Array Program Research Articles

The Thousand Pulsar Array program on MeerKAT – IX. The time-averaged properties of the observed pulsar population

ABSTRACT We present the largest single survey to date of average profiles of radio pulsars, observed and processed using the same telescope and data reduction software. Specifically, we present measurements for 1170 pulsars, observed by the Thousand Pulsar Array programme at the 64-dish SARAO MeerKAT radio telescope, in a frequency band from 856 to 1712 MHz. We provide rotation measures (RM), dispersion measures, flux densities, and polarization properties. The catalogue includes 254 new RMs that substantially increase the total number of known pulsar RMs. Our integration times typically span over 1000 individual rotations per source. We show that the radio (pseudo-) luminosity has a strong, shallow dependence on the spin-down energy, proportional to $\dot{E}^{0.15\pm 0.04}$, that contradicts some previous proposals of population synthesis studies. In addition, we find a significant correlation between the steepness of the observed flux density spectra and $\dot{E}$, and correlations of the fractional linear polarization with $\dot{E}$, the spectral index, and the pulse width, which we discuss in the context of what is known about pulsar radio emission and how pulsars evolve with time. On the whole, we do not see significant correlations with the estimated surface magnetic field strength, and the correlations with $\dot{E}$ are much stronger than those with the characteristic age. This finding lends support to the suggestion that magnetic dipole braking may not be the dominant factor for the evolution of pulsar rotation over the lifetimes of pulsars. A public data release of the high-fidelity time-averaged pulse profiles in full polarization accompanies our catalogue.

The design of a portable seismograph used in aftershock seismic array observation

This paper introduces the design of a portable wireless-linked seismograph used in aftershock ultra-dense seismic array observation, which features easy-to-install, low-power consumption, real-time data transmission and remote control capability. Compared to traditional instruments, such as the combination of Reftek 130s data recorder and Guralp CMG-40T seismometer for China Seismic Array Program, it integrates the seismic sensor, seismic data recording unit, GPS timing service and wireless data link into a compact sealed housing. To verify the system’s functionality, both laboratory testing and preliminary field experiments were conducted. The exceptional feature of this newly-developed portable wireless-linked seismograph makes it very suitable for aftershock seismic array observation.

Precision Millimeter Astrometry of the α Centauri AB System

Abstract Alpha Centauri A is the closest solar-type star to the Sun and offers the best opportunity to find and ultimately to characterize an Earth-sized planet located in its habitable zone. Here, we describe initial results from an Atacama Large Millimeter/submillimeter Array (ALMA) program to search for planets in the α Cen AB system using differential astrometry at millimeter wavelengths. Our initial results include new absolute astrometric measurements of the proper motion, orbital motion and parallax of the α Cen system. These lead to an improved knowledge of the physical properties of both α Cen A and B. Our estimates of ALMA’s relative astrometric precision suggest that we will ultimately be sensitive to planets of a few tens of Earth mass in orbits from 1 to 3 au, where stable orbits are thought to exist.

Modeling of program Vth distribution for 3-D TLC NAND flash memory

This paper proposes a simulation method to model the program Vth distribution of 3-D vertical channel TLC/QLC charge-trapping NAND flash memory. The program Vth distribution can be calculated by considering ISPP noise, WL-WL interference, and the RTN effect of tunneling oxide and poly Si, which are the major physical factors affecting the width of program Vth distribution. Then, the program Vth distribution shapes with different ISPP incremental voltage steps are compared, and the results are found to be consistent with the experimental results. Code and layer-dependent coupling coefficients of WL-WL interference in 3-D vertical channel NAND flash memory are considered. The effect of RTN on the program Vth distribution is comprehensively studied. The program Vth distribution of a WL is calibrated with the measurement, and a good agreement is obtained, validating the array program Vth distribution simulation method. The simulation method can help in improving the reliability of 3-D TLC NAND flash memory and provides guidance for the design and optimization of 3-D QLC NAND flash memory technology.

