Optimal Control Applied to a Visceral Leishmaniasis Model

In this article, we developed a deterministic model for the transmission dynamics of visceral leishmaniasis in humans, canine reservoirs and sandflies, which is the only vector that transmits the disease parasite. The theoretical and epidemiological findings of this study indicates that the diseasefree equilibrium of the model is locally and globally asymptotically stable when the associated reproduction number is less than unity. We perform sensitivity analysis on the model parameter to determine the parameter with the most impact on the reproduction number. Following the results obtained from the sensitivity analysis, we apply optimal control theory using three time dependent control variables representing personal protection, insecticide spraying and culling of infected canine reservoirs. Simulation results are presented for various outbreak scenarios which indicates that leishmaniasis can be eliminated from a region by the application of three time dependent controls representing respectively, personal protection, insecticide spraying and culling infected canine reservoir

Oscillatory behavior of two nonlinear microbial models of soil carbon decomposition

A number of nonlinear models have recently been proposed for simulating soil carbon decomposition. Their predictions of soil carbon responses to fresh litter input and warming differ significantly from conventional linear models. Using both stability analysis and numerical simulations, we showed that two of those nonlinear models (a two-pool model and a three-pool model) exhibit damped oscillatory responses to small perturbations. Stability analysis showed the frequency of oscillation is proportional to √(ε⁻¹-1) Ks/Vs in the two-pool model, and to √(ε⁻¹-1) Kl/Vl in the three-pool model, where ε is microbial growth efficiency, Ks and Kl are the half saturation constants of soil and litter carbon, respectively, and /Vs and /Vl are the maximal rates of carbon decomposition per unit of microbial biomass for soil and litter carbon, respectively. For both models, the oscillation has a period of between 5 and 15 years depending on other parameter values, and has smaller amplitude at soil temperatures between 0 and 15°C. In addition, the equilibrium pool sizes of litter or soil carbon are insensitive to carbon inputs in the nonlinear model, but are proportional to carbon input in the conventional linear model. Under warming, the microbial biomass and litter carbon pools simulated by the nonlinear models can increase or decrease, depending whether ε varies with temperature. In contrast, the conventional linear models always simulate a decrease in both microbial and litter carbon pools with warming. Based on the evidence available, we concluded that the oscillatory behavior and insensitivity of soil carbon to carbon input are notable features in these nonlinear models that are somewhat unrealistic. We recommend that a better model for capturing the soil carbon dynamics over decadal to centennial timescales would combine the sensitivity of the conventional models to carbon influx with the flexible response to warming of the nonlinear model.15 page(s

Mathematical Modeling for Studying the Sustainability of Plants Subject to the Stress of Two Distinct Herbivores

Viability of plants, especially endangered species, are usually affected by multiple stressors, including insects, herbivores, environmental factors and other plant species. We present new mathematical models, based on systems of ordinary differential equations, of two distinct herbivore species feeding (two stressors) on the same plant species. The new feature is the explicit functional form modeling the simultaneous feedback interactions (synergistic or additive or antagonistic) between the three species in the ecosystem. The goal is to investigate whether the coexistence of the plant and both herbivore species is possible (a sustainable system) and under which conditions sustainability is feasible. Our theoretical analysis of the novel model without including competitions among the two herbivores reveals that the number of equilibrium states and their local stability depends on the type of interaction between the stressors: synergistic or additive or antagonistic. Our numerical results, based on value of parameters available, suggest that a sustainable system requires significant herbivore inter- or intra-species competition or both types. Additionally, our numerical findings indicate that competition and interaction of additive type promotes coexistence equilibrium states with the highest plant biomass. Furthermore, the system can exhibit periodic behavior and show the potential for multi-stability

Modeling of Community- and Hospital-acquired Methicillin-resistant Staphylococcus Aureus Transmission in Hospital Settings

In this paper we developed both deterministicand stochastic models of community- and hospital-acquired methicillin-resistant staphylococcus aureus transmission (MRSA) to quantify their interactions in a hospital settings. The disease-free equilibrium of the model is locally-asymptotically stable whenever the associated reproduction number is less than unity. The disease persists in the community whenever the reproduction number is greater than unity. Although our stochastic model evolves on an unbounded state space, we show it is positive recurrent. The result obtained from the sensitivity analysis using the deterministic model indicates that the dominant parameters are the hand washing compliance rate, the health-care workers decolonization rate, environmental contamination rate, the admission rates into the hospital, isolation rate of patients with CA-MRSA and isolation rate of patients with HA-MRSA, the transmission probabilities of CA- and HA-MRSA  per contact with health-care workers and transmission probability of health-care workers  per contact with patients. Numerical simulations of the deterministic model obtained from using the dominate parameters as combination of control strategies such as low-, moderate and high-effectiveness control strategies show that disease prevalence among the hospital patients and the bacterial in the hospital environment can be controlled by moderate- and high-effectiveness control strategies. However, for health-care workers the disease prevalence can only be effectively controlled by the high-effectiveness control strategy

