Response of maize yield and nitrogen recovery efficiency to nitrogen fertilizer application in field with various soil fertility.

Appropriate nitrogen (N) management system is essential for effective crop productivity and minimizing agricultural pollution. However, the underlying mechanistic understanding of how N fertilizer regulates crop yield via soil properties in soils with different fertilities remains unresolved. Here, we used a field experiment that spanned 3 cropping seasons to evaluate the grain yield (GY), aboveground biomass and N recovery efficiency (NRE) after treatment with five N fertilizer application rates (N0, N75, N112, N150, and N187) in soils with three levels of fertility. Our results indicated that the highest GY across low, moderate, and high fertility soils were 1.5 t hm-2 (N150), 4.9 t hm-2 (N187), and 5.4 t hm-2 (N112), respectively. The highest aboveground biomass and NRE were observed at N150 for all three levels of soil fertility, while only the N uptake by aboveground biomass of low and high fertility soils decreased at N187, confirming that excessive N fertilization results in a further decline in crop N uptake. The relationship between GY, NRE and N fertilizer application rates fit the unary quadratic polynomial model. To achieve a balance between grain production and environmental benefits in N fertilizer, appropriate N fertilizer rates were determined to be 97.5 kg hm-2, 140 kg hm-2 and 131 kg hm-2 for low, moderate and high fertility soils, respectively. Structural equation modeling suggested that GY was significant correlated with soil microbial biomass carbon (SMBC) and N directly in low fertility field, with SMBC directly in moderate fertility field, and via SOC and NO3 -N in high fertility field. Therefore, a soil-based management strategy for N fertilizers could enhance food security while reducing agricultural N fertilizer inputs to mitigate environmental impacts.

Three-Dimensional Printed Biomimetic Robotic Fish for Dynamic Monitoring of Water Quality in Aquaculture.

The extensive water pollution caused by production activities is a key issue that needs to be addressed in the aquaculture industry. The dynamic monitoring of water quality is essential for understanding water quality and the growth of fish fry. Here, a low-cost, low-noise, real-time monitoring and automatic feedback biomimetic robotic fish was proposed for the dynamic monitoring of multiple water quality parameters in aquaculture. The biomimetic robotic fish achieved a faster swimming speed and more stable posture control at a swing angular velocity of 16 rad/s by using simulation analysis. A fast swimming speed (0.4 m/s) was achieved through the control of double-jointed pectoral and caudal fins, exhibiting various types of movements, such as straight swimming, obstacle avoidance, turning, diving, and surfacing. As a demonstration of application, bionic robotic fish were placed in a lake for on-site water sampling and parameter detection. The relative average deviations in water quality parameters, such as water temperature, acidity and alkalinity, and turbidity, were 1.25%, 0.07%, and 0.94%, respectively, meeting the accuracy requirements for water quality parameter detection. In the future, bionic robotic fish are beneficial for monitoring water quality, fish populations, and behaviors, improving the efficiency and productivity of aquaculture, and also providing interesting tools and technologies for science education and ocean exploration.

Effect of replacing synthetic nitrogen fertilizer with animal manure on grain yield and nitrogen use efficiency in China: a meta-analysis.

To reduce reliance on synthetic nitrogen (N) fertilizer and sustain food production, replacing synthetic N fertilizer with animal manure as an effective method is widely used. However, the effects of replacing synthetic N fertilizer with animal manure on crop yield and nitrogen use efficiency (NUE) remain uncertain under varying fertilization management practices, climate conditions, and soil properties. Here, we performed a meta-analysis of wheat (Triticum aestivum L.), maize (Zea mays L.), and rice (Oryza sativa L.) based on 118 published studies conducted in China. Overall, the results indicated that substituting synthetic N fertilizer with manure increased yield by 3.3%-3.9% for the three grain crops and increased NUE by 6.3%-10.0%. Crop yields and NUE did not significantly increase at a low N application rate (≤120 kg ha-1) or high substitution rate (>60%). Yields and NUE values had higher increases for upland crops (wheat and maize) in temperate monsoon climate/temperate continental climate regions with less average annual rainfall (AAR) and lower mean annual temperature (MAT), while rice had higher increases in subtropical monsoon climate regions with more AAR and higher MAT. The effect of manure substitution was better in soil with low organic matter and available phosphorus. Our study shows that the optimal substitution rate was 44% and the total N fertilizer input cannot be less than 161 kg ha-1 when substituting synthetic N fertilizer with manure. Moreover, site-specific conditions should also be considered.

