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Comprehensive Constraints On Dark Radiation Injection After BBN
No full textWe derive constraints on the injection of free-streaming dark radiation after big bang nucleosynthesis by considering the decay of a massive hidden sector particle into dark radiation. Such a scenario has the potential to alleviate the Hubble tension by introducing a new energy component to the evolution of the early Universe. We employ observations of the cosmic microwave background (CMB) from Planck 2018 and South Pole Telescope 2018, measurements of the primordial deuterium abundance, Pantheon+ type Ia supernovae data, and baryon acoustic oscillation measurements from BOSS DR12 to constrain these decay scenarios. Prerecombination decays are primarily restricted by observations of the CMB via their impact on the effective number of relativistic species. On the other hand, long-lived decay scenarios in which the massive particle lifetime extends past recombination tend to decrease the late-time matter density inferred from the CMB and are thus subject to constraints from Pantheon+ and baryon acoustic oscillations. We find that, when marginalizing over lifetimes of =[10−12.08,10−1.49] Gyr, the decaying particle is limited at 2 to only contribute a maximum of 3% of the energy density of the Universe. With limits on these decays being so stringent, neither short-lived nor long-lived scenarios are successful at substantially mitigating the Hubble tension
Brain Mechanisms Underlying The Emotion Processing Bias In Treatment-Resistant Depression
No full textDepression is associated with a cognitive bias towards negative information and away from positive information. This biased emotion processing may underlie core depression symptoms, including persistent feelings of sadness and a reduced capacity to experience pleasure. The neural mechanisms responsible for this biased emotion processing remain unknown. Here we had a unique opportunity to record stereotactic electroencephalography signals in the amygdala and prefrontal cortex (PFC) from 5 patients with treatment-resistant depression (TRD) and 12 patients with epilepsy (as control) while they participated in an affective bias task in which happy and sad faces were evaluated. First, compared with the control group, patients with TRD showed increased amygdala responses to sad faces in the early stage (around 300 ms) and decreased amygdala responses to happy faces in the late stage (around 600 ms) following the onset of faces. Furthermore, during the late stage of happy-face processing, alpha-band activity in the PFC as well as alpha-phase locking between the amygdala and the PFC were significantly greater in patients with TRD compared with the control group. The increased amygdala activation during the early stage of sad-face processing suggests an overactive bottom-up processing system in TRD. Meanwhile, the reduced amygdala response during the late stage of happy-face processing could be attributed to increased top-down inhibition by the PFC through alpha-band oscillation, which may be relieved following deep brain stimulation in the subcallosal cingulate and the ventral capsule/ventral striatum
Implied Occlusion And Subset Underestimation Explain The Weak-Outnumber-Strong Numerosity Illusion
No full textWhen equal numbers of white and gray dots are scattered against a dark gray background without overlapping, the number of white dots appears, subjectively, to be fewer than the number of gray dots (Lei & Reeves, 2018, 2022). This has been dubbed the weak-outnumber-strong numerosity illusion. Whereas previous reports of this illusion have argued that it is due to the gray dots creating a false pedestal in computing the total contrast of the white dots (thus lowering their perceived number), we report here evidence that two other principles seem to determine the effect. Four experiments will be reported. In Experiment 1, we show that subset estimation (as for the white dots) occurs equally for most subsets of different-color dots, but not for gray dots, suggesting that it is the gray dots that are primarily the cause of the illusion. In Experiments 2 and 3, we used partial occlusion or stereopsis to separate the white and gray dots into two depth planes. In both cases, the illusion is eliminated when the gray dots are in front, suggesting that it may be caused as a result of perceiving the dimmer gray dots as “filled in” behind the white dots. In Experiment 4, we re-evaluated the false floor illusion by varying the contrast of the gray dots. Our results suggest a U-shaped function, consistent with the idea that the subset underestimation of white is reduced when the gray dots are sufficiently dim, and is applied more equally to the gray dots as they are made much brighter, resulting in less relative difference at low and high gray levels. The weak-outnumber-strong illusion is visually compelling, but appears to be due to both an issue with underestimating subsets and with implied occlusion of the dimmer dots
