Exponential growth constants for spanning forests on Archimedean lattices: Values and comparisons of upper bounds

We compare our upper bounds on the exponential growth constant [Formula: see text] characterizing the asymptotic behavior of spanning forests on Archimedean lattices [Formula: see text] with recently derived upper bounds.Our upper bounds on [Formula: see text], which are very close to the respective values of [Formula: see text] that we have calculated, are shown to be significantly better for these lattices than the new upper bounds.

Modelos cinéticos sigmoidales aplicados al crecimiento de Saccharomyces boulardii

Predictive microbiology is an interesting tool that allows evaluating the behavior of biomass and metabolites in different culture media, providing multiple benefits, whether scientific or industrial, for these and other reasons the objective of this research was to evaluate applied sigmoidal kinetic models to the growth of Saccharomyces boulardii in milk. For this purpose, flasks were prepared with 200 mL of fresh cow's milk, previously sterilized at 121 ° C x 15 min, then the strains were inoculated at a temperature of 37 ° C and incubated at the same temperature under constant shaking of 20 revolutions per minute (rpm) in a water bath with shaking, for 7 h; To construct the curves and obtain the growth constants, colony-forming units were counted per milliliter (cfu / ml) at one-hour intervals, with a monocular microscope and Neubauer chamber. Also, the pH and titratable acidity expressed in lactic acid were measured. The data obtained were converted to a logarithmic scale to apply the sigmoidal equations of Gompertz, Logistic, Modified Logistic and Weibull. The results of the kinetic modeling gave us that the modified Logistics and Logistics models presented a better fit compared to the rest. Likewise, the Weibull model presented the lowest value of adjustment, on the other hand, in the analysis of the statistical criteria, all models except Weibull present similarity. Finally, each sigmoidal model allowed to evaluate the growth of Saccharomyces boulardii with each of its kinetic constants.

A Statistical Analysis of the Most Affected Countries by COVID-19 (Preprint)

BACKGROUND It is almost more than six months elapsed since the crisis of COVID-19 pandemic has hit the globe. It becomes utterly crucial for policy formulation to know up to which period and up to what magnitude the disease will impact us. OBJECTIVE Aim of this study is to predict the saturation level of COVID-19 cases in USA, Brazil, India, Russia, Italy and UK. METHODS Trend analysis is used to fit exponential trend line to the weekly cumulative positive cases. Forecasted growth constants obtained by fitting power series trend to the observed values and prediction of weekly cumulative cases done. Growth constant value of 0.0039 (Doubling time 180 days), observed mean, median and maximum reported COVID-19 cases per million for countries with more than 90% recovery is used to obtain saturation levels. RESULTS Italy and UK reached saturation with growth constant values 0.0007 and 0.0025. Brazil and USA projected to achieve saturation by 26 September 2020 and 19 December 2020 with 8.24 and 9.17 million cases. India and Russia expected to reach the saturation by 16 January 2021and 27 February 2021 with 56.72 and 3.86 million cases. CONCLUSIONS The USA and Russia are predicted to reach saturation due to decrease in growth constant value. Growth constant values for Brazil and India are high and these countries are estimated to reach saturation by infecting the maximum reported per million population. It is therefore eternally essential to take more proactive decisions and to test more and isolate patients effectively to contain COVID-19. CLINICALTRIAL Nil

Asymptotic behavior of spanning forests and connected spanning subgraphs on two-dimensional lattices

We calculate exponential growth constants [Formula: see text] and [Formula: see text] describing the asymptotic behavior of spanning forests and connected spanning subgraphs on strip graphs, with arbitrarily great length, of several two-dimensional lattices, including square, triangular, honeycomb, and certain heteropolygonal Archimedean lattices. By studying the limiting values as the strip widths get large, we infer lower and upper bounds on these exponential growth constants for the respective infinite lattices. Since our lower and upper bounds are quite close to each other, we can infer very accurate approximate values for these exponential growth constants, with fractional uncertainties ranging from [Formula: see text] to [Formula: see text]. We show that [Formula: see text] and [Formula: see text] are monotonically increasing functions of vertex degree for these lattices.

Interfacial Reactions between Mg-40Al and Mg-30Y Master Alloys

Interfacial reactions between Mg-40Al and Mg-30Y master alloys were investigated at intervals of 25 °C in the 350–400 °C by using a diffusion couple method. Noticeable reaction layers were formed at the interfaces of the diffusion couples. The concentration profiles of the reaction layers were characterized. The diffusion path of the diffusion couple at 400 °C is constructed on the Mg-Al-Y ternary isothermal temperature phase diagram. The phases of the reaction layer were characterized by X-ray diffraction. The interfacial reaction thermodynamics of diffusion couples were studied. These results indicate that Al2Y is the only new formed intermetallic phase in the reaction layers. The growth constants of the reaction layers were calculated. In the reaction layer II, the integrated interdiffusion coefficients of Al are higher than Y, the diffusion activation energy of Y is higher than that of Al.

SIMULATION MODEL OF THE GROWTH KINETICS OF Fe2B LAYERS WITH CONSIDERATION OF THE BORIDE INCUBATION TIME EFFECT

In this work, a mathematical model for simulating the thermochemical boronizing process is presented. The diffusion model used in this paper is based on Fick’s laws by solving the mass balance equation of the (FeB/Fe2B) interface. In this developed model, the effect of boride incubation times during the formation of Fe2B layers on Armco iron was considered. To demonstrate the validity of our calculations, the simulation results are compared with experimentally obtained data on borided Armco iron, which allowed us to verify the validity of the model. Therefore, a good concordance was observed when comparing the experimental parabolic growth constants taken from the literature with our simulated values of the parabolic growth constants from the present diffusion model. From this study, it has been found that the incubation time has a very important influence on the evolution of the kinetics of the boride layers.

Relationships between fish and otolith dimensions of Pomatomus saltatrix (Linnaeus, 1766) (Perciformes: Pomatomidae) in southeastern Brazil

ABSTRACT The bluefish, Pomatomus saltatrix (Linnaeus, 1766), was used as a species-specific model to study morphometric relationships between otolith size and relative growth variables. Length-weight relationships between Otolith (Length-OL, Height-OH, and Weight-OW) and fish measurements (Total Length-TL and Total Weight-TW) were determined for fishes captured monthly during the year 2015 off the southeastern coast of Brazil. The ANCOVA and Kruskal-Wallis analysis did not indicate significant differences in the relative growth constants between sexes and length frequency distributions (p > 0.05). The condition factor also did not present significant differences between sexes, and right and left otolith measurements (p > 0.05). A total of 398 specimens were sampled: TL = 43.6-67.0 cm, TW = 365-2400 g, OL = 9.65-15.25 mm, OH = 3.65 - 5.45 mm and OW = 0.03-0.11 g. The LWR for grouped sexes was TW = 0.050TL2.55 and otoliths OW = 6.17E-05OL2.59. The best adjustments were TL vs OL (r2 = 0.90); OL vs OW (r2 = 0.90); TW vs OW (r2 = 0.81); and TW vs OL (r2 = 0.80). These results showed that such relationships are helpful tools for predicting the fish size and weight from otoliths, which may be used in food habits and paleontology studies, and other fisheries management applications.