Chemotactic properties of Escherichia coli mutants having abnormal Ca2+ content

The calA, calC, and calD mutants of Escherichia coli are known to be sensitive to Ca2+ (R. N. Brey and B. P. Rosen, J. Bacteriol. 139:824-834, 1979). In the absence of any added stimuli for chemotaxis, both the calC and the calD mutants swam with a tumbly bias. Both the calC and the calD mutants were defective in chemotaxis as measured by computer analysis, use of swarm plates, and capillary assays. The calA mutant was only slightly defective in motility and only slightly impaired in chemotaxis. Chemotactically wild-type cells had an intra-cellular free-Ca2+ level of about 105 nM. The intracellular free-Ca2+ levels of the mutants, as determined by use of the fluorescent Ca2+ indicator dye fura-2 or fluo-3, were about 90, about 1,130, and about 410 nM for calA, calC, and calD, respectively. Lowering the intracellular free-Ca2+ levels in wild-type cells and in the tumbly cal mutants by use of Ca2+ chelators promoted running (smooth swimming). Overexpression of CheZ (which causes dephosphorylation of CheY-phosphate) in the wild type and in the tumbly cal mutants decreased the level of tumbliness (which is caused by CheY-phosphate). The calA mutant was 4- to 10-fold more resistant than the wild type to the inhibitory effect of omega-conotoxin on chemotaxis. omega-Conotoxin had no effect on Ca2+ extrusion by wild-type E. coli; that result suggests that omega-conotoxin affects Ca2+ transport at the point of entry instead of exit

Maximal and inextensible polynomials and the geometry of the spectra of normal operators

We consider the set S(n,0) of monic complex polynomials of degree $n\ge 2$ having all their zeros in the closed unit disk and vanishing at 0. For $p\in S(n,0)$ we let $|p|_{0}$ denote the distance from the origin to the zero set of $p'$. We determine all 0-maximal polynomials of degree $n$, that is, all polynomials $p\in S(n,0)$ such that $|p|_{0}\ge |q|_{0}$ for any $q\in S(n,0)$. Using a second order variational method we then show that although some of these polynomials are inextensible, they are not necessarily locally maximal for Sendov's conjecture. This invalidates the recently claimed proofs of the conjectures of Sendov and Smale and shows that the method used in these proofs can only lead to (already known) partial results. In the second part of the paper we obtain a characterization of the critical points of a complex polynomial by means of multivariate majorization relations. We also propose an operator theoretical approach to Sendov's conjecture, which we formulate in terms of the spectral variation of a normal operator and its compression to the orthogonal complement of a trace vector. Using a theorem of Gauss-Lucas type for normal operators, we relate the problem of locating the critical points of complex polynomials to the more general problem of describing the relationships between the spectra of normal matrices and the spectra of their principal submatrices.Comment: A condensed version of the first half of this paper appeared in Math. Scand., see arXiv:math/0601600. Parts of the second half appeared in Trans. Amer. Math. Soc., see arXiv:math/0601519. The current version contains the full details of the counterexample constructions and some other result

Inhibition of Escherichia coli chemotaxis by omega-conotoxin, a calcium ion channel blocker

Escherichia coli chemotaxis was inhibited by omega-conotoxin, a calcium ion channel blocker. With Tris-EDTA-permeabilized cells, nanomolar levels of omega-conotoxin inhibited chemotaxis without loss of motility. Cells treated with omega-conotoxin swam with a smooth bias, i.e., tumbling was inhibited

Malawi’s Maize Marketing System

National food security in Malawi depends on improving the performance of maize markets. Ensuring that grain is consistently available at tolerable prices is crucial for consumers’ food security. At the same time, surplus producing farmers need to receive farm-gate prices consistently above production costs to intensify the use of fertilizer and other productivity enhancing technologies in a sustainable manner. These concerns give rise to the classic food price dilemma for policy makers in Malawi: how to keep prices low enough to ensure low income consumers’ access to food while keeping prices high enough to promote farm production incentives. These tensions cannot be avoided but they can be relieved through reducing food marketing margins, which shrink the wedge between producer and consumer prices. Moreover, Malawi faces major political and economic problems associated with food price instability especially given its dependence on rain fed agriculture in a region prone to drought. These issues show that improving the performance of maize markets is at the core of achieving sustainable food security and poverty reduction in Malawi.food security, Malawi, maize, marketing, food policy, Agricultural and Food Policy, Community/Rural/Urban Development, Food Security and Poverty, International Development, Marketing, q12, q18,

Marketing Policy Options for Consumer Price Mitigation Actions in the 2008/09 Maize Marketing Season in Zambia.

