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61.
In this paper, we extend the well-known result “the predual of Hardy space \(H^1\) is VMO” to the product setting, associated with differential operators. Let \(L_i\), \(i = 1, 2\), be the infinitesimal generators of the analytic semigroups \(\{e^{-tL_i}\}\) on \(L^2({\mathbb {R}})\). Assume that the kernels of the semigroups \(\{e^{-tL_i}\}\) satisfy the Gaussian upper bounds. We introduce the VMO spaces VMO\(_{L_1, L_2}(\mathbb {R}\times \mathbb {R})\) associated with operators \(L_1\) and \(L_2\) on the product domain \(\mathbb {R}\times \mathbb {R}\), then show that the dual space of VMO\(_{L_1, L_2}(\mathbb {R}\times \mathbb {R})\) is the Hardy space \(H^1_{L_1^*, L_2^*}(\mathbb {R}\times \mathbb {R})\) associated with the adjoint operators \(L^*_1\) and \(L^*_2\).  相似文献   
62.
Let L be a Schrdinger operator of the form L =-? + V acting on L~2(R~n), n≥3, where the nonnegative potential V belongs to the reverse Hlder class B_q for some q≥n. Let BMO_L(R~n) denote the BMO space associated to the Schrdinger operator L on R~n. In this article, we show that for every f ∈ BMO_L(R~n) with compact support, then there exist g ∈ L~∞(R~n) and a finite Carleson measure μ such that f(x) = g(x) + S_(μ,P)(x) with ∥g∥∞ + |||μ|||c≤ C∥f∥BMO_L(R~n), where S_(μ,P)=∫(R_+~(n+1))Pt(x,y)dμ(y, t),and Pt(x, y) is the kernel of the Poisson semigroup {e-~(t(L)~(1/2))}t0 on L~2(R~n). Conversely, if μ is a Carleson measure, then S_(μ,P) belongs to the space BMO_L(R~n). This extends the result for the classical John-Nirenberg BMO space by Carleson(1976)(see also Garnett and Jones(1982), Uchiyama(1980) and Wilson(1988)) to the BMO setting associated to Schrdinger operators.  相似文献   
63.
Defluorinative manipulation of polyfluorinated molecules has shown great promise due to its granting of synthetic versatility to inert C−F bonds. The development of chemo-, stereo- and regioselective strategies to realize highly efficient formation of either the linear/branched or E/Z products from gem-difluorocyclopropanes (gem-F2CPs) is a challenging task. Herein, we have realized palladium/NHC-catalyzed fluoroallylation/annulation of hydrazones with gem-F2CPs that incorporate the hydrazone N2 moiety into the products. The thermodynamically unstable fluorinated E-allylation products with aryl ketone hydrazones were obtained for the first time, while the di-alkyl ketone hydrazones yielded the monofluorinated products with branched selectivity under similar reaction conditions. With aldehyde hydrazones, two kinds of pyrazoles were obtained via a defluorinative allylation/annulation cascade, in which different carbon atoms of gem-F2CPs could be incorporated into the pyrazole rings regiospecifically. DFT calculations revealed that the divergent selectivity was kinetically controlled and the final C−C bond formation proceeded through a 7-membered TS.  相似文献   
64.
We used correlative transmission electron microscopy (TEM) and nanoscale secondary ion mass spectrometry (NanoSIMS) imaging to quantify the contents of subvesicular compartments, and to measure the partial release fraction of 13C-dopamine in cellular nanovesicles as a function of size. Three modes of exocytosis comprise full release, kiss-and-run, and partial release. The latter has been subject to scientific debate, despite a growing amount of supporting literature. We tailored culturing procedures to alter vesicle size and definitively show no size correlation with the fraction of partial release. In NanoSIMS images, vesicle content was indicated by the presence of isotopic dopamine, while vesicles which underwent partial release were identified by the presence of an 127I-labelled drug, to which they were exposed during exocytosis allowing entry into the open vesicle prior to its closing again. Demonstration of similar partial release fractions indicates that this mode of exocytosis is predominant across a wide range of vesicle sizes.  相似文献   
65.
Surfactants are used to control the macroscopic properties of the air-water interface. However, the link between the surfactant molecular structure and the macroscopic properties remains unclear. Using sum-frequency generation spectroscopy and molecular dynamics simulations, two ionic surfactants (dodecyl trimethylammonium bromide, DTAB, and sodium dodecyl sulphate, SDS) with the same carbon chain lengths and charge magnitude (but different signs) of head groups interact and reorient interfacial water molecules differently. DTAB forms a thicker but sparser interfacial layer than SDS. It is due to the deep penetration into the adsorption zone of Br counterions compared to smaller Na+ ones, and also due to the flip-flop orientation of water molecules. SDS alters two distinctive interfacial water layers into a layer where H+ points to the air, forming strong hydrogen bonding with the sulphate headgroup. In contrast, only weaker dipole-dipole interactions with the DTAB headgroup are formed as they reorient water molecules with H+ point down to the aqueous phase. Hence, with more molecules adsorbed at the interface, SDS builds up a higher interfacial pressure than DTAB, producing lower surface tension and higher foam stability at a similar bulk concentration. Our findings offer improved knowledge for understanding various processes in the industry and nature.  相似文献   
66.