Quantifying substantial carcinogenesis of genetic and environmental factors from measurement error in the number of stem cell divisions.

BACKGROUND: The relative contributions of genetic and environmental factors versus unavoidable stochastic risk factors to the variation in cancer risk among tissues have become a widely-discussed topic. Some claim that the stochastic effects of DNA replication are mainly responsible, others believe that cancer risk is heavily affected by environmental and hereditary factors. Some of these studies made evidence from the correlation analysis between the lifetime number of stem cell divisions within each tissue and tissue-specific lifetime cancer risk. However, they did not consider the measurement error in the estimated number of stem cell divisions, which is caused by the exposure to different levels of genetic and environmental factors. This will obscure the authentic contribution of environmental or inherited factors. METHODS: In this study, we proposed two distinct modeling strategies, which integrate the measurement error model with the prevailing model of carcinogenesis to quantitatively evaluate the contribution of hereditary and environmental factors to cancer development. Then, we applied the proposed strategies to cancer data from 423 registries in 68 different countries (global-wide), 125 registries across China (national-wide of China), and 139 counties in Shandong province (Shandong provincial, China), respectively. RESULTS: The results suggest that the contribution of genetic and environmental factors is at least 92% to the variation in cancer risk among 17 tissues. Moreover, mutations occurring in progenitor cells and differentiated cells are less likely to be accumulated enough for cancer to occur, and the carcinogenesis is more likely to originate from stem cells. Except for medulloblastoma, the contribution of genetic and environmental factors to the risk of other 16 organ-specific cancers are all more than 60%. CONCLUSIONS: This work provides additional evidence that genetic and environmental factors play leading roles in cancer development. Therefore, the identification of modifiable environmental and hereditary risk factors for each cancer is highly recommended, and primary prevention in early life-course should be the major focus of cancer prevention.

Efficacy and safety of dual antiplatelet therapy after percutaneous coronary drug-eluting stenting: A network meta-analysis.

BACKGROUND: To evaluate the efficacy and safety of dual antiplatelet regimens after coronary drug-eluting stenting by network meta-analysis (NMA). METHODS: PubMed, The Cochrane Library, Embase, and Web of Science databases were electronically searched to collect randomized controlled trials (RCTs) of the comparison of different dual antiplatelet regimens after coronary drug-eluting stenting from inception to September 1st, 2021. Two reviewers independently screened literature, extracted data, and assessed the risk bias of included studies. Stata 16.0 software was used for NMA. RESULTS: A total of 27 RCTs involving 79,880 patients were included. The results of NMA: in terms of myocardial infarction (MI), other 3 interventions were higher than the long-term dual antiplatelet therapy (L-DAPT) (the standard dual antiplatelet therapy [Std-DAPT] [odds ratio [OR] = 1.82, 95%confidence interval [CI]: 1.49-2.21), the aspirin monotherapy after short-term dual antiplatelet therapy (S-DAPT + As) (OR = 2.06, 95%CI: 1.57-2.70), the P2Y12 inhibitor monotherapy after short-term dual antiplatelet therapy (S-DAPT + P2Y12) (OR = 1.71, 95%CI: 1.29-2.28)]. In terms of stent thrombosis, other 3 interventions were higher than L-DAPT [Std-DAPT (OR = 2.18, 95%CI: 1.45-3.28), S-DAPT + As (OR = 2.32, 95%CI: 1.52-3.54), S-DAPT + P2Y12 (OR = 2.31, 95%CI: 1.22-4.36)]. There was no statistically significant difference among the 4 interventions in prevention of stroke and all-cause mortality (P > .05). In terms of cardiovascular and cerebrovascular adverse events, other 3 interventions were higher than L-DAPT (Std-DAPT [OR = 1.28, 95%CI: 1.12-1.45], S-DAPT + As [OR = 1.27, 95%CI: 1.09-1.48], S-DAPT + P2Y12 [OR = 1.24, 95%CI: 1.01-1.52]). In terms of safety, bleeding rate of other 3 interventions were lower than L-DAPT (Std-DAPT [OR = 0.67, 95%CI: 0.52-0.85], S-DAPT + As [OR = 0.51, 95%CI: 0.39-0.66], S-DAPT + P2Y12 [OR = 0.36, 95%CI: 0.26-0.49]). Two interventions were lower than L-DAPT (S-DAPT + As [OR = 0.77, 95%CI: 0.65-0.90], S-DAPT + P2Y12 [OR = 0.54, 95%CI: 0.44-0.66]). S-DAPT + As was higher than L-DAPT (OR = 1.42, 95%CI: 1.10-1.83). CONCLUSIONS: S-DAPT + P2Y12 has the lowest bleeding risk, while L-DAPT has the highest bleeding risk. In the outcome of MI, stent thrombosis, and cardiovascular and cerebrovascular adverse events, L-DAPT has the best efficacy. In the outcome of stroke and all-cause mortality, the 4 interventions were equally effective.

