Preparation and properties of Zn delta-doped GaAs/AlGaAs heterojunction phototransistor

We have prepared, characterized and discussed the performance of AlGaAs/GaAs heterojunction bipolar phototransistor (HPT) including Zn delta-doped base. Due to the existence of δ-doped sheets located in the middle of undoped GaAs base the δ-doped HPT devices exhibit low dark current, nearly zero offset voltage, saturation voltage ∼0.4 V, and rise and fall times in ns range at wavelength of 850 nm up to 6 V of applied voltage. Due to avalanche multiplication behavior at the collector junction, an increased optical gain G>10 can be reached for applied voltages in the range of 6-12 V. For voltages higher than the device breakdown voltage (∼12 V) switching and negative differential resistance (NDR) effect is measurable in the inverted mode of operation.     

Quest for the Molecular Basis of Improved Selective Toxicity of All-Trans Isomers of Aromatic Heptaene Macrolide Antifungal Antibiotics

Three aromatic heptaene macrolide antifungal antibiotics, Candicidin D, Partricin A (Gedamycin) and Partricin B (Vacidin) were subjected to controlled cis-trans → all trans photochemical isomerization. The obtained all-trans isomers demonstrated substantially improved in vitro selective toxicity in the Candida albicans cells: human erythrocytes model. This effect was mainly due to the diminished hemotoxicity. The molecular modeling studies on interactions between original antibiotics and their photoisomers with ergosterol and cholesterol revealed some difference in free energy profiles of formation of binary antibiotic/sterol complexes in respective membrane environments. Moreover, different geometries of heptaene: sterol complexes and variations in polyene macrolide molecule alignment in cholesterol-and ergosterol-containing membranes were found. None of these effects are of the crucial importance for the observed improvement of selective toxicity of aromatic heptaene antifungals but each seems to provide a partial contribution.     

Relationships of rapeseed strength properties to seed size,colour and coat fibre composition

BACKGROUND: The size and strength of rapeseeds are factors likely to determine their suitability for storage and processing. The mechanical properties of whole seeds depend mainly on their coat composition. This study investigates variations in seed strength and colour between different‐sized rapeseeds. The paper also presents an explanation of the differences in seed mechanical properties through analyses of coat fibre composition. RESULTS: The strength properties of seeds were dependent on seed size and correlated with seed equivalent diameter. All measured strength indices showed that seeds of diameter above 2 mm were the most resistant. The mechanical properties of seeds were also correlated with the colour of seed surface, indicating that the most resistant seeds were those with values of H > 60°, S < 15% and I < 19% in the HSI colour space. The resistance of individual seeds was attributed to the surface density of soluble and insoluble dietary fibre, especially cellulose and lignin. CONCLUSION: The results suggest that the highest mechanical resistance shown by the largest and blackest rapeseeds can be associated with the high surface density of fibre components in the seed coat. Copyright © 2008 Society of Chemical Industry     

Heterogeneous chlorination of formaldehyde with HCl in the presence of zeolite Y

Zinc substituted zeolite Y is a potential catalyst in the CH₂Cl₂ formation in a one step gas phase reaction of CH₂O with CHl. Methanol and dimetoxymethane are suggested as possible intermediates in the formation of CH₃Cl and CH₂Cl₂. The decomposition pathway of CH₂O on zeolites seems to play an important role in the chlorination reaction mechanism. A certain combination of such factors as temperature, catalyst acidity and cation action must occur in order to activate CH₂O molecules for the reaction with HCl. The chlorination reaction is accompanied by side reactions resulting in the formation of nonchlorinated compounds such as methyl formate, ethers, aldehyde.     

