5 Current Events in Physics (Highlights)

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5 Current Events in Physics (Highlights)

Physics is a scientific discipline concerned primarily with matter and energy. Though it is a branch of science, physics is also relevant to philosophical questions concerning our existence and the nature of the universe. Additionally, physics has been used to solve a variety of technological issues.

Physics is a very complex area of study. Nonetheless, it concentrates on some of the most basic principles of our existence. It is divided into quantum mechanics, relativity and classical physics. Classical physics refers to everyday velocities and sizes. Relativity relates to larger objects and high speeds. Finally, quantum mechanics concerns itself with extremely small sizes and distances. All three branches involve complicated, high-level mathematics.

Scientists and researchers are always making new discoveries in the field, and physics as an area of study is continually evolving. Let’s take a look at some of the most interesting current events in physics:

Breakdown of Diffusivity

Glass, as a substance, has baffled physics experts for decades. For most substances, their structure experiences significant changes when transitioning between a solid and liquid state. However, glass is very different. When glass is in its liquid state, its structure is hardly any different from its solid state. In essence, glass appears like a liquid that has lost its ability to flow. A recent study used this as its central point. The methods used to investigate this strange occurrence came from highly complex theories and equations, and the results showed that thermodynamical entropy plays a large part in glass transitions.

Naturally, glass is something that we see everywhere. Most homes, commercial buildings, electronic devices, and vehicles use glass as part of their basic structure. It has wide-ranging uses for people. However, many (including experts in physics) do not fully understand how glass works.

Kinetic Slowdown

A central problem that many scientists point to is “kinetic slowdown,” which is the process by which a liquid loses its ability to flow when it is cooling. The reason why a given substance undergoes such a slowdown while not experiencing any kind of structural change remains a mystery to researchers.

The unique approach taken in the study shows that the kinetic slowdown proportionally related to enthalpy and entropy. Researchers reached this conclusion using the topography of the free-energy landscape. However, the results were not entirely conclusive.

Even with an abundance of theories on this issue, there are a lot of gaps in our understanding of glass transitions. Researchers continue to try different methods, and this most recent study has shown some interesting findings, but there is still no clear link between kinetics and thermodynamics during glass transition.

Nonetheless, according to the scientists involved, their study “shed light on the study of molecular glasses and emphasized the crucial role that thermodynamical entropy plays in the kinetic slowdown during glass transition.”

Determining the Best Conditions for Ultrashort High Harmonics

A recent study on ellipticity of high harmonics led to interesting findings. These results could have a significant impact on the world of physics research. According to the authors of the study:

“High harmonics generated by counter-rotating laser fields at the fundamental and second harmonic frequencies have raised important interest as a table-top source of circularly polarized ultrashort extreme-ultraviolet light. However, this emission has not yet been fully characterized: in particular it was assumed to be fully polarized, leading to an uncertainty on the effective harmonic ellipticity.

Here we show, through simulations, that ultrashort driving fields and ultrafast medium ionization lead to a breaking of the dynamical symmetry of the interaction, and consequently to deviations from perfectly circular and fully polarized harmonics, already at the single-atom level. We perform the complete experimental characterization of the polarization state of high harmonics generated along that scheme, giving direct access to the ellipticity absolute value and sign, as well as the degree of polarization of individual harmonic orders. This study allows defining optimal generation conditions of fully circularly polarized harmonics for advanced studies of ultrafast dichroisms.”

The Results

The study is very technical and complex in nature. However, it essentially defines the optimal conditions for ultrashort high harmonics generation (HHG). In layman’s terms, high harmonics generation refers to a process in which an intense laser pulse illuminates a given substance. When the substance experiences illumination, it emits the same high harmonics as the laser pulse. However, in the past, measurements of these high harmonics have been difficult to observe. Thanks to this study, researchers have a better understanding of how to bring about ultrashort HHG.

Electrical Conductivity of Nanowires

Another recent study seeks to find a method for controlling the electrical conductivity of nanowire composites. Here is an abstract of the study provided by its authors:

“Quantitative models to predict the electrical performance of 1-D nanowire (NW) composite networks under external deformation such as bending and patterning are developed by Monte-Carlo based computations, and appropriate solutions are addressed to enhance the tolerance of the sheet resistance (Rs) of the NW networks under the deformation.

[Additionally], several strategies are employed to improve further the robustness of the sheet resistance against the network deformation. In the case of bending, outstanding bending durability of a hybrid NW network coated on a 2-D sheet is confirmed with a numerical model, and a network of NWs aligned unidirectionally toward bend axis is introduced to alleviate the sheet resistance degradation. [For] a narrowly patterned channel, the conductivity enhancement of a network of NWs aligned in parallel to the channel with reduced channel is validated, and a network made with two types of NWs with different lengths is suggested to enhance the tolerance of the electrical conductivity. The results offer useful design guidelines to the use of the 1-D NW percolation network for flexible transparent conducting electrodes.”

