Moisture content monitoring in industrial-scale composting systems using low-cost sensor-based machine learning techniques

Moisture is a key aspect for proper composting, allowing greater efficiency and lower environmental impact. Low-cost real-time moisture determination methods are still a challenge in industrial composting processes. The aim of this study was to design a model of hardware and software that would allow self-adjustment of a low-cost capacitive moisture sensor. Samples of organic composts with distinct waste composition and from different composting stages were used. Machine learning techniques were applied for self-adjustment of the sensor. To validate the model, results obtained in a laboratory by the gravimetric method were used. The proposed model proved to be efficient and reliable in measuring moisture in compost, reaching a correlation coefficient of 0.9939 between the moisture content verified by gravimetric analysis and the prediction obtained by the Sensor Node.

5-year incidence of suicide-risk in youth: A gradient tree boosting and SHAP study

BACKGROUND

Machine learning methods for suicidal behavior so far have failed to be implemented as a prediction tool. In order to use the capabilities of machine learning to model complex phenomenon, we assessed the predictors of suicide risk using state-of-the-art model explanation methods.

METHODS

Prospective cohort study including a community sample of 1,560 young adults aged between 18 and 24. The first wave took place between 2007 and 2009, and the second wave took place between 2012 and 2014. Sociodemographic and clinical characteristics were assessed at baseline. Incidence of suicide risk at five-years of follow-up was the main outcome. The outcome was assessed using the Mini Neuropsychiatric Interview (MINI) at both waves.

RESULTS

The risk factors for the incidence of suicide risk at follow-up were: female sex, lower socioeconomic status, older age, not studying, presence of common mental disorder symptoms, and poor quality of life. The interaction between overall health and socioeconomic status in relation to suicide risk was also captured and shows a shift from protection to risk by socioeconomic status as overall health increases.

LIMITATIONS

Proximal factors associated with the incidence of suicide risk were not assessed.

CONCLUSIONS

Our findings indicate that factors related to poor quality of life, not studying, and common mental disorder symptoms of young adults are already in place prior to suicide risk. Most factors present critical non-linear patterns that were identified. These findings are clinically relevant because they can help clinicians to early detect suicide risk.

Evaluation of the microbiological quality of reclaimed water produced from a lagooning system

The use of lagooning as a complementary natural method of treating secondary effluents of wastewater treatment plants has been employed as an affordable and easy means of producing reclaimed water. However, using reclaimed water for some purposes, for example, for food irrigation, presents some risks if the effluents contain microbial pathogens. Classical bacterial indicators that are used to assess faecal contamination in water do not always properly indicate the presence of bacterial or viral pathogens. In the current study, the presence of faecal indicator bacteria (FIB), heterotrophic bacterial counts (HBC), pathogens and opportunistic pathogens, such as Legionella spp., Aeromonas spp., Arcobacter spp., free-living amoeba (FLA), several viral indicators (human adenovirus and polyomavirus JC) and viral pathogens (noroviruses and hepatitis E virus) were analysed for 1 year in inlet and outlet water to assess the removal efficiency of a lagooning system. We observed 2.58 (1.17-4.59) and 1.65 (0.15-3.14) log reductions in Escherichia coli (EC) and intestinal enterococci (IE), respectively, between the inlet and outlet samples. Genomic copies of the viruses were log reduced by 1.18 (0.24-2.93), 0.64 (0.12-1.97), 0.45 (0.04-2.54) and 0.72 (0.22-2.50) for human adenovirus (HAdV), JC polyomavirus (JCPyV) and human noroviruses (NoV GI and GII), respectively. No regrowth of opportunistic pathogens was observed within the system. FLA, detected in all samples, did not show a clear trend. The reduction of faecal pathogens was irregular with 6 out of 12 samples and 4 out of 12 samples exceeding the EC and IE values, specified in the Spanish legislation for reclaimed water (RD 1620/2007). This data evidences that there is a need for more studies to evaluate the removal mechanisms of lagooning systems in order to optimize pathogen reduction. Moreover, surveillance of water used to irrigate raw edible vegetables should be conducted to ensure the fulfilment of the microbial requirements for the production of safe reclaimed water.

