We herein report the preparation of solid and salt‐stabilized silylzinc pivalates from the corresponding silyllithium reagents via transmetalation with Zn(OPiv)2. These resulting organosilylzinc ...pivalates show enhanced air and moisture stability and unique reactivity in the silylative difunctionalization of alkenes. Thus, a practical chelation‐assisted nickel‐catalyzed regioselective alkyl and benzylsilylation of alkenes has been developed, which provides an easy method to access alkyl silanes with broad substrate scope and wide functional group compatibility. Kinetic experiments highlight that the OPiv‐coordination is crucial to improve the reactivity of silylzinc pivalates. Furthermore, late‐stage functionalizations of druglike molecules and versatile modifications of the products illustrate the synthetical utility of this protocol.
A new type of salt‐stabilized solid silylzinc pivalate prepared from the silyllithium reagents via transmetalation with Zn(OPiv)2 is reported. These silylzinc pivalates showed enhanced air and moisture stability and unique reactivity in the nickel‐catalyzed regioselective alkyl and benzylsilylation of alkenes. Kinetic experiments highlighted the crucial involvement of OPiv‐coordination in improving the reactivity of silylzinc pivalates.
We propose a low-insertion-loss electro-optic modulator formed with LNOI bonded on a D-shaped SMF. The proposed modulator employs high-performance Mach-Zehnder interferometer (MZI) formed with ridge ...LNOI waveguides and driven by travelling-wave electrodes. The light from the fiber core is coupled into a thin strip LNOI waveguide and then launched into the MZI via a ridge LNOI waveguide with tapered slab height and vice versa. Such all-fiber configuration exempts the need of the butt-coupling with an SMF. The calculated results show that our proposed modulator is capable of achieving a low insertion loss of less than 1.5 dB, an EO modulation efficiency ( V π ·L ) of 2.05 V·cm, and a 3-dB modulation bandwidth of larger than 80 GHz. Our all-fiber LNOI modulator is feasible in practice and opens a new door to realize high-speed fiber devices by the integration of an optical fiber and thin film LN.
We propose a simple thermo-optic mode-selective switch based on an asymmetric directional coupler formed with a two-mode waveguide and a single-mode waveguide, where two electrodes heaters are ...deposited, respectively, on the two waveguides. Depending on which heater is turned on, either one of the two modes in the two-mode waveguide can be selectively switched to the single-mode waveguide or vice versa. Our typical experimental device fabricated with polymer material, which has a total length of 16.5 mm, shows extinction ratios higher than ~10 dB in the C-band for both modes. The switching powers for the two modes are 52 and 109 mW, respectively, and the corresponding switching times are 300 and 400 μs. This device could be used in reconfigurable mode-division-multiplexing systems.
With the rapid development of the remote sensing monitoring and computer vision technology, the deep learning method has made a great progress to achieve applications such as earth observation, ...climate change and even space exploration. However, the model trained on existing data cannot be directly used to handle the new remote sensing data, and labeling the new data is also time-consuming and labor-intensive. Unsupervised Domain Adaptation (UDA) is one of the solutions to the aforementioned problems of labeled data defined as the source domain and unlabeled data as the target domain, i.e., its essential purpose is to obtain a well-trained model and tackle the problem of data distribution discrepancy defined as the domain shift between the source and target domain. There are a lot of reviews that have elaborated on UDA methods based on natural data, but few of these studies take into consideration thorough remote sensing applications and contributions. Thus, in this paper, in order to explore the further progress and development of UDA methods in remote sensing, based on the analysis of the causes of domain shift, a comprehensive review is provided with a fine-grained taxonomy of UDA methods applied for remote sensing data, which includes Generative training, Adversarial training, Self-training and Hybrid training methods, to better assist scholars in understanding remote sensing data and further advance the development of methods. Moreover, remote sensing applications are introduced by a thorough dataset analysis. Meanwhile, we sort out definitions and methodology introductions of partial, open-set and multi-domain UDA, which are more pertinent to real-world remote sensing applications. We can draw the conclusion that UDA methods in the field of remote sensing data are carried out later than those applied in natural images, and due to the domain gap caused by appearance differences, most of methods focus on how to use generative training (GT) methods to improve the model’s performance. Finally, we describe the potential deficiencies and further in-depth insights of UDA in the field of remote sensing.