Gaia-DR2 Confirms VLBA Parallaxes in Ophiuchus, Serpens, and Aquila

Abstract We present Gaia-DR2 astrometry of a sample of YSO candidates in Ophiuchus, Serpens Main, and Serpens South/W40 in the Aquila Rift, which had been mainly identified by their infrared excess with Spitzer. We compare the Gaia-DR2 parallaxes against published and new parallaxes obtained from our Very Long Baseline Array (VLBA) program Gould’s Belt Distances Survey. We obtain consistent results between Gaia and the VLBA for the mean parallaxes in each of the regions analyzed here. We see small offsets, when comparing mean values, of a few tens of microarcseconds in the parallaxes, which are either introduced by the Gaia zero-point error or due to a selection effect by Gaia toward the brightest, less obscured stars. Gaia-DR2 data alone conclusively places Serpens Main and Serpens South at the same distance, as we first inferred from VLBA data alone in a previous publication. Thus, Serpens Main, Serpens South, and W40 are all part of the same complex of molecular clouds, located at a mean distance of 436 ± 9 pc. In Ophiuchus, both Gaia and VLBA suggest a small parallax gradient across the cloud, and the distance changes from 144.2 ± 1.3 to 138.4 ± 2.6 pc when going from L1689 to L1688.

Dense-gas tracers and carbon isotopes in five 2.5 < z < 4 lensed dusty star-forming galaxies from the SPT SMG sample

The origin of the high star formation rates (SFR) observed in high-redshift dusty star-forming galaxies is still unknown. Large fractions of dense molecular gas might provide part of the explanation, but there are few observational constraints on the amount of dense gas in high-redshift systems dominated by star formation. In this paper, we present the results of our Atacama large millimeter array (ALMA) program targeting dense-gas tracers (HCN(5-4), HCO+(5-4), and HNC(5-4)) in five strongly lensed galaxies from the South Pole Telescope (SPT) submillimeter galaxy sample. We detected two of these lines (S/N > 5) in SPT-125-47 at z = 2.51 and tentatively detected all three (S/N ∼ 3) in SPT0551-50 at z = 3.16. Since a significant fraction of our target lines is not detected, we developed a statistical method to derive unbiased mean properties of our sample taking into account both detections and non-detections. On average, the HCN(5-4) and HCO+(5-4) luminosities of our sources are a factor of ∼1.7 fainter than expected, based on the local L′HCN(5-4) − LIR relation, but this offset corresponds to only ∼2σ if we consider sample variance. We find that both the HCO+/HCN and HNC/HCN flux ratios are compatible with unity. The first ratio is expected for photo-dominated regions (PDRs) while the second is consistent with PDRs or X-ray dominated regions (XDRs) and/or mid-infrared (IR) pumping of HNC. Our sources are at the high end of the local relation between the star formation efficiency, determined using the LIR/[CI] and LIR/CO ratios, and the dense-gas fraction, estimated using the HCN/[CI] and HCN/CO ratios. Finally, in SPT0125-47, which has the highest signal-to-noise ratio, we found that the velocity profiles of the lines tracing dense (HCN, HCO+) and lower-density (CO, [CI]) molecular gas are similar. In addition to these lines, we obtained one robust and one tentative detection of 13CO(4-3) and found an average I 12CO(4-3)/I13CO(4-3) flux ratio of 26.1−3.5+4.5, indicating a young but not pristine interstellar medium. We argue that the combination of large and slightly enriched gas reservoirs and high dense-gas fractions could explain the prodigious star formation in these systems.

The Effects of Repeated Exposure to the ARRAY Program With Offenders With Mental Illness

The Effects of Repeated Exposure to the ARRAY Program With Offenders With Mental Illness

Carbon nanotube memory cell array program error analysis and tradeoff between reset voltage and verify pulses

In emerging non-volatile memories, nano-random access memory (NRAM) has advantages of small program current and high endurance compared with resistive RAM (ReRAM) and phase-change RAM (PRAM). This work comprehensively investigates NRAM set and reset program characteristics by measuring a 116 nm 4 Mbit NRAM cell array. Specifically, reset is found more dependent on reset voltage than reset current. Next, NRAM set and reset bit error rates (BERs) have less significant reduction compared with the increased ratio of set and reset pulse widths. The reset BER can also be reduced by applying multiple reset pulses. Moreover, 108 write cycles are measured on 256 bytes NRAM cells, no wear-out or broken cell is found. Finally, the program characteristics of two verify-reset schemes are compared. The maximum verify-reset voltage can be reduced by increasing the number of reset pulses.

