Anomalous Spectral Characteristics of Ultrathin sub-nm Colloidal CdSe Nanoplatelets

We demonstrate high quantum yield broad photoluminescence emission of ultrathin sub-nanometer CdSe nanoplatelets (two-monolayer). They also exhibit polarization-characterized lateral size dependent anomalous heavy hole and light/split-off hole absorption intensities.Comment: Published in Conference on Lasers and Electro-Optics (CLEO): Science and Innovations 2017, San Jose, CA, USA, 14-19 May 2017 (2 pages, 3 figures

Quantum efficiency enhancement in nanocrystals using nonradiative energy transfer with optimized donor-acceptor ratio for hybrid LEDs

Cataloged from PDF version of article.The quantum efficiency enhancement in nanocrystal solids is critically important for their efficient use as luminophors on color-conversion light emitting diodes (LEDs). For this purpose, we investigate energy gradient mixture of nanocrystal solids for recycling their trapped excitons by varying their donor-acceptor nanocrystal ratios and study the resulting quantum efficiency enhancement as a function of the donor-acceptor ratio in the solid film for hybrid LEDs. We achieve a maximum quantum efficiency enhancement of 17% in these nanocrystal solids when the donor-acceptor ratio is 1:1, demonstrating their highly modified time-resolved photoluminescence decays to reveal the kinetics of strong energy transfer between them

Effects of gestational and lactational exposure to low dose mercury chloride (HgCl2) on behaviour, learning and hearing thresholds in WAG/Rij rats

We investigated the effects of inorganic mercury exposure during gestational/lactational periods on the behaviour, learning and hearing functions in a total of 32, 5-week-old and 5-month-old WAG/Rij rats (equally divided into 4 groups as 5-week and 5-month control mercury exposure groups). We evaluated the rats in terms of locomotor activity (LA), the Morris-water-maze (MWM) test and the passive avoidance (PA) test to quantify learning and memory performance; we used distortion product otoacoustic emission (DPOAE) tests to evaluate hearing ability. There were no significant differences between the 5-week-old rat groups in LA, and we detected a significant difference (p < 0.05) in the HgCl2-treated group in PA, MWM and DPOAE tests compared with the control group. The HgCl2-treated 5-week-old group exhibited worse emotional memory performance in PA, worse spatial learning and memory performances in MWM. There were no significant differences between the groups of 5-month-old rats in LA, MWM or PA. However, the DPOAE tests worsened in the mid- and high-frequency hearing thresholds. The HgCl2-treated 5-month-old group exhibited the most hearing loss of all groups. Our results convey that mercury exposure in young rats may worsen learning and memory performances as well as hearing at high-frequency levels. While there was no statistically significant difference in the behavior and learning tests in adult rats, the DPOAE test produced poorer results. Early detection of effects of mercury exposure provides medicals team with an opportunity to determinate treatment regimens and mitigate ototoxicity. DPOAE test can be used in clinical and experimental research investigating heavy metal ototoxicity

Intimate Monolithic integration of Chip-scale Photonic Circuits

Cataloged from PDF version of article.In this paper, we introduce a robust monolithic integration technique for fabricating photonic integrated circuits comprising optoelectronic devices (e.g., surface-illuminated photodetectors, waveguide quantum-well modulators, etc.) that are made of completely separate epitaxial structures and possibly reside at different locations across the wafer as necessary. Our technique is based on the combination of multiple crystal growth steps, judicious placement of epitaxial etch-stop layers, a carefully designed etch sequence, and self-planarization and passivation steps to compactly integrate optoelectronic devices. This multigrowth integration technique is broadly applicable to most III-V materials and can be exploited to fabricate sophisticated, highly integrated, multifunctional photonic integrated circuits on a single substrate. As a successful demonstration of this technique, we describe integrated photonic switches that consume only a 300 x 300 mu m footprint and incorporate InGaAs photodetector mesas and InGaAsP/InP quantum-well modulator waveguides separated by 50 mu m on an InP substrate. These switches perform electrically-reconfigurable optically-controlled wavelength conversion at multi-Gb/s data rates over the entire center telecommunication wavelength band

