In this work we report simulation and experimental results for an MWIR HgCdTe photodetector designed by computer simulation and fabricated in a joint laboratory run by VIGO Sytems S.A. and Military University of Technology. The device is based on a modified N+pP+ heterostructure grown on 2”., epiready, semi-insulating (100) GaAs substrates in a horizontal MOCVD AIX 200 reactor.
The devices were examined by measurements of spectral and time responses as a function of a bias voltage and operating temperatures. The time response was measured with an Optical Parametric Oscillator (OPO) as the source of ~25 ps pulses of infrared radiation, tuneable in a 1.55–16 μm spectral range. Two-stage Peltier cooled devices (230 K) with a 4.1 μm cut-off wavelength were characterized by 1.6 × 1012 cm Hz1/2/W peak detectivity and < 1 ns time constant for V > 500 mV.
Samples of CdTe single crystals which are used as radiation detectors were periodically measured during a long time interval with different values of an applied voltage. The samples were also periodically exposed during long time periods to high temperatures of 390 K and to rapid changes of temperature from 300 K to 390 K. After 1.5 years of measurements we observed ageing of the samples which resulted in deterioration of their transport characteristics. The resistance of the samples increased significantly and current-voltage characteristics were unstable in time. Noise spectroscopy showed that low frequency noise can be used for detection of CdTe sample ageing as its spectral density increases significantly comparing to the 1/f noise of a high quality sample
The paper reports on the photoelectrical performance of the long wavelength infrared (LWIR) HgCdTe high operating temperature (HOT) detector. The detector structure was simulated with commercially available software APSYS by Crosslight Inc. taking into account SRH, Auger and tunnelling currents. A detailed analysis of the detector performance such as dark current, detectivity, time response as a function of device architecture and applied bias is performed, pointing out optimal working conditions.
The paper reports on a long-wave infrared (cut-off wavelength ~ 9 μm) HgCdTe detector operating under nbiased condition and room temperature (300 K) for both short response time and high detectivity operation. The ptimal structure in terms of the response time and detectivity versus device architecture was shown. The response time of the long-wave (active layer Cd composition, xCd = 0.19) HgCdTe detector for 300 K was calculated at a level of τs ~ 1 ns for zero bias condition, while the detectivity − at a level of D* ~ 109 cmHz1/2/W assuming immersion. It was presented that parameters of the active layer and P+ barrier layer play a critical role in order to reach τs ≤ 1 ns. An extra series resistance related to the processing (RS+ in a range 5−10 Ω) increased the response time more than two times (τs ~ 2.3 ns).
The aim was to explore the feasibility of using bamboo vinegar powder as an antibiotics substitute in weaning piglets. Forty-five healthy Duroc × Landrance × Yorshire piglets (weight 6.74 ± 0.17 kg; age 31 days) were randomly divided into the control group (basic diet), ANT group (basic diet + 0.12% compound antibiotics), BV1 group (basic diet + 0.1% bamboo vinegar powder), BV5 group (basic diet + 0.5% bamboo vinegar powder) and BV10 group (basic diet + 1% bamboo vinegar powder). MyD88 and CD14 expression in immune tissues was examined using real-time PCR. MyD88 expression in the control group were significantly lower than that in other groups in all tissues (p<0.05), while CD14 expression showed the opposite trend. MyD88 expression was significantly higher in the BV10 group than in other groups in lung tissue (P<0.05), significantly higher in the ANT group than in the BV1 group in the kidneys (P<0.05), significantly higher in the BV10 group than in the BV1 group in the thymus (P<0.05), and signifi- cantly higher in the BV1 group than in the BV10 group in the lymphatic tissue (P<0.05). These differences between experimental groups were not observed for the CD14 gene (P>0.05). Thus, adding bamboo vinegar powder to the basic diet of weaning piglets had immune effects similar to antibiotics and the effect was dose-dependent. Moreover, the MyD88 and CD14 genes appear to play a role in these immune effects
In the paper recent progress at VIGO/MUT (Military University of Technology) MOCVD Laboratory in the growth of Hg1-xCdxTe (HgCdTe) multilayer heterostructures on GaAs/CdTe substrates is presented. The optimum conditions for the growth of single layers and complex multilayer heterostructures have been established. One of the crucial stages of HgCdTe epitaxy is CdTe nucleation on GaAs substrate. Successful composite substrates have been obtained with suitable substrate preparation, liner and susceptor treatment, proper control of background fluxes and appropriate nucleation conditions. The other critical stage is the interdiffused multilayer process (IMP). The growth of device-quality HgCdTe heterostructures requires complete homogenization of CdTe-HgTe pairs preserving at the same time suitable sharpness of composition and doping profiles. This requires for IMP pairs to be very thin and grown in a short time.
