Several recent studies have shown the presence of genes for the key enzyme associated with archaeal methane/alkane metabolism, methyl-coenzyme M reductase (Mcr), in metagenome-assembled genomes ...(MAGs) divergent to existing archaeal lineages. Here, we study the mcr-containing archaeal MAGs from several hot springs, which reveal further expansion in the diversity of archaeal organisms performing methane/alkane metabolism. Significantly, an MAG basal to organisms from the phylum Thaumarchaeota that contains mcr genes, but not those for ammonia oxidation or aerobic metabolism, is identified. Together, our phylogenetic analyses and ancestral state reconstructions suggest a mostly vertical evolution of mcrABG genes among methanogens and methanotrophs, along with frequent horizontal gene transfer of mcr genes between alkanotrophs. Analysis of all mcr-containing archaeal MAGs/genomes suggests a hydrothermal origin for these microorganisms based on optimal growth temperature predictions. These results also suggest methane/alkane oxidation or methanogenesis at high temperature likely existed in a common archaeal ancestor.
Microbes of the phylum Aigarchaeota are widely distributed in geothermal environments, but their physiological and ecological roles are poorly understood. Here we analyze six Aigarchaeota metagenomic ...bins from two circumneutral hot springs in Tengchong, China, to reveal that they are either strict or facultative anaerobes, and most are chemolithotrophs that can perform sulfide oxidation. Applying comparative genomics to the Thaumarchaeota and Aigarchaeota, we find that they both originated from thermal habitats, sharing 1154 genes with their common ancestor. Horizontal gene transfer played a crucial role in shaping genetic diversity of Aigarchaeota and led to functional partitioning and ecological divergence among sympatric microbes, as several key functional innovations were endowed by Bacteria, including dissimilatory sulfite reduction and possibly carbon monoxide oxidation. Our study expands our knowledge of the possible ecological roles of the Aigarchaeota and clarifies their evolutionary relationship to their sister lineage Thaumarchaeota.
We provide a perspective on polymer glass formation, with an emphasis on models in which the fluid entropy and collective particle motion dominate the theoretical description and data analysis. The ...entropy theory of glass formation has its origins in experimental observations relating to correlations between the fluid entropy and liquid dynamics going back nearly a century ago, and it has entered a new phase in recent years. We first discuss the dynamics of liquids in the high-temperature Arrhenius regime, where transition state theory is formally applicable. We then summarize the evolution of the entropy theory from a qualitative framework for organizing and interpreting temperature-dependent viscosity data by Kauzmann to the formulation of a hypothetical “ideal thermodynamic glass transition” by Gibbs and DiMarzio, followed by seminal measurements linking entropy and relaxation by Bestul and Chang and the Adam–Gibbs (AG) model of glass formation rationalizing the observations of Bestul and Chang. These developments laid the groundwork for the generalized entropy theory (GET), which merges an improved lattice model of polymer thermodynamics accounting for molecular structural details and enabling the analytic calculation of the configurational entropy with the AG model, giving rise to a highly predictive model of the segmental structural relaxation time of polymeric glass-forming liquids. The development of the GET has occurred in parallel with the string model of glass formation in which concrete realizations of the cooperatively rearranging regions are identified and quantified for a wide range of polymeric and other glass-forming materials. The string model has shown that many of the assumptions of AG are well supported by simulations, while others are certainly not, giving rise to an entropy theory of glass formation that is largely in accord with the GET. As the GET and string models continue to be refined, these models progressively grow into a more unified framework, and this Perspective reviews the present status of development of this promising approach to the dynamics of polymeric glass-forming liquids.
Based on an equivalent single-conductor (ESC) model of multilayer graphene nanoribbon (MLGNR) interconnects with side contacts, comparative study on their distributed parameters and transmission ...characteristics is performed in this paper. It is found that the number of conducting channels of a metallic MLGNR interconnect is the linear function of its width and Fermi energy, which can be described by an analytical equation. Its equivalent inductance and capacitance in the ESC model can also be characterized by a set of closed-form equations. Furthermore, according to the ITRS projection, transmission performance of the MLGNR interconnects with different contacts are predicted and compared with their Cu and carbon nanotube counterparts at different technology nodes. Also, some numerical results prove that MLGNR interconnects can provide better performance than Cu wires in particular at intermediate level. Even with the maximum crosstalk impacts considered, the advantage of MLGNR interconnects over Cu wires can still be kept.
