Least squares estimator for stochastic differential equations driven by small fractional Lévy noises from discrete observations

In this paper, we consider the problem of parameter estimation for stochastic differential equations with small fractional Lévy noises, based on discrete observations. Under certain regularity conditions on drift function, the consistency of least squares estimation has been established as a small dispersion coefficient [Formula: see text] and the number of discrete points [Formula: see text] simultaneously. We also obtain the asymptotic behavior of the estimator.

On the Spectral and Polarimetric Signatures of a Bright Scatterer before and after Hardware Replacement

A previous study has used the stable and peculiar echoes backscattered by a single “bright scatterer” (BS) during five winter days to characterize the hardware of C-band, the dual-polarization radar located at Monte Lema (1625 m altitude) in Southern Switzerland. The BS is the 90 m tall metallic tower on Cimetta (1633 m altitude, 18 km range). In this note, the statistics of the echoes from the BS were derived from other ten dry days with normal propagation conditions in winter 2015 and January 2019. The study confirms that spectral signatures, such as spectrum width, wideband noise and Doppler velocity, were persistently stable. Regarding the polarimetric signatures, the large values (with small dispersion) of the copolar correlation coefficient between horizontal and vertical polarization were also confirmed: the average value was 0.9961 (0.9982) in winter 2015 (January 2019); the daily standard deviations were very small, ranging from 0.0007 to 0.0030. The dispersion of the differential phase shift was also confirmed to be quite small: the daily standard deviation ranged from a minimum of 2.5° to a maximum of 5.3°. Radar reflectivities in both polarizations were typically around 80 dBz and were confirmed to be among the largest values observed in the surveillance volume of the Monte Lema radar. Finally, another recent 5-day data set from January 2020 was analyzed after the replacement of the radar calibration unit that includes low noise amplifiers: these five days show poorer characteristics of the polarimetric signatures and a few outliers affecting the spectral signatures. It was shown that the “historical” polarimetric and spectral signatures of a bright scatterer could represent a benchmark for an in-depth comparison after hardware replacements.

Numerical model of gravity segregation of two-phase fluid in porous media based on hybrid upwinding

The paper discusses the numerical algorithm constructing a three-dimensional model for a flow of two-phase incompressible fluid caused by the mass force of gravity in a porous medium. The algorithm is based on a combination of a hybrid upwind method with an explicit scheme for determination of the saturation. The hybrid upwinding allows us to take into account flows of fluid of various nature (in this case, viscous and gravitational flows) separately, which is extremely important in the case of gravitational flow with opposite directions of phase flows. The explicit scheme being extremely simple in implementation provides a small dispersion of solutions on discontinuities. The proposed algorithm is illustrated by the results of numerical experiments demonstrating the monotonicity of the method considered in this paper.

On the radial abundance gradients of nitrogen and oxygen in the inner Galactic disc

ABSTRACT We present optical spectra of nine Galactic H ii regions observed with the 10.4 m Gran Telescopio Canarias telescope and located at Galactocentric distances (RG) from 4 to 8 kpc. The distances of the objects have been revised using Gaia DR2 parallaxes. We determine the electron temperature for all the nebulae, which allows a precise computation of their ionic abundances. We have included published data of an additional sample of Galactic H ii regions, providing a final data set of 42 objects. The shape of the radial gradients of O/H and N/H is linear and constant, discarding any substantial change of the slope, at least for RG between 4 and 17 kpc. The small dispersion of the O/H and N/H values with respect to the computed gradients imply the absence of significant azimuthal variations of the chemical abundances, at least in the quadrant covered by our observations. We find an almost flat N/O versus O/H diagram relation. This result is not observed in other nearby spiral galaxies except M31. Finally, we compare our computed gradients with those obtained using far-infrared (FIR) spectra. We confirm the significant offset in the N/O distribution between the optical and FIR observations. Possible explanations involve ionization correction factors and the strong dependence on density of the abundance determinations based on FIR lines.

THE MORPHOMETRIC STUDY OF THE EFFECTS OF BISPEROXOVANADIUM (BPV(PHEN)) ON NEONATAL DRG NEURONS IN CULTURE

Unlike the neurons in the CNS, the peripheral neurons have certain intrinsic regenerative capacity. After injury, peripheral neurons can switch to a cellular “state for growth”, with the expression profiles similar to early developmental stages. We looked at the changes of morphometric parameters induced in young peripheral neurons with treatments that in adult neurons have growth-stimulatory effect. The experimental treatments compared to control were: BpV (phen), an inhibitor of PTEN; and bFGF, basic fibroblast growth factor. The neurite growth was measured on cultured dissociated dorsal root ganglia neonatal neurons fixed 24h after treatment and immunostained with anti-neurofilament H (NF-H) phosphorylated antibody. FIJI Simple Neurite Tracer was used for morphometry of individual neurons. 24h post treatment, compared to control, total neurite length, length of primary and length of terminal branches, were increased by bFGF but not by BpV treatment. In all measured parameters related to the degree of branching, BpV- treated neurons had small dispersion of values and small mean values, reminiscent of literature data stating that BpV treated neurons are elongated and less branched. However, the BpV did not have a positive influence on neurite elongation, as was reported on adult neurons. In contrast, bFGF stimulated elongation of young neurons in the manner similar to the effects described on the adult neurons.

