Passive Regime Research Articles

Petrogenesis of Neogene polymagmatic suites at a monogenetic low-volume volcanic province, Bahariya depression, Western Desert, Egypt

Monogenetic volcanoes can yield eruptive suites displaying substantial complexity in compositional characteristics. The Bahariya monogenetic volcanoes (BMV) in the Western Desert, Egypt are a good example. They comprise complex stratigraphic deposits involving scoria cone, lava flows, and subvolcanic sills and dikes related to diverse eruptive styles. Whole-rock and mineral chemistry and 40Ar–39Ar geochronology are used here to document the petrogenesis, source characteristics, and evolution of the Bahariya volcanoes. The architecture of the BMV is the product of two alkali magma batches: pyroclastics and lava flows forming explosive scoria cone (batch 1) and subvolcanic sills (batch 2). The two batches show contrast in the concentrations of incompatible trace elements and REE as well as element ratios such as Nb/Yb, Gd/Yb, Nb/U, and Ce/Pb (36, 5.0, 44, 30 vs. 17, 4.0, 39, 24 for batch 1 and 2, respectively). New whole-rock 40Ar/39Ar dating displays consistent age of 23.71 ± 0.06 and 23.73 ± 0.01 Ma for magma emplacement of batch 2. Batches 1 and 2 share common LILE and LREE enrichments and HFSE depletions, analogous to a HIMU-like, mantle-derived OIB source described from other Paleogene–Oligocene intraplate magmatic provinces in North Africa and worldwide. Trace element modeling proposes a derivation of the Bahariya volcanoes from parental melts generated by 8–12% partial melting of garnet lherzolite and amphibole-bearing garnet lherzolite at 2.18 ± 0.33 and 1.77 ± 0.33 GPa for batch 1 and batch 2, respectively, across the lithosphere–asthenosphere boundary at c. 70–90 km depth (2.14–2.76 GPa). These sources had been earlier metasomatized by volatile-, LILE- and HFSE-rich fluid(s) originating from Neoproterozoic subduction or a Phanerozoic plume. Fractional crystallization involved olivine + clinopyroxene in both batches followed by Fe–Ti oxides + apatite in batch 2. Furthermore, crust contamination/assimilation was an irrelevant process at crustal level during magma ascend to the surface. Data results of the geo-barometric computations disclose two magma storage levels involving intermediate to lower crustal levels at c. 35 km (1.05 GPa) for batch 1 and mid-crustal level at c. 25 km depth (0.75 GPa) for batch 2. This study delivers proof that magmas emitted at Bahariya depression can undergo complex polymagmatic processes during their storage and passage in the crust, mainly due to the existence of a multilevel plumbing system. The origin of the BMV, as with other within-plate volcanoes in North Egypt, appears to be allied to extension-induced asthenosphere upwelling activated by limited exclusion of thickened lithospheric root under a passive rift tectonic regime coupled with the development of lithospheric thinning and continental breakup in North Africa.

Fiscal Stress and Monetary Policy Stance in Oil-Exporting Countries

We documented that for some oil-exporting countries, the correlation between exchange rates and oil prices is strongly negative during periods of significant oil price drop but is much weaker during other periods. To interpret this time-varying asymmetric correlation, we develop and estimate a Markov-switching small open economy New Keynesian model with oil income as a source of government revenue. In particular, we allow monetary and fiscal policy coefficients to switch across and passive regimes. Using data on Russia, our result shows that the policy combinations fluctuate. We find that active monetary policy isolates the exchange rate from oil price variations but changes to passively tolerate depreciation and inflation to support government debt when oil price drops place fiscal policy in a state of stress. Counterfactual policy experiments suggest policy regime switching is crucial to account for the observed asymmetric impact of oil prices on the exchange rate and that the transmission channels of oil price shocks differ significantly across policy regimes.

Lithogeochemistry and depositional environments of sedimentary rocks of the upper Vendian and lower Cambrian of the North-West Baltic monocline

«Вестник Санкт-Петербургского университета. Науки о Земле» — научно-теоретический рецензируемый журнал, обобщающий результаты исследований в области геологии, гидрогеологии и геохимии, петрологии и экологии, ландшафтного планирования и геоморфологии, экономической и социальной географии.

