ABSTRACT
We perform a suite of simulations with realistic gravity and thermal balance in shells to quantify the role of the ratio of cooling time to the free-fall time (tcool/tff) and the amplitude ...of density perturbations (δρ/ρ) in the production of multiphase gas in the circumgalactic medium (CGM). Previous idealized simulations, focusing on small amplitude perturbations in the intracluster medium (ICM), found that cold gas can condense out of the hot ICM in global thermal balance when the background tcool/tff ≲ 10. Recent observations suggest the presence of cold gas even when the background profiles have somewhat large values of tcool/tff. This partly motivates a better understanding of additional factors such as large density perturbations that can enhance the propensity for cooling and condensation even when the background tcool/tff is high. Such large density contrasts can be seeded by galaxy wakes or dense cosmological filaments. From our simulations, we introduce a condensation curve in the (δρ/ρ) – min(tcool/tff) space, which defines the threshold for condensation of multiphase gas in the CGM. We show that this condensation curve corresponds to (tcool/tff)blob ≲ 10 applied to the overdense blob instead of the background for which tcool/tff can be higher. We also study the modification in the condensation curve by varying entropy stratification. Steeper (positive) entropy gradients shift the condensation curve to higher amplitudes of perturbations (i.e. make condensation difficult). A constant entropy core, applicable to the CGM in smaller haloes, shows condensation over a larger range of radii as compared to the steeper entropy profiles in the ICM.
Background: Spirulina is a multicellular, filamentous cyanobacterium, belonging to the Phormidiaceae family which appears as blue-green filaments composed of cylindrical cells arranged in unbranched ...helicoidal trichomes. It contains a wide spectrum of nutrients that include proteins with all essential amino acids, carbohydrates, vitamins, minerals, pigments, carotenoids and super antioxidants apart from trace elements. Methods: The aim of the present study is to optimize the growth of cyanobacterium i.e., Spirulina platensis in selected media such as Zarrouk’s modified medium, Zarrouk’s medium, BG11 medium and F-2 medium. The growth analyses were recognized after 30 days. The temperature was maintained at 30±2°C under 12:12 hour light-dark cycles, light illuminated (4500 lux). Result: The maximum biomass of 0.641 gm/ml was achieved in Zarrouk’s modified medium. The inoculation of S. platensis in the F-2 medium showed the least growth of alga. The maximum concentration of phycocyanin content (0.19 mg/ml) and total carotenoid contents (5.99 µg/ml) were observed in Zarrouk’s modified medium followed by Zarrouk’s medium (0.12 mg/ml and 5.51 µg/ml) and minimum amounts were observed in F-2 medium (0.08 mg/ml and 3.08 µg/ml). According to the results, this study concluded that the growth and biomass of Spirulina with significant cell count and higher pigment proteins can be enhanced by using the naturally modified medium.
Debate surrounding the performance outcomes of a firm’s strategic commitment to digitalization and environmental sustainability (namely, digital orientation and environmental orientation, ...respectively) is gathering pace. Despite progress, there remains no conclusive evidence on whether, and how digital orientation and environmental orientations enhance innovation outcomes, especially for small and medium-sized enterprises (SMEs). Therefore, this paper examines the direct and complementary effects of digital and environmental orientations on the likelihood that SMEs introduce product and/or process innovations (i.e., product and process innovation performance). The study tests its hypotheses on a sample of 369 North American SMEs. Results demonstrate that digital and environmental orientation have a positive direct effect on product and process innovation performance. Instead, the complementary effect of pursuing a dual strategy towards digitization and environmental sustainability has a negative impact on process innovation performance and is not significant for product innovation performance. These results add new insights to theory linking strategic orientation to innovation performance, with specific regard to smaller firms.
Abstract
On its journey through the Galaxy, the Sun passes through diverse regions of the interstellar medium. High-resolution spectroscopic measurements of interstellar absorption lines in spectra ...of nearby stars show absorption components from more than a dozen warm partially ionized clouds within 15 pc of the Sun. The two nearest clouds—the Local Interstellar Cloud (LIC) and Galactic (G) cloud—move toward each other. Their bulk heliocentric velocities can be compared with the interstellar neutral helium flow velocity obtained from space-based experiments. We combine recent results from Ulysses, IBEX, and STEREO observations to find a more accurate estimate of the velocity and temperature of the very local interstellar medium. We find that, contrary to the widespread viewpoint that the Sun resides inside the LIC, the locally observed velocity of the interstellar neutral helium is consistent with a linear combination of the velocities of the LIC and G cloud, but not with either of these two velocities. This finding shows that the Sun travels through a mixed-cloud interstellar medium composed of material from both these clouds. Interactions between these clouds explain the substantially higher density of the interstellar hydrogen near the Sun and toward stars located within the interaction region of these two clouds. The observed asymmetry of the interstellar helium distribution function also supports this interaction. The structure and equilibrium in this region require further studies using in situ and telescopic observations.