Biophysical characterization of non-canonical DNA structures with small-molecule ligands
No full textA single strand of guanine-rich DNA can fold into a non-canonical four stranded secondary structure called the G-quadruplex (GQ) where guanines arrange into guanine tetrads via Hoogsteen hydrogen bonds. GQs can fold into either right- or left-handed helical conformations. The left-handed conformation is quite novel and has not been characterized extensively. We have characterized a lefthanded minimal motif (GGTGGTGGTGTG) that is found as a transcript variant in the KRAS proto-oncogene on chromosome 11. The KRAS gene is an important target as the protein it encodes is essential to the RAS/MAPK signaling pathway and is challenging to target with cancer therapeutics due to the protein’s small size. Biophysical techniques like circular dichroism, UV-Vis melting, and native PAGE were used to characterize the conservation and stability of left-handedness with the addition of nucleotides to the KRAS motif. Our data indicate that the addition of nucleotides disrupts left-handedness and that the left-hand construct has a complex UV-Vis melting profile with high hysteresis. The interactions between a left-handed KRAS variant and GQ-stabilizing small-molecule ligands like NMM, Braco19, and PhenDC3 were also characterized using similar biophysical techniques. NMM, Braco19, and PhenDC3 all confer a right-handed helicity to left-handed KRAS sequences. NMM, a selective ligand for parallel GQs, binds weakly (Ka = 0.124 ± 0.009 μM-1) and with a 1:1 binding stoichiometry. This work seeks to understand the conditions in which left-handed GQs form, the targeting of left-handed GQs with small-molecule ligands, and the biological relevance of left-handed GQs
Thinking Outside the Membrane: Investigating the Structure of the Influenza A M2 Ectodomain
Get PDFInfluenza A leads to annual epidemics that result in three-to-five million cases of severe illness each year and occasional devastating pandemics. Some current prevention and treatment methods target the M2 membrane protein on the surface of the virus. However, viral mutability and drug resistance require the targeting of more conserved parts of the protein.
The goal of this thesis was to investigate the secondary structure and dynamics of the M2 ectodomain (M2e), which is highly conserved across influenza viruses and across evolutionary time. The structure of M2e has previously been challenging to study because of its flexibility. In this study, I reconstituted full-length M2 protein into nanodiscs, which are model membrane bilayers surrounded by a structural membrane scaffold protein. To analyze the structure and dynamics of M2e, I used site-directed spin labeling electron paramagnetic resonance (SDSL-EPR).
I found that M2e is dynamic and flexible, with evidence of a turn between residues 14 and 21. Additionally, I found that residue 14 is membrane embedded, suggesting potential interactions between the M2e peptide and the lipid headgroups. These data are different from the trends found on the C-terminal tail of M2. In the presence of the antiviral drug rimantadine, M2e becomes less membrane embedded, indicating the presence of drug-induced conformational changes. In the presence of cholesterol, M2e similarly becomes less membrane embedded, which could provide evidence for interdomain coupling between M2e and the other domains of M2
Electronics Enclosure for Strawberry Harvesting Robot
No full textThis project presents the development of an electronic enclosure designed for integration onto a strawberry harvesting robot at L5 Automation. The enclosure aims to enhance the robot\u27s reliability and performance in challenging environmental conditions by housing the central computer in a weather-proof and dust-proof box. Key considerations in the design include vibration and shock management, heat management, waterproofing and dustproofing, as well as seamless integration with the existing robot setup. The enclosure is constructed from stainless steel sheet metal and 3D-printed PET components. Testing was conducted at Swarthmore for waterproofing and vibration resistance, while L5 Automation facilitated heat management and in-field performance evaluations. The tests demonstrated robust waterproofing and effective heat dissipation, enabling the computer to remain within safe operating temperatures. Moreover, the enclosure successfully mitigated vibrations, ensuring the protection of the computer and the robot\u27s overall functionality. This project represents a significant step towards upgrading the strawberry harvesting robot\u27s capabilities, offering improved durability and efficiency in diverse environmental conditions. The first prototype sets the foundation for future enhancements, including potential design iterations and material optimizations
