Slow Temperature Changes Research Articles

Comparative study of the performance of quantum annealing and simulated annealing.

Relations of simulated annealing and quantum annealing are studied by a mapping from the transition matrix of classical Markovian dynamics of the Ising model to a quantum Hamiltonian and vice versa. It is shown that these two operators, the transition matrix and the Hamiltonian, share the eigenvalue spectrum. Thus, if simulated annealing with slow temperature change does not encounter a difficulty caused by an exponentially long relaxation time at a first-order phase transition, the same is true for the corresponding process of quantum annealing in the adiabatic limit. One of the important differences between the classical-to-quantum mapping and the converse quantum-to-classical mapping is that the Markovian dynamics of a short-range Ising model is mapped to a short-range quantum system, but the converse mapping from a short-range quantum system to a classical one results in long-range interactions. This leads to a difference in efficiencies that simulated annealing can be efficiently simulated by quantum annealing but the converse is not necessarily true. We conclude that quantum annealing is easier to implement and is more flexible than simulated annealing. We also point out that the present mapping can be extended to accommodate explicit time dependence of temperature, which is used to justify the quantum-mechanical analysis of simulated annealing by Somma, Batista, and Ortiz. Additionally, an alternative method to solve the nonequilibrium dynamics of the one-dimensional Ising model is provided through the classical-to-quantum mapping.

Monte Carlo simulation of temperature-induced reversible morphological changes between sphere and vesicle formed by AB diblock copolymers

Temperature-induced reversible morphological changes of micelles formed by AB diblock copolymers in a selective solvent for A blocks was studied through Monte Carlo simulation. When only hydrophobic B blocks are temperature-sensitive, the micelle morphology changes from sphere at high temperature to vesicle with a decrease in temperature. When the system was heated back to high temperature, the vesicles transform into spheres, indicating reversible morphological changes with temperature. However, the simulation results show that the pathways of morphological changes between sphere and vesicle depend on temperature change rate. The pathway of the sphere changing into vesicle under a quenching process is different from the pathway of the vesicle changing into sphere when the system was directly heated to the higher temperature. Moreover, the time consumed in the simulation for vesicle transformation into sphere upon heating is significantly shorter than that for the reverse process upon quenching. By contrast, when changing the temperature gradually, the pathways of morphological transitions from sphere to vesicle and from vesicle to sphere are almost identical. Moreover, the time consumed in the simulation for the annealing and gradual heating processes are nearly the same. This pathway differences observed when directly and gradually changing the temperature of the system are further elucidated by investigating the contact number variation between B blocks and solvents with simulation time. On the other hand, when the hydrophilic blocks and hydrophobic blocks are both temperature-sensitive, the introduction of the temperature-sensitivity of hydrophilic blocks hinders the morphological transition from sphere to vesicle under annealing conditions, and only larger spheres can be obtained after the annealing process when the degree of temperature-sensitivity of blocks A is rather high. Meanwhile, the simulation results show that the morphological transitions are still reversible under a slow temperature change rate when the hydrophilic blocks and hydrophobic blocks are both temperature-sensitive.

Modelling of photo-thermal control of biological cellular oscillators.

We study the transient dynamics of biological oscillators subjected to brief heat pulses. A prospective well-defined experimental system for thermal control of oscillators is the peripheral electroreceptors in paddlefish. Epithelial cells in these receptors show spontaneous voltage oscillations which are known to be temperature sensitive. We use a computational model to predict the effect of brief thermal pulses in this system. In our model thermal stimulation is realized through the light excitation of gold nanoparticles delivered in close proximity to epithelial cells and generating heat due to plasmon resonance. We use an ensemble of modified Morris-Lecar systems to model oscillatory epithelial cells. First, we validate that the model quantitatively reproduces the dynamics of epithelial oscillations in paddlefish electroreceptors, including responses to static and slow temperature changes. Second, we use the model to predict transient responses to short heat pulses generated by the light actuated gold nanoparticles. The model predicts that the epithelial oscillators can be partially synchronized by brief 5 - 15 ms light stimuli resulting in a large-amplitude oscillations of the mean field potential.

Intrinsic creep of a granular column subjected to temperature changes

Minute external perturbations, such as temperature variations, can lead to a creep of the fragile structures that are the granular piles. We report a study, resolved in space and time, of the dynamics associated with the slow compaction of a granular column submitted to thermal cycles. Avoiding the thermal dilations of the container, we observe that the material still creeps, even in the absence of external mechanical perturbations. The latter intrinsic creep of the material exhibits several surprising features: the compaction of the material is not homogeneous along the column height, and sudden collapses involve the entire system even if one could expect arches to screen the mechanical interaction between regions far apart from one another. In addition, the analysis of the dependence of the flow rate on the frequency of the temperature cycles suggests that the creep is mainly induced by the propagation of the temperature profile, slow temperature changes being less efficient than rapid ones in making the material flow.