•The possibility of optical soliton propagation in thermal optical medium with power nonlinearity and feedback is described theoretically.•New generalization of equations describing the light ...propagation in such medium is proposed.•Exact solutions of the considered system corresponding to the simplest solitons in the term of hyperbolic cosine are found.•A bifurcation in the system is found when the power nonlinearity coefficient is negative one and the coupling nonlinearity coefficient is a positive one.
The possibility of optical soliton propagation in thermal optical medium with power nonlinearity and feedback is described theoretically. New generalization of equations describing the light propagation in such medium is proposed. Exact solutions of the considered system corresponding to the simplest solitons in the term of hyperbolic cosine are found. It is shown that the propagation constant and the parameters of such solitons are determined by the power nonlinearity and the coupling nonlinearity coefficients. Conditions of existence of the simplest solitons are analyzed. A bifurcation in the system is found when the power nonlinearity coefficient is negative one and the coupling nonlinearity coefficient is a positive one.
Abstract
The IBEX-Lo instrument on board the Interstellar Boundary Explorer (IBEX) mission samples interstellar neutral (ISN) helium atoms penetrating the heliosphere from the very local interstellar ...medium (VLISM). In this study, we analyze the IBEX-Lo ISN helium observations covering a complete solar cycle, from 2009 through 2020 using a comprehensive uncertainty analysis including statistical and systematic sources. We employ the Warsaw Test Particle Model to simulate ISN helium fluxes at IBEX, which are subsequently compared with the observed count rate in the three lowest energy steps of IBEX-Lo. The
χ
2
analysis shows that the ISN helium flows from ecliptic
λ
,
β
=
(
255
.°
59
±
0
.°
23
,
5
.°
14
±
0
.°
08
)
, with speed
v
HP
= 25.86 ± 0.21 km s
−1
and temperature
T
HP
= 7450 ±140 K at the heliopause. Accounting for gravitational attraction and elastic collisions, the ISN helium speed and temperature in the pristine VLISM far from the heliopause are
v
VLISM
= 25.9 km s
−1
and
T
VLISM
= 6150 K, respectively. The time evolution of the ISN helium fluxes at 1 au over 12 yr suggests significant changes in the IBEX-Lo detection efficiency, higher ionization rates of ISN helium atoms in the heliosphere than assumed in the model, or an additional unaccounted for signal source in the analyzed observations. Nevertheless, we do not find any indication of the evolution of the derived parameters of ISN helium over the period analyzed. Finally, we argue that the continued operation of IBEX-Lo to overlap with the Interstellar Mapping and Acceleration Probe will be pivotal in tracking possible physical changes in the VLISM.
Prior studies suggest that open innovation activities positively influence innovation outcomes in large firms. However, few studies have investigated the implications of small and medium-sized ...enterprises' (SMEs) adoption of open innovation. We address this research gap by investigating the effects of four inbound open innovation activities on innovation performance of SMEs. In doing so, we draw on data from 252 high-tech SMEs. Our results reveal that different open innovation activities are beneficial for different innovation outcomes. For instance, technology sourcing is linked to radical innovation performance, whereas technology scouting is linked to incremental innovation performance. These findings hold several important theoretical and practical implications.
Abstract
The Voyager spacecraft are providing the first in situ measurements of physical properties in the outer heliosphere beyond the heliopause. These data, together with data from the IBEX and ...Hubble Space Telescope and physical models consistent with these data, now provide critical measurements of pressures in the heliosphere and surrounding interstellar medium. Using these data, we assemble the first comprehensive survey of total pressures inside and outside of the heliopause, in the interstellar gas surrounding the heliosphere, and in the surrounding Local Cavity to determine whether the total pressures in each region are in balance with each other and with the gravitational pressure exerted by the galaxy. We intercompare total pressures in each region that include thermal, nonthermal, plasma, ram, and magnetic pressure components. An important result is the role of dynamic (ram) pressure. Total pressure balance at the heliopause can only be maintained with a substantial contribution of dynamic pressure from the inside. Also, total pressure balance between the outer heliosphere and pristine very local interstellar medium (VLISM) and between the pristine VLISM and the Local Cavity requires large dynamic pressure contributions.
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