A Microgel Construction Kit for Bioorthogonal Encapsulation and pH‐Controlled Release of Living Cells

pH‐Cleavable cell‐laden microgels with excellent long‐term viabilities were fabricated by combining bioorthogonal strain‐promoted azide–alkyne cycloaddition (SPAAC) and droplet‐based microfluidics. Poly(ethylene glycol)dicyclooctyne and dendritic poly(glycerol azide) served as bioinert hydrogel precursors. Azide conjugation was performed using different substituted acid‐labile benzacetal linkers that allowed precise control of the microgel degradation kinetics in the interesting pH range between 4.5 and 7.4. By this means, a pH‐controlled release of the encapsulated cells was achieved upon demand with no effect on cell viability and spreading. As a result, the microgel particles can be used for temporary cell encapsulation, allowing the cells to be studied and manipulated during the encapsulation and then be isolated and harvested by decomposition of the microgel scaffolds.     

The effect of elevated temperature on conventional stationary phases used in SFC

Summary The effect of elevated temperatures on conventional packed bonded-phase columns used in supercritical-fluid chromatography (SFC) has been investigated. The impact of column conditioning temperature on the capacity factor, peak width, and peak asymmetry on octadecyl and propylamino columns from five commerical suppliers is reported.     

Mott–Hubbard transition in a 2D He fluid monolayer

We discuss recent observations of the heat capacity and magnetization of a fluid ³He monolayer adsorbed on graphite plated with a bilayer of HD. Approaching the density at which the monolayer solidifies into a commensurate solid, we observe an apparent divergence of the effective mass. However, the inferred values of F₀^a tend to a constant. We interpret this in terms of a Mott–Hubbard transition between a 2D Fermi liquid and a magnetically disordered solid occurring via the Brinkman–Rice–Anderson–Vollhardt scenario.     

Characterization of complex assemblages of organic acids in geological samples by negative electrospray ionization mass spectrometry using a double‐focusing magnetic sector field mass spectrometer

Four different geological sample types (a crude oil, a crude oil asphaltene, a reservoir core extract and a reservoir core asphaltene) have been characterized by negative ionization electrospray mass spectrometry at low and high mass resolution using a double‐focusing magnetic sector field mass spectrometer. The mass range, shape of the spectra and the signal distribution of the acidic constituents as well as the average molecular weights, the total ion abundance and signal intensity in the spectra were compared for the different sample types. Nominal mass classes have been evaluated and Kendrick mass plots were generated in order to identify homologous series. For the crude oil sample, accurate mass assignments were made by high‐resolution double‐focusing magnetic sector field mass spectrometry (DFMSFMS) and were compared with those obtained by negative ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). With both instrument types, compounds with the molecular composition C_nH_2n+zO₂, among which carboxylic acids predominated, were the main acidic compound class detectable in negative ESI mass spectra. Good agreement was achieved for the double bond class distribution and the carbon number distribution of the O₂ class. In addition, minor compound classes could be identified using FTICRMS. Copyright © 2010 John Wiley & Sons, Ltd.     

Hydrophilic Carotenoids: Surface Properties and Aggregation Behavior of the Potassium Salt of the Highly Unsaturated Diacid Norbixin

The oft‐claimed ‘good’ water solubility of the food color norbixin ( 3 ) could not be confirmed. In contrast, the potassium salt 5 of norbixin formed suitable dispersions. The surface and aggregation properties of salt 5 were investigated and compared with other naturally occurring and synthetic hydrophilic carotenoids (Table).     

Preparation and Conformation of Organo‐Bridged Bis[tris(arylchalcogenolato)tin] Compounds – An Experimental and Quantum Chemical Study

Seven organo‐bridged bis[tris(arylchalcogenolato)tin] compounds with the general formulae (R′E)₃Sn–R–Sn(ER′)₃ (R = –(CH₂)₄–, 1,4‐bis(methyl)benzene, 4,4′‐bis(methyl)biphenyl; R′ = Ph, 1‐Np, 2‐Np; E = S, Se) were synthesized and characterized by means of X‐ray diffractometry as well as NMR spectroscopy. Three different conformations of the arylchalcogenolato groups ER′ with respect to the bridging group R were rationalized and explained by means of quantum chemical investigations.     

First observation ofΩ * resonances

In a experiment at the CERN SPS charged hyperon beam using incident Ξ^?, we have obtained evidence for the production of two Ω^* resonances decaying into Ξ^?π⁺ K ^?, with the following parameters:M ₁=2251±12,Γ ₁=48±20 MeV/c², 78 ±23 events, andM ₂=2284±12,Γ ₂=26±23 MeV/c² 45±10 events. The first state is also observed as a 4.2σ effect in a subsample which contains an additionalK ⁺ orK ⁰ in the final state. Production cross sections and branching ratios to Ξ^* K ^? and Ξ^? K ^* are presented.