The Search for the Sidereal and Solar Diurnal Modulations in the Total MACRO Muon Data Set

We have analyzed 44.3M single muons collected by MACRO from 1991 through 2000 in 2,145 live days of operation. We have searched for the solar diurnal, apparent sidereal, and pseudo-sidereal modulation of the underground muon rate by computing hourly deviations of the muon rate from 6 month averages. We find evidence for statistically significant modulations with the solar diurnal and the sidereal periods. The amplitudes of these modulations are <0.1%, and are at the limit of the detector statistics. The pseudo-sidereal modulation is not statistically significant. The solar diurnal modulation is due to the daily atmospheric temperature variations at 20 km, the altitude of primary cosmic ray interactions with the atmosphere; MACRO is the deepest experiment to report this result. The sidereal modulation is in addition to the expected Compton-Getting modulation due to solar system motion relative to the Local Standard of Rest; it represents motion of the solar system with respect to the galactic cosmic rays toward the Perseus spiral arm.Comment: 18 pages, 8 of which are figures, 1 is a table. Accepted by Phys. Rev.

Nitric oxide and cyclic nucleotides: Their roles in junction dynamics and spermatogenesis

Spermatogenesis is a highly complicated process in which functional spermatozoa (haploid, 1n) are generated from primitive mitotic spermatogonia (diploid, 2n). This process involves the differentiation and transformation of several types of germ cells as spermatocytes and spermatids undergo meiosis and differentiation. Due to its sophistication and complexity, testis possesses intrinsic mechanisms to modulate and regulate different stages of germ cell development under the intimate and indirect cooperation with Sertoli and Leydig cells, respectively. Furthermore, developing germ cells must translocate from the basal to the apical (adluminal) compartment of the seminiferous epithelium. Thus, extensive junction restructuring must occur to assist germ cell movement. Within the seminiferous tubules, three principal types of junctions are found namely anchoring junctions, tight junctions, and gap junctions. Other less studied junctions are desmosome-like junctions and hemidesmosome junctions. With these varieties of junction types, testes are using different regulators to monitor junction turnover. Among the uncountable junction modulators, nitric oxide (NO) is a prominent candidate due to its versatility and extensive downstream network. NO is synthesized by nitric oxide synthase (NOS). Three traditional NOS, specified as endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS), and one testis-specific nNOS (TnNOS) are found in the testis. For these, eNOS and iNOS were recently shown to have putative junction regulation properties. More important, these two NOSs likely rely on the downstream soluble guanylyl cyclase/cGMP/protein kinase G signaling pathway to regulate the structural components at the tight junctions and adherens junctions in the testes. Apart from the involvement in junction regulation, NOS/NO also participates in controlling the levels of cytokines and hormones in the testes. On the other hand, NO is playing a unique role in modulating germ cell viability and development, and indirectly acting on some aspects of male infertility and testicular pathological conditions. Thus, NOS/NO bears an irreplaceable role in maintaining the homeostasis of the microenvironment in the seminiferous epithelium via its different downstream signaling pathways

Predation on seeds of the seagrass Posidonia australis in Western Australia

Despite much evidence that predation governs seed abundance, and ultimately seedling and adult plant distribution and abundance in terrestrial ecosystems, there is a dearth of information from seagrass dominated ecosystems. We report here on the first study to examine predation rates from seeds of Posidonia australis measured during field tethering experiments at 5 locations in Western Australia. Seeds that were recently dehisced from ripe fruits and at a similar stage of development were tethered in seagrass and adjacent unvegetated sand for 24 h and then assessed for damage. Seed predation was noted at all sites and ranged from partially to completely eaten seeds. Higher daily proportional damage was observed in seagrass (34 to 53%) than on unvegetated sand (3 to 20%), but was significantly greater at only 3 of the 5 sites. There was no significant difference in proportional mortality for seeds among seagrass meadows, whereas in sand, there was a significant site effect. While we were unable to identify specific seed predators, the type of damage we observed on the seeds suggest small fish or invertebrates are the primary causative agents. Our results add to the growing body of evidence that seagrass seed predation does occur, that it has the potential to affect recruitment, and has implications for understanding the dynamics of P. australis meadows. Finally, our data present an interesting contrast to the paradigm for seagrass faunal studies, which almost invariably have shown higher proportional mortality in bare sand than in seagrass