The relationship between high hepatic Fibrosis – 4 (FIB-4) index and asymptomatic thyroid nodules

Amaç: Asemptomatik hastalarda yapılan tiroid ultrasonu sırasında rastlanan insidental tiroid nodüllerinin karaciğer fibrozis skoruolan hepatik Fibrozis – 4 (FİB-4) indeksi ile ilişkisinin araştırılmasıdir. . Yöntemler: Hastanemiz iç hastalıkları polikliniğine genel kontrol amaçlı başvurmuş, herhangi bir semptomu olmayan ve yapılan tiroid ultrasonunda tiroid nodülü tesbit edilen veardışık seçilen100 hasta ile tiroid nodülü olmayan ardışık seçilen 100 kontrol hastası retrospektif olarak taranarak toplam 200 hastaçalışmaya dahil edildi. Hastaların yaşları, cinsiyetleri, Tiroid USG sonuçları , Abdominal USG sonuçları her bir hasta için ayrı ayrı kaydedildi. Tüm hastalar içinhepatik FİB-4 indeks skorlarıhesaplandı.Tek değişkenli ve çok değişkenli analizler için Spearman'ın korelasyon analizi ve ikili lojistik modeli kullanıldı. Bulgular: Hasta grubunun yaş ortalaması, hepatosteatoz derecesi, kreatinin duzeyive FİB-4dahayüksekti (p<0.05).. Yapilan Spearman'skorelasyon analizi sonucunda;tiroid nodülü ilecinsiyet (r=-0.331; p<0.01), yaş (r=0.344; p<0.01), kreatinin (r=-0.259; p<0.01)arasinda anlamli pozitif korelasyon olduğu gösterildi. (r=-0.154; p<0.05) ve FİB-4 (r=0.227; p<0.01). İkili lojistik regresyon analizi sonuçları, cinsiyetin (B=1,351; p<0,01) ve FIB-4'ün (B=1,603; p<0,01) tiroid nodülü üzerinde anlamlı etkisi olduğunu gösterdi. Sonuç: Hepatik FİB-4indeksi kolay hesaplanan ve ucuz bir parametre olması nedeniyle, asemptomatik hastalarda tiroid USG yapılacak hastaları belirlemede bir tarama testi olarak kullanılabilir.Objective: To investigate the relationship between incidental thyroid nodules found during thyroid ultrasound performed in asymptomatic patients and the hepatic Fibrosis – 4 (FIB-4) index. Methods: A total of 200 asymptomatic patients were included in the study by retrospectively screening those who applied to our hospital's internal medicine outpatient clinic for check-ups and 100 consecutively selected patients were diagnosed with thyroid nodules on thyroid ultrasonography and 100 consecutive patients were chosen without thyroid nodules on thyroid ultrasonography. Patients' ages, genders, thyroid USG results, and abdominal USG results were recorded separately for each patient. Hepatic FIB-4 index scores were calculated for all patients. Spearman's correlation analysis and a binary logistic model were used for univariate and multivariate analyses. Results: The patient group's mean age, hepatosteatosis grade; creatinine leveland mean FIB-4 werehigher (p<0.05). As a result of Spearman's correlation analysis; It was shown that there was a significant positive correlation between a thyroid nodule and gender (r=-0.331; p<0.01), age (r=0.344; p<0.01), and creatinine (r=-0.259; p<0.01). (r=-0.154; p<0.05) and FIB-4 (r=0.227; p<0.01). Binary logistic regression analysis results showed that gender (B=1.351; p<0.01) and FIB-4 (B=1.603; p<0.01) had significant effect on thyroid nodule. Conclusion: Since the hepatic FIB-4 index is an easily calculated and inexpensive parameter, it can be used as a screening test to identify patients who will undergo thyroid USG in asymptomatic patients

Exciton Dynamics of Colloidal Semiconductor Quantum Well Stacks

Colloidal semiconductor nanoplatelets (NPLs) have recently emerged as a new class of colloidal nanocrystals. NPLs are quasi two-dimensional nanocrystals having atomically flat surfaces and have unique properties such as narrow photoluminescence (PL) emission (similar to 10 nm) and giant oscillator strength. NPLs can be self-assembled into stacks. These are one-dimensional superstructures that can contain tens or hundreds of NPLs in one chain

