N-structure based on InAs/AlSb/GaSb superlattice photodetectors

We have studied the theoretical and experimental properties of InAs/AlSb/GaSb based type-II superlattice (T2SL) pin photodetector called N-structure. Electronic properties of the superlattice such as HH-LH splitting energies was investigated using first principles calculations taking into account InSb and AlAs as possible interface transition alloys between AlSb/InAs layers and individual layer thicknesses of GaSb and InAs. T2SL N-structure was optimized to operate as a MWIR detector based on these theoretical approaches tailoring the band gap and HH-LH splitting energies with InSb transition layers between InAs/AlSb interfaces. Experimental results show that AlSb layers in the structure act as carrier blocking barriers reducing the dark current. Dark current density and R0A product at 125 K were obtained as 1.8 × 10-6 A cm-2 and 800ωcm2 at zero bias, respectively. The specific detectivity was measured as 3 × 1012 Jones with cut-off wavelengths of 4.3 μm at 79 K reaching to 2 × 109 Jones and 4.5 μm at 255 K. ©2014 Elsevier Ltd. All rights reserved

Theoretical investigation of InAs/GaSb type-II pin superlattice infrared detector in the mid wavelength infrared range

In this study, we present the theoretical investigation of type-II InAs/GaSb superlattice p-i-n detector. Kronig-Penney and envelope function approximation is used to calculate band gap energy and superlattice minibands. Variational method is also used to calculate exciton binding energies. Our results show that carriers overlap increases at GaSb/InAs interface on the higher energy side while it decreases at InAs/GaSb interface on the lower energy side with increasing reverse bias due to shifting the hole wavefunction toward to the GaSb/InAs interface decisively. Binding energies increase with increasing electric field due to overall overlap of electron and hole wave functions at the both interfaces in contrast with type I superlattices. This predicts that optical absorption is enhanced with increasing electric field. © 2013 American Institute of Physics

Electronic and optical properties of 4.2 μm"N" structured superlattice MWIR photodetectors

We report on the development of a new structure for type II superlattice photodiodes that we call the "N" design. In this new design, we insert an electron barrier between InAs and GaSb in the growth direction. The barrier pushes the electron and hole wavefunctions towards the layer edges and under bias, increases the overlap integral by about 25% leading to higher detectivity. InAs/AlSb/GaSb superlattices were studied with density functional theory. Both AlAs and InSb interfaces were taken into account by calculating the heavy hole-light hole (HH-LH) splittings. Experiments were carried out on single pixel photodiodes by measuring electrical and optical performance. With cut-off wavelength of 4.2 μm at 120 K, temperature dependent dark current and detectivity measurements show that the dark current is 2.5 × 10 -9 A under zero bias with corresponding R0A resistance of 1.5 × 104 Ω cm2 for the 500 × 500 μm2 single pixel square photodetectors. Photodetector reaches BLIP condition at 125 K with the BLIP detectivity (DBLIP) of 2.6 × 10 10 Jones under 300 K background and -0.3 V bias voltage. © 2012 Elsevier B.V. All rights reserved

Relationship between Lymphocytes, IL2 and the Hormones E2, LH, PRG and FSH in Menopausal and Postmenopausal Women

Proble

A new surgical technique for hepatic vein reconstruction in pediatric live donor liver transplantation

PubMed ID: 18208439The hepatic venous reconstruction is one of the corner stones of pediatric LDLT. However, problems associated with hepatic venous outflow still remain to be an issue. In this study, we aimed at comparing two methods used in hepatic venous reconstruction. Between November 1999 and December 2006, 61 consecutive left lateral segment pediatric LDLT were performed at Ege University Organ Transplant Center, and two methods were used for hepatic venous reconstruction. In the former group (group 1: 32 patients) continuous anastomosis was performed between the donor LHV and common orifice of the recipient HV. In the later group (group 2: 29 patients), the posterior wall of the anastomosis was sutured continuously while the anterior wall was sutured with interrupted sutures. HV thrombosis was detected in one patient and stenosis was detected in four patients in group 1. No hepatic venous outflow obstruction was detected in group 2 (p < 0.05). In both groups, mortality was not associated with hepatic venous outflow obstruction. As our results indicate, the novel technique used in this study is a simple and safe anastomosis procedure that has contributed into overcoming hepatic venous outflow problems in pediatric LDLT. © 2008 Wiley Periodicals, Inc

Clinical evaluations of cell-free fetal DNA quantities in pre-eclamptic pregnancies

