Coded Cooperative Data Exchange for a Secret Key

We consider a coded cooperative data exchange problem with the goal of generating a secret key. Specifically, we investigate the number of public transmissions required for a set of clients to agree on a secret key with probability one, subject to the constraint that it remains private from an eavesdropper. Although the problems are closely related, we prove that secret key generation with fewest number of linear transmissions is NP-hard, while it is known that the analogous problem in traditional cooperative data exchange can be solved in polynomial time. In doing this, we completely characterize the best possible performance of linear coding schemes, and also prove that linear codes can be strictly suboptimal. Finally, we extend the single-key results to characterize the minimum number of public transmissions required to generate a desired integer number of statistically independent secret keys.Comment: Full version of a paper that appeared at ISIT 2014. 19 pages, 2 figure

Azimuth quadrupole component spectra on transverse rapidity yt{\bf y_t} for identified hadrons from Au-Au collisions at sNN=\sqrt{s_{NN}} = 200 GeV

I present the first isolation of azimuth quadrupole components from published $v_2(p_t)$ data (called elliptic flow) as spectra on transverse rapidity $y_t$ for identified pions, kaons and lambdas/protons from minimum-bias Au-Au collisions at 200 GeV. The form of the spectra on $y_t$ indicates that the three hadron species are emitted from a common boosted source with boost $\Delta y_{t0} \sim 0.6$. The quadrupole spectra have a L\'evy form similar to the soft component of the single-particle spectrum, but with significantly reduced ($\sim 0.7\times$) slope parameters $T$. Comparison of quadrupole spectra with single-particle spectra suggests that the quadrupole component comprises a small fraction ($< 5$%) of the total hadron yield, contradicting the hydrodynamic picture of a thermalized, flowing bulk medium. The form of $v_2(p_t)$ is, within a constant factor, the product of $p'_t$ ($p_t$ in the boost frame) times the ratio of quadrupole spectrum to single-particle spectrum. That ratio in turn implies that above 0.5 GeV/c the form of $v_2(p_t)$ is dominated by the hard component of the single-particle spectrum (interpreted as due to minijets). It is therefore unlikely that so-called {\em constituent-quark scaling} attributed to $v_2$ is relevant to soft hadron production mechanisms (e.g., chemical freezeout).Comment: 22 pages, 17 figure

On the relation of protein dynamics and exciton relaxation in pigment–protein complexes: An estimation of the spectral density and a theory for the calculation of optical spectra

A theory for calculating time– and frequency–domain optical spectra of pigment–protein complexes is presented using a density matrix approach. Non-Markovian effects in the exciton–vibrational coupling are included. A correlation function is deduced from the simulation of 1.6 K fluorescence line narrowing spectra of a monomer pigment–protein complex (B777), and then used to calculate fluorescence line narrowing spectra of a dimer complex (B820). A vibrational sideband of an excitonic transition is obtained, a distinct non-Markovian feature, and agrees well with experiment on B820 complexes. The theory and the above correlation function are used elsewhere to make predictions and compare with data on time–domain pump–probe spectra and frequency–domain linear absorption, circular dichroism and fluorescence spectra of Photosystem II reaction centers

Access courses as a site of engagement: a research project

This research project was funded by the Greater Manchester Strategic Alliance and Aimhigher Research Network North West. A database of Access students was held at the University of Salford that included students from 1998-2006. The names of the students were gathered by the Access Unit from their Enrichment Programme over the period. Ethical approval for the research was sought from the IRIS Director and advice on the Data Protection Act sought from the manager responsible within the university. The database contained information on name, age, address, telephone contact, gender, ethnicity, college and Access course attended. There were approximately 6000 entries on the database. “Access to higher education courses offer a route into higher education (HE) for those who do not have the educational qualifications which are usually required for entry. These courses provide the underpinning knowledge and skills needed for university-level study, and lead to the award of the Access to HE qualification, which is of an equivalent standard to Level 3 qualifications, such as A levels.” UCAS website. Individuals can study a range of courses in different subject areas such as health, science or humanities. Access courses can be studied over one year as a full time course or over two-three years as a part time course. The starting point for the study is the view that to enrol on an Access to HE course means that a major decision or turning point in an adult’s life has taken place and that the individual wants to change direction. This change of direction is important and suggests that individuals may have missed an opportunity earlier in their lives or do not wish to continue in the same employment situation or in the case of many women who are carers their circumstances have changed. The engagement in learning is an agentic act on the part of the individual that may be prompted by others in the immediate family or friends. However, a necessary aspect of this engagement is the provision of Access courses as a means to enter higher education or change employment

The electromagnetic Nucleon to Delta transition in Chiral Effective Field Theory

We present a calculation of the three complex form factors parametrizing the nucleon to Delta transition matrix element in the framework of chiral effective field theory with explicit Delta degrees of freedom. The interplay between short and long range physics is discussed and estimates for systematic uncertainties due to higher order effect are given.Comment: Talk given at the 2nd international workshop "Shape of Hadrons", April 27-29, 2006, Athens, Greec

Transition States in Protein Folding Kinetics: The Structural Interpretation of Phi-values

Phi-values are experimental measures of the effects of mutations on the folding kinetics of a protein. A central question is which structural information Phi-values contain about the transition state of folding. Traditionally, a Phi-value is interpreted as the 'nativeness' of a mutated residue in the transition state. However, this interpretation is often problematic because it assumes a linear relation between the nativeness of the residue and its free-energy contribution. We present here a better structural interpretation of Phi-values for mutations within a given helix. Our interpretation is based on a simple physical model that distinguishes between secondary and tertiary free-energy contributions of helical residues. From a linear fit of our model to the experimental data, we obtain two structural parameters: the extent of helix formation in the transition state, and the nativeness of tertiary interactions in the transition state. We apply our model to all proteins with well-characterized helices for which more than 10 Phi-values are available: protein A, CI2, and protein L. The model captures nonclassical Phi-values 1 in these helices, and explains how different mutations at a given site can lead to different Phi-values.Comment: 26 pages, 7 figures, 5 table

Implications of \u3cem\u3eCaritas in Veritate\u3c/em\u3e for Marketing and Business Ethics

In an effort to assess the latest thinking in the Roman Catholic Church on economic matters, we examine the newest encyclical by Pope Benedict XVI, Caritas in Veritate (Charity in Truth) for guidance concerning marketing and business strategy. Core ethical values, consistent with historical Catholic Social Teachings (CST), are retained. However, some important nuances are added to previous treatments, and, reflecting the mind of the current Pontiff, certain points of emphasis are shifted to account for recent global developments. Key areas of consistency and differences (as we perceive them) are spelled out along with some brief commentary on the evolution of the CST position on matters of importance to business decision makers. We close our analysis with a brief discussion of how the lessons of the encyclical can be applied to selected marketing problems embedded with ethical issues, including some criteria for evaluating marketing programs. Finally, we note some editorial commentary published in the wake of the letter’s release along with our own summation