Progress of the ECHo SDR Readout Hardware for Multiplexed MMCs

The electron capture in $^{163}$Holmium (ECHo) experiment seeks to achieve sub-eV sensitivity of the electron neutrino mass through calorimetric decay spectroscopy of $^{163}$Ho in large arrays of cryogenic magnetic microcalorimeters (MMCs). Microwave SQUID multiplexing serves to efficiently increase the number of readout channels, thus calorimeters per array and ultimately per cryostat. A corresponding frequency multiplexing room temperature software-defined radio (SDR) system is in development to enable the readout of this increased number of MMCs per cable. The SDR consists of a custom FPGA platform that provides signal generation and analysis capabilities, as well as tailored signal conversion and analog conditioning front end electronics that enable the room-temperature-to-cryogenic interface. Ultimately, the system will read out 400 multiplexer channels with double pixel detectors through a bandwidth of 4 GHz (IEEE C band). As high-resolution data converters are limited in sample rate, the C-band is split into five sub-bands using a two-stage mixing method. In this contribution, a prototype of the heterodyne RF design is presented. It comprises one of the five 800 MHz sub-bands for a target frequency range between 4 and 8 GHz. Furthermore, the second version of the A/D converter stage is presented, capable of generating and digitizing up to five complex basebands using 1 GSs$^{-1}$ converters, the reference clocks and a flux-ramp signal. We will show first results of their single and combined characterization in the lab. The current state of the prototype hardware enables preliminary measurements, only limited in bandwidth and with slightly higher noise. Potential improvements could be derived and will be implemented in the full bandwidth, 5-sub-band RF PCB design

Dopamine receptor 4 promoter polymorphism modulates memory and neuronal responses to salience

Animal models and human functional imaging data implicate the dopamine system in mediating enhanced encoding of novel stimuli into human memory. A separate line of investigation suggests an association between a functional polymorphism in the promoter region for the human dopamine 4 receptor gene (DRD4) and sensitivity to novelty. We demonstrate, in two independent samples, that the -521Cmayor queT DRD4 promoter polymorphism determines the magnitude of human memory enhancement for contextually novel, perceptual oddball stimuli in an allele dose-dependent manner. The genotype-dependent memory enhancement conferred by the C allele is associated with increased neuronal responses during successful encoding of perceptual oddballs in the ventral striatum, an effect which is again allele dose-dependent. Furthermore, with repeated presentations of oddball stimuli, this memory advantage decreases, an effect mirrored by adaptation of activation in the hippocampus and substantia nigra/ventral tegmental area in C carriers only. Thus, a dynamic modulation of human memory enhancement for perceptually salient stimuli is associated with activation of a dopaminergic-hippocampal system, which is critically dependent on a functional polymorphism in the DRD4 promoter region

SDR-Based Readout Electronics for the ECHo Experiment

Due to their excellent energy resolution, the intrinsically fast signal rise time, the huge energy dynamic range, and the almost ideally linear detector response, metallic magnetic calorimeters (MMC)s are very well suited for a variety of applications in physics. In particular, the ECHo experiment aims to utilize large-scale MMC-based detector arrays to investigate the mass of the electron neutrino. Reading out such arrays is a challenging task which can be tackled using microwave SQUID multiplexing. Here, the detector signals are transduced into frequency shifts of superconducting microwave resonators, which can be deduced using a high-end software-defined radio (SDR) system. The ECHo SDR system is a custom-made modular electronics, which provides 400 channels equally distributed in a 4 to 8 GHz frequency band. The system consists of a superheterodyne RF frequency converter with two successive mixers, a modular conversion, and an FPGA board. For channelization, a novel heterogeneous approach, utilizing the integrated digital down conversion (DDC) of the ADC, a polyphase channelizer, and another DDC for demodulation, is proposed. This approach has excellent channelization properties while being resource-efficient at the same time. After signal demodulation, on-FPGA flux-ramp demodulation processes the signals before streaming it to the data processing and storage backend

Nanoscale Confinement and Fluorescence Effects of Bacterial Light Harvesting Complex LH2 in Mesoporous Silicas

Many key chemical and biochemical reactions, particularly in living cells, take place in confined space at the mesoscopic scale. Toward understanding of physicochemical nature of biomacromolecules confined in nanoscale space, in this work we have elucidated fluorescence effects of a light harvesting complex LH2 in nanoscale chemical environments. Mesoporous silicas (SBA-15 family) with different shapes and pore sizes were synthesized and used to create nanoscale biomimetic environments for molecular confinement of LH2. A combination of UV-vis absorption, wide-field fluorescence microscopy, and in situ ellipsometry supports that the LH2 complexes are located inside the silica nanopores. Systematic fluorescence effects were observed and depend on degree of space confinement. In particular, the temperature dependence of the steady-state fluorescence spectra was analyzed in detail using condensed matter band shape theories. Systematic electronic-vibrational coupling differences in the LH2 transitions between the free and confined states are found, most likely responsible for the fluorescence effects experimentally observed

Delivery modulation in silica mesoporous supports via alkyl chain pore outlet decoration

