Integration of Metal Catalysis and Organocatalysis in a Metal Nanocluster with Anchored Proline.

Chiral metal nanoclusters have recently been attracting great attention. It is challenging to realize asymmetric catalysis via atomically precise metal nanoclusters. Herein, we report the synthesis and total structure determination of chiral clusters [Au7Ag8(dppf)3(l-/d-proline)6](BF4)2 (l-/d-Au7Ag8). Superatomic clusters l-/d-Au7Ag8 display intense and mirror-image Cotton effects in their CD spectra. Density functional theory (DFT) calculations were carried out to understand the correlation between electronic structures and the optical activity of the enantiomeric pair. Surprisingly, the incorporation of proline in a metal nanocluster can significantly promote the catalytic efficiency in asymmetric Aldol reactions. The increase of catalytic activity of Au7Ag8 in comparison with organocatalysis by proline is attributed to the cooperative effect of the metal core and prolines, showing the advantages of the integration of metal catalysis and organocatalysis in a metal nanocluster.

[Accumulation Characteristics and Influencing Factors of Heavy Metals in Cultivated Land Surface Soil in Lanzhou].

In this study, As, Cd, Cr, Hg, and Pb in the surface soil of cropland in Lanzhou were studied, and the combination of descriptive statistics, single-factor accumulation index, comprehensive accumulation index, geostatistical method, and a geographically weighted regression model (GWR) was used to investigate their accumulation status, spatial distribution, and influencing factors, in order to provide scientific basis for the precise control of heavy metal accumulation risk in the study area. The results showed that:①the single-factor accumulation index showed that the accumulation of Hg and Cd in the study area was the largest, followed by that of Pb and As, and that of Cr was the smallest; the comprehensive accumulation index showed that the accumulation rate of heavy metals was as high as 98.11%, of which 54.81% was mild accumulation and 43.30% was moderate and above accumulation. However, there was no heavy metal pollution in the surface soil of cultivated land in Lanzhou. ② Spatial autocorrelation analysis showed that there was no heavy metal pollution in the surface soil of Lanzhou, but there was accumulation in a few areas. The spatial autocorrelation analysis showed that the spatial autocorrelation of the Cr, Hg, and Pb single-factor accumulation indices was moderate, indicating that they were influenced by both random and structural factors; the spatial autocorrelation of the other two heavy metals was weak, indicating that they were mainly influenced by random factors, among which human factors were more influential. The Hg single-factor accumulation index was high in the middle and low in the fourth; the integrated accumulation index increased from northwest to southeast and decreased from the middle to both sides. ③ Geographically weighted regression (GWR) analysis showed that altitude, slope length, distance from rivers, soil organic matter (SOM) content, precipitation, air temperature, and surface temperature all showed positive driving effects, whereas the rest of the factors showed negative driving effects and significant spatial heterogeneity and instability (P<0.05). The magnitudes of the factor effects were in the order of soil characteristics>topographic characteristics>climate characteristics>location characteristics>socioeconomic characteristics>vegetation characteristics, with the largest contribution of SOM content, followed by that of altitude and air temperature, and the smallest of normalized difference vegetation index (NDVI) values. Compared with the other feature factors, the location feature factors had stronger spatial heterogeneity.

[Risk Assessment and Attribution Analysis of "Five Toxic" Heavy Metals in Cultivated Land in Lanzhou].

Heavy metals in cultivated soil may migrate and transform through the food chain to harm the ecological environment and human health. At present, the ecological environment and human health risks of heavy metals in cultivated soil in Lanzhou city remain unclear, which impacts the effective management and control of heavy metals. The potential ecological risk hazard index was used to evaluate the ecological environmental risks of As, Cd, Cr, Hg, and Pb in the surface soil of cultivated land in Lanzhou, and the health risk model proposed by USEPA and the recommended standard were used to evaluate their human health risk. The main factors influencing the spatial differentiation of human health risk were explored by using geographic detectors. The risk of heavy metals to the ecological environment of the cultivated land surface soil in the study area was mainly medium (65.25%), and small portions were low (13.80%) and high (20.95%). The low-risk areas were mainly located in the southeast of Yongdeng County, the middle and north of Yuzhong County, and the southwest of Gaolan County. Moderate risk areas were distributed in three counties and five districts. The high-risk areas were located in the north and southeast of Yongdeng County, the south of Chengguan District, the northeast of Qilihe, the east of Xigu District, and the middle of Yuzhong County. The non-carcinogenic and carcinogenic risks of five types of heavy metal exposure pathways were as follows:oral ingestion>skin contact>respiratory ingestion; generally speaking, children were at higher risk than adults. The non-carcinogenic risk in children was higher than that in adults; however, there was no such risk for local residents, as they were all less than 1. At the same time, the carcinogenic risk of As was greater than 1×10-5 (children 2.04×10-5) and less than 1×10-4 (adults 1.91×10-5), respectively. This indicated an acceptable medium risk to the local residents, and the risk to children was again greater than that to adults. Geographical detector analysis showed that average precipitation during the sampling season had the greatest impact on the spatial differentiation of human health risks of As and Cd, GDP had the greatest impact on the spatial differentiation of human health risks of Cr, and distance from the railway had the greatest impact on the spatial differentiation of human health risks of Hg and Pb. Interaction detection showed that all factors were enhanced by double factors. In addition to leading factors, other factors such as pH, slope, and altitude also enhanced the influence of leading factors on the spatial differentiation of heavy metal risk in cultivated soil.