100 GHz Multiple Colliding Pulse Generation From Cleaved Facet-Free Multi-Section Semiconductor Laser Diode

We present a monolithically integrated mode-locked laser (MLL) with 25 GHz fundamental repetition rate frequency, which has been designed to operate in a fourth-order colliding regime, to generate 100 GHz. This device has been fabricated within a multi-project wafer (MPW) run in an InP-based active-passive generic foundry. The Fabry-Perot laser resonator, of around 1.66 mm length, is defined by two on-chip reflectors, eliminating the need of cleaved facet. Three saturable absorber sections are symmetrically located by spacing them a quarter of this total length, dividing the cavity into four gain segments. We show that this structure can generate an electrical beat note at 25 GHz as well as 100 GHz, with a linewidth of 350 kHz and 150 kHz, respectively, operating in passive operation regime.

Passive mode-locking operation of a diode-pumped Tm:YAG laser with a MoS2 saturable absorber

In this paper, we demonstrate the first passive mode-locking operations of a diode-pumped Tm:YAG laser with a MoS2 saturable absorber. In the absence of a MoS2 saturable absorber, the Tm:YAG laser produced a 2.68 W continuous-wave (CW) output power at 2013.8 nm. Under passive mode-locking regime, a maximum average output power of 0.2 W at a pulse repetition rate of 232.2 MHz and a pulse width of about 280 ps were achieved in the experiment. In addition, the near-diffraction limited beam qualities of the CW Tm:YAG laser were achieved.

Optical shutters for a compact femtosecond Yb:KYW laser

A stable passive mode-locking regime for a Yb3+ :KY(WO4)2 laser with optical pumping by a continuous diode laser was obtained using two types of optical shutter with a saturable absorber based on coupled GaAs/In0.25Ga0.75As/GaAs quantum wells. The shutters differed in their reflecting part: the first type was a semiconductor mirror and the second type was a dielectric one. The typical parameters of the mode-locking regime were as follows: a pulse duration of about 200 fs for both types of shutter, an average power of 2.54 W for the all-semiconductor shutter (SESAM) and 0.92 W for the dielectric mirror with a saturable absorber (DSAM). The efficiency relative to the incident pump power was 57% for the SESAM and 19% for the DSAM. The maximum pulse repetition rate was 982 MHz. The measured recovery time was about 2 ps for both saturable absorbers. The mirror damage threshold estimate for the SESAM was at least 8.87 mJ cm−2.

Stably stratified exact coherent structures in shear flow: the effect of Prandtl number

We examine how known unstable equilibria of the Navier-Stokes equations in plane Couette flow adapt to the presence of an imposed stable density difference between the two boundaries for varying values of the Prandtl number $Pr$, the ratio of viscosity to density diffusivity, and fixed moderate Reynolds number, $Re=400$. In the two asymptotic limits $Pr \to 0$ and $Pr \to \infty$, it is found that such solutions exist at arbitrarily high bulk stratification but for different physical reasons. In the $Pr \to 0$ limit, density variations away from a constant stable density gradient become vanishingly small as diffusion of density dominates over advection, allowing equilibria to exist for bulk Richardson number $Ri_b \lesssim O(Re^{-2}Pr^{-1})$. Alternatively, at high Prandtl numbers, density becomes homogenised in the interior by the dominant advection which creates strongly stable stratified boundary layers that recede into the wall as $Pr\to\infty$. In this scenario, the density stratification and the flow essentially decouple, thereby mitigating the effect of increasing $Ri_b$. An asymptotic analysis is presented in the passive scalar regime $Ri_b \lesssim O(Re^{-2})$, which reveals $O(Pr^{-1/3})$-thick stratified boundary layers with $O(Pr^{-2/9})$-wide eruptions, giving rise to density fingers of $O(Pr^{-1/9})$ length and $O(Pr^{-4/9})$ width that invade an otherwise homogeneous interior. Finally, increasing $Re$ to $10^5$ in this regime reveals that interior stably stratified density layers can form away from the boundaries, separating well-mixed regions.

