Reaction-Induced Liquid Crystalline Polybenzoxazine Bearing Aromatic Amide Side Branches.

In this study, a nematic phase structure is incorporated into polybenzoxazine to increase its thermal conductivity. A simple route for the synthesis of a thermally conductive polybenzoxazine containing liquid crystalline (LC) structure by grafting oligomeric p-sulfophenylene-terephthalamide (PSTA) is offered. Benzoxazine monomer of pHBA-da is synthesized via Mannich reaction of p-hydroxy benzoic acid, p-formaldehyde, and dodecyl amine. After ring-opening polymerization, the oligomer benzoxazine of OBZ─COOH is obtained. The OBZ─COOH/PSTA mixture is prepared by mixing PSTA with OBZ─COOH. Afterward, the grafted copolymer is named OBZ─PSTA copolymer. The liquid crystalline behavior of OBZ─COOH/PSTA is studied by polarized optical microscopy and small angle X-ray scattering analysis. The results show that the OBZ─PSTA forms the LC structure during isothermal and non-isothermal curing. The LC structure displays a floral textured nematic phase. The phase formation is induced by an amidation reaction. Due to the grafts of LC PSTA, the thermal conductivity of OBZ─PSTA is 0.296 W m-1 K-1 , which is 26% greater than OBZ─COOH. The glass transition temperature (Tg ) of OBZ─PSTA is 241 °C. The 5% (Td5 ) and 10% weight loss temperatures (Td10 ) of OBZ─PSTA are 346 and 362 °C, respectively.

Divalent Heterometal Doped Titanium-Oxide Cluster Polymers: Structures, Photoresponse, and Photocatalysis.

Five cluster polymers based on heterometal-doped titanium-oxide cluster (TOC) monomers are reported. The monomers feature Ti10-oxide cluster cores and are connected to the divalent closed-shell heterometal anchors by salicylate ligands. The Sr2+, Ba2+, and Pb2+ dopants cause the monomers to bind head-to-head and generate linear chains, while the Ca2+ and Cd2+ lead to head-to-tail connections and zigzag chains. The cluster polymers are responsive to visible-light up to 565 nm and photo-catalytically active in both H2 evolution and CO2/epoxide cycloaddition reactions. The photo-absorption, photo-charge separation, and photocatalytic properties of the cluster polymers are dependent on the heterometal dopants in order Cd > Pb > Ba > Sr > Ca. Heterometals serve as the catalytic sites in the cluster polymers, which depending on the contribution of the pCB bottom, facilitate photo-charge separation and interfacial charge transfer, further enhancing catalytic activity. The tunable compositions and topologies of the cluster polymers shown herein may inspire the design and synthesis of more multidimensional functional metal-oxide cluster materials for a variety of applications in the future.

Lead-Decorated Titanium Oxide Compound with a High Performance in Catalytic CO2 Insertion to Epoxides.

The CO2 cycloaddition to epoxides is an efficient method for CO2 capture and storage, important not only for reducing greenhouse gas emission but also for producing cyclic carbonates, which are valuable industrial materials. In this study, we report a novel high-nuclearity titanium oxide cluster (TOC) inlayed with main-group element Pb2+, H2Ti16Pb9O24(SA)18(DMF)10(OH2)2 (denoted as 1; SA = salicylate; DMF = N,N-dimethylformamide), which has the property of visible-light absorption and has shown high catalytic activities for cycloadditions of CO2 under visible-light irradiation. The cluster was synthesized in a high yield in a facial solvothermal process. Its structure and electronic structure were characterized by single-crystal X-ray diffraction, density functional theory calculations, and complementary techniques. The cycloaddition reactions were performed under solvent-free conditions. While the catalytic activity due to the Lewis acidity was moderate, visible-light irradiation further folded the reaction rates. The turnover number reached 3400 with a turnover frequency of 120 h-1. Mechanism studies indicated a synergistic effect of the Lewis acidity and photogenerated charge carriers. The performance of 1 in reversible I2 uptake was also investigated. This study demonstrates the high potential of heterometal-decorated TOCs in the cost-effective and efficient CO2 cycloaddition reaction under mild conditions.

A Mesoporous Lead-Doped Titanium Oxide Compound with High Performance and Recyclability in I2 Uptake and Photocatalysis.

