Ketones are among the most useful functional groups in organic synthesis, and they are commonly encountered in a broad range of compounds with various applications. Herein, we describe the mesoionic ...carbene‐catalyzed coupling reaction of aldehydes with non‐activated secondary and even primary alkyl halides. This metal‐free method utilizes deprotonated Breslow intermediates derived from mesoionic carbenes (MICs), which act as super electron donors and induce the single‐electron reduction of alkyl halides. This mild coupling reaction has a broad substrate scope and tolerates many functional groups, which allows to prepare a diversity of simple ketones as well as bio‐active molecules by late‐stage functionalization.
A metal‐free protocol for the coupling reaction of aldehydes and alkyl halides was successfully developed with mesoionic carbenes (MICs) as catalysts. This versatile strategy delivers a large diversity of simple ketones as well as bio‐active molecules by late‐stage functionalization.
Evapotranspiration (ET) is one of the key variables in the water and energy exchange between land surface and atmosphere. This paper develops an end-member-based two-source approach for estimating ...land surface ET (i.e., the ESVEP model) from remote sensing data, considering the differing responses of soil water content at the upper surface layer to soil evaporation and at the deeper root zone layer to vegetation transpiration. The ESVEP model first diverges the soil-vegetation system net radiation into soil and vegetation components by considering the transmission of direct and diffuse shortwave radiation separately from the transmission of longwave radiation through the canopy, then calculates the four dry/wet soil/vegetation end-members with the diverged soil and vegetation net radiations, and last separates soil evaporation from vegetation transpiration based on the two-phase ET dynamics and the four end-member temperatures. The model can overall produce reasonably good surface energy fluxes and is no more sensitive to meteorology, vegetation, and remote sensing inputs than other two-source energy balance models and surface temperature versus vegetation index (T_{R} -VI) trapezoid models. A reasonable agreement could be found with a small bias of ±8 W/\text{m}^{2} and a root-mean-square error within 60 W/\text{m}^{2} (comparable to accuracies published in other studies) when both model-estimated sensible heat flux and latent heat flux from MODIS remote sensing data are validated with ground-based large aperture scintillometer measurements.
The time formative time lag (t f ) in the breakdown process of polymers on a nanosecond time scale is calculated. By reviewing the mechanisms related to breakdown of solid dielectrics, it is ...concluded that the avalanche breakdown mechanism is mainly responsible for the breakdown phenomenon of polymers on a nanosecond time scale, which is similar to the Townsend theory of gas breakdown under short pulses. In addition, the maximum functioning time of this theory is ascertained as 1 μs. When the time is longer than 1 μs, the thermal breakdown mechanism and other mechanisms begin to play the role. A formula to calculate t f for the avalanche breakdown mechanism is presented. This formula takes into account different factors that have an influence on t f , such as the dielectric size, type and purity. With this formula, it is calculated that t f for common polymers with a thickness ranging from 0.001-1 mm is about 0.01-100 ns. Experimental results in literatures were summarized to support the calculation results. The formative time lag is a key parameter to evaluate the pulse width effect on the electric breakdown strength on a nanosecond time scale.
The Internet of Things (IoT) has evolved significantly with advances in gathering data that can be extracted to provide knowledge and facilitate decision-making processes. Currently, IoT data ...analytics encountered challenges such as growing data volumes collected by IoT devices and fast response requirements for time-sensitive applications in which traditional Cloud-based solution is unable to meet due to bandwidth and high latency limitations. In this paper, we develop a distributed analytics framework for fog-enabled IoT systems aiming to avoid raw data movement and reduce latency. The distributed framework leverages the computational capacities of all the participants such as edge devices and fog nodes and allows them to obtain the global optimal solution locally. To further enhance the privacy of data holders in the system, a privacy-preserving protocol is proposed using cryptographic schemes. Security analysis was conducted and it verified that exact private information about any edge device’s raw data would not be inferred by an honest-but-curious neighbor in the proposed secure protocol. In addition, the accuracy of solution is unaffected in the secure protocol comparing to the proposed distributed algorithm without encryption. We further conducted experiments on three case studies: seismic imaging, diabetes progression prediction, and Enron email classification. On seismic imaging problem, the proposed algorithm can be up to one order of magnitude faster than the benchmarks in reaching the optimal solution. The evaluation results validate the effectiveness of the proposed methodology and demonstrate its potential to be a promising solution for data analytics in fog-enabled IoT systems.
