SIDVI: a model for secure distributed data integration

The new millennium has brought about an increase in the use of business intelligence and knowledge management systems. The very foundations of these systems are the multitude of source databases that store the data. The ability to derive information from these databases is brought about by means of data integration. With the current emphasis on security in all walks of information and communication technology, a renewed interest must be placed in the systems that provide us with information; data integration systems. This dissertation investigates security issues at specific stages in the data integration cycle, with special reference to problems when performing data integration in a peer-topeer environment, as in distributed data integration. In the database environment we are concerned with the database itself and the media used to connect to and from the database. In distributed data integration, the concept of the database is redefined to the source database, from which we extract data and the storage database in which the integrated data is stored. This postulates three distinct areas in which to apply security, the data source, the network medium and the data store. All of these areas encompass data integration and must be considered holistically when implementing security. Data integration is never only one server or one database; it is various geographically dispersed components working together towards a common goal. It is important then that we consider all aspects involved when attempting to provide security for data integration. This dissertation will focus on the areas of security threats and investigates a model to ensure the integrity and security of data during the entire integration process. In order to ensure effective security in a data integration environment, that security, should be present at all stages, it should provide for end-to-end protection

KNDy neurone activation prior to the LH surge of the ewe is disrupted by LPS

In the ewe, steroid hormones act on the hypothalamic arcuate nucleus (ARC) to initiate the GnRH/LH surge. Within the ARC, steroid signal transduction may be mediated by estrogen receptive dopamine-, β-endorphin- or neuropeptide Y (NPY)-expressing cells, as well as those co-localising kisspeptin, neurokinin B (NKB) and dynorphin (termed KNDy). We investigated the time during the follicular phase when these cells become activated (i.e., co-localise c-Fos) relative to the timing of the LH surge onset and may therefore be involved in the surge generating mechanism. Furthermore, we aimed to elucidate whether these activation patterns are altered after lipopolysaccharide (LPS) administration, which is known to inhibit the LH surge. Follicular phases of ewes were synchronised by progesterone withdrawal and blood samples were collected every 2 h. Hypothalamic tissue was retrieved at various times during the follicular phase with or without the administration of LPS (100 ng/kg). The percentage of activated dopamine cells decreased before the onset of sexual behaviour, whereas activation of β-endorphin decreased and NPY activation tended to increase during the LH surge. These patterns were not disturbed by LPS administration. Maximal co-expression of c-Fos in dynorphin immunoreactive neurons was observed earlier during the follicular phase, compared to kisspeptin and NKB, which were maximally activated during the surge. This indicates a distinct role for ARC dynorphin in the LH surge generation mechanism. Acute LPS decreased the percentage of activated dynorphin and kisspeptin immunoreactive cells. Thus, in the ovary-intact ewe, KNDy neurones are activated prior to the LH surge onset and this pattern is inhibited by the administration of LPS

Activation of Cells Containing Estrogen Receptor Alpha or Somatostatin in the Medial Preoptic Area, Arcuate Nucleus, and Ventromedial Nucleus of Intact Ewes During the Follicular Phase, and Alteration after Lipopolysaccharide

Cells in the medial preoptic area (mPOA), arcuate nucleus (ARC), and ventromedial nucleus (VMN) that possess estrogen receptor alpha (ER alpha) mediate estradiol feedback to regulate endocrine and behavioral events during the estrous cycle. A percentage of ER alpha cells located in the ARC and VMN express somatostatin (SST) and are activated in response to estradiol. The aims of the present study were to investigate the location of c-Fos, a marker for activation, in cells containing ER alpha or SST at various times during the follicular phase and to determine whether lipopolysaccharide (LPS) administration, which leads to disruption of the luteinizing hormone (LH) surge, is accompanied by altered ER alpha and/or SST activation patterns. Follicular phases were synchronized with progesterone vaginal pessaries, and control animals were killed at 0, 16, 31, and 40 h (n = 4–6/group) after progesterone withdrawal (PW [time 0]). At 28 h, other animals received LPS (100 ng/kg) and were subsequently killed at 31 h or 40 h (n = 5/group). Hypothalamic sections were immunostained for c-Fos and ER alpha or SST. LH surges occurred only in control ewes with onset at 36.7 ± 1.3 h after PW; these animals had a marked increase in the percentage of ER alpha cells that colocalized c-Fos (%ER alpha/c-Fos) in the ARC and mPOA from 31 h after PW and throughout the LH surge. In the VMN, %ER alpha/c-Fos was higher in animals that expressed sexual behavior than in those that did not. SST cell activation in the ARC and VMN was greater during the LH surge than in other stages in the follicular phase. At 31 or 40 h after PW (i.e., 3 or 12 h after treatment, respectively), LPS decreased %ER alpha/c-Fos in the ARC and the mPOA, but there was no change in the VMN compared to that in controls. The %SST/c-Fos increased in the VMN at 31 h after PW (i.e., 3 h after LPS) with no change in the ARC compared to controls. These results indicate that there is a distinct temporal pattern of ER alpha cell activation in the hypothalamus during the follicular phase, which begins in the ARC and mPOA at least 6–7 h before the LH surge onset and extends to the VMN after the onset of sexual behavior and LH surge. Furthermore, during the surge, some of these ER alpha-activated cells may be SST-secreting cells. This pattern is markedly altered by LPS administered during the late follicular phase, indicating that the disruptive effects of this stressor are mediated by suppressing ER alpha cell activation at the level of the mPOA and ARC and enhancing SST cell activation in the VMN, leading to the attenuation of the LH surge

