Georgia Southern University
  • Georgia, United States
Recent publications
A new species of Heligmosomoides Hall, 1916 is proposed for nematodes collected from deer mice, Peromyscus maniculatus, in western Canada. The unequivocal diagnostic character for this species is the presence of two internal bursal membranes. Only four species, Heligmosomoides bullosus, Heligmosomoides douglasi, Heligmosomoides montanus and Heligmosomoides vandegrifti, are characterized as possessing a single internal bursal membrane. The genetic distance between Heligmosomoides bibullosus sp. nov., and its putative sister clade Heligmosomoides vandegrifti is congruent with their geographic separation by the mountain range of the Rockies and 4000 km; both morphological difference as well as geography and genetic distance suggest isolation among the two species. Further, H. bibullosus sp. nov. infects deer mice (P. maniculatus) whereas H. vandegrifti is frequently collected in white-footed mice (P. leucopus). Finally, this study supports the taxonomic importance of the monodelphic/didelphic condition as a diagnostic trait within the family, the paraphyly of Heligmosomoides, and reveals undocumented diversity of Heligmosomoides in Nearctic rodents of the Neotominae. The present taxon is the third species in members of this subfamily of rodents.
Background There is growing potential for nanocarrier-based drug delivery in cancer. However, an incomplete understanding of nano–bio interactions and the challenges regarding processing and fabrication in scale-up engineering techniques, controls over drug release, efficacy, and cytotoxicity to the human cell are the major challenges for its clinical success. The purpose of the study was to develop an electrospraying processing of injectable nanonized encapsulated chemotherapeutics to target primary and metastatic breast cancer tumor microenvironment for precise and controlled delivery. Results A novel coaxial electrospraying of multiple cancer drugs (paclitaxel and GW2580) as core and polycaprolactam (PCL) as the shell has been developed to produce multi-cancer drug nanocapsules. Using electrospraying process, we have successfully made nanocapsules containing paclitaxel to target breast cancer cells and GW2580, a colony-stimulating factor 1 receptor (CSF1R) inhibitor to target CSF1R+ myeloid cells in the tumor microenvironments (TME). The UV–vis drug release test for 14 days shows a prolonged and sustained release pattern of both the drugs. In vitro and in vivo results showed the effects of nanocapsules containing multiple drugs in controlling the growth of tumor cells and increased survival of the animal bearing breast cancers. Conclusion Nanonized multi-cancer drugs were encapsulated in a PCL shell. The drug doses ratio and the polymer-to-drug ratio were controlled by engineered process parameters. The studies showed the importance of making nanocapsules containing nanocrystals of multiple drugs, which will pave the way of making multiple drug combinations in a controlled manner and capsules can be designed for sustained release of the drugs after accumulation into the TME. TME-directed therapy can be a norm in future cancer treatment strategies. These injectable nanocapsules will allow cancer site-specific precision and controlled delivery to cure primary and metastatic breast cancer and to overcome the chemotherapy resistance.
The number of subtrees, also referred to as the subtrees index, is a key parameter to measure graph structures such as networks. In this paper, we investigate the number of subtrees of planar two-tree networks. By “adding a virtual edge” and “edge orientation”, we present a linear time algorithm for computing the number of subtrees of planar two-tree networks, as well as a family of planar two-connected networks. As applications, we provide the formulae for the number of subtrees of the famous small-world Farey network and GDURT network. We also discuss the relationship between the spanning subtree number and the subtree number of these networks.
In this paper we provide measurements of the underlying complex dynamic structure in bitcoin market activity. More specifically, we present empirical estimates of extremity (large fluctuations) in bitcoin market action variables such as price returns, trading volume, and number of trades using a block maxima estimation for the tail exponent. We juxtapose the estimated scale exponents in bitcoin market dynamics to those for traditional financial assets as well as to the theoretical predictions for stock market activity variables as modelled by Gabaix et al. (2006). Based on a dynamic stability analysis, the tail exponent for bitcoin price returns appears to have undergone a substantial temporal shift in the sample period.