Land surface temperature (LST) is a crucial parameter that reflects land–atmosphere interaction and has thus attracted wide interest from geoscientists. Owing to the rapid development of Earth ...observation technologies, remotely sensed LST is playing an increasingly essential role in various fields. This review aims to summarize the progress in LST estimation algorithms and accelerate its further applications. Thus, we briefly review the most‐used thermal infrared (TIR) LST estimation algorithms. More importantly, this review provides a comprehensive collection of the widely used TIR‐based LST products and offers important insights into the uncertainties in these products with respect to different land cover conditions via a systematic intercomparison analysis of several representative products. In addition to the discussion on product accuracy, we address problems related to the spatial discontinuity, spatiotemporal incomparability, and short time span of current LST products by introducing the most effective methods. With the aim of overcoming these challenges in available LST products, much progress has been made in developing spatiotemporal seamless LST data, which significantly promotes the successful applications of these products in the field of surface evapotranspiration and soil moisture estimation, agriculture drought monitoring, thermal environment monitoring, thermal anomaly monitoring, and climate change. Overall, this review encompasses the most recent advances in TIR‐based LST and the state‐of‐the‐art of applications of LST products at various spatial and temporal scales, identifies critical further research needs and directions to advance and optimize retrieval methods, and promotes the application of LST to improve the understanding of surface thermal dynamics and exchanges.
Plain Language Summary
Land surface temperature (LST) is a crucial geophysical parameter related to surface energy and water balance of the land‐atmosphere system. Satellite remote sensing provides the best way to measure LST and generate various LST products at regional and global scales. In this review, to facilitate the application of LST products in different fields, we first present the physical meaning of satellite‐derived LST. Subsequently, we summarize recent advances in LST retrieval and validation methods, with a special focus on the state‐of‐the‐art product collections, product accuracies and intercomparisons, and main problems in current LST products as well as their possible solutions. Additionally, we also review the major applications of LST products in agricultural drought monitoring, thermal environment monitoring, thermal anomaly monitoring, and climate change. Finally, we offer recommendations or perspectives to promote LST retrieval methods and their applications. This review will aid the user in gaining a thorough comprehensive understanding of satellite‐derived LST products and promoting their appropriate applications.
Key Points
State‐of‐the‐art satellite‐derived land surface temperature (LST) product levels, sources, uncertainties, and differences are provided
Typical applications of LST products in various fields are summarized
Future directions for the generation and applications of LST products are recommended
Land surface temperatures (LSTs) at high spatial resolution are crucial for hydrological, meteorological, and ecological studies. Downscaling LSTs from coarse resolution to finer resolution is an ...alternative way to obtain LSTs at high spatial resolution. In this paper, we proposed a new algorithm based on geographically weighted regression (GWR) to downscale Moderate Resolution Imaging Spectroradiometer LST data from 990 to 90 m. Unlike previous LST downscaling algorithms, this algorithm built the nonstationary relationship between LST and other environmental factors (including the normalized difference vegetation index and a digital elevation model) using geographically varying regression coefficients. The uncertainty in this algorithm was evaluated with a sensitivity analysis. The results show that the total uncertainty in this algorithm is less than 2 K. The performance of the GWR-based algorithm was assessed using concurrent ASTER LST data as a reference LST data set. Moreover, this algorithm was compared against the TsHARP algorithm, which was widely used for LST downscaling. The results indicate that the GWR-based algorithm outperforms the TsHARP algorithm in terms of statistical results. The root mean square error (mean absolute error) value decreases from 3.6 K (2.7 K) for the TsHARP algorithm to 3.1 K (2.3 K) for the GWR-based algorithm.
