Diffusion Enhancement in Core-softened fluid confined in nanotubes

We study the effect of confinement in the dynamical behavior of a core-softened fluid. The fluid is modeled as a two length scales potential. This potential in the bulk reproduces the anomalous behavior observed in the density and in the diffusion of liquid water. A series of $NpT$ Molecular Dynamics simulations for this two length scales fluid confined in a nanotube were performed. We obtain that the diffusion coefficient increases with the increase of the nanotube radius for wide channels as expected for normal fluids. However, for narrow channels, the confinement shows an enhancement in the diffusion coefficient when the nanotube radius decreases. This behavior, observed for water, is explained in the framework of the two length scales potential.Comment: 17 pages, 8 figures, accept for publication at J. Chem. Phy

Thermodynamic and dynamic anomalies for a three dimensional isotropic core-softened potential

Using molecular dynamics simulations and integral equations (Rogers-Young, Percus-Yevick and hypernetted chain closures) we investigate the thermodynamic of particles interacting with continuous core-softened intermolecular potential. Dynamic properties are also analyzed by the simulations. We show that, for a chosen shape of the potential, the density, at constant pressure, has a maximum for a certain temperature. The line of temperatures of maximum density (TMD) was determined in the pressure-temperature phase diagram. Similarly the diffusion constant at a constant temperature, $D$, has a maximum at a density $\rho_{max}$ and a minimum at a density $\rho_{min}<\rho_{max}$. In the pressure-temperature phase-diagram the line of extrema in diffusivity is outside of TMD line. Although in this interparticle potential lacks directionality, this is the same behavior observed in SPC/E water.Comment: 16 page

Entropy, diffusivity and the energy landscape of a water-like fluid

Molecular dynamics simulations and instantaneous normal mode (INM) analysis of a fluid with core-softened pair interactions and water-like liquid-state anomalies are performed to obtain an understanding of the relationship between thermodynamics, transport properties and the poten- tial energy landscape. Rosenfeld-scaling of diffusivities with the thermodynamic excess and pair correlation entropy is demonstrated for this model. The INM spectra are shown to carry infor- mation about the dynamical consequences of the interplay between length scales characteristic of anomalous fluids, such as bimodality of the real and imaginary branches of the frequency distribu- tion. The INM spectral information is used to partition the liquid entropy into two contributions associated with the real and imaginary frequency modes; only the entropy contribution from the imaginary branch captures the non-monotonic behaviour of the excess entropy and diffusivity in the anomalous regime of the fluid

Liquid crystal phase and waterlike anomalies in a core-softened shoulder-dumbbells system

Using molecular dynamics we investigate the thermodynamics, dynamics and structure of 250 diatomic molecules interacting by a core-softened potential. This system exhibits thermodynamics, dynamics and structural anomalies: a maximum in density-temperature plane at constante pressure and maximum and minimum points in the diffusivity and translational order parameter against density at constant temperature. Starting with very dense systems and decreasing density the mobility at low temperatures first increases, reach a maximum, then decreases, reach a minimum and finally increases. In the pressure-temperature phase diagram the line of maximum translational order parameter is located outside the line of diffusivity extrema that is enclosing the temperature of maximum density line. We compare our results with the monomeric system showing that the anisotropy due to the dumbbell leads to a much larger solid phase and to the appearance of a liquid crystal phase. the double ranged thermodynamic and dynamic anomalies.Comment: 14 pages, 5 figure

