Torsion pendulum facility for direct force measurements of LISA GRS related disturbances

A four mass torsion pendulum facility for testing of the LISA GRS is under development in Trento. With a LISA-like test mass suspended off-axis with respect to the pendulum fiber, the facility allows for a direct measurement of surface force disturbances arising in the GRS. We present here results with a prototype pendulum integrated with very large-gap sensors, which allows an estimate of the intrinsic pendulum noise floor in the absence of sensor related force noise. The apparatus has shown a torque noise near to its mechanical thermal noise limit, and would allow to place upper limits on GRS related disturbances with a best sensitivity of 300 fN/Hz^(1/2) at 1mHz, a factor 50 from the LISA goal. Also, we discuss the characterization of the gravity gradient noise, one environmental noise source that could limit the apparatus performances, and report on the status of development of the facility.Comment: Submitted to Proceedings of the 6th International LISA Symposium, AIP Conference Proceedings 200

Reliability analysis of wireless sensor network for smart farming applications

Wireless Sensor Networks are subjected to some design constraints (e.g., processing capability, storage memory, energy consumption, fixed deployment, etc.) and to outdoor harsh conditions that deeply affect the network reliability. The aim of this work is to provide a deeper understanding about the way redundancy and node deployment affect the network reliability. In more detail, the paper analyzes the design and implementation of a wireless sensor network for low-power and low-cost applications and calculates its reliability considering the real environmental conditions and the real arrangement of the nodes deployed in the field. The reliability of the system has been evaluated by looking for both hardware failures and communication errors. A reliability prediction based on different handbooks has been carried out to estimate the failure rate of the nodes self-designed and self-developed to be used under harsh environments. Then, using the Fault Tree Analysis the real deployment of the nodes is taken into account considering the Wi-Fi coverage area and the possible communication link between nearby nodes. The findings show how different node arrangements provide significantly different reliability. The positioning is therefore essential in order to obtain maximum performance from a Wireless sensor network

The Dusty Starburst Nucleus of M33

We have thoroughly characterized the ultraviolet to near-infrared (0.15 - 2.2 micron) spectral energy distribution (SED) of the central parsec of the M33 nucleus through new infrared photometry and optical/near-infrared spectroscopy, combined with ultraviolet/optical observations from the literature and the HST archive. The SED shows evidence for a significant level of attenuation, which we model through a Monte Carlo radiative transfer code as a shell of clumpy Milky Way-type dust (tau_V ~ 2 +/- 1). The discovery of Milky Way-type dust (with a strong 2175 A bump) internal to the M33 nucleus is different from previous work which has found SMC-like dust (no bump) near starburst regions. The amount by which dust can be processed may be related to the mass and age of the starburst as well as the extent to which the dust can shield itself. Our starburst models include the effects of this dust and can fit the SED if the nucleus was the site of a moderate (~10^8 L_sun at 10 Myrs) episode of coeval star formation about 70 Myrs ago. This result is quite different from previous studies which resorted to multiple stellar populations (between 2 and 7) attenuated by either no or very little internal dust. The M33 nuclear starburst is remarkably similar to an older version (70 Myr versus 10 Myr) of the ultra-compact starburst in the center of the Milky Way.Comment: 29 pages, 9 embedded figures, ApJ, in pres

Small optic suspensions for Advanced LIGO input optics and other precision optical experiments

We report on the design and performance of small optic suspensions developed to suppress seismic motion of out-of-cavity optics in the Input Optics subsystem of the Advanced LIGO interferometric gravitational wave detector. These compact single stage suspensions provide isolation in all six degrees of freedom of the optic, local sensing and actuation in three of them, and passive damping for the other three

Thermal gradient-induced forces on geodetic reference masses for LISA

The low frequency sensitivity of space-borne gravitational wave observatories will depend critically on the geodetic purity of the trajectories of orbiting test masses. Fluctuations in the temperature difference across the enclosure surrounding the free-falling test mass can produce noisy forces through several processes, including the radiometric effect, radiation pressure, and outgassing. We present here a detailed experimental investigation of thermal gradient-induced forces for the LISA gravitational wave mission and the LISA Pathfinder, employing high resolution torsion pendulum measurements of the torque on a LISA-like test mass suspended inside a prototype of the LISA gravitational reference sensor that will surround the test mass in orbit. The measurement campaign, accompanied by numerical simulations of the radiometric and radiation pressure effects, allows a more accurate and representative characterization of thermal-gradient forces in the specific geometry and environment relevant to LISA free-fall. The pressure dependence of the measured torques allows clear identification of the radiometric effect, in quantitative agreement with the model developed. In the limit of zero gas pressure, the measurements are most likely dominated by outgassing, but at a low level that does not threaten the LISA sensitivity goals.Comment: 21 pages, 16 figures, submitted to Physical Review

Between Andes and Amazon: The genetic profile of the Arawak-speaking Yanesha

The Yanesha are a Peruvian population who inhabit an environment transitional between the Andes and Amazonia. They present cultural traits characteristic of both regions, including in the language they speak: Yanesha belongs to the Arawak language family (which very likely originated in the Amazon/Orinoco lowlands), but has been strongly influenced by Quechua, the most widespread language family of the Andes. Given their location and cultural make-up, the Yanesha make for an ideal case study for investigating language and population dynamics across the Andes-Amazonia divide. In this study, we analyze data from high and mid-altitude Yanesha villages, both Y chromosome (17 STRs and 16 SNPs diagnostic for assigning haplogroups) and mtDNA data (control region sequences and 3 SNPs and one INDEL diagnostic for assigning haplogroups). We uncover sex-biased genetic trends that probably arose in different stages: first, a male-biased gene flow from Andean regions, genetically consistent with highland Quechua-speakers and probably dating back to Inca expansion; and second, traces of European contact consistent with Y chromosome lineages from Italy and Tyrol, in line with historically documented migrations. Most research in the history, archaeology and linguistics of South America has long been characterized by perceptions of a sharp divide between the Andes and Amazonia; our results serve as a clear case-study confirming demographic flows across that \u2018divide\u2019

Emergence of a non trivial fluctuating phase in the XY model on regular networks

We study an XY-rotor model on regular one dimensional lattices by varying the number of neighbours. The parameter $2\ge\gamma\ge1$ is defined. $\gamma=2$ corresponds to mean field and $\gamma=1$ to nearest neighbours coupling. We find that for $\gamma<1.5$ the system does not exhibit a phase transition, while for $\gamma > 1.5$ the mean field second order transition is recovered. For the critical value $\gamma=\gamma_c=1.5$, the systems can be in a non trivial fluctuating phase for whichthe magnetisation shows important fluctuations in a given temperature range, implying an infinite susceptibility. For all values of $\gamma$ the magnetisation is computed analytically in the low temperatures range and the magnetised versus non-magnetised state which depends on the value of $\gamma$ is recovered, confirming the critical value $\gamma_{c}=1.5$