Blind Search | ScienceGate

It’s altogether too easy to reduce all method in science to a simple algorithm. Hypothesize, deduce (or predict), test, evaluate, conclude. It seems like a handy formula for authority. “The” Scientific Method (expressed in this way) haunts the introductions of textbooks, lab report guidelines, and science fair standards. Yet it is a poor model for learning about method in science. One might endorse instead teaching about the scientist’s toolbox. Science draws on a suite of methods, not just one. The methods also include model building, analogy, pattern recognition, induction, blind search and selection, raw data harvesting, computer simulation, experimental tinkering, chance, and (yes) play, among others. The toolbox concept remedies two major problems in the conventional view. First, it credits the substantial work—scientific work—in developing concepts or hypotheses. Science is creative. Even to pursue the popular strategy of falsification, one must first have imaginative conjectures. We need to foster such creative thinking skills among students. Second, the toolbox view supports many means for finding evidence—some direct, some indirect, some experimental, some observational, some statistical, some based on controls, some on similarity relationships, some on elaborate thought experiments, and so on. Again, students should be encouraged to think about evidence and argument broadly. Consider just a few historical examples. First, note Watson and Crick’s landmark model of DNA. It was just that: a model. They drew on data already available. They also played with cardboard templates of nucleotide bases. Yes, their hypothesis of semiconservative replication was eventually tested by Meselson and Stahl—later. But even that involved enormous experimental creativity (essay 4). Consider, too, Mendel’s discoveries in inheritance (essay 22). Mendel did not test just seven traits of pea plants, cleverly chosen in advance (as the story is often told). Rather, he seems to have followed twenty-two varieties exhibiting fifteen traits, hoping for patterns to emerge. He ultimately abandoned those varieties whose results he called confusing. Nobelist Thomas Hunt Morgan, in Mendel’s wake, did not discover sex linkage through any formal hypothesis about inheritance.

Download Full-text

Search for point sources of ultra-high-energy photons with the Telescope Array surface detector

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3618 ◽

2020 ◽

Vol 492 (3) ◽

pp. 3984-3993 ◽

Cited By ~ 1

Author(s):

R U Abbasi ◽

M Abe ◽

T Abu-Zayyad ◽

M Allen ◽

R Azuma ◽

...

Keyword(s):

Point Source ◽

Cosmic Ray ◽

High Energy ◽

Point Sources ◽

Ultra High Energy ◽

Telescope Array ◽

Air Shower ◽

Upper Limits ◽

Surface Detector ◽

Blind Search

ABSTRACT The surface detector (SD) of the Telescope Array (TA) experiment allows us to detect indirectly photons with energies of the order of 1018 eV and higher, and to separate photons from the cosmic ray background. In this paper, we present the results of a blind search for point sources of ultra-high-energy (UHE) photons in the Northern sky using the TA SD data. The photon-induced extensive air showers are separated from the hadron-induced extensive air shower background by means of a multivariate classifier based upon 16 parameters that characterize the air shower events. No significant evidence for the photon point sources is found. The upper limits are set on the flux of photons from each particular direction in the sky within the TA field of view, according to the experiment’s angular resolution for photons. The average 95 per cent confidence level upper-limits for the point-source flux of photons with energies greater than 1018, 1018.5, 1019, 1019.5 and 1020 eV are 0.094, 0.029, 0.010, 0.0073 and 0.0058 km−2yr−1, respectively. For energies higher than 1018.5 eV, the photon point-source limits are set for the first time. Numerical results for each given direction in each energy range are provided as a supplement to this paper.

Download Full-text

Detection of gamma-ray transients with wild binary segmentation

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa263 ◽

2020 ◽

Vol 493 (3) ◽

pp. 4428-4441

Author(s):

S Antier ◽

K Barynova ◽

P Fryzlewicz ◽

C Lachaud ◽

G Marchal-Duval

Keyword(s):

Gamma Ray ◽

Change Point Detection ◽

Archival Data ◽

Data Set ◽

Temporal Properties ◽

Background Removal ◽

Segmentation Analysis ◽

Binary Segmentation ◽

Blind Search ◽

Detection Search

ABSTRACT In the context of time domain astronomy, we present an offline detection search of gamma-ray transients using a wild binary segmentation analysis called F-WBSB targeting both short and long gamma-ray bursts (GRBs) and covering the soft and hard gamma-ray bands. We use NASA Fermi/GBM archival data as a training and testing data set. This paper describes the analysis applied to the 12 NaI detectors of the Fermi/GBM instrument. This includes background removal, change-point detection that brackets the peaks of gamma-ray flares, the evaluation of significance for each individual GBM detector, and the combination of the results among the detectors. We also explain the calibration of the ∼ 10 parameters present in the method using one week of archival data. Finally, we present our detection performance result for 60 d of a blind search analysis with F-WBSB by comparing to both the onboard and offline GBM search as well as external events found by others surveys such as Swift-BAT. We detect 42/44 onboard GBM events but also other gamma-ray flares at a rate of 1 per hour in the 4–50 keV band. Our results show that F-WBSB is capable of recovering gamma-ray flares, including the detection of soft X-ray long transients. FWBSB offers an independent identification of GRBs in combination with methods for determining spectral and temporal properties of the transient as well as localization. This is particularly useful for increasing the GRB rate and that will help the joint detection with gravitational-wave events.

