O kreowaniu wirtualnych tożsamości w Second Life na przykładzie perypetii bohatera „Sali samobójców” w reżyserii Jana Komasy

"Od otwarcia serwisu w 2003 roku gra sieciowa Second Life zgromadziła miliony zarejestrowanych na całym świecie użytkowników. SL to nie tylko rozrywka, lecz także wirtualna symulacja życia i interakcji międzyludzkich, która stanowi zarówno warty badań fenomen, jak i natchnienie dla artystycznych wizji współczesnego społeczeństwa zachodniego świata. Second Life początkowo nazywane było grą (najczęściej klasyfikowaną jako MMORPG1), z czasem jednak utrwaliło się w świadomości użytkowników jako darmowy, wirtualny, trójwymiarowy świat, osobne uniwersum, istniejące obok namacalnej rzeczywistości. (...)" (fragm.

Enzymatic Activities of Isolated Cytochrome bc1-like Complexes Containing Fused Cytochrome b Subunits with Asymmetrically Inactivated Segments of Electron Transfer Chains

Homodimeric structure of cytochrome bc_1, a common component of biological energy conversion systems, builds in four catalytic quinone oxidation/reduction sites and four chains of cofactors (branches) that, connected by a centrally located bridge, form a symmetric H-shaped electron transfer system. The mechanism of operation of this complex system is under constant debate. Here, we report on isolation and enzymatic examination of cytochrome bc1-like complexes containing fused cytochrome b subunits in which asymmetrically introduced mutations inactivated individual branches in various combinations. The structural asymmetry of those forms was confirmed spectroscopically. All the asymmetric forms corresponding to cytochrome bc_1 with partial or full inactivation of one monomer retain high enzymatic activity but at the same time show a decrease in the maximum turnover rate by a factor close to 2. This strongly supports the model assuming independent operation of monomers. The cross-inactivated form corresponding to cytochrome bc_1 with disabled complementary parts of each monomer retains the enzymatic activity at the level that, for the first time on isolated from membranes and purified to homogeneity preparations, demonstrates that intermonomer electron transfer through the bridge effectively sustains the enzymatic turnover. The results fully support the concept that electrons freely distribute between the four catalytic sites of a dimer and that any path connecting the catalytic sites on the opposite sides of the membrane is enzymatically competent. The possibility to examine enzymatic properties of isolated forms of asymmetric complexes constructed using the cytochrome b fusion system extends the array of tools available for investigating the engineering of dimeric cytochrome bc1 from the mechanistic and physiological perspectives

Cryo-EM structure of the spinach cytochrome b6 f complex at 3.6 Å resolution.

The cytochrome b6 f (cytb6 f ) complex has a central role in oxygenic photosynthesis, linking electron transfer between photosystems I and II and converting solar energy into a transmembrane proton gradient for ATP synthesis1-3. Electron transfer within cytb6 f occurs via the quinol (Q) cycle, which catalyses the oxidation of plastoquinol (PQH2) and the reduction of both plastocyanin (PC) and plastoquinone (PQ) at two separate sites via electron bifurcation2. In higher plants, cytb6 f also acts as a redox-sensing hub, pivotal to the regulation of light harvesting and cyclic electron transfer that protect against metabolic and environmental stresses3. Here we present a 3.6 Å resolution cryo-electron microscopy (cryo-EM) structure of the dimeric cytb6 f complex from spinach, which reveals the structural basis for operation of the Q cycle and its redox-sensing function. The complex contains up to three natively bound PQ molecules. The first, PQ1, is located in one cytb6 f monomer near the PQ oxidation site (Qp) adjacent to haem bp and chlorophyll a. Two conformations of the chlorophyll a phytyl tail were resolved, one that prevents access to the Qp site and another that permits it, supporting a gating function for the chlorophyll a involved in redox sensing. PQ2 straddles the intermonomer cavity, partially obstructing the PQ reduction site (Qn) on the PQ1 side and committing the electron transfer network to turnover at the occupied Qn site in the neighbouring monomer. A conformational switch involving the haem cn propionate promotes two-electron, two-proton reduction at the Qn site and avoids formation of the reactive intermediate semiquinone. The location of a tentatively assigned third PQ molecule is consistent with a transition between the Qp and Qn sites in opposite monomers during the Q cycle. The spinach cytb6 f structure therefore provides new insights into how the complex fulfils its catalytic and regulatory roles in photosynthesis

The reasons of damages and accelerated technical wear of reinforced concrete container of copper concentrate

W artykule przedstawiono problem uszkodzeń i nieprawidłowości żelbetowego zbiornika koncentratu rudy miedzi po ponad 20-letnim okresie eksploatacji. Opisano przeprowadzone obserwacje i pomiary konstrukcji oraz wyniki laboratoryjnych badań fizycznych, chemicznych i wytrzymałościowych pobranych rdzeni betonowych. Powyższe dane oraz statyczno-wytrzymałościowa analiza obliczeniowa z zastosowaniem metody elementów skończonych (MES) pozwoliły na określenie przyczyn występujących nieprawidłowości. Wykazano, że błędy projektowe, niska jakość robót budowlanych oraz eksploatacja w agresywnym środowisku przemysłowym przyczyniły się do powstania uszkodzeń oraz przyspieszonego zużycia obiektu.The paper presents the problem of damages and abnormalities of reinforced concrete container of copper ore concentrate after more then 20 years of operating. Observations and measurements of structures, results of physical, chemical and strength laboratory tests of taken concrete cores were described. The reasons of abnormalities was evaluated on the basis of above data and structural analysis (Finite Elements Method). Low quality of building works, design errors and operating in industrial corrosion aggressiveness caused damages and accelerated technical wear of this object