Kisspeptin, c-Fos and CRFR type 2 expression in the preoptic area and mediobasal hypothalamus during the follicular phase of intact ewes, and alteration after LPS

Increasing estradiol concentrations during the late follicular phase stimulate sexual behavior and the GnRH/LH surge, and it is known that kisspeptin signaling is essential for the latter. Administration of LPS can block these events, but the mechanism involved is unclear. We examined brain tissue from intact ewes to determine: i) which regions are activated with respect to sexual behavior, the LH surge and LPS administration, ii) the location and activation pattern of kisspeptin cells in control and LPS treated animals, and iii) whether CRFR type 2 is involved in such disruptive mechanisms. Follicular phases were synchronized with progesterone vaginal pessaries and control animals were killed at 0 h, 16 h, 31 h or 40 h (n = 4–6/group) after progesterone withdrawal (time zero). At 28 h, other animals received endotoxin (LPS; 100 ng/kg) and were subsequently killed at 31 h or 40 h (n = 5/group). LH surges only occurred in control ewes, during which there was a marked increase in c-Fos expression within the ventromedial nucleus (VMN), arcuate nucleus (ARC), and medial preoptic area (mPOA), as well as an increase in the percentage of kisspeptin cells co-expressing c-Fos in the ARC and mPOA compared to animals sacrificed at all other times. Expression of c-Fos also increased in the bed nucleus of the stria terminalis (BNST) in animals just before the expected onset of sexual behavior. However, LPS treatment increased c-Fos expression within the VMN, ARC, mPOA and diagonal band of broca (dBb), along with CRFR type 2 immunoreactivity in the lower part of the ARC and median eminence (ME), compared to controls. Furthermore, the percentage of kisspeptin cells co-expressing c-Fos was lower in the ARC and mPOA. Thus, we hypothesize that in intact ewes, the BNST is involved in the initiation of sexual behavior while the VMN, ARC, and mPOA as well as kisspeptin cells located in the latter two areas are involved in estradiol positive feedback only during the LH surge. By contrast, disruption of sexual behavior and the LH surge after LPS involves cells located in the VMN, ARC, mPOA and dBb, as well as cells containing CRFR type 2 in the lower part of the ARC and ME, and is accompanied by inhibition of kisspeptin cell activation in both the ARC and mPOA

A Gravitational Redshift Determination of the Mean Mass of White Dwarfs. DBA and DB Stars

We measure apparent velocities (v_app) of absorption lines for 36 white dwarfs (WDs) with helium-dominated atmospheres -- 16 DBAs and 20 DBs -- using optical spectra taken for the European Southern Observatory SN Ia progenitor survey (SPY). We find a difference of 6.9+/-6.9 km/s in the average apparent velocity of the H-alpha lines versus that of the HeI 5876AA for our DBAs. This is a measure of the blueshift of this He line due to pressure effects. By using this as a correction, we extend the gravitational redshift method employed by Falcon et al. (2010) to use the apparent velocity of the HeI 5876AA line and conduct the first gravitational redshift investigation of a group of WDs without visible hydrogen lines. We use biweight estimators to find an average apparent velocity, _BI, (and hence average gravitational redshift, _BI) for our WDs; from that we derive an average mass, _BI. For the DBAs, we find _BI = 40.8+/-4.7 km/s and derive _BI = 0.71 +0.04 -0.05 Msun. Though different from of DAs (32.57 km/s) at the 91% confidence level and suggestive of a larger DBA mean mass than that for normal DAs derived using the same method (0.647 +0.013 -0.014 Msun; Falcon et al. 2010), we do not claim this as a stringent detection. Rather, we emphasize that the difference between _BI of the DBAs and of normal DAs is no larger than 9.2 km/s, at the 95% confidence level; this corresponds to roughly 0.10 Msun. For the DBs, we find ^He_BI = 42.9+/-8.49 km/s after applying the blueshift correction and determine _BI = 0.74 +0.08 -0.09 Msun. The difference between ^He_BI of the DBs and of DAs is less than or equal to 11.5 km/s (~0.12 Msun), at the 95% confidence level. The gravitational redshift method indicates much larger mean masses than the spectroscopic determinations of the same sample by Voss et al. (2007)...Comment: Accepted to the Astrophysical Journal, 10 pages double-column, 3 figures, 5 table

Interstellar absorptions and shocked clouds towards supernova remnant RX J0852.0-4622

