External Thermal Perturbations Research Articles

Manipulation of fractionalized charge in the metastable topologically entangled state of a doped Wigner crystal

Metastability of many-body quantum states is rare and still poorly understood. An exceptional example is the low-temperature metallic state of the layered dichalcogenide 1T-TaS2 in which electronic order is frozen after external excitation. Here we visualize the microscopic dynamics of injected charges in the metastable state using a multiple-tip scanning tunnelling microscope. We observe non-thermal formation of a metastable network of dislocations interconnected by domain walls, that leads to macroscopic robustness of the state to external thermal perturbations, such as small applied currents. With higher currents, we observe annihilation of dislocations following topological rules, accompanied with a change of macroscopic electrical resistance. Modelling carrier injection into a Wigner crystal reveals the origin of formation of fractionalized, topologically entangled networks, which defines the spatial fabric through which single particle excitations propagate. The possibility of manipulating topological entanglement of such networks suggests the way forward in the search for elusive metastable states in quantum many body systems.

Certain Mechanisms of Thermostress Field Variations in Layered Pavement Structures

Refined mechanical and mathematical models of pavement deformation and strength were constructed for different structural schemes, materials, and impact of transport and thermomechanical loads. The final stage of computer analysis resulted in the construction of mathematical models with finite element approximation in the form of linear algebraic equations of higher order. They can be used to analyze the initiation of fractures under the action of time-varying temperature perturbations in view of changes in the stiffness characteristics of the pavement material. The distribution of temperature fields in the pavement structure, irrespective of its comparatively simple geometric schemes and shapes, causes the functions of thermal perturbation, involved in thermoelastic phenomena, to become much complicated. It makes those phenomena nontrivial and their simulation labor-intensive. The medium of temperature field evolution is nonuniform layered, and its simulation at chosen thermomechanical characteristics and sizes of an examined area belongs to the class of singularly perturbed. On the external thermal perturbation, the heat flow is not managed to penetrate from the boundary surface deep into the bulk and the temperature field would be noticeably changed only in a narrow zone, acquiring the form of the so-called boundary effect. The temperature function not only essentially increases in the boundary zone but also its gradients acquire high values, i.e., the derivatives with respect to spatial variables that generate intensive stress fields. The effects of rearrangement of temperature and stress fields in nonuniform layered pavement structures under daily and seasonal changes in environmental temperature are examined.

Thermomagnetic resonance affects cancer growth and motility.

The fight against a multifaceted incurable disease such as cancer requires a multidisciplinary approach to overcome the multitude of molecular defects at its origin. Here, a new thermophysical biochemical approach has been suggested and associated with the use of electromagnetic fields to control the growth of cancer cells. In particular, thermodynamic analysis of the heat transfer is developed in correlation with cellular parameters such as the volume/area ratio. We propose that the electromagnetic wave, at the specific frequency calculated as the characteristic response time of any cell type to the external thermal perturbation, can affect resonant intracellular molecular oscillations. The biochemical model hypothesizes that microtubules are stabilized, and the impact is predicted on cell growth, migration and mitochondrial activity. Experimental validation of the theoretical results shows that the thermodynamic analysis allows the application of the specific electromagnetic field able to decrease cancer cell invasion and proliferation.

Degradation of the current-carrying capacity of low-temperature superconducting composites under the action of thermal perturbations

The stability of transport current introduced into a niobium titanium superconducting composite subjected to an external pulsed thermal perturbation has been studied. Stable states have been theoretically analyzed by solving Fourier and Maxwell equations that describe the thermoelectrodynamic states of lowtemperature superconductors with flux creep. It has been shown that, if the transport current is permanently introduced, subcritical thermal perturbations, i.e., perturbations that do not take the composite to a normal state provided that the current does not exceed the quench current, may result in the appearance of unstable current states. The higher the energy of the external thermal perturbation, the lower the instability onset current. It has been found that the degradation of the current-carrying capacity of the superconducting composite is due to intense heat release inside the superconductor, which is initiated by the thermal perturbations, and depends on the current input rate, the instant of time the current input is terminated, and cooling conditions.