Human umbilical cord mesenchymal stem cell‐derived exosomes (hucMSC‐exosomes) have been implicated as a novel therapeutic approach for tissue injury repair and regeneration, but the effects of ...hucMSC‐exosomes on coxsackievirus B3 (CVB3)‐induced myocarditis remain unknown. The object of the present study is to investigate whether hucMSC‐exosomes have therapeutic effects on CVB3‐induced myocarditis (VMC). HucMSC‐exosomes were identified using nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM) and Western blot. The purified hucMSC‐exosomes tagged with PKH26 were tail intravenously injected into VMC model mice in vivo and used to administrate CVB3‐infected human cardiomyocytes (HCMs) in vitro, respectively. The effects of hucMSC‐exosomes on myocardial pathology injury, proinflammatory cytokines and cardiac function were evaluated through haematoxylin and eosin (H&E) staining, quantitative polymerase chain reaction (qPCR) and Doppler echocardiography. The anti‐apoptosis role and potential mechanism of hucMSC‐exosomes were explored using TUNEL staining, flow cytometry, immunohistochemistry, Ad‐mRFP‐GFP‐LC3 transduction and Western blot. In vivo results showed that hucMSC‐exosomes (50 μg iv) significantly alleviated myocardium injury, shrank the production of proinflammatory cytokines and improved cardiac function. Moreover, in vitro data showed that hucMSC‐exosomes (50 μg/mL) inhibited the apoptosis of CVB3‐infected HCM through increasing pAMPK/AMPK ratio and up‐regulating autophagy proteins LC3II/I, BECLIN‐1 and anti‐apoptosis protein BCL‐2 as well as decreasing pmTOR/mTOR ratio, promoting the degradation of autophagy flux protein P62 and down‐regulating apoptosis protein BAX. In conclusion, hucMSC‐exosomes could alleviate CVB3‐induced myocarditis via activating AMPK/mTOR‐mediated autophagy flux pathway to attenuate cardiomyocyte apoptosis, which will be benefit for MSC‐exosome therapy of myocarditis in the future.
The accurate and sensitive detection of biomolecules by surface-enhanced Raman spectroscopy (SERS) is possible, but remains challenging due to the interference from biomolecules in complex samples. ...Herein, a new SERS sensor is developed for background-free detection of hydrogen peroxide (H
O
) with an ultralow detection limit (1 × 10
mol/L), using a Raman-silent strategy. The Au microparticles (Au-RSMPs) resembling rose-stones are devised as SERS substrates with a high enhancement effect, and 4-mercaptophenylboronic acid (4-MPBA) is selected as an H
O
-responsive Raman reporter. Upon the reaction with H
O
, the phenylboronic group of 4-MPBA was converted to a phenol group, which subsequently reacted with 4-diazonium-phenylalkyne (4-DP), an alkyne-carrying molecule via the azo reaction. The formed product exhibits an intense and sharp SERS signal in the Raman-silent region, avoiding interference of impurities and biomolecules. As a proof-of-concept demonstration, we show that this SERS sensor possesses significant merits towards the determination of H
O
in terms of broad linear range, low limit of detection, and high selectivity, showing promise for the quantitative analysis of H
O
in complicated biological samples.
We propose an ultra-broadband mode converter based on the structure of a length-apodized long-period grating, where π-phase shifts are introduced at strategic locations of the grating profile. Using ...a 3-section length-apodized grating structure, we design and fabricate an LP
-LP
and an LP
-LP
mode converter with a sidewall grating and a surface grating formed along a polymer channel waveguide, respectively. The fabricated LP
-LP
and LP
-LP
mode converters provide a conversion efficiency higher than 99% over a bandwidth of ~120 nm and ~150 nm, respectively, or a conversion efficiency higher than 90% over a bandwidth of ~180 nm and ~300 nm, respectively. The transmission characteristics of these devices are weakly sensitive to polarization and temperature variations. These mode converters can find applications in ultra-broadband mode-division-multiplexing transmission systems based on few-mode fibers and the design principle can be applied to general grating-based mode-coupling devices for a wide range of applications.