The prognostic value of arterial stiffness in systolic heart failure

Background: Increased arterial stiffness is an indicator of mortality. This study consists of an 18-month follow-up of the mortality in advanced heart failure patients with increased arterial stiffness.Methods: The study followed up 98 patients with a diagnosis of heart failure in NYHA class III and IV (76 males, 22 females and mean age of 60 ± 12 years) with a left ventricular ejection fraction ≤ 35% as determined by the Simpson method. Augmentation index (Aix) and pulse wave propagation velocity (PWV) parameters were used as indicators of arterial stiffness. Aix and PWV values were measured by arteriography.Results: 36 patients died. Both Aix and PWV were powerful determinants of mortality, independent of other prognostic variables (p = 0.013, OR: 0.805; p = 0.025, OR: 0.853). A cutoff value for Aix of –14.33 gave 91.2%, 80.3% sensitivity and specificity. A cutoff value for PWVof 11.06 gave 82.4%, 65.4% sensitivity and specificity mortality was predicted. Left ventricular ejection fraction (p = 0.008, OR: 0.859) and B-type natriuretic peptide (p = 0.01, OR: 0.833) was the other independent determinant of mortality. A significant difference was found inboth Aix and PWV between the compensated measurements and decompensated heart failure measurements made in 70 patients (p = 0.035, p = 0.048).Conclusions: Measurement of arterial stiffness is a convenient, inexpensive and reliable method for predicting mortality in patients with advanced heart failure

Nonradiative energy transfer in colloidal CdSe nanoplatelet films

Nonradiative energy transfer (NRET) has been extensively studied in colloidal nanocrystal (quantum dots) and nanorod (quantum wires) assemblies. In this work, we present the first account of spectroscopic evidence of NRET in solid thin films of CdSe based colloidal nanoplatelets (NPLs), also known as colloidal quantum wells. The NRET was investigated as a function of the concentration of two NPL populations with different vertical thicknesses via steady state and time resolved spectroscopy. NRET takes place from the NPLs with smaller vertical thickness (i.e., larger band gap) to the ones with a larger vertical thickness (i.e., smaller band gap) with efficiency up to similar to 60%. Here, we reveal that the NRET efficiency is limited in these NPL solid film assemblies due to the self-stacking of NPLs within their own population causing an increased distance between the donor-acceptor pairs, which is significantly different to previously studied colloidal quantum dot based architectures for nonradiative energy transfer

Orientation-Controlled Construction of Superstructures of Atomically-Flat Nanocrystals: Pushing the Limits of Ultra-Thin Colloidal Gain Media

We propose and demonstrate a method for the construction of highly uniform, multilayered, orientation-controlled superstructures of CdSe/CdZnS core/shell colloidal nanoplatelets (NPLs) using bi-phase liquid interface. These atomically-flat nanocrystals are sequentially deposited, all face-down onto a solid substrate, into slabs having monolayer-precise thickness and excellent homogeneity over several tens of cm2 areas. Owing to the near-unity surface coverage and film uniformity of this deposition technique, amplified spontaneous emission (ASE) is observed from an uncharacteristically thin colloidal film having only 6 layers of NPLs, which corresponds to a mere 42 nm thickness. Furthermore, systematic studies of optical gain properties of these NPL superstructures constructed having precise numbers of NPL layers tuned from 6 to 15 revealed the reduction in the gain threshold with the increasing number of NPL monolayers, along with a continuous spectral shift in the position of the ASE peak (by ~18 nm). These observations can be well explained by the variation of the optical field confinement factor with the NPL waveguide thickness and propagation wavelength. This work demonstrates the possibility of fabricating thickness-tunable, large-area three-dimensional superstructures made of NPL building blocks, which can be additively constructed one monolayer at a time. The proposed technique can also be extended to build hybrid NPL films of mixed orientations and allow for precise large-area device engineering.Comment: 23 pages, 4 figure