Self-assembly of amphiphilic liquid crystal block copolymers containing a cholesteryl mesogen: Effects of block ratio and solvent

We report on the self-assembly, in water and in bulk, of amphiphilic liquid crystal block copolymers consisting of a cholesterol-based smectic LC polymer block (PAChol) and poly(ethylene glycol) (PEG) block. Two series of block copolymers, PEG₄₅-b-PAChol and PEG₁₁₄-b-PAChol (45 and 114 are the degree of polymerization of PEG blocks) with different hydrophilic/hydrophobic weight ratios were synthesized and characterized in detail. Depending on the diblock composition, smectic polymer vesicles and/or nanofibers were formed by adding water into a dilute solution of copolymers in dioxane. If THF is used instead of dioxane as solvent, solid spherical aggregates were obtained upon water addition for PEG₄₅-b-PAChol series, while macroscopic precipitation occurred for PEG₁₁₄-b-PAChol series. The mesomorphic and microphase segregation structures of the block copolymers in bulk were studied by X-ray scattering, DSC and POM. The interdigital smectic A (SmA_d) phase with a lamellar period of 4.25 nm was detected in all block copolymers. For PEG₁₁₄-b-PAChol₅ (PEG/PAChol weight ratio = 66/34) and PEG₁₁₄-b-PAChol₁₂ (45/55), lamellar type of microphase segregation was observed.     

Microstructure,Hardness, and Residual Stress Distributions in T-Joint Weld of HSLA S500MC Steel

This paper investigates the characterization of the microstructure, hardness, and residual stress distributions of MIG-welded high-strength low-alloy S500MC steel. The T-joint weld for 10-mm-thick plates was joined using a two passes MIG welding technology. The contour method was performed to measure longitudinal welding residual stress. The obtained results highlighted a good correlation between the metallurgical phase constituents and hardness distribution within the weld zones. In fact, the presence of bainite and smaller ferrite grain size in the weld-fusion zone might be the reason for the highest hardness measured in this region. A similar trend of the residual stress and hardness distributions was also obtained.     

The impact of strain-induced crystallization on strain during mechanical cycling of cross-linked natural rubber

The improvement of X-ray diffraction techniques since the last ten years allowed a renewal of the study of strain-induced crystallization in natural rubber. In particular real-time measurements are now commonplace. However, due to experimental difficulties, the exploitation of the X-ray data as far as the strain state of the remaining molten fraction is concerned has been left aside. Indeed the knowledge of the local extension of the molten chains is crucial for understanding the peculiar stress behavior observed during the crystallization process. This paper presents a systematic study of this parameter during mechanical cycling performed at various temperatures. It is shown that crystallization limits the amplitude of strain endured by the molten fraction during traction. This process of strain regulation may be one explanation for the protective effect of crystallization against tearing. A precise evaluation of the contribution of the molten fraction to the retraction force during mechanical cycling is made. The role of crystallites as nanofillers may be quantified this way.     

Stable carbon isotope content in ethanol of EC data bank wines from Italy, France and Germany

In the present work we discuss the usefulness of carbon isotope analysis of wine ethanol for the assignment of origin and the proof of adulteration of Italian, French and German wines. At first the comparability of the results from three laboratories is demonstrated by the results of inter-laboratory comparison measurement and by tests of the distillation procedures applied to the same samples. Furthermore, a close correlation of carbon isotope content in sugars from must and ethanol from the related wine could be found for samples from all countries. Using the ¹³C values of EC data bank wines from 1991 to 1993 for Italy, France and Germany, we describe and discuss the main factors of influence which are responsible for the variation of those values. By examination of spiked samples, the usefulness of the ¹³C analysis in the detection of certain types of wine enrichment is demonstrated; especially if the carbon isotope analysis by¹³C-8 isotope ratio mass spectrometry is employed as an additional tool for improving the security of the already officially performed determination of the site-specific hydrogen isotope content in wine ethanol by²H-NMR.     

