Landim Introduce Fractional Dark Energy Model (Cosmology / Astronomy / Quantum)

A satisfactory theoretical explanation for the current accelerated expansion of the Universe is an open question that indicates the necessity of new physics. Discovered in 1998 using type-Ia supernovae, the acceleration of the Universe is described by a fluid with negative pressure (dark energy, hereafter DE), whose simplest candidate is a cosmological constant ‘Λ’. However, the observed value of the vacuum energy (10¯47 GeV4) is extremely much smaller than any estimate of the zero-point energy of all modes of a field up to a cutoff scale. The lack of a good explanation for the origin of ‘Λ’ and its smallness leads to the search of alternative candidates, such as scalar or vector fields, metastable DE, holographic DE, interacting DE, usage of extra dimensions, among others.

DE has the unusual property that its pressure is negative, thus given the unsolved theoretical issues related to the origin of DE, one may wonder if it can be described by a matter with new properties. In the recent paper, Ricardo Landim introduced the fractional dark energy (FDE) model, in which the accelerated expansion of the Universe is driven by a non-relativistic gas (composed by either fermions or bosons) with a non-canonical kinetic term: an inverse momentum term.

The DE equation of state parameter ‘w’ is simply the power of the inverse momentum term and the resulting energy density ends up mimicking the one of the cosmological constant. The observed vacuum energy can be obtained from the integral of the corresponding Fermi-Dirac (or Bose-Einstein) distribution with an appropriate lower limit of integration, which is related to the minimum allowed energy of a FDE particle.

This non-canonical kinetic term is the eigenvalue of the inverse momentum operator, in the fractional quantum mechanics (FQM) framework. In this case, the operator is the inverse of the Riesz derivative, which in turn appears in the generalized Schodinger equation.

He also investigated a phenomenological decay of the FDE particles into another non-relativistic particle and showed that the phenomenological decay depends on the volume of the Universe or you can say on the FDE temperature (since V ~ T for w = – 1), which means that after the critical volume, the energy (𝜀 = C/p³) reaches a maximum and stops increasing, thus decaying to another non-relativistic particle. However, DE’s fate can be different if other mechanisms are evoked to avoid an infinite energy.

“When the FDE temperature reaches a critical value (Tc), the decay is turned on. A more detailed explanation of this phenomenon is expected to come from first principles and is subject of study in future work.”

— Told Ricardo Landim, author of the study

Featured image: Parameter space in which the abundance of FDE in the non-relativistic regime (ε ∼ m) is equal to the one in the inverse momentum phase (ε ∼ C/p³). The particle is non-relativistic for m ≳ 1 GeV. © Ricardo Landim


Reference: Ricardo G. Landim, “Fractional Dark energy”, ArXiv, pp. 1-8, 23 Mar, 2021. https://arxiv.org/abs/2101.05072


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Consumption of Ultra-Processed Foods Increases the Risk of Cardiovascular Disease and Mortality (Food)

Consumption of ultra-processed foods increases the risk of cardiovascular disease and mortality, according to a study published in the Journal of the American College of Cardiology. Researchers compared processed food intake with cardiovascular disease incidence and mortality in participants from the Framingham Offspring Cohort. For every additional daily serving of processed foods, such as ice cream, hot dogs, and doughnuts, there was an increased risk for cardiovascular disease, coronary heart disease, and death from heart disease by as much as 9%. Possible mechanisms for the increased heart disease risk include higher consumption of trans fats, sugar, and sodium and lower intakes of potassium, cardioprotective nutrients found in fruits and vegetables, and dietary fiber in diets high in processed foods, as well as changes to gut microbiota. Previous research also links processed food consumption with increased energy intake and obesity. These findings and a corresponding commentary support minimizing processed food intake for disease prevention through policy reform.

