A general test of the Copernican principle

To date, there has been no general way of determining if the Copernican principle--that we live at a typical position in the Universe--is in fact a valid assumption, significantly weakening the foundations of cosmology as a scientific endeavor. Here we present an observational test for the Copernican assumption which can be automatically implemented while we search for dark energy in the coming decade. Our test is entirely independent of any model for dark energy or theory of gravity and thereby represents a model-independent test of the Copernican principle.     

Virtual crystal approximation study of nitridosilicates and oxonitridoaluminosilicates

We present a density functional theory study of a variety of nitridosilicate and oxonitridoaluminosilicate systems. For the nitridosilicates, we have shown that the DFT-calculated equilibrium structures of BaYb-Si₄N₇, SrYb-Si₄N₇ and EuYb-Si₄N₇ are in good agreement with experiment. We then used the virtual crystal approximation (VCA) to study the effects of oxygen-doping on the nitrogen sites. We then added Si/Al disorder into our system, in order to model the properties of BaYb-SiAlON for pressures up to 50 GPa, in order to investigate recent experimental findings. We have found that this system is stable over the whole pressure range, and that the compression mechanism is pure bond length shortening.     

A two-stage process with temperature-shift for enhanced anthocyanin production in strawberry cell suspension cultures

A two-stage process with temperature-shift has been developed to enhance the anthocyanin yield in suspension cultures of strawberry cells. The effect of the temperature-shift interval and the shift-time point was investigated for the optimization of this strategy. In this process, strawberry cells were grown at 30℃ (the optimum temperature for cell growth) for a certain period as the first stage, with the temperature shifted to a lower temperature for the second stage. In response to the temperature shift-down, anthoeyanin synthesis was stimulated and a higher content could be achieved than that at both boundary temperatures but cell growth was suppressed. When the lower boundary temperature was deereased, cell growth was lowered and a delayed, sustained maximum anthocyanin content was achieved. Anthocyanin synthesis was strongly influeneed by the shift-time point but cell growth was not. Consequently, the maximum anthocyanin content of 2.7 mg(?)g-fresh cell~(-1) was obtained on day 9 by a temperature-     

Translating IΔ0 + exp Proofs into Weaker Systems

The purpose of this paper is to explore the relationship between IΔ₀ + exp and its weaker subtheories. We give a method of translating certain classes of IΔ₀ + exp proofs into weaker systems of arithmetic such as Buss' systems S₂. We show if IE_i (exp) ⊢ A with a proof P of expind‐rank(P) ≤ n + 1where all (∀ ≤: right) or (∃ ≤: left) have bounding terms not containing function symbols, then Sⁱ ₂ ⊇ IE_i,2 ⊢ Aⁿ. Here A is not necessarily a bounded formula. For IOpen(exp) we prove a similar result. Using our translations we show IOpen(exp) ⊊ IΔ₀(exp). Here IΔ₀(exp) is a conservative extension of IΔ₀ + exp obtained by adding to IΔ₀ a symbol for 2 ^x to the language as well as defining axioms for it.     

Materials analysis using confocal Raman microscopy

The recent development of Raman microscopes with high optical throughput and very sensitive CCD cameras has led to Raman spectroscopy again competing effectively with FTIR methods for materials analysis. Modern Raman instruments, designed to operate confocally without serious alignment or energy trade-off problems, allow depth profiling of optically transparent polymers and polymer matrices to be routinely obtained with a spatial resolution of 1–2 μm. The use of such an instrument is illustrated by describing recent work on polymeric material problems including, 1 The distribution and redistribution of small molecules in polymeric matrices. 2 The monitoring of adhesion primer diffusion at a polymer/silica interface. 3 The determination of the extent of interdiffusion and interaction at a polymer/polymer interface. 4 A comparison of confocal and micotoming approaches to polymer laminate analysis. The range of possible applications is increasing rapidly. It is clear that Raman microscopy will become a very important tool for future materials analysis, both in the polymer area and many other areas.