Modified silica gel with 5-amino-1,3,4-thiadiazole-2-thiol for heavy metal ions removal

A two sorbents was to synthesize for heavy metals removal: silica gel modified with 5-amino-1,3,4-thiadiazole-2-thiol (S5A) and pure silica gel. Modification of silica gel is achieved by tetraethyl orthosilicate (TEOS) preliminary hydrolyzed at room temperature. 5-Amino-1,3,4-thiadiazole-2-thiol is added, with continuous stirring with a magnetic stirrer, to the hydrolyzed TEOS. Pure silica gel (sample SG) is obtained by the classical sol–gel method using the same conditions and initial component ratios. The sorbents have been characterized as to their surface area, pore volumes, content of the functional groups, IR spectra, sulfur and nitrogen content. Their sorption properties to heavy (Cu(II), Co(II), Ni(II), Cd(II), Pb(II) and Hg(II) metals are investigated. The investigations indicate that modified silica gel is characterized by a relatively higher sorption capacity than is the unmodified one. The highest sorption capacity belongs to Hg(II) in presence of unmodified silica gel due to which this sorbent can be used for selective extraction of mercury ions from aqueous solutions.     

Microstructural changes in m. rectus abdominis bovine muscle after heating

A histological and ultrastructural study was conducted to characterize changes in beef muscle structure after heating. Pieces of rectus abdominis muscle were heated at 100 °C over varying time frames from 15 min to 60 min and at 270 °C for 1 min; samples were then prepared for optical and transmission electron microscopy. After 15 min of heating, at 100 °C, a lateral shrinkage in fibre of 48% and an increase in gaps between the myofibrillar masses of 27% was noted. No more significant evolution was observed as heating duration escalated. The ultrastructure showed strong myofibril to sarcolemma detachments in which granular aggregates, coming in part from myofibrillar proteins, are stored. Neighbouring muscle fibres showed strong heterogeneity in morphological behaviour after thermal treatment, suggesting that differences in composition and structure of the cytoskeleton proteins in the different fibres can cause denaturation/shrinkage of the proteins at different times along the timescale of microstructural changes during heating. Short heating at high temperatures expanded the gaps between myofibrillar mass, but the overall changes in the ultrastructure were similar to those obtained when heating at 100 °C.     

Removal of ammonium ions from aqueous solutions with coal-based activated carbons modified by oxidation

The main purpose of this work is to study the possibilities for removal of ammonium ions from aqueous solutions by the two coal-based activated carbons (one obtained from Bulgarian lignite from the Chukurovo deposit, and the second, available as commercial product) and their oxidized modifications. The porous texture and surface chemistry of the adsorbents were characterized. Adsorption of ions was investigated using solutions with different concentrations in the range 35-280 mg l⁻¹ in a static mode. Equilibrium modeling data were fitted to linear Langmuir’s and Freundlich’s equations and maximum adsorption capacities were calculated.     

How to improve intrinsic and extrinsic reliability of vias by process optimization

A systematic study of various processes and their impact on intrinsic reliability has been performed on Cu dual damascene interconnects. The most significant improvement for intrinsic reliability is the ‘break-through’ liner. A strong impact on stressmigration (SM) was revealed using a HDP based SiN deposition on top of Cu lines. Early failures in electromigration (EM) studies are present with insufficient cleaning processes. No reliability impact was detected with different plating and slurry chemistries and liner thickness increase. Extrinsic via reliability is assessed with a special test chip comprising 3E9 via/wafer. High ohmic vias are identified before and after thermal stress. As an example, the failure rates in Cu dual damascene levels with relaxed pitch before and after cleaning optimization are discussed.     

Direct starch conversion into L‐(+)‐lactic acid by a novel amylolytic strain of Lactobacillus paracasei B41

A new amylolytic strain of Lactobacillus paracasei able to convert starch directly into L ‐(+)‐lactic acid (LA) was isolated. The identification of the by 16S rDNA sequencing proved that this strain, B41, is the first amylolytic representative of Lactobacillus casei group. The amylase activity assay revealed that L. paracasei B41 produced extracellular amylolytic enzyme, reaching 62 U/mL in the cell‐free supernatants. The optimal conditions for its action were pH 5.0 and temperature 45°C. The gene amy1 (1779 bp) encoding the putative B41 amylopullulanase was cloned, sequenced, and analyzed. The deduced protein contained a leader peptide of 28 amino acids and a mature peptide of 564 amino acids. Compared to the amylases of closely related species, B41 enzyme had several amino acid substitutions. An inducible control at amy1 expression was demonstrated. The starch fermentation abilities of L. paracasei B41 were studied in batch processes performed with and without pH control. The highest amount of LA from starch was obtained during 48 h fermentation from 40 g/L substrate at pH maintained at 5.0–37.3 g/L. In addition, 93.3% starch conversion into LA and the highest reported productivity for 24 h were achieved – 1.30 g/L/h.     