Featured image: Processed meat © gettyimages


References

(1) Juul F, Vaidean G, Lin Y, Deierlein AL, Parekh N. Ultra-processed foods and incident cardiovascular disease in the Framingham Offspring Study. J Am Coll Cardiol. 2021;77(12):1520-1531. doi: 10.1016/j.jacc.2021.01.047 (2) Ostfeld R, Allen KE. Ultra-processed foods and cardiovascular disease: where do we go from here? J Am Coll Cardiol. 2021;77(12):1532-1534. doi: 10.1016/j.jacc.2021.02.003


Provided by Physicians Committee for Responsible Medicine

Liquid Metal Droplet Intelligence Applied in Soft Logic Devices (Science and Technology)

Soft robot has advantages of flexible actuating strategies, various patterns of movement, and friendly interaction with humans. However, due to the lack of suitable practical methods and soft controllers, fabricating a fully integrated flexible robot remains a major challenge.   

Based on the deformation and locomotion behavior of liquid metals (LMs) via electrical stimulus, Prof. LIU Jing’s team from the Technical Institute of Physics and Chemistry (TIPC) of the Chinese Academy of Sciences proposed and demonstrated a new type of liquid metal droplet electronic device. The new device could be organized further into gate logics to execute logical computing.

The study, published in Advanced Intelligent Systems on March 18, showed the importance of LMs in intelligent electronic control systems for the first time. It also provided a new method to manufacture soft electronic devices.  

“As a new class of smart materials, liquid metal is inherently flexible, electrically conductive and responsive to stimuli. It is highly possible to develop soft intelligent electronic devices and explore the potential application of LMs in control systems,” said Prof. LIU.  

The new device removes the reliance on semiconductor by directly constructing electronic devices on soft materials to perform logical operations and calculations.   

A variety of logic gates can be easily manufactured through different connections to liquid metal droplets electronic devices, which have shown stable functionality for binary logic calculation.   

To demonstrate the feasibility of application, researchers constructed a soft four-degree logic accumulator via LMs droplet electronic device, which could regulate a pneumatic soft gripper within four states of inflation.   

The spatial scale of LM involved motion is quite small without bulky ancillary equipment and easy for miniaturization and integration.   

In this research, the trial of LM-based logic devices demonstrated the potential that electrically-induced variations of liquid in a macroscale could be designed as processors for reception, conversion and exportation of electrical signals. Owing to the natural harmony with soft structures, they may hold a promise for the ultimate autonomy and control of soft robots in the near future.

Featured image: Structural principles of LM droplet electronic devices (Image by LIU Jing et al.)


Reference: Li, D., Liu, T., Ye, J., Sheng, L. and Liu, J. (2021), Liquid Metal‐Enabled Soft Logic Devices. Adv. Intell. Syst. 2000246. https://doi.org/10.1002/aisy.202000246


Provided by Chinese Academy of Sciences

635 Million-year-old Fungi-like Microfossil that Bailed Us out of an Ice Age Discovered (Paleontology)

When you think of fungi, what comes to mind may be a crucial ingredient in a recipe or their amazing ability to break down dead organic matter into vital nutrients. But new research by Shuhai Xiao, a professor of geosciences with the Virginia Tech College of Science, and Tian Gan, a visiting Ph.D. student in the Xiao lab, highlights yet another important role that fungi have played throughout the Earth’s history: helping the planet recover from an ice age.

A team of scientists from Virginia Tech, the Chinese Academy of Sciences, Guizhou Education University, and University of Cincinnati has discovered the remains of a fungi-like microfossil that emerged at the end of an ice age some 635 million years ago. It is the oldest terrestrial fossil ever found. To put it into perspective, this microfossil predates the oldest dinosaurs about three times over.

Their findings were published in Nature Communications on Jan. 28.

The fossil was found in small cavities within well-studied sedimentary dolostone rocks of the lowermost Doushantuo Formation in South China. Although the Doushantuo Formation has provided a plethora of fossils to date, researchers did not expect to find any fossils toward the lower base of the dolostones.

But against all odds, Gan found a few long, thread-like filaments – one of the key characteristics of fungi.

“It was an accidental discovery,” said Gan. “At that moment, we realized that this could be the fossil that scientists have been looking for a long time. If our interpretation is correct, it will be helpful for understanding the paleoclimate change and early life evolution.”

This discovery is key for understanding multiple turning points throughout Earth’s history: the Ediacaran period and the terrestrialization of fungi.

