Thin films with antireflective/antibacterial properties

downloadHave you ever thought that touchscreens can host bacteria? Think about it and you will realise why this happens….However chinese researchers have created new silica thin films containing silver nanoparticles, which not only have antibacterial properties but are also antireflective.

These new materials are very promising for technological applications…Curious to know more? Read the full article here!

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Mineral carbonation – a relatively simple way to reduce CO2 emissions

Rodolfo Marin Rivera

1.pngIt is well known that emissions of carbon dioxide (CO2), originating mainly from burning oil and coal, contribute enormously to the so-called greenhouse effect. Due to its increase in the atmosphere during the last two and a half centuries, it has been estimated that by 2100, atmospheric CO2 concentrations could reach approximately 1150 ppm, resulting in a global temperature increase about 5.5 °C [1] … It doesn’t look so much, eh? However, such minor increase of temperature will have harmful effect on water and food availability, human health, ecosystem, coastlines and biodiversity. Therefore, if we are not able to perceive the danger of this situation, we will not be able to react to this threat on time… as the frog that is slowly cooked to death once the water is heated.

Today there is a worldwide concern about such drastic implications and, governments 2have made commitment to reduce their greenhouse gas emissions. The EU has committed to reduce its greenhouse gas emissions by 80-95% by 2050. Moreover, in countries like Sweden, Norway, Netherlands, Denmark, Finland, Italy, UK and Ireland have been implemented regulations in the form of CO2 taxes. However, despite of these efforts, it is estimated that the emissions of CO2 can only be reduced up to 30% by reducing the amount of carbon energy sources and the use of non-fossil energies. For instance, whatever is the way to have under control the greenhouse effect, it is essential to concentrate our efforts on the reduction of both the emissions and the atmospheric CO2 level.

If we consider the increase in demand for energy and the fact to reconcile the rising demand for fossil fuels, we have to start developing technologies that fall under the concept of Carbon Capture and Storage (CCS). With the development of such technologies, it will be possible to separate CO2 from gaseous waste streams, transport CO2 to storage locations and make its long-term isolation from the atmosphere. It is expected that the development of such technologies may contribute up to 55% of the cumulative global climate change mitigation effort [2].

A number of technologies exist for each phase of CCS, which consider the use of sorbents, membranes and/or chemical-looping for storing, while transporting can be made by using pipelines, rail and road tankers.

CO2 “sequestration” by mineral carbonation is a technology based on the process of natural rock weathering where carbonic acid, H2CO3, formed during the dissolution of CO2 in water, is neutralized with high pH minerals to form stable carbonates such as CaCO3 and MgCO3. The products remain as solids and there is no possibility of CO2 to be released after “sequestration”. The concept behind the mineral carbonation is shown in the diagram: CO2 from the industry or power plants is transported to a carbonation reactor, combined with some silicate compounds from a nearby mine and held at the appropriate reaction conditions until the desired degree of carbonation is reached. The products of the reaction, which might be slurry of carbonated minerals and residues in aqueous CO2, are separated. The CO2 is recycled, useful materials are collected and the carbonated materials and residue are returned to the mine site.

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The carbonation process can be done directly or indirectly. The main difference between them is the number of step needed in each case. Thus, while direct carbonation requires only one step, indirect carbonation requires two or more steps. However, despite that both two routes have demonstrated quite good results in laboratories, their application at industrial scale are still being evaluated in terms of cost and benefits [3].

Currently, several industries must deal not only with CO2 emissions, but also with solid waste products (e.g. metallurgical slags, incineration ashes, mining tailings, asbestos containing materials, bauxite residues and oil shale processing residues), which represent a significant environmental liability for the companies. In most of the cases, such residues must be deposited in special dumps, which must be isolated from the ground and/or be able to treat with an excess of water. After the limit capacity, the deposit must be neutralized and stored, which requires great investment and strict security and environmental policy. During the last decades, scientists have demonstrated with great success the use of mineral carbonation when it is applied to such residues. Nevertheless, despite of the great number of research already developed, still there exist an uncertainty regarding the application of such technology at industrial scale, as it is not possible to compare the results obtained with different waste materials due to differences between chemical, mineralogical and morphological properties. However, the method offers a permanent sequestration for CO2, and the solid products can be used in applications ranging from land reclamation to iron- and steelmaking.

REFERENCES:

[1] http://carboncycle.aos.wisc.edu/carbon-budget-tool/

[2] http://www.netl.doe.gov/research/coal/carbon-storage/carbon-storage-faqs/does-ccs-really-make-a-difference-for-the-environment-and-reduce-co2-in-the-atmosphere

[3] http://www.netl.doe.gov/research/coal/carbon-storage/carbon-storage-faqs/does-ccs-really-make-a-difference-for-the-environment-and-reduce-co2-in-the-atmosphere

 

What does make a radioactive element radioactive?

