An investigation of standard thermodynamic quantities as determined via models of nuclear multifragmentation

Both simple and sophisticated models are frequently used in an attempt to understand how real nuclei breakup when subjected to large excitation energies, a process known as nuclear multifragmentation. Many of these models assume equilibriumthermodynamics and produce results often interpreted as evidence of a phase transition. This work examines one class of models and employs standard thermodynamical procedure to explore the possible existence and nature of a phase transition. The role of various terms, e.g. Coulomb and surface energy, is discussed.Comment: 19 two-column format pages with 24 figure

Pseudo-single crystal electrochemistry on polycrystalline electrodes : visualizing activity at grains and grain boundaries on platinum for the Fe2+/Fe3+ redox reaction

The influence of electrode surface structure on electrochemical reaction rates and mechanisms is a major theme in electrochemical research, especially as electrodes with inherent structural heterogeneities are used ubiquitously. Yet, probing local electrochemistry and surface structure at complex surfaces is challenging. In this paper, high spatial resolution scanning electrochemical cell microscopy (SECCM) complemented with electron backscatter diffraction (EBSD) is demonstrated as a means of performing ‘pseudo-single-crystal’ electrochemical measurements at individual grains of a polycrystalline platinum electrode, while also allowing grain boundaries to be probed. Using the Fe2+/3+ couple as an illustrative case, a strong correlation is found between local surface structure and electrochemical activity. Variations in electrochemical activity for individual high index grains, visualized in a weakly adsorbing perchlorate medium, show that there is higher activity on grains with a significant (101) orientation contribution, compared to those with (001) and (111) contribution, consistent with findings on single-crystal electrodes. Interestingly, for Fe2+ oxidation in a sulfate medium a different pattern of activity emerges. Here, SECCM reveals only minor variations in activity between individual grains, again consistent with single-crystal studies, with a greatly enhanced activity at grain boundaries. This suggests that these sites may contribute significantly to the overall electrochemical behavior measured on the macroscale

From DNA sequence to application: possibilities and complications

The development of sophisticated genetic tools during the past 15 years have facilitated a tremendous increase of fundamental and application-oriented knowledge of lactic acid bacteria (LAB) and their bacteriophages. This knowledge relates both to the assignments of open reading frames (ORF’s) and the function of non-coding DNA sequences. Comparison of the complete nucleotide sequences of several LAB bacteriophages has revealed that their chromosomes have a fixed, modular structure, each module having a set of genes involved in a specific phase of the bacteriophage life cycle. LAB bacteriophage genes and DNA sequences have been used for the construction of temperature-inducible gene expression systems, gene-integration systems, and bacteriophage defence systems. The function of several LAB open reading frames and transcriptional units have been identified and characterized in detail. Many of these could find practical applications, such as induced lysis of LAB to enhance cheese ripening and re-routing of carbon fluxes for the production of a specific amino acid enantiomer. More knowledge has also become available concerning the function and structure of non-coding DNA positioned at or in the vicinity of promoters. In several cases the mRNA produced from this DNA contains a transcriptional terminator-antiterminator pair, in which the antiterminator can be stabilized either by uncharged tRNA or by interaction with a regulatory protein, thus preventing formation of the terminator so that mRNA elongation can proceed. Evidence has accumulated showing that also in LAB carbon catabolite repression in LAB is mediated by specific DNA elements in the vicinity of promoters governing the transcription of catabolic operons. Although some biological barriers have yet to be solved, the vast body of scientific information presently available allows the construction of tailor-made genetically modified LAB. Today, it appears that societal constraints rather than biological hurdles impede the use of genetically modified LAB.

The Social Studies Curriculum in Atlanta Public Schools During the Desegregation Era

This historical investigation explores how teachers, students, and education officials viewed the social studies curriculum in the local context of Atlanta, and the broader state of Georgia, during the post-Civil Rights era, when integration was a court-ordered reality in the public schools. During the desegregation era, Atlanta schools were led by Atlanta Public Schools (APS) Superintendent, Dr. Alonzo Crim. Brought to Atlanta as part of a desegregation compromise, Dr. Crim became APS\u27s first African American superintendent. In particular, the authors investigate how national social studies movements, such as Man: A Course of Study (MACOS), inquiry-based learning, co-curriculum activities, and standards movements, adapted to fit this Southeastern locale, at a time when schools were struggling to desegregate. Local curriculum documents written in the 1970s reveal a traditional social studies curriculum. By the 1980s, APS\u27s social studies curriculum guides broadened to include a stronger focus on an enacted community—inside the classroom and around the world. In oral history interviews, however, former teachers, students, and school officials presented contrasting perspectives of how the social studies curriculum played out in the reality of Atlanta\u27s public schools during the desegregation era

Exploring an Origin of the QCD Critical Endpoint

We discuss a new way to develop the exactly solvable model of the QCD critical endpoint by matching the deconfinement phase transition line for the system of quark-gluon bags with the line of their vanishing surface tension coefficient. In contrast to all previous findings in such models the deconfined phase is defined not by an essential singularity of the isobaric partition function, but by its simple pole. As a result we find out that the first order deconfinement phase transition which is defined by a discontinuity of the first derivative of system pressure is generated by a discontinuity of the derivative of surface tension coefficient.Comment: 5 pages, 2 figures, minor changes are mad