Femtosecond laser direct writing of evanescently-coupled planar waveguide laser arrays

We report on the fabrication of evanescently-coupled one-dimensional waveguide laser arrays in Nd:YAG crystals by employing femtosecond-laser direct writing (FsLDW). The far-field discrete diffraction patterns of fabricated waveguide arrays under a passive regime can be observed at the active regime. By adjusting the incoupling condition, diffraction patterns with different laser intensity distribution can be realized, which is also supported by our simulation. Results in this study suggest promising applications of such an active arrayed device for complex integrated photonic circuits.

Array signal processing methods for achieving super-resolution using vortex waves

Helicoidal (vortex) acoustic waves have received much interest lately and can be generated by a variety of means, such as applying a prescribed phase shift to the elements of conventional 2-D planar arrays or by employing a leaky wave antenna in a circular arrangement. In the context of array signal processing, the beampattern associated with vortex wave generation has a strong central null that can be exploited to achieve far field super-resolution in a variety of applications. Although recent physical acoustics research into vortex waves has focused on active applications such as particle manipulation or propagating sub-diffraction-limit features into the far field, vortex waves can also be utilized in passive applications such as source localization. This work investigates the signal processing implications of using vortex waves in both active and passive regimes. Key trade-offs between conventional, adaptive, and vortex-wave-based array signal processing methods are examined by simulating a variety of array geometries and source/target configurations. Results indicate the potential for vortex wave methods to provide performance improvements over conventional and adaptive methods such as MVDR (minimum variance distortionless response) and MUSIC (multiple signal classification) in snapshot-deficient and high-bearing-rate target scenarios.

Technical Note: Suppression of Anodic Kinetics of Stainless Steels During Biofilm Development in Natural Seawater

The anodic kinetics of three stainless steels, viz. UNS S31600, S44660, and N08367, in gently flowing natural seawater was investigated. Potentiodynamic anodic polarization showed two distinct passive regimes emerging with biofilm development. A dramatic decrease of anodic current densities (p < 10−4) was recorded in the lower passive region near the ennobled open-circuit potential, accompanied by an increase of the breakdown potential by over 0.2 V for Alloy S31600. However, significant broadening of the transpassive region was observed on all the three alloys tested. Further, for Alloys S44660 and N08367, the second passive region was altered during biofilm growth, which resulted in enhanced peak current densities. These seemingly undesired effects, nonetheless, were detected far beyond the domain of practical significance. Potentiostatic current-time curves for Alloy N08367 further confirmed the suppression of anodic kinetics in the lower passive region. Evans diagrams constructed from actual polarization curves provided fundamentally important insights that passivity promotion can be independent of microbially enhanced cathodic kinetics.

Characterizing Monetary and Fiscal Policy Rules and Interactions when Commodity Prices Matter

We examine the extent to which commodity price fluctuations matter for monetary and fiscal policy formulation in high primary commodity export economies. Markov mixture specifications of monetary and fiscal policy rules, stylized to account for commodity price slacks are estimated using specifically designed Bayesian techniques. We find that policymakers do indeed respond to commodity price slacks, and with varying degrees, depending on the policy regime in place and the country under investigation. Policy is characterized by distinctive episodes of active and passive policy regimes, driven by the response of monetary policy to inflation and the response of fiscal policy to past government debt. Moreover, monetary authorities fail to act aggressively enough to achieve announced inflation targets or to synchronize with fiscal authorities. The results hold implications for the correct specification of policy rules and interactions in DSGE models for these economies.

Efficient diode pumped Yb:Y2O3 cryogenic laser

We report on continuous-wave and pulsed laser characteristics of Yb:Y2O3 transparent ceramic at cryogenic temperatures. A VBG stabilized pump diode emitting at 976 nm which matches with the zero-phonon line of the gain media was employed. At 100 K, a maximum continuous-wave output power of 12 W, around three times than that of 300 K and a slope efficiency of 54.4%, 2.4 times than that of 300 K was achieved using an output coupler transmission of 50% with respect to incident power. In passive Q-switched regime, using a Cr:YAG saturable absorber with an initial transmission of 85%, a maximum energy of 0.46 mJ per pulse was obtained with a peak power of 1.64 kW at a repetition rate of 19.6 kHz.

