Organofluorine compounds are widely used in pharmaceutical, agrochemical, and materials sciences. The syntheses and applications of fluorinated organoborons facilitate the rapid and modular ...assemblies of fluorine‐containing molecules because of the versatility of C−B bonds in diverse chemical transformations. Reported herein is a migratory geminal difluorination of aryl‐substituted alkenyl N‐methyliminodiacetyl (MIDA) boronates using commercially available Py⋅HF as the fluorine source and hyperiodine as the oxidant. The protocol offers facile access to α‐ and β‐difluorinated alkylboron compounds, both of which have previously been challenging to prepare. Mild reaction conditions, broad substrate scope, good functional‐group tolerance, and moderate to good yields were observed. The utility of these products is demonstrated by further transformations of the C−B bond into other valuable functional groups.
On the move: A migratory geminal difluorination of aryl‐substituted alkenyl N‐methyliminodiacetyl (MIDA) boronates using commercially available Py⋅HF as the fluorine source is reported. The protocol offers an unprecedented opportunity for the synthesis of α‐ and β‐difluorinated alkylboron compounds. Mild reaction conditions, broad substrate scope, good functional‐group tolerance, and moderate to good yields were observed.
Adaptive Huber Regression Sun, Qiang; Zhou, Wen-Xin; Fan, Jianqing
Journal of the American Statistical Association,
01/2020, Letnik:
115, Številka:
529
Journal Article
Recenzirano
Odprti dostop
Big data can easily be contaminated by outliers or contain variables with heavy-tailed distributions, which makes many conventional methods inadequate. To address this challenge, we propose the ...adaptive Huber regression for robust estimation and inference. The key observation is that the robustification parameter should adapt to the sample size, dimension and moments for optimal tradeoff between bias and robustness. Our theoretical framework deals with heavy-tailed distributions with bounded
th moment for any
. We establish a sharp phase transition for robust estimation of regression parameters in both low and high dimensions: when
, the estimator admits a sub-Gaussian-type deviation bound without sub-Gaussian assumptions on the data, while only a slower rate is available in the regime
and the transition is smooth and optimal. In addition, we extend the methodology to allow both heavy-tailed predictors and observation noise. Simulation studies lend further support to the theory. In a genetic study of cancer cell lines that exhibit heavy-tailedness, the proposed methods are shown to be more robust and predictive.
Supplementary materials
for this article are available online.
In this article, we study the problem of testing the mean vectors of high dimensional data in both one-sample and two-sample cases. The proposed testing procedures employ maximum-type statistics and ...the parametric bootstrap techniques to compute the critical values. Different from the existing tests that heavily rely on the structural conditions on the unknown covariance matrices, the proposed tests allow general covariance structures of the data and therefore enjoy wide scope of applicability in practice. To enhance powers of the tests against sparse alternatives, we further propose two-step procedures with a preliminary feature screening step. Theoretical properties of the proposed tests are investigated. Through extensive numerical experiments on synthetic data sets and an human acute lymphoblastic leukemia gene expression data set, we illustrate the performance of the new tests and how they may provide assistance on detecting disease-associated gene-sets. The proposed methods have been implemented in an R-package HD test and are available on CRAN.
A series of stable heterometallic Fe2M cluster‐based MOFs (NNU‐31‐M, M=Co, Ni, Zn) photocatalysts are presented. They can achieve the overall conversion of CO2 and H2O into HCOOH and O2 without the ...assistance of additional sacrificial agent and photosensitizer. The heterometallic cluster units and photosensitive ligands excited by visible light generate separated electrons and holes. Then, low‐valent metal M accepts electrons to reduce CO2, and high‐valent Fe uses holes to oxidize H2O. This is the first MOF photocatalyst system to finish artificial photosynthetic full reaction. It is noted that NNU‐31‐Zn exhibits the highest HCOOH yield of 26.3 μmol g−1 h−1 (selectivity of ca. 100 %). Furthermore, the DFT calculations based on crystal structures demonstrate the photocatalytic reaction mechanism. This work proposes a new strategy for how to design crystalline photocatalyst to realize artificial photosynthetic overall reaction.
