Obviating Ligand Exchange Preserves the Intact Surface of HgTe Colloidal Quantum Dots and Enhances Performance of Short Wavelength Infrared Photodetectors

A large volume, scalable synthesis procedure of HgTe quantum dots (QDs) capped initially with short-chain conductive ligands ensures ligand exchange-free and simple device fabrication. An effective n- or p-type self-doping of HgTe QDs is achieved by varying cation-anion ratio, as well as shifting the Fermi level position by introducing single- or double-cyclic thiol ligands, that is, 2-furanmethanethiol (FMT) or 2,5-dimercapto-3,4-thiadiasole (DMTD) in the synthesis. This allows for preserving the intact surface of the HgTe QDs, thus ensuring a one order of magnitude reduced surface trap density compared with HgTe subjected to solid-state ligand exchange. The charge carrier diffusion length can be extended from 50 to 90 nm when the device active area consists of a bi-layer of cation-rich HgTe QDs capped with DMTD and FMT, respectively. As a result, the responsivity under 1340 nm illumination is boosted to 1 AW-1 at zero bias and up to 40 AW-1 under -1 V bias at room temperature. Due to high noise current density, the specific detectivity of these photodetectors reaches up to 1010 Jones at room temperature and under an inert atmosphere. Meanwhile, high photoconductive gain ensures a rise in the external quantum efficiency of up to 1000% under reverse bias.

[Changes in basic hemodynamic and electrocardiographic parameters in patients with severe vasorenal hypertension]

Major hemodynamic and electrocardiographic parameters were examined in 47 patients with severe vasorenal hypertension at rest, and in 20 patients after stress exposure. Three (hyper-, eu- and hypokinetic) types of circulation were demonstrated, like the ones seen in essential hypertension. Hemodynamic values at rest were indicative of relative cardiovascular compensation in severe vasorenal hypertension. Stress testing demonstrated that exercise disrupted that compensation. Arterial blood pressure response to physical stress showed no correlation to baseline values of the parameters examined.

[Variability of sinus rhythm during deep respiration]

A possibility was studied of applying the deep and infrequent respiration test with an object of increasing the informativeness of the statistical parameters of the ECG sequence interval as applicable to the quantitative evaluation of the functional state of man. Examination of patients with wound infection shown that the deep respiration test makes in possible to assess quantitatively the status of test subjects on the basis of two statistical parameters (the mean value of RR interval of ECG and root-mean-square deviation).

[Hemodynamic changes during the orthostatic test in patients with spinal cord damage at different levels]

Hemodynamics were studied during orthostatic load on a special orthotable in 54 patients with different levels of spinal cord interruption. With the patient in a horizontal and then in a vertical position, the arterial pressure, pulse, volume rate of blood flow in the forearm, and the cardiac output were recorded every minute. The total resistance of the vessels was calculated. Absence of constrictor reactions in the lower half of the trunk was revealed in patients with a high level of spinal cord damage, due to whicorthostatic collapse developed within the first minutes after they had been placed in a vertical posture. The orthostatic stability of such patients may be somewhat improved by producing additional external pressure to the lower part of the trunk (with special suits) and by means of other forms of special training. Patients with the spinal cord damaged at a low level (below the sixth thoracic vertebra) tolerate a 10-minute orthostatic load quite satisfactorily.