On non hadronic origin of high energy neutrinos

Some of the non hadronic interactions, such as the \eta resonance formation in the \gamma \gamma interactions and the muon pair production in the e\gamma interactions, are identified as possible source interactions for generating high energy neutrinos in the cosmos.Comment: 9 pages, 1 figure, talk given at First NCTS Workshop on Astroparticle Physics, 6-9 December, 2001, Kenting, Taiwan (to appear in its proceedings edited by H. Athar, Guey-Lin Lin, and K.-W. Ng

Radio Planetary Nebulae in the Small Magellanic Cloud

We present ten new radio continuum (RC) detections at catalogued planetary nebula (PN) positions in the Small Magellanic Cloud (SMC): SMPS6, LIN 41, LIN 142, SMP S13, SMP S14, SMP S16, J18, SMP S18, SMP S19 and SMP S22. Additionally, six SMC radio PNe previously detected, LIN 45, SMP S11, SMPS17, LIN321, LIN339 and SMPS24 are also investigated (re-observed) here making up a population of 16 radio detections of catalogued PNe in the SMC. These 16 radio detections represent ~15 % of the total catalogued PN population in the SMC. We show that six of these objects have characteristics that suggest that they are PN mimics: LIN 41, LIN 45, SMP S11, LIN 142, LIN 321 and LIN 339. We also present our results for the surface brightness - PN radius relation ({\Sigma}-D) of the SMC radio PN population. These are consistent with previous SMC and LMC PN measurements of the ({\Sigma}-D) relation.Comment: Accepted for publication in Astrophysics and Space Scienc

The lin-3/let-23 pathway mediates inductive signalling during male spicule development in Caenorhabditis elegans

During Caenorhabditis elegans male spicule development, four pairs of precursor cells respond to multiple positional cues and establish a pattern of fates that correlates with relative anterior-posterior cell position. One of the extracellular cues is provided by the F and U cells, which promote anterior fates. We show that the genes in the lin-3/let-23 signalling pathway required for hermaphrodite vulval induction also mediate this F/U signal. Reduction-of-function mutations in lin-3, let-23, sem-5, let-60 or lin-45 disrupt the fate of anterior cells. Likewise, activation of the pathway with ubiquitously produced signal results in posterior cells inappropriately adopting the anterior fates even in the absence of F and U. We have further used this genetic pathway to begin to understand how multiple positional cues are integrated to specify cell fate. We demonstrate that lin-15 acts in spicule development as it does in vulval induction, as a negative regulator of let-23 receptor activity. A second extracellular cue, from Y.p, also acts antagonistically to the lin-3/let-23 pathway. However, this signal is apparently integrated into the lin-3/let-23 pathway at some step after lin-45 raf and is thus functionally distinct from lin-15. We have also investigated the role of lin-12 in forming the anterior/posterior pattern of fates. A lin-12 gain-of-function defect is masked by redundant positional information from F and U

Using mobile group dynamics and virtual time to improve teamwork in large-scale collaborative virtual environments

Mobile group dynamics (MGDs) assist synchronous working in collaborative virtual environments (CVEs), and virtual time (VT) extends the benefits to asynchronous working. The present paper describes the implementation of MGDs (teleporting, awareness and multiple views) and VT (the utterances of 23 previous users were embedded in a CVE as conversation tags), and their evaluation using an urban planning task. Compared with previous research using the same scenario, the new MGD techniques produced substantial increases in the amount that, and distance over which, participants communicated. With VT participants chose to listen to a quarter of the conversations of their predecessors while performing the task. The embedded VT conversations led to a reduction in the rate at which participants traveled around, but an increase in live communication that took place. Taken together, the studies show how CVE interfaces can be improved for synchronous and asynchronous collaborations, and highlight possibilities for future research

Resonance scattering at lyman-alpha by an atomic hydrogen cell

Hydrogen cell and ion chamber for obtaining photoelectric data on resonance scattering at lyman alpha lin

Fate specification and tissue-specific cell cycle control of the <i>Caenorhabditis elegans</i> intestine

Coordination between cell fate specification and cell cycle control in multicellular organisms is essential to regulate cell numbers in tissues and organs during development, and its failure may lead to oncogenesis. In mammalian cells, as part of a general cell cycle checkpoint mechanism, the F-box protein β-transducin repeat-containing protein (β-TrCP) and the Skp1/Cul1/F-box complex control the periodic cell cycle fluctuations in abundance of the CDC25A and B phosphatases. Here, we find that the Caenorhabditis elegans β-TrCP orthologue LIN-23 regulates a progressive decline of CDC-25.1 abundance over several embryonic cell cycles and specifies cell number of one tissue, the embryonic intestine. The negative regulation of CDC-25.1 abundance by LIN-23 may be developmentally controlled because CDC-25.1 accumulates over time within the developing germline, where LIN-23 is also present. Concurrent with the destabilization of CDC-25.1, LIN-23 displays a spatially dynamic behavior in the embryo, periodically entering a nuclear compartment where CDC-25.1 is abundant