Efficacy of three novel drugs in the treatment of heart failure: A network meta-analysis.

BACKGROUND: Angiotensin receptor neprilysin inhibitors (ARNI), sodium-glucose cotransporter 2 inhibitors (SGLT2i), soluble guanylate cyclase stimulators (sGCs), and the traditional golden triangle standard-of-care (SOC) are effective drugs for heart failure. We aimed to assess the efficacy of 4 interventions in these patients. METHODS: PubMed, The Cochrane Library, Embase, and Web of Science databases were electronically searched to collect randomized controlled trials of 3 novel drugs in the treatment of heart failure from inception to September 1st, 2021. Two reviewers independently screened literature, extracted data, and assessed the risk bias of included studies. Stata 16.0 software was used for network meta-analysis. RESULTS: A total of 17 randomized controlled trial involving 38,088 patients were included. The results of network meta-analysis: in terms of heart failure rehospitalization rate, 3 novel drugs lower than SOC [ARNI (OR = 0.77, 95% CI: 0.71-0.83), SGLT2i (OR = 0.70, 95% CI: 0.63-0.77), sGCs (OR = 0.88, 95% CI: 0.78-0.99)], and SGLT2i was also lower than sGCs (OR = 0.79, 95% CI: 0.68-0.93). In terms of all-cause mortality, ARNI was lower than SOC (OR = 0.81, 95% CI: 0.66-0.99). In terms of cardiovascular mortality, ARNI and SGLT2i was lower than SOC (ARNI [OR = 0.80, 95% CI: 0.70-0.92], SGLT2i [OR = 0.87, 95% CI: 0.76-0.99]). In terms of rates of cardiovascular death or heart failure rehospitalization, 3 novel drugs lower than SOC (ARNI [OR = 0.76, 95% CI: 0.71-0.82], SGLT2i [OR = 0.76, 95% CI: 0.70-0.82], sGCs [OR = 0.87, 95% CI: 0.78-0.97]). In terms of Kansas city cardiomyopathy questionnaire score, ARNI and SGLT2i was superior to SOC (ARNI [MD = 1.43, 95% CI: 0.43-2.42], SGLT2i [MD = 1.88, 95% CI: 1.12-2.65]). In terms of N-terminal pro-B-type natriuretic peptide outcome indexes, SGLT2i was superior to SOC (MD = -134.63, 95% CI: -237.70 to -31.56). The results of Surface under the cumulative ranking sequencing: in terms of heart failure rehospitalization rate and rates of cardiovascular death or heart failure rehospitalization, the ranking was SGLT2i>ARNI>sGCs>SOC. in terms of all-cause mortality and cardiovascular mortality, the ranking was ARN>SGLT2i>sGCs>SOC. in terms of Kansas city cardiomyopathy questionnaire score and N-terminal pro-B-type natriuretic peptide outcome indexes, the ranking was SGLT2i>ARN>SOC. CONCLUSIONS: The available evidence suggests that all 3 novel heart failure drugs can improve the prognosis of heart failure. ARNI may be the most effective in reducing mortality, SGLT2i may be the most effective in improving quality of life, while sGCs may be inferior to ARNI and SGLT2i.