Rodolfo Marin Rivera

1The periodic table as we know contains 118 elements,

which are organised according to their atomic number, electron configuration, and chemical properties thanks to discovery done be Dmitri Mendeleev (1869). However, all of them may have some level of radioactivity.

As we know, atoms are made up of small, positively charged nucleus surrounded by a relatively large space (orbitals) occupied by tiny, fast-moving, negatively charged electrons, which are 10,000 to 100,000 times smaller than the atoms. Despite its relatively small size, the nucleus contains over 99.9% of the mass of the atom. A very close approximation about what is going on during the interaction between the electrons and nucleus was given by Bohr (1913) who depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus with attraction provided by electrostatic forces.

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The nucleus is made of positively charged protons and neutral neutrons. The number of protons is equal to the atom atomic number and determines, for instance, what element it is. For example, an atom with 8 protons in its nucleus is an oxygen atom, the eight-element listed in the periodic table. The number of neutrons will simple affect the mass of the atom and determine which isotope of oxygen is. Therefore, every chemical element has one or more isotopes that, for a given element, the number of protons and neutrons may change or not. Isotopes are better known as nuclide. Nuclide refers to any isotope of any element, or in other words, a nucleus with any number of protons and neutrons. Therefore, the radioactivity of a certain element is given by the transformation of a certain nuclide, or by the intensity at which the nuclide may decay. This means that a radioactive nuclide is one that spontaneously undergoes nuclear decay.

3During nuclear reactions (as the big bang), the interaction between a particle (like a neutron) or a photon with a nucleus leads to the formation of another nuclide. This transformation is known as nuclear decay. A nuclear decay stars with an unstable nuclide (parent isotope) that typically spits out a particle and/or a photon while turning itself into something more stable. Therefore, energy is released as part of all nuclear decay. There are three different kinds of decay: alpha (i.e. ejection of neutrons and protons at once, formation of the helium atom), beta (ejection of electrons) and gamma (no particles are emitted or absorbed, and both the numbers of protons and neutrons remains the same). In this last type of decay, at the beginning, neutrons and protons are arranged poorly, in terms of energy. That is to say one or more neutrons/protons occupy a higher energy state than they need to, and that the nucleus is said to be in an excited state. Rearrangement allows the neutrons/protons that are in unusually high-energy states to drop down into lower ones. The lowest energy configuration would be called the ground state. Rearrangement from a higher energy state to a lower one requires the release of energy, which can be done in the form of a high-energy photon, or gamma ray.

Nowadays, about 20 radioactive nuclides are recognised, which will take a very long time to decay. One of the most notable is 40K. Since all isotopes of an element have the same chemical behaviour, and because we humans need potassium in our bodies, we all have some 40K in our bodies. Anything that contains potassium (bananas, Gatorade®, your friends) is naturally radioactive, i.e. of natural radioactive origin (also known as Naturally-Occurring Radioactive Materials, NORM).

All but three of these 20 long-lived radioactive nuclides decay to stable nuclides. The three that don’t are 232Th, 235U and 238U. They all eventually decay to stable isotopes of lead, but along the way, they produce a number of other naturally occurring radioactive nuclides (e.g., 222Rn).

4You must know that from all the ionizing radiation that exist around us, not all of them is related to our activities as human being, because radionuclides exist everywhere in nature (in soil and rocks, air and water, in plants and in our bodies). Some of the isotopes have been there since the creation of Earth, others are being constantly produced or brought in from outer space as cosmogenic radiation.

Like this topic? You can  find more information in the following links:

 

 

Cell-sized robots that can change their shape

imagesResearchers at Cornell University built origami machines that can modify their shape in response to different stimuli and carry loads such as embedded electronics. These small robots are extremely small and are produced by graphene actuators that can fold 2D patterns into targeted 3D structures.

This research has no application for the moment, however it opens new paths to robotics for cells and biological systems.

Getting interested? Read more:

 

 

Andacollo: A place where the extraction of gold and faith meet

Rodolfo Marin Rivera

1Andacollo, a town on the fringes of Chile’s Atacama Desert, has a long pre-Hispanic history, and it is today known not only for its massive festival honouring the Virgin of the Rosary, but also for its gold mining history.

About 90% of the population is involved in mining activities. Many are generations of miners committed to extract hope from the deep earth day after day.