Advantages and Disadvantages of Different Treatment Methods in Achondroplasia: A Review

Achondroplasia (ACH) is a disease caused by a missense mutation in the FGFR3 (fibroblast growth factor receptor 3) gene, which is the most common cause of short stature in humans. The treatment of ACH is necessary and urgent because untreated achondroplasia has many complications, both orthopedic and neurological, which ultimately lead to disability. This review presents the current and potential pharmacological treatments for achondroplasia, highlighting the advantages and disadvantages of all the drugs that have been demonstrated in human and animal studies in different stages of clinical trials. The article includes the potential impacts of drugs on achondroplasia symptoms other than short stature, including their effects on spinal canal stenosis, the narrowing of the foramen magnum and the proportionality of body structure. Addressing these effects could significantly improve the quality of life of patients, possibly reducing the frequency and necessity of hospitalization and painful surgical procedures, which are currently the only therapeutic options used. The criteria for a good drug for achondroplasia are best met by recombinant human growth hormone at present and will potentially be met by vosoritide in the future, while the rest of the drugs are in the early stages of clinical trials.     

Hypoxia-Induced FAM13A Regulates the Proliferation and Metastasis of Non-Small Cell Lung Cancer Cells

Hypoxia in non-small cell lung cancer (NSCLC) affects cancer progression, metastasis and metabolism. We previously showed that FAM13A was induced by hypoxia in NSCLC but the biological function of this gene has not been fully elucidated. This study aimed to investigate the role of hypoxia-induced FAM13A in NSCLC progression and metastasis. Lentiviral shRNAs were used for FAM13A gene silencing in NSCLC cell lines (A549, CORL-105). MTS assay, cell tracking VPD540 dye, wound healing assay, invasion assay, BrdU assay and APC Annexin V staining assays were performed to examine cell proliferation ability, migration, invasion and apoptosis rate in NSCLC cells. The results of VPD540 dye and MTS assays showed a significant reduction in cell proliferation after FAM13A knockdown in A549 cells cultured under normal and hypoxia (1% O₂) conditions (p < 0.05), while the effect of FAM13A downregulation on CORL-105 cells was observed after 96 h exposition to hypoxia. Moreover, FAM13A inhibition induced S phase cell cycle arrest in A549 cells under hypoxia conditions. Silencing of FAM13A significantly suppressed migration of A549 and CORL-105 cells in both oxygen conditions, especially after 72 and 96 h (p < 0.001 in normoxia, p < 0.01 after hypoxia). It was showed that FAM13A reduction resulted in disruption of the F-actin cytoskeleton altering A549 cell migration. Cell invasion rates were significantly decreased in A549 FAM13A depleted cells compared to controls (p < 0.05), mostly under hypoxia. FAM13A silencing had no effect on apoptosis induction in NSCLC cells. In the present study, we found that FAM13A silencing has a negative effect on proliferation, migration and invasion activity in NSCLC cells in normal and hypoxic conditions. Our data demonstrated that FAM13A depleted post-hypoxic cells have a decreased cell proliferation ability and metastatic potential, which indicates FAM13A as a potential therapeutic target in lung cancer.     

Wide Area Reversible Adhesive for In‐Space Assembly

The design of future space structures may anticipate a greater need for in‐space assembly due to larger planned space structures and changes in mission profiles over their operational lifetimes. A rapid and reversible adhesive coating over the structure’s surface would allow additional components to be bonded at any arbitrary time in the future. A scalable wide‐area reversible adhesive utilizing a high glass transition thermoset polymer possessing thermally exchangeable bonds can serve as an enabling technology for in‐space assembly. Coatings of aromatic thermosetting copolyesters can be deposited on aluminum and titanium coupons, which bond when heated to 400 °C with the counterpart surfaces under pressure. Reversibility over multiple cycles is shown within a dynamic mechanical analyzer with the limiting constraint being the necessity of nondelaminatory (cohesive) debonding of the bonded coupons. Bonded coupons can sustain a thermal cycle spanning the representative temperatures in low earth orbit under tension with no failure. A localized rapid heating method amenable for in‐space assembly can be used to bond titanium coupons using induction heating with a bonding time of 40 s.