The Galerkin-truncated Burgers equation: crossover from inviscid-thermalized to Kardar-Parisi-Zhang scaling.

The one-dimensional Galerkin-truncated Burgers equation, with both dissipation and noise terms included, is studied using spectral methods. When the truncation-scale Reynolds number [Formula: see text] is varied, from very small values to order 1 values, the scale-dependent correlation time [Formula: see text] is shown to follow the expected crossover from the short-distance [Formula: see text] Edwards-Wilkinson scaling to the universal long-distance Kardar-Parisi-Zhang scaling [Formula: see text]. In the inviscid limit, [Formula: see text], we show that the system displays another crossover to the Galerkin-truncated inviscid-Burgers regime that admits thermalized solutions with [Formula: see text]. The scaling forms of the time-correlation functions are shown to follow the known analytical laws and the skewness and excess kurtosis of the interface increments distributions are characterized. This article is part of the theme issue 'Scaling the turbulence edifice (part 2)'.

Transcriptional analysis of metabolic and virulence genes associated with biofilm formation in Piscirickettsia salmonis strains.

Piscirickettsia salmonis is a facultative intracellular bacterium that generates piscirickettsiosis affecting salmonids in Chile. The bacterium has the adaptability to survive in the marine environment under multiple stressful conditions. In this sense, this work focused on the analysis of a gene battery associated with biofilm formation under different culture conditions and on the adaptability of this biofilm to different media. The results indicated that the strains LF-89, IBM-034 and IBM-040 were strong biofilm producers, evidencing adaptability to the media by increasing the amount of biofilm through successive growths. Transcript levels of six genes described in various bacteria and P. salmonis, considered to have metabolic functions, and playing a relevant role in biofilm formation, were analyzed to evaluate bacterial functionality in the biofilm. The genes mazE-mazF, implicated in biofilm and stress, were markedly overexpressed in the biofilm condition in the three strains. For its part, gene gltA, an indicator of metabolic activity and related to virulence inhibition in Salmonella typhimurium, also seems to restrain the pathogenesis process in P. salmonis by inhibiting the expression of the virulence-associated genes liso and tcf. Finally, the expression of the glnA gene suggests the use of glutamine as an essential element for the growth of the biofilm.

Dry eye is matched by increased intrasubject variability in tear osmolarity as confirmed by machine learning approach. / El ojo seco está relacionado con un aumento intrasujeto de la variabilidad de osmolaridad lagrimal confirmado por tecnología de aprendizaje de máquinas.

OBJECTIVE: Because of high variability, tear film osmolarity measures have been questioned in dry eye assessment. Understanding the origin of such variability would aid data interpretation. This study aims to evaluate osmolarity variability in a clinical setting. MATERIAL AND METHODS: Twenty dry eyes and 20 control patients were evaluated. Three consecutive osmolarity measurements per eye at 5min intervals were obtained. Variability was represented by the difference between both extreme readings per eye. Machine learning techniques were used to quantify discrimination capacity of tear osmolarity for dry eye. RESULTS: Mean osmolarities in the control and dry eye groups were 295.1±7.3mOsm/L and 300.6±11.2mOsm/L, respectively (P=.004). Osmolarity variabilities were 7.5±3.6mOsm/L and 16.7±11.9mOsm/L, for the control and dry eye groups, respectively (P<.001). Based on osmolarity, a logistic classifier showed an 85% classification accuracy. CONCLUSIONS: In the clinical setting, both mean osmolarity and osmolarity variability in the dry eye group were significantly higher than in the control group. Machine learning techniques showed good classification accuracy. It is concluded that higher variability of tear osmolarity is a dry eye feature.

High prevalence of Demodex spp. infestation among patients with posterior blepharitis: correlation with age and cylindrical dandruff. / Alta prevalencia de infestación por Demodex spp. en pacientes con blefaritis posterior: correlación con edad y caspa cilíndrica.

OBJECTIVE: To determine prevalence of Demodex spp. and infestation index (II) by the parasite among patients of different ages with blepharitis and to assess association with occurrence of cylindrical dandruff (CC). MATERIALS AND METHODS: Prospective study including patients diagnosed with posterior blepharitis between 2013 and 2015, without previous acaricide treatment, was conducted by Fundación Oftalmológica Los Andes (Chile). Four eyelashes were randomly extracted from each eyelid for parasite detection. The II was calculated as the ratio between the total number of demodex specimens found in the total number of eyelashes removed. A semi-quantitative determination of the CC was performed. RESULTS: A total of 178 patients (91 men, 87 women), with a mean age of 58.49±20.66 years, were included. It was found that 83.7% of patients were infested with Demodex folliculorum with a mean II of 0.96±0.84 mites/eyelash. The II was significantly higher in patients over 50 years (p<.0001). Patient age and II showed a Pearson correlation coefficient (R2) of 0.12 (p<.0001). CC was observed in 71.4% of patients, with those over 50 years-old showing significantly higher values. A positive correlation was also observed between the amount of CC and the II (R2=.33; p<.0001). CONCLUSIONS: The prevalence of infestation by Demodex folliculorum is high in patients with posterior blepharitis. The II by the parasite is positively correlated with age and with the occurrence of CC on the eyelid border.

