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Teachers' treatment of mathematical conventions
Get PDFMathematics curriculum can be delineated as either arbitrary conventions—names, labels, symbols, notations, or usages which have been historically agreed upon by “mathematicians” — or necessary rules, relationships, and properties (Hewitt, 1999). This dissertation is a collection of three distinct articles: (1) a rhetorical essay arguing for a greater awareness of mathematical conventions and a student-centered approach in the instruction of mathematical conventions, (2) a study focusing on how conventions are taught in classrooms, and (3) a practioners’ piece highlighting the study. The study was guided by the question, “How are mathematical conventions introduced and treated by teachers in elementary classrooms in the context of introducing coordinate graphing?” A common set of 12 early algebra lessons enacted in 78 classrooms across the grades 3-5 were coded using a modified analytic induction approach. Teachers rarely explicitly addressed conventions as such, and when spoken of they were often attributed to external agents (e.g., “they”, “people”, “mathematicians”). The phenomena of “(mis)conventions” describes the unnecessarily rigid language used by some teachers in the treatment of some conventions. Also addressed are findings pertaining to instructional supports, student responses to conventions, and cases of delegate authority to students for exploration of alternatives to canonical conventions.Curriculum and Instructio
How a US “Suez Moment” Could Hollow the US Alliance System
Get PDFThis article contends that while the United States still fields potent military capabilities, the narrowing military balance with China means that a future Indo-Pacific clash in which Beijing gains a regional edge is no longer implausible. Using the 1956 Suez Crisis as an analogue, the study asks how a public exposure of US capability shortfalls—an American “Suez moment”—would reverberate through Washington’s global alliance network. The article employs a five-factor theory of defense cooperation—covering three structural and two situational factors—to evaluate two post-setback scenarios. In the first, multiple factors erode simultaneously, hollowing NATO and Indo-Pacific hub-and-spoke ties into nominal shells. In the second, enduring structural and favorable situational factors allow the alliances to adapt, with the United States reemerging as first among equals. The study concludes that credible remedies to underlying US capability deficits and thoughtful alliance management based on the studied five factors will determine which path prevails after a potential US “Suez moment.”LBJ School of Public Affair
Analyzing deception through Theory of Mind strategies and Machiavellian Intelligence in Don Juan Manuel’s El Conde Lucanor
Get PDFThis dissertation analyzes Theory of Mind and Machiavellian Intelligence in Don Juan Manuel's El Conde Lucanor, one of the most famous collections of Spanish didactic tales. Didactic literature lends itself to cognitive literary studies because of its inherently manipulative nature, and its intent to persuade a reader through short, moralistic stories. The goal of this analysis is to show how Juan Manuel’s characters employ deception as a means for acquiring agency and power, advancing their social positions and negotiating complex social circumstances. These characters’ deceptions are effective due to the Theory of Mind they create about their victims, which informs their process of manipulation. I argue that the behaviors of Juan Manuel’s characters reflect the historical circumstances of a pluralistic medieval Iberia, and the real-life anxieties his readers may have been experiencing as Spain transitioned to a homogenous Christian state. Readers could reap various cognitive benefits from these exempla, such as providing a space for them to rehearse difficult situations, and exposing them to characters who defy their expectations and stereotypes, and challenge the reader’s Theory of Mind.Spanish and Portugues
Understanding women's perspectives of mental health literacy within the context of postpartum depression : a qualitative descriptive study
