Development of an equatorial carbonate platform across the Triassic-Jurassic boundary and links to global palaeoenvironmental changes (Musandam Peninsula, UAE/Oman)

The Triassic - Jurassic boundary is marked by one of the ‘big five’ mass extinctions of the Phanerozoic. This boundary event was accompanied by several carbon cycle pert urbations, potentially induced by the opening of the Central Atlantic and associated volcanism, and accompanied by an ocean acidification event. Continuous carbonate successions covering this interval of environmental change are however rare. Here data fro m a shallow - marine equatorial mixed carbonate - siliciclastic succession is presented, that was studied on a regional scale. Four sections that are 48 km apart were examined on the Musandam Peninsula (United Arab Emirates and Sultanate of Oman). The system w as analysed for its sedimentology, vertical and lateral facies changes, and stable carbon and oxygen isotopes. Strontium isotope analysis was used to determine the position of the Triassic - Jurassic boundary horizon. The studied ramp experienced an episode of demise during the Late Triassic, followed by a restricted microbialite dominated ramp, containing large amounts of siliciclastic facies. During the Latest Triassic the diverse carbonate factory revived and flourished across the Triassic - Jurassic boundar y. No clear evidence for a biocalcification crisis or an ocean acidification event across the Triassic - Jurassic boundary is visible. Lateral facies heterogeneities can be observed across the studied interval, attributed to hydrodynamic activity, including tropical storms, crossing the extensive shelf area. Although evidence for synsedimentary tectonic activity is present, the vertical stacking pattern is largely controlled by changes in relative sea level. The refined chronostratigraphy accompanied by the d etailed environment of deposition analysis allows for a refinement of the regional palaeogeography. The neritic equatorial carbonate ramp has archived a negative carbon isotope excursion preceding the Triassic - Jurassic boundary that has also been reported from other study sites. The lack of evidence for a biocalcification crisis across the equatorial Triassic - Jurassic boundary indicates that the Tethys did not experience a distinct global acidification event

Learning-Focused Leadership and Leadership Support: Meaning and Practice in Urban Systems

Synthesizes three reports on what good education leadership means and how it can best be supported, including the role of the school leader and the transformation of central district offices to focus more on improving instruction. Outlines key practices

Churn: The High Cost of Principal Turnover

This new report challenges the myth that developing a strong principal pipeline is where America should be focused. CHURN reveals the multitude of signicant impacts principal turnover has on schools and school systems -- including teachers and students, and highlights the cost implications of a typical system in churn. This report shows that investing in the backend of principal retention will carry front-end pipeline investments much further, proposing specific solutions to reverse the current flood of leadership out the door

Older Women: Pushed into Retirement by the Baby Boomers?

Older women's patterns of labor supply over the past forty years have differed markedly from those of younger women. Their labor force participation declined sharply during a period of rapid increase for younger women, and then increased significantly while younger women's plateaued and even declined. But there has been an apparent correspondence between the pattern of retirement among women aged 55-69, and the proportion of workers aged 25-34 working part-year and/or part-time. The latter was an effect of overcrowding among the baby boomers as they moved through the labor market. The former is hypothesized here to be a function of the increasing difficulty older women experienced in obtaining "bridge jobs" – part-year and/or part-time – between career and retirement. It has been demonstrated in earlier studies that older women – especially those in lower-wage jobs – often seek such bridge jobs before retirement. And in many cases these bridge jobs are not in the same industry or even occupation as the career job, leading one to suspect that in many cases there might be little transfer of skill or human capital. If this is the case, then the older workers would at least to some extent be in direct competition with younger workers for these jobs. Given difficulty in finding bridge jobs, a higher proportion of older workers might choose to enter retirement directly from career jobs, skipping the bridge jobs. A relative cohort size measure – the number of 25-34 year old women working part-year and/or part-time, relative to the number of older women, at the state level – has been shown here to be highly significant – both statistically and substantively – in explaining changes in older women's annual hours worked, labor force participation, and propensity to retire. In general terms, relative cohort size can be said to have generated between 15-30% of the observed changes in these variables, with the strongest effects being on the propensity to claim Social Security benefits. Somewhat stronger effects were found for older men, in a companion to this study.retirement, women's labor supply, labor force participation, relative cohort size, relative wage, part-time employment, bridge jobs, baby boom

Central limit theorem for signal-to-interference ratio of reduced rank linear receiver

Let $\mathbf{s}_k=\frac{1}{\sqrt{N}}(v_{1k},...,v_{Nk})^T,$ with $\{v_{ik},i,k=1,...\}$ independent and identically distributed complex random variables. Write $\mathbf{S}_k=(\mathbf{s}_1,...,\mathbf {s}_{k-1},\mathbf{s}_{k+1},... ,\mathbf{s}_K),$ $\mathbf{P}_k=\operatorname {diag}(p_1,...,p_{k-1},p_{k+1},...,p_K)$, $\mathbf{R}_k=(\mathbf{S}_k\mathbf{P}_k\mathbf{S}_k^*+\sigma ^2\mathbf{I})$ and $\mathbf{A}_{km}=[\mathbf{s}_k,\mathbf{R}_k\mathbf{s}_k,... ,\mathbf{R}_k^{m-1}\mathbf{s}_k]$. Define $\beta_{km}=p_k\mathbf{s}_k^*\mathbf{A}_{km}(\mathbf {A}_{km}^*\times\ mathbf{R}_k\mathbf{A}_{km})^{-1}\mathbf{A}_{km}^*\mathbf{s}_k$, referred to as the signal-to-interference ratio (SIR) of user$k$under the multistage Wiener (MSW) receiver in a wireless communication system. It is proved that the output SIR under the MSW and the mutual information statistic under the matched filter (MF) are both asymptotic Gaussian when$N/K\to c>0$. Moreover, we provide a central limit theorem for linear spectral statistics of eigenvalues and eigenvectors of sample covariance matrices, which is a supplement of Theorem 2 in Bai, Miao and Pan [Ann. Probab. 35 (2007) 1532--1572]. And we also improve Theorem 1.1 in Bai and Silverstein [Ann. Probab. 32 (2004) 553--605].Comment: Published in at http://dx.doi.org/10.1214/07-AAP477 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Evidence for mass renormalization in LaNiO$"" sub 3_: an in situ soft x-ray photoemission study of epitaxial films

We investigate the electronic structure of high-quality single-crystal LaNiO$_3$ (LNO) thin films using in situ photoemission spectroscopy (PES). The in situ high-resolution soft x-ray PES measurements on epitaxial thin films reveal the intrinsic electronic structure of LNO. We find a new sharp feature in the PES spectra crossing the Fermi level, which is derived from the correlated Ni 3$d$ $e_g$ electrons. This feature shows significant enhancement of spectral weight with decreasing temperature. From a detailed analysis of resistivity data, the enhancement of spectral weight is attributed to increasing electron correlations due to antiferromagnetic fluctuations.Comment: 4 pages, 4 figures. submitted to Phys. Rev.