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Search Results: 1 - 10 of 401577 matches for " M. M. Dalton "
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Rescue of Infectious Birnavirus from Recombinant Ribonucleoprotein Complexes
Romy M. Dalton, José F. Rodríguez
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0087790
Abstract: Birnaviruses are unconventional members of the icosahedral double-stranded (dsRNA) RNA virus group. The main differential birnavirus trait is the lack of the inner icosahedral transcriptional core, a ubiquitous structure conserved in all other icosahedral dsRNA viruses, that shelters the genome from cellular dsRNA sensors and provide the enzymatic machinery to produce and extrude mature messenger RNAs. In contrast, birnaviral particles enclose ribonucleoprotein (RNP) complexes formed by the genome segments, the dsRNA-binding VP3 polypeptide and the virus-encoded RNA polymerase (RdRp). The presence of RNPs suggests that the birnavirus replication program might exhibit significant differences with respect to those of prototypal dsRNA viruses. However, experimental evidences supporting this hypothesis are as yet scarce. Of particular relevance for the understanding of birnavirus replication is to determine whether RNPs act as intracellular capsid-independent transcriptional units. Our study was focused to answer this question using the infectious bursal disease virus (IBDV), the best characterized birnavirus, as model virus. Here, we describe the intracellular assembly of functional IBDV RNPs in the absence of the virus-encoded VP2 capsid polypeptide. Recombinant RNPs are generated upon coexpression of the IBDV VP1 and RdRp polypeptides and transfection of purified virus dsRNA. Presented data show that recombinant RNPs direct the expression of the IBDV polypeptide repertoire and the production of infectious virus in culture cells. Results described in this report constitute the first direct experimental evidence showing that birnaviral RNPs are intracellularly active in the absence of the virus capsid. This finding is consistent with presented data indicating that RNP formation precedes virus assembly in IBDV-infected cells, and supports the recently proposed IBDV replication model entailing the release of RNPs during the initial stages of the infection. Indeed, results presented here also support the previously proposed evolutionary connection between birnaviruses and positive-strand single-stranded RNA viruses.
Non-Markovian Decay of a Three Level Cascade Atom in a Structured Reservoir
B. J. Dalton,B. M. Garraway
Physics , 2003, DOI: 10.1103/PhysRevA.68.033809
Abstract: We present a formalism that enables the study of the non-Markovian dynamics of a three-level ladder system in a single structured reservoir. The three-level system is strongly coupled to a bath of reservoir modes and two quantum excitations of the reservoir are expected. We show that the dynamics only depends on reservoir structure functions, which are products of the mode density with the coupling constant squared. This result may enable pseudomode theory to treat multiple excitations of a structured reservoir. The treatment uses Laplace transforms and an elimination of variables to obtain a formal solution. This can be evaluated numerically (with the help of a numerical inverse Laplace transform) and an example is given. We also compare this result with the case where the two transitions are coupled to two separate structured reservoirs (where the example case is also analytically solvable).
Theory of non-Markovian decay of a cascade atom in high-Q cavities and photonic band-gap materials
B. M. Garraway,B. J. Dalton
Physics , 2006, DOI: 10.1088/0953-4075/39/15/S21
Abstract: The dynamics of a three-level atom in a cascade configuration with both transitions coupled to a single structured reservoir of quantized field modes is treated using Laplace transform methods applied to the coupled amplitude equations. Results are also obtained from master equations by two different approaches, that is, involving either pseudomodes or quasimodes. Two different types of reservoir are considered, namely a high-Q cavity and a photonic band-gap system, in which the respective reservoir structure functions involve Lorentzians. Non-resonant transitions are included in the model. In all cases non-Markovian behaviour for the atomic system can be found, such as oscillatory decay for the high-Q cavity case and population trapping for the photonic band-gap case. In the master equation approaches, the atomic system is augmented by a small number of pseudomodes or quasimodes, which in the quasimode approach themselves undergo Markovian relaxation into a flat reservoir of continuum quasimodes. Results from these methods are found to be identical to those from the Laplace transform method including two-photon excitation of the reservoir with both emitting sequences. This shows that complicated non-Markovian decays of an atomic system into structured EM field reservoirs can be described by Markovian models for the atomic system coupled to a small number of pseudomodes or quasimodes.
Cascade atom in high-Q cavity: The spectrum for non-Markovian decay
B. J. Dalton,B. M. Garraway
Physics , 2007,
Abstract: The spontaneous emission spectrum for a three level cascade configuration atom in a single mode high-Q cavity coupled to a zero temperature reservoir of continuum external modes is determined from the atom-cavity mode master equation using the quantum regression theorem. Initially the atom is in its upper state and the cavity mode empty of photons. Following Glauber, the spectrum is defined via the response of a detector atom. Spectra are calculated for the detector located inside the cavity (case A), outside the cavity end mirror (Case B-end emission), or placed for emission out the side of the cavity (Case C). The spectra for case A and case B are found to be essentially the same. In all the cases the predicted lineshapes are free of instrumental effects and only due to cavity decay. Spectra are presented for intermediate and strong coupling regime situations (where both atomic transitions are resonant with the cavity frequency), for cases of non-zero cavity detuning, and for cases where the two atomic transition frequencies differ. The spectral features for Cases B(A) and C are qualitatively similar, with six spectral peaks for resonance cases and eight for detuned cases. These general features of the spectra can be understood via the dressed atom model. However, Case B and C spectra differ in detail, with the latter exhibiting a deep spectral hole at the cavity frequency due to quantum interference effects.
