Small Temperature Variations Research Articles

Evaluation of glazing retrofitting solution for the tropics

With the increase in the stock of old buildings in urban cities, there is an imperative demand to retrofit the old buildings to reduce their energy consumption and also maximize the use of natural daylight to enhance the well-being of the occupants in the buildings. For old commercial buildings, one of the solutions to reduce energy consumption is to reduce the heat transfer through the building envelope to the air-conditioned interior spaces. However, there are very limited solutions to alter the building envelope without the involvement of major construction works. The glass is usually an indispensable part of the building envelope for commercial buildings. Many old commercial buildings in Singapore and several other South-East Asian countries near the equator are fitted with monolithic glass as the window facade due to small variation in outdoor air temperature in the region throughout the year. By converting the monolithic glass facade into a double glazing unit, some energy savings will result, but it is unclear if the benefit is substantial.A new retrofitting solution known as the “ATTOCH Inner Window” or AIW in short, was developed by AGC recently. The retrofitting solution, AIW, basically converts an existing single pane glass facade into a double glazing unit by adding a secondary glass from the interior of the building. With a low-emissivity coated glass as the secondary glass, the effective g-value (solar transmittance) and U-value (thermal transmittance) of the double glazing unit are both reduced. Thus, the aim of this manuscript is to evaluate the performance of AIW when subjected to the tropical climate in selected Southeast Asian cities.

Physical and chemical properties of natural and anthropogenic groundwater outflows in the cieszyn foothills

The purpose of this article is to present the hydrographic and hydrochemical properties of the waters of old adits, which drained excavations after exploitation of iron ores. For this research, both the natural springs and control object have been identified. These are located in the Cieszyn Foothills. It has been shown that adit water has a higher average electrolytic conductivity (> 600 µS/cm) than natural spring water (<300 µS/cm). The increase in conductivity is undoubtedly influenced by the air supply to the excavations, which accelerates the rock weathering process. However, the increase in water mineralisation has no effect on the hydrochemical type of water. Adit waters and spring waters represent the same bicarbonate calcium (HCO3− - Ca2+) hydrochemical type. Adit waters show a small variation in water temperature in the annual cycle (Cv < 8%) compared to a natural spring (Cv -18%). Changes in the water temperature in the adits and the spring show high synchronism (r> 0.7).

A Temperature-Controlled Patch Clamp Platform Demonstrated on Jurkat T Lymphocytes and Human Induced Pluripotent Stem Cell-Derived Neurons.

Though patch clamping at room temperature is a widely disseminated standard procedure in the electrophysiological community, it does not represent the biological system in mammals at around 37 °C. In order to better mimic the natural environment in electrophysiological studies, we present a custom-built, temperature-controlled patch clamp platform for upright microscopes, which can easily be adapted to any upright patch clamp setup independently, whether commercially available or home built. Our setup can both cool and heat the platform having only small temperature variations of less than 0.5 °C. We demonstrate our setup with patch clamp measurements at 36 °C on Jurkat T lymphocytes and human induced pluripotent stem cell-derived neurons. Passive membrane parameters and characteristic electrophysiological properties, such as the gating properties of voltage-gated ion channels and the firing of action potentials, are compared to measurements at room temperature. We observe that many processes that are not explicitly considered as temperature dependent show changes with temperature. Thus, we believe in the need of a temperature control in patch clamp measurements if improved physiological conditions are required. Furthermore, we advise researchers to only compare electrophysiological results directly that have been measured at similar temperatures since small variations in cellular properties might be caused by temperature alterations.

Drying Rate of Turmeric Herbal (Curcuma Longa L.) Using Tray Dryer

This study reports the turmeric of drying operation. Variables that have been compared are size or surface area of the sample, drying air rate and drying temperature. In this case it was found that the effect of increasing surface area would be able to increase the amount of water evaporated from the sample. The effect of drying air flow rate at the same temperature decreases the ability to evaporate air in turmeric samples. This is due to the reduced time of interaction of the drying air with the sample surface. Relatively small temperature variations do not show significant differences. The optimal drying rate is achieved by using drying air temperature at 39°C with drying flow of 4,5 m/s and the turmeric sample with surface area of 0,00525 m2. The effect of this drying variable obtained significantly on the size of the dried turmeric.