Transit times and mean ages for nonautonomous and autonomous compartmental systems

We develop a theory for transit times and mean ages for nonautonomous compartmental systems. Using the McKendrick-von F\"orster equation, we show that the mean ages of mass in a compartmental system satisfy a linear nonautonomous ordinary differential equation that is exponentially stable. We then define a nonautonomous version of transit time as the mean age of mass leaving the compartmental system at a particular time and show that our nonautonomous theory generalises the autonomous case. We apply these results to study a nine-dimensional nonautonomous compartmental system modeling the terrestrial carbon cycle, which is a modification of the Carnegie-Ames-Stanford approach (CASA) model, and we demonstrate that the nonautonomous versions of transit time and mean age differ significantly from the autonomous quantities when calculated for that model

PENGARUH KERAGAMAN PRODUK DAN KUALITAS PELAYANAN TERHADAP KEPUASAN KONSUMEN (Studi Kasus pada Metro Department Store Bandung)

ABSTRAK Penelitian ini bertujuan untuk mengetahui dan menganalisa pengaruh keragaman produk dan kualitas pelayanan terhadap kepuasan konsumen dan mengetahui seberapa besar pengaruh kedua variabel tersebut terhadap kepuasan konsumen secara simultan maupun parsial di Metro Department Store Bandung. Data yang digunakan dalam penelitian ini adalah data primer. Penelitian ini menggunakan teknik pengumpulan data non probability sampling dengan metode incidental. Metode analisis yang digunakan dalam penelitian ini adalah analisis deskriptif dan verifikatif serta sampel pada penelitian ini berjumlah 93 orang . Teknik pengumpulan data yang digunakan adalah observasi, wawancara dan menyebarkan kuisioner. Hasil penelitian menggunakan metode analisis regresi linier berganda, korelasi berganda, uji hipotesis dan koefisien determinasi. Dan hasil penelitian menunjukkan bahwa variabel keragaman produk dan kualitas pelayanan berpengaruh positif dan signifikan terhadap kepuasan konsumen. Hasil penelitian analisis koefisien determinasi adalah terdapat pengaruh keragaman produk sebesar 0,646 atau 64,6% dan kualitas pelayanan sebesar 0,124 atau 12,4% sehingga kedua variabel tersebut memiliki kontribusi sebesar 0,770 atau 77% terhadap kepuasan konsumen sehingga sisanya 23% merupakan pengaruh variabel yang tidak diteliti pada penelitian ini. Sehingga dari kedua variabel tersebut maka keragaman produk memiliki pengaruh lebih besar dibandingkan kualitas pelayanan. Kata Kunci: Keragaman Produk, Kualitas Pelayanan, Kepuasan Konsume

Carbon dioxide diffuse emission and thermal energy release from hydrothermal systems at Copahue-Caviahue Volcanic Complex (Argentina).

The north-western sector of Caviahue caldera (Argentina), close to the active volcanic system of Copahue, is characterized by the presence of several hydrothermal sites that host numerous fumarolic emissions, anomalous soil diffuse degassing of CO2 and hot soils. In March 2014, measurements of soil CO2 fluxes in 5 of these sites (namely, Las M\ue1quinas, Las Maquinitas I, Las Maquinitas II, Anfiteatro, and Termas de Copahue) allowed an estimation that ~165t of deeply derived CO2 is daily released. The gas source is likely related to a relatively shallow geothermal reservoir containing a single vapor phase as also suggested by both the geochemical data from the 3 deep wells drilled in the 1980s and gas geoindicators applied to the fumarolic discharges. Gas equilibria within the H-C-O gas system indicate the presence of a large, probably unique, single phase vapor zone at 200-210\ub0C feeding the hydrothermal manifestations of Las M\ue1quinas, Las Maquinitas I and II and Termas de Copahue. A natural thermal release of 107MW was computed by using CO2 as a tracer of the original vapor phase. The magmatic signature of the incondensable fumarolic gases, the wide expanse of the hydrothermal areas and the remarkable high amount of gas and heat released by fluid expulsion seem to be compatible with an active magmatic intrusion beneath this portion of the Caviahue caldera

Geochemistry of fluid discharges from Peteroa volcano (Argentina-Chile) in 2010-2015: Insights into compositional changes related to the fluid source region(s).