Web Application: Object Detection and Tracking
No full textWith the rapid advancement of computer vision and artificial intelligence, object detection and tracking have become more relevant with increasing potential practical applications within the society. This project simulates these applications by developing a web application for object detection and tracking based on the Streamlit framework. The object detection implementation is based on two cutting-edge object detection algorithms: You Only Look Once Version 8 (YOLOv8) and Mask Region-based Convolutional Neural Network (Mask R-CNN). For YOLOv8, the advantages are fast and reasonable accuracy that is ideal for real-time applications, but the disadvantages is lower efficiency with smaller objects and object segmentation. Meanwhile, Mask R-CNN is more effective at object segmentation and detecting objects of varied sizes with higher accuracy, in exchange for slower run time and using more computational resources. To enable object tracking capabilities, the application leverages two popular tracking algorithms, BoT-SORT and ByteTrack. The strengths of BoT-SORT are higher accuracy with the usage of appearance and motions cue, but its weaknesses are in slower run time with higher demands for computational power and sensitivity to changes in appearance. Conversely, ByeTrack is generally faster with less consumption for computational power and better at tracking despite missing intermediate frames, but it has relatively lower accuracy and higher tendency for incorrect tracking in crowded scenes
Cost-effective PV Panel Back Mount for Temperature Control and Heat Utilization
Get PDFThe efficiency of a PV panel is limited by its temperature, where panel efficiency drops with increasing operating temperature, resulting in low panel efficiency in hot summers. This project aims to design and implement a cheap and efficient cooling system for a PV panel in the form of a panel back mount. For this project, Solar Lab facilities were updated and used as systems for testing the functionalities of the back-panel mount design. These facilities include a Q.PEAK DUO BLK-G8+ 340 Monocrystalline silicon module PV panel, a Prostar PS-15M solar charge controller for power maximization and PV panel power monitoring, a Seahawk deepcycle battery as a load for the panel output, and a solar thermal fluid circulation and data acquisition system consisting of various pumps, valves, and sensors. Testing was done on a sunny, cloudless, and warm day in late April.
The results show that the system operating at a relatively low temperature and small temperature difference, with a maximum panel temperature of less than 41℃ and a maximum panel temperature drop of 6 ℃, starts to experience a significant decrease in PV panel temperature and induce a reasonable increase in electrical output of around 20 Watts. Because of relatively cool ambient temperatures, the effectiveness of the heat transfer is not as large as estimated, and more experiments are recommended during mid-summer for a better understanding of the system. Future efforts should focus on increasing the thermal contact area, downsizing the system, and closing the circulation loop to generate conclusive results on system efficiency and cost-benefit evaluation
The Cuban Daycare System and the Gendered Division of Labor
No full textThe gendered division of labor refers to how work is divided according to gender. This has historically resulted in women’s exclusion from paid labor, and an unequal distribution of household and caregiving responsibilities. Marxist-feminist theory suggests that socialized systems of care can help mitigate the consequences of this division. This project seeks to examine the relationship between the universal daycare system in Cuba and the extent to which it impacts the gendered division of labor. Ideological, structural, and economic limitations constrain the system from realizing its full potential, offering broader insights into the limitations of policy in regards to achieving egalitarian relationships.
La división sexual del trabajo se refiere a cómo se divide el trabajo en función del género. Históricamente, esto ha dado lugar a la exclusión de las mujeres del trabajo remunerado y a una distribución desigual de las responsabilidades domésticas y de cuidado. La teoría marxista-feminista sugiere que los sistemas socializados de cuidados pueden ayudar a mitigar las consecuencias de esta división. Este proyecto pretende examinar la relación entre el Sistema universal de los círculos infantiles en Cuba y la medida en que influye en la división del trabajo en función del género. Las limitaciones ideológicas, estructurales y económicas impiden que el sistema desarrolle todo su potencial, lo que ofrece una visión más amplia de las limitaciones de las políticas para lograr relaciones igualitarias