Coherent Transport in Periodically Driven Mesoscopic Conductors: From Scattering Amplitudes to Quantum Thermodynamics

Abstract Scattering theory is a standard tool for the description of transport phenomena in mesoscopic systems. Here, we provide a detailed derivation of this method for nano-scale conductors that are driven by oscillating electric or magnetic fields. Our approach is based on an extension of the conventional Lippmann–Schwinger formalism to systems with a periodically time-dependent Hamiltonian. As a key result, we obtain a systematic perturbation scheme for the Floquet scattering amplitudes that describes the transition of a transport carrier through a periodically driven sample. Within a general multi-terminal setup, we derive microscopic expressions for the mean values and time-integrated correlation functions, or zero-frequency noise, of matter and energy currents, thus recovering the results of earlier studies in a unifying framework. We show that this framework is inherently consistent with the first and the second law of thermodynamics and prove that the mean rate of entropy production vanishes only if all currents in the system are zero. As an application, we derive a generalized Green–Kubo relation, which makes it possible to express the response of any mean currents to small variations of temperature and chemical potential gradients in terms of time integrated correlation functions between properly chosen currents. Finally, we discuss potential topics for future studies and further reaching applications of the Floquet scattering approach to quantum transport in stochastic and quantum thermodynamics.

Electronic noise generated by a temperature gradient across a hybrid normal metal–superconductor nanojunction

Understanding electronic noise in hybrid junctions is essential for designing efficient nanoscale electronics at the quantum limit. Recently, a new (previously overlooked) noise contribution, generated by the temperature difference across a conducting heterostructure and denoted as delta-T noise, was predicted and revealed experimentally in atomic-scale contacts (Shein Lambroso et al. in Nature 562:240–244, 2018). While the new type of electronic noise and the well-known voltage-generated shot noise have the same partition origin, they are activated by different stimuli. In the paper by Shein Lambroso et al. (2018), transmission probabilities for electrons flowing through the considered setups were assumed to be constant, a very good approximation for normal metal contacts within the used temperature range. In this work, we propose and study theoretically the delta-T noise in hybrid normal metal–superconductor nanojunctions where it has to be more pronounced at low temperatures due to the strongly nonlinear energy dependence of interface scattering characteristics in the gap region. Such experiments can be useful to probe quantum effects and to reveal small temperature variations along electronic nanoscale circuits.

Stationary Non equilibrium States in Kinetic Theory

Stationary non equilibrium solutions to the Boltzmann equation, despite their relevance in applications, are much less studied than time dependent solutions, and no general existence theory is yet available, due to serious technical difficulties. Here we review some results on the construction of stationary non equilibrium solutions, in a general domain in contact with a slightly non-homogeneous thermal reservoir, both for finite and small Knudsen number. We will describe different approaches and different techniques developed. The main focus will be on stationary solutions close to hydrodynamics. In particular, we will give an answer to the longstanding open problem of the rigorous derivation of the steady incompressible Navier–Stokes–Fourier system from the Boltzmann theory, in the presence of a small external force and diffuse boundary condition with small boundary temperature variations.

Understanding and optimization of the secondary drying step of a freeze-drying process: a case study

The objective of this study was to build an understanding and optimize the secondary drying step of a freeze-drying process using a drug formulation from Fresenius Kabi (FK1) as a case study. For this purpose, a design of experiments (DoE) was developed to study the influence of drying temperature, drying time, vial position, and chamber pressure on moisture content and glass transition temperature of FK1. The results obtained herein showed that the influence of drying temperature on moisture content and glass transition temperature was strong at short drying time, implying that increasing drying temperature could lead to a significant decrease in the required drying time to achieve a designed moisture content and glass transition temperature. Variation in chamber pressure from 0.05-0.40 mbar showed insignificant influence on moisture content and glass transition temperature. Small variations in moisture content and glass transition temperature with respect to vial position were also observed, where edge vials had higher moisture content and, consequently, lower glass transition temperature than center vials. Further, the results from the DoE were utilized to construct a process design space (PDS) for the secondary drying step of FK1. Experimental verification of the PDS demonstrated an excellent agreement between the PDS-defined and experimentally-determined moisture content and glass transition temperature values. Thus, the PDS facilitated process optimization of FK1 and could serve as an important tool during scale-up and transfer of the process.

