Fairness in Multiuser Systems with Polymatroid Capacity Region

For a wide class of multi-user systems, a subset of capacity region which includes the corner points and the sum-capacity facet has a special structure known as polymatroid. Multiaccess channels with fixed input distributions and multiple-antenna broadcast channels are examples of such systems. Any interior point of the sum-capacity facet can be achieved by time-sharing among corner points or by an alternative method known as rate-splitting. The main purpose of this paper is to find a point on the sum-capacity facet which satisfies a notion of fairness among active users. This problem is addressed in two cases: (i) where the complexity of achieving interior points is not feasible, and (ii) where the complexity of achieving interior points is feasible. For the first case, the corner point for which the minimum rate of the active users is maximized (max-min corner point) is desired for signaling. A simple greedy algorithm is introduced to find the optimum max-min corner point. For the second case, the polymatroid properties are exploited to locate a rate-vector on the sum-capacity facet which is optimally fair in the sense that the minimum rate among all users is maximized (max-min rate). In the case that the rate of some users can not increase further (attain the max-min value), the algorithm recursively maximizes the minimum rate among the rest of the users. It is shown that the problems of deriving the time-sharing coefficients or rate-spitting scheme can be solved by decomposing the problem to some lower-dimensional subproblems. In addition, a fast algorithm to compute the time-sharing coefficients to attain a general point on the sum-capacity facet is proposed.Comment: Submitted To IEEE Transactions on Information Theory, June 200

Hepatoprotective effects of Artemia salina L. extract against carbon tetrachloride-induced toxicity

The protective effects of Artemia salina L. extract was examined against carbon tetrachloride (CCl4)-induced cell toxicity. In the in vitro model of study, markers such as cell viability, cellular reduced and oxidized glutathione, and lipid peroxidation in HepG2 cells was evaluated. Human liver cancer cell line HepG2 was treated with CCl4 and Artemia salina extract, and markers of hepatotoxicity were investigated. Artemia salina extract showed significant dose-dependent protective effects against the cytotoxicity of CCl4. This extract was able to normalize the levels of GSH, and thiobarbituric acid-reactive (TBARs), which were altered due to CCl4 intoxication in HepG2 cells. As the oxidative stress markers were ameliorated, it might be concluded that Artemia salina extract possesses protective effects probably due to its antioxidant constituents.</p

The stellar content of low redshift radio galaxies from near-infrared spectroscopy

We present medium spectral resolution near-infrared (NIR) HK-band spectra for 8 low redshift (z<0.06) radio galaxies to study the NIR stellar properties of their host galaxies. As a homogeneous comparison sample, we used 9 inactive elliptical galaxies that were observed with similar resolution and wavelength range. The aim of the study is to compare the NIR spectral properties of radio galaxies to those of inactive early-type galaxies and, furthermore, produce the first NIR HK-band spectra for low redshift radio galaxies. For both samples spectral indices of several diagnostic absorption features, SiI(1.589microns), CO(1.619microns), NaI(2.207microns), CaI(2.263microns), CO(>2.29microns), were measured. To characterize the age of the populations, the measured EWs of the absorption features were fitted with the corresponding theoretical evolutionary curves of the EWs calculated by the stellar synthesis model. On average, EW(CO 2.29) of radio galaxies is somewhat greater than that of inactive ellipticals. Most likely, EW(CO 2.29) is not significantly affected by dilution, and thus indicating that elliptical galaxies containing AGN are in a different stage in their evolution than inactive ellipticals. This is also supported by comparing other NIR features, such as CaI and NaI, with each other. Absorption features are consistent with the intermediate age stellar population, suggesting that host galaxies contain both an old and intermediate age components. It is consistent with previous optical spectroscopy studies which have shown evidence on the intermediate age (~2 Gyr) stellar population of radio galaxies, and also in some of the early-type galaxies. The existence of intermediate age population is a link between the star formation episode, possibly induced by interaction or merging event, and the triggering of the nuclear activity.Comment: 10 pages, 7 figure

Exploring the Correlation between Hα\rm{H}\alpha-to-UV Ratio and Burstiness for Typical Star-forming Galaxies at z∼2z\sim2

The $\rm{H}\alpha$-to-UV luminosity ratio ($L(\rm H\alpha)/L(\rm UV)$) is often used to probe SFHs of star-forming galaxies and it is important to validate it against other proxies for burstiness. To address this issue, we present a statistical analysis of the resolved distribution of $\Sigma_{\rm{SFR}}$ as well as stellar age and their correlations with the globally measured $L(\rm H\alpha)/L(\rm UV)$ for a sample of 310 star-forming galaxies in two redshift bins of $1.37 < z < 1.70$ and $2.09 < z < 2.61$ observed by the MOSDEF survey. We use the multi-waveband CANDELS/3D-HST imaging of MOSDEF galaxies to construct $\Sigma_{\rm{SFR}}$ and stellar age maps. We analyze the composite rest-frame far-UV spectra of a subsample of MOSDEF targets obtained by the Keck/LRIS, which includes 124 star-forming galaxies (MOSDEF-LRIS) at redshifts $1.4 < z < 2.6$, to examine the average stellar population properties, and the strength of age-sensitive FUV spectral features in bins of $L(\rm H\alpha)/L(\rm UV)$. Our results show no significant evidence that individual galaxies with higher $L(\rm H\alpha)/L(\rm UV)$ are undergoing a burst of star formation based on the resolved distribution of $\Sigma_{\rm{SFR}}$ of individual star-forming galaxies. We segregate the sample into subsets with low and high $L(\rm H\alpha)/L(\rm UV)$. The high-$L(\rm H\alpha)/L(\rm UV)$ subset exhibits, on average, an age of $\log[\rm{Age/yr}]$ = 8.0, compared to $\log[\rm{Age/yr}]$ = 8.4 for the low-$L(\rm H\alpha)/L(\rm UV)$ galaxies, though the difference in age is significant at only the $2\sigma$ level. Furthermore, we find no variation in the strengths of Siiv$\lambda\lambda1393, 1402$ and Civ$\lambda\lambda1548, 1550$ P-Cygni features from massive stars between the two subsamples.Comment: 16 pages, 10 figures, published by the Monthly Notices of the Royal Astronomical Societ