Selective Oxidation of Belt[4]arene[4]tropilidene and Its Application to Construct Hydrocarbon Belts of Truncated Cone Structure with Expand Cavity.

Despite their unique structures, tantalizing properties, and potential applications in carbon nanoscience and technology, the synthesis and functionalization of zigzag hydrocarbon nanobelts have remained largely unexplored until recently. Reported herein is the selective transformations of belt[4]arene[4]tropilidenes and their application in the construction of novel belts. The oxidation of belt[4]arene[4]tropilidene with benzeneseleninic anhydride under controlled conditions selectively afforded mono- to tetrakis(α-diketone)-functionalized belt intermediates. A subsequent condensation reaction with 1,2-phenylenediacetonitrile and 1,2-phenylenediamine produced a diversity of unprecedented belts with various macrocyclic cavities.

Research on a Dynamic Algorithm for Cow Weighing Based on an SVM and Empirical Wavelet Transform.

Weight is an important indicator of the growth and development of dairy cows. The traditional static weighing methods require considerable human and financial resources, and the existing dynamic weighing algorithms do not consider the influence of the cow motion state on the weight curve. In this paper, a dynamic weighing algorithm for cows based on a support vector machine (SVM) and empirical wavelet transform (EWT) is proposed for classification and analysis. First, the dynamic weight curve is obtained by using a weighing device placed along a cow travel corridor. Next, the data are preprocessed through valid signal acquisition, feature extraction, and normalization, and the results are divided into three active degrees during motion for low, medium, and high grade using the SVM algorithm. Finally, a mean filtering algorithm, the EWT algorithm, and a combined periodic continuation-EWT algorithm are used to obtain the dynamic weight values. Weight data were collected for 910 cows, and the experimental results displayed a classification accuracy of 98.6928%. The three algorithms were used to calculate the dynamic weight values for comparison with real values, and the average error rates were 0.1838%, 0.6724%, and 0.9462%. This method can be widely used at farms and expand the current knowledgebase regarding the dynamic weighing of cows.

Catalytic Enantioselective Synthesis and Switchable Chiroptical Property of Inherently Chiral Macrocycles.

We report herein a strategy to construct enantiopure inherently chiral macrocycles, ABCD-type heteracalix[4]aromatics, through a catalytic enantioselective intramolecular C-N bond forming reaction. A chiral ligand-palladium complex was found to efficiently induce the inherent chirality of molecules during the macrocyclization process with ee values up to >99%. The resulting ABCD-type heteracalix[4]aromatics displayed excellent and pH-triggered switchable electronic circular dichroism and circularly polarized luminescence properties.

Hydrocarbon Belts with Truncated Cone Structures.

We report in this communication the synthesis, structure, and application of a novel type of hydrocarbon belts. Starting from inexpensive and easily available resorcin[n]arenes, a closing-all-fjords strategy featuring exhaustive triflation of phenolic hydroxyl groups followed by consecutively the transition-metal-catalyzed vinylation and intramolecular olefin metathesis allowed facile construction of belt[n]arene[n]tropilidenes (n = 4, 6), which adopt double-stranded macrocyclic belt structures with unique truncated cone cavities. Selective hydrogenation reactions of olefin and benzene subunits led to diverse hydrocarbon belts with varied structures. Moreover, the resulting molecular belts acted as synthetic host materials to include selectively small molecules such as nitromethane and p-xylene.

[Research on maize multispectral image accurate segmentation and chlorophyll index estimation].

