High-aperture EUV microscope using multilayer mirrors and a 3D reconstruction algorithm based on z-tomography.

The article is devoted to the development of an EUV microscope using a wavelength of 13.84 nm. Due to the use of a mirror lens with a large numerical aperture, NA = 0.27, and a short depth of focus, it has been possible to carry out z-tomography of bio-samples for the first time with this type of microscope. A 3D image was reconstructed, and a pixel resolution of 140 nm was obtained. A new simple algorithm for the 3D reconstruction of absorption images from z-tomography data has been proposed that takes into account lens aberrations and a point spread function. The algorithm reduces the inverse absorption task to the corresponding well-studied task of fluorescence microscopy, with an error of 10% for cells up to 10 µm thick.

Problems in the application of a null lens for precise measurements of aspheric mirrors.

Problems in the application of a null lens for surface shape measurements of aspherical mirrors are discussed using the example of manufacturing an aspherical concave mirror for the beyond extreme ultraviolet nanolithographer. A method for allowing measurement of the surface shape of a sample under study and the aberration of a null lens simultaneously, and for evaluating measurement accuracy, is described. Using this method, we made a mirror with an aspheric surface of the 6th order (i.e., the maximum deviation from the best-fit sphere is 6.6 µm) with the parameters of the deviations from the designed surface PV=5.3 nm and RMS=0.8 nm. An approximation of the surface shape was carried out using Zernike polynomials {Z(n)(m)(r,φ),m+n≤36}. The physical limitations of this technique are analyzed. It is shown that for aspheric measurements to an Angstrom accuracy, one needs to have a null lens with errors of less than 1 nm. For accurate measurements, it is necessary to establish compliance with the coordinates on the sample and on the interferogram.

Reflective Schmidt-Cassegrain system for large-aperture telescopes.

A reflective modification of the Schmidt-Cassegrain system was built and tested. Ultraviolet (UV) and soft x-ray applications are discussed. The system consists of a planoid mirror with an aspheric profile and prime concave and secondary convex spherical mirrors. Spherical aberration in a wide field of view and astigmatism are compensated by the aspheric profile of the planoid. The main parameters of the scheme are as follows: an entrance aperture of 180 mm, a focal ratio F/3.2, an angular resolution better than 3'' (corresponding to a pixel size of a back-side illuminated CCD), a field of view of ±1.5° (2ω=3°) and a flat image field with a diameter of 30.4 mm. Due to the absence of chromatic aberrations and wide field of view, the scheme is of considerable interest for hyperspectral instruments. In particular, the operating range of the instruments can be expanded into vacuum UV and UV regions.

Soft X-ray Microscopy in Cell Biology: Current Status, Contributions and Prospects.

The recent advances achieved in microscopy technology have led to a significant breakthrough in biological research. Super-resolution fluorescent microscopy now allows us to visualize subcellular structures down to the pin-pointing of the single molecules in them, while modern electron microscopy has opened new possibilities in the study of protein complexes in their native, intracellular environment at near-atomic resolution. Nonetheless, both fluorescent and electron microscopy have remained beset by their principal shortcomings: the reliance on labeling procedures and severe sample volume limitations, respectively. Soft X-ray microscopy is a candidate method that can compensate for the shortcomings of both technologies by making possible observation of the entirety of the cellular interior without chemical fixation and labeling with an isotropic resolution of 40-70 nm. This will thus bridge the resolution gap between light and electron microscopy (although this gap is being narrowed, it still exists) and resolve the issue of compatibility with the former, and possibly in the near future, the latter methods. This review aims to assess the current state of soft X-ray microscopy and its impact on our understanding of the subcellular organization. It also attempts to look into the future of X-ray microscopy, particularly as relates to its seamless integration into the cell biology toolkit.

High-resolution laboratory reflectometer for the study of x-ray optical elements in the soft and extreme ultraviolet wavelength ranges.

A high-resolution laboratory reflectometer designed for operation in the soft x-ray (SXR) and extreme ultraviolet (EUV) ranges is described. High spectral resolution, up to 0.028 nm, in a wide spectral range is achieved due to the Czerny-Turner monochromator. A laser plasma generated by irradiating a solid-state target with a focused laser beam (wavelength 1.06 µm, pulse energy 0.5 J, duration 4 ns, and pulse repetition rate 10 Hz) is used as a source of SXR and EUV radiation. The goniometer allows the study of curved optical elements with an aperture up to NA = 0.5 and a diameter of up to 500 mm. The methods providing high efficiency of the optical system and spectral resolution in a wide range of wavelengths are described in detail. The problem of taking into account high orders in the recorded spectra of a laser plasma is discussed. A comparison of the measurement results with the described reflectometer and the optics beamline at the BESSY-II synchrotron is given.

Family of human Na+, K+-ATPase genes. Structure of the gene for the catalytic subunit (alpha III-form) and its relationship with structural features of the protein.

The primary structure of a gene of the Na+, K+-ATPase multigenic family in the human genome has been determined. The gene corresponds to a hypothetical alpha III-form of the enzyme catalytic subunit. The gene comprises over 25,000 bp, and its protein coding region includes 23 exons and 22 introns. Possible correlation between structural features of the protein and location of introns in the gene are discussed.

Family of human Na+,K+-ATPase genes. Structure of the putative regulatory region of the alpha+-gene.