An Analysis of the Spatio-temporal Characteristics of Hotels’ Network Attention -Taking Xi’an three-star and above hotels as an example

Network attention is the degree of public attention to things on the Internet. With the rapid development of Web 2.0, the network attention of hotels on the tourism network platform has become an important reference for tourists to select an appropriate hotel. Based on the above, taking 371 hotels with three stars and more in Xi’an as the research object and gathering the data of hotels’ network attention from www.ctrip.com., we explore the temporal and spatial characteristics of hotels’ network attention. The result shows that: (1) From 2016 to 2018, due to the development of hotel online booking business, Consumers’ attention to Xi’an three-star and above hotels on www.ctrip.com. has increased significantly; (2) With the Bell and Drum Tower business district as the core, the spatial distribution of network attention of hotels with three stars and above in Xi’an presents the pattern of “large agglomeration and small dispersion”; (3) The network attention of different levels of hotels has obvious differences in spatial agglomeration;

Comparison between evapotranspiration estimation models for Macapá, Amapá

The aim of the study was to evaluate evapotranspiration (ET) estimation models for the municipality of Macapá, AP. The models studied were Hargreaves-Samani (HS), Turc, Camargo (CM), Jensen-Haise (JH) and Solar Radiation (RS). The ET estimated by the models were compared with those obtained by the standard Penman-Monteith method. Statistical tests of Willmot's Concordance index (d), Correlation Coefficient (r), Performance coefficient (c), Mean Absolute Error (EAM), Mean Square Error and Residual Mass Coefficient (CMR) were performed. With the results of "c" only HS, in August (c = 0.71; "good") and December (c = 0.73; "good") presented a performance considered good. JH had the worst result, between 0.05 and 0.22, considered terrible. In relation to “d”, HS also had a better result, with 0.79 and 0.83 in August and December. The worst was JH, with a minimum value of 0.09 for May. For CMR, CM, JH and RS overestimated ET. TC, on the other hand, presented both underestimation and overestimation. HS overestimated from January to July and underestimated in the other months. For EAM, the models tended to overestimate ET. For MSE, HS presented the lowest values. JH was the one with the worst results, above 4. And the coefficient of determination showed a small dispersion of data, with R2 above 0.90 for HS, TC, JH and RS. Based on what was exposed, HS was the method that presented the best responses, followed by CT and RS. And JH was the one with the highest overestimation rate.

Extinction in the 11.2 µm PAH band and the low L11.2/LIR in ULIRGs

ABSTRACT We present a method for recovering the intrinsic (extinction-corrected) luminosity of the 11.2 μm PAH band in galaxy spectra. Using 105 high S/N Spitzer/IRS spectra of star-forming galaxies, we show that the equivalent width ratio of the 12.7 and 11.2 μm PAH bands is independent on the optical depth (τ), with small dispersion (∼5 per cent) indicative of a nearly constant intrinsic flux ratio Rint = (f12.7/f11.2)int = 0.377 ± 0.020. Conversely, the observed flux ratio, Robs = (f12.7/f11.2)obs, strongly correlates with the silicate strength (Ssil) confirming that differences in Robs reflect variation in τ. The relation between Robs and Ssil reproduces predictions for the Galactic Centre extinction law but disagrees with other laws. We calibrate the total extinction affecting the 11.2 μm PAH from Robs, which we apply to another sample of 215 galaxies with accurate measurements of the total infrared luminosity (LIR) to investigate the impact of extinction on L11.2/LIR. Correlation between L11.2/LIR and Robs independently on LIR suggests that increased extinction explains the well-known decrease in the average L11.2/LIR at high LIR. The extinction-corrected L11.2 is proportional to LIR in the range LIR = 109–1013 L⊙. These results consolidate L11.2 as a robust tracer of star formation in galaxies.

Evidence for Non-smooth Quenching in Massive Galaxies at z ∼ 1

We investigate a large sample of massive galaxies at z ∼ 1 with combined HST broad-band and grism observations to constrain the star-formation histories of these systems as they transition from a star-forming state to quiescence. Among our sample of massive ($M_*>10^{10}~\hbox{${\rm M}_{\odot }$}{}$) galaxies at 0.7 < z < 1.2, dust-corrected Hα and UV star-formation indicators agree with a small dispersion (∼0.2 dex) for galaxies on the main sequence, but diverge and exhibit substantial scatter (∼0.7 dex) once they drop significantly below the star-forming main sequence. Significant Hα emission is present in galaxies with low dust-corrected UV SFR values as well as galaxies classified as quiescent using the UVJ diagram. We compare the observed Hα flux distribution to the expected distribution assuming bursty or smooth star-formation histories, and find that massive galaxies at z ∼ 1 are most consistent with a quick, bursty quenching process. This suggests that mechanisms such as feedback, stochastic gas flows, and minor mergers continue to induce low-level bursty star formation in massive galaxies at moderate redshift, even as they quench.