In order to rapidly acquire maize growing information in the field, a non-destructive method of maize chlorophyll content index measurement was conducted based on multi-spectral imaging technique and imaging processing technology. The experiment was conducted at Yangling in Shaanxi province of China and the crop was Zheng-dan 958 planted in about 1 000 m X 600 m experiment field. Firstly, a 2-CCD multi-spectral image monitoring system was available to acquire the canopy images. The system was based on a dichroic prism, allowing precise separation of the visible (Blue (B), Green (G), Red (R): 400-700 nm) and near-infrared (NIR, 760-1 000 nm) band. The multispectral images were output as RGB and NIR images via the system vertically fixed to the ground with vertical distance of 2 m and angular field of 50°. SPAD index of each sample was'measured synchronously to show the chlorophyll content index. Secondly, after the image smoothing using adaptive smooth filtering algorithm, the NIR maize image was selected to segment the maize leaves from background, because there was a big difference showed in gray histogram between plant and soil background. The NIR image segmentation algorithm was conducted following steps of preliminary and accuracy segmentation: (1) The results of OTSU image segmentation method and the variable threshold algorithm were discussed. It was revealed that the latter was better one in corn plant and weed segmentation. As a result, the variable threshold algorithm based on local statistics was selected for the preliminary image segmentation. The expansion and corrosion were used to optimize the segmented image. (2) The region labeling algorithm was used to segment corn plants from soil and weed background with an accuracy of 95. 59 %. And then, the multi-spectral image of maize canopy was accurately segmented in R, G and B band separately. Thirdly, the image parameters were abstracted based on the segmented visible and NIR images. The average gray value of each channel was calculated including red (ARed), green (AGreen), blue (ABlue), and near-infrared (ANIR). Meanwhile, the vegetation indices (NDVI (normalized difference vegetation index), RVI (ratio vegetation index); and NDGI(normalized difference green index)) which are widely used in remote sensing were applied. The chlorophyll index detecting model based on partial least squares regression method (PLSR) was built with detecting R2=0. 5960 and predicting R2= 0. 568 5. It was feasible to diagnose chlorophyll index of maize based on multi-spectral images.

[Expression of Foxa2 and its early alarm value of cancerous in gastric polyps].

OBJECTIVE: To explore the expression of Foxa2 in different pathological types of gastric polyps and examine the correlation with cancerous risk. METHODS: According to computerize random number, a total of 2000 patients were selected to receive endoscopic biopsy during November 2011 to October 2012. Tissues were harvested from 170 with gastric polyps and suspicious cancerous lesions and their histological types detected. There were hyperplastic polyps(n = 35), adenomatous polyps(n = 31), fundic gland polyps(n = 42), advanced gastric cancer tissues (n = 32)and normal gastric mucosa tissues (n = 30). ABC immunohistochemical staining and reverse transcription(RT)-PCR were employed to detect the expression of Foxa2 in these different types of tissues. Imagepro plus was used for quantitative and statistical analyses. RESULTS: A low-level expression of Foxa2 was 3.6% ± 1.3% in normal gastric mucosa group. And its expreesion gradually higher in proliferative inflammatory polyp group(33.1% ± 8.0%), adenomatous polyp group (71.4% ± 1.7%) and gastric cancer group(96.3% ± 0.9%, all P < 0.05). Its expression was 35.6% ± 5.6% in fundic gland polyps, similar to that of proliferative inflammatory polyp group (P > 0.05), it was markedly lower than the gastric cancer group (P < 0.05) and higher than the normal gastric mucosa group (P < 0.05). Correlation analyses of clinicopathological parameters showed that no significant correlation existed between its expression and patient gender, age, predilection, Helicobacter. pylori infection or proton pump inhibitor used (all P > 0.05). However, the size of polyps was correlated with Foxa2 (rs = 0.69, P < 0.05). CONCLUSION: The expression level of Foxa2 in different types of gastric polyps may be used as a clinical predicator of polyps risk.

[Detection of corn chlorophyll content using canopy spectral reflectance].