A three-dimensional (3D) mesoporous material with an atomically precise structure, Ti16Pb5O16(C6H5CO2)2(OCH3)40 (Ti16Pb5), comprised of a novel high-nuclearity Pb-doped titanium oxide cluster (TOC), was synthesized. Ti16Pb5 exhibited a surface area of 45 m2 g-1 and a pore diameter of 3.5 nm. It exhibited an uptake capacity of I2 of ≤2.2 g g-1 in vapor, and the performance was maintained after seven uptake-release cycles. Ti16Pb5 also showed a high adsorption ratio and capacity (93% and 3.1 g g-1) in hexane. The characterization data, including Fourier transform infrared, Raman, and powder X-ray diffraction, suggested the lattice structure of Ti16Pb5 was rigid and I2 was accommodated in the pores of Ti16Pb5. To the best of our knowledge, this is the first example of using a TOC in I2 adsorption. In addition, Ti16Pb5 showed excellent activity and recyclability in visible-light degradation of dye pollutants and photocurrent generation. Our structural analysis suggested the alkoxide ligands within the channels of Ti16Pb5 build up a confined polar environment and thereby facilitate I2 accommodation, and meanwhile, the improved performances and stabilities of Ti16Pb5 are correlated with its cluster-based, 3D hierarchical structure.

Cr-Ti Mixed Oxide Molecular Cages: Synthesis, Structure, Photoresponse, and Photocatalytic Properties.

The solvothermal reaction of titanium isopropoxide and chromate in the presence of benzoate produced two novel host-guest clusters encapsulating Cs+ or H3O+, (H3O)@Ti7Cr14 and Cs@Ti7Cr14. The most remarkable feature is that the Ti7O7 ring is concentrically embraced by a Cr14O14 ring to form a rigid Ti7Cr14 host. ESI-MS and 133Cs NMR revealed that the overall framework structures are preserved, whereas the benzoate ligands on the two clusters may be labile in solutions. Both (H3O)@Ti7Cr14 and Cs@Ti7Cr14 exhibit good UV-vis light-responsive properties and photocatalytic activities, with absorption edges extending up to 780 nm. Cs@Ti7Cr14 is an effective visible-light-responsive photocatalyst in both the heterogeneous methylene dye degradation and homogeneous CO2 cycloaddition reaction under mild conditions like room temperature and 1 bar of CO2. According to the mechanism studies, Cs+, as a rigid guest, can significantly improve the photogenerated charge separation efficiency of the Ti7Cr14 host, thereby improving its interface charge separation properties, photocurrent, and photocatalytic activities. Our findings not only provide new members of heterometallic titanium oxide clusters to enrich the metal oxide cluster family but also open up new possibilities for their photoresponses, which may play an important role in solar energy harvesting for sustainable chemistry.

Polyethylene glycol capped copper ferrite porous nanostructured materials for efficient photocatalytic degradation of bromophenol blue.

Three different types (blank, annealed, and functionalized) of copper ferrite nanoparticles (CuFe2O4) were synthesized by the co-precipitation method. The CuFe2O4 NPs were characterized by Fourier transform infrared (FTIR), Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Energy-dispersive X-ray spectroscopy (EDX) techniques. FTIR analysis confirmed that 3-APTES is successfully grafted on the surface of CuFe2O4 NPs. XRD results show the amorphous nature of blank CuFe2O4 NPs, and crystalline structure was observed for annealed and functionalized CuFe2O4 NPs. XRD results revealed that crystallite size ranges from 23.6 to 34.6 nm. SEM micrographs of blank CuFe2O4 NPs show the irregular shape and size of the nanostructure. The spherical and strongly linked structure was seen in the micrograph of functionalized CuFe2O4 NPs. EDX analysis revealed the nanostructure composed of Fe, Cu, O, and a small percentage of Si. The photocatalytic degradation efficiency of synthesized CuFe2O4 NPs was examined under UV irradiation in an aqueous medium against bromophenol blue (BPB) dye. The effect of different parameters such as irradiation time and pH on the photodegradation of BPB dye was studied by all three types of CuFe2O4 photocatalyst. Results show that the maximum photocatalytic degradation efficiency was observed for functionalized CuFe2O4 nanoparticles that degraded 98% of BPB dye in the acidic medium at pH = 1. The optimum contact time for dye degradation was 120 min by synthesized photocatalyst. Photodegradation performance of blank and annealed CuFe2O4 NPs is less than 90%. The synthesized CuFe2O4 NPs were recycled and reused, which shows good photocatalytic degradation efficiency up to 4 consecutive cycles. The kinetic model displayed that degradation reaction followed pseudo 1st order kinetics. The blank, annealed, and functionalized CuFe2O4 NPs have turnover numbers of 10.7x10 (Mudhoo et al., 2019), 12.9x10 (Mudhoo et al., 2019), and 22.2x10 (Mudhoo et al., 2019) (kg-1 sec-1) accordingly. In conclusion, all results revealed the high efficiency of prepared photocatalyst for tested hazardous dye from wastewater and encouraged more work on photodegradation of organic pollutants from wastewater.