When the Ediacaran period began, the planet was recovering from a catastrophic ice age, also known as the “snowball Earth.” At that time, ocean surfaces were frozen to a depth of more than a kilometer and it was an incredibly harsh environment for virtually any living organism, except for some microscopic life that managed to thrive. Scientists have long wondered how life ever returned to normalcy – and how the biosphere was able to grow larger and more complex than ever before.

With this new fossil in hand, Tian and Xiao are certain that these microscopic, low profile cave dwellers played numerous roles in the reconditioning of the terrestrial environment in the Ediacaran time. One role involved their formidable digestive system.

Fungi have a rather unique digestive system that plays an even greater role in the cycling of vital nutrients. Using enzymes secreted into the environment, terrestrial fungi can chemically break down rocks and other tough organic matter, which can then be recycled and exported into the ocean.

“Fungi have a mutualistic relationship with the roots of plants, which helps them mobilize minerals, such as phosphorus. Because of their connection to terrestrial plants and important nutritional cycles, terrestrial fungi have a driving influence on biochemical weathering, the global biogeochemical cycle, and ecological interactions,” said Gan.

Although previous evidence stated that terrestrial plants and fungi formed a symbiotic relationship around 400 million years ago, this new discovery has recalibrated the timeline of when these two kingdoms colonized the land.

“The question used to be: ‘Were there fungi in the terrestrial realm before the rise of terrestrial plants’,” said Xiao, an affiliated faculty member of the Fralin Life Sciences Institute and the Global Change Center. “And I think our study suggests yes. Our fungus-like fossil is 240 million years older than the previous record. This is, thus far, the oldest record of terrestrial fungi.”

Now, new questions have arisen. Since the fossilized filaments were accompanied by other fossils, Gan will set out to explore their past relationships.

“One of my goals is to constrain the phylogenetic affinities of these other types of fossils that are associated with the fungal fossils,” said Gan.

Xiao is thrilled to tackle the environmental aspects of these microorganism. Sixty years ago, few believed that microorganisms, like bacteria and fungi, could be preserved as fossils. Now that Xiao has seen them with his very eyes, he plans to learn more about how they have been virtually frozen in time.

“It is always important to understand the organisms in the environmental context,” said Xiao. “We have a general idea that they lived in small cavities in dolostone rocks. But little is known about how exactly they lived and how they were preserved. Why can something like fungi, which have no bones or shells, be preserved in the fossil record?”

However, it can’t be said for sure if this fossil is a definitive fungus. Although there is a fair amount of evidence behind it, the investigation into these microfossils is ongoing.

“We would like to leave things open for other possibilities, as a part of our scientific inquiry,” said Xiao. “The best way to put it is that perhaps we have not disapproved that they are fungi, but they are the best interpretation that we have at the moment.”

Three distinct groups and labs at Virginia Tech were crucial for the identification and timestamping of this fossil. The Confocal Laser Scanning and Microscopy lab at the Fralin Life Sciences Institute helped Tian and Xiao perform initial analysis that prompted further investigation at the University of Cincinnati.

The Department of Biological Sciences’ Massey Herbarium, which houses over 115,000 specimens of vascular plants, fungi, bryophytes, and lichens, provided modern fungal specimens for comparison with the fossils.

The team called in technicians to conduct geochemical analysis using Secondary Ion Mass Spectrometry, which ionize nanomoles of material from small areas that are a fraction the thickness of a hair strand, to analyze the isotopic abundance of sulfur-32 and sulfur-34 in order to understand the fossilization environment.

Advanced computerized tomography was crucial to getting the 3D morphology of the filaments, which are just a few micrometers thick. And a combination of Focused Ion Beam Scanning Electron Microscopy and Transmission Electron Microscopy allowed researchers to cut samples with surgical precision and take an even closer look at every nanometer of the filaments.

“This wasn’t a single person or even a single lab that did this work,” said Xiao.

Xiao also emphasized the importance of interdisciplinary research in this study and many others.

“It’s very important to encourage the next generation of scientists to be trained in an interdisciplinary light because new discoveries always happen at the interface of different fields,” said Xiao. (VIRGINIA TECH)

The first author Gan Tian and one of the corresponding authors Luo Taiyi are affiliated with the Institute of Geochemistry of the Chinese Academy of Sciences (IGCAS). 

