Showing 1561 - 1570 of 5709 Items
Modeling UV Light Through N95 Filters
Date: 2023-01-01
Creator: Lorenzo Hess
Access: Open access
- Reuse of N95 FFRs helps mitigate the effects of shortages. UV-C exposure is an ideal method for the decontamination necessary for FFR reuse. Recent research quantifies the transmittance of UV-C through the 3M1870+ and 3M9210+ FFRs [1]. Other research measures the reduction in viral load in relation to UV-C exposure time [11]. We design and program a ray tracing simulator in MATLAB to characterize the distribution of scattered photons in N95 FFRs. We implement an object-oriented FFR with configurable physical characteristics. We use the simulator to record the number of photons available for decontamination in each sub-layer of the filtering layers of the 3M1870+ and 3M9210+ for a given number of photons incident to the layers. We make assumptions about the photon absorption and viral deactivation in each sub-layer to derive a relation between the number of incident photons and the number of viruses remaining. The transmittance computed by our simulator matches the experimentally measured transmittance. The diameter of the simulated scattered beam also matches the experimentally measured scattered beam diameters. Our data, combined with our assumptions about absorption and deactivation, however, fail to account for the dropoff in viral load observed at about 25 seconds of exposure time in the 3M1870+.
Molecular, mass spectral, and physiological analyses of orcokinins and orcokinin precursor-related peptides in the lobster Homarus americanus and the crayfish Procambarus clarkii
Date: 2009-02-01
Creator: Patsy S. Dickinson, Elizabeth A. Stemmler, Elizabeth E. Barton, Christopher R. Cashman, Noah P., Gardner, Szymon Rus, Henry R. Brennan, Timothy S. McClintock, Andrew E. Christie
Access: Open access
- Recently, cDNAs encoding prepro-orcokinins were cloned from the crayfish Procambarus clarkii; these cDNAs encode multiple copies of four orcokinin isoforms as well as several other peptides. Using the translated open reading frames of the P. clarkii transcripts as queries, five ESTs encoding American lobster Homarus americanus orthologs were identified via BLAST analysis. From these clones, three cDNAs, each encoding one of two distinct prepro-hormones, were characterized. Predicted processing of the deduced prepro-hormones would generate 13 peptides, 12 of which are conserved between the 2 precursors: the orcokinins NFDEIDRSGFGFN (3 copies), NFDEIDRSGFGFH (2 copies) and NFDEIDRSGFGFV (2 copies), FDAFTTGFGHN (an orcomyotropin-related peptide), SSEDMDRLGFGFN, GDY(SO3)DVYPE, VYGPRDIANLY and SAE. Additionally, one of two longer peptides (GPIKVRFLSAIFIPIAAPARSSPQQDAAAGYTDGAPV or APARSSPQQDAAAGYTDGAPV) is predicted from each prepro-hormone. MALDI-FTMS analyses confirmed the presence of all predicted orcokinins, the orcomyotropin-related peptide, and three precursor-related peptides, SSEDMDRLGFGFN, GDYDVYPE (unsulfated) and VYGPRDIANLY, in H. americanus neural tissues. SAE and the longer, unshared peptides were not detected. Similar complements of peptides are predicted from P. clarkii transcripts; the majority of these were detected in its neural tissues with mass spectrometry. Truncated orcokinins not predicted from any precursor were also detected in both species. Consistent with previous studies in the crayfish Orconectes limosus, NFDEIDRSGFGFN increased mid-/hindgut motility in P. clarkii. Surprisingly, the same peptide, although native to H. americanus, did not affect gut motility in this species. Together, our results provide the framework for future investigations of the regulation and physiological function of orcokinins/orcokinin precursor-related peptides in astacideans. © 2008 Elsevier Inc. All rights reserved.