Near-infrared spectroscopy of stellar populations in nearby spiral galaxies

We present high spatial resolution, medium spectral resolution near-infrared (NIR) H- and K-band long-slit spectroscopy for a sample of 29 nearby (z < 0.01) inactive spiral galaxies, to study the composition of their NIR stellar populations. These spectra contain a wealth of diagnostic stellar absorption lines, e.g. MgI 1.575 micron, SiI 1.588 micron, CO (6-3) 1.619 micron, MgI 1.711 micron, NaI 2.207 micron, CaI 2.263 micron and the 12CO and 13CO bandheads longward of 2.29 micron. We use NIR absorption features to study the stellar population and star formation properties of the spiral galaxies along the Hubble sequence, and we produce the first high spatial resolution NIR HK-band template spectra for low redshift spiral galaxies along the Hubble sequence. These templates will find applications in a variety of galaxy studies. The strength of the absorption lines depends on the luminosity and/or temperature of stars and, therefore, spectral indices can be used to trace the stellar population of galaxies. The entire sample testifies that the evolved red stars completely dominate the NIR spectra, and that the hot young star contribution is virtually nonexistent.Comment: 13 pages, 5 figures. Accepted to MNRAS. arXiv admin note: text overlap with arXiv:astro-ph/040313

The clustering of typical Lyαα emitters from z∼2.5−6z \sim 2.5 - 6: host halo masses depend on Lyαα and UV luminosities

We investigate the clustering and halo properties of $\sim 5000$ Ly$\alpha$-selected emission line galaxies (LAEs) from the Slicing COSMOS 4K (SC4K) and from archival NB497 imaging of SA22 split in 15 discrete redshift slices between $z \sim 2.5 - 6$. We measure clustering lengths of $r_0 \sim 3 - 6\ h^{-1}$ Mpc and typical halo masses of $\sim 10^{11}$ M$_\odot$ for our narrowband-selected LAEs with typical $L_{\rm{Ly}\alpha} \sim 10^{42 - 43}$ erg s$^{-1}$. The intermediate band-selected LAEs are observed to have $r_0 \sim 3.5 - 15\ h^{-1}$ Mpc with typical halo masses of $\sim 10^{11 - 12}$ M$_\odot$ and typical $L_{\rm{Ly}\alpha} \sim 10^{43 - 43.6}$ erg s$^{-1}$. We find a strong, redshift-independent correlation between halo mass and Ly$\alpha$ luminosity normalized by the characteristic Ly$\alpha$ luminosity, $L^\star(z)$. The faintest LAEs ($L \sim 0.1\ L^\star(z)$) typically identified by deep narrowband surveys are found in $10^{10}$ M$_\odot$ halos and the brightest LAEs ($L \sim 7\ L^\star(z)$) are found in $\sim 5 \times 10^{12}$ M$_\odot$ halos. A dependency on the rest-frame 1500 \AA~UV luminosity, M_\rm{UV}, is also observed where the halo masses increase from $10^{11}$ to $10^{13}$ M$_\odot$ for M_\rm{UV} \sim -19 to $-23.5$ mag. Halo mass is also observed to increase from $10^{9.8}$ to $10^{12.3}$ M$_\odot$ for dust-corrected UV star formation rates from $\sim 0.6$ to $10$ M$_\odot$ yr$^{-1}$ and continues to increase up to $10^{13.5}$ M$_\odot$ in halo mass, where the majority of those sources are AGN. All the trends we observe are found to be redshift-independent. Our results reveal that LAEs are the likely progenitors of a wide range of galaxies depending on their luminosity, from dwarf-like, to Milky Way-type, to bright cluster galaxies. LAEs therefore provide unique insight into the early formation and evolution of the galaxies we observe in the local Universe

Textile-to-mortar bond behaviour in lime-based textile reinforced mortars

Lime-based textile-reinforced mortars (TRM) have recently found a growing interest for repair and strengthening of masonry and historical structures. Despite extensive experimental and numerical investigations performed in the last years on the performance of these composites, there is still a lack of fundamental understanding of the fabric-to-mortar bond behaviour (as one of the main mechanisms affecting the cracking and nonlinear response of these composites) and the parameters affecting that. This paper, aimed at addressing this gap, presents a comprehensive experimental and analytical investigation on how the test setup, embedded length, load rate, mortar age and fabric configuration affect the bond behaviour in lime-based TRMs. In total 160 pull-out tests are performed on a glass-based and a steel-based TRM commonly used for strengthening of masonry structures. The results contribute to standardization of the test procedures for characterization of the fabric-to-mortar bond behaviour, to fundamental understanding of this mechanism and to optimization of the design of these composites for enhancing their mechanical response.This work was partly financed by FEDER funds through the Competitivity Factors Operational Programme (COMPETE) and by national funds through the Foundation for Science and Technology (FCT) within the scope of project POCI-01-0145-FEDER-007633. The support to the first author through grant SFRH/BD/131282/2017 is acknowledged