A Fast Method for Power Spectrum and Foreground Analysis for 21 cm Cosmology
We develop and demonstrate an acceleration of the Liu & Tegmark quadratic estimator formalism for inverse variance foreground subtraction and power spectrum estimation in 21 cm tomography from O(N^3) to O(N log N), where N is the number of voxels of data. This technique makes feasible the megavoxel scale analysis necessary for current and upcoming radio interferometers by making only moderately restrictive assumptions about foreground models and survey geometry. We exploit iterative and Monte Carlo techniques and the symmetries of the foreground covariance matrices to quickly estimate the 21 cm brightness temperature power spectrum, P(k_parallel, k_perpendicular), the Fisher information matrix, the error bars, the window functions, and the bias. We also extend the Liu & Tegmark foreground model to include bright point sources with known positions in a way that scales as O[(N log N)(N point sources)] < O(N^5/3). As a first application of our method, we forecast error bars and window functions for the upcoming 128-tile deployment of the Murchinson Widefield Array, showing that 1000 hours of observation should prove sufficiently sensitive to detect the power spectrum signal from the Epoch of Reionization.
Congrats to Josh on submitting his first paper for publication!
Buddhist Iron Man found by Nazis is from space
Researchers from Oxford University released a new study in the international medical journal Psychopharmacology showing that taking propranolol reduces “implicit negative racial bias.”
Thirty-six white people were used in the study, with half getting propranolol and the other half getting a placebo. Researchers then used a feeling thermometer to rate how “warm” they felt toward different groups.
Researchers found that the heart disease drug “significantly lowered heart rate.” They also found that there was no significant difference between the propranolol and placebo groups toward religious or sexual prejudice.
“The main finding of our study is that propranolol significantly reduced implicit but not explicit racial bias,” researchers concluded.
The largest solar flare in five years is racing toward Earth, threatening to unleash a torrent of charged particles that could disrupt power grids, GPS and airplane flights.
The sun erupted Tuesday evening, and the effects should start smacking Earth around 7 a.m. EST Thursday (1200 GMT), according to forecasters at the federal government’s Space Weather Prediction Center. They say the flare is growing as it speeds outward from the sun.
“It’s hitting us right in the nose,” said Joe Kunches, a scientist for the National Oceanic and Atmospheric Administration.
The idea is simple. Psychologists have known for some years that it is almost impossible to speak when your words are replayed to you with a delay of a fraction of a second.
Kurihara and Tsukada have simply built a handheld device consisting of a microphone and a speaker that does just that: it records a person’s voice and replays it to them with a delay of about 0.2 seconds. The microphone and speaker are directional so the device can be aimed at a speaker from a distance, like a gun.
In tests, Kurihara and Tsukada say their speech jamming gun works well: “The system can disturb remote people’s speech without any physical discomfort.”
Richard Hamming, The Art of Doing Science and Engineering
From cable TV news pundits to red-meat speeches in Iowa and New Hampshire, our nation’s deep political stereotypes are on full display: Conservatives paint self-indulgent liberals as insufferably absent on urgent national issues, while liberals say fear-mongering conservatives are fixated on exaggerated dangers to the country.
A new study from the University of Nebraska-Lincoln suggests there are biological truths to such broad brushstrokes.
In a series of experiments, researchers closely monitored physiological reactions and eye movements of study participants when shown combinations of both pleasant and unpleasant images. Conservatives reacted more strongly to, fixated more quickly on, and looked longer at the unpleasant images; liberals had stronger reactions to and looked longer at the pleasant images compared with conservatives.
“It’s been said that conservatives and liberals don’t see things in the same way,” said Mike Dodd, UNL assistant professor of psychology and the study’s lead author. “These findings make that clear – quite literally.”
To gauge participants’ physiological responses, they were shown a series of images on a screen. Electrodes measured subtle skin conductance changes, which indicated an emotional response. The cognitive data, meanwhile, was gathered by outfitting participants with eyetracking equipment that captured even the most subtle of eye movements while combinations of unpleasant and pleasant photos appeared on the screen.
While liberals’ gazes tended to fall upon the pleasant images, such as a beach ball or a bunny rabbit, conservatives clearly focused on the negative images – of an open wound, a crashed car or a dirty toilet, for example.
Consistent with the idea that conservatives seem to respond more to negative stimuli while liberals respond more to positive stimuli, conservatives also exhibited a stronger physiological response to images of Democratic politicians – presumed to be a negative to them – than they did on pictures of well-known Republicans. Liberals, on the other hand, had a stronger physiological response to the Democrats – presumed to be a positive stimulus to them – than they did to images of the Republicans.
Breaking: Living with a political frame from the moment you are born changes your brain.
Nobody likes getting shots. But what if you could make the needles so tiny that they broke the skin painlessly? Engineers from Tufts University have created such micro-needles—made from the major protein in silk, fibroin.
The researchers created molds for arrays of needles just 500 microns tall and 10 microns wide. That’s a tenth the width of the average human hair. They then poured a solution of fibroin mixed with a drug into the molds. The resulting micro-needles are dried and undergo further processing.
In tests, a patch containing numerous micro-needles successfully released the drug, which maintained its biological activity. The tiny needles are too short to reach the nerves under the skin, so they can deliver drugs without the pain of a traditional shot. Even better, they can gradually release medication over time. While skin patches and slow-release pills are currently used for this purpose, they only work with certain kinds of medication. The new micro-needle system could make the gradual delivery of many drugs smooth as silk.