This article focuses on the study of the release rate in a family of modified silica mesoporous supports. A collection of solids containing ethyl, butyl, hexyl, octyl, decyl, octadecyl, docosyl, and triacontyl groups anchored on the pore outlets of mesoporous MCM-41 has been prepared and characterized. Controlled release from pore voids has been studied through the delivery of the dye complex tris(2,2¿-bipyridyl)ruthenium(II). Delivery rates were found to be dependent on the alkyl chain length anchored on the pore outlets of the mesoporous scaffolding. Moreover, release rates follow a Higuchi diffusion model, and Higuchi constants for the different hybrid solids have been calculated. A decrease of the Higuchi constants was observed as the alkyl chain used to tune the release profile is longer, confirming the effect that the different alkyl chains anchored into the pore mouths exerted on the delivery of the cargo. Furthermore, to better understand the relation between pore outlets decoration and release rate, studies using molecular dynamics simulations employing force-field methods have been carried out. A good agreement between the calculations and the experimental observations was observed.Financial support from the Spanish Government (projects MAT2009-14564-C04-01 and MAT2009-14564-C04-04) and the Generalitat Valencia (project PROMETEO/2009/016) is gratefully acknowledged.Aznar Gimeno, E.; Sancenón Galarza, F.; Marcos Martínez, MD.; Martínez Mañez, R.; Stroeve, P.; Cano, J.; Amoros Del Toro, P. (2012). Delivery modulation in silica mesoporous supports via alkyl chain pore outlet decoration. Langmuir. 28:2986-2996. https://doi.org/10.1021/la204438jS298629962

Mechanism of eIF6 release from the nascent 60S ribosomal subunit.

SBDS protein (deficient in the inherited leukemia-predisposition disorder Shwachman-Diamond syndrome) and the GTPase EFL1 (an EF-G homolog) activate nascent 60S ribosomal subunits for translation by catalyzing eviction of the antiassociation factor eIF6 from nascent 60S ribosomal subunits. However, the mechanism is completely unknown. Here, we present cryo-EM structures of human SBDS and SBDS-EFL1 bound to Dictyostelium discoideum 60S ribosomal subunits with and without endogenous eIF6. SBDS assesses the integrity of the peptidyl (P) site, bridging uL16 (mutated in T-cell acute lymphoblastic leukemia) with uL11 at the P-stalk base and the sarcin-ricin loop. Upon EFL1 binding, SBDS is repositioned around helix 69, thus facilitating a conformational switch in EFL1 that displaces eIF6 by competing for an overlapping binding site on the 60S ribosomal subunit. Our data reveal the conserved mechanism of eIF6 release, which is corrupted in both inherited and sporadic leukemias.Supported by a Federation of European Biochemical Societies Long term Fellowship (to FW), Specialist Programme from Bloodwise [12048] (AJW), the Medical Research Council [MC_U105161083] (AJW) and [U105115237] (RRK), Wellcome Trust strategic award to the Cambridge Institute for Medal Research [100140], Tesni Parry Trust (AJW), Ted’s Gang (AJW) and the Cambridge NIHR Biomedical Research Centre.This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nsmb.311

Final Pre-40S Maturation Depends on the Functional Integrity of the 60S Subunit Ribosomal Protein L3

Ribosomal protein L3 is an evolutionarily conserved protein that participates in the assembly of early pre-60S particles. We report that the rpl3[W255C] allele, which affects the affinity and function of translation elongation factors, impairs cytoplasmic maturation of 20S pre-rRNA. This was not seen for other mutations in or depletion of L3 or other 60S ribosomal proteins. Surprisingly, pre-40S particles containing 20S pre-rRNA form translation-competent 80S ribosomes, and translation inhibition partially suppresses 20S pre-rRNA accumulation. The GTP-dependent translation initiation factor Fun12 (yeast eIF5B) shows similar in vivo binding to ribosomal particles from wild-type and rpl3[W255C] cells. However, the GTPase activity of eIF5B failed to stimulate processing of 20S pre-rRNA when assayed with ribosomal particles purified from rpl3[W255C] cells. We conclude that L3 plays an important role in the function of eIF5B in stimulating 3′ end processing of 18S rRNA in the context of 80S ribosomes that have not yet engaged in translation. These findings indicate that the correct conformation of the GTPase activation region is assessed in a quality control step during maturation of cytoplasmic pre-ribosomal particles

Functional group distributions on mesoporous silica

Most applications of mesoporous silica require some degree of functionalization. The surface of porous materials can be divided into external and internal (pore) surfaces, and in many cases, a selective functionalization of these surface subsections is desired. This short review outlines our recent work in this field and focuses on the postsynthetic functionalization of mesoporous silica with aminopropylalkoxysilanes and on the analysis of the respective functional group distributions by confocal laser scanning microscopy. Methods to obtain an amino-functionalized external surface and functional group gradients on the pore surface are reported. Arrays of silica nanochannels (ASNCs) serve as a model system for mesoporous silica

Controlling and Imaging the Functional-Group Distribution on Mesoporous Silica

In, out, shake it all about: The distribution of fluorescence-labeled amino groups on mesoporous silica was imaged by confocal laser scanning microscopy. The mobility of the aminosilane precursor determines the degree of external vs. pore-surface functionalization. This observation was used to develop a simple and general method for the modification of external mesoporous silica surfaces