Physics
851 views | +0 today

 Scooped by Mikko Hakala onto Physics

# Scientific method: Statistical errors

P values, the 'gold standard' of statistical validity, are not as reliable as many scientists assume. One researcher suggested rechristening the methodology “statistical hypothesis inference testing”, presumably for the acronym it would yield. Here we explain why if you think you can trust 'em, you should think again. http://www.nature.com/news/scientific-method-statistical-errors-1.14700"

Mikko Hakala's insight:

"... all [the P-value] can do is summarize the data assuming a specific null hypothesis. It cannot work backwards and make statements about the underlying reality."

No comment yet.

# Physics

Curated by Mikko Hakala
 Scooped by Mikko Hakala

## Introduction to Correlation

This introduction to correlation by Data Scientist Ruslana Dalinina provides examples of how to determine three main correlation types — Pearson, Spearman, and Kendall — using the Python library pandas.
Mikko Hakala's insight:
Overview of the basic correlation types.
No comment yet.
 Scooped by Mikko Hakala

## [1702.01361] Deep learning and the Schrödinger equation

We have trained a deep (convolutional) neural network to predict the ground-state energy of an electron in four classes of confining two-dimensional electrostatic potentials. On randomly generated potentials, for which there is no analytic form for either the potential or the ground-state energy, the neural network model was able to predict the ground-state energy to within chemical accuracy, with a median absolute error of 1.49 mHa. We also investigate the performance of the model in predicting other quantities such as the kinetic energy and the first excited-state energy of random potentials. While we demonstrated this approach on a simple, tractable problem, the transferability and excellent performance of the resulting model suggests further applications of deep neural networks to problems of electronic structure.
Mikko Hakala's insight:
Convolutional neural network predicts the energy of one electron in a random 2d electrostatic potential to within chemical accuracy. To be demonstrated for bigger multielectron systems. If successful, would lead to important saving in computational time.
No comment yet.
 Scooped by Mikko Hakala

## Combining theory and experiment in electrocatalysis: Insights into materials design

Chemists have known how to use electricity to split water into hydrogen and oxygen for more than 200 years. Nonetheless, because the electrochemical route is inefficient, most of the hydrogen made nowadays comes from natural gas. Seh et al. review recent progress in electrocatalyst development to accelerate water-splitting, the reverse reactions that underlie fuel cells, and related oxygen, nitrogen, and carbon dioxide reductions. A unified theoretical framework highlights the need for catalyst design strategies that selectively stabilize distinct reaction intermediates relative to each other.

Science , this issue p. [10.1126/science.aad4998][1]

Mikko Hakala's insight:
Good review and insight into developing new electrocatalytic materials for clean energy conversion
No comment yet.
 Scooped by Mikko Hakala

## Molecular selfie reveals how a chemical bond breaks: Proton is seen escaping the molecule - Scienmag

Credit: ICFO/Scixel
Imagine what it would be like to watch how the individual atoms of molecules rearrange during a chemical reaction to form a new substance, or to see the compounds of DNA move, r..
Mikko Hakala's insight:
Cool stuff. 20 years ago impossible, now realized experimentally: Imaging chemical bond breaking (here deprotonation of a molecule). After ionization of the target the ejected electron was driven back to scatter off the parent molecule, and the collision products recorded  - in other words the molecule was taught to take a selfie.
No comment yet.
 Scooped by Mikko Hakala

## Surface Defects on Natural MoS2 - ACS Applied Materials & Interfaces (ACS Publications)

* MoS2, and other TMDs, are promising new materials for devices such as beyond-CMOS transitors, LEDs, sensor and solar cells

* Changes in electrical properties (e.g. p/n type behavior) are likely related to local stoichiometry,, metal-like and structural defects and impurities on the surface

* The work studies intrinsic defects detected by STM, STS, XPS and ICPMS,, finds significantly high concentrations

* Before industrial scale can be reached, the structural factors affecting electronic and optical properties need to be understood and controlled

[Image: 3113Ian - Made with vesta, CC BY-SA 3.0, https://en.wikipedia.org/w/index.php?curid=42615855]
No comment yet.
 Rescooped by Mikko Hakala from Nuclear Physics

## X-ray breakthrough 'opens door' to controlled nuclear fusion

Scientists have for the first time been able to monitor the flow of energy during fast ignition, a process that it hoped to be capable of creating controlled nuclear fusion

Via Theo J. Mertzimekis
Mikko Hakala's insight:

X-ray imaging helps develop fast ignition methods in nuclear fusion. The challenge is to follow where the energy of the high-intensity laser goes in the 2nd step of the ignition, the target area being the densest region of the compressed fuel.

