New Ecotoxicologically and Biogenetically Relevant Terpenes of the tropical green seaweed Caulerpa taxifolia which is invading the Mediterranean

The tropical green seaweed Caulerpa taxifolia (VAHL ) C. AGARDH (Caulerpales) which is invading the Mediterranean is shown to contain trace amounts of two further novel terpenes, 7,7-C-didehydro-6-hydroxy-6,7-dihydrocaulerpenyne (= (4S, 6S,1E)-3-[(Z)-acetoxymethylidene]-6-hydroxy-11-methyl-7-methylidenedodeca-1,10-dien-8-yne-1,4-diyl diacetate; 3a ) and taxifolione (= 6-methylhept-5-en-3-yn-2-one; 4 ). The former is the most active of the toxins so far isolated from this seaweed, both as an in vitro inhibitor of the growth of marine bacteria and as a cytotoxic agent toward marine ciliate protists. This suggests a central ecotoxicological role for triacetate 3a as an adjuvant factor in the invasion of the Mediterranean by this seaweed. Moreover, the almost equally toxic 10,11 -epoxycaulerpenyne ( 2 ) which is scarcely available from Nature for bioassays can now be obtained by peroxy-acid epoxidation of caulerpenyne ( 1 ), along with the 6,7-epoxycaulerpenynes 6b and 6a . The latter are very labile, 6a giving triacetate 3a , suggesting epoxides to be late biogenetic intermediates in C. taxifolia.     

Workshop on coherent synchrotron radiation in storage rings

The annual UK SR User meeting at Diamond Light Source welcomed 250 members of the international synchrotron community to the site in South Oxfordshire, UK. This is the first time that Diamond has hosted this event as an operational facility.     

The use of rheology in the study of the composition effects on the fresh behaviour of hydraulic lime grouts for injection of masonry walls

The injection of grouts inside multi-leaf stone masonries is a technique widely used for structural consolidation. To ensure an adequate flow of the grout inside the masonry, it is crucial to assure good fresh grout properties, such as good rheological behaviour. The scope of this paper is to provide preliminary indications and valuable data about the effects of specific hydraulic lime grout composition on their rheological behaviour with the purpose of a successful injection process. Through the use of rotational rheometer together with the Taguchi method, it was possible to study the influence of water/binder ratio, the type and dosage of superplasticizer and the partial replacement of hydraulic lime by silica fume, upon the grout rheological properties. The study leads to the conclusion that polycarboxylate-based superplasticizers present better performance from a rheological point of view than the naphthalene-based superplasticizer and that the water/binder ratio and superplasticizer dosage are the most determinant factors in the fresh grout rheological behaviour. On the other hand, silica fume dosage turned out to be the factor with the least contribution to improve the grout rheological behaviour compared to the other two factors reported in this study. The results summarised in this paper are part of a larger study and precede the analysis of the performance of those grouts when injected into different porous media that simulate old masonries.     

Alpo4 and Alpo4-Al2O3 as New Heterogeneous Catalysts for the Solvent-Free Tetrahydropyranylation of Alcohols and Phenols

OH-protection of alcohols and phenols by heating the hydroxylated compound with 3,4-dihydro-2H-pyrane in the presence of an AlPO₄ or AlPO₄-Al₂O₃ heterogeneous acid catalyst is described. Isolated yields, not optimized, were in the range 50–99%.     

Studies on the Stereoselectivity of the Preparation of α,β-UNSATURATED ESTERS FROM α-Lithio-α-Silyl Esters

The reaction o f the lithium enolate o f a-trimethylsilyl esters with aldehydes and ketones has been shown to be an excellent entry into a, B-unsaturated esters as a result of the facile elimination o f the B-oxidosilane intermediate produced in the initial step of the reaction. (eq. 1) More recently it was shown that the bromomagnesium enolate o f trimethylsilyl acetates a1 lowed for the highly stereoselective preparation of (E) a, B-unsaturated esters via the isolable B-hydroxy-a-silyl ester, which was treated with BF₃0Et₂ to effect a trans elimination of the elements of trimethylsilanol⁵ (eq. 2) If this elimination were carried out with base, however, the stereoselectivity is much lower.     

EFFECTS OF SURFACTANTS ON THE TERMINAL VELOCITY OF PHENOL SOLUTION DROPS FALLING IN n-BUTYL ACETATE

ABSTRACT

Measurements of formation times and terminal velocities of aqueous phenol solution drops falling through a continuous phase of n-butyl acetate at 20°C are presented. The influence of two commercial surfactants, Medialan KF and Triton X-100 on the indicated parameters is also reported. A comparison is made between experimental results and predicted values from correlations available for terminal velocities and critical diameters, in the absence of surfactants.     

Electrical contacting of glucose dehydrogenase by the reconstitution of a pyrroloquinoline quinone-functionalized polyaniline film associated with an Au-electrode: an in situ electrochemical SPR study

A novel method to generate an integrated electrically contacted glucose dehydrogenase electrode by the surface reconstitution of the apo-enzyme on a pyrroloquinoline quinone (PQQ)-modified polyaniline is described. In situ electrochemical surface plasmon resonance (SPR) is used to characterize the bioelectrocatalytic functions of the system.     

Cascade reactions for constructing heterocycles containing a pyrimidino-pyrazino-pyrimidine core using 1,2,4-triazole scaffolds

The regioselective cyclocondensation of aminoethyl-1,2,4-triazoles and glyoxal provides pentacyclic heterocycles in which two 7,8-dihydro-5H-6λ²-[1,2,4]triazolo[1,5-c]pyrimidine systems are connected through CH(OH) bridges generating a central piperazine-2,5-diol ring. The structure of the new compounds was elucidated based on ¹H, ¹³C and ¹⁵N NMR spectroscopic methods. The molecular structure of the parent compound generated from aminoethyl-1,2,4-triazole was established by single crystal X-ray diffraction.     

Excited‐State Charge Transfer in Covalently Functionalized MoS2 with a Zinc Phthalocyanine Donor–Acceptor Hybrid

The functionalization of MoS₂ is of paramount importance for tailoring its properties towards optoelectronic applications and unlocking its full potential. Zinc phthalocyanine (ZnPc) carrying an 1,2‐dithiolane oxide linker was used to functionalize MoS₂ at defect sites located at the edges. The structure of ZnPc‐MoS₂ was fully assessed by complementary spectroscopic, thermal, and microscopy imaging techniques. An energy‐level diagram visualizing different photochemical events in ZnPc‐MoS₂ was established and revealed a bidirectional electron transfer leading to a charge separated state ZnPc^{. +} ‐MoS₂^.?. Markedly, evidence of the charge transfer in the hybrid material was demonstrated using fluorescence spectroelectrochemistry. Systematic studies performed by femtosecond transient absorption revealed the involvement of excitons generated in MoS₂ in promoting the charge transfer, while the transfer was also possible when ZnPc was excited, signifying their potential in light‐energy‐harvesting devices.