Testing core creation in hydrodynamical simulations using the HI kinematics of field dwarfs

The majority of recent hydrodynamical simulations indicate the creation of central cores in the mass profiles of low-mass halos, a process that is attributed to star formation-related baryonic feedback. Core creation is regarded as one of the most promising solutions to potential issues faced by the lambda cold dark matter (LambdaCDM) cosmology on small scales. For example, the reduced dynamical mass enclosed by cores can explain the low rotational velocities measured for nearby dwarf galaxies, thus possibly lifting the seeming contradiction with the LambdaCDM expectations (the so-called "too big to fail" problem). Here we test core creation as a solution of cosmological issues by using a sample of dwarfs with measurements of their atomic hydrogen (HI) kinematics extending to large radii. Using the NIHAO hydrodynamical simulation as an example, we show that core creation can successfully reproduce the kinematics of dwarfs with small kinematic radii, R <~ 1.5 kpc. However, the agreement with observations becomes poor once galaxies with kinematic measurements extending beyond the core region, R ~ 1.5 - 4 kpc, are considered. This result illustrates the importance of testing the predictions of hydrodynamical simulations that are relevant for cosmology against a broad range of observational samples. We would like to stress that our result is valid only under the following set of assumptions: i) that our sample of dwarfs with HI kinematics is representative of the overall population of field dwarfs, ii) that there are no severe measurement biases in the observational parameters of our HI dwarfs (e.g., related to inclination estimates), and iii) that the HI velocity fields of dwarfs are regular enough to allow the recovery of the true enclosed dynamical mass.Comment: v2 matches version accepted by A&A. About 5 pages, 1 figur

Pressure-induced spin-state transition of iron in magnesiow\"ustite (Fe,Mg)O

We present a detailed theoretical study of the electronic, magnetic, and structural properties of magnesiow\"ustite Fe$_{1-x}$Mg$_x$O with $x$ in the range between 0$-$0.875 using a fully charge self-consistent implementation of the density functional theory plus dynamical mean-field theory (DFT+DMFT) method. In particular, we compute the electronic structure and phase stability of the rock-salt B1-structured (Fe,Mg)O at high pressures relevant for the Earth's lower mantle. We obtain that upon compression paramagnetic (Fe,Mg)O exhibits a spin-state transition of Fe$^{2+}$ ions from a high-spin to low-spin (HS-LS) state which is accompanied by a collapse of local magnetic moments. The HS-LS transition results in a substantial drop of the lattice volume by about 4$-$8 %, implying a complex interplay between electronic and lattice degrees of freedom. Our results reveal a strong sensitivity of the calculated transition pressure $P_{\rm tr.}$ upon addition of Mg. While for Fe-rich magnesiow\"ustite, Mg $x < 0.5$, $P_{\rm tr.}$ exhibits a rather weak variation at $\sim$80 GPa, for Fe-poor (Fe,Mg)O it drops, e.g., by about 35 % to 52 GPa for Mg $x=0.75$. This behavior is accompanied by a substantial change of the spin transition range from 50$-$140 GPa in FeO to 30$-$90 GPa for $x=0.75$. In addition, the calculated bulk modulus (in the HS state) is found to increase by $\sim$12 % from 142 GPa in FeO to 159 GPa in (Fe,Mg)O with Mg $x=0.875$. We find that the pressure-induced HS-LS transition has different consequences for the electronic properties of the Fe-rich and poor (Fe,Mg)O. For the Fe-rich (Fe,Mg)O, the transition is found to be accompanied by a Mott insulator to (semi-) metal phase transition. In contrast to that, for $x>0.25$, (Fe,Mg)O remains insulating up to the highest studied pressures, implying a Mott insulator to band insulator phase transition at the HS-LS transformation.Comment: 9 pages, 9 figure

The Multi-Wavelength Tully-Fisher relation with spatially resolved HI kinematics

In this paper we investigate the statistical properties of the Tully-Fisher relation for a sample of 32 galaxies with measured distances from the Cepheid period-luminosity relation and/or TRGB stars. We take advantage of panchromatic photometry in 12 bands (from FUV to 4.5 $\mu$m) and of spatially resolved HI kinematics. We use these data together with three kinematic measures ($W^{i}_{50}$, $V_{max}$ and $V_{flat}$) extracted from the global HI profiles or HI rotation curves, so as to construct 36 correlations allowing us to select the one with the least scatter. We introduce a tightness parameter $\sigma_{\perp}$ of the TFr, in order to obtain a slope-independent measure of the goodness of fit. We find that the tightest correlation occurs when we select the 3.6 $\mu$m photometric band together with the $V_{flat}$ parameter extracted from the HI rotation curve.Comment: 16 pages, 16 figures, accepted for publication in MNRAS, minor changes due to proof correction

The Health and Labor Market Effects of Spouse Choice, Maternity Leave and Parental Work