Synergetic Anticorrosion Mechanism of Main Constituents in Chinese Yam Peel for Copper in Artificial Seawater.

Active constituents of Chinese yam peel (CYPE), namely, diosgenin (DOG), batatasin-I (BTS-I), batatasin-III (BTS-III), and yam polysaccharide (Y-PS), were extracted via an ultrasonic soaking strategy. The synergetic anticorrosion mechanism among these compounds for copper in artificial seawater (ASW) was clarified by gravimetric measurements, electrochemical evaluations, surface analyses, quantum chemical calculations under a dominant solvent model, and molecular dynamics (MD) simulations. The results of weight loss revealed that CYPE strongly inhibited the corrosion of copper in ASW, and the elevating temperature boosted the anticorrosion efficacy of CYPE. The inhibition efficiency could attain 96.33% with 900 mg/L CYPE in ASW at 298 K due to effective adsorption. CYPE simultaneously suppressed the anodic and cathodic reactions for copper in ASW, which could be categorized as the mixed-type corrosion inhibitor with the predominant anodic effect. Similar electrochemical kinetics was evidenced by electrochemical frequency modulation (EFM). Electrochemical impedance spectroscopy (EIS) indicated that CYPE prominently increased the charge-transfer resistance at the copper/electrolyte interface without altering the corrosion mechanism. Extending the immersion time was also conducive for CYPE to further minimize the corrosion of copper in ASW, which was demonstrated by the time-course polarization, EIS, and EFM tests. Owing to the adsorption of CYPE, the copper surface was well-protected and showed reduced wettability and limited variation of roughness. From the outcomes of quantum chemical calculations, global and local reactive descriptors of DOG implied the cross-linked deposition of actually formed dioscin on the copper surface; otherwise, those of BTS-I/-III showed the propensity for parallel adsorption, which could chemically anchor on the voids uncovered by dioscin and thereby synergistically inhibit the corrosion process. The adsorption orientations of DOG, BTS-I, and BTS-III were also consolidated by MD simulations. The findings of this study might be beneficial to inspire the development of eco-friendly corrosion inhibitors from plant wastes for copper in marine environments.

Cloning and characterisation of four catA genes located on the chromosome and large plasmid of Pseudomonas putida ND6

Background: Although the functional redundancy of catechol 1,2-dioxygenase (C12O) genes has been reported in several microorganisms, limited enzymes were characterised, let alone the advantage of the coexistence of the multiple copies of C12O genes. Results: In this study, four novel C12O genes, designated catA, catAI, catAII and catAIII, in the naphthalene-degrading strain Pseudomonas putida ND6, were cloned and characterised. Phylogenetic analysis of their deduced amino acid sequences revealed that the four C12O isozymes each formed independent subtrees, together with homologues from other organisms. All four enzymes exhibited maximum activity at pH 7.4 and higher activity in alkaline than in acidic conditions. Furthermore, CatA, CatAI and CatAIII were maximally active at a temperature of 45°C, whereas a higher optimum temperature was observed for CatAII at a temperature of 50°C. CatAI exhibited superior temperature stability compared with the other three C12O isozymes, and kinetic analysis indicated similar enzyme activities for CatA, CatAI and CatAII, whereas that of CatAIII was lower. Significantly, among metal ions tested, only Cu2+ substantially inhibited the activity of these C12O isozymes, thus indicating that they have potential to facilitate bioremediation in environments polluted with aromatics in the presence of metals. Moreover, gene expression analysis at the mRNA level and determination of enzyme activity clearly indicated that the redundancy of the catA genes has increased the levels of C12O. Conclusion: The results clearly imply that the redundancy of catA genes increases the available amount of C12O in P. putida ND6, which would be beneficial for survival in challenging environments.

