The effect of secondary electrons on radiolysis as observed by in liquid TEM: The role of window material and electrical bias

The effect of window material on electron beam induced phenomena in liquid phase electron microscopy (LPEM) is an interesting yet under-explored subject. We have studied the differences of electron beam induced gold nanoparticle (AuNP) growth subject to three encapsulation materials: Silicon Nitride (Si3N4), carbon and formvar. We find Si3N4 liquid cells (LCs) to result in significantly higher AuNP growth yield as compared to LCs employing the other two materials. In all cases, an electrical bias of the entire LC structures significantly affected particle growth. We demonstrate an inverse correlation of the AuNP growth rate with secondary electron (SE) emission from the windows. We attribute these differences at least in part to variations in SE emission dynamics, which is seen as a combination of material and bias dependent SE escape flux (SEEF) and SE return flux (SERF). Furthermore, our model predictions qualitatively match electrochemistry expectations

Matter-wave recombiners fro trapped Bose-Einstein condensates

Interferometry with trapped atomic Bose-Einstein condensates (BECs) requires the development of techniques to recombine the two paths of the interferometer and map the accumulated phase difference to a measurable atom number difference. We have implemented and compared two recombining procedures in a double-well-based BEC interferometer. The first procedure utilizes the bosonic Josephson effect and controlled tunneling of atoms through the potential barrier, similar to laser light in an optical fiber coupler. The second one relies on the interference of the reflected and transmitted parts of the BEC wave function when impinging on the potential barrier, analogous to light impinging on a half-silvered mirror. Both schemes were implemented successfully, yielding an interferometric contrast of similar to 20% and 42% respectively. Building efficient matter-wave recombiners represents an important step towards the coherent manipulation of external quantum superposition states of BECs

Elemental bioimaging and transcriptomics reveal unchanged gene expression in mouse cerebellum following a single injection of Gadolinium-based contrast agents

Gadolinium (Gd) deposition in the brain, first and foremost in the dentate nucleus in the cerebellum, following contrast enhanced MRI, rose awareness of potential adverse effects of gadolinium-based contrast agent (GBCA) administration. According to previous in vitro experiments, a conceivable side-effect of Gd deposition could be an alteration of gene expression. In the current study, we aimed to investigate the influence of GBCA administration on gene expression in the cerebellum of mice using a combination of elemental bioimaging and transcriptomics. In this prospective animal study, three groups of eight mice each were intravenously injected with either linear GBCA gadodiamide, macrocyclic GBCA gadoterate (1 mmol GBCA/kg body weight) or saline (NaCl 0.9%). Animals were euthanized four weeks after injection. Subsequently, Gd quantification via laser ablation-ICP-MS and whole genome gene expression analysis of the cerebellum were performed. Four weeks after single application of GBCAs to 24-31 days old female mice, traces of Gd were detectable in the cerebellum for both, the linear and macrocyclic group. Subsequent transcriptome analysis by RNA sequencing using principal component analysis did not reveal treatment-related clustering. Also differential expression analysis did not reveal any significantly differentially expressed genes between treatments

A single atom detector integrated on an atom chip: fabrication, characterization and application

We describe a robust and reliable fluorescence detector for single atoms that is fully integrated into an atom chip. The detector allows spectrally and spatially selective detection of atoms, reaching a single atom detection efficiency of 66%. It consists of a tapered lensed single-mode fiber for precise delivery of excitation light and a multi-mode fiber to collect the fluorescence. The fibers are mounted in lithographically defined holding structures on the atom chip. Neutral 87Rb atoms propagating freely in a magnetic guide are detected and the noise of their fluorescence emission is analyzed. The variance of the photon distribution allows to determine the number of detected photons / atom and from there the atom detection efficiency. The second order intensity correlation function of the fluorescence shows near-perfect photon anti-bunching and signs of damped Rabi-oscillations. With simple improvements one can boost the detection efficiency to > 95%.Comment: 24 pages, 11 figure

The Problem Of Social Well-Being In The Period Of Perestroika

A qualitatively new stage in the development of the scientific-educational complex in Tomsk, as well as in the whole country, came with the speech of the General Secretary of the CPSU Central Committee M.S. Gorbachev at the April plenum of the party, which marked the beginning of the period of "perestroika" in 1985. The era of perestroika was marked by a number of contradictory tendencies in the science and educational institutions of the country in general and SPhTI in particular. "Perestroika" went under the slogans of "glasnost", "new political thinking". On the one hand, the processes of democratization that began in the country served as a powerful impetus for the academic community to find new ways to solve the urgent economic, environmental and social problems. On the other hand, at that time the alarming tendencies of the obsolescence of the material and technical base for research and academic institutions, ineffectiveness or the lack of active implementation of applied developments began to make themselves felt. Particular attention is paid to identify and analyze the dynamics of the transformation of organizational forms of research development in the Tomsk scientific-educational complex; analyze the specifics of state budget financing and contractual activity as reasons for the reduction of the staff of physicists and analyze the specifics of the material and living conditions of the academic community of Tomsk in the period of Perestroika. For all who are interested in the history of science, the history of Siberia and Russia