Quasi-Phase Matched Second Harmonic Generation in Plasmonic–Organic Hybrid Structures

In this article, we propose the design and analyze a plasmonic-organic-hybrid (POH) waveguide structure for efficient forward and backward second harmonic generation (SHG) to bridge the mid-infrared (IR) to near-IR. The required phase matching is satisfied by quasi-phase matching (QPM) technique through periodically altering the material of the metal-insulator-metal slot region between a nonlinear polymer (with second-order nonlinear coefficient of χ (2) ≠ 0) and Al2O3 (with χ (2) = 0) leading to modulation of χ (2) coefficient along the propagation direction. The strong field confinement offered by surface plasmon polaritons (SPPs) significantly enhances the normalized efficiency up to 1.75 × 106 W−1cm−2 in the case of backward SHG over a short device length of 17 μm with only 20 mW input power. Also, a slightly lower efficiency is achieved for forward configuration with broadband response, high fabrication tolerance, and small temperature-variation sensitivity. Furthermore, our proposed structure is based on standard nanofabrication technologies and can be used for all-optical signal processing, low-noise detection of a mid-IR signal in the near-IR windows, and (mirrorless) optical parametric oscillator.

Small temperature variations are a key regulator of reproductive growth and assimilate storage in oil palm (Elaeis guineensis)

Oil palm is an important crop for global vegetable oil production, and is widely grown in the humid tropical regions of Southeast Asia. Projected future climate change may well threaten palm oil production. However, oil palm plantations currently produce large amounts of unutilised biological waste. Oil palm stems – which comprise two-thirds of the waste - are especially relevant because they can contain high levels of non-structural carbohydrates (NSC) that can serve as feedstock for biorefineries. The NSC in stem are also considered a potent buffer to source-sink imbalances. In the present study, we monitored stem NSC levels and female reproductive growth. We then applied convergent cross mapping (CCM) to assess the causal relationship between the time-series. Mutual causal relationships between female reproductive growth and the stem NSC were detected, with the exception of a relationship between female reproductive organ growth and starch levels. The NSC levels were also influenced by long-term cumulative temperature, with the relationship showing a seven-month time lag. The dynamic between NSC levels and long-term cumulative rainfall showed a shorter time lag. The lower temperatures and higher cumulative rainfall observed from October to December identify this as a period with maximum stem NSC stocks.

Coupling of piezo- and pyro-electric effects in miniature thermal energy harvesters

Thermal energy harvesting from ambient heat into electricity is of interest due to its wide potential applicability. This paper demonstrates a moving beam thermal energy harvesting mechanism exploiting both pyro- and piezo-electric effects simultaneously, for use adjacent to a heat source with small temperature variations at low frequency (below 0.1 Hz). For the first time, the relative contributions of these two mechanisms in such a device is established both theoretically and experimentally, and a dynamic model is provided. The relative phase of the contributed currents is shown to be a critical factor, and methods are introduced to optimise this phase relationship, particularly by selection of the mechanical configuration. The reported prototype achieves around 0.4 μW for a temperature difference of around 15 K at frequency 0.02 Hz with an optimal condition in the fixed-fixed configuration about 90% above the fixed-free end configuration.

Thermal imaging of the structural damping induced by an acoustic black hole

An Acoustic Black Hole (ABH) is a passive and efficient way to control the flexural vibrations of beams or plates. In its classical form, an ABH consists of a local reduction of the thickness of a structure according to a power law profile, associated with a thin viscoelastic coating placed in the thinnest region. A focalization and a wave trap effect occur, leading to a localized energy dissipation, which induces a local temperature increase. The objective of this paper is twofold. First, the goal is to develop an adequate experimental methodology capable of accurately mapping the small temperature variations induced by the local dissipation mechanism. Second, from the thermal standpoint, the goal is to provide experimental evidence of a local temperature increase associated with a damping effect in the case of an ABH beam. This paper thus describes a new kind of experimental methodology able to provide original data, bringing some new insight into the ABH physical understanding and the analysis of structural damping.

Novel Wood Resistance Measurement Method Reducing the Initial Transient Instabilities Arising in DC Methods Due to Polarization Effects

A novel method for measuring the electrical resistance in wood is presented. It is based on applying an Alternating Current (AC) to two electrodes rammed into the wood. The method reduces the transient time for value stabilization. In case of Direct Current (DC) resistance measurement methods, typically used in wood measurement, an initial transient exists, invalidating the measured value during an initial transient period. This measurement method uses an electronic circuit based on a relaxation oscillator where the wood automatically sets the oscillation frequency depending on its electrical resistance. Compared to other AC methods, this circuit greatly simplifies the measurement process, not requiring any previous analysis for wood AC frequency estimation. Experimental results for four different wood species showed that, in all cases, the transient response of the measured wood resistance is improved when compared to the DC resistance method, reducing the stabilization time from 10–12 min in DC measurements to almost zero for the novel measurement method. The deviation between the initial wood resistance measurement and the stable value resulted in a range between 0.2% and 5% with the proposed method, while a range between 6% and 10% was obtained when using the DC method. Moreover, the proposed circuit is able to detect changes in wood resistance produced by small variations in temperature and environmental relative humidity during continuous long term measurements. For repeatability analysis, it was verified that similar ambient conditions of temperature and relative humidity (variations lower than 1 °C and 1%, respectively) in different moments provided variations lower than 1.5%. The method can also be applied to other fiber materials affectd by polarization effects when an electrical current is applied into them.