Applications

Flexible, transparent conducting materials are an important component for a variety of modern electronic gadgets. These include pieces of equipment like wearable sensors, batteries, malleable displays, and solar cells, among others. ITO is especially popular due to its high electrical conductivity, however it is not as flexible as other materials. By conducting the above experiment, researchers were able to put the electrical conductivity, flexibility, and optical transmittance of various materials to the test. In the end, the researchers hope that this study will help manufacturers develop higher-quality products using flexible, transparent conducting materials.

Thermal Transport Crossover From Crystalline to Partial-liquid State

In a study published in Nature Communications, a research time sought to report on the underlying mechanisms of the thermal transport and thermal conductivity of certain phase-change materials. These materials are vital for many kinds of batteries and thermoelectric converters. In the crystalline state, thermal conductivity shows two different kinds of behaviors. One of these behaviors trends below 800 K, and the other trends above 800 K . However, when they trend above 800 K, they generally do not go above 1000 K.

In the past, scientists spent a great deal of time and resources studying heat transfer in perfect crystals. These studies proved extremely important for many disciplines. It is particularly useful in the research of thermoelectrics, photonic materials, and thermal management. Thermal transport is partially crystalline and partially liquid state.

The researchers provide the following summary of their methods:

“we quantitatively investigate the mechanisms of heat transport in PCMs by taking Li2S as a case study using the reactive force field (ReaxFF)10 Green-Kubo equilibrium molecular dynamics (GK-EMD)13, the first-principles-based Boltzmann transport equation (BTE)14, as well as the frequency domain direct decomposition method (FDDDM)15,16 or the Sääskilahti method17. Although, the phase transition of PCM Li2S is widely studied18, the thermal transport behaviors have never been explored. We find that there is a transition from pure phonon transport to phonon-convection interactions in two-components transport in Li2S.”

In the end, the experiment showed that, when the temperature rose, Li2S changed from a solid state to a crystalline/liquid state. This is drastically different from the melting process for Li2S. This discovery led the researchers to believe that the phonon contribution’s negative temperature dependence caused the virial term to decrease.

The Fluid Mechanics of Bubbly Drinks

For most bubbly drinks, the explanation is simple: carbonation. Carbon dioxide dissolves in the water and then the water experiences pressure. This usually takes the form of a pressurized plastic bottle. The pressure releases at the moment a person unscrews the cap. When this pressure releases, the liquid expels the gas, causing the bubbles to rise to the surface. However, two researchers in the field of fluid mechanics explain the complexities of carbonation in bubbly drinks.

There is a lot going on in your bubbly drink in just the few seconds between opening the bottle and taking your first sip. So, the researchers take a look at a variety of factors to determine exactly what is going on during this fascinating process.

How bubbles behave in water is generally determined by two physicochemical laws. This law (commonly known as Henry’s Law) states that the concentration of a dissolved gas will be proportional to the partial pressure of the gas. The second law is called Fick’s Law of Molecular Diffusion. This law states that, when there is a concentration gradient, there is also a mass flux that is proportional to the gradient, but going in the opposite direction.

The Process

Researchers use an equation to determine the bubble size as it grows. Gas cavities tend to form on the glass walls and then attach to the crevices, enabling them to stabilize. Buoyancy drives the upward movement of bubbles, which increases proportionally with bubble volume and viscous drag. The radius of a bubble moving upwards in a liquid increases at a gradual rate.

While it all seems so simple on the surface, the physicochemical laws that allow for carbonated beverages to exist are quite complex. Beverage manufacturers are well-versed on the science, and actually use these laws and formulas to sell more drinks. For example, there is generally a certain level of carbonation that is ideal for our taste buds. As a result, beverage manufacturers bottle their drinks in such a way to create the optimum drinking experience!

Conclusion

With the increased application of physics in the health sector, education, energy, and the environment, the role of research in physics remains paramount for the continued betterment of society.

In today’s world, we can travel to far away places in comfort, carrying out business around the globe with little effort. We have physics to thank for this (and the scientists working hard to make new discoveries in the field). Physics has seen the entire world interconnected, especially through technological advancements.

Despite the role that physics has played in connecting people from around the globe, a lot of division still exists. This is especially true in developing countries. For instance, in developed countries, you may find a life expectancy of 80 years. This compares to a life expectancy of 40 years in the developing countries. Advancements in physics often lead to incredible medical discoveries, but often times, businesses and governments do not implement or distribute these findings to everyone.

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