Sub shot-noise interferometry from measurements of the one-body density

We derive the asymptotic maximum-likelihood phase estimation uncertainty for any interferometric protocol where the positions of the probe particles are measured to infer the phase, but where correlations between the particles are not accessible. First, we apply our formula to the estimation of the phase acquired in the Mach-Zehnder interferometer and recover the well-know momentum formula for the phase sensitivity. Then, we apply our results to interferometers with two spatially separated modes, which could be implemented with a Bose-Einstein condensate trapped in a double-well potential. We show that in a simple protocol which estimates the phase from an interference pattern a sub shot-noise phase uncertainty of up to $\Delta\theta\propto N^{-2/3}$ can be achieved. One important property of this estimation protocol is that its sensitivity does not depend on the value of the phase $\theta$, contrary to the sensitivity given by the momentum formula for the Mach-Zehnder transformation. Finally, we study the experimental implementation of the above protocol in detail, by numerically simulating the full statistics as well as by considering the main sources of detection noise, and argue that the shot-noise limit could be surpassed with current technology.Comment: 19 pages. 4 figure

Topological phase transitions in the non-Abelian honeycomb lattice

Ultracold Fermi gases trapped in honeycomb optical lattices provide an intriguing scenario, where relativistic quantum electrodynamics can be tested. Here, we generalize this system to non-Abelian quantum electrodynamics, where massless Dirac fermions interact with effective non-Abelian gauge fields. We show how in this setup a variety of topological phase transitions occur, which arise due to massless fermion pair production events, as well as pair annihilation events of two kinds: spontaneous and strongly-interacting induced. Moreover, such phase transitions can be controlled and characterized in optical lattice experiments.Comment: RevTex4 file, color figure

Avaliação da atividade enzimática de fungos isolados do Bioma Amazônico / Evaluation of the enzymatic activity of fungi isolated from the Amazonian Biome

A geração de energia renovável é uma das maneiras de solucionar o acúmulo deresíduos agroindustriais. A estratégia de sucesso para produzir enzimas celulolíticas inclui seleção de microrganismos e melhorias nas condições do processo fermentativo. Este trabalho descreve aanálise das atividades enzimáticas de celulases usando diferentes fontes de substratos a partir de fungos degradantes de biomassa da floresta Amazônica. As fermentações foram realizadas em agitadores a 150 rpm, 30 °C durante 240 h. Foram determinadas três atividades enzimáticas: CMCase, FPase e ?-glicosidase. O substrato comercial AVICEL® apresentou as maiores atividades enzimáticas, principalmente após 96 horas de fermentação, tanto para a cepa 511 quanto 519

A colonic organoid model challenged with the large toxins of Clostridioides difficile TcdA and TcdB exhibit deregulated tight junction proteins

BACKGROUND: Clostridioides difficile toxins TcdA and TcdB are responsible for diarrhea and colitis. Lack of functional studies in organoid models of the gut prompted us to elucidate the toxin’s effects on epithelial barrier function and the molecular mechanisms for diarrhea and inflammation. METHODS: Human adult colon organoids were cultured on membrane inserts. Tight junction (TJ) proteins and actin cytoskeleton were analyzed for expression via Western blotting and via confocal laser-scanning microscopy for subcellular localization. RESULTS: Polarized intestinal organoid monolayers were established from stem cell-containing colon organoids to apply toxins from the apical side and to perform functional measurements in the organoid model. The toxins caused a reduction in transepithelial electrical resistance in human colonic organoid monolayers with sublethal concentrations. Concomitantly, we detected increased paracellular permeability fluorescein and FITC-dextran-4000. Human colonic organoid monolayers exposed to the toxins exhibited redistribution of barrier-forming TJ proteins claudin-1, -4 and tricellulin, whereas channel-forming claudin-2 expression was increased. Perijunctional F-actin cytoskeleton organization was affected. CONCLUSIONS: Adult stem cell-derived human colonic organoid monolayers were applicable as a colon infection model for electrophysiological measurements. The TJ changes noted can explain the epithelial barrier dysfunction and diarrhea in patients, as well as increased entry of luminal antigens triggering inflammation