Nonequilibrium calorimetry

We consider stationary driven systems in contact with a thermal equilibrium bath. There is a constant (Joule) heat dissipated from the steady system to the environment as long as all parameters are unchanged. As a natural generalization from equilibrium thermodynamics, the nonequilibrium heat capacity measures the excess in that dissipated heat when the temperature of the thermal bath is changed. To improve experimental accessibility we show how the heat capacity can also be obtained from the response of the instantaneous heat flux to small periodic temperature variations.

Time-of-Sight Liquid Flow Measurements in the Low Nanoliters per Minute Scale.

We describe an affordable and robust measurement technique applicable to nanoscale liquid flow. The approach can provide good precision (<1% RSD) in the 1.5-15 nL/min flow range. The motion of a conductive/nonconductive immiscible segmental interface in a capillary is followed by an admittance detector. The conductive marker segment, e.g., a salt solution, is protected on both sides from the principal flow stream by immiscible guard segments, typically a fluorocarbon (FC) liquid, of significantly greater impedance. Fluorosilylation of the capillary ensures no other liquid film between the FC segments and the wall (perfect piston). A given interface/marker can typically be used only once in interface/front tracking systems. We overcome this by putting the sensor capillary in a valved configuration where the flow direction in the sensor is reversed before the guard/marker segments escape. Several strategies are possible to interpret flow rate from the sensor output, including the rate of the interface movement. During the measurement process, a change in this rate of movement can be detected in <1 s. Small temperature variations in the 25-35 °C range did not affect sensor behavior.

Fixed Grid Numerical Models for Solidification and Melting of Phase Change Materials (PCMs)

Phase change materials (PCMs) are classified according to their phase change process, temperature, and composition. The utilization of PCMs lies mainly in the field of solar energy and building applications as well as in industrial processes. The main advantage of such materials is the use of latent heat, which allows the storage of a large amount of thermal energy with small temperature variation, improving the energy efficiency of the system. The study of PCMs using computational fluid dynamics (CFD) is widespread and has been documented in several papers, following the tendency that CFD nowadays tends to become increasingly widespread. Numerical studies of solidification and melting processes use a combination of formulations to describe the physical phenomena related to such processes, these being mainly the latent heat and the velocity transition between the liquid and the solid phases. The methods used to describe the latent heat are divided into three main groups: source term methods (E-STM), enthalpy methods (E-EM), and temperature-transforming models (E-TTM). The description of the velocity transition is, in turn, divided into three main groups: switch-off methods (SOM), source term methods (STM), and variable viscosity methods (VVM). Since a full numerical model uses a combination of at least one of the methods for each phenomenon, several combinations are possible. The main objective of the present paper was to review the numerical approaches used to describe solidification and melting processes in fixed grid models. In the first part of the present review, we focus on the PCM classification and applications, as well as analyze the main features of solidification and melting processes in different container shapes and boundary conditions. Regarding numerical models adopted in phase-change processes, the review is focused on the fixed grid methods used to describe both latent heat and velocity transition between the phases. Additionally, we discuss the most common simplifications and boundary conditions used when studying solidification and melting processes, as well as the impact of such simplifications on computational cost. Afterwards, we compare the combinations of formulations used in numerical studies of solidification and melting processes, concluding that “enthalpy–porosity” is the most widespread numerical model used in PCM studies. Moreover, several combinations of formulations are barely explored. Regarding the simulation performance, we also show a new basic method that can be employed to evaluate the computing performance in transient numerical simulations.

