Room temperature plasmon laser by total internal reflection

Plasmon lasers create and sustain intense and coherent optical fields below light's diffraction limit with the unique ability to drastically enhance light-matter interactions bringing fundamentally new capabilities to bio-sensing, data storage, photolithography and optical communications. However, these important applications require room temperature operation, which remains a major hurdle. Here, we report a room temperature semiconductor plasmon laser with both strong cavity feedback and optical confinement to 1/20th of the wavelength. The strong feedback arises from total internal reflection of surface plasmons, while the confinement enhances the spontaneous emission rate by up to 20 times.Comment: 8 Page, 2 Figure

Search for Bs0B^{0}_{s} oscillations using inclusive lepton events

A search for Bs oscillations is performed using a sample of semileptonic b-hadron decays collected by the ALEPH experiment during 1991-1995. Compared to previous inclusive lepton analyses, the prop er time resolution and b-flavour mistag rate are significantly improved. Additional sensitivity to Bs mixing is obtained by identifying subsamples of events having a Bs purity which is higher than the average for the whole data sample. Unbinned maximum likelihood amplitude fits are performed to derive a lower limit of Dms>9.5 ps-1 at 95% CL. Combining with the ALEPH Ds based analyses yields Dms>9.6 ps-1 at 95% CL.A search for B0s oscillations is performed using a sample of semileptonic b-hadron decays collected by the ALEPH experiment during 1991-1995. Compared to previous inclusive lepton analyses, the proper time resolution and b-flavour mistag rate are significantly improved. Additional sensitivity to B0s mixing is obtained by identifying subsamples of events having a B0s purity which is higher than the average for the whole data sample. Unbinned maximum likelihood amplitude fits are performed to derive a lower limit of Deltam_s>9.5ps^-1 at 95% CL. Combining with the ALEPH D-s based analyses yields Deltam_s>9.6ps^-1 at 95% CL

Evolution and geodynamic significance of the Upper Cretaceous Gosau basin in the Apuseni Mountains (Romania)

