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Search Results: 1 - 10 of 307793 matches for " Matthew J. Ryan "
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Simulation of an Antimatter Beam Core Engine for Space Travel  [PDF]
Matthew Dubiel, Ryan J. Hooper
Journal of Modern Physics (JMP) , 2019, DOI: 10.4236/jmp.2019.1011089
Abstract: An exciting prospect is the use of antimatter as a fuel source due to its ability to convert mass energy to kinetic energy. Upon annihilation of antimatter with matter, tremendous amounts of energy are carried away by charged and neutral particles. By redirecting the charged particles through an exhaust using a non-uniform magnetic field, an impulse can be generated capable of supplying thrust to an engine. Using the Geant 4 simulation toolkit developed by CERN, we simulate this process using a beam core engine design. By analyzing charged pions that result from antiproton-proton annihilation, we optimize the engine parameters and derive a specific impulse for antiproton fuel as used in the beam core configuration. A specific impulse of (2.49 ± 0.08) × 106 s was determined. This value is significantly higher than specific impulses of current chemical rocket fuels which range from 240 - 400 s.
NOTCH1 inhibition in vivo results in mammary tumor regression and reduced mammary tumorsphere-forming activity in vitro
Matthew J Simmons, Ryan Serra, Nicole Hermance, Michelle A Kelliher
Breast Cancer Research , 2012, DOI: 10.1186/bcr3321
Abstract: Mammary gland development was analyzed by using whole-mount analysis and by flow cytometry in nulliparous transgenic mice maintained in the presence/absence of doxycycline (or intracellular NOTCH1). Mammary tumors were examined histologically and immunophenotyped by staining with antibodies followed by flow cytometry. Tumors were transplanted into mammary fat pads under limiting dilution conditions, and tumor-initiating cell frequency was calculated. Mammary tumor cells were also plated in vitro in a tumorsphere assay in the presence/absence of doxycycline. RNA was isolated from mammary tumor cell lines cultured in the presence/absence of doxycycline and used for gene-expression profiling with Affymetrix mouse arrays. NOTCH1-regulated genes were identified and validated by using quantitative real-time polymerase chain reaction (PCR). Mammary tumor-bearing mice were treated with doxycycline to suppress NOTCH1 expression, and disease recurrence was monitored.Similar to published studies, we show that constitutive expression of human intracellular NOTCH1 in the developing mouse mammary gland inhibits side branching and promotes luminal cell fate. These mice develop mammary adenocarcinomas that express cytokeratin (CK) 8/18. In vivo limiting-dilution analyses revealed that these mammary tumors exhibit functional heterogeneity and harbor a rare (1/2,978) mammary tumor-initiating cell population. With this dox-regulated NOTCH1 mammary tumor model, we demonstrate that NOTCH1 inhibition results in mammary tumor regression in vivo and prevents disease recurrence in four of six tumors tested. Consistent with the in vivo data, NOTCH1 inhibition reduces mammary tumorsphere activity in vitro. We also identify the embryonic stem cell transcription factor Nanog as a novel NOTCH1-regulated gene in tumorspheres and in mouse and human breast cancer cell lines.These data indicate that NOTCH1 inhibition results in mammary tumor regression in vivo and interferes with disease recurrence.
Dependent Multinomial Models Made Easy: Stick Breaking with the Pólya-Gamma Augmentation
Scott W. Linderman,Matthew J. Johnson,Ryan P. Adams
Statistics , 2015,
Abstract: Many practical modeling problems involve discrete data that are best represented as draws from multinomial or categorical distributions. For example, nucleotides in a DNA sequence, children's names in a given state and year, and text documents are all commonly modeled with multinomial distributions. In all of these cases, we expect some form of dependency between the draws: the nucleotide at one position in the DNA strand may depend on the preceding nucleotides, children's names are highly correlated from year to year, and topics in text may be correlated and dynamic. These dependencies are not naturally captured by the typical Dirichlet-multinomial formulation. Here, we leverage a logistic stick-breaking representation and recent innovations in P\'olya-gamma augmentation to reformulate the multinomial distribution in terms of latent variables with jointly Gaussian likelihoods, enabling us to take advantage of a host of Bayesian inference techniques for Gaussian models with minimal overhead.