Get PDFThe purpose of this study was to use the mental health literacy framework to understand women’s abilities to recognize postpartum depression, implement self-help interventions for depressive symptoms, obtain professional help, and seek information about the disorder. The objective was to provide a descriptive representation of women’s perspectives of mental health literacy that may be considered when providing mental health care, designing instruments that assess mental health literacy, and developing interventions to improve mental health literacy. Twelve women aged 25 to 38 years old with a history of postpartum depressive symptoms provided from twenty-two to sixty-six pages of interview transcripts that described their experiences of mental health literacy regarding postpartum depression, and these data were examined through qualitative content analysis. Qualitative content analysis of the contextual factors that affected participants’ mental health literacy from a phenomenologically-inspired perspective revealed 3 themes: Sinking into the Abyss, Drowning from Constraints, and Hitting Rock Bottom. Next, qualitative content analysis was performed to describe themes that portrayed salient aspects of participants’ experiences of mental health literacy regarding postpartum depression. Findings indicated that, despite being well-informed about many aspects of mental health literacy regarding postpartum depression, the women were unable to perform most functional aspects of the mental health literacy framework because of the constraints and restrictions imposed on them postpartum. Women were unable to recognize that they were experiencing postpartum depression through self-appraisal and were unaware of risk factors for the disorder. They believed the causes of their depressive symptoms were circumstantial factors and personal failings. Women were knowledgeable about self-help interventions for postpartum depression but deemed such interventions impractical in the context of the postpartum period. Professional help was considered beneficial by women so long as it was provided in a caring manner that was tailored to their unique treatment preferences by professionals with whom they had pre-established relationships. The attitudes of hope, determination, and self-advocacy facilitated help-seeking and treatment compliance. Women knew how to seek information about postpartum depression, but at times this activity caused distress. Recommendations for future research and implications for nursing practice were discussed.Nursin
Biosynthetic studies of oxetanocin A and mechanistic studies of a B₁₂-dependent radical SAM enzyme
Get PDFOxetanocin A (OXT-A) is a potent antitumour, antiviral and antibacterial natural product isolated from Bacillus megaterium NK 84-0218. OXT-A possesses an unusual oxetane sugar attached to adenine. The oxetane sugar is rare among natural products and is of particular interest for biosynthetic study due to the strained four-membered ring. This dissertation describes the biosynthetic study of OXT-A and the mechanistic study of the enzymes responsible for oxetane ring formation. Genetic experiments were carried out to show that a B₁₂-dependent radical S-adenosyl-L-methionine (SAM) enzyme, OxsB, and an HD-domain phosphohydrolase, OxsA, are both required for the biosynthesis of OXT-A. The aldehyde form of OXT-A 5′-monophosphate was observed as the reaction product and fully characterized in the enzymatic assay of OxsA and OxsB with 2′-deoxyadenosine phosphate as the substrate. Thus, OxsB represents the first example of a B₁₂-dependent radical SAM enzyme that catalyzes a ring contraction reaction. In collaboration with Dr. Catherine L. Drennan’s lab from MIT, we solved the structure of OxsB which represents the first crystal structure of this superfamily member. Further biochemical experiments indicated that OxsA and OxsB have to interact with each other to catalyze the ring contraction reaction. The aldehyde form of OXT-A 5′-monophosphate could be further reduced by an alcohol dehydrogenase, which is not encoded in the OXT-A biosynthetic gene cluster, to afford OXT-A 5′-monophosphate. Finally, OXT-A 5′-monophosphate could be dephosphorylated by OxsA to afford OXT-A. Besides the aldehyde product, a tetrahydrothiazine side product was also observed and fully characterized in the OxsA and OxsB reaction. Several labeled compounds were prepared to investigate the ring contraction reaction catalyzed by OxsA and OxsB. The reaction is proposed to be initiated by hydrogen atom abstraction from C2′ of the substrate based on the labeling experiments with [2′-²H₂]-2′-dAMP and [3′-²H]-2′-dAMP. Labeling experiments with (2′R)-[2′-²H]-2′-dAMP and (2′S)-[2′-²H]-2′-dAMP indicated that hydrogen atom abstraction from the pro-R site is favored compared with the pro-S site. Further labeling experiments revealed that hydrogen atom abstraction is performed by the radical SAM machinery, rather than Ado-Cbl. Me-Cbl is not directly involved in the OxsA and OxsB reaction neither. In order to gain further mechanistic insights into the OxsA and OxsB reaction, several substrate analogs were also tested. OxsB was found to have methyltransferase activity in addition to oxidative mutase activity.Pharmaceutical Science
