Cadmium and lead recovery from yeast biomass

Properties of metal solution, environmental conditions and the type of biomaterials (microorganism genus, species or even strain) influence the mechanism of metal biosorption and consequently metal adsorption capacity, affinity and specificity. Cell surface properties determine the metal-microorganism interactions to a large extent. In this work the relationship between yeast surface properties and yeast’s ability to bind cadmium, lead and copper was studied. Surface charge and hydrophobicity before and after biosorption were determined using dye retention and solvent partition assays, respectively. There were differences in the surface charge and relative hydrophobicity among different yeast strains. A higher metal adsorption capacity for more negatively charged yeast cells was observed. Biosorption of heavy metals resulted in modifications to the surface charge and hydrophobicity of yeast cells. However, there were not statistically significant changes in the yeast surface charge and hydrophobicity after binding of heavy metals depending on the nature of the metal, initial metal concentration and solution pH.     

Quantification via X-ray fluorescence analysis of oxygen in the surface layer of a Si-sphere used as a new mass standard

The distribution of oxygen present in the surface layer of the Si-sphere used as new mass standard is measured and quantified using the combined X-ray fluorescence (XRF)/X-ray photoelectron spectroscopy (XPS) surface analysis system in the Center for Measurement Standards, Industrial Technology Research Institute (CMS/ITRI). A radiometric calibration of the X-ray source is not possible because the spectral distribution of the X-ray tube used is complex and not stable over the long term. Hence, the quantification of oxygen on the Si-sphere is based on a calibration curve that establishes a correlation between the mass deposition of oxygen from the calibration samples qualified by PTB and the ratio of the oxygen fluorescence to silicon RRS (resonant Raman scattering) intensities in the in-house system. This paper presents the methodology for and the results of an oxygen quantification performed using the combined XRF/XPS surface analysis system. With a relative uncertainty of less than 10%, the average mass deposition of oxygen on the Si-sphere was 133 ± 12 ng/cm². The oxygen quantified via XRF is treated as a reference for the quantification of other elements on the surface layer. The quantification of carbon mass deposition in the surface layer in relation to the oxygen mass deposition is also described in this paper. The surface analysis system is part of our contribution to the realization and dissemination of the unit of the kilogram (based on its new definition) via the XRCD method.     

Effect of pH and high pressure at sub-zero temperature on the viability of some bacteria

The objective of this study was to investigate the viability of Escherichia coli and Staphylococcus aureus in apple juice after treatment with high pressure at sub-zero temperature and during subsequent storage at 5 and 20 °C. The viability of E. coli and S. aureus cells suspended in the apple juice with a pH of 3.8 did not decrease considerably after pressure treatment at 193 MPa and?20 °C. However, viability losses occurred during storage of samples after pressure treatment. Living cells of both strains were not detected in pressurized samples of apple juice stored for 10 days at 20°C. The lethal effect was lower when the samples after pressure treatment were incubated at refrigerated temperature; the number of E. coli and S. aureus decreased by 6 log cycles when the juice was stored for 10 days at 5 °C.     

Structural Characterization of a Macrocyclic Peptide Modulator of the PD-1/PD-L1 Immune Checkpoint Axis

The clinical success of PD-1/PD-L1 immune checkpoint targeting antibodies in cancer is followed by efforts to develop small molecule inhibitors with better penetration into solid tumors and more favorable pharmacokinetics. Here we report the crystal structure of a macrocyclic peptide inhibitor (peptide 104) in complex with PD-L1. Our structure shows no indication of an unusual bifurcated binding mode demonstrated earlier for another peptide of the same family (peptide 101). The binding mode relies on extensive hydrophobic interactions at the center of the binding surface and an electrostatic patch at the side. An interesting sulfur/π interaction supports the macrocycle-receptor binding. Overall, our results allow a better understanding of forces guiding macrocycle affinity for PD-L1, providing a rationale for future structure-based inhibitor design and rational optimization.     