Dynamics control in pipe cold rolling mill main drive

Elimination of unstable and critical states of deformed systems of pipes pilger cold rolling mill, heavy-loaded equipment of which functions under conditionsof increase dynamic loads, is mainly intended for mechanic system dynamics stabilization until the accepted level of loading. Active mechanicties in the initial dynamic model revealed, which stipulate the demonstration of pronounced parametric processes in the studied system of pipes cold rolling mill main driver. Analysis of reasons of parametric oscillations originating carried out for systems of pipes cold rolling mill main driver. Zones of dynamic instability of mechanic system functioning according to Eins–Strett diagram determined, that enable to make the choice of passive optimal rolling regimes at the stage of technological processes designing of pipes pilger cold rolling.A system of active control by main driver of pipes cold rolling mill elaborated based on its mathematical model. A structure of optimal control by angular oscillations driver line elements of pipes cold rolling mill selected and parameters ofactive control impacts of the automated servo control system determined. A mechanism of optimal control by dynamic state ofdriver line elements of pipes cold rolling mill proposed. Also proposed an outline of critical and instablestates elimination for the main driver line driver of pipes cold rolling mill, which is realized by means of adaptive active automated servo control facility. The modernized main driver line of pipes cold rolling mill is equipped by facilities and control systems, enabling to switch the initial mechanic system from a critical state into a zone ofdesired states in a servo regime. Sensors of threshold moments level of elasticity forcesare installed on the drive shaft of main driver of pipes cold rolling mill. During the drive shaft angular elastic oscillations, comprising of actual and desired parameters of mechanicsystem is made based on sensors signals. Next, a correspondent control impact is formed based on algorithm embedded into the electric drive servo control system. When the displayed point of the drive shaft reaches the desired area of system dynamic stability, the active drive control is switched off. If further the disturbing load, applied from the side of deformation seat, makes the drive line dynamic characteristics off the desired status, then the dynamic system control process is repeated in anautomated mode. Reliability of the results received confirmed by calculation example and experiments at the main driver of pipes cold rolling mill ХПТ-32.

Nanomedicines for Reactive Oxygen Species Mediated Approach: An Emerging Paradigm for Cancer Treatment.

Growth in the knowledge of cancer biology has led to the emergence and evolution of cancer nanomedicines by providing the rationale for leveraging nanotechnology to develop better treatment options. The discovery of nanometer-sized intercellular openings in the defective angiogenic tumor vasculature contributed to the development of an idea for the well-known cancer passive targeting regime, enhanced permeability and retention (EPR) effect, of the nanomedicines. Recently, reactive oxygen species (ROS) have been highlighted as one of the key players that underlie the acquisition of the various hallmarks of cancer. As ROS are associated with all stages of cancer, their applications in cancer treatment based on the following concentration-dependent implications have attracted much attention: (1) low to moderate levels of ROS as key signaling molecules, (2) elevated levels of ROS in cancer cells as one of the unique characteristics of cancer, and (3) excessive levels of ROS as cytotoxic agents. Considering ROS from a different point of view, various cancer nanomedicines have been designed to achieve spatiotemporal control of therapeutic action, the main research focus in this area. This Account includes our efforts and preclinical achievements in development of nanomedicines for a range of ROS-mediated cancer therapies. It begins with general background regarding cancer nanomedicines, the significance of ROS in cancer, and a brief overview of ROS-mediated approaches for cancer therapy. Then, this Account highlights the two key roles of ROS that define therapeutic purposes of cancer nanomedicines: (1) ROS as drug delivery enhancers and (2) ROS as cell death inducers. The former inspired us to develop nitric oxide-generating nanoparticles for improved EPR effect, endogenous ROS-responsive polymeric micelles for enhanced intracellular drug delivery, and exogenous ROS-activated micelles for subcellular localization via photochemical internalization. While refining conventional chemotherapy, recent researches also have focused on the latter, the cytotoxic ROS, to advance alternative treatment modalities such as oxidation therapy, photodynamic therapy (PDT), and sonodynamic therapy (SDT). In particular, we have been motivated to develop polymeric nanoreactors containing enzymes to produce H2O2 for oxidation therapy, photosensitizer-loaded gold-nanoclustered polymeric nanoassemblies for photothermally activated PDT overcoming the oxygen dependency of PDT, and hydrophilized TiO2 nanoparticles and Au-TiO2 nanocomposites as novel sonosensitizers for improved SDT efficiency. The integration of nanomedicine and ROS-mediated therapy has emerged as the new paradigm in the treatment of cancer, based on promising proof-of-concept demonstrations in preclinical studies. Further efforts to ensure clinical translation along with more sophisticated cancer nanomedicines to address relevant challenges are expected to be made in the coming years.

