Faint Blue Galaxies as a Probe of the X-ray Background at High Redshift

We present a formalism describing the physical content of cross-correlation functions between a diffuse background and a population of discrete sources. The formalism is used to interpret cross-correlation signals between the unresolved X-ray background and a galaxy population resolved to high redshift in another spectral band. Specifically, we apply it to the so-called faint blue galaxy population and constrain their X-ray emissivity and clustering properties. A model is presented which satisfies the recently measured constraints on all 3 correlation functions (galaxy/galaxy, background/background and galaxy/background). This model predicts that faint galaxies in the magnitude range B=18-23 (cvering redshifts z \lsim 0.5) make up $\sim 22 \%$ of the X-ray background in the 0.5-2 keV band. At the mean redshift of the galaxy sample, $\bar z=0.26$, the comoving volume emissivity is $\rho_X \sim 6-9 \times 10^{38}h$ ergs s$^{-1}$Mpc$^{-3}$ . When extrapolated to fainter magnitudes, the faint blue galaxy population can account for most of the residual background at soft energy. We show how the measurement of the angular and zero-lag cross-correlation functions between increasingly faint galaxies and the X-ray background can allow us to map the X-ray emissivity as a function of redshift.Comment: uuencoded compressed postscript, without figures. The preprint is available with figures at http://www.ast.cam.ac.uk/preprint/PrePrint.htm

The X-Ray Background as a Probe of Density Fluctuations at High Redshift

The X-Ray Background (XRB) probes structure on scales intermediate between those explored by local galaxy redshift surveys and by the COBE Microwave Background measurements. We predict the large scale angular fluctuations in the XRB, expressed in terms of spherical harmonics for a range of assumed power-spectra and evolution scenarios. The dipole is due to large scale structure as well as to the observer's motion (the Compton-Getting effect). For a typical observer the two effects turn out to be comparable in amplitude. The coupling of the two effects makes it difficult to use the XRB for independent confirmation of the CMB dipole being due to the observer's motion. The large scale structure dipole (rms per component) relative to the monopole is in the range $a_{1m}/a_{00} \sim (0.5-9.0) \times 10^{-3}$. The spread is mainly due to the assumed redshift evolution scenarios of the X-ray volume emissivity $\rho_x(z)$. The dipole's prediction is consistent with a measured dipole in the HEAO1 XRB map. Typically, the harmonic spectrum drops with $l$ like $a_{lm} \sim l^{-0.4}$. This behaviour allows us to discriminate a true clustering signal against the flux shot noise, which is constant with $l$, and may dominate the signal unless bright resolved sources are removed from the XRB map. We also show that Sachs-Wolfe and Doppler (due to the motion of the sources) effects in the XRB are negligible. Although our analysis focuses on the XRB, the formalism is general and can be easily applied to other cosmological backgrounds.Comment: 14 pages, 3 postscript figures, available from ftp://cass41.ast.cam.ac.uk/pub/lahav/xrb accepted for publication in MNRA

A failure in consensus or a successful advocacy strategy?

Initiated in 2002 by the World Bank and the Food and Agriculture Organization (FAO), the International Assessment of Agricultural Knowledge, Science and Technology for Development (IAASTD, www.agassessment.org) is an interesting experience of an international expertise process aiming at improving global governance for sustainable development. It aimed to understand how agricultural knowledge, technologies and sciences could contribute to reduce hunger and poverty, improve rural livelihoods and at the same time reach environmental objectives. It involved the large mobilization of international scientific expertise, but also the participation of a diversity of stakeholders, and a validation of reports by an intergovernmental plenary. The design of the process was inspired by other global assessments like the IPCC and the Millennium Ecosystem Assessment. Among these international assessments, IAASTD is particularly important as its focus on agriculture necessarily puts the stress on trade-offs and synergies between social and environmental implications of development. Assessing if and how IAASTD managed to reach its objectives will prove useful for other assessment processes, particularly in order to understand how social and economical controversies at the heart of the debate on sustainable development might be structured and dealt with by international expertise processes. Regarding the initial objectives of this assessment and its participatory approach, many analysts criticize IAASTD because it did not reach a consensus among all stakeholders. In this paper, we propose to consider also the alternative perspective of analysis, where this assessment serves an advocacy strategy for a new approach of global agriculture. In this alternative perspective, IAASTD can be considered successful. We also propose to consider that the difference between the two analytical frameworks can be useful in order to re-analyze recommendations for global assessments, and to reopen the diversity of the roles that expertise might play in global debates about environment and development where controversies are central

Molecular mechanisms controlling the phenotype and the EMT/MET dynamics of hepatocyte

