Hydrogen bond studies: 80. A deuteron magnetic resonance and infrared spectroscopic study of the water molecule in lithium formate monohydrate,LiHCOO · H2O

A deuteron magnetic resonance and infrared study of the water molecules in lithium formate monohydrate, LiHCOO · H₂O, has been made. The quadrupole coupling constants (e²qQ/h) and asymmetry parameters (η) were found to be 198.7±0.4 and 231.3±0.6 kHz, and 0.060±0.005 and 0.097±0.003, respectively, at 25 ° C.An interpretation is given of the infrared spectra in the OH-stretching region in terms of intra- and intermolecular couplings of the water molecules. It is found that the water molecules are vibrationally distorted by their environments such that the OH-stretching modes consist of independent stretchings of the two O-H bonds.     

Note on a theoretical interpretation of the isotopic ratio vOH/vOD versus vOH in isotopically diluted HDO molecules in solid hydrates

A simple intra- and inter-molecular potential for water molecules engaged in hydrogen bonding has been used in a one-dimensional approximation for a theoretical interpretation of the experimental correlation $\text{v}$_OH/$\text{v}$_OD versus $\text{v}$_OH in solid hydrates. The variation in the equilibrium OH(D) distance has also been considered.     

Hydrogen bond studies: Part 118. A deuteron magnetic resonance study of BeSO4· 4D2O and Li2SO4· D2O

The electric field gradient (EFG) tensors at the deuterons in the water molecules in BeSO₄ · 4D₂O at 25°C are reported. The quadrupole coupling constants (e²Q/h) and asymmetry parameters (η) for the two independent deuterons are 181.1(4) and 194.8(3) kHz, and 0.226(4) and 0.123(3), respectively. The EFG tensor corresponding to the smallest e²qQ/h is considerably distorted by the beryllium ion, which causes a high η value as well as a deviation of the y-principal axis by 21.8(6)° from the normal to the water molecule plane. A redetermination of the EFG tensors at the deuterons in the water molecule in Li₂SO₄ · D₂O at 25°C and ?110°C is also reported. The e²Q/h and η values for the two deuterons are 236.6(1.2) and 239.8(1.1) kHz, and 0.091(8) and 0.126(7), respectively, at ?110°C. The corresponding e²qQ/h and η values for the averaged EFG tensor at 25°C are 125.8(1.1) kHz and 0.813(13), respectively. The results are in good agreement with those from the pioneer work by Ketudat and Pound, 20 years ago on the same compound.     

Separation of parasites from human blood using deterministic lateral displacement

We present the use of a simple microfluidic technique to separate living parasites from human blood. Parasitic trypanosomatids cause a range of human and animal diseases. African trypanosomes, responsible for human African trypanosomiasis (sleeping sickness), live free in the blood and other tissue fluids. Diagnosis relies on detection and due to their often low numbers against an overwhelming background of predominantly red blood cells it is crucial to separate the parasites from the blood. By modifying the method of deterministic lateral displacement, confining parasites and red blood cells in channels of optimized depth which accentuates morphological differences, we were able to achieve separation thus offering a potential route to diagnostics.     

O-H and O-D stretching vibrations in isotopically dilute HDO molecules in some solid hydrates

Vibrational frequencies v_OH and v_OD have been measured for isotopically-dilute HDO molecules in eleven solid hydrates at 90 K. The results have been used to prepare a plot of the ratio v_OH/v_OD versus v_OH. The ratios fall on a smooth curve and decrease with decreasing frequencies v_OH. The anharmonicity constants ω_ex_e have been estimated. They were found to increase with decreasing v_OH.     

Overview of DWDM/ODC Project

Abstract

This article introduces the main achievements resulting from the DWDM/ODC project. The five areas of research activity within the DWDM/ODC project cover some of the main issues of design and development of dense wavelength division multiplexing systems for transparent optical networks. These issues are: performance assessment with arbitrary optical filtering; performance of signaling formats; dispersion compensation strategies for directly and externally modulated systems in presence of nonlinear transmission-induced degradation; and the impact of noise and crosstalk in the extent of transparent optical networks. All five areas of research activity have contributed significantly to a better understanding of the limitations present in dense wavelength division multiplexing systems.     

Fusion around the barrier for 7Li+12C

Fusion cross-sections for the ⁷Li + ¹²C reaction have been measured at energies above the Coulomb barrier by the direct detection of evaporation residues. The heavy evaporation residues with energies below 3 MeV could not be separated out from the α-particles in the spectrum and hence their contribution was estimated using statistical model calculations. The present work indicates that suppression of fusion cross-sections due to the breakup of ⁷Li may not be significant for ⁷Li + ¹²C reaction at energies around the barrier.     

Hydrogen bond studies 70. ab initio calculations of some properties of water molecules in the free state and in solid hydrates

Equilibrium geometry, infrared frequencies and intensities, and electrostatic field gradients have been calculated for the free water molecule and water molecules in solid hydrates. The calculations have been performed within the MO-LCAO framework, using Gaussian expansions for the molecular orbitals. The values so obtained are compared to experimental values and found to be in good qualitative agreement.     

Antibacterial Activity of Biosynthesized Selenium Nanoparticles Using Extracts of Calendula officinalis against Potentially Clinical Bacterial Strains

The use of selenium nanoparticles (SeNPs) in the biomedical area has been increasing as an alternative to the growing bacterial resistance to antibiotics. In this research, SeNPs were synthesized by green synthesis using ascorbic acid (AsAc) as a reducing agent and methanolic extract of Calendula officinalis L. flowers as a stabilizer. Characterization of SeNPs was performed by UV-vis spectrophotometry, infrared spectrophotometry (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) techniques. SeNPs of 40–60 nm and spherical morphologies were obtained. The antibacterial activity of marigold extracts and fractions was evaluated by disk diffusion methodology. The evaluation of SeNPs at different incubation times was performed through the colony-forming unit (CFU) count, in both cases against Serratia marcescens, Enterobacter cloacae, and Alcaligenes faecalis bacteria. Partial antibacterial activity was observed with methanolic extracts of marigold leaves and flowers and total inhibition with SeNPs from 2 h for S. marcescens, 1 h for E. cloacae, and 30 min for A. faecalis. In addition, SeNPs were found to exhibit antioxidant activity. The results indicate that SeNPs present a potentiated effect of both antimicrobial and antioxidant activity compared to the individual use of marigold extracts or sodium selenite (Na₂SeO₃). Their application emerges as an alternative for the control of clinical pathogens.