Implementation of an Improved Water Change Tracking (IWCT) Algorithm: Monitoring the Water Changes in Tianjin over 1984–2019 Using Landsat Time-Series Data

Tianjin is the largest open city along the coastline in Northern China, which has several important wetland ecosystems. However, no systematic study has assessed the water body changes over the past few decades for Tianjin, not to mention their response to human activities and climate change. Here, based on the water change tracking (WCT) algorithm, we proposed an improved water change tracking (IWCT) algorithm, which could remove built-up shade noise (account for 0.4%~6.0% of the final water area) and correct omitted water pixels (account for 1.1%~5.1% of the final water area) by taking the time-series data into consideration. The seasonal water product of the Global Surface Water Data (GSWD) was used to provide a comparison with the IWCT results. Significant changes in water bodies of the selected area in Tianjin were revealed from the time-series water maps. The permanent water area of Tianjin decreased 282.5 km2 from 1984 to 2019. Each time after the dried-up period, due to government policies, the land reclamation happened in Tuanbo Birds Nature Reserve (TBNR), and, finally, 12.6 km2 of the lake has been reclaimed. Meanwhile, 488.6 km2 of land has been reclaimed from the sea along the coastal zone in the past 16 years at a speed of 28.74 km2 yr−1 in the Binhai New Area (BHNA). The method developed in this study could be extended to other sensors which have similar band settings with Landsat; the products acquired in this study could provide fundamental reference for the wetland management in Tianjin.

Refined Band Structure plus Enhanced Phonon Scattering Realize Thermoelectric Performance Optimization in CuI-Mn Codoped SnTe

With the same crystal structure and similar band structure, SnTe is regarded as an eco-friendly alternative of PbTe for the mid-temperature power generation application, but its thermoelectric performance suffers from...

Electron-hole hybridization in bilayer graphene

Band structure determines the motion of electrons in a solid, giving rise to exotic phenomena when properly engineered. Drawing an analogy between electrons and photons, artificially designed optical lattices indicate the possibility of a similar band modulation effect in graphene systems. Yet due to the fermionic nature of electrons, modulated electronic systems promise far richer categories of behaviors than those found in optical lattices. Here, we uncovered a strong modulation of electronic states in bilayer graphene subject to periodic potentials. We observed for the first time the hybridization of electron and hole sub-bands, resulting in local band gaps at both primary and secondary charge neutrality points. Such hybridization leads to the formation of flat bands, enabling the study of correlated effects in graphene systems. This work may provide a novel way to manipulate electronic states in layered systems, which is important to both fundamental research and application.

Thermoelectric Properties of Tin Telluride Quasi Crystal Grown by Vertical Bridgman Method

Tin telluride (SnTe), with the same rock salt structure and similar band structure of PbTe alloys, was developed as a good thermoelectric material. In this work, SnTe quasi crystal was grown by vertical Bridgman method, with texturing degree achieved at 0.98. Two sets of samples, perpendicular and parallel to the growth direction, were cut to investigate thermoelectric properties. As a result, a carrier concentration (pH) of ~9.5 × 1020 cm−3 was obtained, which may have originated from fully generated Sn vacancies during the long term crystal growth. The relatively high Seebeck coefficient of ~30 μVK−1 and ~40 μVK−1 along the two directions was higher than most pristine SnTe reported in the literature, which leads to the room temperature (PF) for SnTe_IP and SnTe_OP achieved at ~14.0 μWcm−1K−2 and ~7.0 μWcm−1K−2, respectively. Finally, the maximum dimensionless figure of merit (ZT) values were around 0.55 at 873 K.

OLIGOMERIC SILSESQUIOXANES COMBINING AZO- AND FLUORESCENT DYES IN ORGANIC SHELL

A method for the synthesis of reactive oligomeric silsesquioxanes, combining fragments of azo dye 4-(phenylazo)phenol and fluorescent dye Rhodamine B in various proportions in an organic shell was developed. These compounds were obtained by the reaction between the oligosilsesquioxane nanoparticles consisting of a mixture of linear, branched, ladder and polyhedral structures with epoxy groups in an organic frame (OSS–Ep) and the dyes. The structure of the synthesized substances was characterized by the methods of IR and 1H NMR spectroscopy. The UV-Vis spectra of OSS–Pp–Rh in DMF solution contain absorption bands characteristic of both acidic (560 and 350 nm) and lactone (in the range of 318–326 nm) forms of Rhodamine B. The absorption band of 4-(phenylazo) phenol fragments corresponding to π−π* transition is observed at 348 nm and overlaps the absorption band of Rhodamine B at 350 nm.The intensity of the absorption bands of fragments of various dyes depends on their content in organic frame of the silsesquioxane core. The intensity of the absorption bands at 348 nm and at 560 nm increases with an increase in the content of 4-(phenylazo)phenol and Rhodamine B correspondingly.It should be noted that when using DMF as a solvent the absorption band corresponding to acidic form of Rhodamine B at 560 nm in the UV-Vis spectra of the compounds obtained is more intense than similar band in the spectrum of the original Rhodamine B. Therefore, the attachment of Rhodamine B to the silsesquioxane core of oligomeric silsesquioxanes mixture does not have a significant effect on the position of absorption maxima in the UV-spectrum and prevents dye’s fragments from converting to the colorless lactone form. In the fluorescence spectra of OSS–Pp–Rh obtained using DMF as a solvent a peak at λ max = 592 nm (λex= 520 nm) is observed. The position of the fluorescence peak and its intensity in the spectra at the same optical density of the medium practically do not depend on the ratio of fragments of 4-(phenylazo)phenol and Rhodamine B in organic frame of OSS–Pp–Rh. The combination of two different chromophores in organic shell of the silsesquioxane core broadens the range of absorbed light and the change of their ratio allows to adjust the absorption intensity in a certain area. The presence of hydroxyl groups makes it possible to introduce the obtained compounds into the composition of polymeric organic-inorganic nanocomposites by covalent bonding.

