Studies on the Autoxidation of Phenyl Cycloalkanes

The products of the autoxidation of phenyl cyclopropane ( I ), phenyl cyclobutane ( II ), phenyl cyclopentane ( III ), phenyl cyclohexane ( IV ), phenyl cycloheptane ( V ) and phenyl cyclooctane ( VI ) were analyzed after reduction of the reaction mixtures with LiAlH₄. As products of the attack on the α-C H bonds the corresponding 1-phenyl cycloalkanols and 1-phenyl alkan-1-ols were found. In the case of phenyl cyclopropane some S_R2 ring opening probably takes place. The oxidabilities $ {\rm k}_{\rm p} /\sqrt {{\rm k}_{\rm t}} $, the chain termination constants k_t, the absolute chain propagation constants k_p and the relative chain propagation constant (k_p)_rel were determined for the phenyl cycloalkanes I — VI . As it is to be expected on the basis of the I-strain concept the autoxidation rate of phenyl cyclopentane ( III ) is considerably higher than that of phenyl cyclobutane ( II ) and phenyl cyclohexane ( IV ).     

iFlash:80℃活化漂白与新型皂洗

加工技术与设备的发展通常会使加工时间缩短.但是新型助剂的应用也可减少加工时间,大大降低成本.随着iFlash系统的应用,漂白温度可降至80℃,活性染料染色后皂洗的时间也大大缩短.因此,织物间歇式染色得到优化,在不增加额外投资的情况下运行更经济.     

CD-R产品检测:高的品质来自成熟的工艺

根据最新的市场调查显示：在2004年，CD-R产品的市场需求将小于之前的2年。这源于在2003年期间，CD-R产品的生产能力以非常迅速的速度同市场的需求之间达到平衡。特别是在印度、中东和远东地区，新的风险企业家在偶然情况下发现可记录光盘领域的市场需求，从而大量进入来填补这个空白。     

Nitrous oxide emission as affected by liming an acidic mineral soil used for arable agriculture

The effect of liming an acidic mineral soil (Dystric Nitosol from southern China), used for arable agriculture, on N₂O emission was studied in an incubation experiment. After the soil pH had been raised from pH 4.4 to 5.2, 6.7 and 8.1, soil samples were either amended with NH₄ ⁺ and incubated aerobically, favoring nitrification or, after application of NO₃ ^–, the incubation took place under anaerobic conditions, favoring denitrification. Gas sampling for N₂O determination and soil analyses were performed at regular intervals up to 13 days. Under nitrification conditions only small N₂O emission rates were observed (max. 6 g N kg^–1 d^–1) with significant differences between high and low pH values during the first 2 days of incubation. The nitrifying activity was low, even with high pH, and this, together with good aeration conditions, could partly explain the small N₂O evolution. During denitrification, however, cumulative N₂O emissions reached much higher values (1600 g N kg^–1 in comparison to 40 g N kg^–1 under nitrification conditions). N₂O emission during denitrification was significantly enhanced by increasing soil pH. Under alkaline conditions (pH 8.1) a large nitrite accumulation occurred, which was in line with the highest nitrate reductase activity determined in this treatment. The limited availability of organic carbon is probably the main reason for the absence of further reduction of NO₂ ^– to N₂O or N₂. At pH 6.7 the total N₂O emission was slightly higher than at pH 8.1, although the start of pronounced emissions was retarded and only small amounts of NO₂ ^– accumulated. Acid soil conditions caused either negligible (pH 4.4) or only small (pH 5.2) N₂O emissions. It can be concluded that these kinds of soil, used alternatively for production of upland crops or paddy rice, are prone to high N₂O emissions after flooding, particularly under neutral to alkaline conditions. In order to avoid major N₂O evolution and accumulation of nitrite, which can be leached into groundwater, the pH should not be raised to values above 5.5–6.     

