Fixed-Size Quadruples for a New, Hardware-Oriented Representation of the 4D Clifford Algebra

Clifford algebra (geometric algebra) offers a natural and intuitive way to model geometry in fields as robotics, machine vision and computer graphics. This paper proposes a new representation based on fixed-size elements (quadruples) of 4D Clifford algebra and demonstrates that this choice leads to an algorithmic simplification which in turn leads to a simpler and more compact hardware implementation of the algebraic operations. In order to prove the advantages of the new, quadruple-based representation over the classical representation based on homogeneous elements, a coprocessing core supporting the new fixed-size Clifford operands, namely Quad-CliffoSor (Quadruple-based Clifford coprocesSor) was designed and prototyped on an FPGA board. Test results show the potential to achieve a 23× speedup for Clifford products and a 33× speedup for Clifford sums and differences compared to the same operations executed by a software library running on a general-purpose processor.     

Application of lag-k autocorrelation coefficient and the TGA signals approach to detecting and quantifying adulterations of extra virgin olive oil with inferior edible oils

The combination of lag-k autocorrelation coefficients (LCCs) and thermogravimetric analyzer (TGA) equipment is defined here as a tool to detect and quantify adulterations of extra virgin olive oil (EVOO) with refined olive (ROO), refined olive pomace (ROPO), sunflower (SO) or corn (CO) oils, when the adulterating agents concentration are less than 14%. The LCC is calculated from TGA scans of adulterated EVOO samples. Then, the standardized skewness of this coefficient has been applied to classify pure and adulterated samples of EVOO. In addition, this chaotic parameter has also been used to quantify the concentration of adulterant agents, by using successful linear correlation of LCCs and ROO, ROPO, SO or CO in 462 EVOO adulterated samples. In the case of detection, more than 82% of adulterated samples have been correctly classified. In the case of quantification of adulterant concentration, by an external validation process, the LCC/TGA approach estimates the adulterant agents concentration with a mean correlation coefficient (estimated versus real adulterant agent concentration) greater than 0.90 and a mean square error less than 4.9%.     

Optical properties of a polyethylene dispersion with a luminescent silica prepared by surface grafting of a perylene derivative

A micrometric silica modified with perylene derivative (SiO₂–TES) has been prepared by hydrolysis–condensation reactions between silica and N,N’-bis-(3-triethoxysilylpropyl)-perylene-tetracarboxyldiimide (P-TES) and utilized as filler in LLDPE films together with a compatibilizer. Spectroscopic analyses on SiO₂–TES confirmed the grafting of P-TES on silica, while its amount was determined by thermogravimetric analysis. Solid state NMR provided information about the structure of silicon atoms involved in the condensation of SiO₂ and P-TES that resulted mainly in silicon atoms grafted with bi-dentate anchorages.UV–Vis and fluorescence analyses carried out on P-TES showed the ability of the dye to generate J-type aggregates in apolar solvents. The same analyses on SiO₂–TES revealed the presence of both isolated and aggregated dye molecules grafted on silica surface, while on polymeric dispersions of SiO₂–TES, they have shown only the presence of P-TES aggregates grafted to silica.Thanks to the direct correlation between optical properties (obtained both by UV–Vis and by fluorescence analyses) and the chemical environment of composites, the luminescent silica SiO₂–TES could be used to estimate the filler dispersion extent in different microcomposite polymer materials.     

Ionic azo-codendrimers: Influence of the acids contents in the liquid crystalline properties and the photoinduced optical anisotropy

A series of codendrimers has been prepared by the grafting of poly(propylene imine) PPI-(NH₂)₁₆ (G = 3) with two different carboxylic acids: the aromatic-based 5-[4′-(4-cyanophenylazo)phenyloxy]pentanoic acid (AZO) and the aliphatic 2,2-bis(undecanoyloxymethylene)propionic acid (BUPA) in different proportions. Their thermal properties, liquid crystalline behavior and photoinduced optical anisotropy have been investigated. The formation of the ionic compounds was confirmed by nuclear magnetic resonance (NMR) spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. The influence of the acid percentage in the liquid crystalline behavior was investigated by means of differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffractometry (XRD). All the resulting co-dendrimers present liquid crystalline properties displaying an evolution from nematic mesophase for the azo-richer dendrimers to smectic A mesophase for the BUPA-richer dendrimers. Only materials with low azobenzene contents up to four AZO units per dendrimer on average were processable by casting from dichloromethane solutions and resulted in transparent thin films appropriate for optical studies. The photoinduced dichroism reached was higher in the dendrimer with higher azo content (four units per dendrimer) being this material a good compromise between processability and optical response.     

