Tunable Metamaterial Absorber Based on Archimedean Spiral-Shaped Structure

In recent times, the Archimedean spiral structure has been considered as a promising design element in construction for specific purposes and opening up new possibilities in various applications. Its distinctive geometry exhibits a continuous growth pattern with a constant separation between its successive turns. One notable application of the Archimedean spiral structure in metamaterial absorbers is in achieving broadband absorption. This paper presents a comprehensive simulation of a tunable metamaterial absorber with an Archimedean spiral structure in the frequency range of 60 to 600 terahertz. The absorber's absorption spectrum is controlled by temperature variations that induce changes in the conductivity of vanadium dioxide. The absorber is composed of three layers: a bottom layer made of gold, a middle layer consisting of vanadium dioxide, and an upper layer is constructed using a gold cylinder, from which the Archimedean spiral with the same thickness as the gold is subtracted. This research provides valuable insights into the design and optimization of tunable metamaterial absorber

Rise time of proton cut-off energy in 2D and 3D PIC simulations

The Target Normal Sheath Acceleration (TNSA) regime for proton acceleration by laser pulses is experimentally consolidated and fairly well understood. However, uncertainties remain in the analysis of particle-in-cell (PIC) simulation results. The energy spectrum is exponential with a cut-off, but the maximum energy depends on the simulation time, following different laws in two and three dimensional (2D, 3D) PIC simulations, so that the determination of an asymptotic value has some arbitrariness. We propose two empirical laws for rise time of the cut-off energy in 2D and 3D PIC simulations, suggested by a model in which the proton acceleration is due to a surface charge distribution on the target rear side. The kinetic energy of the protons that we obtain follows two distinct laws, which appear to be nicely satisfied by PIC simulations. The laws depend on two parameters: the scaling time, at which the energy starts to rise, and the asymptotic cut-off energy. The values of the cut-off energy, obtained by fitting the 2D and 3D simulations for the same target and laser pulse, are comparable. This suggests that parametric scans can be performed with 2D simulations, since 3D ones are computationally very expensive. In this paper, the simulations are carried out for $a_0=3$ with the PIC code ALaDyn by changing the target thickness $L$ and the incidence angle $\alpha$. A monotonic dependence, on $L$ for normal incidence and on $\alpha$ for fixed $L$, is found, as in the experimental results for high temporal contrast pulses

Bacteriostatic Effects of Apatite-Covered Ag/AgBr/TiO2 Nanocomposite in the Dark: Anomaly in Bacterial Motility

In this paper, we report a unique property of inactivating Gram-positive/negative bacteria in the dark via apatite-covered Ag/AgBr/TiO2 nanocomposites (AAAT). We demonstrate that the inactivation mechanism is bacteriostatic based on the cellular integrity and motility of bacteria, low toxicity and high durability of AAAT. From straight observations, the catalytic loading affects the bacterial replication and cell envelope as well as inducing an anomaly in bacterial motility (continuous rotation) for both types of bacteria. Both simulation and experimental analyses suggest that the anomaly could be due to posterior intracellular signals rather than purely mechanical effects (e.g., size enlargement and motility retardation). Provoked by chemomechanical stimuli, these signals increase the frequency of flagellar tumbling and eventually entangle the bacteria

Serotype-specific mortality from invasive Streptococcus pneumoniae disease revisited

BACKGROUND: Invasive infection with Streptococcus pneumoniae (pneumococci) causes significant morbidity and mortality. Case series and experimental data have shown that the capsular serotype is involved in the pathogenesis and a determinant of disease outcome. METHODS: Retrospective review of 464 cases of invasive disease among adults diagnosed between 1990 and 2001. Multivariate Cox proportional hazard analysis. RESULTS: After adjustment for other markers of disease severity, we found that infection with serotype 3 was associated with an increased relative risk (RR) of death of 2.54 (95% confidence interval (CI): 1.22–5.27), whereas infection with serotype 1 was associated with a decreased risk of death (RR 0.23 (95% CI, 0.06–0.97)). Additionally, older age, relative leucopenia and relative hypothermia were independent predictors of mortality. CONCLUSION: Our study shows that capsular serotypes independently influenced the outcome from invasive pneumococcal disease. The limitations of the current polysaccharide pneumococcal vaccine warrant the development of alternative vaccines. We suggest that the virulence of pneumococcal serotypes should be considered in the design of novel vaccines

