Electron interferometry with nano-gratings

We present an electron interferometer based on near-field diffraction from two nanostructure gratings. Lau fringes are observed with an imaging detector, and revivals in the fringe visibility occur as the separation between gratings is increased from 0 to 3 mm. This verifies that electron beams diffracted by nanostructures remain coherent after propagating farther than the Talbot length $z_T = 2d^2/\lambda$ = 1.2 mm, and hence is a proof of principle for the function of a Talbot-Lau interferometer for electrons. Distorted fringes due to a phase object demonstrates an application for this new type of electron interferometer.Comment: 4 pgs, 6 figure

Pecuária familiar na Amazônia: uma abordagem dessa realidade esquecida.

bitstream/item/100281/1/1428.pd

Non-Restarting CUSUM charts and Control of the False Discovery Rate

Cumulative sum (CUSUM) charts are typically used to detect changes in a stream of observations e.g. shifts in the mean. Usually, after signalling, the chart is restarted by setting it to some value below the signalling threshold. We propose a non-restarting CUSUM chart which is able to detect periods during which the stream is out of control. Further, we advocate an upper boundary to prevent the CUSUM chart rising too high, which helps detecting a change back into control. We present a novel algorithm to control the false discovery rate (FDR) pointwise in time when considering CUSUM charts based on multiple streams of data. We prove that the FDR is controlled under two definitions of a false discovery simultaneously. Simulations reveal the difference in FDR control when using these two definitions and other desirable definitions of a false discovery.Comment: 10 pages, 2 figure

Helical Tubes in Crowded Environments

When placed in a crowded environment, a semi-flexible tube is forced to fold so as to make a more compact shape. One compact shape that often arises in nature is the tight helix, especially when the tube thickness is of comparable size to the tube length. In this paper we use an excluded volume effect to model the effects of crowding. This gives us a measure of compactness for configurations of the tube, which we use to look at structures of the semi-flexible tube that minimize the excluded volume. We focus most of our attention on the helix and which helical geometries are most compact. We found that helices of specific pitch to radius ratio 2.512 to be optimally compact. This is the same geometry that minimizes the global curvature of the curve defining the tube. We further investigate the effects of adding a bending energy or multiple tubes to begin to explore the more complete space of possible geometries a tube could form.Comment: 10 page

Rapid and sound assessment of well-being within a multi-dimensional approach: The Well-being Numerical Rating Scales (WB-NRSs)

The assessment of well-being remains an important topic for many disciplines including medical, psychological, social, educational, and economic fields. The present study assesses the reliability and validity of a five-item instrument for evaluating physical, psychological, spiritual, relational, and general well-being. This measure uniquely utilizes a segmented numeric version of the visual analog scale in which a respondent selects a whole number that best reflects the intensity of the investigated characteristic. In study one, 939 clinical (i.e., diagnosed with cancer and liver disease with cirrhosis) and non-clinical (i.e., undergraduate students and their family and acquaintances) participants between the ages of 18 to 87 years (M = 47.20 years, SD = 19.62, 54% males) were recruited. Results showed items have strong discriminant ability and the spread of threshold parameters attests to the appropriateness of the response categories. Moreover, convergent and discriminant validity were found with other self-report measures (e.g., depression, anxiety, optimism, well-being) and the measure showed responsiveness to two separate interventions for clinical populations. In study two, 287 Canadian (ages ranged from 18 to 30 years; M = 20.78, SD = 3.32; 23% males) and 342 Italian undergraduate psychology students (age ranged from 18 to 29 years, M = 21.21 years, SD = 1.73, 38% males) were recruited to complete self-report questionnaires. IRT-based differential item functioning analyses provided evidence that the item properties were similar for the Italian and English versions of the scale. Additionally, the validity results obtained in study one were replicated and similar relationships between criterion variables were found when comparing the Italian- and the English-speaking samples. Overall, the current study provides evidence that the Italian and English versions of the WB-NRSs offer added value in research focused on well-being and in assessing well-being changes prompted by intervention programs

Decoherence and dephasing errors caused by D.C. Stark effect in rapid ion transport

We investigate the error due to D.C. Stark effect for quantum information processing for trapped ion quantum computers using the scalable architecture proposed in J. Res. Natl. Inst. Stan. 103, 259 (1998) and Nature 417, 709 (2002). As the operation speed increases, dephasing and decoherence due to the D.C. Stark effect becomes prominent as a large electric field is applied for transporting ions rapidly. We estimate the relative significance of the decoherence and dephasing effects and find that the latter is dominant. We find that the minimum possible of dephasing is quadratic in the time of flight, and an inverse cubic in the operational time scale. From these relations, we obtain the operational speed-range at which the shifts caused by D.C. Stark effect, no matter follow which trajectory the ion is transported, are no longer negligible. Without phase correction, the maximum speed a qubit can be transferred across a 100 micron-long trap, without excessive error, in about 10 ns for Calcium ion and 50 ps for Beryllium ion. In practice, the accumulated error is difficult to be tracked and calculated, our work gives an estimation to the range of speed limit imposed by D.C. Stark effect.Comment: 7 pages, 1 figure. v2: Title is changed in this version to make our argument more focused. Introduction is rewritten. A new section IV is added to make our point more prominent. v3: Title is changed to make our argument more specific. Abstract, introduction, and summary are revise

Statistical Properties of Contact Maps

A contact map is a simple representation of the structure of proteins and other chain-like macromolecules. This representation is quite amenable to numerical studies of folding. We show that the number of contact maps corresponding to the possible configurations of a polypeptide chain of N amino acids, represented by (N-1)-step self avoiding walks on a lattice, grows exponentially with N for all dimensions D>1. We carry out exact enumerations in D=2 on the square and triangular lattices for walks of up to 20 steps and investigate various statistical properties of contact maps corresponding to such walks. We also study the exact statistics of contact maps generated by walks on a ladder.Comment: Latex file, 15 pages, 12 eps figures. To appear on Phys. Rev.