Damage to ceramic flues in multiple-flue chimneys

Artykuł dotyczy problemów eksploatacyjnych żelbetowych kominów wieloprzewodowych. Zaprezentowano w nim wpływ reologicznego niejednakowego skrócenia żelbetowych trzonów nośnych (wewnętrznego i zewnętrznego) oraz ugięć stalowych pomostów wewnętrznych na wychylenia i spękania segmentów ceramicznych przewodów spalin.This article relates to operational problems in multiple-flue reinforced concrete chimneys. It describes the effect of nonuniform rheological shortening of the load-bearing reinforced concrete shafts (internal and external) and bending of internal steel platforms on the deflection and cracking of ceramic flue segments

The influence of high- and low-heeled shoes on balance in young women

Purpose: To evaluate the influence of two different heel heights on static balance and on limits of stability during functional reach test, with both the eyes open and eyes closed, in young women (age 22–27) who did not wear heeled shoes habitually. Methods: Thirtyone young women (age 22–27) performed balance tests on a stabilometric platform without footwear and in shoes with 4 cm and 10 cm heels. The center of pressure (COP) deviations range and velocity in anteroposterior (AP) and mediolateral (ML) directions were assessed. The limits of stability were measured when the subject leaned the body in sagittal plane. Results: The ranges of COP deviations in AP and ML directions were already significantly higher in 4 cm heels in comparison to the barefoot condition. COP deviation velocity significantly raised with increasing heel height as well as when the eyes were closed. Conclusions: A more pronounced increase of COP deviation velocity than COP deviation range when measurement conditions become more difficult may indicate that young women anticipate postural corrections by stimulation of ankle proprioception when heeled shoes are worn. High-heeled shoes may lead to alterations in velocity feedback balance mechanism, which may increase the risk of musculoskeletal injuries. Observed in our study adverse effect of heeled footwear on balance may predispose women to falls and injuries. Permanent use of stiletto high heels should be avoided by women

Hyperfine interaction and some thermomagnetic properties of amorphous and partially crystallized Fe70−xMxMo5Cr4Nb6B15 (M = Co or Ni, x = 0 or 10) alloys

As revealed by Mössbauer spectroscopy, replacement of 10 at.% of iron in the amorphous Fe70Mo5Cr4Nb6B15 alloy by cobalt or nickel has no effect on the magnetic structure in the vicinity of room temperature, although the Curie point moves from 190 K towards ambient one. In the early stages of crystallization, the paramagnetic crystalline Cr12Fe36Mo10 phase appears before α-Fe or α-FeCo are formed, as is confi rmed by X-ray diffractometry and transmission electron microscopy. Creation of the crystalline Cr12Fe36Mo10 phase is accompanied by the amorphous ferromagnetic phase formation at the expense of amorphous paramagnetic one

Photosensitization of TiO2 P25 with CdS Nanoparticles for Photocatalytic Applications

A TiO2/CdS coupled system was prepared by mixing the TiO2 P25 with CdS synthesized by means of the precipitation method. It was found that the specific surface area (SSA) of both components is extremely different and equals 49.5 for TiO2 and 145.4 m2·g-1 for CdS. The comparison of particle size distribution and images obtained by means of transmission electron microscopy (TEM) showed agglomeration of nanocomposites. X-ray diffraction (XRD) patterns suggest that CdS crystallizes in a mixture of cubic and hexagonal phases. Optical reflectance spectra revealed a gradual shift of the fundamental absorption edge towards longer wavelengths with increasing CdS molar fraction, which indicates an extension of the absorption spectrum of TiO2. The photocatalytic activity in UV and UV-vis was tested with the use of methyl orange (MO). The Langmuir–Hinshelwood model described well the photodegradation process of MO. The results showed that the photocatalytic behaviour of the TiO2/CdS mixture is significantly better than that of pure nanopowders

Hyperfine interaction and some thermomagnetic properties of amorphous and partially crystallized Fe70−xMxMo5Cr4Nb6B15 (M = Co or Ni, x = 0 or 10) alloys

As revealed by Mössbauer spectroscopy, replacement of 10 at.% of iron in the amorphous Fe70Mo5Cr4Nb6B15 alloy by cobalt or nickel has no effect on the magnetic structure in the vicinity of room temperature, although the Curie point moves from 190 K towards ambient one. In the early stages of crystallization, the paramagnetic crystalline Cr12Fe36Mo10 phase appears before α-Fe or α-FeCo are formed, as is confi rmed by X-ray diffractometry and transmission electron microscopy. Creation of the crystalline Cr12Fe36Mo10 phase is accompanied by the amorphous ferromagnetic phase formation at the expense of amorphous paramagnetic one