Prediction of fully compensated ferrimagnetic spin-gapless semiconducting FeMnGa/Al/In half Heusler alloys

Materials with full spin polarization that exhibit zero net magnetization attract great scientific interest because of their potential applications in spintronics. Here, the structural, magnetic and electronic properties of a C1 b -ordered FeMnGa alloy are reported using first-principles calculations. The results indicate that the corresponding band structure exhibits a considerable gap in one of the spin channels and a zero gap in the other thus allowing for high mobility of fully spin-polarized carriers. The localized magnetic moments of Fe and Mn atoms have an antiparallel arrangement leading to fully compensated ferrimagnetism, which possesses broken magnetic inversion symmetry. Such magnetic systems do not produce dipole fields and are extremely stable against external magnetic fields. Therefore, this will improve the performance of spintronic devices. Using this principle, similar band dispersion and compensated magnetic moments were predicted in a C1 b -ordered FeMnAl0.5In0.5 Heusler alloy.

Magnetic and optical investigations on LaFeO3 powders with different particle sizes and corresponding ceramics

The optical and magnetic properties of nano-LaFeO3 powders prepared by a starchassisted soft-chemistry synthesis and corresponding ceramics have been investigated.Magnetic measurements on LaFeO3 powders with crystallite sizes of 37−166 nm showpronounced magnetization hysteresis loops. Measurements at 300 K reveal that the coercivity(Hc) of 19−32 kOe depends on the crystallite size, whereas the low remanence values (Mr) ofroughly 0.2 emu/g and the maximal magnetization (Mmax) at 90 kOe of 1.05−0.85 emu/g areonly slightly changing. Investigations at 10 K reveal a loop shift (exchange bias) up to 12 kOein the negative direction depending on the crystallite size. Ceramic bodies, sintered at ³ 1300°C possess a considerably reduced hysteresis loop. Hc is decreased up to 3.0 kOe, whereas Mr and Mmax are slightly increasing. None of the samples reaches saturation at 90 kOe indicating an anti-ferromagnetic ordering of the spins. The optical band gaps of the LaFeO3 sampleswere determined by means of diffuse reflectance spectra. For all LaFeO3 powders similar band gaps of 2.65 eV were observed. However, ceramics with grain-size significantly larger than 250 nm show smaller band gap values up to 2.12 eV.

Opto-Electrical Properties of Composite Materials Based on Two Benzotrithiophene Copolymers and Fullerene Derivatives

Two donor–acceptor copolymers based on a benzotrithiophene acceptor unit and an electron-donor segment of 4,8-didodecyloxybenzo[1,2-b;4,5-b′]dithiophene were investigated in the view of photovoltaic application. We provided the complete synthesis procedure supported with NMR spectra of the monomers obtained. The resulting copolymers, labeled P1 and P2 in this work, exhibit strong absorption in the visible region with a similar band gap of about 2.2 eV. In spite of the chemical similarity of both copolymers, the photovoltaic and carrier transport properties of the P1- and P2-based devices demonstrated a noticeable difference. Applying an optimization procedure, a power conversion efficiency of 4.6% has been achieved for the P2/PC71BM solar cells.

Comparison of electron injection and recombination on TiO 2 nanoparticles and ZnO nanorods photosensitized by phthalocyanine

Titanium dioxide (TiO 2 ) and zinc oxide (ZnO) semiconductors have similar band gap positions but TiO 2 performs better as an anode material in dye-sensitized solar cell applications. We compared two electrodes made of TiO 2 nanoparticles and ZnO nanorods sensitized by an aggregation-protected phthalocyanine derivative using ultrafast transient absorption spectroscopy. In agreement with previous studies, the primary electron injection is two times faster on TiO 2 , but contrary to the previous results the charge recombination is slower on ZnO. The latter could be due to morphology differences and the ability of the injected electrons to travel much further from the sensitizer cation in ZnO nanorods.

Identification of Single Nucleotide Polymorphism in GnRHR gene in Murrah bulls

The present study was undertaken with the objectives of molecular characterization and detection of genetic polymorphism in the GnRHR gene in Murrah bulls. Blood samples were collected from 109 Murrah bulls maintained at three different organized semen stations viz., Centralized Semen Collection Centre of Livestock Breeding and Training Centre, Dharwad; Nandini Sperm Station and State Livestock Breeding and Training Centre, Hessarghatta, Bengaluru, Karnataka, India. Genomic DNA was isolated from the blood samples within 24 hours of collection . Mutations were screened using Polymerase Chain Reaction – Single Stranded Conformational Polymorphism (PCR-SSCP) technique followed by Sanger Sequencing. PCR-SSCP method revealed similar band pattern within Murrah bulls. To confirm monomorphism in the studied population with respect to GnRHR gene, duplicate samples from each primer fragment were custom sequenced. PCR-SSCP and sequence analysis revealed monomorphism within the studied population that is coding region as well as exon-intron boundaries of GnRHR gene is highly conserved among Murrah bulls. However, a total of 28 Single Nucleotide variations (SNV’s) have been found when compared with Bos Taurus reference sequence for GnRHR gene.