Nonnegative matrix factorization (NMF) has been recently applied to solve the hyperspectral unmixing problem because it ensures nonnegativity and needs no assumption for the presence of pure pixels. ...However, the algorithm has a large amount of local minima due to the obvious nonconvexity of the objective function. In order to improve its performance, auxiliary constraints can be introduced into the algorithm. In this paper, we propose a new approach named abundance separation and smoothness constrained NMF by introducing two constraints, namely, abundance separation and smoothness, into the NMF algorithm. These constraints are based on two properties of hyperspectral imagery. First, usually, every ground object presents dominance in a specific region of the entire image scene and the correlation is weak between different endmembers. Second, moving through various regions, ground objects usually vary slowly and abrupt changes rarely appear. We also propose a learning algorithm to further improve the performance of our method, from which the auxiliary constraints are removed at an appropriate time. The proposed algorithm retains all the advantages of NMF and effectively overcomes the shortcoming of local minima at the same time. Experimental results based on synthetic and real hyperspectral data show the superiority of the proposed algorithm with respect to other state-of-the-art approaches.
By taking advantage of cellulose, graphene oxide (GO), and the process for crosslinking using epichlorohydrin (ECH), we propose a simple and novel method to prepare GO/cellulose hydrogel with good ...potential to adsorb metal ions. GO nanosheets containing carboxyl and hydroxyl groups were introduced into the surface of the cellulose hydrogel with retention of the gel structure and its nanoporous property. Due to the introduction of GO, the GO/cellulose composite hydrogels exhibited good compressive strength. Adsorption capacity of Cu
significantly increases with an increase in the GO/cellulose ratio and GO/cellulose hydrogel showed high adsorption rates. The calculated adsorption capacities at equilibrium ( q e cal ) for GO/cellulose hydrogel (GO:cellulose = 20:100 in weight) was up to 94.34 mg·g
, which was much higher than that of the pristine cellulose hydrogels. Furthermore, GO/cellulose hydrogel exhibited high efficient regeneration and metal ion recovery, and high adsorption capacity for Zn
, Fe
, and Pb
.
5-hydroxymethylfurfural (HMF) is an important platform molecule in the synthesis of various chemicals and materials. Herein, we reported a simple and effective dehydration of glucose-based ...carbohydrates to HMF in a biphasic system containing cyclopentyl methyl ether as the organic phase and AlCl
with minute amounts of HCl as co-catalysts. The results showed that the mixed catalysts had a positive synergistic catalytic effect on glucose conversion to HMF compared with single AlCl
or HCl catalyst. For glucose, the highest HMF yield of 54.5% was achieved at 175 °C for 20 min. More importantly, the optimal catalytic system was so efficient that it achieved one of the highest reported yields of HMF (30.5%) directly from corncob acid hydrolysis residues. Thus, the catalytic system can become a promising route for effective utilization of biomass in future biorefineries.
Gold rush: A combination of oxidative gold(I)/gold(III) catalysis and CH functionalization led to the first oxidative coupling between in situ generated alkyl gold reagents and C sp 2H bonds, ...affording tricyclic indolines through a formal 3+2 annulation between a vinyl group and an aniline moiety see scheme; Tf=trifluoromethanesulfonyl, Selectfluor=1‐chloromethyl‐4‐fluoro‐1,4‐diazoniabicyclo2.2.2octane bis(tetrafluoroborate).
A protocol for the quantitative fractionation of lignin carbohydrate complexes (LCC) from wood under mild conditions has been developed. All operations occur at near-neutral pH conditions and low ...temperatures, in order to preserve the native structure. The protocol also achieved the fractionation of hemicelluloses of relatively high purity enabling for the first time estimates of hemicelluloses fractions not chemically bound to lignin in wood. 2D HSQC NMR was applied to decipher the structure of LCCs and was complemented by thioacidolysis-GC MS techniques. The carbohydrates linked to lignin in LCC are hemicelluloses, mainly arabinoglucuronoxylan (AGX) and galactoglucomannan (GGM). Benzyl ether (BE) and phenyl glycosidic (PG) linkages were detected. Significant structural differences in the lignin part of LCCs are also reported. The novelty of this work is that we report the first quantitative pH neutral protocol for LCC fractionation and detailed chemical analyses unveil important structural differences of relevance to fundamental knowledge in lignin polymerization and wood-based bio-refineries.
A gold-catalyzed dearomatization reaction of indole derivatives was realized in the presence of JohnPhosAuCl/AgOMs to afford a series of spiroindolenines in excellent yields (≤99%). In addition, when ...the Hantzsch ester was used as the hydrogen transfer reagent, various spiroindolines were obtained in a cascade fashion starting from readily available indole derivatives in modest to good yields (≤79%). Both reactions feature readily available substrates, mild conditions, and good functional group tolerance.