Identification of genomic islands in Chilean Piscirickettsia salmonis strains and analysis of gene expression involved in virulence.

Piscirickettsia salmonis, an agent of Piscirickettsiosis, is the cause of major losses in the Chilean salmon industry. We identified, characterized and bioinformatically analysed genomic islands in field strains of P. Salmonis, using the bioinformatic software PIPS, that uses the characteristics of the islands of pathogenicity to identify them. We analysed nine partially sequenced genomes in different new field strains, and compared them with the LF-89 (Type strain) genome, selecting a genomic island present in all of them. We then evaluated the relative expression of three genes present in that island. From the obtained results, we conclude that the expression of the tcf gene is directly proportional to the cytopathogenicity in vitro of the bacteria; the product of the dnsa gene could contribute to its pathogenicity, but would be potentiated by one or more factors. The product of the gene liso is necessary for the virulence process and could have functions in early stages of infection. Regarding the strains, the IBM-040 strain showed a significant increase in the expression of all the genes in the study. Contrarily, LF-89 only presented a significant increase in expression of the gene liso, which correlates with the cytopathogenicity in vitro observed in the SHK-1 cells.

Search and analysis of genes involved in antibiotic resistance in Chilean strains of Piscirickettsia salmonis.

Piscirickettsia salmonis is the pathogen causing Piscirickettsiosis. For treatment, the industry mainly uses oxytetracycline and florfenicol, so it is essential to understand the degree of susceptibility of this pathogen to these drugs. But this is still unknown for a large number of P. salmonis strains, as are the molecular mechanisms responsible for greater or lesser susceptibility. However, genes that confer resistance to these antimicrobials have been reported and characterized for this and other bacterial species, among which are membrane proteins that take out the drug. Our results identified differences in the degree of susceptibility to both antibiotics among different Chilean isolated of these bacteria. We analysed 10 available genomes in our laboratory and identified ~140 genes likely to be involved in antibiotic resistance. We analysed six specific genes, which suggests that some of them would eventually be relevant in conferring resistance to both antibiotics, as they encode for specific transporter proteins, which increase the number of transcripts when grown in media with these antibiotics. Our results were corroborated with EtBr permeability analysis, which revealed that the LF-89 strain accumulates this compound and has a reduced capacity to expulse it compared with the field strains.

[Telemedicine correlation in retinopathy of prematurity between experts and non-expert observers]. / Correlación en telemedicina de retinopatía del prematuro entre observadores expertos y no expertos.

OBJECTIVE: To study the correlation between expert and non-expert observers in the reporting images for the diagnosis of retinopathy of prematurity (ROP) in a telemedicine setting. METHODS: A cross-sectional, multicenter study, consisting of 25 sets of images of patients screened for ROP. They were evaluated by two experts in ROP and 1 non-expert and classified according to telemedicine classification, zone, stage, plus disease and Ells referral criteria. The telemedicine classification was: no ROP, mild ROP, type 2 ROP, or ROP that requires treatment. Ells referral criteria is defined as the presence at least one of the following: ROP in zone I, Stage 3 in zone I or II, or plus+ For statistical analysis, SPSS 16.0 was used. For correlation, Kappa value was performed. RESULTS: There was a high correlation between observers for the assessment of ROP stage (0.75; 0.54-0.88) plus disease (0.85; 0.71-0.92), and Ells criteria (0.89; 0.83-1.0). However, inter-observer values were low for zone (0.41; 0.27-0.54) and telemedicine classification (0.43; 0.33-0.6). CONCLUSIONS: When evaluating telemedicine images by examiners with different levels of expertise in ROP, the Ells criteria gave the best correlation. In addition, stage of disease and plus disease have good correlation among observers. In contrast, the correlation between observers was low for zone and telemedicine classification.

van der Waals normal form for a one-dimensional hydrodynamic model.

Phase separation in a fluidized granular system is studied. We consider a one-dimensional hydrodynamic model that mimics a two-dimensional fluidized granular system with a vibrating wall and without gravity, which exhibits a phase separation. Close to the critical point, by means of an adiabatic elimination of the temperature, we deduce the van der Waals normal form, which is the equation that describes the slow dynamics of the system and predicts the qualitative behavior in different regions of parameters. This allows us to understand the origin of the effective viscosity and the spatial saturation at the onset of the bifurcation. The hydrodynamic model and van der Waals normal form exhibit a behavior similar to the one observed in molecular dynamics simulations.