The present-day shape of the Alpine chain is a consequence of Mesozoic to Tertiary plate movements within the Tethys region. As part of this orogen, the Apuseni Mts. were formed during the Upper Cretaceous convergence between the Tisia and Dacia microplates. The subduction of the Transylvanian ocean between the Tisia and Dacia microcontinents can be traced into the East-Alpine region, where the South Penninic ocean was subducted at the same time. In both orogens (the Apuseni Mts. and the Eastern Alps) an Upper Cretaceous basin evolved, which commonly is known as Gosau basin. This work focuses on the sedimentologic and geodynamic evolution of the Gosau basins of the Apuseni Mts. It combines various methods, which enable a reconstruction of the geological evolution in the sedimentation area and allow direct comparison to the well studied Austroalpine Gosau sediments in the Eastern Alps. Sedimentologic records yield facies differences within the Apuseni Mts: the southern and eastern parts of the Apuseni Mts. record both, deep marine and shallow marine sediments, which, according to the Austroalpine definition, are grouped into the Lower Gosau Subgroup (shallow marine facies) and Upper Gosau Subgroup (deep marine facies). In the northern Apuseni Mts. only shallow marine sediments were deposited. Paleontological data constrain the stratigraphic range: sedimentation started in Upper Turonian time and ended in the uppermost Cretaceous. The sedimentation onset of the Lower Gosau Subgroup occurred diachronously with a lateral shift from southwest to northeast. The sedimentation onset of the Upper Gosau Subgroup does not show a diachronous pattern. Heavy mineral assemblages prove the erosion of areas lying on both sides of the elongated basin. Basin modeling based on vitrinite reflectance confirms maximum sediment thickness of approximately 3000 m, similar to what is know from the Eastern Alps. Fission-track age populations of detrital zircons from the Gosau sediments reflect three Mesozoic tectonothermal events in the hinterland: at 90 – 110 Ma, 130 – 150 Ma and 170 - 200 Ma. Two additional age populations record Paleozoic ages (250 – 300 Ma and ~ 400 Ma). The convergence of the Tisia and Dacia microplates resulted in a “soft” collision, which is indicated by non-resetting of detrital apatite fission-track ages from the Gosau sediments. However, there was increased exhumation in the crystalline hinterland, which is shown by thermal modeling of apatite fission-track lengths. The achieved data lead to a reinterpretation of the plate tectonic evolution of the studied area and the proposal of a geodynamic model for the generation of such type of basins. Initial basin subsidence is a consequence of high-strain forced subduction with high frictional shear at the contact between the overriding and subducting plate, accompanied by flexure of the overriding plate and low basin subsidence rates during the deposition of the Lower Gosau Subgroup. Change to retreating subduction due to dehydrating and thus increasing slab density, accompanied by downward pull from the downbending plate, is responsible for the rapid basin subsidence and sedimentation of the Upper Gosau Subgroup. The installation of a cornerflow after the beginning of retreating subduction is inferred to be responsible for the Late Cretaceous banatite magmatism. Retreating subduction resulted in a “soft” continental collision, which occurred around the Cretaceous/Tertiary boundary. The similarities to the Gosau occurrences of the Eastern Alps lead to direct correlation with the Alpine paleogeographic evolution and the assumption that a continuous ocean basin (South Penninic and Transylvanian ocean basin) has been consumed during Upper Cretaceous times. Depositioning of Upper Cretaceous flysch sediments (e.g. Bozes flysch, South Apuseni Mts.) occurred into a second basin, which is interpreted as a deep sea subduction-trench basin. The difference to the Gosau basin is supported by basin modeling based on vitrinite reflectance.Die mesozoischen bis tertiären plattentektonischen Bewegungen im Tethysraum verursachten die gegenwärtige Form der alpinen Gebirgskette. Das Apusenigebirge ist Teil dieses Orogens. Es entstand als Folge der Konvergenz der beiden Mikroplatten Tisia und Dacia. Die hierfür verantwortliche Subduktion des Transilvanischen Ozeans kann bis in den ostalpinen Raum verfolgt werden. Hier wurde zur gleichen Zeit der Südpenninische Ozean subduziert. In beiden Orogenen (Apusenigebirge und Ostalpen) bildet sich während der Oberkreide ein Becken, das als Gosaubecken bezeichnet wird. Die vorliegende Arbeit richtet ihr Augenmerk auf die Gosauablagerungen des Apusenigebirges. Zur Untersuchung der Gosauabfolgen wurden unterschiedliche Methoden angewandt, mit deren Hilfe die geologische Entwicklung im Sedimentationsraum rekonstruiert werden kann und ein direkter Vergleich zu den alpinen Gosausedimenten ermöglicht wird. Anhand von detaillierten sedimentologischen Untersuchungen wurden sedimentfazielle Unterschiede festgestellt: im südlichen und östlichen Apusenigebirge lagerten sich flachmarine und tiefmarine Sedimente ab, die, vergleichbar zu den Ostalpen, in Untere Gosau (flachmarine Fazies) und Obere Gosau (tiefmarine Fazies) eingeteilt werden. Im Nordapuseni wurden nur Flachwassersedimente abgelagert. Der stratigraphische Umfang der Gosauablagerungen ist durch paläontologische Untersuchungen für die Zeit vom obersten Turon bis ins oberste Maastricht eingegrenzt worden. Die Sedimentation der Unteren Gosau setzte diachron ein, wobei ein Wandern des Sedimentationsbeginns von Südwesten nach Nordosten festgestellt wurde. Der Wechsel zur Oberen Gosau findet ohne diachrones Wandern statt. Schwermineralanalysen zeigen Erosion und Sedimenttransport von beiden Seiten des länglich geformten Beckens. Die maximale Sedimentmächitgkeit der Gosausedimente wurde anhand von Beckenmodellierungen mit Hilfe von Vitrinitreflexion auf ca. 3000 m berechnet und weist ähnliche Werte wie die der ostalpinen Gosauabfolgen auf. Aus den Spaltspurenaltern detritischer Zirkone wurden fünf Alterspopulationen separiert: drei mesozoische (90 – 110 Ma, 130 – 150 Ma und 170 – 200 Ma) und zwei paläozische (250 – 300 Ma und ~ 400 Ma), die thermische Überprägungen im Hinterland anzeigen. Die Konvergenz zwischen den Mikroplatten Tisia und Dacia führt zu einer „weichen“ Kollision, da die Spaltspurenalter detritischer Apatite aus den Gosauabfolgen keine postsedimentäre thermische Überprägung aufweisen. Thermische Modellierungen anhand von Apatit-Spaltspurenlängen des kristallinen Autochthons zeigen, daß die Kollision der beiden Krustenblöcke mit einer Hebung des Hinterlandes verbunden ist. Aufgrund dieser Daten wird die plattentektonische Entwicklung des Untersuchungsgebietes neu interpretiert und ein geodynamisches Modell für die Entstehung des Gosaubecken erstellt. Als Folge der erzwungenen Subduktion und der damit verbundenen hohen Spannung an der Kontaktfläche zwischen der Oberplatte und der subduzierten Kruste wurde in der Oberplatte eine Flexur erzeugt. In dem hierdurch gebildeten flachmarinen Becken wurden die Sedimente der Unteren Gosau abgelagert. Aufgrund der Dehydrierung und Dichtezunahme der subduzierten ozeanischen Kruste wurde ein Wechsel im Ablauf der Subduktionsprozesse eingeleitet. Die nun folgende rückschreitende Subduktion war Ursache für die rasche Beckensubsidenz im Sedimentationsraum. Eine im Mantelkeil einsetzende Konvektion mit Winkelfluß war für den kalk-alkalinen Banatit-Magmatismus verantwortlich. Als Folge der rückschreitenden Subduktion kam es zu einer „weichen“ Kollision an der Kreide/Tertiär Grenze. Die Ähnlichkeiten zu den Gosau Abfolgen der Ostalpen ermöglichen eine Korrelation der beiden Sedimentationsräume und führen zur Annahme, daß ein von den Ostalpen bis zum Apuseni Gebirge durchgehender Ozean (Südpenninischer und Transilvanischer Ozean) während der Oberkreide subduziert wurde. Zeitgleich zur Gosausedimentation wurden im Südapuseni bis in die oberste Kreide Turbidite (Bozes Flysch) in eine Tiefseerinne abgelagert. Beckenmodellierungen mit Hilfe von Vitrinitreflexion zeigen deutliche Unterschiede dieser beiden Sedimentationsräume und legen somit den Schluß nahe, daß während der Oberkreide zwei unterschiedliche Becken im Apusenigebirge existierten