The canopy spectral reflectance and chlorophyll content of corn were measured and analyzed under different nitrogen treatments. The correlation between spectral reflectance and chlorophyll content was discussed based on different growth stages and different nitrogen levels. The results showed positive correlations under high and normal nitrogen treatment, while negative correlation under low nitrogen treatment. The relation between reflectance of normal fertilizer region and chlorophyll content was better than others, with r(Normal) > r(High) > r(Low). Normal fertilizer was the best condition to detect the corn chlorophyll content using spectral reflectance. Analysis of the relations at different growth stages showed that on the band of 400-1000 nm the absolute value of correlation coefficient increased and reached the maximum at shooting stage, it decreased until anthesis-silking stage, and then rebounded at milking stage. The positive correlations were found at shooting and milking stage, while negative correlations were found at seedling, trumpet and anthesis-silking stage. It was indicated that the sensitive stages to detect the chlorophyll content were shooting and trumpet stage with high absolute value of correlation coefficient above 0.6 around 550 nm. In order to detect the chlorophyll content of corn, 558, 667, 714 and 912 nm were selected to establish the MLR model and PLSR model. The results showed that PLSR was more capable of building chlorophyll content models reflecting correct relations among multi-variables compared with MLR. In the meanwhile, three wavelengths were selected (558, 667 and 714 nm) to build different vegetation indices such as GDVI, GRVI, GNDVI, DVI, RVI and NDVI. The correlation between DVI and chlorophyll con tent was better than others and DVI was used to establish binomial model and exponential model at shooting stage (R2 = 0.80) and trumpet stage (R2 = 0.66) respectively which was higher than PLSR It also provided a feasible method to detect chlorophyll content non-destructively.

[Spectral characteristics of corn under different nitrogen treatments].

The canopy spectral reflectance and chlorophyll content of corn were measured and analyzed under different nitrogen treatments. The trends of chlorophyll content were discussed based on different growth stages and different nitrogen levels. It was observed that the chlorophyll content increased with the increase in nitrogen, and could be affected by the environment changes including the temperature, rain, fertilizer treatment and so on. The characteristics of canopy spectral reflectance indicated that the canopy spectral reflectance changed significantly at different stages. In the visible region (400-750 nm), the reflectance increased and reached the maximum until the shooting stage, and decreased subsequently with the growth progress. In near-infrared region (750-1 000 nm), the spectral reflectance climbed sharply. It increased from tillering stage to shooting stage first, and then began to decline at trumpet stage and was raised again at anthesis-silking stage. At milking stage, the reflectance was decreased again. There were clear distinctions of visible reflectance in different nitrogen regions. At shooting stage, with the increase in nitrogen the reflectance decreased at chlorophyll absorption band (430-450 nm, 640-660 nm). Investigating the reflectance of the corn canopy under the different nitrogen treatment, it was found that the reflectance was higher in normal fertilizing region than others in 550 nm, with R(Normal) > R(Low) > R(High). At trumpet stage, the canopy reflectance in low fertilizing region was higher than others in the visible region. It was clear that the corn canopy reflectance of normal fertilizing region was the same as high fertilizing region. The results indicated over fertilizing could not help increase the corn nitrogen uptake. The study provided the basic information of chlorophyll measurement based on spectral technology and could help to guide the precision fertilizer in the field.

[The spectral characteristics and chlorophyll content at winter wheat growth stages].

The canopy spectral reflectance and chlorophyll content of winter wheat were measured and analyzed in the whole growing season. The characteristics of canopy spectral reflectance indicated that the canopy spectral reflectance changed signifi cantly at different stages. It decreased first and increased later with growth progress in the visible region (400-750 nm) after jointing stage, then the reflectance was lowest at booting stage. In near-infrared region (750-1000 nm) the spectral reflectance climbed sharply. The canopy reflectance was declined at booting stage and rose to the highest point at flowering stage. It dropped to minimum level subsequently at milk-ripe stage. However, the spectral reflectance characteristics at jointing stage and booting stage were used to detect the chlorophyll content. High correlation was observed between the canopy spectral reflectance and chlorophyll content. The positive correlation of canopy spectral reflectance with chlorophyll content was found at jointing stage and booting stage. Because the plant spectral reflectance was effected by chlorophyll greatly in visible region, the correlation coefficient reached 0.89 at 552 nm in booting stage. On the contrary, there was a negative correlation at flowering stage. Meanwhile, the red edge inflection point as one of the most important spectral parameters was analyzed at winter wheat growth stages based on the first derivative of reflectance spectra. The relation between the red edge inflection point and chlorophyll content was observed in each plot and the analysis results illustrated that the red edge inflection points could help detect the chlorophyll content at jointing stage and booting stage. The linear model of chlorophyll content with red edge inflection points was built at jointing stage (R2 = 0.92). High correlation was found between thered edge inflection point and chlorophyll content at booting stage. It was showed that the binomial model (R2 = 0.91) was better than linear model (R2 = 0.73). It was indicated that using spectral analysis to detect the winter wheat chlorophyll content non-destructively was feasible. The obtained conclusions also provided theoretical basis for further researches on measuring methods of chlorophyll content in the field.