To monitor this, Cu tracers are used, which are hit by fast electrons generated by the intensive laser. The resulting X-ray fluorescence radiation from Cu is then used for advanced spatial imaging of the energy deposition.

No comment yet.
 Scooped by Mikko Hakala

## Manufacturing thin film tandem solar cells using thin perovskite layer for low cost roll-to-roll production

Latest breakthroughs in sustainable technology, business and market analysis
Mikko Hakala's insight:

* New procedure for a tandem cell with future potential for low-cost roll-to-roll production. (Low cost due to processing at low temperature.)

* Upper layer: semi-transparent methylammonium lead iodide solar cell module (grown as perovskite crystals)

* Interlayer: phenyl-C61-butyric acid methyl ester

* Lower layer: copper indium gallium diselenide (CIGS) second solar cell module.

No comment yet.
 Scooped by Mikko Hakala

## Synchrotron Light Finland 2015

Annual Workshop & School of the Finnish Synchrotron Radiation User Organisation

Helsinki, Kumpula Science Campus, 3.-4.12.2015

Public lectures

*Thursday 3rd December, 12:00-17:00 Physicum building, hall E204

*Friday 4th December, 9:00-12:00 Exactum building, hall CK112

Invited keynote lecturers

*Prof. Olle Björneholm, Uppsala University, Sweden: From molecules to rain: Probing atmospherically relevant aqueous surfaces with XPS

*Dr. Daniel Clare, Diamond Light Source, UK:
The UK national electron microscope facility, direct electron detectors and helical viruses

*Dr. Ulla Vainio, Helmholtz-Zentrum Geesthacht, Germany:Harder, Better, Faster - X-ray scattering experiments at synchrotrons

*Acad. Prof. Maarit Karppinen, Aalto University, Finland:Title TBA

Mikko Hakala's insight:

Welcome to the meeting & visit the page for updates.

No comment yet.
 Rescooped by Mikko Hakala from Nuclear Physics

## The True Alchemists

Ernest Rutherford and Frederick Soddy, true alchemists, achieved the first artificial transmutation (the conversion of a chemical element into another).

Via Theo J. Mertzimekis
Mikko Hakala's insight:

“Rutherford, this is transmutation!”
“For Mike’s sake, Soddy, don’t call it transmutation. They’ll have our heads off as alchemists.”

No comment yet.
 Scooped by Mikko Hakala

## Ψk 2015 Conference / September 6-10 / Donostia-San Sebastian

The Psi-k 2015 Conference is the fifth in a series started in 1996 by the European electronic structure community. Every five years, this conference brings together the global community that is active in the science of electronic structure and properties of condensed matter. The conference is organized and supported by the Psi-k Network**, and its programme covers both the fundamental and theoretical aspects of electronic structure calculations, computational methods and tools, in addition to applications to fundamental scientific and industrial and societal challenges. The application areas of electronic property calculations range from condensed matter and materials physics to nanoscience, chemistry, geophysics and biology, the design and discovery of novel materials, their properties, and their performance in devices (that is, to harvest, store, and convert energy) and to engineer new states of matter to advance fundamental and applied sciences.

Mikko Hakala's insight:

This great conference is starting. Here are the symposia:

* Thirty Years of Car-Parrinello

* GW and BSE

* f- electrons: "In memory of Walter Temmerman and his contributions to Psi-k and the electronic structure community”
* Correlated Electrons
* Theoretical Spectroscopy
* Recent Advances in Diagrammatic Methods for the Total Energy
* Novel Density Functionals
* Recent Developments in Density Matrix Functional Theory
* Density-Functional Theory for Coupled Matter-Photon Systems
* Applications of Quantum Monte Carlo Methods
* Upscaling Electronic Structure: Reduced-Scaling and Multi-Scale Methods
* Spin-Orbit Coupling Effects in First-Principles Quantum Transport
* Magnetic excitations and magnetization dynamics
* Chiral Magnetism
* First-Principles Calculations for Multiferroics and Magnetoelectrics
* Ab Initio Statistical Mechanics
* Topological Insulators
* Electrochemical Energy Storage and Conversion: Solid/Liquid Interfaces
* Materials Design
* Machine Learning Methods in Materials Modeling
* Hybrid Photovoltaic Materials
* Electron Phonon Coupling and Thermoelectricity
* Ultrafast Charge Transfer at the Nanoscale
* Non-­Linear Optics of Materials and Nanoplasmonics
* Novel 2D Materials and Heterostructures
* Modeling of Defect Levels
* Transport Properties
* Matter Under Extreme Conditions
* Electronic Structure Theory for Biophysics

No comment yet.
 Scooped by Mikko Hakala

## Q&A: Researchers Explain a Strange High-Intensity Result at SLAC's X-ray Laser

SLAC National Accelerator Laboratory is a U.S. Department of Energy (DOE) Office of Science laboratory operated by Stanford University.
Mikko Hakala's insight:

This is an interesting experimental study on fundamental X-ray - matter interactions.

