Sensitivity to temperature changes

When the temperature of a solar cell rises, cell conversion efficiency decreases because the additional thermal energy increases the thermally generated minority (dark-drift) current. This increase in dark-drift current is balanced in the cell by lowering the built-in barrier potential, lU, to boost the majority diffusion current. The drop in F causes a decrease in and F. Therefore, a cell s output, ie, the product of F and decreases with increasing cell temperature. is less sensitive to temperature changes than F and actually increases with temperature. 

For example, for most polymers an inerease in pressure of 1000 atm is equivalent to a drop of temperature in the range 30-50°C. It is also found that those polymers most sensitive to temperature changes in their normal processing ranges are the most sensitive to pressure. 

It must be emphasized that all time-dependent chemical phenomena, such as tautomerism, are sensitive to temperature changes. In this section, we treat classic DNMR (dynamic NMR) studies and cases of changes in the NMR spectra with temperature together. In Table XI we have classified these studies according to the physical state of the sample and to the nuclei... 

Discussion. Phosphate ion is determined nephelometrically following the formation of strychnine molybdophosphate. This turbidity is white in colour and consists of extremely fine particles (compare ammonium molybdophosphate, which is yellow and is composed of rather large grains). The precipitate must not be agitated, as it tends to agglomerate easily it is somewhat sensitive to temperature changes. 

Reactions with larger values of ACr° have equilibrium constants that are more sensitive to temperature changes. 

The activation parameters are much less sensitive to temperature changes than are rate or equilibrium constants and usually can be taken as being practically invariant in a narrow temperature interval. The considerations of this paper will be essentially confined to this first approximation with constant A H and AS. (For exceptions, see Section VILA.). 

Equilibrium constants are quite sensitive to temperature changes. A quantitative description... 

All fluid properties are dependent upon temperature. For most fluids the viscosity is the property that is most sensitive to temperature changes. 

Background currents of all NO electrodes are sensitive to changes of temperature and pH. Depending on type of electrodes, the effect may be more or less. Clark type NO electrodes are very sensitive to temperature change. The temperature induced response... 

The first clinical IRET used thermopile sensors to achieve non-contact temperature measurement in the ear. In 1991 a tympanic thermometer for home use was first introduced to the consumer market (Thermoscan HM 1). It utilized a pyroelectric sensor which requires the use of a suitable mechanical shutter or chopper mechanism, since it is only sensitive to temperature changes [3]. The main advantage of the pyroelectric sensor unit was its lower cost. However, prices for thermo-... 

Table 11.5 shows the flow activation energies, a, for PET, PTT and PBT [68], PTT has a higher a compared to PET but similar to that of PBT. The change in its melt viscosity is therefore less sensitive to temperatures changes than PET. However, due to the higher degradation rate, increased melt processing temperatures can have deleterious effect on the melt viscosity and IV. 

The thermal conductivity (TC) detector consists of four filaments embedded in a stainless-steel or brass block which acts as a heat sink. The TC detector is extremely sensitive to temperature changes and should be insulated to prevent temperature excursions during the time in which it takes to complete an adsorption or desorption measurement. Long-term thermal drift is not significant because of the calibration procedure discussed in the next section and therefore, thermostating is not required. 

Rates of reactions with larger values of activation energy are more sensitive to temperature changes. If the activation energy of a reaction is approximately 50 000 kJ kmol , the reaction rate will be doubled with a 10 C increase in reaction temperature at room temperature. Strictly, the Arrhenius equation is valid only for elementary reactions. Apparent activation energies can be obtained for non-elementary reactions. 

In addition to natural quartz. Rochelle salts, and tourmaline, synthetic crystals, such as ethylenediamine tartrate (EDT), dipotassium tartrate (DKT), and ammonium dihydrogen phosphate (ADPj have varying suitability as piezoelectric elements. While Rochelle salt has a greater piezoelectric effect than any other crystal, it has the disadvantage uf a greater sensitivity to temperature change than quartz. EDT has an advantage over quartz when used in frequency-modulated oscillators because of... 

As already observed for C60, by passing from high (523 K) to low temperatures (93 K) there is a systematic shift of the vibrational bands to higher frequencies although there are also bands which appear completely insensitive to the temperature change. For C60 an example of infrared band not sensitive to temperature change, at least in KBr matrix, is that at 524 cm-1 (see Table 10.1). As shown in Table 10.2, a similar phenomenon can be observed also in the infrared spectra of C70 where a series of vibrational absorption bands are quite insensitive to the temperature change of the sample in KBr matrix. However, there are also other... 

The reason that covalent bond is sensitive to temperature change is the fact that electrons can be moved (excited) from one atomic orbital to another with the temperature change. Readers who are not familiar with covalent bond should read VALENCE BOND by C.A.Coulson (Oxford University Press, 1979) [1] or CHEMICAL BONDS by H. B Gray (Benjamin/Cummings, Pub.Co.1973) [2],... 

It was pointed out before, covalent bond is rather sensitive to temperature changes and as a result may change its potential energy curve as attested in the change of Young s modulus in the previous section of Mechanical Properties. The question that needs answer-... 

They are sensitive to temperature changes and may be sensitive to pressure changes. ... 

The pH s of Tris-based buffers are sensitive to temperature changes. Always prepare buffers at the same temperature in which they will be used, and be aware that refrigeration and heating can cause changes in the pH of temperature-sensitive buffers. Always allow reagents to equilibrate to room temperature before use. 

As outlined above, nucleation rates are extremely sensitive to temperature changes. Therefore, precipitation temperature is a decisive factor in controlling precipitate properties such as primary crystallite sizes, surface areas, and even the phases formed. However, it is very difficult to state how the precipitation temperature has to be adjusted to achieve a product with specific properties. The optimum precipitation temperature usually is a parameter which has to be determined experimentally. 

---