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Background: Institutional tuberculosis (TB) transmission is an important public health problem highlighted by the HIV/AIDS pandemic and the emergence of multidrug- and extensively drug-resistant TB. Effective TB infection control measures are urgently needed. We evaluated the efficacy of upper-room ultraviolet (UV) lights and negative air ionization for preventing airborne TB transmission using a guinea pig air-sampling model to measure the TB infectiousness of ward air. Methods and Findings: For 535 consecutive days, exhaust air from an HIV-TB ward in Lima, Perú, was passed through three guinea pig air-sampling enclosures each housing approximately 150 guinea pigs, using a 2-d cycle. On UV-off days, ward air passed in parallel through a control animal enclosure and a similar enclosure containing negative ionizers. On UV-on days, UV lights and mixing fans were turned on in the ward, and a third animal enclosure alone received ward air. TB infection in guinea pigs was defined by monthly tuberculin skin tests. All guinea pigs underwent autopsy to test for TB disease, defined by characteristic autopsy changes or by the culture of Mycobacterium tuberculosis from organs. 35% (106/304) of guinea pigs in the control group developed TB infection, and this was reduced to 14% (43/303) by ionizers, and to 9.5% (29/307) by UV lights (both p < 0.0001 compared with the control group). TB disease was confirmed in 8.6% (26/304) of control group animals, and this was reduced to 4.3% (13/303) by ionizers, and to 3.6% (11/307) by UV lights (both p < 0.03 compared with the control group). Time-to-event analysis demonstrated that TB infection was prevented by ionizers (log-rank 27; p < 0.0001) and by UV lights (log-rank 46; p < 0.0001). Time-to-event analysis also demonstrated that TB disease was prevented by ionizers (log-rank 3.7; p = 0.055) and by UV lights (log-rank 5.4; p = 0.02). An alternative analysis using an airborne infection model demonstrated that ionizers prevented 60% of TB infection and 51% of TB disease, and that UV lights prevented 70% of TB infection and 54% of TB disease. In all analysis strategies, UV lights tended to be more protective than ionizers. Conclusions: Upper-room UV lights and negative air ionization each prevented most airborne TB transmission detectable by guinea pig air sampling. Provided there is adequate mixing of room air, upper-room UV light is an effective, low-cost intervention for use in TB infection control in high-risk clinical settings.

Absolute measurement of radiant power in the X-ray region is essential for many applications in astrophysics, spectroscopy, and X-ray diagnostics. Comparison between different measuring methods is an effective way to check their reliability. In the present work, a comparison of X-ray radiant power absolute measurement between a free-air ionization chamber and a cryogenic electrical substitution radiometer was performed at Beijing Synchrotron Radiation Facility. The absolute radiant power obtained by these two methods were mutually compared via a transfer standard detector’s spectral responsivity at a photon energy of 10 keV. The result of the comparison showed that the difference was 0.47%. A conclusion was reached that the free-air ionization chamber and the cryogenic electrical substitution radiometer agreed within the combined relative uncertainty of 3.35%.

A comprehensive literature review was conducted to summarize and analyze the mechanisms and applications of air ionization for aerosol removal and inactivation of airborne microorganisms in confined spaces. This review focuses on engineered ionization systems (ionizers) that generate negative ions through corona discharge. Numerous studies have proven that air ionization is effective in removing aerosols and inactivating airborne microorganisms in confined spaces. Multiple physical, chemical, and biological processes may be involved in air ionization, including corona discharge and ion generation, attachment of ions to aerosol particles, transport of ions and aerosols in the air, electrostatic drift, deposition of aerosol particles on surfaces, and inactivation of biological agents if air ionization is used to prevent the spread of airborne pathogens. Each of these processes, as well as their interactions, is extremely complex, and only a limited number of studies have explored the interplays of these processes or attempted to integrate them into models that quantify the fundamental behavior of air ionization.

