The most-read MDPI articles in January covered many topics and themes – from ethics in animal welfare to a novel solution for long-term energy storage. We have a look at the importance of these fields of research and discuss the implications of the studies below.

The Association between Sugar-Sweetened Beverages and Male Pattern Hair Loss in Young Men

This is the second month running that this paper has made the top 5 list. Read last month’s article to view the authors’ statement.

Usage of Children’s Makeup and Body Products in the United States and Implications for Childhood Environmental Exposures

More and more research is suggesting that cosmetic and personal care products may contain toxic ingredients. This is also true for children’s make up and body products (CMBPs), which lack rigorous regulation. So, this study assesses the motivation behind the use of CMBPs by young children.

First, the researchers administered a survey to the parents/guardians of children aged 12 or younger. In total, 312 responses were collected, of which 207 had used CMPBs (70%). Then, through qualitive analysis, the authors found that children use CMBPs for play as opposed to beautification purposes. This will be important for the development of CMBPs in the future, helping with the characterization of risk and improving their safety.

The Rise of Heatstroke as a Method of Depopulating Pigs and Poultry: Implications for the US Veterinary Profession

Disease outbreaks and supply chain disruption have led to an increase in the use of depopulation techniques by farmers. Depopulation refers to the killing of animals en masse, which has long been conducted to control disease outbreak. In recent years, heatstroke-based methods have been increasingly used to achieve this. These involve “ventilation shutdown”, where fans are turned off and openings are closed so that the temperature will increase due to the animals’ body heat, resulting in them suffering from hyperthermia.

This study looks at the ethics of such practices in the US from an animal welfare perspective. It is highlighted that these methods prolong animal suffering. With the increase in the use of depopulation techniques, it is hugely important to ensure that these practices are humane. So, the researchers of this paper call for heatstroke-based methods to be discouraged in favor of higher-welfare alternatives.

Underground Gravity Energy Storage: A Solution for Long-Term Energy Storage

“Renewable energy sources are central to the energy transition toward a more sustainable future. However, as sources like sunlight and wind are inherently variable and inconsistent, finding ways to store energy in an accessible and efficient way is crucial. While there are many effective solutions for daily energy storage, the most common being batteries, a cost-effective long-term solution is still lacking.

In a new IIASA-led study, an international team of researchers developed a novel way to store energy by transporting sand into abandoned underground mines. The new technique, called Underground Gravity Energy Storage (UGES), is an effective long-term energy storage solution that also makes use of now-defunct mining sites, which likely number in the millions globally. 

UGES generates electricity when the price is high by lowering sand into an underground mine and converting the potential energy of the sand into electricity via regenerative braking and then lifting the sand from the mine to an upper reservoir using electric motors to store energy when electricity is cheap.”

• Statement from authors Julian Hunt and Benham Zakeri

Foliar Symptomology, Nutrient Content, Yield, and Secondary Metabolite Variability of Cannabis Grown Hydroponically with Different Single-Element Nutrient Deficiencies

This study looks at cannabis growth under nutrient-deficient conditions. Cannabis plants require high levels of nutrients to maintain their fast growth. So, the authors subjected plants to various treatments – a nitrogen-deficient treatment, potassium-deficient treatment, etc. – and recorded symptoms. This will help ensure a high yield and quality for commercially grown cannabis plants. Thus, the authors call for an integrated approach to monitor nutrient dynamics and take appropriate action to minimize losses.

If you want to find out more about any of the studies mentioned in this article, you can read them for free on the MDPI website.