Teaching "Symmetry" in the Introductory Physics Curriculum

Modern physics is largely defined by fundamental symmetry principles and Noether's Theorem. Yet these are not taught, or rarely mentioned, to beginning students, thus missing an opportunity to reveal that the subject of physics is as lively and contemporary as molecular biology, and as beautiful as the arts. We prescribe a symmetry module to insert into the curriculum, of a week's length.Comment: 15 pages, 4 figure

Testing and Learning on Distributions with Symmetric Noise Invariance

Kernel embeddings of distributions and the Maximum Mean Discrepancy (MMD), the resulting distance between distributions, are useful tools for fully nonparametric two-sample testing and learning on distributions. However, it is rarely that all possible differences between samples are of interest -- discovered differences can be due to different types of measurement noise, data collection artefacts or other irrelevant sources of variability. We propose distances between distributions which encode invariance to additive symmetric noise, aimed at testing whether the assumed true underlying processes differ. Moreover, we construct invariant features of distributions, leading to learning algorithms robust to the impairment of the input distributions with symmetric additive noise.Comment: 22 page

An Implementation of External-Memory Depth-First Search

In many different areas of computing, problems can arise which are too large to fit in main memory. For these problems, the I/O cost of moving data between main memory and secondary storage (for example, disks) becomes a significant bottleneck affecting the performance of the program. Since most algorithms do not take into account the size of main memory, new algorithms have been developed to optimize the number of I/O\u27s performed. This paper details the implementation of one such algorithm, for external-memory depth-first search. Depth-first search is a basic tool for solving many problems in graph theory, and since graph theory is applicable for many large computational problems, it is important to make sure that such a basic tool is designed to avoid the bottleneck of main memory to secondary storage I/O\u27s. The algorithm whose implementation is described in this paper is sketched out in an extended abstract by Chiang et al. We attempt to improve the given algorithm by minimizing I/O\u27s performed, and to extend the algorithm by finding disjoint trees, and by classifying all the edges in the problem

The influence of proactive personality on social entrepreneurial intentions among African American and Hispanic undergraduate students: the moderating role of hope

The primary purpose of this study was two-fold: 1) to determine if a relationship exists between proactive personality and social entrepreneurial intentions among African American and Hispanic undergraduate students; and 2) to determine if hope moderates the relationship between proactive personality and social entrepreneurial intentions. The findings demonstrated that there was indeed a positive relationship between having a proactive personality and social entrepreneurial intentions among students; these findings supported the conclusions made by Crant (1996) which demonstrated that proactive students tend to have intentions to become entrepreneurs. Also, the findings demonstrated that hope did not moderate the relationship between proactive personality and social entrepreneurial intentions. This was surprising, however, it may be that African American and Hispanic undergraduate students need more than hope to increase their desire to become social entrepreneurs. The researcher concluded that it is likely that the moderated relationship was not supported because some students may not yet possess the knowledge, skills, and abilities necessary to create social enterprises. Future research should consider other possible moderating mechanisms involved in the proactive personality and social entrepreneurial intentions relationship. It is possible that entrepreneurial parents, entrepreneurial self-efficacy, socio-economic status, and other variables may moderate the relationship between proactive personality and social entrepreneurial intentions. Researchers and practitioners may have to conceptualize frameworks that can aid in training and developing social entrepreneurs. Critical pedagogy and the Center of Creative Leadership’s Assessment, Challenge, and Support (ACS) model can be utilized

Thermal Shift-induced Gene Expression And Regulation In Maize (zea Mays L)

Rapid elevation in the incubation temperature of maize seedlings leads to the new and(or) enhanced synthesis of a group of heat shock polypeptides (HSPs). The response is: (a) rapid (HSP synthesis is detectable within 15 minutes following thermal shifts); (b) reversible (the pre-shift pattern of polypeptide synthesis is re-established when seedlings are returned to the control temperature); and (c) transitory (maintenance of seedlings at the elevated temperature leads to a gradual reduction of HSP production and the establishment of a new pattern of polypeptide synthesis). The synthesis of an apparently identical set of HSPs is noted in maize plumules, mesocotyls, radicles and young leaves.;In vitro translational analyses indicate that the HSPs represent the products from translation of polyadenylated messenger RNAs. Post-transcriptional and post-translational regulatory mechanisms may determine the final array of polypeptides which are produced.;In maize, changes in the synthesis of polypeptides and their mRNAs appear to represent a normal response not only to heat shock but to any thermal shift; the array of gene products and the degree to which they are synthesized are determined by several factors including: (a) the initial growing temperature; (b) the temperature shift increment; (c) the temperature regime within which the shift is carried out; (d) the rate of increase of seedling temperature; and (e) the duration of the temperature treatment.;While HSP synthesis in maize is analogous to the response observed in other species, maize HSPs exhibit different degrees of immunological relatedness to HSPs from other organisms. High molecular weight HSPs from maize, soybean and pea exhibit similar degress of cross-reactivity with antibodies to maize 73-89 kD HSPs. Antibodies to maize 18 kD HSPs react strongly with maize 18 kD HSPs, to a lesser extent with soybean 18 kD HSPs, and very little with 17 kD HSPs from pea. Quail, mouse and tadpole HSPs do not react with antibodies to maize HSPs. Thus, while the synthesis of polypeptides in response to thermal shifts or stresses may be universal, differences exist in the classes of polypeptides which are synthesized, and in the degree of relatedness of polypeptides of apparently similar size from different species

