Conventional transportation systems are facing many challenges related to reducing fuel consumption, noise, and pollutants to satisfy rising environmental and economic criteria. These requirements have prompted many researchers and manufacturers in the transportation sector to look for cleaner, more efficient, and more sustainable alternatives. Powertrains based on fuel cell systems could partially or completely replace their conventional counterparts used in all modes of transport, starting from small ones, such as scooters, to large mechanisms such as commercial airplanes. Since hydrogen fuel cells (HFCs) emit only water and heat as byproducts and have higher energy conversion efficiency in comparison with other conventional systems, it has become tempting for many scholars to explore their potential for resolving the environmental and economic concerns associated with the transportation sector. This paper thoroughly reviews the principles and applications of fuel cell systems for the main transportation schemes, including scooters, bicycles, motorcycles, cars, buses, trains, and aerial vehicles. The review showed that fuel cells would soon become the powertrain of choice for most modes of transportation. For commercial long-rage airplanes, however, employing fuel cells will be limited due to the replacement of the axillary power unit (APU) in the foreseeable future. Using fuel cells to propel such large airplanes would necessitate redesigning the airplane structure to accommodate the required hydrogen tanks, which could take a bit more time.

The traditional quark model ^1,2 accounts for the existence of baryons, such as protons and neutrons, which consist of three quarks, as well as mesons, composed of a quark–antiquark pair. Only recently has substantial evidence started to accumulate for exotic states composed of four or five quarks and antiquarks ³ . The exact nature of their internal structure remains uncertain ^4–29 . Here we report the first measurement of quantum numbers of the recently discovered family of three all-charm tetraquarks ^30–32 , using data collected by the CMS experiment at the Large Hadron Collider from 2016 to 2018 (refs. ^33,34 ). The angular analysis techniques developed for the discovery and characterization of the Higgs boson ^35–37 have been applied to the new exotic states. Here we show that the quantum numbers for parity P and charge conjugation C symmetries are found to be +1. The spin J of these exotic states is determined to be consistent with 2 ħ , while 0 ħ and 1 ħ are excluded at 95% and 99% confidence levels, respectively. The J ^{P C} = 2 ⁺⁺ assignment implies particular configurations of constituent spins and orbital angular momenta, which constrain the possible internal structure of these tetraquarks.

A measurement of the Higgs boson mass and width via its decay to two Z bosons is presented. Proton-proton collision data collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb − 1 at a center-of-mass energy of 13 TeV, is used. The invariant mass distribution of four leptons in the on-shell Higgs boson decay is used to measure its mass and constrain its width. This yields the most precise single measurement of the Higgs boson mass to date, 125.04 ± 0.12 GeV , and an upper limit on the width Γ H < 330 MeV at 95% confidence level. A combination of the on- and off-shell Higgs boson production decaying to four leptons is used to determine the Higgs boson width, assuming that no new virtual particles affect the production, a premise that is tested by adding new heavy particles in the gluon fusion loop model. This result is combined with a previous CMS analysis of the off-shell Higgs boson production with decay to two leptons and two neutrinos, giving a measured Higgs boson width of 3.0 − 1.5 + 2.0 MeV , in agreement with the standard model prediction of 4.1 MeV. The strength of the off-shell Higgs boson production is also reported. The scenario of no off-shell Higgs boson production is excluded at a confidence level corresponding to 3.8 standard deviations. © 2025 CERN, for the CMS Collaboration 2025 CERN

Wingtip vortices generated from aircraft wingtips, as a result of the pressure differential at the wingtip, constitute a major component of the total drag force, especially during take-off and landing. In addition to the drag issue, these vortices also pose a significant hazard to smaller aircraft flying in the wake of the larger airplane. The wingtip vortices play a crucial role in aerodynamic efficiency, fuel consumption, flight range, and aircraft stability. This paper presents an overview of the volume of work conducted over the past six decades to encapsulate the phenomena and the techniques devised to mitigate the wingtip vortices. It is shown that the aerodynamic efficiency of the examined wingtip devices ranges from 1% to 15%, depending on the type of wingtips and the flight conditions. Furthermore, it is pointed out that the decrease in fuel consumption ranges from 3.4% to 10%, and the reduction in the induced drag ranges from 5% to 20%.