Focus the power of LCLS X-ray free-electron laser to a 0.1 micron size point on a beryllium sample. The result is concerted non-linear Compton scattering: Two photons hit the sample, scatter from the Be's nearly-free electrons, and the end result is an outgoing electron and a photon.

However, the experiment shows an anomalous redshift of the outgoing photons, which suggest some new scattering mechanism to be understood.

For other X-ray news, visit: http://twitter.com/helixsfi

No comment yet.
 Scooped by Mikko Hakala

## RIXS reveals where TiO2 nanoparticles store electrons after plasmon-induced electron transfer from Au

The photo-catalytic performance of TiO2 nanoparticles can be improved by attaching metal particles that have strong absorption bands in the visible region of the light spectrum. An optically excited surface plasmon in Au metal particles may trigger a charge transfer to the TiO2 particle thus improving its ability to catalyse chemical reactions. In this work, the modification of the TiO2 electronic structure following the charge transfer was studied in order to address the question of where the TiO2 particle stores the additional charge.

Mikko Hakala's insight:

An X-ray scattering technique called RIXS can be used to detect the local electronic structure at the Ti sites of TiO2 during charge injection. This information is important to clarify the basic physical processes in photocatalysts in view of improving the performance.

Here, laser pump - X-ray probe (RIXS) technique was used with Au nanoparticles attached on the TiO2 surface. The study finds evidence of charge to be trapped at Ti sites and a distortion of the TiO6 octahedra at the surface during the injection.

The reserach article: http://onlinelibrary.wiley.com/doi/10.1002/anie.201412030/abstract

No comment yet.
 Scooped by Mikko Hakala

## Chameleons change their colors by rearranging nanocrystals in their skin

Chameleons may do their quick-change color camouflage by changing the positions of light-reflecting cells in their skin, according to a new study.
Mikko Hakala's insight:

Cool physics by chameleons! They tune the structure of guanine nanoparticles to quickly switch colour.

Original article (optical physics):

http://www.nature.com/ncomms/2015/150302/ncomms7368/full/ncomms7368.html

No comment yet.
 Scooped by Mikko Hakala

## Machine learning: New tool in the box

A recent burst of activity in applying machine learning to tackle fundamental questions in physics suggests that associated techniques may soon become as common in physics as numerical simulations or calculus. Nature Physics | doi:10.1038/nphys4053

Mikko Hakala's insight:
New tools to tackle questions in physics.
No comment yet.
 Scooped by Mikko Hakala

## Z2Pack released - a tool for computing topological invariants - General announcements - Psi-k

Dear members of the Psi-k community,it is our pleasure to announce the release of Z2Pack - a tool to calculate topological invariants for real materials. The code can identify topological phases from k.p or tight-binding models, or directly from some first principles codes. The method is based on tr
Mikko Hakala's insight:
Numerical Implementation of Hybrid Wannier Centers for Identifying Topological Materials

Search and classify topological materials with this tool. Can be used as a post-processing tool with ab initio calculations or standalone with k.p or tight-binding Hamiltonians.

Pint it for later: https://fi.pinterest.com/pin/318981586093479639/

No comment yet.
 Scooped by Mikko Hakala

## Machine learning enables predictive modeling of 2-D materials

Machine learning, a field focused on training computers to recognize patterns in data and make new predictions, is helping doctors more accurately diagnose diseases and stock analysts forecast the rise and fall of financia
Mikko Hakala's insight:

Modeling of stanene nanostructures with atomic potential based on machine learning

Original paper: http://pubs.acs.org/doi/abs/10.1021/acs.jpclett.6b01562

Pin it for later:
https://fi.pinterest.com/pin/318981586092609000/
No comment yet.
 Rescooped by Mikko Hakala from Nuclear Physics

## Fundamental Fission Modeling Finds a Foothold

Time-dependent superfluid local density approximation model captures detailed dynamics of splitting plutonium-240 nucleus.