A series of stable heterometallic Fe2M cluster‐based MOFs achieve the overall conversion of CO2 and H2O into HCOOH and O2 without the assistance of additional sacrificial agent and photosensitizer. A strategy is proposed to design crystalline photocatalysts to realize the overall artificial photosynthetic reaction.
•The ability to innovate increases sustainable business performance.•Green innovations are hard to imitate in the market.•Green technology companies should not focus only on creating products.•They ...should also provide business solutions to end-users.
In response to greater environmental awareness among stakeholders, companies have become increasingly interested in practices such as eco-innovation. Despite the expanding literature on eco-innovation, scholars have so far paid little attention to the study of eco-innovation and its impact on business sustainability, particularly considering the mediating effect of service innovation capability. To fill this research gap, this study extends the concepts of green business by investigating an original conceptual framework, which proposes that the capacity for service innovation has a mediating effect on the relationship between sustainable organizational performance and environmental innovation. This conceptual framework is subjected to empirical testing, implemented through a survey involving 95 Malaysian firms which use green technology. Data is collected through both postal and online questionnaires and analyzed through structural equation modeling using partial least squares. Respondents for this paper were identified using the directories of MyHijau (2013) and the Malaysia External Trade Development Corporation, 2014. The results suggest that: (1) eco-innovations unlock better sustainable performance; (2) service innovation capability has a partially significant positive mediating effect; (3) service innovation capability ultimately benefits companies by allowing them to differentiate through an emphasis on value creation; (4) service capability can also act as a business strategy to create barriers to new entry by competitors. Thus, eco-innovation and service innovation capability tend to represent significant intangible resources and enable an organization to achieve long-term objectives, competitive advantage and business sustainability. To date, this is the first study relating eco-innovation, service innovation capability and sustainability performance in the Malaysian corporate context and using a specific sample of companies that make use of green technologies.
ℓ1‐penalized quantile regression (QR) is widely used for analysing high‐dimensional data with heterogeneity. It is now recognized that the ℓ1‐penalty introduces non‐negligible estimation bias, while ...a proper use of concave regularization may lead to estimators with refined convergence rates and oracle properties as the signal strengthens. Although folded concave penalized M‐estimation with strongly convex loss functions have been well studied, the extant literature on QR is relatively silent. The main difficulty is that the quantile loss is piecewise linear: it is non‐smooth and has curvature concentrated at a single point. To overcome the lack of smoothness and strong convexity, we propose and study a convolution‐type smoothed QR with iteratively reweighted ℓ1‐regularization. The resulting smoothed empirical loss is twice continuously differentiable and (provably) locally strongly convex with high probability. We show that the iteratively reweighted ℓ1‐penalized smoothed QR estimator, after a few iterations, achieves the optimal rate of convergence, and moreover, the oracle rate and the strong oracle property under an almost necessary and sufficient minimum signal strength condition. Extensive numerical studies corroborate our theoretical results.
This paper studies reverse space and/or time nonlocal Fokas–Lenells (FL) equation, which describes the propagation of nonlinear light pulses in monomode optical fibers when certain higher-order ...nonlinear effects are considered, by Hirota bilinear method. Firstly, we construct variable transformations from reverse space nonlocal FL equation to reverse time and reverse space-time nonlocal FL equations. Secondly, the multisoliton and quasi-periodic solutions of the reverse space nonlocal FL equation are derived through Hirota bilinear method, and the soliton solutions of reverse time and reverse space-time nonlocal FL equations are given through variable transformations. Also, dynamical behaviors of the multisoliton solutions are discussed in detail by analyzing their wave structures. Thirdly, asymptotic analysis of two- and three-soliton solutions of reverse space nonlocal FL equation is used to investigate the elastic interaction and inelastic interaction. Finally, the infinite conservation laws of three types of nonlocal FL equations are found by using their lax pairs. The results obtained in this paper possess new properties that different from the ones for FL equation, which are useful in exploring novel physical phenomena of nonlocal systems in nonlinear media.
Background
The Footscan® platform system is one of the most commonly used clinical tools for the measurement of the foot pressure. The present study was designed to assess the repeatability of the ...system and identify the range of loading parameters observed in the normal foot.
