Magnetic Structure and Spin Waves in the Kagom\'{e} Jarosite compound KFe3(SO4)2(OH)6{\bf KFe_3(SO_4)_2(OH)_6}

We present a detailed study of the magnetic structure and spin waves in the Fe jarosite compound ${\rm KFe_3(SO_4)_2(OH)_6}$ for the most general Hamiltonian involving one- and two-spin interactions which are allowed by symmetry. We compare the calculated spin-wave spectrum with the recent neutron scattering data of Matan {\it et al.} for various model Hamiltonians which include, in addition to isotropic Heisenberg exchange interactions between nearest ($J_1$) and next-nearest ($J_2$) neighbors, single ion anisotropy and Dzyaloshinskii-Moriya (DM) interactions. We concluded that DM interactions are the dominant anisotropic interaction, which not only fits all the splittings in the spin-wave spectrum but also reproduces the small canting of the spins out of the Kagom\'e plane. A brief discussion of how representation theory restricts the allowed magnetic structure is also given.Comment: 23 pages, 17 figures, submitted to Phys. Rev. B (March 2006

A new lower bounding scheme for the total weighted tardiness problem

Cataloged from PDF version of article.We propose a new dominance rule that provides a sufficient condition for local optimality for the 1\\Sigma w(i)T(i) problem. We prove that if any sequence violates the proposed dominance rule, then switching the violating jobs either lowers the total weighted tardiness or leaves it unchanged. Therefore, it can be used in reducing the number of alternatives for finding the optimal solution in any exact approach. We introduce an algorithm based on the dominance rule, which is compared to a number of competing approaches for a set of randomly generated problems. We also test the impact of the dominance rule on different lower bounding schemes. Our computational results over 30,000 problems indicate that the amount of improvement is statistically significant for both upper and lower bounding schemes. (C) 1998 Elsevier Science Ltd. All rights reserved

Changes of micronutrients, dry weight and plant development in canola (Brassica napus L.) cultivars under salt stress

This study was carried out to determine the effects of salt stress on the growth, dry weights and micronutrient contents of canola (Brassica napus L.) cultivars grown in greenhouse conditions. 12 canola cultivars (Marinca, Kosa, Spok, Semu DNK207 NA, Tower, Liraspa, Star, Tobin, Helios, Semu 209/81, Regent and Lirawell) were exposed to salinity treatments (150 mM NaCl and control). Shoot, leaf and root dry weights of all the cultivars at 45-day-old plants were determined. Micronutrient contents (Fe, Mn, Cu and Zn) of the leaves, stems and roots were also analyzed. Salinity stress negatively affected the canola cultivars and the extent of effects varied depending on the salt tolerance of the cultivars. Generally, salinity reduced the plant growth and dry weights. Fe, Mn, Cu and Zn concentrations were high in the roots when compared with those in the leaves and shoots in the salt applied samples. It was observed that, micronutrient contents showed some variation in the different plant parts of the canola cultivars as a result of salt applications to the growing media. Iron (Fe), manganese (Mn) and copper (Cu) content increased in all the plant parts with salt applications except for some cultivars. On the other hand, when mean data of the cultivars were considered, it could be said that zinc (Zn) content of the leaves was not significantly affected by the salt stress.Key words: Canola, Brassica napus, dry weight, micronutrient accumulation, salt stress

Effect of salinity stress on plant fresh weight and nutrient composition of some Canola (Brassica napus L.) cultivars

Soil salinity is a major limitation to crop production in many areas of the world. A pot experiment was carried out with rapeseed cultivars in order to investigate the effects of salinity stress on plant development and nutrient composition. For the salinity studies, 150 mM NaCl concentration was applied to12 rapseed cultivars (Marinca, Kosa, Spok, Semu DNK207 NA, Tower, Liraspa, Star, Tobin, Helios, Semu 209/81, Regent and Lirawell) under the greenhouse conditions. All the cultivars were harvested after 45 days from planting. Green plants parts were weighted. Harvested rapeseed plants were separated into root, shoot and leaf parts for nutrient (K+, Na+, K+/Na+, Ca2+ and Cl-) analysis. As shown in this study, salinity stress affected negatively all the canola cultivars investigated. Generally, salinity reduced the green parts’ weight. K+, Ca2+ and K+/Na+ contents in plants decreased by salt stress, but Na+ and Cl- content in the roots, shoots and leaves of all the cultivars significantly increased. In the salt treatment, the K+ and Ca2+ concentrations were the highest in the leaf samples as compared to root and shoot samples. Furthermore, the highest concentration of Na+ and Cl- was observed in the leaf and shoot. Under salinity, Regent and Lirawell cultivars retained the highest K+ and Ca2+ content in leaves, with respect to the K+ content. The effect of NaCl treatment on the canola cultivars’ growth was not considerable.Key words: Canola cultivars, green plant parts, nutrient content, salt stress

