Electron-lattice kinetics of metals heated by ultrashort laser pulses

We propose a kinetic model of transient nonequilibrium phenomena in metals exposed to ultrashort laser pulses when heated electrons affect the lattice through direct electron-phonon interaction. This model describes the destruction of a metal under intense laser pumping. We derive the system of equations for the metal, which consists of hot electrons and a cold lattice. Hot electrons are described with the help of the Boltzmann equation and equation of thermoconductivity. We use the equations of motion for lattice displacements with the electron force included. The lattice deformation is estimated immediately after the laser pulse up to the time of electron temperature relaxation. An estimate shows that the ablation regime can be achieved.Comment: 7 pages; Revtex. to appear in JETP 88, #1 (1999

A new class of nonlinear optical materials based on push-pull quinonoid molecules

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MHz Unidirectional Rotation of Molecular Rotary Motors

A combination of cryogenic UV-vis and CD spectroscopy and transient absorption spectroscopy at ambient temperature is used to study a new class of unidirectional rotary molecular motors. Stabilization of unstable intermediates is achieved below 95 K in propane solution for the structure with the fastest rotation rate, and below this temperature measurements on the rate limiting step in the rotation cycle can be performed to obtain activation parameters. The results are compared to measurements at ambient temperature using transient absorption spectroscopy, which show that behavior of these motors is similar over the full temperature range investigated, thereby allowing a maximum rotation rate of 3 MHz at room temperature under suitable irradiation conditions

Targeted knock-down of miR21 primary transcripts using snoMEN vectors induces apoptosis in human cancer cell lines

We have previously reported an antisense technology, 'snoMEN vectors', for targeted knock-down of protein coding mRNAs using human snoRNAs manipulated to contain short regions of sequence complementarity with the mRNA target. Here we characterise the use of snoMEN vectors to target the knock-down of micro RNA primary transcripts. We document the specific knock-down of miR21 in HeLa cells using plasmid vectors expressing miR21-targeted snoMEN RNAs and show this induces apoptosis. Knock-down is dependent on the presence of complementary sequences in the snoMEN vector and the induction of apoptosis can be suppressed by over-expression of miR21. Furthermore, we have also developed lentiviral vectors for delivery of snoMEN RNAs and show this increases the efficiency of vector transduction in many human cell lines that are difficult to transfect with plasmid vectors. Transduction of lentiviral vectors expressing snoMEN targeted to pri-miR21 induces apoptosis in human lung adenocarcinoma cells, which express high levels of miR21, but not in human primary cells. We show that snoMEN-mediated suppression of miRNA expression is prevented by siRNA knock-down of Ago2, but not by knock-down of Ago1 or Upf1. snoMEN RNAs colocalise with Ago2 in cell nuclei and nucleoli and can be co-immunoprecipitated from nuclear extracts by antibodies specific for Ago2

Spallative ablation of dielectrics by X-ray laser

Short laser pulse in wide range of wavelengths, from infrared to X-ray, disturbs electron-ion equilibrium and rises pressure in a heated layer. The case where pulse duration $\tau_L$ is shorter than acoustic relaxation time $t_s$ is considered in the paper. It is shown that this short pulse may cause thermomechanical phenomena such as spallative ablation regardless to wavelength. While the physics of electron-ion relaxation on wavelength and various electron spectra of substances: there are spectra with an energy gap in semiconductors and dielectrics opposed to gapless continuous spectra in metals. The paper describes entire sequence of thermomechanical processes from expansion, nucleation, foaming, and nanostructuring to spallation with particular attention to spallation by X-ray pulse

RNA Modulators of Complex Phenotypes in Mammalian Cells

RNA-mediated gene silencing, in the form of RNA interference (RNAi) or microRNAs (miRNAs) has provided novel tools for gene discovery and validation in mammalian cells. Here, we report on the construction and application of a random small RNA expression library for use in identifying small interfering RNA (siRNA) effectors that can modify complex cellular phenotypes in mammalian cells. The library is based in a retroviral vector and uses convergent promoters to produce unique small complementary RNAs. Using this library, we identify a range of small RNA-encoding gene inserts that overcome resistance to 5-fluorouracil (5-FU)- or tumour necrosis factor alpha (TNF-α)- induced cell death in colorectal cancer cells. We demonstrate the utility of this technology platform by identifying a key RNA effector, in the form of a siRNA, which overcomes cell death induced by the chemotherapeutic 5-FU. The technology described has the potential to identify both functional RNA modulators capable of altering physiological systems and the cellular target genes altered by these modulators

ИССЛЕДОВАНИЯ БИОЛОГИЧЕСКИХ ОБЪЕКТОВ НА КЛЕТОЧНОМ И СУБКЛЕТОЧНОМ УРОВНЕ С ПОМОЩЬЮ ФЕМТОСЕКУНДНОГО ЛАЗЕРНОГО ОПТИЧЕСКОГО ПИНЦЕТА-СКАЛЬПЕЛЯ

The aim of this work was developing of elements of the precise three-dimensional positioning technology of one or several micron and submicron size biological objects. Thereto a laboratory unit of hardware-software complex of optical femtosecond laser tweezers-scalpel was developed and constructed in the Joint institute for high temperatures RAS using material resources of Russia. Experimental data concerning a maximal manipulation speed of CHO and cells, produced from mammalian spinal ganglia (using protocols for producing pure culture of Schwann cells) was received. Besides facts of interaction of laser radiation with intracellular structures that lead to unexpected behavior of cell in the zone of optical trap and change of maximal speed of cell manipulation were determined. Целью данной работы является разработка элементов технологии прецизионного трехмерного позицио- нирования одного или нескольких биологических объектов микронного и субмикронного размеров. Для этого в Объединенном институте высоких температур РАН разработан и изготовлен лабораторный обра- зец программно-аппаратного комплекса оптического фемтосекундного лазерного пинцета-скальпеля на основе приборной базы, производимой в России. Получены экспериментальные результаты о максималь- ной скорости манипулирования CHO и клетками культуры, полученной из спинального ганглия млекопи- тающего (по протоколам получения очищенных культур шванновских клеток), а также о взаимодействии излучения с внутриклеточными структурами, которое приводит к изменению предполагаемого поведе- ния клетки в области оптической ловушки и максимальной скорости манипулирования последней.