Assembly of Interlocked Superstructures with a Titanium Oxide Molecular Ring in Water.

[2]Catenane, [2]rotaxane, and [2]pseudorotaxane based on a cyclic titanium oxide cluster, [Ti8O8(SO4)16]16- (Ti8), and cyclic/linear alkylammonium cations are reported. Their syntheses, structures, spectroscopy, and stability in water were studied. These molecules were synthesized from and remained intact upon redissolution in acidic water. Hence, the cluster Ti8 is a promising metal oxide ring that can be used as an inorganic analogue of crown ether to assemble inorganic-organic hybrid mechanical interlocked supramolecular assemblies in water.

Enhancing the photocatalytic performance of a rutile unit featuring a titanium-oxide cluster by Pb2+ doping.

Titanium-oxide clusters (TOCs) are well-defined molecular models for TiO2 materials and provide the opportunity to study the structure-activity relationships of TiO2. Here, we report a new Pb-doped TOC, Ti12Pb2, which resembles a two-layer decker of the {TiTi6} structural units of rutile TiO2 with two Ti4+ ions replaced by two Pb2+ ions. Its electronic structure, photoresponse, and photocatalytic performances were investigated and compared with those of the Ti14 cluster, which is isostructural to Ti12Pb2. Our results indicate that Pb2+ does not affect the electronic structure, but it greatly enhances the photocatalytic activity by improving the charge-separation and interfacial charge-transfer properties of the TOC. The successful synthesis of Ti12Pb2 highlights the roles of closed-shell heterometal ions in the construction of new TOCs. Our mechanism may be an inspiration for understanding the structure-activity relationships of closed-shell heterometal-doped TiO2.

Altitudinal distribution and seasonal migration of asiatic black bear (Ursus thibetanus) in kaghan and Siran Valleys, Pakistan.

The Asiatic black bear (Ursus thibetanus) is considered one of the largest carnivores inhabiting different territories including coniferous and broad-leaved forests, extending from sea level to the elevation of 4300 m. The Kaghan and Siran Valleys in Pakistan's District Mansehra were the location of the current study. To evaluate the altitudinal distribution and seasonal movement of Asiatic black bears in the region, we used three approaches (sign distribution survey, questionnaire-based survey, and scat collecting). A total of 1858 bear signs were observed during the field survey, the highest number of signs was dig marks (1213) followed by plant uprooting. Dig marks (MER: 7.574) were observed repeatedly in each potential site of both valleys followed by plant uprooting (MER: 1.594). Similarly, the altitudinal distribution of black bears was determined through the frequency of signs concerning elevation (m). Elevation of the study area ranged from 1300 to 3500 m and the most abundant population was recorded at the elevation of 2501-3000 m followed by 2001-2500 m. About 52% of local communities encountered black bears during the summer season in the field followed by Spring (23%.8) and winter (15.3%). Manshi Reserver forest (24.5%) from Kaghan and Panjul Reserve forest (31.6) from Siran Valley are the potential summer migratory spots. Eleven scat samples were collected with a 0.103 encounter rate (ER). Most of the scats (about 70%) were observed within the maize crop field in the summer season at low elevation, while just 30% of the scat was observed in the winter season in the forest.

A butterfly-like lead-doped titanium-oxide compound with high performance in photocatalytic cycloaddition of CO2 to epoxide.

