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To hum or not to hum: analyzing and provoking sound production in the American lobster (Homarus americanus)
Full text linkAmerican lobsters (Homarus americanus) produce humming sounds by vibrating their carapace. These sounds have a fundamental frequency on the order of 100 Hz, with multiple higher harmonics. Though I found no relationship between lobster carapace length and hum frequency, I observed sounds similarly structured to hums but with frequencies an order of magnitude higher, suggesting that lobsters may use a wider range of sounds than previously thought. Using laser vibrometry, I was able to pick up high frequencies of carapace vibration that were similar to those I observed on sound recordings. Lobsters seem to hum most readily when approached from above, but many studies have found it difficult to reliably find soniferous lobsters. To find a way to reliably evoke sound production in American lobsters without contributing to the sound environment, lobsters were exposed to overhead abstract visual stimuli on a screen, after which their behavioral reactions were recorded, as well as any sound production in response to the stimulus. Lobsters responded to the screen stimulus with the same types of behaviors with which they responded to general overhead physical stimuli. This study demonstrates that American lobsters may produce high-pitched sounds and that abstract visual cues can be used as a silent tool to elicit lobster behaviors, but not sound production
Investigating the Impacts of Drought on Turfgrass (\u3ci\u3eFestuca arundinacea\u3c/i\u3e) Chlorophyll-a Fluorescence Emission
Full text linkWhen photons from sunlight are absorbed by plants, they can take paths of photosynthesis, fluorescence, or energy dissipation. Instruments to quantify fluorescence have expanded in scale to allow measurements from satellites and flux towers using Solar-Induced Chlorophyll Fluorescence (SIF). Studies have found a positive correlation between SIF and gross primary productivity (GPP; representative of photosynthesis), suggesting SIF is a proxy for GPP. This conclusion encourages the use of SIF to inform decisions about carbon budgets and responding to climate change. Studies of fluorescence on the single-leaf scale have revealed that SIF measurements do not account for all variables nor is there an understanding of the impact of environmental factors, such as drought, on these measurements.
In this project, tall fescue turfgrass was placed in one of four differing drought severities for 19 days. Leaf-level measurements of photosynthesis and pulse-amplitude modulated fluorescence were made, demonstrating stomatal closure and inhibition of photosynthesis. This physiological change caused greater photon allocation to energy dissipation. Changes in greenness and the utilization of photoprotective mechanisms such as senescence and anthocyanin accumulation were observed. This study has provided an understanding of the temporal, physiological, and visible impacts of drought on turfgrass to inform interpretations of SIF in future experiments. Caution is crucial in utilizing SIF as a proxy for GPP before further research into the impact of drought on SIF is completed
Characterizing the Motor Activity Patterns of the Mammalian Thoracic Spinal Cord Neural Network
No full textVertebrate motor control employs central and peripheral neural circuitry to activate muscles within the forelimb, hindlimb, and axial regions. Within the cervical and lumbar regions of the mammalian spinal cord, central pattern generator (CPG) networks produce rhythmic activity that governs forelimb and hindlimb locomotion, respectively. Between these limb-controlling segments, thoracic spinal nerves innervate trunk muscles and organs critical for everyday function. However, investigation of the rhythmic capabilities of the thoracic network is limited. Current literature generally consigns the thoracic network to serving as a connective synaptic highway between limb CPGs, leaving questions regarding its intrinsic rhythmogenic abilities unanswered. To characterize the rhythmic capabilities and investigate the structural organization of thoracic neural circuitry, spinal cords from postnatal mice (P1-P6) were extracted. Spinal preparations were maintained as full thoracolumbar cords or isolated thoracic preparations (T2-T12). Motor activity recordings were obtained extracellularly from thoracic or lumbar ventral roots. To assess the effects of neuromodulation on thoracic motor rhythms, pharmacological experiments using serotonin, NMDA, or dopamine were conducted. The organization of thoracic neural circuitry was investigated though the introduction of glutamatergic receptor antagonists. The present study determined that the thoracic spinal network can produce and sustain its own distinct rhythmic motor activity patterns once released from lumbar entrainment that seem to correspond to motor and autonomic trunk behaviors. Preliminary findings suggest that contralateral synchronization, typical of thoracic rhythms, is mediated by excitatory glutamatergic synapses. Further, elimination of glutamatergic activity revealed an underlying left-right alternating circuitry, posing intriguing evolutionary and functional questions
Fall forward, spring back: Drivers of synchrony in the sea star crawl-bounce gait transition
Full text linkThe Froude number is the ratio of kinetic energy to gravitational potential energy used during locomotion and is often used to analyze gait transitions. Here, I compare and contrast the human walk-run gait transition, which occurs at a consistent Froude number of 1 because there exists a mechanical speed limit to walking, and the sea star crawl-bounce gait transition, which occurs around Froude numbers of 1*10^-3. In this thesis I investigate why sea stars exhibit two gaits despite lacking brains and moving at Froude numbers far below other known gait transitions, hypothesizing (1) that the crawl-bounce transition may be mechanical and thus still depends on the Froude number, and (2) that the crawl-bounce transition is best modeled gradually compared to the instantaneous human walk-run transition. Thirty sea stars were filmed and the resulting kinematic data is used here to inform thinking about the crawl-bounce transition. I first discuss damped driven harmonic motion of a single oscillator, but eventually turn to using coupled oscillators and deriving that a coupling constant between metronomes on a moving base is the Froude number, which is therefore relevant for the crawl-bounce transition. I lastly discuss a purely mathematical analogue of the crawl-bounce transition as a Hopf bifurcation in horizontal speed and vertical velocity phase space, which leads to a rough model with results qualitatively similar to observed kinematic data from films, and indicates that a gradual transition is in fact a good fit for the crawl-bounce transition