Disturbed sensory perception of changes in thermoalgesic stimuli in patients with small fiber neuropathies

The assessment of functional deficits in small fibre neuropathies (SFN) requires using ancillary tests other than conventional neurophysiological techniques. One of the tests with most widespread use is thermal threshold determination, as part of quantitative sensory testing. Thermal thresholds typically reflect one point in the whole subjective experience elicited by a thermal stimulus. We reasoned that more information could be obtained by analyzing the subjective description of the ongoing sensation elicited by slow temperature changes (dynamic thermal testing, DTT). Twenty SFN patients and 20 healthy subjects were requested to describe, by using an electronic visual analog scale system, the sensation perceived when the temperature of a thermode was made to slowly change according to a predetermined pattern. The thermode was attached to the left ventral forearm or the distal third of the left leg and the stimulus was either a monophasic heat or cold stimuli that reached 120% of pain threshold and reversed to get back to baseline at a rate of 0.5°C/s. Abnormalities seen in patients in comparison to healthy subjects were: (1) delayed perception of temperature changes, both at onset and at reversal, (2) longer duration of pain perception at peak temperature, and (3) absence of an overshoot sensation after reversal, ie, a transient perception of the opposite sensation before the temperature reached again baseline. The use of DTT increases the yield of thermal testing for clinical and physiological studies. It adds information that can be discriminant between healthy subjects and SFN patients and shows physiological details about the process of activation and inactivation of temperature receptors that may be abnormal in SFN.

Malaria epidemics and the influence of the tropical South Atlantic on the Indian monsoon

The influence of relatively slow changes in sea surface temperature on regional climate variability can provide a basis for medium-term (seasonal to decadal) prediction of many environmental factors. Research now shows that the sea surface temperature in the tropical South Atlantic can act as a dominant driver of rainfall variability, and hence outbreaks of malaria in northwest India.

The acute and chronic effect of low temperature on survival, heart rate and neural function in crayfish (<i>Procambarus clarkii</i>) and prawn (<i>Macrobrachium rosenbergii</i>) species

The effect of acute and chronic cold exposure on heart rate (HR) and neuronal function in crayfish Procambarus clarkii and prawns Macrobrachium rosenbergii was addressed. This is particularly important since prawn farms of this species are used for aquaculture in varied climates world wide. The success of P. clarkii as an invasive species throughout the world may in part be due to their ability to acclimate to cold and warm habitats. A set of experiments was devised to address the physiological abilities of these species in managing rapid changes to cold environments as well as their ability to respond to sensory stimuli by using behavior and a bioindex of HR. Prawns died within 2 hrs when moved from 21℃ to 5℃. Crayfish reduced their HR but survived for at least a week with this rapid change. Changes in temperature of 5℃ each week resulted in death of the prawns when 10℃ was reached. Some died at 16℃ and some lasted at 10℃ for 1 day before dying. Crayfish remained responsive to sensory stimuli and survived with either rapid or slow changes in temperature from 21℃ to 5℃. Primary sensory neurons were rapidly inhibited in prawns with an acute change to 5℃, where as in crayfish the activity was reduced but not completely inhibited. An induced sensory-CNS-motor circuit elicited activity at neuromuscular junctions in prawns and crayfish at 21℃ but with acute changes to 5℃only in crayfish was the circuit functionally intact. The ability to survive rapid environmental temperature changes will impact survival and in time the distribution of a species. The significance of these findings is that they may account, in part, for the wide ecological distribution of P. clarkii as compared to M. rosenbergii. The invasiveness of organisms, as for P. clarkii, is likely linked to the physiological robustness to acute and chronic temperature changes of habitats.