Download Full-text

Stellar Magnetic Dynamos and Activity Cycles

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314002038 ◽

2013 ◽

Vol 9 (S302) ◽

pp. 190-193

Author(s):

Nicholas J. Wright

Keyword(s):

Coronal Emission ◽

X Ray ◽

Rotation Periods ◽

Early Results ◽

Uniform Sample ◽

Activity Cycles ◽

Blind Search ◽

The Relationship ◽

Interface Type ◽

Stellar Dynamo

AbstractUsing a new uniform sample of 824 solar and late-type stars with measured X-ray luminosities and rotation periods we have studied the relationship between rotation and stellar activity that is believed to be a probe of the underlying stellar dynamo. Using an unbiased subset of the sample we calculate the power law slope of the unsaturated regime of the activity – rotation relationship as LX / Lbol ∝ Roβ, where β = − 2.70 ± 0.13. This is inconsistent with the canonical β = − 2 slope to a confidence of 5σ and argues for an interface-type dynamo. We map out three regimes of coronal emission as a function of stellar mass and age, using the empirical saturation threshold and theoretical super-saturation thresholds. We find that the empirical saturation timescale is well correlated with the time at which stars transition from the rapidly rotating convective sequence to the slowly rotating interface sequence in stellar spin-down models. This may be hinting at fundamental changes in the underlying stellar dynamo or internal structure. We also present the first discovery of an X-ray unsaturated, fully convective M star, which may be hinting at an underlying rotation - activity relationship in fully convective stars hitherto not observed. Finally we present early results from a blind search for stellar X-ray cycles that can place valuable constraints on the underlying ubiquity of solar-like activity cycles.

Download Full-text

A Blind Search for Transient Bursts of Very High Energy γ Rays With Milagro

10.1063/1.2943530 ◽

2008 ◽

Cited By ~ 1

Author(s):

Vlasios Vasileiou ◽

M. Galassi ◽

David Palmer ◽

Ed Fenimore ◽

Keyword(s):

High Energy ◽

Very High Energy ◽

Γ Rays ◽

Blind Search ◽

Very High

Download Full-text

An Automatic Marking System for Interactive Exercises on Blind Search Algorithms

Lecture Notes in Computer Science - Artificial Intelligence in Education ◽

10.1007/978-3-642-39112-5_112 ◽

2013 ◽

pp. 783-786 ◽

Cited By ~ 4

Author(s):

Foteini Grivokostopoulou ◽

Ioannis Hatzilygeroudis

Keyword(s):

Search Algorithms ◽

Blind Search ◽

Interactive Exercises

Download Full-text

FLASH early science – discovery of an intervening H i 21-cm absorber from an ASKAP survey of the GAMA 23 field

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa949 ◽

2020 ◽

Vol 494 (3) ◽

pp. 3627-3641 ◽

Cited By ~ 4

Author(s):

J R Allison ◽

E M Sadler ◽

S Bellstedt ◽

L J M Davies ◽

S P Driver ◽

...

Keyword(s):

Path Length ◽

Column Density ◽

Radio Sources ◽

Early Type ◽

Absorption Path Length ◽

Spin Temperature ◽

Upper Limits ◽

Blind Search ◽

Cross Matching ◽

Early Type Galaxy

ABSTRACT We present early science results from the First Large Absorption Survey in H i (FLASH), a spectroscopically blind survey for 21-cm absorption lines in cold hydrogen (H i) gas at cosmological distances using the Australian Square Kilometre Array Pathfinder (ASKAP). We have searched for H i absorption towards 1253 radio sources in the GAMA 23 field, covering redshifts between z = 0.34 and 0.79 over a sky area of approximately 50 deg2. In a purely blind search, we did not obtain any detections of 21-cm absorbers above our reliability threshold. Assuming a fiducial value for the H i spin temperature of Tspin = 100 K and source covering fraction cf = 1, the total comoving absorption path-length sensitive to all Damped Lyman α Absorbers (DLAs; NH i ≥ 2 × 1020 cm−2) is ΔX = 6.6 ± 0.3 (Δz = 3.7 ± 0.2) and super-DLAs (NH i ≥ 2 × 1021 cm−2) is ΔX = 111 ± 6 (Δz= 63 ± 3). We estimate upper limits on the H i column density frequency distribution function that are consistent with measurements from prior surveys for redshifted optical DLAs, and nearby 21-cm emission and absorption. By cross-matching our sample of radio sources with optical spectroscopic identifications of galaxies in the GAMA 23 field, we were able to detect 21-cm absorption at z = 0.3562 towards NVSS J224500−343030, with a column density of $N_{\rm H\,\small{I}} = (1.2 \pm 0.1) \times 10^{20}\, (T_{\rm spin}/100\, \mathrm{K})$ cm−2. The absorber is associated with GAMA J22450.05−343031.7, a massive early-type galaxy at an impact parameter of 17 kpc with respect to the radio source and which may contain a massive (MH i ≳ 3 × 109 M⊙) gas disc. Such gas-rich early types are rare, but have been detected in the nearby Universe.

Download Full-text