Coordination-driven inversion of handedness in ligand-modified PNA

Peptide nucleic acid (PNA) is a synthetic analogue of DNA, which has the same nucleobases as DNA but typically has a backbone based on aminoethyl glycine (Aeg). PNA forms duplexes by Watson Crick hybridization. The Aeg-based PNA duplexes adopt a chiral helical structure but do not have a preferred handedness because they do not contain a chiral center. An L-lysine situated at the C-end of one or both strands of a PNA duplex causes the duplex to preferably adopt a left-handed structure. We have introduced into the PNA duplexes both a C-terminal L-lysine and one or two PNA monomers that have a γ-(S)-methyl-aminoethyl glycine backbone, which is known to induce a preference for a right-handed structure. Indeed, we found that in these duplexes the γ-methyl monomer exerts the dominant chiral induction effect causing the duplexes to adopt a right-handed structure. The chiral PNA monomer had a 2,2':6',2'-terpyridine (Tpy) ligand instead of a nucleobase and PNA duplexes that contained one or two Tpys formed [Cu(Tpy)(2)](2+) complexes in the presence of Cu(2+). The CD spectroscopy studies showed that these metal-coordinated duplexes were right-handed due to the chiral induction effect exerted by the S-Tpy PNA monomer(s) except for the cases when the [Cu(Tpy)(2)](2+) complex was formed with Tpy ligands from two different PNA duplexes. In the latter case, the metal complex bridged the two PNA duplexes and the duplexes were left-handed. The results of this study show that the preferred handedness of a ligand-modified PNA can be switched as a consequence of metal coordination to the ligand. This finding could be used as a tool in the design of functional nucleic-acid based nanostructures.     

Dynamics by solid-state NMR: detailed study of ibuprofen Na salt and comparison with ibuprofen

The various internal rotations and interconformational jumps of the Na-salt form of ibuprofen in the solid state were characterized in detail by means of the simultaneous analysis of a variety of low- and high-resolution NMR experiments aimed at measuring several (13)C and (1)H spectral and relaxation properties at different temperatures and frequencies. The results were first qualitatively analyzed to identify the motions of the different molecular fragments and to assign them to specific frequency regimes (slow, <10(3) Hz; intermediate, 10(3)-10(6) Hz; and fast, >10(6) Hz). Subsequently, a simultaneous fit of the experimental data sets most sensitive to each frequency range was performed by using suitable motional models, thus obtaining, for each motion, correlation times and activation energies. The motions so characterized were: the rotations of the three methyl groups and of the isobutyl group, occurring in the fast regime, and the π-flip of the phenyl ring, belonging to the intermediate motional regime. The results obtained for the Na-salt form were compared with those of the acidic form of ibuprofen, previously obtained from a similar solid-state NMR approach: despite the very similar chemical structure of the two compounds, their dynamic properties in the solid state are noticeably different.     

Application of a chiral metal-organic framework in enantioselective separation

A modular approach for the synthesis of highly ordered porous and chiral auxiliary (Evans auxiliary) decorated metal-organic frameworks is developed. Our synthesis strategy, which uses known porous structures as model materials for incorporation of chirality via linker modification, can provide access to a wide range of porous materials suitable for enantioselective separation and catalysis. Chiral analogues of UMCM-1 have been synthesized and investigated for the enantioseparation of chiral compounds in the liquid phase and first promising results are reported.     

Yeast cell wall particles: a promising class of nature-inspired microcarriers for multimodal imaging

This communication demonstrates that yeast cell wall particles (YCWPs) are a promising class of nature-inspired biocompatible microcarriers for the delivery of amphipathic/lipophilic imaging reporters. When a paramagnetic MRI agent is loaded, the longitudinal relaxivity per particle at 0.5 T is the highest ever reported for Gd-based systems.     

Understanding the role of carbamate reactivity in fatty acid amide hydrolase inhibition by QM/MM mechanistic modelling

QM/MM modelling of FAAH inactivation by O-biphenyl-3-yl carbamates identifies the deprotonation of Ser241 as the key reaction step, explaining why FAAH is insensitive to the electron-donor effect of conjugated substituents; this may aid design of new inhibitors with improved selectivity and in vivo potency.     

Lipophilic toxin profile in Mytilus galloprovincialis during episodes of diarrhetic shellfish poisoning (DSP) in the N.E. Adriatic Sea in 2006

Dinophysis spp. blooms and related shellfish toxicity events of diarrhetic shellfish poisoning (DSP) have been the most reported toxicity event through the Croatian National monitoring program. With the aim to characterize the DSP toxin profile in shellfish farmed in Croatia, for the first time a complete analysis of the toxin profile of Croatian mussels has been carried out using the LC-MS/MS technique. The obtained results showed okadaic acid (OA) as the main toxin contaminating Croatian mussels at that time. The maximum concentration of OA in shellfish tissue was recorded 12 days after the Dinophysis fortii bloom, thus suggesting that rapid growth of the toxin level in the shellfish occurred in the first week after the bloom while it was slower in the second week. Furthermore, the presence of only OA at concentrations which could endanger human health suggests D. fortii as the main organism responsible for the toxic event that occurred in Lim Bay. The presence of gymnodimine and spirolides in Croatian mussel has been detected for the first time, while the presence of yessotoxin and pectenotoxin-2 is confirmed.