Type 2 Diabetes Mellitus (T2D) is a chronic, obesity-related, and inflammatory disorder characterize by insulin resistance, inadequate insulin secretion, hyperglycemia, and excessive glucagon secretion. Exendin-4 (EX), a clinically established antidiabetic medication that acts as a glucagon-like peptide-1 receptor agonist, is effective in lowering glucose levels and stimulating insulin secretion while significantly reducing hunger. However, the requirement for multiple daily injections due to EX's short half-life is a significant limitation in its clinical application, leading to high treatment costs and patient inconvenience. To address this issue, an injectable hydrogel system is developed that can provide sustained EX release at the injection site, reducing the need for daily injections. In this study, the electrospray technique is examine to form EX@CS nanospheres by electrostatic interaction between cationic chitosan (CS) and negatively charged EX. These nanospheres are uniformly dispersed in a pH-temperature responsive pentablock copolymer, which forms micelles and undergoes sol-to-gel transition at physiological conditions. Following injection, the hydrogel gradually degraded, exhibiting excellent biocompatibility. The EX@CS nanospheres are subsequently released, maintaining therapeutic levels for over 72 h compared to free EX solution. The findings demonstrate that the pH-temperature responsive hydrogel system containing EX@CS nanospheres can be a promising platform for the treatment of T2D.  相似文献   
67.
In recent years, there has been an increased interest in injectable, in situ crosslinking hydrogels due to their minimally invasive application and ability to conform to their environment. Current in situ crosslinking chitosan hydrogels are either mechanically robust with poor biocompatibility and limited biodegradation due to toxic crosslinking agents or the hydrogels are mechanically weak and undergo biodegradation too rapidly due to insufficient crosslinking. Herein, the authors developed and characterized a thermally-driven, injectable chitosan-genipin hydrogel capable of in situ crosslinking at 37 °C that is mechanically robust, biodegradable, and maintain high biocompatibility. The natural crosslinker genipin is utilized as a thermally-driven, non-toxic crosslinking agent. The chitosan-genipin hydrogel's crosslinking kinetics, injectability, viscoelasticity, swelling and pH response, and biocompatibility against human keratinocyte cells are characterized. The developed chitosan-genipin hydrogels are successfully crosslinked at 37 °C, demonstrating temperature sensitivity. The hydrogels maintained a high percentage of swelling over several weeks before degrading in biologically relevant environments, demonstrating mechanical stability while remaining biodegradable. Long-term cell viability studies demonstrated that chitosan-genipin hydrogels have excellent biocompatibility over 7 days, including during the hydrogel crosslinking phase. Overall, these findings support the development of an injectable, in situ crosslinking chitosan-genipin hydrogel for minimally invasive biomedical applications.  相似文献   
68.
69.
Microfluidic particle focusing has been a vital prerequisite step in sample preparation for downstream particle separation, counting, detection, or analysis, and has attracted broad applications in biomedical and chemical areas. Besides all the active and passive focusing methods in Newtonian fluids, particle focusing in viscoelastic fluids has been attracting increasing interest because of its advantages induced by intrinsic fluid property. However, to achieve a well-defined focusing position, there is a need to extend channel lengths when focusing micrometer-sized or sub-microsized particles, which would result in the size increase of the microfluidic devices. This work investigated the sheathless viscoelastic focusing of particles and cells in a zigzag microfluidic channel. Benefit from the zigzag structure of the channel, the channel length and the footprint of the device can be reduced without sacrificing the focusing performance. In this work, the viscoelastic focusing, including the focusing of 10 μm polystyrene particles, 5 μm polystyrene particles, 5 μm magnetic particles, white blood cells (WBCs), red blood cells (RBCs), and cancer cells, were all demonstrated. Moreover, magnetophoretic separation of magnetic and nonmagnetic particles after viscoelastic pre-focusing was shown. This focusing technique has the potential to be used in a range of biomedical applications.  相似文献   
70.
A highly sensitive amperometric Prussian blue-based hydrogen peroxide sensor was developed using 3D pyrolytic carbon microelectrodes. A 3D printed multielectrode electrochemical cell enabled simultaneous highly reproducible Prussian blue modification on multiple carbon electrodes. The effect of oxygen plasma pre-treatment and deposition time on Prussian blue electrodeposition was studied. The amperometric response of 2D and 3D sensors to the addition of hydrogen peroxide in μM and sub-μM concentrations in phosphate buffer was investigated. A high sensitivity comparable to flow injection systems and a detection limit of 0.16 μM was demonstrated with 3D pyrolytic carbon microelectrodes at stirred batch condition  相似文献   
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