The complex spatial and paracrine relationships between the various liver histotypes are essential for proper functioning of the hepatic parenchymal cells. Only within a correct tissue organization, in fact, they stably maintain their identity and differentiated phenotype. The loss of histotype identity, which invariably occurs in the primary hepatocytes in culture, or in vivo in particular pathological conditions (fibrosis and tumors), is mainly due to the phenomenon of epithelial-to-mesenchymal transition (EMT). The EMT process, that occurs in the many epithelial cells, appears to be driven by a number of general, non- tissue-specific, master transcriptional regulators. The reverse process, the mesenchymal-to epithelial transition (MET), as yet much less characterized at a molecular level, restores specific epithelial identities, and thus, must include tissue-specific master elements. In this review, we will summarize the so far unveiled events of EMT/MET occurring in liver cells. In particular, we will focus on hepatocyte and describe the pivotal role in the control of EMT/MET dynamics exerted by a tissue-specific molecular mini-circuitry. Recent evidence, indeed, highlighted as two transcriptional factors, the master gene of EMT Snail, and the master gene of hepatocyte differentiation HNF4α, exhorting a direct reciprocal repression, act as pivotal elements in determining opposite cellular outcomes. The different balances between these two master regulators, further integrated by specific microRNAs, in fact, were found responsible for the EMT/METs dynamics as well as for the preservation of both hepatocyte and stem/precursor cells identity and differentiation. Overall these findings impact the maintenance of stem cells and differentiated cells both in in vivo EMT/MET physio-pathological processes as well as in culture.The complex spatial and paracrine relationships between the various liver histotypes are essential for proper functioning of the hepatic parenchymal cells. Only within a correct tissue organization, in fact, they stably maintain their identity and differentiated phenotype. The loss of histotype identity, which invariably occurs in the primary hepatocytes in culture, or in vivo in particular pathological conditions (fibrosis and tumors), is mainly due to the phenomenon of epithelial-to-mesenchymal transition (EMT). The EMT process, that occurs in the many epithelial cells, appears to be driven by a number of general, non- tissue-specific, master transcriptional regulators. The reverse process, the mesenchymal-to epithelial transition (MET), as yet much less characterized at a molecular level, restores specific epithelial identities, and thus, must include tissue-specific master elements. In this review, we will summarize the so far unveiled events of EMT/MET occurring in liver cells. I

Wirkung der Blutegeltherapie auf die Schmerzintensität bei Patienten mit Arthrose: systematische Literaturübersicht

Problembeschreibung: Arthrose ist ein Krankheitsbild, welches weltweit verbreitet ist. Ab dem 65 Lebensjahr, sind bis zu 90% der Menschen von Arthrose betroffen. Zum jetzigen Zeitpunkt gilt die Arthrose als unheilbar. Deshalb ist das vorrangige Ziel der Therapie und Behandlung, die Symptome zu kontrollieren. Zentrales Problem der Arthrosepatienten ist der Schmerz, welcher zu einer eingeschränkten Beweglichkeit führt und viele Lebensbereiche beeinflusst. Die Pflege übernimmt eine wichtige Rolle bei der effizienten und sicheren Schmerzbehandlung. Hierbei wird auf eine grosse Palette von Interventionsmöglichkeiten zurückgegriffen. Eine dieser Intervention ist die Anwendung der Blutegeltherapie. Ziel: Das Ziel der vorliegenden systematischen Literaturübersicht ist es, den aktuellen Forschungsstand bezüglich der Wirkung der Blutegeltherapie auf die Schmerzintensität bei Patienten mit Arthrose aufzuzeigen. Dadurch soll Pflegefachpersonen neue Erkenntnisse über eine ergänzende Pflegemassnahme bei Arthrose aufgezeigt werden. Methode: Zur Beantwortung der Forschungsfrage wurde eine systematische Literaturübersicht erstellt. In den pflegerelevanten Datenbanken Cochrane, PubMed und Cinahl wurde durch eine systematische Suche über mehrere Monate nach relevanter Literatur gesucht. Anhand definierter Auswahlkriterien konnten schlussendlich acht passende Studien in die Analyse eingeschlossen und die Ergebnisse diskutiert und verglichen werden. Ergebnisse: In allen acht Studien wurde ein positiver Effekt der Blutegeltherapie auf die Schmerzintensität bei Patienten mit Arthrose nachgewiesen werden. In sieben Studien konnte eine signifikante Minderung der Schmerzintensität auf der visuellen Analog Skala (VAS) festgestellt werden (Tag0: VAS=59.6mm, Tag7: VAS=27.1mm , p=0.0003). Zusätzlich zur VAS konnte in einer Studie auf dem Lequesne-Index und bei einer weiteren Studie auf dem WOMAC-Score eine signifikante Reduktion der Schmerzintensität beobachtet werden. Ein deutlicher Rückgang der Schmerzintensität konnte zudem bei einer Studie auf der numerischen Rangskala (NRS) erfasst werden. Weitere signifikante Effekte durch die Blutegeltherapie konnten in der Minderung der Steifheit, der Verbesserung der Gelenkfunktion, in der Steigerung der Mobilität, sowie in der Verbesserung der Lebensqualität und der Medikamentenreduktion gemessen werden. Schlussfolgerungen: Die Anwendung der Blutegeltherapie ist eine wirksame Therapie zur Minderung der Schmerzintensität bei Patienten mit Arthrose, welche nur wenige Nebenwirkungen aufzeigt. Zusätzlich können signifikante Ergebnisse in Bezug auf weitere Arthrosesymptome aufgedeckt werden. Die Blutegeltherapie sollte in die Pflegepraxis integriert werden, wobei Pflegefachpersonen im Umgang mit Blutegeln und Schmerzeinschätzungsinstrumenten geschult werden sollten. Zukünftige Forschungen in verschiedenen Ländern und durch verschiedene Autoren sind erforderlich, da zu diesem Forschungsthema aktuell noch wenig wissenschaftliche Forschungsliteratur vorhanden ist