Creating discussions with classroom voting in linear algebra

We present a study of classroom voting in linear algebra, in which the instructors posed multiple-choice questions to the class and then allowed a few minutes for consideration and small-group discussion. After each student in the class voted on the correct answer using a classroom response system, a set of clickers, the instructor then guided a class-wide discussion of the results. We recorded the percentage of students voting for each option on each question used in 18 sections of linear algebra, taught by 10 instructors, at 8 institutions, over the course of 5 years, together recording the results of 781 votes on a collection of 311 questions. To find the questions most likely to provoke significant discussions, we identify the six questions for which votes were most broadly distributed. Here we present these questions, we discuss how we used them to advance student learning, and we discuss the common features of these questions, to identify why they were so good at stimulating discussions.     

Effect of chain length on the conformation and T cell recognition of synthetic hemagglutinin fragments

Circular dichroism and Fourier-transform infrared spectroscopies were used to compare the conformational mobility of 13-mer peptides covering the 317-329 region of the envelope protein hemagglutinin of human influenza A virus subtypes H1, H2 and H3 with that of their truncated deca- and nonapeptide analogs. These peptides were demonstrated to bind to the murine I-Ed major histocompatibility complex encoded class II and human HLA-B*2705 class I molecules. Despite the amino acid substitutions in the three 13-mer subtype sequences, no significant differences in the conformational properties could be shown. Deletion of the N-terminal three residues resulted in a shift to an increased alpha-helical conformer population in the 317-329 H1 peptide and the breakage of the 3(10) or weakly H-bonded (nascent) alpha-helix in the H2 and H3 peptides. The conformational change observed upon deletion did not influence the efficiency of I-Ed peptide interaction, however, the C-terminal Arg had a beneficial effect both on MHC class II and class I binding without causing any remarkable change in solution conformation.     

DABCO-bis(sulfur dioxide), DABSO, as a convenient source of sulfur dioxide for organic synthesis: utility in sulfonamide and sulfamide preparation

The charge-transfer complex generated from the combination of DABCO and sulfur dioxide, DABSO, is a bench-stable colorless solid suitable for use in organic synthesis as a replacement for gaseous sulfur dioxide. The complex can be combined with Grignard reagents to form sulfinates, which can then be converted in situ to a series of sulfonamides. Alternatively, reaction with anilines and iodine leads to the formation of a series of sulfamides. Cheletropic addition between DABSO and 2,3-dimethylbutadiene provides the corresponding sulfolene.     

Cyclotomic Birman–Wenzl–Murakami Algebras,II: Admissibility Relations and Freeness

The cyclotomic Birman-Wenzl-Murakami algebras are quotients of the affine BMW algebras in which the affine generator satisfies a polynomial relation. We study admissibility conditions on the ground ring for these algebras, and show that the algebras defined over an admissible integral ground ring S are free S-modules and isomorphic to cyclotomic Kauffman tangle algebras. We also determine the representation theory in the generic semisimple case, obtain a recursive formula for the weights of the Markov trace, and give a sufficient condition for semisimplicity.     

A modular system for regeneration of NAD cofactors using graphite particles modified with hydrogenase and diaphorase moieties

Pyrolytic graphite particles modified with hydrogenase and an NAD(+)/NADH cycling enzyme provide a modular heterogeneous catalyst system for regeneration of oxidised or reduced nicotinamide cofactors using H(2) and H(+) as electron source or sink. Particles can be tuned for cofactor supply under different conditions by appropriate choice of hydrogenase.     

Laser bronchoscopy with transglottic/supraglotticventilation to relieve dysphonia and subglottic obstruction

Dysphonia after endotracheal intubation usually indicates a glotticlesion but it can also herald an obstructing subglottic airway mass. Outpatient strobovideolaryngoscopy may be anatomically extended by transglottic videotracheobronchoscopy to achieve a thorough examination of the proximal bronchi, trachea, subglottis, glottis, and supraglottis in selected cases. Combining these techniques with lateral soft tissue x-ray studies of the neck in two patients with dysphonia and stridor, nearly identical postendotracheal intubation subglottic severely obstructing granulation “tumors” were diagnosed. Operative subglottic resection with a rigid ventilating laser bronchoscope combined with transglottic/supraglottic anesthetic ventilation techniques and contact-tip Nd-YAG laser phototherapy relieved the dysphonia and airway obstruction simultaneously. Normal vocal quality and full anatomical airway patency were achieved in both cases. Follow-up postoperative vocal rehabilitation and medical therapy sustained the surgical results.     

A CXCR4‐Targeted Site‐Specific Antibody–Drug Conjugate

A chemically defined anti‐CXCR4–auristatin antibody–drug conjugate (ADC) was synthesized that selectively eliminates tumor cells overexpressing the CXCR4 receptor. The unnatural amino acid p‐acetylphenylalanine (pAcF) was site‐specifically incorporated into an anti‐CXCR4 immunoglobulin G (IgG) and conjugated to an auristatin through a stable, non‐cleavable oxime linkage to afford a chemically homogeneous ADC. The full‐length anti‐CXCR4 ADC was selectively cytotoxic to CXCR4⁺ cancer cells in vitro (half maximal effective concentration (EC₅₀)≈80–100 pM ). Moreover, the anti‐CXCR4 ADC eliminated pulmonary lesions from human osteosarcoma cells in a lung‐seeding tumor model in mice. No significant overt toxicity was observed but there was a modest decrease in the bone‐marrow‐derived CXCR4⁺ cell population. Because CXCR4 is highly expressed in a majority of metastatic cancers, a CXCR4–auristatin ADC may be useful for the treatment of a variety of metastatic malignancies.     

A Model to Evaluate the Effect of Organizational Adaptation

When an organization's output declines due to either internal changes or changes in its external environment, it needs to adapt. In order to evaluate the effectiveness of different adaptation strategies on organizational performance, an organizational model composed of individual models of a five stage interacting decision maker was designed using an object oriented design approach and implemented as a Colored Petri net. The concept of entropy is used to calculate the total activity value, a surrogate for decision maker workload, based on the functional partition and the adaptation strategy being implemented. The individual decision maker's total activity is monitored, as overloaded decision makers constrain organizational performance. A virtual experiment was conducted; organizations implementing local and global adaptation strategies were compared to a control organization with no adaptation. The level of tolerance of the organization, the workload limit based on the concept of the bounded rationality constraint, was used to determined when a decision maker was overloaded: the limiting effect of the workload on performance. The timeliness of the organization's response was used in order to evaluate organizational output as a function of adaptation strategy.