Via Theo J. Mertzimekis
Mikko Hakala's insight:
DFT for superfluid fermionic systems to model real-time nuclear dynamics. Heavy supercomputing (GPUs) needed to solve the 56000 partial differential equations.
No comment yet.
 Scooped by Mikko Hakala

## The Economic Impact of Materials Modelling

This study briefly delineates the types of metrics and methodologies that can be used to quantify the economic impacts of materials modelling from a variety of perspectives including R&D stakeholders, industry stakeholders, and society. The study also investigates how materials modelling impacts the industrial R&D process and outlined the value and potential of materials modelling for industrial research and innovation, competitiveness, and profitability using examples from both the pharmaceutical industry and the molecular modelling industry. Finally, results from a survey of the European manufacturing industry are presented, providing corroboration for the indicators of R&D process improvements found in earlier studies and new data relevant for quantitative economic analyses.
Mikko Hakala's insight:

*Importance of Materials Modelling on R&D and Industry*

The open access report discusses how to quantify the impact of materials modelling

* micro- and macroeconomic impact

* what are the proper KPI's to track business improvements

* innovation, cost savings, ROI perspectives

* bottlenecks (missing business cases, wait-and-see approach)

* excerpts from case studies, e.g., quantum mechanical software CASTEP, its use in battery materials prection

No comment yet.
 Scooped by Mikko Hakala

## Science job opportunities at ESRF

Current openings for science positions:

- 3 PhD Thesis Students

- 1 Post-Doctoral Fellow

Mikko Hakala's insight:

Link to current science job openings: http://www.esrf.eu/Jobs/english/recruitment-portal

3 PhD positions, 1 post-doc position

No comment yet.
 Rescooped by Mikko Hakala from Nuclear Physics

## A new way to make X-rays

MIT researchers have found a phenomenon that might lead to more compact, tunable X-ray devices made of graphene.

Via Theo J. Mertzimekis
Mikko Hakala's insight:

This theoretical research predics a new X-ray generation method based on confined plasmons in graphene. The concept is unique and it would be a highly advantageous method, since low-energy electrons can be used to produce tunable X-rays. In all the current approaches high-energy charged particles are needed (synchrotrons, free-electron lasers), which requires large device sizes and intensities.

Press release: http://news.mit.edu/2015/new-way-make-x-rays

X-rays are used for research and diagnostics purposes in materials and natural sciences, in engineering, and for biomedical and life sciences.

Note the upcoming X-ray workshop in Helsinki 3.-4.12.2015:  http://www.fsruo.fi/index.php/en/workshops-and-schools-2/fsruo2015 (public lectures)

No comment yet.
 Scooped by Mikko Hakala

## This Condensed Life | A Blog About Condensed Matter Physics that Trespasses on Topical Tangents

A Blog About Condensed Matter Physics that Trespasses on Topical Tangents
Mikko Hakala's insight:

Check out this interesting condensed mattery physics blog with five contributing authors.

The following are some of the most popular tags in the posts: BCS theory, charge density wave, superconductivity, experiment, perspective, philosophy, review.

No comment yet.
 Scooped by Mikko Hakala

## Perovskite quantum dots emit single photons - nanotechweb.org

The nanocrystals might find use in light-emitting diodes, with practical applications in displays.
Mikko Hakala's insight:

Early stages in developing organometal trihalide perovskite semiconductors as quantum dots. Advantages could be easy tunability of emission wavelength but challenges remain due to tendency of the material to degrade.

No comment yet.
 Scooped by Mikko Hakala

## Long-sought chiral anomaly detected in crystalline material

A study by Princeton researchers presents evidence for a long-sought phenomenon—first theorized in the 1960s and predicted to be found in crystals in 1983—called the "chiral anomaly" in a metallic compound of sodium and bismuth. The additional finding of an increase in conductivity in the material may suggest ways to improve electrical conductance and minimize energy consumption in future electronic devices.
Mikko Hakala's insight:

Evidence for a new physical phenomenon - "handedness" - in crystalline materials found in a Dirac semimetal.

No comment yet.
 Scooped by Mikko Hakala

## Ask Ethan #93: Newton’s Random Apple

If all the random motions of the molecules inside aligned, how far and fast would it go?
Mikko Hakala's insight:

The question is if thermal energy can be converted to the motion of the apple as a whole - Story of basic physical phenomena why this cannot happen.

No comment yet.
 Scooped by Mikko Hakala

## Electronic structure and phase stability of oxide semiconductors: Performance of dielectric-dependent hybrid functional DFT, benchmarked against GW band structure calculations and experiments

- Mikko's summary -

* New hybrid functional benchmarked, aims to reproduce both ground- and excited state properties within a fully ab initio framework.

* A well-written introductory part, with review of the standard LDA/GGA gap problem, how the fraction 'alpha' in the hybrid calculation scheme relates to macroscopic dielectric constant, and what approaches have been used for alpha.

* Detailed, useful computational methodology part with discussions on codes and chosen parameters.

* The new approach is tested on wide-gap oxide semiconductors that have current or future technological impact (e.g. in photovoltaics and catalysis): ZnO, TiO2, ZrO2 and WO2.

* The paper essentially addresses the question of how to tune hybrid functional scheme to be a more applicable tool that can handle in a reliable way both energetics and electronic (ground and excited state) properties.