Aggregation Mode,Host-Guest Chemistry in Water,and Extraction Capability of an Uncharged,Water-Soluble,Liquid Pillar[5]arene Derivative

An uncharged, water-soluble per-ethylene-glycol pillar[5]arene derivative ( 1 ) was synthesized and its aggregation mode, host-guest chemistry in water and extraction ability was explored. Compound 1 is a liquid at room temperature; in water, limited self-aggregation occurred at high concentrations as deduced from diffusion NMR and dynamic light scattering. Compound 1 forms pseudo-rotaxane-like 1 : 1 host-guest complexes with 1,ω-di-substituted alkanes with association constants on the order of 10³–10⁴ m ⁻¹. Interestingly, NMR experiments showed that the guest location relative to the host ring system differs among the different complexes. In proof-of-concept experiments, compound 1 was shown to extract structurally related organic compounds from benzene into water with significant selectivity. Compound 1 , which is a liquid at room temperature and has only limited interactions with its side arms, can, in principle, be regarded as a complement to or as a kind of type I porous liquid.     

Thermal and base-catalyzed rearrangements of diacyl carbinols

Diacyl carbinols undergo facile thermal and base-catalyzed rearrangements to -ketol esters.     

High-sensitivity measurements of the Kerr constant in gases using a Fabry–Pérot-based ellipsometer

The electromagnetic and geometric characteristics of electron beams generated by molybdenum cathodes illuminated by an excimer laser are reported. To determine the electromagnetic characteristics, a fast Rogowski coil was utilized, while the geometric characteristics were performed by a suitable slit–slit meter system. During the experiment the laser spot on the cathode was fixed to 4 mm². The maximum output current (370 mA) was reached with 0.5 mJ laser energy and 50 kV accelerating voltage. In these conditions the electron beam normalized emittance was 6 (π mm mrad) calculated at 80% level current density. The laser used in this experiment was a singular excimer laser (KrCl) operating in the NUV range. Received: 22 March 2000 / Revised version: 11 July 2000 / Published online: 5 October 2000     

Thickness of hydroxyapatite nanocrystal controls mechanical properties of the collagen-hydroxyapatite interface

Collagen-hydroxyapatite interfaces compose an important building block of bone structures. While it is known that the nanoscale structure of this elementary building block can affect the mechanical properties of bone, a systematic understanding of the effect of the geometry on the mechanical properties of this interface between protein and mineral is lacking. Here we study the effect of geometry, different crystal surfaces, and hydration on the mechanical properties of collagen-hydroxyapatite interfaces from an atomistic perspective, and discuss underlying deformation mechanisms. We find that the presence of hydroxyapatite significantly enhances the tensile modulus and strength compared with a tropocollagen molecule alone. The stiffening effect is strongly dependent on the thickness of the mineral crystal until a plateau is reached at 2 nm crystal thickness. We observe no significant differences due to the mineral surface (Ca surface vs OH surface) or due to the presence of water. Our result shows that the hydroxyapatite crystal with its thickness confined to the nanometer size efficiently increases the tensile modulus and strength of the collagen-hydroxyapatite composite, agreeing well with experimental observations that consistently show the existence of extremely thin mineral flakes in various types of bones. We also show that the collagen-hydroxyapatite interface can be modeled with an elastic network model which, based on the results of atomistic simulations, provides a good estimate of the surface energy and other mechanical features.     

Information elicitation and sequential mechanisms

We study an incomplete information mechanism design problem with three peculiarities. First, access to agents’ private information is costly and unobservable. Second, the mechanism may communicate sequentially with the agents. Third, the mechanism designer and all the agents share a common interest. As an example one can think of N geologists that study the potential oil reserves in some tract. The geologists agree on the right course of action, given their N studies. However, carrying out the study may be costly for a geologist and so he may opt to fabricate a study. The oil company that employs these geologists need not contract them simultaneously and may, furthermore, choose to provide some of the results of early studies to geologists employed later on. Finally, the geologists and the oil company would like the joint study to forecast the quantity of oil reserves as accurate as possible. It turns out that, in such settings, what may not be implementable without communication becomes implementable with communication. Clearly, the possibility for sequential communication introduces a lot of complexity to the design problem. However, we provide a result in the spirit of the revelation principle and argue that whenever implementation is possible with communication it is also possible with a simple communication mechanism. Formally, we extend the model and results in Smorodinsky and Tennenholtz (Games Econ Behav 55(2):385–406, 2006) who consider the similar problem but restrict attention to symmetric social choice functions and IID distributions over the private information.     