Investigation and Improvement of Verify-Program in Carbon Nanotube-Based Nonvolatile Memory

Carbon nanotube (CNT)-based random access memory (NRAM) cells are measured to investigate cell program at different set current compliances and temperatures. Then, a physical model is proposed to explain the mechanism of cell resistance switching. Specifically, the changes in the NRAM cell tunneling current and resistance can be attributed to the variation of the distance between CNTs. An attraction force ( $F_{\mathrm {attraction}})$ , generated by electrical induction, reduces the distance, whereas a repulsion force ( $F_{\mathrm {repulsion}})$ , generated by phonon-induced temperature, increases the distance. It is proposed that the dominance of these two forces is reversed during set and reset programs, possibly due to the reduction of $F_{\mathrm {repulsion}}$ in set program. Finally, two verify-reset schemes are proposed to improve the NRAM cell verify-program performance. The first proposal, multiple-pulse reset demonstrates 23% program time reduction by skipping a cell resistance read between two successive reset pulses. The second proposal, gate-pulse reset is calculated to decrease more than 40% program energy by reducing bitline charge energy in array program.

A Pilot Evaluation of the ARRAY Program With Offenders With Mental Illness

The authors implemented a small, A‐B‐A single‐case research design (n = 3) to evaluate the effectiveness of a cognitive behavior counseling intervention for offenders with mental illness who were incarcerated in a large correctional facility. Visual and nonoverlap analyses revealed that the intervention was within the effective to very effective range for decreasing psychiatric symptoms for 2 of the participants; 1 participant showed little change throughout treatment. Implications for program development and evaluation are discussed.

Fitting Cells Into a Narrow <inline-formula> <tex-math notation="LaTeX">$V_{T}$ </tex-math></inline-formula> Interval: Physical Constraints Along the Lifetime of an Extremely Scaled NAND Flash Memory Array

This paper presents an in-depth comparative analysis of the major physical constraints to the width of the threshold-voltage distribution of a state-of-the-art NAND Flash array. The analysis addresses both time-0 placement by program-and-verify algorithms on fresh and cycled arrays and distribution widening during idle/bake periods. Results allow to identify how each physical effect impacts the threshold-voltage distribution as a function of array program conditions, temperature, cycling, and duration of idle/bake periods, providing clear hints for the design of next generation technology nodes.

Program Cache Busy Time Control Method for Reducing Peak Current Consumption of NAND Flash Memory in SSD Applications

In current NAND flash design, one of the most challenging issues is reducing peak current consumption (peak ICC), as it leads to peak power drop, which can cause malfunctions in NAND flash memory. This paper presents an efficient approach for reducing the peak ICC of the cache program in NAND flash memory — namely, a program Cache Busy Time (tPCBSY) control method. The proposed tPCBSY control method is based on the interesting observation that the array program current (ICC2) is mainly decided by the bit-line bias condition. In the proposed approach, when peak ICC2 becomes larger than a threshold value, which is determined by a cache loop number, cache data cannot be loaded to the cache buffer (CB). On the other hand, when peak ICC2 is smaller than the threshold level, cache data can be loaded to the CB. As a result, the peak ICC of the cache program is reduced by 32% at the least significant bit page and by 15% at the most significant bit page. In addition, the program throughput reaches 20 MB/s in multiplane cache program operation, without restrictions caused by a drop in peak power due to cache program operations in a solid-state drive.