Arsenic and iodine have been used for acceptor and donor doping. Suitable growth conditions and post growth anneal is essential for stable and reproducible doping. In situ anneal seems to be sufficient for iodine doping at any required level. In contrast, efficient As doping with near 100% activation requires ex situ anneal at near saturated mercury vapours. As a result we are able to grow multilayer fully doped (100) and (111) heterostructures for various infrared devices including photoconductors, photoelectromagnetic and photovoltaic detectors. The present generation of uncooled long wavelength infrared devices is based on multijunction photovoltaic devices. The technology steps in fabrication of devices are described. It is shown that near-BLIP performance is possible to achieve at ≈ 230 K with optical immersion. These devices are especially promising as 7.8–9.5 um detectors, indicating the potential for achieving detectivities above 109 cmHz1/2/W.
Introduction: Uterine leiomyoma is the most widespread benign tumor affecting women of childbearing age. There are still gaps in the understanding of its pathogenesiss. Telocytes are unique cells described in greater than 50 different locations inside the human body. The functional relationship of cells could clarify the pathogenesis of leiomyomata. In the current study, we focused on the identification of telocytes in all regions of the human uterus to explain their involvement in leiomyoma development.
Materials and Methods: Tissue samples from a healthy and myomatous uterus were stained for c-kit, tryptase, CD34 and PDGFRα to identify telocytes. Routine histology was performed to analyze tissue morphology and collagen deposits.
Results: Telocytes were detected in the cervix, corpus of the uterus and leiomyoma. The density of telocytes in fibroid foci was reduced compared with normal myometrium.
Conclusions: Our results demonstrated the existence of telocytes in all parts of the human body affected and unaff ected by leiomyoma of the uterus. In addition, telocytes were also present in leiomyoma foci. Our results suggest that the reduced density of telocytes is important for the pathomechanisms of myometrial growth, demonstrating its value as a main component of the myomatous architecture.
Telocyte (TC) is an interstitial cell type with a small cellular body and extremely long tentacle-like extensions. TCs were discovered a decade ago and have specific morphological characteristics, immunohistochemical and secretome profi les, electrophysiological properties, microRNA expression. Moreover, they are different in gene expression from other cells. TCs play an important role in plenty of processes. Apparently, they are involved in homeostasis, remodelling, regeneration, repair, embryogenesis, angiogenesis and even tumorigenesis. “Telocytes need the world”, was emphasized by Professor Popescu and it will be actual at any time. This review summarizes particular features of TCs in different organs and systems, emphasizing their involvement in physiological and pathophysiological processes.
The solar photovoltaic technology is one of the renewable technologies with the potential to shape a future-proof, reliable, scalable and affordable electricity system. It is important to provide better resources for any upcoming technology. CdS/CdTe thin films have long been considered as one enticing option for reliable and cost-effective solar cells to be developed. N-type CdS as a transparent window layer in heterojunction structures is one of the best choices for CdTe cells. In a solar cell structure, window layer material plays a very crucial role to improve its performance. For this reason, this review focuses on the basic and significant aspects such as importance of the window layer thickness, degradation effect, use of nano-wire arrays, and an ammonia-free process to deposit the window layer. Also, an attempt has been made to analyze various processes improving window layer properties. Necessary discussions have been included to review the impact of solar cell parameters on the above aspects. It is anticipated that this review article will fulfill the requirement of knowledge to be used in the fabrication of CdS/CdTe solar cells.
