Draft crystal structure of the vault shell at 9-A resolution.

Vaults are the largest known cytoplasmic ribonucleoprotein structures and may function in innate immunity. The vault shell self-assembles from 96 copies of major vault protein and encapsulates two other proteins and a small RNA. We crystallized rat liver vaults and several recombinant vaults, all among the largest non-icosahedral particles to have been crystallized. The best crystals thus far were formed from empty vaults built from a cysteine-tag construct of major vault protein (termed cpMVP vaults), diffracting to about 9-A resolution. The asymmetric unit contains a half vault of molecular mass 4.65 MDa. X-ray phasing was initiated by molecular replacement, using density from cryo-electron microscopy (cryo-EM). Phases were improved by density modification, including concentric 24- and 48-fold rotational symmetry averaging. From this, the continuous cryo-EM electron density separated into domain-like blocks. A draft atomic model of cpMVP was fit to this improved density from 15 domain models. Three domains were adapted from a nuclear magnetic resonance substructure. Nine domain models originated in ab initio tertiary structure prediction. Three C-terminal domains were built by fitting poly-alanine to the electron density. Locations of loops in this model provide sites to test vault functions and to exploit vaults as nanocapsules

Design of Plate-Fin Tube Dehumidifiers for Humidification-Dehumidification Desalination Systems

A two-dimensional numerical model of a plate-fin tube heat exchanger for use as a dehumidifier in a humidification-dehumidification (HDH) desalination systems is developed, because typical heating, ventilating, and air conditioning (HVAC) dehumidifier models and plate-fin tube dehumidifier geometries are not intended for the considerably higher temperature and humidity ratio differences which drive heat and mass transfer in HDH desalination applications. The experimentally validated model is used to investigate the influence of various heat exchanger design parameters. Potential improvements on common plate-fin tube dehumidifier designs are identified by examining various methods of optimizing tube diameter, and longitudinal and transverse tube spacing to achieve maximum heat flow for a given quantity of fin material at a typical HDH operating point. Thicker fins are recommended than for HVAC geometries, as the thermal conductive resistance of HVAC fins restricts dehumidifier performance under HDH operating conditions.Elisabeth Meurer FoundationKarl H. Ditze FoundationGerman Academic Exchange ServiceCenter for Clean Water and Clean Energy at MIT and KFUP

Design of Flat-Plate Dehumidifiers for Humidification–Dehumidification Desalination Systems

Flat-plate heat exchangers are examined for use as dehumidifiers in humidification–dehumidification (HDH) desalination systems. The temperature and humidity ratio differences that drive mass transfer are considerably higher than in air-conditioning systems, making current air-conditioning dehumidifier designs and design software ill-suited to HDH desalination applications. In this work a numerical dehumidifier model is developed and validated against experimental data. The model uses a logarithmic mass transfer driving force and an accurate Lewis number. The heat exchanger is subdivided into many cells for high accuracy. The Ackermann correction takes into account the effect of noncondensable gases on heat transfer during condensation. The influence of various heat exchanger design parameters is thoroughly investigated and suitable geometries are identified. Among others, the relationship between heat flow, pressure drop, and heat transfer area is shown. The thermal resistance of the condensate layer is negligible for the investigated geometries and operating point. A particle-embedded polymer as a flat-plate heat exchanger material for seawater operation substantially improves the heat flux relative to pure polymers and approaches the performance of titanium alloys. Thus, the use of particle-embedded polymers is recommended. The dehumidifier model can be applied in design and optimization of HDH desalination systems.Center for Clean Water and Clean Energy at MIT and KFUP

Towards wafer scale inductive determination of magnetostatic and dynamic parameters of magnetic thin films and multilayers

We investigate an inductive probe head suitable for non-invasive characterization of the magnetostatic and dynamic parameters of magnetic thin films and multilayers on the wafer scale. The probe is based on a planar waveguide with rearward high frequency connectors that can be brought in close contact to the wafer surface. Inductive characterization of the magnetic material is carried out by vector network analyzer ferromagnetic resonance. Analysis of the field dispersion of the resonance allows the determination of key material parameters such as the saturation magnetization MS or the effective damping parameter Meff. Three waveguide designs are tested. The broadband frequency response is characterized and the suitability for inductive determination of MS and Meff is compared. Integration of such probes in a wafer prober could in the future allow wafer scale in-line testing of magnetostatic and dynamic key material parameters of magnetic thin films and multilayers

On the nature of infrared-faint radio sources in the SXDF and VLA-VVDS fields

Infrared-Faint Radio Sources (IFRSs) are an unusual class of objects that are relatively bright at radio wavelengths but have faint or undetected infrared counterparts even in deep surveys. We identify and investigate the nature of IFRSs using deep radio (S$_{\rm 1.4~GHz}$ $\sim$ 100 $\mu$Jy beam$^{-1}$ at 5$\sigma$), optical (m$_{\rm r}$ $\sim$ 26 - 27.7 at 5$\sigma$), and near-IR (S$_{\rm 3.6~{\mu}m}$ $\sim$ 1.3 - 2.0 $\mu$Jy beam$^{-1}$ at 5$\sigma$) data available in two deep fields namely the Subaru X-ray Deep Field (SXDF) and the Very Large Array - VIMOS VLT Deep Survey (VLA-VVDS) field. In 1.8 deg$^{2}$ of the two fields we identify a total of nine confirmed and ten candidate IFRSs. We find that our IFRSs are high-redshift radio-loud AGN, with 12/19 sources having redshift estimates in the range of $z$ $\sim$ 1.7 - 4.3, while a limit of $z$ $\geq$ 2.0 is placed for the remaining seven sources. Notably, our study finds, for the first time, IFRSs with measured redshift $>$ 3.0, and also, the redshift estimates for IFRSs in the faintest 3.6 $\mu$m flux regime i.e., S$_{\rm 3.6~{\mu}m}$ $<$ 1.3 ${\mu}$Jy. Radio observations show that our IFRSs exhibit both compact unresolved as well as extended double-lobe morphologies, and have predominantly steep radio spectra between 1.4 GHz and 325 MHz. The non-detection of all but one IFRSs in the X-ray band and the optical-to-MIR colour (m$_{\rm r}$ - m$_{\rm 24~{\mu}m}$) suggest that a significant fraction of IFRSs are likely to be hosted in dusty obscured galaxies.Comment: 20 pages, 8 figures, 4 tables, accepted for publication in MNRA