50 nm AlxOy resistive random access memory array program bit error reduction and high temperature operation

In order to decrease program bit error rate (BER) of array-level operation in AlxOy resistive random access memory (ReRAM), program BERs are compared by using 4 × 4 basic set and reset with verify methods on multiple 1024-bit-pages in 50 nm, mega-bit class ReRAM arrays. Further, by using an optimized reset method, 8.5% total BER reduction is obtained after 104 write cycles due to avoiding under-reset or weak reset and ameliorating over-reset caused wear-out. Then, under-set and over-set are analyzed by tuning the set word line voltage (VWL) of ±0.1 V. Moderate set current shows the best total BER. Finally, 2000 write cycles are applied at 125 and 25 °C, respectively. Reset BER increases 28.5% at 125 °C whereas set BER has little difference, by using the optimized reset method. By applying write cycles over a 25 to 125 to 25 °C temperature variation, immediate reset BER change can be found after the temperature transition.

Estimating Subsurface Shear Velocity with Radial to Vertical Ratio of Local P Waves

Online Material: Code for computing V S by the r/z ratio method; seismogram plots. In contrast to the western United States where seismicity is high and seismic networks are dense, the central and eastern United States (CEUS) is covered with sparse seismic networks. The relatively low seismicity in the CEUS has also led to a limited dataset of waveform data from local earthquakes, hindering the development of reliable ground‐motion prediction equations in the CEUS. This situation has been changing with the Earthscope Transportable Array (USArray) program that started installing about 1000 broadband and short‐period stations in the CEUS starting in 2009, and will fully cover the CEUS soon. Such large numbers of stations provide a rich dataset for ground‐motion studies in the United States. Also, the increasing number of Advanced National Seismic System (ANSS) broadband stations with high‐sampling rate substantially augments the waveform data. Site responses at each seismic station need to be obtained before the waveform data can be used for ground‐motion studies. For example, Boore (2003) and Atkinson and Boore (2006) find that site amplification needs to be taken into account for ground‐motion modeling in eastern North America, especially for high frequencies. Site response is controlled by the subsurface shear‐velocity profile, and the velocity structure of the top ten to hundreds of meters is particularly important (Wald and Mori, 2000; Boore, 2006). Therefore an essential part of site‐response modeling is determining subsurface velocity structure. A detailed review of methods for determining subsurface velocity structure was made by Boore (2006). Theoretically, invasive methods such as borehole logging provide the most accurate measurement of velocity structure, but their cost prohibits extensive application in site‐response studies. Noninvasive geophysical exploration methods are more often used in determining shallow velocity structure, and these include spectral analysis of surface waves (SASW), multichannel …

Gene expression profiling of ATL patients: compilation of disease-related genes and evidence for TCF4 involvement in BIRC5 gene expression and cell viability

AbstractAdult T-cell leukemia/lymphoma (ATL) is an aggressive and fatal disease. We have examined 32 patients with smoldering, chronic, lymphoma and acute leukemia using Affymetrix HG-U133A2.0 arrays. Using the BRB array program, we identified genes differentially expressed in leukemia cells compared with normal lymphocytes. Several unique genes were identified that were overexpressed in leukemic cells, including TNFSF11, RGS13, MAFb, CSPG2, C/EBP-α, and TCF4; 200 of the most highly overexpressed ATL genes were analyzed by the Pathway Studio, version 4.0 program. ATL leukemia cells were characterized by an increase in genes linked to “central” genes CDC2/cyclin B1, SYK/LYN, proliferating cell nuclear antigen, and BIRC5. Because of its potential therapeutic importance, we focused our studies on the regulation and function of BIRC5, whose expression was increased in 13 of 14 leukemia samples. TCF4 reporter assays and transfection of DN-TCF4 demonstrated that TCF4 regulates BIRC5 gene expression. Functionally, transfection of ATL cells with BIRC5 shRNA decreased BIRC5 expression and cell viability 80%. Clinical treatment of ATL patients with Zenapax or bortezomib decreased BIRC5 expression and cell viability. These experiments represent the first direct experimental evidence that BIRC5 plays an important role in ATL cell viability and provides important insight into ATL genesis and potential targeted therapies.