Investigating the effect of Fuc-O-NAP on the glycosylation of \u3ci\u3eHelicobacter pylori\u3c/i\u3e
No full textThe rise of antibiotic-resistant bacteria is becoming a global health threat, necessitating the discovery of new antibiotics. Bacterial glycans, a dense array of carbohydrates on the surface of bacteria, are a great antibiotic target because of their distinctive bacteria-specific structures and their ties to bacterial fitness and function. Metabolic inhibitors acting as substrate decoys can disrupt proper bacterial glycan biosynthesis and potentially form the basis of new antibiotics. O-glycosides based on bacterial monosaccharides are effective and selective inhibitors of bacteria glycan biosynthesis in the gastric pathogen Helicobacter pylori. Building on previous work in our lab, we crafted 2-naphthalenemethanol (O-NAP) glycosides based on rare bacterial monosaccharide scaffolds. We explored their ability to inhibit glycan biosynthesis in the pathogenic bacteria Helicobacter pylori, in the commensal gut bacteria Bacteroides fragilis, and in mammalian cells. We found that Fuc-O-NAP disrupts glycoprotein biosynthesis and various fitness attributes in H. pylori. This study demonstrates that Fuc-O-NAP is a more potent glycosylation inhibitor than previously reported O-benzyl or S-benzyl analogs while maintaining selectivity against commensal bacteria
Eelgrass meadow structure drives epifaunal community composition more than temperature during a Marine Heat Wave in the Gulf of Maine
No full textAbiotic environmental variation can drive the spatio-temporal variation of macrophyte meadow structure and associated community composition. Temperature directly impacts eelgrass (Zostera marina) meadow structure and epifaunal invertebrate community composition. Marine heat waves (MHW) represent scenarios where temperature may be extreme enough to drive community composition. I conducted a 2-year survey of Gulf of Maine eelgrass meadows across northern and southern sites, repeating the surveys monthly throughout the summer growing season. Sampling coincided with the end of the 2021-2023 Gulf of Maine MHW. During the 2022 MHW, northern meadows were 44.6% more dense, and canopy heights were 156% taller than southern meadows. Southern meadows demonstrated decline and/or die-off throughout the MHW. NMDS analyses revealed that during the MHW, epifaunal communities clustered regionally at all sampling points, while during the recovery period, epifaunal communities were similar in June and diverged by region in July and August. In the post-MHW summer, meadow structure significantly declined across all sites, but northern sites displayed a stronger recovery. Envfit analysis indicated that temperature was not significantly correlated with epifaunal communities, while meadow structure was highly associated with northern epifaunal communities. These results indicate that MHWs may indirectly impact epifaunal communities through decreasing meadow structure and available habitat space. Overall, the effects of warming can have varied impacts for extended periods of time, not only individually impacting species, but impacting the interactions between species. This work shows the need to study global change from an ecosystem-wide scale to help detangle interactive and delayed effects
Group-theory constraints on color-ordered four-point amplitudes in SO(\u3ci\u3eN\u3c/i\u3e) gauge-theories
No full textScattering amplitudes, used for calculating particle interaction probabilities, aredifficult to calculate in theories beyond the Standard Model. These theories areoften formulated as SO(N) gauge theories. This paper addresses this challengeby deriving group-theoretic constraints on four-point color-ordered amplitudesin SO(N) gauge theories at all loop order. We find that there exist 6L − 14linearly independent color factors for L ≥ 5 and we derive their explicit form
The Influence of Polymers on the Solubility of Flufenamic Acid and Mefenamic Acid Cocrystals
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The Body Negotiating Unprecedented Movement
Full text linkA collection of poems exploring threads including the Lower East Side, immigration, stray animals, art, and Chinese-American identity
Beyond Religion: Reframing Liberal Democracy’s Treatment of Exemptions Within the Public-Private Separation
No full textThe question of how liberal democracy should treat religion, and whether this can include offering religious exemptions to general laws, is highly contested. Religious exemptions highlight the difficulty of fairly singling out or treating specially a particular idea of “religion” in a system that promises to put aside controversial questions about the good life in order to have a fair and functioning system of government. Furthermore, the debate about religious exemptions exists within the context of the larger debate about the overall fairness of liberal democracy and the fairness of separating out any matters (including religion) from government. The fairness of exemptions rests upon the fairness of separating the public and private spheres in the first place. This thesis makes two contributions to this debate. Firstly, it places the issue of exemptions within the framework of the public/private and investigates a possible public reason for offering exemptions using a Rawlsian liberal framework. Since the public/private divide is somewhat flexible and evolving, exemptions should be offered not because we treat “religion” specially, but as one of many parts of a continual process of refining the separation between public and private realms. Secondly, the way exemption cases emerge in the U.S. context is shown to be about far more than just religion, but at the nexus of many debates about what areas of life ought to be within or beyond government control, including debates over the public or private nature of the market, corporations, and public schooling