Gambogic acid (GA) is a natural product from the resin of the Garcinia species, which showed significant activity in the induction of apoptosis. .t can be one promising lead compound for the design ...and synthesis of new anticancer drugs.
The objective of the current study is to design novel nitrogen-contained GA derivatives with better anti-cancer activities and study the effect of the introduction of different nitrogen-contained groups on the activity of GA.
The designed 15 derivatives were synthesized via esterification or amidation of 30-carboxylate. The synthetic compounds were characterized
different spectroscopic techniques, including X-ray single crystal diffraction, MS and NMR. The cytotoxic activity of the designed derivatives was evaluated
against A549, HepG-2, and MCF-7 cell lines using methyl thiazolyl tetrazolium (MTT) test.
15 nitrogen-contained GA derivatives were successfully synthesized and established. Based on the IC
values, compounds 9, 10, 11 and 13 showed stronger inhibitory effects on A549, HepG-2, MCF-7 cell lines than GA, while 9 is the most active compound with IC
value of 0.64-1.49 μM. Most derivatives of GA with esterification of C-30 including cyano-benzene ring were generally weaker than those of pyrimidinyl-substituted derivatives. In addition, length of alkyl linkers between C-30 of GA and nitrogen-contained group produced different effects on A549, HepG-2 and MCF-7 cell lines.
The structure-activity relationship results show that aromatic substituent and linker length play important roles to improve the anticancer activities, while compound 9 with pyrimidine substituent and C-C-C linkers is the most active derivative against tested cell lines, and is a promising anti-cancer agent for further development.
The ultrasonic transmission detection method is used to investigate the applicability for the second-harmonic generation (SHG) technology of longitudinal wave to quantitatively assess carbonated ...concrete. The principal of this method is to use the piezoelectric lead zirconate titanate (PZT) patch to detect the second-harmonic of longitudinal waves during the concrete carbonation process and extract non-linear parameters from observed signals. Non-linear parameters of concretes with two water–cement ratios (CI (w/c=0.47), CII (w/c=0.53)), two moisture contents (CI 0%, CI-W 100%), and three ultrasonic incident frequencies (50 kHz, 75 kHz, 100 kHz) were measured in this study. Results of the experiment demonstrate that non-linear ultrasonic parameters of longitudinal ultrasonic waves with high frequencies (75 kHz, 100 kHz) exhibit a better resolution regarding changes in concrete microstructure. Moisture (CI 0%, CI-W 100%) has little effect on the rate (CI: 62.73%, CI-W: 60.25, carbonation depth: 15 mm) for the change in relative non-linear parameters in the same concrete. The carbonation depth of concrete (CI (w/c=0.47), CI-W (w/c=0.47), CII (w/c=0.53)) can be well reflected by the change in relative non-linear parameters. Furthermore, there exists a good fit between the relative non-linear parameters of longitudinal waves and the concrete carbonation process. The relative non-linear parameters of longitudinal waves demonstrate feasibility in the quantitative assessment of concrete carbonation.
The angular displacement sensor is a digital angular displacement measurement device that integrates optics, mechanics, and electronics. It has important applications in communication, servo control, ...aerospace, and other fields. Although conventional angular displacement sensors can achieve extremely high measurement accuracy and resolution, they cannot be integrated because complex signal processing circuitry is required at the photoelectric receiver, which limits their suitability for robotics and automotive applications. The design of a fully integrated line array angular displacement-sensing chip is presented for the first time using a combination of pseudo-random and incremental code channel designs. Based on the charge redistribution principle, a fully differential 12-bit, 1 MSPS sampling rate successive approximation analog-to-digital converter (SAR ADC) is designed for quantization and subdivision of the incremental code channel output signal. The design is verified with a 0.35 μm CMOS process and the area of the overall system is 3.5 × 1.8 mm
. The fully integrated design of the detector array and readout circuit is realized for the angular displacement sensing.
PDF