Molecular architecture and electron transfer pathway of the Stn family transhydrogenase

Abstract The challenge of endergonic reduction of NADP+ using NADH is overcome by ferredoxin-dependent transhydrogenases that employ electron bifurcation for electron carrier adjustments in the ancient Wood-Ljungdahl pathway. Recently, an electron-bifurcating transhydrogenase with subunit compositions distinct from the well-characterized Nfn-type transhydrogenase was described: the Stn complex. Here, we present the single-particle cryo-EM structure of the Stn family transhydrogenase from the acetogenic bacterium Sporomusa ovata and functionally dissect its electron transfer pathway. Stn forms a tetramer consisting of functional heterotrimeric StnABC complexes. Our findings demonstrate that the StnAB subunits assume the structural and functional role of a bifurcating module, homologous to the HydBC core of the electron-bifurcating HydABC complex. Moreover, StnC contains a NuoG-like domain and a GltD-like NADPH binding domain that resembles the NfnB subunit of the NfnAB complex. However, in contrast to NfnB, StnC lost the ability to bifurcate electrons. Structural comparison allows us to describe how the same fold on one hand evolved bifurcation activity on its own while on the other hand combined with an associated bifurcating module, exemplifying modular evolution in anaerobic metabolism to produce activities critical for survival at the thermodynamic limit of life

New U/Pb and Pb/Pb zircon ages from the Biharia terrane rocks, Apuseni Mountains, Romania

The Biharia sequence from the Apuseni Mountains is a component of the Biharia Paleozoic terrane. The Biharia terrane probably evolved as an island arc between the Cadomian Someş and Baia de Arieş terranes. A gneissic metagranodiorite associated with metabasites from the Valea Ierţii creek, was sampled for U/Pb and Pb/Pb zircon age determination. The zircons extracted out of the sampled rock were subjected both to dilution and evaporation methods. Dilution method offered Concordia intercepts at 227±23 Ma, 312±13 Ma, 465.7+8.4/-8.0 Ma, 703±21 Ma and 1604±45 Ma. Evaporated zircon grains gave 450±20 Ma and 543±17 Ma. The 227±23 Ma age and 312±13 Ma age have been interpreted as Pb loss due to the final effect of the Permian widespread magmatism and late Variscan anatexis respectively. The 465.7+8.4/-8.0 Ma and 450±50 Ma ages probably represent the protolith generation time. The 543±17 Ma is viewed as an inherited Cadomian age and the 703±21 and 1604±45 Ma might represent Cadomian and Saharan detrital zircon ages