Red rice competition and control in cultivated rice

Studies were conducted to evaluate rice competitiveness with red rice and how to utilize glufosinate- and imazethapyr-resistant rice in water-seeded rice to control red rice. In the interference study, CL 121, Cocodrie, Drew, and Jasmine were seeded to obtain 95, 190, and 290 plants/sq m. Red rice density was 0 or 20 red rice plants/sq m. Jasmine, a tall, vigorous tillering, mid-season cultivar was more competitive with red rice. With the exception of Cocodrie grown red rice free, no benefit existed from increasing the seeding rate above 190 plants/sq m. Another study examined the effect of permanent flood establishment in a glufosinate- and imazethapyr-resistant rice system. Glufosinate controlled hemp sesbania, red rice, barnyardgrass, and Amazon sprangletop at least 95%. Imazethapyr controlled hemp sesbania less than 35%. With one exception, barnyardgrass, red rice, and Amazon sprangletop control was at least 95%. Two postemergence imazethapyr applications controlled Amazon sprangletop 79%. All treatments reduced red rice panicle number to less than 1/sq m, but did not delay red rice panicle emergence with respect to rice panicle emergence. Delaying the permanent flood improved rice yield in an imazethapyr system, but not for glufosinate. Another study examined the effect of 500 g/ha glufosinate applied 14, 28, 42, 56, and 70 days after emergence fb 410 g/ha applied 7 d later on rice and red rice. All treatments controlled red rice 91 to 98%. Rice yield was optimized when applications occurred within 35 or 49 DAE for the red rice infested and red rice free treatments, respectively. The fourth study examined imazethapyr use in a water-seeded system receiving no tillage or tilled in the water prior to seeding. Herbicide treatments were 70 g/ha imazethapyr applied 1, 3, or 5 d fb 70 g/ha applied 12 or 19 d after draining the seeding flood (DADSF), 140 g/ha applied 12 or 19 DADSF, and a nontreated. All treatments controlled red rice 88 to 95% and barnyardgrass 73 to 94%. Rice yields did not reflect barnyardgrass control and were higher when the two imazethapyr applications were farther apart

Residual Mean Field Model of Valence Quarks in the Nucleon

We develop a non-perturbative model for valence parton distribution functions (PDFs) based on the mean field interactions of valence quarks in the nucleonic interior. The main motivation for the model is to obtain a mean field description of the valence quarks as a baseline to study the short range quark-quark interactions that generate the high $x$ tail of PDFs. The model is based on the separation of the valence three-quark cluster and residual system in the nucleon. Then the nucleon structure function is calculated within the effective light-front diagrammatic approach introducing nonperturbative light-front valence quark and residual wave functions. Within the model a new relation is obtained between the position, $x_p$, of the peak of $xq_V(x)$ distribution of the valence quark and the effective mass of the residual system, $m_R$, in the form: $x_{p} \approx {1\over 4} (1-{m_R\over m_N})$ at starting $Q^2$. This relation explains the difference in the peak positions for d- and u- quarks through the expected difference of residual masses for valence d- and u- quark distributions. The parameters of the model are fixed by fitting the calculated valence quark distributions to the phenomenological PDFs. This allowed us to estimate the overall mean field contribution in baryonic and momentum sum rules for valence d- and u- quarks. Finally, the evaluated parameters of the non-perturbative wave functions of valence 3q-cluster and residual system can be used in calculation of other quantities such as nucleon form factors, generalized partonic and transverse momentum distributions.Comment: 45 pages and 13 figure

Photon super-bunching from a generic tunnel junction

Generating correlated photon pairs at the nanoscale is a prerequisite to creating highly integrated optoelectronic circuits that perform quantum computing tasks based on heralded single-photons. Here we demonstrate fulfilling this requirement with a generic tip-surface metal junction. When the junction is luminescing under DC bias, inelastic tunneling events of single electrons produce a photon stream in the visible spectrum whose super-bunching index is 17 when measured with a 53 picosecond instrumental resolution limit. These photon bunches contain true photon pairs of plasmonic origin, distinct from accidental photon coincidences. The effect is electrically rather than optically driven - completely absent are pulsed lasers, down-conversions, and four-wave mixing schemes. This discovery has immediate and profound implications for quantum optics and cryptography, notwithstanding its fundamental importance to basic science and its ushering in of heralded photon experiments on the nanometer scale