An integrated geologic framework for EarthScope's US array

The GeoFrame initiative is a new geologic venture that focuses on the construction, stabilization, and modification of the North American continent through time. The initiative's goals can be achieved through systematic integration of geologic knowledge—and particularly geologic time—with the unprecedented Earth imaging to be collected under the US Array program of EarthScope (http://wwwearthscope.org/usarray).The GeoFrame initiative encourages a cooperative community approach to collecting and sharing data and will take a coast‐to‐coast perspective of the continent, focusing not only on the major geologic provinces, but also on the boundaries between these provinces. GeoFrame also offers a tangible,‘you can see it and touch it’ basis for a national approach to education and outreach in the Earth sciences.

New candidate GHz peaked spectrum and compact steep spectrum sources

Data from a recent Australia Telescope Compact Array (ATCA) program of multi-frequency, multi-epoch monitoring of 202 active galactic nuclei with declinations < +10 degrees have been searched for GHz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources. Supplementary data at higher and lower frequencies, where available, have been used to further examine the spectral properties of previously reported and new candidate GPS and CSS sources. The ATCA monitoring program has allowed the variability and polarization properties of sources previously reported as GPS and CSS sources, and the majority of new GPS and CSS candidates, to be investigated, confirming that these are useful diagnostics in discriminating genuine GPS and CSS sources from variable sources that display similar spectra only temporarily. GPS sources are confirmed to be generally more compact, and less polarized, than CSS sources, although CSS sources show evidence for being somewhat less variable than GPS sources at 1.4 and 2.5GHz. In addition, the widths of GPS spectra are examined, and a significant difference is found in the GPS sample of Snellen et al. (2000) between sources with compact double (CD) or compact symmetric object (CSO) morphologies and sources with other morphologies, in that CD and CSO sources have generally narrower spectra. Possible reasons for this difference are considered.

Computation by ‘While’ programs on topological partial algebras

The language of while programs is a fundamental model for imperative programming on any data type. It leads to a generalisation of the theory of computable functions on the natural numbers to the theory of computable functions on any many-sorted algebra. The language is used to express many algorithms in scientific computing where while programs are applied to continuous data. In the theory of data, continuous data types are modelled by topological many-sorted algebras. We study both exact and approximate computations by while programs, and while programs with arrays, over topological many-sorted algebras with partial operations. First, we establish that partial operations are necessary in order to compute a wide range of continuous functions. We prove basic continuity properties of our abstract computability: Any partial function computable over a partial topological algebra by a while- array program is continuous. Any set semicomputable, or computable, over a partial topological algebra by a while- array program is open, or clopen, respectively. Secondly, we contrast exact and approximate computations. The class of functions that can be computed exactly can be quite limited. We show that on connected total algebras, the while and while-array computable functions are precisely those that are explicitly definable by terms. We show that for certain general classes of topological algebras, the total functions that can be approximated by while programs are precisely those that can be effectively approximated by terms. This property we call generalised Weierstrass approximation. An application of this result is that a function on the set R of reals is computable in the sense of computable analysis if, and only if, it is while program approximable on a simple algebra based on R .

Space Station Freedom solar array design development

The Space Station Freedom solar array program is required to provide a 75 kW power module that uses eight solar array (SA) wings over a four-year period in low Earth orbit (LEO). Each wing will be capable of providing 23.4 kW at the 4 yr design point. The design of flexible-substrate SAs that must survive exposure to the space environment, including atomic oxygen, for an operating life of fifteen years is discussed. The tradeoff study and development areas being investigated include solar cell module size, solar cell weld pads, panel stiffener frames, materials inherently resistant to atomic oxygen, and weight reduction design alternatives. >

Constructing a pulsar timing array

Arrival time data from a spatial array of millisecond pulsars can be used (1) to provide a time standard for long time scales, (2) to detect perturbations of the earth's orbit, and (3) to search for a cosmic background of gravitational radiation. A polynomial time series representation for these three effects is first developed that is appropriate for analysis of the present data with its limited degrees of freedom. A pulsar timing array program is then described that has been established at the National Radio Astronomy Observatory 43 m telescope with observations of PSR 1620 - 26, PSR 181 - 24, and PSR 1937 + 21. The results cover a 2 yr period beginning in July 1987. The influence of global parameters - clock, earth location, and effects of gravitational radiation is discussed in the context of the polynomial model. 45 refs.