6,317 research outputs found
Design of conditions for emergence of self-replicators
A self-replicator is usually understood to be an object of definite form that
promotes the conversion of materials in its environment into a nearly identical
copy of itself. The challenge of engineering novel, micro- or nano-scale
self-replicators has attracted keen interest in recent years, both because
exponential amplification is an attractive method for generating high yields of
specific products, and also because self-reproducing entities have the
potential to be optimized or adapted through rounds of iterative selection.
Substantial steps forward have been achieved both in the engineering of
particular self-replicating molecules, and also in characterizing the physical
basis for possible mechanisms of self-replication. At present, however, there
is need for a theoretical treatment of what physical conditions are most
conducive to the emergence of novel self-replicating structures from a
reservoir of building blocks on a desired time-scale. Here we report progress
in addressing this need. By analyzing the dynamics of a generic class of
heterogeneous particle mixtures whose reaction rates emerge from basic physical
interactions, we demonstrate that the spontaneous discovery of self-replication
is controlled by relatively generic features of the chemical space, namely: the
dispersion in the distribution of reaction timescales and bound-state energies.
Based on this analysis, we provide quantitative criteria that may aid
experimentalists in designing a system capable of producing self-replicators,
and in estimating the likely timescale for exponential growth to start.Comment: Supplementary Information is under the Ancillary Files ---
Information-theoretic bound on the entropy production to maintain a classical nonequilibrium distribution using ancillary control
There are many functional contexts where it is desirable to maintain a
mesoscopic system in a nonequilibrium state. However, such control requires an
inherent energy dissipation. In this article, we unify and extend a number of
works on the minimum energetic cost to maintain a mesoscopic system in a
prescribed nonequilibrium distribution using ancillary control. For a variety
of control mechanisms, we find that the minimum amount of energy dissipation
necessary can be cast as an information-theoretic measure of distinguishability
between the target nonequilibrium state and the underlying equilibrium
distribution. This work offers quantitative insight into the intuitive idea
that more energy is needed to maintain a system farther from equilibrium.Comment: 6 pages, 2 figure
Morphogen Gradient from a Noisy Source
We investigate the effect of time-dependent noise on the shape of a morphogen
gradient in a developing embryo. Perturbation theory is used to calculate the
deviations from deterministic behavior in a simple reaction-diffusion model of
robust gradient formation, and the results are confirmed by numerical
simulation. It is shown that such deviations can disrupt robustness for
sufficiently high noise levels, and the implications of these findings for more
complex models of gradient-shaping pathways are discussed.Comment: Four pages, three figure
Statistical Physics of Self-Replication
Self-replication is a capacity common to every species of living thing, and
simple physical intuition dictates that such a process must invariably be
fueled by the production of entropy. Here, we undertake to make this intuition
rigorous and quantitative by deriving a lower bound for the amount of heat that
is produced during a process of self-replication in a system coupled to a
thermal bath. We find that the minimum value for the physically allowed rate of
heat production is determined by the growth rate, internal entropy, and
durability of the replicator, and we discuss the implications of this finding
for bacterial cell division, as well as for the pre-biotic emergence of
self-replicating nucleic acids.Comment: 4+ pages, 1 figur
Extending electron orbital precession to the molecular case: Can orbital alignment be used to observe wavepacket dynamics?
