The Influence of Soldering Profile on the Thermal Parameters of Insulated Gate Bipolar Transistors (IGBTs)

The effect of solder joint fabrication on the thermal properties of IGBTs soldered onto glass-epoxy substrate (FR4) was investigated. Glass-epoxy substrate with a thickness of 1.50 mm covered with a 35μm thick Cu layer were used. A surface finish was prepared from a HAL (hot air leveling) Sn99Cu0.7Ag0.3 layer with a thickness of 1÷40 μm. IGBT transistors NGB8207BN were soldered with SACX0307 (Sn99Ag0.3Cu0.7) paste. The samples were soldered in different soldering ovens and at different temperature profiles. The thermal impedance Zth(t) and thermal resistance Rth of the samples were measured. Microstructural and voids analyzes were performed. It was found that the differences for different samples reached 15% and 20% for Zth(t) and Rth, respectively. Although the ratio of the gas voids in the solder joints varied between 3% and 30%, no correlation between the void ratios and Rth increases was found. In the case of the different soldering tech-nologies the microstructure of the solder joint showed significant differences in the thickness of the IMC (intermetallic compounds) layer; these differences correlate well with the time above liquidus during the soldering process. The thermal parameters of IGBTs could be changed due to the increased thermal conductivity of IMC layer as compared to the thermal conductivity of the solder bulk. Our research highlighted the importance of the soldering technology used and the thermal profile in the case of the assembly of IGBT components

In vitro characteristics of Lactobacillus spp. strains isolated from the chicken digestive tract and their role in the inhibition of Campylobacter colonization

Campylobacter jejuni/coli infections are the leading cause of bacterial diarrheal illnesses in humans. Many epidemiological studies indicate that improperly prepared meat from chickens that carry a high load of Campylobacter in their intestinal tracts is the key source of human infections. LAB, mainly members of the Lactococcus and Lactobacillus genera, increasingly have been tested as vehicles for the delivery of heterologous bacterial or viral antigens to animal mucosal immune systems. Thus, the objective of this study was to isolate, identify, and characterize Lactobacillus spp. strains isolated from chickens bred in Poland. Their ability to decrease the level of bird gut colonization by C. jejuni strain was also analyzed. First, the influence of the different chicken rearing systems was evaluated, especially the effect of diets on the Lactobacillus species that colonize the gut of chickens. Next, selected strains were analyzed in terms of their anti-Campylobacter activity in vitro; potential probiotic traits such as adhesion properties, bile and low pH tolerance; and their ability to grow on a defined carbon source. Given that improperly prepared chicken meat is the main source of human infection by Campylobacter, the selected strains were also assessed for their ability to inhibit Campylobacter colonization in the bird's intestine. These experiments revealed enormous physiological diversity among the Lactobacillus genus strains. Altogether, our results showed that L. plantarum strains isolated from the digestive tracts of chickens bred in Poland displayed some probiotic attributes in vitro and were able to decrease the level of bird gut colonization by C. jejuni strain. This suggests that they can be employed as vectors to deliver Campylobacter immunodominant proteins to the bird's immune system to strengthen the efficacy of in ovo vaccination

Influence of SiC reinforcement on microstructural and thermal properties of SAC0307 solder joints

The effect of SiC nano-phases (nano-particles and nano-fibers) addition into SAC0307 solder paste was investigated on the thermal and microstructural properties of the composite solder joints. The nano-phases were used between 0.125 and 1 wt%, and they were mixed into the solder paste by ball milling process. For the study power MOSFET (metal oxide semiconductor field effect transistor) components were soldered onto metal core printed circuit boards (MCPCBs). The thermal impedance Zth(t) and thermal resistance Rth of MOSFETs were measured by an indirect electrical method. Furthermore, the void formation and the microstructure of solder joints were also studied. The solderability and voiding properties of the composite solder alloys were acceptable. It was found that in 0.5 wt% amount, SiC nano-particles have positive effects on the thermal parameters of the solder joints, which could be explained by the IMC (intermetallic compound) layer growth suppression effect of the nano-phases. The microstructural analysis revealed that the microstructural refinement of the composite solder joints differs in the case of nano-particles and nano-fibers

Influence of High Pressure or Autoclaving-Cooling Cycles and Pullulanase Treatment on Buckwheat Starch Properties and Resistant Starch Formation

Buckwheat starch was subjected to cycles of high pressure-cooling (P-CC) or autoclaving-cooling (A-CC) combined with pullulanase debranching to determine changes in resistant starch (RS) content, digestibility, rheological properties and microstructure. Native buckwheat starch had 11.9 g/kg of RS, while the highest RS content (58.7 g/kg) was reached after A-CC and 6 h of pullulanase treatment. Among the P-CC samples, the highest RS content (43.3 g/kg) was obtained after treatment with 600 MPa/9 min and 6 h pullulanase debranching. The digestibility of the starch samples was negatively correlated with RS content and its highest values were noted for native and P-CC 200 MPa preparations subjected to 2 and 16 h of pullulanase treatment (95.18–95.35%). Buckwheat starch A-CC preparations after 6 h of pullulanase treatment exhibited the lowest digestibility (85.87%). Rheological analysis of 6% starch pastes showed that all investigated samples demonstrated a non-Newtonian flow, pseudoplastic properties and thixotropy. The Ostwald de Waele rheological model was very well fitted to the flow curves of the investigated pastes (R2>0.98). Both P-CC and A-CC reduced the consistency coefficient (K) and thixotropy values, while the flow behavior index (n) was increased only after P-CC treatment. The P-CC and A-CC treatment resulted in starch granule breakdown and porous gel structure formation, differing in surface properties