Symmetric miniaturized heating system for active microelectronic devices

To qualify interconnect technologies such as microelectronic fine wire bonds for mass production of integrated circuit (IC) packages, it is necessary to perform accelerated aging tests, e.g., to age a device at an elevated temperature or to subject the device to thermal cycling and measure the decrease of interconnect quality. There are downsides to using conventional ovens for this as they are relatively large and have relatively slow temperature change rates, and if electrical connections are required between monitoring equipment and the device being heated, they must be located inside the oven and may be aged by the high temperatures. Addressing these downsides, a miniaturized heating system (minioven) is presented, which can heat individual IC packages containing the interconnects to be tested. The core of this system is a piece of copper cut from a square shaped tube with high resistance heating wire looped around it. Ceramic dual in-line packages are clamped against either open end of the core. One package contains a Pt100 temperature sensor and the other package contains the device to be aged placed in symmetry to the temperature sensor. According to the temperature detected by the Pt100, a proportional-integral-derivative controller adjusts the power supplied to the heating wire. The system maintains a dynamic temperature balance with the core hot and the two symmetric sides with electrical connections to the device under test at a cooler temperature. Only the face of the package containing the device is heated, while the socket holding it remains below 75 degrees C when the oven operates at 200 degrees C. The minioven can heat packages from room temperature up to 200 degrees C in less than 5 min and maintain this temperature at 28 W power. During long term aging, a temperature of 200 degrees C was maintained for 1120 h with negligible resistance change of the heating wires after 900 h (heating wire resistance increased 0.2% over the final 220 h). The device is also subjected to 5700 thermal cycles between 55 and 195 degrees C, demonstrating reliability under thermal cycling.

Characterization of the Resistive Transition of ${\rm MgB}_{2}$ Nanogranular Films by Current Noise Analysis

An original model for the interpretation of the noise produced during the resistive transition of disordered granular superconductive films, induced by a slow temperature change, has been recently developed and tested on MgB2 films. Both the amplitude and frequency behavior of the noise power spectrum, simulated on the basis of this model, are in very good agreement with the experimental data, practically without the introduction of adjustable parameters. The model is based on the onset of correlated transitions of large sets of grains, forming resistive layers through the film cross-section area during the transition process. The strong non-linear behavior and correlation of the grains produces abrupt resistance variations, giving rise to the large noise, of the 1/f3 type, observed in experiments. Presently this model is tested under more general conditions, producing the resistive transition under an external magnetic field. The results show that the field reduces the grain critical current density but does not change the mechanism of the transition process. An alternative transition model, based on fluxoids depinning and motion, which would produce a much lower, 1/f type transition noise, can thus be excluded by the present analysis.

Transcriptional expression levels of cell stress marker genes in the Pacific oyster Crassostrea gigas exposed to acute thermal stress

During the annual cycle, oysters are exposed to seasonal slow changes in temperature, but during emersion at low tide on sunny summer days, their internal temperature may rise rapidly, resulting in acute heat stress. We experimentally exposed oysters to a 1-h acute thermal stress and investigated the transcriptional expression level of some genes involved in cell stress defence mechanisms, including chaperone proteins (heat shock proteins Hsp70, Hsp72 and Hsp90 (HSP)), regulation of oxidative stress (Cu-Zn superoxide dismutase, metallothionein (MT)), cell detoxification (glutathione S-transferase sigma, cytochrome P450 and multidrug resistance (MDR1)) and regulation of the cell cycle (p53). Gene mRNA levels were quantified by reverse transcription-quantitative polymerase chain reaction and expressed as their ratio to actin mRNA, used as a reference. Of the nine genes studied, HSP, MT and MDR1 mRNA levels increased in response to thermal stress. We compared the responses of oysters exposed to acute heat shock in summer and winter and observed differences in terms of magnitude and kinetics. A larger increase was observed in September, with recovery within 48 h, whereas in March, the increase was smaller and lasted more than 2 days. The results were also compared with data obtained from the natural environment. Though the functional molecule is the protein and information at the mRNA level only has limitations, the potential use of mRNAs coding for cell stress defence proteins as early sensitive biomarkers is discussed.

Adaptation as a Mechanism for Gain Control in an Insect Thermoreceptor

Adaptation controls the gain of the input-function of the cockroach's cold cell during slowly oscillating changes in temperature. When the oscillation period is long, the cold cell improves its gain for the rate of temperature change at the expense of its ability to code instantaneous temperature. When the oscillation period is brief, however, the cold cell reduces this gain and improves its sensitivity for instantaneous temperature. This type of gain control has an important function. When the cockroach ventures from under cover and into moving air, the cold cell is confronted constantly with brief changes in temperature. To be of any use, a limit in the gain for the rate of change seems to be essential. Without such a limit, the cold cell will always indicate temperature change. The decrease in gain for the rate of change involves an increase in gain for instantaneous temperature. Therefore the animal receives precise information about the temperature at which the change occurs and can seek an area of different temperature. If the cockroach ventures back under cover, the rate of change will become slow. In this situation, a high gain improves the ability to signal slow temperature changes. The cockroach receives the early warning of slow fluctuations or even creeping changes in temperature. A comparison of the cold cell's responses with the temperature measured inside of small, cylindrical model objects indicates that coding characteristic rather than passive thermal effects of the structures enclosing the cold cell are responsible for the observed behavior.