A study of the convergence of and error estimation for the homotopy perturbation method for the Volterra–Fredholm integral equations

In this work the solution of the Volterra–Fredholm integral equations of the second kind is presented. The proposed method is based on the homotopy perturbation method, which consists in constructing the series whose sum is the solution of the problem considered. The problem of the convergence of the series constructed is formulated and a proof of the formulation is given in the work. Additionally, the estimation of the approximate solution errors obtained by taking the partial sums of the series is elaborated on.     

A Parallel Randomized Algorithm for Finding a Maximal Independent Set in a Linear Hypergraph

We present a randomized parallel algorithm with polylogarithmic expected running time for finding a maximal independent set in a linear hypergraph.     

Assessment of the Effectiveness of Rehabilitation after Total Knee Replacement Surgery Using Sample Entropy and Classical Measures of Body Balance

Exercises in virtual reality (VR) have recently become a popular form of rehabilitation and are reported to be more effective than a standard rehabilitation protocol alone. The aim of this study was to assess the efficacy of adjunct VR training in improving postural control in patients after total knee replacement surgery (TKR). Forty-two patients within 7–14 days of TKR were enrolled and divided into a VR group and a control group (C). The C group underwent standard postoperative rehabilitation. The VR group additionally attended twelve 30-min exercise sessions using the Virtual Balance Clinic prototype system. Balance was assessed on the AMTI plate in bipedal standing with and without visual feedback before and after the four-week rehabilitation. Linear measures and sample entropy of CoP data were analyzed. After four weeks of rehabilitation, a significant reduction in parameters in the sagittal plane and ellipse area was noted while the eyes remained open. Regression analysis showed that sample entropy depended on sex, body weight, visual feedback and age. Based on the sample entropy results, it was concluded that the complexity of the body reaction had not improved. The standing-with-eyes-closed test activates automatic balance mechanisms and offers better possibilities as a diagnostic tool.     

Characterization of the surface topography and nano-hardness of Cu/Ni multilayer structures

This article describes the results of a study of Cu/Ni multilayer coatings applied on a monocrystalline Si(100) silicon substrate by the deposition magnetron sputtering technique. Composed of 100 bilayers each, the multilayers were differentiated by the Ni sublayer thickness (1.2 to 3 nm), while maintaining the constant Cu sublayer thickness (2 nm). The multilayer coatings were characterized by assessing their surface topography using atomic force microscopy and their mechanical properties with nano-hardness measurements by the Berkovich method. The tests showed that the hardness of multilayers was substantially influenced by the thickness ratio of Cu and Ni sublayers and by surface roughness. The highest hardness and, at the same time, the lowest roughness was exhibited by a multilayer structure with a Cu-to-Ni sublayer thickness ratio of 2:1.5.     

Study on the Chemistry and Structure of (Na(1−x)Bix)(Nb(1−y)Mny)O3 Ceramics by XPS, AES and EPMA

The (Na_1–xBi_x)(Mn_yNb_1–y)O₃ ceramics are new compounds, obtained for the first time, on the base of sodium niobate with substitution of bismuth manganite. It was shown that the solubility limit for Mn ions in sodium niobate lattice does not exceed 1% at. Therefore, the co-doping with Bi ions was proposed to increase this limit. Bismuth ions are expected to replace Na ions and to ensure charge compensation in the formed compound, thus enhancing possibility of accumulation of the Mn ions in solution without losing the appropriate electrical and optical properties. To study the morphology of produced ceramic four methods of sample characterization were used: X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), electron microprobe analysis (EPMA) and Scanning Electron Microscopy (SEM).     

Vibrational spectra and chemical quantum calculations for 2-adamantylamino-5-nitropyridine crystals--a novel material for laser Raman converters

Polycrystalline infrared and polarized FT-Raman spectra have been measured for 2-adamantylamino-5-nitropyridine, a novel organic material for laser Raman converters. The assignment of IR and Raman bands is given on the basis of DFT calculations. The spectroscopic studies have not indicated the presence of any significant intermolecular interactions in the crystal structure of this compound. The lines observed in the stimulated Raman spectrum of this crystal are assigned to the respective molecular vibrations.