Sep 28, · The systematic review of studies on NAIs initiated by literature searches. Three databases were selected including PubMed database One of the examples is the negative ion generator using an ultraviolet source to irradiate electrically conductive material, which was patented as early as (Patent No. US A) Nov 04, · Authors of a systematic review ask a specific clinical question, perform a comprehensive literature search, eliminate the poorly done studies and attempt to make practice recommendations based on the well-done studies. A meta-analysis is a systematic review that combines all the results of all the studies into a single statistical analysis of How to write an essay about article, type my best expository essay on hillary clinton: pursuit happyness review essay. Proposal for a thesis format. Top annotated bibliography writer website for school cover letter salon examples generator introduction Essay sample resume for control system engineer
Negative Air Ions and Their Effects on Human Health and Air Quality Improvement
Try out PMC Labs and tell us what you think, literature review generator. Learn More, literature review generator. Negative air ions NAIs have been discovered for more than years and are widely used for air cleaning. The presence of NAIs is credited literature review generator increasing psychological health, productivity, and overall well-being but without consistent or reliable evidence in therapeutic effects and with controversy in anti-microorganisms.
Reports also showed that NAIs could help people in relieving symptoms of allergies to dust, mold spores, and other allergens. Particulate matter PM is a literature review generator air pollutant that affects human health. Experimental data showed that NAIs could be used to high-efficiently remove PM. Finally, we have reviewed the plant-based NAI release system under the pulsed electric field PEF stimulation.
This is a new NAI generation system which releases a huge amount of NAIs under the PEF treatment. The system may be used to freshen indoor air and reduce PM concentration in addition to enriching oxygen content and indoor decoration at home, school, hospital, airport, and other indoor areas.
Negative air ions Literature review generator have been discovered for more than years [ 1 ]. Now, NAI generators are widely available for home or industrial uses. In the meantime, various new technologies were developed and used to further improve NAI generation and reduce the release of its byproduct ozone.
Here, we have carried out a comprehensive reviewing on NAIs. On the other hand, strong evidence had shown the roles of NAIs in high-efficiently reducing particulate matter PM concentration.
Thus, more work should be done to further improve NAI release by new methods or devices so that NAIs could be more widely used for air cleaning. Here, literature review generator, we review the generation of NAIs and their effects on humans, animals, and microorganisms.
We then discussed the involvement of superoxide ions in biological effects of NAIs. Subsequently, we focused on plant-based Literature review generator generation systems as these are relatively new NAI generation systems with some advantages on traditional corona discharge NAI generators.
We also reviewed the air cleaning ability of NAIs, especially in removing PM with diameters less than 10 micrometers PM The systematic review of studies on NAIs initiated by literature searches. The coverage period of the database search is around years from to the updated search date is 10 September The database searches harvested a total ofliterature review generator,and articles that contain all of the three keywords in either titles or abstracts when the PubMed database, ScienceDirect, and IEEE Xplore databases were employed, literature review generator, respectively.
Only peer-reviewed and English-language articles were considered. We then screened these articles by manually reviewing titles, which led to, and studies selected duplicated references were excluded ; the remaining were excluded due to no relationship to the NAI topic. We further carried out abstract screening to exclude more unrelated articles.
Based on the abstract reviewing, 93,and 57 references were selected, which were subjected to full-length reviewing. During full-length article reviewing, some cited references, which were not included in the full-length review list, were also selected for additional reviewing. Air ions are electrically charged molecules or atoms in the atmosphere [ 2 ].
An air literature review generator is formed when a gaseous molecule or atom receives sufficiently high energy to eject an electron [ 3 ]. NAIs are those that gain an electron, while positive air ions lose an electron, literature review generator. The natural and artificial energy sources include 1 radiant or cosmic rays in the atmosphere; 2 sunlight including ultraviolet; 3 natural and artificial corona discharge including thunder and lightning; 4 the shearing forces of water Lenard effect ; 5 plant-based sources of energy.
The radioactive elements such as uranium, radium, actinium, and thorium widely exist in our planet. They are also the principal energy sources that generate NAIs over the oceans [ 5 ].
The concentration of NAIs produced by these rays might reach from ions per cm 3 in land surface [ 6 ] to more than ions per cm 3 at 15 km away from the land surface [ 7 ]. The photoelectric effect is the emission of electrons when a certain wavelength of light is shone onto a metallic surface. NAIs are generated by accepting these emitted electrons. The photoelectric effect may contribute less to the NAI generation as only some wavelength of lights shows the ability to emit electrons by lighting, literature review generator.
One of the examples is the negative ion generator using an ultraviolet source to irradiate electrically conductive material, which was patented as early as Patent No. US A. In this patent, an ultraviolet lamp was used to irradiate metal materials, literature review generator, which photo-electrically eject electrons, literature review generator. The electrons then collide with air molecules and generate NAIs.
On the other hand, NAIs can be generated by a certain wavelength of lights through directly ionizing air molecules. For example, ultraviolet UV can be used to directly ionize air molecules to literature review generator NAIs [ 58 ]. Actually, UV-mediated ionization is the dominant NAI sources in the above 60 km altitude of atmosphere [ 5 ].
These highly concentrated NAIs from UV in the upper layers of the atmosphere are diffused to the ground surface at low speeds.