The near net shaped manufacturing ability of squeeze casting process requiresto set the process variable combinations at their optimal
levels to obtain both aesthetic appearance and internal soundness of the cast parts. The aesthetic and internal soundness of cast parts deal
with surface roughness and tensile strength those can readily put the part in service without the requirement of costly secondary
manufacturing processes (like polishing, shot blasting, plating, hear treatment etc.). It is difficult to determine the levels of the process
variable (that is, pressure duration, squeeze pressure, pouring temperature and die temperature) combinations for extreme values of the
responses (that is, surface roughness, yield strength and ultimate tensile strength) due to conflicting requirements. In the present
manuscript, three population based search and optimization methods, namely genetic algorithm (GA), particle swarm optimization (PSO)
and multi-objective particle swarm optimization based on crowding distance (MOPSO-CD) methods have been used to optimize multiple
outputs simultaneously. Further, validation test has been conducted for the optimal casting conditions suggested by GA, PSO and
MOPSO-CD. The results showed that PSO outperformed GA with regard to computation time.
The paper presents the method and results of low-frequency noise measurements of modern mid-wavelength infrared photodetectors. A type-II InAs/GaSb superlattice based detector with nBn barrier architecture is compared with a high operating temperature (HOT) heterojunction HgCdTe detector. All experiments were made in the range 1 Hz - 10 kHz at various temperatures by using a transimpedance detection system, which is examined in detail. The power spectral density of the nBn’s dark current noise includes Lorentzians with different time constants while the HgCdTe photodiode has more uniform 1/f - shaped spectra. For small bias, the low-frequency noise power spectra of both devices were found to scale linearly with bias voltage squared and were connected with the fluctuations of the leakage resistance. Leakage resistance noise defines the lower noise limit of a photodetector. Other dark current components give raise to the increase of low-frequency noise above this limit. For the same voltage biasing devices, the absolute noise power densities at 1 Hz in nBn are 1 to 2 orders of magnitude lower than in a MCT HgCdTe detector. In spite of this, low-frequency performance of the HgCdTe detector at ~ 230K is still better than that of InAs/GaSb superlattice nBn detector.
Effect of annealing on the structural properties of arsenic-implanted mercury cadmium telluride film grown by molecular beam epitaxy was studied with the use of transmission electron microscopy and optical reflection. Strong influence of the graded-gap surface layer grown on top of the film on the behaviour of implantation-induced defects under arsenic activation annealing was revealed and interpreted.
We report on the status of long-wave infrared Auger suppressed HgCdTe multilayer structures grown on GaAs substrates designed for high operating temperature condition: 200-300 K exhibiting, detectivity -1011 cmHz1/2/W, time response within a –120 ps range at 230 K. Abnormal responsivity within the range of -30 A/W for electrical area 30×30 μm2 under reverse bias V = 150 mV is reported. Maximum extraction coefficient of -2.3 was estimated for analysed structures.
Due to the unrecognized effect of tigecycline (TIG) on CD4+ and CD8+ T cells, the present study has been undertaken in order to determine whether the drug can affect these cells in respect of their counts, and the production of IFN-γ, IL-17 (pro-inflammatory and immune-protective cytokines), IL-4 (anti-inflammatory and immune-protective cytokine), IL-10 and TGF-β (anti-inflammatory and immune-suppressive cytokines). Murine lymphocytes were treated with TIG for 48 and 96 h at concentrations reflecting its plasma levels obtained in vivo at therapeutic doses, and at 10-fold lower concentrations. It was found that TIG neither affected substantially the percentage and absolute counts of entire CD4+ and CD8+ T cell populations nor influenced the Foxp3+CD25+CD4+ regulatory/suppressive T cell subset. Furthermore, the percentages of IL-4-, IL-10-, IL-17- and TGF-β-producing CD4+ T cells were not altered following the exposure to TIG. Similarly, TIG did not influence IFN-γ production by CD8+ T cells. Thus, with respect to the parameters evaluated, TIG does not seem to exert immune-suppressive and anti-inflammatory effects.