Methods
Measurements were collected from 32 healthy participants, 15 females and 17 males, twice at an interval of 1 week. Peak pressure (PP), contact time (CT), contact area (CA), pressure‐time integral (PTI), and maximum force (MaF) were recorded; these parameters were investigated in 10 areas of the foot: medial heel, lateral heel, midfoot, first to fifth metatarsals, hallux, and toes 2–5. The intra‐session repeatability was evaluated by calculating the intraclass correlation coefficients (ICCs) and coefficients of variation (CVs) across the three repeated trials within the same session. The inter‐session repeatability was assessed using the average of the three trials in each session to determine the ICCs and CVs.
Results
The ICCs showed moderate to good repeatability for every variable of interest, and the CVs were all <28%. The highest zones of PP were found under the second and third metatarsals, followed by the medial heel. The CT was 68.5–82.8% of the total stance time under the metatarsal heads. CA was highest under the midfoot, PTI was highest under the second metatarsal, and MaF was highest under the medial heel.
Conclusions
Footscan® platform system was found to be repeatable. Thus, it can be used as a valuable tool in the assessment of plantar pressure distribution, and the normal values of the foot loading parameters identified in this study can be employed to provide a reference range for the gait analysis performed by the Footscan® system.
Abstract We investigate the suppression of star formation in galaxy pairs based on the isolated galaxy pair sample derived from the Sloan Digital Sky Survey survey. By comparing the star formation ...rate between late-type galaxies (LTGs) in galaxy pairs and those in the isolated environment, we detect a signal of the suppression of star formation in galaxy pairs at d p < 100 kpc and 200 kpc < d p < 350 kpc. The occurrence of the suppression of star formation in these LTGs requires their companion galaxies to have an early-type morphology ( n s > 2.5). The suppression of star formation in wide galaxy pairs at 200 kpc < d p < 350 kpc mainly occurs in massive LTGs, while in close galaxy pairs at d p < 100 kpc, it only appears in LTGs with a massive companion ( log M ⋆ > 11.0 ), nearly independent of their own stellar mass. Based on these findings, we infer that the suppression of star formation in wide galaxy pairs is actually a result of galaxy conformity, while in close galaxy pairs, it stems from the influence of hot circumgalactic medium surrounding companion galaxies.
On the Security of Permutation-Only Image Encryption Schemes Jolfaei, Alireza; Xin-Wen Wu; Muthukkumarasamy, Vallipuram
IEEE transactions on information forensics and security,
2016-Feb., 2016-2-00, 20160201, Letnik:
11, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Permutation is a commonly used primitive in multimedia (image/video) encryption schemes, and many permutation-only algorithms have been proposed in recent years for the protection of multimedia data. ...In permutation-only image ciphers, the entries of the image matrix are scrambled using a permutation mapping matrix which is built by a pseudo-random number generator. The literature on the cryptanalysis of image ciphers indicates that the permutation-only image ciphers are insecure against ciphertext-only attacks and/or known/chosenplaintext attacks. However, the previous studies have not been able to ensure the correct retrieval of the complete plaintext elements. In this paper, we revisited the previous works on cryptanalysis of permutation-only image encryption schemes and made the cryptanalysis work on chosen-plaintext attacks complete and more efficient. We proved that in all permutationonly image ciphers, regardless of the cipher structure, the correct permutation mapping is recovered completely by a chosenplaintext attack. To the best of our knowledge, for the first time, this paper gives a chosen-plaintext attack that completely determines the correct plaintext elements using a deterministic method. When the plain-images are of size M × N and with L different color intensities, the number n of required chosen plain-images to break the permutation-only image encryption algorithm is n = Γlog L (MN)1. The complexity of the proposed attack is O (n · M N) which indicates its feasibility in a polynomial amount of computation time. To validate the performance of the proposed chosen-plaintext attack, numerous experiments were performed on two recently proposed permutation-only image/video ciphers. Both theoretical and experimental results showed that the proposed attack outperforms the state-of-theart cryptanalytic methods.
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