and NaH/DMF procedures with yields of 65–89% and 80–96%, respectively. 1H-1,2,3-Triazole-tethered 4H-chromene−d-glucose conjugates 7a-t were synthesized using click chemistry of propargyl ethers 5a-t and tetra-O-acetyl-β-d-glucopyranosyl azide. Cu@MOF-5 was the optimal catalyst for this chemistry. The yields of 1H-1,2,3-triazoles were 80–97.8%. All triazoles 7a-t were evaluated in vitro for anti-microorganism activities. Among tested compounds with MIC values of 1.56–6.25 μM, there were four compounds against B. subtilis, four compounds against S. aureus, and four compounds against S. epidermidis; five compounds against E. coli, four compounds against K. pneumoniae, five compounds against P. aeruginosa, and six compounds against S. typhimurium. Compounds 7c,7d,7f,7h, and 7r had MIC values of 1.56–6.25 μM for three clinical MRSA isolates. Some compounds had inhibitory activities against four fungi, including A. niger, A. flavus, C. albicans, and S. cerevisiae, with MIC values of 1.56–6.25 μM. Some 1H-1,2,3-triazoles had comparatively low toxicity against RAW 264.7 cells.
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•Novel 1H-1,2,3-triazole-tethered 4H-chromene−d-glucose conjugates by click chemistry.•Several triazoles were active for three strains of Gram-(+), four strains of Gram-(−) bacteria (MICs = 1.56–6.25 μM).•Some triazoles had activity against four strains of fungi with MICs of 1.56–6.25 μM.•7c,7d,7f,7h, 7r exerted anti-MRSA activities against all strains with MIC of 1.56–6.25 μM.•1H-1,2,3-Triazoles 7c,7d,7f,7h, 7r had comparatively low cytotoxicity against RAW 264.7 cells.
Some substituted thioureas (
6a-i
) containing a 1,3,4-thiadiazole ring were synthesized by the reaction of the corresponding substituted 2-amino-1,3,4-thiadiazoles
3a-i
with
p
-toluenesulfonyl ...isocyanate in a one-pot procedure. The antibacterial and antifungal activities of these sulfonyl thioureas were estimated using a minimum inhibitory concentration protocol. Almost all the thioureas exhibited remarkable antimicrobial activity. Amongst the studied compounds, thioureas
6a
,
6c
,
6h
, and
6i
were better inhibitors against the bacterium
S. aureus
, with MIC values of 0.78-3.125 μg mL
−1
. These compounds were also tested for their inhibition against
S. aureus
enzymes, including enzymes of DNA gyrase, DNA topoisomerase IV (Topo IV), and dihydrofolate reductase. Amongst the compounds,
6h
was a strong inhibitor, with IC
50
values of 1.22, 53.78, and 0.23, respectively. Induced fit docking calculations were performed to observe the binding efficiency and steric interactions of these compounds. The obtained results showed that compound
6h
was compatible with the active sites of
S. aureus
DNA gyrase
2XCS
. This ligand interacted with residues ASP1083 (chain D), MET1121 (chain B), ARG1122 (chain D), and also with HOH2035, HOH2089, HOH2110, HOH2162. Molecular dynamics simulation in a water solvent system showed that the active interactions with residues ASP083 and MET1121 (chain B), along with ASP1083, MET1121, and ARG1122 (chain D), played an important role in stabilizing complex
6h
/
2XCS
in the active pocket.
Sulfonylthioureas of 2-amino-1,3-thiadiazoles and 4-toluenesulfonyl isocyanate had inhibitions for bacteria, fungi,
S. aureus
DNA gyrase, TopoIV and DHF reductase. IFD, MM-GBSA and MD were performed.
Influence of the structure of the Rh@MOF catalyst on the catalytic performance in the hydroformylation of n-hexene-1 with synthesis gas to aldehydes. Display omitted
► Rh@IRMOF-3 supported catalyst ...has been prepared and characterized. ► The catalytic performance has been studied in the hydroformylation of olefins. ► Rh@IRMOF-3 is active and selective in the hydroformylation of olefins. ► The catalytic properties were compared to Rh-loaded MOF-5, MIL-77 and MIL-101. ► The MOF support structure has a significant influence on catalytic properties.