New U/Pb and Pb/Pb zircon ages from the Biharia terrane rocks, Apuseni Mountains, Romania

The Biharia sequence from the Apuseni Mountains is a component of the Biharia Paleozoic terrane. The Biharia terrane probably evolved as an island arc between the Cadomian Someş and Baia de Arieş terranes. A gneissic metagranodiorite associated with metabasites from the Valea Ierţii creek, was sampled for U/Pb and Pb/Pb zircon age determination. The zircons extracted out of the sampled rock were subjected both to dilution and evaporation methods. Dilution method offered Concordia intercepts at 227±23 Ma, 312±13 Ma, 465.7+8.4/-8.0 Ma, 703±21 Ma and 1604±45 Ma. Evaporated zircon grains gave 450±20 Ma and 543±17 Ma. The 227±23 Ma age and 312±13 Ma age have been interpreted as Pb loss due to the final effect of the Permian widespread magmatism and late Variscan anatexis respectively. The 465.7+8.4/-8.0 Ma and 450±50 Ma ages probably represent the protolith generation time. The 543±17 Ma is viewed as an inherited Cadomian age and the 703±21 and 1604±45 Ma might represent Cadomian and Saharan detrital zircon ages

Membrane-anchored HDCR nanowires drive hydrogen-powered CO2 fixation

Filamentous enzymes have been found in all domains of life, but the advantage of filamentation is often elusive. Some anaerobic, autotrophic bacteria have an unusual filamentous enzyme for CO2 fixation-hydrogen-dependent CO2 reductase (HDCR)-which directly converts H2 and CO2 into formic acid. HDCR reduces CO2 with a higher activity than any other known biological or chemical catalyst, and it has therefore gained considerable interest in two areas of global relevance: hydrogen storage and combating climate change by capturing atmospheric CO2. However, the mechanistic basis of the high catalytic turnover rate of HDCR has remained unknown. Here we use cryo-electron microscopy to reveal the structure of a short HDCR filament from the acetogenic bacterium Thermoanaerobacter kivui. The minimum repeating unit is a hexamer that consists of a formate dehydrogenase (FdhF) and two hydrogenases (HydA2) bound around a central core of hydrogenase Fe-S subunits, one HycB3 and two HycB4. These small bacterial polyferredoxin-like proteins oligomerize through their C-terminal helices to form the backbone of the filament. By combining structure-directed mutagenesis with enzymatic analysis, we show that filamentation and rapid electron transfer through the filament enhance the activity of HDCR. To investigate the structure of HDCR in situ, we imaged T. kivui cells with cryo-electron tomography and found that HDCR filaments bundle into large ring-shaped superstructures attached to the plasma membrane. This supramolecular organization may further enhance the stability and connectivity of HDCR to form a specialized metabolic subcompartment within the cell

On the hyperbolicity of Maxwell's equations with a local constitutive law.

Maxwell's equations are considered in metric-free form, with a local but otherwise arbitrary constitutive law. After splitting Maxwell's equations into evolution equations and constraints, we derive the characteristic equation and we discuss its properties in detail. We present several results that are relevant for the question of whether the evolution equations are hyperbolic, strongly hyperbolic, or symmetric hyperbolic. In particular, we give a convenient characterization of all constitutive laws for which the evolution equations are symmetric hyperbolic. The latter property is sufficient, but not necessary, for well-posedness of the initial-value problem. By way of example, we illustrate our results with the constitutive laws of biisotropic media and of Born–Infeld theory

Susceptibility of Well-Differentiated Airway Epithelial Cell Cultures from Domestic and Wild Animals to Severe Acute Respiratory Syndrome Coronavirus 2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread globally, and the number of worldwide cases continues to rise. The zoonotic origins of SARS-CoV-2 and its intermediate and potential spillback host reservoirs, besides humans, remain largely unknown. Because of ethical and experimental constraints and more important, to reduce and refine animal experimentation, we used our repository of well-differentiated airway epithelial cell (AEC) cultures from various domesticated and wildlife animal species to assess their susceptibility to SARS-CoV-2. We observed that SARS-CoV-2 replicated efficiently only in monkey and cat AEC culture models. Whole-genome sequencing of progeny viruses revealed no obvious signs of nucleotide transitions required for SARS-CoV-2 to productively infect monkey and cat AEC cultures. Our findings, together with previous reports of human-to-animal spillover events, warrant close surveillance to determine the potential role of cats, monkeys, and closely related species as spillback reservoirs for SARS-CoV-2