Diffusion Tensor Imaging in Diagnosis of Post-Traumatic Syringomyelia in Spinal Cord Injury in Rats.

BACKGROUND Post-traumatic syringomyelia (PTS) is a common disease after spinal cord injury (SCI). The present study was performed to evaluate the advantages of diffusion tensor imaging (DTI) in estimating SCI and prognosing PTS in SCI rats. MATERIAL AND METHODS Forty rats were divided into 3 groups based on the extent of the individual SCI and PTS: a control group (n=10), a PTS group (n=8), and an SCI group (n=22). BBB tests were performed preoperatively and postoperatively at (1 d, 3 d, 5 d, 1 w, 2 w, 1 w, 2 w, 3 w, 4 w, 5 w, and 6 w). MRI T2 scanning was conducted postoperatively at (1 w, 2 w, 3 w, 4 w, 5 w, 6 w). DTI and diffusion tensor tractography were used for analyzing neuro-fiber changes after SCI. RESULTS BBB scoring showed no differences between the PTS group and SCI group (P<0.05). PTS was found in 8 rats after SCI. MRI showed PTS formation in 3 rats at 2 w after SCI, and 5 rats showed PTS formation at postoperative 3w after SCI. Compared with the control group, ADC showed significant increase in both the PTS group (P<0.05) and the SCI group (P<0.05), FA showed significant decreases in the PTS (P<0.05) and SCI (P<0.05) groups. Compared with the SCI group, the PTS group showed an increase in ADC, but no statistical difference was found in ADC (P>0.05). The PTS group showed a significant increase in FA (P<0.05). CONCLUSIONS The combination of diffusion tensor imaging and diffusion tensor tractography has characteristics of high-sensitivity and quantitation for PTS prognosis. FA is predictive in the prognosis of PTS formation after SCI.

Comparison operative and conservative management for primary patellar dislocation: an up-to-date meta-analysis.

PURPOSE: The aim of this review was to compare the clinical outcomes between operative and conservative management for primary patella dislocation (PPD). METHODS: PubMed Medline, EMBASE, Google scholar, and the Cochrane Library were systematically searched for randomized controlled trials that compared operative technique versus conservative technique for PPD. The results of eligible studies were independently extracted and analyzed according to the following: patient's satisfaction, Kujala score, Tegner score, and redislocation rate. Random-effect and fixed-effect models were adopted to calculate the weight mean difference and the odds ratio for continuous and dichotomous variables with 95 % confidence interval. RESULTS: Seven studies met the inclusion criteria, resulting in 402 (216 surgery and 186 conservation) patients available for the present study. A meta-analysis showed no significant differences between the two treatment groups in terms of patient's satisfaction and Kujala score. However, significant differences in Tegner score (P < 0.00001) and redislocation rate (P = 0.002) were observed in favor of surgical treatment. In the subgroup analysis, surgical intervention achieved higher (P = 0.002) Kujala score in short term (<5 years), while conservation gained advantage (P = 0.003) in long term (>5 years). There was no significant difference in dislocation rate in long term. CONCLUSIONS: Surgical treatment might provide better clinical results in short term. More persuasive evidence is still needed to proof the effect of surgical management in long time.

Spontaneous phase transfer of thermosensitive hairy particles between water and an ionic liquid.

