构成单片正弦波振荡器的可编程模拟电路

可编程逻辑器件为数字设计中复杂功能的实现提供了一种流行的方法。虽然制造商尚未提供能与VLSI数字电路复杂性相比拟的模拟电路,但现场可编程模拟电路正在信号调整和滤波应用中获得广泛采用。这些器件基于CMOS跨导及开关式电容放大器,可为相对复杂的设计问题提供一种便利的解决方案。Lattice     

2-Substituted penems with amino acid-related side chains: synthesis and antibacterial activity of a new series of beta-lactam antibiotics

A new series of 6-(hydroxyethyl)penems 2-substituted with amino acid-related side chains was synthesized. The nature of the amino acyl derivative proved to be crucial both from a synthetic point of view, as beta-lactam ring opening can compete with C-2 nucleophilic substitution, and for antibacterial activity. Primary amino acid amides emerged as the most suitable side chains for enhancing permeability through a Gram-negative outer membrane. In vitro activity of the new 2-[(aminoamido)methyl]penems 3a-u was influenced by the nature and position of the amide moiety, the ring size for cyclic amides, and the configuration of the amino acid. Compounds bearing amides derived from small N-methyl amino acids (such as 3a) or from cyclic amino acids (such as prolinamide 3p and 4-hydroxyprolinamide 3r) showed broad spectrum in vitro activity against both Gram-positive and Gram-negative microorganisms.     

Selectivity in capillary electrophoresis: the use of proteins

Proteins, by their very diverse nature, provide a wide variety of options for generating selectivity in capillary electrophoresis (CE). Their use in different modes of CE will be considered in this review. Proteins added in solution to the background electrolyte allow separations to be made in a similar fashion to other electrokinetic chromatography methods, e.g., micellar separations. Alternatively, different immobilization schemes can be used to secure proteins within the capillary; these have included capillary electrochromatography with the protein grafted onto a silica support, or immobilization of the protein within a gel structure. Compounds varying in size from small inorganic ions to biopolymers may be bound by proteins. There is the potential for any sort of intermolecular interaction to play a role in the binding process (e.g., hydrophobic interactions, electrostatic interactions, etc.). Very specific high-affinity binding often occurs, but also there is often weaker, non-selective binding. Frequently the interactions of chiral compounds with proteins are stereoselective. Obtaining chiral selectivity has been one of the main applications of protein selectors in CE, and this use will be emphasized here in a discussion structured by type of protein. As well as utilizing the selectivity of proteins to develop separations, the role of CE in investigating ligand-protein interactions will be emphasized.     

Heavy metal removal from winery wastewater in the case of restrictive discharge regulation.

In most cases of winery effluent, the heavy metal content, especially zinc (Zn) and copper (Cu), does not meet the limits for the discharge as imposed by the most restrictive regulations at international level (0.4 mgCu/L and 1.0 mgZn/L in the Italian regulations). An alternative for the reduction of Cu and Zn is the on-site pre-treatment of wastewater at the winery in order to meet the limits for the discharge into the public sewerage. The purpose of this study is to evaluate the effectiveness of a pre-treatment based on chemical precipitation with chelating agents (TMT: 2,4,6-trimercaptotriazine), for the reduction of Cu and Zn from raw winery wastewater. The chemical precipitation was optimised at lab-scale through jar tests in order to evaluate the optimal dosages. An average dosage equal to 0.84 mL of TMT (15%) for 1 mg of Cu removed was estimated. Furthermore, the efficiency of the on-site chemical pre-treatment was investigated at pilot scale. The results confirmed the feasibility of using TMT treatment for the reduction of Cu and Zn in order to meet the limits for discharge into the sewerage. Contextually to the removal of heavy metals, the chemical pre-treatment allowed us to obtain the reduction of particulate COD and TSS. Finally, the costs for the operation and the management of the on-site pre-treatment were evaluated.     

Modulation of Amyloid β-Induced Microglia Activation and Neuronal Cell Death by Curcumin and Analogues

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that is not restricted to the neuronal compartment but includes important interactions with immune cells, including microglia. Protein aggregates, common pathological hallmarks of AD, bind to pattern recognition receptors on microglia and trigger an inflammatory response, which contributes to disease progression and severity. In this context, curcumin is emerging as a potential drug candidate able to affect multiple key pathways implicated in AD, including neuroinflammation. Therefore, we studied the effect of curcumin and its structurally related analogues cur6 and cur16 on amyloid-β (Aβ)-induced microglia activation and neuronal cell death, as well as their effect on the modulation of Aβ aggregation. Primary cortical microglia and neurons were exposed to two different populations of Aβ42 oligomers (Aβ42Os) where the oligomeric state had been assigned by capillary electrophoresis and ultrafiltration. When stimulated with high molecular weight Aβ42Os, microglia released proinflammatory cytokines that led to early neuronal cell death. The studied compounds exerted an anti-inflammatory effect on high molecular weight Aβ42O-stimulated microglia and possibly inhibited microglia-mediated neuronal cell toxicity. Furthermore, the tested compounds demonstrated antioligomeric activity during the process of in vitro Aβ42 aggregation. These findings could be investigated further and used for the optimization of multipotent candidate molecules for AD treatment.     

Nanovoid Formation and Dynamics in He+-Implanted Nanocrystalline Silicon

Helium implantation in single crystal silicon is known to lead, after a proper thermal treatment, to the formation of voids with diameters ranging between 10 nm and 30 nm. Formation of voids is governed by the coalescence of vacancies created by implantation, initially trapping helium atoms. At high temperatures ( \({\ge}700^{\circ }\hbox {C}\) ), helium leaves the nanobubbles and outdiffuses, while the now empty voids grow in size and eventually change their shape to form tetrakaidecahedra (Wulff construction). In this communication, we report how He⁺ implantation in heavily boron-doped nanocrystalline silicon shows a completely different dynamics. Annealing at \(500^{\circ }\hbox {C}\) leads to the formation of large voids, located around grain boundaries, along with a large number of nanovoids with an average diameter of 2–4 nm and an estimated density of \(3\times 10^{17}\,\hbox {cm}^{-3}\) distributed throughout the grains. Annealing at higher temperature (up to \(1000^{\circ }\hbox {C}\) ) also induces a decrease of the void size with a change in their density, finally accounting to \(2\times 10^{18}\,\hbox {cm}^{-3}\) . The high temperature annealing also causes vacancy evaporation down to a depth of 80–100 nm from the outer surface. The possibility of obtaining a stable, uniform distribution of nanometer-sized voids is of major relevance as a novel tool for phonon and electron engineering in thermoelectric materials.