A low noise, high thermal stability, 0.1 K test facility for the Planck HFI bolometers

We are developing a facility which will be used to characterize the bolometric detectors for Planck, an ESA mission to investigate the Cosmic Microwave Background. The bolometers operate at 0.1 K, employing neutron-transmutation doped (NTD) Ge thermistors with resistances of several megohms to achieve NEPs~1×10^(–17) W Hz^(–1/2). Characterization of the intrinsic noise of the bolometers at frequencies as low as 0.010 Hz dictates a test apparatus thermal stability of 40 nK Hz^(–1/2) to that frequency. This temperature stability is achieved via a multi-stage isolation and control geometry with high resolution thermometry implemented with NTD Ge thermistors, JFET source followers, and dedicated lock-in amplifiers. The test facility accommodates 24 channels of differential signal readout, for measurement of bolometer V(I) characteristics and intrinsic noise. The test facility also provides for modulated radiation in the submillimeter band incident on the bolometers, for measurement of the optical speed-of-response; this illumination can be reduced below detectable limits without interrupting cryogenic operation. A commercial Oxford Instruments dilution refrigerator provides the cryogenic environment for the test facility

UPON THE CLINICAL CHARACTERISTICS OF PERIODICAL HYPERSOMNIA

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TREATMENT OF CHILDHOOD EPILEPSY WITH DEPAKINE

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PECULIARITIES IN THE CLINICAL COURSE OF GUILLAIN-BARRE'S POLYRADICULONEURITIS

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Performance evaluation of data delivery approaches for wireless sensor networks

AbstractWireless sensor networks are expected to revolutionize our abilities in sensing and controlling the physical environment. Power conservation is a primary research concern for these networks, due to the limited energy resources of the sensor nodes. In this paper we study the data delivery approaches, suitable for hierarchical cluster based wireless sensor networks. A radio energy dissipation model is used to evaluate the energy, needed for both intra-cluster and inter-cluster communication. Based on the results we analyze the performance of various combined data delivery approaches. Additionally we study the impact of the base station location and the number of sensor nodes on the energy dissipation and the network lifetime