Tuesday, May 26, 2015

Sleeping Beauty, the forgotten publications

In science, sleeping beauty refers to several papers whose importance isn't recognized in the moment when they are published, however, after several years have an impact in the science world.
According to new analysis of 22 million studies that had been published over more than a century,  it was found that the "sleeping beauty" phenomenon is very common.
"We followed the history of these papers from the moment they were published to the moment they received maximum citations in other papers," said Alessandro Flammini, one of the study's authors and professor of informatics and computing at Indiana University .
Maybe the most famous example of the sleeping beauty is a paper published in 1935 by Albert Einstein, Boris Podolsky and Nathan Rosen, wich rested unloved for decades, until it started being citated by other researchers in 1994.
Albert Einstein wrote a paper in 1935 that wasn't widely cited until 1994.
Radicchi and his colleagues established  the term "beauty coefficient", a value based on the number of citations and how long after the publication acquired them.
The most known "sleeping beauty" are listed in the following table.
Top 15 sleeping beauty.
Therefore,if you have published something and it haven't been cited, you still can hope about it being cited in the future. However, Radicchi warns about not to hold out too much hope that all publications with not citations are sleeping beauties."I expect, if you look at a paper that is 10 years old (and not cited) my guess is it will continue to have zero citations forever" said Radicchi.

Saturday, May 2, 2015

The zombies exist!

A new research publicated the last week in Scientific Reports in Nature showed that when bacteria are exposed to a solution of silver, can absorbe the silver particles and die, after this dead-bacteria can kill a viable culture of the same bacterium. 

The silver was used since 1893 as antimicrobial for Karl Wilhelm Von Nageli showed the silver's properties as the capacity for permeability of the membrane and once inside the cell, altering its enzymatic system, inhibiting its metabolism and energy production and modifying its genetic material, losing the ability to grow and replication, for this has been employed in the elimination of pathogenic microorganisms. 
But the zombie effect has been recognized to now. This mechanism was show with Pseudomonas aeruginosa (viable bacterial population of ca. 108 CFU/ml) wich was killed when was added nitrate silver solution to different concentrations (1, 2, 5, 15 and 20 ppm) then, this tubes were centrifugated and filtrated and the supernatat was mixed with viable culture of the same bacteria (108 CFU/ml) for 6 hours, then were counted the viable cells. 

P. aureginosa before to treatment with silver (Wakshlak et al., 2015).
P. aeruginosa after to treatment with silver; the white granules represent silver deposition which account for the ‘‘zombies’’ biocidal action (Wakshlak et al., 2015). 

The results showed that at all concentrations the dead-bacterias act as biocidal agents, they achieved to kill the 99.999% of viable cells and this elimination increased with the silver concentration. 
This is due to the dead-bacteria serve as reservoir of silver and the metallic cations are released which are lethal for the live bacteria, the explanation of this phenomenon is given by the principle of Le-Chatelier wich says that if in a equilibrium system is modificated some factor (pressure, temperature, concentration, ..) the system evolves in the direction that tends to oppose this modification. It is said that the equilibrium is shifted to the right (if increases products concentration and decreases the reactive to the initial equilibrium), or left (if increases the reactants concentration and the product concentration decrease).

In this experiment the principle was demonstrated when the silver cations were transferred to dead-bacteria and the viable bacteria because they acted as new unoccupied adsorption sites for silver, and the equilibrium of silver between the reservoir and the liquid, is shifted. 

This investigation proposed a new biocidal agent for microbial infection when the silver concentration adequate is added. Although exist diverse factors involved that can be reviewed in future researches.