Evaluation of HemogloBindTM treatment for preparation of samples for cholinesterase analysis  [PDF]
Kevin G. McGarry, Ryan A. Bartlett, Nicholas J. Machesky, Thomas H. Snider, Robert A. Moyer, David T. Yeung, Matthew K. Brittain
Advances in Bioscience and Biotechnology (ABB) , 2013, DOI: 10.4236/abb.2013.412136
Abstract: Acetylcholine is an essential neurotransmitter found throughout the nervous system. Its action on postsynaptic receptors is regulated through hydrolysis by various carboxylesterases, especially cholinesterases (ChEs). The acute toxicity of organophosphate (OP) compounds is directly linked to their action as inhibitors of ChE. One widely used assay for evaluating ChE activity is a spectrophotometric method developed by Ellman et al. When the enzyme source is from tissues or, in particular, blood, hemoglobin displays a spectrophotometric peak at the same wave-length used to analyze cholinergic activity. This creates a substantial background that interferes with the Ellman’s assay and must be overcome in order to accurately monitor cholinesterase activity. Herein, we directly compare blood processing methods: classical method (1.67 ± 0.30 U/mL) and HemogloBindTM treatment (1.51 ± 0.17 U/mL), and clearly demonstrate that pretreatment of blood samples with HemoglobindTM is both a sufficient and rapid sample preparation method for the assessment of ChE activity using the Ellman’s method.
The Effects of Prenatal Protein Restriction on -Adrenergic Signalling of the Adult Rat Heart during Ischaemia Reperfusion
Kevin J. P. Ryan,Matthew J. Elmes,Simon C. Langley-Evans
Journal of Nutrition and Metabolism , 2012, DOI: 10.1155/2012/397389
Abstract: A maternal low-protein diet (MLP) fed during pregnancy leads to hypertension in adult rat offspring. Hypertension is a major risk factor for ischaemic heart disease. This study examined the capacity of hearts from MLP-exposed offspring to recover from myocardial ischaemia-reperfusion (IR) and related this to cardiac expression of β-adrenergic receptors (β-AR) and their associated G proteins. Pregnant rats were fed control (CON) or MLP diets (=12 each group) throughout pregnancy. When aged 6 months, hearts from offspring underwent Langendorff cannulation to assess contractile function during baseline perfusion, 30 min ischemia and 60 min reperfusion. CON male hearts demonstrated impaired recovery in left ventricular pressure (LVP) and /max (<0.01) during reperfusion when compared to MLP male hearts. Maternal diet had no effect on female hearts to recover from IR. MLP males exhibited greater membrane expression of β2-AR following reperfusion and urinary excretion of noradrenaline and dopamine was lower in MLP and CON female rats versus CON males. In conclusion, the improved cardiac recovery in MLP male offspring following IR was attributed to greater membrane expression of β2-AR and reduced noradrenaline and dopamine levels. In contrast, females exhibiting both decreased membrane expression of β2-AR and catecholamine levels were protected from IR injury.
Are depredation rates by reef sharks influenced by fisher behaviour?
Magen Schifiliti,Dianne L McLean,Tim J Langlois,Matthew J Birt,Peter Barnes,Ryan Kempster
PeerJ , 2015, DOI: 10.7287/peerj.preprints.708v1
Abstract: Shark depredation (damage to gear and loss of bait or hooked fish by a non-target species) is a common global occurrence. Depredation events by sharks can have negative impacts for the fishers, fishery targeted species and the sharks. It is, therefore important to better understand if learning behaviour of sharks can influence rates of depredation. Recreational fishers within the World Heritage Ningaloo Reef have reported increased rates of depredation by sharks over the last 5 years. This study aimed to determine if sharks are capable of learning to associate intensive recreational fishing activities with a food reward. We also aimed to test if sharks in areas frequently fished were more habituated to recreational fishing activities than those sharks within a no-take marine sanctuary. To simulate fishing activities baited underwater video systems were deployed in the morning (A.M.), midday, and afternoon (P.M.) for six consecutive days in Fished and Unfished sites. A significant decrease in time of arrival and time to first feed of sharks was seen across days at the Fished sites. The Unfished sites had very low numbers of sharks observed (n=3) and therefore was not statistically analysed. The relative abundance of sharks did not significantly increase across days, however there was a negative correlation between lemon sharks (Negaprion sp.) and whalers (Carcharhinus sp.). Our study suggests sharks are capable of being classically conditioned to recreational fishing activities and depredation rates are influenced by fisher behaviour. We have highlighted possible mitigation strategies designed to un-condition sharks to recreational fishing, including modifying fishing practices, use of deterrents based on the sensitivity of shark senses and management strategies. The best approach is likely to be enabling fishers to become more knowledgeable of how and why shark depredation events happen and take appropriate steps to avoid them.
