25,206 research outputs found
Epitope mapping using mRNA display and a unidirectional nested deletion library
In vitro selection targeting an anti-polyhistidine monoclonal antibody was performed using mRNA display with a random, unconstrained 27-mer peptide library. After six rounds of selection, epitope-like peptides were identified that contain two to five consecutive, internal histidines and are biased for arginine residues, without any other identifiable consensus. The epitope was further refined by constructing a high-complexity, unidirectional fragment library from the final selection pool. Selection by mRNA display minimized the dominant peptide from the original selection to a 15-residue functional sequence (peptide Cmin: RHDAGDHHHHHGVRQ; K-D = 38 nM). Other peptides recovered from the fragment library selection revealed a separate consensus motif (ARRXA) C-terminal to the histidine track. Kinetics measurements made by surface plasmon resonance, using purified Fab (antigen-binding fragment) to prevent avidity effects, demonstrate that the selected peptides bind with 10- to 75-fold higher affinities than a hexahistidine peptide. The highest affinity peptides (K-D approximate to 10 nM) encode both a short histidine track and the ARRXA motif, suggesting that the motif and other flanking residues make important contacts adjacent to the core polyhistidine-binding site and can contribute > 2.5 kcal/mol of binding free energy. The fragment library construction methodology described here is applicable to the development of high-complexity protein or cDNA expression libraries for the identification of protein-protein interaction domains
Organic farming and multicriteria decisions: An economic survey
Organic food production is a sphere where decision making is multi-facetted and complex. This applies to producers, political decision makers and consumers alike. This paper provides an overview of the economic methods that can aid such multi criteria decision making. We first provide an outline of the many different Multi-Criteria Analysis (MCA) techniques available and their relative advantages and disadvantages. In addition, theoretical and practical problems related to the use of Cost-Benefit Analysis (CBA) and MCA respectively are briefly discussed. We then review the MCA literature on case studies on organic farming. Based on this review we provide directional markers for future research where MCA may possibly be applied and adapted in order to provide useful knowledge and support for decision makers in the context of organic farming
Coulomb corrections to bremsstrahlung in electric field of heavy atom at high energies
The differential and partially integrated cross sections are considered for
bremsstrahlung from high-energy electrons in atomic field with the exact
account of this field. The consideration exploits the quasiclassical electron
Green's function and wave functions in an external electric field. It is shown
that the Coulomb corrections to the differential cross section are very
susceptible to screening. Nevertheless, the Coulomb corrections to the cross
section summed up over the final-electron states are independent of screening
in the leading approximation over a small parameter ( is
a screening radius, is the electron mass, ). Bremsstrahlung from
an electron beam of the finite size on heavy nucleus is considered as well.
Again, the Coulomb corrections to the differential probability are very
susceptible to the beam shape, while those to the probability integrated over
momentum transfer are independent of it, apart from the trivial factor, which
is the electron-beam density at zero impact parameter. For the Coulomb
corrections to the bremsstrahlung spectrum, the next-to-leading terms with
respect to the parameters ( is the electron energy) and
are obtained.Comment: 13 pages, 4 figure
Value added or misattributed? A multi-institution study on the educational benefit of labs for reinforcing physics content
Instructional labs are widely seen as a unique, albeit expensive, way to
teach scientific content. We measured the effectiveness of introductory lab
courses at achieving this educational goal across nine different lab courses at
three very different institutions. These institutions and courses encompassed a
broad range of student populations and instructional styles. The nine courses
studied had two key things in common: the labs aimed to reinforce the content
presented in lectures, and the labs were optional. By comparing the performance
of students who did and did not take the labs (with careful normalization for
selection effects), we found universally and precisely no added value to
learning from taking the labs as measured by course exam performance. This work
should motivate institutions and departments to reexamine the goals and conduct
of their lab courses, given their resource-intensive nature. We show why these
results make sense when looking at the comparative mental processes of students
involved in research and instructional labs, and offer alternative goals and
instructional approaches that would make lab courses more educationally
valuable.Comment: Accepted to Phys Rev PE
Transient excitation and data processing techniques employing the fast fourier transform for aeroelastic testing
The development of testing techniques useful in airplane ground resonance testing, wind tunnel aeroelastic model testing, and airplane flight flutter testing is presented. Included is the consideration of impulsive excitation, steady-state sinusoidal excitation, and random and pseudorandom excitation. Reasons for the selection of fast sine sweeps for transient excitation are given. The use of the fast fourier transform dynamic analyzer (HP-5451B) is presented, together with a curve fitting data process in the Laplace domain to experimentally evaluate values of generalized mass, model frequencies, dampings, and mode shapes. The effects of poor signal to noise ratios due to turbulence creating data variance are discussed. Data manipulation techniques used to overcome variance problems are also included. The experience is described that was gained by using these techniques since the early stages of the SST program. Data measured during 747 flight flutter tests, and SST, YC-14, and 727 empennage flutter model tests are included
Adjustment Costs, Firm Responses, and Labor Supply Elasticities: Evidence from Danish Tax Records
We show that the effects of taxes on labor supply are shaped by interactions between adjustment costs for workers and hours constraints set by firms. We develop a model in which firms post job offers characterized by an hours requirement and workers pay search costs to find jobs. In this model, micro elasticities are smaller than macro elasticities because they do not account for adjustment costs and firm responses. We present evidence supporting three predictions of the model by analyzing bunching at kinks using the universe of tax records in Denmark. First, larger kinks generate larger taxable income elasticities because they are more likely to overcome search costs. Second, kinks that apply to a larger group of workers generate larger elasticities because they induce changes in hours constraints. Third, firms tailor job offers to match workers.aggregate tax preferences in equilibrium. Calibrating our model to match these empirical findings, we obtain a lower bound on the intensive-margin macro elasticity of 0:34, an order of magnitude larger than the estimates obtained using standard microeconometric methods for wage earners in our data.
Neutron skin uncertainties of Skyrme energy density functionals
Background: Neutron-skin thickness is an excellent indicator of isovector
properties of atomic nuclei. As such, it correlates strongly with observables
in finite nuclei that depend on neutron-to-proton imbalance and the nuclear
symmetry energy that characterizes the equation of state of neutron-rich
matter. A rich worldwide experimental program involving studies with rare
isotopes, parity violating electron scattering, and astronomical observations
is devoted to pinning down the isovector sector of nuclear models. Purpose: We
assess the theoretical systematic and statistical uncertainties of neutron-skin
thickness and relate them to the equation of state of nuclear matter, and in
particular to nuclear symmetry energy parameters. Methods: We use the nuclear
superfluid Density Functional Theory with several Skyrme energy density
functionals and density dependent pairing. To evaluate statistical errors and
their budget, we employ the statistical covariance technique. Results: We find
that the errors on neutron skin increase with neutron excess. Statistical
errors due to uncertain coupling constants of the density functional are found
to be larger than systematic errors, the latter not exceeding 0.06 fm in most
neutron-rich nuclei across the nuclear landscape. The single major source of
uncertainty is the poorly determined slope L of the symmetry energy that
parametrizes its density dependence. Conclusions: To provide essential
constraints on the symmetry energy of the nuclear energy density functional,
next-generation measurements of neutron skins are required to deliver precision
better than 0.06 fm.Comment: 5 pages, 4 figure
Henri Temianka Correspondence; (olsen)
https://digitalcommons.chapman.edu/temianka_correspondence/2538/thumbnail.jp
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