Ionization by UV radiation is not a major contributor of NAIs in the lower atmosphere due to the low dose of UV rays available in this layer [ literature review generator ]. Although reports showed that the UV rays significantly mediated the air ionization, literature review generator, little systematical study was carried out on the effect of artificial UV light on NAI generation.
We carried out an experiment to investigate the contribution of UV light to the generation of NAIs Figure 1 ; Literature review generator S1. The experiment was carried out in a growth chamber with 80 cm length × 80 cm width × 80 cm height and detailed description was provided in the Supplementary Experiment. NAIs were measured under UV light conditions with the normal light condition as a control. The data from three replicates of experiments showed that UV lights indeed promoted the NAI generation.
Further observation showed that there were peaks of NAI generation within 8 min after UV lighting Figure 1 B—D; Table S1. After the peaks, NAI concentration was kept at a relatively literature review generator value but was still higher than the control. The analysis further confirmed the promoting effect of UV lighting on NAI generation. Thus, our experiment showed that UV lighting could be used to generate NAIs.
However, only low concentrations of NAIs were generated under our UV light conditions. NAI generation by UV lighting. The literature review generator was carried out in a growth chamber with dimensions of 80 cm length, 80 cm width and 80 cm height. A 30 watts of UV light UV-C, — nm was provided by Safer Electric Ltd. NAI concentration was measured by the DLY-4G air ion counter Kilter Electronic Institute Co.
A The average NAI concentrations of control CK, no UV light and UV lighting, literature review generator. B — D Graphs to show the curves of NAI concentrations among three different replicates.
NAI: negative air ions. The atmosphere surrounding the earth is subjected to a natural electric field and its intensity is continuously fluctuating under both local and global influences [ 9 ]. The local influences include geographical location and weather conditions such as thunderstorms, rain, fog, mist, and so on; the global facts refer to classical daily electric field variations [ 4 ].
When leaf points or branches of trees have a high potential difference from their surroundings in their electric fields, corona discharge also called point discharge occurs and NAIs may be released [ 510 ]. Generally, corona discharge occurs at the atmosphere conditions under high average electric fields [ 5 ]. For example, in a mountain area, high electric fields and low atmospheric pressure promote the onset of corona discharge [ 11 ].
Thunderstorms and lightning will generate very high electric field conditions and corona discharge subsequently occurs. Therefore, NAIs will be released at a huge amount after thunderstorms and lightning. However, literature review generator, released NAIs will be gradually decayed with the discontinuous thunderstorms.
In addition to thunderstorms and lightning, mist may also contribute to NAI generation. In a forest, electric field variations were observed during the mist formation and dissipation, which may trigger corona discharge and NAI generation [ 9 ]. Artificial corona discharge is an efficient way to generate NAIs. Intensity of corona discharge depends on the shape and size of the conductors as well as applied voltage.
Irregular conductor, especially with a sharp point, gives rise to more corona than a smooth conductor and large-diameter conductors produce lower corona than small-diameter conductors; the higher the voltage applied, more NAIs are generated [ 1415 ]. The closer the distance literature review generator corona point, the higher NAI concentration is detected as continuous generation of NAIs by corona discharge is related to a chain reaction process called an electron avalanche [ 16 ], literature review generator.
The application of artificial electric field and corona discharge on plants was carried out as early as the s [ 1718 ]. Bachman and Hademenos showed that under high voltage, artificially applied electrical fields near the pointed barley leaf tips were intensified [ 19 ] and as a result, corona discharge occurred and air ions and ozone were generated. Studies mainly focused on biological effects such as growth response, literature review generator, evaporation, and plant damage as well as the effects of generated ozone and NAIs literature review generator plant growth [ 111819202122 ].
The considerable numbers of NAIs are found under waterfalls or in the seashores. These NAIs are generated by Lenard effect. Lenard effect was also called spray electrification or waterfall effect and was first systematically studied by Philipp Lenard [ 23 ], who won the Nobel Prize for Physics in for his research on cathode rays and the discovery of many of their properties.
Literature review generator study showed that NAIs were generated from the surrounding air molecules by charging themselves negatively when water droplets collide with each other or with a wetted solid to form fine spray of drops. The study also showed that several factors may affect the degree of charge separation in spray processes and, therefore, literature review generator affect the generation and concentration of NAIs.
These factors literature review generator water drop temperature, dissolved impurities, speed of the impinging air blast, and foreign impinging surfaces of droplets.
Plants were reported to have the ability to generate NAIs under normal growth conditions and have been regarded as natural resources for NAI generation [ 2627 ]. Different plants released different amounts of NAIs under natural growth conditions Table 1. Bachman and Hademenos reported the NAI generation by applying high-voltage electric field to plants [ 19 ].
Later, Tikhonov et al, literature review generator. Since then, several other studies were carried out to investigate the effect of PEF stimulation on plant NAI generation Table 2. However, after PEF stimulation, more than 3. Several parameters may affect the NAI release under PEF stimulation including plant species and output voltages in PEF stimulation Table 2 as well as light intensity, temperature, pulse interval, and the pulse width of PEF [ 282930 ], literature review generator.
Studies of plant morphology on NAI release showed that species with blade shapes literature review generator higher concentration of NAIs [ 27 ]. All these studies may provide an alternative to artificially generate NAIs through a plant-based method.
NAIs released by different plants under natural growth conditions without pulse electric field PEF stimulation, literature review generator. Average values for all used plant species under 60 min of experiment.
kv: kilovoltage.
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