Stationary Cycling Induced by Switched Functional Electrical Stimulation Control
Matthew J. Bellman,Teng-Hu Cheng,Ryan J. Downey,Warren E. Dixon
Computer Science , 2013,
Abstract: Functional electrical stimulation (FES) is used to activate the dysfunctional lower limb muscles of individuals with neuromuscular disorders to produce cycling as a means of exercise and rehabilitation. However, FES-cycling is still metabolically inefficient and yields low power output at the cycle crank compared to able-bodied cycling. Previous literature suggests that these problems are symptomatic of poor muscle control and non-physiological muscle fiber recruitment. The latter is a known problem with FES in general, and the former motivates investigation of better control methods for FES-cycling.In this paper, a stimulation pattern for quadriceps femoris-only FES-cycling is derived based on the effectiveness of knee joint torque in producing forward pedaling. In addition, a switched sliding-mode controller is designed for the uncertain, nonlinear cycle-rider system with autonomous state-dependent switching. The switched controller yields ultimately bounded tracking of a desired trajectory in the presence of an unknown, time-varying, bounded disturbance, provided a reverse dwell-time condition is satisfied by appropriate choice of the control gains and a sufficient desired cadence. Stability is derived through Lyapunov methods for switched systems, and experimental results demonstrate the performance of the switched control system under typical cycling conditions.
Tracking Control for FES-Cycling based on Force Direction Efficiency with Antagonistic Bi-Articular Muscles
Hiroyuki Kawai,Matthew J. Bellman,Ryan J. Downey,Warren E. Dixon
Computer Science , 2013,
Abstract: A functional electrical stimulation (FES)-based tracking controller is developed to enable cycling based on a strategy to yield force direction efficiency by exploiting antagonistic bi-articular muscles. Given the input redundancy naturally occurring among multiple muscle groups, the force direction at the pedal is explicitly determined as a means to improve the efficiency of cycling. A model of a stationary cycle and rider is developed as a closed-chain mechanism. A strategy is then developed to switch between muscle groups for improved efficiency based on the force direction of each muscle group. Stability of the developed controller is analyzed through Lyapunov-based methods.
Visual Diagnosis: A Young Woman with Acute Abdominal Pain  [PDF]
Talib Dosani, Lars Beattie, Matthew F. Ryan
Open Journal of Emergency Medicine (OJEM) , 2017, DOI: 10.4236/ojem.2017.51002
Abstract: A 27-year-old female with a history of Crohn’s disease and familial adenomatous polyposis (FAP) presented to the emergency department (ED) with severe abdominal pain after an endoscopic exam. Chest and abdominal radiographs revealed massive pneumoperitoneum and the patient underwent emergent exploratory surgery. Herein, we discuss the management and outcomes of this case. The importance of a thorough history and physical exam when evaluating for an acute abdomen and thus the development of a successful management plan is also underscored.
The Effect and Relative Importance of Neutral Genetic Diversity for Predicting Parasitism Varies across Parasite Taxa
María José Ruiz-López, Ryan J. Monello, Matthew E. Gompper, Lori S. Eggert
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0045404
Abstract: Understanding factors that determine heterogeneity in levels of parasitism across individuals is a major challenge in disease ecology. It is known that genetic makeup plays an important role in infection likelihood, but the mechanism remains unclear as does its relative importance when compared to other factors. We analyzed relationships between genetic diversity and macroparasites in outbred, free-ranging populations of raccoons (Procyon lotor). We measured heterozygosity at 14 microsatellite loci and modeled the effects of both multi-locus and single-locus heterozygosity on parasitism using an information theoretic approach and including non-genetic factors that are known to influence the likelihood of parasitism. The association of genetic diversity and parasitism, as well as the relative importance of genetic diversity, differed by parasitic group. Endoparasite species richness was better predicted by a model that included genetic diversity, with the more heterozygous hosts harboring fewer endoparasite species. Genetic diversity was also important in predicting abundance of replete ticks (Dermacentor variabilis). This association fit a curvilinear trend, with hosts that had either high or low levels of heterozygosity harboring fewer parasites than those with intermediate levels. In contrast, genetic diversity was not important in predicting abundance of non-replete ticks and lice (Trichodectes octomaculatus). No strong single-locus effects were observed for either endoparasites or replete ticks. Our results suggest that in outbred populations multi-locus diversity might be important for coping with parasitism. The differences in the relationships between heterozygosity and parasitism for the different parasites suggest that the role of genetic diversity varies with parasite-mediated selective pressures.
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