“Have a good day” and its variant “have a nice day” are among our most common forms of modern leave-taking. Although these expressions may seem modern, they can be traced back to a twelfth century English romance, entitled King Horn , and can also be found in a number of other mediaeval works. Linguists typically treat the expression as token politeness that does not warrant detailed analysis. However, an examination of the mediaeval works containing the expression shows that, from its earliest recording, it appears in unexpected contexts and can carry deeper meaning. Rather than being merely a phatic phrase, the expression has long been used as a meaningful rhetorical device. This diachronic study explores the expression “have a good day” from its earliest occurrence to modern times and shows its potential to move beyond phatic use.
Background: Orphans and vulnerable children (OVC) are a high-risk group for HIV infection, particularly in Sub-Saharan Africa. Purpose: This study aims to portray the socioeconomic profile of OVC and examine the association of household and parent/guardian characteristics with the HIV status of OVC. Methods: For this quantitative retrospective study, we obtained data from ICAP/DRC for a total of 1,624 OVC from households enrolled for social, financial, and clinical services between January 2017 and April 2020 in two provinces of the Democratic Republic of Congo, Haut-Katanga and Kinshasa. We computed descriptive statistics for OVC and their parents’ or guardians’ characteristics. We used the chi-square test to determine bivariate associations of the predictor variables with the dichotomous dependent variable, HIV positivity status. To analyze the association between these independent variables and the dichotomous dependent variable HIV status after controlling for other covariates, we performed firth’s logistic regression. Results: Of the OVC included in this study, 18% were orphans, and 10.9% were HIV+. The chi-square analysis showed that among parents/guardians that were HIV+, a significantly lower proportion of OVC (11.7%) were HIV+ rather than HIV- (26.3%). In contrast, for parents/guardians with HIV- status, 9.0% of OVC were HIV-negative, and 11.7% of OVC were OVC+. The firth’s logistic regression also showed the adjusted odds of HIV+ status were significantly lower for OVC with parents/guardians having HIV+ status themselves (AOR, 0.335; 95% CI, 0.171–0.656) compared with HIV-negative parents/guardians. The adjusted odds of HIV+ status were significantly lower for OVC with a monthly household income of < $30 (AOR, 0.421; 95% CI, 0.202–0.877) compared with OVC with a monthly household income > $30. Conclusions: Our results suggest that, with the exception of a few household and parent/guardian characteristics, the risk of HIV+ status is prevalent across all groups of OVC within this study, which is consistent with the existing body of evidence showing that OVC are in general vulnerable to HIV infection. With a notable proportion of children who are single or double orphans in DRC, HIV+ OVC constitute a high-risk group that merits customized HIV services. The findings of this study provide data-driven scientific evidence to guide such customization of HIV services. Keywords: HIV, DRC, orphans, vulnerable children, socioeconomic status
A derangement is a permutation in which no entry is at its original position. The number of derangements of [n] is called the “derangement number” or “de Montmort number”, and is denoted by Dn. The sequence {Dn} enumerates, in addition to the number of derangements, many other permutations under various constraints. In this paper, we explore the connections between these combinatorial objects and provide bijective proofs. Some related enumerative problems are also mentioned.
State-level decisions to initiate militarized conflicts are the result of various factors, ranging from geographic proximity to the previous actions of potential foes. However, we know little about how the reputations of hostile actions shape future conflict and whether they vary for different types of country pairs. Through the adoption of a social network perspective, this research examines the role of post-Cold War hostility on the likelihood of future conflicts using the Militarized Interstate Dispute data from the Correlates of War project. We apply temporal exponential random graph models to evaluate whether the previous hostility levels of a country can determine future patterns of interstate conflict. Additionally, we consider how this association varies based on whether a country’s experience with an adversary is direct (a result of previous conflict with the adversary) or indirect (based on extra-dyadic disputes). Consistent with previous research, results suggest that pairs of countries with a direct history of hostile actions are more likely to fight in the future. However, in absence of this shared history, states are less likely to initiate conflict with those that have a particularly hostile or peaceful history, and instead target adversaries with middling levels of previous hostility.
The global positioning system (GPS) must be familiar to every user of a smartphone as a way to locate one’s position on Earth to within several meters. The constellation of orbiting atomic clocks equipped with radio transmitters allows receivers on Earth to determine their own position by measuring the travel times of radio signals from multiple satellites. A physics laboratory for an upper-level majors course involving GPS signals might be assumed to focus on relativistic effects (either special or general), but this paper demonstrates that the ultra-precise time signal from a GPS receiver can be used for a variety of data collection purposes.
