Enamine Acylation Enabled Desymmetrization of Malonic Esters.

Asymmetric enamine alkylation represents a powerful tool for stereoselective C-C bond formation; in contrast, the development of enantioselective enamine acylation remains elusive. Here, we report that a chiral phosphoric acid can render an in-situ-formed enamine to undergo a stereoselective intramolecular α-carbon acylation, providing an alternative approach for the synthesis of useful pyrrolinones and indolinones bearing tetrasubstituted stereocenters. Utilizing an effective integration of the desymmetrization strategy and bifunctional organocatalysis, the first example of enantioselective enamine acylation is achieved by employing readily available aminomalonic esters and cyclic ketones. Instead of reactive and moisture-sensitive acyl chlorides, common esters with low electrophilicity were successfully used as efficient acylating reagents via hydrogen bonding interactions. The utility is demonstrated in the concise and enantioselective synthesis of (+)-LipidGreen I and II. Experimental studies and DFT calculations establish the reaction pathway and the origin of stereocontrol.

Catalytic Enantioselective Biltz Synthesis.

The Biltz synthesis establishes straightforward access to 5,5-disubstituted (thio)hydantoins by combining a 1,2-diketone and a (thio)urea. Its appealing features include inherent atom and step economy together with the potential to generate structurally diverse products. However, control of the stereochemistry of this reaction has proven to be a daunting challenge. Herein, we describe the first example of enantioselective catalytic Biltz synthesis which affords more than 40 thiohydantoins with high stereo- and regio-control, irrespective of the symmetry of thiourea structure. A one pot synthesis of corresponding hydantoins is also documented. Remarkably, experimental studies and DFT calculations establish the reaction pathway and origin of stereoselectivity.

Effect of Human Immunodeficiency Virus Infection on Human Papillomavirus Clearance Among Women in Senegal, West Africa.

BACKGROUND: Persistent infection with high-risk human papillomavirus (HPV) is associated with development of invasive cervical cancer. METHODS: Longitudinal data was collected from 174 Senegalese women. We employed marginal Cox proportional hazards models to examine the effect of human immunodeficiency virus (HIV) status (HIV positive vs HIV negative) and HIV type (HIV-1 vs HIV-2 vs dual HIV-1/HIV-2) on clearance of type-specific HPV infection. Analyses were stratified by incident versus prevalent HPV infection. RESULTS: Incident HPV infections in HIV-positive women were less likely to clear than those in HIV-negative women (adjusted hazard ratio [HR] = 0.60; 95% confidence interval [CI], .38-.94). Among HIV-positive women, HIV-2-infected women and HIV-1/2 dually infected women were more likely to clear HPV incident infections than HIV-1-infected women (HR = 1.66; 95% CI, .95-2.92 and HR = 2.17; 95% CI, 1.12-4.22, respectively). Incident HPV infections in HIV-positive women with CD4 cell count ≤500 cells/µL were less likely to clear than those in HIV-positive women with CD4 cell count >500 cells/µL (HR = 0.65; 95% CI, .42-1.01). No significant associations were observed for prevalent HPV infections. CONCLUSIONS: HIV infection reduced the likelihood of clearance of incident HPV infection. Furthermore, among HIV-positive women, low CD4 cell count and dual HIV infection were each associated with reduced likelihood of clearance.

Recognition method for the bionic camouflage click communication trains modulated by time delay difference.

Bionic camouflage covert underwater acoustic communication has recently attracted great attention. However, we have not found relevant methods or literature to recognize these bionic camouflage communication signals (BCCSs) in the area of anti-reconnaissance. Focused on recognizing the BCCSs, this article proposes a recognition method based on the statistics of inter-click intervals to recognize the camouflaged click communication train (CCCT), which is modulated by time delay difference (TDD). We first analyze the characteristics of TDD distributions of CCCT and real click train (RCT). According to the coding principle, the TDDs of CCCTs present a ladder-like distribution with a fixed time step, and the TDDs are equal to the integral multiple of the fixed time step. On the contrary, the TDDs of RCTs are approximately random distribution within a certain time range. Therefore, based on the different TDD distributions, this article classifies CCCTs and RCTs by utilizing the statistical property of TDD distributions. To measure the TDDs of diverse cetacean clicks accurately, a new click location scheme based on the dynamic window energy ratio is proposed. Next, based on the statistics of TDD distribution, the influences of the TDDs that are caused by multipath interferences are eliminated by iteration. Simulations demonstrate the accuracy of the recognition method under different conditions.