This account provides a comprehensive overview of the development of gold and platinum catalysis of the enyne cycloisomerization. The use of these soft, alkynophilic metals enables mild, ...chemoselective and efficient transformations of a variety of readily available acyclic enynes to a wide range of synthetically useful carbocyclic and heterocyclic products. The review is organized according to diverse structural types of enynes that undergo skeletal cycloisomerizations. The account begins with an overview of transformations of primarily 1,6‐enynes to 1‐alkenylcyclopentenes, bicyclo4.1.0heptenes, methylenecycloalkenes, bicyclo4.3.0nonadienes and bicyclo3.2.0heptenes. This section is followed by the discussion of cycloisomerizations of 1,5‐enynes, which enable a rapid access to a range of other cyclic products, including bicyclo3.1.0hexenes, cyclohexadienes, heterobicycloalkenes, methylenecyclopentenes, naphthalenes and methyleneindenes. In addition, the 3,3 rearrangement of 1,5‐enynes provides efficient access to the corresponding allenes. The account concludes with an overview of the most recent studies on gold‐ and platinum‐catalyzed cycloisomerizations of 1,4‐ and 1,3‐enynes. Due to the rapidly increasing interest in this area during the past three to five years, we believe that this review provides a timely and comprehensive discussion of the development gold‐ and platinum‐catalyzed cycloisomerization starting from the initial pioneering investigations to the latest advances in the field. A significant emphasis is placed on the mechanistic discussion of the observed manifolds of skeletal reorganizations.
Coronavirus disease-19 (COVID-19) has become a world health threaten. Its risk factors with death were still not known. White blood cells (WBC) count as a reflection of inflammation has played a ...vital role in COVID-19, however its level with death is not yet investigated.
In this retrospective, single-center study, all confirmed patients with COVID-19 at West Branch of Union Hospital from Jan 29 to Feb 28, 2020 were collected and analyzed. Demographic and clinical data including laboratory examinations were analyzed and compared between recovery and death patients.
A total of 163 patients including 33 death cases were included in this study. Significant association was found between WBC count and death (HR = 1.14, 95%CI: 1.09-1.20, p < 0.001). The regression analysis results showed there was a significant association between WBC count and death (HR = 5.72, 95%CI: 2.21-14.82, p < 0.001) when use the second quartile as a cutoff value (> 6.16 × 10^9/L). The difference was still exist after adjusting for confounding factors (HR = 6.26, 95%CI: 1.72-22.77, p = 0.005). In addition, Kaplan-meier survival analysis showed that there was a significant decline of the cumulative survival rate (p < 0.001) in those with WBC count ≥6.16 × 10^9/L.
WBC count at admission is significantly corelated with death in COVID-19 patients. Higher level of WBC count should be given more attention in the treatment of COVID-19.
Optical antenna enhanced spontaneous emission Eggleston, Michael S.; Messer, Kevin; Zhang, Liming ...
Proceedings of the National Academy of Sciences - PNAS,
02/2015, Letnik:
112, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Significance Since the invention of the laser over 50 y ago, stimulated emission has been stronger and far more important than spontaneous emission, the ordinary light we are accustomed to. Indeed ...spontaneous emission has been looked down upon as a weak effect. Now a new science of enhanced spontaneous emission is emerging that makes spontaneous emission faster than stimulated emission. This new science depends upon the use of optical antennas to increase the spontaneous emission rate. Antennas emerged at the dawn of radio for concentrating electromagnetic energy to a small volume. Despite the importance of radio antennas, 100 y went by before optical antennas began to be used to help extract optical frequency radiation from very small sources such as dye molecules and quantum dots.
Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ∼200 THz optical frequency show a spontaneous emission intensity enhancement of 35× corresponding to a spontaneous emission rate speedup ∼115×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ∼2,500× spontaneous emission speedup at d ∼ 10 nm, proportional to 1/ d ². Unfortunately, at d < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, I ₒ = qω | x ₒ|/ d , feeding the antenna-enhanced spontaneous emission, where q | x ₒ| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Moreover, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency.
To investigate methods for predicting bursts induced by the shear failure of structural planes in the deeply buried hard rock tunnels, shear tests were performed under various normal stresses on ...completely occlusive granite joints that were created via tension splitting. In these experiments, stress drops resulting from shear off of asperities on the surface of granite rigid structural plane, which can trigger a fault-slip rockburst, were reproduced, and the acoustic emissions (AEs) were monitored during shearing. The AE characteristics were analysed, and a method based on the AE b-value was developed to predict stress drops and the fault-slip rockbursts induced by the stress drops. The b-value continuously decreased before the stress drop and dropped to approximately 0.8 or less at the point of the violent post-peak shear stress drop. Moreover, the b-value tended to decrease to a relative minimum during the stick-slip period when the energy increased sharply if the energy rate was greater than 104, and a lower b-value was associated with a higher rockburst probability and intensity. The b-value generally decreased as the normal stress increased, which increased the risk of rockburst induced by the dynamic shear failure of granite joints. Moreover, the static and dynamic shear failure of the joints was easily distinguished when the b-value was used as a predictor.
•Shear tests were performed on completely interlocked rigid granite structural planes.•Acoustic emission (AE) was monitored during the shear failure of the joints.•Rockbursts can be induced by violent post-peak stress drops or unstable stick-slip.•Rockbursts caused by dynamic shear failure can be predicted from the AE b-value.•The b-value tends to decrease as the normal stress increases.
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