A challenge in interpreting research is that the construct of ‘distance’ has multiple dimensions that influence acquisition performance. We expand Ghemawat's (2001) typology of distance with its dimensions of cultural, administrative, geographic, and economic distance (CAGE) from a review of 61 empirical research studies of how distance affects acquisition performance. We identify different impacts of distance dimensions on acquisition performance to find that distance dimensions are interdependent. As a result, context matters, when considering the impact of distance on acquisition performance. Supporting institutional theory, the direction of distance may matter, as the results may be different for acquirers in developed and emerging economies. Additional implications for research and management practice are identified.
The down-shifting of ultraviolet (UV) photons to the near-infrared (NIR) relevant to solar spectral converters and IR lasers is demonstrated for the first time in Yb3+-containing glass via monovalent copper. Glass with a barium phosphate matrix was prepared by melt-quenching, adding 2 mol% Yb2O3 alongside CuO and SnO at 10 mol% to stabilize Cu+ ions. The effect of heat treatment (HT) promoting the precipitation of Cu nanoparticles (NPs) was also investigated. This study entailed measurements by differential scanning calorimetry (DSC), UV-Vis-NIR absorption, X-ray diffraction (XRD), and photoluminescence (PL) spectroscopy with an emission dynamics assessment. The DSC data indicate an influence from Yb3+ increasing the glass transition and crystallization temperatures in the copper co-doped glass. The optical absorption and PL data supported the presence of Cu+ ions, and in the heat-treated glass the presence of Cu NPs was evidenced by the surface plasmon resonance and XRD data. The NIR PL data showed that exciting Cu+ ions in the near-UV preferentially around 375 nm results in the sensitized NIR emission from Yb3+ near 1000 nm. However, it becomes diminished in the heat-treated glass. The Yb3+ decay curves revealed a rise time for the 2F5/2 emitting level followed by a single exponential decay. An energy transfer process proceeding via a Cu2+–Yb2+ charge transfer state is proposed to account for the UV-excited NIR emission from Yb3+ ions. Possible interactions ensuing the weaker NIR emission following the HT are discussed.
In the last few decades, tremendous effort has been dedicated to mimicking the efficient ionic current rectification (ICR) of biological nanopores. Nanoporous membranes and singular nanopores with ICR functionality have been fabricated using advanced, yet costly technologies. We herein demonstrate that a simple, novel, and robust ICR platform can be constructed using 80 nm silica nanoparticles and a piece of 15 nm track-etched polycarbonate membrane. Efficient ICR can be obtained when voltages of different polarities are applied across the membrane, due to the asymmetric electrophoretic migration of silica nanoparticles whose surfaces are modified with different functional groups. The effect of pore size, ionic strength, pH, voltage magnitude, and density of silica nanoparticles on the efficiency of the ICR system has been systematically investigated in this report. Our results clearly show that smaller pore, lower ionic strength, appropriate pH value, higher electrical field strength, lower density of silica nanoparticles can generally enhance the efficiency of the ICR system. The principles of this new ionic current rectification system may find many potential applications in controllable drug delivery, energy storage and water purification.
Motivated by various applications in the online platforms for ride-hailing and crowd-sourcing delivery, we study the edge-weighted online bipartite matching (EWOBM) problem. We assume a part of online vertices are released in advance to mimic historical information that the algorithm is able to access. Different from traditional approaches that usually learn informative distributions from large enough history sets, our algorithms enable to extra useful information for the history set of any size. When the online vertices arrive in a random order, we present an online algorithm, named as h-TP-OM, achieving a competitive ratio that increases as more historical information is considered. However, once enough historical information has been fed to the algorithm, additional historical information becomes useless. Based on h-TP-OM, we then propose a time-efficient greedy heuristic, named as h-TP-G, which even has better performances in applications, particularly on large-scale instances. When the arrival order of online vertices is determined by an adversary, we present another greedy heuristic algorithm, named as Greedy-RT. Experiments on both synthetic and real-world datasets are conducted to evaluate the practical performances of the proposed algorithms. The experiment results demonstrate the usefulness of historical information for both h-TP-OM and h-TP-G, and also show the time efficiency of h-TP-G and Greedy-RT.
