Chiral Symmetry Restoration and Realisation of the Goldstone Mechanism in the U(1) Gross-Neveu Model at Non-Zero Chemical Potential

We simulate the Gross-Neveu model in 2+1 dimensions at nonzero baryon density (chemical potential mu =/= 0). It is possible to formulate this model with a real action and therefore to perform standard hybrid Monte Carlo simulations with mu =/= 0 in the functional measure. We compare the physical observables from these simulations with simulations using the Glasgow method where the value of mu in the functional measure is fixed at a value mu_upd. We find that the observables are sensitive to the choice of mu_upd. We consider the implications of our findings for Glasgow method QCD simulations at mu =/= 0. We demonstrate that the realisation of the Goldstone mechanism in the Gross-Neveu model is fundamentally different from that in QCD. We find that this difference explains why there is an unphysical transition in QCD simulations at mu =/= 0 associated with the pion mass scale whereas the transition in the Gross-Neveu model occurs at a larger mass scale and is therefore consistent with theoretical predictions. We note classes of theories which are exceptions to the Vafa-Witten theorem which permit the possibility of formation of baryon number violating diquark condensates.Comment: 28 pages RevTe

Results on Finite Density QCD

A brief summary of the formulation of QCD at finite chemical potental, $\mu$, is presented. The failure of the quenched approximation to the problem is reviewed. Results are presented for dynamical simulations of the theory at strong and intermediate couplings. We find that the problems associated with the quenched theory persist: the onset of non-zero quark number does seem to occur at a chemical potential $\approx { {m_{\pi}} \over 2}$. However analysis of the Lee-Yang zeros of the grand canonical partition function in the complex fugacity plane, ($e^{\mu/T}$), does show signals of critical behaviour in the expected region of chemical potential. Results are presented for a simulation at finite density of the Gross-Neveu model on a $16^3$ lattice near to the chiral limit. Contrary to our simulations of QCD no pathologies were found when $\mu$ passed through the value m_{\pi}/2}.Comment: 14 pages, Latex, 18 eps figures, Review for Tsukuba worksho

Using a student response system to provide formative feedback in large classes : a phenomenographic study at the University of Cape Town

Includes abstract.The purpose of this study was to gain a better understanding of students' conceptions of the use of a student response system to provide formative feedback in large university classes. The main aim of formative feedback is to increase a student's knowledge, skills, and understanding of specific subject matter, by indicating a gap between the actual knowledge of the student and the required standard. However, in large classes the opportunities for formative assessment are limited, often resulting in little or no immediate feedback given to the students on their learning. One way of addressing this lack of assessment of students' understanding in the classroom is to incorporate a student response system into the lecture in order to facilitate learning and provide immediate formative feedback. A student response system is a tool that enables students to wirelessly send their responses to questions presented by a lecturer, using a small hand-held remote-controlled device

The electro and photoproduction of pions

Abstract Not Provided

Determination of the Relative and Absolute Configurations of the Female-produced Sex Pheromone of the Cerambycid Beetle Prionus californicus

We previously identified the basic structure of the female-produced sex attractant pheromone of the cerambycid beetle, Prionus californicus Motschulsky (Cerambycidae: Prioninae), as 3,5-dimethyldodecanoic acid. A synthesized mixture of the four stereoisomers of 3,5-dimethyldodecanoic acid was highly attractive to male beetles. Here, we describe stereoselective syntheses of three of the four possible stereoisomers, and the results of laboratory and field bioassays showing that male beetles are attracted specifically to (3R,5S)-3,5-dimethyldodecanoic acid, but not to its enantiomer, (3S,5R)-3,5-dimethyldodecanoic acid, indicating that the (3R,5S)-enantiomer is the active pheromone component. The diastereomeric (3R,5R)- and (3S,5S)-enantiomers were excluded from consideration because their gas chromatographic retention times were different from that of the insect-produced compound. The mixture of the four stereoisomers of 3,5-dimethyldodecanoic acid was as attractive to male P. californicus as the (3R,5S)-enantiomer, indicating that none of the other three stereoisomers inhibited responses to the active enantiomer. Beetles responded to as little as 10 ng and 10 μg of synthetic 3,5-dimethyldodecanoic acid in laboratory and field studies, respectively. Field studies indicated that capture rate did not increase with dosages of 3,5-dimethyldodecanoic acid greater than 100 μg. In field bioassays, males of a congeneric species, P. lecontei Lameere, were captured in southern California but not in Idaho

1,1′-(Ethane-1,2-di­yl)bis­(1,4,7-triazonane)

In the centrosymmetric title compound (dtne), C14H32N6, two 1,4,7-triaza­cyclo­nonane (tacn, or 1,4,7-triazonane) moieties are linked together each at an amino position by a single ethyl­ene spacer. The mol­ecular packing is supported by pairs of inter­molecular N—H⋯N hydrogen bonds, which form R 2 2(22) ring motifs and link the mol­ecules into infinite chains running parallel to the a axis

Characterisation of silent and active genes for a variable large protein of Borrelia recurrentis

BACKGROUND: We report the characterisation of the variable large protein (vlp) gene expressed by clinical isolate A1 of Borrelia recurrentis; the agent of the life-threatening disease louse-borne relapsing fever. METHODS: The major vlp protein of this isolate was characterised and a DNA probe created. Use of this together with standard molecular methods was used to determine the location of the vlp1(B. recurrentis A1) gene in both this and other isolates. RESULTS: This isolate was found to carry silent and expressed copies of the vlp1(B. recurrentis A1) gene on plasmids of 54 kbp and 24 kbp respectively, whereas a different isolate, A17, had only the silent vlp1(B. recurrentis A17) on a 54 kbp plasmid. Silent and expressed vlp1 have identical mature protein coding regions but have different 5' regions, both containing different potential lipoprotein leader sequences. Only one form of vlp1 is transcribed in the A1 isolate of B. recurrentis, yet both 5' upstream sequences of this vlp1 gene possess features of bacterial promoters. CONCLUSION: Taken together these results suggest that antigenic variation in B. recurrentis may result from recombination of variable large and small protein genes at the junction between lipoprotein leader sequence and mature protein coding region. However, this hypothetical model needs to be validated by further identification of expressed and silent variant protein genes in other B. recurrentis isolates

Di-tert-butyl N-[2,6-bis­(methoxy­meth­oxy)phen­yl]imino­diacetate

The title mol­ecule, C20H31NO8, has pseudo-C2 symmetry about the C—N bond, with the bis­(tert-butoxy­carbon­yl)amino group twisted from the benzene ring plane by ca 60° and the bulky tert-butoxy­carbonyl (Boc) groups are orientated away from the substituted aniline group. As part of an anti­bacterial drug discovery programme furnishing analogues of platensimycin, we unexpectedly synthesized the bis-Boc-protected aniline