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Shot noise suppression in double barrier resonant tunnelling diodes with a Fano factor well below the value of 0.5 is theoretically predicted. This giant suppression is found to be a signature of coherent transport regime and can occur at zero temperature as a consequence of the Pauli principle or at sufficiently high temperatures above 77 K as a consequence of a long-range Coulomb interaction. These predictions are in agreement with experimental data.Since its realization [1], the double barrier resonant diode (DBRD) proved to be an electron device of broad physical interest because of its peculiar non-Ohmic current voltage (I-V) characteristic. Indeed, after a strong superOhmic increase of current, it exhibits a negative differential conductance and eventually hysteresis effects [2]. Even the shot noise characteristics are of relevant interest, since suppressed as well as enhanced shot noise with respect to its full Poissonian value has been observed (see [3] for a review on the subject). These electrical and noise features are controlled by the mechanism of carrier tunnelling through the double potential barriers. The microscopic interpretation of these features is found to admit a coherent [4] or a sequential [5] tunnelling approach. The intriguing feature of these two approaches is that from the literature, it emerges that both of them explain the I-V experimental data as well as most of the shot noise characteristics. Therefore, to our knowledge, there is no way to distinguish between these two transport regimes and the natural question whether the tunnelling transport is coherent or sequential remains an unsolved one.The coherent approach to shot noise in DBRD has received wide attention since the first experimental evidence by Li et al [6] of shot noise suppression with a minimum value of the Fano factor γ = S I /(2qI ) = 0.5, where S I is the current spectral density and q the absolute value of the unit charge responsible of current. Remarkably, most of the coherent approaches developed so far predict a maximum suppression γ = 0.5 even if there is clear experimental evidence of suppression below this value (here referred as giant suppression) [7][8][9] down to values of γ = 0.25 [8,9]. To this purpose, some authors obtained theoretical values of the Fano factor just below the value of 0.5, 0.45 [10] and 0.38 [11], respectively. However, the physical interpretation of these results remains mostly qualitative and quoting [3] this direction of research looks promising but certainly requires more efforts.In this letter, we announce that a giant suppression of shot noise occurring before the peak value of the current is a signature of coherent transport in DBRDs. To this purpose, we present a theoretical model which predicts this phenomenon and is validated by experiments.The typical structure here investigated is the standard symmetric double well reported in figure 1. We denote by

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We implement a quantum approach which includes long range Coulomb interaction and investigate current voltage characteristics and shot noise in double-barrier resonant diodes. The theory applies to the region of low applied voltages up to the region of the current peak and considers the wide temperature range from zero to room temperature. The shape of the current voltage characteristic is well reproduced and we confirm that even in the presence of Coulomb interaction the shot noise can be suppressed with a Fano factor well below the value of 0.5. This feature can be an indication of coherent tunneling since the standard sequential tunneling predicts in general a Fano factor equal to or greater than the value 0.5. This giant suppression is a consequence of Pauli principle as well as long range Coulomb interaction. The theory generalizes previous findings and is compared with experiments.

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Abstract. A capacitive sensor was proposed and tested for the monitoring and control of a freeze drying process of a vaccine against the Newcastle disease of birds. The residual moisture of the vaccine was measured by the thermogravimetric method. The vaccine activity was determined by titration in chicken embryos. It was shown that, at the stages of freezing and primary drying, a capacitive sensor measured the fraction of unfrozen liquid phase in a material and allowed one to control the sublimation stage of drying in an optimal way. This prevented the foaming of the material and shortened the total drying time approximately twice. The control range at the sublimation stage of drying expanded up to −70°C. It was found at the final stage of drying that the signal of a capacitive sensor passed through a maximum value. We supposed that this maximum corresponds to the minimum of intramolecular mobility of biological macromolecules and hence to the optimal residual moisture of the material, which ensures long-term preservation of its activity. We also suppose that using the capacitive sensor at the final stage of drying allows one to more precisely detect the time when the residual moisture of dried material reaches the optimal value.KEY WORDS: biological materials; capacitive sensor; freeze drying; optimal residual moisture.At present, most biological materials containing live viruses or bacteria are exposed to lyophilization (i.e., drying from the frozen state); this ensures long-term preservation of their activity. Typically, this process consists of preliminary freezing and subsequent freeze drying. The latter process, in turn, consists of two stages: primary drying and secondary drying. During primary drying or sublimation, frozen water is removed from a biological product under vacuum and at temperatures below 0°C. At this stage, the drying rate is limited because of the foaming of a product that occurs due to its high temperature and the excess amount of liquid phase in it. The secondary drying, or final stage, begins after the end of the sublimation stage and occurs at temperatures above 0°C. The goal of the secondary drying is to bring the residual moisture of a biological product to an optimum level, which provides longterm preservation of its activity. Note that the moisture content both above and below the optimum value reduces the effective life of biological materials (1,2)To increase the shelf life of biological products, the following should be investigated: (1) the influence of the composition of the dried biological product and the residual moisture on the change in its activity over the time (3); (2) it is needed to optimize the sublimation drying process for different types of biological products (4). For the investigation of the of the state of water in the dried biologic drugs and the influence of the humidity of the biological on the change in their activity during shelf life, different physical methods are used such as neutron scattering (5), nuclear magnetic resonance (NMR) (6,7), Raman spec...