Preventing Refrigerated Foodstuffs in Supermarkets from Being Discarded on Hot Days by MPC

This paper presents an optimization strategy for supermarket refrigeration systems. It deals with one special condition when the extremely high outdoor temperature causes the compressor to saturate, and work at its maximum capacity. In a traditional control, refrigerated foodstuffs inside display cabinets will suffer from a consequential higher temperature storage, which is detrimental to the food quality, and in worst cases they have to be discarded according to the regulation from authorities. This will cause a big economic loss to the shop owner. By utilizing the thermal mass of foodstuffs and their relative slow temperature change, Model Predictive Control (MPC), foreseeing this situation, it will use more compressor power to cool down the foodstuffs in advance, preventing the high temperature storage from happening, thus saving them from being discarded.

Spawning induction and early development of the Caribbean scallops Argopecten nucleus and Nodipecten nodosus

Argopecten nucleus and Nodipecten nodosus are two commercially valuable bivalve species from the Caribbean region, and are interesting candidates for mass culture in the sea based on laboratory production of juvenile “spat” organisms. An experiment of artificial spawning was performed with the two species as the initial part of a study on the feasibility of producing their spat. Stimulation of spawning was carried out, determining the percentages of individuals spawning, response time, numbers of gametes produced, and fertilization of the oocytes. Five external stimuli and eight combinations of those were tested: slow changes in temperature (ST), fast changes in temperature (FT), desiccation ( D), high concentrations of microalgae ( M), exposure to water currents ( C), ST + D, ST + M, ST + C, FT + D, FT + M, FT + C, D + M and D + C. Four internal stimuli were applied, including intragonadal injection of serotonin (Se), dopamine (Da), Da + prostaglandin E 2 (Da + PE 2) and Se + PE 2. The results showed that A. nucleus spawned in response to all 17 stimuli tested, while N. nodosus responded to only eight of these (47%), suggesting that spawning in the first species was more sensitive to both external and internal stimuli. Larger percentages of individuals of A. nucleus spawned, with specially high values (100%) obtained with the ST + M, ST + D and Da stimuli; in N. nodosus, the Da stimulus was the most effective. N. nodosus gave shorter response times to stimuli than A. nucleus, with the shortest times in both scallop species (16 to 32 min) obtained using the internal stimuli. The production of gametes was similar between the two species, with about 5 × 10 9 spermatozoa, and 1.9 × 10 6 oocytes released per individual. A. nucleus produced higher numbers of spermatozoa using the ST + M stimulus, and higher numbers of oocytes using the FT + M, ST + D and Se stimuli; these values did not differ among treatments in N. nodosus. Abnormal spawning was observed in some of the internal stimuli tested, including release of immature gametes, simultaneous release of both male and female gametes, or sole production of male gametes. Fertilization was about 63% for both species, and was not influenced by the type of stimulation used to obtain the gametes. In summary, the most efficient stimuli for inducing the normal spawning of viable gametes in A. nucleus were ST + M and ST + D, and Se + PE 2 in N. nodosus. Early embryonic and larval development in A. nucleus were significantly more rapid than in N. nodosus, while the sizes of early embryos and larvae were similar in both species, and comparable to previous descriptions of scallops' early development.

Die stress characterization in flip chip on laminate assemblies

Minimizing device side die stresses is especially important when multiple copper/low-k interconnect redistribution layers are present. Mechanical stress distributions in packaged silicon die resulting during assembly or environmental testing can be accurately characterized using test chips incorporating integral piezoresistive sensors. In this paper, measurements of thermally induced stresses in flip chip on laminate assemblies are presented. Transient die stress measurements have been made during underfill cure, and the room temperature die stresses in final cured assemblies have been compared for several different underfill encapsulants. In addition, stress variations have been monitored in the assembled flip chip die as the test boards were subjected to slow temperature changes from -40 to +150/spl deg/C. Using these measurements and ongoing numerical simulations, valuable insight has been gained on the effects of assembly variables and underfill material properties on the reliability of flip chip packages.

Ethanol effects on temperature-sensitive hypothalamic neurons in rat brain slices

1. We recorded impulse activity of thermosensitive hypothalamic neurons in rat brain slices during superfusion with ethanol at constant temperatures and during slow sinusoidal temperature changes. 2. At constant temperatures of 37 °C, ethanol application typically induced a triphasic change of the firing rate: An initial excitation turned into complete inhibition followed by spontaneous recovery to higher firing rates. 3. Ethanol application increased the neurons’ temperature sensitivity remarkably. 4. Our data indicate complex neuromodulatory effects of ethanol with different time delays which interfere with basic mechanisms of temperature transduction.