This article describes the temperature-induced phase transfer behavior of a series of thermosensitive polymer brush-grafted particles between water and a hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]). Six samples were made by surface-initiated atom transfer radical polymerization: silica particles grafted with poly(methoxypoly(ethylene glycol) methacrylate) (PPEGMMA) with two different molecular weights, poly(methoxytri(ethylene glycol) methacrylate) (PTEGMMA), poly(methoxydi(ethylene glycol) methacrylate) (PDEGMMA), and two copolymers of PEGMMA and TEGMMA with different compositions (P(PEGMMA-co-TEGMMA)-82 and P(PEGMMA-co-TEGMMA)-74). The cloud points of free PPEGMMA with M(n,SEC) of 23 and 40 kDa, P(PEGMMA-co-TEGMMA)-82, P(PEGMMA-co-TEGMMA)-74, and PTEGMMA in [EMIM][TFSI]-saturated water were 95, 94, 80, 72, and 43 °C, respectively. PDEGMMA was not soluble in the ionic liquid-saturated water. PPEGMMA brush-grafted particles moved spontaneously and completely from water to the [EMIM][TFSI] phase upon heating at 80 °C. When cooled to 22 °C, all particles returned to the water layer. From UV-vis absorbance measurements, the transfer temperature (T(tr)) of PPEGMMA-grafted particles from water to the ionic liquid was 42 °C. Thermodynamic analysis showed that the particle transfer was an entropically driven process. P(PEGMMA-co-TEGMMA)-82, P(PEGMMA-co-TEGMMA)-74, and PTEGMMA brush-grafted particles also underwent reversible and quantitative transfer between the two phases upon heating at 70 °C and cooling at 0 °C; their transfer temperatures from water to [EMIM][TFSI] were 36, 30, and 16 °C, respectively. T(tr) was a linear function of the cloud point of the corresponding free polymer in ionic liquid-saturated water. In contrast, PDEGMMA-grafted particles moved spontaneously to the ionic liquid layer upon heating but did not return to water even after prolonged stirring at 0 °C.

Thermosensitive water-dispersible hairy particle-supported pd nanoparticles for catalysis of hydrogenation in an aqueous/organic biphasic system.

We report in this article the use of thermosensitive water-dispersible polymer brush-grafted polymeric particles as carriers for Pd nanoparticles for the catalysis of hydrogenation of styrene in an aqueous/organic biphasic system. Thermoresponsive poly(methoxytri(ethylene glycol) methacrylate) brushes were grown from initiator-functionalized core-shell cross-linked poly( t-butyl acrylate) (P tBA) particles via surface-initiated atom-transfer radical polymerization. The t-butyl group of P tBA in the core was removed with trifluoroacetic acid, followed by loading of Pd2+ cations through ion exchange. Pd nanoparticles were prepared by reduction of Pd2+ ions with ethanol at 70 degrees C. Dynamic light scattering studies showed that the Pd nanoparticle-loaded thermosensitive hairy particles in water began to shrink when the temperature was above 30 degrees C. The supported Pd nanoparticles efficiently catalyzed hydrogenation of styrene in an aqueous/octane biphasic system and were reused five times with no changes in the yields in the first three cycles and slight decreases in the fourth and fifth cycles after the same period of time. Kinetics studies showed that the catalytic activity of Pd nanoparticles was modulated by the phase transition of the thermosensitive brush layer, resulting in a non-Arrhenius dependence of apparent initial rate constant, k app, on temperature.

Temperature-induced transport of thermosensitive hairy hybrid nanoparticles between aqueous and organic phases.

This paper reports on the temperature-induced transport of thermosensitive polymer brush-grafted silica nanoparticles between aqueous and organic phases. Poly(methoxytri(ethylene glycol) methacrylate), a thermosensitive water-soluble polymer with a cloud point of approximately 48 degrees C in H2O, was grown on silica nanoparticles by surface-initiated atom transfer radical polymerization in the presence of a free initiator. These hairy particles were found to quantitatively transfer from aqueous to ethyl acetate phases upon heating at 60 degrees C under the stirring condition. Cooling in an ice/water bath caused the particles to move from ethyl acetate to the aqueous layer. The concentrations of the particles in the original phases during the transport processes were monitored by UV-vis spectrometry. When mutually saturated water and ethyl acetate were used, the transport rates of the particles between the two phases were enhanced. The faster transport was attributed to the solvent phase separation, which produced liquid droplets, dramatically increased the interfacial area, and hence facilitated the transport of the particles. The reversible transfer of the particles between the aqueous and ethyl acetate phases upon heating at 60 degrees C and cooling in an ice/water bath can be repeated consecutively at least 10 times. The hairy particles can also be quantitatively transported from 1-butanol and toluene to H2O by stirring in an ice/water bath. However, only 60% of the particles transferred from water to 1-butanol and no particles to toluene upon heating at 60 degrees C. The reasons are discussed.