Comparing Three Instructional Modes for an Engineering Economy Course

This study compares three instructional modes in an “Engineering Economy” course: online, face-to-face (FtF), and flipped. Engineering Economy is a core course in this study and incorporates students with diverse backgrounds from different engineering majors. To discern the relation between student characteristics and teaching modality, an online questionnaire was designed for each mode and distributed over a two-year period. Data was collected and several statistical analyses were conducted to study the relationship between pedagogical delivery modes and various student-based factors such as gender, age, course load, living distance from campus, computer skills, work status, and first language. Students’ performance, persistence, and knowledge self-evaluation were also compared in different modes. The statistical analyses of data at 95% confidence level show that among all the factors, only the ratio of native English speakers, course load and work category differ significantly in different instructional modes. No statistically significant difference was observed between different modes for other factors

Noncovalent funstionalization of mesoporous silica nanoparticles with amphiphilic peptides

Cataloged from PDF version of article.The surface of mesoporous silica nanoparticles (MSNs) has been modified for enhancing their cellular uptake, cell targeting, bioimaging, and controlled drug release. For this purpose, covalent anchorage on the silica surface was predominantly exploited with a wide range of bioactive molecules. Here, we describe a facile self-assembly method to prepare a hybrid peptide silica system composed of octyl-modified mesoporous silica nanoparticles (MSNs) and peptide amphiphiles (PAs). The hydrophobic organosilane surface of mesoporous silica was coated with amphiphilic peptide molecules. The peptide functionalized particles exhibited good cyto-compatibility with vascular smooth muscle and vascular endothelial cells. The peptide coating also improved the cellular uptake of particles up to 6.3 fold, which is promising for the development of highly efficient MSN based theranostic agents. © 2014 the Partner Organisations

Parasitic Appendicitis From Past to Present in Turkey

Background: Understanding the etiology of appendicitis is important for developing effective treatments the rela­tionship between parasitic appendicitis and various socio-cultural factors were examined, particu­larly with respect to the incidence of literacy. The aim of the article was to research the relations between para­sitic appendicitis and literacy ratio in population.Methods: Cases of parasitic appendicitis resulting in surgery performed at Buca Seyfi Demirsoy Large State Hospital Surgery Clinic between 2002 and 2009 were retrospectively reviewed and classified accord­ing to age, sex, type of parasite, morbidity, and mortality. Studies conducted in different regions of Turkey as well as in other countries were reviewed to determine if there was a relationship between para­sitic appendicitis and literacy. Results: Of the 1,969 appendectomy cases reviewed, nine were classified as parasitic appendicitis (0.45%). Enterobius vermicularis was observed in seven cases and Taenia spp. in two. The average age was 26.4 yr. No morbidity or mortality was found.Conclusion: The data were compared with a retrospective review of studies conducted in the same regions and a decrease in the rate of parasitic appendicitis was observed during the period between the two re­views. It was determined that a low literacy rate was associated with an increase in the incidence of para­sitic appendicitis. Observations made between different countries also produced similar results. In coun­tries where the incidence of parasitic appendiciticis was greater than 1.5%, the literacy rate was less than 88%. To avoid appendectomy resulting from parasites, it is important to increase education and literacy. In some areas, individuals with appendicitis undergo surgery due to a lack of education or poor literacy

Coarse-grained model of entropic allostery

Many signaling functions in molecular biology require proteins to bind to substrates such as DNA in response to environmental signals such as the simultaneous binding to a small molecule. Examples are repressor proteins which may transmit information via a conformational change in response to the ligand binding. An alternative entropic mechanism of "allostery" suggests that the inducer ligand changes the intramolecular vibrational entropy, not just the mean static structure. We present a quantitative, coarse-grained model of entropic allostery, which suggests design rules for internal cohesive potentials in proteins employing this effect. It also addresses the issue of how the signal information to bind or unbind is transmitted through the protein. The model may be applicable to a wide range of repressors and also to signaling in trans-membrane proteins