Application of positron emission tomography and 2-[18F]fluoro-2-deoxy-d-glucose for visualization and quantification of solute transport in plant tissues

The aim of the presented work was to evaluate the uptake and distribution of 2-fluoro-2-deoxy-d-glucose spiked with ¹⁸F (2-[¹⁸F]FDG) in tissues of tobacco plants (Nicotiana tabacum L.) by positron emission tomography and multivariate data analysis after the immersion of the petiole of excised leaf or root of a tobacco plant in a glucose solution. From individual experiments it was found that increasing glucose concentration (c _glu) in the applied solution resulted in significantly higher 2-[¹⁸F]FDG diffusion and translocation within the leaf parenchyma. More than a four times increase of the 2-[¹⁸F]FDG translocation into the aboveground parts of the tobacco plant in case of the root immersion in solution with 100-times higher c _glu in comparison with the control (c _glu = 0.00762 mg cm^?3) was determined. These facts were not confirmed only visually on basis of the obtained 3D images, but also by the increasing coincidence transfer factor (TF_c) values defined by the ratio of the number of analyzed coincidences in the non-immersed parts of leaf or plant to coincidences in leaf petiole or root immersed in the solution. Cluster and principal component analysis suggest that the 2-[¹⁸F]FDG uptake by the petiole of excised leaf and root system was realized by different mechanisms; also, the 3D image quality is influenced by the initial radioactivity of the applied solution.     

Ternary K2Zn5As4‐type pnictides Rb2Cd5As4 and Rb2Zn5Sb4, and the solid solution Rb2Cd5(As,Sb)4

Dirubidium pentacadmium tetraarsenide, Rb₂Cd₅As₄, dirubidium pentazinc tetraantimonide, Rb₂Zn₅Sb₄, and the solid‐solution phase dirubidium pentacadmium tetra(arsenide/antimonide), Rb₂Cd₅(As,Sb)₄ [or Rb₂Cd₅As_3.00(1)Sb_1.00(1)], have been prepared by direct reaction of the component elements at high temperature. These compounds are charge‐balanced Zintl phases and adopt the orthorhombic K₂Zn₅As₄‐type structure (Pearson symbol oC44), featuring a three‐dimensional [M₅Pn₄]²⁻ framework [M = Zn or Cd; Pn is a pnicogen or Group 15 (Group V) element] built of linked MPn₄ tetrahedra, and large channels extending along the b axis which host Rb⁺ cations. The As and Sb atoms in Rb₂Cd₅(As,Sb)₄ are randomly disordered over the two available pnicogen sites. Band‐structure calculations predict that Rb₂Cd₅As₄ is a small‐band‐gap semiconductor and Rb₂Zn₅Sb₄ is a semimetal.     

Electrochemical Nanoparticle Sizing Via Nano-Impacts: How Large a Nanoparticle Can be Measured?

The field of nanoparticle (NP) sizing encompasses a wide array of techniques, with electron microscopy and dynamic light scattering (DLS) having become the established methods for NP quantification; however, these techniques are not always applicable. A new and rapidly developing method that addresses the limitations of these techniques is the electrochemical detection of NPs in solution. The ‘nano-impacts’ technique is an excellent and qualitative in situ method for nanoparticle characterization. Two complementary studies on silver and silver bromide nanoparticles (NPs) were used to assess the large radius limit of the nano-impact method for NP sizing. Noting that by definition a NP cannot be larger than 100 nm in diameter, we have shown that the method quantitatively sizes at the largest limit, the lower limit having been previously reported as ∼6 nm.¹     

Complex Ginzburg–Landau Equation with Absorption: Existence,Uniqueness and Localization Properties

In this paper we study the time-dependent complex Ginzburg–Landau equation with a nonlinear absorbing term in ${\Omega \times(0,T),\, \Omega }$ open bounded set in ${\mathbb{R}^{n}}$ . We prove global existence and uniqueness of solutions for the initial and boundary-value problem and study the properties of localization and extinction of solutions in some special cases.     

Simulation of nanostructure evolution under helium implantation in Fe–(2.5–12.5)at% Cr alloys at a temperature of 343 K

Characterization of helium-implanted Fe–(2.5–12.5)at% Cr alloys with the flux of 7?×?10^–6?dpa/s at a temperature of 343?K has been performed by means of cluster dynamics simulations. We have suggested a model for simulating an Fe–C–Cr system under helium implantation based on a selection of the latest data from atomistic studies and available experiments. Kinetics of carbon-vacancy and helium-vacancy complexes has been studied. Only one parameter is used to guarantee the best reproduction possible of experimental positron annihilation lifetime spectroscopy data for Fe–Cr alloys on dependences of vacancy cluster size on chromium content and irradiation dose via fitting. This is an effective binding energy of self-interstitial atoms to dislocation loops decorated by chromium atoms. It has a “snaky” dependence of chromium content with a minimum of about 9%Cr.     

Removability theorems for Sobolev functions and quasiconformal maps

We establish several conditions, sufficient for a set to be (quasi)conformally removable, a property important in holomorphic dynamics. This is accomplished by proving removability theorems for Sobolev spaces inR ⁿ . The resulting conditions are close to optimal. The first author is supported by N.S.F. Grant No. DMS-9423746. The second author is supported by N.S.F. Grants No. DMS-9304580 and DMS-9706875.     

Electronographic investigation of short-range order in the surface layers of melts

The examination of the structure of the surface layers in melts by the reflection electron diffraction has detected a shift of the diffraction bars due to the surface monolayer and subsequent atomic layers. The magnitude of the shift depends on the surface layer thickness. An analysis of structure curves revealed a difference between the first monoatomic layer and the bulk.