Effect of thermal treatment on free-living amoeba inactivation

AIMS

To evaluate the effect of temperature on two amoeba strains of the genera Acanthamoeba and two amoeba strains of the genera Hartmannella separately treated depending on their life stage, trophozoite or cyst, when cells are directly exposed under controlled conditions.

METHODS AND RESULTS

For thermal treatments, three temperatures were selected 50, 60 and 70°C, and a microcosm was designed using dialysis bags. The inactivation of each strain was determined using a method based on the most probable number quantification on agar plates. The results showed that for all amoeba strains, thermal treatment was more effective against trophozoites compared with cyst stages. The inactivation patterns showed statistical differences between the two genera analysed at temperatures above 50°C. The effectiveness of the thermal treatments at 60 and 70°C was higher for both life stages of Hartmannella vermiformis strains compared with Acanthamoeba strains, being the most resistant Acanthamoeba cysts.

CONCLUSIONS

Free-living amoebae have been isolated in a wide range of environments worldwide due to their capacity to survive under harsh conditions. This capacity is mainly based on the formation of resistant forms, such as double-walled cysts, which confers a high level of resistance as shown here for thermal treatments.

SIGNIFICANCE AND IMPACT OF STUDY

Free-living amoebae survival can promote a rapid recolonization of drinking water systems and is a likely source of emerging opportunistic pathogens such as Legionella. Because of that a better understanding of the factors that affect micro-organism inactivation in water systems would allow more efficient application of disinfection treatments.

Tuberculosis control in conflict-affected East Timor, 1996-2004

SETTING

East Timor has undergone major political changes in the past 10 years. Tuberculosis (TB) control has flourished, despite chronic low tension conflict, a brief but intense period of high-level conflict and post-conflict reconstruction.

OBJECTIVE

To assess TB control in East Timor from 1996 to 2004.

DESIGN

Data were collected from a variety of sources. Key TB programme indicators were analysed with reference to WHO targets to assess the performance of the three TB control programmes that operated during the study period.

RESULTS

Before 1999, a non-governmental TB control programme was established in several districts in parallel with the government TB programme, and showed optimistic results. External donor funds, technical assistance and local control strategies were key components. In 1999, conflict led to complete disruption of both programmes. In 2000, a National Tuberculosis Control Programme (NTP) was established from the non-governmental programme in collaboration with other partners. The smear-positive TB case notification rate of 108 per 100000 population is the highest in the region and reflects high population coverage. The cure rate of 81% is close to reaching the WHO target.

CONCLUSION

High-quality TB control has been introduced in conflict-affected East Timor. Further research is needed to examine Timorese approaches to inform other, similar settings.

Microleakage and nanoleakage: influence of laser in cavity preparation and dentin pretreatment

OBJECTIVE

The purpose of this study was to verify if the application of the Nd:YAG laser following pretreatment of dentin with adhesive systems that were not light cured in class V cavities and were prepared with Er:YAG laser would promote better sealing of the gingival margins when compared to cavities prepared the conventional way.

BACKGROUND DATA

Previous studies had shown that the pretreatment of dentin with laser irradiation after the application of an adhesive system is efficient in achieving higher shear bond and tensile bond strength.

MATERIALS AND METHODS

Er:YAG laser (Kavo-Key, Germany) with 350 mJ, 4 Hz, and 116.7 J/cm2 was used for cavity preparation. The conventional preparation was made with diamond bur mounted in high-speed turbine. Dentin treatment was accomplished using an Nd:YAG laser (Pulse Master 1000, ADT. USA) at 60 mJ, 10 Hz, and 74.65/cm2 following application of the adhesive system. The cavities were stored with Single Bond/Z100 and Prime & Bond NT/TPH. Eighty bovine incisors were used, and class V preparations were done at buccal and lingual surfaces divided into eight groups: (1) Er:YAG preparation + Prime & Bond NT + TPH; (2) Er:YAG preparation + Single Bond + Z100; (3) Er:YAG preparation + Single Bond + Nd:YAG + Z100; (4) Er:YAG preparation + Prime & Bond NT + Nd:YAG + TPH; (5) conventional preparation + Prime & Bond NT + TPH; (6) conventional preparation + Single Bond + Z100; (7) conventional preparation + Single Bond + Nd:YAG + Z100; (8) conventional preparation + Prime & Bond NT + Nd:YAG + TPH. All specimens were thermocycled for 300 full cycles between 5 degrees C+/-2 degrees C and 55 degrees C+/-2 degrees C (dwell time of 30 sec), and stored in 50% silver nitrate solution for 24 h soaked in photodeveloping solution and exposed to fluorescent light for 6 h. After this procedure, the specimens were sectioned longitudinally in 3 portions and the extension of microleakage at the gingival wall was determined following a criteria ranging from 0 to 4 using scanning electron microscopy (SEM). The medium portion sectioned of each specimen was polished and prepared for nanoleakage avaliation by SEM.

