128 research outputs found
Crosstalk effects in microwave SQUID multiplexed TES bolometer readout
Transition-edge sensor (TES) bolometers are broadly used for
background-limited astrophysical measurements from the far-infrared to
mm-waves. Many planned future instruments require increasingly large detector
arrays, but their scalability is limited by their cryogenic readout
electronics. Microwave SQUID multiplexing offers a highly capable scaling
solution through the use of inherently broadband circuitry, enabling readout of
hundreds to thousands of channels per microwave line. As with any multiplexing
technique, the channelization mechanism gives rise to electrical crosstalk
which must be understood and controlled so as to not degrade the instrument
sensitivity. Here, we explore implications relevant for TES bolometer array
applications, focusing in particular on upcoming mm-wave observatories such as
the Simons Observatory and AliCPT. We model the relative contributions of the
various underlying crosstalk mechanisms, evaluate the difference between
fixed-tone and tone-tracking readout systems, and discuss ways in which
crosstalk nonlinearity will complicate on-sky measurements.Comment: Submitted to the Journal of Low Temperature Physic
Targeting transcription regulation in cancer with a covalent CDK7 inhibitor
Tumour oncogenes include transcription factors that co-opt the general transcriptional machinery to sustain the oncogenic state, but direct pharmacological inhibition of transcription factors has so far proven difficult. However, the transcriptional machinery contains various enzymatic cofactors that can be targeted for the development of new therapeutic candidates, including cyclin-dependent kinases (CDKs). Here we present the discovery and characterization of a covalent CDK7 inhibitor, THZ1, which has the unprecedented ability to target a remote cysteine residue located outside of the canonical kinase domain, providing an unanticipated means of achieving selectivity for CDK7. Cancer cell-line profiling indicates that a subset of cancer cell lines, including human T-cell acute lymphoblastic leukaemia (T-ALL), have exceptional sensitivity to THZ1. Genome-wide analysis in Jurkat T-ALL cells shows that THZ1 disproportionally affects transcription of RUNX1 and suggests that sensitivity to THZ1 may be due to vulnerability conferred by the RUNX1 super-enhancer and the key role of RUNX1 in the core transcriptional regulatory circuitry of these tumour cells. Pharmacological modulation of CDK7 kinase activity may thus provide an approach to identify and treat tumour types that are dependent on transcription for maintenance of the oncogenic state.National Institutes of Health (U.S.) (Grant HG002668)National Institutes of Health (U.S.) (Grant CA109901
The changing role of china in the global illegal cigarette trade
This study explores the history of the illegal production, distribution, and smuggling of cigarettes in mainland China. Data were obtained from a content analysis of 931 media reports retrieved from LexisNexis for the time period 1975 until 2010, and from other open sources. The illegal cigarette trade first emerged in the form of violations of state tobacco monopoly regulations. In the course of the restructuring of the legal tobacco sector, which occurred under external political pressure to open the Chinese market to foreign competition, an illegal cigarette industry emerged which at first primarily produced fake Chinese brand cigarettes for the domestic black market. At the same time, China became a destination country for smuggled genuine Western brand cigarettes. It was only after effective crackdowns against cigarette smuggling and domestic distribution channels in the late 1990s that the Chinese illegal cigarette industry shifted to exporting large numbers of counterfeit Western brand cigarettes to black markets abroad. China’s current role as a leading supplier of counterfeit cigarettes is a result of the contradictions of the economic reform process and of external licit and illicit forces that worked toward opening up the Chinese tobacco sector to the outside world
The POLARBEAR-2 and Simons Array Focal Plane Fabrication Status
We present on the status of POLARBEAR-2 A (PB2-A) focal plane fabrication.
The PB2-A is the first of three telescopes in the Simon Array (SA), which is an
array of three cosmic microwave background (CMB) polarization sensitive
telescopes located at the POLARBEAR (PB) site in Northern Chile. As the
successor to the PB experiment, each telescope and receiver combination is
named as PB2-A, PB2-B, and PB2-C. PB2-A and -B will have nearly identical
receivers operating at 90 and 150 GHz while PB2-C will house a receiver
operating at 220 and 270 GHz. Each receiver contains a focal plane consisting
of seven close-hex packed lenslet coupled sinuous antenna transition edge
sensor bolometer arrays. Each array contains 271 di-chroic optical pixels each
of which have four TES bolometers for a total of 7588 detectors per receiver.
We have produced a set of two types of candidate arrays for PB2-A. The first we
call Version 11 (V11) and uses a silicon oxide (SiOx) for the transmission
lines and cross-over process for orthogonal polarizations. The second we call
Version 13 (V13) and uses silicon nitride (SiNx) for the transmission lines and
cross-under process for orthogonal polarizations. We have produced enough of
each type of array to fully populate the focal plane of the PB2-A receiver. The
average wirebond yield for V11 and V13 arrays is 93.2% and 95.6% respectively.
The V11 arrays had a superconducting transition temperature (Tc) of 452 +/- 15
mK, a normal resistance (Rn) of 1.25 +/- 0.20 Ohms, and saturations powers of
5.2 +/- 1.0 pW and 13 +/- 1.2 pW for the 90 and 150 GHz bands respectively. The
V13 arrays had a superconducting transition temperature (Tc) of 456 +/-6 mK, a
normal resistance (Rn) of 1.1 +/- 0.2 Ohms, and saturations powers of 10.8 +/-
1.8 pW and 22.9 +/- 2.6 pW for the 90 and 150 GHz bands respectively
The Simons Observatory microwave SQUID multiplexing detector module design
Advances in cosmic microwave background (CMB) science depend on increasing
the number of sensitive detectors observing the sky. New instruments deploy
large arrays of superconducting transition-edge sensor (TES) bolometers tiled
densely into ever larger focal planes. High multiplexing factors reduce the
thermal loading on the cryogenic receivers and simplify their design. We
present the design of focal-plane modules with an order of magnitude higher
multiplexing factor than has previously been achieved with TES bolometers. We
focus on the novel cold readout component, which employs microwave SQUID
multiplexing (mux). Simons Observatory will use 49 modules containing
60,000 bolometers to make exquisitely sensitive measurements of the CMB. We
validate the focal-plane module design, presenting measurements of the readout
component with and without a prototype detector array of 1728
polarization-sensitive bolometers coupled to feedhorns. The readout component
achieves a yield and a 910 multiplexing factor. The median white noise
of each readout channel is 65 . This impacts the
projected SO mapping speed by , which is less than is assumed in the
sensitivity projections. The results validate the full functionality of the
module. We discuss the measured performance in the context of SO science
requirements, which are exceeded.Comment: Accepted to The Astrophysical Journa
Cross-correlation of CMB polarization lensing with High-z submillimeter Herschel-ATLAS galaxies
We report a 4.8σ measurement of the cross-correlation signal between the cosmic microwave background (CMB) lensing convergence reconstructed from measurements of the CMB polarization made by the Polarbear experiment and the infrared-selected galaxies of the Herschel-ATLAS survey. This is the first measurement of its kind
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