2The mining history of Andacollo is related to the invasion of the Incas that mainly happened before that the Spaniards were conquering Chile. 500 years ago, the Incas were the first to extract gold from the mountains close to the town. Nowadays, the mining activity is carried out by the so-called “pirquineros” (miners) that work independently in small and artisan operations using ancient techniques and tools that are not so different from the ones used by their ancestors. The minerals continue being extracted from the mountains not so far from the town, where the gold grade is very low and it is located in “veins” very deep in the earth, making the work difficult and extremely dangerous. The pirquineros appeal to their faith and devotion to the Virgin, and ask for protection and health to extract the precious metal from the bowels of the Earth.

3Nowadays, the scanty pirquineros that still remain in the town, still continue performing the process of grinding minerals in “maray” and “trapiches”. Gold is recovered by the amalgam formed with mercury during or after continuous milling.

Both milling devices are pre-hispanic techniques that have been adapted to recover gold. The “maray” are handcrafted systems used by the Incas to grind corn, wheat and barley, adapted by the Spaniards to grind minerals. It is driven by hand using a grinding cylindrical stone that rests on a cup, which in the past was made of stone and now concrete. It is still possible to see it in the courts of some houses.

4The “trapiches”, similarly to the “maray”, are a sophisticated mechanical system used to grind gold minerals, which are in use since the end of the XIX century. It is a kind of circular tray full of water, on which the miners turn two heavy wheels to grind the mineral. Coarser particles of gold are recovered at the back of the “trapiche” caught by the amalgam formed with mercury. Middle size particles of gold are collected at the edges of metallic sheets made of copper and mercury alloy. The finest gold particles are collected and re-washed by a flotation process.

Mercury is used extensively during the rustic gold mining, so that a mercury-gold amalgam is formed. The gold is produced by boiling away the mercury from the amalgam. Mercury is effective in extracting small gold particles, but the process is hazardous due to the toxicity of the vapours. Today, new technological processes based on nitric acid or aqua regia have been developed, but their application is only economically feasible at larger scales.

REFERENCES:

http://www.andacollochile.cl/portal/index.php/comuna/resena-historica

http://mine-engineer.com/mining/minproc/MercAmal.htm

 

3D-Printing human tissues using cellulose: will science fiction become reality?

Carmen Piras

imagesMost of you have probably heard about the Frankenstein’s monster, a novel written by the English author Mary Shelley. For those who don’t know it, it is the story of Victor Frankenstein, a scientist who invented a secret technique to impart life to unanimated matter. This technique allowed him to create a monstrous creature with human emotions and sensations.

This is of course only science fiction. However, nowadays, the on-demand growth of human tissues and organs using artificial instruments is becoming reality. One emerging manufacturing technique with promise in tissue engineering and regenerative medicine is 3D printing, which is based on the 3D deposition of material in specific shapes. This technology can be applied in biology (3D bioprinting) to produce 3D scaffolds of our tissues. The cells are directly embedded inside the scaffolds and different cell types can be distributed in different locations. The material loaded with the cells is then 3D printed into the desired shape. This method allows the fabrication of bone and cartilage tissues, skin and cardiac constructs and the regeneration of hepatic tissue.

One of the most important factors in 3D bioprinting is the choice of the material used as ink (or, more specifically, bioink), which should be biocompatible and allow cell survival during the printing process. Beside this, the ink should have an optimal viscosity to allow printing and to avoid the 3D printed shape to collapse. Water based gels (also called hydrogels) are ideal inks for 3D bioprinting. These materials are mainly composed of water (> 99 %) and therefore can closely mimic the natural environment of cells.

Hydrogels can be obtained from a wide range of molecules including natural derivatives such as gelatine, alginate, collagen, hyaluronic acid and cellulose. Being an abundant, renewable, low-cost resource, cellulose represents an ideal candidate for the production of hydrogels for 3D bioprinting. This molecule is formed of long glucose chains and it is obtained by extraction from plants or can be produced by bacteria. Mechanical and chemical treatments of raw materials allow the extraction of cellulose in the form of nanofibers or nanocrystals. The suffix nano- refers to the fact that the extracts have one dimension (length or width) in the nanometre range (1.000.000 smaller than 1 mm).

UnknownA variety of bioinks based on cellulose nanofibers and nanocrystals has been created by a number of research groups. These could be applied for the regeneration of human tissues (such as cartilage) or to obtain 3D printed drug delivery systems and wound dressings. Although very promising, this research field is still new and growing. We hope that in the future cellulose will be further exploited to develop new bioinks. Will this be the route towards a new Frankenstein’s monster? Stay tuned!

Want to know more about this? Read this article: http://pubs.rsc.org/en/content/articlepdf/2017/bm/c7bm00510e

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