Developing And Evaluating A Machine‐Scorable, Constrained Constructed‐Response Item

The use of constructed response items in large scale standardized testing has been hampered by the costs and difficulties associated with obtaining reliable scores. The advent of expert systems may signal the eventual removal of this impediment. This study investigated the accuracy with which expert systems could score a new, non‐multiple choice item type. The item type presents a faulty solution to a computer programming problem and asks the student to correct the solution. This item type was administered to a sample of high school seniors enrolled in an Advanced Placement course in Computer Science who also took the Advanced Placement Computer Science (APCS) Test. Results indicated that the expert systems were able to produce scores for between 82% and 97% of the solutions encountered and to display high agreement with a human reader on which solutions were and were not correct. Diagnoses of the specific errors produced by students were less accurate. Correlations with scores on the objective and free‐response sections of the APCS examination were moderate. Implications for additional research and for testing practice are offered.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108589/1/ets200144.pd

Symmetry adapted finite-cluster solver for quantum Heisenberg model in two-dimensions: a real-space renormalization approach

We present a quantum cluster solver for spin-$S$ Heisenberg model on a two-dimensional lattice. The formalism is based on the real-space renormalization procedure and uses the lattice point group-theoretical analysis and nonabelian SU(2) spin symmetry technique. The exact diagonalization procedure is used twice at each renormalization group step. The method is applied to the spin-half antiferromagnet on a square lattice and a calculation of local observables is demonstrated. A symmetry based truncation procedure is suggested and verified numerically.Comment: willm appear in J. Phys.

A connection between stress and development in the multicelular prokaryote Streptomyces coelicolor

Morphological changes leading to aerial mycelium formation and sporulation in the mycelial bacterium Streptomyces coelicolor rely on establishing distinct patterns of gene expression in separate regions of the colony. sH was identified previously as one of three paralogous sigma factors associated with stress responses in S. coelicolor. Here, we show that sigH and the upstream gene prsH (encoding a putative antisigma factor of sH) form an operon transcribed from two developmentally regulated promoters, sigHp1 and sigHp2. While sigHp1 activity is confined to the early phase of growth, transcription of sigHp2 is dramatically induced at the time of aerial hyphae formation. Localization of sigHp2 activity using a transcriptional fusion to the green fluorescent protein reporter gene (sigHp2–egfp) showed that sigHp2 transcription is spatially restricted to sporulating aerial hyphae in wild-type S. coelicolor. However, analysis of mutants unable to form aerial hyphae (bld mutants) showed that sigHp2 transcription and sH protein levels are dramatically upregulated in a bldD mutant, and that the sigHp2–egfp fusion was expressed ectopically in the substrate mycelium in the bldD background. Finally, a protein possessing sigHp2 promoter-binding activity was purified to homogeneity from crude mycelial extracts of S. coelicolor and shown to be BldD. The BldD binding site in the sigHp2 promoter was defined by DNase I footprinting. These data show that expression of sH is subject to temporal and spatial regulation during colony development, that this tissue-specific regulation is mediated directly by the developmental transcription factor BldD and suggest that stress and developmental programmes may be intimately connected in Streptomyces morphogenesis

Spectral Geometry of Heterotic Compactifications

The structure of heterotic string target space compactifications is studied using the formalism of the noncommutative geometry associated with lattice vertex operator algebras. The spectral triples of the noncommutative spacetimes are constructed and used to show that the intrinsic gauge field degrees of freedom disappear in the low-energy sectors of these spacetimes. The quantum geometry is thereby determined in much the same way as for ordinary superstring target spaces. In this setting, non-abelian gauge theories on the classical spacetimes arise from the K-theory of the effective target spaces.Comment: 14 pages LaTe

It Takes a Village: UN Peace Operations and Social Networks in Post-conflict Environments

Why civil society organizations (CSOs) so often are unable to make a difference during the transition process to peace despite the widespread recognition of their potential role in fostering peace? I argue that the involvement and contributions of local civil society organizations and women’s organizations (WOs) in post-conflict peacebuilding should be understood in terms of social networks and connections that emerge in the peacebuilding process. Both linking and bridging social capital shape social interactions essential for successful post-conflict reconstruction. Yet, external actors often implement policies that strengthen hierarchical networks at the expense of horizontal networks; thus, undermining the creation of bridging social capital. To explore the types of networks that emerge in post-conflict reconstruction I use semi-structured interviews conducted in Liberia. The evidence suggests that emerging horizontal networks are more robust in areas where local communities and women have a tradition of organizing. However, these networks remain fairly unstable. The assistance is mostly channeled centrally strengthening hierarchical ties and leading to distortions in the distribution of resources. This type of external intervention has negative implications and hinders bridging social networks even when these networks are present

A reduced subduction graph and higher multiplicity in S_n transformation coefficients

Transformation coefficients between {\it standard} bases for irreducible representations of the symmetric group $S_n$ and {\it split} bases adapted to the $S_{n_1} \times S_{n_2} \subset S_n$ subgroup ($n_1 +n_2 = n$) are considered. We first provide a \emph{selection rule} and an \emph{identity rule} for the subduction coefficients which allow to decrease the number of unknowns and equations arising from the linear method by Pan and Chen. Then, using the {\it reduced subduction graph} approach, we may look at higher multiplicity instances. As a significant example, an orthonormalized solution for the first multiplicity-three case, which occurs in the decomposition of the irreducible representation $[4,3,2,1]$ of $S_{10}$ into $[3,2,1] \otimes [3,1]$ of $S_6 \times S_4$, is presented and discussed.Comment: 12 pages, 1 figure, iopart class, Revisited version (several typographical errors have been corrected). Accepted for publication in J. Phys. A: Math. Ge