Ultrasound assisted modulation of yeast growth and inactivation kinetics

[EN] The yeast Saccharomyces cerevisiae is well known for its application in the food industry for the purpose of developing fermented food. The ultrasound (US) technology offer a wide range of applications for the food industry, including the enhancement of fermentation rates and inactivation of microbial cells. However, a better understanding and standardization of this technology is still required to ensure the scaling-up process. This study investigated the effect of the US technology on the growth of S. cerevisiae using frequencies of 20, 25, 45 and 130 kHz, treatment periods from 2 to 30 min. Furthermore, yeast kinetics subjected to US treatments were evaluated using modelling tools and scanning electron microscopy (SEM) analysis to explore the impact of sonication on yeast cells. Yeast growth was monitored after different US treatments plotting optical density (OD) at 660 nm for 24 h at 30 ⁰C. Growth curves were fitted using models of modified Gompertz and Scale-Free which showed good parameters of the fit. In particular, US frequencies of 45 and 130 kHz did not have a disruptive effect in lag phase and growth rate of the yeast populations, unlike the frequency of 20 kHz. Moreover, inactivation curves of yeast cells obtained after exposure to 20 and 25 kHz also observed the best fit using the Weibull model. US frequency of 20 kHz achieved significant reductions of 1.3 log cfu/mL in yeast concentration and also induced important cell damage on the external structures of S. cerevisiae. In conclusion, the present study demonstrated the significant effect of applying different US frequencies on the yeast growth for potential application in the food industrySIThis study was funded by the Teagasc Walsh Fellowship program, Department of Agriculture, Food, and Marine (DAFM) under the Food Institutional Research Measure (FIRM) program [Grant number: DAFM/ 17/F/275

SYBR Green-based Real-Time PCR targeting kinetoplast DNA can be used to discriminate between the main etiologic agents of Brazilian cutaneous and visceral leishmaniases

<p>Abstract</p> <p>Background</p> <p>Leishmaniases control has been hampered by the unavailability of rapid detection methods and the lack of suitable therapeutic and prophylactic measures. Accurate diagnosis, which can distinguish between <it>Leishmania </it>isolates, is essential for conducting appropriate prognosis, therapy and epidemiology. Molecular methods are currently being employed to detect <it>Leishmania </it>infection and categorize the parasites up to genus, complex or species level. Real-time PCR offers several advantages over traditional PCR, including faster processing time, higher sensitivity and decreased contamination risk.</p> <p>Results</p> <p>A SYBR Green real-time PCR targeting the conserved region of kinetoplast DNA minicircles was able to differentiate between <it>Leishmania </it>subgenera. A panel of reference strains representing subgenera <it>Leishmania </it>and <it>Viannia </it>was evaluated by the derivative dissociation curve analyses of the amplified fragment. Distinct values for the average melting temperature were observed, being 78.95°C ± 0.01 and 77.36°C ± 0.02 for <it>Leishmania </it>and <it>Viannia</it>, respectively (p < 0.05). Using the Neighbor-Joining method and Kimura 2-parameters, the alignment of 12 sequences from the amplified conserved minicircles segment grouped together <it>L</it>. (<it>V</it>.) <it>braziliensis </it>and <it>L</it>. (<it>V</it>.) <it>shawii </it>with a bootstrap value of 100%; while for <it>L</it>. (<it>L</it>.) <it>infantum </it>and <it>L</it>. (<it>L</it>.) <it>amazonensis</it>, two groups were formed with bootstrap values of 100% and 62%, respectively. The lower dissociation temperature observed for the subgenus <it>Viannia </it>amplicons could be due to a lower proportion of guanine/cytosine sites (43.6%) when compared to species from subgenus <it>Leishmania </it>(average of 48.4%). The method was validated with 30 clinical specimens from visceral or cutaneous leishmaniases patients living in Brazil and also with DNA samples from naturally infected <it>Lutzomyia </it>spp. captured in two Brazilian localities.</p> <p>Conclusions</p> <p>For all tested samples, a characteristic amplicon melting profile was evidenced for each <it>Leishmania </it>subgenus, corroborating the data from reference strains. Therefore, the analysis of thermal dissociation curves targeting the conserved kinetoplast DNA minicircles region is able to provide a rapid and reliable method to identify the main etiologic agents of cutaneous and visceral leishmaniases in endemic regions of Brazil.</p

Density anomaly in a competing interactions lattice gas model

We study a very simple model of a short-range attraction and an outer shell repulsion as a test system for demixing phase transition and density anomaly. The phase-diagram is obtained by applying mean field analysis and Monte Carlo simulations to a two dimensional lattice gas with nearest-neighbors attraction and next-nearest-neighbors repulsion (the outer shell). Two liquid phases and density anomaly are found. The coexistence line between these two liquid phases meets a critical line between the fluid and the low density liquid at a tricritical point. The line of maximum density emerges in the vicinity of the tricritical point, close to the demixing transition

Is urinary density an adequate predictor of urinary osmolality?