This study presents the first geochemical data of fluid discharges collected from February 2010 to March 2015 from the Planchon-Peteroa-Azufre Volcanic Complex (PPAVC), located in the Transitional Southern Volcanic Zone (TSVZ) at the border between Argentina and Chile. During the study period, from January 2010 to July 2011, Peteroa volcano experienced phreatic to phreatomagmatic eruption possibly related to the devastating Maule earthquake occurred on February 27, 2010. The compositional dataset includes low temperature (from 43.2 to 102 degrees C) gas discharges from (i) the summit of Peteroa volcano and (ii) the SE flank of Azufre volcano, both marked by a significant magmatic fluid contribution, as well as bubbling gases located at the foothill of the Peteroa volcanic edifice, which showed a chemical signature typical of hydrothermal fluids. In 2012, strong compositional changes affected the Peteroa gases from the summit area: the acidic gas species, especially SO2, increased, suggesting an input of fluids from magma degassing. Nevertheless, the R/Ra and delta C-13-CO2 values decreased, which would imply an enhanced contribution from a meteoric-hydrothermal source. In 2014-2015, the chemical and isotopic compositions of the 2010-2011 gases were partially restored. The anomalous decoupling between the chemical and the isotopic parameters was tentatively interpreted as produced by degassing activity from a small batch of dacitic magma that in 2012 masked the compositional signature of the magmatic fluids released from a basaltic magma that dominated the gas chemistry in 2010-2011. This explanation reliably justifies the observed geochemical data, although the mechanisms leading to the change in time of the dominating magmatic fluid source are not clear. At this regard, a geophysical survey able to provide information on the location of the two magma batches could be useful to clarify the possible relationships between the compositional changes that affected the Peteroa fluid discharges and the 2010-2011 eruptive activity.FONDECYT Iniciacion Project 11100372 FONDAP "Centro de Excelencia en Geotermia de los Andes" 15090013 Universidad de Buenos Aires UBACyT 20020120300077BA IDEAN institute (UBA-CONICET) Laboratory of Fluid and Rock Geochemistry of the Department of Earth Sciences (Florence, Italy

Primeros datos de degasificación difusa de CO2 desde la caldera volcán Planchón - Peteroa

El ComplejoVolcánico Planchón - Peteroa (CVPP) se encuentra localizado en un sector de la Cordillera de los Andes llamado Zona Volcánica Sur Transicional, sobre el límite chileno - argentino. Las emisiones fluidas de este sistema se localizan en la caldera del volcán Peteroa y en las áreas termales periféricas, que en territorio argentino corresponden a los valles de Baños del Azufre y del Peñón.A lo largo de dos campañas en los meses de febrero de 2016 y 2017, un relevamiento de datos de flujo de dióxido de carbono difuso fue llevado a cabo en las áreas mencionadas. El origen del gas muestreado fue estudiado a través del método gráfico estadístico y se realizaron mapas de las estructuras de desgasificación difusa de CO2 y estimaciones de la cantidad de gas emitido a la atmósfera con simulaciones secuenciales gaussianas. En los sitios termales, las emisiones difusas de CO2 son de limitada extensión y están ligadas a la surgencia de aguas termales. De acuerdo con el métodográfico estadístico, tres poblaciones de CO2 constituyen la muestra total de la data de las áreas termales. Dos de estas poblaciones fueron interpretadas como poblaciones de fondo, mientras que la tercera, con una mayor media de flujo de CO2, fue interpretada como una población de tipo endógena. El valle Baños del Azufre y el del Peñón emiten aproximadamente 3,7 y4,7 tn/día de CO2. Respecto a la caldera del volcán Peteroa, se detectaron anomalías tanto de CO2 como de temperatura en el suelo muestreado. Debido a la ausencia total de vegetación, las dos poblaciones de flujo de CO2 difuso que constituyen la muestra se interpretan como endógenas. La simulación secuencial gaussiana permitió estimar una emisión de6,5 tn/día de CO2 a través del suelo presente en la caldera del volcán Peteroa.Fil: Agusto, Mariano Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Lamberti, María Clara Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Núñez, N.. Comisión Nacional de Energía Atómica; ArgentinaFil: Sánchez, H.. Comisión Nacional de Energía Atómica; ArgentinaFil: García, S.. Secretaría de Industria y Minería. Servicio Geológico Minero Argentino; ArgentinaFil: Gómez, M.. Comisión Nacional de Energía Atómica; Argentina12º Encuentro del Centro Internacional de Ciencias de la TierraMendozaArgentinaUniversidad Nacional de Cuy