Homologous and unique G protein alpha subunits in the nematode Caenorhabditis elegans

A cDNA corresponding to a known G protein alpha subunit, the alpha subunit of Go (Go alpha), was isolated and sequenced. The predicted amino acid sequence of C. elegans Go alpha is 80-87% identical to other Go alpha sequences. An mRNA that hybridizes to the C. elegans Go alpha cDNA can be detected on Northern blots. A C. elegans protein that crossreacts with antibovine Go alpha antibody can be detected on immunoblots. A cosmid clone containing the C. elegans Go alpha gene (goa-1) was isolated and mapped to chromosome I. The genomic fragments of three other C. elegans G protein alpha subunit genes (gpa-1, gpa-2, and gpa-3) have been isolated using the polymerase chain reaction. The corresponding cosmid clones were isolated and mapped to disperse locations on chromosome V. The sequences of two of the genes, gpa-1 and gpa-3, were determined. The predicted amino acid sequences of gpa-1 and gpa-3 are only 48% identical to each other. Therefore, they are likely to have distinct functions. In addition they are not homologous enough to G protein alpha subunits in other organisms to be classified. Thus C. elegans has G proteins that are identifiable homologues of mammalian G proteins as well as G proteins that appear to be unique to C. elegans. Study of identifiable G proteins in C. elegans may result in a further understanding of their function in other organisms, whereas study of the novel G proteins may provide an understanding of unique aspects of nematode physiology

Negative-Energy Spinors and the Fock Space of Lattice Fermions at Finite Chemical Potential

Recently it was suggested that the problem of species doubling with Kogut-Susskind lattice fermions entails, at finite chemical potential, a confusion of particles with antiparticles. What happens instead is that the familiar correspondence of positive-energy spinors to particles, and of negative-energy spinors to antiparticles, ceases to hold for the Kogut-Susskind time derivative. To show this we highlight the role of the spinorial ``energy'' in the Osterwalder-Schrader reconstruction of the Fock space of non-interacting lattice fermions at zero temperature and nonzero chemical potential. We consider Kogut-Susskind fermions and, for comparison, fermions with an asymmetric one-step time derivative.Comment: 14p

Natural Expectations and Macroeconomic Fluctuations

Economic

Vanishing of Gravitational Particle Production in the Formation of Cosmic Strings

We consider the gravitationally induced particle production from the quantum vacuum which is defined by a free, massless and minimally coupled scalar field during the formation of a gauge cosmic string. Previous discussions of this topic estimate the power output per unit length along the string to be of the order of $10^{68}$ ergs/sec/cm in the s-channel. We find that this production may be completely suppressed. A similar result is also expected to hold for the number of produced photons.Comment: 10 pages, Plain LaTex. Minor improvements. To appear in PR

Does pubescence increase uptake of nutrient deposition on leaves?

1. Leaf hairs have been associated with reducing environmental stress by increasing reflectance and the thickness of the boundary layer, however, such effects are more obvious in species with dense trichome layers. The adaptive functions for species with sparse leaf hair cover, such as in the Cape Proteaceae species of the Cape Floristic Region (CFR), remain unknown. 2. We postulated that leaf hairs of the Proteaceae in the CFR facilitate both nutrient absorption and water retention on the leaf surface. Leaf hair distribution is expected to show a pattern relative to the higher levels of atmospheric nutrients with proximity to the coast. 3. We followed a three pronged approach, this involved (i) evaluating the relationship of leaf pubescence with leaf surface water holding capacity, water uptake and nitrogen absorption from wet deposition for 12 Proteaceae species from the CFR, under controlled conditions; (ii) evaluating the relationship between leaf pubescence and plant height of 39 Proteaceae species from the CFR and (iii) comparing visual scores of pubescence with the relative proximity of the plants to the coast (oceanic index/continentality) of 205 Proteaceae species. 4. There was a positive correlation between leaf pubescence (0 to 8 x 10⁶ m⁻²) and water holding capacity for the 12 experimental Proteaceae species, however, water uptake did not vary with hairiness. ¹⁵NO₃⁻, ¹⁵NH₄⁺ and ¹⁵N-glycine solutions were each independently applied as wet deposition to the 12 experimental Proteaceae species. The uptake of glycine showed a positive correlation with hairiness overall and for Protea, whereas nitrate and ammonium uptake were positively correlated only with hairiness of Leucospermum. 5. Average plant height was positively correlated with leaf hair density of the 39 Proteaceae species. The visual score of pubescence was significantly different for each genus and there was no correlation between leaf pubescence and distance from the coast for the 205 field Proteaceae species. 6. Leaf hairs probably play a role in reducing environmental stresses, however, it is also possible that they play a role in water retention and nutrient absorption. Hairs on leaves vary in arrangement and morphological characteristics, thus they accordingly, probably serve different functions

