Synthesis of tritium-labeled PAM-43

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Templating Irreversible Covalent Macrocyclization by Using Anions

Inorganic anions were used as templates in the reaction between a diamine and an activated diacid to form macrocyclic amides. The reaction conditions were found to perform the macrocyclization sufficiently slow to observe a template effect. A number of analytical methods were used to clarify the reaction mechanisms and to show that the structure of the intermediate plays a decisive role in determining the product distribution. For the macrocyclization under kinetic control, it was shown that the amount of a template, the conformational rigidity of building blocks, and the anion affinities of reaction components and intermediates are important parameters that one should take into consideration to achieve high yields.     

Methyl methacrylate particles with amino groups on the surface: Colloid stability and sorption of biologically active substances

The present article investigates the influence of dispersion medium on the aggregate stability of cross-linked poly-(methyl methacrylate) particles on the surface layer of which aliphatic amino groups are localized. It is shown that particle size depends on the ionic strength of dispersion medium. The research determines the optimal content of cross-linked agent, ethylene glycol dimetharylate that results in the formation of cationic particles being stable in saline. Particle modification is performed by bovine serum albumin and luminophore fluorescein 5(6)-isothiocyanate. Protein sorption is observed not to influence luminescent properties of the particles. It is also determined that due to the aggregate stability of particles obtained from 5?wt% of ethylene glycol dimethacrylate in saline, the monodispersity and the absence of inversion of zeta potential in wide pH range is retained, such particles may be considered as perspective carriers of biologically active substances.     

3D Metal–Organic Frameworks Based on Co(II) and Bithiophendicarboxylate: Synthesis,Crystal Structures,Gas Adsorption,and Magnetic Properties

Three new 3D metal-organic porous frameworks based on Co(II) and 2,2′-bithiophen-5,5′-dicarboxylate (btdc²⁻) [Co₃(btdc)₃(bpy)₂]·4DMF, 1; [Co₃(btdc)₃(pz)(dmf)₂]·4DMF·1.5H₂O, 2; [Co₃(btdc)₃(dmf)₄]∙2DMF∙2H₂O, 3 (bpy = 2,2′-bipyridyl, pz = pyrazine, dmf = N,N-dimethylformamide) were synthesized and structurally characterized. All compounds share the same trinuclear carboxylate building units {Co₃(RCOO)₆}, connected either by btdc^2– ligands (1, 3) or by both btdc^2– and pz bridging ligands (2). The permanent porosity of 1 was confirmed by N₂, O₂, CO, CO₂, CH₄ adsorption measurements at various temperatures (77 K, 273 K, 298 K), resulted in BET surface area 667 m²⋅g⁻¹ and promising gas separation performance with selectivity factors up to 35.7 for CO₂/N₂, 45.4 for CO₂/O₂, 20.8 for CO₂/CO, and 4.8 for CO₂/CH₄. The molar magnetic susceptibilities χ_p(T) were measured for 1 and 2 in the temperature range 1.77–330 K at magnetic fields up to 10 kOe. The room-temperature values of the effective magnetic moments for compounds 1 and 2 are μ_eff (300 K) ≈ 4.93 μ_B. The obtained results confirm the mainly paramagnetic nature of both compounds with some antiferromagnetic interactions at low-temperatures T < 20 K in 2 between the Co(II) cations separated by short pz linkers. Similar conclusions were also derived from the field-depending magnetization data of 1 and 2.     

Spectral Photoluminescent Parameters of Barley Seeds (Hordéum vulgáre) Infected with Fusarium ssp

We needed effective and sustainable technologies for better microbiological control of crops, including Fusarium. However, photoluminescent UV–Vis methods are potential for diagnosing plant diseases with Fusarium. It has not been sufficiently studied despite the application of these methods for other biological researches. The excitation spectrum of the seeds during infection shifts to the shorter wavelength and a new maximum appears in the region λ ≈ 232 nm. The photoluminescence of infected seeds increases with excitation by radiation of wavelengths λ_e,1 = 232 nm, λ_e,2 = 362 nm and λ_e,3 = 424 nm by 1.33–3.14 times, and λ_e,3 = 424 nm—decreases by 1.1 times. Statistical moments μ₃ and μ₄, asymmetry and kurtosis change only with short-wave excitation. When analyzing the decomposition of the frequency spectrum into Gaussian curves, the most informative ratio is the ratio of right-handed and left-handed Gaussians under excitation λ_e,2 = 362 nm and λ_e,3 = 424 nm. The ratios of their maxima change during infection by 1.36–3.2 times, and for excitation by radiation λ_e,2, the frequency boundaries of Gaussians change. The results of measurements and calculations provide a basis for the development of a method and device for photoluminescence diagnostics of fusarium seeds in UV–Vis ranges.     

Frequencies of Free Oscillations of a Truncated Spherical Sector Covered with a Thin Elastic Spherical Shell

An analytic solution of the problem concerning the frequencies and shapes of free axially symmetric oscillations of a truncated spherical sector filled with an ideal compressible fluid is constructed. A spherical wall of smaller radius and the radial wall of the sector are absolutely rigid. A thin elastic shell whose edge is clamped in the radial wall is located on a spherical boundary of larger radius. The outer surface of the shell borders vacuum. The phenomenon of an anomalous decrease in the fundamental frequency as the spherical walls approach each other is discovered. An approximate formula for determination of the lowest fundamental frequencies, which are approximately proportional to the square root of the difference of the radii of spherical walls for small values of this difference, is constructed and tested numerically. Bibliography: 13 titles.     

Application of lidar in ultraviolet,visible and infrared ranges for early forest fire detection

The efficiencies of direct lidars operating at 355, 532, 1064 and 1540-nm radiation wavelengths for early forest fire detection were compared. For each wavelength, the range for reliable smoke-plume detection was estimated on the basis of a computer simulation plume using a one-dimensional “top-hat” gas dynamic model for the calculation of the backscattering and extinction-coefficient profiles within the plume. The agreement between the predicted signal-to-noise ratio (SNR) and experimental results for 532 and 1064-nm wavelength radiation is good. The decrease of the signal-to-noise ratio with distance is maximum for 355 nm and minimum for 1064 nm. At 1540 nm, the decay of SNR with distance is slightly faster, but the SNR is higher than for other wavelengths, leading to the highest detection efficiency for the same energy of the probing laser pulse. For a burning rate of 2 kg/s and a laser beam divergence of 2.5 mr, the maximum distance for reliable detection varies between 6 and 12 km, depending on the wavelength. Received: 15 May 2002 / Revised version: 13 September 2002 / Published online: 22 January 2003 RID="*" ID="*"Corresponding author. Fax: +351-21/841-8120, E-mail: rui.vilar@ist.utl.pt     

Ignition of a Fuel Mixture Using a Multipoint Pulsed Spark Discharge under Various Initial Conditions

Technical Physics - The development of efficient and reliable ignition systems for fuel mixtures is of interest for many practical applications associated with the use of combustion power plants....     

Polarization switching in perforated ferroelectric films

The polarization switching in ferroelectric films of barium strontium titanate with a planar structure of interdigitated electrodes has been studied experimentally. The local polarization distribution in an interelectrode gap of these films in an applied electric field has been investigated using nonlinear optical microscopy. The polarization switching parameters of unperforated and perforated films have been compared.