1) Maize prices are rising rapidly in 2008 and are fast approaching import parity levels. 2) Maize traders, millers and farmers all agree that Zambia will likely require imports by early 2009 in order to avoid domestic maize supply shortages. 3) Official food balance sheets appear to have underestimated the demand for maize this year. They may also have slightly overestimated the size of the 2007/08 maize crop. Hence the slow government recognition of the need for maize imports. 4) As of late September 2008, neither the Government of Zambia (GRZ) nor the private sector have arranged to import maize from South Africa. Trade sources suggest informal imports from Tanzania are helping to relieve the likely shortfall. 5) Zambian policy makers face a delicate balancing act: they need to maintain remunerative prices for farmers, in order to stimulate maize supply response during the coming 2008/09 production season, while at the same time moderating maize meal price increases to protect urban consumers and the many rural households who are net buyers of maize. 6) The time to respond to this balancing act challenge is now rather than later in the marketing season when costs of supplies and transport will increase. 7) Several policy actions offer potential win/win options for balancing these twin concerns:food security, food policy, Zambia, maize, marketing, Crop Production/Industries, Q20,

Hubungan Antara Konformitas Dengan Intensi Membeli Smartphone Pada Remaja SMA Karangturi Semarang

Intensi membeli yang tinggi smartphone, dapat menurunkan minat belajar, kemudahan mengakses gambar dan video porno membuat remaja lebih menyukai budaya barat tanpa melakukan proses filterisasi. Secara teoritis intensi membeli dipengaruhi oleh konformitas. Penelitian ini bertujuan menguji secara empiris hubungan konformitas dengan intensi membeli smartphone siswa SMA Karangturi Semarang. Penelitian ini merupakan korelasi dengan mengambil subjek dengan metode cluster sampling dan didapatkan sampel sebanyak 57 siswa. Metode penggalian data dengan menggunakan dua skala psikologi, Skala Intensi Membeli dengan 22 item valid (α = 0,880) dan Skala Konformitas dengan 22 item valid (α = 0,919). Analisis data menggunakan regresi linier sederhana. Hasil menunjukkan koefisien korelasi rxy = 0,686 dengan p = 0,000 (

Mitochondrially-Encoded Adenosine Triphosphate Synthase 6 Gene Haplotype Variation Among World Population During 2003-2013

Background: Adaptation and natural selection serve as an important part of evolution. Adaptation in molecular level can lead to genetic drift which causes mutation of genetic material; one of which is polymorphism of mitochondrial DNA (mtDNA). The aim of this study is to verify the polymorphism of mitochondrially-encoded Adenosine Triphosphate synthase6gene (MT-ATP6) as one of mtDNA building blocks among tropic, sub-tropic, and polar areas. Methods: This descriptive quantitative research used 3,210 mtDNA sequences, taken from GenBank, as secondary data from 27 different populations. The data were grouped into 3 population groups based on the climates of their location. After grouping, the sequences were then aligned and trimmed using Unipro EUGENE, and analysed by Arlequin and MitoTool. Results: Results demonstrated 21 haplotypes distributed among 3 populations with variations between each climate population. In the tropic and sub-tropic populations, the dominant haplotype is h1 while h6 is dominant in the polar population. Conclusions: There is a variation of haplotype polymorphism between tropic, sub-tropic, and polar climate population. &nbsp

How Will the Proposed Crop Marketing Authority Affect Food Market Performance in Zambia: An Ex Ante Assessment to Guide Government Deliberation

This paper aims to summarize the rationale and objectives of the Crop Marketing Authority and the possible consequences of adopting the proposed legislation. We also identify where the proposal, in its current form, requires additional specificity in order to evaluate its ability to meet Government’s objectives of enhancing food security and sustainable crop marketing.food security, food policy, crop marketing authority, Zambia, Marketing, Q18,

Regression Models for Mixed Over-Dispersed Poisson and Continuous Clustered Data: Modeling BMI and Number of Cigarettes Smoked Per Day

Clustered data, multiple observations collected on the same experimental unit, is common in epidemiological studies. Bivariate outcome data is often the result of interest in two correlated response variables. An efficient method is presented for dealing with bivariate outcomes when one outcome is continuous and the other is a count using a simple transformation to handle over-dispersed Poisson data. A multilevel analysis was performed on data from the National Health Interview Survey (NHIS) with body mass index (BMI) and the number of cigarettes smoked per day (NCS) as responses. Results show that these random effects models yield misleading results in cases where the data is not transformed