The metal-organic framework IRMOF-3 has been synthesized and functionalized with supported rhodium species. The samples have been characterized by XRD, FTIR, SEM, TEM, XPS, AAS, and nitrogen sorption measurements. It is found that originally precipitated big particles consist of hierarchically structured agglomerated nanocrystals of ca. 10–15nm size. The big particles contain a combined macro–meso–micro pore system allowing easy access to the catalytic sites. The Rh@IRMOF-3 supported catalyst has been catalytic tested in the hydroformylation of olefins to the corresponding aldehydes. Double bond shift isomerization has been observed as side reaction. n-Alkenes-1 of different chain lengths and bulky or less flexible olefins as cyclohexene, 2,2,4-trimethylpentene, and hexadiene-1,5 have been studied. The Rh@IRMOF-3 catalyst shows high activity and selectivity to n-aldehydes in the hydroformylation of linear alkene-1. The comparison of catalytic data obtained with the hydroformylation of n-hexene-1 over the different rhodium loaded MOFs as MOF-5, MIL-77, and MIL-101 show a significant influence of the MOF-structure on the catalytic properties.
A series of sulfonyl thioureas 6a–q containing a benzodthiazole ring with an ester functional group was synthesized from corresponding substituted 2‐aminobenzodthiazoles 3a–q and p‐toluenesulfonyl ...isothiocyanate. They had remarkable inhibitory activity against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), monoamine oxidase (MAO)‐A, and MAO‐B. Among thioureas, several compounds had notable activity in the order of 6k > 6 h > 6c (AChE), 6j > 6g > 6k (BChE), 6k > 6g > 6f (MAO‐A), and 6i > 6k > 6h (MAO‐B). Compound 6k was an inhibitor of interest due to its potent or good activity against all studied enzymes, with IC50 values of 0.027 ± 0.008 μM (AChE), 0.043 ± 0.004 μM (BChE), 0.353 ± 0.01 μM (MAO‐A), and 0.716 ± 0.02 μM (MAO‐B). This inhibitory capacity was comparable to that of the reference drugs for each enzyme. Kinetic studies of two compounds with potential activity, 6k (against AChE) and 6j (against BChE), had shown that both 6k and 6j followed competitive‐type enzyme inhibition, with Ki constants of 24.49 and 12.16 nM, respectively. Induced fit docking studies for enzymes 4EY7, 7BO4, 2BXR, and 2BYB showed active interactions between sulfonyl thioureas of benzodthiazoles and the residues in the active pocket with ligands 6k, 6i, and 6j, respectively. The stability of the ligand–protein complexes while each ligand entered the active site of each enzyme (4EY7, 7BO4, 2BXR, or 2BYB) was confirmed by molecular dynamics simulations.
Substituted 2‐(3‐tosylthioureido)benzodthiazoles 6a–q were synthesized and studied for inhibition of acetylcholinesterase, butyrylcholinesterase, and monoamine oxidase (MAO)‐A and MAO‐B. Compounds 6k and 6j followed competitive‐type enzyme inhibition kinetics. Induced fit docking and molecular dynamics simulation studies of 6i, 6j, and 6k on the four enzymes showed the stability of the ligand–protein complexes and the structural mode of binding.
SUMMARY
In the realisation of the International Height Reference System, the determination of the geopotential value and its variations in time plays an important role. In this study, the geodetic ...boundary value problem approach is applied for direct determination of the gravity potential value using a GOCE global gravity field model enhanced with terrestrial gravity data. This determination is carried out on the Global Navigation Satellite System-Continuously Operating Reference Stations (GNSS-CORS) stations towards the realisation of the International Height Reference System in Vietnam. First, the effects of the GOCE global gravity field model omission error, the indirect bias term on the disturbing potential and the systematic cumulative errors in levelling data are estimated. These errors affect the estimated geopotential value. The results calculated on the GNSS/levelling points show that the effect of the GOCE DIR-R5 (up to degree/order 260) omission error on the offset potential value is quite significant. This effect was eliminated using high-resolution terrestrial gravity data using the remove-compute-restore technique. The indirect bias term on the disturbing potential can be safely neglected by using a GOCE global gravity field model for degrees higher than 60 for this study region. The systematic cumulative errors in levelling data can be modelled and removed using a third-order polynomial model. Then, the mean zero-height gravity potential of the Vietnam local vertical datum is estimated equal to ${\rm{W}}_0^{{\rm{LVD}}}$ = 62 636 846.69 m2 s–2 with standard deviation of 0.70 m2 s–2 based on the proposed approach. Finally, the geodetic boundary value problem approach was used to determine the geopotential on the surface of three GNSS-CORS stations in Vietnam. Based on time-series of the vertical component derived from the GNSS observations as well as InSAR data, temporal variations in geopotential are also estimated on these permanent GNSS stations. The purpose is to monitor deformation of the vertical datum. The results indicate that the geopotential value needs to be monitored and determined with the time-dependent component on the three Vietnamese permanent GNSS stations for a vertical datum. These stations may contribute to increase the density of reference points in the International Terrestrial Reference Frame, which is being researched and implemented by the International Association of Geodesy.
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