Protein-resistant polymer coatings on silicon oxide by surface-initiated atom transfer radical polymerization.

The modification of silicon oxide with poly(ethylene glycol) to effectively eliminate protein adsorption has proven to be technically challenging. In this paper, we demonstrate that surface-initiated atom transfer radical polymerization (SI-ATRP) of oligo(ethylene glycol) methyl methacrylate (OEGMA) successfully produces polymer coatings on silicon oxide that have excellent protein resistance in a biological milieu. The level of serum adsorption on these coatings is below the detection limit of ellipsometry. We also demonstrate a new soft lithography method via which SI-ATRP is integrated with microcontact printing to create micropatterns of poly(OEGMA) on glass that can spatially direct the adsorption of proteins on the bare regions of the substrate. This ensemble of methods will be useful in screening biological interactions where nonspecific binding must be suppressed to discern low probability binding events from a complex mixture and to pattern anchorage-dependent cells on glass and silicon oxide.

Thermosensitive hairy hybrid nanoparticles synthesized by surface-initiated atom transfer radical polymerization.

This article reports on the synthesis of thermosensitive polymer brushes on silica nanoparticles by atom transfer radical polymerization (ATRP) and the study of thermo-induced phase transitions in water. Silica nanoparticles were prepared by the Stöber process and the surface was functionalized by an ATRP initiator. Surface-initiated ATRPs of methoxydi(ethylene glycol) methacrylate (DEGMMA) and methoxytri(ethylene glycol) methacrylate (TEGMMA) were carried out in THF at 40 degrees C in the presence of a free initiator, benzyl 2-bromoisobutyrate. The polymerizations were monitored by 1H NMR spectroscopy and gel permeation chromatography. The hairy hybrid nanoparticles were characterized by thermogravimetric analysis and scanning electron microscopy, and the thermoresponsive properties were investigated by variable temperature 1H NMR spectroscopy and dynamic light scattering. The cloud points of free poly(DEGMMA) and poly(TEGMMA) in water were around 25 and 48 degrees C, respectively. The thermo-induced phase transitions of polymer brushes on silica nanoparticles began at a lower temperature and continued over a broader range (4-10 degrees C) than those of free polymers in water (< 2 degrees C).

Environmentally responsive "hairy" nanoparticles: mixed homopolymer brushes on silica nanoparticles synthesized by living radical polymerization techniques.

This article reports on the preparation of environmentally responsive "hairy" nanoparticles by growth of mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brushes from silica particles using living radical polymerization techniques and subsequent hydrolysis of PtBA to produce amphiphilic mixed poly(acrylic acid) (PAA)/PS brushes. Silica particles were synthesized by the Stober process and were functionalized with an asymmetric difunctional initiator-terminated monolayer. Surface-initiated atom transfer radical polymerization of tBA was carried out in the presence of a free initiator. Kinetics study showed that the polymerization was well controlled. By cleaving PtBA off the particles, the molecular weights of the grafted and free polymers were found to be essentially identical. Mixed PtBA/PS brushes were obtained by the nitroxide-mediated radical polymerization of styrene from PtBA particles. The M(n) of the grafted PS was found to be the same as that of the free PS formed in the solution from the free initiator. Amphiphilic mixed PAA/PS brush-coated nanoparticles were synthesized from mixed PtBA/PS particles by hydrolysis of PtBA with iodotrimethylsilane. Tyndall scattering experiments and (1)H NMR study showed that the mixed PAA/PS particles can be dispersed and form a stable suspension in CHCl(3), a selective solvent for PS, and also in CH(3)OH, a selective solvent for PAA, demonstrating the capability of these hairy nanoparticles to undergo chain reorganization in response to environmental changes.

A novel, solventless reductive coupling of carbonyl compounds by alkali metals, catalysed by bromobenzene.

Catalysed by bromobenzene, alkali metals including Li, Na, and K can mediate the reductive coupling of carbonyl compounds under mild, solventless conditions to furnish the corresponding pinacol products.