Evapotranspiration (ET) is a primary mechanism for water and heat transfer between land and the atmosphere. One approach to estimate ET is from instantaneous remotely sensed data. The constant ...evaporative fraction (EF) method is then usually used to estimate integrated daily fluxes, which are typically underestimated values. Here we present a theoretical improvement to the conventional EF. The improved EF is shown to be robust and superior to the conventional approach, and it significantly reduces the underestimation bias.
Key Points
A new constant EF method is developed to improve the conversion of remotely sensed instantaneous LE to a daily scale
The improved constant EF method significantly reduces the underestimation of the daily LE encountered in the conventional method
The improved constant EF method is demonstrated to be robust and superior to the conventional method
Abstract
Background
This study aimed to compare the clinical efficacy of microplate trans-carpometacarpal joint fixation and non-trans-carpometacarpal joint fixation in treating fractures and ...dislocation or subluxation of the base of the fourth and fifth metacarpal bones.
Method
From 2015 to 2021, 100 cases of metacarpal basal fractures with dislocation or subluxation were randomly divided into the trans-carpometacarpal joint fixation group (group A) and non-trans-carpometacarpal joint fixation group (group B). Group A (n = 50) comprised 44 males and 6 females, with an average age of 28.8 ± 6.1 y and an Orthopedic Trauma Association (OTA) fracture classification of type B1 (n = 29) or C1 (n = 21). Group B (n = 50) comprised 45 males and 5 females, with an average age of 28.9 ± 5.7 y and an OTA fracture classification of type B1 (n = 28) or C1 (n = 22). All patients were complicated with dislocation or subluxation. The surgery time, fracture healing time, postoperative handgrip strength, and total active motion (TAM) scores of the ring and little fingers were recorded and compared between the two groups. The clinical efficacy of patients was evaluated using scoring methods such as DASH (disabilities of the arm, shoulder and hand), visual analogue scale (VAS), and Mayo at 3, 6, and 12 months after surgery.
Results
There was no significant difference in the general indexes, surgery time, or fracture healing time between the two groups (
P
> 0.05). There were no significant differences in handgrip strength and TAM scores of the ring and little fingers between the two groups at 3 and 12 months postoperatively (
P
> 0.05), but there were significant differences in these indexes 6 months postoperatively (
P
< 0.05). There were no significant differences in the DASH, VAS, and Mayo scores at 3 and 12 months postoperatively (
P
> 0.05), but there were significant differences between the two groups in the DASH and Mayo scores (
P
< 0.05) but not the VAS score (
P
> 0.05) 6 months postoperatively.
Conclusion
In the treatment of fourth and fifth metacarpal basal fractures with dislocation or subluxation, both microplate transarticular fixation and non-transarticular fixation could achieve fracture fixation and healing, and each method had advantages and disadvantages. The clinically appropriate fixation method should be selected according to the experience of the surgeon and the degree and type of fracture and dislocation.
Summary
Engrailed‐1 (EN1) is a developmental gene that encodes En1, a highly conserved transcription factor involved in regionalization during early embryogenesis and in the later maintenance of ...normal neurons. After birth, EN1 still plays a role in the development and physiology of the body; for example, it exerts a protective effect on midbrain dopaminergic (mDA) neurons, and loss of EN1 causes mDA neurons in the ventral midbrain to gradually die approximately 6 weeks after birth, resulting in motor and nonmotor symptoms similar to those observed in Parkinson's disease. Notably, EN1 has been identified as a possible susceptibility gene for idiopathic Parkinson's disease in humans. EN1 is involved in the processes of wound‐healing scar production and tissue and organ fibrosis. Additionally, EN1 can lead to tumorigenesis and thus provides a target for the treatment of some tumors. In this review, we summarize the effects of EN1 on embryonic organ development, describe the consequences of the deletion or overexpression of the EN1 gene, and discuss the pathways in which EN1 is involved. We hope to clarify the role of EN1 as a developmental gene and present potential therapeutic targets for diseases involving the EN1 gene.