New chemosensors based on thiomacrocycle-containing coumarin-343 fluoroionophor: X-ray structures and previous results on the effect of cation binding on the photophysical properties

Two new emissive chemosensors based on coumarin-343 have been synthesized, and their photophysical studies conducted. L1 contains an aza-thio macrocycle ring as the chelating unit, which has great affinity for soft metal ions, whereas L2 is a parent species without macrocyclic unit. Both compounds were separated by column chromatography and characterized by elemental analysis, ¹H,¹³C NMR, UV–vis and FAB mass spectroscopy. The X-ray structures of L1 and L2 and the supramolecular interactions in the solid state are discussed. Preliminary results on the metal–ion sensing effects of the ligands are presented. Titrations with Ag⁺, Pd²⁺ and Ni²⁺ have been studied by UV–vis absorption and fluorescence spectroscopy.     

A Third-Order Representation of the λμ-Calculus

Higher-order logical frameworks provide a powerful technology to reason about object languages with binders. This will be demonstrated for the case of the λμ-calculus with two different binders which can most elegantly be represented using a third-order constant. Since cases of third- and higher-order encodings are very rare in comparison with those of second order, a second-order representation is given as well and equivalence to the third-order representation is proven formally.     

用μC控制比较器的电路

在许多μC应用中。传感器的模拟输入信号经过信号调节器调节后送入μC进行处理。一般信号调节的最后一级是一个器件,它的任务是将信号电平转换成μC输入端可以接受的电平。这个器件通常就是比较器。此信号通道通常是在一定的可编程时段开启或闭合。为达到此目的,可以采     

Enterotoxin production and DNA fingerprinting in Staphylococcus aureus isolated from human and food samples. Relations between genetic types and enterotoxins

A total of 224 Staphylococcus aureus strains from human carriers (110 strains) and manually handled foods (114 strains) collected in the Principality of Asturias, Spain over 1995-1999 were analysed for the production of enterotoxins (SEs) A, B, C, and D by a reversed passive latex agglutination test and by amplification of ent genes (A, B, C, D, E, and J) using PCR. Sixty-two strains were enterotoxigenic and a good relation between detection of SEs and their ent genes was found. No strain carried entE and all strains producing SED carried entD and entJ genes. Among the enterotoxigenic strains the percentages registered were 29, 8, 35, 18, 2, 2, and 6 for SEA, SEB, SEC, SEDJ, SEAC, SEADJ and SECDJ, respectively. DNA fingerprinting of 77 strains (the SE prototypes, 62 enterotoxigenic and 10 non-enterotoxigenic [NE]) was carried out by randomly amplified polymorphic DNA using two selected primers independently. Combining results from both primers, 10 genetic types were defined, which showed a different degree of relationship (similarity coefficient: 0.9-0.36) and were clustered into three lineages. One lineage clustered five genetic types and a wide diversity of strains, mainly SEA, SEB, SEDJ, and NE. Another lineage clustered only SEC, SECDJ and NE strains. These two lineages showed a low genetic relationship and appeared as endemic in healthy humans living in the Principality of Asturias. The third lineage included only the prototype strains for SEA and SEE.     

Crystallization in a soda–lime-silicate glass after high pressure

This work explored the permanent changes a high pressure (HP) processing could cause on nucleation, Raman vibrational modes, thermal, and mechanical properties of the Na₂O • 2CaO • 3SiO₂ (N₁C₂S₃) glass. It was shown that, with higher pressure values, the number of nuclei per unit of volume, N_V, has decreased. Raman spectra showed no significant changes in the vibrational modes; however, the differential thermal analysis performed indicated that the glass transition temperatures, T_g, were higher than the pristine glass sample and that HP caused the glass to be less stable. The Vickers indentation radial cracks remained constant; however, the lateral cracks increased in size, indicating that the glass is more stressed after HP, and therefore, the relaxation time for nucleation will be higher, lowering N_V further, as observed.     

Effects of lanthanum modification on dielectric properties of Pb(Zr<Subscript>0.90</Subscript>,Ti<Subscript>0.10</Subscript>)O<Subscript>3</Subscript> ceramics: enhanced antiferroelectric stability

Lanthanum modified lead zirconate titanate ceramics with lanthanum content changing from 2 to 6 at% La and a Zr/Ti ratio of 90/10 (PLZT x/90/10) have been analyzed by using X-ray diffraction, dielectric response, differential scanning calorimetry, and ferroelectric hysteresis. An antiferroelectric state was found to be stabilized, whereas the long-range ferroelectric state was disrupted by lanthanum substitution on the lead sites. A ferroelectric state is shown to be stable over an antiferroelectric state for low lanthanum contents in a wide temperature range, where both phases coexist. With the increase of the lanthanum concentration, the long-range coherency of the ferroelectric state is suppressed, i.e., the temperature range of the ferroelectric state stability decreased, disappearing for x > 3 at% La.