Influence of Ion Beam-Assisted Deposition on the Wetting Properties of Al-1.0 at.% Cr Alloy Films

The surface microstructure and wettability of Al-1.0 at.% Cr alloy films obtained by ion-beam-assisted deposition on glass substrates have been investigated using atomic force microscopy, scanning electron microscopy and the sessile drop method. In the passive deposition regime, the surface roughness of the films increased from 8.9[Formula: see text]nm to 21.6[Formula: see text]nm with an increase in coating time from 3[Formula: see text]h to 9[Formula: see text]h. A quantitative analysis of the morphology evolution of the films during their growth was performed. The results revealed that Al-1.0 at.% Cr alloy films are hydrophilic. The mechanism of heterogeneous water wetting of Al-1.0 at.% Cr alloy films was considered, when the increasing surface roughness accounts for a decrease of hydrophilicity.

Campano-Maastrichtian paleoenvironment, paleotectonics and sediment provenance of western Anambra Basin, Nigeria: Multi-proxy evidences from the Mamu Formation

This article presents the results of a high-resolution evaluation of the sedimentological, mineralogical, palynofacies, and geochemical aspects of the Mamu Formation aimed at deciphering the sediment provenance, as well as the prevailing paleoenvironmental, paleoclimatic and paleotectonic conditions that occurred during the late Campanian-middle Maastrichtian age in the less studied western section of the Anambra Basin, Nigeria. Four measured sections exposed in Uzebba (composite), Auchi, Okpekpe, and Imiegba were investigated using sedimentological (outcrop studies and laser diffraction particle size analysis), mineralogical (XRD), geochemical (ICP-MS and XRF) and palynofacies techniques. Seven lithofacies were identified and grouped into central basin, marsh, bay, barrier, beach, and washover fan facies association as well as meandering fluvial-tidal channel facies association interpreted as indicative of a tidally influenced wave dominated estuarine paleoenvironment. In addition, mineralogical and palynofacies characterization revealed the heterogeneous nature of the dark mudstone lithofacies, varying from a more proximal low salinity phytoclast and quartz dominated marsh and bay mudstones to a more distal higher salinity palynomorph and clay dominated central basin accumulating deep-water mudstones. Consistent with recent Campano-Maastrichtian paleogeographic and paleoclimatic models we observed a dominance of kaolinite, a high chemical index of alteration above 90%, and a predominantly low index of compositional variability values (<1%), which signifies mineralogical maturity of the sediments due to sediment recycling and intensive chemical weathering under humid tropical paleoclimate. Furthermore, trace and major element discriminant plots revealed a felsic-intermediate provenance for the sediments under passive margin paleotectonic regime, which is in agreement with the regional distribution, geology, and geochemistry of the pre-Santonian rocks and the Precambrian basement rocks in the area.

Can resistant infections be perceptible in UK dairy farming?

This paper interrogates the claim that antimicrobial-resistant infections are rarely encountered in animal agriculture. This has been widely reiterated by a range of academic, policy and industry stakeholders in the UK. Further support comes from the UK's Animal and Plant Health Agency’s (APHA) passive clinical surveillance regime, which relies on veterinarians to submit samples for analysis and similarly reports low levels of resistance amongst key animal pathogens. Building on social science work on knowledge-practices of animal health and disease, and insights from emerging literature on non-knowledge or ‘agnotology’, we investigate the conditions shaping what is known about antimicrobial-resistant infections on farms. In so doing, we find that how on-farm knowledge is produced about resistant infection is concurrently related to domains of imperceptibility or what cannot be known in the context of current practices. The paper discusses the findings of ethnographic research undertaken on an East Midlands dairy farm that highlight the following specific findings. First, farmers and veterinarians, when observing instances of treatment failure, draw on an experiential repertoire that effaces resistances and instead foregrounds the complexities of host-pathogen interaction, or failings in human behaviour, over pathogen-antibiotic interactions. Second, the knowledge-practices of both farmers and veterinarians, although adept at identifying and diagnosing infectious disease are not equipped to make resistance perceptible. Third, this imperceptibility has implications for antibiotic use practices. Most notably, veterinarians anticipate resistance when making antibiotic choices. However, because of the absence of farm level knowledge of resistance this anticipatory logic is informed through the prevalence of resistance ‘at large’. The analysis has implications for the existing passive resistance surveillance regime operating in the dairy sector, which relies on veterinarians and farmers voluntarily submitting samples for diagnostic and susceptibility testing. In effect this entrenches farm level imperceptibility and effacement by farmers and veterinarians within the national dairy surveillance regime. However, we also highlight opportunities for providing farm specific knowledge of resistance through the anticipatory logic of veterinarians and a more active regime of surveillance.