Urinary density (UD) has been routinely used for decades as a surrogate marker for urine osmolality (U-osm). We asked if UD can accurately estimate U-osm both in healthy subjects and in different clinical scenarios of kidney disease. UD was assessed by refractometry. U-osm was measured by freezing point depression in spot urines obtained from healthy volunteers (N = 97) and in 319 inpatients with acute kidney injury (N = 95), primary glomerulophaties (N = 118) or chronic kidney disease (N = 106). UD and U-osm correlated in all groups (p < 0.05). However, a wide range of U-osm values was associated with each UD value. When UD was <= 1.010, 28.4% of samples had U-osm above 350 mOsm/kg. Conversely, in 61.6% of samples with UD above 1.020, U-osm was below 600 mOsm/kg. As expected, U-osm exhibited a strong relationship with serum creatinine (S-creat), whereas a much weaker correlation was found between UD and Screat. We found that UD is not a substitute for U-osm. Although UD was significantly correlated with U-osm, the wide dispersion makes it impossible to use UD as a dependable clinical estimate of U-osm. Evaluation of the renal concentrating ability should be based on direct determination of U-osm1

Collagen and Elastic Fibers in Odontogenic Entities: Analysis Using Light and Confocal Laser Microscopic Methods

Dentigerous cyst (DC) and keratocystic odontogenic tumor (KOT) are odontogenic lesions arising from epithelial elements, such as those observed in dental follicles (DF), that have been part of the tooth forming apparatus. These lesions show different clinical and histological characteristics, as well as distinct biological behavior. This study aimed to qualify and quantify collagen and elastic fibers by means of histochemical techniques with light and confocal laser microscopic methods in three odontogenic entities. Eleven DF, 13 DC (n=10 with inflammation, n=3 without inflammation) and 13 KOT were processed to the following techniques: Hematoxylin and Eosin, Masson’s Trichrome, Picrosirius, Direct Blue, and Orcein. DF and DC without inflammation exhibited collagen with similar characteristics: no parallel pattern of fiber orientation, thick fibers with dense arrangement, and absence of distinct layers. A comparison between DC with inflammation and KOT revealed similar collagen organization, showing distinct layers: thin collagen fibers with loose arrangement near the epithelium and thick fibers with dense arrangement in distant areas. The only difference found was that KOT exhibited a parallel collagen orientation in relation to the odontogenic epithelia. It may be suggested that the connective tissue of DC is a reactive tissue, inducing an expansive growth associated with fluid accumulation and inflammatory process, which in turn may be present as part of the lesion itself. In KOT, loosely arranged collagen may be associated with the behavior of the neoplastic epithelium

Visible and NIR hyperspectral imaging and chemometrics for prediction of microbial quality of beef Longissimus dorsi muscle under simulated normal and abuse storage conditions

peer-reviewedThere is a need to develop a rapid technique to provide real time information on the microbial load of meat along the supply chain. Hyperspectral imaging (HSI) is a rapid, non-destructive technique well suited to food analysis applications. In this study, HSI in both the visible and near infrared spectral ranges, and chemometrics were studied for prediction of the bacterial growth on beef Longissimus dorsi muscle (LD) under simulated normal (4 °C) and abuse (10 °C) storage conditions. Total viable count (TVC) prediction models were developed using partial least squares regression (PLS-R), spectral pre-treatments, band selection and data fusion methods. The best TVC prediction models developed for storage at 4 (RMSEp 0.58 log CFU/g, RPDp 4.13, R2p 0.96), 10 °C (RMSEp 0.97 log CFU/g, RPDp 3.28, R2p 0.94) or at either 4 or 10 °C (RMSEp 0.89 log CFU/g, RPDp 2.27, R2p 0.86) were developed using high-level data fusion of both spectral regions. The use of appropriate spectral pre-treatments and band selection methods was key for robust model development. This study demonstrated the potential of HSI and chemometrics for real time monitoring to predict microbial growth on LD along the meat supply chain.Food Institutional Research Measur