Precise point positioning (PPP) service is of great significance for BDS. The design and implementation of the service are presented. The PPP‐B2b signal of the service is constructed, which is ...efficient multiplexed with other signal components, and achieves compatibility between two service phases. A customized message format that can augment all visible satellites of four core constellations in mainland China is proposed. The high‐gain, 64‐ary, low‐density parity check (LDPC) coding is used, which facilitates the integrated design of the receivers. A signal quality test has revealed that the S‐curve bias (SCB) of PPP‐B2b does not exceed 0.0165 ns and the coherence between the code and the carrier of the signal is only 0.137∘. A performance evaluation has indicated that at its current stage, the positioning accuracy in the horizontal and vertical directions is better than 0.15 m and 0.3 m, respectively, and the convergence time does not exceed 800 s.
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•A new method for the synthesis of carbodiimides from thioureas catalyzed by DMAP is developed.•Di-tert-butyl dicarbonate (Boc)2O is used as a new dehydrosulfurizative reagent.•No ...more organic wastes are generated beside the SCO and t-BuOH.
A concise method for the preparation of carbodiimides from thioureas using di-tert-butyl dicarbonate (Boc)2O as the dehydrosulfurizative reagent has been developed. Using DMAP as the catalyst, a variety of symmetric and asymmetric 1,3-diaryl thioureas were converted into the corresponding carbodiimides efficiently in a short time.
Rapid detection of picric acid in real sample is of outmost importance from the perspective of health, safety, and environment. In this study, a very simple and cost-effective detection of picric ...acid is accomplished by developing a couple of biobased conjugates curcumin–cysteine (CC) and curcumin–tryptophan (CT), which undergo efficient fluorescence turn on toward picric acid in aqueous media. Both the probes experience about 26.5-fold fluorescence enhancements at 70 nM concentration of the analyte. Here, the fluorescence turn on process is governed by the aggregation induced emission, which is induced from the electrostatic interaction between the conjugates with picric acid. The detection limit of CC and CT are about 13.51 and 13.54 nM of picric acid, respectively. Importantly, both the probes exhibit high selectivity and low interference of other analogues toward the detection of picric acid. In addition, the probes are highly photostable, show low response time and are practically applicable for sensing picric acid in real environmental samples, which is the ultimate goal of this work.
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The aim of this study was to evaluate the safety and efficacy for hydrophobic ion-pairing of surfactants based on arginine (Arg). The prepared Arg-cholesteryl ester (ACE) and ...Arg-diosgenyl ester (ADE) were characterized regarding solubility, pKa, critical micellar concentration (CMC), biodegradability as well as membrane- and aquatic toxicity using DOTAP as reference. The ability for hydrophobic ion-pairing was evaluated and the lipophilicity of formed complexes was determined.
NMR, FT-IR and MS confirmed successful synthesis of Arg-surfactants. The slightly soluble single-charged Arg-surfactants (pH < pKa3 (ACE = 10.42 ± 0.52; ADE = 10.38 ± 0.27)) showed CMCs of 27.17 µM for ACE and 35.67 µM for ADE. CMCs of the sparingly soluble double-charged species (pH < pKa2 (ACE = 5.30 ± 0.20; ADE = 5.55 ± 0.06)) were determined at concentrations of ≥ 250 µM for ACE and ≥ 850 µM for ADE. The enzymatic- and environmental biodegradability was proven by an entire cleavage of Arg-surfactants within 24 h, whereas DOTAP remained stable. Arg-surfactants exhibited lower membrane- (> 2-fold) and aquatic toxicity (> 15-fold) than DOTAP. The complexes formed with Arg-surfactants and insulin showed higher lipophilicity than the DOTAP-complex. According to these results, Arg-surfactants might be a promising safe tool for the delivery of peptide drugs.
Florisil (magnesium polysilicate) is an efficient and eco-friendly reagent for the deprotection of tert-butyl carbamates, carbonates, and ethers. Moderate to excellent yields could be achieved in the ...presence of other acid-sensitive groups. The separation of products is easy, and Florisil can be recycled several times without observing a decrease in yields.
