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•A new polycation PVBTAC-modified ZnO/SiO2 nanocomposite based on rice husk was successfully fabricated.•The optimum conditions for DCF removal using PVBTAC-modified ZnO/SiO2 were ...contact time 90 min, pH 8 and dosage 10 mg/mL.•The maximum adsorption capacity of DCF was 66 mg/g and the removal efficiency was 91.8%.•After four regenerations, the DCF removal using PVBTAC modified ZnO/SiO2 was still greater than 84%.•The E.coli removal was greater than 88 % that was controlled by electrostatic and non-electrostatic interactions.
The present study investigated the adsorptive removal of non-steroidal medication diclofenac (DCF) using polycation, PVBTAC modified zinc oxide/silica nanocomposite (ZnO/SiO2). The ZnO/SiO2 which was fabricated based on nanosilica rice, was examined by XRD, FT-IR, TEM, EDX, and zeta potential measurements. Surface of ZnO/SiO2 was modified by PVBTAC adsorption at pH 9 and 100 mM KCl to reverse the high charge of material. The optimum parameters for DCF removal using PVBTAC-modified ZnO/SiO2 were contact time 90 min, pH 8 and adsorbent dosage 10 mg/mL. The maximum adsorption capacity and the removal efficiency of DCF were found to be 66 mg/g and 91.8%, respectively, while the bacteria Escherichiacoli(E.coli) removal reached greater than 88 %. Adsorption of DCF on PVBTAC-modified ZnO/SiO2 was mainly controlled by electrostatic attraction between anionic DCF molecules and positively charged PVBTAC-modified ZnO/SiO2 surface whereas the E.coli removal was controlled by both electrostatic and non-electrostatic interactions. Adsorption isotherms of DCF on PVBTAC-modified ZnO/SiO2 at different ionic strengths were reasonably represented by a two-step model while adsorption kinetics fitted well with the pseudo-second-order model. After four regenerations of PVBTAC modified ZnO/SiO2, the DCF removal still exceeded 84%. Our materialis agreat performance adsorbent to remove pharmaceutical and bacteria.
Limited capability and political will have caused the great powers to fail to demonstrate their global leadership in the fight against the COVID-19 pandemic, which has created greater room to ...manoeuvre for other countries to influence international affairs. Preliminary achievements in the fight against the COVID-19 crisis have buttressed the rising global status of small and medium-sized states, including Vietnam. Although Vietnam has recently been recognised as an emerging middle power, scepticism looms regarding whether this higher international status is beyond its capacity. We argue that the pandemic may act as a catalyst for Vietnam to further elevate its strategic role as a middle power on the international stage in the medium and long term.
One hundred days after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first reported in Vietnam on 23 January, 270 cases were confirmed, with no deaths. We describe the control ...measures used by the government and their relationship with imported and domestically acquired case numbers, with the aim of identifying the measures associated with successful SARS-CoV-2 control.
Clinical and demographic data on the first 270 SARS-CoV-2 infected cases and the timing and nature of government control measures, including numbers of tests and quarantined individuals, were analyzed. Apple and Google mobility data provided proxies for population movement. Serial intervals were calculated from 33 infector-infectee pairs and used to estimate the proportion of presymptomatic transmission events and time-varying reproduction numbers.
A national lockdown was implemented between 1 and 22 April. Around 200 000 people were quarantined and 266 122 reverse transcription polymerase chain reaction (RT-PCR) tests conducted. Population mobility decreased progressively before lockdown. In total, 60% (163/270) of cases were imported; 43% (89/208) of resolved infections remained asymptomatic for the duration of infection. The serial interval was 3.24 days, and 27.5% (95% confidence interval CI, 15.7%-40.0%) of transmissions occurred presymptomatically. Limited transmission amounted to a maximum reproduction number of 1.15 (95% CI, .·37-2.·36). No community transmission has been detected since 15 April.
Vietnam has controlled SARS-CoV-2 spread through the early introduction of mass communication, meticulous contact tracing with strict quarantine, and international travel restrictions. The value of these interventions is supported by the high proportion of asymptomatic and imported cases, and evidence for substantial presymptomatic transmission.