The Arsenal of Democracy: Keeping China Deterred in an Age of Hard Choices
Get PDFThe margin of deterrence against China is rapidly shrinking, driven not by a failure of US technological innovation, but by the American and allied defense industrial base’s inability to field and sustain cutting edge capabilities at scale, at speed, and under constant pressure. To counter China’s rapid conventional and nuclear buildup in scouting and strike capabilities, the United States must urgently expand its defense industrial base to revitalize its deterrence system. This article argues that defending vital US interests requires a comprehensive focus on systemic vulnerabilities that offer the fastest path to defeat, chiefly the brittleness of scouting (C4ISR) and logistics networks. The most time-sensitive industrial investments are in munitions, to close a widening missile gap; drones, to compete with China’s mass production; and submarines, to address the profound crisis in the attack submarine force’s industrial capacity and sustainment. Stabilizing the balance does not require a doubling of the defense budget, but rather a coordinated, whole-of-system effort by the Pentagon and Congress to make hard choices, prioritize key industrial programs, and reform the allied acquisition process to produce what the evolving force requires. Achieving these goals requires a political mandate to discard the notion of “business as usual.”LBJ School of Public Affair
Effects of preceding vowels on physiological responses to successive consonants
Get PDFAntecedent to speech understanding is speech perception, which relies on accurate information transmission in both ascending and descending auditory neural pathways. The auditory brainstem encodes the strength and fidelity of incoming signals as they travel through the afferent pathway en route to the auditory cortex. Unlike the recognition of environmental sounds, listeners need to detect, discriminate and then identify the critical characteristics of individual speech sounds before meaning is assigned. For example, a syllable consists of two successive phonemes arranged as consonants preceding a vowel (C-V) or vice versa (V-C). Because the subcortical mechanisms for encoding time-varying speech sound before cortical involvement remain less understood, these experiments measured transient auditory brainstem responses (ABRs) and frequency-following responses (FFRs) to speech. The analyses of ABRs focused on the burst onset of the stimulus, and FFRs targeted the formant transition and fₒ. This study aims to tap the subcortical mechanisms responsible for encoding speech sounds when there are effects of preceding sounds by using non-invasive means. Synthesized C-V syllables /bɑ/, /dɑ/, and /gɑ/, were used to create the syllabic context for “consonant leading” (e.g., /bɑ/) and “consonant trailing” conditions (e.g., /ɑb/) to assess the preceding phoneme effects. Additionally, “abbreviated vowel” and “typical vowel” lengths were created to test further the preceding phoneme’s effects. ABR peak picking analysis concentrated on transient onset in the C-V syllable; the FFR analyses consisted of phase consistency, frequency-following amplitude, and stimulus-to-response correlation and focused on the formant transition and fₒ to describe the preceding phoneme effects. Decreased ABR and FFR measurements in the consonant trailing condition suggested decreased subcortical neural encoding of speech features when there is a preceding phoneme. The trend of increased ABR amplitude implied more robust neural encoding to burst onset when lengthening the preceding vowel. However, decreased phase consistency to fₒ suggested possible interference from spectral leakage, change-evoked cortical activity during the C-V transition, and oscillatory entrainment. As the first study using non-invasive measurements of speech-ABRs on preceding phonemes, we observed the negative effects of prior occurring vowels on successive stop consonants. Increasing the preceding vowel duration may strengthen the neural encoding to burst onset. The variation in response magnitude may relate to neural re-synchronization after recovery.Communication Sciences and Disorder
Second throat : Black persona poetry and the archive, 2000-2015