Aim Quantitative changes of cell-free fetal DNA in maternal plasma as an indicator for impending pre-eclampsia was reported in different studies. Cell-free fetal nucleic acids can be detected in maternal circulation during pregnancy. Our aim was to determine the higher rate of fetal DNA levels in maternal blood in pre-eclampsia compared to normal pregnancies and the clinical use of real-time polymerase chain reaction (PCR) in the Turkish population as a marker. Material and Methods According to their gestational ages, the plasma levels of 30 pre-eclamptic women at 2640 weeks of pregnancy were matched with 18 healthy pregnant women. Cell-free fetal DNA levels in maternal plasma were compared using real-time PCR technology. For the quantitative measurement of fetal DNA from maternal blood, the relative quantification PCR process was applied to all samples, using SRY and GAPDH genes. These patients were classified as pre-eclamptic and control groups and were matched according to weeks of pregnancy. Results Free fetal DNA levels of 30 pre-eclamptic patients were compared to healthy pregnant women and an average 3.06-fold increase was observed. During the second trimester, free fetal DNA levels were 1.5 times higher in pre-eclamptic patients. This increase was 3.5-fold during the third trimester. The DNA increase of pre-eclamptic patients was 4.1-fold and 3.4-fold during 29th33rd and 34th40th weeks, respectively. Conclusions Cell-free fetal DNA in maternal blood could be used as a marker for identifying subjects at increased risk of developing pre-eclampsia

Clinical evaluations of cell‐free fetal DNA

Aim Quantitative changes of cell-free fetal DNA in maternal plasma as an indicator for impending pre-eclampsia was reported in different studies. Cell-free fetal nucleic acids can be detected in maternal circulation during pregnancy. Our aim was to determine the higher rate of fetal DNA levels in maternal blood in pre-eclampsia compared to normal pregnancies and the clinical use of real-time polymerase chain reaction (PCR) in the Turkish population as a marker. Material and Methods According to their gestational ages, the plasma levels of 30 pre-eclamptic women at 2640 weeks of pregnancy were matched with 18 healthy pregnant women. Cell-free fetal DNA levels in maternal plasma were compared using real-time PCR technology. For the quantitative measurement of fetal DNA from maternal blood, the relative quantification PCR process was applied to all samples, using SRY and GAPDH genes. These patients were classified as pre-eclamptic and control groups and were matched according to weeks of pregnancy. Results Free fetal DNA levels of 30 pre-eclamptic patients were compared to healthy pregnant women and an average 3.06-fold increase was observed. During the second trimester, free fetal DNA levels were 1.5 times higher in pre-eclamptic patients. This increase was 3.5-fold during the third trimester. The DNA increase of pre-eclamptic patients was 4.1-fold and 3.4-fold during 29th33rd and 34th40th weeks, respectively. Conclusions Cell-free fetal DNA in maternal blood could be used as a marker for identifying subjects at increased risk of developing pre-eclampsia

Electrical Performance Of Inas/Alsb/Gasb Superlattice Photodetectors

Temperature dependence of dark current measurements is an efficient way to verify the quality of an infrared detector. Low dark current density values are needed for high performance detector applications. Identification of dominant current mechanisms in each operating temperature can be used to extract minority carrier lifetimes which are highly important for understanding carrier transport and improving the detector performance. InAs/AlSb/GaSb based T2SL N-structures with AISb unipolar barriers are designed for low dark current with high resistance and detectivity. Here we present electrical and optical performance of such N-structure photodetectors. (C) 2016 Elsevier Ltd. All rights reserved.Wo

Genomic and proteomic investigation of preeclampsia

The aim of this study was to use proteomic and transcriptomic approaches to examine differences in protein and gene expression in maternal plasma between normal and preeclamptic pregnancies. Preeclampsia and control groups were compared with respect to the expression of CD34 and CD133 genes by quantitative polymerase chain reaction (qPCR) and heat shock protein (Hsp) 27 and 70 by western blotting in blood samples from the pregnant women. Blood samples were obtained at gestational week 12-14 from 65 healthy pregnant women. Fetal DNA was isolated from the maternal blood and CD34 and CD133 were amplified by qPCR. Western blot analysis was used to examine the expression levels of Hsp27 and Hsp70 proteins. The analysis of CD133 by qPCR was unsuccessful in 7 women as the levels of fetal DNA were in the collected maternal blood samples were insufficient. Measurements of CD34 and CD133 were performed in 57 and 50 women, respectively. Preeclampsia developed in 6 (10.5%) of 57 women. qPCR results of 8 healthy pregnant women were used for the calibration of CD34 and CD133 levels, and the results for the remaining women were compared with the calibration values. CD34 expression was decreased in 30 (52.6%) and increased in 27 (47.4%) of 57 women. CD133 expression was decreased in 14 (28%) and increased in 36 (72%) of 50 women. CD34 expression was increased in 2 (33%) and 25 (49%) and decreased in 4 (66%) and 25 (51%) women with and without preeclampsia, respectively (P= 0.467). CD133 expression was increased in 4 (66%) and 32 (72%); and decreased in 2 (33%) and 12 (28%) women with and without preeclampsia, respectively (P= 0.756). Western blotting showed that the expression of Hsp27 and Hsp70 in the maternal serum of the preeclampsia group was significantly higher than that in the normal pregnancy group. CD34 and CD133 were found to be inadequate for use in the prediction of preeclampsia. However, it is noteworthy that CD133 levels were increased in 66 and 72% of women with and without preeclampsia, respectively. Hsps are expressed under various pathological conditions. These results suggest that conditions of oxidative stress increased the Hsp27 and Hsp70 protein levels