Midgut epithelial endocrine cells are a rich source of the neuropeptides APSGFLGMRamide (Cancer borealis tachykinin-related peptide Ia) and GYRKPPFNGSIFamide (Gly1-SIFamide) in the crabs Cancer borealis, Cancer magister and Cancer productus
Date: 2007-02-01
Creator: Andrew E. Christie, Kimberly K. Kutz-Naber, Elizabeth A. Stemmler, Alexandra Klein, Daniel I., Messinger, Christopher C. Goiney, Anna J. Conterato, Emily A. Bruns, Yun Wei A. Hsu, Lingjun Li, Patsy S. Dickinson
Access: Open access
- Over a quarter of a century ago, Mykles described the presence of putative endocrine cells in the midgut epithelium of the crab Cancer magister (Mykles, 1979). In the years that have followed, these cells have been largely ignored and nothing is known about their hormone content or the functions they play in this species. Here, we used a combination of immunohistochemistry and mass spectrometric techniques to investigate these questions. Using immunohistochemistry, we identified both SIFamide-and tachykinin-related peptide (TRP)-like immunopositive cells in the midgut epithelium of C. magister, as well as in that of Cancer borealis and Cancer productus. In each species, the SIFamide-like labeling was restricted to the anterior portion of the midgut, including the paired anterior midgut caeca, whereas the TRP-like immunoreactivity predominated in the posterior midgut and the posterior midgut caecum. Regardless of location, label or species, the morphology of the immunopositive cells matched that of the putative endocrine cells characterized ultrastructurally by Mykles (Mykles, 1979). Matrix-assisted laser desorption/ ionization-Fourier transform mass spectrometry identified the peptides responsible for the immunoreactivities as GYRKPPFNGSIFamide (Gly 1-SIFamide) and APSGFLGMRamide [Cancer boreatis tachykinin-related peptide Ia (CabTRP Ia)], respectively, both of which are known neuropeptides of Cancer species. Although the function of these midgut-derived peptides remains unknown, we found that both Gly1-SIFamide and CabTRP Ia were released when the midgut was exposed to high-potassium saline. In addition, CabTRP Ia was detectable in the hemolymph of crabs that had been held without food for several days, but not in that of fed animals, paralleling results that were attributed to TRP release from midgut endocrine cells in insects. Thus, one function that midgut-derived CabTRP Ia may play in Cancer species is paracrine/hormonal control of feeding-related behavior, as has been postulated for TRPs released from homologous cells in insects.
Identification and characterization of genes involved in Helicobacter pylori lipopolysaccharide and glycoprotein biosynthesis Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2021-01-01
Creator: Andrew James Mulholland
Access: Access restricted to the Bowdoin Community
Focusing Surface-Acoustic-Wave Microcavities on GaAs
Date: 2020-01-22
Creator: Madeleine E. Msall, Paulo V. Santos
Access: Open access
- Focusing microcavities for surface acoustic waves (SAWs) produce highly localized strain and piezoelectric fields that can dynamically control excitations in nanostructures. Focusing transducers (FIDTs) that generate SAW beams that match nanostructure dimensions require pattern correction due to diffraction and wave-velocity anisotropy. The anisotropy correction is normally implemented by adding a quadratic term to the dependence of the wave velocity on the propagation angle. We show that a SAW focusing to a diffraction-limited size in GaAs requires corrections that more closely follow the group-velocity wave front, which is not a quadratic function. Optical interferometric mapping of the resultant SAW displacement field reveals tightly focused SAW beams on GaAs with a minimal beam waist. An additional set of Gouy-phase-corrected passive fingers creates an acoustic microcavity in the focal region with a small volume and a high quality factor. Our λSAW=5.6μm FIDTs are expected to scale well to the approximately 500-nm wavelength regime needed to study strong coupling between vibrations and electrons in electrostatic GaAs quantum dots.
Determining the sites at which neuromodulators exert peripheral effects in the cardiac neuromuscular system of the American Lobster, Homarus americanus
Date: 2021-01-01
Creator: Audrey Elizabeth Jordan
Access: Open access
- Networks of neurons known as central pattern generators (CPGs) generate rhythmic patterns of output to drive behaviors like locomotion. CPGs are relatively fixed networks that produce consistent patterns in the absence of other inputs. The heart contractions of the Homarus americanus are neurogenic and controlled by the CPG known as the cardiac ganglion. Neuromodulators can enable flexibility in CPG motor output, and also on muscle contractions by acting on the neuromuscular junction and the muscle itself. A tissue-specific transcriptome gleaned from the cardiac ganglion and cardiac muscle of the American lobster was used to predict the sites and sources of a variety of crustacean neuromodulators. If corresponding receptors were predicted to be expressed in the cardiac muscle, then it was hypothesized that the neuropeptide had peripheral effects. One peptide for which a cardiac muscle receptor was identified is myosuppressin. Myosuppressin has been shown to have modulatory effects at the cardiac neuromuscular system of the American lobster. In previous research, myosuppressin had modulatory effects on the periphery of cardiac neuromuscular system alone. It remains an open question of whether myosuppressin acts on the cardiac muscle directly, if it is exerting its effects at the neuromuscular junction (NMJ), or both. To test this, I performed physiological experiments on the isolated NMJ. Myosuppressin did not modulate the amplitude of the excitatory junction potentials. Since no modulatory effects were seen at the NMJ, the cardiac muscle was isolated from the cardiac ganglion and then glutamate-evoked contractions were stimulated. I showed that myosuppressin increased glutamate-evoked contraction amplitude. These data suggest myosuppressin exerts its peripheral effects at the cardiac muscle and not the NMJ.