In this work, Pt-SiO2/graphene nanocomposites have been synthesized under solvothermal conditions and investigated as electrocatalysts for methanol oxidation. Structure and morphology of these ...catalysts are characterized by transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and nitrogen adsorption/desorption studies. The Pt and SiO2 contents of these nanocomposites are determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Their electrocatalytic properties are investigated by cyclic voltammetry, chronoamperometry, chronopotentiometry and electrochemical impendence spectroscopy. The as-prepared nanocomposites show the improved catalytic performance, better stability and good antiposoining ability compared with Pt supported on graphene catalyst. Particularly, the catalyst containing 9.24% of SiO2 exhibits the best electrocatalytic performance for methanol oxidation with mass activity of 1047mAmg−1.
Finding renewable energy sources to replace fossil energy has been an essential demand in recent years. Hydrogen gas has been becoming a research hotspot for its clean and free-carbon energy. ...However, hydrogen storage technology is challenging for mobile and automotive applications. Metal–organic frameworks (MOFs) have emerged as one of the most advanced materials for hydrogen storage due to their exceptionally high surface area, ultra-large and tuneable pore size. Recently, computer simulations allowed the designing of new MOF structures with significant hydrogen storage capacity. However, no studies are available to elucidate the hydrogen storage in M(BDC)(TED) 0.5 , where M = metal, BDC = 1,4-benzene dicarboxylate, and TED = triethylenediamine. In this report, we used van der Waals-dispersion corrected density functional theory and grand canonical Monte Carlo methods to explore the electronic structure properties, adsorption energies, and gravimetric and volumetric hydrogen loadings in M(BDC)(TED) 0.5 (M = Mg, V, Co, Ni, and Cu). Our results showed that the most favourable adsorption site of H 2 in M(BDC)(TED) 0.5 is the metal cluster–TED intersection region, in which Ni offers the strongest binding strength with the adsorption energy of −16.9 kJ mol −1 . Besides, the H 2 @M(BDC)(TED) 0.5 interaction is physisorption, which mainly stems from the contribution of the d orbitals of the metal atoms for M = Ni, V, Cu, and Co and the p orbitals of the O, C, N atoms for M = Mg interacting with the σ* state of the adsorbed hydrogen molecule. Noticeably, the alkaline-earth metal Mg strongly enhanced the specific surface area and pore size of the M(BDC)(TED) 0.5 MOF, leading to an enormous increase in hydrogen storage with the highest absolute (excess) gravimetric and volumetric uptakes of 1.05 (0.36) wt% and 7.47 (2.59) g L −1 at 298 K and 7.42 (5.80) wt% and 52.77 (41.26) g L −1 at 77 K, respectively. The results are comparable to the other MOFs found in the literature.
A series of small chromium-doped silicon clusters CrSin with n = 3–10 in the cationic, neutral and anionic charge states were investigated using quantum chemical methods. The CrSin+ cations with n = ...6–10 were produced in the gas phase and characterized by far-IR multiple photon dissociation (IR-MPD) spectroscopy. Good agreement between experimental spectra in the 200–600 cm−1 frequency range and those determined for the lowest-energy isomers by density functional theory calculations (B3P86/6-311+G(d)) provide a strong support for the geometrical assignments. An extensive structural comparison for the three different charge states shows that the structural growth mechanism inherently depends on the charge. While the structures of the cationic clusters are preferentially formed by addition of the Cr dopant to the corresponding pure silicon cluster, it favors substitution in both the neutral and anionic counterparts. The Si–Cr bonds of the studied CrSin+/0/− clusters are polar covalent. Apart from a basket-like Cr@Si9− and an endohedral Cr@Si10− cage, the Cr dopant takes an exohedral position and bears a large positive charge in the clusters. The exohedrally doped clusters also have a high spin density on Cr, manifesting the fact that the intrinsic magnetic moment of the transition metal dopant is well conserved. Three CrSin clusters have a pair of enantiomeric isomers in their ground state, namely the cationic n = 9 and the neutral and anionic n = 7. Those can be distinguished from each other by their electronic circular dichroism spectra, calculated using time-dependent density functional theory. Those enantiomers, being intrinsically chiral inorganic compounds, might be used as building blocks of optical-magnetic nanomaterials because of their high magnetic moments and ability to rotate the plane of polarization.
Imidazolium, pyridinium, pyrrolidinium, piperidinium, morpholinium, and quaternary ammonium bis(trifluoromethylsulfonyl)imide salts were functionalized with a carboxyl group. These ionic liquids are ...useful for the selective dissolution of metal oxides and hydroxides. Although these hydrophobic ionic liquids are immiscible with water at room temperature, several of them form a single phase with water at elevated temperatures. Phase separation occurs upon cooling. This thermomorphic behavior has been investigated by 1H NMR, and it was found that it can be attributed to the temperature-dependent hydration and hydrogen-bond formation of the ionic liquid components. The crystal structures of four ionic liquids and five metal complexes have been determined.