Get PDF“Second Throat: Black American Persona Poetry and the Archive, 2000-2015” investigates the prevalence of the use of persona within contemporary Black American poetry. Persona poetry is by no means a new form. Nor is the increased use of persona limited to Black American poets. Yet, from Cornelius Eady’s Brutal Imagination (2001) to Tyehimba Jess’s Pulitzer-Prize-winning Olio (2016), the 2000s have seen a sharp rise in Black American poets employing persona poetry, often including and interrogating archival materials as they do so. In “Second Throat,” I contend that this use of persona constitutes a significant trend and argue that these poets utilize persona as means to reclaim Black voices that have been silenced or misheard in the Archive—a site that propagates and perpetuates power-knowledge. Persona provides a vehicle both for signifyin’ on the Archive’s historical portrayal of Blackness, and, in complicating how past constructions of Blackness are read, a concomitant means of broadening the boundaries of contemporary Black identity and the corresponding racial imaginary. After an introduction that contextualizes this recent body of Black American persona poetry and establishes my hermeneutic for interpreting its texts, “Second Throat” contains two sections that organize contemporary Black persona poetry according their personae’s varying levels of audibility in the Archive. The first section, “The Spoken,” examines subjects whose voices have been heard, but often misinterpreted or appropriated, juxtaposing Elizabeth Alexander’s treatment of the Amistad Africans in American Sublime (2005) with Adrian Matejka’s The Big Smoke (2013), which takes heavyweight boxer Jack Johnson as its persona. The second section, “The Unspoken,” pairs Natasha Trethewey’s Native Guard (2006), voiced by an unnamed Native Guardsmen, with Frank X. Walker’s creative imagining of York, the enslaved Black man who played an integral role in the Lewis and Clark Expedition, in Buffalo Dance (2004). These subjects are seen, but not heard in the Archive. The coda, “The Unspeakable,” discusses child-murderer Susan Smith’s imagined alibi Mr. Zero from Cornelius Eady’s Brutal Imagination (2001) as inanimate personae. Together, the chapters reveal how these poets conjure a counterarchival poetics, one that pressures and reframes existing archival narratives of Blackness.Englis
The Changing Face of War—And of Our Work
Get PDFIn their introduction to Volume 9, Issue 1, directors Adam Klein and Joseph Maguire discuss the changes to TNSR and their vision for the future of the journal.LBJ School of Public Affair
Enhancing the performance of chip-scale passive electronic network components by the self-rolled-up membrane technology
Get PDFPower inductors typically need hundreds of micro-Henries in inductance and ampere-level current carrying capacity as magnetic energy storage devices. Driven by the requirement of compact power converters in Internet-of-Things and Cyber-Physical-System applications, making inductors with small footprints but considerable power-handling abilities often mandates conflicting requirements in designs and processes. 3D air-core microtubes fabricated using the self-rolled-up membrane (S-RuM) technology can achieve a higher inductance density than planar structures. Metal and core post-S-RuM fabrication electroplating methods then further solve the S-RuM design limitations where the metal film thickness limited resistive loss and air-core limited magnetic material integration. A DC resistance improvement of over 10x and an inductance boost of more than 30x in parallel-processed Cu-shell plated and permalloy partial core-plated 3D inductors are achieved. The improvement is projected to reach hundreds of times boost to inductance density once the entire core is filled based on 3D electromagnetic modeling, paving the way for scaling this technology for applications in power electronics such as converters and power supplies. Interdigital capacitor and angled inductor designs are then proposed and fabricated, both serving as starting points to push for high-frequency filter network devices. 3D microwave (~1-10 GHz) S-RuM L-C filter that combines inductive and capacitive components monolithically into a single L-C network architecture is realized, reducing the on-chip area footprint significantly. The network layouts of the L and C components are reconfigurable by selecting appropriate input, output, and ground contact routing topographies. Their area and volume footprints are 0.095 mm² and 0.01 mm³, respectively, which are ~10x smaller than most of the comparable conventional filter designs. Finally, the overlapping and non-overlapping status of the interdigital capacitors further paved the way to integrate piezoelectrically tunable material into the stack, enabling the frequency tuning of the L-C network. These S-RuM-enabled L-C filter networks represent a significant advancement in the miniaturization and integration of RF devices for applications in mobile connectivity.Electrical and Computer Engineerin