In this paper, at first for a given set of real or complex numbers $sigma$ with nonnegative summation, we introduce some special conditions that with them there is no nonnegative tridiagonal matrix in which $sigma$ is its spectrum. In continue we present some conditions for existence such nonnegative tridiagonal matrices.

Two sigma factors, sigma 35 and sigma 28, direct transcription from the Bt I and Bt II promoters of the cryIA(a) gene of Bacillus thuringiensis; this gene encodes a lepidopteran-specific crystal protoxin. These sigma factors were biochemically characterized in previous work (K. L. Brown and H. R. Whiteley, Proc. Natl. Acad. Sci. USA 85:4166-4170, 1988; K. L. Brown and H. R. Whiteley, J. Bacteri...

Abstract The dispute about whether the 1 s core-hole is localized on one atom or delocalized over both in a homonuclear diatomic molecule has continued for decades, which been extensively studied by photoelectron and electron–ion coincidence spectroscopies. For N 2 , if delocalized, K-shell excitation into π g orbital should split two components, i.e., dipole-allowed transition from ungerade σ ...

As Bacillus subtilis proceeds through sporulation, the principal vegetative cell sigma subunit (sigma(A)) persists in the cell but is replaced in the extractable RNA polymerase (RNAP) by sporulation-specific sigma factors. To explore how this holoenzyme changeover might occur, velocity centrifugation techniques were used in conjunction with Western blot analyses to monitor the associations of R...

The Sec translocon is a protein-conducting channel that allows polypeptides to be transferred across or integrated into a membrane. Although protein translocation and insertion in Escherichia coli have been studied using only a small set of specific model substrates, it is generally assumed that most secretory proteins and inner membrane proteins use the Sec translocon. Therefore, we have studi...

Measurements from galaxies spanning a broad range of morphology reveal linear scaling enclosed dark to luminous mass that is not anticipated by standard galaxy formation cosmology. The found extend the inner galactic region outermost data point. Uncertainties in relation are narrow, with rms = 0.31 and {\sigma} 0.31. It unclear what would produce this linearity mass. Baryonic processes challeng...