This paper presents a differential microwave microfluidic sensor based on the microstrip complementary split-ring resonator (MCSRR) structure for liquid characterization. At the resonance, the ...electric field concentrates along the slot, where the microfluidic channel is located. As the liquid sample is injected, the corresponding reflection coefficient is changed, while the reference response is unaffected. The relative permittivity and loss tangent of the liquid can be extracted from the variations in the resonant frequency and quality factor. A prototype of the proposed sensor is fabricated and measured for functionality validation. The proposed sensor exhibits a high sensitivity of 0.626% on average and is capable of suppressing unwanted environmental influences.
We study the photoelectric current generated by a driving light with nonclassical photon statistics. Due to the nonclassical input photon statistics, it is no longer enough to treat the driving light ...as a planar wave as in classical physics. We make a quantum approach to study such problems, and find that: when the driving light starts from a coherent state as the initial state, our quantum treatment well returns the quasi-classical driving description; when the the driving light is a generic state with a certain P function, the full system dynamics can be reduced as the P function average of many 'branches'-in each dynamics branch, the driving light starts from a coherent state, thus again the system dynamics can be obtained in the above quasi-classical way. Based on this quantum approach, it turns out the different photon statistics does make differences to the photoelectric current. Among all the classical light states with the same light intensity, we prove that the input light with Poisson statistics generates the largest photoelectric current, while a nonclassical sub-Poisson light could exceed this classical upper bound.
The adrenal gland is a vital endocrine organ, and adrenal steroid synthesis and secretion are closely regulated by the hypothalamic–pituitary–adrenal (HPA) axis in response to various stimuli. ...Surgery or trauma can activate the HPA axis and induce the secretion of cortisol. Different cortisol responses vary with the grade of surgery. Perioperative medications have the potential to decrease the cortisol level in the body, and both excessive and insufficient cortisol levels after surgery are disadvantageous. The effect of perioperative medications on the HPA response to surgery can be divided into three levels: “adrenal insufficiency (AI)”, “stress response inhibition”, and “uncertainty”. The clinical presentation of AI includes fatigue, nausea, vomiting, abdominal pain, muscle cramps, hypotension, hypovolemic shock and prerenal failure, which may result in fatal consequences. Stress response inhibition can reduce postoperative complications, such as pain and cognitive dysfunction. This is protective to patients during perioperative and postoperative periods. The aim of the present review is to shed light on current evidence regarding the exact effects and mechanisms of perioperative medications on the HPA response to surgical injury and provide the applicable guidance on clinical anesthesia.
•Etomidate-induced AI occurred centrally in critically ill patients and the inhibition of steroidogenesis occurred at the level of the adrenal gland.•Both prolonged and acute routes of opioids can induce AI, and the inhibition of the HPA axis occurred mainly at the hypothalamic level.•Perioperative injection of glucocorticoid via the conventional route and dose can induce AI with a long-term recovery, but the clinical symptoms are atypical and easily ignored by anesthesiologists.•Prolonged intravenous infusion of α2-adrenoceptor agonists in children carries the risk of transient AI.
Origami technology has applications in diverse areas, such as metamaterials, space structures, and haptic interfaces due to the low-cost manufacturing, rapid assembly, and compact structures. ...Existing origami robots, however, often lack variable stiffness due to the intrinsic properties of conventional origami structures made of rigid facets and flexible joints. In this article, we present a design of magnetorheological (MR) fluid-filled origami joints with variable stiffness characteristics. Compared with existing approaches to realize controllable origami joints stiffness, our proposed method has the advantage of magnetically remote control. To predict the joint stiffness under different magnetic flux densities, we derive a theoretical model and calibrate it by test. Subsequently, to demonstrate MR fluid-filled origami joints can apply in more complex origami structures, we design a modified thick Yoshimura structure and a Kresling structure that can achieve stiffness enhancement of 59.2 and 83.6%, respectively. Also, we introduce jamming behavior into the joint to achieve the same capability of variable stiffness while utilizing a relatively weak magnetic setup. Additionally, we fill MR fluid into the origami facets to develop an origami robot that can carry loads while crawling on flat ground and climbing on an inclined surface.
The concept of graphene-based two-dimensional leaky-wave antenna (LWA), allowing both frequency tuning and beam steering in the terahertz band, is proposed in this paper. In its design, a graphene ...sheet is used as a tuning part of the high-impedance surface (HIS) that acts as the ground plane of such 2-D LWA. It is shown that, by adjusting the graphene conductivity, the reflection phase of the HIS can be altered effectively, thus controlling the resonant frequency of the 2-D LWA over a broad band. In addition, a flexible adjustment of its pointing direction can be achieved over a wide range, while keeping the operating frequency fixed. Transmission-line methods are used to accurately predict the antenna reconfigurable characteristics, which are further verified by means of commercial full-wave analysis tools.
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