Theory of Pseudomodes in Quantum Optical Processes
B. J. Dalton,S. M. Barnett,B. M. Garraway
Physics , 2001, DOI: 10.1103/PhysRevA.64.053813
Abstract: This paper deals with non-Markovian behaviour in atomic systems coupled to a structured reservoir of quantum EM field modes, with particular relevance to atoms interacting with the field in high Q cavities or photonic band gap materials. In cases such as the former, we show that the pseudo mode theory for single quantum reservoir excitations can be obtained by applying the Fano diagonalisation method to a system in which the atomic transitions are coupled to a discrete set of (cavity) quasimodes, which in turn are coupled to a continuum set of (external) quasimodes with slowly varying coupling constants and continuum mode density. Each pseudomode can be identified with a discrete quasimode, which gives structure to the actual reservoir of true modes via the expressions for the equivalent atom-true mode coupling constants. The quasimode theory enables cases of multiple excitation of the reservoir to now be treated via Markovian master equations for the atom-discrete quasimode system. Applications of the theory to one, two and many discrete quasimodes are made. For a simple photonic band gap model, where the reservoir structure is associated with the true mode density rather than the coupling constants, the single quantum excitation case appears to be equivalent to a case with two discrete quasimodes.
Determina??o da potência mecanica no limite entre os domínios pesado/severo do crawl-atado
Pess?a Filho, Dalton Müller;Denadai, Benedito Sérgio;
Motriz: Revista de Educa??o Física , 2010, DOI: 10.5016/1980-6574.2010v16n4p820
Abstract: the aim of this study was to access the p-tlim model in swimming, applying the load control available in full tethered swim condition. its physiological meaning for the determination of boundary of heavy/severe domains was assessed from the relationships with critical velocity (cv), critical power (cp) and maximal lactate steady state (mlss). the velocity at mlss (vmlss = 1.17 ± 0.11 m/s) and cv (1.19 ± 0.12 m/s) were significantly different. similarly, the power at mlss (pmfel = 89.2 ± 15.1 w) and cp (99.4 ± 22.9 w) were significantly different. there was no difference between lactate concentration at vmlss (3.54 ± 0.9 mm) and pmlss (3.76 ± 0.6 mm). significant pearson's coefficients (r > 0.70) were observed among vmlss and pmlss with their respective values on time-limited model. thus, the tethered-crawl condition seems to be valid to determine the boundary of heavy/severe domains, and to access the aerobic capacity of swimmers.
Medication diaries do not improve outcomes with highly active antiretroviral therapy in Kenyan children: a randomized clinical trial
Wamalwa Dalton C,Farquhar Carey,Obimbo Elizabeth M,Selig Sara
Journal of the International AIDS Society , 2009, DOI: 10.1186/1758-2652-12-8
Abstract: Background As highly active antiretroviral therapy (HAART) becomes increasingly available to African children, it is important to evaluate simple and feasible methods of improving adherence in order to maximize benefits of therapy. Methods HIV-1-infected children initiating World Health Organization non-nucleoside reverse transcriptase-inhibitor-containing first-line HAART regimens were randomized to use medication diaries plus counselling, or counselling only (the control arm of the study). The diaries were completed daily by caregivers of children randomized to the diary and counselling arm for nine months. HIV-1 RNA, CD4+ T cell count, and z-scores for weight-for-age, height-for-age and weight-for-height were measured at a baseline and every three to six months. Self-reported adherence was assessed by questionnaires for nine months. Results Ninety HIV-1-infected children initiated HAART, and were followed for a median of 15 months (interquartile range: 2–21). Mean CD4 percentage was 17.2% in the diary arm versus 16.3% in the control arm at six months (p = 0.92), and 17.6% versus 18.9% at 15 months (p = 0.36). Virologic response with HIV-1 RNA of <100 copies/ml at nine months was similar between the two arms (50% for the diary arm and 36% for the control, p = 0.83). The weight-for-age, height-for-age and weight-for-height at three, nine and 15 months after HAART initiation were similar between arms. A trend towards lower self-reported adherence was observed in the diary versus the control arm (85% versus 92%, p = 0.08). Conclusion Medication diaries did not improve clinical and virologic response to HAART over a 15-month period. Children had good adherence and clinical response without additional interventions. This suggests that paediatric HAART with conventional counselling can be a successful approach. Further studies on targeted approaches for non-adherent children will be important.