The complexity of ultrafast molecular photoionization presents an obstacle to
the modelling of pump-probe experiments. Here, a simple optimized model of
atomic rubidium is combined with a molecular dynamics model to predict
quantitatively the results of a pump-probe experiment in which long range
rubidium dimers are first excited, then ionized after a variable delay. The
method is illustrated by the outline of two proposed feasible experiments and
the calculation of their outcomes. Both of these proposals use Feshbach 87Rb2
molecules. We show that long-range molecular pump-probe experiments should
observe spin-orbit precession given a suitable pump-pulse, and that the
associated high-frequency beat signal in the ionization probability decays
after a few tens of picoseconds. If the molecule was to be excited to only a
single fine structure state state, then a low-frequency oscillation in the
internuclear separation would be detectable through the timedependent
ionization cross section, giving a mechanism that would enable observation of
coherent vibrational motion in this molecule.Comment: 9 pages, 10 figures, PRA submissio
Oxidation processes in magneto-optic and related materials
The surface oxidation processes of thin films of magneto-optic materials, such as the rare-earth transition metal alloys have been studied, starting in ultrahigh vacuum environments, using surface analysis techniques, as a way of modeling the oxidation processes which occur at the base of a defect in an overcoated material, at the instant of exposure to ambient environments. Materials examined have included FeTbCo alloys, as well as those same materials with low percentages of added elements, such a Ta, and their reactivities to both O2 and H2O compared with materials such as thin Fe films coated with ultrathin adlayers of Ti. The surface oxidation pathways for these materials is reviewed, and XPS data presented which indicates the type of oxides formed, and a critical region of Ta concentration which provides optimum protection
The University of Alabama Libraries and Student Support Services Partnership: Non-Traditional Outreach to Academic Support Programs
Abstract:
At the University of Alabama Libraries we have partnered with the Student Support Services TRiO program, a grant-funded program through the U. S. Department of Education that works to increase the retention and graduation rates of first generation college students, students with limited family income, and students with disabilities. We have developed a program that utilizes a combination of classroom instruction in the library and outreach hours at the Student Support Services building, we are able to engage with the students on multiple levels while remaining cognizant of any accommodations they may require. We provide instruction on utilizing the library’s website as well as one-on-one consultations for students who need research support. Although this program is only in its second semester it has proved quite successful and we see great potential for expansion to other non-traditional academic services on campus.
Originally presented at the Atlanta Area Bibliographic Instruction Group conference, June 2016.https://ir.una.edu/libfacpresentation/1002/thumbnail.jp
Outreach to Student Support Services at the University of Alabama: Engaging While Including
Outreach programs on university campuses are crucial to reducing anxiety in students from diverse backgrounds who may not have been introduced to an academic library environment, its resources, and its role in their academic success. Traditional liaison programs are geared towards students within their majors; as the campus evolves, so must the role of the liaison.
At the University of Alabama Libraries we have partnered with the Student Support Services (SSS) TRiO program, a grant-funded program through the U. S. Department of Education that works to increase the retention and graduation rates of first generation college students, students with limited family income, and students with disabilities. Boasting a 91% average retention rate, the program works with a broad spectrum of students. By the numbers, the students in the program are 65% female, 74% are low income and first generation, and 62% are Black or African American. The presenters, working in conjunction with the Academic Counselors in SSS, have created a comprehensive outreach program through which they are able to engage with the students on multiple levels while remaining cognizant of the pressures and needs of the individual students in the program.
In addition to open houses, instruction, and Libguides, the presenters have also secured spaces within the Student Support Services building during high traffic periods for visibility and ease of interaction. Meeting with students in familiar spaces provides them a comfortable way to interact and learn research skills, website navigation, and other services that the library provides. Once the student has established a relationship with the librarian, they are more likely to visit the library and utilize more library services, which contributes to the student’s overall academic success.https://ir.una.edu/libfacpresentation/1004/thumbnail.jp
Partnering with Academic Support Programs to Promote Student Success
Outreach programs on university campuses are crucial to reducing anxiety in students from diverse backgrounds who may not have been introduced to an academic library environment, its resources, and its role in their academic success. Traditional liaison programs are geared towards students within their majors; as the campus evolves, so must the role of the liaison.
At the University of Alabama Libraries we have partnered with the Student Support Services (SSS) TRiO program, a grant-funded program through the U. S. Department of Education that works to increase the retention and graduation rates of first generation college students, students with limited family income, and students with disabilities. The presenters, working in conjunction with the Academic Counselors in SSS, have created a comprehensive outreach program through which they are able to engage with the students on multiple levels while remaining cognizant of the pressures and needs of the individual students in the program.https://ir.una.edu/libfacpresentation/1009/thumbnail.jp
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