RESULTS

Kruskall-Wallis and Miller statistical tests determined that group 3 presented less microleakage and nanoleakage.

CONCLUSION

Application of the Nd:YAG laser following pretreatment of dentin with adhesive Single Bond non-photocured Single Bond adhesive in cavities prepared with Er:YAG promote better sealing of the gingival margins.

Phages of enteric bacteria in fresh water with different levels of faecal pollution

Levels of somatic and F-specific coliphages, and phages infecting Bacteroides fragilis were measured in 257 samples collected in different freshwater environments with different levels and characteristics of faecal pollution. In samples with recent pollution of domestic origin, the numbers of the three groups of phages were highly correlated, thus showing that their excretion is fairly constant. In this set of samples somatic coliphages, which were the most abundant, and F-specific coliphages outnumbered significantly Bact. fragilis phages. Normalized lines of the numbers of the three groups of phages in water samples and their sediments show that they settle similarly. The correlation between the values of the three groups of phages was not observed in waters with intermediate levels of pollution. An increase in the relative numbers of coliphages with respect to numbers of phages infecting Bact. fragilis was observed. In waters with persistent faecal pollution a dramatic change was recorded in the relative numbers of the different groups of phages. Phages infecting Bact. fragilis suffered the lowest reduction in numbers.

Distribution of Aeromonas species in waters with different levels of pollution

Strains of Aeromonas spp. (883) were isolated from 10 stations in the north-west of Spain. Biotyping of the strains gave: 55% Aeromonas caviae, 34% A. hydrophila, 6% A. sobria and 5% Aeromonas spp. Phenotypic characters that have been claimed to be related to virulence such as haemolysis and the Voges-Proskauer reaction were detected mostly in A. hydrophila and A. sobria. The distribution of the species was significantly related to levels of faecal pollution in waters. Aeromonas caviae predominated in sewage and waters with a high degree of faecal pollution. In less polluted waters, either fresh or marine, A. caviae and A. hydrophila were almost equally distributed. In waters with low or no faecal pollution, the proportion of A. sobria to other species increased considerably.

The effect of terrestrial effluents on the incidence of Aeromonas spp. in coastal waters

The numbers of Aeromonas species were monitored for one year at 18 stations on the Barcelona coast. Their concentrations exceed those of faecal coliforms and faecal streptococci in all samples, both on the shoreline and at 500 m from the coast. The mean values of the three bacterial counts reflected the proximity of the terrestrial effluents. There was a positive correlation between aeromonads and faecal indicators on the shoreline but not at 500 m offshore. This reflected their common origin and different survival rates in seawater. When sterile sea water was inoculated with A. hydrophila ATCC 7966, the numbers decreased initially by three orders of magnitude before they began to multiply. The final count was related to the concentration of organic matter in the water.

Relation between Aeromonas and faecal coliforms in fresh waters

A possible correlation between the presence of mesophilic aeromonads and the number of faecal coliforms present in three fresh-water habitats subject to differing levels of faecal pollution was investigated. Concentration of Aeromonas spp. between 10(2)-10(9) cfu/100 ml and faecal coliforms of between 9-10(7) cfu/100 ml were found in the waters. In water free from faecal pollution there was no correlation but in polluted waters there was a significant relationship between the numbers of aeromonads, faecal coliform and the concentration of organic matter measured by biological oxygen demand.