Chromatin Structure in the Cellular Slime Mold Dictyostelium discoideum

The structure of Dictyostelium discoideum chromatin has been studied by the following techniques: electron microscopy, staphylococcal nuclease digestion, acrylamide gel electrophoresis, sucrose gradient centrifugation, and melting. The basic unit of chromatin is the nucleosome, which is a particle 98.6 angstrom in diameter. Approximately 50% of the chromatin is protected from nuclease digestion, but this decreases when protease activity is not inhibited. The nucleosome contains 187 base pairs of DNA, including a 137-base-pair core and a 50-base-pair linker. The monomer nucleosome has an s20,w value of 11.5 S on isokinetic sucrose gradients. When the chromatin is melted, four transitions are observed, at 54.5 degrees, 66.7 degrees, 74.9 degrees, and 79.7 degrees. The structure of Dictyostelium chromatin is very similar to that seen in higher eukaryotes

An absorption tube for the investigation of gases in the photographic infrared

An absorption cell of novel design is described, which combines the advantages of long path and relatively small volume

Liquidity regulation and bank behavior

In response to the 2007-08 financial crisis, the Basel Committee on Banking Supervision proposed two liquidity standards to reinforce banks’ resilience to liquidity risks. The purpose of this thesis is to analyze the impact of liquidity regulation on bank behavior. The first of four main chapters analyzes the development of global liquidity standards, their objectives as well as their interaction with capital standards. The analysis suggests that regulating capital is associated with declining liquidity buffers. The interaction of liquidity regulation and monetary policy, the view that regulating capital also addresses liquidity risks as well as a lack of supervisory momentum were important factors hampering the harmonization of liquidity regulation. Chapter 3 takes a wide view on the impact of liquidity regulation on banks' liquidity management. The key question is whether the presence of liquidity regulation substitutes banks' incentives to hold liquid assets. The cross-country analysis suggests that most bank-specific and country-specific determinants of banks’ liquidity buffers are substituted by liquidity regulation while a bank's disclosure requirements become more important. The complementary nature of disclosure and liquidity requirements provides a strong rationale for considering them jointly in the design of regulation. Chapter 4 zooms in on one of the key questions regarding the interaction of the LCR with monetary policy transmission. The analysis shows that a liquidity requirement causes short-term and long-term interest rates as well as demand for long-term loans to increase. However, banks do not seem able to pass on the increased funding costs in the interbank market to their private sector clients. Rather, a liquidity requirement seems to decrease banks' interest margins, which might require central banks to use a representative real economy interest rate as additional target for monetary policy implementation. Chapter 5 is motivated by the European sovereign debt crisis and analyzes the impact of preferential regulatory treatment on banks’ demand for government bonds. The analysis suggests that preferential treatment in liquidity and capital regulation increases banks' demand for government bonds beyond their own risk appetite. Liquidity and capital regulation also seem to incentivize banks to substitute other bonds with government bonds. The thesis concludes with an epilogue on liquidity stress testing

Generalized Heisenberg Quantum Spin Chains (Invited)

Since the Heisenberg spin chain can be considered the simplest realistic model of magnetism, surprise and some degree of controversy have resulted from recent work of Haldane. The prediction is that quantum spin chains with half‐integer spin should all display T = 0 phase behavior equivalent to that of the Bethe Ansatz integrable (solvable) spin‐1/2 quantum chain. More remarkably, the class of integerspin chains is predicted to show very different phase behavior. In particular, a gap should be present in the spectrum of a Heisenberg antiferromagnetic chain. This remarkable feature is counterintuitive in terms of accepted wisdom in magnetism (spin‐wave theory, spin‐Peierls theory) and critical phenomena. Consequently the vertification of the prediction is of great interest. A considerable amount of numerical work has been done, involving finite‐chain, finite‐size scaling, variational, Monte Carlo and other calculations, which will be reviewed here. The present consensus is that the weight of numerical evidence supports the prediction, although puzzling features still remain. Adding additional interactions to the basic Heisenberg Hamiltonian such as spin (X X Z) anisotropy, single‐ion anisotropy, biquadratic exchange, and an applied magnetic field, generates a rich and complicated phase diagram for chains with spin \u3e1/2, particularly for the case of integer spin. The s = 1 phase diagram seems to display critical behavior of a type not previously encountered. A theoretical appraisal of the Haldane phenomenon will include a discussion of the possible role of nonintegrability. Mention will also be made of current progress in experimental investigation of the phenomenon, including problems that might be encountered. More recent work of Affleck has greatly generalized the field‐theoretic mappings which underlay the original work of Haldane. A number of interesting problems have been mapped into quantum spin chains of various types, including field theoretic phenomena and the localization problem of the quantum Hall effect

Crystal Structure and Magnetism of the Linear-Chain Copper Oxides Sr5Pb3-xBixCuO12

The title quasi-1D copper oxides (0=< x =<0.4) were investigated by neutron diffraction and magnetic susceptibility studies. Polyhedral CuO4 units in the compounds were found to comprise linear-chains at inter-chain distance of approximately 10 A. The parent chain compound (x = 0), however, shows less anisotropic magnetic behavior above 2 K, although it is of substantially antiferromagnetic (mu_{eff}= 1.85 mu_{B} and Theta_{W} = -46.4 K) spin-chain system. A magnetic cusp gradually appears at about 100 K in T vs chi with the Bi substitution. The cusp (x = 0.4) is fairly characterized by and therefore suggests the spin gap nature at Delta/k_{B} ~ 80 K. The chain compounds hold electrically insulating in the composition range.Comment: To be published in PR