Given a graph G=(V,E)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$G = (V, E)$$\end{document}, the 3-path partition problem is to find a minimum collection of vertex-disjoint paths each of order at most 3 to cover all the vertices of V. The previous best approximation algorithm for the 3-path partition problem has a performance ratio 13/9, which is based on a simple local search strategy. We propose a more involved local search and show by an amortized analysis that it is a 4/3-approximation; we also design an instance to illustrate that the approximation ratio is tight.
An accurate medical image registration is crucial in a variety of neuroscience and clinical studies. In this paper, we proposed a new unsupervised learning network, DAVoxelMorph to improve the accuracy of 3D deformable medical image registration. Based on the VoxelMorph model, our network presented two modifications, one is adding a dual attention architecture, specifically, we model semantic correlation on spatial and coordinate dimensions respectively, and the location attention module selectively aggregates the features of each location by weighting the features of all locations. The coordinate attention module further puts the location information into the channel attention. The other is introducing the bending penalty as regularization in the loss function to penalize the bending in the deformation field. Experimental results show that DAVoxelMorph achieved better registration performance including average Dice scores (0.714) and percentage of locations with non-positive Jacobian (0.345) compare with VoxelMorph (0.703, 0.355), CycleMorph (0.705, 0.133), ANTs SyN (0.707, 0.137) and NiftyReg (0.694, 0.549). Our model increases both model sensitivity and registration accuracy.
An effort was made to improve the separation issue of styrene-butadiene-styrene modifiers in styrene-butadiene-styrene-modified asphalt binders and to further enhance their performance by adding nano-ZnO to the styrene-butadiene-styrene-modified asphalt binder to prepare compound modified binder. First, the optimum nano-ZnO dosage was determined based on conventional tests, i.e., penetration, ring and ball softening point, and ductility at a fixed styrene-butadiene-styrene dosage; then, dynamic shear rheometer, bending beam rheometer, and fluorescence microscopy tests were conducted to evaluate the properties of the nano-ZnO/styrene-butadiene-styrene hybrid-modified asphalt binders. Finally, the rutting test, trabecular bending test, submerged Marshall test, and the freeze-thaw splitting test was conducted to evaluate the properties of the asphalt mixtures produced with the hybrid-modified binders. The main results showed that: the optimum nano-ZnO dosage, which was 4% by weight to the asphalt binder, and an improvement of the separation issue of the styrene-butadiene-styrene, and the flexural tensile strength and the maximum bending tensile strain of the hybrid-modified asphalt mixtures increased by 13.4% and 16.4%, respectively. In addition, the residual stability and the tensile strength ratio also increased by 4.3% and 4.8%, respectively, compared to the styrene-butadiene-styrene-modified asphalt mixtures. In conclusion, nano-ZnO improves the low-temperature and water stability performances of the styrene-butadiene-styrene-modified asphalt mixture.
As climate change progresses, it is crucial to understand how animals will respond to shifts in their local environments. One component of this response involves changes in the microbial communities living in and on host organisms.
This paper describes a predictive control method to search for unstable periodic orbits of the generalized tent map. The invariant set containing periodic orbits is a repelling set with a complicated Cantor-like structure. Therefore, a simple local stabilization of the orbit may not be enough to find a periodic orbit, due to the small measure of the basin of attraction. It is shown that for certain values of the control parameter, both the local behaviour and the global behaviour of solutions change in the controlled system; in particular, the invariant set enlarges to become an interval or the entire real axis. The computational particularities of using the control system are considered, and necessary conditions for the orbit to be periodic are given. The question of local asymptotic stability of subcycles of the controlled system's stable cycles is fully investigated, and some statistical properties of the subset of the classical Cantor middle thirds set that is determined by the periodic points of the generalized tent map are described.
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4,601 members
Stacy Smallwood
  • Jiann-Ping Hsu College of Public Health
Hani Samawi
  • Department of Biostatistics
Asli Aslan
  • Jiann-Ping Hsu College of Public Health
Daniel V. Hagan
  • Department of Biology
Lorenza Beati
  • Institute for Coastal Plain Science
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https://www.georgiasouthern.edu/