Oligosaccharide mimics containing galactose and fucose specifically label tumour cell surfaces and inhibit cell adhesion to fibronectin

With the aim of establishing a versatile and easy synthesis of branched saccharides for biological applications, we used molecular-dynamics simulations to model Lewis(y) to two classes of di- or triantennary saccharide mimetics. One set of mimetics was based on 1,3,5-tris(hydroxymethyl)cyclohexane (TMC) as the core, the other on furan, and both were derivatised with galactose and/or fucose. The TMC-based saccharides were biotinylated, while the furan disaccharides were treated with maleimide-activated biotin in a Diels-Alder fashion to yield oxazatricyclodecanes (OTDs). These were then assayed as cell-surface labels in human colon (SW480 and CaCo-2), liver (PLC), Glia (U333 CG 343) and ovary (SKOV-3) tumour cell lines. Discrete staining patterns were observed in all cells, usually at one or two poles of the cells, particularly with the asymmetric 3-beta-L-fucopyranosyloxymethyl-4-beta-D-galactopyranosyloxymethyl-OTD. Normal SV40-transformed fibroblasts (SV80) showed no staining. Adhesion of the highly metastatic mouse melanoma line B16 F10 to fibronectin was inhibited by 80 % by the TMC-digalactoside and by 30 % by 3,4-bis-(beta-D-galactopyranosyloxymethyl)furan. None of the saccharide mimetics inhibited the adhesion of the less metastatic B16 F1 line. Migration of B16 F10 cells through Matrigel was greatly inhibited by the TMC-digalactoside and weakly inhibited by the TMC-trigalactoside. The saccharide mimetics that had shown the best structural agreements with the terminal saccharides of Lewis(y) in the molecular dynamics simulation were also the most biologically potent compounds; this underlines the predictive nature of molecular dynamics simulations. The use of the non-saccharide cores enabled us to adapt spacer lengths and terminal saccharides to optimise the structures to bind more avidly to cell-surface lectins.     

Towards artificial intelligence at scale in the chemical industry

In the Industry 4.0 era, the chemical industry is embracing broad adoption of artificial intelligence (AI) and machine learning (ML) methods. This article provides a holistic view of how the industry is transforming digitally towards AI at scale. First, a historical perspective on how the industry used AI to aid humans in better decision-making is shown. Then state-of-the-art AI research addressing industrial needs on reliability and safety, process optimization, supply chain, material discovery, and reaction engineering is highlighted. Finally, a vision of the plant of the future is illustrated with critical components of AI-ready culture, model life cycle management, and renewed role of humans in chemical manufacturing.     

Visualizing biochemical activities in living cells through chemistry

The development of molecular probes to visualize cellular processes is an important challenge in chemical biology. One possibility to create such cellular indicators is based on the selective labeling of proteins with synthetic probes in living cells. Over the last years, our laboratory has developed different labeling approaches for monitoring protein activity and for localizing synthetic probes inside living cells. In this article, we review two of these labeling approaches, the SNAP-tag and CLIP-tag technologies, and their use for studying cellular processes.     

Cuticular hydrocarbons of Tetramorium ants from central Europe: analysis of GC-MS data with self-organizing maps (SOM) and implications for systematics

Cuticular hydrocarbons were extracted from workers of 63 different nests of five species of Tetramorium ants (Hymenoptera: Formicidae) from Austria, Hungary, and Spain. The GC-MS data were classified (data mining) by self-organizing maps (SOM). SOM neurons derived from primary neuron separation were subjected to hierarchical SOM (HSOM) and were grouped to neuron areas on the basis of vicinity in the hexagonal output grid. While primary neuron separation and HSOM resulted in classifications on a level more sensitive than species differences, neuron areas resulted in chemical phenotypes apparently of the order of species. These chemical phenotypes have implications for systematics: while the chemical phenotypes for T. ferox and T. moravicum correspond to morphological determination, in T. caespitum and T. impurum a total of six chemical phenotypes is found. Three hypotheses are discussed to explain this disparity between morphological and chemical classifications, including in particular the possibility of hybridization and the existence of cryptic species. Overall, the GC-MS profiles classified by SOM prove to be a practical alternative to morphological determination (T. ferox, T. moravicum) and indicate the need to revisit systematics (T. caespitum, T. impurum).