NMR studies of the products of hydrolysis of 3-ethyl-2-methylbenzo[d]azol-3-ium iodides

N-(2-Hydroxyphenyl)- and N-(2-mercaptophenyl)-N-ethylacetamides were found as the main reaction products of the hydrolysis of the corresponding 3-ethyl-2-methylbenzazol-3-ium iodides in boiling ethanol in the presence of piperidinium base; the same products were obtained in aq. DMSO. The thiol undergoes spontaneous or accelerated oxidative coupling to the corresponding disulfide and forms a methylene-bridged dimer in the presence of CH₂Cl₂. All amides displayed diastereotopicity of the N-methylene group protons due to restricted rotation around the N–aryl bond, which is additional to the normal restricted rotation around the N–CO amide bond. This hydrolysis might be of crucial importance in cyanine dye synthesis in which benzazolium salt precursors are used; the findings provide an explanation for the process of obtaining ramified compounds. Structural elucidation of all products was based on detailed NMR analysis. The revision of several dye structures has been proposed.     

Thiouracil modified activated carbon as a sorbent for some precious and heavy metal ions

A new sorbent is prepared by modifying activated carbon obtained from apricot stones with 2-hydroxy-2-mercaptopyrimidine (2-thiouracil). The products have been characterized as to their surface area, pore volumes, content of the functional groups with basic and acidic properties, IR spectra, sulfur content. Their sorption properties with respect to some precious (Au(III), Ag(I), Pt(II)) and heavy (Cu(II), Mn(II), Ni(II), Hg(II)) metals are investigated. The sorption is studied as a function of pH (in the interval 1÷8) and stirring time (1÷24 h). The static sorption capacities towards the metal ions are determined under optimum conditions at room temperature. The new sorbent containing thiouracil is appropriate for simultaneous preconcentration of the precious and heavy metal ions within a wide pH range. It shows a significantly higher capacity for the investigated metal ions than the original carbon.     

Activated carbon sorbent with thioetheric sites—preparation and characterization

An activated carbon sorbent containing thioetheric sites (ACTS) was prepared by modification of the activated carbon with 2,2′-thiodiethanol. The specific surface area, pore volume, concentration of oxygen-containing groups and sulfur content of the sorbent were determined. The sorption behavior towards ions of some precious metals—Au(III), Pt(IV), Pd(II) and heavy metals—Ni(II), Zn(II), Fe(III), Cu(II), Pb(II), Cd(II) and Co(II) was studied. Selectivity towards gold, palladium and platinum in the pH range 1–9 was observed. The capacity for gold was 80 mg g⁻¹. The sorption of Au(III) at pH 1 is not affected by milligram amounts of Ni(II), Zn(II), Fe(III), Cu(II), Pb(II), Cd(II) and Co(II). The sorbed gold species is Au(0).     

On the weathering of modified PVC based compounds during the polymerization process

The variations of molecular spectra, colours and characteristic viscosity of modified and unmodified PVC compounds during the polymerization process in various periods of time of natural ageing have been investigated. The PVC types modified during synthesis by 0,25 % vol. plasticizers or plasticizers' mixture are characterized by 10 – 12°C lower glass transition temperature, higher thermal stability, long-term behaviour and better physical and mechanical properties. The Charpy-impact resistance is increased by 50 to 85%. The rate of the relative UV-sorption variation during outdoor exposure was lower for compounds based on the modified PVC types. The polyene parts amount of chain length n = 13, evaluated by means of Raman spectra, was increased during the first and second month, both on non-irradiated and irradiated surface. The total colour variation Δ^E_ab of the new PVC grades in a 10-month poriod of weathering was of 10-30% less compared to the unmodified PVC grades. By means of IR-spectroacopy the variations of the hydroxyl- and carbonyl groups were .valuated and the diffemncee in the oxidation kinetica were establiehed.     

The role of relaparoscopy in the management of bile leaks after laparoscopic cholecystectomy

An ultrasound phantom is described which allows practice of ultrasound-guidance of needle placement over variable depths and into targets of variable size. The phantom mimics a solid organ in its echogenicity and can be cheaply and easily made from resources of the domestic kitchen.