Air quality on swine farms has long been a concern for both human and swine health as it has been previously linked with respiratory issues; the main cause being the inhalation of small airborne particulate matter (PM) < 10 μm in diameter. Negative ionizing systems have previously been successfully used to improve air quality in human residential- and commercial buildings as well in agricultural settings. However, less is known about the efficacy of negative ionizing systems in commercial swine farrowing environments. Thus, the objective of this study was to use a swine farrowing environment to evaluate the effects of a negative air ionization system on 1) the quantity of airborne gaseous and particulate matter, and 2) swine health and production parameters. Six farrowing rooms containing 60 sows each were installed with 30 negative ionization systems per room. Three out of six rooms were randomly allocated between active ionization (L-ON) or inactive ionization (L-OFF) between farrowing rounds (N =  4). For each round, measurements of PM 2.5 , PM 10 , Ammonia (NH 3 ), hydrogen sulfide gas (H 2 S), temperature, and humidity were collected twice a week, in the morning and afternoon at two heights, pig level (61 cm) and human level (152 cm). Pig performance metrics (parity, number of piglets born, number of live piglets born, piglet mortality, fostered piglets, and number of weaned pigs) were collected at the end of each batch. Comparisons between L-ON and L-OFF treatments were conducted by averaging room and day specific measurements for all days when rotating rooms shared contrasting treatments. Each room-specific L-ON treatment was then compared to all other L-OFF rooms using a linear regression model. No statistically significant differences were found between treatments for PM 2.5 or PM 10 at the pig nor human level. However, numerical reductions in the cumulative increase of PM 2.5 , and PM 10 for L-ON rooms compared to L-OFF rooms were found in 60% of the L-ON rooms. One out of five L-ON rooms showed statistically slower buildup of NH 3 concentrations compared to L-OFF rooms ( P <  0.01) and 60% of the L-ON rooms had significantly slower buildup of H 2 S concentrations compared to L-OFF rooms ( P < 0.01). No effect on production metrics were found between treatments. In conclusion, indications of improved air quality were found in this study, but given the complexity of these types of assessments, further work is needed to conclude the efficacy of negative ionization systems in commercial farrowing systems.

For the practical use of femtosecond laser ablation, inputs of higher laser intensity are preferred to attain high-throughput material removal. However, the use of higher laser intensities for increasing ablation rates can have detrimental effects on ablation quality due to excess heat generation and air ionization. This paper employs ablation using BiBurst femtosecond laser pulses, which consist of multiple bursts (2 and 5 bursts) at a repetition rate of 64 MHz, each containing multiple intra-pulses (2–20 pulses) at an ultrafast repetition rate of 4.88 GHz, to overcome these conflicting conditions. Ablation of silicon substrates using the BiBurst mode with 5 burst pulses and 20 intra-pulses successfully prevents air breakdown at packet energies higher than the pulse energy inducing the air ionization by the conventional femtosecond laser pulse irradiation (single-pulse mode). As a result, ablation speed can be enhanced by a factor of 23 without deteriorating the ablation quality compared to that by the single-pulse mode ablation under the conditions where the air ionization is avoided. BiBurst femtosecond laser, which emits pulses combining GHz bursts in MHz bursts, can attain higher ablation speed in silicon ablation as compared with the conventional irradiation scheme (single-pulse mode). Temporal control of energy deposition by the BiBurst mode avoids air ionization and excess heat generation to perform high quality ablation. BiBurst mode can enhance ablation speed by a factor of 23 without deteriorating the ablation quality compared to the single-pulse mode ablation.

Ensuring the effective removal of airborne particles is essential for maintaining indoor air quality, particularly in environments with limited ventilation. This study examines how ion polarity regime, voltage, and relative humidity influence aerosol particle removal in a controlled, room-sized chamber (35.8 m3) using a custom-built air ionizer. Experiments were conducted under stagnant and ventilated conditions (0.5 h−1) while varying ionizer polarity (positive, negative, bipolar, alternating), voltage (6 kV, 10 kV), humidity (40%, 70%), and aerosol type (incense smoke, nebulized KCl). Positive and negative unipolar ionization achieved over 90% removal within 60 min, with decay rates of 0.04–0.05 min−1, half-lives of 13–17 min, and clean air delivery rates (CADR) of 60–90 m3 h−1. Bipolar ionization was less efficient due to ion-ion recombination, yielding CADR values below 25 m3 h−1, while alternating polarity improved deposition (40–70 m3 h−1) by reducing recombination losses. Relative humidity had a minimal influence on unipolar performance but moderated efficiency in bipolar and alternating modes. Under low ventilation, unipolar negative ionization sustained high removal (96.7%), while ozone remained below the detection limits of the methods used. These findings indicate that ion polarity control and field strength strongly influence particle removal and that unipolar or alternating-polarity operation can provide effective particle removal under controlled chamber conditions, including a low-ventilation case of 0.5 h−1.