Spin-Forbidden Formation of Amide Molecules in the Interstellar Medium

In this study, two-state spin-forbidden mechanisms are proposed for the barrierless formation of amide isomers in the C2H5NO family of molecules. This family belongs to the first level of complexity among the molecules with peptide bond that are precursors to proteins, which are building blocks of life, and therefore are highly relevant to astrochemistry and astrobiology. Our density functional theory study demonstrates the significance of spin-forbidden pathways in the formation of acetamide (CH3CONH2), N-methyl-formamide (CH3NHCHO), and acetimidic acid (CH3COHNH) from the acetaldehyde, imidogen, formamide, and methylene reactants. Considering the rate constants of analogous reactions in the interstellar medium (ISM), we anticipate that the detected abundances of acetamide and N-methyl-formamide in the Sagittarius B2 North region can be rationalized by the suggested formation pathways. The proposed mechanism also predicts the synthesis of acetimidic acid, motivating future observational efforts to identify this molecule in the ISM

Determination of Contamination Ratio and Risk Factors Associated with Alveolar and Cystic Echinococcosis by ELISA and Portable Ultrasonography in Moghan Plain, Ardabil Province, Northwest of Iran

Background & objectives: Alveolar and cystic echinococcosis (CE and AE) are caused by the larval stages of Echinococcus multilocularis and Echinococcus granolosus, respectively. This study was conducted to determine the spread of human AE and CE diseases among the tribes and livestock breeders and farmers in the Moghan plain. The prevalence of infection (CE and AE) significantly increases with a rise in age. Methods: In this study, using ELISA and HCF-Ag (raw liquid antigen of hydatid cyst) was used for the first time to perform screening, and then the prevalence of cystic echinococcosis and alveolar echinococcosis was evaluated by specific anti-genes Ag-5 and EM2+, respectively. A total of 2003 serum samples were collected randomly from normal populations of five different areas of Moghan plain. In the first stage, serum screening was tested using an enzyme-linked immunosorbent assay and HCF-Ag. After that, the serology of all sera was evaluated by ELISA and specific antigens for alveolar and cystic Echinococcus. Results: From 2003 samples, 24 serum samples were (1.19%) AE-positive. Infection was higher in men than women (2.1% vs. 0.6%). The age group of 5-19years had the lowest infection rate and the age group 40- 59 years had the highest infection rate (2%). In the case of cystic ecinococcosis, 164 serum samples were positive for Ag-5 specific antigen, i.e. 7.6% infection, and 156 serum samples were positive for Ag-B-specific antigen. Conclusion: The findings showed that the highest infection rate was found in the Boran and Eivazlou (Palanglou) regions of Moghan plain and the lowest level of human infection was reported in Parsabad region (Nadar-kandi and Agh-ghabagh). In areas with higher contamination, the risk factor associated with CE and AE were the type of water used, the method of washing edible and wild vegetables, occupation and having or not having knowledge of hydatid disease. The infection of Moghan region dogs is one of the main indicators and potential risk factors for human infection

Second Order Saddle Points Dictate the Products of Electrocyclic Reactions

The conventional understanding of chemical reactions, primarily focused on one-dimensional minimum energy pathways, has been expanded in recent years to include phenomena like second order saddle points or bifurcations. In this study, we explore these intricacies within the context of electrocyclizations and present a novel approach that moves beyond the traditional view of activation barriers, revealing that second order saddle points are crucial in dictating the competition between disrotatory and conrotatory pathways. Our findings suggest opportunities to manipulate the competition between conrotatory and disrotatory pathways through geometric constraints, fundamentally altering the connectivity of the potential energy surface. Through the development of a minimal model Hamiltonian, we illustrate the generality of our findings and highlight the importance of the multi-reference nature of states near the second order saddle point. This study emphasizes the necessity of multi-reference methods and the need to conduct higher-dimensional explorations for competing pathways. It opens new avenues for systematic control of selectivity in electrocyclic reactions and offers a rich perspective on the complex interplay of steric considerations and electronic correlations