Jeremy Fleury

In plants, light direction is perceived by the phototropin photoreceptors, which trigger directional growth responses known as phototropism. The formation of a phototropin activation gradient across a photosensitive organ initiates this response. However, the optical tissue properties that functionally contribute to phototropism remain unclear. In this work, we show that intercellular air channels limit light transmittance through various organs in several species. Air channels enhance light scattering in Arabidopsis hypocotyls, thereby steepening the light gradient. This is required for an efficient phototropic response in Arabidopsis and Brassica. We identified an embryonically expressed ABC transporter required for the presence of air channels in seedlings and a structure surrounding them. Our work provides insights into intercellular air space development or maintenance and identifies a mechanism of directional light sensing in plants.

Summary: In light-limiting conditions, aerial organs of most plants reorient their growth towards the light to improve photosynthesis, through a process known as phototropism ^1-3 . The blue light receptors phototropin control phototropic responses through light-induced protein kinase activity ⁴ . Current models posit that asymmetric activation of these sensory receptors across a unilaterally illuminated organ leads to asymmetric distribution of the growth hormone auxin ultimately leading to growth re-orientation ^4,5 . However, the tissue properties required to generate a light gradient across the stem triggering phototropism remain unclear ¹ . Here we show that inter-cellular air channels ^6,7 are required for an efficient phototropic response. These channels enhance light scattering (refraction and reflection) in Arabidopsis hypocotyls thereby enhancing the light gradient across the photo-stimulated organ. We identify an embryonically expressed ABC transporter that is required to keep air in inter-cellular spaces in seedlings and for efficient phototropism. Our work suggests that this transporter shapes cell wall properties to maintain air between cells. Moreover, we establish the functional importance of inter-cellular air channels in the hypocotyl for phototropism.

The integrated performance assessment of buildings can orient their design in the early stages. Despite the wide availability of physics simulation-based, data-driven, and hybrid techniques, it is often difficult to rely on a single, appropriate technique to obtain reliable results. A set of methods, each featuring advantages and limitations, help to refine the performance assessment in an iterative comparative process until a comprehensive picture of the building is achieved. The approach was implemented on a nearly zero-energy building, recently built-up as a combined living and office space (e.g., the SolAce unit) on the NEST infrastructure in Dübendorf (Switzerland). The proposed approach showed that the unit reaches high energy performance accordingly requiring optimal cooling management, involving the control of the opening of blinds and windows. A sound convergence between the computer simulations and data-driven analysis were observed, attesting to the overall energy consumption, of around 26 kWh/m²year, in continuous decrease, aiming at an annual energy-positive balance. The unit was ranked first according to the dynamic energy exchange scheme of the energy trading hub within the NEST facility, which features high-level building modules as a testbed of future building technologies. Embodied energy is estimated at 39 kWh/m²year, which is below the commended limits of Swiss eco-building standards. By considering the carbon sequestration of the wood products during their lifespan, the unit is very close to carbon neutrality with the CO₂ emitted annually by the unit over its lifetime being compensated by those stored within wood products during the same period. Highlights: An innovative combined living/office space is connected to an ‘Energy-hub’. The unit includes novel bioclimatic developments of the building industry. Energy performance is assessed in the concept phase, construction, and operation. Used and compared simulation vs data monitoring for energy and comfort assessment. High energy performance and neutral CO₂ emission; plus-energy exported to the hub.

With the purpose of reducing the heating energy in buildings, it is common practice to install energy-efficient windows to increase the thermal insulation of a façade. These insulating glass units (IGIJ) include a thin silver coating acting as an infrared mirror which reduces the thermal losses that occur through radiation, but at the same time reflects the microwaves for mobile communication. To address this drawback, a specific laser treatment is performed on the silver coating which strongly improves the transmission of microwaves through the window. In this study, the attenuation of microwaves signal was analyzed inside the SolAce unit in the "NEST" research building at the Swiss Federal Laboratories for Materials Science and Technology (EMPA) in Dübendorf. Two configurations (with and without laser-treated glazing) were carried out by interchanging two hinged windows. The results showed a significant improvement in signal strength in the configuration with laser-treated IGUs. A transmission loss contour plot of the SolAce unit showed a highly directional propagation of the wave which suggests that more than two windows should be treated to achieve better mobile communication in the entire unit. The novel patterned coating is thus especially valuable in the building sector to increase the microwave signal for mobile communication. To the best of our knowledge, this is the first implementation and testing of laser-treated coating for energy-efficient glazing in the building sector.

Novel mobile communication technology such as 5G will provide a more efficient and reliable platform for the development of the Internet of Things. However, microwaves in the range of 5G frequencies are strongly attenuated by modern energy-efficient glazing found in most recent buildings. This paper presents major steps towards microwave transparent glazing which allows a flawless transmission of 5G frequencies while maintaining the thermal energy efficiency of the window. Several double glazing windows with different properties were fabricated with a laser treatment and their effect on the signal attenuation in the frequency range between 0.7 and 3.5 GHz was measured. The results showed that the laser treated windows produced a transmission of the microwave as good as a non-coated window. In comparison, an energy-efficient window without laser treatment reduces the signal strength up to 300 times.