Citation Help in Databases: Helpful or Harmful?

A review of the help files in several major databases revealed that database vendors have begun including information on citing sources, which has the potential to be very useful to students. Surprisingly, 94% of the citation examples in the databases reviewed had errors. The average number of errors per example was 4.3. The citation help appears to have been put together quickly, with little thought and no proofreading. Librarians must insist that vendors correct or remove this information

Microscopic Selection of Fluid Fingering Pattern

We study the issue of the selection of viscous fingering patterns in the limit of small surface tension. Through detailed simulations of anisotropic fingering, we demonstrate conclusively that no selection independent of the small-scale cutoff (macroscopic selection) occurs in this system. Rather, the small-scale cutoff completely controls the pattern, even on short time scales, in accord with the theory of microscopic solvability. We demonstrate that ordered patterns are dynamically selected only for not too small surface tensions. For extremely small surface tensions, the system exhibits chaotic behavior and no regular pattern is realized.Comment: 6 pages, 5 figure

Influence of the temperature on the depinning transition of driven interfaces

We study the dynamics of a driven interface in a two-dimensional random-field Ising model close to the depinning transition at small but finite temperatures T using Glauber dynamics. A square lattice is considered with an interface initially in (11)-direction. The drift velocity v is analyzed for the first time using finite size scaling at T = 0 and additionally finite temperature scaling close to the depinning transition. In both cases a perfect data collapse is obtained from which we deduce beta = 1/3 for the exponent which determines the dependence of v on the driving field, nu = 1 for the exponent of the correlation length and delta = 5 for the exponent which determines the dependence of v on T.Comment: 5 pages, Latex, Figures included, to appear in Europhys. Let

The Out‐of‐Plane Deformation Frequency of the NH Group in the Peptide Link

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70613/2/JCPSA6-21-3-570-2.pd

Anti-melanocortin-4 receptor autoantibodies in obesity

Background: The melanocortin-4 receptor (MC4R) is part of an important pathway regulating energy balance. Here we report the existence of autoantibodies (autoAbs) against the MC4R in sera of obese patients. Methods: The autoAbs were detected after screening of 216 patients' sera by using direct and inhibition ELISA with an N-terminal sequence of the MC4R. Binding to the native MC4R was evaluated by flow cytometry and pharmacological effects by measuring adenylyl cyclase activity. Results: Positive results in all tests were obtained in patients with overweight or obesity (prevalence: 3.6%) but not in normal weight patients. The selective binding properties of anti-MC4R autoAbs were confirmed by surface plasmon resonance and by immunoprecipitation with the native MC4R. Finally it was demonstrated that these autoAbs increased food intake in rats after passive transfer via intracerebroventricular injection. Conclusion: These observations suggest that inhibitory anti-MC4R autoAbs might contribute to the development of obesity in a small subpopulation of patients

Simulation and analysis of in vitro DNA evolution

We study theoretically the in vitro evolution of a DNA sequence by binding to a transcription factor. Using a simple model of protein-DNA binding and available binding constants for the Mnt protein, we perform large-scale, realistic simulations of evolution starting from a single DNA sequence. We identify different parameter regimes characterized by distinct evolutionary behaviors. For each regime we find analytical estimates which agree well with simulation results. For small population sizes, the DNA evolutional path is a random walk on a smooth landscape. While for large population sizes, the evolution dynamics can be well described by a mean-field theory. We also study how the details of the DNA-protein interaction affect the evolution.Comment: 11 pages, 11 figures. Submitted to PNA

Complex Systems Science: Dreams of Universality, Reality of Interdisciplinarity

Using a large database (~ 215 000 records) of relevant articles, we empirically study the "complex systems" field and its claims to find universal principles applying to systems in general. The study of references shared by the papers allows us to obtain a global point of view on the structure of this highly interdisciplinary field. We show that its overall coherence does not arise from a universal theory but instead from computational techniques and fruitful adaptations of the idea of self-organization to specific systems. We also find that communication between different disciplines goes through specific "trading zones", ie sub-communities that create an interface around specific tools (a DNA microchip) or concepts (a network).Comment: Journal of the American Society for Information Science and Technology (2012) 10.1002/asi.2264

THETA-rhythm makes the world go round:dissociative effects of TMS theta versus alpha entrainment of right pTPJ on embodied perspective transformations

Being able to imagine another person's experience and perspective of the world is a crucial human ability and recent reports suggest that humans "embody" another's viewpoint by mentally rotating their own body representation into the other's orientation. Our recent Magnetoencephalography (MEG) data further confirmed this notion of embodied perspective transformations and pinpointed the right posterior temporo-parietal junction (pTPJ) as the crucial hub in a distributed network oscillating at theta frequency (3-7 Hz). In a subsequent transcranial magnetic stimulation (TMS) experiment we interfered with right pTPJ processing and observed a modulation of the embodied aspects of perspective transformations. While these results corroborated the role of right pTPJ, the notion of theta oscillations being the crucial neural code remained a correlational observation based on our MEG data. In the current study we therefore set out to confirm the importance of theta oscillations directly by means of TMS entrainment. We compared entrainment of right pTPJ at 6 Hz vs. 10 Hz and confirmed that only 6 Hz entrainment facilitated embodied perspective transformations (at 160° angular disparity) while 10 Hz slowed it down. The reverse was true at low angular disparity (60° between egocentric and target perspective) where a perspective transformation was not strictly necessary. Our results further corroborate right pTPJ involvement in embodied perspective transformations and highlight theta oscillations as a crucial neural code

Phase-Field Model of Mode III Dynamic Fracture

We introduce a phenomenological continuum model for mode III dynamic fracture that is based on the phase-field methodology used extensively to model interfacial pattern formation. We couple a scalar field, which distinguishes between ``broken'' and ``unbroken'' states of the system, to the displacement field in a way that consistently includes both macroscopic elasticity and a simple rotationally invariant short scale description of breaking. We report two-dimensional simulations that yield steady-state crack motion in a strip geometry above the Griffith threshold.Comment: submitted to PR