The cycloaddition reaction of CO2 to epoxides is quite promising for CO2 capture and storage as well as the production of value-added fine chemicals. Herein, a novel atomically precise lead-doped titanium-oxide cluster with the formula Ti10Pb2O16(phen)4(Ac)12(DMF)2 (denoted as Ti10Pb2; phen = 1,10-phenanthroline; Ac = acetate; DMF = dimethylformamide) was synthesized through a facile solvothermal process, and is a molecular photocatalyst with surface-anchored main-group metal active sites. Its structure was characterized by single-crystal X-ray diffraction and other complementary techniques. Ti10Pb2 showed high photo-response and charge-separation efficiency under simulated sunlight irradiation. Ti10Pb2 was successfully used in the cycloaddition reaction of CO2 with epoxides under solvent-free conditions. While its catalytic activity due to the Lewis acidity was moderate, simulated solar light irradiation further enhanced the reaction rate, demonstrating the synergistic effect of photocatalysis and Lewis-acid thermocatalysis.

A blind algorithm for reverberation-time estimation using subband decomposition of speech signals.

An algorithm for blind estimation of reverberation time (RT) in speech signals is proposed. Analysis is restricted to the free-decaying regions of the signal, where the reverberation effect dominates, yielding a more accurate RT estimate at a reduced computational cost. A spectral decomposition is performed on the reverberant signal and partial RT estimates are determined in all signal subbands, providing more data to the statistical-analysis stage of the algorithm, which yields the final RT estimate. Algorithm performance is assessed using two distinct speech databases, achieving 91% and 97% correlation with the RTs measured by a standard nonblind method, indicating that the proposed method blindly estimates the RT in a reliable and consistent manner.

Syntheses, structures and ligand binding modes of titanium-oxide complexes of 2-picolinate.

Six titanium-oxide clusters (TOCs) comprised of 6-19 Ti atoms all of which are of nanometer size were synthesized with the functionalization of 2-picolinate (PA). Their structures were determined by single-crystal X-ray diffraction and a few complementary spectroscopic techniques. The binding modes of PA on the surface of the TOCs were analyzed and found to be limited to only one binding mode, that is, PA acts as a bidentate ligand through both pyridyl-N and the carboxylate-O. UV-vis diffuse reflection spectra and electron paramagnetic resonance spectra indicate the ligand-to-metal charge transfer (LMCT) through the N-Ti bond. However, the LMCT band in the visible light region (400-600 nm) is very weak. Hence, picolinates do not bring about intense visible light absorption to TOCs. The binding mode of PA on the TOC surfaces and the LMCT revealed herein may be inspiring for studies on classical picolinate/TiO2-based dye-sensitized solar cells.

New picolinate-functionalized titanium-oxide clusters: syntheses, structures and photocatalytic H2 evolution.

Two nanosized titanium-oxide clusters (TOCs), Ti12(µ2-O)14(µ3-O)4PA16 (1; PA = 2-picolinate) and Ti12(µ2-O)18PA18 (2) were synthesized by using 2-picolinic acid and Ti(OiPr)4 in one-pot reactions. Their structures were determined using single-crystal X-ray diffractometry. Although both have the same core composition of Ti12O18, 1 exhibited superior H2 evolution activity of up to 180 µmol h-1 g-1, which is nearly eight times faster than 2. Mechanism studies revealed that 1 could induce the assembly of 2.3 nm PtNPs into 10-30 nm supra-nanoparticle structures, which contributed to the increased H2 evolution rate.

Utilization of Biomass Fly Ash for Improving Quality of Organic Dye-Contaminated Water.