Background: Uterine leiomyoma is the most widespread benign tumor affecting women of childbearing age. There are still gaps in the understanding of its pathogenesis. Telocytes are unique cells found in more than 50 different locations inside the human body. The functional relationship between cells could clarify the pathogenesis of leiomyomata. Examination of membrane receptors on telocytes could explain their role in fibrosis, oxidative stress, and myometrial contractility.
Aim: This research was conducted to assess the density of telocytes in terms of their putative role in leiomyoma formation by focusing on their correlation with the expression of estrogen and progesterone receptors.
Methods: For gross evaluation of uterine tissue samples from leiomyoma, routine histology of adjacent and unaffected myometrium was performed. Immunohistochemical analysis of c-kit, tryptase, CD34, PDGFRα (telocyte-specific), and ER and PRs (estrogen and progesterone receptors) was performed to examine uterine telocytes and the expression of sex steroid receptors.
Results: The decline in telocyte density in leiomyoma foci was correlated with high progesterone expression and low estrogen receptor expression. The unchanged myometrium showed the opposite correlation and balance between both steroid hormone receptors. The difference in sex steroid receptor expression is correlated with the density of uterine telocytes, which emphasizes their conductor function.
Conclusions: A reduction in telocyte density and the changes in examined marker expression demon-strate the involvement of telocytes in local homeostasis. The expression of membrane receptors explicitly indicates their functional potential in the human myometrium, focusing attention on contractility and local homeostasis.
I n t r o d u c t i o n: Hydronephrosis is an actual pediatric problem, affecting children in the anteand neonatal periods. Intrinsic stenosis is due to external obstruction and creates a pathophysiological basis of this urological pathology. Co-localization of ureter with a renal vasculature also could not be omitted from this point of view. Mesenchymal cells, partially telocytes, are important for local fibrosis development and hydronephrosis formation as well. In the current study, we focused on identification of telocytes in the human ureters to hypothesize their role in hydronephrosis pathophysiology.
M a t e r i a l a n d Me t h o d s: The samples were taken from 18 surgically treated patients with hydronephrosis (due to ureteral obstruction and crossing renal vessel). The control group consisted of 10 patients suffered from a non-obstructive disease of the urinary tract — predominantly renal tumors. Tissue samples from a ureter were stained for c-kit, tryptase, CD34 and PDGFRα to identify telocytes. Routine histology was performed to analyze tissue morphology, collagen deposits and mast cell’s profile.
R e s u l t s: Telocytes were detected in the ureteral wall. In patients with hydronephrosis we revealed decreasing density of telocytes, the prevalence of collagen, rise in mast cells amount and the ureteral wall thickening. In ureters with crossing renal vessels as a primary etiologic factor more telocytes have been observed in comparison with the obstructive hydronephrosis.
C o n c l u s i o n s: A declined density of telocytes accompanied hydronephrosis development. Increased number of mast cells in the ureteral wall reflects a local inflammation, while detailed observation of collagen/muscle deposits and density of telocytes reveal a difference depended on etiologic factor (obstruction or crossing vessel) in patients with hydronephrosis.
Analysis is performed of the contemporary views on the effect of ion etching (ion-beam milling and reactive ion etching) on physical properties of HgCdTe and on the mechanisms of the processes responsible for modification of these properties under the etching. Possibilities are discussed that ion etching opens for defect studies in HgCdTe, including detecting electrically neutral tellurium nanocomplexes, determining background donor concentration in the material of various origins, and understanding the mechanism of arsenic incorporation in molecular-beam epitaxy-grown films.
We review recently proposed concepts of infrared and terahertz photodetectors based on graphene van der Waals heterostructures and HgTe-CdHgTe quantum well heterostructures and demonstrate their potential.
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