A comparative study of the evolution of enzymes and nucleic acids Semiannual progress report, 1 May - 30 Nov. 1967

Immunological and enzymological approaches to evolution of enzymes and nucleic acid

Were Bush Tax Cut Supporters “Simply Ignorant?” A Second Look at Conservatives and Liberals in “Homer Gets a Tax Cut”

In a recent edition of Perspectives on Politics, Larry Bartels examines the high levels of support for tax cuts signed into law by President Bush in 2001. In so doing, he characterizes the opinions of “ordinary people” as being based on “simple-minded and sometimes misguided considerations of self interest” and concludes that “the strong plurality support for Bush’s tax cut...is entirely attributable to simple ignorance.” Our analysis of the same data reveals different results. We show that for a large and politically relevant class of respondents – people who describe themselves as “conservative” or “Republican” – increasing information levels increase support for the tax cuts to the extent that they have any affect at all. Indeed, using Bartels’ measure of political information, we show that the Republican respondents rated most informed supported the tax cuts at extraordinarily high levels (over 96%). For these citizens, Bartels’ claim that “better-informed respondents were much more likely to express negative views about the 2001 tax cut” is simply untrue. We then show that Bartels’ results depend on a very strong assumption about how information affects public opinion. He restricts all respondents -- whether liberal or conservative, Republican or Democrat – to respond to increasing information levels in identical ways. In other words, he assumes that if more information about the tax cut makes liberals less likely to support it, then conservatives must follow suit. This assumption is very presumptive about the policy and value trade- offs that different people should make. Our analysis, by contrast, allows people of different partisan or ideological identities to react to higher information levels in varying ways. This flexibility has many benefits, one of which is a direct test of Bartels’ restrictive assumption. We demonstrate that the assumption is untrue. Examined several ways, our findings suggest that much of the support for the tax cut was attributable to something other than “simple ignorance.” Bartels’ approach is based on a very strong presumption about how citizens should think and what they should think about. We advocate a different approach, one that takes questions of public policy seriously while respecting ideological and partisan differences in opinion and interest. Indeed, citizens have reasons for the opinions and interests they have. We may or may not agree with them. However, we, as social scientists, can contribute more by offering reliable explanations of these reasons than we can by judging them prematurely. By turning our attention to explaining differences of opinion, we can help to forge a stronger and more credible foundation for progress in meeting critical social needs.public opinion, tax policy, incomplete information, welfare economics

Weak Charge Quantization as an Instanton of Interacting sigma-model

Coulomb blockade in a quantum dot attached to a diffusive conductor is considered in the framework of the non-linear sigma-model. It is shown that the weak charge quantization on the dot is associated with instanton configurations of the Q-field in the conductor. The instantons have a finite action and are replica non--symmetric. It is argued that such instantons may play a role in the transition regime to the interacting insulator.Comment: 4 pages. The 2D case substantially modifie

Haemophilus influenzae type b and Streptococcus pneumoniae as causes of pneumonia among children in Beijing, China.

To determine if Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae could be identified more often from the nasopharynx of patients with pneumonia than from control patients, we obtained nasopharyngeal swab specimens from 96 patients with chest x-ray-confirmed pneumonia and 214 age-matched control patients with diarrhea or dermatitis from the outpatient department at Beijing Children's Hospital. Pneumonia patients were more likely to be colonized with Hib and S. pneumoniae than control patients, even after the data were adjusted for possible confounding factors such as day-care attendance, the presence of other children in the household, and recent antibiotic use. In China, where blood cultures from pneumonia patients are rarely positive, the results of these nasopharyngeal cultures provide supporting evidence for the role of Hib and S. pneumoniae as causes of childhood pneumonia

Exact renormalization-group analysis of first order phase transitions in clock models

We analyze the exact behavior of the renormalization group flow in one-dimensional clock-models which undergo first order phase transitions by the presence of complex interactions. The flow, defined by decimation, is shown to be single-valued and continuous throughout its domain of definition, which contains the transition points. This fact is in disagreement with a recently proposed scenario for first order phase transitions claiming the existence of discontinuities of the renormalization group. The results are in partial agreement with the standard scenario. However in the vicinity of some fixed points of the critical surface the renormalized measure does not correspond to a renormalized Hamiltonian for some choices of renormalization blocks. These pathologies although similar to Griffiths-Pearce pathologies have a different physical origin: the complex character of the interactions. We elucidate the dynamical reason for such a pathological behavior: entire regions of coupling constants blow up under the renormalization group transformation. The flows provide non-perturbative patterns for the renormalization group behavior of electric conductivities in the quantum Hall effect.Comment: 13 pages + 3 ps figures not included, TeX, DFTUZ 91.3

Unfolding cross-linkers as rheology regulators in F-actin networks

We report on the nonlinear mechanical properties of a statistically homogeneous, isotropic semiflexible network cross-linked by polymers containing numerous small unfolding domains, such as the ubiquitous F-actin cross-linker Filamin. We show that the inclusion of such proteins has a dramatic effect on the large strain behavior of the network. Beyond a strain threshold, which depends on network density, the unfolding of protein domains leads to bulk shear softening. Past this critical strain, the network spontaneously organizes itself so that an appreciable fraction of the Filamin cross-linkers are at the threshold of domain unfolding. We discuss via a simple mean-field model the cause of this network organization and suggest that it may be the source of power-law relaxation observed in in vitro and in intracellular microrheology experiments. We present data which fully justifies our model for a simplified network architecture.Comment: 11 pages, 4 figures. to appear in Physical Review

Influence of the structural modulations and the Chain-ladder interaction in the Sr_14−xCa_xCu_24O_41Sr\_{14-x}Ca\_{x}Cu\_{24}O\_{41} compounds

We studied the effects of the incommensurate structural modulations on the ladder subsystem of the $Sr\_{14-x}Ca\_{x}Cu\_{24}O\_{41}$ family of compounds using ab-initio explicitly-correlated calculations. From these calculations we derived $t-J$ model as a function of the fourth crystallographic coordinate $\tau$ describing the incommensurate modulations. It was found that in the highly calcium-doped system, the on-site orbital energies are strongly modulated along the ladder legs. On the contrary the two sites of the ladder rungs are iso-energetic and the holes are thus expected to be delocalized on the rungs. Chain-ladder interactions were also evaluated and found to be very negligible. The ladder superconductivity model for these systems is discussed in the light of the present results.Comment: 8 octobre 200