This dissertation explores the health and labor market effects of spousal and parental choices. First chapter of this dissertation studies international marriages in Europe. The effect of international marriage - a union between a country native and an immigrant - on social and family outcomes is endogenous due to the selection into marriage markets and non-random spousal choice. In this paper I use European Union membership and availability of cheap travel as region-specific instrumental variables that increased the probability of intermarriage in Europe. The two-stage least squares analysis applied to 1977-2006 IPUMS International Project Census micro data shows no significant difference in the family size or number of children between intermarried and same-nativity couples. However, it does reveal higher labor force participation rates and much lower marriage rates among mixed nationality couples. In the second chapter, I use Russia’s 1981-82 maternity benefit expansion to estimate the long-run effects of maternity leave on health and other outcomes of children. The program was rolled out in stages and has extended both partially paid and unpaid leave for the vast majority of women. To estimate the effects of the program I apply a difference-in-differences framework to the recent 2000-2014 Russian Longitudinal Monitoring Survey data that contain information on both affected and unaffected cohorts, while also taking advantage of the fact that not all regions implemented the program simultaneously. While the results suggest there is no difference in the overall health of individuals that are born before and after the benefit roll-out, there is strong evidence that those born after the reform are less likely to have chronic gastrointestinal diseases, which could be attributed to better nutrition and breastfeeding duration in the first year of life.Third chapter proposes a new way to estimate the effect of maternal labor supply on the achievement of children. I use a country-specific measure of gender inequality as an instrumental variable for the female immigrant’s decision to work. For the married women in the New Immigrant Survey, higher values of the Gender Inequality Index were positively correlated with the propensity to work for pay and work longer hours, suggesting their self-selection into the US immigration. ¬¬Two-stage estimates further show that children of working mothers have reading and math scores that are over one standard deviation above average. An additional 10 hours a week of maternal work is estimated to increase reading scores by 37% relative to mean and quantitative reasoning scores by 24% relative to the mean. I also find that working mothers visit their children’s classes and attend school meetings more frequently than others; hence, the observed improvement in test scores could be due to a higher involvement of parents in their child’s school curriculum

A new astrophysical solution to the Too Big To Fail problem - Insights from the MoRIA simulations

We test whether advanced galaxy models and analysis techniques of simulations can alleviate the Too Big To Fail problem (TBTF) for late-type galaxies, which states that isolated dwarf galaxy kinematics imply that dwarfs live in lower-mass halos than is expected in a {\Lambda}CDM universe. Furthermore, we want to explain this apparent tension between theory and observations. To do this, we use the MoRIA suite of dwarf galaxy simulations to investigate whether observational effects are involved in TBTF for late-type field dwarf galaxies. To this end, we create synthetic radio data cubes of the simulated MoRIA galaxies and analyse their HI kinematics as if they were real, observed galaxies. We find that for low-mass galaxies, the circular velocity profile inferred from the HI kinematics often underestimates the true circular velocity profile, as derived directly from the enclosed mass. Fitting the HI kinematics of MoRIA dwarfs with a theoretical halo profile results in a systematic underestimate of the mass of their host halos. We attribute this effect to the fact that the interstellar medium of a low-mass late-type dwarf is continuously stirred by supernova explosions into a vertically puffed-up, turbulent state to the extent that the rotation velocity of the gas is simply no longer a good tracer of the underlying gravitational force field. If this holds true for real dwarf galaxies as well, it implies that they inhabit more massive dark matter halos than would be inferred from their kinematics, solving TBTF for late-type field dwarf galaxies.Comment: 21 pages, 21 figures. Accepted for publication in A&A. Corrected certain values in Table

Numerical simulation of the electromagnetic wave reflection from 2D random semi-infinite strongly scattering media

Light scattering in disordered media plays an important role in various areas of applied science from biophysics to astronomy. In this paper we study two approaches to calculate scattering properties of semi-infinite densely packed media with high contrast and wavelength scale inhomogeneities by combining the Fourier Modal Method and the super-cell approach. Our work reveals capabilities to attain ensemble averaged solutions for the Maxwell's equations in complex media, and demonstrated numerical convergence supports the consistency of the considered approaches.Comment: 10 pages, 7 figure

Substantial features of speech in business communication

Substantial features of the text which was specially prepared for a public speech of the first person of a company in the business sphere, namely in the petroleum field in the Russian Federation, were analyzed in the actual article. The analysis showed that speech contains a number of constant and optional micro topics which are used to position a company in a positive way in the B2B market.В статье выявляются содержательные особенности текста публичного выступление первого лица базисного субъекта PR в бизнес среде, а именно: в нефтяной отрасли Российской Федерации. Автором выявлен набор постоянных и факультативных микротем, которые позиционируют компанию с положительной стороны на рынке B2B

Mentoring as a form of interaction in the course of professional adaptation of youth

Mentoring is one of the oldest and most effective ways to transfer knowledge and skills to young members of the enterprise, in the process of adapting to a new team. Working with new coaching staff mentoring has the character of a permanent method of training of employees at the workplace.Наставничество считается одним из самых старых и эффективных способов передачи знаний и навыков молодым сотрудникам предприятия, в процессе их адаптации в новом коллективе. При работе с новыми кадрами наставничество носит характер постоянного метода обучения сотрудников непосредственно на рабочем месте

Corporate education as a way of training company

The article discusses the possibility of using corporate training for the formation of professional competence of the personnel of enterprisesВ статье рассматриваются возможности использования корпоративного обучения для формирования профессиональной компетентности кадров предприяти

Corporate training

The article discusses the possibility of using corporate training for the formation of professional competence of the personnel of enterprisesВ статье рассматриваются возможности использования корпоративного обучения для формирования профессиональной компетентности кадров предприяти