Aircraft and satellite measurement of ocean wave directional spectra using scanning-beam microwave radars

A microwave radar technique for remotely measuring the vector wave number spectrum of the ocean surface is described. The technique, which employs short-pulse, noncoherent radars in a conical scan mode near vertical incidence, is shown to be suitable for both aircraft and satellite application, the technique was validated at 10 km aircraft altitude, where we have found excellent agreement between buoy and radar-inferred absolute wave height spectra

Radiocarbon dates from the Oxford AMS system: archaeometry datelist 35

This is the 35th list of AMS radiocarbon determinations measured at the Oxford Radiocarbon Accelerator Unit (ORAU). Amongst some of the sites included here are the latest series of determinations from the key sites of Abydos, El Mirón, Ban Chiang, Grotte de Pigeons (Taforalt), Alepotrypa and Oberkassel, as well as others dating to the Palaeolithic, Mesolithic and later periods. Comments on the significance of the results are provided by the submitters of the material

Experiments with a Slow Neutron Velocity Spectrometer

Neutron bursts were produced by modulation of the arc source of a small cyclotron. Neutrons subsequently slowed down in paraffin were detected by a BF_3 ionization chamber and linear amplifier. Modulation of an additional amplifier allowed the counting of all detected neutrons as well as those arriving in a specified time interval. Time of flight experiments were carried out at 3.0 meters with "on" times of 50 or 100 μsec. (microseconds) out of a period of 2500 μsec. The modulation of the source and detector was accurate to about 5 μsec. The absorption of thin Cd (0.052 g/cm^2) shows a resolved resonance absorption with maximum at 0.14 ev. The thick Cd (0.45 g/cm^2) absorption was also examined and it was found that the absorption edge was not sharp, the transmission being 0.5 at 0.47 ev. Experiments with thick absorbers of Rh and In showed definite evidence of resonance absorption at 1.0 ev for both elements. Experiments were also carried out to study the delayed emission of thermal neutrons from the paraffin surrounding the source. An effective mean life of 170 μsec. was found. The effect of the resolution of the apparatus was examined and found to be small except for the resonances at 1.0 ev. The effect of the delayed emission of thermal neutrons on the time of flight measurements was also examined. From the thin Cd absorption curve T, the total width of the resonance level, was found to be 0.12 ev and from the cross section at resonance [1±(1/2i+1)]Γn, where Γn is the neutron width and i is the angular momentum of the absorbing nucleus, it was found to be 5×10^(−4) ev. In this calculation 13 percent abundance of the effective isotope was assumed

The phase transition in the localized ferromagnet EuO probed by muSR

We report results of muon spin rotation measurements performed on the ferromagnetic semiconductor EuO, which is one of the best approximations to a localized ferromagnet. We argue that implanted muons are sensitive to the internal field primarily through a combination of hyperfine and Lorentz fields. The temperature dependences of the internal field and the relaxation rate have been measured and are compared with previous theoretical predictions.Comment: 4 pages, 4 figure

On the establishment of a mutant

How long does it take for an initially advantageous mutant to establish itself in a resident population, and what does the population composition look like then? We approach these questions in the framework of the so called Bare Bones evolution model Klebaner et al (2011) that provides a simplified approach to the adaptive population dynamics of binary splitting cells. As the mutant population grows, cell division becomes less probable, and it may in fact turn less likely than that of residents. Our analysis rests on the assumption of the process starting from resident population, with sizes proportional to a large carrying capacity $K$. Actually, we assume carrying capacities to be $a_1K$ and $a_2K$ for the resident and the mutant populations, respectively, and study the dynamics for $K\to\infty$. We find conditions for the mutant to be successful in establishing itself alongside the resident. The time it takes turns out to be proportional to $\log K$. We introduce the time of establishment through the asymptotic behavior of the stochastic nonlinear dynamics describing the evolution, and show that it is indeed $\log K/\log \rho$, where $\rho>1$ is twice the probability of successful division of the mutant at its appearance. Looking at the composition of the population, at times $\log K/\log \rho +n, n \in \mathbb{Z}_+$, we find that the densities (i.e. sizes relative to carrying capacities) of both populations follow closely the corresponding two dimensional nonlinear deterministic dynamics that starts at {\it a random point}. We characterise this random initial condition in terms of the scaling limit of the corresponding dynamics, and the limit of the properly scaled initial binary splitting process of the mutant. The deterministic approximation with random initial condition is in fact valid asymptotically at all times $\log K/\log \rho +n$ with $n\in \mathbb{Z}$

Constraints and subsequent limitations to parental involvement in primary schools in Abu Dhabi: stakeholders' perspective

The United Arab Emirates (UAE) is developing its public schools by initiating reform agendas for school improvement. High on the list of reforms is the call to increase parental involvement in schools. For this reform to work successfully, it is important to identify and examine the constraints and subsequent limitations that exist. Seven primary Public, Private Partnership schools (PPP) in Abu Dhabi were the focus of this qualitative case study. Participants were school stakeholders: school administrators, social workers, teachers and parents. The findings will assist in developing continuing policies and practices which take these limitations into account and work to mitigate them. Recommendations are made based within the context of the findings

Thermodynamic and magnetic properties of the layered triangular magnet NaNiO2

We report muon-spin rotation, heat capacity, magnetization, and ac magnetic susceptibility measurements of the layered spin-1/2 antiferromagnet NaNiO2. These show the onset of long-range magnetic order below T_N = 19.5K. Rapid muon depolarization persisting to about 5K above T_N is consistent with the presence of short-range magnetic order. The temperature and frequency dependence of the ac susceptibility suggests that magnetic clusters persist above 25K in the paramagnetic state and that their volume fraction decreases with increasing temperature. A frequency dependent peak in the ac magnetic susceptibility at T_sf = 3K is observed, consistent with a slowing of spin fluctuations at this temperature. A partial magnetic phase diagram is deduced.Comment: 4 pages, 4 figure