Featured image: Microscopic image of the fungus-like filamentous microfossils. Credit: Andrew Czaja of University of Cincinnati.


Reference: Gan, T., Luo, T., Pang, K. et al. Cryptic terrestrial fungus-like fossils of the early Ediacaran Period. Nat Commun 12, 641 (2021). https://doi.org/10.1038/s41467-021-20975-1


Provided by Chinese Academy of Sciences

Rapid Super-resolution Microscopy: What You See Is What You Get (Physics)

Optical microscopy is widely used in biological and medical research, but it’s resolution is subject to the Abbe diffraction limit and cannot meet the requirement of resolving organism structures inside a cell. The super-resolution (SR) microscopy that emerged in recent years can beat the Abbe diffraction limit and achieve tens of nanometers in resolution. Among which, structured illumination microscopy (SIM) outperforms the most.

However, SIM routinely performs image reconstruction in the frequency domain using an approach termed frequency-domain reconstruction (FDR). Due to multiple Fourier transforms between the spatial and frequency domains, SIM suffers from low reconstruction speed, significantly constraining its applications in real-time, dynamic imaging.

Recently, a research team led by Prof. YAO Baoli from the Xi’an Institute of Optics and Precision Mechanics (XIOPM) of the Chinese Academy of Sciences (CAS) developed a new pipeline for SIM image reconstruction, termed spatial domain reconstruction (SDR), and thus addressed the challenge to SIM.

According to the researchers, SDR is intrinsically simpler than FDR, it does not require Fourier transforms, and the theory predicts it to be a rapid image reconstruction method.

Results show that SDR reconstructs a super-resolution image 7-fold faster than FDR, producing images equal to FDR or the widely-used FairSIM. With SDR, the researchers can real-time track two adjacent nanometer beads with super-resolution. This work was recently published in IEEE Photonics Journal. 

The two components of the scheme improve the speed and of image quality generated by SDR. The method is elegant, simple, produces images rapidly, and is therefore ideal for live-cell imaging.

Featured image: The concept and simple implementation for SDR-SIM. (Image by XIOM)


Reference: Dan et al., “Rapid Image Reconstruction of Structured Illumination Microscopy Directly in the Spatial Domain,” in IEEE Photonics Journal, vol. 13, no. 1, pp. 1-11, Feb. 2021, Art no. 3900411.
doi: 10.1109/JPHOT.2021.3053110 URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=9329035&isnumber=9311900


Provided by Chinese Academy of Sciences

Researchers Reveal Missing Optical Localized Gap Modes (Physics)

Electromagnetically induced transparency (EIT) is a typical quantum destructive interference effect, which possesses many striking properties such as elimination of optical absorption, reduction of group velocity and remarkable enhancement of Kerr nonlinearity. Due to its rich physical properties and important practical applications, the study of EIT is extremely important. Many works have demonstrated the ways for manipulating light pulses via dynamically controlled EIT-induced photonic band gap in coherently prepared atomic gases.

Although various effects including solitons have been widely studied in multilevel atomic systems with electromagnetically induced lattices formed by EIT in recent years, the gap solitons are still missing. Are there any methods to reveal this phenomenon?

A research team led by Prof. Dr. ZENG Jianhua from the Xi’an Institute of Optics and Precision Mechanics (XIOPM) of the Chinese Academy of Sciences (CAS) theoretically investigate one-dimensional (1D) localized gap modes in a coherent atomic gas. The results were published in Optics Express. 

In this research, the new platform to generate localized gap modes is a 1D coherent atomic system consisting of a Λ-type three-level atomic gases that are excited under EIT condition and trapped by an optical lattice formed by a pair of counterpropagating far-detuned Stark laser fields.

The model supports two types of localized gap modes, fundamental gap solitons and dipole ones. Both localized gap modes can be constructed as on-site and off-site modes, with their central profiles placing respectively into the maximum and minimum values of the optical lattice.

The systematic simulations based on linear-stability analysis and the direct perturbed simulations demonstrate the (in)stability regions of both localized gap modes in the respective linear band-gap spectrum.