A comprehensive literature review was conducted to summarize and analyze the mechanisms and applications of air ionization for aerosol removal and inactivation of airborne microorganisms in confined spaces. This review focuses on engineered ionization systems (ionizers) that generate negative ions through corona discharge. Numerous studies have proven that air ionization is effective in removing aerosols and inactivating airborne microorganisms in confined spaces. Multiple physical, chemical, and biological processes may be involved in air ionization, including corona discharge and ion generation, attachment of ions to aerosol particles, transport of ions and aerosols in the air, electrostatic drift, deposition of aerosol particles on surfaces, and inactivation of biological agents if air ionization is used to prevent the spread of airborne pathogens. Each of these processes, as well as their interactions, is extremely complex, and only a limited number of studies have explored the interplays of these processes or attempted to integrate them into models that quantify the fundamental behavior of air ionization.

The paper presents the author’s vision of the problem of earthquake hazards from the physical point of view. The first part is concerned with the processes of precursor’s generation. These processes are a part of the complex system of the lithosphere–atmosphere–ionosphere–magnetosphere coupling, which is characteristic of many other natural phenomena, where air ionization, atmospheric thermodynamic instability, and the Global Electric Circuit are involved in the processes of the geosphere’s interaction. The second part of the paper is concentrated on the reliable precursor’s identification. The specific features helping to identify precursors are separated into two groups: the absolute signatures such as the precursor’s locality or equatorial anomaly crests generation in conditions of absence of natural east-directed electric field and the conditional signatures due to the physical uniqueness mechanism of their generation, or necessity of the presence of additional precursors as multiple consequences of air ionization demonstrating the precursor’s synergy. The last part of the paper is devoted to the possible practical applications of the described precursors for purposes of the short-term earthquake forecast. A change in the paradigm of the earthquake forecast is proposed. The problem should be placed into the same category as weather forecasting or space weather forecasting.

Recent years have seen increased attention given to radon from two scientific directions. After neglecting radon as an earthquake precursor in the 1990s, it has become the subject of discussions in earthquake-forecast papers due to growing networks of radon monitoring in different countries, particularly the technologies of real-time radon measurements where gamma spectrometers are of great interest as sources of 222Rn identification. The second fast-developing direction involves radon in Lithosphere–Atmosphere–Ionosphere Coupling (LAIC) models as a source of boundary layer ionization. Here we address the second topic, which is not connected with the earthquake forecast problems, namely, the role of air ionization by radon as a source of the Global Electric Circuit (GEC) modification. In this publication, we try to unite all of these problems to present a more complex view of radon as an important element in our environment. Special attention is paid to the dependence of radon variability on environmental conditions.

On 22 January 2024, at 18 UT, a strong earthquake (EQ), Mw = 7, occurred with the epicenter at 41°N, 79°E. This seismic event generated a complex response, the elements of which correspond to the concept of lithosphere–atmosphere–ionosphere coupling through electromagnetic processes. While flying over the EQ area on the night-ide of the Earth, the tandem of low-orbiting Swarm satellites observed small-scale irregularities in the plasma density with an amplitude of ~1.5 × 104 el/cm3, which are likely associated with the penetration of the coseismic electric field into the ionosphere. The local anomaly was detected against the background of a global increase in total electron content, TEC (although geomagnetic indices remained quiet), since the moment of EQ coincided with the ionospheric response to a solar flare. In the troposphere, specific humidity decreased while latent heat flux and aerosol optical depth increased, all exhibiting the co-located disturbances that can be attributed to the effect of increased air ionization rates, resulting in greater electrical conductivity in the near-Earth boundary layer. Anomalies started developing over the epicenter the day before and maximized on the day of the main shock and aftershocks.