Can presepsin uniformly respond to various pathogens? - an in vitro assay of new sepsis marker.

BACKGROUND: Presepsin (soluble CD14 subtype) is a novel biomarker of sepsis used for early diagnosis. Originally, CD14 is known as the pattern recognition receptor for the lipopolysaccharide (LPS)/LBP complexes, and the diagnostic value of this molecule for gram-positive bacteria, which contain less amount of LPS, is uncertain. To confirm its effectiveness in the diagnosis of bacteremia caused by gram positive bacteria, and to evaluate the interspecies difference of presepsin production against various bacterial strains, we conducted an in vitro assay to evaluate presepsin levels in response to five Gram negative and four Gram positive bacteria. RESULTS: Whole blood was yielded from five healthy volunteers and co-cultured with bacterial strains at 37 °C for 4 h. Twenty seven clinical isolates of nine species (E. coli, K. pneumoniae, E. cloacae, P. aeruginosa, S. maltophilia, S. aureus, S. pyogenes, B. cereus, and C. striatum) derived from blood cultures of non-neutropenic bacteremia patients were used. Culture supernatants were harvested and presepsin levels were measured. The presepsin level in the gram-negative bacteria 273 (218-352) pg/mL was significantly higher than in the gram-positive bacteria 200 (143-275) pg/mL (p = 0.0002). The presepsin levels were significantly lower in C. striatum, in comparison to other bacteria, and S. pyogenes showed similar results. And the presepsin levels in P. aeruginosa were significantly lower compared to E. cloacae, K. pneumoniae, and S. aureus. CONCLUSIONS: Presepsin production can also be evoked by gram-positive bacteria, and interspecies differences of presepsin response may exist, which should be considered in the diagnosis of sepsis, especially in certain gram-positive bacteremia such as S. pyogenes or C. striatum.

Origin of the phase separation into B2 and L21 ordered phases in X-Al-Ti (X: Fe, Co, and Ni) alloys based on the first-principles cluster variation method.

The phase separation behaviors from a single B2 ordered phase into two separate B2 and L21 ordered phases in X-Al-Ti (X: Fe, Co, and Ni) alloys are analyzed utilizing the cluster variation method (CVM), based on interaction energies derived from electronic band structure calculations. A cubic approximation of the CVM is adopted for X2Al2-x Ti x ([Formula: see text]) alloys limiting the interchange between Al and Ti atoms on the [Formula: see text]- and [Formula: see text]-sublattices of an L21 ordered structure with X atoms fixed on the [Formula: see text]-sublattice. The phase stabilities of the B2 and L21 structures are examined, and phase diagrams at the pseudo-binary section, XAl-XTi, are determined. The two-phase regions of the B2 and L21 phases (i.e. phase separation behavior) are successfully produced in Co- and Ni-Al-Ti alloy systems, and no phase separation is observed in the Fe-Al-Ti alloy. The origins of phase separation in the Co- and Ni-Al-Ti alloys are mechanical instability and a combination of mechanical instability and chemical repulsions of unlike pairs, respectively.

Sharp Phase Field Method.

Phase field modeling offers an extremely general framework to predict microstructural evolutions in complex systems. However, its computational implementation requires a discretization scheme with a grid spacing small enough to preserve the continuous character of the theory. We present here a new formulation, which is intrinsically discrete, in which the interfaces are resolved with essentially one grid point with no pinning on the grid and an accurate rotational invariance, improving drastically the numerical capabilities of the method. We show that interfacial kinetic properties are reproduced with a high accuracy. Finally, we apply the model to a situation where conserved and nonconserved fields are coupled.

Ternary eutectic dendrites: Pattern formation and scaling properties.

Extending previous work [Pusztai et al., Phys. Rev. E 87, 032401 (2013)], we have studied the formation of eutectic dendrites in a model ternary system within the framework of the phase-field theory. We have mapped out the domain in which two-phase dendritic structures grow. With increasing pulling velocity, the following sequence of growth morphologies is observed: flat front lamellae → eutectic colonies → eutectic dendrites → dendrites with target pattern → partitionless dendrites → partitionless flat front. We confirm that the two-phase and one-phase dendrites have similar forms and display a similar scaling of the dendrite tip radius with the interface free energy. It is also found that the possible eutectic patterns include the target pattern, and single- and multiarm spirals, of which the thermal fluctuations choose. The most probable number of spiral arms increases with increasing tip radius and with decreasing kinetic anisotropy. Our numerical simulations confirm that in agreement with the assumptions of a recent analysis of two-phase dendrites [Akamatsu et al., Phys. Rev. Lett. 112, 105502 (2014)], the Jackson-Hunt scaling of the eutectic wavelength with pulling velocity is obeyed in the parameter domain explored, and that the natural eutectic wavelength is proportional to the tip radius of the two-phase dendrites. Finally, we find that it is very difficult/virtually impossible to form spiraling two-phase dendrites without anisotropy, an observation that seems to contradict the expectations of Akamatsu et al. Yet, it cannot be excluded that in isotropic systems, two-phase dendrites are rare events difficult to observe in simulations.