Transient Myocarditis Associated with Fulminant Colitis
J. M. L. Williamson,R. S. J. Dalton
ISRN Surgery , 2011, DOI: 10.5402/2011/652798
Abstract: Case Summary. An 18-year old man presented with a three-week history of abdominal pain, weight loss and bloody diarrhoea. He was profoundly septic, with generalised abdominal tenderness. CT and flexible sigmoidosopy confirmed colitis of the colon with rectal sparing. Laparotomy was performed when conservative management failed to improve his condition. Subtotal colectomy, with end ileostomy and mucus fistula formation, was performed in light of active colitis. Despite successful operative intervention the patient acute left ventricular failure, raising the possibility of giant cell myocarditis, which fully resolved before a definitive diagnosis could be reached. Discussion. It is possible that the transient cardiac failure in this case may represent an overwhelming inflammatory response or myocarditis. Inflammatory bowel disease is rarely associated with giant cell myocarditis (GCM). GCM usually affects a young population and its prognosis is variable, ranging from complete recovery, remission with recurrence and fatality. The management of this group of patients is still relatively experimental. Conclusion. Fulminant colitis can be associated with a rapid deterioration in cardiac function. Causes include sepsis, systemic inflammatory response syndrome or myocarditis. GCM should be considered in patients with new onset of left ventricular failure that decline rapidly. 1. Case Report A previously well 18-year-old carpet fitter presented with a three-week history of progressive abdominal pain, anorexia, and 10?Kg weight loss. There was associated diarrhoea, with blood and mucus mixed with stool, nausea, and vomiting. He denied any pyrexia or rigors, foreign travel, or ingesting any unusual food. There was no significant medical history or family history. On examination the patient was severely dehydrated, cahexic, hypotensive, and tachycardic. Cardiovascular examination was otherwise unremarkable and a soft, nonperitonitic abdomen with generalised tenderness was detected. The abdomen was not distended and no organomegaly was identified. Rectal examination detected no abnormality, except for a small perianal fistula. A diagnosis of severe dehydration secondary to either colitis or gastroenteritis was made, and aggressive fluid resuscitation commenced. The patient’s condition deteriorated after aggressive fluid resuscitation (five litres of crystalloid fluid over 2 hours). He remained in shock (pulse 160?bpm, blood pressure 86/50?mm?Hg) and became tachypnoeic (respiratory rate 50) and hypoxic (saturations 83% on air). Repeat examination revealed an elevated
Self-Referencing Method for Relative Color Intensity Analysis Using Mobile-Phone  [PDF]
Wellington S. Souza, Marcos A. S. de Oliveira, Gabrielli M. F. de Oliveira, Dalton P. de Santana, Renato E. de Araujo
Optics and Photonics Journal (OPJ) , 2018, DOI: 10.4236/opj.2018.87022
Abstract: Mobile-phones have been widely explored on colorimetric evaluations. However, their use with different built-in image systems and acquisition configuration, in an environment with non-controlled illumination, limits the establishment of an accurate color analysis. To overcome this restriction, the determination of the absolute color of an object can be overlooked and a relative color value determined. In this work, we establish a new approach for spectroscopic evaluation based on cell-phone imaging, with no previous calibration, determining relative color values. The standalone relative color intensity method is evaluated under the use of four distinct mobile-phones and different illumination conditions. The capability to distinguish different color shades exploring the proposed self-referenced relative color intensity technique is appraised. Moreover, the potential use of the method is demonstrated by evaluating the chemical-adsorption process of Cysteamine molecules on gold nanoparticle surfaces. The proposed self-referenced technique can improve and expand the use of mobile-phones in spectroscopic applications.
The Plasmodium falciparum Malaria M1 Alanyl Aminopeptidase (PfA-M1): Insights of Catalytic Mechanism and Function from MD Simulations
Peter M. Jones, Mark W. Robinson, John P. Dalton, Anthony M. George
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0028589
Abstract: Malaria caused by several species of Plasmodium is major parasitic disease of humans, causing 1–3 million deaths worldwide annually. The widespread resistance of the human parasite to current drug therapies is of major concern making the identification of new drug targets urgent. While the parasite grows and multiplies inside the host erythrocyte it degrades the host cell hemoglobin and utilizes the released amino acids to synthesize its own proteins. The P. falciparum malarial M1 alanyl-aminopeptidase (PfA-M1) is an enzyme involved in the terminal stages of hemoglobin digestion and the generation of an amino acid pool within the parasite. The enzyme has been validated as a potential drug target since inhibitors of the enzyme block parasite growth in vitro and in vivo. In order to gain further understanding of this enzyme, molecular dynamics simulations using data from a recent crystal structure of PfA-M1 were performed. The results elucidate the pentahedral coordination of the catalytic Zn in these metallo-proteases and provide new insights into the roles of this cation and important active site residues in ligand binding and in the hydrolysis of the peptide bond. Based on the data, we propose a two-step catalytic mechanism, in which the conformation of the active site is altered between the Michaelis complex and the transition state. In addition, the simulations identify global changes in the protein in which conformational transitions in the catalytic domain are transmitted at the opening of the N-terminal 8 ?-long channel and at the opening of the 30 ?-long C-terminal internal chamber that facilitates entry of peptides to the active site and exit of released amino acids. The possible implications of these global changes with regard to enzyme function are discussed.
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