Preparation and characterisation of silica monoliths using a triblock copolymer (F68) as porogen

Silica-based monoliths with co-continuous structure were successfully prepared through a sol–gel process in the presence of a poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (F68). The triblock copolymer was compared to the classical PEG, in the formation of silica monoliths and was demonstrated to lead to co-continuous structures in a wider composition range, presenting smaller through pores. Moreover, mesoporous structures templated at the sol–gel transition were assumed to occur at the surface of the silica skeleton while PEG exhibited no mesopore templating.     

3D tracking of foraging belugas from their clicks: Experiment from a coastal hydrophone array

A simple passive acoustic monitoring (PAM) setup was used to localize and track beluga whales underwater in three dimensions (3D) in a fjord. In June 2009, beluga clicks were recorded from a cabled hydrophone array in a regularly frequented habitat in Eastern Canada. Beluga click energy was concentrated in the 30-50 kHz frequency band. The click trains detected on several hydrophones were localized from their time difference of arrivals. Cluster analysis linked localizations into tracks based on criteria of spatial and temporal proximity. At close ranges from the array, the localized click-train series allowed three-dimensional tracking of a beluga during its dive. Clicks within a train spanned a large range of durations, inter-click intervals, source levels and bandwidths. Buzzes sometimes terminated the trains. Repeated click packets were frequent. All click characteristics are consistent with oblique observations from the beam axis, and ordered variation of the source pattern during a train, likely resulting from a scan of angles from the beam axis, was observed before click trains indicated focusing of the echolocation clicks in one direction. The click-train series is interpreted as echolocation chasing for preys during a foraging dive. Results show that a simple PAM system can be configured to passively and effectively 3D track wild belugas and small odontocetes in their regularly frequented habitat.     

Gas Chromatographic Fingerprint Analysis for the Comparison of Seized Cannabis Samples

Cannabis sativa L. is widely used as recreational illegal drugs. Illicit Cannabis profiling, comparing seized samples, is challenging due to natural Cannabis heterogeneity. The aim of this study was to use GC–FID and GC–MS herbal fingerprints for intra (within)- and inter (between)-location variability evaluation. This study focused on finding an acceptable threshold to link seized samples. Through Pearson correlation-coefficient calculations between intra-location samples, ‘linked’ thresholds were derived using 95% and 99% confidence limits. False negative (FN) and false positive (FP) error rate calculations, aiming at obtaining the lowest possible FP value, were performed for different data pre-treatments. Fingerprint-alignment parameters were optimized using Automated Correlation-Optimized Warping (ACOW) or Design of Experiments (DoE), which presented similar results. Hence, ACOW data, as reference, showed 54% and 65% FP values (95 and 99% confidence, respectively). An additional fourth root normalization pre-treatment provided the best results for both the GC–FID and GC–MS datasets. For GC–FID, which showed the best improved FP error rate, 54 and 65% FP for the reference data decreased to 24 and 32%, respectively, after fourth root transformation. Cross-validation showed FP values similar as the entire calibration set, indicating the representativeness of the thresholds. A noteworthy improvement in discrimination between seized Cannabis samples could be concluded.     

DRIC: A dynamic version of the RIC method

A new incomplete factorization method is proposed, differing from previous ones by the way in which the diagonal entries of the triangular factors are defined. A comparison is given with the dynamic modified incomplete factorization methods of Axelsson–Barker and Beauwens, and with the relaxed incomplete Cholesky method of Axelsson and Lindskog. Theoretical arguments show that the new method is at least as robust as both previous ones, while numerical experiments made in the discrete PDE context show an effective improvement in many practical circumstances, particularly for anisotropic problems.     

Opening of tartrate acetals using dialkylboron bromide: evidence for stereoselectivity downstream from ring fission

Johnson-type acetals derived from dimethyl tartrate give, after opening with Me(2)BBr and cuprate displacement, secondary alcohols with high diastereoselectivity (>30:1). The mechanism proposed for the induction of diastereoselectivity is downstream from the ring fission. It implies a direct participation of the Lewis acid as a source of nucleophile and the stereospecific transformation of the resulting bromo acetal through an invertive and temperature-dependent process. The acetals are prepared by reaction of the desired aldehyde with dimethyl tartrate. Removal of the auxiliary is accomplished through SmI(2) reduction or by an addition-elimination protocol using methoxide.     

tert-Butylmethoxyphenylsilyl ether - a new selective,stable alcohol protecting group with remarkable lability to fluoride.

$\text{tert}$-Butylmethoxyphenylsilyl ethers, which can be formed from primary, secondary or tertiary alcohols and $\text{tert}$-butylmethoxyphenylsilyl bromide, are selectively cleaved by fluoride in the presence of other silyl ethers.     

Synthesis of postulated molecular probes: stereoselective free-radical-mediated C-glycosylation in tandem with hydrogen transfer

Reported herein is a strategy employing an addition reaction in tandem with a hydrogen-transfer reaction for the elaboration of C-glycoside-based sialyl Lewis X (sLe(X)) analogues. Significant stereocontrol was noted when alkyl radicals were reacted with a series of alkoxytaconates. Transition states were proposed to explain the obtained selectivity. Further reaction between an anomeric-centered fucosyl-derived radical and a galactosylated hydroxytaconate provided easy access to C,O-diglycosides as mimics of sLe(X). In this case, two 1,3-distant stereocenters were created with high diastereoselectivity using free radical intermediates in a tandem process.     

反应挤出合成带不饱和官能团端基的聚己内酯

用带双键官能团的2-烯丙氧基乙醇与四丙醇钛酸酯进行酯交换,可合成用于ε-己内酯配位开环聚合的钛化合物引发剂;利用此引发剂,引发ε-己内酯聚合得到了分子链一端为双键的功能化聚己内酯.研究了物料配比和反应温度对聚合转化率和速率的影响,进而在双螺杆挤出机中实施快速本体聚合,合成了带活性双键的功能化聚己内酯.引发剂和聚合物的化学结构由 1H-NMR予以表征,GPC测定的结果表明聚合物的分子量与物料摩尔比相关.