The primary structure of the putative regulatory region of a gene of the Na+,K+-ATPase multigene family in the human genome has been determined. This region includes the first exon with all of the untranslatable sequence of mRNA and a dozen nucleotides, coding for the first four amino acids of the hypothetic precursor of the alpha+-subunit. The entire region comprises over 1400 bp. The possible role of specific nucleotide blocks within this region in comparison with other genes is discussed.

The family of human Na+,K+-ATPase genes. No less than five genes and/or pseudogenes related to the alpha-subunit.

Five different nucleotide sequences have been found in the human genome homologous to the gene of the alpha-subunit of Na+,K+-ATPase. A comparative analysis of the primary structure of these genes in the region 749-1328 (in coordinates of cDNA from the pig alpha-subunit) is presented.

[Bank of sequences specific for human genome. I. The structure of one of the repeats in the Alu family]. / Poluchenie banka posledovatel'nostei, spetsifichnykh dlia genoma cheloveka. I. Struktura odnogo iz povtorov Alu-semeistva.

A bank enriched in sequences specific for the human genome was obtained. In course of the analysis, a clone containing an Alu family repeat was identified and its primary structure determined.

[Primary structure of the alpha-subunit of Na+,K+-ATPase from the swine kidney. III. Complete nucleotide sequence corresponding to the structural region of the gene]. / Pervichnaia struktura alpha-sub''edinitsy Na+,K+-ATP-azy pochek svin'i. III. Opredelenie polnoi nukleotidnoi posledovatel'nosti, sootvetstvuiushchei strukturnoi chasti gena.

The nucleotide sequence of the cDNA, containing coding region of the alpha-subunit of the pig kidney Na+, K+-ATPase, was determined. The region contains 3063 b.p. coding for 1021 amino acid residues. In the course of processing, five amino acid residues are cleaved to yield the mature Na+, K+-ATPase alpha-subunit containing 1016 amino acid residues.

[The prognosis and prevention of syncopal states and sudden death in patients with a complete atrioventricular block in disorders of permanent cardiac electrostimulation]. / Prognozirovanie i profilaktika sinkopal'nykh sostoianii i vnezapnoi smerti u bol'nykh s polnoi atrioventrikuliarnoi blokadoi pri narusheniiakh postoiannoi élektrikardiostimuliatsii.

A total of 105 patients with implantable pacemakers were examined. Whether the pacemaker disconnection test can be used to predict syncopes in failure of permanent cardiac pacing was studied. The spontaneous ventricular activity was evaluated in 62 patients with acquired complete atrioventricular block (CAVB) and in 43 patients with artificial CAVB. The patients with varying pacemaker dependence were grouped. It was ascertained that 7% of patients with artificial CAVB and 19% of those with acquired CAVB were dependent on pacemakers. In possible failure of stimulation or in reimplantation of a pacemaker on its disconnection, 93% of patients with artificial CAVB and 81% with acquired CAVB could develop their own cardiac rhythm. Lowering the frequency of pacing enabled the duration of asystole to be decreased. The usage of isadrin was demonstrated to enhance spontaneous ventricular activity.

[The use of multiprogrammable cardiac electrostimulators for treating brady- and tachyarrhythmias in patients with ischemic heart disease]. / Primenenie mul'tiprogrammiruemykh élektrokardiostimuliatorov dlia lecheniia braditakhiaritmii u bol'nykh ishemicheskoi bolezn'iu serdtsa.

Examined were 54 patients with different disorders of the cardiac rhythm with an implanted programmed electrocardiostimulator (ECS-200). The authors worked out methods and criteria of choosing individual regimes of electrostimulation, evaluated their effect on the severity of stenocardia and grade of circulatory insufficiency. The threshold frequency of stenocardia is of major significance in determining the optimal frequency of electrostimulation for patients with stable atrioventricular block. For patients with sinus node weakness and transitory atrioventricular blocks the criteria of choice of electrostimulation parameters is maximum maintenance of the sinus node rhythm with a frequency of not less 50/min.

A comparative analysis of the putative regulatory regions in human genes for the alpha-subunit family of Na(+)-K+ ATPase.

The sequences of a 1.5 kb long stretch of the 5' flanking region of the gene for the alpha 3 isoform of the catalytic subunit of human Na(+)-K+ ATPase (located on chromosome 19) and of more than a 2 kb stretch of the 5' flanking region of the gene for the alpha 2 isoform (located on chromosome 1) have been determined. Transcription start sites for the gene for the alpha 3 isoform have been mapped at positions -152 and -155 relative to the translation initiation codon by primer extension analysis and S1-nuclease mapping of mRNA from human brain. The 5' flanking region of the gene for isoform alpha 3 contains a CCAAT box on the noncoding chain and six putative Sp1 binding sites. Absence of a conventional TATA box and a high GC content are other features of the region. The 5' upstream region of the gene for the alpha 2 isoform contains potential TATA and CCAAT boxes and one potential Sp1 binding site. Upstream of the putative TATA box there is an octanucleotide repeat, GGGGGAGA, which is also found in several eukaryotic genes in analogous positions. Pairwise comparison of the putative 5' regulatory regions of the genes coding for the different isoforms of the Na(+)-K(+)-ATPase catalytic subunit shows the existence of conserved elements, as well as of oligonucleotide blocks with very different structures. It is suggested that the differences in the primary structure of the 5' upstream regions may provide the basis for tissue-specific expression of the Na(+)-K(+)-ATPase isoforms.