Coarse and uniform embeddings between Orlicz sequence spaces

We give an almost complete description of the coarse and uniform embeddability between Orlicz sequence spaces. We show that the embeddability between two Orlicz sequence spaces is in most cases determined only by the values of their upper Matuszewska-Orlicz indices. On the other hand, we present examples which show that sometimes the embeddability is not determined by the values of these indices.Comment: 12 pages. This is the final version. To appear in Mediterr. J. Mat

Radiative Decay B→lνγ B \to l \nu \gamma in the Light Cone QCD Approach

We calculate to the leading twist 2 accuracy the rate for the decay $B_{u} \rightarrow l \nu \gamma$ using the light cone QCD sume rules. We find $Br( B_{u} \rightarrow l \nu \gamma) \simeq 2 \cdot 10^{-6}$. The results are used to test the applicability of the constituent quark model approximation to the same process.The latter estimate is proportional to $1/m_{u}^{2}$, where $m_{u} \simeq \bar{\Lambda}_{u}$ is the "constituent quark mass", indicating that the process is of long distance type. We find that the two approaches yield similar results for the rate with the choice $m_{u} \simeq 430-480 \;MeV$. This indicates that the constituent quark model may be used for estimates of the radiative "annihilation" contribution to this and other radiative decays. We point out that this decay may be useful for the measurement of $|V_{ub}|$.Comment: latex, 14 pages, one figure is available upon reques

Maximum gradient embeddings and monotone clustering

Let (X,d_X) be an n-point metric space. We show that there exists a distribution D over non-contractive embeddings into trees f:X-->T such that for every x in X, the expectation with respect to D of the maximum over y in X of the ratio d_T(f(x),f(y)) / d_X(x,y) is at most C (log n)^2, where C is a universal constant. Conversely we show that the above quadratic dependence on log n cannot be improved in general. Such embeddings, which we call maximum gradient embeddings, yield a framework for the design of approximation algorithms for a wide range of clustering problems with monotone costs, including fault-tolerant versions of k-median and facility location.Comment: 25 pages, 2 figures. Final version, minor revision of the previous one. To appear in "Combinatorica

A Comprehensive Study of the Efficiency of Type-Reduction Algorithms

Improving the efficiency of type-reduction algorithms continues to attract research interest. Recently, there have been some new type-reduction approaches claiming that they are more efficient than the well-known algorithms such as the enhanced Karnik-Mendel (EKM) and the enhanced iterative algorithm with stopping condition (EIASC). In a previous paper, we found that the computational efficiency of an algorithm is closely related to the platform, and how it is implemented. In computer science, the dependence on languages is usually avoided by focusing on the complexity of algorithms (using big O notation). In this paper, the main contribution is the proposal of two novel type-reduction algorithms. Also, for the first time, a comprehensive study on both existing and new type-reduction approaches is made based on both algorithm complexity and practical computational time under a variety of programming languages. Based on the results, suggestions are given for the preferred algorithms in different scenarios depending on implementation platform and application context