A stroboscopic X-ray apparatus for the study of the kinetics of strain-induced crystallization in natural rubber

A stroboscopic X-ray diffraction machine is described that allows studying kinetics aspects of strain-induced crystallization in natural rubber. Besides conventional mechanical cycling in extension, samples may be submitted to periodic extension cycling over a 0.05 Hz–30 Hz frequency range and for various amplitudes of elongation. Pertinent parameters as crystalline content, crystallite orientation and segmental order parameter for the amorphous fraction are determined. The existence of a regulation process of the strain experienced by the chains that remain molten due to the phenomenon of strain-induced crystallization is clearly demonstrated during conventional mechanical cycling at low deformation rate. Melting retardation is shown to lead to an equalization of crystalline content in conditions of periodic cycling of moderate amplitude and below some average elongation. On the other hand, crystallization appears to be a rapid process subsisting up to the maximal cycling frequency corresponding to a stretching time of 17 ms. This is confirmed by periodic cycling of higher amplitude that suggests that strain-induced crystallization may appear within millisecond time. An approximate logarithmic dependence of the crystalline content and elongation of the amorphous fraction upon stretching time is further found.     

Characterisation of authentic Italian extra-virgin olive oils by stable isotope ratios of C,O and H and mineral composition

The paper shows the isotopic ratios (¹³C/¹²C, D/H, ¹⁸O/¹⁶O) in oil and extracted glycerol and the mineral composition of authentic PDO and PGI Italian extra-virgin olive oils, officially collected from 2000 to 2005 (N=539$N=539$) to establish a national databank. ¹³C/¹²C and ¹⁸O/¹⁶O increased from Trentino to Sicily, each year distinguishing Northern Italy from Sicily and Calabria. Significant differences were found among the years and in some cases also between PDOs from the same region. ¹³C/¹²C and ¹⁸O/¹⁶O in bulk oil were significantly correlated with those in glycerol. D/H, measured in 2005 for the first time in oil, showed promising geographical discrimination capability. The content of 26 elements – Li, Rb, Cs, La, Ce and Yb rarely reported in the literature – was measured in well settled 2005 oils after ultrasound acid extraction.     

Using optimisation for integrated water network management

The water industry has undergone radical change in the late 1980s and changes continue apace. We have been, and will continue to be, under increasing pressure to reduce costs and increase service within a framework where regulations are becoming tighter and demanding more information to achieve and substantiate performance. The major challenge will lie with the leaders of the industry. They have to achieve the right attitude, management technique and technical excellence to meet the requirements of change and to create adaptable organizations that can manage the challenges of change in a positive and proactive way. Cultural change has started but has a long way to go. We must overcome the traditional attitude of many water suppliers, which has typically been one of the ‘professional stewardship’ of a resource in which they supply water in the way they believe to be best. This must change and is changing to a more commercially minded management which is ‘customer centred’ rather than ‘product centred’. We must realize that our organizations manage a complex asset base which has to work towards strictly defined objectives of service quality, operational efficiency and regulatory requirements, all of which, as time goes on, are influenced more and more by substantial external forces.     

ViP MRI: virtual phantom magnetic resonance imaging

Object

The ability to generate reference signals is of great benefit for quantitation of the magnetic resonance (MR) signal. The aim of the present study was to implement a dedicated experimental set-up to generate MR images of virtual phantoms.

Materials and methods

Virtual phantoms of a given shape and signal intensity were designed and the k-space representation was generated. A waveform generator converted the k-space lines into a radiofrequency (RF) signal that was transmitted to the MR scanner bore by a dedicated RF coil. The k-space lines of the virtual phantom were played line-by-line in synchronization with the magnetic resonance imaging data acquisition.

Results

Virtual phantoms of complex patterns were reproduced well in MR images without the presence of artifacts. Time-series measurements showed a coefficient of variation below 1 % for the signal intensity of the virtual phantoms. An excellent linearity (coefficient of determination r ² = 0.997 as assessed by linear regression) was observed in the signal intensity of virtual phantoms.

Conclusion

Virtual phantoms represent an attractive alternative to physical phantoms for providing a reference signal. MR images of virtual phantoms were here generated using a stand-alone, independent unit that can be employed with MR scanners from different vendors.     

2nd PSL Chemical Biology Symposium (2019): At the Crossroads of Chemistry and Biology

Chemical Biology is the science of designing chemical tools to dissect and manipulate biology at different scales. It provides the fertile ground from which to address important problems of our society, such as human health and environment.