The proposed physical scheme and the predicted gap modes therein can enlarge the nonlinear spectrum of coherent atomic gases and open up a new avenue for implications including optical communication and information processing.

Featured image: Band-gap structure and profiles of gap solitons. (Image by XIOPM)


Reference: Zhiming Chen and Jianhua Zeng, “Localized gap modes of coherently trapped atoms in an optical lattice,” Opt. Express 29, 3011-3025 (2021). https://doi.org/10.1364/OE.412554


Provided by Chinese Academy of Sciences

Novel H2S Sensor Developed to Challenge Lower Temperature (Physics)

Hydrogen sulfide is one of the most common toxic contaminants frequently utilized in various fields, including the oil, gas, waste treatment, and paper industries. Even trace amounts of H2S gas are extremely toxic to many organisms, such as human respiratory and nerve systems. Generally, it is recommended that the acceptable ambient levels of H2S for a healthy condition are in the range of 20 -100 ppb.

A research group led by Professor FANG Xiaodong and MENG Gang from the Anhui Institute of Optics and Fine Mechanics (AIOFM) of the Hefei Institutes of Physical Science explored a novel H2S sensor which is made of a new fabricated material (Sr0.6Bi0.305)2Bi2O7/ZnO. This sensor, abbreviated as SBO/ZnO, possesses excellent H2S sensing performances.

“We use facile one-step hydrothermal method to develop the material,” said CHANG Junqing, a student who joined the research, “it boasts high response, low limit of detection, good selectivity and long-term stability.”

In this research, scientists found that when the concentration of H2S was 10 ppm and the sensitivity reached 107.6. Besides, the limit of the detection was lowered to 20 ppb.

Such enhanced response is contributed to the increased oxygen vacancy and the reversible sulfurization-desulfurization reaction. The material has the merits of low operation temperature of 75 °C and weak humidity dependence.

This novel heterostructural sensor paves the way for the practical monitoring of trace H2S pollutants in diverse workplaces including petroleum and natural gas industries.

These works were financially supported by the projects of the International Cooperation, the National Natural Science Foundation of China, and the CAS-JSPS Joint Research Projects, etc.

Featured image: (a) selectivity, (b) long-term stability, (c)humidity dependence. (Image by CHANG Junqing)


Reference: Junqing Chang, Zanhong Deng, Xiaodong Fang, Chaohao Hu, Lei Shi, Tiantian Dai, Meng Li, Shimao Wang, Gang Meng, Heterostructural (Sr0.6Bi0.305)2Bi2O7/ZnO for novel high-performance H2S sensor operating at low temperature, Journal of Hazardous Materials, Volume 414, 2021, 125500, ISSN 0304-3894, https://doi.org/10.1016/j.jhazmat.2021.125500. (https://www.sciencedirect.com/science/article/pii/S0304389421004635)


Provided by Chinese Academy of Sciences

How Do Optical Components Survive from High-intensity Laser in Inertial Confinement Fusion? (Physics)

Laser-driven inertial confinement fusion (ICF) is regarded as a promising method of obtaining high-gain fusion energy to solve the energy crisis and produce clean new energy. It is realized by using a focused high-intensity ultraviolet (UV) laser to compress a helium fuel target to obtain controllable high-gain fusion energy. As the laser energy reaching the final optics assembly (FOA) is on the order of kilojoules, making it hard for the critical optical components there to resist being damaged. The risk of being damaged and the short lifetimes of these components affect the stable operation and run cost of ICF devices. Therefore, the higher the laser-induced damage threshold (LIDT) of these components’ materials, the better it is. Traditional materials used in the optical components were fused silica, but it’s not good enough to avoid the damaging risks.

Recently, a series of fluoride-containing phosphate-based glasses were developed and tested to explore their performance as potential UV optics for FOAs at the Chinese ICF facility, SG-III. When exposed to the high-energy laser, yellowish-orange luminescence passes through the glass bulk. The appearance of stronger luminescence intensity was suspected to be attributed to its higher LIDT. And the strong laser-induced fluorescence phenomenon differs from that of fused silica, indicating a different laser-material interaction mechanism.