Time-resolved single-photon detection module based on silicon photomultiplier: A novel building block for time-correlated measurement systems

We present the design and preliminary characterization of the first detection module based on Silicon Photomultiplier (SiPM) tailored for single-photon timing applications. The aim of this work is to demonstrate, thanks to the design of a suitable module, the possibility to easily exploit SiPM in many applications as an interesting detector featuring large active area, similarly to photomultipliers tubes, but keeping the advantages of solid state detectors (high quantum efficiency, low cost, compactness, robustness, low bias voltage, and insensitiveness to magnetic field). The module integrates a cooled SiPM with a total photosensitive area of 1 mm(2) together with the suitable avalanche signal read-out circuit, the signal conditioning, the biasing electronics, and a Peltier cooler driver for thermal stabilization. It is able to extract the single-photon timing information with resolution better than 100 ps full-width at half maximum. We verified the effective stabilization in response to external thermal perturbations, thus proving the complete insensitivity of the module to environment temperature variations, which represents a fundamental parameter to profitably use the instrument for real-field applications. We also characterized the single-photon timing resolution, the background noise due to both primary dark count generation and afterpulsing, the single-photon detection efficiency, and the instrument response function shape. The proposed module can become a reliable and cost-effective building block for time-correlated single-photon counting instruments in applications requiring high collection capability of isotropic light and detection efficiency (e.g., fluorescence decay measurements or time-domain diffuse optics systems).

Detection of the adsorption of water monolayers through the ion oscillation frequency in the magnesium oxide lattice by means of low energy electron diffraction

We investigate the variation of the oscillation frequency of the Mg2+ and O2− ions in the magnesium oxide lattice due to the interactions of the surface with water monolayers by means of Low Energy Electron Diffraction. Our key result is a new technique to determine the adsorbate vibrations produced by the water monolayers on the surface lattice as a consequence of their change in the surface Debye temperature and its chemical shift. The latter was systematically investigated for different annealing times and for a constant external thermal perturbation in the range of 110–300 K in order to accomplish adsorption or desorption of water monolayers in the surface lattice.

Heat evolution due to pulsed thermal perturbations in superconducting composites with a nonuniformly distributed current

Dissipative processes in superconducting composites under the action of current and pulsed thermal perturbations are studied. Results obtained are compared with the predictions following from the existing theory of thermal stabilization of superconducting composites. It is shown that, if the current is nonuniformly distributed over the composite's cross section and the thermal perturbations are short, intense additional energy dissipation may arise both before and after the occurrence of thermomagnetic instability. Associated Joule heat evolution may substantially exceed the thermal loss predicted by the adopted theory of thermal stabilization throughout the temperature range of the composite. Additional dissipation in composite superconductors narrows the range of stable superconductivity, especially when the current is applied continuously, even if external thermal perturbations are weak.

Nonisothermal conditions for limitation of the current injected into a composite superconductor exposed to pulsed perturbations

This study is devoted to solving one of the major problems of superconductivity engineering — the thermal stability of the superconducting state of a composite superconductor. The formulated problem is analyzed most comprehensively with allowance for the nonisothermal dynamics of the magnetic flux inside the composite. This approach allowed us to formulate the main aspects of the behavior under the simultaneous influence of various perturbing factors, i.e., varying current and external thermal perturbation.

Identification of nonsteady heat fluxes by using the output signals of thin-membrane gardon-type sensors

An operator comparing the nonsteady output signals of a sensor to the characteristics of an external thermal perturbation is constructed.

Analysis of nonsteady thermal model of a thinmembrane sensor of heat-flux density

An operator comparing the nonsteady output signal of a sensor to the characteristics of the external thermal perturbation is constructed.

Penetration of external thermal perturbations into homeothermic organisms, part II (author's transl)

The penetration of external thermal perturbations into parts of the body with different surface curvatures is discussed. For areas with approximate rotational symmetry a theoretical treatment by means of the variation theory is possible. the mean surface curvature on the rotation axis is constant. Therefore the solution of the partial differential equation given in part I can be applied without change, if the correct value of the mean surface curvature of the body part is used. Also for an exponential form of alteration of the heat loss a solution is deduced. Combining small parts of sudden and exponential changes of heat loss it is possible to approximate almost any reasonable type of external thermal perturbation. Superimposing single solutions with different parameters allows then a complete solution of the problem. The importance of the theoretical results in view of homeothermia is discussed.