Modelling of Fiscal and Monetary Policy Interactions in the Republic of Belarus

The article discusses classical and modern macroeconomic models of interaction of fiscal and monetary policies in Belarus. The hypothesis of this research is that the interaction of fiscal and monetary policies has a synergistic effect on economic growth and that at certain stages, one of these policies prevails over the other. This hypothesis was tested with the help of an IS-LM model, which was used to investigate the joint effects of monetary and fiscal policies on business activity in Belarus. A Markov switching model was developed in Eviews software to analyze the interaction between these policies. Regression dependences of the average tax burden (including the burden imposed by social security contributions) and GDP, investment and the refinancing rate were built by using Excel software. To solve the IS-LM model, the value of autonomous consumption was computed with the help of the adjusted value of the average propensity to consume. It was found that autonomous consumption is comparable with the budget of subsistence minimum in Belarus. The share of government spending in the GDP structure was on average 35.01%. The comparison of gross savings and investment showed that in the majority of periods, gross savings insignificantly exceeded the amount of investment, that is, the available funds were used for consumer lending rather than for investment. Analysis of the Markov switching model has led us to the conclusion that from the first quarter 2005 until the fourth quarter of 2009, the fiscal policy in Belarus was in the active regime. The passive fiscal policy regime was observed in the period between the first quarter of 2010 and the first quarter of 2019. In this period, a rise in the public debt was accompanied by an increase in the budget surplus. In the second quarter of 2019, there was a transition to a more active fiscal policy, which points to the need to intensify tax reforms.

Influence of Surface Strain on Passive Film Formation of Duplex Stainless Steel and Its Degradation in Corrosive Environment

The effect of surface strain on the passive film evolution of SAF 2507 super duplex stainless steel exposed to ambient air and 0.1 M NaCl solution with varying anodic polarization at room temperature has been investigated using in-situ grazing incidence X-ray diffraction (GIXRD) in combination with electrochemical measurements. Surface strain affected the crystallinity of the passive film as such that the surface oxides/hydroxides were predominantly amorphous, with some minor crystalline CrOOH and FeOOH present in the film. Crystalline CrOOH was seen to diminish in volume upon immersion in the NaCl solution, well-possibly becoming amorphous during anodic polarization, whereas crystalline FeOOH was seen to increase in volume during polarization to the passive potential regime. Strain relaxation, associated with metal dissolution, occurred in both austenitic and ferritic grains during immersion in the electrolyte. Anodic polarization to the transpassive regime led to maximum strain relaxation, occurring more on the austenite than the ferrite. The selective transpassive dissolution nature of the ferrite was significantly reduced due to large strains in the austenite. Passive film breakdown was reflected by enhanced dissolution of Fe, Cr, Mo and Ni occurring simultaneously around 1300 mV vs. Ag/AgCl.

Simulation and experimental investigation of beam distortions in end-pumped laser rod amplifiers

Power scaling of end-pumped laser rod amplifiers is challenging due to beam distortions at high powers. It is difficult to understand these distortions since several physical effects also contribute simultaneously to the problem. We present a detailed investigation of the beam distortions by numerical simulation and experiments in different gain regimes (passive regime with no gain, small signal gain regime, and saturated gain regime) to decouple effects caused by thermal lensing from aberrations induced by the transversal gain profile. The simulation and experiment are in good agreement and show the influence of the gain regime in the details and reveal a significant impact of the transversal gain profile on the output beam quality.