A brief gonadotropin-releasing hormone analogues (GnRHa) stimulation test which solely focused on LH 30-minute post-stimulation was considered to identify girls with central precocious puberty (CPP). ...However, it was tested using traditional statistical methods. With advanced computer science, we aimed to develop a machine learning-based diagnostic model that processed baseline CPP-related variables and a brief GnRHa stimulation test for CPP diagnosis.
We recruited girls suspected of precocious puberty and underwent a GnRHa stimulation test at Children Hospital 2, Vietnam, and Cathay General Hospital, Taiwan. Clinical data, bone age measurement, and 30-min post-stimulation blood test were used to build up the predictive model. The candidate model was developed by different machine learning algorithms that were mainly evaluated by sensitivity, specificity, the area under the receiver operator characteristic curve (AUC), and F1-score in internal and external validation data to classify girls as CPP and non-CPP at different time-points (0-min, 30-min, 60-min, and 120-min post-stimulation).
Among the 614 girls diagnosed with PP, 524 (85.3%) had CPP. The random forest algorithm yielded the highest value of F1-score (0.976), specificity (0.893), positive predicted value (0.987), and relatively high value of AUC (0.972) that contributed to high probability to identify CPP. The performance metrics of the 30-min post-stimulation diagnostic model including sensitivity and specificity surpassed those of the 0-minute model (0-min) and were equivalent to those of the model obtained 60-min and 120-min post-stimulation. Hence, our machine learning-based model helps shorten the stimulation test to 30 minutes after GnRHa injection, in general, it requires 120 minutes for a completed GnRHa stimulation test.
We developed a diagnostic model based on clinical features and a single sample 30-minute post-stimulation to identify CPP in girls that can reduce distress for children caused by multiple blood samplings.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•Peak shape enhancement using diethylamine as mobile phase modifier.•DEA reduced retention of methionine due to competition in electrostatic interaction and silanol end-capping effect.•A simple and ...robust HILIC method for simultaneous determination of paracetamol and methionine.
Methionine (MET) is combined with paracetamol (PAR) in a pain relief soft capsule in order to prevent the haematologic damage of paracetamol. A hydrophillic liquid chromatographic (HILIC) method was developed for simultaneous determination of PAR and MET in the combined formulation. Various analytical conditions were investigated, and the final method was chosen using silica column (150 × 4,6 mm; 5 μm), mobile phase of acetonitrile – aqueous solution of 10 mM formic acid 5 mM diethylamine (60:40, v/v), UV detection at 254 nm for PAR and 210 nm for MET. The method was validated according to ICH guidelines in terms of selectivity, linearity, accuracy, precision and robustness. The method was successfully applied for quantitation of both compounds in soft capsule preparations bought from the market. Notably, in this study, a novel approach was proposed to improve peak shape of amino acid – a problem often observed in HILIC. The addition of diethylamine to mobile phase shortened the retention time of MET and significantly improved peak shape on both silica and cyano columns, due to electrostatic interaction competition and silanol end-capping effect. The result of this research demonstrated the advantages of HILIC in simultaneous analysis of a polar compound amino acid, especially in combination with a less polar substance. The use of diethylamine as a mobile phase modifier to enhance peak shape is a new suggestion that can be used in further studies on amino acid analysis by HILIC.
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•Pt/rGO catalysts were successfully synthesized using either NaBH4 or ethylene glycol.•Synthesis using NaBH4 could improve electrocatalytic towards methanol oxidation of Pt/rGO ...catalyst.•40%Pt/rGO synthesized using NaBH4 showed the best electrocatalytic performance.
The synthesis processes of Platinum (Pt) on reduced graphene oxide (rGO) catalysts from graphene oxide (GO) using two reducing agents including sodium borohydride and ethylene glycol is reported. Structure and morphology of Pt/rGO catalysts are characterized by X-ray powder diffraction, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Electrocatalytic methanol oxidation properties of these catalysts are evaluated by cyclic voltammetry and chronoamperometry. The results show that catalyst synthesized using sodium borohydride has a higher metallic Pt content and an improved catalytic performance in comparison to catalyst synthesized using ethylene glycol. Moreover, effect of Pt loading amount on electrocatalytic methanol oxidation performance of catalysts synthesized using sodium borohydride is systematically investigated. The optimal Pt loading amount on graphene is determined to be 40%.
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