Strong hemispheric coupling of glacial climate through freshwater discharge and ocean circulation.

The climate of the last glacial period was extremely variable, characterized by abrupt warming events in the Northern Hemisphere, accompanied by slower temperature changes in Antarctica and variations of global sea level. It is generally accepted that this millennial-scale climate variability was caused by abrupt changes in the ocean thermohaline circulation. Here we use a coupled ocean-atmosphere-sea ice model to show that freshwater discharge into the North Atlantic Ocean, in addition to a reduction of the thermohaline circulation, has a direct effect on Southern Ocean temperature. The related anomalous oceanic southward heat transport arises from a zonal density gradient in the subtropical North Atlantic caused by a fast wave-adjustment process. We present an extended and quantitative bipolar seesaw concept that explains the timing and amplitude of Greenland and Antarctic temperature changes, the slow changes in Antarctic temperature and its similarity to sea level, as well as a possible time lag of sea level with respect to Antarctic temperature during Marine Isotope Stage 3.

Replacement of lead baths for the tempering of spring wire

Molten lead is used for tempering of valve‐spring wire. Lead has drawbacks due to slow temperature changes. In 1991 the Swedish Parliament passed a Government Bill, in which proposals were made to phase out the use of lead in the long term, primarily through voluntary measures. Tempering of SIS 2090 (SAE 9254, DIN 55SiCr7) wire with different dimensions using induction heating was tested in a pilot process line. An induction coil for six wires and two coils with different lengths designed for single wires were tested. The results showed that an induction coil for six wires gave excessive temperature and property variations between the wires. The shorter of the single wire coils gave fluctuations in temperature and properties using a 3.00‐mm wire. No such fluctuations were observed with the longer coil. One of the experiments showed that the process might need time to reach stable conditions. The results so far indicate that it is possible to produce valve‐spring wire with induction tempering. The process needs more control and monitoring compared to tempering in molten lead.

A general model describing flow stress of copper alloys in different deformation conditions

A general model describing flow stress as a function of internal state of materials and such deformation conditions as temperature, strain, strain rate, sudden changes of temperature and strain rate as well as time intervals in deformation process is presented in the paper. The model describes strain hardening as well as softening processes taking place during deformation defined as dynamic softening and during interval or after deformation defined as static softening. The model was developed on the basis of internal state fundamental function that is completed with the modified Garofalo equation describing internal state characteristic level, characteristic strain values related to the Zener–Hollomon parameter, kinetics of dynamic and static softening processes, and reaction of materials to slow and sudden changes in strain rate and temperature. The model can be used in numerical simulation and design of metal forming processes.

Reducing image distortions due to temperature-related microscope stage drift.

Distortions in confocal 3D image data sets were related to movements of the microscope stage that matched fluctuations in laboratory temperature. Movement was apparent in all three axes. Adding a draught-proof enclosure, covering the stage, objective lenses and supporting structures, minimized these short-term fluctuations. However, the stage still tracked slow changes in laboratory temperature and was sensitive to heat sources mounted on the microscope. Suggestions are made about microscope design.

Permanent strain of thermal expansion and thermally induced microcracking in Inada granite

I made measurements of the permanent strain of thermal expansion, compressional wave velocity, and density of microcracks of Inada granite, which was subjected to slow and homogeneous temperature change under atmospheric pressure. The permanent strain implying the cumulative amount of newly generated microcracks and the opening of preexisting microcracks appeared distinctly at a temperature between 100° and 125°C and increased almost exponentially in the range from 200°C to immediately before the temperature of α‐β transition in quartz (573°C) as the peak temperature of the thermal cycle was elevated. At 600°C, the strain increased further. The density of the microcracks was heightened as the peak temperature increased. Moreover, the said trend coincided with that of the crack density parameter estimated from the compressional wave velocity. At the same time, the maximum width of the microcracks, which was determined by microscopic observation, and the average width increment of the microcracks, calculated from the permanent strain and microcrack density, showed a similar trend. Using the mercury intrusion porosimetry method, the average width increment of the microcracks coincided with the equivalent width of the microcracks measured. There are two causes of thermally induced microcracking: the mismatching of the coefficients of thermal expansion between the adjacent mineral grains and the decrepitation of the fluid inclusions. The density of the fluid inclusion microcracks showed a remarkable increase starting from the peak temperature of 300°C. At temperatures equal to or higher than 400°C, the fluid inclusion microcracks accounted for approximately 35% of all the intragranular cracks.