The effect of conduction and convective conditions at interstitial regions on 3D thermoelastic contact problems

Contact variables can be greatly affected by small temperature variations occurring in the contact zone and the surrounding areas. So it is essential to take into account the temperatures and heat fluxes on these regions to obtain the deformations and tractions that appear in the bodies. This work studies how the 3D thermomechanical contact variables are affected by the thermal conductive and convection boundary conditions at the interstitial regions (i.e., possible heat interchange between the bodies due to a material or a fluid contained in the separation zones between them). For this purpose, considering the previous works of Giannopoulos and Anifantis, this work extends their 2D incremental contact methodology based on the Boundary Element Method to solve steady-state 3D thermoelastic contact problems where interstitial conductive and convective boundary conditions are considered. So the equilibrium configuration of the system is determined incrementally by solving the uncoupled thermal and thermoelastic problems for each incremental thermal and mechanical load. The proposed scheme is validated solving several benchmark problems presented in the literature and later applied to solve different 3D thermoelastic contact problems where the response is clearly influenced by the boundary conditions at interstitial regions.

Titan's neutral atmosphere seasonal variations up to the end of the Cassini mission

In this paper we report new results concerning the seasonal atmospheric evolution near Titan's poles and equator in terms of temperature and composition using nadir spectra acquired by the Cassini Composite Infrared Spectrometer (CIRS) at high spectral resolution during the last year of the Cassini mission in 2017 complementing previous investigations covering almost two Titan seasons. In recent previous papers (Coustenis et al., 2016, 2018), we have reported on monitoring of Titan's stratosphere near the poles after the mid-2009 northern spring equinox. In particular we have reported on the observed strong temperature decrease and compositional enhancement above Titan's southern polar latitudes since 2012 and until 2014 of several trace species, such as complex hydrocarbons and nitriles, which were previously observed only at high northern latitudes. This effect accompanied the transition of Titan's seasons from northern winter in 2002 to northern summer in 2017, while at that latter time, the southern hemisphere was entering winter. Our new data, acquired in 2017 and analyzed here, are important because they are the only ones recorded since 2014 close to the south pole in the mid-infrared nadir mode at high resolution. A large temperature increase in the southern polar stratosphere (by 10–50 K in the 0.1 mbar–0.01 mbar pressure range) is found associated with a change in the temperature profile's shape. The 2017 observations also show a related significant decrease in most of the southern abundances which must have started sometime between 2014 and 2017. For the north, the spectra indicate a continuation of the decrease of the abundances which we first reported to have started in 2015 and small temperature variations. We discuss comparisons with other results and with current photochemical and dynamical models which could be updated and improved by the new constraints set by the findings presented here.

Compatibility Studies of Valsartan with Different Pharmaceutical Excipients

Compatibility studies between active drugs and excipients are substantial in the pharmaceutical technology. Thermal analysis has been extensively used to obtain information about drug-excipient interactions and to perform pre-formulation studies of pharmaceutical dosage forms. The objective of the present study was to evaluate the compatibility of the valsartan (VALS) with pharmaceutical excipients of common use including diluents, binders, disintegrants, lubricants and solubilising agents. Thermogravimetry (TG), derivative thermogravimetry (DTG), but especially differential scanning calorimetry (DSC) were used for a first screening to find small variations in peak temperature and/or their associated enthalpy for six drug/excipient mixtures (starch, cross caramelose sodique, microcrystalline cellulose 102, povidone K30, lactose monohydrate and magnesium stearate), which indicate some degree of interaction. Additional methods using Fourier transformed infrared spectroscopy (FT-IR) and X-ray powder diffraction (XRPD) confirmed the incompatibility of VALS with starch, povidone K30, lactose monohydrate and magnesium stearate. Those excipients should be avoided in the development of solid dosage forms.

Phenology of the tree community in a seasonal forest in southern Brazil

Seasonal variations in environmental factors, such as precipitation, influence plant phenology and the relative importance of each factor, differ according to the ecosystem in question. In this study, we evaluated the phenology of 60 tree species in a seasonal semi-deciduous forest located at the southern border of the tropical zone (23°26′35ʺS and 51°15′30ʺW) during 3 years. We aimed to investigate the relationship of leaf fall, leaf flushing, budding, flowering, immature and mature fruit phenophases with precipitation, temperature and photoperiod. We also analyzed whether the phenological patterns of tree community were seasonal and similar between consecutive years. Although the climate of the region is classified as Cfa, there are two distinct season: a hot humid summer and a cold drier winter. Leaf fall occurred predominantly in the dry season, with leaf flushing and flowering at the end of the dry and early wet season. The mature fruits were observed throughout the year. For the six phenophases analyzed, the percentage of species did not differ among the three study years. The tree community presented, in general, weakly seasonal phenological patterns, mainly in response to variations in temperature and photoperiod. The mature fruits showed seasonal patterns when the species were grouped by dispersal syndrome. This predictability suggests that small inter-annual variations in precipitation and temperature are not relevant for the studied tree species’ phenology.