Approaches for ultrafast imaging of transient materials processes in the transmission electron microscope

The growing field of ultrafast materials science, aimed at exploring short-lived transient processes in materials on the microsecond to femtosecond timescales, has spawned the development of time-resolved, in situ techniques in electron microscopy capable of capturing these events. This article gives a brief overview of two principal approaches that have emerged in the past decade: the stroboscopic ultrafast electron microscope and the nanosecond-time-resolved single-shot instrument. The high time resolution is garnered through the use of advanced pulsed laser systems and a pump-probe experimental platforms using laser-driven photoemission processes to generate time-correlated electron probe pulses synchronized with laser-driven events in the specimen. Each technique has its advantages and limitations and thus is complementary in terms of the materials systems and processes that they can investigate. The stroboscopic approach can achieve atomic resolution and sub-picosecond time resolution for capturing transient events, though it is limited to highly repeatable (>10(6) cycles) materials processes, e.g., optically driven electronic phase transitions that must reset to the material's ground state within the repetition rate of the femtosecond laser. The single-shot approach can explore irreversible events in materials, but the spatial resolution is limited by electron source brightness and electron-electron interactions at nanosecond temporal resolutions and higher. The first part of the article will explain basic operating principles of the stroboscopic approach and briefly review recent applications of this technique. As the authors have pursued the development of the single-shot approach, the latter part of the review discusses its instrumentation design in detail and presents examples of materials science studies and the near-term instrumentation developments of this technique.     

Efficient One‐Pot Friedel–Crafts Acylation of Benzene and its Derivatives with Unprotected Aminocarboxylic Acids in Polyphosphoric Acid

A number of aminobenzophenones have been synthesized by acylation of benzene and its derivatives with different 2‐,3‐,4‐aminobenzoic and 4‐aminophenylacetic acids in polyphosphoric acid via Friedel–Crafts reaction as compounds with expected antitumor activity.     

Anthracene-Derived Bis-Aminophosphonates: Crystal Structure,In Vitro Antitumor Activity,and Genotoxicity In Vivo

Abstract

The X-ray crystal structures of the anthracene-derived bis-aminophosphonates 4.4′-bis[N-methyl(diethoxyphosphonyl)-1-(9-anthryl)]diaminodiphenylmethane (1) and 1,3-bis

[N-methyl(diethoxyphosphonyl)-1-(9-anthryl)]diaminobenzene (3) are reported. The X-ray analyses demonstrated that both compounds crystallize in a centrosymmetric manner containing a meso-form (1) and a pair of enantiomers (3).

The cytotoxic potential, genotoxicity, and antiproliferative activity of bis-aminophosphonates 1 and bis[N-methyl(diethoxyphosphonyl)-1-(9-anthryl)]benzidine (2), as well as their subcellular distribution in a tumor cell culture system, are also discussed. Compounds 1 and 2 showed optimal antiproliferative activity to human tumor cells from colon carcinoma line HT-29. In vitro and in vivo safety testing revealed that the compounds exert lower toxicity to normal cells as compared with well-known anticancer and cytotoxic agents.

Supplemental materials are available for this article. Go to the publisher's online edition ofPhosphorus, Sulfur, and Silicon and the Related Elementsto view the free supplemental file.     

Electrotransport properties of ions in aqueous solutions of H<Subscript>2</Subscript>SeO<Subscript>4</Subscript> and Na<Subscript>2</Subscript>SeO<Subscript>4</Subscript>

Coefficients of self-diffusion, absolute speeds of movement of ions and the activation energy of electrical conductivity are found from the conductance measurements of aqueous solutions of selenic acid and sodium selenate at different concentrations in a temperature range of 288–318 K. Both the Stokes and effective radii of ions and their hydrate numbers at 298 K are calculated. The obtained results are interpreted in the frames of Samoilov theory on positive and negative hydration of ions.     

Generalized connection forms in the unification of gauge interactions

Within a differential-geometrical framework, the notion of a generalized connection form on a principal fibre bundle is applied to a generalized model for the unification of two (or more) gauge interactions. An example with gauge groups SU(2) and U(1) is considered.     

Interpolation of Limited and Weakly Compact Operators on Families of Banach Spaces

In this paper, we study how the limited and weakly compact properties of operators are preserved by interpolation of the real method for infinite families of Banach spaces introduced by Carro in Studia Math. 109 (1994). We apply these results to the case of Sparr, Fernández and Cobos–Peetre methods of interpolation for finite families.     

Some new inequalities involving the Hardy operator

In this paper we derive some new inequalities involving the Hardy operator, using some estimates of the Jensen functional, continuous form generalization of the Bellman inequality and a Banach space variant of it. Some results are generalized to the case of Banach lattices on $(0,b],0<b\le \infty$.     

Growth and characterization of large La1‐xPbxMnO3+δ (x=0.32–0.35) crystals

Large crystals of La_0.63Pb_0.37Mn O_3+δ with small La(Pb)‐ deficiency of about 0.005‐0.01 at.% were grown by high temperature solution growth method. The structure of the grown crystals was determined as rhombohedral with R‐3 space group by single‐crystal X‐ray diffractometry. The surface morphology of the crystals and the exact chemical composition was examined by scanning electron microscopy and energy dispersive X‐ray analysis methods, respectively. The IR‐transmission spectrum reveals the presence of Mn³⁺O₆‐ and Mn⁴⁺O₆‐ octahedra in the lattice of La_0.63Pb_0.37Mn O_3+δ crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Surface photovoltage spectroscopy study of CdS thin films

The method of surface photovoltage spectroscopy has been applied to the study of the surface properties of thin CdS films deposited by vacuum evaporation. The energy spectrum of the surface states is obtained and their kinetic parameters are calculated. A comparison is made of the results obtained in air and in vacuum for non-recrystallized and recrystallized samples. The results for thin films are compared with the data on monocrystal CdS in the literature. It is assumed that the surface states established in the films are of a donor-like type.