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The photoreaction of an N-Boc secondary amine and N-Boc N-methyl α-amino acid ester with acrylonitrile using inexpensive two-molecule photoredox catalysts results in the production of α-alkylated ...amine through the generation of an α-carbamy radical under mild conditions. In particular, this mothed leads to a regioselective modification of N-Boc N-methyl α-amino acid ester with the retention of α-chirality through the generation of the less stable primary α-carbamyl radical.
Sulfonic acid-functionalized ordered nanoporous Na
+-montmorillonite (SANM) was used as an efficient catalyst for
N-
tert-butoxycarbonylation of amines with di-
tert-butyl dicarbonate under ...solvent-free conditions at room temperature. Various aliphatic, aromatic, heterocyclic amines and aminols were protected as their corresponding mono-carbamates in excellent yields and short reaction times. No competitive side reactions such as isocyanate, urea, and
N,
N-di-Boc formation were observed. The reported method is mild, chemoselective and has the advantages such as heterogeneous catalysis, low cost and the recyclability of the catalyst.
Sulfonic acid-functionalized ordered nanoporous Na
+-montmorillonite (SANM) was found to be a mild, novel, efficient and reusable catalyst for
N-
tert-butoxycarbonylation of amines with di-
tert-butyl dicarbonate under solvent-free conditions at room temperature.
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► Synthesis of sulfonic acid-functionalized ordered nanoporous Na
+-montmorillonite. ► Characterization and application of SANM for
N-
tert-butoxycarbonylation of amines. ► Catalysis under solvent-free conditions at room temperature. ► Heterogeneous catalysis and recyclability of the catalyst.
•Synthesis of polymerizable TLAs as the styrene and methacrylate derivatives.•Therman deprotection and decomposition behavior of the TLA homopolymers.•Copolymerization of PBHEMA with the TLAs and the ...characterization of the resulting copolymers.•Achievement of thermal stability during storage and quick deprotection on heating using the methacrylate -type TLAs.
Poly((2‑tert-butoxycarbonyloxy)ethyl methacrylate) (PBHEMA) is converted to poly(2-hydroxyethyl methacrylate) (PHEMA) with the release of isobutene and CO2 by heating and this reaction is accelerated by an acid. The thermally latent acid catalysts (TLA) are useful for the control of a working temperature for the deprotection of the tert‑butoxycarbonyl (BOC) groups included in PBHEMA. In this study, styrene- and methacrylate-type sulfonic esters were synthesized and copolymerized with BHEMA in order to investigate the effect of the TLAs incorporated into the polymer chains. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were carried out for the copolymers of BHEMA with the polymerizable TLAs in order to discuss the deprotection features of the BOC group in comparison with the results for the systems of PBHEMA blended with the low-molecular-weight TLAs.
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We reported the base-promoted cyclization of N-Boc arylimidrazone toward 1,2-dihydro 3H-1,2,4-triazol-3-one. This procedure tolerated methyl, methoxy, chloro, bromo, fluoro, cyano, ...methylcarbonyl groups well. Thus, it represents a facile and high efficient pathway leading to 1,2-dihydro 3H-1,2,4-triazol-3-one. Mechanism study revealed this procedure proceeded with the intramolecular nucleophilic cyclization rather than N-isocyanate intermediate.
Pleomorphic adenoma (PA) is the most common benign salivary gland tumor. Fine‐needle aspiration (FNA) of PA exhibits variable combinations of bland ductal epithelial cells, myoepithelial cells, and ...characteristic magenta fibrillary stroma on Diff–Quik/Romanowsky stain. However, a cellular PA with scant chondromyxoid stroma can be a diagnostic challenge on FNA. Around 70% of PAs have a translocation involving PLAG1 or HMGA2. The presence of either PLAG1 or HMGA2 fusion gene can be used to diagnose PA since they have not been reported in other salivary gland tumors except for carcinoma ex PA. In this case report, we describe a case of cellular PA initially diagnosed on FNA as a “low grade salivary gland neoplasm, favor PA.” RNA next‐generation sequencing performed on the cell block showed a BOC‐PLAG1 fusion gene. The presence of PLAG1 fusion gene in conjunction with cytomorphology supported a diagnosis of PA. The mass was surgically removed and proved to be a cellular PA with scattered foci of chondromyxoid and collagenous stroma. To our knowledge, this is the first reported PA bearing BOC‐PLAG1. RNA next‐generation sequencing performed on cytology specimens can be helpful in achieving a more specific diagnosis of salivary gland tumors.
