Time-reversed sound beams of finite amplitude.

Numerical simulations based on the nonlinear parabolic wave equation are used to investigate time reversal of sound beams radiated by unfocused and focused sources. Emphasis is placed on nonlinear propagation distortion in the time-reversed beam, and specifically its effect on field reconstruction. Distortion of this kind, due to amplification during time reversal, has been observed in recent experiments [A. P. Brysev et al., Acoust. Phys. 44, 641-650 (1998)]. Effects of diffraction introduced by time-reversal mirrors with finite apertures are also considered. It is shown that even in the presence of shock formation, the ability of time reversal to retarget most of the energy on the source or focal region of the incident beam is quite robust.     

A Potentiometric and Spectroscopic Study on the Interaction Between Human Immunoglobulin G and Sodium Perfluorooctanoate in Aqueous Solution

The interaction between human immunoglobulin G (IgG) and sodium perfluorooctanate (SPFO) has been characterized by a combination of UV-vis and UV-CD spectroscopies and ion selective electrodes. The study determined that there were true specific unions between SPFO and IgG. The conformational changes at the bulk solution, induced by SPFO, were well characterized by UV-vis and UV-CD spectroscopies. Chemical and thermal unfolding were analysed and the thermodynamic parameters were determined.     

丰中子奇A核145,147Ce的集体带结构

通过对²⁵²Cf自发裂变产生的瞬发γ谱的测量,对丰中子奇A核^145,147Ce的高自旋态进行了研究,首次识别了¹⁴⁵Ce的集体带结构,扩展了¹⁴⁷Ce的集体带结构,扩展了¹⁴⁷Ce的能级,并新识别了3个边带,粒子–转子模型的计算指出,^145,147Ce的晕带可能来自于νi_13/2轨道的耦合,¹⁴⁵Ce基态起源于(νh_9/2νf_7/2)组态混合,而¹⁴⁷Ce基态则起源于νh_9/2轨道.在这两个核中未观测到明显的八极形变带,然而,在¹⁴⁷Ce中观测到的一个边带,可能显露出八极关联的迹象.     

Piper tectoniifolium Kunth: A New Natural Source of the Bioactive Neolignan (−)-Grandisin

The Piper species are a recognized botanical source of a broad structural diversity of lignans and its derivatives. For the first time, Piper tectoniifolium Kunth is presented as a promising natural source of the bioactive (−)-grandisin. Phytochemical analyses of extracts from its leaves, branches and inflorescences showed the presence of the target compound in large amounts, with leaf extracts found to contain up to 52.78% in its composition. A new HPLC-DAD-UV method was developed and validated to be selective for the identification of (−)-grandisin being sensitive, linear, precise, exact, robust and with a recovery above 90%. The absolute configuration of the molecule was determined by X-ray diffraction. Despite the identification of several enantiomers in plant extracts, the major isolated substance was characterized to be the (−)-grandisin enantiomer. In vascular reactivity tests, it was shown that the grandisin purified from botanical extracts presented an endothelium-dependent vasorelaxant effect with an IC₅₀ of 9.8 ± 1.22 μM and around 80% relaxation at 30 μM. These results suggest that P. tectoniifolium has the potential to serve as a renewable source of grandisin on a large scale and the potential to serve as template for development of new drugs for vascular diseases with emphasis on disorders related to endothelial disfunction.     

Cucurbit[7]uril Inhibits Islet Amyloid Polypeptide Aggregation by Targeting N Terminus Hot Segments and Attenuates Cytotoxicity

Two “hot segments” within an islet amyloid polypeptide are responsible for its self-assembly, which in turn is linked to the decline of β-cells in type 2 diabetes (T2D). A readily available water-soluble, macrocyclic host, cucurbit[7]uril (CB[7]), effectively inhibits islet amyloid polypeptide (IAPP) aggregation through ion–dipole and hydrophobic interactions with different residues of the monomeric peptide in its random-coil conformation. A HSQC NMR study shows that CB[7] likely modulates IAPP self-assembly by interacting with and masking major residues present in the “hot segments” at the N terminus. CB[7] also prevents the formation of toxic oligomers and inhibits seed-catalyzed fibril proliferation. Importantly, CB[7] recovers rat insulinoma cells (RIN-m) from IAPP-assembly associated cytotoxicity.