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Simple Model of the Hydrogen Molecule Potential**
No full textWe apply a one dimensional classical model of a diatomic molecule in one-dimension to the hydrogen molecule. We obtain the unknown parameters of our model from published theoretical electron correlation calculation as well as experiment. From the one dimensional classical model we expect to calculate the coefficients of our model potential so as to enable us to estimate the theoretical real molecule\u27s vibrational frequency
Stochastic And Deterministic Methods For Biochemical Reaction Networks - L1 Gene Transcription
No full textDeterministic models for chemical and biochemical reactions have been around for a long time. However, in recent years researchers are giving much attention to stochastic simulation methods due to their detailed understanding of the biochemical reaction networks. In this article, we present both deterministic and stochastic simulation methods for analyzing dynamics of biochemical reaction networks and their application to L1 gene transcription model. We will also discuss the connection between stochastic and deterministic modelling approaches
The Moon\u27s Brightness during the January 21, 2019 Total Lunar Eclipse
No full textThe writer measured the brightness of the Moon during the January 21, 2019 total lunar eclipse. He used a single channel SSP-3 photometer along with filters transformed to the Johnson B and V system. He also used a small telescope having a diameter of 0.030 m with a focal length of 0.12 m. This combination produced a field of view of 56 arc-minutes which is large enough to cover the entire Moon. Data were collected between 4:43 and 5:31 U.T. on January 21, 2019. The V-filter brightness dropped from -3.18 at 4:43 UT to -2.04 at 5:13:30 UT. Afterwards, it rose back to -2.70 magnitude by 5:31 UT. The B-filter brightness (in magnitudes) went from -1.76 at 4:45 UT to -0.32 at 5:14:30 to -0.98 at 5:30:30 UT. The corresponding B-V value was 1.72 at minimum brightness. This is much higher than the corresponding value of the uneclipsed Moon. It is concluded that fully eclipsed Moon reached a similar brightness as similar events since 2000
A DNA-BARCODING APPROACH TO THE IDENTIFICATION OF INVASIVE AMBROSIA BEETLES IN LUMPKIN COUNTY, GEORGIA
No full textAmbrosia beetles (Curculionidae: Scolytinae and Platypodinae) are native and non-native pests of dead, unhealthy, and/or even healthy trees which can have major commercial impact. Boring galleries in which they grow fungi to feed their larvae, beetles injure or kill host trees and devalue wood. Although native ambrosia beetles exist in Georgia, an increase in global trade has introduced at least 19 exotic species into the state. In the spring of recent years, SAW has noted large enough numbers of ambrosia beetles locally in Lumpkin County, Georgia, to suggest invasive activity. In some cases beetle numbers were sufficient to force people indoors. To determine if these beetles were exotic, collections were made, and identifications were established using a DNA barcoding approach. About two-hundred beetles belonging to five morphotypes were collected March-July 2021. DNA was extracted from crushed whole beetles from one or more representatives of each type. We amplified and sequenced 712 nucleotides of mitochondrial cytochrome c oxidase subunit I following standard molecular methods. Sequences were proofread by hand from both strands, and compared against publicly-available sequences using standard bioinformatics approaches. Homology assessment using percent identity (100% match criterion) resulted in the identification of four known exotic ambrosia beetles (numbers sequenced given): Xylosandrus crassiusculus (6), Euwallacea interjectus (3), Cnestus mutilatus (1), and Xyleborinus saxesenii (1). All four of these non-native species have been previously collected in Georgia, however C. mutilatus might represent a range extension. No native ambrosia beetles have been identified from our collections. Additionally, one sequenced individual was identified as a weevil of the Molytinae (non-ambrosia beetle curculionid). While we did not discover any exotic taxa new to the state of Georgia, further research regarding the spread of invasive ambrosia beetles, especially in regions with lumber and fruit trees at high density, could be useful for the protection of trees and the state economy
Relationship between Size and Foraging in Dusky Salamanders (Genus Desmognathus)
No full textForaging is important ecologically because it determines an animal’s ability to maintain a positive energy budget, which is necessary for growth and reproduction. Biologists have traditionally categorized foraging mode in animals as active hunting or lying in ambush. Salamanders in the genus Desmognathus forage at night when humidity is high. Large species often remain in refugia with their heads protruding while waiting to ambush approaching prey. Small species commonly forage outside of refugia, presumably as active hunters. We tested the hypothesis that foraging mode in these salamanders depends on body size rather than species. We collected large samples of four species that span most of the range of adult body size within the genus including the small D. ocoee, the moderately large D. monticola and D. folkertsi, and the large D. quadramaculatus. We collected all specimens at night along two streams in the Georgia Piedmont and two streams in the Blue Ridge. We categorized salamanders with heads sticking out of refugia versus those out wandering. Mean body size of refuge-inhabiting individuals of all four species was significantly larger than in wandering individuals. Moreover, as maximum size of the population increased, the proportion of individuals that hunted from refugia also increased. We concluded that larger desmognathans more commonly ambush prey from refugia, and small salamanders appear to be active hunters. This pattern of foraging may be a consequence of variation in metabolic rate. Small animals including amphibians have a higher metabolic rate than large ones. If small salamanders require more food per gram of body weight than do large ones, they may need to seek out prey in order to meet nutritional requirements
‘Best by’ date: Reliability of Species Identification Based on Freshness of Material