Biological control of fungal pathogens

Biological control of soil-borne plant pathogens is a potential alternative to the use of chemical pesticides, which have already been proved to be harmful to the environment. Several strains of the fungusTrichoderma have been isolated and found to be effective biocontrol agents of various soil-borne plant pathogenic fungi under greenhouse and field conditions. Different application approaches have been used including integration ofTrichoderma with reduced doses of chemical agents. Biochemical and molecular biology studies carried out to explore the mechanisms involved in biological control revealed thatTrichoderma is a rather specific mycoparasite. Lectins were found to be involved in the recognition betweenTrichoderma and its host fungi, whereas chitinase is involved in the degradation of the host cell wall. Genetic engineering techniques were employed in order to increase the effectiveness, stability, and biocontrol capacity ofTrichoderma spp. as well as other biocontrol agents, such asPseudomonass spp. andRhizobium.     

High-sensitivity CW Fabry–Pérot enhanced spectroscopy of CO2 and C2H2 using a 1064-nm Nd:YAG laser

2 (20⁰3←00⁰0) R(6), C₂H₂ (2100⁰1¹←0000⁰0⁰) R(12), and C₂H₂ (1200⁰3¹←0000⁰0⁰) P(6) near 1064 nm using CW cavity ring-down spectroscopy and CW cavity transmission. An effective interaction length of more than 30 km was achieved (cavity finesse ≈86000) and the sensitivity was ≈10^-8 cm^-1. Higher sensitivity of 3.3×10^-11 cm^-1/ was obtained by cavity-enhanced wavelength modulation spectroscopy. The absorption coefficients, pressure broadening coefficients, lineshapes, line strengths, and absolute wavelengths of those lines were determined, some of them for the first time. The measurements were carried out over a wide range of pressures from the strongly inhomogeneous to the strongly homogeneous region. Received: 25 May 1998/Revised version: 28 July 1998     

Spectroscopy and photophysics of self-organized zinc porphyrin nanolayers. 3. Fluorescence detected magnetic resonance of triplet States

Fluorescence detected magnetic resonance (FDMR) has been applied to approximately 25-nm-thick porphyrin films, containing ordered domains of zinc tetra-(p-octylphenyl)-porphyrin (ZnTOPP) spin-coated onto quartz slides. Illuminating the films at 1.4 K with 457.9-nm light from a continuous wave Ar(+) laser produces at least two different, Jahn-Teller-distorted, ZnTOPP triplet species, labeled i and ii. Microwave-induced magnetic resonance of i and ii in the absence or presence of an externally applied magnetic field affects the fluorescence intensity of ZnTOPP, thus allowing FDMR. For triplet species i, formed in films spin-coated from toluene solution, the zero-field splitting (ZFS) parameters were determined as |D| = (316.9 +/- 0.1) x 10(-4) cm(-1) and |E| = (32.0 +/- 0.5) x 10(-4) cm(-1). By exposure of the spin-coated films to chloroform vapor at room temperature, triplet i is converted into species ii, with |D| = (295 +/- 3) x 10(-4) cm(-1) and |E| = (121 +/- 3) x 10(-4) cm(-1). For the excited triplet state of ZnTOPP in a toluene glass, ZFS parameters with values of |D| = (295 +/- 1) x 10(-4) cm(-1) and |E| = (91 +/- 1) x 10(-4) cm(-1) are found. From a combined study of the FDMR- and microwave-induced fluorescence spectra, i and ii are identified as unligated and ligated ZnTOPP triplet species, respectively. From the asymmetrically shaped zero-field FDMR signals of i, we conclude that the local crystal field perturbations of the stacked molecules are anisotropic. The FDMR results of the ZnTOPP films are compared with those for a film of zinc tetraphenylporphyrin (ZnTPP), which lacks the octyl substituents, and therefore is nonordered. Upon illumination, the ZnTPP films contain only a single, ligated, triplet species with ZFS parameters very similar to those of ligated ZnTOPP. At approximately 5 K, the lifetime of triplet i is considerably shortened compared to that of ZnTOPP in a glass at the same temperature.