Development of innovative methodologies to convert biomass ash into useful materials is essential to sustain the growing use of biomass for energy production. Herein, a simple chemical modification approach is employed to functionalize biomass fly ash (BFA) with 3-aminopropyltriethoxy silane (APTES) to develop an inexpensive and efficient adsorbent for water remediation. The amine-functionalized BFA (BFA-APTES) was fully characterized by employing a range of characterization techniques. Adsorption behavior of BFA-APTES was evaluated against two anionic dyes, namely, alizarin red S (ARS) and bromothymol blue (BTB). In the course of experimental data analysis, the computation tools of data fitting for linear and nonlinear form of Langmuir, Freundlich, and the modified Langmuir-Freundlich adsorption isotherms were used with the aid of Matlab R2019b. In order to highlight the misuse of linearization of adsorption models, the sum of the squares of residues (SSE) values obtained from nonlinear models are compared with R 2 values obtained from the linear regression. The accuracy of the data fitting was checked by the use of SSE as an error function instead of the coefficient of determination, R 2. The dye adsorption capacity of BFA-APTES was also compared with the nonfunctionalized BFA. The maximum adsorption capacities of BFA-APTES for ARS and BTB dye molecules were calculated to be around 13.42 and 15.44 mg/g, respectively. This value is approximately 2-3 times higher than the pristine BFA. A reasonable agreement between the calculated and experimental values of q e obtained from the nonlinear form of kinetic models verified the importance of using equations in their original form. The experimentally calculated thermodynamic parameters including molar standard Gibbs free energy (Δad G m 0) and molar standard enthalpy change (Δad H m 0) reflected that the process of adsorption of dye molecules on the BFA-APTES adsorbent was spontaneous and exothermic in nature. Moreover, the used BFA-APTES adsorbent could be regenerated and reused for several cycles with significant dye adsorption capacity. The remediation capability of the BFA-APTES adsorbent against ARS dye was also demonstrated by packing a small column filled with the BFA-APTES adsorbent and passing a solution of ARS through it. Overall, we provide a simple and scalable route to convert BFA into an efficient adsorbent for water remediation applications.

Joint Separable and Non-Separable Transforms for Next-Generation Video Coding.

Throughout the past few decades, the separable Discrete Cosine Transform (DCT), particularly the DCT type II, has been widely used in image and video compression. It is well known that, under first-order stationary Markov conditions, DCT is an efficient approximation of the optimal Karhunen-Loève transform. However, for natural image and video sources, the adaptivity of a single separable transform with fixed core is rather limited for the highly dynamic image statistics, e.g., textures and arbitrarily directed edges. It is also known that non-separable transforms can achieve better compression efficiency for images with directional texture patterns, yet they are computationally complex, especially when the transform size is large. In order to achieve higher transform coding gains with relatively low-complexity implementations, we propose a joint separable and non-separable transform. The proposed separable primary transform, named Enhanced Multiple Transform (EMT), applies multiple transform cores from a pre-defined subset of sinusoidal transforms, and the transform selection is signaled in a joint block level manner. Moreover, a Non-Separable Secondary Transform (NSST) method is proposed to operate in conjunction with EMT. Unlike the existing non-separable transform schemes which require excessive amounts of memory and computation, the proposed NSST efficiently improves coding gain with much lower complexity. Extensive experimental results show that the proposed methods, in a state-of-the-art video codec, such as HEVC, can provide significant coding gains (average 6.9% and 4.5% bitrate reductions for intra and random-access coding, respectively).

No-reference blur assessment of digital pictures based on multifeature classifiers.

In this paper, we address the problem of no-reference quality assessment for digital pictures corrupted with blur. We start with the generation of a large real image database containing pictures taken by human users in a variety of situations, and the conduction of subjective tests to generate the ground truth associated to those images. Based upon this ground truth, we select a number of high quality pictures and artificially degrade them with different intensities of simulated blur (gaussian and linear motion), totalling 6000 simulated blur images. We extensively evaluate the performance of state-of-the-art strategies for no-reference blur quantification in different blurring scenarios, and propose a paradigm for blur evaluation in which an effective method is pursued by combining several metrics and low-level image features. We test this paradigm by designing a no-reference quality assessment algorithm for blurred images which combines different metrics in a classifier based upon a neural network structure. Experimental results show that this leads to an improved performance that better reflects the images' ground truth. Finally, based upon the real image database, we show that the proposed method also outperforms other algorithms and metrics in realistic blur scenarios.

The African Millennium Villages.

We describe the concept, strategy, and initial results of the Millennium Villages Project and implications regarding sustainability and scalability. Our underlying hypothesis is that the interacting crises of agriculture, health, and infrastructure in rural Africa can be overcome through targeted public-sector investments to raise rural productivity and, thereby, to increased private-sector saving and investments. This is carried out by empowering impoverished communities with science-based interventions. Seventy-eight Millennium Villages have been initiated in 12 sites in 10 African countries, each representing a major agro-ecological zone. In early results, the research villages in Kenya, Ethiopia, and Malawi have reduced malaria prevalence, met caloric requirements, generated crop surpluses, enabled school feeding programs, and provided cash earnings for farm families.