High presure-modified starches as carriers for phenolic compounds

Resumen del póster presentado a la XVI Conference EuroFoodChem: "Translating food chemistry into health benefits" celebrada en Gdansk (Polonia) del 6 al 8 de julio de 2011.Starch material may be used as a matrix for controlled release of aroma and bioactive compounds or the selective adsorption of bitter components. The binding of organic compounds to starch is based on inclusion complexes formation through hydrophobic bonding in the amylose helix, and/or polar interaction between the hydroxyl groups of starch and ligands, or non-specific sorption to the starch surface. It is known that high hydrostatic pressure evoked changes in starch physicochemical properties what in turn might affect its capability for binding organic compounds. In view of the above, the studies were subjected to the effect of high pressure treatment on the ability of binding catechin and quercetin by sorghum and amaranth starches. Sorghum (17% of amylose) and amaranth (pure amylopectin) starch were isolated from the commercial grains. The starch-water suspensions (30%, w/v) were subjected to pressure treatment (650 MPa/ 9 mins), and freez-dried. Catechin (10 mg/1g starch) and quercetin (5mg/ 1g of starch) were separately added to the starch-water suspensions. The suspensions were stirred at room temperature (24h), centrifuged and the collected pellets were freez-dried. The compounds bound by the starches were isolated from the pellets by extraction with methanol/water, and the extracts were characterized by HPLC-PAD-MS. The obtained starchphenolic complexes were examined regarding their thermodynamic (DSC) and structural (13C CP/MAS NMR) properties. The antioxidant activity of phenolic compounds bound by analyzed starches was additionally performed using oxygen radical absorption capacity (ORAC) assay. The HPLC analysis showed that catechin and quercetin demonstrated higher binding affinity to sorghum than to amaranth starch. The high pressure treatment resulted in an increase in sorption of bioactive compounds by the starch preparations obtained. High pressure-treated amaranth starch demonstrated lower sorption of catechin, however. Although binding of ligand to starch was related to surface sorption, formation of bioactive compounds with fully hydrated starch can be also assigned to inclusion complexation. However, the results obtained from thermodynamic and 13C CP/MAS NMR analysis did not reveal that the complexation phenomenon took place in the studied case. The distinct increase in melting enthalpy values observed for starch-phenolic complexes in melting thermograms resulted probably from non-covalent binding of polysaccharides with the phenolic compounds due to hydrophobic cooperative interaction, mostly. The changes in antioxidant capacity of phenolic compounds bound by the starches (native and high pressure-treated) were found to be irregular.The study was financed by a grant of the Ministry of Science and Higher Education (Grant No. N N312 101938).Peer Reviewe

Isolation and Self-Association Studies of Beta-Lactoglobulin

The aim of this study was to investigate isolated β-lactoglobulin (β-LG) from the whey protein isolate (WPI) solution using the column chromatography with SP Sephadex. The physicochemical characterization (self-association, the pH stability in various salt solutions, the identification of oligomeric forms) of the protein obtained have been carried out. The electrophoretically pure β-LG fraction was obtained at pH 4.8. The fraction was characterized by the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/TOF MS) technique. The use of the HCCA matrix indicated the presence of oligomeric β-LG forms, while the SA and DHB matrices enabled the differentiation of A and B isoforms in the sample. The impact of sodium chloride, potassium chloride, ammonium sulfate, and sodium citrate in dispersion medium on β-LG electrophoretic stability in solution was also studied. Type of the dispersion medium led to the changes in the isoelectric point of protein. Sodium citrate stabilizes protein in comparison to ammonium sulfate. Additionally, the potential of capillary electrophoresis (CE) with UV detection using bare fused capillary to monitor β-LG oligomerization was discussed. Obtained CE data were further compared by the asymmetric flow field flow fractionation coupled with the multi-angle light scattering detector (AF4-MALS). It was shown that the β-LG is a monomer at pH 3.0, dimer at pH 7.0. At pH 5.0 (near the isoelectric point), oligomers with structures from dimeric to octameric are formed. However, the appearance of the oligomers equilibrium is dependent on the concentration of protein. The higher quantity of protein leads to the formation of the octamer. The far UV circular dichroism (CD) spectra carried out at pH 3.0, 5.0, and 7.0 confirmed that β-sheet conformation is dominant at pH 3.0, 5.0, while at pH 7.0, this conformation is approximately in the same quantity as α-helix and random structures

The Paleozoic Origin of Enzymatic Lignin Decomposition Reconstructed from 31 Fungal Genomes

Wood is a major pool of organic carbon that is highly resistant to decay, owing largely to the presence of lignin. The only organisms capable of substantial lignin decay are white rot fungi in the Agaricomycetes, which also contains non-lignin-degrading brown rot and ectomycorrhizal species. Comparative analyses of 31 fungal genomes (12 generated for this study) suggest that lignin-degrading peroxidases expanded in the lineage leading to the ancestor of the Agaricomycetes, which is reconstructed as a white rot species, and then contracted in parallel lineages leading to brown rot and mycorrhizal species. Molecular clock analyses suggest that the origin of lignin degradation might have coincided with the sharp decrease in the rate of organic carbon burial around the end of the Carboniferous period

Supplementary Electronic Files

Supplementary Electronic File