Chemical constituents of Nepeta distans

Phytochemical investigation of Nepeta distans Raul resulted in the isolation of a new phenolic compound, nepatanol (1), and eight known compounds, markhamioside F, netidiol, nepedinol, thymoquinone, eugenol, oleanolic acid, ursolic acid, and beta-sitosterol, which have been isolated for the first time from this source. Structures of all the isolates were established on the basis of MS, and 1D and 2D NMR spectral data and by comparison with reported data.     

Study of Saudi Arabian climatic conditions using Hurst exponent and climatic predictability index

This paper utilizes Hurst exponent to study the persistency of meteorological parameters individually and dependency of rainfall/precipitation on pressure and temperature using climate predictability index. For the purpose, daily averages of surface pressure and temperature and daily total rainfall data for a period of 7 years for three locations and 14 years for seven locations has been utilized. The Hurst exponents (H) for above mentioned meteorological parameters were calculated using rescaled range analysis (R/S) and absolute moments methods. These H values were used to calculate the fractal dimension D for pressure, temperature and rainfall data. Finally, these D’s were used to calculate the climate predictability index PI_C in terms of pressure predictability index (PI_P), temperature predictability index (PI_T) and rainfall predictability index (PI_R). The Hurst exponent analysis showed that H values for rainfall, relative humidity and wind speed time series data for all the stations were >0.5 which is indicative of persistence behavior of the parameters on the previous values while for pressure and temperature H values were <0.5 means anti-persistence behavior. The climate predictability index showed that in most of the cases the rainfall was dependent on both pressure and temperature predictability indices. In some cases it was more dependent on pressure index than the temperature and in some cases otherwise. In Saudi Arabia there is no prevalent or established rainy season and the present analysis could not result into concrete results. It is therefore recommended to analyze the data by breaking the entire data set into seasons and further into different years.     

Nepethalates A and B: Two New Phthalate Derivatives from Nepeta clarkei

The structure elucidation of two new phthalate derivatives named nepethalates A ( 1 ) and B ( 2 ) is reported. Both of these secondary metabolites were isolated from the MeOH extract of Nepeta clarkei. HR‐EI‐MS, IR and UV absorption spectrometry, and NMR experiments including COSY, HMQC, and HMBC were used for the determination of the structures and complete ¹H‐ and ¹³C‐NMR assignments.     

Instant nano-hydroxyapatite: a continuous and rapid hydrothermal synthesis

Nano-particle hydroxyapatite (HA) rods, were rapidly synthesised using a three pump continuous hydrothermal process (using a water feed at up to 400 degrees C and at 24 MPa): the product was obtained as a highly crystalline and phase pure material, without the need for an ageing step or subsequent heat treatment.     

Molecular assembly of tetracene on the (2 × 1)O reconstructed Cu(1 1 0) surface

Using a combination of scanning tunneling microscopy (STM) and density functional theory calculations, we have studied the adsorption of tetracene on the Cu(1 1 0) (2 × 1)O substrate. At monolayer coverage the adsorbed molecules are in the flat-laying geometry with their long axis along the close-packed [0 0 1] direction of the substrate and a long-range ordered structure on the length scale up to 100 nm has been observed. DFT calculation results indicate a stronger interaction between tetracene molecules and Cu(1 1 0) substrate than Cu(1 1 0) (2 × 1)O substrate. The preferential adsorption sites have also been pointed out on both substrates. The observed wavelike structure is explained by the interdigitation of C-H bonds of adjacent molecules.     

Existence and characterization of optimal dynamic pricing strategies with reference-price effects

Central European Journal of Operations Research - In this paper, we revisit the problem of existence of an optimal dynamic pricing strategy when the demand depends on a reference price. Using...     

Metal-Free Oxyacetoxylation of Arylynamines and Ynamides To Construct α-Acetoxyl Amides

Ynamides/arylynamines are challenging substrates for oxyacetoxylation, especially due to various reactive sites of the N-heteroaryl ring. Herein, we report a metal-free PhI(OAc)₂-mediated oxyacetoxylation of arylynamines/ynamides to provide α-acetoxyl amides in good to excellent yields. The transformation completes in a short time to afford solely the product in a highly regio- and chemo-selective manner through β-iodo keteneiminium intermediate, without functionalising the N-heteroaryl moiety.     

Photocatalytic CO2 Reduction Using TiO2-Based Photocatalysts and TiO2 Z-Scheme Heterojunction Composites: A Review

Photocatalytic CO₂ reduction is a most promising technique to capture CO₂ and reduce it to non-fossil fuel and other valuable compounds. Today, we are facing serious environmental issues due to the usage of excessive amounts of non-renewable energy resources. In this aspect, photocatalytic CO₂ reduction will provide us with energy-enriched compounds and help to keep our environment clean and healthy. For this purpose, various photocatalysts have been designed to obtain selective products and improve efficiency of the system. Semiconductor materials have received great attention and have showed good performances for CO₂ reduction. Titanium dioxide has been widely explored as a photocatalyst for CO₂ reduction among the semiconductors due to its suitable electronic/optical properties, availability at low cost, thermal stability, low toxicity, and high photoactivity. Inspired by natural photosynthesis, the artificial Z-scheme of photocatalyst is constructed to provide an easy method to enhance efficiency of CO₂ reduction. This review covers literature in this field, particularly the studies about the photocatalytic system, TiO₂ Z-scheme heterojunction composites, and use of transition metals for CO₂ photoreduction. Lastly, challenges and opportunities are described to open a new era in engineering and attain good performances with semiconductor materials for photocatalytic CO₂ reduction.     

Thermal performance enhancement of shell and helical coil heat exchanger using MWCNTs/water nanofluid

Journal of Thermal Analysis and Calorimetry - Heat exchangers serve as pivotal components in industries. Enhancement in the performance of heat exchangers has been the focus of researchers in the...