A research team led by Dr. WANG Pengfei from the Xi’an Institute of Optics and Precision Mechanics (XIOPM) of the Chinese Academy of Sciences (CAS) synthesized three kinds of multi-component fluoride-containing phosphate-based glasses and damaged them by a pulsed UV laser.

The researchers investigated the defect nature of laser-induced fluorescence (LIF) emissions in these glasses, their decay properties, and the intrinsic relationship between the LIF and high LID resistance.

They observed that the third fluoride-containing phosphate-based glass with higher LIF intensity, longer fluorescence lifetime and lower UV absorption coefficient than the other two kinds of glasses, has the highest LID resistance, confirming that the special LIF emission properties of fluoride-containing phosphate-based glass mitigate the thermal deposition during the laser operation and therefore, help them to survive from UV laser with higher energy intensity.

The results provide theoretical guidance for developing UV optical elements with higher damage resistance for potential ICF applications and were published in Ceramics International. 

Featured image: Decay processes of 450 nm and 780 nm fluorescence in the series of fluoride-containing phosphate-based glasses. (Image by XIOPM)


Reference: Shengwu Li, Yanqiang Yang, Yunfei Song, Rui Wan, Yuan Ma, Bo Peng, Guangwei Zhang, Pengfei Wang, Laser-induced fluorescence and its effect on the damage resistance of fluoride-containing phosphate-based glasses, Ceramics International, Volume 47, Issue 9, 2021, Pages 13164-13172, ISSN 0272-8842, https://doi.org/10.1016/j.ceramint.2021.01.181. (https://www.sciencedirect.com/science/article/pii/S0272884221002182)


Provided by Chinese Academy of Sciences

Inactivation and Regeneration of Niobium Oxide Catalyst Electrocatalyze N2 Reduction (Chemistry)

A research group led by Prof. ZANG Haimin from the Institute of Solid State Physics of the Hefei Institutes of Physical Science reported their finding about inactivation and regeneration of highly ordered Nb2O5 (niobium oxide) nanochannel film catalyst for electrocatalytic N2 reduction.

Ammonia (NH3) has been widely applied in fuel of vehicles, agricultural, plastic and textile industries. Its production from N2 and H2 release a large amount of CO2. Electrocatalytic N2 reduction reaction (NRR) at ambient condition has been regarded as a promising NH3 synthesis method for replacing the traditional energy- and capital-intensive Haber-Bosch process.

“Our goal is to develop an efficient and economic catalyst for NRR”, said Prof. ZHANG Haimin, a chemist, “so we fabricated highly ordered Nb2O5 nanochannel film (Nb2O5-NCF) on niobium foil substrate with facile anodization method.”

After thermal treatment in air, the as-fabricated Nb2O5-NCF with pseudo hexagonal phase contains rich oxygen vacancy defects. The researchers found it displayed high electrocatalytic NRR activity with an NHyield rate of 2.52×10-10 mol cm-2 s-1 and a FE of 9.81% at -0.4 V in 0.1 M Na2SO4 solution.

During electrocatalytic NRR, the crystalline phase transformation of Nb2O5-NCF results in the electrochromism phenomenon and the decrease of NRR activity.

The used Nb2O5-NCF electrode can be readily regenerated by low-temperature thermal treatment or applying an anodic potential, recovering high NH3 yield rate and FE with superior recycling stability.

This work was financially supported by the National Key Research and Development Program of China and the Natural Science Foundation of China.

Featured image: Highly ordered Nb2O5 nanochannel film with rich oxygen vacancies for electrocatalytic N2 reduction: inactivation and regeneration of electrode. (Image by KANG shenghong and WANG Jialu)


Reference: Jialu Wang, Shenghong Kang, Xiaoguang Zhu, Guozhong Wang, Haimin Zhang, Highly ordered Nb2O5 nanochannel film with rich oxygen vacancies for electrocatalytic N2 reduction: Inactivation and regeneration of electrode, Chinese Chemical Letters, 2021, , ISSN 1001-8417, https://doi.org/10.1016/j.cclet.2021.01.020. (https://www.sciencedirect.com/science/article/pii/S100184172100022X)


Provided by Chinese Academy of Sciences