Heating and Cooling Dynamics of Carbon Nanotubes Observed by Temperature-Jump Spectroscopy and Electron Microscopy

Microscopy imaging indicates that in situ carbon nanotubes (CNTs) irradiation with relatively low dosages of infrared radiation results in significant heating of the tubes to temperatures above 1300 K. Ultrafast temperature-jump experiments reveal that CNTs laser-induced heating and subsequent cooling in solution take tens and hundreds of picoseconds, respectively. Given the reported transient behavior, these observations suggest novel ways for a T-jump methodology, unhindered by the requirement for excitation of water in the study of biological structures. They also provide the rate information needed for optimization of photothermal therapy that invokes infrared irradiation to selectively heat and annihilate cancer cells

Scanning ultrafast electron microscopy

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability

4D Scanning Ultrafast Electron Microscopy: Visualization of Materials Surface Dynamics

The continuous electron beam of conventional scanning electron microscopes (SEM) limits the temporal resolution required for the study of ultrafast dynamics of materials surfaces. Here, we report the development of scanning ultrafast electron microscopy (S-UEM) as a time-resolved method with resolutions in both space and time. The approach is demonstrated in the investigation of the dynamics of semiconducting and metallic materials visualized using secondary-electron images and backscattering electron diffraction patterns. For probing, the electron packet was photogenerated from the sharp field-emitter tip of the microscope with a very low number of electrons in order to suppress space–charge repulsion between electrons and reach the ultrashort temporal resolution, an improvement of orders of magnitude when compared to the traditional beam-blanking method. Moreover, the spatial resolution of SEM is maintained, thus enabling spatiotemporal visualization of surface dynamics following the initiation of change by femtosecond heating or excitation. We discuss capabilities and potential applications of S-UEM in materials and biological science

Optimal Parameters for Nonlinear Hirota-Satsuma Coupled KdV System by Using Hybrid Firefly Algorithm with Modified Adomian Decomposition

In this paper, several parameters of the non-linear Hirota-Satsuma coupled KdV system were estimated using a hybrid between the Firefly Algorithm (FFA) and the Modified Adomian decomposition method (MADM). It turns out that optimal parameters can significantly improve the solutions when using a suitably selected fitness function for this problem. The results obtained show that the approximate solutions are highly compatible with the exact solutions and that the hybrid method FFA_MADM gives higher efficiency and accuracy compared to the classic MADM method

Improved Operational Matrices of DP-Ball Polynomials for Solving Singular Second Order Linear Dirichlet-type Boundary Value Problems

Solving Dirichlet-type boundary value problems (BVPs) using a novel numerical approach is presented in this study. The operational matrices of DP-Ball Polynomials are used to solve the linear second-order BVPs. The modification of the operational matrix eliminates the BVP\u27s singularity. Consequently, guaranteeing a solution is reached. In this article, three different examples were taken into consideration in order to demonstrate the applicability of the method. Based on the findings, it seems that the methodology may be used effectively to provide accurate solutions

Anodyne therapy versus exercise therapy in improving the healing rates of venous leg ulcer

Objective: The purpose of this study was to determine the best physical therapy program to increase wound healing rates in patients suffering from venous leg ulcer.Methods: Forty patients who had venous leg ulcer for more than 4 weeks and not respondent well to medical treatment. Patients were classified into 4 equal groups 10 of each, Group (1): received 40 minute of monochromatic infrared energy (MIRE), Group (2): received 40 minutes of exercise program consisted of stretching and resisted exercise (RE), Group (3): received 20 minutes of exercise in addition to 20 minutes of resisted exercise (MIRE/RE), and group (4): control group which received conventional therapy of the ulcer. All groups received treatment 5days per week for 12days. Measurements of ulcer surface area and PUSH scale were conducted before treatment, post 6 days of treatment, and after 12 days of treatment.Results: The one way analysis of variance was used to compare ulcer surface area and PUSH score which revealed that both treatment groups (MIRE and RE) had significant (P< 0.05) decrease in ulcer surface area and PUSH scale after 6 and 12days post application of treatment. On the other hand, the combination of MIRE and RE showed a highly significant decrease in ulcer surface area and PUSH score when compared with control or with individual treatment.Conclusion: The results of this study suggest that combination of MIRE to RE is more effective than individual treatment to enhance the healing rate of venous ulcer of the leg.

Electrical and Magnetic Properties of Mn-Bi-Sb Alloys

MnBi1-xSbx alloys were prepared by the conventional melt technique. The Seebeck coefficient (S), electrical resistivity (ρ), and magnetic susceptibility (c) were measured at various temperatures ranging from ~100 to 400 K. The electrical resistivity of x £ 0.15 shows both semiconducting and metallic behavior depending on temperature and Sb content, whereas samples x 3 0.2 have only semiconductor behavior in all the temperature range. The negative sign of the Seebeck coefficient increases, i.e., the positivity decreases with the increasing Sb content. The magnetic susceptibility (χ) shows that alloys undergo ferro-paramagnetic transition at a certain temperature (TC) and the TC values decrease with increasing Sb content. From thermoelectric measurements and electronic thermal conductivity calculated, it was observed that Sb doping increases the power factor (PF) and the figure of merit (ZT). Thus, Sb content plays an essential role in making these alloys applicable in the thermoelectric industry

Next-generation HVAC: Prospects for and limitations of desiccant and membrane-based dehumidification and cooling

Recently, next-generation HVAC technologies have gained attention as potential alternatives to the conventional vapor-compression system (VCS) for dehumidification and cooling. Previous studies have primarily focused on analyzing a specific technology or its application to a particular climate. A comparison of these technologies is necessary to elucidate the reasons and conditions under which one technology might outperform the rest. In this study, we apply a uniform framework based on fundamental thermodynamic principles to assess and compare different HVAC technologies from an energy conversion standpoint. The thermodynamic least work of dehumidification and cooling is formally defined as a thermodynamic benchmark, while VCS performance is chosen as the industry benchmark against which other technologies, namely desiccant-based cooling system (DCS) and membrane-based cooling system (MCS), are compared. The effect of outdoor temperature and humidity on device performance is investigated, and key insights underlying the dehumidification and cooling process are elucidated. In spite of the great potential of DCS and MCS technologies, our results underscore the need for improved system-level design and integration if DCS or MCS are to compete with VCS. Our findings have significant implications for the design and operation of next-generation HVAC technologies and shed light on potential avenues to achieve higher efficiencies in dehumidification and cooling applications