No full textAmphipod crustaceans can be useful environmental indicators if identified correctly and baseline data are available. Changes in species composition over time can signal environmental degradation before it moves up the food web. Baseline data are often gathered from natural history specimens that have been preserved and stored for many years. Collection methods, sorting, and storage of specimens affect the integrity of natural history specimens. Aged specimens lose defining characteristics that are crucial to proper identification, especially if not carefully sorted and preserved immediately after collecting. Freshly collected specimens have clearly defined morphological characteristics and color patterns that allow for easy identification of species. Freshly collected specimens are also more malleable than those stored in ethanol for a period of time. We hypothesize that there will be fewer identification in specimens collected more recently than in those stored for long periods of time. Amphipod collection from Panama were completed in 2005 and 2021 using similar methods (ie. coral rubble elutriation and invertebrate host dissections), sorted and preserved immediately after collection. Stacked imaging shows the differences between ethanol-preserved amphipods collected in 2005 and live material collected in 2021, supporting the hypothesis that fresh material is more easily identified than material that has been stored for long periods of time. Having access to freshly collected and sorted specimens is crucial to proper identification and, therefore, to the application of amphipods as environmental indicators
ON GOING INVESTIGATIONS OF DWARF SEAHORSE (HIPPOCAMPUS ZOSTERAE) REPRODUCTIVE ECOLOGY IN A LAB ENVIRONMENT
No full textThe decline of seagrass beds in Tampa Bay poses a threat to the species biodiversity in coastal communities. By studying the reproductive efforts in seahorses as a flagship species for seagrass ecosystems, we can better understand the reproductive mechanisms in wild populations found in threatened environments. This pilot experiment followed ten broods of lab-born dwarf seahorses (Hippocampus zosterae), whose parents were collected from Tampa Bay and paired in lab trials. The three primary goals of the project were to determine reproductive rates, growth rates of the offspring, and the survivorship of the broods in the lab environment. To control for different levels of animal handling, offspring for each brood were separated at birth into a photo, weight, or non-treatment group to collect data every eight days. Seahorse photographs were used to measure body sizes using the program ImageJ to calculate growth curves. Counts were conducted every four days to create survivorship curves for each treatment. Brood sizes ranged from 4 to 57 offspring with an overall average of 26 offspring per male (n=10). The average sizes for dwarf seahorse offspring at birth were 11.6942 mm for total body length and 2.63 mg for the ten broods. The variation of these brood sizes may provide evidence for a tradeoff between brood sizes and size at birth for this r-selected species. Trends show relatively high offspring survivorship for the first 30 days before declining drastically in all ten broods, with no differences across the three manipulation treatments within broods. These results will provide guidance for designing future survivorship experiments using a comparative approach across several species of seahorses. Conclusions from this study will offer insight into reproductive, growth, and survival rates of dwarf seahorses in a lab environment, which will be beneficial for future considerations of conservation statuses in the natural environment
Perovskite solar cells
Get PDFThe semiconductor perovskite CsPbBr2I was doped with Mn2+ to modulate its optical and photovoltaic performance. The Mn2+-doped CsPb0.9Mn0.1Br2I exhibited improved crystalline quality. Ultraviolet and visible spectroscopy of Mn2+-doped CsPb0.9Mn0.1Br2I revealed enhanced absorption capacity. Although the efficiency was not as good as desired, the enhanced light absorption of CsPb0.9Mn0.1Br2I still boosted the photovoltaic performance when it was utilized as a light absorber in perovskite solar cells, along with a low-cost carbon electrode. Compared with its counterpart CsPbBr2I, the doped CsPb0.9Mn0.1Br2I based solar cells demonstrated long-term air stability. Not only long-lasting stability was achieved by doping with Mn2+, the toxicity was also lessened by replacing the amount of hazardous lead in perovskite with harmless manganese
OPTIMIZATION OF A WILD-TYPE HEMOGLOBIN CATALYZED CYCLOPROPANATION REACTION FOR UNDERGRADUATE LABORATORY COURSE**
No full textBiocatalysis is the use of enzymes/proteins as catalyst to perform chemical reactions. Protein/enzyme catalyzed reactions are chemo-selective, regioselective, and stereoselective. Proteins/enzymes are cost effective, environmentally friendly, and can be used under mild reaction conditions. The intent of this study is to design a practical Biocatalysis experiment that can be performed in an undergraduate, organic laboratory. In this study, wild-type hemoglobin was used as a biocatalyst to perform a cyclopropanation reaction between commercially available Styrene and Ethyl Diazoacetate (EDA). Various reaction conditions were optimized; the optimal enzyme concentration was found to be 40 μM, EDA concentration was 10 mM, and Styrene concentration was 30 mM, making the substrate ratio 1:3. The pH of the reaction medium and the time in which the reaction occurs will also be optimized. Another objective to be investigated is measuring the recyclability of the enzyme/protein. A Chiral Gas Chromatography (GC) was used to calculate the enzyme activity and stereoselectivity. Our results indicate that the trans diastereomer was formed in excess, and around 25% enantiomeric excess (%ee) for the trans (SS) product. A calibration curve was constructed and used to standardize the results. By optimizing various reaction conditions, the percent yield has been increased to be in the 86%-87% range. Later, the optimized reaction will be tested with first semester undergraduate organic laboratory students. This experiment is designed to be an inexpensive and sustainable way to incorporate biocatalysis in an organic undergraduate teaching lab
THE CHEMICAL DEPOLYMERIZATION OF POLYLACTIC ACID (PLA) ACCELERATED BY MICROWAVE HEATING**
No full textThe production of materials from renewable resources is an important area of research. Numerous commercial materials made of biodegradable polylactic acid (PLA) are now available. PLA is known to break down by hydrolytic, photo-degrative, microbial, and enzymatic processes. The conversion of PLA into methyl lactate using methanol and zinc catalysis has been reported. This study focuses on the successful accelerated conversion of PLA into methyl lactate monomers by microwave heating