An automated piecewise synthesis method for cetacean tonal sounds based on time-frequency spectrogram.

Bionic signal waveform design plays an important role in biological research, as well as bionic underwater acoustic detection and communication. Most conventional methods cannot construct high-similarity bionic waveforms to match complex cetacean sounds or easily modify the time-frequency structure of the synthesized bionic signals. In our previous work, we proposed a synthesis and modification method for cetacean tonal sounds, but it requires a lot of manpower to construct each bionic signal segment to match the tonal sound contour. To solve these problems, an automated piecewise synthesis method is proposed. First, based on the time-frequency spectrogram of each tonal sound, the fundamental contour and each harmonic contour of the tonal sound is automatically recognized and extracted. Then, based on the extracted contours, four sub power frequency modulation bionic signal models are combined to match cetacean sound contours. Finally, combining the envelopes of the fundamental frequency and each harmonic, the synthesized bionic signal is obtained. Experimental results show that the Pearson correlation coefficient (PCC) between all true cetacean sounds and their corresponding bionic signals are higher than 0.95, demonstrating that the proposed method can automatically imitate all kinds of simple and complex cetacean tonal sounds with high similarity.

Chlorination behaviors for green and efficient vanadium recovery from tailing of refining crude titanium tetrachloride.

The refined tailing, generated from refining of titanium tetrachloride (TiCl4) for vanadium (V) removal, is a hazardous material to environment due to the high content of V. Aiming at effective and selective extraction of V from the refined tailing, a fluidized chlorination process was proposed in present work. The chlorination behaviors of the refined tailing which determine the efficiency and selectivity of V extraction were emphatically investigated. A resultant 96.36% of V and 4.23% of Ti can be synchronously extracted from the tailing at the optimum conditions of 800 °C for 60 min, with the pressure fraction of chlorine [P(Cl2)/P(Cl2 +N2)] = 0.5 and the mass fraction of petroleum coke in raw materials for chlorination at 10 wt%. High purity vanadium oxytrichloride (VOCl3, higher than 99.99 wt%) can be finally obtained via further simple purification of the collected chloride product. Moreover, the chlorination residue containing concentrated TiO2 has the potential to be further utilized for Ti extraction. Thus the process provides a new prospect for effective, clean and comprehensive utilization of the refined tailing, which can solve the hazardous waste recycle and environmental concerns simultaneously.

Association Between Diet Quality and Cardiometabolic Risk Factor Clustering Stratified by Socioeconomic Status Among Chinese Children.

BACKGROUND: Few studies have evaluated the long-term relationship between diet quality and cardiometabolic risk factor clustering among children. The moderating effect of socio-economic status (SES) is of interest. OBJECTIVE: To investigate the association between diet quality with cardiometabolic risk among Chinese children and to explore the moderating effect of SES. DESIGN: In this cohort study, 5 waves (1997-2009) of the China Health and Nutrition Survey were used. Diet quality was measured by a modified version of the Chinese Children Dietary Index (mCCDI) based on Dietary Guidelines for Chinese. PARTICIPANTS: Children between the ages of 7 and 17 (n = 2903) who completed at least 2 surveys were included. Those who missed measures or had hypertension or diabetes at baseline were excluded. MAIN OUTCOME MEASURES: The fasting blood samples were collected in 2009. Waist circumference (WC) and blood pressure (BP) were measured in each survey. STATISTICAL ANALYSIS PERFORMED: A continuous cardiometabolic risk score (MetScore) was derived by a confirmatory factor analysis of 5 components: WC, BP, glucose, triglycerides, and high-density lipoprotein cholesterol. Considering the latency period of the effect of behaviors, the mCCDI was lagged by the period between surveys. Linear regression was used to analyze the association of mCCDI with MetScore and its components. Mixed effect linear regression and lagged mCCDI were used for WC and BP models. RESULTS: Higher mCCDI was independently associated with a lower MetScore at follow-up (ß: -.11; 95% CI: -.18 to -.04). Higher lagged mCCDI over time was associated with a lower WC z score overall (ß: -.05; 95% CI: -.08 to -.01) and among children in the low SES group (ß: -.09; 95% CI: -.14 to -.04) but not those in the high SES group. When examining the 15 mCDDI components separately, scores for 5 components: more grains, vegetables, soybeans and its products; less sugar-sweetened beverages; and more diet variety were significantly associated with a lower MetScore. CONCLUSIONS: Among Chinese children, higher diet quality measured by mCCDI was independently associated with a lower MetScore at follow-up.