We present results of survey of interstellar absorptions towards supernova remnant (SNR) RX J0852.0-4622. The distribution of KI absorbers along the distance of the background stars is indicative of a local region (d<600pc) strongly depopulated by KI line-absorbing clouds. This fact is supported by the behavior of the interstellar extinction. We find four high-velocity CaII components with velocities of >100km/s towards three stars and identify them with shocked clouds of Vela SNR. We reveal and measure acceleration of two shocked clouds at the approaching and receding sides of Vela SNR along the same sight line. The clouds acceleration, velocity, and CaII column density are used to probe cloud parameters. The total hydrogen column density of both accelerating clouds is found to be similar (~6*10^{17} cm$^{-2}$) which indicates that possibly there is a significant amount of small-size clouds in the vicinity of Vela SNR.Comment: accepted in MNRA

Do Damped and Sub-damped Lyman-alpha Absorbers Arise in Galaxies of Different Masses?

We consider the questions of whether the damped Lyman-alpha (DLA) and sub-DLA absorbers in quasar spectra differ intrinsically in metallicity, and whether they could arise in galaxies of different masses. Using the recent measurements of the robust metallicity indicators Zn and S in DLAs and sub-DLAs, we confirm that sub-DLAs have higher mean metallicities than DLAs, especially at $z \lesssim 2$. We find that the intercept of the metallicity-redshift relation derived from Zn and S is higher than that derived from Fe by 0.5-0.6 dex. We also show that, while there is a correlation between the metallicity and the rest equivalent width of Mg II $\lambda 2796$ or Fe II $\lambda 2599$ for DLAs, no correlation is seen for sub-DLAs. Given this, and the similar Mg II or Fe II selection criteria employed in the discovery of both types of systems at lower redshifts, the difference between metallicities of DLAs and sub-DLAs appears to be real and not an artefact of selection. This conclusion is supported by our simulations of Mg II $\lambda 2796$ and Fe II $\lambda 2599$ lines for a wide range of physical conditions. On examining the velocity spreads of the absorbers, we find that sub-DLAs show somewhat higher mean and median velocity spreads ($\Delta v$), and an excess of systems with $\Delta v > 150$ km s$^{-1}$, than DLAs. Compared to DLAs, the [Mn/Fe] vs. [Zn/H] trend for sub-DLAs appears to be steeper and closer to the trend for Galactic bulge and thick disk stars, possibly suggesting different stellar populations. The absorber data appear to be consistent with galaxy down-sizing. The data are also consistent with the relative number densities of low-mass and high-mass galaxies. It is thus plausible that sub-DLAs arise in more massive galaxies on average than DLAs.Comment: 27 pages, 5 figures, 4 tables. Accepted for publication in New Astronom

An absorption-selected survey of neutral gas in the Milky Way halo

We aim at analysing systematically the distribution and physical properties of neutral and mildly ionised gas in the Milky Way halo, based on a large absorption-selected data set. Multi-wavelength studies were performed combining optical absorption line data of CaII and NaI with follow-up HI 21-cm emission line observations along 408 sight lines towards low- and high-redshift QSOs. We made use of archival optical spectra obtained with UVES/VLT. HI data were extracted from the Effelsberg-Bonn HI survey and the Galactic All-Sky survey. For selected sight lines we obtained deeper follow-up observations using the Effelsberg 100-m telescope. CaII (NaI) halo absorbers at intermediate and high radial velocities are present in 40-55% (20-35%) of the sightlines, depending on the column density threshold chosen. Many halo absorbers show multi-component absorption lines, indicating the presence of sub-structure. In 65% of the cases, absorption is associated with HI 21-cm emission. The CaII (NaI) column density distribution function follows a power-law with a slope of -2.2 (-1.4). Our absorption-selected survey confirms our previous results that the Milky Way halo is filled with a large number of neutral gas structures whose high column density tail represents the population of common HI high- and intermediate-velocity clouds seen in 21-cm observations. We find that CaII/NaI column density ratios in the halo absorbers are typically smaller than those in the Milky Way disc, in the gas in the Magellanic Clouds, and in damped Lyman-alpha systems. The small ratios (prominent in particular in high-velocity components) indicate a lower level of Ca depletion onto dust grains in Milky Way halo absorbers compared to gas in discs and inner regions of galaxies.Comment: 17 pages, 20 figures, accepted by A&

Is the Sun Embedded in a Typical Interstellar Cloud?

The physical properties and kinematics of the partially ionized interstellar material near the Sun are typical of warm diffuse clouds in the solar vicinity. The interstellar magnetic field at the heliosphere and the kinematics of nearby clouds are naturally explained in terms of the S1 superbubble shell. The interstellar radiation field at the Sun appears to be harder than the field ionizing ambient diffuse gas, which may be a consequence of the low opacity of the tiny cloud surrounding the heliosphere. The spatial context of the Local Bubble is consistent with our location in the Orion spur.Comment: "From the Outer Heliosphere to the Local Bubble", held at International Space Sciences Institute, October 200